Reactive oxygen species as glucose signaling molecules in mesangial cells cultured under high glucose

Background Oxidative stress is one of the important mediators of vascular c omplications in diabetes including nephropathy. High glucose (HG) generates reactive oxygen species (ROS) as a result of glucose auto-oxidation, metab olism, and formation of advanced glycosylation end products. Thc concept of ROS-induced tissue injury has recently been revised with the appreciation of new roles for ROS in signaling pathways and gene: expression. Methods and Results High glucose rapidly generated dichlorofluorescein-sens itive cytosolic ROS in rat and mouse mesangial cells. Neither L-glucose nor 3-O-methyl-D-glucose increased cytosolic ROS and cytochalasin B, an inhibi tor of glucose transporter, effectively inhibited HG-induced ROS generation , suggesting that glucose uptake and subsequent metabolism are required in HG-induced cytosolic ROS generation. H2O2 up-regulated fibronectin mRNA exp ression and protein synthesis; this up-regulation was effectively inhibited by protein kinase C (PKC) inhibitor or by depletion of PKC. The HG-induced generation of ROS was, in turn, related to activation of PKC and transcrip tion factors nuclear factor-kappa B (NF-kappa B) and activator protein-1 (A P-1) as well as to the up-regulation of transforming growth factor-beta 1 ( TGF-beta 1), fibronectin mRNA expression and protein synthesis, because ant ioxidants effectively inhibited NG-induced PKC, NF-kappa B, AP-I activation , and TGF-beta 1 and fibronectin expression in mesangial cells cultured und er HG. Conclusions. Although signal transduction pathways linking HG, ROS, PKC, tr anscription factors, and extracellular matrix (ECM) protein synthesis in me sangial cells have not been fully elucidated, the current data provide evid ence that ROS generated by glucose metabolism may act as integral signaling molecules under HG as in other membrane receptor signaling.