Src inhibition blocks renal interstitial fibroblast activation and ameliorates renal fibrosis

Increased Src activity has been associated with the pathogenesis of renal tumors and some glomerular diseases, but its role in renal interstitial fibrosis remains elusive. To evaluate this, cultured renal interstitial fibroblasts (NRK-49F) were treated with PP1, a selective inhibitor of Src. This resulted in decreased expression of α-smooth muscle actin, fibronectin, and collagen I in response to serum, angiotension II, or transforming growth factor-β1 (TGF-β1). Silencing Src with siRNA also inhibited expression of those proteins. Furthermore, inhibition of Src activity blocked renal fibroblast proliferation. In a murine model of renal interstitial fibrosis induced by unilateral ureteral obstruction, the active form of Src (phopsho-Src Tyr416) was upregulated in both renal interstitial fibroblasts and renal tubular cells of the fibrotic kidney. Its inactivation reduced renal fibroblast activation and attenuated extracellular matrix protein deposition. Src inhibition also suppressed activation of TGF-β1 signaling, activation of the epidermal growth factor receptor and STAT3, and reduced the number of renal epithelial cells arrested at the G2/M phase of the cell cycle after ureteral obstruction. Thus, Src is an important mediator of renal interstitial fibroblast activation and renal fibrosis, and we suggest that Src is a potential therapeutic target for treatment of chronic renal fibrosis.