Hydrogen peroxide signaling mediates DHEA-induced vascular endothelial cell proliferation

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▸ H2O2 mediates rapid DHEA-induced vascular endothelial cell proliferation in vitro. ▸ DHEA-induced H2O2 signaling is dependent on prior activation of Gi/o protein. ▸ DHEA-induced cyclin D1 expression is dependent on initial H2O2 stimulation.

Dehydroepiandrosterone (DHEA) activates a putative plasma membrane Gi-protein coupled receptor to induce vascular endothelial proliferation. We now test the hypothesis that hydrogen peroxide (H2O2) signaling mediates this effect. Incubation of EA.hy926 cells, a human vascular endothelial cell line, with DHEA for 5 min produced a significant increase in H2O2 production, measured by oxidation of either p-hydroxyphenylacetate or dichlorodihydrofluorescein. The DHEA effect on H2O2 production was maximal at 1 nM DHEA, was evident within the first minute of incubation, and remained for 10 min. Similar results were present in primary bovine aortic endothelial cells. The induction of H2O2 in EA.hy926 cells was mimicked by a membrane-impermeable albumin-conjugated DHEA and was inhibited by either catalase or pertussis toxin. Incubation of endothelial cells with DHEA for 5 min resulted in a 2-fold increase of cyclin D1 mRNA and protein expression at 4 h. These effects were abolished by co-incubation with catalase. DHEA induced a 50 ± 7% increase in cell proliferation over 24 h, measured as cellular Ki-67 immunoreactivity. This proliferative effect was abolished by either catalase or pertussis toxin co-incubation, indicating an H2O2 and Gi-protein-dependent effect. We conclude that H2O2 is a key signaling molecule mediating the proliferative effects of DHEA in vascular endothelial cells, possibly by up-regulating cell-cycle associated genes, such as cyclin D1.

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