High Glucose-Induced Oxidative Stress Increases Transient Receptor Potential Channel Expression in Human Monocytes

OBJECTIVE-Transient receptor potential (TRP) channel-induced cation influx activates human monocytes, which play an important role in the pathogenesis of atherosclerosis. In the present study, we investigated the effects of high glucose-induced oxidative stress on TRP channel expression in human monocytes. RESEARCH DESIGN AND METHODS-Human monocytes were exposed to control conditions (5.6 mmol/l D-glucose), high glucose (30 mmol/l D-glucose or L-glucose), 100 mu mol/l peroxynitrite, or high glucose in the presence of the superoxide dismutase mimetic tempol (100 mu mol/l). TRP mRNA and TRP protein expression was measured using quantitative real-time RT-PCR and quantitative in-cell Western assay, respectively. Calcium influx and intracellular reactive oxygen species were measured using fluorescent dyes. RESULTS-Administration of high D-glucose significantly increased reactive oxygen species. High D-glucose or peroxynitrite significantly increased the expression of TRP canonical type 1 (TRPC1), TRPC3, TRPC5, TRPC6, TRP melastatin type 6 (TRPM6), and TRPM7 mRNA and TRPC3 and TRPC6 proteins. High D-glucose plus tempol or high L-glucose did not affect TRP expression. Increased oxidative stress by lipopolysaccharide or tumor necrosis factor-alpha increased TRP niRNA expression, whereas the reduction of superoxide radicals using diphenylene iodonium significantly reduced TRP niRNA expression. Increased TRPC3 and TRPC6 protein expression was accompanied by increased 1-oleoyl-2-acetyl-sn-glycerol-induced calcium influx, which was blocked by the TRPC inhibitor 2-aminoethoxydiphenylborane. TRPC6 mRNA was significantly higher in monocytes from 18 patients with type 2 diabetes compared with 28 control subjects (P < 0.05). CONCLUSIONS-High D-glucose-induced oxidative stress increases TRP expression and calcium influx in human monocytes, pointing to a novel pathway for increased activation of monocytes and hence atherosclerosis in patients with diabetes. Diabetes 59:844-849, 2010