PreproEndothelin-1 expression in human mesangial cells: Evidence for a p38mitogen-activated protein kinase/protein kinases-C-dependent mechanism

Endothelin-1 (ET-1) has been implicated in the pathogenesis of renal inflam mation. This study investigated the mechanisms underlying the synergistic u pregulation of preproET-1 gene expression in human mesangial cells after co -stimulation with thrombin and tumor necrosis factor alpha (TNF alpha). Whe reas thrombin induced a moderate upregulation of preproET-1 mRNA, co-stimul ation with TNF alpha resulted in a strong and protracted upregulation of th is mRNA species. Thrombin + TNF alpha -induced upregulation of preproET-1 e xpression was found to require p38 mitogen-activated protein kinase and pro tein kinases C, whereas activation of extracellular signal-regulated kinase , c-Jun-N-terminal kinase, or intracellular Ca2+ release were not required. Actinomycin D chase experiments suggested that enhanced stability of prepr oET-1 mRNA did not account for the increase in transcript levels. PreproET- 1 promoter analysis demonstrated that the 5'-flanking region of preproET-1 encompassed positive regulatory elements engaged by thrombin. Negative modu lation of thrombin-induced activation exerted by the distal 5' portion of p reproET-1 promoter (-4.4 kbp to 204 bp) was overcome by co-stimulation with TNF alpha, providing a possible mechanism underlying the synergistic upreg ulation of preproET-1 expression by these two agonists. In conclusion, huma n mesangial cell expression of preproET-1 may be increased potently in the presence of two common proinflammatory mediators, thereby providing a poten tial mechanism for ET-1 production in inflammatory renal disease.