Regulation of endogenous Kv7 potassium channels by histamine in primary cultured human airway smooth muscle cells.

Abstract

Kv7 potassium channels were recently found to be expressed in airway smooth muscle cells (ASMCs) of different species including humans. Previous research studies on guinea pigs and rats suggests that native Kv7 currents are inhibited following treatment of ASMCs with bronchoconstrictor agonists; in intact airways this inhibition is sufficient to stimulate L‐type Ca2+ channels in ASMCs, resulting in ASMC contraction and bronchiolar constriction. Although KCNQ genes which encode for Kv7 channels are expressed in human tracheal smooth muscle, no human ASMC culture model has been developed to investigate the regulation of native Kv7 currents or its role in Ca2+ signaling. Here we found that bronchoconstrictor agonist histamine (1 μM) induced Ca2+ influx in monolayers of primary cultured human ASMCs. This Ca2+ influx was prevented by application of L‐type Ca2+ channel blocker verapamil (10 μM). Perforated‐patch clamp electrophysiology was employed to detect endogenous Kv7 currents in primary cultured human ASMCs. Small endogenous Kv7 currents sensitive to Kv7.2–7.5 activator retigabine (10 μM) were detected in 60% of ASMCs. After washout of retigabine, Kv7 currents returned to the control level and were inhibited by subsequent application of histamine (10 μM, 43 ± 11% inhibition at −20 mV, n=6). Histamine induced inhibition of endogenous human Kv7 currents in ASMCs was completely reversed by addition of histamine H1 receptor antagonist chlorpheniramine (100 μM). Pan Kv7 channel blocker XE991 (10 μM) applied at the end of each experiment inhibited 84 ± 8% of the current at −20 mV. The present study provides new evidence for a role of Kv7 channels in bronchoconstrictor Ca2+ signaling in cultured human ASMCs.Support or Funding InformationThe project described was supported by Award Number I01BX007080 from the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development.