Homocysteine-induced Oxidative Stress Research Articles

Amentoflavone and thymoquinone: Natural antioxidants in the attenuation of homocysteine-induced oxidative stress

Amentoflavone and thymoquinone: Natural antioxidants in the attenuation of homocysteine-induced oxidative stress

Pterostilbene antagonizes homocysteine-induced oxidative stress, apoptosis and lipid deposition in vascular endothelial cells

Hyperhomocysteinemia (HHcy) causes oxidative stress, induces apoptosis, and leads to damage to the vascular endothelium is the starting point of atherosclerosis. Pterostilbene (Pte) has been reported to have antioxidant and anti-apoptotic effects under various pathological conditions. The purpose of this study was to explore whether Pte can inhibit the oxidative stress and apoptosis of vascular endothelium induced by homocysteine (Hcy) and to explain the possible mechanism by which it occurs. The results showed that 20 μmol/L Pte significantly reduced the accumulation of reactive oxygen species, malondialdehyde, and lipids in cells induced by Hcy and promoted the activities of superoxide dismutase and catalase. The Hoechst 33342/PI staining assay showed that Pte antagonized Hcy-induced apoptosis. Pte inhibited Hcy-induced Akt dephosphorylation, increased p53, and decreased the Bcl-2/Bax ratio and caspase-9/caspase-3 activation in a dose-dependent manner. LY294002 pretreatment partially reversed the protective effect of Pte by blocking the PI3K/Akt pathway. Moreover, Pte reduced lipid deposition in human umbilical vein endothelial cells (HUVECs). This study proposes that Pte can inhibit Hcy-induced oxidative stress and apoptosis of HUVECs, and the PI3K/Akt/p53 signaling pathway of apoptosis was revealed. These results suggest that Pte exhibits significant potential for dealing with HHcy-induced vascular endothelial injury, such as atherosclerosis.

Vitamin B12 in Relation to Oxidative Stress: A Systematic Review.

The triage theory posits that modest micronutrient deficiencies may induce reallocation of nutrients to processes necessary for immediate survival at the expense of long-term health. Neglected processes could in time contribute to the onset of age-related diseases, in which oxidative stress is believed to be a major factor. Vitamin B12 (B12) appears to possess antioxidant properties. This review aims to summarise the potential antioxidant mechanisms of B12 and investigate B12 status in relation to oxidative stress markers. A systematic query-based search of PubMed was performed to identify eligible publications. The potential antioxidant properties of B12 include: (1) direct scavenging of reactive oxygen species (ROS), particularly superoxide; (2) indirect stimulation of ROS scavenging by preservation of glutathione; (3) modulation of cytokine and growth factor production to offer protection from immune response-induced oxidative stress; (4) reduction of homocysteine-induced oxidative stress; and (5) reduction of oxidative stress caused by advanced glycation end products. Some evidence appears to suggest that lower B12 status is related to increased pro-oxidant and decreased antioxidant status, both overall and for subclinically deficient individuals compared to those with normal B12 status. However, there is a lack of randomised controlled trials and prospective studies focusing specifically on the relation between B12 and oxidative stress in humans, resulting in a low strength of evidence. Further work is warranted.

Morphine pre- and post-conditioning exacerbates apoptosis in rat hippocampus cells in a model of homocysteine-induced oxidative stress

Morphine pre- and post-conditioning exacerbates apoptosis in rat hippocampus cells in a model of homocysteine-induced oxidative stress

Homocysteine‑induced oxidative stress through TLR4/NF‑κB/DNMT1‑mediated LOX‑1 DNA methylation in endothelial cells.

Atherosclerosis (AS) is a progressive disease of multifactorial origin, which occurs in response to endothelial injury. Increased homocysteine (Hcy) is considered a major cause of endothelial dysfunction, oxidative stress and DNA methylation; however, the mechanisms remain to be fully elucidated. The aim of the present study was to investigate whether Hcy causes injury to endothelial cells (ECs) by the effect of lectin‑like oxidized‑low density lipoprotein receptor‑1 (LOX‑1) DNA methylation through toll‑like receptor 4(TLR4)/nuclear factor (NF)‑κB/DNA methyltransferase (DNMT)1. The ECs were treated with different concentrations of Hcy, and it was found that Hcy promoted the expression of TLR4, leading to EC injury. The effect of oxidative stress was analyzed by measuring superoxide dismutase, malondialdehyde and hydrogen peroxide in the ECs. In addition, the association between NF‑κB and DNMT1 was examined by treatment of the ECs with pyrrolidine dithiocarbamate (PDTC). The results suggested that Hcy induced LOX‑1 DNA hypomethyaltion to promote the expression levels of LOX‑1. Taken together, Hcy injured the ECs through the effect of methylation and trans‑sulfuration metabolism of LOX‑1 through TLR4/NF‑κB/DNMT1. Following injury to the ECs, lipids, particularly ox‑LDL, accumulated in the sub‑endothelial layer to promote the formation of AS.

Morphine pre- and post-conditioning exacerbates apoptosis in rat hippocampus cells in a model of homocysteine-induced oxidative stress.

Recent investigations indicated that morphine has protective effects in different ischemia/reperfusion models and may protect against neuronal cell death, while other evidence showed that morphine induces apoptosis in neurons. Therefore, the current study was conducted to investigate pre- and post-conditioning effects of morphine on hippocampal cell apoptosis in a rat model of homocysteine (Hcy)-induced oxidative stress. In the present study, 0.5 µmol/µl Hcy was injected into bilateral intrahipocampal in the rat brain and morphine at a therapeutic dose of 10 mg/kg was injected intraperitoneally 5 days before and after Hcy injection in rats. The left and right rat hippocampus were removed for biochemical and histopathological analysis. In addition, hippocampal cell apoptosis was assayed by the TUNEL kit. Our results indicated that malondialdehyde (MDA) and superoxide anion (SOA) levels in the Hcy group were increased significantly compared to the control group (P<0.001). In addition, morphine pre- and post-treatment increased the MDA and SOA levels significantly in rat hippocampus compared with other groups (P<0.001). It was found that Hcy alone induced apoptosis in hippocampus cells and significantly increased the number of TUNEL-positive cells in rat hippocampus compared to the other group (P<0.001). Notably, our results indicated that pre- and post-treatment by morphine increased apoptosis in hippocampus cells compared with the other group (P<0.001). In conclusion, morphine neuroprotection and neurotoxicity needs to be further investigated to determine morphine side-effects in medical applications and to identify new targets for potential therapies.

Protective effect of quercetin on homocysteine-induced oxidative stress

ObjectiveThe aim of this study was to evaluate whether quercetin (QUER) treatment could have a protective effect against oxidative stress induced by homocysteinemia in rats. Materials and methodsThirty-two male Sprague-Dawley rats (adult) were assigned randomly to four groups: the control group was given physiological saline (PS; 1.5 mL/d); the QUER group was given QUER (50 mg/kg body weight [BW] daily) in distilled water and 0.25 mL PS; the homocysteine (HCY) group was given HCY (1 mg/kg BW daily) in distilled water and 1.25 mL PS; and the QUER + HCY group was given QUER 1 h before the administration of HCY. QUER, HCY, and PS were injected intraperitoneally every other day for 30 d. Plasma malondialdehyde (MDA), carbonyl, erythrocyte-reduced glutathione (GSH), plasma sulphydril (−SH) levels, erythrocyte catalase (CAT), and superoxide dismutase (SOD) activities were determined. ResultsPlasma CAT levels in the QUER group were found to be significantly higher than in the control group, whereas plasma MDA levels in the QUER group significantly decreased compared with the control group. In the HCY group, plasma MDA and carbonyl levels significantly increased and GSH and SOD levels significantly decreased compared with the control group. Plasma MDA levels significantly decreased and GSH and CAT levels significantly increased in the QUER + HCY group compared with the HCY group. Plasma −SH levels were significantly lower in the HCY group than in the control group. Plasma −SH levels were higher in the QUER + HCY group than in the HCY group, but they were not significant. ConclusionThe exposure of rats to HCY leads to oxidative stress reflected in increased MDA and decreased antioxidant enzyme levels. Administration of QUER might attenuate oxidative damage induced by HCY or have a protective effect against it.

17β-estradiol attenuates homocysteine-induced oxidative stress and inflammatory response as well as MAPKs cascade via activating PI3-K/Akt signal transduction pathway in Raw 264.7 cells.

Oxidative stress, inflammatory response, and mitogen-activated protein kinases (MAPKs) cascade are significant pathogenic factors of osteoporosis. It has been reported that elevated homocysteine (Hcy) may activate oxidative stress and reduce bone mineral density in post-menopausal osteoporosis. Moreover, hormone replacement therapy has been widely used in clinic to prevent and treat post-menopausal women with osteoporosis and osteoporotic fracture, but the molecular mechanisms and relevant signal transduction pathways underlying the action of Hcy remain unclear. In this study, we investigated the effects of 17β-estradiol (17β-E2) on the Hcy-induced oxidative stress, inflammatory response and MAPKs cascade, as well as the underlying signal transduction pathway in murine Raw 264.7 cells. The reactive oxygen species (ROS) was assessed by fluorospectrophotometry. The proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β were analyzed by double-immunofluorescence labeling and reverse transcriptase polymerase chain reaction assay, respectively. Furthermore, phosphorylation levels of MAPKs cascade were measured by western blot analysis. A specific phosphatidylinositol 3-kinase (PI3-K) inhibitor, Wortmannin (1 μM) was employed to determine whether PI3-K/Akt signaling pathway mediated the 17β-E2's effect on Raw 264.7 cells. 17β-E2 markedly decreased the ROS production induced by Hcy, the expression of TNF-α and IL-1β at protein and mRNA levels, and down-regulated the phosphorylation of MAPKs (ERK1/2, JNK and p38). These suppressing effects of 17β-E2 on Hcy-induced changes were reversed by pretreatment with PI3-K inhibitor Wortmannin. The results indicate that 17β-estradiol may attenuate Hcy-induced oxidative stress, inflammatory response and up-regulation of MAPKs in Raw 264.7 cells via PI3-K/Akt signal transduction pathway.

Role of vitamin B6 status on antioxidant defenses, glutathione, and related enzyme activities in mice with homocysteine-induced oxidative stress

BackgroundVitamin B6 may directly or indirectly play a role in oxidative stress and the antioxidant defense system.ObjectiveThe purpose of this study was to examine the associations of vitamin B6 status with cysteine, glutathione, and its related enzyme activities in mice with homocysteine-induced oxidative stress.DesignFour-week-old male BALB/c mice were weighed and divided into one of four dietary treatment groups fed either a normal diet (as a control group and a homocysteine group), a vitamin B6-deficient diet (as a B6-deficient group), or a B6-supplemented diet (a pyridoxine-HCl-free diet supplemented with 14 mg/kg of pyridoxine-HCl, as a B6 supplement group) for 28 days. Homocysteine thiolactone was then added to drinking water in three groups for 21 days to induce oxidative stress. At the end of the study, mice were sacrificed by decapitation and blood and liver samples were obtained.ResultsMice with vitamin B6-deficient diet had the highest homocysteine concentration in plasma and liver among groups. Significantly increased hepatic malondialdehyde levels were observed in the vitamin B6-deficient group. Among homocysteine-treated groups, mice with vitamin B6-deficient diet had the highest plasma glutathione concentration and relatively lower hepatic glutathione concentration. The glutathione peroxidase activities remained relatively stable in plasma and liver whether vitamin B6 was adequate, deficient, or supplemented.ConclusionsMice with deficient vitamin B6 intakes had an aggravate effect under homocysteine-induced oxidative stress. The vitamin B6-deficient status seems to mediate the oxidative stress in connection with the redistribution of glutathione from liver to plasma, but not further affect glutathione-related enzyme activities in mice with homocysteine-induced oxidative stress.

Prospective Role of β-Cell-Specific IGF-1 for Oxidative Stress in the Pathogenesis of Diabetic Neuropathy

Diabetic neuropathy is a well-known complication of diabetes mellitus. The mechanism for progression of diabetic neuropathy is unclear, but many risk factors, such as abnormalities of glucose metabolism and oxidative stress, have been given much attention for their contributory role in the loss or degeneration of neurons. Homocysteine is a risk factor of cardiovascular disease and diabetes/metabolic disease. Homocysteine metabolism is dependent on vitamin B12 the deficiency of which induces peripheral neuropathy. On the other hand, the examination of generative pathology showed the potential involvement of many growth factors in neuroprotection and regeneration. This review implicates Insulin-like growth factor-1(IGF-1) as playing a crucial role in pancreatic β-cell functions and homocysteine-induced oxidative stress. A defense mechanism against diabetic neuropathy via homocysteine-induced oxidative stress due to a protective effect of β-cell-specific IGF-1 will be discussed.

Additive Effect of Homocysteine‐ and Cholesterol‐Lowering Therapy on Endothelium‐Dependent Vasodilation in Patients with Cardiovascular Disease

Endothelial dysfunction is a marker for development and progression of atherosclerosis. Statin therapy improves endothelial function in cardiovascular patients by reducing LDL-cholesterol and by pleiotropic effects. B-group vitamin supplementation restores endothelial function mainly by reducing homocysteine-induced oxidative stress. Thus, we evaluated the effect of rosuvastatin, B-group vitamins and their combination on endothelial function in high-risk cardiovascular patients. Thirty-six patients with cardiovascular disease were randomly, double-blinded assigned to either rosuvastatin 10 mg (group R, n = 18) or vitamin supplementation consisting of folic acid 1 mg, vitamin B12 0.4 mg, and B6 10 mg (group V, n = 18) for 6 weeks. After 6 weeks all patients received rosuvastatin and vitamin supplementation in combination for additional 6 weeks. Endothelial function was assessed by flow-mediated vasodilation (FMD) at baseline and after 6- and 12-week treatment. At baseline, FMD, plasma lipids, vitamins, and homocysteine were comparable between both groups. After 6 weeks, FMD improved in both groups (from 4.4 ± 1.6 to 6.9 ± 1.4% group R, P= 0.0004 and from 4.9 ± 1.8 to 6.4 ± 1.8% group V, P= 0.0002). This improvement in FMD was mainly associated with a decrease of plasma lipids in group R and a decrease of homocysteine in group V. After 12 weeks, the combined therapy with rosuvastatin and vitamins further improved FMD to the normal range in 26/33 patients compared to 5/36 at baseline (P < 0.0001). In conclusion, both treatments, rosuvastatin and B-group vitamin supplementation, improved endothelial function in high-risk cardiovascular patients. The combination of both therapies had an additive effect on endothelial function suggesting different mechanisms of action.

ACS6, a Hydrogen sulfide-donating derivative of sildenafil, inhibits homocysteine-induced apoptosis by preservation of mitochondrial function

BackgroundThe hydrogen sulfide-releasing sildenafil, ACS6, has been demonstrated to inhibit superoxide formation through donating hydrogen sulfide (H2S). We have found that H2S antagonizes homocysteine-induced oxidative stress and neurotoxicity. The aim of the present study is to explore the protection of ACS6 against homocysteine-triggered cytotoxicity and apoptosis and the molecular mechanisms underlying in PC12 cells.MethodsCell viability was determined by Cell Counting Kit-8 assay. Cell apoptosis was observed using the chromatin dye Hoechst 33258 and analyzed by Flow Cytometry after propidium iodide staining. Mitochondrial membrane potential was monitored using the fluorescent dye Rh123. Intracellular reactive oxygen species were determined by oxidative conversion of cell permeable 2',7'-dichlorfluorescein-diacetate to fluorescent 2',7'-dichlorfluorescein. The expression of cleaved caspase-3 and bcl-2 and the accumulation of cytosolic cytochrome c were analyzed by Western blot.ResultsWe show that ACS6 protects PC12 cells against cytotoxicity and apoptosis induced by homocysteine and blocks homocysteine-triggered cytochrome c release and caspase-3 activation. ACS6 treatment results in not only prevention of homocysteine-caused mitochondrial membrane potential (Δψ) loss and reactive oxygen species (ROS) overproduction but also reversal of Bcl-2 down-expression.ConclusionsThese results indicate that ACS6 protects PC12 cells against homocysteine-induced cytotoxicity and apoptosis by preservation of mitochondrial function though inhibiting both loss of Δψ and accumulation of ROS as well as modulating the expression of Bcl-2. Our study provides evidence both for a neuroprotective effect of ACS6 and for further evaluation of ACS6 as novel neuroprotectants for Alzheimer's disease associated with homocysteine.

Role of fenofibrate alone and in combination with telmisartan on renal ischemia/reperfusion injury

It was demonstrated that fenofibrate and telmisartan exerted renoprotective effects in ischemia/reperfusion (I/R) injury. Because the combination of fenofibrate and telmisartan synergistically enhanced peroxisome proliferator-activated receptor (PPAR) activation, we hypothesized that the combination of both drugs may exert prolonged beneficial effects in renal I/R injury than fenofibrate alone. Forty-eight male Wistar albino rats were divided into eight groups. Hyperlipidemia was induced by cholesterol feeding for 4 weeks. At the end of the fourth week, renal I/R injury was performed by occlusion of both renal vascular pedicles for 60 minutes, followed by 24 hours of reperfusion. In the treatment group, fenofibrate alone and in combination with telmisartan was administered 2 weeks prior to renal ischemia. At the end of the experiment, blood and kidneys were isolated for biochemical and histological analysis. I/R in hyperlipidemic rat shows significantly increased lipid peroxidation, nitric oxide, and myeloperoxidase activity, and depletion of antioxidant enzyme compared with control rats, and that was significantly restored after fenofibrate and telmisartan treatment. Also, significant increases in serum homocysteine level were detected following I/R. Fenofibrate treatment further elevated homocysteine level, which was reduced by telmisartan in combination with fenofibrate. The most significant histological damage was found in the hyperlipidemic rat subjected to renal I/R, which was reduced significantly with combination therapy. The results of this study concluded that fenofibrate alone and in combination with telmisartan significantly ameliorated renal I/R injury. The additive beneficial effect of telmisartan is predicted to reduce homocysteine-induced oxidative stress through reduced nitric oxide production during I/R.

The activation of endothelin-1 pathway during methionine-induced homocysteinemia mediates endothelial dysfunction in hypertensive individuals

Endothelin-1 (ET-1) is a key regulator of arterial blood pressure in humans, and homocysteinemia is associated with increased oxidative stress. It is still unclear whether homocysteine-induced oxidative stress is implicated in the regulation of ET-1 expression. We examined the impact of acute homocysteinemia on endothelial function in hypertensive patients and healthy individuals, and the potential role of ET-1. In this double-blind, placebo-controlled study, 39 hypertensive and 49 healthy individuals were randomized to receive high-dose vitamins (2 g vitamin C and 800IU vitamin E) or placebo followed by methionine loading 100 mg/kg body weight. Endothelium-dependent dilation (EDD) and endothelium-independent dilation (EID) of the brachial artery were evaluated by plethysmography, at baseline and 4 h postloading (4 h PML). ET-1 was measured by ELISA, whereas total lipid hydroperoxides (per-ox) levels were measured by a commercially available photometric technique. Acute, methionine-induced homocysteinemia decreased EDD in all study groups (P < 0.001 for all), whereas vitamins pretreatment failed to prevent this effect, despite the vitamins-induced reduction of peroxidation in the hypertensives group (P < 0.05). On the contrary, methionine loading significantly increased plasma ET-1 levels only in hypertensives (P < 0.05), an effect which was not prevented by antioxidant vitamins (P < 0.05). EID remained unchanged after methionine loading, in all study groups (P = NS for all groups). Experimental homocysteinemia rapidly blunts endothelial function in both hypertensive individuals and healthy individuals. The rapid elevation of ET-1 levels observed only in hypertensives, suggests that ET-1 may be the key mediator of homocysteine-induced endothelial dysfunction, independently of oxidative stress.

Homocysteine-induced oxidative stress upregulates chymase in mouse mastocytoma cells

Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)), O(*-)(2) and OH(*) participate in the pathogenesis of ischemia/reperfusion injury, inflammation and atherosclerosis. Our previous studies have suggested that increased angiotensin II (Ang II)-forming chymase may be involved in the development of atherosclerosis. However, the regulatory mechanism of chymase expression has not yet been clarified. In this study, we tested whether oxidative stress upregulates mouse mast cell proteinase chymase, mouse mast cell proteinase (MMCP)-5 or MMCP-4. We also examined the expression and activity of these proteins after treatment. Cultured mouse mastocytoma cells (MMC) displaying chymase-dependent Ang II-forming activity were treated with H(2)O(2) and several aminothiols with or without anti-oxidants. The levels of MMCP-5 and MMCP-4 expression were determined by quantitative RT-PCR; the level of chymase-dependent Ang II-forming activity was measured by high performance liquid chromatography using Ang I as a substrate. Treatment of MMC with homocysteine (0.1-3 mmol l(-1)) significantly increased MMCP-5 and MMCP-4 expression, as well as Ang II-forming activity. These effects were significantly inhibited by the addition of catalase and further suppressed by the combination of catalase and superoxide dismutase. Incubation with hydrogen peroxide alone caused a significant increase in Ang II-forming activity, which was completely suppressed by co-treatment with catalase. Furthermore, MMCP-5 and MMCP-4 expression levels were drastically suppressed and chymase induction by homocysteine was diminished under the GATA-inhibited condition. Homocysteine increased mast cell chymase expression and activity through the mechanism of oxidative stress. Our results suggest that there is a biochemical link between oxidative stress and the local Ang II-forming system.

Atorvastatin inhibits homocysteine-induced oxidative stress and apoptosis in endothelial progenitor cells involving Nox4 and p38MAPK

Previous studies showed that homocysteine (Hcy) reduces endothelial progenitor cells (EPCs) numbers and impairs functional activity. Atorvastatin, HMG-CoA inhibition has been showed to have protective effects on EPCs. Recent studies have demonstrated that reduced EPCs numbers and activity are associated with EPCs apoptosis. However, the protective mechanisms of atorvastatin on HHcy-induced EPCs apoptosis remain to be determined. This study was designed to examine the effect of atorvastatin on homocysteine-induced reactive oxygen species (ROS) production and apoptosis in EPCs. EPCs were isolated from peripheral blood and characterized, then challenged with Hcy (50–500μmol/L) in the presence or absence of atorvastatin (0.01–1μmol/L) or various stress signaling inhibitors, including mevalonate (100μmol/L), antioxidants N-acetyl cysteine (NAC, 10μmol/L), the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (DPI 10μmol/L), the eNOS inhibitor NGmono-methyl-l-arginine LNMA (1mmol/L), and the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 (10μmol/L). Apoptosis was evaluated by FACS analysis and cell viability was determined by MTT assay. ROS were detected by 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFH-DA). NADPH oxidases were evaluated with lucigenin-enhanced chemiluminescence. Expression of Nox4 mRNA and p-p38MAPK protein was measured by RT-PCR and Western blot analysis, respectively. Our data revealed that atorvastatin significantly suppressed Hcy-induced ROS accumulation and EPCs apoptosis. Atorvastatin also antagonized homocysteine-induced activation of NADPH oxidase and overexpression of Nox4 mRNA and p-p38MAPK protein. Similar effects occurred with EPCs transfected with Nox4 siRNA. These findings demonstrated that atorvastatin may inhibit Hcy-induced NADPH oxidase activation, ROS accumulation, and EPCs apoptosis through Nox4/p38MAPK dependent mechanisms, all of which may contribute to atorvastatin-induced beneficial effects on EPCs function.

Anti-inflammatory strategies for homocysteine-related cardiovascular disease

Homocysteine may induce vascular damage for atherosclerosis. Vitamin/folate supplementation has been proposed to reduce the cardiovascular disease risk. Nevertheless, there is no randomized clinical trial clearly proving the efficacy of reducing the homocysteine as a means of lowering the incidence of cardiovascular disease. Homocysteine induces oxidative stress leading to endothelial dysfunction. In addition, homocysteine-induced oxidative stress favors lipid peroxidation and induces production of inflammatory factors, thus accelerating atherosclerosis. In this paper, we reviewed the available evidence concerning the association between homocysteine and cardiovascular disease, with the objective of discussing the pertinence of screening, treatment, and prevention of hyperhomocysteinemia-related cardiovascular disease. Our previous findings also indicated the significant role of mononuclear cells activation in homocysteine-induced endothelial dysfunction; treatment with statins attenuated homocysteine-induced endothelial adhesiveness, indicating the novel endothelial protection effects of statins in the presence of homocysteine. Since inflammation and oxidative stress are critical to homocysteine-induced vascular damage, the improvement of endothelial dysfunction and the inhibition of mononuclear cell activation by anti-inflammatory and/or antioxidative drugs/agents may serve as the potential therapeutic strategy for hyperhomocysteinemia-related cardiovascular disease.

Effect of Homocysteine-Induced Oxidative Stress on Endothelial Function in Coronary Slow-Flow

Background and Objective: Coronary slow-flow (CSF) phenomenon is characterized by delayed opacification of vessels in a normal coronary angiogram, but its etiopathogenesis remains unclear. Plasma homocysteine (Hcy) level can severely disturb vascular endothelial function and may play a role in the pathogenesis of CSF. In our study, endothelial function in patients with CSF and their relationship with Hcy and oxidative stress parameters are investigated. Method: Forty-four patients with angiographically proven CSF and 44 cases with normal coronary flow pattern with similar risk profile were enrolled in the study. Coronary flow patterns of the cases are determined by Thrombolysis in Myocardial Infarction (TIMI) frame count method. Endothelium dependent flow mediated dilatation (FMD) and independent vasodilatation characteristics are evaluated by high frequency ultrasound over the brachial artery. Superoxide dismutase (SOD) and reduced glutathione (GSH) and reduction of oxidative material in the body and the end product of lipid peroxidation, malondialdehyde (MDA) are measured as oxidative stress markers in blood samples. Results: Plasma Hcy level (µmol/l) of patients with CSF was found to be significantly higher than in controls (12.2 ± 4.9 vs. 8.5 ± 2.8, p = 0.0001). FMD was 7.87 ± 2.0% in controls and 4.98 ± 1.1% in patients with CSF (p = 0.0001). GSH was reduced in patients with CSF. SOD and MDA activity were found higher in patients with CSF than control subjects. Plasma Hcy level was significantly positively correlated with mean TIMI frame count and negatively correlated with FMD in correlation analysis (r = 0.58, p = 0.0001; r = –0.41, p = 0.022; respectively). Conclusion: The present findings allow us to conclude that patients with CSF have increased levels of Hcy and oxidative stress markers and impaired endothelial cell function.

Homocysteinylation of Metallothionein Impairs Intracellular Redox Homeostasis

Heart disease and stroke are major causes of death and morbidity in North America, and they exact high personal, community, and health care costs. Most heart attacks and strokes are caused by thrombosis superimposed on disrupted atherosclerotic lesions, a process known as atherothrombosis.1,2 A number of risk factors are known to accelerate atherothrombosis, including hypercholesterolemia, smoking, diabetes, hypertension, and obesity. Numerous clinical and epidemiological studies have established hyperhomocysteinemia as an independent risk factor for cardiovascular disease and stroke.3–8 Patients with inborn errors of methionine metabolism caused by deficiencies in cystathionine β-synthase or 5,10-methylenetetrahydrofolate reductase present with severe hyperhomocysteinemia and have a 50% chance of developing a major vascular event by the age of 30 years if untreated.6 This vascular risk is substantially decreased by homocysteine-lowering therapy (dietary supplementation with folic acid, B-vitamins, and/or betaine), even if the treatment does not completely normalize total plasma homocysteine levels.8 Unlike severe hyperhomocysteinemia, mild hyperhomocysteinemia attributable to deficiencies in dietary folic acid and/or B-vitamins is common in the general population. Despite the association between hyperhomocysteinemia and increased cardiovascular risk, several recent clinical trials have failed to show a preventative benefit of homocysteine-lowering therapy in cardiovascular patients with mild hyperhomocysteinemia.9,10 Although not completely understood, the results of these studies could imply that homocysteine-lowering therapy is ineffective in patients with established cardiovascular disease or that vitamin therapy has other, potentially adverse effects that neutralize its homocysteine-lowering benefit.11 See page 49 A direct causal relationship between hyperhomocysteinemia and atherosclerosis has been reported in diet- and/or genetic-induced mouse models of hyperhomocysteinemia.12–15 Previous studies have also reported that human cells relevant to atherothrombotic disease, including vascular endothelial cells and smooth muscle cells, are particularly sensitive to the cytotoxic effects of homocysteine that may result from the limited capacity of these cells to …

Effects of hydrogen sulfide on homocysteine-induced oxidative stress in vascular smooth muscle cells

Hydrogen sulfide (H 2S) is an important gasotransmitter that generated in mammalian cells from l-cysteine metabolism. Little is known about its protective role in oxidative stress. In the present study, we investigated whether H 2S could affect homocysteine (HCY)-induced cytotoxicity and oxidative stress in vascular smooth muscle cells. Cultured A-10 cells were exposed to HCY treatment in the presence or absence of NaHS (donor of H 2S). HCY induced cytotoxicity, increased levels of H 2O 2, ONOO −, and O 2 - in a time- and concentration-dependent manner. Low levels of NaHS (30 or 50 μM) protected A-10 cells from cytotoxicity, decreased the production of H 2O 2, ONOO −, and O 2 - in the presence of HCY. Furthermore, NaHS enhanced inhibitory effects of NAC, GSH, DPI, SOD, L-NAME, or vitamin C on oxidized DCF or O 2 - formation induced by HCY. In conclusion, our findings provide the first evidence that low levels of H 2S decrease reactive oxygen species and improve cell viability and by doing so limit cellular damage induced by HCY.