|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 2003 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 2002 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Hyperglycemia increases the production of reactive oxygen species (ROS) from the mitochondrial electron transport chain in bovine endothelial cells (Nishikawa et al. 2000 ; Nature 404:787-90). Because several studies have postulated a role for prostaglandins (PGs) in the glomerular hyperfiltration seen in early diabetes, we evaluated the effect of mitochondrial ROS on expression of the inducible isoform of cyclooxygenase (COX-2) in cultured human mesangial cells (HMC). We first confirmed that incubation of HMC with 30 mM glucose significantly increased C0X-2 mRNA, but not COX-1 mRNA, compared with 5.6 mM glucose. Similarly, incubation of HMC with 30 mM glucose significantly increased mitochondrial membrane potential, intracellular ROS production, COX-2 protein expression and PGE_2 synthesis, and these events were completely suppressed by TTFA or CCCP, inhibitors of mitochondrial metabolism, or by overexpression of uncoupling protein-1 or manganese superoxide dismutase. In vivo study, it was confirmed that expression of COX-2 mRNA and protein was increased in glomeruli of diabetic mice. In addition, hyperglycemia induced activation of the COX-2 gene promoter, which was completely abrogated by mutation of two NF-κB (nuclear factor κB) binding sites in the promoter region. Our results suggest that hyperglycemia increases mitochondrial ROS production, resulting in NF-κB activation, COX-2 mRNA induction, COX-2 protein production and PGE_2 synthesis. This chain of events might contribute to the pathogenesis of diabetic nephropathy.