The stimulating effects of nitric oxide on intermediate conductance Ca²⁺-activated K⁺ channels in human dermal fibroblasts through PKG pathways but not the PKA pathways.

Abstract

Nitric oxide (NO) is produced by nitric oxide synthase (NOS) in dermal fibroblasts and is important during wound healing. Intermediate conductance Ca²⁺-activated K+ (IK; IK1; KCa3.1; IKCa; SK4; KCNN4) channels contribute to NOS upregulation, NO production, and various NO-mediated essential functions in many kinds of cells. To determine if the action of NO is linked to IK channel regulation in human dermal fibroblasts, we investigated the expression of IK channels in the cells and the effects and mechanisms of NO on the channels using RT-PCR, western blot analysis, immunocytochemistry and whole-cell and single-channel patch-clamp techniques. The presence of functional IK channels at the RNA, protein and membrane levels was demonstrated and S-nitroso-N-acetylpenicillamine (SNAP) was shown to significantly increase IK currents. The effects of NO were abolished by pretreatment with KT5823 or 1H-[1,2,4]-oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) but not with KT5720. In addition, IK currents were increased by protein kinase G1α or 8-bromo-cGMP but not by forskolin, 8-bromo-cAMP, or catalytic subunits of protein kinase A (PKAcs). On the other hand, PKAcs with cGMP did not increase IK currents, and pretreatment with KT5720 did not block the stimulating effects of 8-Br-cGMP on the IK channels. These data suggest that NO activates IK channels through the PKG but not the PKA pathways, and it seems there is no cross activation between PKG and PKA pathways in human dermal fibroblasts.