Hepatocyte growth factor (HGF) was recently reported to ameliorate renal inflammation in a rat model of chronic renal failure. HGF exerted its action through suppression of RANTES expression in renal tubules. In the present study, we utilized an in vitro model of human kidney proximal tubule epithelial cells (HKC) to elucidate the mechanisms of RANTES suppression by HGF. HGF significantly suppressed basal and TNF-alpha-induced mRNA and protein expression of RANTES in a time and dose dependent fashion. HGF elicited P13K-Akt activation and inhibited GSK3, a downstream transducer of P13K-Akt, by inhibitory phosphorylation at Ser-9. When the P13K-Akt pathway was blocked by wortmannin, HGF inhibition of RANTES was abrogated, demonstrating that the P13K-Akt pathway is necessary for HGF action. In addition, specific inhibition of GSK3 activity by lithium ion suppressed basal and TNF-alpha-induced RANTES expression, reminiscent of the action of HGF. To further investigate the role of GSK3 in modulating RANTES expression, we examined the effect of forced expression of wild type GSK3 beta or an uninhibitable mutant GSK3 beta, in which the regulatory Ser-9 residue is changed to alanine (S9A-GSK3 beta) in HKC. Overexpression of wild type GSK3 beta did not alter the inhibitory action of HGF on RANTES. In contrast, expression of S9A-GSK3 beta abolished HGF inhibition of basal and TNF-alpha stimulated RANTES expression. These findings suggest that P13K-Akt activation and subsequent inhibitory phosphorylation of GSK3 beta are required for HGF-induced suppression of RANTES in HKC. (c) 2005 Elsevier Inc. All rights reserved.