Role of voltage-gated Ca2+ channels and Ano1 Ca2+-activated Cl- channels in M2 muscarinic receptor-dependent contractions of murine airway smooth muscle.
Srijit Ghosh, Tuleen Alkawadri, Lorcan P McGarvey, Mark A Hollywood, Keith D Thornbury, Gerard P Sergeant
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引用次数: 0
Abstract
Cholinergic tone is elevated in obstructive lung conditions such as chronic obstructive pulmonary disease (COPD) and asthma, but the cellular mechanisms underlying cholinergic contractions of airway smooth muscle (ASM) are still unclear. Some studies report an important role for L-type Ca2+ channels (LTCC) and Ano1 Ca2+-activated Cl- channels (CACC) in these responses, but others dispute their importance. Cholinergic contractions of ASM involve activation of M3Rs, however, stimulation of M2Rs exerts a profound hypersensitization of these responses. Here, we show that M2R-dependent potentiation of cholinergic nerve-evoked contractions of ASM was reversed by the LTCC blocker nifedipine and the Ano1 CACC inhibitors Ani9 and CaCCinh-A01. Carbachol induced sustained contractions of ASM that were converted into oscillatory contractions when M3Rs were blocked with 4-DAMP. The 4-DAMP-resistant contractions were absent in preparations taken from M2R knockout (KO) mice. The remaining M2R-dependent responses, observed in wild-type (WT) mice, were abolished by nifedipine and Ani9. Inhibition of sarcoplasmic endoplasmic reticulum Ca2+ ATPases (SERCA) with thapsigargin increased the amplitude of contractions induced by electrical field stimulation (EFS) and these effects were also reversed by nifedipine and Ani9. Thapsigargin also potentiated contractions of ASM induced by the LTCC activator FPL64176. Therefore, contractions of ASM that involved Ca2+ influx via LTCC were enhanced by inhibition of SERCA. Immunocytochemistry experiments revealed prominent SERCA staining around the periphery of ASM cells. These data indicate that M2R-dependent contractions of ASM involve Ano1 CACC and LTCC by a mechanism involving inhibition of buffering of Ca2+ influx by SERCA.NEW & NOTEWORTHY The role of L-type Ca2+ channels and Ano1 Ca2+-activated Cl- channels in cholinergic contractions of airway smooth muscle is disputed. Here, we show that both channels are involved in M2 muscarinic receptor-dependent contractions of murine airway smooth muscle via inhibition of buffering of Ca2+ influx by sarcoplasmic endoplasmic reticulum Ca2+ ATPases.
期刊介绍:
The American Journal of Physiology-Lung Cellular and Molecular Physiology publishes original research covering the broad scope of molecular, cellular, and integrative aspects of normal and abnormal function of cells and components of the respiratory system. Areas of interest include conducting airways, pulmonary circulation, lung endothelial and epithelial cells, the pleura, neuroendocrine and immunologic cells in the lung, neural cells involved in control of breathing, and cells of the diaphragm and thoracic muscles. The processes to be covered in the Journal include gas-exchange, metabolic control at the cellular level, intracellular signaling, gene expression, genomics, macromolecules and their turnover, cell-cell and cell-matrix interactions, cell motility, secretory mechanisms, membrane function, surfactant, matrix components, mucus and lining materials, lung defenses, macrophage function, transport of salt, water and protein, development and differentiation of the respiratory system, and response to the environment.