Endogenous Nitric Oxide Generation Linked to Ryanodine Receptors Activates Cyclic GMP / Protein Kinase G Pathway for Cell Proliferation of Neural Stem/Progenitor Cells Derived From Embryonic Hippocampus

Abstract

Nitric oxide (NO) activates the cyclic GMP (cGMP) / protein kinase G (PKG) pathway during physiological processes in numerous types of cells. Here, we evaluated whether this NO/cGMP/PKG pathway is involved in the proliferation of neural stem/progenitor cells (NPCs) derived from the hippocampus of embryonic mice. In culture, the exposure to the NO synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) significantly decreased the number of viable cells and 5-bromo-2′-deoxyuridine (BrdU) incorporation into the cells, as well as the levels of intracellular reactive oxygen species, extracellular NO2, and intracellular cGMP. Like l-NAME, the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and PKG inhibitor KT5823 also decreased cell viability and BrdU incorporation. The membrane-permeable cGMP analogue 8-bromo-cGMP partially abolished the l-NAME–induced decrease in the BrdU incorporation. BrdU incorporation was decreased by Ca2+-channel blockers, including dantrolene, MK-801, ifenprodil, and nifedipine. Interestingly, the NO2 level was decreased by dantrolene, but not by the other 3 blockers. l-NAME and ODQ attenuated phosphorylation of Akt, but not that of extracellular signal-regulated kinases or epidermal growth factor receptors. Our data suggest that endogenous NO generation linked to dantrolene-sensitive ryanodine receptors activates the cGMP/PKG signaling pathway for positive regulation of proliferation of hippocampal NPCs derived from embryonic mice. Keywords:: cyclic GMP / protein kinase G pathway, neural stem/progenitor cells, nitric oxide, proliferation, ryanodine receptor channel