Rhinoviruses (RV) have been impugned in the development of asthma and are the leading cause of acute asthma exacerbations. RV exposure elicits inflammation of the airways, but how RV modulates human airway smooth muscle cell (HASM) function to engender airway hyperresponsiveness (AHR) is unclear. HASM is the pivotal cell modulating bronchomotor tone, shortening in response to contractile agonist stimulation through increases in intracellular calcium, through activation of Rho kinase, and through modulation of actin dynamics. We show that RV exposure evokes AHR in human precision cut lung slices (hPCLS), increases [Ca2+]i in HASM, and increases agonist-induced phosphorylation of myosin light chain in HASM from human airway epithelial cell (HAEC)/HASM co-cultures stimulated with RV-C15. We also demonstrate that RVC attenuates ?2 agonist- induced bronchodilation in hPCLS and cAMP production in HASM. Additionally, we show that VEGF exposure of hPCLS induces AHR and attenuates bronchodilation of small airways. Therefore we posit RVC modulates both contractile and relaxation signaling in HASM to alter responsiveness of the airways. We propose a central hypothesis that RVC exposure of HAEC induces release of VEGF to: (1) promote AHR via the modulation of calcium mobilization, and (2) attenuate ?2 agonist-induced bronchodilation via modulation of cAMP- mobilizing pathways. We will utilize HASM cells, air-liquid interface-differentiated HAEC, and hPCLS to examine the aims of this proposal.
In Aim 1, we will determine how RV exposure modulates agonist-induced calcium homeostasis in HASM and how asthma alters these mechanisms.
Aim 2 will examine how RVC exposure modulates agonist-induced bronchodilation/relaxation of HASM and how asthma alters these mechanisms. Utilizing primary HAEC/HASM co-cultures and an ex vivo system of human small airways, we will delineate signaling pathway alterations regulating bronchomotor tone that can be targeted in the treatment of RV-induced exacerbations of asthma.
Rhinovirus-induced exacerbations of asthma represent a significant health burden to children and adults, and pose a significant challenge in controlling and preventing asthma-related deaths. Our proposal aims to identify novel therapies to get rid of rhinovirus-induced airway spasms and restore efficacy of bronchodilators, thereby alleviating symptoms of the common cold that cause shortness of breath and wheezing.
