Correlation between Neuritogenic Action of Nitric Oxide and the Rate of Nitric Oxide Production in PC12h Cells

Abstract

To investigate the effects of the nitric oxide (NO) generating rate on neuritogenesis, we compared the neuritogenic activity of several NO donors with varying generating rates; NOR1 (t1/2 = 1.8 min), NOR2 (t1/2 = 28 min), NOR3 (t1/2 = 30 min), and NOR4 (t1/2 = 60 min). Each NO donor promoted neurite outgrowth in PC12h cells in a concentration-dependent manner. However, the profiles were not dependent on the NO-generating rate. The neuritogenesis promoted by NOR4 was inhibited by the NO trapping agent carboxy-2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl-3-oxide, sodium salt (PTIO). NOR2 and NOR3, which have similar generating rates, were more toxic than NOR1 and NOR4 in PC12h cells. NOR2 and NOR3 induced cytotoxicity at concentrations of 100 μM and above, while NOR1 and NOR4 induced cytotoxicity at concentrations of 200 μM and above. Preconditioning medium containing these NO donors in the absence of cells were less cytotoxic towards PC12h cells. Therefore, we conclude that the neuritogenic action of NO in PC12h cells is dependent on a suitable generating rate, but not dependent on the amount of NO.