Volume-Regulated Anion Channel Complex Modulates Mechano-Electrical Signal Responses in Human Airway Smooth Muscle Shortening.

LRRC8A (leucine-rich repeat containing 8A) is an obligatory constituent of the volume-regulated anion channel (VRAC) that is fundamental to a wide range of biological processes, including regulating cell size, proliferation, and migration. Here we explored the physiological role of VRAC in excitation-contraction (E-C) coupling and shortening of human airway smooth muscle (HASM). In HASM cells, pharmacological inhibition of VRAC with DCPIB (4-[2-butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl]) (0.1-10 μM) markedly attenuated swell-activated Cl conductance, and contractile agonist (histamine or carbachol)-induced cellular stiffening as measured by single-cell patch-clamp and optical magnetic twisting cytometry, respectively. In addition, HASM cells treated with DCPIB or transfected with LRRC8A-targeting siRNA showed reduced agonist-induced phosphorylation of protein kinase B (i.e., AKT), paxillin, MYPT1, and myosin light chain. Consistent with the changes of these E-C coupling effectors, DCPIB appreciably decreased agonist-induced small airways narrowing in human precision-cut lung slices. Taken together, our findings shed new light on the mechanistic link between HASM shortening and regulatory volume decrease via LRRC8A, revealing a previously unrecognized nodal point for modulation of E-C coupling and acute airway constriction.