Disruption of Interleukin-17 receptor A (IL-17RA) gene in mice aggravates renal interstitial fibrosis in obstructive nephropathy

Abstract Renal fibrosis is the final outcome of obstructive nephropathy and a major cause of chronic renal failure. Renal fibrosis results from an imbalance between extracellular matrix (ECM) synthesis and degradation, which is regulated by multiple inflammatory mediators in the kidney. Recently, Interleukin-17 (IL-17) emerged as a key cytokine in lung and liver fibrosis. Although IL-17 producing cells were detected in the obstructed kidney, the role of IL-17 in renal fibrosis is unknown. We sought to define the contribution of IL-17 in renal fibrosis in obstructive nephropathy. Mice deficient in IL-17 receptor signaling (IL-17RA−/−) were assessed for renal fibrosis following unilateral ureteral obstruction (UUO), a well-characterized mouse model of obstructive nephropathy. We determined IL-17 receptor signaling is required for protection against renal fibrosis following UUO. IL-17RA−/− mice developed severe morphological injury and displayed increased deposition of collagen in the obstructed kidney compared to controls. We observed a significant decrease in the level of matrix degrading enzymes in the kidney of IL-17RA−/− mice, despite normal ECM synthesis, correlating with increased fibrosis. Overexpression of IL-17 increased the level of matrix degrading enzymes and protected mice from renal fibrosis. We also show that IL-17R signaling in tubular epithelial cells up regulated multiple genes of Kallikrein-kinin system, known to play a critical role in renal protection against kidney fibrosis. Our data clearly indicate a previously unappreciated role of IL-17 in renal protection against fibrosis. These results offer the opportunity for the development of potential therapies in the treatment of chronic kidney diseases.