GRK2/β‐arrestin mediates arginine vasopressin‐induced cardiac fibroblast proliferation

Summary Cardiac fibrosis is a pathological feature commonly found in hearts exposed to haemodynamic orneurohormonal stress. Elevated levels of arginine vasopressin (AVP) are closely associated with the progression of heart failure and could be an underlying cause of cardiac fibrosis. The aim of this study is to characterize the effect ofAVPon neonatal rat cardiac fibroblasts (NRCFs) and to illustrate its signalling mechanism. The proliferative effect ofAVPwas assessed by methylthiazolyldiphenyl‐tetrazolium assay and 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation assay, and the amounts of cellular signalling proteins α‐smooth muscle actin (α‐SMA), matrix metalloproteinase (MMP) 2,MMP9, and phosphorylatedERK1/2were determined by western blotting.AVP, in a time‐ and concentration‐dependent manner, promotedNRCFproliferation and the expression ofMMP2 andMMP9. Inhibition of G protein‐coupled receptor kinase2 (GRK2) by the inhibitory peptideGRK2‐Ct or knock‐down ofGRK2 suppressedAVP‐induced BrdU incorporation and the expression ofMMP2 and α‐SMAinNRCFs. Moreover, shRNA‐mediated silencing of β‐arrestin1 or β‐arrestin 2 abolishedAVP‐induced BrdU incorporation andMMP2 expression.AVP‐inducedNRCFproliferation depended on the phosphorylation ofERK1/2, and inhibition ofGRK2 or silencing of β‐arrestins blockedAVP‐inducedERK1/2phosphorylation. The effects ofAVPonNRCFproliferation and α‐SMAexpression were blocked bySR45059, a vasopressin receptor type1A (V1AR) selective antagonist. In conclusion,AVPpromotesNRCFproliferation through V1AR‐mediatedGRK2/β‐arrestin/ERK1/2signalling.