Cellular Redox State and Endothelial Dysfunction in Mildly Hyperhomocysteinemic Cystathionine β-Synthase–Deficient Mice

Abstract

Abstract-Previous in vitro experiments have shown that hyperhomocysteinemia leads to oxidative inactivation of nitric oxide, in part by inhibiting the expression of cellular glutathione peroxidase (GPx-1). To elucidate the role of intracellular redox status on homocysteine-induced endothelial dysfunction and oxidant stress, heterozygous cystathionine ␤-synthase-deficient (CBS -/ϩ ) and wild-type (CBS ϩ/ϩ ) mice were treated with the cysteine donor L-2-oxothiazolidine-4-carboxylic acid (OTC). CBS -/ϩ mice had significantly lower GPx-1 activity compared with their CBS ϩ/ϩ littermates, and OTC treatment led to a modest increase in tissue GPx-1 activity and significant increases in total thiols and in reduced glutathione levels in both CBS ϩ/ϩ and CBS -/ϩ mice. Superfusion of the mesentery with ␤-methacholine or bradykinin produced dose-dependent vasodilation of mesenteric arterioles in CBS ϩ/ϩ mice and in CBS ϩ/ϩ mice treated with OTC. In contrast, mesenteric arterioles from CBS -/ϩ mice manifested dose-dependent vasoconstriction in response to both agonists. OTC treatment of CBS -/ϩ mice restored normal microvascular vasodilator reactivity to ␤-methacholine and bradykinin. These findings demonstrate that mild hyperhomocysteinemia leads to endothelial dysfunction in association with decreased bioavailable nitric oxide. Increasing the cellular thiol and reduced glutathione pools and increasing GPx-1 activity restores endothelial function. These findings emphasize the importance of intracellular redox balance for nitric oxide bioactivity and endothelial function. Key Words: homocysteine Ⅲ endothelial function Ⅲ oxidant stress Ⅲ nitric oxide Ⅲ P-selectin M ild hyperhomocysteinemia, ie, an elevation of the plasma levels of homocysteine, homocystine, or homocysteine-mixed disulfides, has been shown to be a risk factor for atherosclerotic vascular disease and its thrombotic complications. Population-based, nested case-control studies demonstrate that a 5 mol/L increase in plasma homocysteine concentrations leads to a 30% increase in cardiovascular risk (reviewed in the first 5 references). [1][2][3][4][5] In addition, several prospective studies indicate that the increased risk is higher during short-term follow-up and declines after 3 to 4 years. Hyperhomocysteinemia is an even stronger predictor of cardiovascular risk in patients with preexisting conditions, such as chronic renal failure, 6 coronary heart disease, 7 diabetes mellitus, 8 peripheral arterial occlusive disease, 9 systemic lupus erythematosus, 10 or venous thromboembolism. 11 In accordance with these observations, elevated homocysteine levels are more strongly associated with recurrent cardiovascular events than with first stroke or myocardial infarction. 12 These data suggest that homocysteine promotes acute thrombotic events in the presence of preexisting vascular lesions rather than induces atherosclerotic lesions de novo.The mechanisms by which elevated homocysteine levels alter the vascular environment to facilitate the development and progression of ...

Hyperhomocysteinemia: the protein C pathway to thrombosis

“…2,3 The study is consistent with the demonstrated presence of ADAMTS13 mRNA in endothelial cells 4 and, more importantly, puts the metalloprotease where its substrate ULVWF is synthesized, released, and likely cleaved. Although the data are generated in cell culture, endothelial cells are likely to synthesize the metalloprotease in vivo.…”

“…In contrast to the in vitro platelet studies by Dayal and colleagues, Weiss et al 4 showed that mildly hyperhomocysteinemic mice have higher circulating levels of P-selectin, indicating that platelets are activated in vivo by elevated homocysteine. Importantly, Dayal and colleagues found that washed platelets, free from the hyperhomocysteinemic environment, are not altered in their response to thrombin activation.…”

Role of hyperhomocysteinemia in endothelial dysfunction and atherothrombotic disease

“…Heterozygous CBSdeficient mice develop endothelial dysfunction by decreasing vascular nitric oxide bioavailability, thereby leading to impaired vasorelaxation. 41,46 This association is not unique to CBS-deficient mice, as endothelial dysfunction has also been observed in other animal models of HHcy, including rabbits and monkeys. 67,[110][111][112][113] Although CBS-deficient mice or non-murine models of HHcy exhibit endothelial dysfunction, there is no evidence of atherosclerotic lesion development.…”

“…41 It is likely, therefore, that HHcy decreases nitric oxide bioavailability through alternative mechanisms, such as accelerated oxidative inactivation of nitric oxide. 40 Homocysteine-induced oxidative inactivation of nitric oxide has been observed in vitro in cultured endothelial cells, 42 and evidence for increased oxidative inactivation of nitric oxide during HHcy has been obtained in animals using both pharmacological 41,[43][44][45][46] and genetic 47,48 approaches. Several types of reactive oxygen species (ROS), including superoxide, hydrogen peroxide, and peroxynitrite, may contribute to the oxidative inactivation of endothelium-derived nitric oxide in HHcy.…”

Hyperkeratosis in cystathionine beta synthase‐deficient mice: An animal model of hyperhomocysteinemia

“…These mice, which have elevated level of plasma homocysteine concentrations (Watanabe et al, 1995), also exhibit some pathological features of hyperhomocysteinemia such as endothelial dysfunctions (Eberhardt et al, 2000;Lentz et al, 2000;Dayal et al, 2001;Weiss et al, 2001Weiss et al, , 2002Denis et al, 2003).…”