Transglutaminase 3 crosslinks the secreted gel-forming mucus component Mucin-2 and stabilizes the colonic mucus layer

The colonic mucus layer is organized as a two-layered system providing a physical barrier against pathogens and simultaneously harboring the commensal flora. The factors contributing to the organization of this gel network are not well understood. In this study, the impact of transglutaminase activity on this architecture was analyzed. Here, we show that transglutaminase TGM3 is the major transglutaminase-isoform expressed and synthesized in the colon. Furthermore, intrinsic extracellular transglutaminase activity in the secreted mucus was demonstrated in vitro and ex vivo. Absence of this acyl-transferase activity resulted in faster degradation of the major mucus component the MUC2 mucin and changed the biochemical properties of mucus. Finally, TGM3-deficient mice showed an early increased susceptibility to Dextran Sodium Sulfate-induced colitis. Here, we report that natural isopeptide cross-linking by TGM3 is important for mucus homeostasis and protection of the colon from inflammation, reducing the risk of colitis.

Identification and characterization of a novel Enterococcus bacteriophage with potential to ameliorate murine colitis

Increase of the enteric bacteriophages (phage), components of the enteric virome, has been associated with the development of inflammatory bowel diseases. However, little is known about how a given phage contributes to the regulation of intestinal inflammation. In this study, we isolated a new phage associated with Enterococcus gallinarum, named phiEG37k, the level of which was increased in C57BL/6 mice with colitis development. We found that, irrespective of the state of inflammation, over 95% of the E. gallinarum population in the mice contained phiEG37k prophage within their genome and the phiEG37k titers were proportional to that of E. gallinarum in the gut. To explore whether phiEG37k impacts intestinal homeostasis and/or inflammation, we generated mice colonized either with E. gallinarum with or without the prophage phiEG37k. We found that the mice colonized with the bacteria with phiEG37k produced more Mucin 2 (MUC2) that serves to protect the intestinal epithelium, as compared to those colonized with the phage-free bacteria. Consistently, the former mice were less sensitive to experimental colitis than the latter mice. These results suggest that the newly isolated phage has the potential to protect the host by strengthening mucosal integrity. Our study may have clinical implication in further understanding of how bacteriophages contribute to the gut homeostasis and pathogenesis.

A Mediterranean-like fat blend protects against the development of severe colitis in the mucin-2 deficient murine model

The Mediterranean diet (MD) is a health-promoting diet containing approximately 40% total fat. It is not known if the blend of fats found in the MD contribute to the beneficial protective effects. We compared the MD fat blend (high monounsaturated, 2:1 n-6:n-3 polyunsaturated and moderate saturated fat) to isocaloric diets composed with corn oil (CO, n-6 polyunsaturated-rich), olive oil (high monounsaturated-rich) or milk fat (MF, saturated-rich) on spontaneous colitis development in Muc2-/- mice. The MD resulted in lower clinical and histopathological scores, and induced tolerogenic CD103+CD11b+ dendritic, Th22 and IL-17+IL-22+ cells important for intestinal barrier repair. MD also reduced attendant insulin resistance and a shift to a higher health-promoting gut microbes including Lactobacillus animalis and Muribaculaceae, whereas CO showed higher prevalence of mucin-degraders (Akkermansia muciniphila) and colitis promoters (Enterobacteriaceae). Our findings suggest that the MD fat blend could be recommended as a maintenance diet for colitis.

Ameliorative Effects of Peptides Derived from Oyster (Crassostrea gigas) on Immunomodulatory Function and Gut Microbiota Structure in Cyclophosphamide-Treated Mice

The intestinal flora is recognized as a significant contributor to the immune system. In this research, the protective effects of oyster peptides on immune regulation and intestinal microbiota were investigated in mice treated with cyclophosphamide. The results showed that oyster peptides restored the indexes of thymus, spleen and liver, stimulated cytokines secretion and promoted the relative mRNA levels of Th1/Th2 cytokines (IL-2, IFN-γ, IL-4 and IL-10). The mRNA levels of Occludin, Claudin-1, ZO-1, and Mucin-2 were up-regulated, and the NF-κB signaling pathway was also activated after oyster peptides administration. Furthermore, oyster peptides treatment reduced the proportion of Firmicutes/Bacteroidetes, increased the relative abundance of Alistipes, Lactobacillus, Rikenell and the content of short-chain fatty acids, and reversed the composition of intestinal microflora similar to that of normal mice. In conclusion, oyster peptides effectively ameliorated cyclophosphamide-induced intestinal damage and modified gut microbiota structure in mice, and might be utilized as a beneficial ingredient in functional foods for immune regulation.

Functional Morphology of Goblet Cells of the Small Intestine under the Influence of Various Factors

The gastrointestinal tract is constantly exposed to various physical and chemical factors. In the intestine, the contact of bacteria and the epithelium largely depends on mucus, which mainly consists of highly glycosylated mucin-2 secreted by goblet cells in the epithelium. Goblet cells are located along the entire length of the small and large intestine and are responsible for the production and maintenance of a protective layer of mucus through the synthesis and secretion of high-molecular glycoproteins known as mucins. The article presents data on the embryogenesis of the small intestine in general and goblet cells, in particular, a literary review of the role of goblet cells in the morphology of the intestinal tract, the functional aсtivity of their secretion is carried out. Due to the unique nature of this highly polarized exocrine cell, the cellular mechanisms by which goblet cells secrete their products are discussed.

Aged Pu-Erh Tea Reduced Oxidative Stress-Mediated Inflammation in DSS-Induced Colitis Mice by Regulating Intestinal Microbes

Background: Colitis is associated with gut microbiological disorders and oxidative stress-mediated intestinal inflammation. Pu-erh tea has been used as a beverage for bioactive potential in antioxidation and anti-inflammation. With increase of storage, the change of its bioactive components creates the difference of health care function. However, there is no evidence to show whether the storage period of Pu-erh tea affects its anti-inflammatory and anti-oxidant capacity in the colitis, or even intestinal protection. Results: In this study, 3.5% DSS-induced colitis mice were treated with 10 mg/kg bw/day extracts, aged 14 years (P2006) and unaged (P2020) Pu-erh tea respectively, for 1 week. It was found that Pu-erh tea, especially P2006, inhibited the intestinal oxidative stress-mediated inflammation signaling pathway (TLR4/MyD88/ROS/p38 MAPK/NF-κB p65), up-regulated the expression of intestinal tight junction proteins (Mucin-2, zonula occludens 1, occluding), promoted M2 polarization of macrophages, and in turn, improved the intestinal immune barrier, which stemmed from the reshaping of intestinal microbiota (e.g., increased Lachnospiraceae_NK4A136_group and Akkermansia levels). Conclusions: These results indicate that the changes of intestinal microflora caused by aged Pu-erh are the key to alleviate DSS-induced colitis, and speculate that drinking aged Pu-erh tea (10 mg/kg bw/day in mice, a human equivalent dose of 7 g/60 kg bw /day) has a practical effect on alleviating and preventing the development of intestinal inflammation.