BILLIARY CIRRHOSIS: CONFORMATIONAL EFFECTS AND CONSEQUENCES OF THE OXIDATION OF HEPATIC SERPINS

Abstract

Introduction: Billiary cirrhosis is associated with the production of exacerbated levels of reactive oxygen species (ROS) that might alter the normal folding of serpins, as we previously showed in vitro. Methods: The aims of our work were to evaluate in vivo the conformational effects of high levels of circulating ROS on two hepatic serpins, antithrombin (AT) and alpha1-antitrypsin (alpha1-AT) in a rat model of billiary cirrhosis. Billiary cirrhosis was established in Sprague Dawley rats by means of bile duct ligation and maintained during 7, 14 or 21 days. Two groups of rats were prophilactically treated before the procedure with the antioxidants vitamin E or L-NAME. We used two control groups, a sham group and another that did not experience surgery. In all cases the levels of ROS (circulating and hepatic), and the levels, activity and conformational features of plasma AT were evaluated. We also evaluated the intrahepatic distribution and features of AT and alpha1-AT. Results: Billiary cirrhosis produced a massive time-dependent increase of circulating and hepatic ROS that triggered the intracellular aggregation and retention of AT, leading to a circulating type I deficiency of the protein, associated with a mild increase of its latent form. This effect was similar for alpha1-AT. Treatment with antioxidants, especially L-NAME, reduced all the noxious conformational effects of massive oxidation. Conclusions: In conclusion, billiary cirrhosis-induced oxidative stress, although producing a mild increase of latent AT, does not produce significant alterations of the circulating AT molecule. However, this stress has pronounced conformational effects on the intracellular pool of hepatic serpins, leading to the retention of aggregated AT and alpha1-AT and the subsequent type I deficiency with the associated prothrombotic status. Treatment with antioxidants such as L-NAME reduce the noxious effects of high circulating levels of ROS and might prove potentially therapeutic.