Submitted on April 5, 2008
Revised on May 31, 2008
Accepted on June 30, 2008
HSP27 is involved in the pathogenesis of kidney tubulointerstitial fibrosis
Aparna Vidyasagar, Shannon Reese, Zeki Acun1, Debra A Hullett2, and Arjang Djamali3*
1 UW Madison Wisconsin
2 University of Wisconsin-Madison
3 UW Madison
* To whom correspondence should be addressed. E-mail: axd{at}medicine.wisc.edu.
We hypothesized that Heat shock protein 27 (HSP27) a small HSP with actin-remodeling properties is involved in the pathogenesis of kidney tubulointerstitial fibrosis. We first examined its expression in the rat unilateral ureteral obstruction (UUO) model of kidney fibrosis and epithelial-to-mesenchymal transition (EMT). Immunoblot analyses showed that UUO resulted in significant upregulation of TGF-
1, 
-SMA, total and phosphorylated HSP27 and phosphorylated p38MAPK. Immunofluorescence studies showed that HSP27 costained with TGF-1, -SMA and E-cadherin in areas of tubulointerstitial injury. We next attempted to translate these studies in an in vitro model of EMT using rat proximal tubular epithelial cells (NRK52E). TGF-1 (20 ng/ml) treatment resulted in EMT (upregulation of -SMA and downregulation of E-cadherin) and significant upregulation of total and phosphorylated HSP27 and p38MAPK after three days. Real-time PCR analyses showed that HSP27, vimentin and fibronectin increased whereas E-cadherin mRNA levels decreased. Double-staining immunofluorescence studies showed intracytoplasmic colocalization of HSP27 with both F-actin and E-cadherin in cells undergoing EMT. HSP27 overexpression by transient transfection significantly increased E-cadherin while decreasing E-cadherin repressor Snail levels. In aggregate, these studies show that HSP27 is involved in the pathogenesis of TGF-1-induced EMT and chronic tubulointerstitial fibrosis. HSP27 overexpression may delay injury by upregulating E-cadherin through downregulation of Snail.
