Mechanisms Altering Airway Smooth Muscle Cell Ca²⁺ Homeostasis in Two Asthma Models

Abstract

Background: Asthma is characterized by airway remodeling, altered mucus production and airway smooth muscle cell (ASMC) contraction causing extensive airway narrowing. In particular, alterations of ASMC contractility seem to be of crucial importance. The elevation of the cytoplasmic Ca²⁺ concentration is a key event leading to ASMC contraction and changes in the agonist-induced Ca²⁺ increase in ASMC have been reported in asthma. Objective: The aim of this study was to investigate mechanisms underlying these changes. Methods: Murine tracheal smooth muscle cells (MTSMC) from T-bet KO mice and human bronchial smooth muscle cells (HBSMC) incubated with IL-13 and IL-4 served as asthma models. Acetylcholine-induced changes in the cytoplasmic Ca²⁺ concentration were recorded using fluorescence microscopy and the expression of Ca²⁺ homeostasis regulating proteins was investigated with Western blot analysis. Results: Acetylcholine-induced Ca²⁺ transients were elevated in both asthma models. This correlated with an increased Ca²⁺ content of the sarcoplasmic reticulum (SR). In MTSMC from T-bet KO mice, the expression of the SR Ca²⁺ buffers calreticulin and calsequestrin was higher compared to wild-type mice. In HBSMC incubated with IL-13 or IL-4, the expression of ryanodine receptors, inositol-3-phosphate receptors and sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPases 2 was increased compared to HBSMC without incubation with interleukins. The enlarged acetylcholine-induced Ca²⁺ transients could be reversed by blocking inositol-3-phosphate receptors. Conclusions: We conclude that in the murine asthma model the SR Ca²⁺ buffer capacity is increased, while in the human asthma model the expression of SR Ca²⁺ channels is altered. The investigation of the Ca²⁺ homeostasis of ASMC has the potential to provide new therapeutical options in asthma.

Contribution of theOBSCNNonsynonymous Variants to Aspirin Exacerbated Respiratory Disease Susceptibility in Korean Population

“…Recently, many studies have suggested the important role of intracellular Ca 2 + , indicating that an increase of cytosolic Ca 2 + concentration in bronchial smooth muscle cells might cause bronchial obstruction and bronchospam (Parekh and Penner, 1997;Sweeney et al, 2002). In the airway smooth muscle cells, the altered Ca 2 + homeostasis of the SR has also been shown to affect airway remodeling, including changes in expressions of immune-related molecules (Kellner et al, 2008). Furthermore, the correlation between SR Ca 2 + regulation and proinflammatory cytokines has been reported in human airway smooth muscle (Sathish et al, 2009).…”

“…In addition, the elevated concentration of cytoplasmic Ca 2 + is a crucial event leading to the contraction of airway smooth muscle cells that causes extensive airway narrowing (Cox et al, 2007;Kellner et al, 2008). The SR is a complex internal membrane system that releases and reuptakes Ca 2 + during muscle contraction and relaxation.…”

Schistosomiasis differentially affects vasoconstrictor responses: up-regulation of 5-HT receptor-mediated aorta contraction

“…Of note, Nippostrongylus brasilienses infection up-regulates the expression of 5-HT 2A receptors in non-vascular smooth muscle and this effect is ascribed to IL-13 (Zhao et al 2006). Concerning intracellular receptors, IL-4 and IL-13, cytokines involved in the pathophysiology of asthma and schistosomiasis, upregulate the expression of ryanodine receptors in airway smooth muscle cells (Jude et al 2008, Kellner et al 2008. Therefore, these vascular alterations involving 5-HT 2A receptors and their signalling pathways could implicate 5-HT both in portal hypertension (Bosch et al 1992, Kaumann & Levy 2006 and secondary extra-portal vascular alterations occasionally observed in schistosomiasis as, for example, pulmonary hypertension (de Cleva et al 2003, Franco-Paredes et al 2007).…”

Anti-cholinergic effect of singulair on isolated rat’s tracheal smooth muscle

“…During an asthma attack, the tracheal smooth muscle plays an important role in reducing pulmonary function as it contracts [1][2][3][4]. Singulair (Montelukast) is commonly used to solve this problem.…”