Mucin-2 knockout is a model of intercellular junction defects, mitochondrial damage and ATP depletion in the intestinal epithelium

Mariya A Borisova,Kseniya M Achasova,Maryana V Morozova,Evgeniya N Andreyeva,Elena Kiseleva,Elena N Kozhevnikova,Ksenia N Morozova,Ekaterina A Litvinova,Anna A Ogienko,Mariya B Berkaeva

doi:10.1038/s41598-020-78141-4

Abstract

The disruption of the protective intestinal barrier—the ‘leaky gut’—is a common complication of the inflammatory bowel disease. There is limited data on the mechanisms of the intestinal barrier disruption upon low-grade inflammation characteristic of patients with inflammatory bowel disease in clinical remission. Thus, animal models that recapitulate the complexity of chronic intestinal inflammation in vivo are of particular interest. In this study, we used Mucin-2 (Muc2) knockout mice predisposed to colitis to study intestinal barrier upon chronic inflammation. We used 4-kDa FITC-Dextran assay and transmission electron microscopy to demonstrate the increased intestinal permeability and morphological defects in intercellular junctions in Muc2 knockout mice. Confocal microscopy revealed the disruption of the apical F-actin cytoskeleton and delocalization of tight junction protein Claudin-3 from the membrane. We further demonstrate mitochondrial damage, impaired oxygen consumption and the reduction of the intestinal ATP content in Muc2 knockout mice. Finally, we show that chemically induced mitochondrial uncoupling in the wild type mice mimics the intestinal barrier disruption in vivo and causes partial loss of F-actin and membrane localization of Claudin-3. We propose that mitochondrial damage and metabolic shifts during chronic inflammation contribute to the leaky gut syndrome in Muc2 knockout animal model of colitis.

Highlights

One of the prominent features of the inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC) is the disruption of the intestinal protective barrier known as the leaky gut syndrome[1]
We first aimed to investigate whether the state of intestinal inflammation in the descending colon of adult, specific pathogen free (SPF) Muc2−/− mice in our housing conditions is comparable to that found p reviously[44,45]
Colonic crypts were significantly longer in Muc2−/− mice due to the over-proliferation of epithelial cells, as described p reviously[44,45], so that hyperplasia score was higher in Muc2−/− mice (Z = 2.80, p = 0.005, Mann–Whitney U test, Fig. 1B)

Summary

Introduction

One of the prominent features of the inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC) is the disruption of the intestinal protective barrier known as the leaky gut syndrome[1]. Numerous reports demonstrate that leaky gut is associated with the morphological defects in the intercellular contacts of the epithelial cells of UC and CD p atients[1,2,3,4]. These contacts comprise tight junctions (TJs), adherens junctions (AJs) and d esmosomes[5]. The leaky gut is still very common in chronic colitis and IBD that is not associated with pathogenic infection or acute inflammation[23,24,25,26], which raises the question of the mechanisms underlying the intestinal barrier disruption during remission. The validity of this hypothesis still requires experimental support using appropriate in vivo experimental models

Methods

Results

Conclusion