Homocysteine decreases endothelin-1 production by cultured human endothelial cells

Hyperhomocysteinemia is believed to be responsible for the development of v ascular disease via several mechanisms, including the impairment of endothe lial-cell functionality. In-vitro studies have demonstrated that homocystei ne decreases the production or bioavailability of vasodilator autacoids, su ch as prostacyclin and NO. Here, we show that the treatment of human endoth elial cells with noncytotoxic homocysteine concentrations leads to a dose-d ependent decrease in both the secretion of the vasoconstrictor agent endoth elin-1 (ET-1) and the level of its mRNA. Homocysteine had an inhibitory eff ect at pathophysiological (0.1 and 0.5 mmol.L-1) and pharmacological noncyt otoxic (1.0 and 2.0 mmol.L-1) concentrations. Mean percentage variation fro m control for ET-1 production was -36.2 +/- 18.9% for 0.5 mmol.L-1 homocyst eine and -41.5 +/- 26.8% for 1.0 mmol.L-1 homocysteine, after incubation fo r 8 h. Mean percentage variation from control for steady-state mRNA was - 1 7.3 +/- 7.1% for 0.5 mmol.L-1 homocysteine and -46.0 +/- 10.1 for 1.0 mmol . L-1 homocysteine, after an incubation time of 2 h. ET-1 production was al so reduced by incubation with various other thiol compounds containing free thiol groups, but not by incubation with thiol compounds with no free thio l group. Go-incubation of cells with homocysteine and the sulfhydryl inhibi tor N-ethylmaleimide prevented the effect of homocysteine on ET-1 productio n, confirming a sulfhydryl-dependent mechanism. Based on the reciprocal fee dback mechanism controlling the synthesis of vasoactive mediators, these pr eliminary data suggest a mechanism by which homocysteine may selectively im pair endothelium-dependent vasodilation by primary inhibition of ET-1 produ ction.