ACTIVATION OF GLOMERULAR MESANGIAL CELLS BY HEPATOCYTE GROWTH-FACTOR THROUGH TYROSINE KINASE AND PROTEIN-KINASE-C

Hepatocyte growth factor (HGF) induces mitogenesis, chemotaxis, and tu bule formation in renal epithelial cells. This study examined the effe cts of wortmannin and protein kinase C (PKC) inhibitors on HGF-mediate d changes in metabolic activity in glomerular mesangial cells and rena l epithelial carcinoma A498 cells. The extracellular acidification rat e of transformed mouse glomerular mesangial cells and A498 cells was m easured as an index of metabolic activity with a microphysiometer. HGF increased the acidification rate of mesangial cells and A498 cells in a concentration-dependent fashion that was inhibited completely by th e tyrosine kinase inhibitor tyrphostin-23 (100 mu M). The PKC inhibito rs RO-32-0432 and SKF-57048 also inhibited HGF-induced acidification. The IC50 values for SKF-57048 were 59 +/- 2 and 20 +/- 10 nM in mesang ial cells and A498 cells, respectively (P < 0.05). 12-O-Tretradecanoyl yhorbol 13-acetate (TPA), a phorbol ester that activates PKC, increase d acidification in mesangial and epithelial cells similar to HGF. Wort mannin, an inhibitor of phosphatidylinositol (PI) 3-kinase (IC50 value 1-10 nM), inhibited HGF-induced acidification with an IC50 of 93 +/- 31 and 9 +/- 1 nM in mesangial and A498 cells, respectively (P < 0.05) . In contrast, there was no significant difference in the IC50 value o f wortmannin for epidermal growth factor (EGF)-induced acidification b etween mesangial and A498 cells (23 +/- 9 vs 14 +/- 1 nM, respectively ). Because the IC50 value for wortmannin in inhibiting HGF but not EGF -induced acidification was an order of magnitude higher in mesangial c ells than in epithelial A498 cells, a wortmannin-sensitive PI 3-kinase pathway may not be involved in HGF-mediated acidification in mesangia l cells. (C) 1998 Elsevier Science Inc.