ArticleLiterature Review

Free cholesterol in atherosclerotic plaques: Where does it come from?

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Free cholesterol in plaques is an emerging contributing factor to lesion instability and, until recently, apoptosis of lipid-laden macrophages was considered the major source of free cholesterol. The validity of this concept is beginning to be challenged since there is recent evidence of erythrocyte membrane-derived cholesterol in plaques. Therefore, intraplaque hemorrhage may not be a passive event, as once considered as studies continue to support the relationship of intraplaque hemorrhage and necrotic core expansion. The association of intraplaque hemorrhage, accumulated free cholesterol, and necrotic core expansion is beginning to unfold and recent MRI studies suggest the value of intraplaque hemorrhage as a predictor of recurrent cerebrovascular events. The amount of erythrocyte membrane-derived cholesterol is also suggested to be a measure of lesion vulnerability in acute coronary syndromes. Recent inhibitors studies of vascular permeability factors further emphasize the importance of intraplaque hemorrhage in plaque progression. Finally, DNA microarray analysis is starting to reveal key molecules involved in the accumulation of free cholesterol that are selectively induced in high-risk plaques. These recent findings emphasize the importance of intraplaque hemorrhage as a contributor of free cholesterol in plaques and point to its provocative role in lesion destabilization.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... But a recent hypothesis proposes that coronary atherosclerosis is an inflammatory process associated with lipid infiltration and inflammatory damage.Red blood cell membrane is involved in lipid infiltration and the inflammatory process, thus playing an essential part in the development and instability of coronary atherosclerosis. 3 Previous studies have shown that in patients with acute coronary syndrome (ACS), erythrocyte membrane contains higher level of cholesterol than that in patients with stable coronary heart disease. 4 Also, the level of inflammatory com-ponents on erythrocyte membrane, such as IL-8, in ACS patients is higher than that in the patients with stable coronary artery disease. ...
... (2) The increase of free cholesterol within the plaque: during the development of atherosclerosis, the accumulation of free cholesterol is a cardinal factor in plaque vulnerability. 3 Accumulation of intracellular cholesterol may trigger a series of apoptotic pathways, leading to the death of macrophages and the formation of foam cells. This is an essential step in the transformation of stable plaques into vulnerable plaques, and this process can cause oxidation of cholesterol, releasing multiple reactive oxygen species, and eventually leading to inflammatory processes. ...
... Journal of Geriatric CardiologyDece 2010Vol 7,[3][4] ...
Article
Objective To examine the changes of red blood cell levels in the obese and non-obese patients with coronary heart disease (CHD) and its clinical significance. Methods 230 cases of coronary heart disease were selected and divided into the obese group and the non-obese group. Obesity and non-obesity were defined based on the body mass index (BMI ¡Ý 28.0kg/m2), or waist-hip ratio (men> 0.9, women> 0.85). In addition, 130 healthy subjects were recruited as controls. The pathological status of coronary lesions was quantita-tively analyzed according to the Coronary Vascular Image Segmentation Evaluation Criteria (American Heart Association 1984) and the Gensini scoring system. Results of the changes of both the hemoglobin levels and the red blood cell count in the obese group, the non-obese group with CHD and the control group were compared. Besides, Multivariant Logistic Regression Analysis was applied to assess the correlation between the red blood cells and the coronary artery disease. Results The red blood cell count and the level of hemoglobin in the obese group with CHD was higher than that in the non-obese group with CHD [(4.35 ± 0.55) and (4.13 ± 0.56) 109/L; (136.71 ± 15.87) and (129.96 ± 16.23) g/L, P < 0.05 in both]; the proportion of acute coronary syndrome in the obese group with CHD was higher in the obese group with CHD than that in the non-obese group with CHD (P<0.05); Multivariant logistic regression analysis also showed that the red blood cell count was positively correlated with obesity with CHD.Conclusion The red blood cell count and the level of hemoglobin in the obese group were higher than those in the non-obese group; the increase of red blood cell count and hemoglobin level is one of the independent risk factors for the obese patients with CHD (J Geriatr Cardiol 2010; 7:143-146).
... Cholesterol in the form of cholesterol crystals (CC) plays an important role in the atherosclerotic lesion formation, for which reason, it is classified as a prognostic marker for atherosclerosis (12). Several studies have reported that CC are present at the sites of plaque rupture, suggesting an important link between plasma cholesterol levels and the pathogenesis of atherosclerosis (13)(14)(15). Many studies have also reported the involvement of CC in the early atherosclerotic lesion formation (12). ...
... CD36 plays a crucial role in foam cell formation, one of the underlying factors in atherogenesis (25, 26). The presence of CC in the advanced athreosclerotic lesions of human and animal models and its effects on CD36 expression suggest a role for cholesterol in atherogenesis (13)(14)(15). To understand the mechanisms by which CC regulate foam cell formation, we have studied its effects on scavenger receptor expression in human monocytic THP1 cells. ...
... In this aspect, the present findings demonstrate that CC induces ROS production leading to activation of BTK. These (14)(15)(16). Cholesterol is known to accumulate in atherosclerotic plaques in the form of cholesterol crystals in foam cells (14,15). In addition to this information, the present results as summarized in Figure 9 reveal that CC via XO and NADPH oxidasedependent ROS production and BTK activation leads to p300 tyrosine phosphorylation and activation, which in turn, by acetylating STAT1 facilitates STAT1 interaction with PPARJ in mediating CD36 expression, oxLDL uptake and foam cell formation. ...
Article
Full-text available
In understanding the mechanisms of cholesterol in the pathogenesis of atherosclerosis, previous studies from other laboratories have demonstrated that cholesterol crystals (CC) induce scavenger receptor CD36 expression and NLRP3-mediated inflammasome formation. In elucidating the mechanisms by which CC could enhance CD36 expression and foam cell formation, here we report that CC via NADPH and xanthine oxidases-mediated ROS production activates BTK, a non-receptor tyrosine kinase. In addition, CC induce p300 tyrosine phosphorylation and activation in a BTK-dependent manner, which in turn, leads to STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation. Furthermore, p300, STAT1 and PPARγ bound to a STAT binding site at -107 nt in CD36 promoter and enhanced its activity in ROS and BTK-dependent manner. Disruption of this STAT binding site by site-directed mutagenesis abolished CC-induced CD36 promoter activity. Together these results reveal for the first time that CC via producing ROS and activating BTK causes p300-mediated STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation.
... fatty streak, minimal sudanophilic intimal deposit both intra-and extracellular "globules" of lipid, slight increase in interstitial mucinous material conversion into fibrous plaques [2] type I (initial) lesion isolated macrophage foam cells small pools of lipid droplets and dead cell remnants as a source of extracellular lipid in addition to macrophage foam cells (preatheroma) [3,4] intimal xanthoma isolated macrophage foam cells extracellular lipid accumulation (lipid pools) that are rich in extracellular matrix proteoglycans (pathologic intimal thickening (PIT)) [5][6][7] grade of lipid deposition 1 fatty streaks with extracellular lipids colocalizing with biglycan and decorin in the outer layer of the intima n/a [8] early lesion plasma albumin and apolipoprotein B insudation n/a [9] early lesion interstitial lipid deposits resulting from the encrustation or imbibition of fibrin onto or into the intima n/a [10] gelatinous lesion balances of intact LDL/"deposited" cholesterol and of fibrinogen/fibrin loss of steady state concentrations reflecting rates of egress of macromolecules depending on molecular sieving (immobilization of LDL by fibrin) [11] n/a n/a influx-efflux imbalance in the cell and blood vessel wall [12] epicardial coronary atherosclerosis impairment of lymphatic drainage from the coronary arteries (absence of a potential system for removing protein, fluid and lipids from the arterial wall) impairment of lymphatic drainage from the coronary arteries (absence of a potential system for removing protein, fluid and lipids from the arterial wall) [13] prelesional stage 'inert' lipoprotein insudation without monocyte/ macrophage infiltration, lipoprotein modification and complement activation overload of the cholesterol removal machinery, enzymatic modification of LDL, complement activation, persisting macrophages secreting a variety of molecules accelerating lipoprotein retention, plaque instability, and clotting on rupture [14][15][16][17][18][19][20][21][22][23][24][25] ...
... Stary himself, however, claimed that preatheroma lesions contain small pools of lipid droplets and dead cell remnants as a source of extracellular lipid in addition to macrophage foam cells [4]. The earliest feature of a morphological bridge to more advanced plaques (progressive atherosclerosis) as described by the AHA classification is PIT, which is characterized by extracellular lipid accumulation (lipid pools) that are rich in extracellular matrix proteoglycans [5][6][7]. ...
Article
Full-text available
Atherosclerosis research typically focuses on the evolution of intermediate or advanced atherosclerotic lesions rather than on prelesional stages of atherogenesis. Yet these early events may provide decisive leads on the triggers of the pathologic process, before lesions become clinically overt. Thereby, it is mandatory to consider extracellular lipoprotein deposition at this stage as the prerequisite of foam cell formation leading to a remarkable accumulation of LDL (Low Density Lipoproteins). As progression of atherosclerosis displays the characteristic features of a chronic inflammatory process on the one hand and native LDL lacks inflammatory properties on the other hand, the lipoprotein must undergo biochemical modification to become atherogenic. During the last 25 years, evidence was accumulated in support of a different concept on atherogenesis proposing that modification of native LDL occurs through the action of ubiquitous hydrolytic enzymes (enzymatically modified LDL or eLDL) rather than oxidation and contending that the physiological events leading to macrophage uptake and reverse transport of eLDL first occur without inflammation (initiation with reversion). Preventing or reversing initial atherosclerotic lesions would avoid the later stages and therefore prevent clinical manifestations. This concept is in accordance with the response to retention hypothesis directly supporting the strategy of lowering plasma levels of atherogenic lipoproteins as the most successful therapy for atherosclerosis and its sequelae. Apart from but unquestionable closely related to this concept, there are several other hypotheses on atherosclerotic lesion initiation favoring an initiating role of the immune system (‘vascular-associated lymphoid tissue’ (VALT)), defining foam cell formation as a variant of lysosomal storage disease, relating to the concept of the inflammasome with crystalline cholesterol and/or mitochondrial DAMPs (damage-associated molecular patterns) being mandatory in driving arterial inflammation and, last but not least, pointing to miRNAs (micro RNAs) as pivotal players. However, direct anti-inflammatory therapies may prove successful as adjuvant components but will likely never be used in the absence of strategies to lower plasma levels of atherogenic lipoproteins, the key point of the perception that atherosclerosis is not simply an inevitable result of senescence. In particular, given the importance of chemical modifications for lipoprotein atherogenicity, regulation of the enzymes involved might be a tempting target for pharmacological research.
... In the early stages of atherosclerosis LDL cholesterol is oxidized by free radicals. The oxidized LDL particles are scavenged by macrophages or smooth muscle cells and become aggregated in the arterial wall (Moore and Freeman 2006); accumulation of lipids leads to the formation of foam cells and further to fatty streaks, which may also contain lymphocytes and platelets (Moore and Freeman 2006, Gossi et al. 2007, Kolodgie et al. 2007). ...
Article
Tibolone, a synthetic steroid, is effective in the treatment of postmenopausal symptoms. Its cardiovascular safety profile has been questioned, because tibolone reduces the levels of high-density lipoprotein (HDL) cholesterol. Soy-derived isoflavones may offer health benefits, particularly as regards lipids and also other cardiovascular disease (CVD) risk factors. The soy-isoflavone metabolite equol is thought to be the key as regards soy-related beneficial effects. We studied the effects of soy supplementation on various CVD risk factors in postmenopausal monkeys and postmenopausal women using tibolone. In addition, the impact of equol production capability was studied. A total of 18 monkeys received casein/lactalbumin (C/L) (placebo), tibolone, soy (a woman s equivalent dose of 138 mg of isoflavones), or soy with tibolone in a randomized order for 14 weeks periods, and there was a 4-week washout (C/L) in between treatments. Postmenopausal women using tibolone (N=110) were screened by means of a one-week soy challenge to find 20 women with equol production capability (4-fold elevation from baseline equol level) and 20 control women, and treated in a randomized cross-over trial with a soy powder (52 g of soy protein containing 112 mg of isoflavones) or placebo for 8 weeks. Before and after the treatments lipids and lipoproteins were assessed in both monkeys and women. In addition, blood pressure, arterial stiffness, endothelial function, sex steroids, sex hormone-binding globulin (SHBG), and vascular inflammation markers were assessed. A 14% increase in plasma low-density lipoprotein (LDL) + very low-density lipoprotein (VLDL) cholesterol was observed in tibolone-treated monkeys vs. placebo. Soy treatment resulted in a 18% decrease in LDL+VLDL cholesterol, and concomitant supplementation with tibolone did not negate the LDL+VLDL cholesterol-lowering effect of soy. A 30% increase in HDL cholesterol was observed in monkeys fed with soy, whereas HDL cholesterol levels were reduced (48%) after tibolone. Interestingly, Soy+Tibolone diet conserved HDL cholesterol levels. Tibolone alone increased the total cholesterol (TC):HDL cholesterol ratio, whereas it was reduced by Soy or Soy+Tibolone. In postmenopausal women using tibolone, reductions in the levels of total cholesterol and LDL cholesterol were seen after soy supplementation compared with placebo, but there was no effect on HDL cholesterol, blood pressure, arterial stiffness or endothelial function. Soy supplementation decreased the levels of estrone in equol producers, and those of testosterone in the entire study population. No changes were seen in the levels of androstenedione, dehydroepiandrosterone sulfate, or SHBG. The levels of vascular cell adhesion molecule-1 increased, and platelet-selectin decreased after soy treatment, whereas C-reactive protein and intercellular adhesion molecule-1 remained unchanged. At baseline and unrelated to soy treatment, equol producers had lower systolic, diastolic and mean arterial pressures, less arterial stiffness and better endothelial function than non-producers. To conclude, soy supplementation reversed the tibolone-induced fall in HDL cholesterol in postmenopausal monkeys, but this effect was not seen in women taking tibolone. Equol production capability was associated with beneficial cardiovascular changes and thus, this characteristic may offer cardiovascular benefits, at least in women using tibolone. Soijalisä ja ekvolin tuotto vaihdevuosi-ikäisillä tibolonia käyttävillä naisilla: vaikutukset sydän- ja verisuonisairauksien merkkiaineisiin Suomessa noin 20 000 naista käyttää tibolonia vaihdevuosioireiden hoitoon. Tiboloni on keinotekoinen valmiste, joka muistuttaa vaikutuksiltaan monin tavoin perinteistä vaihdevuosien hormonihoitoa. Tiboloni voi kuitenkin pienentää hyvän HDL-kolesterolin pitoisuutta veressä. Samanaikaisesti tibolonin kanssa monet naiset käyttävät myös vaihtoehtoisia hoitoja, joista tavallisimpia ovat kasviestrogeenejä sisältävät soijavalmisteet. Aasialainen ravinto sisältää runsaasti soijaperäisiä kasviestrogeenejä, minkä on ajateltu pienentävän sydän- ja verisuonisairauksien vaaraa. Tarkoin ei tiedetä, miten kasviestrogeenit toimivat, mutta noin 30%:lla ihmisistä suoliston bakteerifloora muuttaa niitä ekvoliksi, joka voi viime kädessä olla se vaikuttava aine. Tutkin soijalisän vaikutusta eräisiin sydän- ja verisuonisairauksien riskiä mittaaviin tekijöihin vaihdevuosi-ikäisissä apinoissa (n=18) ja naisissa (n=40) tiboloni-hoidon aikana. Soija esti apinoilla tibolonin aiheuttaman hyvän HDL-kolesterolin laskun ja vaikutti suotuisasti muutenkin veren rasva-aineisiin. Naisilla sen sijaan soija ei nostanut tibolonin aiheuttamaa hyvän HDL-kolesterolin laskua, vaikkakin se jonkin verran laski kokonaiskolesterolia ja huonoa LDL-kolesterolia. Naisilla soijalisä ei vaikuttanut myöskään verenpaineeseen tai verisuonen seinämän toimintaan. Sen sijaan se muutti naisen omien sukupuolihormonien pitoisuuksia tavalla, jonka saattoi katsoa sydän- ja verisuonitautiriskin kannalta hyödylliseksi. Tämä vaikutus oli voimakkain naisilla, joiden suolistossa soija muuttui ekvoliksi; näillä naisilla myös verenpaine oli matalampi ja verisuonen seinämän muukin toiminta oli parempi. Näiden tulosten perusteella voidaan sanoa, että soijalisä vaikuttaa vain vähän tai ei juuri ollenkaan verisuonen seinämän toimintaan terveillä tibolonia käyttävillä naisilla. Ne naiset (noin 30% kaikista), jotka pystyvät muuttamaan soijaa ekvoliksi, voivat saada mahdollista suojaa sydän- ja verisuonisairauksia vastaan.
... Other major sources include dying foam cells and red blood cells with rich cholesterol membranes released from injured vasa vasorum contribute to the lipid pool. 22 The release of cellular contents from dying cells can also alter the local pH milieu. Many of these local physical changes can enhance cholesterol crystallization. ...
Article
Full-text available
Evolution of plaque that is prone to rupture is characterized by inflammation and physical changes. Accumulation of low-density lipoprotein in the sub-intima provides esterified cholesterol (ESC) to macrophages and smooth muscle cells that convert it into free cholesterol (FRC) by cholesteryl ester hydrolases (CEHs). Membrane-bound cholesterol carriers transport FRC to high-density lipoprotein (HDL). Impaired HDL transport function and altered composition can lead to extracellular accumulation of FRC, whereas impaired membrane carrier activity can lead to intracellular FRC accumulation. Saturation of FRC can result in cholesterol crystallization with cell death and intimal injury. Disequilibrium between ESC and FRC can impact foam cell and cholesterol crystal (CC) formation. Cholesterol crystals initiate inflammation via NLRP3 inflammasome leading to interleukin-1β (IL-1β) production inducing C-reactive protein. Eventually, crystals growing from within the plaque and associated inflammation destabilize the plaque. Thus, inhibition of inflammation by antagonists to IL-1β or agents that dissolve or prevent CC formation may stabilize vulnerable plaques.
... But the cholesterol content of erythrocyte membranes exceeds that of all other cells in the body, with lipids constituting 40% of their weight. 49 Acyl coenzyme A:cholesterol acyltransferase inhibitors highly enhance cholesterol crystal formation by blocking cholesterol esterification and solubilization. 50 The relationship between cholesterol crystals and erythrocyte membranes was first suggested by Arbustini et al. 22 who demonstrated that atheroma observed in pulmonary hypertension is only observed in thromboembolic pulmonary hypertension, and that pultaceous cores with cholesterol clefts are co-localized with glycophorin A immunostaining. ...
Article
Full-text available
Atherothrombosis remains one of the main causes of morbidity and mortality in the western countries. Human atherothrombotic disease begins early in life in relation to circulating lipid retention in the inner vascular wall. Risk factors enhance the progression towards clinical expression: dyslipidaemia, diabetes, smoking, hypertension, ageing, etc. The evolution from the initial lipid retention in the arterial wall to clinical events is a continuum of increasingly complex biological processes. Current strategies to fight the consequences of atherothrombosis are orientated either towards the promotion of a healthy life style1 and preventive treatment of risk factors, or towards late interventional strategies.2 Despite this therapeutic arsenal, the incidence of clinical events remains dramatically high,3 dependent, at least in part, on the increasing frequency of type 2 diabetes and ageing. But some medical treatments, focusing only on prevention of the metabolic risk, have failed to reduce cardiovascular mortality, thus illustrating that our understanding of the pathophysiology of human atherothrombosis leading to clinical events remain incomplete. New paradigms are now emerging which may give rise to novel experimental strategies to improve therapeutic efficacy and prediction of disease progression. Recent studies strengthen the concept that the intraplaque neovascularization and bleeding (Figure 1, upper panel) are events that could play a major role in plaque progression and leucocyte infiltration, and may also serve as a measure of risk for the development of future events. The recent advances in our understanding of IntraPlaque Hemorrhage as a critical event in triggering acute clinical events have important implications for clinical research and possibly future clinical practice. Figure 1Macroscopic view and schematic representation of the detrimental consequences of intraplaque haemorrhages on plaque biology and stability.
... In general, HU<0 indicates existence of lipid. Several reports have shown that increased free cholesterol, cholesterol esters, and free-to-esterified cholesterol ratio in carotid plaques is associated with progression and vulnerability of plaques16171819. Therefore, accurate detection of lipid deposits is important for monitoring the progression of atherosclerosis and for predicting plaque vulnerability. ...
Article
We aimed to assess the relationship between atherosclerotic carotid plaque composition analyzed using multidetector computed tomography (MDCT) and the appearance of new ischemic lesions detected by diffusion-weighted images (DWI) after carotid artery stenting (CAS). We quantitatively and qualitatively analyzed plaque characteristics in carotid arteries using MDCT before CAS in 19 patients. Carotid plaques were expediently subdivided into four components with Hounsfield unit (HU) values of <0, 0-60, 60-130, and >600. The incidence of distal embolism was evaluated with DWI. Pearson's correlation analyses were used to assess the association between plaque composition and the incidence of cerebral embolization. Fifteen patients (79%) demonstrated new DWI lesions after CAS. High-signal DWIs were noted as follows: one in six patients, 2 ~ 5 in five patients, 6 ~ 10 in two patients, and >10 in two patients. The mean volumes of the plaque components for HU < 0, 0-60, 60-130, and >600 were 5.4, 200, 260, and 59 mm(3), respectively. There was a strong correlation between the number of high-signal DWI lesions in the ipsilateral side and the plaque volume of HU < 0 (r = 0.927; P < 0.0001). There was a moderate correlation between the number of high-signal DWI lesions and the plaque volume of HU 0-60 (r = 0.568; P = 0.0099) and the sum total of HU < 0 and HU 0-60 (r = 0.609; P = 0.0047). Quantitative and qualitative tissue characterization of carotid plaques using MDCT might be a useful predictor for silent ischemic lesions after CAS.
... The prevalence of cholesterol monohydrate crystals is also consistent with previous observations in atherosclerotic lesions and other pathologies such as lithogenic bile (46,48). In this regard, several studies have suggested the contribution of cholesterol-rich erythrocyte membrane to the accumulation of free-cholesterol and subsequent crystallization in the plaque (7,49). Solomonov et al. (50) have shown the importance of sterol-water interface in ChC formation within cell membranes, supporting the hypothesis of cholesterol monohydrate crystallization within the erythrocyte membrane. ...
Article
Cholesterol crystals (ChCs) have been identified as a major factor of plaque vulnerability and as a potential biomarker for atherosclerosis. Yet, due to the technical challenge of selectively detecting cholesterol in its native tissue environment, the physiochemical role of ChCs in atherosclerotic progression remains largely unknown. In this work, we demonstrate the utility of hyperspectral stimulated Raman scattering (SRS) microscopy combined with second-harmonic generation (SHG) microscopy to selectively detect ChC. We show that despite the polarization sensitivity of the ChC Raman spectrum, cholesterol monohydrate crystals can be reliably discriminated from aliphatic lipids, from structural proteins of the tissue matrix and from other condensed structures, including cholesteryl esters. We also show that ChCs exhibit a nonvanishing SHG signal, corroborating the noncentrosymmetry of the crystal lattice composed of chiral cholesterol molecules. However, combined hyperspectral SRS and SHG imaging reveals that not all SHG-active structures with solidlike morphologies can be assigned to ChCs. This study exemplifies the merit of combining SRS and SHG microscopy for an enhanced label-free chemical analysis of crystallized structures in diseased tissue.
... There is increasing evidence that red blood cells, especially their membranes, play an important role in atherosclerotic plaque progression and instability (1,13,23). The stability of the plaque appears to be largely determined by the size of the lipid core (24). ...
Article
Full-text available
Introduction. Numerous studies suggest that total cholesterol content of erythrocyte membranes (CEM) might play a critical role in atherosclerotic plaque progression and instability. However, the exact role of CEM in atherosclerosis remains obscure. Our study was designed to investigate the association between CEM and the severity of coronary artery disease (CAD), and to assess the effect of rosuvastatin on CEM levels. Methods. CEM levels were assessed in 136 participants, including acute coronary syndrome (ACS) (non-ST-segment elevation ACS (NSTEACS) and ST-segment elevation myocardial infarction (STEMI)), stable angina pectoris (SAP), and controls. The Gensini score was used to estimate the severity of CAD. Additionally, 54 patients with CAD were medicated with rosuvastatin, 5 or 10 mg once daily, and then checked at 6 months. Results. The highest level of CEM was found in the STEMI group, followed by the NSTEACS, the SAP, and the control groups. Gensini score in group IV (CEM > 141.6 μg/mg) was markedly higher compared with group I (CEM ≤77.6 μg/mg). Gensini scores in group II (77.6 < CEM ≤111.1 μg/mg) and group III (111.1 < CEM ≤141.6 μg/mg) were also higher than in group I (all P < 0.001). Furthermore, a positive correlation was found between CEM levels and Gensini score (r = 0.714, P < 0.001). CEM levels were dose-dependently reduced by rosuvastatin therapy. Conclusions. CEM levels are positively associated with the severity of CAD, meaning that CEM might contribute to the development of CAD. Importantly, rosuvastatin could decrease CEM levels in patients with CAD and might effectively help to attenuate the progression of CAD.
... In early lesions, inflammatory processes influence the accumulation of low-viscosity lipid, 13,14 and in advanced plaques, the apoptosis of foam cells and intraplaque hemorrhage results in large necrotic lipid pools of further reduced viscosity. 15,16 The mechanical properties of the atheroma determine the extent of induced deformations or strains in response to extrinsic hemodynamic stresses. Higher strains are measured in lipidrich regions of lower viscosity, 17 and cyclic mechanical strain within the arterial wall in turn affects macrophage gene expression and SMC proliferation. ...
Article
During the pathogenesis of coronary atherosclerosis, from lesion initiation to rupture, arterial mechanical properties are altered by a number of cellular, molecular, and hemodynamic processes. There is growing recognition that mechanical factors may actively drive vascular cell signaling and regulate atherosclerosis disease progression. In advanced plaques, the mechanical properties of the atheroma influence stress distributions in the fibrous cap and mediate plaque rupture resulting in acute coronary events. This review paper explores current optical technologies that provide information on the mechanical properties of arterial tissue to advance our understanding of the mechanical factors involved in atherosclerosis development leading to plaque rupture. The optical approaches discussed include optical microrheology and traction force microscopy that probe the mechanical behavior of single cell and extracellular matrix components, and intravascular imaging modalities including laser speckle rheology, optical coherence elastography, and polarization-sensitive optical coherence tomography to measure the mechanical properties of advanced coronary lesions. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in elucidating the mechanical aspects of coronary atherosclerosis in the future.
... 37,38 Accumulation of erythrocytes promotes plaque instability. 37,39,40 The concept is supported by higher levels of total cholesterol in the erythrocyte membrane from patients presenting with acute coronary syndrome compared with patients with chronic stable angina 41 and a positive association between cholesterol content of erythrocyte membranes and RDW values in patients with coronary disease. 42 An association between the total cholesterol content of the erythrocyte membrane and the severity of coronary artery disease has also been reported. ...
Article
Full-text available
Background Red cell distribution width (RDW), a measure of the variability in size of circulating erythrocytes, is associated with mortality and adverse outcome in selected populations with cardiovascular disease. It is scarcely known whether RDW is associated with incident myocardial infarction (MI). We aimed to investigate whether RDW was associated with risk of first‐ever MI in a large cohort study with participants recruited from a general population. Methods and Results Baseline characteristics, including RDW, were collected for 25 612 participants in the Tromsø Study in 1994–1995. Incident MI during follow‐up was registered from inclusion through December 31, 2010. Cox regression models were used to calculate hazard ratios with 95% confidence intervals for MI, adjusted for age, sex, body mass index, smoking, hemoglobin, white blood cells, platelets, and other traditional cardiovascular risk factors. A total of 1779 participants experienced a first‐ever MI during a median follow‐up time of 15.8 years. There was a linear association between RDW and risk of MI, for which a 1% increment in RDW was associated with a 13% increased risk (hazard ratio 1.13; 95% CI, 1.07 to 1.19). Participants with RDW above the 95th percentile had 71% higher risk of MI compared with those with RDW in the lowest quintile (hazard ratio 1.71; 95% CI, 1.34 to 2.20). All effect estimates were essentially similar after exclusion of participants with anemia (n=1297) from the analyses. Conclusion RDW is associated with incident MI in a general population independent of anemia and cardiovascular risk factors.
... Low-density lipoprotein (LDL)cholesterol is recognized as a risk factor of atherosclerosis, hypertension, and coronary heart disease. [157][158][159] The direct effects of cholesterol on blood flow include growth of atherosclerotic plaques that reduce the lumen of coronary arteries, as well as blunted endothelium-dependent vasodilation at the coronary microcirculation level that leads to an impairment of myocardial perfusion. Indirect effects of hypercholesterolemia involve blood rheology; in fact, a high level of cholesterol may affect whole blood viscosity, platelet activation, and RBC deformability, leading again to impaired coronary circulation. ...
Article
Red blood cells (RBCs) possess a unique capacity for undergoing cellular deformation to navigate across various human microcirculation vessels, enabling them to pass through capillaries that are smaller than their diameter and to carry out their role as gas carriers between blood and tissues. Since there is growing evidence that red blood cell deformability is impaired in some pathological conditions, measurement of RBC deformability has been the focus of numerous studies over the past decades. Nevertheless, reports on healthy and pathological RBCs are currently limited and, in many cases, are not expressed in terms of well-defined cell membrane parameters such as elasticity and viscosity. Hence, it is often difficult to integrate these results into the basic understanding of RBC behaviour, as well as into clinical applications. The aim of this review is to summarize currently available reports on RBC deformability and to highlight its association with various human diseases such as hereditary disorders (e.g., spherocytosis, elliptocytosis, ovalocytosis, and stomatocytosis), metabolic disorders (e.g., diabetes, hypercholesterolemia, obesity), adenosine triphosphate-induced membrane changes, oxidative stress, and paroxysmal nocturnal hemoglobinuria. Microfluidic techniques have been identified as the key to develop state-of-the-art dynamic experimental models for elucidating the significance of RBC membrane alterations in pathological conditions and the role that such alterations play in the microvasculature flow dynamics.
... Recently it has been shown that in human atherosclerotic lesions cholesterol crystals are co-localized with glyophorin A, a characteristic protein of RBC membrane, suggesting that cholesterol content of RBC membrane contributes to lipid deposition and lipid core expansion upon IPH (Kolodgie et al., 2003(Kolodgie et al., , 2007. In fact, RBC membrane is particularly abundant in cholesterol (Yeagle, 1985). ...
Article
Full-text available
For decades plaque neovascularization was considered as an innocent feature of advanced atherosclerotic lesions, but nowadays growing evidence suggest that this process triggers plaque progression and vulnerability. Neovascularization is induced mostly by hypoxia, but the involvement of oxidative stress is also established. Because of inappropriate angiogenesis, neovessels are leaky and prone to rupture, leading to the extravasation of red blood cells (RBCs) within the plaque. RBCs, in the highly oxidative environment of the atherosclerotic lesions, tend to lyse quickly. Both RBC membrane and the released hemoglobin (Hb) possess atherogenic activities. Cholesterol content of RBC membrane contributes to lipid deposition and lipid core expansion upon intraplaque hemorrhage. Cell-free Hb is prone to oxidation, and the oxidation products possess pro-oxidant and pro-inflammatory activities. Defense and adaptation mechanisms evolved to cope with the deleterious effects of cell free Hb and heme. These rely on plasma proteins haptoglobin (Hp) and hemopexin (Hx) with the ability to scavenge and eliminate free Hb and heme form the circulation. The protective strategy is completed with the cellular heme oxygenase-1/ferritin system that becomes activated when Hp and Hx fail to control free Hb and heme-mediated stress. These protective molecules have pharmacological potential in diverse pathologies including atherosclerosis.
... An example of such vessels is identified in Figure 1b with a dotted red circle. This intraplaque hemorrhage results in accumulation of free phospholipids, cholesterol and hemoglobin within the arterial wall from the membrane of the lysed red blood cells [10]. These molecules increase the size of the "necrotic core" of the plaque and cause further inflammation which degrades the fibrous cap leading to an increased likelihood of plaque rupture. ...
... The size distribution of erythrocytes may influence their ability to be incorporated into atherosclerotic plaques. The erythrocyte membrane contains large amounts of free cholesterol (34), and accumulation of erythrocytes within the atheromatous plaque may promote plaque growth and instability (35). Unstable plaques rich in cholesterol are vulnerable to rupture and thereby prone to cause acute atherothrombotic events. ...
Article
Red cell distribution width (RDW), a measure of the size variability of circulating erythrocytes, is associated with cardiovascular morbidity and mortality. We aimed to investigate whether RDW was associated with progression of atherosclerotic plaques in subjects recruited from the general population. Baseline characteristics, including RDW, were collected from 4677 participants in the fourth survey of the Tromsø Study conducted in 1994/95. Prevalence of carotid plaques and total plaque area (TPA) were assessed by ultrasonographic imaging at baseline and after seven years of follow-up. Generalised linear models were used to analyse change in TPA across tertiles of RDW. Change in TPA was significantly higher across tertiles of RDW in crude analysis and in multivariable analysis adjusted for cardiovascular risk factors. The mean change in TPA increased from 5.6 mm² (4.9-6.4) in tertile 1 (RDW ≤ 12.6 %) to 6.7 mm² (5.9-7.6) in tertile 3 (RDW ≥ 13.3) in multivariable analysis adjusted for body mass index, total cholesterol, HDL cholesterol, systolic blood pressure, self-reported diabetes, smoking status, platelet count, white blood cell count, and hs-CRP levels (p for trend 0.003). A 1 % increase in RDW was associated with 0.6 mm² (0.1-1.2) increase in TPA in multivariable analysis (p=0.03). RDW was associated with progression of atherosclerosis after adjustments for traditional atherosclerotic risk factors. Our findings suggest that the link between RDW and cardiovascular morbidity and mortality may be explained by atherosclerosis.
... Furthermore, the structural integrity of plaque neovascularization was incomplete in AS 34) . Thus, vasa vasorum neovascularization was considered as the major entry portals for leukocytes and lipids into the atherosclerotic lesions, which accelerates the progression and destabilization of AS plaque 35,36) . These observations suggest that vasa vasorum neovascularization, inflammation, and lipids were potential therapeutic targets to prevent AS. ...
Vasa vasorum neovascularization is a key feature of atherosclerosis (AS) and is strongly associated with inflammatory infiltration, lipid deposition, intraplaque hemorrhage, and hemosiderin deposit. Here we investigate the effects of Endostar, a strong anti-angiogenic drug, on vasa vasorum neovascularization in the experimental porcine model of early AS. Eighteen adult male Ba-Ma mini pigs were randomized into three groups, with six animals in each group. The pigs in the normal (N) group were fed a normal diet for 18 weeks, without balloon injury surgery. The animals in the atherosclerotic (AS) control and AS+Endostar groups were fed a hypercholesterolemic diet for 12 weeks after balloon injury surgery; they received either saline or Endostar for an additional six weeks, while continuing the hypercholesterolemic diet. The atherosclerotic abdominal aorta and levels of serum lipids, TNF-alpha, IL-6, and hs-CRP were analyzed at 18 weeks. The AS group had a significantly higher body weight and serum lipid concentration levels than the N group (p<0.05), confirming the success of the hypercholesterolemic diet. However, no statistical differences were noted between the AS and AS+Endostar groups. Histopathology results revealed that vasa vasorum density and intima-media thickness (IMT) had also increased in the AS group compared with those in the N group (p<0.05). The Endostar treatment significantly alleviated AS with decreased vasa vasorum density and IMT (AS vs. AS+Endostar, p<0.05). Western blot analysis indicated that the expression of VEGF, β-catenin, and TNF-alpha in the atherosclerotic abdominal aorta was considerably reduced by the Endostar treatment. In addition, immunohistochemistry results showed that the angiogenesis markers VEGF and β-catenin were predominately localized in endothelial cells of the adventitial vasa vasorum. The levels of the serum inflammatory markers TNF-alpha, hs-CRP, and IL-6 were markedly higher in the AS group than in the N group (p<0.05) but showed no marked difference during the Endostar treatment, suggesting that the local inhibition of angiogenesis was not accompanied by a change in serum inflammatory markers and that the inhibitive effect of Endostar on local TNF-alpha expression could be because of the prevention of vasa vasorum neovascularization. Our results demonstrated that the Endostar treatment inhibited vasa vasorum neovascularization and AS progression in the experimental porcine model of early AS, supporting the role of vasa vasorum neovascularization in the development of AS and the therapeutic potential of anti-angiogenesis intervention in AS.
... Cholesterol crystals are resulted from free cholesterol of cell membrane or from cholesterol esters hydrolysed in macrophage lysosomes (Tangirala et al. 1994, Brown et al. 2000. Compared with all other cells, erythrocyte membrane is rich in cholesterol and other lipids that could count up to 40% of cell weight (Kolodgie et al. 2007). Kolodgie et al. (2003) found that glycophorin A and iron are colocalized with cholesterol crystals in atherosclerotic lesions and hypothesized that these crystals could originate from erythrocytes phagocytized by macrophages. ...
Article
Atherosclerosis is a continuous pathologic process that starts early in life and progresses frequently to unstable plaques. Plaque rupture leads to deleterious consequences such as acute coronary syndrome, stroke, and atherothrombosis. The vulnerable lesion has several structural and functional hallmarks that distinguish it from the stable plaque. The unstable plaque has large necrotic core (over 40% plaque volume) composed of cholesterol crystals, cholesterol esters, oxidized lipids, fibrin, erythrocytes and their remnants (heme, iron, hemoglobin), and dying macrophages. The fibrous cap is thin, depleted of smooth muscle cells and collagen, and is infiltrated with proinflammatory cells. In unstable lesion, formation of neomicrovessels is increased. These neovessels have weak integrity and leak thereby leading to recurrent hemorrhages. Hemorrhages deliver erythrocytes to the necrotic core where they degrade promoting inflammation and oxidative stress. Inflammatory cells mostly presented by monocytes/macrophages, neutrophils, and mast cells extravagate from bleeding neovessels and infiltrate adventitia where they support chronic inflammation. Plaque destabilization is an evolutionary process that could start at early atherosclerotic stages and whose progression is influenced by many factors including neovascularization, intraplaque hemorrhages, formation of cholesterol crystals, inflammation, oxidative stress, and intraplaque protease activity.This article is protected by copyright. All rights reserved.
... Indeed, atherosclerotic plaques with subsequent neovascularization and intra-plaque hemorrhage may constitute an important source of iron deposition in blood vessels and the brain parenchyma, but in a more localized fashion than what is observed after an intracerebral hemorrhage. Furthermore, in atherosclerotic plaques, cholesterol crystals coincide with glycophorin A (distinctive protein of red cell membranes), implying cholesterol from erythrocyte membranes could participate in the deposition of lipids and expansion of the lipid core following intra-plaque bleeding [33] . Moreover, some data support the fact that hypercholesterolemia might enhance the crossing of iron into the brain parenchyma via an augmentation of endothelial permeability to iron [34] . ...
Article
Full-text available
Alzheimer's disease (AD) is a chronic neurodegenerative disorder presenting as progressive cognitive decline with dementia that does not, to this day, benefit from any disease-modifying drug. Multiple etiologic pathways have been explored and demonstrate promising solutions. For example, iron ion chelators, such as deferoxamine, are a potential therapeutic solution around which future studies are being directed. Another promising domain is related to thrombin inhibitors. In this minireview, a common pathophysiological pathway is suggested for the pathogenesis of AD to prove that all these mechanisms converge onto the same cascade of neuroinflammatory events. This common pathway is initiated by the presence of vascular risk factors that induce brain tissue hypoxia, which leads to endothelial cell activation. However, the ensuing hypoxia stimulates the production and release of reactive oxygen species and pro-inflammatory proteins. Furthermore, the endothelial activation may become excessive and dysfunctional in predisposed individuals, leading to thrombin activation and iron ion decompartmentalization. The oxidative stress that results from these modifications in the neurovascular unit will eventually lead to neuronal and glial cell death, ultimately leading to the development of AD. Hence, future research in this field should focus on conducting trials with combinations of potentially efficient treatments, such as the combination of intranasal deferoxamine and direct thrombin inhibitors.
... The core of the plaque is enriched by the influx of blood cells during bleeding events. The cholesterol-rich membranes of circulating cells, namely activated platelets, leukocytes and erythrocytes [295] may release free cholesterol within the hemorrhagic plaque. Free cholesterol can form cholesterol crystals, which can disrupt biological membranes, erode the fibrous cap and protrude into the lumen where they may cause embolism or thrombosis [296]. ...
Article
Full-text available
Atherosclerosis is a multifocal alteration of the vascular wall of medium and large arteries characterized by a local accumulation of cholesterol and non-resolving inflammation. Atherothrombotic complications are the leading cause of disability and mortality in western countries. Neovascularization in atherosclerotic lesions plays a major role in plaque growth and instability. The angiogenic process is mediated by classical angiogenic factors and by additional factors specific to atherosclerotic angiogenesis. In addition to its role in plaque progression, neovascularization may take part in plaque destabilization and thromboembolic events. Anti-angiogenic agents are effective to reduce atherosclerosis progression in various animal models. However, clinical trials with anti-angiogenic drugs, mainly anti-VEGF/VEGFR, used in anti-cancer therapy show cardiovascular adverse effects, and require additional investigations.
... 51 Notably, cells with rich cholesterol membranes including dying foam cells are thought to be the additional sources of FRC. 52 The release of cellular contents from dying cells favors CC formation by means of inducing local physical change. 53 Cholesterol efflux restrains the production of inflammatory mediators in macrophages. ...
... Erythrocytes play an important role in atherosclerotic plaque development and stability. Deposition of the free cholesterol contained in the erythrocyte membrane is considered an important contributor to atherosclerotic plaque growth, 37,38 and atherosclerotic plaques susceptible to rupture tend to have a higher lipid content than stable plaques. 39 RDW is associated with a higher cholesterol content in the erythrocyte membranes, 40 and intraplaque hemorrhage could thereby have a greater impact on plaque growth and instability in subjects with high RDW. ...
Article
Full-text available
Red cell distribution width (RDW), a measure of variability in size of circulating erythrocytes, is associated with arterial cardiovascular disease (CVD), but the underlying mechanism remains unclear. We aimed to investigate the impact of chronic inflammation as measured by high-sensitivity C-reactive protein (hs-CRP) on this relationship, and explore whether RDW could be a mediator in the causal pathway between inflammation and arterial CVD. Baseline characteristics, including RDW and hs-CRP, were obtained from 5,765 individuals attending a population-based cohort study. We followed up participants from inclusion in the fourth survey of the Tromsø Study (1994/1995) until December 31, 2012. Multivariable Cox-regression models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI) for incident myocardial infarction (MI) and ischemic stroke across quintiles of hs-CRP and RDW. Subjects with hs-CRP in the highest quintile had 44% higher risk of MI (HR: 1.44, 95% CI: 1.14–1.80), and 64% higher risk of ischemic stroke (HR: 1.64, 95% CI: 1.20–2.24) compared with subjects in the lowest quintile. RDW mediated 7.2% (95% CI: 4.0–30.8%) of the association between hs-CRP and ischemic stroke. Subjects with RDW in the highest quintile had 22% higher risk of MI (HR: 1.22, 95% CI: 0.98–1.54) and 44% higher risk of ischemic stroke (HR: 1.44, 95% CI: 1.06–1.97) compared with subjects in the lowest quintile. These risk estimates were slightly attenuated after adjustments for hs-CRP. Our findings suggest that chronic inflammation is not a primary mechanism underlying the relationship between RDW and arterial CVD.
... This can originate directly from free cholesterol or from cholesterol esters endocytosed by foam cells. RBC membranes have a high cholesterol content with a percentage of lipids up to 40% of the total weight of the cells (Kolodgie et al., 2007). It has been suggested that RBC membranes are very important contributors to lipid deposition and lipid core expansion upon IPH. ...
Article
Full-text available
Acute cardiovascular events, due to rupture or erosion of an atherosclerotic plaque, represent the major cause of morbidity and mortality in patients. Growing evidence suggests that plaque neovascularization is an important contributor to plaque growth and instability. The vessels' immaturity, with profound structural and functional abnormalities, leads to recurrent intraplaque hemorrhage. This review discusses new insights of atherosclerotic neovascularization, including the effects of leaky neovessels on intraplaque hemorrhage, both in experimental models and humans. Furthermore, modalities for in vivo imaging and therapeutic interventions to target plaque angiogenesis will be discussed.
... Serum samples were collected by low speed centrifugation at 3000 x g at 5°C, for 15 min. The glycemia was measured according to Tietz (1995), the plasma cholesterol according to the method of Kolodgie and al (2007), the triglycerides plasma according Varela-Lopez and al. (1995), while the HDL-cholesterol fraction was determined according to Gordon and al. (1981). Furthermore, the concentration of LDL cholesterol was calculated according to the Friedewald and al. formula (1972): LDL cholesterol = total cholesterol -HDL cholesterol -1/5 (triglycerides). ...
... RBCs lose their cellular structure, and release membranous lipids and hemoglobin. RBC membranes are particularly rich in free and unesterified cholesterol [21], and are hence a source of cholesterol crystal formation in intraplaque hemorrhage [10] [22]. ...
Article
Full-text available
Background: In-stent neoatherosclerosis is characterized by the delayed appearance of markers of atheroma in the subintima, but the pathophysiology underlying this new disease entity remains unclear. Methods and results: We collected 20 human coronary artery stents by removal from explanted hearts. The mean duration of stent implantation was 34 months. In all samples, neoatherosclerosis was detected, particularly in peristrut areas. It consisted of foam cells and cholesterol clefts, with or without calcification, associated with neovascularization. Iron and glycophorin-A were present in peristrut areas, as well as autofluorescent ceroids. Moreover, in response to neoatherosclerosis, tertiary lymphoid organs (tissue lymphoid clusters) often developed in the adventitia. Some of these features could be reproduced in an experimental carotid stenting model in rabbits fed a high-cholesterol diet. Foam cells were present in all samples, and peristrut red blood cells (RBCs) were also detected, as shown by iron deposits and Bandeiraea simplicifiola isolectin-B4 staining of RBC membranes. Finally, in silico models were used to evaluate the compliance mismatch between the rigid struts and the distensible arterial wall using finite element analysis. They show that stenting approximately doubles the local von Mises stress in the intimal layer. Conclusions: We show here that stent implantation both in human and in rabbit arteries is characterized by local peristrut microhemorrhages and finally by both cholesterol accumulation and oxidation, triggering together in-stent neoatherosclerosis. Our data indicate that these processes are likely initiated by an increased mechanical stress due to the compliance mismatch between the rigid stent and the soft wall.
Article
Neuropeptide Y (NPY), a sympathetic and platelet-derived vascular mitogen and angiogenic factor, has been implicated in atherosclerosis in animal and human genetic studies. Here we evaluate its association with human and murine atherosclerosis, and assess the role of platelet-derived NPY in lesion vulnerability. NPY immunoreactivity (NPY-ir) was measured in the platelet-poor and platelet-rich (PRP) plasmas, and NPY receptors (mitogenic Y1R and angiogenic Y2 and Y5Rs), CD26/DPPIV (a protease forming Y2/Y5-selective agonist), CD31-positive vascularity, and lesion morphology assessed by histo- and immunocyto-chemistry—in patients with peripheral artery disease (PAD) and healthy volunteers, and in lard-fed ApoE−/− mice. NPY and NPY-R immunostaining was greater in lesions from PAD patients compared to normal vessels of healthy volunteers (p DPPIV staining co-localized with CD31-positive endothelial cells only in atherosclerotic lesions. NPY-ir in PRP (but not plasma) and vascular immunostaining was higher (p p = 0.03), necrotic core area, and the necrotic core-to-lesion area ratio (p p DPPIV expression by microvascular endothelium in atherosclerotic tissue may shift NPY’s affinity toward angiogenic Y2/Y5Rs, and thus enhance angiogenesis and lesion vulnerability. Remarkably, plaque neovascularization was associated with increased NPY-ir in PRP in males but not females, suggesting that platelet NPY may be a novel mediator/marker of lesion vulnerability particularly in males, for reasons that remain to be determined. Both animal and human data suggest that NPY is an important contributor to, and platelet NPY-ir a marker of, atherosclerotic lesion burden and vulnerability but only in males, perhaps due to androgen-dependent up-regulation of NPY, previously shown in rats.
Article
Full-text available
Background Intimal calcification typically develops in advanced atherosclerosis, and microcalcification may promote plaque progression and instability. Conversely, intraplaque hemorrhage and erythrocyte extravasation may stimulate osteoblastic differentiation and intralesional calcium phosphate deposition. The presence of erythrocytes and their main cellular components (membranes, hemoglobin, and iron) and colocalization with calcification has never been systematically studied. Methods and Results We examined three types of diseased vascular tissue specimens, namely, degenerative aortic valve stenosis (n = 46), atherosclerotic carotid artery plaques (n = 9), and abdominal aortic aneurysms (n = 14). Biomaterial was obtained from symptomatic patients undergoing elective aortic valve replacement, carotid artery endatherectomy, or aortic aneurysm repair, respectively. Serial sections were stained using Masson–Goldner trichrome, Alizarin red S, and Perl's iron stain to visualize erythrocytes, extracelluar matrix and osteoid, calcium phosphate deposition, or the presence of iron and hemosiderin, respectively. Immunohistochemistry was employed to detect erythrocyte membranes (CD235a), hemoglobin or the hemoglobin scavenger receptor (CD163), endothelial cells (CD31), myofibroblasts (SMA), mesenchymal cells (osteopontin), or osteoblasts (periostin). Our analyses revealed a varying degree of intraplaque hemorrhage and that the majority of extravasated erythrocytes were lysed. Osteoid and calcifications also were frequently present, and erythrocyte membranes were significantly more prevalent in areas with calcification. Areas with extravasated erythrocytes frequently contained CD163-positive cells, although calcification also occurred in areas without CD163 immunosignals. Conclusion Our findings underline the presence of extravasated erythrocytes and their membranes in different types of vascular lesions, and their association with areas of calcification suggests an active role of erythrocytes in vascular disease processes.
Thesis
HINTERGRUND UND ZIELE: Immunologische Prozesse sind in die Entstehung, Progression und Destabilisierung atherosklerotischer Läsionen involviert. Neben dem Einfluss anderer inflammatorischer Zellen konnte auch für eine relativ neu beschriebene Subpopulation von T-Helferzellen, die Th17-Zelllinie, eine Beteiligung an der in Plaques ablaufenden Immunantwort gezeigt werden. Die Bedeutung der Th17-Zellen in der Atherosklerose wird nach wie vor kontrovers diskutiert. Um zu einem besseren Verständnis des stattfindenden Inflammationsgeschehens bei der Atherosklerose beizutragen, lag der Schwerpunkt dieser Arbeit darauf, das Vorkommen von Th17-Zellen in atherosklerotischen Läsionen in Abhängigkeit des Plaquephänotyps zu untersuchen. METHODEN: Im ersten Teil der Arbeit erfolgte anhand histologischer Verfahren die phänotypische Klassifizierung humaner Karotisplaques (n = 61) in „vulnerable“ (n = 31) und „stabile“ (n= 30) Läsionen. Immunhistochemische Analysen von Plaquequerschnitten dienten zur Beurteilung des Inflammationsstatus (CD68⁺ Makrophagen, CD3⁺ T-Zellen), sowie zur Detektion neovaskulatorischer Prozesse und aktivierten Endothels (CD31⁺/CD106⁺ Endothelzellen). Darüber hinaus wurden die Karotisläsionen anhand etablierter Marker (CD3, IL-1R1, IL-23R) auf den Gehalt an Th17-Zellen untersucht. Zur Verifizierung der erhobenen Daten wurden die Ergebnisse quantitativer PCR-Analysen, anhand derer die Transkriptionsraten eines T-Zell-Aktivierungsmarkers (HLA-DR) und eines Th17-Zell-assoziierten Markers (IL-17A) in den jeweiligen Plaques (n = 12) untersucht worden waren, zu Assoziationsanalysen herangezogen. Im zweiten Abschnitt wurden Patienten mit koronarer Herzkrankheit (n = 57) hinsichtlich der Manifestationsform dieser in zwei Subgruppen unterteilt, um die Konzentration verschiedener Th17-assoziierter Zytokine im Serum mittels eines Bead-basierten Multiplex Immunoassays zu untersuchen. Hierzu wurden Patienten mit akutem Koronarsyndrom (n = 29) versus stabiler Angina pectoris (n = 28) miteinander verglichen. ERGEBNISSE UND BEOBACHTUNGEN: Wie zu erwarten, waren Plaques mit vulnerablem Phänotyp, verglichen mit stabilen Läsionen, durch eine erhöhte Anzahl an Makrophagen und T-Zellen sowie durch ein erhöhtes Ausmaß an Neovaskularisation charakterisiert. Hierbei waren die Immunzellen gehäuft in der Nähe neu einsprossender Gefäße zu finden. Hinsichtlich der Expression des endothelialen Aktivierungsmarkers CD106 durch neu gebildete Gefäße fand sich kein signifikanter Unterschied zwischen den zwei Plaquephänotypen. Verglichen mit stabilen Läsionen, war der Gehalt an IL-1R1- und IL-23R-exprimierenden T-Zellen in der inflammatorischen Plaqueschulter vulnerabler Läsionen signifikant höher. Gegenüber stabilen Läsionen erwiesen sich die Transkriptionsraten von HLA-DR und IL-17A in vulnerablen Läsionen ebenfalls als signifikant erhöht. Bezüglich der Genexpression von HLA-DR konnte keine signifikante Assoziation mit der Anzahl an IL-1R1⁺ bzw. IL-23R⁺ T-Zellen der inflammatorischen Plaqueschulter nachgewiesen werden. Jedoch war für die Transkription von IL-17A eine positive Korrelation mit der Anzahl IL-23R-exprimierender T-Zellen im Bereich der Plaqueschulter detektierbar. Das Zytokin-Panel ergab für IL-1β und IL-18 signifikant erhöhte Konzentrationen im Serum der Patienten mit akutem Koronarsyndrom, verglichen zum Serum der Patienten mit stabiler koronarer Herzkrankheit. SCHLUSSFOLGERUNGEN: Im Hinblick auf die stetige Rekrutierung von Immunzellen in atherosklerotische Plaques unterstützen die Beobachtungen dieser Arbeit die Annahme, dass neu einsprossende Gefäße als zusätzliche Eintrittspforte für zirkulierende Immunzellen in Plaques dienen können. In Bezug auf Th17-Zellen weisen die Ergebnisse auf eine essentielle Beteiligung dieses Zelltyps am Inflammationsprozess, der verstärkt in vulnerablen Plaques stattfindet, hin. Zudem wird den bei Patienten mit akutem Myokardinfarkt in höheren Konzentrationen zu findenden Zytokinen IL-1β und IL-18 eine Rolle bei der systemischen Aktivierung des Th17-Zelltyps zugeschrieben. Zusätzliche Untersuchungen hinsichtlich der Bedeutung der Th17-Zellen sind notwendig, um deren Stellenwert in der Atherogenese weiter aufzuklären.
Article
Reducing the residual risk of cardiovascular events (CV) in patients with atherosclerosis continues to be a challenge. Thus, understanding how cholesterol spontaneously self assembles into metastable structures that evolve into flat plate cholesterol crystals (CCs) in atherosclerotic plaque, and why they fundamentally change the nature of the disease provides a paradigm for the development of additional therapies. Specifically, flat plate CCs that form within lysosomes of macrophages may become large enough to disrupt lysosomal membranes leading to the release of cathepsin B and CCs fragments directly into the cytosol. In the cytosol the surface of flat plate CCs can be recognized by complosome, that together with cathepsin B may trigger NLRP3 inflammasome. In addition, flat plate CCs in the cytosol may trigger caspase 8 initiating apoptosis. In the interstitial space the surface of flat plate CCs can be recognized by complement and receptors on pro-inflammatory cells, and larger fragments can induce ‘frustrated phagocytosis’ that together perpetuate inflammatory injury. In addition, rapid transition of metastable CCs into large flat plate CCs within lipid rich plaques can lead to traumatic injury by expansion of the plaque’s necrotic core causing plaque disruption or rupture that may precipitate further inflammation. Other crystalloids in plaque including monosodium urate and calcium phosphate crystals can augment these processes. Thus, therapies that further limit the deposition of cholesterol in the vascular bed, slow the formation of flat plate CCs and inhibit crystal induced inflammation may lead to further reduce CV risk in patients with established CV disease. (232)
Article
Full-text available
The accumulation of lipids, including cholesterol, in the arterial wall plays a key role in the pathogenesis of atherosclerosis. Although several advances have been made in the detection and imaging of these lipid structures in plaque lesions, their morphology and composition have yet to be fully elucidated, particularly in different animal models of disease. To address this issue, we analyzed lipid morphology and composition in the atherosclerotic plaques of two animal models of disease, the low density lipoprotein receptor-deficient (LDLR(-/-)) mouse and the ApoE lipoprotein-deficient (ApoE(-/-)) mouse, utilizing hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy in combination with principal component analysis (PCA). Hyperspectral CARS imaging revealed lipid-rich macrophage cells and condensed needle-shaped and plate-shaped lipid crystal structures in both mice. Spectral analysis with PCA and comparison to spectra of pure cholesterol and cholesteryl ester derivatives further revealed these lipid structures to be pure cholesterol crystals, which were predominantly observed in the ApoE(-/-) mouse model. These results illustrate the ability of hyperspectral CARS imaging in combination with multivariate analysis to characterize atherosclerotic lipid morphology and composition with chemical specificity, and consequently, provide new insight into the formation of cholesterol crystal structures in atherosclerotic plaque lesions.
Article
Recent studies reported that total cholesterol erythrocyte membrane (CEM) levels were associated with the presence of acute coronary syndrome (ACS). However, little is known about the mechanisms of CEM elevation in these patients. The aim of this study was to investigate the association between CEM and the circulating lipid profile to delineate the possible mechanisms of CEM elevation in patients with ACS. CEM levels, serum concentrations of triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, lipoprotein (a), apolipoprotein A-I (Apo A-I), apolipoprotein B (Apo B), and high-sensitive C-reactive protein levels were measured in 418 Chinese patients undergoing coronary artery angiography, including ACS (n=311) and stable angina pectoris (n=107). CEM levels in the ACS group were significantly higher (median, 129.82; interquartile range, 110.99-156.54 μg/mg, P<0.001) compared with the stable angina pectoris group (median, 80.88; interquartile range, 66.69-98.57 μg/mg). Multivariable logistic regression analyses showed a significantly independent relationship between CEM levels and the presence of ACS (odds ratio, 10.257; 95% confidence interval, 5.380-19.556, P<0.001). CEM levels were positively correlated with plasma lipoprotein (a) levels (r=0.175; P<0.001) and negatively correlated with serum Apo A-I levels (r=-0.149; P=0.002). CEM levels are closely associated with the occurrence of ACS as an independent determinant. The correlation of CEM with lipoprotein (a) and Apo A-I suggests that changes to these lipid proteins could be one possible mechanism for CEM increase in patients with ACS.
Article
It is known that deformation of red blood cells (RBCs) is linked to ATP release from the cells. Further, membrane cholesterol has been shown to alter properties of the cell membrane such as fluidity and bending stiffness. Membrane cholesterol content is increased in some cardiovascular diseases, for example, in individuals with acute coronary syndromes and chronic stable angina, and therefore, because of the potential clinical relevance, we investigated the influence of altered RBC membrane cholesterol levels on ATP release. Because of the correlation between statins and reduced membrane cholesterol in vivo, we also investigated the effects of simvastatin on RBC deformation and ATP release. We found that reducing membrane cholesterol increases cell deformability and ATP release. We also found that simvastatin increases deformability by acting directly on the membrane in the absence of the liver, and that ATP release was increased for cells with enriched cholesterol after treatment with simvastatin.
Article
Atherosclerotic plaque contains materials, such as cholesterol, oxysterols, cell debris, modified fatty acids, and infiltrated cells. Among them, cholesterol is the major component in plaque. Cholesterol is known to originate from the influx of extracellular materials, but this explanation is not enough for the cholesterol accumulation observed in atherosclerotic plaque. This study examined the origins of cholesterols in plaques. The main focus was to determine if the intracellular cholesterol levels are affected by oxysterols in human vascular smooth muscle cells. The results showed that the cholesterol levels increased in response to a 7-ketocholesterol (7K)-treatment in a dose-dependent manner. Eight enzymes involved in cholesterol biosynthesis were examined. Among them, squalene epoxidase (SQLE) was increased by 7K but not by 7α-hydroxycholesterol, 27-hydroxycholesterol (27OH-chol), or cholesterol. The 7K-induced SQLE expression was suppressed in the presence of the enzyme inhibitor SB203580 but not by UO126 and SP600125. The SQLE immunoreactivity was detected in the atherosclerotic plaque of the aortic roots from apoE mice. In addition, 7K increased the cholesterol level and SQLE expression in murine bone marrow-derived macrophages. This suggests that 7K increases the intracellular cholesterol level through an elevation of SQLE expression, which might affect the progress of cholesterol accumulation in the atherosclerotic lipid core.
Article
Background and aims In focal areas of advanced human atherosclerotic lesions, the intimal fluid is acidic. An acidic medium impairs the ABCA1-mediated cholesterol efflux from macrophages, so tending to increase their content of free cholesterol, which is then available for esterification by the macrophage enzyme ACAT1. Here we investigated whether low extracellular pH would affect the activity of ACAT1. Methods – Human monocyte-derived macrophages were first incubated with acetyl-LDL at neutral and acidic conditions (pH 7.5, 6.5, and 5.5) to generate foam cells, and then the foam cells were incubated with [3H]oleate-BSA complexes, and the formation of [3H]oleate-labeled cholesteryl esters was measured. ACAT1 activity was also measured in cell-free macrophage extracts. Results – In acidic media, ACAT1-dependent cholesteryl [3H]oleate generation became compromised in the developing foam cells and their content of free cholesterol increased. In line with this finding, ACAT1 activity in the soluble cell-free fraction derived from macrophage foam cells peaked at pH 7, and gradually decreased under acidic pH with a rapid drop below pH 6.5. Incubation of macrophages under progressively more acidic conditions (until pH 5.5) lowered the cytosolic pH of macrophages (down to pH 6.0). Such intracellular acidification did not affect macrophage gene expression of ACAT1 or the neutral CEH. Conclusions Exposure of human macrophage foam cells to acidic conditions lowers their intracellular pH with simultaneous decrease in ACAT1 activity. This reduces cholesterol esterification and thus leads to accumulation of potentially toxic levels of free cholesterol, a contributing factor to macrophage foam cell death.
Article
Full-text available
Objective: Native C-reactive protein (nCRP) is a soluble acute phase reactant whose expression in the vascular wall; in particular, in reactive plaque regions, and circulating levels increase in patients with inflammatory disease. We have recently demonstrated a specific role for the insoluble, monomeric form of CRP (mCRP) in direct stimulation of an-giogenesis and therefore decided to investigate its expression in carotid adventitial vasa vasorum and plaque intimal neovessels to determine if it could be involved in the development of unstable plaque lesions. Methods: We have used immunohistochemistry to examine the expression of both mCRP and nCRP in a series of carotid arterial plaques obtained at transplant (n=20) and employed double immunoflourescent labelling to identify any associa-tion of CRP with active-CD105-positive microvessels. Results: Using characterised and specific antibodies we have identified strong expression of mCRP in adventitial vasa vasorum and angiogenic neovessels from unstable regions of complicated carotid plaques. mCRP was also found to be as-sociated with infiltrating macrophages in inflammatory regions but infrequently with vascular smooth muscle cells. nCRP was expressed much more weakly and only in some regions rich in inflammatory cells. Many of the mCRP-positive ves-sels also stained positive for CD105 suggesting they were actively involved in the process of angiogenesis. Conclusions: Based on our previously published observations of the highly angiogenic nature of mCRP in vitro, we hy-pothesise that mCRP is intimately involved in promotion of neovascularization and possibly, subsequent destabilization of atherosclerotic plaques and could be considered as a possible target for therapeutic manipulation of angiogenesis.
Article
Neovascularization of atherosclerotic lesions favors their progression toward rupture. Despite this pathophysiological importance, data regarding the mechanism(s) initiating plaque neovascularization are scarce. Recent findings indicate that smooth muscle cells located underneath early aortic atheromatous lesions display a pro-angiogenic phenotype, and that lipid mediators derived from these lesions are potent inducers of this phenotypic change. Here, we discuss these new data suggesting that smooth muscle cells could be the central organizers of an angiogenic response initiated by the very first cause of the atheromatous disease, the accumulation and retention of lipids in the arterial wall.
Article
Intraplaque hemorrhages are mainly related to inward neoangiogenesis, initiated from the adventitia by lipid-dependent outwardly convected signals, and by the immaturity of these neovessels, allowing leaks and hemorrhages. Repeated intraplaque hemorrhages play a major role in the evolution of thrombotic occlusive disease, similar to the role of intraluminal thrombus in the progression of abdominal aortic aneurysm toward rupture. Red blood cells (RBCs) are an important source of unesterified cholesterol, because their membranes are particularly cholesterol rich. This unesterified cholesterol is rapidly organized in cholesterol crystals, highly toxic for cell and membranes. Oxidized cholesterol and LDL provoke the irreversible covalent aggregation of proteins, including hemoglobin, forming ceroids, which are also highly toxic. Hemoglobin play a major role of prooxydant molecules in this context, by its ability to release heme and iron, the main catalyser of oxidative reaction. In the context of type 2 diabetes, the oxidative potential of intraplaque-free hemoglobin play a predominant role in the progression of atherothrombotic disease toward clinical expression. Associated to RBC, intraplaque hemorrhages convey leukocyte, mainly neutrophils in human, and plasma zymogen that are the main source of proteases, including coagulation proteases, activation of the fibrinolytique system, release of leukocyte serine proteases and cathepsins and activation of MMPs. These proteases concentrate in the hemorrhagic/necrotic core rendered plaque highly vulnerable. An adaptive immune response takes place in the adventitia, in regard of hemorrhagic plaques, in relation to outwardly convected oxidized or proteolyzed neoantigens, and chemokinic signals. Finally, intraplaque hemorrhages and thrombi are the site of weak pathogen entrapment, which promote all these oxydative and proteolytic phenomenons.
Article
Full-text available
Atherosclerosis is the underlying reason for nearly all causes of coronary artery disease and peripheral arterial disease and many cases of stroke. Atherosclerosis is a systemic inflammatory process characterised by the accumulation of lipids and macrophages/lymphocytes within the intima of large arteries. The deposition of these blood borne materials and the subsequent thickening of the wall often significantly compromise the residual lumen leading to ischaemic events distal to the arterial stenosis. However, these initial fatty streak lesions may also evolve into vulnerable plaques susceptible to rupture or erosion. Plaque disruption initiates both platelet adhesion and aggregation on the exposed vascular surface and the activation of the clotting cascade leading to the so-called atherothrombotic process. Yet, platelets have also been shown to be transporters of regulatory molecules (micro-RNA), to drive the inflammatory response and mediate atherosclerosis progression. Here we discuss our current understanding of the pathophysiological mechanisms involved in atherogenesis - from fatty streaks to complex and vulnerable atheromas - and highlight the molecular machinery used by platelets to regulate the atherogenic process, thrombosis and its clinical implications.
Article
Lipid abnormalities play important roles in the development of atherosclerosis. Lipid therapies result in alterations in atherosclerotic plaques including halting of progression of the plaque, lipid transport out of the plaque and reducing inflammatory activity, which lead to plaque morphologies that are less prone to disruption, the main cause of clinical events. In order to investigate and monitor plaque morphological changes during lipid therapy in vivo we need an imaging method that can provide accurate assessment of plaque tissue components and activity. MRI of atherosclerosis has been validated as a reliable assessment of the size of the vessel lumen, but also the size of the plaque, its tissue composition and plaque activity, including inflammation. The purpose of this review is to summarize the state of evidence for the direct assessment of atherosclerotic plaque and its change by MRI, and to establish the proven role of MRI of atherosclerosis in pharmaceutical trials with lipid therapy.
Article
Polyphenols are largely studied for their beneficial action in various pathologies, but the correlation with their effects on cell membranes is still elusive. In the present study we assessed the effects exerted in vitro by quercetin, epigallocatechin gallate and curcumin on membrane fluidity and transmembrane potential of human umbilical vein endothelial cells and Jurkat T lymphoblasts, in experimental conditions mimicking diabetes mellitus, i.e. high glucose conditions or increased concentration of advanced glycation end products. Results showed that the investigated polyphenols had beneficial effects on cell membranes altered in diabetic conditions, by restoring transmembrane potential and by membrane "stiffening". Moreover, they limited the release of pro-inflammatory factors, like monocyte chemotactic protein - 1. These effects were more obvious for cells exposed to advanced glycation end products specific for the late stages of diabetes. Apparently, the inhibitory action of polyphenols on lipid peroxidation was associated with a decrease of membrane fluidity. Concluding, our in vitro study highlighted the potential beneficial action of polyphenols mainly in the late stages of diabetes, exerted at the level of membrane fluidity and transmembrane potential, accompanied by an anti-inflammatory effect on endothelial and immune cells.
Article
Introduction Free cholesterol (FC) is the marker of atherosclerosis less required in spite of its description in the atherosclerotic plaques and the vessels of the coronarian subjects. The objective of this work is to evaluate and validate a FC enzymatic method in order to apply it in daily practice in the exploration of the lipid parameters. Methods FC is oxidized, in the presence of cholesterol oxidase, in cholestene-3-one with hydrogen peroxide release; this last product oxidizes 4-aminoantipyrine, in the presence of phenol and peroxidase in a coloured quinoneimine evaluated at 510 nm. Results A perfect linearity between the absorbance and the concentration of FC was noted with a calibration curve of the type Y = aX. Precision and exactitude Coefficients were lower than 5% until a concentration of 4,1 mmol/L. Repeatability and reproducibility are very satisfactory (< 5%) and without significant difference between the averages for the titrated serums. A good exactitude evaluated by the processes of mixture and dilution was noted. A perfect correlation with the results of the kit marketed DiaSys is found. Conclusion The colorimetric enzymatic technique for the determination of free cholesterol is precise, exact and fast. It can be introduced in daily routine for the determination of FC. Its adaptation to the determination of the FC of the HDL constitutes a second subject of study.
Article
The maladaptation of endothelial cells to disturbed flow at arterial bifurcations increases permeability for lipoproteins. Additional injury by chemically modified lipoproteins disrupts the continuous repair of maladapted endothelial cells and triggers intimal macrophage accumulation. Macrophages remove modified lipoproteins from the extracellular space until the cholesterol overload leads to macrophage death and insufficient efferocytosis. This macrophage failure promotes the progression to advanced lesions by formation of a lipid-rich necrotic core, which may rupture and cause myocardial infarction and stroke. In this article, we summarize the fundamental roles of microRNAs (miRNAs) in the regulation of endothelial maladaptation and macrophage failure during atherosclerosis. We describe how miRNAs coordinate the mutual interaction between chronic endothelial repair and endothelial senescence and mechanistically link the regulation of macrophage cholesterol homeostasis with defective efferocytosis. Lastly, we discuss how miRNAs may challenge and extend current theories about atherosclerosis.
Article
It is now accepted that during the early stages of development of coronary and carotid atherosclerotic plaques, activation of vasa vasorum (VV) at specific sites in the adventitia initiates their proliferation or 'angiogenesis', and migration through the media into the intima of unstable developing lesions. Plaques regions containing these immature vessels tend to exhibit increased inflammation and haemorrhage due to the structural deficiencies of the microvessels. Potential therapeutic agents could be designed to target and prevent activation of VV at specific susceptible sites of the adventitia in order to slow down or prevent development of unstable plaques. Secondary therapies may involve stabilisation or 'maturation' of existing plaque microvessels in more advanced already symptomatic patients. This review will investigate the possibility of future design of nano-targeting devices, which home to the endothelial cells of VV or are delivered to the sites of existing plaques and which can deliver specific anti-angiogenic genes or those which will encourage development of mature functional and patent microvessels with a view to prevention and/or treatment of this disease.
Article
High-density lipoprotein (HDL) plays a main role in reverse cholesterol transport (RCT), one of the most important functions for preventing atherosclerosis. Recent reports have shown that red blood cells (RBCs) can be associated with RCT, an interaction facilitated by albumin. However, the RCT function of RBCs has not been thoroughly elucidated. In this study, the RCT function of RBCs was assessed using cholesterol efflux capacity (CEC) assays, in which 3H-labeled cholesterol-loaded human acute monocytic leukemia (THP-1) macrophages were incubated with RBCs as a cholesterol acceptor in the presence or absence of HDL or its main component protein apolipoprotein A-I (apoA-I). The CEC of RBCs was found to be dose dependent, enabling uptake of cholesterol from THP-1 macrophages through apoA-I and HDL, and directly from apoA-I and HDL in medium without the presence THP-1 macrophages. Moreover, RBCs could exchange cholesterol with HDL in a bidirectional manner, but could only exchange cholesterol with apoA-I in a single direction. Although albumin promoted the movement of cholesterol, synergistic effects were not observed for both apoA-I and HDL, in contrast to previous findings. These results strongly suggested that RBCs may play important roles in RCT by mediating cholesterol efflux as temporary cholesterol storage.
Thesis
Les maladies cardiovasculaires représentent la première cause de mortalité en France avec une prévalence encore plus importante à La Réunion. La plupart des décès sont attribuables aux cardiopathies ischémiques due à la rupture d'une plaque d'athérosclérose et à la formation d'un caillot entrainant une ischémie cardiaque. L'oxydation des lipoprotéines de basse densité (LDL) et la dysfonction de l'endothélium représentent des étapes importantes dans la déstabilisation de la plaque, d'où l’intérêt de rechercher un traitement capable de diminuer l'oxydation des LDL ou de protéger les cellules endothéliales de leurs effets cytotoxiques. Les polyphénols sont des molécules antioxydantes très présentes dans le règne végétal. Des études préliminaires du laboratoire sur des adipocytes humain on montré que des extraits riches en polyphénols d'Antirhea borbonica et de Doratoxylon apetalum, deux espèces respectivement endémique et indigène de l'Île de La Réunion, possédaient des propriétés antioxydantes et anti-inflammatoires (Marimoutou, M et al. 2015). Le But de cette thèse était, dans un premier temps, de tester les capacités antioxydantes et cytoprotectrices d'extraits riches en polyphénols de ces deux espèces sur des cellules endothéliales. Puis dans un second temps nous avons testé l'extrait de Doratoxylon apetalum sur un modèle murin d'athérosclérose (souris ApoE KO) pour évaluer son effet anti-inflammatoire sur les plaques d'athérome.
Article
The accumulation of free cholesterol in macrophage lysosomes significantly enhances atherogenesis. Our recent study demonstrated that the cluster of differentiation 38 (CD38)/nicotinic acid adenine dinucleotide phosphate (NAADP)/Ca ²⁺ signaling pathway plays a critical role in the efflux of lysosomal free cholesterol from macrophages in atherosclerosis. Niacin, known as nicotinic acid, is one of the oldest lipid-lowering medications showing unique anti-atherosclerotic activity. However, it is unknown whether this anti-atherosclerosis activity is associated with the efflux of lysosomal compartmentalized cholesterol in macrophages. In this study, we investigated the anti-atherosclerotic effects of niacin on the reduction of lysosomal free cholesterol via CD38/NAADP signaling in macrophages derived from low-density lipoprotein receptor (LDLr −/− ) mice. Fluorescent filipin and Nile red labeling coupled with confocal microscopy demonstrated that niacin reduced free cholesterol accumulation in lysosomes in a concentration-dependent manner. Transmission electron microscopy also showed that niacin markedly decreased cholesterol crystal formation in lysosomes in oxidized LDL-containing LDLr −/− bone marrow–derived macrophages. Enzyme-linked immunosorbent assays showed that niacin increased NAADP production in a concentration-dependent manner, which was inhibited by small interfering RNA interference of CD38. Therefore, niacin may promote the efflux of lysosomal cholesterol from macrophages via the CD38/NAADP signaling pathway.
Article
Red cell distribution width (RDW), a measure of the variability in size of the circulating erythrocytes, is associated with cardiovascular morbidity and mortality. We aimed to investigate whether RDW was associated with incident stroke and case fatality in subjects recruited from the general population. Baseline characteristics were obtained from 25,992 subjects participating in the fourth survey of the Tromsø Study, conducted in 1994/95. Incident stroke was registered from inclusion until December 31, 2010. Cox regression models were used to calculate hazard ratios (HR) with 95 % confidence intervals (95 % CI) for stroke, adjusted for age, sex, body mass index, smoking, haemoglobin level, white blood cell count, thrombocyte count, hypertension, total cholesterol, triglycerides, self-reported diabetes, and red blood cell count. During a median follow-up of 15.8 years, 1152 participants experienced a first-ever stroke. A 1 % increment in RDW yielded a 13 % higher risk of stroke (multivariable HR: 1.13, 95 % CI: 1.07-1.20). Subjects with RDW in the highest quintile compared to the lowest had a 37 % higher risk of stroke in multivariable analysis (HR: 1.37, 95 % CI: 1.11-1.69). Subjects with RDW above the 95-percentile had 55 % higher risk of stroke compared to those in the lowest quintile (HR: 1.55, 95 % CI: 1.16-2.06). All risk estimates remained unchanged after exclusion of subjects with anaemia (n=1102). RDW was not associated with increased risk of death within one year or during the entire follow-up after an incident stroke. RDW is associated with incident stroke in a general population, independent of anaemia and traditional atherosclerotic risk factors.
Chapter
Pathology of high risk atherosclerotic plaque provides the basis for understanding the imaging and treatment of atherosclerosis. The earliest vascular change described microscopically are adaptive intimal thickening and fatty streaks, whereas pathologic intimal thickening are the first of the progressive plaques subtypes. Fibroatheromas are characterized by an acellular necrotic core, accumulated cellular debris and cholesterol monohydrate, and a lack of extracellular matrix. The development of the necrotic core is believed to originate from apoptotic macrophages. Thinning of the fibrous cap leads to plaques vulnerable to rupture, or thin-cap fibroatheromas. Overlying thrombosis can arise from one of several mechanisms including ruptures, erosion, or calcified nodules. Calcium within atherosclerosis is a common imaging target which increases with lesion progression and is present in greatest frequent in healed plaque ruptures and fibrous plaques. Thin cap fibroatheromas most frequently contain speckled calcification but may show heavily calcified areas or an absence of calcification. which is not very useful in diagnosing these lesions by calcium-based imaging. Coronary lesions with thrombi in the absence of rupture (erosions) exclusively show stippled or no calcification. Rupture in the absence of calcification is rare. In contrast, diffuse calcification is almost always associated with healed ruptures.
Article
Background: Cholesterol crystals (CCs) are regular microstructures found within the necrotic core of atherosclerotic plaques and have been hypothesized to be related to plaque destabilization. We attempted to investigate the potential association between CCs and non-culprit plaque vulnerability in patients with ST-segment elevated myocardial infarction (STEMI) and study morphological features of CCs in ruptured non-culprit plaques. Methods: A total of 261 patients with ST-segment elevation myocardial infarction who underwent 3-vessel optical coherence tomography (OCT) imaging were included. Non-culprit plaques were divided into two groups according to the presence or absence of CCs in the plaque to compare the morphological characteristics of the plaques. The differences in parameters of the non-culprit plaque CCs were explored between ruptured plaques and unruptured plaques. Results: Totally, 530 non-culprit plaques (29 ruptured plaques and 501 unruptured plaques) were identified by OCT. The incidence of CCs was 21.1%. Compared with non-culprit plaques without CCs, those with CCs had a larger lipid burden. Macrophages (p < 0.001) and spotty calcification (p = 0.002) were more frequently observed in non-culprit plaques with CCs. The frequency of CCs was significantly higher (p = 0.001) and the CCs were larger (p = 0.046) and more superficial (p = 0.005) in ruptured non-culprit plaques than in unruptured non-culprit plaques. The maximum lipid arc and fibrous cap thickness were independent predictors of plaque rupture, but the presence of CCs was not. Conclusions: Non-culprit plaques with CCs have more vulnerable features. CCs are more frequently found in ruptured non-culprit plaques and larger and more superficial CCs are associated with plaque rupture.
Article
Full-text available
The compositions of lesion types that precede and that may initiate the development of advanced atherosclerotic lesions are described and the possible mechanisms of their development are reviewed. While advanced lesions involve disorganization of the intima and deformity of the artery, such changes are absent or minimal in their precursors. Advanced lesions are either overtly clinical or they predispose to the complications that cause ischemic episodes; precursors are silent and do not lead directly to complications. The precursors are arranged in a temporal sequence of three characteristic lesion types. Types I and II are generally the only lesion types found in children, although they may also occur in adults. Type I lesions represent the very initial changes and are recognized as an increase in the number of intimal macrophages and the appearance of macrophages filled with lipid droplets (foam cells). Type II lesions include the fatty streak lesion, the first grossly visible lesion, and are characterized by layers of macrophage foam cells and lipid droplets within intimal smooth muscle cells and minimal coarse-grained particles and heterogeneous droplets of extracellular lipid. Type III (intermediate) lesions are the morphological and chemical bridge between type II and advanced lesions. Type III lesions appear in some adaptive intimal thickenings (progression-prone locations) in young adults and are characterized by pools of extracellular lipid in addition to all the components of type II lesions.
Article
Full-text available
CD163 is a member of the group B scavenger receptor cysteine-rich (SRCR) superfamily. This study describes aspects of the tissue distribution, the regulation of expression, and signal transduction after cross-linking of this receptor at the cell surface of macrophages. CD163 showed an exclusive expression on resident macrophages (e.g., red pulp macrophages, alveolar macrophages). The expression was inducible on monocyte-derived macrophages by glucocorticoids but not by interleukin-4 (IL-4), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon-gamma. The combination of IL-4 or GM-CSF with glucocorticoids resulted in a further increase. Subcellular analysis of alveolar macrophages by immunoelectron microscopy showed a plasma membrane localization of the antigen. Cross-linking of CD163 with monoclonal antibody induced a protein tyrosine kinase-dependent signal that resulted in (1) slow-type calcium mobilization, (2) inositol triphosphate production, and (3) secretion of IL-6 and GM-CSF. The data suggest a function for the SRCR-superfamily receptor CD163 in the regulation of inflammatory processes by macrophages.
Article
Full-text available
Most of the lipid in atherosclerotic fibrous plaques is extracellular. How does it get there? Hakala and coworkers1 describe in this issue of Arteriosclerosis, Thrombosis, and Vascular Biology a pathway involving enzymatic hydrolysis of phospholipids in LDL, leading to lipoprotein aggregation and fusion and hence, to accumulation of lipid droplets. The process is enabled and enhanced in the presence of arterial proteoglycans. This extracellular pathway should be distinguished from the commonly postulated cellular pathway involving uptake of modified LDL in macrophage foam cells, which subsequently die and leave the accumulated lipid in an extracellular location. Although macrophages and macrophage antigens can be found in the “necrotic,” lipid-rich core of plaques, several lines of evidence strongly suggest that most of the lipid derives not from dead foam cells but from the extracellular trapping and processing of LDL.2 The evidence can be sketched briefly as follows: (1) The earliest core regions are located deep within the intima of atherosclerotic fatty streaks (in the musculoelastic intimal sublayer) below the level of macrophage foam cells.3 4 (2) The lipid core, especially in smaller fibrous plaques, shows a markedly increased ratio of free to esterified cholesterol, whereas the hypothesis of foam cell death would predict more esterified cholesterol.3 4 5 (3) The fatty acyl pattern of core cholesteryl esters has more linoleate than oleate, similar to the pattern of plasma lipoproteins, but quite different from the oleate predominance of lesion foam cells.4 5 (4) Extracellular lipid droplets in human arterial intima tend to be associated with elastic fibers, are much smaller than foam cell lipid droplets, and sometimes appear in homogeneous fields that do not correspond to foam cell contours (eg, see Figure 9 in Guyton and …
Article
Full-text available
Background: . The beneficial effects of statins on clinical events may involve mechanisms that modify endothelial dysfunction, plaque stability, thrombus formation, and inflammatory responses. To determine the effect of atorvastatin on blood rheology in patients with familial hypercholesterolemia (FH), we prospectively studied serum lipid concentration, red cell cholesterol content, lipid peroxidation and erythrocyte membrane fluidity. The aim of this paper was to evaluate the effects of atorvastatin therapy on the erythrocyte membrane structure and the hypolipemic efficacy in patients with FH. MATERIALS, METHODS AND SUBJECTS STUDIED:. The study involved 31 patients with FH and 20 healthy individuals as a control group. The program lasted 20 weeks. For the first 8 weeks, the patients were on a hypolipemic diet only and for the subsequent 12 weeks, alongside the diet they were given 10 mg atorvastatin per day. Laboratory tests were carried out before and after 4 weeks and 12 weeks of the pharmacological treatment. Erythrocyte membrane fluidity was determined using the spin labeled method. The peroxidation of lipids was measured in whole erythrocytes as well as in erythrocyte plasma membranes by means of the thiobarbituric acid technique. Results: . Treatment with atorvastatin reduced serum total cholesterol concentration from 310+/-29 mg/dl in a basal situation to 203+/-34 mg/dl ( P<0.001) at the end of the treatment and low-density lipoprotein (LDL) cholesterol concentration from 225+/-30 mg/dl to 126+/-30 mg/dl ( P<0.001), respectively. The changes observed in the plasma lipids correlate with a significant decrease in erythrocyte membrane cholesterol, from 2.24+/-1.69 to 1.17+/-0.75 mg/mg protein ( P<0.001) after 12 weeks of treatment. The lipid peroxidation in membranes of erythrocytes was lowered from the basal value 0.171+/-0.097 to 0.100+/-0.024 mmol/mg protein ( P<0.05) after 4 weeks of treatment and to 0.057+/-0.020 mmol/mg protein ( P<0.001) after 12 weeks of treatment, and in total erythrocytes from 4.78+/-1.49 to 3.99+/-1.39 mmol/g Hb ( P<0.02) and 2.43+/-0.87 mmol/g Hb ( P<0.001), respectively. The membrane fluidity was estimated by means of parameter S at the depth of the fifth carbon atom. Atorvastatin in hypercholesterolemic erythrocytes enhances the fluidity of the superficial layer from 0.758+/-0.009 up to the values observed in the control group 0.744+/-0.009 ( P<0.001). There is no impact on the microviscosity of the hydrophobic core observed. Conclusion: . Our findings suggest that the atorvastatin therapy reverses the alteration of erythrocyte plasma membrane properties. It may improve blood rheology in patients with FH. This improvement in blood properties may contribute to the well-known beneficial effects of atorvastatin on cardiovascular risk in patients with severe hyperlipidemia and atherosclerotic vascular disease.
Article
Full-text available
Intraplaque hemorrhage is common in advanced coronary atherosclerotic lesions. The relation between hemorrhage and the vulnerability of plaque to disruption may involve the accumulation of free cholesterol from erythrocyte membranes. We stained multiple coronary lesions from 24 randomly selected patients who had died suddenly of coronary causes with an antibody against glycophorin A (a protein specific to erythrocytes that facilitates anion exchange) and Mallory's stain for iron (hemosiderin), markers of previous intraplaque hemorrhage. Coronary lesions were classified as lesions with pathologic intimal thickening, fibrous-cap atheromas with cores in an early or late stage of necrosis, or thin-cap fibrous atheromas (vulnerable plaques). The arterial response to plaque hemorrhage was further defined in a rabbit model of atherosclerosis. Only traces of glycophorin A and iron were found in lesions with pathologic intimal thickening or fibrous-cap atheromas with cores in an early stage of necrosis. In contrast, fibroatheromas with cores in a late stage of necrosis or thin caps had a marked increase in glycophorin A in regions of cholesterol clefts surrounded by iron deposits. Larger amounts of both glycophorin A and iron were associated with larger necrotic cores and greater macrophage infiltration. Rabbit lesions with induced intramural hemorrhage consistently showed cholesterol crystals with erythrocyte fragments, foam cells, and iron deposits. In contrast, control lesions from the same animals had a marked reduction in macrophages and lipid content. By contributing to the deposition of free cholesterol, macrophage infiltration, and enlargement of the necrotic core, the accumulation of erythrocyte membranes within an atherosclerotic plaque may represent a potent atherogenic stimulus. These factors may increase the risk of plaque destabilization.
Article
Full-text available
Angiopoietin-1 (Ang1) has powerful vascular protective effects: suppressing plasma leakage, inhibiting vascular inflammation, and preventing endothelial death. Preclinical studies indicate that Ang1 may be therapeutically useful in a number of situations, including treatment of edema, endotoxemia, and transplant arteriosclerosis. However, the ligand has also been implicated in vessel remodeling, induction of angiogenesis and pulmonary hypertension, indicating that strategies to minimize any deleterious effects while optimizing vessel protection are likely to be needed. This review surveys the published data on vascular protective effects of Ang1 and highlights the therapeutic potential of this ligand, as well as possible limitations to its use. We also consider the data on Ang1 receptors and speculate on how to maximize therapeutic benefit by targeting the Tie receptors.
Article
Full-text available
Spontaneously arising tumor cells are not usually angiogenic at first. The phenotypic switch to angiogenesis is usually accomplished by a substet that induces new capillaries that then converge toward the tumor. The switch clearly involves more than simple upregulation of angiogenic activity and is thought to be the result of a net balance of positive and negative regulators. Tumor growth is although to require disruption of this balance and hence this switch must turned on for cancer progression. Progenitor endothelial cells, the crosstalk between angiogenic factors and their receptors and the interaction between vasculogenesis and lymphangiogenesis are all factors that may contribute to the switch. Its promotion is also the outcome of genetic instability resulting in the emergence of tumor cell lines. This review describes the history of the angiogenic switch illustrated in the literature and with particular reference to the three transgenic mouse models, namely RIP1-TAG2, keratin-14 (K14) (human papilloma virus) HPV16 and papilloma virus, used for stage-specific assessment of the effects of antiangiogenic and antitumorigenic agents.
Article
Cholesterol granuloma is usually associated with chronic middle ear disease and is common in the mastoid antrum and air cells of the temporal bone. It has also been reported in other parts of the skull, such as the frontal and maxillary sinuses and orbit. Cholesterol granuloma is rare in the paranasal sinuses. We report a new case of cholesterol granuloma in the maxillary sinus of a 38-year-old man who underwent surgical excision. We also review the literature and discuss the mechanism of development for this lesion. The resected specimen showed fragments of respiratory mucosa with cholesterol clefts surrounded by multinucleated foreign-body giant cells. Some multinucleated foreign-body giant cells showed asteroid bodies. Hemorrhagic areas, hemosiderin-laden macrophages, chronic inflammatory cells, and dilated lymphatics vessels were seen as well. Increased intrasinus pressure due to drainage obstruction may affect venous and lymphatic drainage from the sinus cavity, leading to venule microhemorrhages while still allowing arterial blood into the sinus mucosa and further contributing to a large localized hemorrhage. Lymphatic drainage may be insufficient to completely remove the lipid components of the red blood cells, and the lipid accumulation may contribute to the formation of cholesterol crystals and their esters.
Article
An improved immunohistochemical method has been used to assess neovascularization within the vulnerable ‘shoulder’ regions of atherosclerotic plaques from carotid arteries. A combination of monoclonal antibodies (CD31, CD34, ± von Willebrand factor) was shown to be far more effective than conventional techniques in demonstrating extensive vascularizations within the ‘shoulder’ and cap regions of late‐stage plaques. Such sites were shown to be microfocal, often appearing as a plexus of both large and small vessels which occupied a significant proportion of the ‘shoulder’ area. These regions of marked neovascularization were commonly associated with accumulations of macrophages, mast cells, and T‐cells, indicative of local inflammatory reactions. The matrix components elastin and collagen type VI showed variable distributions which suggested extensive tissue remodelling, whereas collagen type IV was recognized as a basement membrane protein of most blood vessels, as well as being associated with ‘stellate’ smooth muscle cells. Evidence of local microvascular damage within the shoulder regions of some specimens was demonstrated by extravascular red blood cells, macrophages containing haemosiderin, and perivascular fibrin deposition. These local haemorrhages derived from microvessels beneath the lining of the arterial lumen are a further indication of how the microfocal vascularization of the plaque ‘shoulder’ might contribute to further complications of inflammation and plaque destabilization in late‐stage disease. Copyright © 1999 John Wiley & Sons, Ltd.
Article
Recent studies concerning cholesterol, its behavior and its roles in cell growth provide important new clues to the role of this fascinating molecule in normal and pathological states.
Article
We hypothesized that cholesterol content is increased in the circulating erythrocytes of patients with acute coronary syndrome (ACS) and may be a marker of clinical instability. We therefore sought to investigate whether cholesterol content differs in erythrocyte membranes of patients presenting with ACS compared to patients with chronic stable angina (CSA). Plaque rupture in ACS depends at least partly on the volume of the necrotic lipid core. Histopathologic studies have suggested that cholesterol transported by erythrocytes and deposited into the necrotic core of atheromatous plaques contributes to lipid core growth. Consecutive angina patients were prospectively assessed; 120 had CSA (83 men, age 64 +/- 11 years) and 92 ACS (67 men, 66 +/- 11 years). Total cholesterol content in erythrocyte membranes (CEM) was measured using an enzymatic assay, and protein content was assessed by the Bradford method. The CEM (median and interquartile range) was higher (p < 0.001) in ACS patients (184 microg/mg; range 130.4 to 260.4 microg/mg) compared with CSA patients (81.1 microg/mg; range 53.9 to 109.1 microg/mg) (analysis of covariance). Total plasma cholesterol concentrations did not correlate with CEM levels (r = -0.046, p = 0.628). This study shows, for the first time, that CEM is significantly higher in patients with ACS compared with CSA patients. These findings suggest a potential role of CEM as a marker of atheromatous plaque growth and vulnerability. Large ad hoc studies are required to establish the clinical importance and pathogenic significance of CEM measurement.
Article
Coronary vasospasm has been implicated as a cause of myocardial ischemia and sudden cardiac death in cocaine abusers. However, the mechanism or mechanisms remain unknown. Autopsy records (n = 5,871) from the medical examiner's files at Baltimore, Maryland and northern Virginia were examined and 495 persons (8.4%) were identified with positive toxicologic findings for cocaine. Of these, six subjects (1.2%) had total thrombotic occlusion, involving primarily the left anterior descending coronary artery. The mean number of adventitial mast cells per coronary segment and the degree of atherosclerosis were determined. These observations were compared with findings in age- and gender-matched subjects who died from cocaine overdose and in patients who had sudden cardiac death (acute thrombosis) without a history of illicit drug abuse.There were significantly more mast cells in subjects with cocaine-associated thrombosis than in the other groups. The number of mast cells showed a significant correlation with the degree of cross-sectional luminal narrowing (r = 0.68) in subjects with cocaine-associated thrombosis but not in subjects with sudden death due to thrombosis (r = 0.34, p < 0.03). Subjects with cocaine-associated thrombosis also had significant coronary atherosclerosis without plaque hemorrhage (five had one or more vessels with >75% cross-sectional area luminal narrowing) despite a mean age of 29 ± 2 years.These findings suggest that adventitial mast cells may potentiate atherosclerosis and vasospasm, thrombosis and premature sudden death in long-term cocaine abusers.
Article
Fourteen patients with familial hypercholesterolemia treated with lovastatin (40 mg/day) for three months were studied to find out whether the expected changes in plasma lipids are accompanied by modifications in the lipid composition of the erythrocyte membrane and whether these in turn induce changes in the rheological behavior of the red blood cell.Our results demonstrate the efficacy of lovastatin in reducing the plasma concentration of cholesterol and LDL cholesterol. The changes observed in the plasma lipids correlate with a significant decrease in the cholesterol/phospholipid ratio of the red blood cell membrane, from 1.19±0.19 in a basal situation to 0.92±0.23 (p<0.01) at the end of treatment. These changes in the lipid composition of the cell are statistically related to a decrease in erythrocyte aggregability and an improvement in blood filterability, which means beneficial change in the patients' hemorheological situation.
Article
MRI is able to quantify carotid plaque size and composition with good accuracy and reproducibility and provides an opportunity to prospectively examine the relationship between plaque features and subsequent cerebrovascular events. We tested the hypothesis that the characteristics of carotid plaque, as assessed by MRI, are possible predictors of future ipsilateral cerebrovascular events. A total of 154 consecutive subjects who initially had an asymptomatic 50% to 79% carotid stenosis by ultrasound with > or =12 months of follow-up were included in this study. Multicontrast-weighted carotid MRIs were performed at baseline, and participants were followed clinically every 3 months to identify symptoms of cerebrovascular events. Over a mean follow-up period of 38.2 months, 12 carotid cerebrovascular events occurred ipsilateral to the index carotid artery. Cox regression analysis demonstrated a significant association between baseline MRI identification of the following plaque characteristics and subsequent symptoms during follow-up: presence of a thin or ruptured fibrous cap (hazard ratio, 17.0; P< or =0.001), intraplaque hemorrhage (hazard ratio, 5.2; P=0.005), larger mean intraplaque hemorrhage area (hazard ratio for 10 mm2 increase, 2.6; P=0.006), larger maximum %lipid-rich/necrotic core (hazard ratio for 10% increase, 1.6; P=0.004), and larger maximum wall thickness (hazard ratio for a 1-mm increase, 1.6; P=0.008). Among patients who initially had an asymptomatic 50% to 79% carotid stenosis, arteries with thinned or ruptured fibrous caps, intraplaque hemorrhage, larger maximum %lipid-rich/necrotic cores, and larger maximum wall thickness by MRI were associated with the occurrence of subsequent cerebrovascular events. Findings from this prospective study provide a basis for larger multicenter studies to assess the risk of plaque features for subsequent ischemic events.
Article
95 individual human atherosclerotic lesions from 26 persons were classified into three groups under the dissecting microscope: fatty streaks, fibrous plaques, and gruel (atheromatous) plaques. Each lesion was isolated by microdissection, its lipid composition determined by chromatography, and the physical states of the lipids identified by polarizing microscopy and in some cases by X-ray diffraction. The composition of each lesion was plotted on the in vitro phase diagram of the major lipids of plaques: cholesterol, cholesterol ester, and phospholipid. The observed physical states were compared with those predicted by the location of the lipid composition on the phase diagram. The most severe lesions (gruel plaques) had an average lipid composition of cholesterol 31.5+/-1.9%, cholesterol ester 47.2+/-2.3%, and phospholipid 15.3+/-0.5%. Their compositions fell within the three-phase zone of the phase diagram, predicting the lipids to be separated into a cholesterol crystal phase, a cholesterol ester oily phase and a phospholipid liquid crystalline phase. In addition to the phospholipid liquid crystalline phase of membranes and myelin-like figures demonstrable by electron microscopy, polarizing microscopy revealed the other two predicted phases, isotropic cholesterol ester-rich droplets and cholesterol crystals. X-ray diffraction studies verified the identity of the crystals as cholesterol monohydrate. Fibrous plaques also had an average lipid composition within the three-phase zone of the phase diagram. Polarizing microscopy revealed the presence of cholesterol monohydrate crystals and lipid droplets in all of these lesions; the droplets were predominately isotropic in 28 of the 31 fibrous plaques. Although these lesions had less free cholesterol and more cholesterol ester than gruel plaques, they were otherwise similar. Fatty streaks had compositions within both the two- and three-phase zones of the phase diagram. Compared with gruel plaques, the fatty streaks within the two-phase zone, defined as "ordinary," had more cholesterol ester, less free cholesterol, a higher cholesteryl oleate/cholesteryl linoleate ratio, a lower sphingomyelin/lecithin ratio, more anisotropic lipid droplets, and rare or no cholesterol crystals. Those lesions within the three-phase zone had many chemical and physical features intermediate between ordinary fatty streaks and gruel plaques. Moreover, 68% of these "intermediate" lesions had no cholesterol crystals by polarizing microscopy in spite of their compositions being within the three-phase zone, indicating the cholesterol ester oily phase or the phospholipid phase or both were supersaturated with cholesterol. Identification of this group of intermediate lesions provides evidence that some fatty streaks may be precursors of advanced plaques.
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they are relevant and appropriate but comments will not be edited. The ultimate decision on publication of an online comment is at the Editors' discretion. Formatting: Please include a title for the comment and your affiliation. Note that symbols (e.g. Greek letters) may not transmit properly in this form due to potential software compatibility issues. Please spell out the words in place of the symbols (e.g. replace “α” with “alpha”). Comments should be no more than 8,000 characters (including spaces ) in length. References may be included when necessary but should be kept to a minimum. Be careful if copying and pasting from a Word document. Smart quotes can cause problems in the form. If you experience difficulties, please convert to a plain text file and then copy and paste into the form.
Article
Activated monocytic cells and neutrophils adhere to substrates coated with a wide variety of proteins including albumins, catalase, casein, and various extracellular matrix proteins. This adhesion can be specifically inhibited by antibodies directed to the beta 2 integrin subunit. This adhesion to protein substrates shares some similarities with two known protein-protein recognition systems with little apparent binding specificity, namely, the interactions of heat shock proteins and histocompatibility antigens with denatured proteins or peptides. Cell adhesion and affinity chromatography experiments were performed to test the hypothesis that monocytes and neutrophils adhere to and migrate on protein substrates due to the presence of cell surface receptors that recognize common protein structures such as denatured protein epitopes. Adhesion experiments revealed that activated monocytic cells adhere more rapidly and extensively on substrates coated with denatured protein versus native protein. Both adhesion and migration on such substrates in vitro was dependent on beta 2 integrins since blocking antibodies completely interfered with these cellular responses. Affinity chromatography experiments revealed that the Mac-1 and p150,95 integrins could be isolated from monocyte-differentiated HL-60 cells or neutrophils on a denatured protein-Sepharose column. Much greater yields of the receptors were obtained on a denatured versus native protein Sepharose column. The binding of these receptors was specific in that the LFA-1 beta 2 integrin did not bind to the denatured protein column. These data provide evidence that the adhesion of activated monocytes and neutrophils to many protein substrates in vitro is due to the ability of Mac-1 and p150,95 to directly bind to denatured proteins. A model of leukocyte adhesion and invasion whereby activated leukocytes denature extracellular proteins during diapedesis, making them suitable for recognition by beta 2 integrins, is proposed.
Article
IL-8 (also known as neutrophil-activating peptide 1) is recognized as a potent effector of neutrophil functions. Several different cell types that contact blood, namely T lymphocytes, monocytes, and endothelial cells, secrete this polypeptide following stimulation by cytokines, or lipopolysaccharide. Here we show that when IL-8 is added to blood it rapidly partitions from the plasma fluid to the blood cells and that erythrocytes account for the vast majority of this binding. Analysis of 125I-IL-8 binding [( ala-IL-8]77 form) to human red cells indicates a single, 5 nM Kd affinity class of binding sites, present at approximately 2,000 per red cell representing approximately 15 nmol of red cell IL-8 binding sites per liter of blood. These sites are protease sensitive. Their binding of IL-8 is rapidly reversible and does not result in receptor internalization, although bound IL-8 is resistant to extraction by pH 3 buffer at 5 degrees C. 125I-IL-8 binding to red cells was not inhibited by epidermal growth factor or interleukin 1, but was inhibited by monocyte chemotactic peptide-1, which is not a neutrophil chemotaxin, but is a member of the same family of polypeptides as IL-8. FACS analysis of IL-8-mediated mobilization of Ca2+ in neutrophils indicates that the IL-8 bound to red cells is incapable of stimulating neutrophils. Thus, red cell absorption of IL-8 may function to limit stimulation of leukocytes by IL-8 released into blood.
Article
Cholesterol exchange between plasma and human platelets and erythrocytes and guinea pig platelets, erythrocytes and megakaryocytes was studied. The characteristics of exchange of cholesterol between [3H]cholesterol-labeled plasma and human platelets and erythrocytes were similar: exchange per cell was independent of cell concentration in whole plasma, decreased only 2-fold over a wide range of cell concentrations in low concentrations of plasma and approached a plateau at 1/3 normal plasma cholesterol concentration, and there was no net change in the cholesterol content of either cell. The activation energy for exchange for both cells was 47 kJ/mol. In all experiments, erythrocyte cholesterol was labeled to approximately twice the specific activity of platelet cholesterol. Guinea pig megakaryocyte cholesterol exchanged at 25-33% of the rate of guinea pig platelet cholesterol in vitro. Similarly, when guinea pigs were fed [3H]cholesterol, erythrocyte cholesterol specific activity after 24 h was 90%, platelet 50-65%, and megakaryocyte 20-26% that of plasma. Guinea pig platelets incubated with plasma radiolabeled in free and esterified cholesterol incorporated radioactivity from free but not esterified cholesterol. The similarity of free cholesterol exchange in platelets and erythrocytes in vitro and in vivo and the apparent inability of platelets to take up cholesterol esters from lipoproteins suggest that the interaction between normal platelets and normocholesterolemic plasma is limited to cholesterol exchange.
Article
Mast cell products, such as histamine, may contribute to the initiation and progression of the atherosclerotic plaque. To determine the relationship that may exist between early atherosclerotic plaques and mast cells we studied the aortas and coronary arteries of 115 young subjects aged 15 to 34 years who had traumatic deaths. Lesions were classified as normal intima, fatty streaks, fibro-fatty plaques, and fibrous plaques. Aortic and coronary artery segments with raised lesions had significantly greater numbers of mast cells in the adventitia (and occasionally intima and outer media) compared with those with a normal intima. In the aortic segments greater numbers of mast cells were located in the dorsal portion (lesion "prone") compared with the ventral half (lesion "resistant") (P < .05). These data support the concept that increased numbers of mast cells are associated with atherosclerosis and suggest a role for mast cell products in the evolution of the atherosclerotic plaque.
Article
The propensity of atherosclerotic plaques to disrupt may be influenced by their lipid content and the distribution of these lipids within the plaque. To investigate this, we analyzed the morphological and lipid profiles of 668 human aortic plaques from 30 males who had died of ischemic heart disease. Plaques were classified as disrupted or as intact types A or B, the latter distinction being based on the absence or presence, respectively, of disrupted plaques within the same aorta. Disrupted plaques have a greater content of lipid (P < .001) and macrophages (P < .001) as well as a thinner cap (P < .001) than intact plaques. Lipid concentrations are positively associated with macrophage accumulation in all plaque types and are negatively associated with minimum cap thickness at the edge of disrupted plaques (P < .05). Free cholesterol concentration is inversely associated with minimum cap thickness at the center of type B plaques only (P < .05). At the center of intact type A and B and disrupted plaques, the free-to-esterified cholesterol ratios were 0.9 (range, 0.0 to 2.7), 0.8 (0.0 to 3.9), and 1.6 (0.2 to 4.0), respectively. Esterified cholesterol concentrations were higher at the center of type B plaques, and those of free cholesterol were higher at the center of disrupted plaques. At the edge of disrupted plaques, the free-to-esterified cholesterol ratio was 0.5 (0.0 to 2.7) because of the accumulation of esterified cholesterol. Concentrations of all fatty acids were increased at the edge of disrupted plaques compared with the center, but as a proportion of total fatty acids, omega 6-polyunsaturated fatty acids (PUFAs) were lower (44% versus 46%, P < .01), possibly reflecting oxidation of PUFAs. These data demonstrate differences in lipid composition and intraplaque lipid distribution between intact and disrupted plaques. At the edge of advanced plaques, increased esterified lipid concentrations, inversely associated with cap thickness, may reflect macrophage activity and a predisposition to rupture.
Article
Most of the major extracranial arteries have vasa vasorum which play an important role in some pathological conditions. However, in the intracranial arteries, the existence of vasa vasorum and their pathological implication have not been adequately investigated. We examined the distribution and incidence of vasa vasorum in the major cerebral arteries and their relationships to certain clinical factors in 50 autopsy cases performed between 1987 and 1994. By light microscopy, vasa vasorum were found in 36 of 50 patients. Of 36 patients, vasa vasorum in 30 cases were localizedly observed in the tunica adventitia and the in other 6 were distributed in the tunica media accompanied by intramural haemorrhage. Existence of vasa vasorum was more common in the proximal arteries (vertebral, internal carotid, and basilar arteries) than in the distal arteries (middle cerebral and anterior cerebral arteries). Vasa vasorum were found more frequently in aged patients with severe atherosclerosis and those with cerebrovascular diseases. Our results indicated that intracranial vasa vasorum existed with a higher frequency in the tunica adventitia of the vertebral and internal cerebral arteries, and the incidence of vasa vasorum related to severity of atherosclerosis. The development of vasa vasorum in the tunica media may reflect some pathological changes of cerebral arteries.
Article
Histamine, a product of mast cells, is an effective vasoconstrictor of atherosclerotic coronary arteries. Because it has been suggested that coronary spasm plays a role in acute coronary syndromes such as myocardial infarction (MI), we quantified and characterized the mast cells in the adventitia of infarct-related coronary arteries. In a series of 17 autopsied MI patients, we identified the segment of the left coronary artery with ruptured plaque responsible for the infarction. More distal segments from the infarct-related coronary artery, either with nonruptured plaques or with normal intima, were also studied. Corresponding segments taken from left coronary arteries obtained from 17 patients who had died of noncardiac causes served as controls. Adventitial mast cells in the infarct-related and the control coronary arteries were identified immunohistochemically by staining for tryptase. In the infarct-related coronary arteries, we also stained for chymase and histamine. Moreover, T lymphocytes and macrophages were identified immunohistochemically and counted. In the infarct-related coronary arteries, significantly larger numbers of mast cells were present in the adventitia backing ruptured plaques (98+/-40 mast cells/mm2, mean+/-SD) than in the adventitia backing nonruptured plaques (41+/-12 mast cells/mm2; P<0.001) or backing normal intima (19+/-8 mast cells/mm2; P<0.001). No such difference was found among the 3 different segments in the control coronary arteries. The majority of mast cells contained not only tryptase but also chymase. Mast cells were the only cells in the coronary adventitia that contained histamine. The proportion of adventitial mast cells that were degranulated was highest in the segments with ruptured plaques. The numbers of adventitial macrophages and T lymphocytes were also increased in the segments with plaque rupture. In infarct-related coronary arteries, the number of degranulated mast cells in the adventitia backing ruptured plaques is increased. Histamine released from the degranulated mast cells may reach the media, where it may locally provoke coronary spasm and thus contribute to the onset of MI.
Article
An improved immunohistochemical method has been used to assess neovascularization within the vulnerable 'shoulder' regions of atherosclerotic plaques from carotid arteries. A combination of monoclonal antibodies (CD31, CD34, +/- von Willebrand factor) was shown to be far more effective than conventional techniques in demonstrating extensive vascularizations within the 'shoulder' and cap regions of late-stage plaques. Such sites were shown to be microfocal, often appearing as a plexus of both large and small vessels which occupied a significant proportion of the 'shoulder' area. These regions of marked neovascularization were commonly associated with accumulations of macrophages, mast cells, and T-cells, indicative of local inflammatory reactions. The matrix components elastin and collagen type VI showed variable distributions which suggested extensive tissue remodelling, whereas collagen type IV was recognized as a basement membrane protein of most blood vessels, as well as being associated with 'stellate' smooth muscle cells. Evidence of local microvascular damage within the shoulder regions of some specimens was demonstrated by extravascular red blood cells, macrophages containing haemosiderin, and perivascular fibrin deposition. These local haemorrhages derived from microvessels beneath the lining of the arterial lumen are a further indication of how the microfocal vascularization of the plaque 'shoulder' might contribute to further complications of inflammation and plaque destabilization in late-stage disease.
Article
Leakiness of blood vessels in tumors may contribute to disease progression and is key to certain forms of cancer therapy, but the structural basis of the leakiness is unclear. We sought to determine whether endothelial gaps or transcellular holes, similar to those found in leaky vessels in inflammation, could explain the leakiness of tumor vessels. Blood vessels in MCa-IV mouse mammary carcinomas, which are known to be unusually leaky (functional pore size 1.2-2 microm), were compared to vessels in three less leaky tumors and normal mammary glands. Vessels were identified by their binding of intravascularly injected fluorescent cationic liposomes and Lycopersicon esculentum lectin and by CD31 (PECAM) immunoreactivity. The luminal surface of vessels in all four tumors had a defective endothelial monolayer as revealed by scanning electron microscopy. In MCa-IV tumors, 14% of the vessel surface was lined by poorly connected, overlapping cells. The most superficial lining cells, like endothelial cells, had CD31 immunoreactivity and fenestrae with diaphragms, but they had a branched phenotype with cytoplasmic projections as long as 50 microm. Some branched cells were separated by intercellular openings (mean diameter 1.7 microm; range, 0.3-4.7 microm). Transcellular holes (mean diameter 0.6 microm) were also present but were only 8% as numerous as intercellular openings. Some CD31-positive cells protruded into the vessel lumen; others sprouted into perivascular tumor tissue. Tumors in RIP-Tag2 mice had, in addition, tumor cell-lined lakes of extravasated erythrocytes. We conclude that some tumor vessels have a defective cellular lining composed of disorganized, loosely connected, branched, overlapping or sprouting endothelial cells. Openings between these cells contribute to tumor vessel leakiness and may permit access of macromolecular therapeutic agents to tumor cells.
Article
This review will reconsider the current paradigm for understanding the critical, final steps in the progression of atherosclerotic lesions. That scheme, largely an outgrowth of observations of autopsy tissues by Davies and colleagues,1 2 asserts that the cause of death in atherosclerotic coronary artery disease is rupture of an advanced atherosclerotic lesion. Although this assumption may be partially true, recent autopsy studies suggest that it is incomplete. To reconsider this paradigm, we reexamined the morphological classification scheme for lesions proposed by the American Heart Association (AHA).3 4 This scheme is difficult to use for 2 reasons. First, it uses a very long list of roman numerals modified by letter codes that are difficult to remember. Second, it implies an orderly, linear pattern of lesion progression. This tends to be ambiguous, because it is not clear whether there is a single sequence of events during the progression of all lesions. We have therefore tried to devise a simpler classification scheme that is consistent with the AHA categories but is easier to use, able to deal with a wide array of morphological variations, and not overly burdened by mechanistic implications. The current paradigm is based on the belief that type IV lesions, or “atheromas,” described by the AHA are stable because the fatty, necrotic core is contained by a smooth muscle cell–rich fibrous cap. Virchow’s analysis5 in 1858 pointed out that historically, the term “atheroma” refers to a dermal cyst (“Grutzbalg”), a fatty …
Article
Cholesterol granuloma is usually associated with chronic middle ear disease and is common in the mastoid antrum and air cells of the temporal bone. It has also been reported in other parts of the skull, such as the frontal and maxillary sinuses and orbit. Cholesterol granuloma is rare in the paranasal sinuses. We report a new case of cholesterol granuloma in the maxillary sinus of a 38-year-old man who underwent surgical excision. We also review the literature and discuss the mechanism of development for this lesion. The resected specimen showed fragments of respiratory mucosa with cholesterol clefts surrounded by multinucleated foreign-body giant cells. Some multinucleated foreign-body giant cells showed asteroid bodies. Hemorrhagic areas, hemosiderin-laden macrophages, chronic inflammatory cells, and dilated lymphatics vessels were seen as well. Increased intrasinus pressure due to drainage obstruction may affect venous and lymphatic drainage from the sinus cavity, leading to venule microhemorrhages while still allowing arterial blood into the sinus mucosa and further contributing to a large localized hemorrhage. Lymphatic drainage may be insufficient to completely remove the lipid components of the red blood cells, and the lipid accumulation may contribute to the formation of cholesterol crystals and their esters.
Article
CD163 is a highly expressed macrophage membrane protein belonging to the scavenger receptor cysteine rich (SRCR) domain family. The CD163 expression is induced by interleukin-6, interleukin-10 and glucocorticoids. Its function has remained unknown until recently when CD163 was identified as the endocytic receptor binding hemoglobin (Hb) in complex with the plasma protein haptoglobin (Hp). This specific receptor-ligand interaction leading to removal from plasma of the Hp-Hb complex-but not free Hp or Hb-now explains the depletion of circulating Hp in individuals with increased intravascular hemolysis. Besides having a detoxificating effect by removing Hb from plasma, the CD163-mediated endocytosis of the Hp-Hb complex may represent a major pathway for uptake of iron in the tissue macrophages. The novel functional linkage of CD163 and Hp, which both are induced during inflammation, also reveal some interesting perspectives relating to the suggested anti-inflammatory properties of the receptor and the Hp phenotypes.
Article
The cells of most organs and tissues satisfy their requirements for membrane cholesterol via endogenous cholesterol biosynthesis (1). Many cell types, however, have acquired mechanisms to internalize exogenous sources of cholesterol, usually in the form of plasma-derived lipoproteins (2). Examples include steroid-synthesizing cells, hepatocytes, and macrophages and smooth muscle cells in atherosclerotic lesions, often referred to as foam cells. In the case of steroidogenic cells, the internalization of lipoprotein-cholesterol represents a physiological process that provides cells with precursor cholesterol stores, to be used for “acute” steroid hormone production (3). Hepatocyte lipoprotein uptake mediates the clearance of various classes of plasma lipoproteins (1), which can lead to whole-body elimination of excess diet-derived cholesterol in the bile, a process known as reverse cholesterol transport (Tall, this Perspective series, ref. 4). The uptake of arterial-wall lipoproteins by macrophages and smooth muscle cells may be a type of physiological scavenging response that initially helps rid the endothelium of potentially harmful lipoprotein material (5). As will be discussed below, however, this cellular process eventually contributes to the progression and complications of atherosclerotic vascular disease.
Article
Specialized functions of macrophages have evolved to protect the body from infection. However, the same mechanisms that enable phagocytosis of pathogens and activation of leukocytes also permit the uptake of lipoproteins and release of reactive oxygen species and immune mediators that collectively contribute to atherosclerosis. New approaches to inhibit lipid accumulation in macrophage foam cells and reduce inflammatory responses may be of therapeutic value in preventing coronary artery disease.
Article
Previously, we demonstrated that activated inducible NO synthase (iNOS)-expressing foam cells in human carotid plaques often produce autofluorescent (per)oxidized lipids (ceroid). Here, we investigate whether intraplaque microvessels can provide foam cells with lipids and trigger macrophage activation. Microvessels (von Willebrand factor [vWf] immunoreactivity), activated macrophages (iNOS immunoreactivity), and ceroid were systematically mapped in longitudinal sections of 15 human carotid endarterectomy specimens. An unbiased hierarchical cluster analysis classified vascular regions into 2 categories. One type with normal vWf expression and without inflammatory cells was seen, and another type with cuboidal endothelial cells, perivascular vWf deposits, and iNOS and ceroid-containing foam cells was seen in 4 (27%) of 15 plaques. The perivascular foam cells frequently contained platelets (glycoprotein Ibalpha) and erythrocytes (hemoglobin, iron), pointing to microhemorrhage/thrombosis and subsequent phagocytosis. Similar lipid-containing cells, expressing both ceroid and iNOS, were generated in atherosclerosis-free settings by incubating murine J774 macrophages with platelets or oxidized erythrocytes and also in vivo in organizing thrombi in normocholesterolemic rabbits. Focal intraplaque microhemorrhages initiate platelet and erythrocyte phagocytosis, leading to iron deposition, macrophage activation, ceroid production, and foam cell formation. Neovascularization, besides supplying plaques with leukocytes and lipoproteins, can thus promote focal plaque expansion when microvessels become thrombotic or rupture prone.
Article
Intraplaque neovascularization and hemorrhage may facilitate plaque progression. We studied expression of basic fibroblast growth factor (bFGF), a potent angiogenic mediator, by mast cells (MCs) in human coronary plaques with increasing degrees of atherosclerosis. Normal and atherosclerotic coronary segments were collected from 30 autopsied subjects. Immunohistochemical methods were used to detect MCs, bFGF, and microvessels. Both adventitial and intimal MCs showed intracytoplasmic granular staining for bFGF, and bFGF-positive extracellular granules were observed close to the MCs. Increased numbers of bFGF-positive MCs were detected in neovascularized areas of plaques, and there was a positive correlation between numbers of bFGF-positive MCs and microvessels in both the intima and adventitia. In plaques, the highly neovascularized areas contained increased numbers of bFGF-positive MCs compared with the adjacent nonvascularized areas, where only few MCs were present. Importantly, the proportion of intimal MCs expressing bFGF increased with increasing severity of atherosclerosis. The present work reveals a novel source of bFGF in human coronary arteries, the intimal and adventitial MCs. The association of bFGF-positive MCs with microvessels and with the severity of atherosclerosis suggests that coronary MCs, by releasing bFGF, may play a role in angiogenesis and progression of coronary plaques.