Pancreastatin Reduces Alternatively Activated Macrophages, Disrupts the Epithelial Homeostasis and Aggravates Colonic Inflammation. A Descriptive Analysis

Pancreastatin Inhibition Alters the Colonic Epithelial Cells Profile in a Sex-Dependent Manner

The impaired mucosal barrier is a hallmark of ulcerative colitis (UC), an inflammatory colonic disorder with epidemiological and pathophysiology sex bias. UC Patients overexpress the colonic epithelial cells (CECs)-derived peptide pancreastatin (PST). Pancreastatin inhibitor 8 (PSTi8), an inhibitor of PST, has shown promising anti-inflammatory effects on UC. However, no data exist in the context of CEC barrier function and integrity. We investigated the impact of PSTi8 treatment on CECs in homeostatic and colitic conditions. PSTi8 (2.5 mg/mL/kg, i.r.) or PBS treatment started one day before colitis induction (5% dextran sodium sulfate for five days) in male and female C57BL/6 mice. The disease activity score was assessed daily. Epithelial-associated cytokines, markers specific to differentiation, proliferation, differentiated CECs, stem cells, CECs regulators, and the PSTi8 G-protein coupled receptor 78 (GPR78) signaling pathway, were evaluated using ELISA, immunofluorescence and qRT-PCR. PSTi8 treatment reduced the epithelial-associated cytokines and differentiated CECs while promoting CEC proliferation and self-renewal in females at a steady state through the GRP78 signaling pathway. PSTi8 treatment exacerbated colitis severity and increased CEC differentiation while reducing proliferation in colitic females. Conversely, PSTi8 treatment reduced males' susceptibility to colitis by preserving stem cells and differentiated CECs. PST regulated colonic mucosal maintenance in a sex- and disease-dependent manner.

The immunomodulatory functions of chromogranin A-derived peptide pancreastatin

Chromogranin A (CgA) is a 439 amino acid protein secreted by neuroendocrine cells. Proteolytic processing of CgA results in the production of different bioactive peptides. These peptides have been associated with inflammatory bowel disease, diabetes, and cancer. One of the chromogranin A-derived peptides is ∼52 amino acid long Pancreastatin (PST: human (h)CgA250-301, murine (m)CgA263-314). PST is a glycogenolytic peptide that inhibits glucose-induced insulin secretion from pancreatic islet β-cells. In addition to this metabolic role, evidence is emerging that PST also has inflammatory properties. This review will discuss the immunomodulatory properties of PST and its possible mechanisms of action and regulation. Moreover, this review will discuss the potential translation to humans and how PST may be an interesting therapeutic target for treating inflammatory diseases.

Chromogranin A regulates gut permeability via the antagonistic actions of its proteolytic peptides

AIM

A "leaky" gut barrier has been implicated in the initiation and progression of a multitude of diseases, for example, inflammatory bowel disease (IBD), irritable bowel syndrome and celiac disease. Here we show how pro-hormone Chromogranin A (CgA), produced by the enteroendocrine cells, and Catestatin (CST: hCgA_352-372 ), 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 analysed by immunohistochemistry, western blot, ultrastructural and flowcytometry studies. FITC-dextran assays were used to measure intestinal barrier function. Mice were supplemented with CST or CgA fragment pancreastatin (PST: CgA_250-301 ). The microbial composition of cecum was determined. CgA and CST levels were measured in blood of IBD patients.

RESULTS

Plasma levels of CST were elevated in IBD patients. CST-KO mice displayed (a) elongated tight, adherens junctions and desmosomes similar to IBD patients, (b) elevated expression of Claudin 2, and (c) gut inflammation. Plasma FITC-dextran measurements showed increased intestinal paracellular permeability in the CST-KO mice. This correlated with a higher ratio of Firmicutes to Bacteroidetes, a dysbiotic pattern commonly encountered in various diseases. Supplementation of CST-KO mice with recombinant CST restored paracellular permeability and reversed inflammation, whereas CgA-KO 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 by antagonizing PST.