Cyclic stretch-induced TGF-beta 1 and fibronectin expression is mediated by(31-integrin through c-Src- and STAT3-dependent pathways in renalepithelial cells

摘要

Ex-tracellular matrix (ECM) proteins, including fibronectin, may contrib-ute to the early development and progression of renal interstitialfibrosis associated with chronic renal disease. Recent studies showedthat P 1-integrin is associated with the development of renal fibrosis ina murine model of unilateral ureteral obstruction (UUO). However,the molecular events responsible for p 1 -integrin-mediated signaling,following UUO, have yet to be determined. In this study, we inves-tigated the mechanism by which mechanical stretch, an in vitro modelfor chronic obstructive nephropathy, regulates fibronectin and trans-forming growth factor-pi (TGF-pl) expression in cultured humanproximal tubular epithelium (HK-2) cells. Mechanical stretch upregu-lated fibronectin and TGF-pi expression and activated signal trans-ducer and transcription factor 3 (STAT3) in a time-dependent manner.Stretch-induced fibronectin and TGF-P1 were suppressed by a STAT3inhibitor, S3I-201, and by small interfering RNA (siRNA) targetinghuman STAT3 (STAT3 siRNA). Similarly, fibronectin and TGF-p 1expression and STAT3 activation induced by mechanical stretch weresuppressed by the Src family kinase inhibitor PP2 and by transfectionof HK-2 cells with a dominant-negative mutant of c-Src (DN-Src),whereas PP3, an inactive analog of PP2, had no significant effect.Furthermore, mechanical stretch resulted in increased p 1-integrinmRNA and protein levels in HK-2 cells. Furthermore, neutralizingantibody against p 1-integrin and silencing of P 1-integrin expressionwith siRNAs resulted in decreased c-Src and STAT3 activation andTGF-P 1 and fibronectin expression evoked by mechanical stretch.This work demonstrates, for the first time, a role for p 1-integrin instretch-induced renal fibrosis through the activation of c-Src andSTAT3 signaling pathways.