Cystic fibrosis transmembrane conductance regulator dysfunction in VIP knockout mice

Abstract

Vasoactive intestinal peptide (VIP), a neuropeptide, controls multiple functions in exocrine tissues, including inflammation, and relaxation of airway and vascular smooth muscles, and regulates CFTR-dependent secretion, which contributes to mucus hydration and local innate defense of the lung. We had previously reported that VIP stimulates the VPAC1 receptor, PKCϵ signaling cascade, and increases CFTR stability and function at the apical membrane of airway epithelial cells by reducing its internalization rate. Moreover, prolonged VIP stimulation corrects the molecular defects associated with F508del, the most common CFTR mutation responsible for the genetic disease cystic fibrosis. In the present study, we have examined the impact of the absence of VIP on CFTR maturation, cellular localization, and function in vivo using VIP knockout mice. We have conducted pathological assessments and detected signs of lung and intestinal disease. Immunodetection methods have shown that the absence of VIP results in CFTR intracellular retention despite normal expression and maturation levels. A subsequent loss of CFTR-dependent chloride current was measured in functional assays with Ussing chamber analysis of the small intestine ex vivo, creating a cystic fibrosis-like condition. Interestingly, intraperitoneal administration of VIP corrected tissue abnormalities, close to the wild-type phenotype, as well as associated defects in the vital CFTR protein. The results show in vivo a primary role for VIP chronic exposure in CFTR membrane stability and function and confirm in vitro data.

Disrupted local innervation results in less VIP expression in CF mice tissues

“…Previous human studies have shown that the rich intrinsic neuronal networks for VIP secretion around exocrine glands could be lost in tissues from patients with cystic fibrosis. Our research has since confirmed, in vitro and in vivo , the need for chronic VIP exposure to maintain functional CFTR chloride channels at the cell surface of airways and intestinal epithelium, as well as normal exocrine tissues morphology [1] . The goal of the present study was to examine changes in VIP in the lung, duodenum and sweat glands of 8-and 17-weeks old F508del/F508del mice and to investigate VIPergic innervation in the small intestine of CF mice, before important signs of the disease development.…”

Animal Models in the Pathophysiology of Cystic Fibrosis

“…It is well known to work in synergy with ACh to regulate secretions (Lundberg et al, 1980; Heinz-Erian et al, 1985, 1986). Interestingly, VIP KO mice generated in the C57BL/6 background demonstrated, in vivo , the central role of VIP in CFTR regulation (Chappe and Said, 2012; Alcolado et al, 2014). Originally developed to study airway diseases, such as bronchial asthma (Hamidi et al, 2006; Szema et al, 2006; Said, 2009), VIP-KO mice were used by Alcolado et al (2014) to demonstrate the molecular link between VIP and CFTR regulation in the airways and small intestines, and observed a CF-like phenotype.…”

Lack of applicability of the Enterocyte Chloride ion secretion paradigm to the Pathology of Cystic Fibrosis

“…In addition, the maximal venodilatation achieved was less in CF patients [54]. The apparent increase in smooth muscle thickness is also seen in VIP knock-out mice both in the lung and the intestine [55], together with interference with CFTR localisation.…”