Glomerular Oxidative and Antioxidative Systems in Experimental Mesangioproliferative Glomerulonephritis

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Abstract
Increased mesangial cell proliferation is a hallmark of many glomerulopathies in humans. Whereas the pathogenic role of reactive oxygen species (ROS) in the development of experimental mesangioproliferative glomerulonephritis (GN) is well established, very little is known about the mechanisms leading to increased ROS concentrations in the glomerulus. This study therefore examined glomerular ROS and the activities of oxidative and antioxidative enzymes during the early course of mesangioproliferative anti-Thy 1.1 GN. Anti-Thy 1.1 GN was induced in male Wistar rats, and glomeruli were isolated 2, 24, and 120 h after disease induction to examine ROS levels as well as oxidative and antioxidative enzyme expression in comparison to non-nephritic controls. At all time points, increased glomerular ROS levels, particularly of hydrogen peroxide and superoxide anions, were observed. Activities of NADH-dependent and NADPH-dependent oxidative enzymes were also increased during the course of GN, whereas no increased activity of xanthine oxidase, another potential source of ROS, was detectable. Despite glomerular oxidative stress, no compensatory increase of antioxidative enzyme activities occurred. On the contrary, catalase, superoxide dismutase, and glutathione peroxidase activities even decreased during the course of disease. In tubulointerstitial samples, no increase in oxidative activity was observed in the course of disease, thus confirming that detected ROS were of glomerular origin. Our data document for the first time a pronounced dysregulation of pro-oxidative and antioxidative enzymes in mesangioproliferative GN, leading to a net increase in glomerular ROS levels. Detailed knowledge of such pathways may lead to new therapeutic approaches for GN in humans.