Nitric oxide promotes nicotine-triggered ERK signaling via redox reactions in PC12 cells.

Nitric oxide (NO), produced by neuronal NO synthase (nNOS), serves as a signaling molecule with diverse biological responses in the central nervous system (CNS). In the present study, we demonstrated that nNOS expression enhances the nicotine-triggered activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in nNOS-transfected PC12 (NPC12) cells. Treatment with nicotine increased the phosphorylation level of ERK1/2 in the NPC12 cells as compared with that in control PC12 cells. However, nicotine treatment failed to enhance ERK1/2 phosphorylation when NPC12 cells were pretreated with several selective inhibitors of NOS, the nicotinic acetylcholine receptors, L-type voltage-dependent Ca(2+) channels, protein kinase C, Src, epidermal growth factor receptor, and MEK. The nicotine-induced ERK1/2 phosphorylation in PC12 cells was observed by their pretreatment with a NO donor. Moreover, the enhancement of nicotine-induced ERK1/2 phosphorylation in the NPC12 cells was regulated by intracellular glutathione levels, but not by the soluble guanylate cyclase-cGMP-protein kinase G signaling. Meanwhile, depolarization stimulated ERK1/2 phosphorylation in both PC12 and NPC12 cells. Taken together, these findings suggest that nicotine modulates NO-dependent redox condition; the resulting calcium influx, would increase ERK1/2 phosphorylation in nNOS expressing cells. Blockade of NO pathway may be selective target to reduce ERK1/2 phosphorylation via attenuation of the nicotine responses in the CNS.