Role of oxidative stress in advanced glycation end product-induced mesangial cell activation

Role of oxidative stress in advanced glycation end product-induced mesangial cell activation.BackgroundLevels of advanced glycation end products (AGE) are elevated in individuals with advancing age, renal failure, and diabetes, and accumulation of these molecules may contribute to disease progression. The mechanism by which AGE proteins alter glomerular mesangial cell function, however, is not completely understood. The present study assessed the involvement of oxidative stress in AGE-dependent mesangial cell signaling events.MethodsPrimary cultures of rat renal mesangial cells were exposed to in vitro AGE-BSA and H2O2. Nuclear factor-κB (NF-κB) and protein kinase C (PKC) isoform activation were studied using confocal microscopy and Western blotting. Quantitative polymerase chain reaction (PCR) was used to measure transforming growth factor-β1 (TGF-β1) levels. The involvement of oxidative stress was assessed by supplementing or compromising cellular antioxidant capacity.ResultsNF-κB was dose-dependently activated by AGE. PKC activation was not involved in this response, but analysis of PKC-β1 activation showed a stimulatory effect of AGE proteins on this isoform. Transcription of TGF-β1 was stimulated by AGE and was prevented by PKC inhibition. Challenge with H2O2 had similar downstream effects on mesangial cell signaling. Antioxidants, vitamin E and nitecapone, prevented AGE-dependent NF-κB activation and normalized PKC activity and associated TGF-β1 transcription. Depletion of the intracellular antioxidant, glutathione, effectively lowered the AGE concentration needed for mesangial cell activation of NF-κB and PKC-β1. Treatment with a suboptimal AGE dose, under glutathione-depleted conditions, revealed a synergistic effect on both parameters.ConclusionThe results support a central role for oxidative stress in AGE-dependent mesangial cell signaling and emphasize the importance of ROS in determining cell responsiveness.