[Show abstract][Hide abstract] ABSTRACT: The cytokine growth differentiation factor-15 (GDF-15), a member of the TGF beta superfamily, has recently been discovered to play an important role in cardiovascular diseases. It is mostly expressed in macrophages of atherosclerotic lesions, but its impact on advanced atherosclerosis is still unknown. This study was performed to evaluate the effects of GDF-15 in an established mouse model of advanced atherosclerosis.
Thirty-eight LDL receptor deficient mice received a lethal body radiation. Half of the group was transplanted with bone marrow of GDF-15 deficient mice. Nineteen mice were transplanted with bone marrow from wild-type controls. After 24 weeks on an atherogenic diet, animals were euthanized and sections of the aortic sinus were prepared. Lesion size and lesion composition, as well as macrophage content,were evaluated.
While demonstrating no difference in lesion size, LDL-receptor knockout mice transplanted with bone marrow from GDF-15 deficient mice showed enhanced macrophage accumulation and features of atherosclerotic plaque destabilization, such as thinning of fibrous caps. Immunostaining against intercellular adhesion molecule-1 further revealed an increased expression in mice receiving GDF-15-deficient bone marrow.
This is the first study that demonstrates a protective role of GDF-15 in advanced atherosclerosis and macrophage accumulation, possibly due to the reduced expression of adhesion molecules.
European journal of medical research. 06/2013; 18(1):19.
[Show abstract][Hide abstract] ABSTRACT: Psychosocial stress has been shown to be a contributing factor for development of atherosclerosis. Although the underlying mechanisms have not been entirely elucidated, it has previously been shown that the transcription factor NFκB is an important component of stress activated-signaling pathway. In this study, we aimed to decipher the mechanisms of stress-induced NFκB mediated gene expression, using in vitro and in vivo model of psychosocial stress. Induction of stress led to NFκB dependent expression of proinflammatory (tissue factor, ICAM-1) and protective genes (MnSOD) via p50, p65 or cRel. Selective inhibition of the different subunits and the respective kinases showed that inhibition of cRel leads to the reduction of atherosclerotic lesions in ApoE-/- mice via suppression of proinflammatory gene expression. This observation may therefore provide a possible explanation for ineffectiveness of antioxidant therapies and suggests that selective targeting of cRel activation may provide a novel approach for the treatment of stress-related inflammatory vascular disease.
[Show abstract][Hide abstract] ABSTRACT: Atherosclerosis is a chronic inflammatory process. Poly(ADP-ribose) polymerase-1 (PARP), a nuclear enzyme linked to DNA repair, has been shown to be involved in atherogenesis; however, the effects on dendritic cells, T cells and serum auto-antibody levels are not fully understood.
Male Apoe-/- mice on a western diet were treated with the PARP inhibitor INO-1001 (n = 15), while the control group (n = 15) received 5% glucose solution for 10 weeks.
Inhibition of PARP markedly reduced atherosclerotic lesion development (p = 0.001). Immunohistochemistry and mRNA analysis revealed a reduced inflammatory compound inside the lesion. Focusing on dendritic cells, INO-1001 reduced number of cells (p = 0.04), grade of activation, represented by Il12 (p = 0.04) and Cd83 (p = 0.03), and grade of attraction, represented by Mip3α (p = 0.02) in the plaque. Furthermore, INO-1001 decreased number of T lymphocyte (p = 0.003) in the lesion and grade of activation after stimulation with oxLDL in vitro. Moreover, serum IgM antibody levels to oxLDL were significantly lower in INO-1001 treated mice (p = 0.03).
Functional blockade of PARP by INO-1001 reduces atherosclerotic lesion development. The anti-atherogenic effect is beside already known mechanisms also moderated due to modulation of DC and T cell invasion and activation, DC attraction as well as IgM antibody levels to oxLDL.
European journal of medical research 08/2011; 16(8):367-74. · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The multiligand receptor for advanced glycation end products (RAGE) of the immunoglobulin superfamily is expressed on multiple cell types implicated in the inflammatory response in atherosclerosis. We sought to determine the role of bone marrow-derived RAGE in different stages of atherosclerotic development in apolipoprotein E-deficient mice (apoE(-/-)).
Seven- and 23-week-old apoE(-/-) mice (n = 40) were lethally irradiated and given bone marrow from RAGE null (RAGE(-/-)/apoE(-/-)) or RAGE-bearing (RAGE(+/+)/apoE(-/-)) mice to apoE(-/-) mice to generate double knockout bone marrow chimera (RAGE(-/-)/apoE(-/-bmc) and RAGE(+/+)/apoE(-/-bmc)-, respectively). After 16 weeks on a standard chow diet, mice were sacrificed and atherosclerotic lesion formation was evaluated.
Plaques in the aortic root of the young mice showed no significant difference in maximum plaque size (217,470 ± 17,480 μm(2) for the RAGE(-/-) /apoE(-/-bmc) mice compared to 244,764 ± 45,840 μm(2)), whereas lesions in the brachiocephalic arteries of the older RAGE(-/-)/apoE(-/-bmc) mice had significantly smaller lesions (94,049 ± 13,0844 μm(2) vs. 145,570 ± 11,488 μm(2), P < 0.05) as well as reduced average necrotic core area (48,600 ± 9220 μm(2) compared to 89,502 ± 10,032 μm(2), P < 0.05) when compared to RAGE(+/+)/apoE(-/-bmc) mice. Reduced plaque size and more stable plaque morphology was associated with significant reduced expression of VCAM-1, ICAM-1 and MCP-1. Accumulation of the RAGE ligand HMGB-1 was also significantly reduced within the lesions of RAGE(-/-)/apoE(-/-bmc) mice.
This study demonstrates that bone marrow-derived RAGE is an important factor in the progression of atherosclerotic plaques.
European Journal of Clinical Investigation 03/2011; 41(11):1164-71. · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Inflammation contributes to atherosclerotic plaque initiation and progression. Recent studies suggest that nicotinic acid has anti-inflammatory effects independent of its lipid-modifying capabilities. We assessed the hypothesis that administration of nicotinic acid to older apolipoprotein E (apoE)-deficient mice with established lesions will reduce lesion size and plaque inflammation independent of its lipid-modifying effects. Therefore nicotinic acid was administered to 27-week-old apo E-deficient mice exhibiting advanced atherosclerotic lesions within the innominate artery. After 27 weeks of treatment both animal groups had no significant changes in plasma lipid levels. Mice treated with nicotinic acid (n = 22) demonstrated a 30% reduction in total lesion area compared with controls (n = 20). Furthermore, they revealed a more stable plaque composition with an increase in fibrous cap thickness and a reduction in the size of the necrotic core. Immunohistochemistry demonstrated a reduced accumulation of macrophages and a reduced expression of vascular cell adhesion molecule-1 and tissue factor. Additionally, administration of nicotinic acid significantly reduced tumor necrosis factor alpha expression in the thoracic aorta as demonstrated by real-time PCR. In conclusion, these data suggest that long-term administration of nicotinic acid has anti-atherogenic and anti-inflammatory properties on advanced atherosclerotic lesions, which are independent of its lipid-modifying actions.
Journal of cardiovascular pharmacology 01/2011; 57(4):447-54. · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A chronic (auto)immune response is the critical mechanism in atherosclerosis. Interleukin-17A is a pivotal effector cytokine, which modulates immune cell trafficking and initiates inflammation in (auto)immune and infectious diseases. However, expression of IL-17A in the context of human atherosclerosis has hardly been explored. Carotid artery plaques were collected from 79 patients undergoing endarterectomy. Patients were grouped according to their symptomatic status (TIA, stroke), plaque morphology and medication. Quantitative RT-PCR was used to analyze tissue inflammation and immunohistochemistry to assess cellular source of IL-17A expression and lesion morphology. Carotid plaques from patients with ischemic symptoms were characterized by a highly activated inflammatory milieu including accumulation of T cells (p = 0.04) and expression of IL-6 and VCAM1 (p = 0.02, 0.01). Expression of IL-17A and its positive regulators IL-21 and IL-23 was present in atherosclerotic lesions, significantly upregulated in atheromas of symptomatic patients (p = 0.005, 0.004, 0.03), and expression of IL-17A and IL-21 showed a strong correlation (p = 0.002, r = 0.52). The cellular sources of lesional IL-17A expression are T cells, macrophages, B cells and plasma cells. Vulnerable/ruptured (complicated) plaques were significantly associated with IL-17A expression levels (p = 0.003). In addition, IL-17A showed a marked negative correlation with the potent anti-inflammatory/atheroprotective cytokine IL-10 (p = 0.0006, r = -0.46). Furthermore, treatment with a HMG-CoA reductase inhibitor or acetylsalicylic acid showed reduced levels of IL-21, IL-23 and VCAM1 (all p < 0.05), but did not influence IL-17A. The association of IL-17A with ischemic symptoms and vulnerable plaque characteristics suggests that the pro-inflammatory cytokine IL-17A may contribute to atherosclerosis und plaque instability.
Archiv für Kreislaufforschung 01/2011; 106(1):125-34. · 7.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Thrombin not only plays a central role in thrombus formation and platelet activation, but also in induction of inflammatory processes. Activated factor X (FXa) is traditionally known as an important player in the coagulation cascade responsible for thrombin generation. We assessed the hypothesis that rivaroxaban, a direct FXa inhibitor, attenuates plaque progression and promotes stability of advanced atherosclerotic lesions in an in vivo model.
Rivaroxaban (1 or 5 mg/kg body weight/day) or standard chow diet was administered for 26 weeks to apolipoprotein E-deficient mice (n = 20 per group) with already established atherosclerotic lesions. There was a nonsignificant reduction of lesion progression in the high-concentration group, compared to control mice. FXa inhibition with 5 mg Rivaroxaban/kg/day resulted in increased thickness of the protective fibrous caps (12.3 ± 3.8 μm versus 10.1 ± 2.7 μm; P < .05), as well as in fewer medial erosions and fewer lateral xanthomas, indicating plaque stabilizing properties. Real time-PCR from thoracic aortas revealed that rivaroxaban (5 mg/kg/day) treatment reduced mRNA expression of inflammatory mediators, such of IL-6, TNF-α, MCP-1, and Egr-1 (P < .05).
Chronic administration of rivaroxaban does not affect lesion progression but downregulates expression of inflammatory mediators and promotes lesion stability in apolipoprotein E-deficient mice.
Mediators of Inflammation 01/2011; 2011:432080. · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Processes of restenosis, following arterial injury, are complex involving different cell types producing various cytokines and enzymes. Among those enzymes, smooth muscle cell-derived matrix metalloproteinases (MMPs) are thought to take part in cell migration, degrading of extracellular matrix, and neointima formation. MMP-9, also known as gelatinase B, is expressed immediately after vascular injury and its expression and activity can be inhibited by statins. Using an established in vivo model of vascular injury, we investigated the effect of the HMG-CoA reductase inhibitor rosuvastatin on MMP-9 expression and neointima formation.
14-week old male Sprague Dawley rats underwent balloon injury of the common carotid artery. Half of the animals received rosuvastatin (20 mg/kg body weight/day) via oral gavage, beginning 3 days prior to injury. Gelatinase activity and neointima formation were analyzed 3 days and 14 days after balloon injury, respectively. 14 days after vascular injury, proliferative activity was assessed by staining for Ki67.
After 14 days, animals in the rosuvastatin group showed a decrease in total neointima formation (0.194±0.01 mm2 versus 0.124±0.02 mm2, p<0.05) as well as a reduced intima/media ratio (1.26±0.1 versus 0.75±0.09, p<0.05). Balloon injury resulted in increased activity of MMP-9 3 days after intervention for both rosuvastatin treated animals and controls with no significant difference observed between the groups. There was a trend towards a reduction in the number of Ki67-positive cells 14 days after injury.
Rosuvastatin attenuates neointima formation without affecting early MMP-9 activity in a rat model of vascular injury.
European journal of medical research 11/2010; 15(11):461-7. · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Early growth response gene-1 (Egr-1) regulates the expression of genes important to cardiovascular disease. Within atherosclerotic lesions, Egr-1 is expressed in smooth muscle cells, endothelial cells, and macrophages. Since macrophages play a pivotal role in atherosclerotic lesion initiation and progression, this study investigated the effects of Egr-1 deficiency within bone marrow-derived cells on the development of atherosclerosis in a hyperlipidaemic mouse model.
Bone marrow from Egr-1-deficient mice and wild-type controls was transplanted into lethally irradiated LDL receptor null mice. After 26 weeks on a high fat diet, atherosclerotic lesion size within the aortic sinus of recipients was evaluated. Mice receiving Egr-1-deficient bone marrow had significantly decreased lesion size compared with controls. Lesions of these mice contained fewer macrophages and had reduced expression of vascular cell adhesion molecule-1 (VCAM-1), tissue factor, as well as transforming growth factor receptor type II, which are target genes of Egr-1. These results were validated by in vitro analysis of Egr-1-deficient peritoneal macrophages which, after lipopolysaccharide stimulation, had decreased VCAM-1 and tissue factor mRNA expression compared with wild-type controls.
This study demonstrates that bone marrow-derived Egr-1 promotes macrophage accumulation, atherosclerotic lesion development, and lesion complexity.
Cardiovascular research 05/2010; 86(2):321-9. · 5.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Even among health care professionals, resuscitation performance has been shown to be poor. So far, it remains unclear whether cardiac arrest staff with frequent practice in resuscitation requires training to adapt to the new International Liaison Committee on Resuscitation (ILCOR) guidelines of 2005. This study evaluated the need for basic life support training in nurses with emergency experience.
Nurses (N = 24) recruited from an intensive care unit self-assessed their resuscitation skills and performed a cardiac arrest scenario using a manikin. After a theoretical instruction and hands-on training followed by feedback, participants once again performed a resuscitation scenario in addition to completing posttraining self-assessments. Participating nurses considered resuscitation skills training--in particular in adapting to the new ILCOR guidelines of 2005--to be important. Pretraining data revealed performance deficits even in this sample of emergency-experienced nursing staff. Training resulted in significant improvement in ventilation volume (P < .001), rate of compressions with correct depth (P < .031) and full release (P < .001), and a reduction in total hands-off time (P < .050). Objective data were mirrored in participants' self-assessed competencies.
Results suggest that basic life support training based on the ILCOR guidelines of 2005 is necessary even in nurses with emergency experience. Training followed by the application of a feedback algorithm seems to improve short-term resuscitation performance and is well accepted by experienced nurses who work on an intensive care unit and who also comprise the inner-hospital cardiac arrest team.
The American journal of emergency medicine 05/2010; 28(4):477-84. · 1.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Chinese extract Rhizoma coptidis is well known for its anti-inflammatory, antioxidative, antiviral, and antimicrobial activity. The exact mechanisms of action are not fully understood.
We examined the effect of the extract and its main compound, berberine, on LPS-induced inflammatory activity in a murine macrophage cell line. RAW 264.7 cells were stimulated with LPS and incubated with either Rhizoma coptidis extract or berberine. Activation of AP-1 and NFkappaB was analyzed in nuclear extracts, secretion of MCP-1/CCL2 was measured in supernatants.
Incubation with Rhizoma coptidis and berberine strongly inhibited LPS-induced monocyte chemoattractant protein (MCP)-1 production in RAW cells. Activation of the transcription factors AP-1 and NFkappaB was inhibited by Rhizoma coptidis in a dose- and time-dependent fashion.
Rhizoma coptidis extract inhibits LPS-induced MCP-1/CCL2 production in vitro via an AP-1 and NFkappaB-dependent pathway. Anti-inflammatory action of the extract is mediated mainly by its alkaloid compound berberine.
Mediators of Inflammation 01/2010; 2010:194896. · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction. The Chinese extract Rhizoma coptidis is well known for its anti-inflammatory, antioxidative, antiviral, and antimicrobial activity. The exact mechanisms of action are not fully understood. Methods. We examined the effect of the extract and its main compound, berberine, on LPS-induced inflammatory activity in a murine macrophage cell line. RAW 264.7 cells were stimulated with LPS and incubated with either Rhizoma coptidis extract or berberine. Activation of AP-1 and NFκB was analyzed in nuclear extracts, secretion of MCP-1/CCL2 was measured in supernatants. Results. Incubation with Rhizoma coptidis and berberine strongly inhibited LPS-induced monocyte chemoattractant protein (MCP)-1 production in RAW cells. Activation of the transcription factors AP-1 and NFκB was inhibited by Rhizoma coptidis in a dose- and time-dependent fashion. Conclusions. Rhizoma coptidis extract inhibits LPS-induced MCP-1/CCL2 production in vitro via an AP-1 and NFκB-dependent pathway. Anti-inflammatory action of the extract is mediated mainly by its alkaloid compound berberine.
Mediators of Inflammation 01/2010; 2010. · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The extent of adverse myocardial remodeling contributes essentially to the prognosis after myocardial infarction (MI). In this study we investigated whether inhibition of "mammalian target of rapamycin" (mTOR) attenuates left ventricular (LV) remodeling after MI.
Therapeutic strategies to inhibit remodeling are currently limited to inhibition of neurohumoral activation. The mTOR-dependent signaling mechanisms are centrally involved in remodeling processes and provide new therapeutic opportunities.
Everolimus (RAD) treatment was initiated on the day after or 3 days after induction of myocardial infarction (MI) in rats.
After 28 days, RAD-treated animals had reduced post-MI remodeling, with improved LV function and smaller LV end-diastolic diameters (8.9 + or - 0.3 mm vs. 11.4 + or - 0.2 mm, p < 0.05), end-diastolic volumes (304 + or - 30 microl vs. 414 + or - 16 microl, p < 0.05), and cardiac myocyte size (-40% vs. vehicle, p < 0.05). Infarct size was significantly reduced compared with vehicle-treated animals. The mTOR inhibition increased autophagy and concomitantly decreased proteasome activity in the border zone of the infarcted myocardium. Measurement of autophagic flux demonstrated that RAD did not decrease autophagosome clearance. When RAD treatment was initiated 3 days after MI, adverse remodeling was still attenuated and increased autophagy was still present. Sustained improvement of LV function was observed 3 months after MI, even when RAD treatment was discontinued after 1 month.
Inhibition of mTOR is a potential therapeutic strategy to limit infarct size and to attenuate adverse LV remodeling after MI.
Journal of the American College of Cardiology 12/2009; 54(25):2435-46. · 14.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The importance of an (auto)immune response in atherogenesis is becoming increasingly well understood. IL-17A-expressing T cells modulate immune cell trafficking, initiating inflammation and cytokine production in (auto)immune diseases. In human carotid artery plaques, we previously showed the presence of IL-17A-producing T cells and IL-23; however, IL-17A effects on atherogenesis have not been studied. Aortic root sections from 8-wk-old apolipoprotein E-deficient mice fed a standard chow diet were examined after 12 wk for lesion area, plaque composition, cellular infiltration, cytokine expression, and apoptosis. The treatment group (n = 15) received anti-IL-17A Ab and the controls (n = 10) received irrelevant Abs. Inhibition of IL-17A markedly reduced atherosclerotic lesion area (p < 0.001), maximal stenosis (p < 0.001), and vulnerability of the lesion. IL-17A mAb-treated mice showed reduced cellular infiltration, down-regulation of activation markers on endothelium and immune cells (e.g., VCAM-1), and reduced cytokine/chemokine secretion (e.g., IL6, TNFalpha, CCL5). To investigate possible mechanisms, different atherogenic cell types (e.g., macrophages, dendritic cells, HUVECs, vascular smooth muscle cells) were stimulated with IL-17A in addition to TNF-alpha, IFN-gamma, or LPS to induce cellular activation or apoptosis in vitro. Stimulation with IL-17A induced proinflammatory changes in several atherogenic cell types and apoptotic cell death in murine cells. Functional blockade of IL-17A reduces atherosclerotic lesion development and decreases plaque vulnerability, cellular infiltration, and tissue activation in apolipoprotein E-deficient mice. The present data support a pathogenic role of IL-17A in the development of atherosclerosis by way of its widespread proinflammatory and proapoptotic effects on atherogenic cells.
The Journal of Immunology 12/2009; 183(12):8167-75. · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Clinical studies failed to provide clear evidence for a proatherogenic role of hypercoagulability. This is in contrast to the well-established detrimental role of hypercoagulability and thrombin during acute atherosclerotic complications. These seemingly opposing data suggest that hypercoagulability might exert both proatherogenic and antiatherogenic effects. We therefore investigated whether hypercoagulability mediates a beneficial effect during de novo atherogenesis.
De novo atherogenesis was evaluated in 2 mouse models with hyperlipidemia and genetically imposed hypercoagulability (TM(Pro/Pro)ApoE(-/-) and FVL(Q/Q)ApoE(-/-) mice). In both mouse models, hypercoagulability resulted in larger plaques, but vascular stenosis was not enhanced secondary to positive vascular remodeling. Importantly, plaque stability was increased in hypercoagulable mice with less necrotic cores, more extracellular matrix, more smooth muscle cells, and fewer macrophages. Long-term anticoagulation reversed these changes. The reduced frequency of intraplaque macrophages in hypercoagulable mice is explained by an inhibitory role of thrombin and protease-activated receptor-1 on monocyte transendothelial migration in vitro. This is dependent on phospholipase-Cbeta, phosphoinositide 3-kinase, and nitric oxide signaling in monocytes but not in endothelial cells.
Here, we show a new function of the coagulation system, averting stenosis and plaque destabilization during de novo atherogenesis. The in vivo and in vitro data establish that thrombin-induced signaling via protease-activated receptor-1, phospholipase-Cbeta, phosphoinositide 3-kinase, and nitric oxide in monocytes impairs monocyte transendothelial migration. This likely accounts for the reduced macrophage accumulation in plaques of hypercoagulable mice. Thus, in contrast to their role in unstable plaques or after vascular injury, hypercoagulability and thrombin convey a protective effect during de novo atherogenesis.
[Show abstract][Hide abstract] ABSTRACT: Proinflammatory cytokines, including TNF family members, have been shown to play a critical role in cardiac remodeling. FGF-inducible 14-kDa protein (Fn14, TNFrsf12a or TWEAKR) is the smallest member of the TNF-receptor family. Currently, little is known about the functional role of Fn14 and its only known ligand TNF-like weak inducer of apoptosis (TWEAK) in the heart. We therefore evaluated the expression and regulation of Fn14 in cardiomyocytes and in experimental myocardial infarction. In order to study the regulation of Fn14, myocardial infarction was induced in CD-1 mice and neonatal rat cardiomyocytes were used for in vitro studies. TWEAK and Fn14 were markedly upregulated in the remodeling myocardium after experimental myocardial infarction in vivo. Likewise, fibroblast growth factor 1, norepinephrine and angiotensin II as well as mechanical stretch were able to strongly induce Fn14 expression in cardiomyocytes. This induction is mediated via the Rho/ROCK pathway, since the known inhibitors C3 exoenzyme for RhoA and Y27632 for ROCK prevented the upregulation of Fn14 in cardiomyocytes. Consistently, pretreatment of cardiomyocytes with siRNA against Rho A and ROCK also abolished Fn14 induction. Moreover, stimulation of cardiomyocytes with TWEAK promoted nuclear translocation of NF-kappaB and subsequent induction of NF-kappaB dependent genes such as RANTES and MCP-1. Conversely, when cells were pretreated with siRNA against Fn14, NF-kappaB activation by TWEAK was inhibited. We here provide the first evidence of a stress-induced regulation of the TWEAK/Fn14 axis in cardiomyocytes implying a role of the TWEAK/Fn14 pathway in cardiac remodeling.
Archiv für Kreislaufforschung 08/2009; 105(2):301-13. · 7.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: LIGHT (TNFSF 14) belongs to the tumor necrosis factor superfamily and is expressed by activated T cells as well as various types of antigen presenting cells. LIGHT binds to its cellular receptors TR2 and LTbetaR and has a co-stimulatory role in T cell activation. Here, we compared the relative expression of LIGHT in different immune cells and the biological activity of immune cell-derived LIGHT on endothelial cells.
Surface expression of LIGHT and mRNA production by PBMC and isolated T cells (CD4+ or CD8+) significantly increased after stimulation with PMA (Phorbolester-12- Myristat-13-Acetat)+ionomycin. No LIGHT expression on PMA stimulated monocytes or monocytic-like THP-1 cells could be detected; differentiation of monocytes and THP-1 cells into macrophages, however, resulted in up-regulation of LIGHT. Supernatants of stimulated T cells contained higher concentrations of soluble LIGHT than macrophage supernatants normalized to cell numbers; release of soluble LIGHT was found to be dependent on metalloproteinase activity. Size determination of released soluble LIGHT by size exclusion chromatography revealed a molecular mass of approximately 60 kDa, suggesting a trimeric form. Released soluble LIGHT induced expression of proinflammatory antigens ICAM-1, tissue factor and IL-8 in human endothelial cells and caused apoptosis of IFN-g pretreated endothelial cells. Soluble LIGHT was detected at low levels in sera of healthy controls and was significantly enhanced in sera of patients with chronic hepatitis C and rheumatoid arthritis (24.93+/-9.41 vs. 129.53+/-49.14 and 172.13+/-77.64; p<0.0005).
These findings suggest that among immune cells activated T lymphocytes are the main source of soluble LIGHT with released amounts of soluble LIGHT markedly higher compared to platelets. Immune cell-derived membrane-bound and soluble trimeric LIGHT is biologically active, inducing proinflammatory changes in endothelial cells. Enhanced plasma levels of soluble LIGHT in patients with chronic infections suggest a role of LIGHT in systemic inflammatory activation.
European journal of medical research 05/2009; 14(4):147-56. · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The treatment of endocarditis remains a challenge for physicians, even in times of modern antibiotic treatment. Depending on its cause, endocarditis can either be of infectious or non-infectious origin. Infective endocarditis is caused by bacterial (or fungal) pathogens, and the clinical course is critically dependent on the virulence factors of the specific microorganisms involved. Therefore, the clinical type of endocarditis can be divided into an acute and more aggressive form and a subacute form (endocarditis lenta). Much of our knowledge regarding the pathogenesis of infective endocarditis is based on studies of the virulence of Staphylococcus aureus, which has become the most frequent cause of infective endocarditis nowadays. However, independently of the underlying cause of endocarditis (infectious or noninfectious), the pathogenesis involves the damage and disturbance of endothelial function and the formation of associated "vegetation". Surprisingly little is known about the specific role of the endothelium in the pathogenesis of endocarditis. This review will thus give insights into current knowledge of the pathogenesis of endocarditis with a focus on the role of the endothelium.
Cell and Tissue Research 12/2008; 335(1):153-63. · 3.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Macrophage-derived products are known to play a crucial role during atherogenesis and vascular calcification. Glucocorticoids (GC) are important modulators of immune cell functions, but their specific effects on macrophages behavior during plaque formation are not defined. The present study was therefore designed to investigate the effects of macrophage-specific deletion of the glucocorticoid receptor (GR(LysMCre)) on atherogenesis and vascular calcification in a hyperlipidemic mouse-model.
Bone marrow was isolated from GR(LysMCre) mice and wild-type controls (GR(flox)) and subsequently transplanted into lethally irradiated LDL-receptor-deficient mice. Animals were fed a Western-type diet for 15 or 24 weeks, and atherosclerotic lesions within the aortic sinus were evaluated. At both time points, no significant difference in serum lipid and corticosterone concentrations, atherosclerotic lesion size and macrophage-content within the lesions could be observed. However, GR(LysMCre) mice showed less calcification as well as a significant reduction of RANKL, BMP2, and Msx2 expression within the vasculature. In vitro studies using conditioned media from macrophages which had been stimulated with dexamethasone demonstrated a dose-dependent increase in calcium deposition by vascular smooth muscle cells.
This study demonstrates that macrophage-specific glucocorticoid receptor inactivation reduces vascular calcification without affecting atherosclerotic lesion size in LDL receptor-deficient mice.
[Show abstract][Hide abstract] ABSTRACT: Hyperhomocysteinemia is an independent risk factor for atherosclerosis. Uptake of homocysteine induces oxidative stress in macrophages. Antioxidant response elements (AREs) are regulatory elements within promoters of genes, which protect cells against oxidative stress. The current study investigated whether homocysteine induces transcription of glutamate-cysteine ligase (Gcl), via ARE driven gene expression in mouse macrophages. Gcl is the rate-limiting enzyme in the synthesis of glutathione, an important endogenous antioxidant. Gcl is heterodimeric and the genes encoding the subunits of Gcl contain several AREs within their 5'-promoter regions. Treatment of mouse macrophages with d-/l-homocysteine (50microM) induced depletion of intracellular glutathione and a compensatory increase in Gcl activity. Electro mobiliy shift assays demonstrated increased binding of nuclear proteins to ARE-containing oligonucleotides. Real-time RT-PCR revealed increased mRNA-expression of the catalytic subunit of Gcl (Gclc) after treatment with homocysteine, and this occurred via increased transcription as demonstrated with luciferase promoter reporter constructs for Gclc. Additional site directed mutagenesis demonstrated that ARE4 plays a direct role in mediating induction of Gclc by homocysteine. Supershift analysis and Western blotting revealed that Nrf2 signalling is critical in homocysteine-induced activation of ARE4. Inhibition of MAP kinase activity reduced binding of nuclear proteins to the AREs, nuclear expression of Nrf2 and mRNA expression of Gclc. Western blotting demonstrated phosporylation of ERK1/2 in homocysteine treated macrophages. These data suggest that ARE-driven gene expression of Gclc via a MEK/Nrf2 pathway could help to protect macrophages from oxidative stress due to hyperhomocysteinemia.