Activation of KCNQ (K_V7) K~+ channels in enteric neurons inhibits epithelial Cl~- secretion in mouse distal colon

摘要

Voltage-gated K_v7 (KCNQ family) K~+ channels are expressed in many neuronal populations and play an important role in regulating membrane potential by generating a hyperpolarizing K~+ current and decreasing cell excitability. However, the role of K_V7 channels in the neural regulation of intestinal epithelial Cl~- secretion is not known. CP secretion in mouse distal colon was measured as a function of short-circuit current (l_Sc)> and pharmacological approaches were used to test the hypothesis that activation of K_V7 channels in enteric neurons would inhibit epithelial Cl~- secretion. Flupirtine, a nonselective K_V7 activator, inhibited basal Cl~- secretion in mouse distal colon and abolished or attenuated the effects of drugs that target various components of enteric neurotransmission, including tetrodotoxin (Na_v channel blocker), veratridine (Na_v channel activator), nicotine (nicotinic ace-tylcholine receptor agonist), and hexamethonium (nicotinic antagonist). In contrast, flupritine did not block the response to epithelium-targeted agents VIP (endogenous VPAC receptor ligand) or carbachol (nonselective cholinergic agonist). Flupirtine inhibited Cl~- secretion in both full-thickness and seromuscular-stripped distal colon (containing the submucosal, but not myen-teric plexus) but generated no response in epithelial T84 cell monolayers. K_V7.2 and K_V7.3 channel proteins were detected by immunofluorescence in whole mount preparations of the submucosa from mouse distal colon. ICA 110381 (K_V7.,2/7.3 specific activator) inhibited Cl~- secretion comparably to flupirtine. We conclude that K_V7 channel activators inhibit neurally driven Cl~- secretion in the colonic epithelium and may therefore have therapeutic benefit in treating pathologies associated with hyperexcitable enteric nervous system, such as irritable bowel syndrome with diarrhea (IBS-D).