Interdependence between Chromogranin-A, Alternatively Activated Macrophages, Tight Junction Proteins and the Epithelial Functions. A Human and In-Vivo/In-Vitro Descriptive Study

• Main Authors: Nour Eissa, Hayam Hussein, Diane M. Tshikudi, Geoffrey N. Hendy, Charles N. Bernstein, Jean-Eric Ghia
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: International Journal of Molecular Sciences
• Subjects: alternatively activated macrophages; chromogranin-A; cytokines; epithelial repair; fibrosis; gut hormones
• Online Access: https://www.mdpi.com/1422-0067/21/21/7976

<b>Background:</b> Ulcerative colitis (UC) is characterized by altered chromogranin-A (CHGA), alternatively activated macrophages (M2) and intestinal epithelial cells (IECs). We previously demonstrated that CHGA is implicated in colitis progression by regulating the macrophages. Here, we investigated the interplay between CHGA, M2, tight junctions (TJ) and IECs in an inflammatory environment. <b>Methods:</b> Correlations between <i>CHGA</i> mRNA expression of and TJ proteins mRNA expressions of (Occludin [<i>OCLN</i>], zonula occludens-1 [<i>ZO1</i>], Claudin-1 [<i>CLDN1</i>]), epithelial associated cytokines (interleukin <i>[IL]-8</i>, <i>IL-18</i>), and collagen (<i>COL1A2</i>) were determined in human colonic mucosal biopsies isolated from active UC and healthy patients. Acute UC-like colitis (5% dextran sulphate sodium [DSS], five days) was induced in <i>Chga</i>-C57BL/6-deficient (<i>Chga^−/−</i>) and wild type (<i>Chga^+/+</i>) mice. <i>Col1a2</i> TJ proteins, <i>Il-18</i> mRNA expression and collagen deposition were determined in whole colonic sections. Naïve <i>Chga^−/−</i> and <i>Chga^+/+</i> peritoneal macrophages were isolated and exposed six hours to IL-4/IL-13 (20 ng/mL) to promote M2 and generate M2-conditioned supernatant. Caco-2 epithelial cells were cultured in the presence of <i>Chga^−/−</i> and <i>Chga^+/+</i> non- or M2-conditioned supernatant for 24 h then exposed to 5% DSS for 24 h, and their functional properties were assessed. <b>Results:</b> In humans, <i>CHGA</i> mRNA correlated positively with <i>COL1A2</i>, <i>IL-8</i> and <i>IL-18</i>, and negatively with TJ proteins mRNA markers. In the experimental model, the deletion of <i>Chga</i> reduced IL-18 mRNA and its release, <i> COL1A2</i> mRNA and colonic collagen deposition, and maintained colonic TJ proteins. <i>Chga^−/−</i> M2-conditioned supernatant protected caco-2 cells from DSS and oxidative stress injuries by improving caco-2 cells functions (proliferation, viability, wound healing) and by decreasing the release of IL-8 and IL-18 and by maintaining the levels of TJ proteins, and when compared with <i>Chga^+/+</i> M2-conditioned supernatant. <b>Conclusions:</b> CHGA contributes to the development of intestinal inflammation through the regulation of M2 and epithelial cells. Targeting CHGA may lead to novel biomarkers and therapeutic strategies in UC.