RSV infection potentiates TRPV1-mediated calcium transport in bronchial epithelium of asthmatic children
Rationale: The transient receptor potential vanilloid 1 (TRPV1) channel is expressed in human bronchial epithelium (HBE), where it transduces Ca2+ in response to airborne irritants. TRPV1 activation results in bronchoconstriction, cough, and mucus production, and may therefore contribute to the pathophysiology of obstructive airway disease. Since asthmatic children face the greatest risk of developing virus-induced airway obstruction, we hypothesized that changes in TRPV1 expression, localization, and function in airway epithelium may play a role in bronchiolitis and asthma in childhood. Objectives: We sought to measure TRPV1 protein expression, localization, and function in HBE cells from asthmatic vs. non-asthmatic children both at baseline and after RSV infection. Methods: We determined changes in TRPV1 protein expression, subcellular localization, and function both at baseline and after RSV infection in primary HBE cells from normal and asthmatic children. Results: Basal TRPV1 protein expression was higher in HBE from asthmatic vs. non-asthmatic children and primarily localized to plasma membranes (PM). During RSV infection, TRPV1 protein increased more in the PM of asthmatic HBE as compared to non-asthmatic cells. TRPV1-mediated increase in intracellular Ca2+ was greater in RSV-infected asthmatic cells, but this increase was attenuated when extracellular Ca2+ was removed. Nerve growth factor (NGF) recapitulated the effect of RSV on TRPV1 activation in HBE cells. Conclusions: Our data suggest that asthmatic children have intrinsically hyperreactive airways due in part to higher TRPV1-mediated Ca2+ influx across epithelial membranes, and this abnormality is further exacerbated by NGF overexpression during RSV infection driving additional Ca2+ from intracellular stores.