ABSTRACTAirway submucosal gland serous cells are sites of expression of the cystic fibrosis transmembrane conductance regulator (CFTR) and are important for fluid secretion in conducting airways from the nose down to small bronchi. We tested if serous cells from human nasal turbinate glands secrete bicarbonate (HCO3−), important for mucus polymerization, during stimulation with the cAMP-elevating agonist vasoactive intestinal peptide (VIP) and if this requires CFTR. Isoalted serous cells stimulated with VIP exhibited a ~20% cAMP-dependent decrease in cell volume and a ~0.15 unit decrease in intracellular pH (pHi), reflecting activation of Cl−and HCO3−secretion, respectively. Pharmacology, ion substitution, and studies using cells from CF patients suggest serous cell HCO3−secretion is mediated by conductive efflux directly through CFTR. Interestingly, we found that neuropeptide Y (NPY) reduced VIP-evoked secretion by blunting cAMP increases and reducing CFTR activation through Gi-coupled NPY1R. Culture of primary gland serous cells in a model that maintained a serous phenotype confirmed the activating and inhibiting effects of VIP and NPY, respectively, on fluid and HCO3−secretion. Moreover, VIP enhanced secretion of antimicrobial peptides and antimicrobial efficacy of gland secretions while NPY reduced antimicrobial secretions. In contrast, NPY enhanced the release of cytokines during inflammatory stimuli while VIP reduced cytokine release through a mechanism requiring CFTR conductance. As levels of VIP and NPY are up-regulated in disease like allergy, asthma, and chronic rhinosinusitis, the balance of these two peptides in the airway may control airway mucus rheology and inflammatory responses through gland serous cells.
cAMP-activated Ca2+ signaling is required for CFTR-mediated serous cell fluid secretion in porcine and human airways