Nitric Oxide Stimulates PC12 Cell Proliferation via cGMP and Inhibits at Higher Concentrations Mainly via Energy Depletion

We investigated how nitric oxide (NO) regulates proliferation of pheochromocytoma PC12 cells, rat aortic endothelial cells and mouse astrocytes. In all cells a NO donor (DETA/NO) stimulated proliferation at low concentrations, but reversibly and completely inhibited proliferation at higher concentrations. The stimulation (but not the inhibition) of proliferation in PC12 cells was prevented by an inhibitor of soluble guanylate cyclase, and replicated by a cell-permeable form of cGMP. The NO-induced cytostasis was not reversed by inhibitors of MEK kinase or poly(ADP-ribose)polymerase, or by treatments that bypass inhibition of ribonucleotide reductase or ornithine decarboxylase, or in cells lacking p53. Cytostatic concentrations of DETA/NO strongly inhibited respiration of PC12 cells, and specific respiratory inhibitors caused complete cytostasis of PC12 and endothelial cells. However, uridine and pyruvate reversed the cytostasis induced by the specific respiratory inhibitors, but not that induced by DETA/NO, although they did so in the additional presence of N-acetyl-cysteine. DETA/NO strongly and progressively inhibited glycolysis measured by glucose consumption, lactate production and ATP level, and a specific glycolytic inhibitor (2-deoxy-D-glucose) caused complete cytostasis. Our results suggest that NO at low concentrations increases cell proliferation via cGMP, while high concentrations of NO block proliferation via inhibition of both glycolysis and respiration.JRC.I.2-Validation of biomedical testing method