Therapeutic Effect of Y-27632 on Chronic Allograft Nephropathy in Rats

Abstract

Chronic allograft nephropathy (CAN) is a major cause of late allograft loss. Recent evidences suggest that Rho and its downstream effector ROCK may be greatly involved in the progression of renal fibrosis. Inhibition of Rho/ROCK pathway might interact with the inflammatory process in the renal interstitium, and antagonize the process of epithelial-to-mesenchymal transition (EMT). We hypothesized that Y-27632 could inhibit the chronic inflammatory process and prevent the progression of CAN. Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. Lewis to Lewis rat kidney transplantation was served as the syngeneic control (Syn group). Allograft recipients were randomized and treated with either cyclosporine A alone (Allo group), or in combination with Y-27632 (30 mg/kg body weight/d intragastric, Y-27632 group). Renal function and urine protein excretion levels of the rats were analyzed. Animals were sacrificed 12 wk post-transplantation for histological and immunohistochemical studies, as well as analysis of the expression levels of chemokines, transforming growth factor (TGF-beta) 1 and alpha smooth muscle actin (alpha-SMA). Renal function deteriorated progressively in the Allo group, and there was typical CAN morphology in the kidneys. However, Y-27632-treatment significantly prevented the deterioration of graft function, lessened the level of urine protein excretion, and preserved the renal structure. Attenuation of ED1 positive mononuclear cell infiltration and amelioration of tubulointerstitial fibrosis were achieved by Y-27632 intervention. This was associated with down-regulation of the expression of tubular monocyte chemoattractant protein-1, RANTES (regulated upon expression normal T cell expressed and secreted), and phosphorylated NF-kappaB (which was a marker for activation). Profibrotic protein (TGF-beta1) and alpha-SMA, a marker of EMT, were significantly down-regulated by Y-27632 treatment as well. The Rho/ROCK pathway plays an important role in the progression of CAN, and specific inhibition of Rho activity by Y-27632 showed favorable effects on blocking renal interstitial inflammation and fibrosis, thus efficiently retarding the development of CAN, which might provide us with a novel strategy to improve long-term renal graft survival.