Abstract
Aim A ‘leaky’ gut barrier has been implicated in the initiation and progression of a multitude of diseases, e.g., inflammatory bowel disease, irritable bowel syndrome, celiac disease, and colorectal cancers. Here we show how pro-hormone Chromogranin A (CgA), produced by the enteroendocrine cells, and Catestatin (CST: hCgA352-372), the most abundant CgA-derived proteolytic peptide, affect the gut barrier.
Methods Colon tissues from region-specific CST-knockout (CST-KO) mice, CgA-knockout (CgA-KO) and WT mice were analyzed by immunohistochemistry, ultrastructural and flowcytometry studies. FITC-dextran assays were used to measure intestinal barrier function. Mice were supplemented with CST or CgA fragment pancreastatin (PST: CgA250-301). The microbial composition of cecum was determined. CgA and CST levels were measured in blood of IBD patients.
Results CST-KO mice displayed (i) elongated tight, adherens junctions and desmosomes similar to IBD patients, and (ii) gut inflammation. Consistently, plasma FITC-dextran measurements showed increased intestinal paracellular permeability in the CST-knockout mice. This correlated with a higher ratio of Firmicutes to Bacteroidetes, a dysbiotic pattern commonly encountered in various diseases. Supplementation of CST-knockout mice with recombinant CST restored paracellular permeability and reversed inflammation, whereas CgA-knockout mice supplementation with CST and/or PST in CgA-KO mice showed that intestinal paracellular permeability is regulated by the antagonistic roles of these two peptides: CST reduces and PST increases permeability.
Conclusion The pro-hormone CgA regulates the intestinal paracellular permeability. CST is both necessary and sufficient to reduce permeability and primarily acts via antagonizing the effects of PST.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
↵* shared co-first authorship
We have revised the original figures with new data and also included new data in new figures. The revised figures on the expression of genes include WT+CST-treated data (Fig. 2F-H, 4G and 5C). The new figures include the following: Western blots of TJ and AJ proteins (Fig. 3A and B); ultrastructural analyses of human colonic mucosa (Fig. 3H-L); histology showing immune cells (Fig. 4A-C); immunohistochemistry (Emr+ staining; Fig. 4D); Masson trichrome staining showing fibrosis (Fig. 5D), transmission electron micrographs showing TJ, AJ and desmosomes in healthy volunteers and IDB patients (Fig. 2H-L) as well as collagen fibers (Fig. 5E), and immunohistochemistry of caspase 3 showing apoptosis (Fig. 6A).