SummaryPrevious study demonstrated that platelets undergoing anoxia-reoxygenation generate superoxide anion (O2
−) and hydroxyl radical (OH°) which in turn contribute to activate arachidonic acid (AA) metabolism. However it has not been clarified if oxygen free radicals (OFRs) are also generated when platelets are aggregated by common agonists. We used two probes, i.e. lucigenin and salicylic acid (SA), to measure platelet release of O2
− and OH°, respectively. Among the agonists used, such as ADP, thrombin and collagen, the release of O2
− and OH° was observed mainly when platelets were stimulated with collagen. Such release was inhibited in platelets pre-treated by aspirin suggesting that AA metabolism was the main source of O2
− and OH° formation. To further analyze this relationship, O2 and OH° formation was measured if other oxidant species, namely O2
− and OH°, contribute to the during AA-stimulated platelet aggregation (PA); we observed that O − and OH° release were dependent upon AA concentration. Furthermore, we found that the incubation of platelets with AACOCF3, a potent inhibitor of cytosolic phospholipase A2, inhibited collagen-induced platelet O− and OH° release. The incubation of platelets with salicylic acid or ascorbic acid, which blunt OH° and O2
− respectively, inhibited both collagen-induced platelet aggregation and AA-release. This study demonstrated that collagen-induced platelet aggregation is associated with O2
− and OH° formation, which is dependent upon AA release and analyzed if O2
− and OH° are released during aggregation induced by metabolism.
Objective-Oxidative stress is believed to play a pivotal role in the initiation and progression of atherosclerosis. We analyzed whether vitamin E supplementation influences oxidative stress in plasma and atherosclerotic plaques of patients with severe atherosclerosis. Methods and Results-In 16 patients who were candidates for carotid endarterectomy and in 32 age-and sex-matched controls, plasma levels of 7-hydroxycholesterol, 7-ketocholesterol, cholesterol, and vitamin E were measured. Patients were randomly allocated to standard treatment with or without 900 mg/d vitamin E. After 6 weeks of treatment, the reported variables were measured in plasma and plaques. The plasma vitamin E/cholesterol ratio was significantly lower in patients than in controls (3.05Ϯ0.6 versus 6.3Ϯ1.7 mol/mmol cholesterol, PϽ0.001). Plasma 7-hydroxycholesterol was significantly higher in patients than in controls (5.0Ϯ1.04 versus 4.4Ϯ0.6 ng/mL, PϽ0.05). Patients who were given vitamin E supplementation showed a significant increase of plasma vitamin E with concomitant decrease of 7-hydroxycholesterol. Conversely, no treatment dependence was observed in oxysterol or vitamin E content of plaques. Conclusions-An imbalance between oxidative stress and antioxidant status is present in patients with advanced atherosclerosis. Vitamin E supplementation improves this imbalance in plasma but not in plaques. Key Words: atherosclerosis Ⅲ oxidative stress Ⅲ vitamin E Ⅲ oxysterols Ⅲ carotid plaques T here is considerable interest in the role of oxidative stress in several disease settings, including atherosclerosis. 1,2 A large number of clinical trials with antioxidants, mainly vitamin E, in patients with or at risk for cardiovascular disease was performed, but in most cases no effect of vitamin E on the incidence of cardiovascular events was noted. 3 Consequently, the usefulness of antioxidants in cardiovascular diseases has been a matter for debate in the scientific community. 4 Several hypotheses have been put forward to explain the discordant results of interventional trials based on antioxidant treatment, including the compliance, design of the trials, and dosage and source of vitamin E used. 5,6 An important argument of debate is the striking difference of vitamin E effects in experimental and clinical studies. In contrast to clinical trials with antioxidants, there is compelling evidence in favor of the antiatherosclerotic effect of vitamin E in experimental models of atherosclerosis. 7 One possible explanation for this discrepancy is that in experimental models, vitamin E treatment has been able to affect the early stage of atherosclerosis, whereas clinical trials enrolled patients with advanced atherosclerosis who are not sensitive to antioxidant treatment. The demonstration that antioxidants are ineffective in advanced human atherosclerosis could help to interpret the negative results of clinical trials and also to modify the design of future trials. To specifically address this issue, we studied candidates for carotid endarterectomy, be...
Oxidative stress is implicated in the pathogenesis of hepatic ischemia-reperfusion injury, a major determinant of initial poor graft function (IPGF) after orthotopic liver transplantation (OLT). We prospectively investigated the association between the recipient plasma preoperative oxidative stress and the occurrence of IPGF after deceased-donor OLT and indirectly studied the sourcehepatic or extra-hepatic-of systemic oxidative stress in vivo in cirrhosis. We used a recently developed specific and sensitive mass spectrometry assay to measure 7-hydroxycholesterol and 7-ketocholesterol (oxysterols), markers of oxidative stress, in biological matrices. At univariate analysis, preoperative recipient 7-hydroxycholesterol plasma concentration was significantly higher in transplants with subsequent IPGF (n ؍ 9) compared with those with initial good graft function (IGGF; n ؍ 23) [mean ؎ SD: 30.63 ؎ 26.42 and 11.57 ؎ 15.76 ng/mL, respectively] (P ؍ 0.017). In a logistic regression model, which included also the Model for End-Stage Liver Disease (MELD) score, 7-hydroxycholesterol plasma concentration was an independent predictor of IPGF with an odds ratio of 1.17 (95% CI, 1.02-1.33, P ؍ 0.028). Patients with cirrhosis (n ؍ 32) had increased oxysterol plasma levels compared with healthy controls (n ؍ 49); livers with cirrhosis (n ؍ 21), however, had oxysterol content comparable with normal livers obtained from organ donors (n ؍ 19). Oxysterols persisted elevated in plasma 1 month after OLT (n ؍ 23). In conclusion, cirrhosis presents upregulated systemic oxidative stress likely of extrahepatic source that is associated with graft failure after OLT. (Liver Transpl 2005;11:1494-1504.)
Background and Objectives: Oxysterols are markers of oxidative stress, levels of which have not yet been reported in hemodialysis (HD) patients. This study was designed to compare levels of the oxysterols 7-ketocholesterol (7KC) and 7β-hydroxycholesterol (7βOH) between a cohort of HD patients and healthy controls. Methods: This nested cross-sectional study reflects baseline (pre-intervention) values for markers of oxidative stress, inflammation and nutrition status in the 160-member vitamin E and carotid intima media thickness progression in end-stage renal disease (VIPER) cohort (age 64.1 ± 8.8, 33.5% female). Age- and sex-matched healthy volunteers served as controls. Plasma oxysterols 7KC and 7βOH were determined by isotope dilution gas chromatography/mass spectrometry. Results: Despite higher plasma α-tocopherol levels in HD patients than controls (36.0 ± 9.3 vs. 31.8 ± 8.4 µmol/l, p = 0.007), 7KC levels (9.8 ± 6.9 vs. 5.9 ± 2.8 nmol/mmol cholesterol, p < 0.0001) and 7βOH levels (8.7 ± 4.3 vs. 2.7 ± 1.6 nmol/mmol cholesterol, p < 0.0001) were higher in HD patients. The oxysterol 7βOH was significantly, inversely associated with prealbumin (r = –0.18, p = 0.03), though neither oxysterol was significantly associated with any other marker of oxidative stress, inflammation or nutrition status and did not discriminate for CVD in HD patients. Conclusions: Elevated levels of the oxysterols 7KC and 7βOH indicate that HD patients are in a state of oxidative stress compared to healthy controls. However, oxysterols 7KC and 7βOH did not appear to contribute additional information about oxidative stress among HD patients.
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