Bacteroides thetaiotaomicron relieves colon inflammation by activating aryl hydrocarbon receptor and modulating CD4+T cell homeostasis

The multifaceted roles of common gut microbiota in immune checkpoint inhibitor-mediated colitis: From mechanism to clinical application

With the arrival of the era of tumor immunotherapy, Immune Checkpoint Inhibitors have benefited countless tumor patients. However, the emergence of Immune-Related Adverse Events, especially Immune Checkpoint Inhibitor-Mediated Colitis (IMC), has become an important obstacle to immunotherapy. Therefore, it is very important to clarify the mechanism and influencing factors of IMC. The effect of gut microbiota on IMC is gradually becoming a research hotspot. Gut microbiota from different phyla can affect IMC by regulating innate and acquired immunity of tumor patients in various ways. In this review, we make a systematic and comprehensive introduction of the effect of gut microbiota on IMC. Through understanding the specific effects of gut microbiota on IMC, and then exploring the possibility of reducing IMC by regulating gut microbiota.

Short- and Long-Term Effects of a Prebiotic Intervention with Polyphenols Extracted from European Black Elderberry—Sustained Expansion of Akkermansia spp

(1) Background: The intestinal microbiome has emerged as a central factor in human physiology and its alteration has been associated with disease. Therefore, great hopes are placed in microbiota-modulating strategies. Among various approaches, prebiotics, substrates with selective metabolization conferring a health benefit to the host, are promising candidates. Herein, we studied the prebiotic properties of a purified extract from European black elderberries, with a high and standardized content of polyphenols and anthocyanins. (2) Methods: The ELDERGUT trial represents a 9-week longitudinal intervention study divided into 3 distinct phases, namely a baseline, an intervention and a washout period, three weeks each. The intervention consisted of capsules containing 300 mg elderberry extract taken twice a day. Patient-reported outcomes and biosamples were collected weekly. Microbiome composition was assessed using 16S amplicon metagenomics. (3) Results: The supplementation was well tolerated. Microbiome trajectories were highly individualized with a profound shift in diversity indices immediately upon initiation and after termination of the compound. This was accompanied by corresponding changes in species abundance over time. Of particular interest, the relative abundance of Akkermansia spp. continued to increase in a subset of participants even beyond the supplementation period. Associations with participant metadata were detected.

Gut Microbiota Regulation of AHR Signaling in Liver Disease

Liver health plays a vital role in human health and disease. Emerging evidence has shown the importance of the aryl hydrocarbon receptor (AHR) in liver diseases such as alcoholic liver disease, fatty liver disease, and liver failure. As a ligand-activated transcription factor, AHR can be activated by endogenous ligands of microbial metabolites such as tryptophan (Trp), kynurenine (Kyn) or indole derivatives locally or distantly. However, the therapeutic effects of the gut microbiota-regulated AHR pathway remain to be clarified. In this review, we summarize recent progress and examine the role of AHR signaling as a target for gut microbiota intervention in liver diseases. The focus on AHR signaling will identify a promising target in the gut microbiota for better understanding and therapeutic opportunities in liver diseases.

Discovery of Novel Imidazo[4,5-c]quinoline Derivatives to Treat Inflammatory Bowel Disease (IBD) by Inhibiting Multiple Proinflammatory Signaling Pathways and Restoring Intestinal Homeostasis

As a complex pathogenesis driven by immune inflammatory factors and intestinal microbiota, the treatment of inflammatory bowel disease (IBD) may rely on the comprehensive regulation of these important pathogenic factors to reach a favorable therapeutic effect. In the current study, we discovered a series of imidazo[4,5-c]quinoline derivatives that potently and simultaneously inhibited two primary proinflammatory signaling pathways JAK/STAT and NF-κB. Especially, lead compound 8l showed potent inhibitory activities against interferon-stimulated genes (IC₅₀: 3.3 nM) and NF-κB pathways (IC₅₀: 150.7 nM) and decreased the release of various proinflammatory factors at the nanomolar level, including IL-6, IL-8, IL-1β, TNF-α, IL-12, and IFN-γ. In vivo, 8l produced a strong anti-inflammatory activity in both dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced acute enteritis models and restored the structural composition of gut microbiota. Collectively, this study provided valuable lead compounds for the treatment of IBD and revealed the great anti-inflammatory potential of the simultaneous suppression of JAK/STAT and NF-κB signals.

Immunomodulatory Mechanisms of Mesenchymal Stem Cells and Their Potential Clinical Applications

Mesenchymal stem cells (MSCs) are multipotent stem cells with the capacity of self-renewal, homing, and low immunogenicity. These distinct biological characteristics have already shown immense potential in regenerative medicine. MSCs also possess immunomodulatory properties that can maintain immune homeostasis when the immune response is over-activated or under-activated. The secretome of MSCs consists of cytokines, chemokines, signaling molecules, and growth factors, which effectively contribute to the regulation of immune and inflammatory responses. The immunomodulatory effects of MSCs can also be achieved through direct cell contact with microenvironmental factors and immune cells. Furthermore, preconditioned and engineered MSCs can specifically improve the immunomodulation effects in diverse clinical applications. These multifunctional properties of MSCs enable them to be used as a prospective therapeutic strategy to treat immune disorders, including autoimmune diseases and incurable inflammatory diseases. Here we review the recent exploration of immunomodulatory mechanisms of MSCs and briefly discuss the promotion of the genetically engineered MSCs. Additionally, we review the potential clinical applications of MSC-mediated immunomodulation in four types of immune diseases, including systemic lupus erythematosus, Crohn’s disease, graft-versus-host disease, and COVID-19.

Pharmacokinetic and gut microbiota analyses revealed the effect of Lactobacillus acidophilus on the metabolism of Olsalazine in ulcerative colitis rats

Olsalazine is a typical 5-aminosalicylic acid (5-ASA) drug that depends on gut microbiota to liberate its anti-inflammatory moiety 5-ASA in the treatment of ulcerative colitis (UC). In recent decades, 5-ASA drugs combined with probiotics have achieved a better effective treatment for UC. Mechanisms of combination therapy have been widely discussed from a pharmacodynamic perspective. However, it is still unclear whether the better therapeutic efficacy of combination therapy was made by changing the metabolism of 5-ASA drugs in the colon under the regulation of probiotics. In the present study, combined with pharmacokinetic and gut microbiota analyses, we systematically evaluated the potential effect of Lactobacillus acidophilus (L. acidophilus) on the metabolism of Olsalazine at three levels (pharmacokinetic characteristics, metabolic microbiota, and metabolic enzymes) to offer some insights into this issue. As pharmacokinetic results showed, L. acidophilus barely had an influence on the pharmacokinetic parameters of Olsalazine, 5-ASA, and N-Ac-5-ASA. Notably, the colonic exposure of 5-ASA was not affected by L. acidophilus. Gut microbiota results also illustrated that L. acidophilus did not change the total abundance of azoreductase (azoR) and N-acetyltransferase (NAT) associated gut microbiota and enzymes, which are involved in the metabolism of Olsalazine. Both pharmacokinetic and gut microbiota results revealed that L. acidophilus did not increase the colonic exposure of 5-ASA to improve the efficacy of combination therapy. L. acidophilus played its role in UC treatment by regulating gut microbiota composition and amino acid, phenolic acid, oligosaccharide, and peptidoglycan metabolic pathways. There was no potential medication risk of combination therapy of Olsalazine and L. acidophilus. In summary, this research provided strong evidence of medication safety and a comprehensive understanding of therapeutic advantages for combination therapy of probiotics and 5-ASA drugs from the pharmacokinetic and gut microbiota perspectives.

Probiotic strains alleviated OVA-induced food allergy in mice by regulating the gut microbiota and improving the level of indoleacrylic acid in fecal samples

Food allergy (FA) is a common immune disorder caused by food antigens. Probiotic strains showed alleviating effects on FA, such as the alleviation of FA pathological symptoms, serum OVA-sIgE levels, and the gut microbiota diversity and composition. The results showed that intragastric administration of Lactiplantibacillus plantarum CCFM1189, Limosilactobacillus reuteri CCFM1190, and Bifidobacterium longum CCFM1029 alleviated the weight loss and FA pathological symptoms of FA mice and decreased OVA-specific IgE and histamine (HIS) levels. CCFM1189 and CCFM1190 decreased IL-4, IL-5, and IL-13 levels, while CCFM1189 and CCFM 1029 decreased IL-17 levels. The gut microbiota analysis demonstrated that CCFM1189 increased the abundance of Akkermansia, while CCFM1190 improved immune regulation bacteria such as Faecalibaculum. CCFM1029 increased Bifidobacterium and the bacteria involved in short-chain fatty acid (SCFA) production, such as Dubosiella. L. plantarum CCFM1189 and L. reuteri CCFM1190 improved indoleacrylic acid levels in mouse fecal samples using untargeted metabolomics analysis. In conclusion, CCFM1189, CCFM1190, and CCFM1029 decreased Th2 immune responses and alleviated FA pathological symptoms by regulating the gut microbiota diversity and composition, and altering gut microbial metabolites, which could provide support in clinical tests and probiotic production in the future.

Untargeted Metabolomic Profiling Reveals Changes in Gut Microbiota and Mechanisms of Its Regulation of Allergy in OVA-Sensitive BALB/c Mice

Gut microbiota plays an important role in the regulation of food allergy. However, the interactions between the gut flora and immune system are not well studied. Here, we obtained ovalbumin (OVA)-sensitive BALB/c mice, combined with serum untargeted metabolomics to investigate the mechanisms of the interactions. The serum metabolomics results showed that 17 serum metabolites were downregulated, enriched in the aminoacyl-tRNA biosynthesis pathway, whereas indole-3-propionic acid (IPA) was increased. Six operational taxonomic units (OTUs) at the family level were altered and correlated with immune endpoints. Combined metabolomic and microbiomic analyses revealed that IPA levels were correlated with differential bacterial OTUs and a positive correlation with Treg in splenic lymphocytes. These results suggest that the regulatory effects of intestinal flora on allergic responses may be achieved by metabolizing tryptophan to produce indole derivatives and the aminoacyl-tRNA biosynthesis pathway. The formation of OVA tolerance in mice may be related to the enrichment of Peptostreptococcaceae, Ruminococcaceae, and Lactobacillaceae.

Acteoside, the Main Bioactive Compound in Osmanthus fragrans Flowers, Palliates Experimental Colitis in Mice by Regulating the Gut Microbiota

The present study investigated the effects of Osmanthus fragrans flowers and acteoside on murine colitis and the underlying mechanisms. The O. fragrans flower extract (OFE) and acteoside were administrated to chemically induced colitic mice. The results showed that OFE or acteoside ameliorates intestinal inflammation, oxidative stress, and activation of nuclear factor-κB (NF-κB) in colitic mice. The dysbiosis of the gut microbiome in colitic mice was also partly restored by OFE or acteoside, which was characterized by the alteration of the gut microbiome structure and the enrichment of beneficial bacteria (Akkermansia muciniphila and Bacteroides thetaiotaomicron). Dextran sulfate sodium (DSS)-induced gut metabolome dysfunctions (e.g., sphingosine metabolism and amino acids metabolism) in colitic mice were also partly restored by OFE and acteoside. A fecal microbiota (FM) transplantation study suggested that, compared with the FM from the normal diet-dosed donor mice, the FM from the OFE- or acteoside-dosed donor mice significantly suppressed colitic symptoms.

Extracellular vesicles produced by the human commensal gut bacterium Bacteroides thetaiotaomicron affect host immune pathways in a cell-type specific manner that are altered in inflammatory bowel disease

The gastrointestinal (GI) tract harbours a complex microbial community, which contributes to its homeostasis. A disrupted microbiome can cause GI-related diseases, including inflammatory bowel disease (IBD), therefore identifying host-microbe interactions is crucial for better understanding gut health. Bacterial extracellular vesicles (BEVs), released into the gut lumen, can cross the mucus layer and access underlying immune cells. To study BEV-host interactions, we examined the influence of BEVs generated by the gut commensal bacterium, Bacteroides thetaiotaomicron, on host immune cells. Single-cell RNA sequencing data and host-microbe protein-protein interaction networks were used to predict the effect of BEVs on dendritic cells, macrophages and monocytes focusing on the Toll-like receptor (TLR) pathway. We identified biological processes affected in each immune cell type and cell-type specific processes including myeloid cell differentiation. TLR pathway analysis highlighted that BEV targets differ among cells and between the same cells in healthy versus disease (ulcerative colitis) conditions. The in silico findings were validated in BEV-monocyte co-cultures demonstrating the requirement for TLR4 and Toll-interleukin-1 receptor domain-containing adaptor protein (TIRAP) in BEV-elicited NF-kB activation. This study demonstrates that both cell-type and health status influence BEV-host communication. The results and the pipeline could facilitate BEV-based therapies for the treatment of IBD.

Genetic and environmental factors shape the host response to Helicobacter hepaticus: insights into IBD pathogenesis

Pathobionts are members of the gut microbiota with the capacity to cause disease when there is malfunctioning intestinal homeostasis. These organisms are thought to be major contributors to the pathogenesis of inflammatory bowel disease (IBD), a group of chronic inflammatory disorders driven by dysregulated responses towards the microbiota. Over two decades have passed since the discovery of Helicobacter hepaticus, a mouse pathobiont which causes colitis in the context of immune deficiency. During this time, we have developed a detailed understanding of the cellular players and cytokine networks which drive H. hepaticus immunopathology. However, we are just beginning to understand the microbial factors that enable H. hepaticus to interact with the host and influence colonic health and disease. Here we review key H. hepaticus-host interactions, their relevance to other exemplar pathobionts and how when maladapted they drive colitis. Further understanding of these pathways may offer new therapeutic approaches for IBD.

Akkermansia muciniphila and its outer protein Amuc_1100 regulates tryptophan metabolism in colitis

Dietary interventions, including dietary ingredients, nutrients and probiotics, exert anti-inflammatory effects in ulcerative colitis (UC). Our previous study showed that Akkermansia muciniphila (Akk), a promising probiotic, could protect against colitis via the regulation of the immune response. However, whether it can restore aberrant tryptophan (Trp) metabolism during colitis remains unclear. In this study, untargeted serum metabolomics of patients with UC and colitis mice showed that Trp metabolism was activated, which was confirmed by quantification of Trp metabolites from a validation cohort and animal study. Integrative analysis of faecal metagenomes and serum metabolomes revealed significant associations between Akk and three Trp metabolites. Live Akk, pasteurised Akk and Amuc_1100 failed to restore the reduction in Trp metabolites involved in the serotonin pathway in colitis mice. However, live Akk, pasteurised Akk and Amuc_1100 increased kynurenine (Kyn) but decreased 2-picolinic acid (PIC) levels and the PIC/Kyn ratio without regulating any of the genes involved in Trp metabolism, suggesting that they could suppress the Kyn pathway (KP) independent of colon tissue. In addition, they could significantly restore the enrichment of Trp metabolism mediated by faecal microbiota. Specifically, live Akk, pasteurised Akk and Amuc_1100 could significantly offset the reduction in indoleacetic acid (IAA) levels. Pasteurised Akk significantly elevated the serum levels of indole acrylic acid (IA). In addition, live Akk, pasteurised Akk and Amuc_1100 could upregulate aryl hydrocarbon receptor (AhR) targeted genes, including CYP1A1, IL-10 and IL-22, suggesting that Akk could activate AhR signaling by regulating Trp metabolism, thereby attenuating colonic inflammation.

Herbal Medicine, Gut Microbiota, and COVID-19

Coronavirus Disease 19 (COVID-19) is a respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has grown to a worldwide pandemic with substantial mortality. The symptoms of COVID-19 range from mild flu-like symptoms, including cough and fever, to life threatening complications. There are still quite a number of patients with COVID-19 showed enteric symptoms including nausea, vomiting, and diarrhea. The gastrointestinal tract may be one of the target organs of SARS-CoV-2. Angiotensin converting enzyme 2 (ACE2) is the main receptor of SARS-CoV-2 virus, which is significantly expressed in intestinal cells. ACE2 links amino acid malnutrition to microbial ecology and intestinal inflammation. Intestinal flora imbalance and endotoxemia may accelerate the progression of COVID-19. Many herbs have demonstrated properties relevant to the treatment of COVID-19, by supporting organs and systems of the body affected by the virus. Herbs can restore the structure of the intestinal flora, which may further modulate the immune function after SARS-CoV-2 infection. Regulation of intestinal flora by herbal medicine may be helpful for the treatment and recovery of the disease. Understanding the role of herbs that regulate intestinal flora in fighting respiratory virus infections and maintaining intestinal flora balance can provide new ideas for preventing and treating COVID-19.

Gut Microbiota Dysbiosis Correlates with Abnormal Immune Response in Moderate COVID-19 Patients with Fever

Background

Most COVID-19 patients are moderate, and fever is the most common clinical manifestation and associated with poorer prognosis. Gut microbiota may also play important roles in COVID-19 pathogenesis. However, the association between gut microbiota and fever in individuals with moderate COVID-19 remains unclear.

Methods

We compared the clinical features and laboratory results of 187 moderate COVID-19 patients with fever and without fever and identified several inflammatory markers in patients with fever. Then, we performed gut metagenome-wide association study for 31 individuals to identify the microbes and their epitopes which have potential role in fever and hyperinflammation.

Results

Among 187 moderate COVID-19 patients, 127 (67.9%) patients presented with fever. Lymphocytes, CD3+ T cells, CD4+ T cells and the ratio of CD4+ T cells to CD8+ T cells were significantly reduced, while AST, LDH, CRP, IL-6 and IL-10 were significantly elevated in patients with fever. Gut microbiome composition was significantly altered in patients with fever compared with those with non-fever. Opportunistic pathogens such as Enterococcus faecalis and Saccharomyces cerevisiae were enriched in patients with fever. E. faecalis was positively correlated with LDH and D-dimer and negatively correlated with CD8+T cells and IL-4, while S. cerevisiae was positively correlated with diarrhea symptom. Furthermore, several species with anti-inflammatory and protective effects, such as Bacteroides fragilis and Eubacterium ramulus, were enriched in patients with non-fever. B. fragilis was positively correlated with lymphocytes, and E. ramulus was negatively correlated with LDH, AST and IL-6. Finally, we found that several bacterial epitopes of GroEL, a homolog of human HSP60, were enriched in patients with fever and positively correlated with IL-6, IL-10, WBC, neutrophils, D-dimer, LDH, CRP, and E. faecalis.

Conclusion

Gut microbiota dysbiosis correlates with abnormal immune response in moderate COVID-19 patients with fever.