Involvement of nitric oxide in glucose toxicity on differentiated PC12 cells: prevention of glucose toxicity by tetrahydrobiopterin, a cofactor for nitric oxide synthase

Effects of high concentrations of glucose on cell survival of differentiated PC12 cells were examined. Seven day-culture with D-glucose (9.0-27.0 mg/ml as 2-6-fold of the optimal level) induced cell death in a dose-related manner but 3-day culture with high concentrations of glucose had no effect on cell viability. L-glucose had no effect on viability of PC12 cells, suggesting that D-glucose toxicity was independent of its osmolarity effect. Seven-day culture with D-glucose (13.5 mg/ml as 3-fold of the optimal level) increased nitric oxide metabolites (NOx) in the culture medium. Glucose-induced increase in NOx was eliminated by 0.1 MM L-nitro-arginine methylester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Intracellular Ca2+ concentration was increased by D-glucose in a dose-related manner, suggesting that D-glucose activated NOS by increasing intracellular Ca2+ concentration in PC12 cells. Glucose-induced cell death was blunted by 0.1 MM L-NAME, showing that nitric oxide (NO) was involved in the glucose toxicity to PC12 cells. Tetrahydrobiopterin (BH4), a cofactor for NOS, attenuated both glucose-induced cell death and NOx production at 1 muM but not at 10 muM. The effects of BH4 on glucose-induced cell death and NOx production were not mimicked by reducing agents such as ascorbate and cysteine. These results taken together suggest that high concentrations of glucose induced cell death via NO production and that low concentration of BH4 had a protective effect against glucose neurotoxicity in differentiated PC12 cells. (C) 2002 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.