Oxidative Stress Increases Endothelin-1 Synthesis in Human Coronary Artery Smooth Muscle Cells

Abstract

Endothelins, nitric oxide, and oxygen-derived free radicals decisively regulate vascular tone. An imbalance in the biosynthesis of these substances in pathophysiologic conditions may trigger vasospasm and promote the development of atherosclerosis. Previous studies have shown that oxygen-derived free radicals can increase the synthesis of endothelin-1 in cultured endothelial cells. Interestingly, conditions of increased oxidative stress within smooth muscle cells as induced by angiotensin II infusion or hypercholesterolemia have been shown to be associated with increased autocrine synthesis of endothelin-1. Because endothelin-1 formed in smooth muscle cells can trigger hypersensitivity to vasoconstrictors, we tested whether oxidative stress per se may affect endothelin expression in vascular smooth muscle cells. Cultured human coronary artery smooth muscle cells were exposed to oxidative stress generated by the xanthine/xanthine oxidase reaction or by hydrogen peroxide. Preproendothelin-1 mRNA content was quantitated by means of quantitative polymerase chain reaction and endothelin-1 protein was measured by radioimmunoassay. Incubation with xanthine/xanthine oxidase significantly increased preproendothelin-1 mRNA synthesis, whereas GAPDH remained unchanged. Likewise, xanthine/xanthine oxidase also led to a dose-dependent increase of intracellular endothelin-1. The increase in ET-1 expression induced by xanthine/xanthine oxidase was significantly inhibited by superoxide dismutase but not by catalase. We conclude that oxygen-derived free radicals can stimulate the synthesis of endothelin-1 in endothelial and vascular smooth muscle cells by increasing preproendothelin-1 mRNA content and that this effect is mediated predominantly by superoxide anions. We therefore have identified a new mechanism in the interaction of oxidative stress and endothelin-1 expression in smooth muscle cells that may have important implications in diseases such as atherosclerosis and hypertension.

The Puzzle of Nitrate Tolerance

“…The production of endothelin is stimulated by both angiotensin II and oxidative stress in endothelial and smooth muscle cells. [57][58][59] An increased endothelin-1-like and big endothelin-1-like immunoreactivity in the tunica media of tolerant vessels has been demonstrated during nitrate treatment in two different animal models. 60,61 In one report, exposure of normal vessels to low concentrations of endothelin-1 caused a hypersensitivity to vasoconstricting agents similar to that observed in nitrate tolerant vessels.…”

Novel Mechanisms Responsible for Postmenopausal Hypertension

“…36 Just as endothelin can cause oxidative stress, endothelin also increases in response to oxidative stress. 50 Therefore, endothelin could be increased in postmenopausal women because of reductions in estradiol and increases in Ang II, oxidative stress, or androgens.…”

Endothelin, Angiotensin, and Oxidative Stress in Hypertension

“…40,41 Whereas ET-1 can increase oxidative stress, there are a number of reports that reactive oxygen species can increase ET-1 production in cultured endothelial cells and vascular smooth muscle cells. [42][43][44][45] Hydrogen peroxide and superoxide can increase ET-1 synthesis, and 8-iso prostaglandin F2ϰ, a product formed by free radical catalyzed lipid peroxidation, also can have similar effects. 42 The relevance of these observations is unclear given that Saito et al observed contrasting findings that hydrogen peroxide actually decreases ET-1 mRNA and protein synthesis in endothelial cells.…”