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

Abstract

Vasoactive Intestinal Peptide (VIP) is the major physiological agonist of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) chloride channel activity. VIP functions as a neuromodulator and neurotransmitter secreted by neurons innervating all exocrine glands. VIP is also a potent vasodilator and bronchodilator that regulates exocrine gland secretions, contributing to local innate defense by stimulating the movement of water and chloride transport across intestinal and tracheobronchial epithelia. 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. Our data show that a low amount of VIP is found in CF tissues prior to tissue damage. Moreover, we found a specific reduction in VIPergic and cholinergic innervation of the small intestine. The general innervation of the primary and secondary myenteric plexus was lost in CF tissues, with the presence of enlarged ganglionic cells in the tertiary layer. We propose that low amount of VIP in CF tissues is due to a reduction in VIPergic and cholinergic innervation and represents an early defect that constitutes an aggravating factor for CF disease progression.

VIP reduction in the pancreas of F508del homozygous CF mice and early signs of Cystic Fibrosis Related Diabetes (CFRD)

“…Our most recent study in the C57Bl/6 homozygous Cftr tm1Kth F508del CF mice, the same model used in this paper, showed that VIP content is significantly reduced in the lungs, duodenum and sweat glands of young CF mice with minimal disease progression. In addition, we found that these mice present a highly discontinuous or sparse VIPergic network in the small intestine and that this VIPergic deficiency was not attributable to disease progression but to a disruption of the intrinsic innervation network [33] .…”

“…Given that VIP is a neuropeptide with pleiotropic abilities, we decided to examine the distribution and abundance of VIP in the pancreas of male C57Bl/6 mice homozygous for the most common mutation in CF, F508del, and evaluate whether changes in VIP would correlate with changes in insulin and glucagon secretion that could contribute to the development of CFRD. We have measured the amount of VIP in both young (8-week-old) and older (17-week-old) CF mice, which reflect very early and late CF disease progression, respectively [33] . Our results show that VIP abundance and localization, semi-quantified by IHC and ELISA, were significantly reduced (~51% reduction) in the pancreas of CF mice at both 8 and 17 weeks of age.…”

“…Based on our previous study, the 17-week-old CF mice display a well-developed CF disease, while in 8-week-old mice, the disease was minimal [33] . The amount of VIP in the pancreas was revealed by IHC using a polyclonal anti-VIP antibody, and in WT tissues, most of the signal was found around the ducts and acinar cells of the exocrine pancreas, with some signal in the islets of Langerhans (D1 cells) of the endocrine pancreas ( Fig.…”

“…In our previous study, we showed that the reduced amount of VIP in the lungs, duodenum and sweat glands of homozygous F508del mice was due to sparse VIPergic neuronal fibers and a disrupted general neural network [33] . In the present study, we found a reduced amount of VIP in both the endocrine and exocrine pancreas; thus, we decided to further test the general innervation of the pancreas using a PGP 9.5 antibody.…”

“…In a recent study, we demonstrated that VIP content is 50% lower in the lungs, sweat glands and small intestine of C57Bl/6 mice homozygous for the F508del-CFTR mutation compared to wild-type (WT) mice. This deficiency results from a reduction in VIPergic and cholinergic innervation starting at a young age, before signs of CF disease are observed [33] . In the present study, we assessed whether there were changes in VIP abundance and innervation of the pancreas at different stages of CF disease progression that could affect insulin and glucagon secretion and contribute to CFRD development.…”