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Homocysteine decreases endothelin-1 production by cultured human endothelial cells
K Demuth1, V Atger, D Borderie
1Laboratoire de Biochimie, Hôpital Broussais, AP-HP, Paris, France. karine.demuth@brs.ap-hop-paris.fr
Insights
High homocysteine levels impair vascular function by reducing endothelin-1 (ET-1) production and mRNA. This sulfhydryl-dependent mechanism may explain how homocysteine impairs endothelium-dependent vasodilation.
Area of Science:
- Vascular Biology
- Endocrinology
- Biochemistry
Background:
- Hyperhomocysteinemia is linked to vascular disease development.
- Homocysteine may impair endothelial cell function by affecting vasodilator autacoids.
- Endothelin-1 (ET-1) is a key vasoconstrictor regulated by endothelial cells.
Purpose of the Study:
- To investigate the effect of homocysteine on endothelin-1 (ET-1) production and mRNA levels in human endothelial cells.
- To determine if the mechanism of homocysteine's effect is sulfhydryl-dependent.
Main Methods:
- Human endothelial cells were treated with varying concentrations of homocysteine.
- ET-1 secretion and mRNA levels were measured.
- The effect of thiol compounds and a sulfhydryl inhibitor (N-ethylmaleimide) was assessed.
Main Results:
- Noncytotoxic homocysteine concentrations significantly decreased ET-1 secretion and mRNA in a dose-dependent manner.
- The inhibitory effect was observed at both pathophysiological and pharmacological concentrations.
- The mechanism was confirmed to be sulfhydryl-dependent, as N-ethylmaleimide blocked the effect.
Conclusions:
- Homocysteine directly inhibits ET-1 production and mRNA levels in endothelial cells.
- This inhibition is mediated through a sulfhydryl-dependent pathway.
- This finding suggests a novel mechanism by which homocysteine contributes to vascular dysfunction via impaired vasodilation.
Abstract:
Hyperhomocysteinemia is believed to be responsible for the development of vascular disease via several mechanisms, including the impairment of endothelial-cell functionality. In-vitro studies have demonstrated that homocysteine decreases the production or bioavailability of vasodilator autacoids, such as prostacyclin and NO. Here, we show that the treatment of human endothelial cells with noncytotoxic homocysteine concentrations leads to a dose-dependent decrease in both the secretion of the vasoconstrictor agent endothelin-1 (ET-1) and the level of its mRNA. Homocysteine had an inhibitory effect at pathophysiological (0.1 and 0.5 mmol.L(-1)) and pharmacological noncytotoxic (1.0 and 2.0 mmol.L(-1)) concentrations. Mean percentage variation from control for ET-1 production was -36. 2 +/- 18.9% for 0.5 mmol.L(-1) homocysteine and -41.5 +/- 26.8% for 1.0 mmol.L(-1) homocysteine, after incubation for 8 h. Mean percentage variation from control for steady-state mRNA was -17.3 +/- 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 also reduced by incubation with various other thiol compounds containing free thiol groups, but not by incubation with thiol compounds with no free thiol group. Co-incubation of cells with homocysteine and the sulfhydryl inhibitor N-ethylmaleimide prevented the effect of homocysteine on ET-1 production, confirming a sulfhydryl-dependent mechanism. Based on the reciprocal feedback mechanism controlling the synthesis of vasoactive mediators, these preliminary data suggest a mechanism by which homocysteine may selectively impair endothelium-dependent vasodilation by primary inhibition of ET-1 production.