Pathogenesis of renal fibrosis: Role of Proteinase‐activated Receptor‐2

Abstract

OBJECTIVESTo evaluate the role of proteinase‐activated receptor‐2 (PAR2) in renal fibrosis.METHODSWe used both cultured acutely isolated human‐derived proximal tubular cells (HPTCs) and an in‐vivo murine unilateral ureteral obstruction (UUO) model of renal fibrosis, with wild‐type and PAR2 null mice (Jackson Labs). HPTCs at passage 3 were activated with a PAR2‐activating peptide (PAR2‐AP) and trypsin without or with co‐stimulation by transforming growth factor‐ β (TGF‐ β) and the expression level of connective tissue growth factor (CTGF) was measured by western blot analysis. Cells were activated with and without the signal pathway inhibitors for MAPKinase (PD98059) and Rho‐kinase (Y‐27632). Kidneys from wild‐type and PAR2‐null mice with or without (sham) UUO were obtained at 7, 14, 21 and 28 days after UUO. Renal tissue was fixed and evaluated histopathologically for morphology (H & E), collagen deposition (Masson's Trichrome) and biochemically (western blot) for α‐smooth muscle actin.RESULTS(1) PAR2‐AP activation of HPTCs alone significantly upregulated CTGF expression and did so synergistically to augment TGF‐β‐induced CTGF production. This synergy was reduced by MAPKinase but not Rho‐kinase inhibition. (2) PAR2 null UUO mice had less tubular injury and fibrosis and reduced alpha‐smooth muscle actin at day 7 but not at 28 days.SUMMARYOur results support a role for PAR2 in acute renal fibrosis.