G alpha(12) overexpression induced by miR-16 dysregulation contributes to liver fibrosis by promoting autophagy in hepatic stellate cells

Abstract

Background & Aims: Hepatic stellate cells (HSCs) have a role in liver fibrosis. Guanine nucleotide-binding alpha-subunit 12 (G alpha(12)) converges signals from G-protein-coupled receptors whose ligand levels are elevated in the environment during liver fibrosis; however, information is lacking on the effect of G alpha(12) on HSC trans-differentiation. This study investigated the expression of G alpha(12) in HSCs and the molecular basis of the effects of its expression on liver fibrosis. Methods: G alpha(12) expression was assessed by immunostaining, and immunoblot analyses of mouse fibrotic liver tissues and primary HSCs. The role of G alpha(12) in liver fibrosis was estimated using a toxicant injury mouse model with G alpha(12) gene knockout and/or HSC-specific G alpha(12) delivery using lentiviral vectors, in addition to primary HSCs and LX-2 cells using microRNA (miR) inhibitors, overexpression vectors, or adenoviruses. miR-16, G alpha(12), and LC3 were also examined in samples from patients with fibrosis. Results: G alpha(12) was overexpressed in activated HSCs and fibrotic liver, and was colocalised with desmin. In a carbon tetrachloride-induced fibrosis mouse model, G alpha(12) ablation prevented increases in fibrosis and liver injury. This effect was attenuated by HSC-specific lentiviral delivery of G alpha(12). Moreover, G alpha(12) activation promoted autophagy accompanying c-Jun N-terminal kinase-dependent ATG12-5 conjugation. In addition, miR-16 was found to be a direct inhibitor of the de novo synthesis of G alpha(12). Modulations of miR-16 altered autophagy in HSCs. In a fibrosis animal model or patients with severe fibrosis, miR-16 levels were lower than in their corresponding controls. Consistently, cirrhotic patient liver tissues showed G alpha(12) and LC3 upregulation in desmin-positive areas. Conclusions: miR-16 dysregulation in HSCs results in G alpha(12) overexpression, which activates HSCs by facilitating autophagy through ATG12-5 formation. This suggests that G alpha(12) and its regulatory molecules could serve as targets for the amelioration of liver fibrosis. (C) 2017 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.