Substance P stimulates CFTR-dependent fluid secretion by mouse tracheal submucosal glands

Abstract

The mucosa of the proximal airways defends itself and the lower airways from inhaled irritants such as capsaicinoids, allergens, and infections by several mechanisms. Sensory nerves monitor the luminal microenvironment and release the tachykinin substance P (SP) to stimulate mucus secretion. Here, we have studied the role of the cystic fibrosis transmembrane conductance regulator (CFTR) in SP stimulation by comparing mouse airway submucosal gland responses in wild-type (WT) and CFTR-/- mice. Capsaicinoids (chili pepper oil) increased fluid secretion by glands from WT mice five-fold, and this response was abolished by exposing the basolateral aspect of the tracheas to L-732,138 (10 micromol/l), a specific antagonist of the neurokinin-1 receptor. Secretion was also stimulated 25-fold by basolateral application of SP, and this response was strongly inhibited by the CFTR inhibitor CFTR(inh)172. In contrast, submucosal glands from CFTR knockout mice failed to secrete when stimulated by SP (1 micromol/l), although those from wild-type control littermates were responsive. SP stimulation of wild-type glands was also abolished by clotrimazole (25 micromol/l), a blocker of Ca(2+)-activated K(+) channels. These results indicate that SP mediates local responses to capsaicinoids through a mechanism involving coordinated activation of CFTR and K(+) channels. To our knowledge, this is the first study in which CFTR-dependent responses to substance P have been directly demonstrated. Since CFTR regulation is qualitatively similar in human and mouse glands, loss of this local regulation in CF may contribute to reduced innate defenses in CF airways.

Pseudomonas aeruginosa triggers CFTR-mediated airway surface liquid secretion in swine trachea

“…CFTR is required for normal fluid secretion, which washes mucins and antimicrobial compounds from the submucosal glands into the airway lumen (7)(8)(9)(10)(12)(13)(14)(15). The loss of CFTR-mediated fluid secretion reduces ASL secretion, supporting the hypothesis that CFTR mutations lead to reduced secretion of antimicrobial compounds and mucins into the airway lumen, facilitating chronic infection and inflammation (3,6,35,36).…”

“…3C). These results indicate that the response to P. aeruginosa is not a general response affecting all glands, but rather a local response by submucosal glands adjacent to the bacteria (10,15).…”

“…In addition, human CF airways, 1-d-old CF piglets, newborn CFTR −/− ferrets, and CFTR −/− mice fail to respond to stimulatory signals that normally elicit strong ASL secretion (6)(7)(8)(9). Consequently, it has been proposed that abnormal secretion of fluid and mucin in response to bacterial infection may contribute to the pathogenesis of CF lung disease (7)(8)(9)(10)(12)(13)(14)(15); however, the central questions of whether bacteria trigger ASL secretion in the airways, and the role of CFTR in such a process, have not been explored previously, owing to the lack of a suitable experimental technique.…”

CGRP induction in cystic fibrosis airways alters the submucosal gland progenitor cell niche in mice

“…In humans with CF, glandular secretion is impaired due to the lack of CFTR-mediated chloride transport from the serous cells in the most distal tubules of the glands (9). Although the mouse has relatively few of these glands in its trachea, the tracheal SMGs from Cftr-knockout mice are similar to those in their human CFTR-mutant counterparts with respect to secretory defects (11,12). Hence, it appears that the mouse retains CF-associated glandular defects, making this species attractive for studying glandular cell biology as it relates to CF.…”

“…Three neuropeptides, including substance P (SP), vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP), have been shown to induce SMG secretions (11,12,15,16). To this end, we evaluated expression of these neuropeptides in CF and non-CF SMGs from 4 species, including human, mouse, ferret, and pig.…”