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 alpha-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 muM). The reactive oxygen species (ROS) production was measured by confocal microscopy. The expressions of NOX1, NOX2, alpha-SMA, transforming growth factor (TGF)-beta1, and collagen Ialpha 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 alpha-SMA compared with BDL rats. The 8-OHdG treatment in BDL rats significantly decreased the mRNA expression of NOX1, NOX2, alpha-SMA, TGF-beta1, and collagen Ialpha, 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.