Molecular and functional significance of Ca2+-activated Cl channels in pulmonary arterial smooth muscle

Abstract

Increased peripheral resistance of small distal pulmonary arteries is a hallmark signature of pulmonary hypertension (PH) and is believed to be the consequence of enhanced vasoconstriction to agonists, thickening of the arterial wall due to remodeling, and increased thrombosis. The elevation in arterial tone in PH is attributable, at least in part, to smooth muscle cells of PH patients being more depolarized and displaying higher intracellular Ca2+ levels than cells from normal subjects. It is now clear that downregulation of voltage-dependent K+ channels (e.g., Kv1.5) and increased expression and activity of voltage-dependent (Cav1.2) and voltage-independent (e.g., canonical and vanilloid transient receptor potential [TRPC and TRPV]) Ca2+channels play an important role in the functional remodeling of pulmonary arteries in PH. This review focuses on an anion-permeable channel that is now considered a novel excitatory mechanism in the systemic and pulmonary circulations. It is permeable to Cl and is activated by a rise in intracellular Ca2+ concentration (Ca2+-activated Cl channel, or CaCC). The first section outlines the biophysical and pharmacological properties of the channel and ends with a description of the molecular candidate genes postulated to encode for CaCCs, with particular emphasis on the bestrophin and the newly discovered TMEM16 and anoctamin families of genes. The second section provides a review of the various sources of Ca2+ activating CaCCs, which include stimulation by mobilization from intracellular Ca2+ stores and Ca2+ entry through voltage-dependent and voltage-independent Ca2+ channels. The third and final section summarizes recent findings that suggest a potentially important role for CaCCs and the gene TMEM16A in PH.

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Topics

Pharmacology: Pharmacokinetics and Pharmacodynamics
Preclinical and Molecular Science
Pulmonary Hypertension

Authors

Normand Leblanc, Abigail S. Forrest, Ramon J. Ayon, Michael Wiwchar, Jeff E. Angermann, Harry A. T. Pritchard, Cherie A. Singer, Maria L. Valencik, Fiona Britton, Iain A. Greenwood

Published in:

Pulmonary Circulation Vol 5: No 2 cover image

June 2015

Pulmonary Circulation Vol 5: No 2

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