Influence of hepatocyte growth factor, epidermal growth factor, and mycophenolic acid on endothelin-1 synthesis in human endothelial cells

Background. Endothelin-1 (ET-1) is a potent vasoconstrictive peptide which plays an important pathophysiological role in ischaemic renal failure and d rug-induced renal injury such as cyclosporin A (CsA)- and tacrolimus-associ ated nephrotoxicity. In contrast, hepatocyte growth factor (HGF) and epider mal growth factor (EGF) seem to accelerate renal regeneration after ischaem ic and drug-induced renal injury. This study aimed to investigate the influ ence of HGF and EGF on ET-1 synthesis in cultured human umbilical vein endo thelial cells (HUVEC) and renal artery endothelial cells (RAEC). In additio n, we have investigated whether mycophenolic acid (MPA), a new immunosuppre ssive drug, which in contrast to CsA and tacrolimus lacks nephrotoxic side effects, modulates ET-1 synthesis in endothelial cells. Methods. ET-1 release was measured with a specific enzyme-linked immunosorb ent assay. ET-1 mRNA expression was investigated by reverse transcription p olymerase chain reaction. Results. HGF and EGF (0.001-10 nM) exerted a significant concentration-depe ndent inhibitory effect on ET-1 release by HUVEC and RAEC (minimum 56.1 +/- 4.3% of control, n = 6, mean +/- SE). The suppressive effect of HGF and EG F on ET-1 synthesis was dose-dependently antagonized by the tyrosine kinase inhibitors tyrphostin AG1478, lavendustin A and methyl 2,5-dihydroxycinnam ate. Incubation of HUVEC and RAEC with MPA (2.5, 10, 25, and 50 pg/ml) for 3-5 h induced a significant reduction of ET-1 mRNA expression. After 48 h i ncubation with MPA (1-50 mug/ml) a significant decrease of ET-1 release and DNA content per culture well was observed, whereas ET-1 release referred t o the DNA content in the corresponding culture well did not differ signific antly from controls. Conclusions. The present findings demonstrate that HGF and EGF reduce ET-1 synthesis in endothelial cells via their receptor tyrosine kinase activity and suggest that the renoprotective effects of HGF and EGF might be linked to their inhibitory action on ET-1 synthesis. This study also provides evid ence that, in contrast to CsA and tacrolimus, MPA does not stimulate ET-1 s ynthesis. This might explain the clinical observation that renal function o ften improves when CsA or tacrolimus is replaced by mycophenolate mofetil.