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

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.

Fat of the Gut: Epithelial Phospholipids in Inflammatory Bowel Diseases

“…In recent years, it has become clear that inflammatory cytokines can regulate genes involved in glucose and lipid metabolism, affecting overall energy homeostasis [ 36 ]. In agreement with this, clinical and animal studies revealed that chronic inflammation is associated with reduced energy metabolism and strong mitochondrial damage, which results in reduced ATP production in the intestinal epithelium [ 37 , 38 , 39 , 40 ]. In turn, ATP depletion triggers intestinal barrier impairment and worsens the course of colitis [ 41 ].…”

“…However, mitochondria are not the only membranous organelles that alter shape and physiology upon colitis. Our previous study, in addition to reports by other authors, revealed the abnormal shape of multiple membranous organelles, including mitochondria, endoplasmic reticulum (ER) and Golgi apparatuses, and cellular and nuclear membranes during inflammation [ 37 , 38 , 39 , 45 , 46 , 47 ]. These indicate that membrane-forming phospholipids may be substantially deregulated upon colitis, which is further supported by experimental data [ 48 , 49 , 50 ].…”

“…Knockout of cytidine triphosphate (CTP): phosphocholine cytidylyltransferase-α–a rate-limiting enzyme in the major pathway for PC biosynthesis results in colitis, lack of a mucus layer and intestinal barrier permeability. Ultrastructural changes in this mouse model strongly resemble those we observed upon direct knockout of the Mucin-2 gene, including mitochondrial shape and microvilli damage [ 37 , 51 ]. Phosphatidylinositol (PI) derivatives are also implicated in the pathogenesis of IBD as signaling molecules with notable changes in the membranous organelle ultrastructure [ 52 ].…”

Reduced acetylcholine and elevated muscarinic receptor 2 in duodenal mucosa contribute to the impairment of mucus secretion in 6-hydroxydopamine-induced Parkinson’s disease rats

“…Mucin 2 (MUC2), an important secretory mucin, is the main structural component of mucus gel in the intestine (Johansson and Hansson 2016). Muc2 knockout (Muc2 −/− ) mice lack a functional mucus layer and exhibit destruction of the duodenal mucosal barrier and increased intestinal permeability (Borisova et al 2020;Gao et al 2016). These studies suggest that mucus has a critical role in maintaining the duodenal mucosal barrier.…”

Colon Innervating TRPA1 Positive Nociceptors Influence Mucosal Health In Mice

“…Muc3 and Muc2 genes were significantly decreased in desensitized animals. In studies on Muc2 knockout animals, increased intestinal permeability has been shown to triggers a cascade of events leading to secondary organ inflammation and translocation of bacterial metabolites and bacteria per se leading to sepsis 21,22 . Different goblet cell markers (Cdx2, Dll1, Foxa2, Tff3, Dll4, Vamp8, Prkd1, and Foxa3) and Fcgbp were significantly decreased in desensitized animals.…”