Decreased expression of MUC2 due to a decrease in the expression of lectins and apoptotic defects in colitis patients

Restore Intestinal Barrier Integrity: An Approach for Inflammatory Bowel Disease Therapy

The intestinal barrier maintained by various types of columnar epithelial cells, plays a crucial role in regulating the interactions between the intestinal contents (such as the intestinal microbiota), the immune system, and other components. Dysfunction of the intestinal mucosa is a significant pathophysiological mechanism and clinical manifestation of inflammatory bowel disease (IBD). However, current therapies for IBD primarily focus on suppressing inflammation, and no disease-modifying treatments specifically target the epithelial barrier. Given the side effects associated with chronic immunotherapy, effective alternative therapies that promote mucosal healing are highly attractive. In this review, we examined the function of intestinal epithelial barrier function and the mechanisms of behind its disruption in IBD. We illustrated the complex process of intestinal mucosal healing and proposed therapeutic approaches to promote mucosal healing strategies in IBD. These included the application of stem cell transplantation and organ-like tissue engineering approaches to generate new intestinal tissue. Finally, we discussed potential strategies to restore the function of the intestinal barrier as a treatment for IBD.

Efficacy and Mechanism of the Action of Live and Heat-Killed Bacillus coagulans BC198 as Potential Probiotic in Ameliorating Dextran Sulfate Sodium-Induced Colitis in Mice

Inflammatory bowel disease alters the gut microbiota, causes defects in mucosal barrier function, and leads to dysregulation of the immune response to microbial stimulation. This study investigated and compared the efficacy of a candidate probiotic strain, Bacillus coagulans BC198, and its heat-killed form in treating dextran sulfate sodium-induced colitis. Both live and heat-killed B. coagulans BC198 increased gut barrier-associated protein expression, reduced neutrophil and M1 macrophage infiltration of colon tissue, and corrected gut microbial dysbiosis induced by colitis. However, only live B. coagulans BC198 could alleviate the general symptoms of colitis, prevent colon shortening, and suppress inflammation and tissue damage. At the molecular level, live B. coagulans BC198 was able to inhibit Th17 cells while promoting Treg cells in mice with colitis, reduce pro-inflammatory MCP-1 production, and increase anti-inflammatory IL-10 expression in the colonic mucosa. The live form of B. coagulans BC198 functioned more effectively than the heat-killed form in ameliorating colitis by enhancing the anti-inflammatory response and promoting Treg cell accumulation in the colon.

Intestinal Barrier and Gut Microbiota in Patients with Overlapping Irritable Bowel Syndrome and Functional Dyspepsia

BACKGROUND

Disturbances in the intestinal barrier and gut dysbiosis have been observed in patients with functional bowel diseases.

AIMS

To investigate the correlation between biomarkers of intestinal barrier disorders at different layers and the severity of symptoms in patients with overlapping diarrhea-predominant irritable bowel syndrome and functional dyspepsia (IDFO), as well as with gut microbiota taxa.

METHODS

This study included 45 patients with IDFO and 16 healthy controls. Endoscopy with biopsy of the duodenum and sigmoid colon (SC) was performed to count intraepithelial lymphocytes (IELs) and mucosal eosinophils (subepithelial layer), assess fatty acid binding protein (FABP; epithelial layer) level, and stain for mucin-2 (MUC-2; pre-epithelial layer). Composition of the gut microbiota was evaluated using 16S rRNA gene sequencing.

RESULTS

Patients with IDFO exhibited an increase in biomarkers of intestinal barrier disorders at all layers studied. IEL count in the duodenum was correlated with the severity of bloating (r = 0.336; p = 0.024) and, in the SC, was correlated with tenesmus severity (r = 0.303; p = 0.042). FABP-1 level in the SC was correlated with the severity of diarrhea (r = 0.577; p = 0.001), and FABP-5 concentration in the SC was correlated with abdominal distension (r = 0.477; p = 0.010). MUC-2 concentration in the duodenum was correlated with the severity of heartburn (r = 0.572; p = 0.025) and burning sensation in the epigastrium (r = 0.518; p = 0.048). All biomarkers of intestinal barrier permeability were correlated with the abundance of some gut microbiota taxa.

CONCLUSION

Patients with IDFO exhibited disrupted intestinal barrier function in all layers, which was associated with clinical symptom severity and changes in the gut microbiota.

The protective effects of electroacupuncture on intestinal barrier lesions in IBS and UC model

Irritable bowel syndrome (IBS) and ulcerative colitis (UC) are two intestinal diseases with different pathological changes. Electroacupuncture (EA) at Zusanli (ST36) on both IBS and UC is widely used in clinic practice. But it is unclear whether acupuncture at one acupoint can treat two different intestinal diseases at different layers of intestinal barrier. To address this question, we explored three intestinal barrier lesions in IBS and UC mice with the aid of transcriptome data analysis and studied the efficacy of EA at ST36 on them. The transcriptome data analysis showed that both UC and IBS had disrupted intestinal barrier in various layers. And both UC and IBS had epithelial barrier lesions with reduction of ZO-1, Occludin and Claudin-1, while UC rather than IBS had the destruction of the mucus barrier with less MUC2 expression. As to the vascular barrier, UC showed a higher CD31 level and mesenteric blood flow reduction, while IBS showed a lower PV-1 level. EA at ST36 can significantly improve the above lesions of intestinal barrier of IBS and UC. Our results gave more details about the comprehensive protective effect of EA for UC and IBS. We guess the effect of acupuncture may be a kind of homeostasis regulation.

L-fucose reduces gut inflammation due to T-regulatory response in Muc2 null mice

Fucose, the terminal glycan of the intestinal glycoprotein Mucin2, was shown to have an anti-inflammatory effect in mouse colitis models and modulate immune response due to macrophage polarization changes. In this study we evaluated the effect of 0.05% L-fucose supplementation of drinking water on immune parameters in the intestine of homozygous mutant Muc2-/-, compared to Muc2+/+ mice. To get into innate and adaptive immunity mechanisms of gut inflammation, we tested PrkdcSCIDMuc2-/- strain, Muc2 knockout on SCID background, that is characterized by lack of lymphocytes, in comparison with PrkdcSCID mice. We evaluated intestinal cytokine profiling, macrophage and eosinophil infiltration, and expression of Nos2 and Arg1 markers of macrophage activation in all strains. Markers of Th1, Treg and Th17 cells (Tbx21, Foxp3, and Rorc expression) were evaluated in Muc2-/- and Muc2+/+ mice. Both Muc2-/- and PrkdcSCIDMuc2-/- mice demonstrated increased numbers of macrophages, eosinophils, elevated levels of TNFa, GM-CSF, and IL-10 cytokines. In Muc2-/- mice we observed a wide range of pro-inflammatory cytokines elevated, such as IFN-gamma, IL-1b, IL-12p70, IL-6, M-CSF, G-CSF, IL-17, MCP-1, RANTES, MIP1b, MIP2. Muc2-/- mice demonstrated increase of Nos2, Tbx21 and Foxp3 genes mRNA, while in PrkdcSCIDMuc2-/- mice Arg1 expression was increased. We found that in Muc2-/- mice L-fucose reduced macrophage infiltration and IL-1a, TNFa, IFNgamma, IL-6, MCP-1, RANTES, MIP1b levels, decreased Nos2 expression, and induced the expression of Treg marker Foxp3 gene. On the contrary, in PrkdcSCIDMuc2-/- mice L-fucose had no effect on macrophage and eosinophil numbers, but increased TNFa, GM-CSF, IL-12p70, IL-6, IL-15, IL-10, MCP1, G-CSF, IL-3 levels and Nos2 gene expression, and decreased Arg1 gene expression. We demonstrated that anti-inflammatory effect of L-fucose observed in Muc2-/- mice is not reproduced in PrkdcSCIDMuc2-/-, which lack lymphocytes. We conclude that activation of Treg cells is a key event that leads to resolution of inflammation upon L-fucose supplementation in Muc2-/- mice.

Pectolinarigenin Suppresses LPS-Induced Inflammatory Response in Macrophages and Attenuates DSS-Induced Colitis by Modulating the NF-κB/Nrf2 Signaling Pathway

Pectolinarigenin (PEC), a natural flavonoid present in cirsium chanroenicum and citrus fruits, has possess the distinct pharmacological activities. However, its molecular mechanisms and pharmacological effects on intestinal illness have not been elucidated. In the present study, we investigated the potential beneficial effects of pectolinarigenin (PEC) on lipopolysaccharide (LPS)-induced macrophage cells and the dextran sulfate sodium (DSS)-induced colitis model. Our findings showed that PEC pretreatment inhibits the LPS-induced nuclear factor-kappa B (NF-κB) activation by interfering with the degradation of IκB-α. Further, increased Nrf2 protein expression was reported on PEC treated RAW 264.7 and THP1 cell lines. In addition, we revealed that PEC mediated the NF-κB/Nrf2 pathway regulation, which in turn inhibits the synthesis of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), interleukin-1beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) on RAW 264.7 and THP1 cells. Furthermore, PEC dose-dependently reduced the DSS-induced inflammation in the colon by regulating NF-κB/Nrf2 signaling pathway and enhancing the myeloperoxidase (MPO) activity and redox regulators such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and lipid peroxidation byproduct malondialdehyde (MDA) in DSS-induced inflamed colon. Similarly, we reported the minimal pathological damages in the PEC-treated mice colon, as well as increase goblet cell population and mucin-2 production. In conclusion, our findings demonstrate that PEC reduces the DSS-induced colitis in mice by regulating the NF-κB/Nrf2 pathway. Thus, PEC might be a promising therapeutic agent for the treatment of inflammatory bowel disease.

Voluntary Wheel Running in Old C57BL/6 Mice Reduces Age-Related Inflammation in the Colon but Not in the Brain

Inflammation is considered a possible cause of cognitive decline during aging. This study investigates the influence of physical activity and social isolation in old mice on their cognitive functions and inflammation. The Barnes maze task was performed to assess spatial learning and memory in 3, 9, 15, 24, and 28 months old male C57BL/6 mice as well as following voluntary wheel running (VWR) and social isolation (SI) in 20 months old mice. Inflammatory gene expression was analyzed in hippocampal and colonic samples by qPCR. Cognitive decline occurs in mice between 15 and 24 months of age. VWR improved cognitive functions while SI had negative effects. Expression of inflammatory markers changed during aging in the hippocampus (Il1a/Il6/S100b/Iba1/Adgre1/Cd68/Itgam) and colon (Tnf/Il6/Il1ra/P2rx7). VWR attenuates inflammaging specifically in the colon (Ifng/Il10/Ccl2/S100b/Iba1), while SI regulates intestinal Il1b and Gfap. Inflammatory markers in the hippocampus were not altered following VWR and SI. The main finding of our study is that both the hippocampus and colon exhibit an increase in inflammatory markers during aging, and that voluntary wheel running in old age exclusively attenuates intestinal inflammation. Based on the existence of the gut-brain axis, our results extend therapeutic approaches preserving cognitive functions in the elderly to the colon.

Enhanced Intestinal Barriers by Puerarin in Combination with Tryptophan

The intestinal barrier is essential for maintaining human intestinal health. The growing number of studies has shown that both puerarin and tryptophan and its metabolites have a beneficial effect on the intestinal barrier. This study aims at the combination of puerarin and tryptophan or its metabolites for improving the intestinal barrier. In our study, 40 female Sprague-Dawley rats were randomly divided into five groups (n = 8) for a 4-week experiment and dextran sodium sulfate was used to induce an intestinal barrier injury in rats. Our results showed that puerarin combined with tryptophan or its metabolites (indole-3-propionic acid, IPA) improved the intestinal barrier by enhancing the mucus layer barrier, which was mainly achieved by increasing the number of goblet cells and promoting the secretion of MUC2. Both TRPM5 and VAMP8 promoted MUC2 secretion in goblet cells through exocytosis, but their mechanisms of action are different. In our study, we found that puerarin and tryptophan showed different effects on TRPM5 and VAMP8, respectively. Puerarin enhances the expression of TRPM5, and tryptophan inhibits the expression of TRPM5; however, puerarin and tryptophan have no significant effect on the expression of VAMP8.

Role of Barrier Integrity and Dysfunctions in Maintaining the Healthy Gut and Their Health Outcomes

Mucosal surface layers are the critical borders throughout epithelial membranes. These epithelial cells segregate luminal material from external environments. However, mucosal linings are also accountable for absorbing nutrients and requiring specific barrier permeability. These functional acts positioned the mucosal epithelium at the epicenter of communications concerning the mucosal immune coordination and foreign materials, such as dietary antigens and microbial metabolites. Current innovations have revealed that external stimuli can trigger several mechanisms regulated by intestinal mucosal barrier system. Crucial constituents of this epithelial boundary are physical intercellular structures known as tight junctions (TJs). TJs are composed of different types transmembrane proteins linked with cytoplasmic adaptors which helps in attachment to the adjacent cells. Disruption of this barrier has direct influence on healthy or diseased condition, as barrier dysfunctions have been interrelated with the initiation of inflammation, and pathogenic effects following metabolic complications. In this review we focus and overview the TJs structure, function and the diseases which are able to influence TJs during onset of disease. We also highlighted and discuss the role of phytochemicals evidenced to enhance the membrane permeability and integrity through restoring TJs levels.

Zebrafish intestinal transcriptome highlights subdued inflammatory responses to dietary soya bean and efficacy of yeast β-glucan

Anti-nutritional factors in dietary components can have a negative impact on the intestinal barrier. Here, we present soya bean-induced changes in the intestine of juvenile zebrafish and the effect of yeast β-glucan through a transcriptomic approach. The inclusion of soya bean meal affected the expression of several intestinal barrier function-related genes like arl4ca, rab25b, rhoub, muc5ac, muc5d, clcn2c and cltb in zebrafish. Several metabolic genes like cyp2x10.2, cyp2aa2, aldh3a2b, crata, elovl4, elovl6, slc51a, gpat2 and ATP-dependent peptidase activity (lonrf, clpxb) were altered in the intestinal tissue. The expression of immune-related genes like nlrc3, nlrp12, gimap8, prdm1 and tph1a, and genes related to cell cycle, DNA damage and DNA repair (e.g. spo11, rad21l1, nabp1b, spata22, tdrd9) were also affected in the soya bean fed group. Furthermore, our study suggests the plausible effect of yeast β-glucan through the modulation of several genes that regulate immune responses and barrier integrity. Our findings indicate a subdued inflammation in juvenile zebrafish fed soya bean meal and the efficacy of β-glucan to counter these subtle inflammatory responses.

A Purified Aspartic Protease from Akkermansia Muciniphila Plays an Important Role in Degrading Muc2

Akkermansia muciniphila can produce various mucin-degrading proteins. However, the functional characteristics of these proteins and their role in mucin degradation are unclear. Of the predicted protein-coding genes, Amuc_1434, which encodes for a hypothetical protein, is the focus in this study. A recombinant enzyme Amuc_1434 containing the 6× His-tag produced in Escherichia coli (hereinafter termed Amuc_1434*) was isolated to homogeneity and biochemically characterised. Results showed that the enzyme can hydrolyse hemoglobin with an activity of 17.21 U/μg. The optimal pH and temperature for hemoglobin hydrolysis of Amuc_1434* were found to be around 8.0 and 40 °C, respectively. Amuc_1434* is identified as a member of the aspartic protease family through the action of inhibitor pepstatin A. Amuc_1434* promotes the adhesion of colon cancer cell line LS174T, which can highly express Muc2. Significantly Amuc_1434* can degrade Muc2 of colon cancer cells. Amuc_1434 is mainly located in the colon of BALB/c mice. These results suggest that the presence of Amuc_1434 from Akkermansia muciniphila may be correlated with the restoration of gut barrier function by decreasing mucus layer thickness.