Exogenous 8‐hydroxydeoxyguanosine ameliorates liver fibrosis through the inhibition of Rac1‐NADPH oxidase signaling

Background and Aim Exogenous 8‐hydroxydeoxyguanosine (8‐OHdG) was suggested as an inhibitor of Rac1 and NADPH oxidase (NOX). The aim of this study was to evaluate the effects of the exogenous 8‐OHdG on hepatic fibrogenesis in vitro and in vivo model of liver fibrosis. Methods Adult Sprague–Dawley rats were allocated to sham‐operated rats (n = 7), rats that underwent bile duct ligation (BDL) (n = 6), and BDL rats treated with 8‐OHdG (60 mg/kg/day by gavage, n = 6). All rats were sacrificed on day 21. Double immunofluorescence staining between either NOX1 or NOX2 and α‐smooth muscle actin (SMA) in liver was performed. Hepatic fibrotic contents were assessed by hydroxyproline assay and quantified by Sirius red staining. In vitro, hepatic stellate cell (HSC) line LX‐2 and HHSteC cells were stimulated by angiotensin II (10 μM). The reactive oxygen species (ROS) production was measured by confocal microscopy. The expressions of NOX1, NOX2, α‐SMA, transforming growth factor (TGF)‐β1, and collagen Iα were analyzed by quantitative real‐time polymerase chain reaction or immunoblotting. Results The 8‐OHdG treatment in BDL rats reduced the NOX1 and NOX2 protein expression, which overlapped with α‐SMA compared with BDL rats. The 8‐OHdG treatment in BDL rats significantly decreased the mRNA expression of NOX1, NOX2, α‐SMA, TGF‐β1, and collagen Iα, and fibrotic contents. Increases of ROS production, Rac1 activation, NOX1, NOX2, and fibronectin expression induced by angiotensin II in HSCs were attenuated by 8‐OHdG. Conclusions Rac1 activation and NOX‐derived ROS are implicated to liver fibrosis. The 8‐OHdG ameliorates liver fibrosis through the inhibition of Rac1 activation and NOX‐derived ROS.