Endothelin-1 is induced by cytokines in human vascular smooth muscle cells: Evidence for intracellular endothelin-converting enzyme

Endothelin-1 (ET-1) is the predominant endothelin isopeptide generated by t he vascular wall and therefore appears to be the most important peptide inv olved in regulation of cardiovascular events. Many pathologic conditions ar e associated with elevations of ET-1 in the blood vessel wall. Because thes e conditions are often cytokine driven, we examined the effects of a mixtur e of cytokines on ET-1 production in human vascular smooth muscle cells (VS MCs) derived from internal mammary artery and saphenous vein (SV), Incubati on of IMA and SV VSMCs with tumor necrosis factor-alpha (10 ng/ml) and inte rferon-gamma (1000 U/ml) in combination for up to 48 h markedly elevated th e expression of mRNA for prepro-ET-1 and the release of ET-1 into the cultu re medium. This cytokine-stimulated release of ET-1 was inhibited by a seri es of dual endothelin-converting enzyme (ECE)/neutral endopeptidase inhibit ors, phosphoramidon, CGS 26303, and CGS 26393, with an accompanying increas e in big ET-1 release but with no effect on expression of mRNA for prepro-E T-1. These same compounds were 10 times more potent at inhibiting the conve rsion of exogenously applied big ET-1 to ET-1, ECE-1b/c mRNA is present in SV VSMCs, however no ECE-1 a is present in these cells. Thus VSMCs most pro bably contain, like endothelial cells, an intracellular ECE responsible for the endogenous synthesis of ET-1. Under the influence of pro-inflammatory mediators the vascular smooth muscle can therefore become an important site of ET-1 production, as has already been established for the dilator mediat ors nitric oxide, prostaglandin I-2, and prostaglandin E-2.