Renoprotective antioxidant effect of alagebrium in experimental diabetes

Background. Despite the beneficial effects of alagebrium (ALA), a putative advanced glycation end-product (AGE) breaker, on diabetic nephropathy, its renoprotective mechanisms are incompletely understood. Since oxidative stress exacerbates diabetic renal injury through interaction with AGE, the present study examined the antioxidative property of ALA in db/db mice, mesangial cells cultured under high glucose or H2O2 and a test tube. Methods. ALA (2 mg/kg/day) was administered intraperitoneally for 12 weeks to 8-week-old db/m and db/db (DALAE) mice or for 4 weeks to 16-week-old db/db mice (DALAL). Oxidative stress markers (nitrotyrosine accumulation, expression and translocation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, cellular DCF-DA fluorescence) together with urinary albumin excretion and histological changes including mesangial expansion were measured. The concentration of H2O2 in the presence and absence of ALA was measured by iodometric analysis in a test tube. Results. ALA significantly reduced not only urinary albumin excretion and renal pathological changes but also accumulation of pentosidine and nitrotyrosine and expression of NADPH oxidase subunits in db/db mice regardless of treatment protocol. In mesangial cells, ALA effectively prevented not only high glucose-but also H2O2-induced membrane translocation of NADPH oxidase subunit (p47 phox, p67 phox and rac1) and protein kinase C isoform (alpha, beta I and beta II) and Nox4 messenger RNA expression concomitant with cellular reactive oxygen species. Furthermore, ALA directly decreased H2O2 in a test tube. Conclusion. ALA has both direct and indirect antioxidant effects that may play important roles in ALA's renoprotective effect in diabetic kidneys.