Airway hyperreactivity in diseases such as asthma involves enhanced airway smooth muscle (ASM) contraction due either to increased intracellular Ca2+ ([Ca2+]i) and/or increased Ca2+ sensitivity (force for a given [Ca2+]i). Airway inflammation is a key aspect of airways disease, and exposure to several inflammatory mediators (such as tumor necrosis factor (TNFa) and interleukin-13 (IL-13)) increase ASM contractility. Several studies showed that cytokines increase agonist-induced [Ca2+]i responses in ASM, thus linking In the current proposal, we will explore inflammation-induced changes in [Ca2+]i regulatory mechanisms that result in overall increased [Ca2+]i responses. In ASM, Ca2+ influx in response to SR depletion (store-operated Ca2+ entry;SOCE) is enhanced by cytokines. Preliminary data suggests that Na+/Ca2+ exchange (NCX)-mediated influx is enhanced by cytokines. Such enhancement of SOCE and influx-mode NCX would lead to increased [Ca2+]i levels. Reduction in [Ca2+]i is normally achieved by plasma membrane (PM) efflux mechanisms (perhaps including NCX-mediated efflux), and by SR Ca2+ reuptake via SR ATPase (SERCA). Organelles such as mitochondria can buffer Ca2+ and alter Ca2+ availability for SR refilling. Normally, these mechanisms help maintain basal [Ca2+]i at low levels, while SR Ca2+ stores are replete until agonist stimulation when [Ca2+]i rises as SR stores deplete. Preliminary studies suggest that SERCA and mitochondrial Ca2+ buffering are impaired by inflammation. Based on these contrasting preliminary findings of enhanced Ca2+ influx, but decreased sequestration or efflux, our central hypothesis is that inflammation promotes mechanisms that increase [Ca2+]i, but impairs those that decrease [Ca2+]i. This leads to an overall increase in basal [Ca2+]i as well as enhanced [Ca2+]i responses to agonist stimulation. In this regard, we propose that PM vs. intracellular mechanisms functionally interact in [Ca2+]i homeostasis under normal circumstances, and that disruption of these mechanisms and their interactions with inflammation leads to increased [Ca2+]i. Our overall approach will be to use human ASM cells or tissue strips to examine the above mechanisms with or without exposure to pro-inflammatory cytokines (TNFa, IL-13). Studies will use complementary techniques including molecular biology (siRNA;overexpression), imaging of [Ca2+]i, [Na+]i and luminal (SR) Ca2+, real-time confocal imaging of fluorescently- tagged proteins, as well as force measurements to address these aims.
Our Specific Aims are: decrease [Ca2+]i Aim 1: To determine the influence of inflammatory cytokines on STIM1, STIM2 and Orai1 interactions in human ASM regulation;
Aim 2 : To determine the influence of inflammatory cytokines on NCX and its role in [Ca2+]i regulation in human ASM;
Aim 3 : To determine the influence of inflammatory cytokines on mitochondria and its role in [Ca2+]i regulation in human ASM;
Aim 4 : To determine the influence of inflammatory cytokines on SERCA and its role in [Ca2+]i regulation in human ASM;[Ca2+]i Aim 5: To determine the influence of inflammatory cytokines on the overall contribution of [Ca2+]i regulatory mechanisms to contractility in human ASM.
There is increasing recognition that abnormalities in airway smooth muscle contractility contribute to exaggerated airway narrowing and accompanying shortness of breath in clinically-important diseases such as asthma and chronic bronchitis. Airway contractility is highly dependent on intracellular calcium levels. The proposed studies will examine the mechanisms by which intracellular calcium is controlled in human airway smooth muscle. These studies will the foundation for better understanding of airway diseases, and potential development of new therapeutic targets.
|Delmotte, Philippe; Sieck, Gary C (2015) Interaction between endoplasmic/sarcoplasmic reticulum stress (ER/SR stress), mitochondrial signaling and Ca(2+) regulation in airway smooth muscle (ASM). Can J Physiol Pharmacol 93:97-110|
|Sassoon, Catherine S H; Zhu, Ercheng; Fang, Liwei et al. (2014) Positive end-expiratory airway pressure does not aggravate ventilator-induced diaphragmatic dysfunction in rabbits. Crit Care 18:494|
|Sathish, Venkatachalem; Thompson, Michael A; Sinha, Sutapa et al. (2014) Inflammation, caveolae and CD38-mediated calcium regulation in human airway smooth muscle. Biochim Biophys Acta 1843:346-51|
|Aravamudan, Bharathi; Kiel, Alexander; Freeman, Michelle et al. (2014) Cigarette smoke-induced mitochondrial fragmentation and dysfunction in human airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 306:L840-54|
|Jia, Li; Delmotte, Philippe; Aravamudan, Bharathi et al. (2013) Effects of the inflammatory cytokines TNF-? and IL-13 on stromal interaction molecule-1 aggregation in human airway smooth muscle intracellular Ca(2+) regulation. Am J Respir Cell Mol Biol 49:601-8|
|Sathish, Venkatachalem; Abcejo, Amard J; Thompson, Michael A et al. (2012) Caveolin-1 regulation of store-operated Ca(2+) influx in human airway smooth muscle. Eur Respir J 40:470-8|
|Delmotte, Philippe; Yang, Binxia; Thompson, Michael A et al. (2012) Inflammation alters regional mitochondrial Ca²+ in human airway smooth muscle cells. Am J Physiol Cell Physiol 303:C244-56|
|Wylam, Mark E; Xue, Ailing; Sieck, Gary C (2012) Mechanisms of intrinsic force in small human airways. Respir Physiol Neurobiol 181:99-108|
|Aravamudan, Bharathi; VanOosten, Sarah K; Meuchel, Lucas W et al. (2012) Caveolin-1 knockout mice exhibit airway hyperreactivity. Am J Physiol Lung Cell Mol Physiol 303:L669-81|
|Ijpma, Gijs; Al-Jumaily, Ahmed M; Cairns, Simeon P et al. (2011) Myosin filament polymerization and depolymerization in a model of partial length adaptation in airway smooth muscle. J Appl Physiol 111:735-42|
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