MO425: Rosuvastatin Activates Hox13-Usag-1 Pathway and Prevents Renal Fibrosis

Abstract

BACKGROUND AND AIMS Statins, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, are primarily cholesterol-lowering drugs that have become standard of care in the primary and secondary prevention of cardiovascular diseases. Apart from lipid-lowering, statins may act beneficially through anti-fibrotic mechanisms to protect the diseased kidney. This study evaluated anti-fibrotic effects of rosuvastatin (RSV) in a chronic kidney fibrosis model and against the TGF-ß1 stimulated Madin-Darby canine kidney (MDCK) cells in vitro. METHOD Mice subjected to unilateral ischemic reperfusion injury with contralateral nephrectomy (uIRIx) were treated with vehicle or RSV (10 mg/kg, by oral gavage) daily for 4 weeks and kidneys were analyzed for markers of fibrosis, bone morphogenetic protein-7 (BMP-7), uterine sensitization-associated gene-1 (USAG-1), and SMAD signaling. Control and homeobox protein Hox-A13 (HOXA13) knocked down MDCK cells were stimulated with TGF- ß1 (5 ng/ml) and then treated with RSV. RESULTS Kidneys from uIRIx mice showed increased expression of α-SMA, Collagen 1 and decrease in BMP-7 (20.35 ± 2.37 versus 1.00 ± 0.27, P < 0.05; 8.43 ± 1.55 versus 1.00 ± 0.35, P < 0.05; 0.75 ± 0.06 versus 1.00 ± 0.15, P < 0.05, respectively). In contrast, expression of USAG-1, a BMP-7 antagonist, was markedly increased in fibrotic kidney (6.60 ± 1.11 versus 1.00 ± 0.02, P < 0.05). Interestingly, RSV treatment not only attenuated expression of USAG-1 (0.72 ± 0.08 versus 1.36 ± 0.14, P < 0.05) but also showed a tendency to activate expression of HOXA13 (0.36 ± 0.14 versus 0.51 ± 0.15, P > 0.05) and improved other markers of fibrosis. Moreover, RSV treatment significantly reduced phosphorylated Smad3 (3.94 ± 0.81 versus 7.17 ± 1.50, P < 0.05) and increased phosphorylation levels of Smad 1/5/9 (0.67 ± 0.10 versus 0.30 ± 0.09, P < 0.05) that is associated with BMP-7 signaling in the fibrotic kidney. MDCK cells stimulated with TGF-β1 in vitro showed increased expression of α-SMA, fibronectin, vimentin, collagen 1, USAG-1, and phosphorylation of Smad3 as well as decreased expression of phosphorylated Smad 1/5/9. RSV treatment significantly reversed these changes as well as increased level of transcriptional factor HOXA13 (0.89 ± 0.12 versus 0.33 ± 0.08, P < 0.05), which negatively regulates USAG-1, without changes in BMP-7 expression. In addition, effect of RSV treatment on USAG-1 expression was significantly decreased in HOXA13 gene knocked down MDCK cells (1.01 ± 0.19 versus 2.04 ± 0.38, P < 0.05; 1.66 ± 0.13 versus 2.04 ± 0.38, P > 0.05; TGF- ß1 + RSV versus TGF- ß1 and TGF- ß1 + RSV + siRNA vs TGF- ß1, respectively). These in vitro data suggest that RSV enhanced anti-fibrotic pathway by downregulating a dominant BMP-7 antagonist USAG-1 via HOXA13 upregulation and not by enhancing BMP-7 production. CONCLUSION The present results demonstrate that RSV inhibits the progression of kidney fibrosis in part by upregulating BMP-7-mediated signaling via HOXA13 expression and down regulation of USAG-1.