Respiratory syncytial virus induces insensitivity to β-adrenergic agonists in mouse lung epithelium in vivo

Abstract

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants and children worldwide. We wished to determine whether intratracheal administration of β-agonists improved alveolar fluid clearance (AFC) across the distal respiratory epithelium of RSV-infected mice. Following intranasal infection with RSV strain A2, AFC was measured in anesthetized, ventilated BALB/c mice by instillation of 5% BSA into the dependent lung. We found that direct activation of protein kinase A by forskolin or 8-bromo-cAMP increased AFC at day 2 after infection with RSV. In contrast, short- and long-acting β-agonists had no effect at either day 2 or day 4. Insensitivity to β-agonists was not a result of elevated plasma catecholamines or lung epithelial cell β-adrenergic receptor degradation. Instead, RSV-infected mice had significantly higher levels of phosphorylated PKCζ in the membrane fractions of their lung epithelial cells. In addition, insensitivity to β-agonists was mediated in a paracrine fashion by KC (the murine homolog of CXCL8) and reversed by inhibition of either PKCζ or G protein-coupled receptor kinase 2 (GRK2). These results indicate that insufficient response to β-agonists in RSV may be caused, at least in part, by impaired β-adrenergic receptor signaling, as a consequence of GRK2-mediated uncoupling of β-adrenergic receptors from adenylyl cyclase.