[Show abstract][Hide abstract] ABSTRACT: Ozone exposure effect on free radical-catalyzed oxidation products of lipids, proteins and DNA in the plasma and urine of rats was studied as a continuation of the international Biomarker of Oxidative Stress Study (BOSS) sponsored by NIEHS/NIH. The goal was to identify a biomarker for ozone-induced oxidative stress and to assess whether inconsistent results often reported in the literature might be due to the limitations of the available methods for measuring the various types of oxidative products. The time and dose-dependent effects of ozone exposure on rat plasma lipid hydroperoxides, malondialdehyde, F2-isoprostanes, protein carbonyls, methionine oxidation, tyrosine- and phenylalanine oxidation products, as well as urinary malondialdehyde and F2-isoprostanes were investigated with various techniques. The criterion used to recognize a marker in the model of ozone exposure was that a significant effect could be identified and measured in a biological fluid seen at both doses at more than one time point. No statistically significant differences between the experimental and control groups at either ozone dose and time point studied could be identified in this study. Tissue samples were not included. Despite all the work accomplished in the BOSS study of ozone, no available product of oxidation in biological fluid has yet met the required criteria of being a biomarker. The current negative findings as a consequence of ozone exposure are of great importance, because they document that in complex systems, as the present in vivo experiment, the assays used may not provide meaningful data of ozone oxidation, especially in human studies.
Full-text · Article · Apr 2013 · Free Radical Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: The mitochondrial phospholipid cardiolipin (CL) is required for oxidative phosphorylation. Oxidation of CL results in the disruption of CL-cytochrome c binding and the induction of apoptosis. Large variations in the acyl-chain residues of CL have been reported, but evidence as to whether these variants exert distinct biological effects has been limited. We have studied the acyl-chain composition of CL in lymphocytes, and found marked differences between highly and slowly proliferating cells. In fast growing cells, we detected a decreased number of double bonds, and a higher amount of C16 acyl-chain residues in CL, compared with slower growing cells. However, fewer C18 acyl-chain residues were found in CL from fast growing cells compared with slower proliferating cells. Our results suggest a functional link between acyl-chain composition of CL and cell proliferation.
No preview · Article · Apr 2012 · Experimental Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: Hepatocytes of a primary cell culture that are exposed to high glucose, insulin, and linoleic (LA) acid concentration respond with lipid accumulation, oxidative stress up to cell death. Such alterations are typically found in patients with non-alcoholic fatty liver disease (NAFLD). We used this cellular model to study the effect of an ethanolic Gynostemma pentaphyllum (GP) extract in NAFLD. When hepatocytes were cultured in the presence of high insulin, glucose, and LA concentration the extract completely protected the cells from cell death. In parallel, the extract prevented accumulation of triglycerides (TGs) and cholesterol as well as oxidative stress. Our data further demonstrate that GP stimulates the production of nitric oxide (NO) in hepatocytes and affects the molecular composition of the mitochondrial phospholipid cardiolipin (CL). We conclude that GP is able to protect hepatocytes from cell death, lipid accumulation, and oxidative stress caused by diabetic-like metabolism and lipotoxicity. Therefore, GP could be beneficial for patients with diabetes mellitus and NAFLD.
Full-text · Article · Mar 2012 · Phytomedicine: international journal of phytotherapy and phytopharmacology
[Show abstract][Hide abstract] ABSTRACT: Lung preservation injury is still a major problem in lung transplantation. The aim of the current study was to evaluate the effects of a new preservation solution (Custodiol-N) for lung preservation.
Using an in vivo pig model, 7 lungs each were preserved for 24 hours after perfusion with: low-potassium dextran (LPD) solution as control (Group I); base solution of Custodiol-N without iron chelators (Group II); Custodiol-N (Group III); or Custodiol-N supplemented with dextran 40 (Group IV). Four animals received a sham operation. After left lung transplantation and contralateral lung exclusion, hemodynamics and blood gases were monitored for 6 hours; tissue samples were taken at the end of the experiments.
All animals survived the transplantation procedure. Base solution- and Custodiol-N-preserved lungs (Groups II and III) showed graft function similar to that of LPD-preserved lungs (Group I), showing a trend toward improved values. Custodiol-N with dextran (Group IV) led to a significant reduction of mean pulmonary arterial pressure (20 ± 2 vs 28 ± 3 mm Hg, p < 0.01) and pulmonary vascular resistance (410 ± 51 vs 588 ± 83 dyne/s/cm(5), p < 0.01), and oxygenation ratio was significantly higher (536 ± 52 vs 313 ± 107 mm Hg at 6 hours, p < 0.01) and PCO(2) values were significantly lower (51 ± 9 vs 77 ± 5 mm Hg at 6 hours, p < 0.01) at 6 hours compared with LPD (Group I). Custodiol-N (Groups II to IV) showed a trend toward a lower wet/dry ratio and reduced oxidative stress; in the presence of dextran (Group IV), the difference was again statistically significant, when compared with LPD (Group I).
Custodiol-N solution is a new alternative preservation solution for lung transplantation that offers significantly superior protection compared with LPD when dextran 40 is added.
No preview · Article · Mar 2012 · The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation
[Show abstract][Hide abstract] ABSTRACT: Atrial fibrillation induces ischaemic microcirculatory flow abnormalities in the ventricle, contributing to the risk for acute coronary syndromes. We evaluated the effect of dronedarone on ventricular perfusion during rapid atrial pacing (RAP).
Coronary and fractional flow reserve (CFR/FFR) were measured in the left anterior descending artery in 29 pigs. Six received RAP, six received RAP with dronedarone (RAP/D), seven received dronedarone alone, four received RAP with amiodarone (RAP/A), and six received neither (sham). In ventricular tissue, oxidative stress/ischaemia-related gene and protein expression was evaluated by RT-PCR and Western blotting; Isoprostanes were measured by GC-MS procedures.
CFR was decreased in the RAP group, compared with other groups. FFR was not different between groups. Effective refractory period was reduced in RAP compared with RAP/D. RAP-activated PKC phosphorylation tended to be decreased by dronedarone (P= 0.055) RAP induced NOX-1 and NOX-2 protein and the mRNA for hypoxia-inducible factor-1α (HIF-1α). Dronedarone reduced the pacing-dependent increase in the expression of NOX-2 protein and of HIF-1α mRNA. The oxidative stress marker, F(2)-isoprostane, was increased by RAP and this increase was attenuated by dronedarone. Other oxidative stress/ischaemia-related genes were induced by RAP compared with sham and were decreased by dronedarone treatment. In HL1 cells, dronedarone significantly inhibited the increased phosphorylation of PKCα after oxidative stress, with an almost significant effect (P= 0.059) on that after RAP.
Dronedarone abolished RAP-induced ventricular microcirculatory abnormalities by decreasing oxidative stress/ischaemia-related gene and protein expression in the ventricle.
Full-text · Article · Nov 2011 · British Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: An apoE4 genotype is an important risk factor for cardiovascular and other chronic diseases. The higher cardiovascular disease risk of apoE4 carriers as compared to the apoE3 genotype has been mainly attributed to the differences in blood lipids between the two genotype subgroups. Recently, a potential protective role of the transcription factor Nrf2 in cardiovascular disease prevention has been suggested. In this study, we show that Nrf2-dependent gene expression is affected by the apoE genotype. ApoE4 vs. apoE3 mice exhibited lower hepatic Nrf2 nuclear protein levels. Furthermore, mRNA and protein levels of Nrf2 target genes including glutathione-S-transferase, heme oxygenase-1 and NAD(P)H dehydrogenase, quinone 1 were significantly lower in apoE4 as compared to apoE3 mice. Lower hepatic mRNA levels of phase II enzymes, as observed in apoE4 vs. apoE3 mice, were accompanied by higher mRNA levels of phase I enzymes including Cyp26a1 and Cyp3a16. Furthermore, miRNA-144, miRNA-125b, and miRNA-29a involved in Nrf2 signaling, inflammation, and regulation of phase I enzyme gene expression were affected by the apoE genotype. We provide first evidence that Nrf2 is differentially regulated in response to the apoE genotype.
Full-text · Article · May 2011 · Journal of Molecular Medicine
[Show abstract][Hide abstract] ABSTRACT: Silt is sediment formed in estuaries and coastal regions along the seashore. It occurs along the entire North Sea coast and it is used in skin therapy. A single mud treatment induces normalization of stratum corneum hydration, transepidermal water loss, skin surface pH and sebum content (1). Mud therapy has been used successfully in several inflammatory skin diseases, such as psoriasis vulgaris (2), atopic dermatitis (3), acne vulgaris (4) and skin ulcers (5). The aim of this study was to elucidate possible anti-inflammatory effects of sea silt and sea salt-containing topical formulations on human skin in vivo. MATERIALS AND METHODS Different topical formulations containing sea silt essences and sea salt were tested: La mer MED Sea-salt cream ® (SSC, 7.5% sea silt, 10% sea salt), La mer MED sea salt lotion ® (SSL, 5% sea silt, 3.5% sea salt) and La mer MED fat cream ® (FC, 7.5% sea silt, 0.5% sea salt) (La mer, Cuxhaven, Germany). The silt extract in these formulations contains approximately 0.6% fatty acids (hexadecanoic acid, hexadecenoic acid, eico-sapentaenoic acid, octadecatrienoic acid and eicosatetraenoic acid) and 0.3% sulphur. All formulations (except for SSL) also contain 1% hydrolysed enteromorpha compressa extract and up to 5% hydrogenated vege table and palm kernel oil, which contains 82% saturated and 18% unsaturated fatty acids (i.e. oleic acid and linoleic acid). Twenty healthy volunteers aged 22–29 years were tested for tolerability and efficacy of sea silt formulations after approval by the local ethics committee. To test tolerability, ten healthy volunteers (age range 22–27 years) applied SSC to one-half of the body's skin surface (either left or right). In addition, five volunteers applied SSL to one side of the body and FC to the other half; the head and back were left as untreated control areas. After 2 h, skin areas on the left and right upper and lower arms, legs and back were measured for skin pH, transepidermal water loss (TEWL) (Derma Unit SSC3 and Tewameter TM300, both from Courage & Khazaka, Cologne, Germany) and skin colour (Chromameter CR-300, Minolta, Osaka, Japan) (6, 7). Measurements were repeated 0.5 h and 24 h after irradiation with a minimal erythematous dose (MED) of ultraviolet A (UVA) and ultraviolet B (UVB) (Waldmann UV 3003K, Herbert Waldmann GmbH & Co. KG, Villingen-Schwenningen, Germany). To test anti-inflammatory efficacy, well-defined areas of 9 cm 2 on the volar forearms of 10 healthy volunteers (age range 23–29 years) were exposed to UVB irradiation with twice the minimal erythematous dose (450–550 mJ/cm 2), followed by treatment with test formula-tions, diclofenac gel (DG, Voltaren Emulgel ® , Novartis AG, Nuremberg, Germany) or base cream (BC, a cream composed primarily of water, paraffin, citric acid, sodium cetearyl sulphate and cetearyl alcohol; Laticort base cream ® , Almirall Hermal, Reinbek, Germany) as a negative control. Two hours after ir-radiation, a thin layer of each formulation (approximately 500 mg) covering the entire test area was applied six times every 2 h and gently rubbed in for approximately 5 min until it was absorbed. Cut-off membranes of 20 kDa (CMA71 60/20 mem-branes, CMA microdialysis, Sweden) were placed in the dermis at 0.7–1.2 mm depth, as determined by 22 MHz ultrasound (taberna pro medicum, Luneburg, Germany) and cutaneous mi-crodialysis was started 24 h after UVB irradiation in irradiated and treated skin as well as in non-irradiated and untreated skin as described earlier (8). After flushing the membranes at a rate of 5 µl/min for 1 h for equilibration, membranes were perfused at a flow rate of 0.5 µl/min with sodium chloride (NaCl) 0.9%, using a CMA107 microdialysis pump (CMA Microdialysis, Solna, Sweden). Microdialysate samples were collected at 30-min intervals for 8 h and analysed for 5-and 8-iso-PGF 2α F 2 -isoprostanes and 9α,11α-PGF 2α and PGE 2 prostaglandins using sensitive gas chromatography-mass spectrometry and negative ion chemical ionization, as described previously (8). Since it has been demonstrated previously that the intensity of skin erythema correlates with levels of prostanoids (9), skin darkness and erythema of all test areas were measured at the end of microdialysis, 36 h after UVB irradiation in six volunteers (Chromameter CR-300, Minolta, Osaka, Japan). Mean values, standard errors (SE), significance (Wilcoxon signed-rank test) and area under the curve (AUC) were calculated with MedCalc 10 (MedCalc, Mariakerke, Belgium).
Full-text · Article · May 2011 · Acta Dermato-Venereologica
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to evaluate a new histidine-tryptophan-ketoglutarate (HTK)-based cold preservation solution in comparison with traditional HTK solution in a mouse cardiac transplant model and to assess the impact of chloride ions and of iron chelators.
After 24 h cold ischaemia, traditional HTK-preserved hearts survived up to 13 days (4.4 ± 1.7 days; n = 8)). Hearts stored in the new solution without iron chelators (N46) showed significantly prolonged survival up to 2 months (N46: 11.9 ± 8.7 days; P < 0.01; n = 7) and with iron chelators (DesfLK) up to 3 months (N46 DesfLK: 12.7 ± 13.7 days; n = 6). Re-beating time was significantly shorter with the new solution (HTK: 14.5 ± 5.9 min, N46: 9.2 ± 2.7 min, N46 DesfLK: 7.1 ± 3.7 min; P < 0.01). The new solution showed significantly decreased release of creatine kinase (HTK: 25998 ± 8471 U/L, N46: 13829 ± 7679 U/L, N46 DesfLK: 3093 ± 597 U/L; P < 0.01 and n = 7 each) and lactate dehydrogenase (HTK: 5391 ± 1062 U/L, N46: 3428 ± 1890 U/L, P < 0.05; N46 DesfLK: 682 ± 344 U/L, P < 0.01) and decreased histological evidence of injury. A chloride-poor variant of the new solution showed inferior graft survival.
The new solution markedly attenuates myocardial injury and yields better graft survival than traditional HTK solution. The presence of chloride ions is crucial for heart preservation. Some protective effects are obviously caused by iron chelators.
No preview · Article · Feb 2011 · European Heart Journal
[Show abstract][Hide abstract] ABSTRACT: Two different model systems that have been successfully used in our lab to induce oxidative stress are described. The first
is the so-called “iron/ascorbate” system, under appropriate conditions suitable to investigate oxidative stress mediated functional
impairment in isolated intact mitochondria in vitro and the second is UV irradiation, which can be used under experimental
and clinical conditions in vitro and in vivo to induce oxidative stress and inflammation in human skin. In the presence of
iron/ascorbate, the induction of lipid and protein oxidation was investigated in isolated mitochondria. Very early events
after treatment of freshly prepared, functionally intact mitochondria consist in the inhibition of active respiration mainly
due to an attack of the complex III activity of the respiratory chain. The membrane potential was sustained nearly unchanged
for a relatively long time and broke down abruptly at the end of the initiation phase of lipid peroxidation, when sufficient
energization and antioxidant protection of mitochondria could not be maintained. UVA irradiation in combination with photosensitizing
agents as 8-methoxypsoralen is successfully used as extracorporeal photoimmunotherapy (ECPI) in the treatment of several skin
diseases, such as cutaneous T-cell lymphoma and systemic scleroderma. We used this system to determine markers of oxidative
stress in plasma and cells from the buffy coat under experimental ECPI-relevant conditions and in patients during ECPI treatment.
Only moderate oxidative stress could be demonstrated by a decrease of the antioxidant defense and a dose-dependent augmentation
of hydroxyeicosatetraenoic acids and F2-isoprostanes as highly specific and sensitive biomarkers of lipid peroxidation and potential mediators of inflammatory and/or
photoimmunomodulatory effects of ECPI. UVB is known as a major skin carcinogen that mainly affects keratinocytes and induces
a complex cascade of inflammation, including reactive oxygen species. Effects of moderate UVB doses on the generation of biomarkers
of oxidative stress and inflammation in HaCaT keratinocytes in vitro and in microdialysates of human skin in vivo were studied.
F2-isoprostanes and prostaglandins were increased UVB dose-dependently, whereas functional integrity of HaCaTs was diminished.
As an adaptive response, protein levels of MnSOD were enhanced, but higher UVB doses lead to irreversible cell damage. The
microdialysis technique allowed for sensitively quantifying the markers of inflammation and oxidative stress and their kinetic
profile in vivo following UVB exposure.
KeywordsHaCaT keratinocytes-Human skin-Inflammation-Iron/ascorbate-Microdialysis-Mitochondria-Oxidative stress-UV irradiation
[Show abstract][Hide abstract] ABSTRACT: Excessive flux of free fatty acids (FFA) into the liver contributes to liver impairment in non-alcoholic fatty liver disease (NAFLD). It remains unclear how FFA contribute to impairment of hepatocytes. This study treated hepatocytes with linoleic acid and palmitate to investigate the early event triggering FFA-mediated impairment. It determined cell viability, content of nitrite/nitrate and triacylglycerides (TG), inducible nitric oxide synthase (iNOS) protein, oxidation of cardiolipin (CL) as well as formation of F(2)-isoprostanes in the presence of insulin and glucose. Linoleic acid caused significant decrease in cell viability. It is shown that palmitate caused induction of iNOS resulting in increased nitrite/nitrate concentration and slight increase in TG content. Linoleic acid led to a decrease in nitrite/nitrate concentration parallelled by massive TG accumulation in combination with increased oxidation of CL and increased F(2)-isoprostane levels. It is concluded that nitric oxide (NO) concentration regulates FFA-dependent TG accumulation and oxidative stress in rat hepatocytes.
Full-text · Article · Dec 2010 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: Lipid peroxidation products like malondialdehyde, 4-hydroxynonenal and F(2)-isoprostanes are widely used as markers of oxidative stress in vitro and in vivo. This study reports the results of a multi-laboratory validation study by COST Action B35 to assess inter-laboratory and intra-laboratory variation in the measurement of lipid peroxidation. Human plasma samples were exposed to UVA irradiation at different doses (0, 15 J, 20 J), encoded and shipped to 15 laboratories, where analyses of malondialdehyde, 4-hydroxynonenal and isoprostanes were conducted. The results demonstrate a low within-day-variation and a good correlation of results observed on two different days. However, high coefficients of variation were observed between the laboratories. Malondialdehyde determined by HPLC was found to be the most sensitive and reproducible lipid peroxidation product in plasma upon UVA treatment. It is concluded that measurement of malondialdehyde by HPLC has good analytical validity for inter-laboratory studies on lipid peroxidation in human EDTA-plasma samples, although it is acknowledged that this may not translate to biological validity.
Full-text · Article · Oct 2010 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.
Full-text · Article · Oct 2010 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: Lipid peroxidation is recognized to be an important contributor to many chronic diseases, especially those of an inflammatory pathology. In addition to their value as markers of oxidative damage, lipid peroxidation products have also been shown to have a wide variety of biological and cell signalling effects. In view of this, accurate and sensitive methods for the measurement of lipid peroxidation products are essential. Although some assays have been described for many years, improvements in protocols are continually being reported and, with recent advances in instrumentation and technology, highly specialized and informative techniques are increasingly used. This article gives an overview of the most currently used methods and then addresses the recent advances in some specific approaches. The focus is on analysis of oxysterols, F(2)-isoprostanes and oxidized phospholipids by gas chromatography or liquid chromatography mass spectrometry techniques and immunoassays for the detection of 4-hydroxynonenal.
Full-text · Article · Oct 2010 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate the effect of oxidative stress on mitochondrial phospholipids. In this context, this study investigated (i) the content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and cardiolipin (CL), (ii) the correlation of CL degradation with mitochondrial function and (iii) the correlation of CL degradation and CL oxidation. Oxidative stress induced by iron/ascorbate caused a dramatic decrease of these phospholipids, in which CL was the most sensitive phospholipid. Even moderate oxidative stress by hypoxia/reoxygenation caused a decrease in CL that was parallelled by a decrease in active respiration of isolated rat heart mitochondria. The relation between oxidative stress, CL degradation and CL oxidation was studied by in vitro treatment of commercially available CL with superoxide anion radicals and H2O2. The degradation of CL was mediated by H2O2 and required the presence of cytochrome c. Other peroxidases such as horse radish peroxidase and glutathione peroxidase had no effect. Cytochrome c in the presence of H2O2 caused CL oxidation. The data demonstrate that oxidative stress may cause degradation of phospholipids by oxidation, in particular CL; resulting in mitochondrial dysfunction.
No preview · Article · Feb 2010 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to determine hepatic paraoxonase 1 (PON1) status in response to apoE genotype and dietary quercetin supplementation in mice.
ApoE3 and apoE4 transgenic mice were fed semi-synthetic diets without (controls) and with quercetin (2 mg/g diet) for 6 weeks. Hepatic mRNA and protein levels of PON1 were significantly lower in apoE4 as compared to apoE3 mice. Feeding quercetin-enriched diets induced hepatic PON1 gene expression with a tendency for greater induction in apoE3 as compared to apoE4 mice. Furthermore, hepatic mRNA and protein levels of beta-glucuronidase and sulfatase, both enzymes centrally involved in the deconjugation of quercetin conjugates, were lower in apoE4 vs. apoE3 mice. PPARgamma (which partly controls PON1 gene expression) mRNA levels were lower in apoE4 vs. apoE3 mice.
We provide first evidence that PON1 is differentially regulated in response to apoE genotype.
[Show abstract][Hide abstract] ABSTRACT: Several studies have demonstrated that proteasome activity decreases whereas protein oxidation increases with aging in various tissues. However, no studies are available correlating both parameters directly comparing different tissues of one organism. Therefore, we determined whether there is an age-related change in proteasome activity and protein oxidation in heart, lung, liver, kidney and skeletal muscle samples of 6-, 10-, 18- and 26-month-old rats. There was a significant age-related increase in protein carbonyls at 18 and 26 months compared to young rats. Thereby, protein carbonyl formation was rather due to a general than a specific protein carbonylation as shown by immunblot studies. The highest increase in protein carbonyl formation was found in liver, lung and kidney samples. Proteasome activity decreased significantly with age in lung and liver samples. Proteasome activity in liver and lung decreased by factor five compared to young rats. Strong correlations between proteasome activity and protein oxidation were found in liver and lung, whereas in other tissues only a trend was found. These results demonstrate that the increase in protein oxidation and the decline in proteasome activity are correlating. Further studies are needed to determine the mechanisms which cause organ-specific aging-rates and their consequences.
No preview · Article · Sep 2009 · Mechanisms of ageing and development
[Show abstract][Hide abstract] ABSTRACT: In patients suffering from chronic lymphedema, increased blood plasma levels of oxysterols/ cholesterol oxidation products (COPs) were measured by means of GC/ FID. This confirms previous results on oxidative stress in chronic lymphedema. The most marked increases were found for β-epoxy, α-epoxy, 7-keto and α-triol derivatives. COPs and other LPO products are known to stimulate inflammatory reactions, fibrosis and tissue remodelling. Combined decongestive therapy (CDT) appears to contribute to a release of those toxic lipid oxidation products from lymphedematous tissue.
No preview · Article · Jun 2009 · Lymphologie in Forschung und Praxis
[Show abstract][Hide abstract] ABSTRACT: Patients with paroxysmal atrial fibrillation (AF) often present with typical angina pectoris and mildly elevated levels of cardiac troponin (non ST-segment elevation myocardial infarction) during an arrhythmic event. However, in a large proportion of these patients, significant coronary artery disease is excluded by coronary angiography. Here we explored the potential underlying mechanism of these events.
A total of 14 pigs were studied using a closed chest, rapid atrial pacing (RAP) model. In five pigs RAP was performed for 7 h (600 b.p.m.; n = 5), in five animals RAP was performed in the presence of angiotensin-II type-1-receptor (AT(1)-receptor) inhibitor irbesartan (RAP+Irb), and four pigs were instrumented without intervention (Sham). One-factor analysis of variance was performed to assess differences between and within the three groups. Simultaneous measurements of fractional flow reserve (FFR) and coronary flow reserve (CFR) before, during, and after RAP demonstrated unchanged FFR (P = 0.327), but decreased CFR during RAP (RAP: 67.7 +/- 7.2%, sham: 97.2 +/- 2.8%, RAP+Irb: 93.2 +/- 3.3; P = 0.0013) indicating abnormal left ventricular (LV) microcirculation. Alterations in microcirculatory blood flow were accompanied by elevated ventricular expression of NADPH oxidase subunit Nox2 (P = 0.039), lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1, P = 0.004), and F(2)-isoprostane levels (P = 0.008) suggesting RAP-related oxidative stress. Plasma concentrations of cardiac troponin-I (cTn-I) increased in RAP (RAP: 613.3 +/- 125.8 pmol/L vs. sham: 82.5 +/- 12.5 pmol/L; P = 0.013), whereas protein levels of eNOS and LV function remained unchanged. RAP+Irb prevented the increase of Nox2, LOX-1, and F(2)-isoprostanes, and abolished the impairment of microvascular blood flow.
Rapid atrial pacing induces AT(1)-receptor-mediated oxidative stress in LV myocardium that is accompanied by impaired microvascular blood flow and cTn-I release. These findings provide a plausible mechanism for the frequently observed cTn-I elevation accompanied with typical angina pectoris symptoms in patients with paroxysmal AF and normal (non-stenotic) coronary arteries.
Full-text · Article · Apr 2009 · European Heart Journal