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Genetic determinants of hyperhomocysteinemia in atherosclerosis.

ABSTRACT: Hyperhomocysteinemia (Hhcy) is an independent risk factor for the development of atherosclerosis. The mechanisms by which HHcy promotes cardiovascular disease may be due to activation of pro-inflammatory factors, endoplasmic reticulum (ER) stress and oxidative stress. We aimed to study (i) gene mutations that cause HHcy. (ii) Estimation of inflammatory marker like ultrasenitive C-reactive proteins (hs-CRP) and total antioxidant levels (iii) determination of Hcy- dependent gene expression in vivo. 25 HHcy patients and 25 healthy controls were taken for this study. Mutation detection in MTHFR, CBS, MS and eNOS gene was by PCR-based restriction enzyme analysis and subsequently expression study was carried out by Reverse Transcriptase PCR and cloning technique. A significant association of HHcy with MTHFR (C677T) and MS (A2756G) genotype was observed (p<0.05). There was no association of Hhcy and eNOS genotype. The Hhcy patients, showed no expression of the ER stress gene, GRP78 in lymphocytes. Our study showed no effect of Hcy on the CD18 gene (pro-inflammatory pathway) expression, but a significant association of tHcy and hs-CRP levels in HHcy grp (t=2.28, p<0.05). This shows that HHcy induces inflammatory response, which could lead to tissue injury in the pathogenesis of the atherosclerotic process. Our findings show higher mRNA expression of manganese superoxide dismutase (Mn SOD) in HHcy group as compared to the control group. The Total Antioxidant Status (TAS) estimated was found to be significantly lower in the HHcy group as compared to healthy normals (t=4.8, p<0.01). Taken together these findings strongly suggest that the adverse effects of homocysteine are at least partly mediated by oxidative stress. Our study supports the hypothesis that Hcy evokes adverse vascular effects by promoting oxidative damage to endothelial cells.

SUBMITTER: Eghlim FF

PROVIDER: S-EPMC3454005 | biostudies-other | 2006 Sep

REPOSITORIES: biostudies-other

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Genetic determinants of hyperhomocysteinemia in atherosclerosis.

Eghlim Farah F FF Ashavaid Tester F TF Nair Kappiareth G KG

Indian journal of clinical biochemistry : IJCB 20060901 2

Hyperhomocysteinemia (Hhcy) is an independent risk factor for the development of atherosclerosis. The mechanisms by which HHcy promotes cardiovascular disease may be due to activation of pro-inflammatory factors, endoplasmic reticulum (ER) stress and oxidative stress. We aimed to study (i) gene mutations that cause HHcy. (ii) Estimation of inflammatory marker like ultrasenitive C-reactive proteins (hs-CRP) and total antioxidant levels (iii) determination of Hcy- dependent gene expression in vivo ...[more]

PMID: 23105606

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Project description:Hyperhomocysteinemia (HHcy) has been shown to promote vascular inflammation and atherosclerosis, but the underlying mechanisms remain largely unknown. The NLRP3 inflammasome has been identified as the cellular machinery responsible for activation of inflammatory processes. In this study, we hypothesized that the activation of NLRP3 inflammasomes contributes to HHcy-induced inflammation and atherosclerosis. ApoE-/- mice were fed regular chow, high-fat (HF) diet, or HF plus high methionine diet to induce HHcy. To assess the role of NLRP3 inflammasomes in HHcy-aggravated atherosclerosis, NLRP3 shRNA viral suspension was injected via tail vein to knock down the NLRP3 gene. Increased plasma levels of IL-1β and IL-18, aggravated macrophage infiltration into atherosclerotic lesions, and accelerated development of atherosclerosis were detected in HHcy mice as compared with control mice, and were associated with the activation of NLRP3 inflammasomes. Silencing the NLRP3 gene significantly suppressed NLRP3 inflammasome activation, reduced plasma levels of proinflammatory cytokines, attenuated macrophage infiltration and improved HHcy-induced atherosclerosis. We also examined the effect of homocysteine (Hcy) on NLRP3 inflammasome activation in THP-1-differentiated macrophages in the presence or absence of NLRP3 siRNA or the caspase-1 inhibitor Z-WEHD-FMK. We found that Hcy activated NLRP3 inflammasomes and promoted subsequent production of IL-1β and IL-18 in macrophages, which were blocked by NLRP3 gene silencing or Z-WEHD-FMK. As reactive oxygen species (ROS) may have a central role in NLRP3 inflammasome activation, we next investigated whether antioxidant N-acetyl-l-cysteine (NAC) prevented Hcy-induced NLRP3 inflammasome activation in macrophages. We found Hcy-induced NLRP3 inflammasome activation was abolished by NAC. Treatment with NAC in HHcy mice also suppressed NLRP3 inflammasome activation and improved HHcy-induced atherosclerosis. These data suggest that the activation of NLRP3 inflammasomes contributes to HHcy-aggravated inflammation and atherosclerosis in apoE-/- mice. Hcy activates NLRP3 inflammasomes in ROS-dependent pathway in macrophages. These results may have implication for the treatment of HHcy-associated cardiovascular diseases.

Project description:RationaleHyperhomocysteinemia (HHcy) accelerates atherosclerosis and increases inflammatory monocytes (MC) in peripheral tissues. However, its causative role in atherosclerosis is not well established and its effect on vascular inflammation has not been studied. The underlying mechanism is unknown.ObjectiveThis study examined the causative role of HHcy in atherogenesis and its effect on inflammatory MC differentiation.Methods and resultsWe generated a novel HHcy and hyperlipidemia mouse model, in which cystathionine β-synthase (CBS) and low-density lipoprotein receptor (LDLr) genes were deficient (Ldlr(-/-) Cbs(-/+)). Severe HHcy (plasma homocysteine (Hcy)=275 μmol/L) was induced by a high methionine diet containing sufficient basal levels of B vitamins. Plasma Hcy levels were lowered to 46 μmol/L from 244 μmol/L by vitamin supplementation, which elevated plasma folate levels. Bone marrow (BM)-derived cells were traced by the transplantation of BM cells from enhanced green fluorescent protein (EGFP) transgenic mice after sublethal irradiation of the recipient. HHcy accelerated atherosclerosis and promoted Ly6C(high) inflammatory MC differentiation of both BM and tissue origins in the aortas and peripheral tissues. It also elevated plasma levels of TNF-α, IL-6, and MCP-1; increased vessel wall MC accumulation; and increased macrophage maturation. Hcy-lowering therapy reversed HHcy-induced lesion formation, plasma cytokine increase, and blood and vessel inflammatory MC (Ly6C(high+middle)) accumulation. Plasma Hcy levels were positively correlated with plasma levels of proinflammatory cytokines. In primary mouse splenocytes, L-Hcy promoted rIFNγ-induced inflammatory MC differentiation, as well as increased TNF-α, IL-6, and superoxide anion production in inflammatory MC subsets. Antioxidants and folic acid reversed L-Hcy-induced inflammatory MC differentiation and oxidative stress in inflammatory MC subsets.ConclusionsHHcy causes vessel wall inflammatory MC differentiation and macrophage maturation of both BM and tissue origins, leading to atherosclerosis via an oxidative stress-related mechanism.

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Genetic determinants of hyperhomocysteinemia in atherosclerosis.

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Genetic determinants of hyperhomocysteinemia in atherosclerosis.

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