Mechanisms of homocysteine-induced atherothrombosis

Elevation of plasma homocysteine level is a risk factor for cardiovascular disease, stroke, and venous thromboembolism. It is still uncertain, however, whether hyperhomocysteinemia is a causative factor or a marker of vascular disease. The strongest evidence that homocysteine plays a causal role in atherothrombosis has been provided by studies using animal models. In the past decade, considerable progress in defining the vascular effects of hyperhomocysteinemia was achieved through the use of genetic and dietary approaches to induce hyperhomocysteinemia in experimental animals. A key vascular phenotype observed in hyperhomocysteinemic animals is endothelial dysfunction, manifested by decreased bioavailability of endothelium-derived nitric oxide. Impairment of endothelial function may be mediated by either accelerated oxidative inactivation of nitric oxide or inhibition of nitric oxide production caused by the endogenous nitric oxide synthase inhibitor, asymmetric dimethylarginine. Hyperhomocysteinemia also increases susceptibility to arterial thrombosis and accelerates the development of atherosclerosis in susceptible models such as the apolipoprotein E-deficient mouse. Mechanisms of atherothrombosis may include homocysteine-induced thiolation or acylation of plasma or endothelial proteins and endoplasmic reticulum stress, which activates signal transduction pathways leading to inflammation and apoptosis.     

Plasma oxidants and antioxidants in acute ischaemic stroke

Plasma levels of the oxidants xanthine oxidase, nitric oxide and malondialdehyde and the antioxidants superoxide dismutase, glutathione peroxidase and glutathione reductase, together with total superoxide scavenger activity and non-enzymatic superoxide scavenger activity, were determined in 19 patients with acute ischaemic stroke and 20 controls. Compared with controls, superoxide dismutase, total superoxide scavenger activity, glutathione peroxidase and glutathione reductase activities were significantly lower, and nitric oxide and malondialdehyde levels significantly higher, in acute stroke patients. Xanthine oxidase showed a slight but non-significant increase in stroke patients compared with controls. There was no significant difference in non-enzymatic superoxide scavenger activity between the two groups. There was a positive correlation between glutathione reductase levels and Glasgow Coma Scale scores, and a negative correlation between malondialdehyde levels and non-enzymatic superoxide scavenger activity. These findings suggest that oxidative stress in patients with acute ischaemic stroke may be the result of an imbalance in oxidant/antioxidant homeostasis.     

Time course of nitric oxide,peroxynitrite, and antioxidants in the endotoxemic heart

OBJECTIVES: To determine the time course for myocardial production of nitric oxide, peroxynitrite, and glutathione, to determine the activities of the myocardial antioxidant enzymes glutathione peroxidase, superoxide dismutase, and glutathione reductase throughout endotoxemia and into recovery, and to correlate the levels of these variables to left ventricular contractility in endotoxemia. DESIGN: Rats were treated with lipopolysaccharide. Endotoxemic hearts were examined at baseline, 4, 16, 24, and 48 hrs after lipopolysaccharide. Saline time-control groups were treated identically. SETTING: A pulmonary research laboratory of a university teaching hospital. MEASUREMENTS AND MAIN RESULTS: Lipopolysaccharide administration resulted in decreased contractility at 16 hrs as assessed by the isolated papillary muscle technique. Contractility recovered by 24 hrs. Myocardial glutathione content initially increased, but it was decreased from baseline by 16 hrs, as was glutathione peroxidase activity. Both superoxide dismutase and glutathione reductase activities were increased early (4 hrs) and remained elevated throughout the course of the experiment. Myocardial nitric oxide content (assessed by the chemiluminescence technique) was increased by 4 hrs and was markedly elevated by 16 hrs. Nitric oxide levels remained elevated despite recovery of contractility at 24 hrs. Similarly, peroxynitrite (assessed by measurement of 3-nitrotyrosine by high-pressure liquid chromatography) was elevated at 16 hrs and remained elevated despite normalization of contractility at 24 and 48 hrs. CONCLUSIONS: Myocardial dysfunction in endotoxemia correlates mainly with decreased glutathione content and glutathione peroxidase activity rather than nitric oxide or peroxynitrite formation. These data indicate that lipopolysaccharide-induced myocardial dysfunction is not solely caused by elevated myocardial nitric oxide levels but rather caused by the sum of complex interactions between various oxygen- and nitrogen-derived radicals.     

Oxidative stress and endothelial dysfunction in heart failure]

Chronic heart failure is characterized by increased vascular systemic resistances secondary to activation of various vasoconstrictor systems and to decreased endothelium-dependent vasodilatation. Endothelial dysfunction, described both in animals and in humans, may be caused by an increased inactivation of nitric oxide (NO) by reactive oxygen species, leading to decreased NO bioavailability and impaired vasodilatation. Increased levels of free radicals in heart failure may result either from increased production or a decrease in the cellular antioxidant reserves. Free radicals are produced by three enzymatic systems: NADH/NADPH oxidase (after stimulation by angiotensin II or TNF-alpha), xanthine oxidase or endothelial NO-synthase (NOS) itself. However, oxidative stress alone cannot explain endothelial dysfunction. Other mechanisms involved in the regulation of the production of NO (e.g. decreased expression and/or activity of the NOS) and/or changes in production of vasoconstrictors may participate in this impaired endothelium-dependent vasodilatation in heart failure.     

大豆异黄酮对氧化损伤血管内皮细胞的抗氧化作用

背景:大豆异黄酮具有多种生物活性,其抗氧化作用成为近年来研究的热点。目前,对大豆异黄酮的研究多注重于动物实验和临床观察,缺少人体细胞水平的研究。目的:观察大豆异黄酮对氧化损伤血管内皮细胞的影响。设计:对照实验观察。材料:实验于2002-01/07在天津医科大学公共卫生学院中心实验室完成。实验材料包括人脐静脉血管内皮细胞株、低密度脂蛋白、大豆异黄酮及维生素E等。方法:体外培养血管内皮细胞,实验分为6组,即空白对照组、氧化损伤对照组(丙二醛含量为1μmol/L)、氧化损伤 维生素E对照组(维生素E50μmol/L)、氧化损伤 大豆异黄酮10,50,100μmol/L组。将氧化低密度脂蛋白作用于预先加入维生素E及不同浓度大豆异黄酮孵育24h的内皮细胞,继续培养24h,测定细胞外及细胞内各抗氧化指标。主要观察指标:各组内皮细胞内外丙二醛含量、超氧化物歧化酶、谷胱甘肽过氧化物酶活性、乳酸脱氢酶释放情况及一氧化氮生成量。结果:①各组内皮细胞丙二醛含量、超氧化物歧化酶及谷胱甘肽过氧化物酶活力的比较:氧化损伤对照组丙二醛含量显著高于空白对照组(P<0.01),而超氧化物歧化酶活性和谷胱甘肽过氧化物酶活性均显著低于空白对照组(P<0.01);氧化损伤 维生素E对照组、氧化损伤 大豆异黄酮10,50,100μmol/L组的丙二醛含量显著低于氧化损伤对照组(P<0.01),而超氧化物歧化酶和谷胱甘肽过氧化物酶活性显著高于氧化损伤对照组(P<0.01)。②各组内皮细胞乳酸脱氢酶释放情况及一氧化氮生成量的比较:氧化损伤对照组乳酸脱氢酶释放百分比明显高于空白对照组(P<0.01),产生的一氧化氮含量明显低于空白对照组(P<0.01);氧化损伤 维生素E对照组、氧化损伤 大豆异黄酮10,50,100μmol/L组的乳酸脱氢酶释放百分比显著低于氧化损伤对照组(P<0.01),一氧化氮的生成量显著高于氧化损伤对照组(P<0.01)。结论:大豆异黄酮可以减轻氧化低密度脂蛋白对血管内皮细胞的氧化损伤,可能通过丙二醛含量、超氧化物歧化酶、谷胱甘肽过氧化物酶活性、乳酸脱氢酶释放情况及一氧化氮生成量等抗氧化指标起作用。     

Sildenafil citrate as a phosphodiesterase inhibitor has an antioxidant effect in the blood of men

Background and objective: Sildenafil citrate enhances the action of nitric oxide by preventing the hydrolysis of cGMP, and is widely used to treat erectile dysfunction. We investigated the effects of sildenafil citrate administration on lipid peroxidation and antioxidant redox enzymes in blood of healthy men. Method: Thirty healthy male subjects were divided equally into two groups. The first group was used as the control. A single dose of sildenafil citrate was administrated orally to subjects constituting the second group. Blood samples were obtained at 0, 2, 6 and 24 h after intake of the single dose of 100 mg sildenafil citrate or placebo. Results and discussion: The dose of sildenafil citrate resulted in significant increase in the erythrocyte superoxide dismutase and catalase activities at 6 and 24 h. Plasma lipid peroxidation levels decreased slightly. There was no statistical difference in erythrocyte glutathione peroxidase activity between the placebo and sildenafil citrate groups. Conclusion: Treatment of blood with 100 mg sildenafil citrate has protective effects on oxidative stress by inhibiting free radical formation and by supporting antioxidant redox systems.     

Effect of sesame oil on oxidative-stress-associated renal injury in endotoxemic rats: involvement of nitric oxide and proinflammatory cytokines

This study aimed to investigate the effect of sesame oil on oxidative stress-associated renal injury induced by lipopolysaccharide in rats. The effects of sesame oil on renal injury, oxidative stress, hydroxyl radical, superoxide anion, nitric oxide, and proinflammatory cytokines were assessed after a lipopolysaccharide challenge. Sesame oil attenuated lipopolysaccharide-induced renal injury, decreased lipid peroxidation, increased the activities of superoxide dismutase, catalase, and glutathione peroxidase, reduced hydroxyl radical generation and nitric oxide production, and had no effect on superoxide anion generation in lipopolysaccharide-challenged rats. In addition, sesame oil significantly decreased tumor necrosis factor-alpha and interleukin 1beta production 1 and 6 h, respectively, after lipopolysaccharide administration in mice. Thus, sesame oil attenuates oxidative stress-associated renal injury via reduction of the production of nitric oxide and the generation of proinflammatory cytokines in endotoxemic rats.     

玉米黄质对高脂诱发鹌鹑模型血管脂质过氧化损伤的保护作用

背景:大多数人工合成的抗氧化药物长期应用均有一定的毒副作用,玉米黄质作为天然药物有其独特的生理效应。目的:观察玉米黄质对高脂诱发血管脂质过氧化损伤效应鹌鹑模型影响的量效关系。方法:建立鹌鹑高脂模型,利用玉米黄质按30,60mg/kg灌胃7周后,取空腹血测定血清总胆固醇、三酰甘油、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇及丙二醛水平、血清超氧化物歧化酶、谷胱甘肽过氧化物酶及诱导型一氧化氮合酶活性;检测各组动物肝脏组织中总胆固醇、三酰甘油水平;并采用苏木精-伊红染色观察主动脉血管病理变化。结果与结论:与高脂模型组相比,玉米黄质组血清三酰甘油、总胆固醇和低密度脂蛋白胆固醇浓度明显降低,而血清高密度脂蛋白胆固醇浓度明显增高;肝脏总三酰甘油及总胆固醇的合成也受到强烈抑制;玉米黄质组血清超氧化物歧化酶活性、谷胱甘肽过氧化物酶活性明显提高,而诱导型一氧化氮合酶活性下降、丙二醛水平减少。说明玉米黄质具有良好的降脂功效,对高脂诱导的血管脂质过氧化损伤有明显的抑制作用,且高剂量较低剂量作用效果更为理想。     

玉米黄质对高脂诱发鹌鹑模型血管脂质过氧化损伤的保护作用

背景：大多数人工合成的抗氧化药物长期应用均有一定的毒副作用,玉米黄质作为天然药物有其独特的生理效应。目的：观察玉米黄质对高脂诱发血管脂质过氧化损伤效应鹌鹑模型影响的量效关系。方法：建立鹌鹑高脂模型,利用玉米黄质按30,60mg/kg灌胃7周后,取空腹血测定血清总胆固醇、三酰甘油、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇及丙二醛水平、血清超氧化物歧化酶、谷胱甘肽过氧化物酶及诱导型一氧化氮合酶活性;检测各组动物肝脏组织中总胆固醇、三酰甘油水平;并采用苏木精-伊红染色观察主动脉血管病理变化。结果与结论：与高脂模型组相比,玉米黄质组血清三酰甘油、总胆固醇和低密度脂蛋白胆固醇浓度明显降低,而血清高密度脂蛋白胆固醇浓度明显增高;肝脏总三酰甘油及总胆固醇的合成也受到强烈抑制;玉米黄质组血清超氧化物歧化酶活性、谷胱甘肽过氧化物酶活性明显提高,而诱导型一氧化氮合酶活性下降、丙二醛水平减少。说明玉米黄质具有良好的降脂功效,对高脂诱导的血管脂质过氧化损伤有明显的抑制作用,且高剂量较低剂量作用效果更为理想。     

Effects of Phonophoresis and Gold Nanoparticles in Experimental Model of Muscle Overuse: Role of Oxidative Stress

The aim of the study described here was to investigate the effects of pulsed ultrasound and gold nanoparticles (AuNPs) on behavioral, inflammatory and oxidative stress parameters in an experimental model of overuse. Wistar rats performed 21 d of exercise on a treadmill at different intensities and were exposed to ultrasound in the presence or absence of AuNPs. The overuse model promoted behavioral changes and increased creatine kinase, superoxide dismutase and glutathione peroxidase activity, as well as the levels of superoxide, nitrotyrosine, nitric oxide, thiobarbituric acid reactive substance, carbonyl, tumor necrosis factor α and interleukin-6. These values were significantly decreased by AuNPs and by AuNPs plus ultrasound. Catalase activity remained unchanged and the glutathione level increased significantly after exposure to AuNPs plus ultrasound. These results suggest a susceptibility to anxiety as well as elevated levels of oxidative stress. However, therapeutic interventions with AuNPs plus ultrasound reduced the production of oxidants and oxidative damage and improved the anti-oxidant defense system.     

Oxidative stress in neurodegenerative diseases: therapeutic implications for superoxide dismutase mimetics

Evidence of oxidative stress is apparent in both acute and chronic neurodegenerative diseases, such as stroke, Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Increased generation of reactive oxygen species simply overwhelm endogenous antioxidant defences, leading to subsequent oxidative damage and cell death. Tissue culture and animal models have been developed to mimic some of the biochemical changes and neuropathology found in these diseases. In doing so, it has been experimentally demonstrated that oxidative stress plays a critical role in neuronal cell death. Antioxidant enzymes, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) have demonstrated therapeutic efficacy in models of neurodegeneration. However, delivery and stability issues have reduced the enthusiasm to clinically develop these proteins. Most recently, SOD mimetics, small molecules which mimic the activity of endogenous superoxide dismutase, have come to the forefront of antioxidant therapeutics. This review will examine the experimental evidence supporting the use of scavengers of superoxide anions in treating some neurodegenerative diseases, such as stroke, PD and ALS, but also the pitfalls that have met antioxidant molecules in clinical trials.     

The effect of dipyridamole on vascular cell-derived reactive oxygen species

Platelet and vascular stimulation leads to release of reactive oxygen species (ROS) that are known to influence vascular reactivity and thrombosis. Dipyridamole is a vasodilator and platelet inhibitor that has previously been shown to have direct antioxidant properties. The antioxidant effects of dipyridamole on vascular cell-derived ROS are not known; therefore, dipyridamole was incubated with endothelial cells and platelets and cellular redox status and release of endogenous ROS were assessed. Dipyridamole decreased intracellular basal ROS generation from endothelial cells as measured by DCFDA (2',7'-dichlorodihydrofluorescein diacetate) oxidation. Incubation of endothelial cells with dipyridamole also attenuated t-butylhydroperoxide-induced oxidative stress. Using a redox-sensitive fluorescent dye, dipyridamole improved cellular activity after treatment with t-butylhydroperoxide. Incubation with dipyridamole did not alter platelet release of nitric oxide or hydrogen peroxide but significantly attenuated superoxide release. Using flow cytometry and confocal microscopy, dipyridamole decreased platelet ROS generation. Dipyridamole also suppressed platelet-soluble CD40 ligand release. In summary, at therapeutically relevant concentrations, dipyridamole suppresses the formation of ROS in platelets and endothelial cells and improves cellular redox status. These data suggest that the redox-dependent properties of dipyridamole have a direct effect on vascular cells.     

Coenzyme Q10 and diabetic endotheliopathy: oxidative stress and the 'recoupling hypothesis'

Increased oxidative stress in diabetes mellitus may underlie the development of endothelial cell dysfunction by decreasing the availability of nitric oxide (NO) as well as by activating pro-inflammatory pathways. In the arterial wall, redox imbalance and oxidation of tetrahydrobiopterin (BH4) uncouples endothelial nitric oxide synthase (eNOS). This results in decreased production and increased consumption of NO, and generation of free radicals, such as superoxide and peroxynitrite. In the mitochondria, increased redox potential uncouples oxidative phosphorylation, resulting in inhibition of electron transport and increased transfer of electrons to molecular oxygen to form superoxide and other oxidant radicals. Coenzyme Q10 (CoQ), a potent antioxidant and a critical intermediate of the electron transport chain, may improve endothelial dysfunction by 'recoupling' eNOS and mitochondrial oxidative phosphorylation. CoQ supplementation may also act synergistically with anti-atherogenic agents, such as fibrates and statins, to improve endotheliopathy in diabetes.     

Activities of xanthine oxidoreductase and antioxidant enzymes in different tissues of diabetic rats

Oxidative stress is an important pathogenic constituent in diabetic endothelial dysfunction. The aim of this study was to investigate whether an increase in oxidative stress related to xanthine oxidoreductase occurs in diabetes. Liver, brain, heart, and kidney xanthine oxidase (XO), xanthine dehydrogenase (XDH), antioxidant enzymes (glutathione peroxidase, superoxide dismutase, catalase), and nitrite levels were measured in control and early and late diabetic rat models. Although diabetes had no impact on liver XO and XDH activity, XDH activity in heart, kidney, and brain was significantly greater in late diabetic rats than in controls. Selenium glutathione peroxidase (GPx) activity was found to be lower in the liver, brain, kidney, and heart of late diabetic rats than in controls. The measured decrease in selenium GPx activity was also observed in early diabetic heart, kidney, and brain. No significant change was observed in liver, brain, and kidney copper/zinc superoxide dismutase (Cu/Zn SOD) activity in early and late diabetic rat models compared with that in controls, whereas heart Cu/Zn SOD activity was significantly decreased in both early and late diabetic rats. Liver and brain catalase activity remained similar among the different experimental groups, whereas increased heart and kidney catalase activity was observed in both early and late diabetic rats. Liver, kidney, and brain nitrite levels were found to be increased in early diabetic rat models compared with those in controls. These data suggest that the increased XDH and decreased selenium GPx activity observed in the later stages of diabetes leads to enhanced oxidative stress in the heart, kidney, and brain, resulting in secondary organ damage associated with the disease.     

Antioxidant enzyme activities and total nitrite/nitrate levels in the collar model. Effect of nicardipine.

There is a large body of literature describing the causative role of oxidative stress mediated by increased levels of reactive oxygen species in the pathogenesis of cardiovascular disease such as atherosclerosis, hypertension, and restenosis after angioplasty. The positioning of a soft silicone collar around the rabbit carotid artery elicits intimal thickening. The findings from recent studies demonstrated that both intimal thickening and atherosclerosis lead to synthesis of inducible nitric oxide synthase, resulting in abundant amounts of nitric oxide. We investigated the effects of collaring and nicardipine treatment on the activities of antioxidant enzymes, superoxide dismutase and catalase, and total nitrite/nitrate levels, stable products of nitric oxide. Placing the collar increased the total nitrite/ nitrate levels and decreased superoxide dismutase activity in collared arteries. Treatment with nicardipine (20 mg/kg/day, s.c.) prevented enhanced nitric oxide degradation without affecting superoxide dismutase and catalase activities. Our results suggest that enhanced nitric oxide production and superoxide anion are generated in response to the collaring, resulting in oxidative stress within the segment in this model.     

Endothelial function

It is well known that diabetes mellitus often combines with hypertension. Diabetes mellitus is associated with endothelial dysfunction. An imbalance of reduced production of nitric oxide or increased production of reactive oxygen species, mainly superoxide, may promote endothelial dysfunction. One mechanism by which endothelium-dependent vasodilation is impaired is an increase in the oxidative stress that inactivates nitric oxide. Both high glucose and insulin resistance reduce the bioavailability of nitric oxide through an increase in oxidative stress. It is unclear that endothelial dysfunction is a cause or consequence of hypertension. In this review, we present the possibility that endothelial dysfunction causes hypertension in diabetes mellitus.     

Effect of macrocyclic binuclear oxovanadium complex on tissue defense system in streptozotocin-induced diabetic rats

BACKGROUND: Oxidative stress plays an important role in chronic complications of diabetes mellitus and hence the regulation of free radicals is essential in the treatment of diabetes. The protective effect of a new macrocyclic binuclear oxovanadium complex on antioxidant defense systems of liver and kidney was examined in streptozotocin-induced experimental diabetes in rats. METHODS: The levels of lipid peroxides, glutathione and the activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase were assayed according to standard procedures in the liver and kidney of control and experimental groups of rats. RESULTS: A significant decrease (p < 0.05) was observed in both the glutathione content and in the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase and a concomitant increase in the level of lipid peroxides in diabetic rats. The observed alterations in the antioxidant status of tissues reverted back to near normal levels after the oral administration of macrocyclic vanadium complex at a dose of 5 mg/kg body weight/rat/day for a period of 30 days. CONCLUSION: The normoglycemic efficacy of the vanadium complex alleviates oxidative stress in streptozotocin-induced diabetes in rats.     

Oxidant/antioxidant parameters and their relationship with chemotherapy in Hodgkin's lymphoma

This study investigated changing levels of serum oxidant/antioxidant with chemotherapy and their relation to treatment in 34 Hodgkin's lymphoma patients. The patient population consisted of 19 males and 15 females. Mean age was 30.41 +/- 12.08 years. All patients received the adriamycin, bleomycin, vincristine and dexamethasone (ABVD) treatment protocol. Blood samples were taken before treatment, and on days 1 and 7 during treatment for measurement of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), malondialdehyde (MDA), nitric oxide (NO) and enzyme activities. After ABVD treatment, mean free radical levels were increased and antioxidant levels were significantly decreased in the serum. ABVD treatment results in an increase of free radical levels and a decrease of antioxidant levels in the serum of patients with Hodgkin's lymphoma.     

Inactivation of antioxidant enzymes by peroxynitrite

Exposure of hemolysates and whole erythrocytes to peroxynitrite (bolus of 50 micromol dm(-3)-2 mmol dm(-3)) was found to inactivate erythrocyte antioxidant enzymes: glutathione peroxidase > superoxide dismutase > catalase. Inactivation of antioxidant enzymes by peroxynitrite may be one reason for the secondary oxidative stress in peroxynitrite-treated cells. When hemoglobin was not converted into the cyanmet form, an apparent activation of glutathione peroxidase activity by peroxynitrite was observed in hemolysates; this effect was artifactual and due to the pseudoenzymatic glutathione peroxidase activity of hemoglobin.