Tauroursodeoxycholate improves 2,4,6-trinitrobenzenesulfonic acid-induced experimental acute ulcerative colitis in mice

Tauroursodeoxycholic Acid Reverses Dextran Sulfate Sodium-Induced Colitis in Mice via Modulation of Intestinal Barrier Dysfunction and Microbiome Dysregulation

Ulcerative colitis (UC) is an immune-mediated inflammatory disease that can lead to persistent damage and even cancer without any intervention. Conventional treatments can alleviate UC symptoms but are costly and cause various side effects. Tauroursodeoxycholic acid (TUDCA), a secondary bile acid derivative, possesses anti-inflammatory and cytoprotective properties for various diseases, but its potential therapeutic benefits in UC have not been fully explored. Mice were subjected to colitis induction using 3% dextran sulfate sodium (DSS). The therapeutic effect of TUDCA was evaluated by body weight loss, disease activity index (DAI), colon length, and spleen weight ratio. Tissue pathology was assessed using H&E staining, while the levels of pro-inflammatory and anti-inflammatory cytokines in colonic tissue were quantified via ELISA. Tight junction proteins were detected by immunoblotting and intestinal permeability was assessed using fluorescein isothiocyanate (FITC)-dextran. Moreover, the gut microbiota was profiled using high-throughput sequencing of the 16S rDNA gene. TUDCA alleviated the colitis in mice, involving reduced DAI, attenuated colon and spleen enlargement, ameliorated histopathological lesions, and normalized levels of pro-inflammatory and anti-inflammatory cytokines. Furthermore, TUDCA treatment inhibited the downregulation of intestinal barrier proteins, including zonula occludens-1 and occludin, thus reducing intestinal permeability. The analysis of gut microbiota suggested that TUDCA modulated the dysbiosis in mice with colitis, especially for the remarkable rise in Akkermansia TUDCA exerted a therapeutic efficacy in DSS-induced colitis by reducing intestinal inflammation, protecting intestinal barrier integrity, and restoring gut microbiota balance. SIGNIFICANCE STATEMENT: This study demonstrates the potential therapeutic benefits of Tauroursodeoxycholic acid (TUDCA) in ulcerative colitis. TUDCA effectively alleviated colitis symptoms in mice, including reducing inflammation, restoring intestinal barrier integrity and the dysbiosis of gut microbiota. This work highlights the promising role of TUDCA as a potentially alternative treatment, offering new insights into managing this debilitating condition.

Gut Microbiota Metabolites: Unveiling Their Role in Inflammatory Bowel Diseases and Fibrosis

In recent years, there has been a growing focus on the intricate interplay between the gut microbiota and host health, specifically in the context of inflammatory bowel diseases (IBDs). The gut microbiota produces a diverse array of metabolites, influencing the host's immune response and tissue homeostasis. Noteworthy metabolites, such as short-chain fatty acids, bile acids, and indoles, exert significant effects on intestinal inflammation and fibrosis. This review integrates current research findings to clarify the mechanisms through which gut microbiota metabolites contribute to the progression of IBD and fibrosis, offering insights into potential therapeutic targets and strategies for managing these intricate gastrointestinal conditions. The unraveling of the complex relationship between gut microbiota metabolites and inflammatory processes holds promise for the development of targeted interventions that could lead to more effective and personalized treatment approaches for individuals affected by IBD and subsequent intestinal fibrosis.

Defective Atg16l1 in intestinal epithelial cells links to altered fecal microbiota and metabolic shifts during pregnancy in mice

Throughout gestation, the female body undergoes a series of transformations, including profound alterations in intestinal microbial communities. Changes gradually increase toward the end of pregnancy and comprise reduced α-diversity of microbial communities and an increased propensity for energy harvest. Despite the importance of the intestinal microbiota for the pathophysiology of inflammatory bowel diseases, very little is known about the relationship between these microbiota shifts and pregnancy-associated complications of the disease. Here, we explored the longitudinal dynamics of gut microbiota composition and functional potential during pregnancy and after lactation in Atg16l1∆IEC mice carrying an intestinal epithelial deletion of the Crohn's disease risk gene Atg16l1. Using 16S rRNA amplicon and shotgun metagenomic sequencing, we demonstrated divergent temporal shifts in microbial composition between Atg16l1 wildtype and Atg16l1∆IEC pregnant mice in trimester 3, which was validated in an independent experiment. Observed differences included microbial genera implicated in IBD such as Lachnospiraceae, Roseburia, Ruminococcus, and Turicibacter. Changes partially recovered after lactation. Additionally, metagenomic and metabolomic analyses suggest an increased capacity for chitin degradation, resulting in higher levels of free N-acetyl-glucosamine products in feces, alongside reduced glucose and myo-inositol levels in serum around the time of delivery. On the host side, we found that the immunological response of Atg16l1∆IEC mice is characterized by higher colonic mRNA levels of TNFα and CXCL1 in trimester 3 and a lower weight of offspring at birth. Understanding pregnancy-dependent microbiome changes in the context of IBD may constitute the first step in the identification of fecal microbial biomarkers and microbiota-directed therapies that could help improve precision care for managing pregnancies in IBD patients.

Bile acids and their receptors: Potential therapeutic targets in inflammatory bowel disease

Chronic and recurrent inflammatory disorders of the gastrointestinal tract caused by a complex interplay between genetics and intestinal dysbiosis are called inflammatory bowel disease. As a result of the interaction between the liver and the gut microbiota, bile acids are an atypical class of steroids produced in mammals and traditionally known for their function in food absorption. With the development of genomics and metabolomics, more and more data suggest that the pathophysiological mechanisms of inflammatory bowel disease are regulated by bile acids and their receptors. Bile acids operate as signalling molecules by activating a variety of bile acid receptors that impact intestinal flora, epithelial barrier function, and intestinal immunology. Inflammatory bowel disease can be treated in new ways by using these potential molecules. This paper mainly discusses the increasing function of bile acids and their receptors in inflammatory bowel disease and their prospective therapeutic applications. In addition, we explore bile acid metabolism and the interaction of bile acids and the gut microbiota.

TLR4 promoted endoplasmic reticulum stress induced inflammatory bowel disease via the activation of p38 MAPK pathway

Endoplasmic reticulum (ER) stress contribute to inflammatory bowel disease (IBD). However, the mechanistic link between toll-like receptor 4 (TLR4) and ER stress in IBD remains elusive. This study aimed to investigate the mechanism by which ER stress and TLR4 promote inflammation in IBD.

IBD mouse model was established by the induction of TNBS, and Grp78 and TLR4 in intestine tissues were detected by immunohistochemistry. THP-1 cells were treated with lipopolysaccharides (LPS), ER stress inducer or inhibitor tauroursodeoxycholic acid (TUDCA), or p38 MAPK inhibitor. The activation of MAPK signaling was detected by Western blot, and the production and secretion of inflammatory factors were detected by PCR and ELISA. We found that the expression levels of TLR4 and GRP78 were significantly higher in the intestine of IBD model mice compared with control mice but were significantly lower in the intestine of IBD model mice treated with ER stress inhibitor TUDCA. ER stress inducer significantly increased while ER stress inhibitor TUDCA significantly decreased the expression and secretion of TNF-α, IL-1β and IL-8 in THP-1 cells treated by LPS. Only p38 MAPK signaling was activated in THP-1 cells treated by ER stress inducer. Furthermore, p38 inhibitor SB203580 inhibited the production and secretion of TNF-α, IL-1β and IL-8 in THP-1 cells treated with LPS. In conclusion, TLR4 promotes ER stress induced inflammation in IBD, and the effects may be mediated by p38 MAPK signaling. TLR4 and p38 MAPK signaling are novel therapeutic targets for IBD.

Critical roles of bile acids in regulating intestinal mucosal immune responses

Bile acids are a class of cholesterol derivatives that have been known for a long time for their critical roles in facilitating the digestion and absorption of lipid from the daily diet. The transformation of primary bile acids produced by the liver to secondary bile acids appears under the action of microbiota in the intestine, greatly expanding the molecular diversity of the intestinal environment. With the discovery of several new receptors of bile acids and signaling pathways, bile acids are considered as a family of important metabolites that play pleiotropic roles in regulating many aspects of human overall health, especially in the maintenance of the microbiota homeostasis and the balance of the mucosal immune system in the intestine. Accordingly, disruption of the process involved in the metabolism or circulation of bile acids is implicated in many disorders that mainly affect the intestine, such as inflammatory bowel disease and colon cancer. In this review, we discuss the different metabolism profiles in diseases associated with the intestinal mucosa and the diverse roles of bile acids in regulating the intestinal immune system. Furthermore, we also summarize recent advances in the field of new drugs that target bile acid signaling and highlight the importance of bile acids as a new target for disease intervention.

Bile Acid Signaling in Inflammatory Bowel Diseases

Bile acids are a group of chemically different steroids generated at the host/microbial interface. Indeed, while primary bile acids are the end-product of cholesterol breakdown in the host liver, secondary bile acids are the products of microbial metabolism. Primary and secondary bile acids along with their oxo derivatives have been identified as signaling molecules acting on a family of cell membrane and nuclear receptors collectively known as "bile acid-activated receptors." Members of this group of receptors are highly expressed throughout the gastrointestinal tract and mediate the bilateral communications of the intestinal microbiota with the host immune system. The expression and function of bile acid-activated receptors FXR, GPBAR1, PXR, VDR, and RORγt are highly dependent on the structure of the intestinal microbiota and negatively regulated by intestinal inflammation. Studies from gene ablated mice have demonstrated that FXR and GPBAR1 are essential to maintain a tolerogenic phenotype in the intestine, and their ablation promotes the polarization of intestinal T cells and macrophages toward a pro-inflammatory phenotype. RORγt inhibition by oxo-bile acids is essential to constrain Th17 polarization of intestinal lymphocytes. Gene-wide association studies and functional characterizations suggest a potential role for impaired bile acid signaling in development inflammatory bowel diseases (IBD). In this review, we will focus on how bile acids and their receptors mediate communications of intestinal microbiota with the intestinal immune system, describing dynamic changes of bile acid metabolism in IBD and the potential therapeutic application of targeting bile acid signaling in these disorders.

Ulcerative colitis: Gut microbiota, immunopathogenesis and application of natural products in animal models

Ulcerative colitis (UC) is an inflammatory bowel disease with increasing incidence in the world, especially in developing countries. Although knowledge of its pathogenesis has progressed over the last years, some details require clarification. Studies have highlighted the role of microbial dysbiosis and immune dysfunction as essential factors that may initiate the typical high-grade inflammatory outcome. In order to better understand the immunopathophysiological aspects of UC, experimental murine models are valuable tools. Some of the most commonly used chemicals to induce colitis are trinitrobenzene sulfonic acid, oxazolone and dextran sodium sulfate. These may also be used to investigate new ways of preventing or treating UC and therefore improving targeting in human studies. The use of functional foods or bioactive compounds from plants may constitute an innovative direction towards the future of alternative medicine. Considering the above, this review focused on updated information regarding the 1. gut microbiota and immunopathogenesis of UC; 2. the most utilized animal models of the disease and their relevance; and 3. experimental application of natural products, not yet tested in clinical trials.

Progress in active compounds effective on ulcerative colitis from Chinese medicines

Ulcerative colitis (UC), a chronic inflammatory disease affecting the colon, has a rising incidence worldwide. The known pathogenesis is multifactorial and involves genetic predisposition, epithelial barrier defects, dysregulated immune responses, and environmental factors. Nowadays, the drugs for UC include 5-aminosalicylic acid, steroids, and immunosuppressants. Long-term use of these drugs, however, may cause several side effects, such as hepatic and renal toxicity, drug resistance and allergic reactions. Moreover, the use of traditional Chinese medicine (TCM) in the treatment of UC shows significantly positive effects, low recurrence rate, few side effects and other obvious advantages. This paper summarizes several kinds of active compounds used in the experimental research of anti-UC effects extracted from TCM, mainly including flavonoids, acids, terpenoids, phenols, alkaloids, quinones, and bile acids from some animal medicines. It is found that the anti-UC activities are mainly focused on targeting inflammation or oxidative stress, which is associated with increasing the levels of anti-inflammatory cytokine (IL-4, IL-10, SOD), suppressing the levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8, IL-23, NF-κB, NO), reducing the activity of MPO, MDA, IFN-γ, and iNOS. This review may offer valuable reference for UC-related studies on the compounds from natural medicines.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Biopsy-derived Intestinal Epithelial Cell Cultures for Pathway-based Stratification of Patients With Inflammatory Bowel Disease

BACKGROUND

Endoplasmic reticulum [ER] stress was shown to be pivotal in the pathogenesis of inflammatory bowel disease. Despite progress in inflammatory bowel disease [IBD] drug development, not more than one-third of patients achieve steroid-free remission and mucosal healing with current therapies. Furthermore, patient stratification tools for therapy selection are lacking. We aimed to identify and quantify epithelial ER stress in a patient-specific manner in an attempt towards personalised therapy.

METHODS

A biopsy-derived intestinal epithelial cell culture system was developed and characterised. ER stress was induced by thapsigargin and quantified with a BiP enzyme-linked immunosorbent assay [ELISA] of cell lysates from 35 patients with known genotypes, who were grouped based on the number of IBD-associated ER stress and autophagy risk alleles.

RESULTS

The epithelial character of the cells was confirmed by E-cadherin, ZO-1, and MUC2 staining and CK-18, CK-20, and LGR5 gene expression. Patients with three risk alleles had higher median epithelial BiP-induction [vs untreated] levels compared with patients with one or two risk alleles [p = 0.026 and 0.043, respectively]. When autophagy risk alleles were included and patients were stratified in genetic risk quartiles, patients in Q2, Q3, and Q4 had significantly higher ER stress [BiP] when compared with Q1 [p = 0.034, 0.040, and 0.034, respectively].

CONCLUSIONS

We developed and validated an ex vivo intestinal epithelial cell culture system and showed that patients with more ER stress and autophagy risk alleles have augmented epithelial ER stress responses. We thus presented a personalised approach whereby patient-specific defects can be identified, which in turn could help in selecting tailored therapies.

CBLB502 administration protects gut mucosal tissue in ulcerative colitis by inhibiting inflammation

BACKGROUND

Ulcerative colitis (UC) is a nonspecific inflammatory disease for which medications and therapeutic strategies have only been moderately successful. CBLB502, a toll-like receptor 5 (TLR5) agonist derived from Salmonella flagellin, exhibits anticancer and radioprotective activities via modulation of TLRs and the nuclear factor kappa B (NF-κB) signaling pathway and can protect against acute renal ischemic failure. In this study, we intend to examine the effects of CBLB502 on both TLR responses and the interleukin (IL) and NF-κB signaling pathways in UC treatment.

METHODS

The UC mouse model was prepared in BALB/c mice by administering 2,4,6-trinitrobenzene sulfonic acid (TNBS). CBLB502 was used as the therapeutic drug. After CBLB502 therapy, the IL and tumor necrosis factor-α (TNF-α) levels were measured by ELISA. Total RNA and protein of colon samples was extracted.

RESULTS

We found that CBLB502 had a distinctive therapeutic effect in the UC model. In control group animals, IL-10 expression in serum was 91.48±24.38 ng/mL; this was higher than in the model group (59.36±14.46 ng/mL, P<0.05) or the treatment group (54.29±5.83 ng/mL, P<0.05). In model group animals, the concentration of TNF-α in serum was 140.11±12.70 ng/mL, which was lower than protein levels in the control group (173.86±29.26 ng/mL, P<0.05). The mRNA levels of TLR1, 2, 3, 4, 6, 7, 8, and 9 in the CBLB502 treatment group were significantly lower than in the model group (P<0.05). Western blot revealed that CBLB502 also reduced NF-κB expression in the mouse colon, but that NF-κB expression was not significantly lower than the model group.

CONCLUSIONS

CBLB502 can reduce mucosal damage induced by TNBS and inhibit inflammation and TLR expression. The inhibition of UC by CBLB502 is strictly TLR-IL-dependent and is dose-dependent within the efficacious dose range. Therefore, our results suggested that CBLB502 might be a candidate drug for the treatment of UC.