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Abstract Background The conversion of primary bile acids to secondary bile acids by the gut microbiota has been implicated in colonic inflammation. This study investigated the role of gut microbiota related bile acid metabolism in colonic inflammation in both patients with inflammatory bowel disease (IBD) and a murine model of dextran sulfate sodium (DSS)-induced colitis. Methods Bile acids in fecal samples from patients with IBD and DSS-induced colitis mice, with and without antibiotic treatment, were analyzed using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). The composition of the microbiota in fecal samples from IBD patients and DSS-colitis mice was characterized via Illumina MiSeq sequencing of the bacterial 16S rRNA gene V3-V4 region. Metagenomic profiling further identified metabolism-related gene signatures in stool samples from DSS-colitis mice. Histological analysis, quantitative PCR (qPCR) and Western Blotting were conducted on colonic samples from DSS-induced colitis mice to assess colonic inflammation, mucosal barrier integrity, and associated signaling pathways. The multivariate analysis of bile acids was conducted using Soft Independent Modelling of Class Analogy (SIMCA, Umetrics, Sweden). The relation between the relative abundance of specific phyla/genera and bile acid concentration was assess through Spearman's correlation analyses. Finally, lithocholic acid (LCA), the key bile acid, was administered via gavage to evaluate its effect on colonic inflammation and mucosal barrier integrity. Results In patients with IBD, the composition of colonic bile acids and gut microbiota was altered. Moreover, changes in the gut microbiota further modulate the composition of bile acids in the intestine. As the gut microbiota continues to shift, the bile acid profile undergoes additional alterations. The aforementioned alterations were also observed in mice with DSS-induced colitis. The study revealed a correlation between dysbiosis of the gut microbiota and modifications in the profile of colonic bile acids, notably LCA observed in both patients with IBD and mice with DSS-induced colitis. Through multivariate analysis, LCA was identified as the key bile acid that significantly affects colonic inflammation and the integrity of mucosal barrier. Subsequent experiments confirmed that LCA supplementation effectively mitigated the inhibitory effects of gut microbiota on colitis progression in mice, primarily through the activation of the sphingosine-1-phosphate receptor 2 (S1PR2)/NF-κB p65 signaling pathway. Analysis of the microbiome and metagenomic data revealed changes in the gut microbiota, notably an increased abundance of an unclassified genus within the family Prevotellaceae in DSS-induced colitis mice. Furthermore, a positive correlation was observed between the relative abundance of Prevotellaceae and bile acid biosynthesis pathways, as well as colonic LCA level. Conclusions These findings suggest that LCA and its positively correlated gut bacteria, Prevotellaceae, are closely associated with intestinal inflammation. Targeting colonic inflammation may involve inhibiting LCA and members of the Prevotellaceae family as potential therapeutic strategies.

Genetic defects in SLC26A3 (DRA), an intestinal Cl−/HCO3− exchanger, result in congenital chloride diarrhea (CLD), marked by lifelong acidic diarrhea and a high risk of inflammatory bowel disease. Slc26a3−/− mice serve as a model to understand the pathophysiology of CLD and search for treatment options. This study investigates the microbiota changes in slc26a3−/− colon, the genotype-related causes for the observed microbiota alterations, its inflammatory potential, as well as the corresponding host responses. The luminal and the mucosa-adherent cecal and colonic microbiota of cohoused slc26a3−/− and wt littermates were analyzed by 16S rRNA gene sequencing. Fecal microbiota transfer from cohoused slc26a3−/− and wt littermates to germ-free wt mice was performed to analyze the stability and the inflammatory potential of the communities.The cecal and colonic luminal and mucosa-adherent microbiota of slc26a3−/− mice was abnormal from an early age, with a loss of diversity, of short-chain fatty acid producers, and an increase of pathobionts. The transfer of slc26a3−/− microbiota did not result in intestinal inflammation and the microbial diversity in the recipient mice normalized over time. A strong increase in the expression of Il22, Reg3β/γ, Relmβ, and other proteins with antimicrobial functions was observed in slc26a3−/− colon from juvenile age, while the mucosal and systemic inflammatory signature was surprisingly mild. The dysbiotic microbiota, low mucosal pH, and mucus barrier defect in slc26a3−/− colon are accompanied by a stark upregulation of the expression of a panel of antimicrobial proteins. This may explain the low inflammatory burden in the gut of these mice.

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein in mammals. When released into the extracellular space, it acts as a damage-associated molecular pattern. This study investigates whether increased HMGB1 levels are found in the intestinal mucosa of ulcerative colitis (UC) patients, and whether an anti-HMGB1 neutralizing-antibody (HnAb) can inhibit the intestinal inflammation elicited by dextran sulfate sodium (DSS) in mice. Because toll-like receptor 4 (TLR4) is implicated in HMGB1-mediated immune cell activation, DSS colitis was also elicited in TLR4-deficient mice in the presence and absence of HnAb. The expression of HMGB1 in UC patients was examined. HnAb was administered via intraperitoneal injection to TLR4 deficient mice and their wild-type littermates, both being induced to colitis with DSS. Finally, the protective effect of HnAb and TLR4 deficiency were evaluated. In UC patients, HMGB1 was up-regulated in the inflamed colon. When administered during DSS application, HnAb alleviated the severity of colitis with a lower disease activity index, limited histological damages, and reduced production of proinflammatory cytokines. This antibody also limited colonic barrier loss, decreased colonic lamina propria macrophages and partially reversed the DSS treatment-associated dysbiosis. The protective effect of this antibody was enhanced in TLR4-deficient mice in some aspects, indicating that both additional HMGB1-mediated as well as TLR4-mediated inflammatory signaling pathways were involved in the induction of colitis by DSS. HnAb ameliorated colitis via macrophages inhibition and colonic barrier protection. It may therefore be a novel treatment option in colitis.

Background: Haploinsufficiency A20 (HA20) is a newly described monogenic disease characterized by a wide spectrum of manifestations and caused by heterozygous mutations in TNFAIP3 which encodes A20 protein. TNFAIP3 mutation leads to disruption of the A20 ovarian tumor (OTU) domain and/or the zinc finger (ZnF) domain. This study aims at exploring the association between the various manifestations of HA20 and different domains disruption of A20.Methods: We reviewed the HA20 cases in previous literature and summarized the clinical features, TNFAIP3 mutation loci and the disrupted domains caused by different sites and patterns of mutations. Patients were classified into three groups according to the A20 domains disruption.Results: A total of 89 patients from 39 families with a genetic diagnosis of HA20 were included. Overall, the age at onset of HA20 was early (median:5.92, IQR:1-10). Patients in the ZnF group showed the earliest onset (median:2.5, IQR:0.6-5), followed by patients in the OTU+ZnF group (median:6, IQR:1-10) and patients in the OTU group (median:10, IQR:8-14). The main manifestations of HA20 patients were recurrent oral ulcers (70%), recurrent fever (42%), gastrointestinal ulcers (40%), skin lesion (38%), genital ulcers (36%), and musculoskeletal disorders (34%). The percentage of patients with musculoskeletal disorders was significantly different among the three groups (p = 0.005). Patients in the OTU+ZnF group and ZnF group were more likely to develop musculoskeletal disorders than patients in the OTU group (p = 0.002 and p = 0.035, respectively). Besides, forty-three percent of HA20 patients were initially diagnosed as Behcet's disease (BD). Compared to the ZnF group, the OTU+ZnF group and OTU group had a higher percentage of patients initially diagnosed as BD (p = 0.006 and p < 0.001, respectively).Conclusion: HA20 is characterized by early-onset and the most common symptoms of HA20 are recurrent oral ulcers, fever and gastrointestinal ulcers. The onset of HA20 in patients with the ZnF domain disruption is earlier than patients with the OTU domain disruption. Compared to the OTU domain, the ZnF domain may be more closely related to musculoskeletal disorders.