Oxidative stress increases endothelin-1 synthesis in human coronary arterysmooth muscle cells

Endothelins, nitric oxide, and oxygen-derived free radicals decisively regu late vascular tone. An imbalance in the biosynthesis of these substances in pathophysiologic conditions may trigger vasospasm and promote the developm ent of atherosclerosis. Previous studies have shown that oxygen-derived fre e radicals can increase the synthesis of endothelin-1 in cultured endotheli al cells. Interestingly, conditions of increased oxidative stress within sm ooth muscle cells as induced by angiotensin II infusion or hypercholesterol emia have been shown to be associated with increased autocrine synthesis of endothelin-1. Because endothelin-1 formed in smooth muscle cells can trigg er hypersensitivity to vasoconstrictors, we tested whether oxidative stress per se may affect endothelin expression in vascular smooth muscle cells. C ultured 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 quant itative polymerase chain reaction and endothelin-1 protein was measured by radioimmunoassay. Incubation with xanthine/xanthine oxidase significantly i ncreased preproendothelin-l mRNA synthesis, whereas GAPDH remained unchange d. Likewise, xanthine/xanthine oxidase also led to a dose-dependent increas e of intracellular endothelin-1. The increase in ET-1 expression induced by xanthine/xanthine oxidase was significantly inhibited by superoxide dismut ase but not by catalase. We conclude that oxygen-derived free radicals can stimulate the synthesis of endothelin-l in endothelial and vascular smooth muscle cells by increasing preproendothelin-1 mRNA content and that this ef fect is mediated predominantly by superoxide anions. We therefore have iden tified a new mechanism in the interaction of oxidative stress and endotheli n-1 expression in smooth muscle cells that may have important implications in diseases such as atherosclerosis and hypertension.