AUTOCRINE REGULATION OF THE ENDOTHELIN-1 GENE IN RAT ENDOTHELIAL-CELLS

We studied whether endothelin (ET)-1 regulates its own transcription in cultured rat aortic endothelial cells (ECs) in an autocrine manner and attempted to elucidate its cellular and molecular mechanism. By Northern blot analysis using rat preproET-1 cDNA as a probe, ET-1 increased steady-state levels of preproET-1 mRNA as early as 30 min, which persisted during 4 h incubation. ET-1 also increased steady-state c-fos mRNA levels, which returned to an undetectable level by 2 h. ET-1 dose-dependently upregulated preproET-1 mRNA expression. The effect was inhibited by a nonselective ET(A)/ET(B) receptor antagonist but not a selective ET(A) receptor antagonist. The ET-1-induced preproET-1 mRNA expression was suppressed by a protein kinase C (PKC) inhibitor and by pretreatment with phorbol ester, which depleted endogenous PKC. The approximate half-life of preproET-1 mRNA stimulated by ET-1 (approximately 20 min) was similar to that stimulated by phorbol ester. Our data demonstrate that ET-1 upregulates its own gene expression through ET(B) receptor-mediated PKC activation, suggesting a possible autocrine positive feedback system in vascular endothelium.