Hyperhomocysteinemia Promotes Inflammatory Monocyte Generation and Accelerates Atherosclerosis in Transgenic Cystathionine β-Synthase–Deficient Mice

Abstract

Background— Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease. Monocytes display inflammatory and resident subsets and commit to specific functions in atherogenesis. In this study, we examined the hypothesis that HHcy modulates monocyte heterogeneity and leads to atherosclerosis. Methods and Results— We established a novel atherosclerosis-susceptible mouse model with both severe HHcy and hypercholesterolemia in which the mouse cystathionine β-synthase (CBS) and apolipoprotein E (apoE) genes are deficient and an inducible human CBS transgene is introduced to circumvent the neonatal lethality of the CBS deficiency ( Tg-hCBS apoE −/− Cbs −/− mice). Severe HHcy accelerated atherosclerosis and inflammatory monocyte/macrophage accumulation in lesions and increased plasma tumor necrosis factor-α and monocyte chemoattractant protein-1 levels in Tg-hCBS apoE −/− Cbs −/− mice fed a high-fat diet. Furthermore, we characterized monocyte heterogeneity in Tg-hCBS apoE −/− Cbs −/− mice and another severe HHcy mouse model ( Tg-S466L Cbs −/− ) with a disease-relevant mutation ( Tg-S466L ) that lacks hyperlipidemia. HHcy increased monocyte population and selective expansion of inflammatory Ly-6C hi and Ly-6C mid monocyte subsets in blood, spleen, and bone marrow of Tg-S466L Cbs −/− and Tg-hCBS apoE −/− Cbs −/− mice. These changes were exacerbated in Tg-S466L Cbs −/− mice with aging. Addition of l -homocysteine (100 to 500 μmol/L), but not l -cysteine, maintained the Ly-6C hi subset and induced the Ly-6C mid subset in cultured mouse primary splenocytes. Homocysteine-induced differentiation of the Ly-6C mid subset was prevented by catalase plus superoxide dismutase and the NAD(P)H oxidase inhibitor apocynin. Conclusion— HHcy promotes differentiation of inflammatory monocyte subsets and their accumulation in atherosclerotic lesions via NAD(P)H oxidase–mediated oxidant stress.

Molecular Biology of Atherosclerosis

“…Zinc removed from water for atherosclerosis studies (2067). Increased atherosclerosis likely due to impaired H 2 S synthesis (118,1586,1759).…”

“…In one recent study in ApoE KO mice (2067), high early mortality seen in prior studies of CBS Ϫ/Ϫ mice was avoided by utilizing a zinc-inducible human CBS transgene in otherwise CBS-deficient, apoE Ϫ/Ϫ mice. During pregnancy and weaning, zinc was added to the drinking water, the transgene was activated, and Hcy levels were only slightly elevated, preventing early mortality.…”

Nutrition in Stroke Prevention

“…44 Homocysteine increases oxidative stress, 45 increases hepatic synthesis of cholesterol, 46 increases levels of asymmetric dimethylarginine (ADMA), a nitric oxide antagonist, 47 appears to be causal in Mendelian randomization studies, 48,49, and is causal in animal models. 50,51 In an analysis of the National Health and Nutrition Examination Survey (NHANES) and the Multi-Ethnic Study of Atherosclerosis (MESA) study, tHcy resulted in a net reclassification of cardiovascular risk by 20 %. 52 Elevated levels of total homocysteine increase deep vein thrombosis, retinal vein thrombosis, and cerebral vein thrombosis, and markedly increase the risk for stroke in atrial fibrillation.…”

Database Mining: Defining the Pathogenesis of Inflammatory and Immunological Diseases

“…The firsttier tissues may have a higher probability of experiencing acute inflammation than the second-tier and third-tier tissues. We and others showed that elevated levels of plasma homocysteine (Hcy), termed hyperhomocysteinemia (HHcy), is an independent risk factor, equivalent to hyperlipidemia, for cardiovascular diseases (CVD) including coronary heart disease and stroke (Maron & Loscalzo, 2009;Wang et al, 2003;Zhang et al, 2009). Recently, we performed an additional database mining study using to examine the expression of more than 20 homocysteine metabolic enzymes and methylation enzymes in >20 tissues in humans and mouse (Chen et al, 2010).…”