Germ-free and Antibiotic-treated Mice are Highly Susceptible to Epithelial Injury in DSS Colitis

MicroRNA and Gut Microbiota: Tiny but Mighty-Novel Insights into Their Cross-talk in Inflammatory Bowel Disease Pathogenesis and Therapeutics

MicroRNAs [miRNAs], small non-coding RNAs, have recently been described as crucial contributors to intestinal homeostasis. They can interact with the gut microbiota in a reciprocal manner and deeply affect host health status, leading to several disorders when unbalanced. Inflammatory bowel disease [IBD] is a chronic inflammation of the gastrointestinal tract that co-occurs with alterations of the gut microbiota, and whose aetiology remains largely unclear. On one hand, host miRNA could be playing a relevant role in IBD pathophysiology by shaping the gut microbiota. The gut microbiome, on the other hand, may regulate the expression of host miRNAs, resulting in intestinal epithelial dysfunction, altered autophagy, and immune hyperactivation. Interestingly, it has been hypothesised that their reciprocal impact may be used for therapeutic goals. This review describes the latest research and suggests mechanisms through which miRNA and intestinal microbiota, as joint actors, may participate specifically in IBD pathophysiology. Furthermore, we discuss the diagnostic power and therapeutic potential resulting from their bidirectional communication after faecal transplantation, probiotics intake, or anti-miRNAs or miRNA mimics administration. The current literature is summarised in the present work in a comprehensive manner, hoping to provide a better understanding of the miRNA-microbiota cross-talk and to facilitate their application in IBD.

MUC2 and related bacterial factors: Therapeutic targets for ulcerative colitis

The mucin2 (MUC2) mucus barrier acts as the first barrier that prevents direct contact between intestinal bacteria and colonic epithelial cells. Bacterial factors related to the MUC2 mucus barrier play important roles in the response to changes in dietary patterns, MUC2 mucus barrier dysfunction, contact stimulation with colonic epithelial cells, and mucosal and submucosal inflammation during the occurrence and development of ulcerative colitis (UC). In this review, these underlying mechanisms are summarized and updated, and related interventions for treating UC, such as dietary adjustment, exogenous repair of the mucus barrier, microbiota transplantation and targeted elimination of pathogenic bacteria, are suggested. Such interventions are likely to induce and maintain a long and stable remission period and reduce or even avoid the recurrence of UC. A better mechanistic understanding of the MUC2 mucus barrier and its related bacterial factors may help researchers and clinicians to develop novel approaches for treating UC.

Oral-Gut-Brain Axis in Experimental Models of Periodontitis: Associating Gut Dysbiosis With Neurodegenerative Diseases

Periodontitis is considered a non-communicable chronic disease caused by a dysbiotic microbiota, which generates a low-grade systemic inflammation that chronically damages the organism. Several studies have associated periodontitis with other chronic non-communicable diseases, such as cardiovascular or neurodegenerative diseases. Besides, the oral bacteria considered a keystone pathogen, Porphyromonas gingivalis, has been detected in the hippocampus and brain cortex. Likewise, gut microbiota dysbiosis triggers a low-grade systemic inflammation, which also favors the risk for both cardiovascular and neurodegenerative diseases. Recently, the existence of an axis of Oral-Gut communication has been proposed, whose possible involvement in the development of neurodegenerative diseases has not been uncovered yet. The present review aims to compile evidence that the dysbiosis of the oral microbiota triggers changes in the gut microbiota, which creates a higher predisposition for the development of neuroinflammatory or neurodegenerative diseases.The Oral-Gut-Brain axis could be defined based on anatomical communications, where the mouth and the intestine are in constant communication. The oral-brain axis is mainly established from the trigeminal nerve and the gut-brain axis from the vagus nerve. The oral-gut communication is defined from an anatomical relation and the constant swallowing of oral bacteria. The gut-brain communication is more complex and due to bacteria-cells, immune and nervous system interactions. Thus, the gut-brain and oral-brain axis are in a bi-directional relationship. Through the qualitative analysis of the selected papers, we conclude that experimental periodontitis could produce both neurodegenerative pathologies and intestinal dysbiosis, and that periodontitis is likely to induce both conditions simultaneously. The severity of the neurodegenerative disease could depend, at least in part, on the effects of periodontitis in the gut microbiota, which could strengthen the immune response and create an injurious inflammatory and dysbiotic cycle. Thus, dementias would have their onset in dysbiotic phenomena that affect the oral cavity or the intestine. The selected studies allow us to speculate that oral-gut-brain communication exists, and bacteria probably get to the brain via trigeminal and vagus nerves.

Modified Gegen Qinlian Decoction Regulates Treg/Th17 Balance to Ameliorate DSS-Induced Acute Experimental Colitis in Mice by Altering the Gut Microbiota

Inflammatory bowel disease (IBD) is characterized by chronic pathology associated with extensive intestinal microbial dysregulation and intestinal inflammation. Thus, efforts are underway to manipulate the gut microbiome to improve inflammatory pathology. Gegen Qinlian decoction (GQD), a traditional Chinese medicine prescription, has been widely utilized for treating diarrhea and ulcerative colitis (UC) for thousands of years. However, the underlying mechanism of its efficacy and whether its protective effect against colitis is mediated by the gut microbiota are poorly understood. In the present study, our data demonstrated that modified GQD (MGQD) administration significantly improved the pathological phenotypes and colonic inflammation challenged by DSS in mice, which were specifically manifested as reduced loss of body weight, shortening of colon length, DAI score, histological score and suppressed inflammatory response. 16S rRNA sequencing and targeted metabonomics analysis showed that MQGD altered the diversity and community landscape of the intestinal microbiota and the metabolic profiles. In particular, MQGD significantly boosted the abundance of the intestinal microbiota producing short-chain fatty acids (SCFAs), which are causally associated with promoting the development of Treg cells and suppressing the differentiation of pro-inflammatory Th17 cells. More importantly, transferring fecal microbiota from MGQD-treated or healthy controls exhibited equivalent alleviative effects on colitis mice. However, this protective effect could not be replicated in experiments of mice with depleted intestinal microbes through broad-spectrum antibiotic cocktails (ABX), further supporting the importance of SCFA-producing gut microbiota in the beneficial role of MGQD. In general, MGQD therapy has the potential to remodel the intestinal microbiome and reestablish immune homeostasis to ameliorate DSS-induced colitis.

Heat-Killed Lactobacilli Preparations Promote Healing in the Experimental Cutaneous Wounds

Probiotics are defined as microorganisms with beneficial health effects when consumed by humans, being applied mainly to improve allergic or intestinal diseases. Due to the increasing resistance of pathogens to antibiotics, the abuse of antibiotics becomes inefficient in the skin and in systemic infections, and probiotics may also provide the protective effect for repairing the healing of infected cutaneous wounds. Here we selected two Lactobacillus strains, L. plantarum GMNL-6 and L. paracasei GMNL-653, in heat-killed format to examine the beneficial effect in skin wound repair through the selection by promoting collagen synthesis in Hs68 fibroblast cells. The coverage of gels containing heat-killed GMNL-6 or GMNL-653 on the mouse tail with experimental wounds displayed healing promoting effects with promoting of metalloproteinase-1 expression at the early phase and reduced excessive fibrosis accumulation and deposition in the later tail-skin recovery stage. More importantly, lipoteichoic acid, the major component of Lactobacillus cell wall, from GMNL-6/GMNL-653 could achieve the anti-fibrogenic benefit similar to the heat-killed bacteria cells in the TGF-β stimulated Hs68 fibroblast cell model. Our study offers a new therapeutic potential of the heat-killed format of Lactobacillus as an alternative approach to treating skin healing disorders.

Gut microbiota modulates the inflammatory response and cognitive impairment induced by sleep deprivation

Sleep deprivation (SD) is increasingly common in modern society, which can lead to the dysregulation of inflammatory responses and cognitive impairment, but the mechanisms remain unclear. Emerging evidence suggests that gut microbiota plays a critical role in the pathogenesis and development of inflammatory and psychiatric diseases, possibly via gut microbiota-brain interactions and neuroinflammation. The present study investigated the impact of SD on gut microbiota composition and explored whether alterations of the gut microbiota play a causal role in chronic inflammatory states and cognitive impairment that are induced by SD. We found that SD-induced gut dysbiosis, inflammatory responses, and cognitive impairment in humans. Moreover, the absence of the gut microbiota suppressed inflammatory response and cognitive impairment induced by SD in germ-free (GF) mice. Transplantation of the "SD microbiota" into GF mice activated the Toll-like receptor 4/nuclear factor-κB signaling pathway and impaired cognitive function in the recipient mice. Mice that harbored "SD microbiota" also exhibited increases in neuroinflammation and microglial activity in the hippocampus and medial prefrontal cortex. These findings indicate that gut dysbiosis contributes to both peripheral and central inflammatory processes and cognitive deficits that are induced by SD, which may open avenues for potential interventions that can relieve the detrimental consequences of sleep loss.

Lactobacillus paracasei L9 improves colitis by expanding butyrate-producing bacteria that inhibit the IL-6/STAT3 signaling pathway

Inflammatory bowel disease (IBD) is a chronic intestinal inflammation that is currently incurable. Increasing evidence indicates that supplementation with probiotics could improve the symptoms of IBD. It is scientifically significant to identify novel and valid strains for treating IBD. It has been reported that the probiotic Lactobacillus paracasei L9 (L9), which is identified from the gut of healthy centenarians, can modulate host immunity and plays an anti-allergic role. Here, we demonstrated that L9 alleviates the pathological phenotypes of experimental colitis by expanding the abundance of butyrate-producing bacteria. Oral administration of sodium butyrate in experimental colitis recapitulates the L9 anti-inflammatory phenotypes. Mechanistically, sodium butyrate ameliorated the inflammatory responses by inhibiting the IL-6/STAT3 signaling pathway in colitis. Overall, these findings demonstrated that L9 alleviates the DSS-induced colitis development by enhancing the abundance of butyrate-producing bacterial strains that produce butyrate to suppress the IL-6/STAT3 signaling pathway, providing new insight into a promising therapeutic target for the remission of IBD.

Metformin Exerts Anti-inflammatory and Mucus Barrier Protective Effects by Enriching Akkermansia muciniphila in Mice With Ulcerative Colitis

The present study aimed to determine if metformin exerts anti-inflammatory and mucus-protective effects via the gut microbiota. Metformin has extensive benefits including anti-inflammatory effects. Previous studies showed that metformin changed the gut microbiota composition and increases the number of goblet cells. Intestinal dysbiosis and goblet cell depletion are important features of ulcerative colitis (UC). The underlying mechanism and whether metformin can improve the mucus barrier in UC remain unclear. Metformin (400 mg/kg/day) was administered to mice with dextran sulfate sodium (DSS)-induced UC for 2 wk to investigate the effects of metformin on the intestinal mucus barrier. The gut microbiota was depleted, using antibiotics, to explore its role in the mucus-protecting effects of metformin. Akkermansia muciniphila (A. muciniphila), which was enriched in metformin-treated mice, was administered to mice to investigate the effects of the bacteria on UC and the mucus barrier. Metformin attenuated DSS-induced UC in mice, as evidenced by the alleviation of diarrhea, hematochezia, and the decrease in body weight. The expression of mucin2, a prominent mucus barrier protein, was increased in the metformin-treated group compared to the DSS-treated group. Furthermore, fecal 16S rRNA analysis showed that metformin treatment changed the gut microbiota composition by increasing the relative abundance of Lactobacillus and Akkermansia species while decreasing Erysipelatoclostridium at the genus level. Antibiotic treatment partly abolished the anti-inflammatory and mucus-protecting effects of metformin. Administration of A. muciniphila alleviated the colonic inflammation and mucus barrier disruption. Metformin alleviated DSS-induced UC in mice and protected against cell damage via affecting the gut microbiota, thereby providing a new mechanism for the therapeutic effect of metformin in patients with UC. This study also provides evidence that A. muciniphila as a probiotic has potential benefits for UC.

Selection strategy of dextran sulfate sodium-induced acute or chronic colitis mouse models based on gut microbial profile

BACKGROUND

Dextran sulfate sodium (DSS) replicates ulcerative colitis (UC)-like colitis in murine models. However, the microbial characteristics of DSS-triggered colitis require further clarification. To analyze the changes in gut microbiota associated with DSS-induced acute and chronic colitis.

METHODS

Acute colitis was induced in mice by administering 3% DSS for 1 week in the drinking water, and chronic colitis was induced by supplementing drinking water with 2.5% DSS every other week for 5 weeks. Control groups received the same drinking water without DSS supplementation. The histopathological score and length of the colons, and disease activity index (DAI) were evaluated to confirm the presence of experimental colitis. Intestinal microbiota was profiled by 16S rDNA sequencing of cecal content.

RESULTS

Mice with both acute and chronic DSS-triggered colitis had significantly higher DAI and colon histopathological scores in contrast to the control groups (P < 0.0001, P < 0.0001), and the colon was remarkably shortened (P < 0.0001, P < 0.0001). The gut microbiota α-diversity was partly downregulated in both acute and chronic colitis groups in contrast to their respective control groups (Pielou index P = 0.0022, P = 0.0649; Shannon index P = 0.0022, P = 0.0931). The reduction in the Pielou and Shannon indices were more obvious in mice with acute colitis (P = 0.0022, P = 0.0043). The relative abundance of Bacteroides and Turicibacter was increased (all P < 0.05), while that of Lachnospiraceae, Ruminococcaceae, Ruminiclostridium, Rikenella, Alistipes, Alloprevotella, and Butyricicoccus was significantly decreased after acute DSS induction (all P < 0.05). The relative abundance of Bacteroides, Akkermansia, Helicobacter, Parabacteroides, Erysipelatoclostridium, Turicibacter and Romboutsia was also markedly increased (all P < 0.05), and that of Lachnospiraceae_NK4A136_group, Alistipes, Enterorhabdus, Prevotellaceae_UCG-001, Butyricicoccus, Ruminiclostridium_6, Muribaculum, Ruminococcaceae_NK4A214_group, Family_XIII_UCG-001 and Flavonifractor was significantly decreased after chronic DSS induction (all P < 0.05).

CONCLUSION

DSS-induced acute and chronic colitis demonstrated similar symptoms and histopathological changes. The changes in the gut microbiota of the acute colitis model were closer to that observed in UC. The acute colitis model had greater abundance of SCFAs-producing bacteria and lower α-diversity compared to the chronic colitis model.

Role of Gut Microbiota in the Anti-Colitic Effects of Anthocyanin-Containing Potatoes

SCOPE

Anthocyanin-containing potatoes exert anti-inflammatory activity in colitic mice. Gut bacterial dysbiosis plays a critical role in ulcerative colitis. This study examined the extent to which the anti-colitic activity of anthocyanin-containing red/purple-fleshed potatoes depends on the gut bacteria using a chemically-induced rodent model of colitis with the intact and antibiotic-ablated microbiome.

METHODS AND RESULTS

Four-week-old male mice (C57BL6) are randomly assigned to the control diet or 20% purple-/red-fleshed potatoes supplemented diet group. The microbiota-ablated group received an antibiotic cocktail in drinking water. At week nine, colitis is induced by 2% dextran sulfate sodium (DSS) in drinking water for five days. Administration of antibiotics resulted in a 95% reduction in gut bacterial load and fecal SCFAs. DSS-induced elevated gut permeability and body weight loss are more pronounced in antibiotic mice compared to non-antibiotic mice. Purple- or red-fleshed potato supplementation (20% w/w) ameliorated DSS-induced reduction in colon length and mucin 2 expression levels, and increase in permeability, spleen weight, myeloperoxidase (MPO) activity, and inflammatory cytokines (IL-6, IL-17, and IL1-β) expression levels in non-antibiotic mice, but not in gut microbiota ablated mice.

CONCLUSIONS

Anthocyanin-containing potatoes are potent in alleviating colitis, and the gut microbiome is critical for the anti-colitic activity of anthocyanin-containing potatoes.

Immunoglobulin A, an Active Liaison for Host-Microbiota Homeostasis

Mucosal surfaces in the gastrointestinal tract are continually exposed to native, commensal antigens and susceptible to foreign, infectious antigens. Immunoglobulin A (IgA) provides dual humoral responses that create a symbiotic environment for the resident gut microbiota and prevent the invasion of enteric pathogens. This review features recent immunological and microbial studies that elucidate the underlying IgA and microbiota-dependent mechanisms for mutualism at physiological conditions. IgA derailment and concurrent microbiota instability in pathological diseases are also discussed in detail. Highlights of this review underscore that the source of IgA and its structural form can dictate microbiota reactivity to sustain a diverse niche where both host and bacteria benefit. Other important studies emphasize IgA insufficiency can result in the bloom of opportunistic pathogens that encroach the intestinal epithelia and disseminate into circulation. The continual growth of knowledge in these subjects can lead to the development of therapeutics targeting IgA and/or the microbiota to treat life threatening diseases.

Synergistic Protective Effect of Konjac Mannan Oligosaccharides and Bacillus subtilis on Intestinal Epithelial Barrier Dysfunction in Caco-2 Cell Model and Mice Model of Lipopolysaccharide Stimulation

As the first line of defense against intestinal bacteria and toxins, intestinal epithelial cells are always exposed to bacteria or lipopolysaccharide (LPS), whereas pathogenic bacteria or LPS can cause intestinal epithelial cell damage. Previous studies have shown that konjac mannan oligosaccharides (KMOS) have a positive effect on maintaining intestinal integrity, and Bacillus subtilis (BS) can promote the barrier effect of the intestine. However, it is still unknown whether KMOS and BS have a synergistic protective effect on the intestines. In this study, we used the LPS-induced Caco-2 cell injury model and mouse intestinal injury model to study the synergistic effects of KMOS and BS. Compared with KMOS or BS alone, co-treatment with KMOS and BS significantly enhanced the activity and antioxidant capacity of Caco-2 cell, protected mouse liver and ileum from LPS-induced oxidative damage, and repaired tight junction and mucus barrier damage by up-regulating the expression of Claudin-1, ZO-1 and MUC-2. Our results demonstrate that the combination of KMOS and BS has a synergistic repair effect on inflammatory and oxidative damage of Caco-2 cells and aIIeviates LPS-induced acute intestinal injury in mice.

Epithelial wound healing in inflammatory bowel diseases: the next therapeutic frontier

Patients with one of the many chronic inflammatory disorders broadly classified as inflammatory bowel disease (IBD) now have a diverse set of immunomodulatory therapies at their disposal. Despite these recent medical advances, complete sustained remission of disease remains elusive for most patients. The full healing of the damaged intestinal mucosa is the primary goal of all therapies. Achieving this requires not just a reduction of the aberrant immunological response, but also wound healing of the epithelium. No currently approved therapy directly targets the epithelium. Epithelial repair is compromised in IBD and normally facilitates re-establishment of the homeostatic barrier between the host and the microbiome. In this review, we summarize the evidence that epithelial wound healing represents an important yet underdeveloped therapeutic modality for IBD. We highlight 3 general approaches that are promising for developing a new class of epithelium-targeted therapies: epithelial stem cells, cytokines, and microbiome engineering. We also provide a frank discussion of some of the challenges that must be overcome for epithelial repair to be therapeutically leveraged. A concerted approach by the field to develop new therapies targeting epithelial wound healing will offer patients a game-changing, complementary class of medications and could dramatically improve outcomes.

Leptin-resistant Zucker rats with trinitrobenzene sulfonic acid colitis present a reduced inflammatory response but enhanced epithelial damage

The role of leptin in the development of intestinal inflammation remains controversial, since proinflammatory and anti-inflammatory effects have been described. This study describes the effect of the absence of leptin signaling in intestinal inflammation. Experimental colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS) to lean and obese Zucker rats (n = 10). Effects on inflammation and mucosal barrier were studied. Bacterial translocation and LPS concentration were evaluated together with colonic permeability to 4-kDa FITC-dextran. Obese Zucker rats showed a lower intestinal myeloperoxidase and alkaline phosphatase activity, reduced alkaline phosphatase sensitivity to levamisole, and diminished colonic expression of Nos2, Tnf, and Il6, indicating attenuated intestinal inflammation, associated with attenuated STAT3, AKT, and ERK signaling in the colonic tissue. S100a8 and Cxcl1 mRNA levels were maintained, suggesting that in the absence of leptin signaling neutrophil activation rather than infiltration is hampered. Despite the lower inflammatory response, leptin resistance enhanced intestinal permeability, reflecting an increased epithelial damage. This was shown by augmented LPS presence in the portal vein of colitic obese Zucker rats, associated with induction of tissue nonspecific alkaline phosphatase, LPS-binding protein, and CD14 hepatic expression (involved in LPS handling). This was linked to decreased ZO-1 immunoreactivity in tight junctions and lower occludin expression. Our results indicate that obese Zucker rats present an attenuated inflammatory response to TNBS, but increased intestinal epithelial damage allowing the passage of bacterial antigens.NEW & NOTEWORTHY Obese Zucker rats, which are resistant to leptin, exhibit a diminished inflammatory response in the trinitrobenzenesulfonic acid (TNBS) model of colitis, suggesting leptin role is proinflammatory. At the same time, obese Zucker rats present a debilitated intestinal barrier function, with increased translocation of LPS. Zucker rats present a dual response in the TNBS model of rat colitis.

Translating Treg Therapy for Inflammatory Bowel Disease in Humanized Mice

Crohn's disease and ulcerative colitis, two major forms of inflammatory bowel disease (IBD) in humans, afflicted in genetically predisposed individuals due to dysregulated immune response directed against constituents of gut flora. The defective immune responses mounted against the regulatory mechanisms amplify and maintain the IBD-induced mucosal inflammation. Therefore, restoring the balance between inflammatory and anti-inflammatory immunepathways in the gut may contribute to halting the IBD-associated tissue-damaging immune response. Phenotypic and functional characterization of various immune-suppressive T cells (regulatory T cells; Tregs) over the last decade has been used to optimize the procedures for in vitro expansion of these cells for developing therapeutic interventional strategies. In this paper, we review the mechanisms of action and functional importance of Tregs during the pathogenesis of IBD and modulating the disease induced inflammation as well as role of mouse models including humanized mice repopulated with the human immune system (HIS) to study the IBD. "Humanized" mouse models provide new tools to analyze human Treg ontogeny, immunobiology, and therapy and the role of Tregs in developing interventional strategies against IBD. Overall, humanized mouse models replicate the human conditions and prove a viable tool to study molecular functions of human Tregs to harness their therapeutic potential.

Ramulus mori polysaccharide-loaded PLGA nanoparticles and their anti-inflammatory effects in vivo

In this study, ramulus mori polysaccharide (RMP) was encapsulated into Poly (lactic-co-glycolicacid) (PLGA) to form PLGA-RMP (PR). The aim of study is to investigate anti-inflammatory effects of PR. The particle size of PR nanoparticles was approximately 205.6 ± 1.86 nm. PR nanoparticles showed significant therapeutic effects on colitis mice model, evidenced by attenuation of the loss of body weight, reduction of the DAI score, and restoration of the colon length. From the histopathological analysis, alleviation of the histopathological damage, less production of IFN-γ and IL-6, and improvement of IL-10 were observed with the treatment of PR. Meanwhile, the treatment of PR not only promoted the expression of ZO-1 and occludin, but also improved the contents of acetate, propionate, and butyrate in the colitis colon. Furthermore, PR extenuated the reduction of the diversity and richness of gut microbiota induced by DSS, and decreased the ratio of Firmicutes to Bacteroidetes while increasing the proportion of Clostridium XIVa, Mucispirillum, and Paraprevotella in the gut microbiota. What's more, PR nanoparticles attenuated the metabolic disorders in the colitis colon induced by DSS. These results indicated that PR nanoparticles could serve as a potent nanomedicine to treat IBD and be used as potential prebiotics.

Gut microbiota mediates cognitive impairment in young mice after multiple neonatal exposures to sevoflurane

Multiple exposures to anesthesia may increase the risk of cognitive impairment in young children. However, the mechanisms underlying this neurodevelopmental disorder remain elusive. In this study, we investigated alteration of the gut microbiota after multiple neonatal exposures to the anesthetic sevoflurane and the potential role of microbiota alteration on cognitive impairment using a young mice model. Multiple neonatal sevoflurane exposures resulted in obvious cognitive impairment symptoms and altered gut microbiota composition. Fecal transplantation experiments confirmed that alteration of the microbiota was responsible for the cognitive disorders in young mice. Microbiota profiling analysis identified microbial taxa that showed consistent differential abundance before and after fecal microbiota transplantation. Several of the differentially abundant taxa are associated with memory and/or health of the host, such as species of Streptococcus, Lachnospiraceae, and Pseudoflavonifractor. The results reveal that abnormal composition of the gut microbiota is a risk factor for cognitive impairment in young mice after multiple neonatal exposures to sevoflurane and provide insight into a potential therapeutic strategy for sevoflurane-related neurotoxicity.

Murine models for studying immunopathogenesis in gastrointestinal lesions: How to go about it

Gastro-intestinal (GI) lesions are common outcome to diverse etiological agents affecting the GI tract. It requires significant expertise to accurately diagnose the fundamental cause and treat accordingly. A better understanding of the immunological underpinning of these lesions is of great importance to ensure their successful management. Availability of specific animal models allows us to understand the subtle differences among diverse disease conditions and help decide upon the treatment trajectories. Since murine models are best suited for studying the immunopathogenesis of any disease, we will restrict our discussions here to the available murine models and their applications to study gastrointestinal lesions. In this review, we have systematically examined and compared the variety of mice models that are routinely used to study Inflammatory Bowel disease (IBD) and also how they can be leveraged to address specific questions relating to IBD.

Microbial and genetic-based framework identifies drug targets in inflammatory bowel disease

Rationale: With increasing incidence and prevalence of inflammatory bowel disease (IBD), it has become one of the major public health threats, and there is an urgent need to develop new therapeutic agents. Although the pathogenesis of IBD is still unclear, previous research has provided evidence for complex interplays between genetic, immune, microbial, and environmental factors. Here, we constructed a gene-microbiota interaction-based framework to discover IBD biomarkers and therapeutics. Methods: We identified candidate biomarkers for IBD by analyzing the publicly available transcriptomic and microbiome data from IBD cohorts. Animal models of IBD and diarrhea were established. The inflammation-correlated microbial and genetic variants in gene knockout mice were identified by 16S rRNA sequences and PCR array. We performed bioinformatic analysis of microbiome functional prediction and drug repurposing. Our validation experiments with cells and animals confirmed anti-inflammatory properties of a drug candidate. Results: We identified the DNA-sensing enzyme cyclic GMP-AMP synthase (cGAS) as a potential biomarker for IBD in both patients and murine models. cGAS knockout mice were less susceptible to DSS-induced colitis. cGAS-associated gut microbiota and host genetic factors relating to IBD pathogenesis were also identified. Using a computational drug repurposing approach, we predicted 43 candidate drugs with high potency to reverse colitis-associated gene expression and validated that brefeldin-a mitigates inflammatory response in colitis mouse model and colon cancer cell lines. Conclusions: By integrating computational screening, microbiota interference, gene knockout techniques, and in vitro and in vivo validation, we built a framework for predicting biomarkers and host-microbe interaction targets and identifying repurposing drugs for IBD, which may be tested further for clinical application. This approach may also be a tool for repurposing drugs for treating other diseases.

Egg white peptides ameliorate dextran sulfate sodium-induced acute colitis symptoms by inhibiting the production of pro-inflammatory cytokines and modulation of gut microbiota composition

Egg white peptides (EWPs) can be effectively used to alleviate and treat inflammatory diseases due to their anti-oxidation, anti-inflammation, and microbiota regulation capabilities. A dextran sodium sulfate (DSS)-induced colitis model was used to clarify the regulatory effects of EWPs on colitis. Forty-three peptide sequences were identified from EWPs using LC-MS/MS. The results demonstrated that EWPs decreased the levels of pro-inflammatory cytokines and the extent of crypt damage in a dose-dependent manner. 16S rRNA gene sequencing results indicated that 200 mg/kg EWPs significantly increased the relative abundance of beneficial bacteria Lactobacillus and Candidatus_Saccharimonas, and reduced the relative abundance of pathogenic bacteria Ruminiclostridium and Akkermansia. In addition, the degree of correlation between pro-inflammatory cytokines and microbiota was as follows: interleukin (IL)-1β > IL-8 > IL-6 > tumor necrosis factor-α To summarize, EWPs contributed to the alleviation of colitis symptoms and the intestinal injury through anti-inflammatory effects, repair of intestinal mucosa, and modulation of gut microbiota.

Microbial recognition regulates intestinal epithelial growth in homeostasis and disease

The intestine is constantly exposed to a dynamic community of microbes. Intestinal epithelial cells respond to microbes through evolutionarily conserved recognition pathways, such as the immune deficiency (IMD) pathway of Drosophila, the Toll-like receptor (TLR) response of flies and vertebrates, and the vertebrate nucleotide-binding oligomerization domain (NOD) pathway. Microbial recognition pathways are tightly controlled to respond effectively to pathogens, tolerate the microbiome, and limit intestinal disease. In this review, we focus on contributions of different model organisms to our understanding of how epithelial microbe recognition impacts intestinal proliferation and differentiation in homeostasis and disease. In particular, we compare how microbes and subsequent recognition by the intestine influences barrier integrity, intestinal repair and tumorigenesis in Drosophila, zebrafish, mice, and organoids. In addition, we discuss the importance of microbial recognition in homeostatic intestinal growth and discuss how immune pathways directly impact stem cell and crypt dynamics.

Human Gut Microbiome and Liver Diseases: From Correlation to Causation

The important role of human gut microbiota in liver diseases has long been recognized as dysbiosis and the translocation of certain microbes from the gut to liver. With the development of high-throughput DNA sequencing, the complexity and integrity of the gut microbiome in the whole spectrum of liver diseases is emerging. Specific patterns of gut microbiota have been identified in liver diseases with different causes, including alcoholic, non-alcoholic, and virus induced liver diseases, or even at different stages, ranging from steatohepatitis, fibrosis, cirrhosis, to hepatocellular carcinoma. At the same time, the mechanism of how microbiota contributes to liver diseases goes beyond the traditional function of the gut-liver axis which could lead to liver injury and inflammation. With the application of proteomics, metabolomics, and modern molecular technologies, more microbial metabolites and the complicated interaction of microbiota with host immunity come into our understanding in the liver pathogenesis. Germ-free animal models serve as a workhorse to test the function of microbiota and their derivatives in liver disease models. Here, we review the current evidence on the relationship between gut microbiota and liver diseases, and the mechanisms underlying this phenotype. In addition to original liver diseases, gut microbiota might also affect liver injury in systemic disorders involving multiple organs, as in the case of COVID-19 at a severe state. A better understanding of the gut microbial contribution to liver diseases might help us better benefit from this guest-host relationship and pave the way for novel therapies.

A role of the subdiaphragmatic vagus nerve in depression-like phenotypes in mice after fecal microbiota transplantation from Chrna7 knock-out mice with depression-like phenotypes

The α7 subtype of the nicotinic acetylcholine receptor (α7 nAChR: coded by Chrna7) regulates the cholinergic ascending anti-inflammatory pathway involved in depression. We previously reported that Chrna7 knock-out (KO) mice show depression-like phenotypes through systemic inflammation. In this study, we investigated whether fecal microbiota transplantation (FMT) from Chrna7 KO mice causes depression-like phenotypes in mice treated with an antibiotic cocktail (ABX). Chrna7 KO mice with depression-like phenotypes show an abnormal gut microbiota composition, although the alpha diversity and beta diversity were not altered. FMT from Chrna7 KO mice caused depression-like phenotypes, systemic inflammation, and downregulation of synaptic proteins in the prefrontal cortex (PFC) in the ABX-treated mice compared to FMT from the control mice. The Principal component analysis based on the OTU level showed that the FMT group from the KO mice were different from the FMT group from the control mice. We found differences in abundance for several bacteria in the FMT group from the KO mice at the taxonomic level when compared with the other group. Interestingly, subdiaphragmatic vagotomy significantly blocked the development of depression-like phenotypes in the ABX-treated mice after FMT from Chrna7 KO mice. These data suggest that FMT from Chrna7 KO mice produce depression-like phenotypes in ABX-treated mice via the subdiaphragmatic vagus nerve. The brain-gut-microbiota axis association with the subdiaphragmatic vagus nerve plays an important role in the development of depression.

Gut microbiota mediates the absorption of FLZ, a new drug for Parkinson's disease treatment

The gut microbiota plays an important role in regulating the pharmacokinetics and pharmacodynamics of many drugs. FLZ, a novel squamosamide derivative, has been shown to have neuroprotective effects on experimental Parkinson's disease (PD) models. FLZ is under phase Ⅰ clinical trial now, while the underlying mechanisms contributing to the absorption of FLZ are still not fully elucidated. Due to the main metabolite of FLZ was abundant in feces but rare in urine and bile of mice, we focused on the gut microbiota to address how FLZ was metabolized and absorbed. In vitro studies revealed that FLZ could be exclusively metabolized to its major metabolite M1 by the lanosterol 14 alpha-demethylase (CYP51) in the gut microbiota, but was almost not metabolized by any other metabolism-related organs, such as liver, kidney, and small intestine. M1 was quickly absorbed into the blood and then remethylated to FLZ by catechol O-methyltransferase (COMT). Notably, dysbacteriosis reduced the therapeutic efficacy of FLZ on the PD mouse model by inhibiting its absorption. The results show that the gut microbiota mediate the absorption of FLZ through a FLZ-M1-FLZ circulation. Our research elucidates the vital role of the gut microbiota in the absorption of FLZ and provides a theoretical basis for clinical pharmacokinetic studies and clinical application of FLZ in the treatment of PD.

Gut Microbiota May Mediate the Influence of Periodontitis on Prediabetes

Mounting evidence has shown that periodontitis is associated with diabetes. However, a causal relationship remains to be determined. Recent studies reported that periodontitis may be associated with gut microbiota, which plays an important role in the development of diabetes. Therefore, we hypothesized that gut microbiota might mediate the link between periodontitis and diabetes. Periodontitis was induced by ligatures. Glycemic homeostasis was evaluated through fasting blood glucose (FBG), serum glycosylated hemoglobin (HbA1c), and intraperitoneal glucose tolerance test. Micro-computed tomography and hematoxylin and eosin staining were used to evaluate periodontal destruction. The gut microbiota was analyzed using 16S ribosomal RNA gene sequencing and bioinformatics. Serum endotoxin, interleukin (IL) 6, tumor necrosis factor α (TNF-α), and IL-1β were measured to evaluate the systemic inflammation burden. We found that the levels of FBG, HbA1c, and glucose intolerance were higher in the periodontitis (PD) group than in the control (Con) group (P < 0.05). When periodontitis was eliminated, the FBG significantly decreased (P < 0.05). Several butyrate-producing bacteria were decreased in the gut microbiota of the PD group, including Lachnospiraceae_NK4A136_group, Eubacterium_fissicatena_group, Eubacterium_coprostanoligenes_group, and Ruminococcaceae_UCG-014 (P < 0.05), which were negatively correlated with serum HbA1c (P < 0.05). Subsequently, the gut microbiota was depleted using antibiotics or transplanted through cohousing. Compared with the PD group, the levels of HbA1c and glucose intolerance were decreased in the gut microbiota-depleted mice with periodontitis (PD + Abx) (P < 0.05), as well as the serum levels of endotoxin and IL-6 (P < 0.05). The serum levels of IL-6, TNF-α, and IL-1β in the PD + Abx group were higher than those of the Con group (P < 0.05). Antibiotics exerted a limited impact on the periodontal microbiota. When the PD mice were cohoused with healthy ones, the elevated FBG and HbA1c significantly recovered (P < 0.05), as well as the aforementioned butyrate producers (P < 0.05). Thus, within the limitations of this study, our data indicated that the gut microbiota may mediate the influence of periodontitis on prediabetes.

The role of gut dysbiosis in Parkinson's disease: mechanistic insights andtherapeutic options

Parkinson's disease is a common neurodegenerative disease in which gastrointestinal symptoms may appear prior to motor symptoms. The gut microbiota of patients with Parkinson's disease shows unique changes, which may be used as early biomarkers of disease. Alteration in gut microbiota composition may be related to the cause or effect of motor or non-motor symptoms, but the specific pathogenic mechanisms are unclear. The gut microbiota and its metabolites have been suggested to be involved in the pathogenesis of Parkinson's disease by regulating neuroinflammation, barrier function and neurotransmitter activity. There is bidirectional communication between the enteric nervous system and the central nervous system, and the microbiota-gut-brain axis may provide a pathway for the transmission of α-synuclein. We highlight recent discoveries and alterations of the gut microbiota in Parkinson's disease, and highlight current mechanistic insights on the microbiota-gut-brain axis in disease pathophysiology. We discuss the interactions between production and transmission of α-synuclein and gut inflammation and neuroinflammation. In addition, we also draw attention to diet modification, use of probiotics and prebiotics and fecal microbiota transplantation as potential therapeutic approaches that may lead to a new treatment paradigm for Parkinson's disease.

Immunoregulatory Effects of Porcine Plasma Protein Concentrates on Rat Intestinal Epithelial Cells and Splenocytes

Simple Summary

Blood contains proteins which have interest as products that may regulate immune function. For this reason some protein-based products are currently used as nutritional supplements for animals, for instance two porcine concentrates, spray dried serum (SDS), and an immunoglobulin concentrate (IC). These products have shown to protect against colonic inflammation in rodents. In the present study we characterize the ability of these products to modulate immune function in isolated cells, namely intestinal epithelial cells (IEC18 cells) and rat spleen cells. Our data indicate that both porcine protein concentrates indeed alter immune cell function, based on the secretion of the modulators known as cytokines. In intestinal epithelial IEC18 cells they promoted the secretion of GROα and MCP-1 cytokines. In spleen cells they mainly inhibited the production of TNF, a key proinflammatory cytokine. In addition, the IC product augmented the release of IL-10, an anti-inflammatory cytokine. Taken together, our data indicate that the immunomodulatory effects observed in vivo are consistent with the direct actions of the protein concentrates on epithelial cells, T lymphocytes, and monocytes.

Abstract

Serum protein concentrates have been shown to exert in vivo anti-inflammatory effects. Specific effects on different cell types and their mechanism of action remain unraveled. We aimed to characterize the immunomodulatory effect of two porcine plasma protein concentrates, spray dried serum (SDS) and an immunoglobulin concentrate (IC), currently used as animal nutritional supplements with established in vivo immunomodulatory properties. Cytokine production by the intestinal epithelial cell line IEC18 and by primary cultures of rat splenocytes was studied. The molecular pathways involved were explored with specific inhibitors and gene knockdown. Our results indicate that both products induced GROα and MCP-1 production in IEC18 cells by a MyD88/NF-κB-dependent mechanism. Inhibition of TNF production was observed in rat primary splenocyte cultures. The immunoglobulin concentrate induced IL-10 expression in primary splenocytes and lymphocytes. The effect on TNF was independent of IL-10 production or the stimulation of NF-kB, MAPKs, AKT, or RAGE. In conclusion, SDS and IC directly regulate intestinal and systemic immune response in murine intestinal epithelial cells and in T lymphocytes and monocytes.

Immune-Mediated Aggravation of the Campylobacter concisus-Induced Epithelial Barrier Dysfunction

Campylobacter concisus is a human-pathogenic bacterium of the gastrointestinal tract. This study aimed at the contribution of the mucosal immune system in the context of intestinal epithelial barrier dysfunction induced by C. concisus. As an experimental leaky gut model, we used in vitro co-cultures of colonic epithelial cell monolayers (HT-29/B6-GR/MR) with M1-macrophage-like THP-1 cells on the basal side. Forty-eight hours after C. concisus infection, the decrease in the transepithelial electrical resistance in cell monolayers was more pronounced in co-culture condition and 22 ± 2% (p < 0.001) higher than the monoculture condition without THP-1 cells. Concomitantly, we observed a reduction in the expression of the tight junction proteins occludin and tricellulin. We also detected a profound increase in 4 kDa FITC-dextran permeability in C. concisus-infected cell monolayers only in co-culture conditions. This is explained by loss of tricellulin from tricellular tight junctions (tTJs) after C. concisus infection. As an underlying mechanism, we observed an inflammatory response after C. concisus infection through pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) released from THP-1 cells in the co-culture condition. In conclusion, the activation of subepithelial immune cells exacerbates colonic epithelial barrier dysfunction by C. concisus through tricellulin disruption in tTJs, leading to increased antigen permeability (leaky gut concept).

Regulation of Intestinal Barrier Function by Microbial Metabolites

The human gastrointestinal tract (GI) harbors a diverse population of microbial life that continually shapes host pathophysiological responses. Despite readily available abundant metagenomic data, the functional dynamics of gut microbiota remain to be explored in various health and disease conditions. Microbiota generate a variety of metabolites from dietary products that influence host health and pathophysiological functions. Since gut microbial metabolites are produced in close proximity to gut epithelium, presumably they have significant impact on gut barrier function and immune responses. The goal of this review is to discuss recent advances on gut microbial metabolites in the regulation of intestinal barrier function. While the mechanisms of action of these metabolites are only beginning to emerge, they mainly point to a small group of shared pathways that control gut barrier functions. Amidst expanding technology and broadening knowledge, exploitation of beneficial microbiota and their metabolites to restore pathophysiological balance will likely prove to be an extremely useful remedial tool.

The Role of Gut Microbiota in Chronic Itch-Evoked Novel Object Recognition-Related Cognitive Dysfunction in Mice

The high incidence of patients with chronic itch highlights the importance of fundamental research. Recent advances in the interface of gut microbiota have shed new light into exploring this phenomenon. However, it is unknown whether gut microbiota plays a role in chronic itch in rodents with or without cognitive dysfunction. In this study, the role of gut microbiota in diphenylcyclopropenone (DCP)-evoked chronic itch was investigated in mice and hierarchical cluster analysis of novel object recognition test (ORT) results were used to classify DCP-evoked itch model in mice with or without cognitive dysfunction (CD)-like phenotype and 16S ribosomal RNA (rRNA) gene sequencing was used to compare gut bacterial composition between CD (Susceptible) and Non-CD phenotypes (Unsusceptible) in chronic itch mice. Results showed that the microbiota composition was significantly altered by DCP-evoked chronic itch and chronic itch induced novel object recognition-related CD. However, abnormal gut microbiota composition induced by chronic itch may not be correlated with novel object recognition-related CD.

Prevention and Alleviation of Dextran Sulfate Sodium Salt-Induced Inflammatory Bowel Disease in Mice With Bacillus subtilis-Fermented Milk via Inhibition of the Inflammatory Responses and Regulation of the Intestinal Flora

The pathogenesis of inflammatory bowel disease (IBD) might be related to the local inflammatory damage and the dysbacteriosis of intestinal flora. Probiotics can regulate the intestinal flora and ameliorate IBD. The probiotic Bacillus subtilis strain B. subtilis JNFE0126 was used as the starter of fermented milk. However, the therapeutic effects of B. subtilis-fermented milk on IBD remain to be explored. In this research, the therapeutic effect of B. subtilis-fermented milk on dextran sulfate sodium salt (DSS)-induced IBD mouse model was evaluated. Besides, the expression of pro-inflammatory/anti-inflammatory cytokines, the proliferation of the intestinal stem cells, and the reconstruction of the mucosa barrier were investigated. Finally, alteration of the gut microbiota was investigated by taxonomic analysis. As shown by the results, the disease activity index (DAI) of IBD was significantly decreased through oral administration of B. subtilis (JNFE0126)-fermented milk, and intestinal mucosa injury was attenuated. Moreover, B. subtilis could reduce the inflammatory response of the intestinal mucosa, induce proliferation of the intestinal stem cell, and promote reconstruction of the mucosal barrier. Furthermore, B. subtilis could rebalance the intestinal flora, increasing the abundance of Bacillus, Alistipes, and Lactobacillus while decreasing the abundance of Escherichia and Bacteroides. In conclusion, oral administration of the B. subtilis-fermented milk could alleviate DSS-induced IBD via inhibition of inflammatory response, promotion of the mucosal barrier reconstruction, and regulation of the intestinal flora.

Fungal lysozyme leverages the gut microbiota to curb DSS-induced colitis

Colitis is characterized by colonic inflammation and impaired gut health. Both features aggravate obesity and insulin resistance. Host defense peptides (HDPs) are key regulators of gut homeostasis and generally malfunctioning in above-mentioned conditions. We aimed here to improve bowel function in diet-induced obesity and chemically induced colitis through daily oral administration of lysozyme, a well-characterized HDP, derived from Acremonium alcalophilum.C57BL6/J mice were fed either low-fat reference diet or HFD ± daily gavage of lysozyme for 12 weeks, followed by metabolic assessment and evaluation of colonic microbiota encroachment. To further evaluate the efficacy of intestinal inflammation, we next supplemented chow-fed BALB/c mice with lysozyme during Dextran Sulfate Sodium (DSS)-induced colitis in either conventional or microbiota-depleted mice. We assessed longitudinal microbiome alterations by 16S amplicon sequencing in both models.Lysozyme dose-dependently alleviated intestinal inflammation in DSS-challenged mice and further protected against HFD-induced microbiota encroachment and fasting hyperinsulinemia. Observed improvements of intestinal health relied on a complex gut flora, with the observation that microbiota depletion abrogated lysozyme's capacity to mitigate DSS-induced colitis.Akkermansia muciniphila associated with impaired gut health in both models, a trajectory that was mitigated by lysozyme administration. In agreement with this notion, PICRUSt2 analysis revealed specific pathways consistently affected by lysozyme administration, independent of vivarium, disease model and mouse strain.Taking together, lysozyme leveraged the gut microbiota to curb DSS-induced inflammation, alleviated HFD-induced gastrointestinal disturbances and lowered fasting insulin levels in obese mice. Collectively, these data present A. alcalophilum-derived lysozyme as a promising candidate to enhance gut health.

Chlamydia muridarum Alleviates Colitis via the IL-22/Occludin Signal Pathway

Ulcerative colitis (UC) is the most common inflammatory bowel disease, and its incidence has increased in recent years. Recent clinical and experimental data indicate that gut microbiota plays a pivotal role in the pathogenesis of UC. Chlamydia establishes a stable and persistent colonization in the gastrointestinal tract without apparent pathogenicity to gastrointestinal or extragastrointestinal tissues. However, the detailed effects of Chlamydia on the gastrointestinal tissue remain unknown. The primary aim of this study is to investigate the effects of Chlamydia muridarum (C. muridarum) on development of colitis induced by dextran sodium sulfate (DSS) and the underlying molecular mechanism. The results suggested that C. muridarum significantly improved colitis symptoms-including weight loss, disease activity index, colon length, and histopathological changes in the colon caused by DSS-and alleviated the reduced expression of interleukin-22 and occludin in the colonic tissue due to DSS administration. Furthermore, the absence of IL-22 completely prevented C. muridarum from alleviating colitis and significantly decreased the levels of occludin, an important downstream effector protein of IL-22. These findings suggest that C. muridarum ameliorates ulcerative colitis induced by DSS via the IL-22/occludin signal pathway.

Innovative Animal Model of DSS-Induced Ulcerative Colitis in Pseudo Germ-Free Mice

The aim of this study was to investigate the use of a standardized animal model subjected to antibiotic treatment, and the effects of this treatment on the course of dextran sodium sulphate (DSS)-induced colitis in mice. By decontamination with selective antibiotics and observation of pathogenesis of ulcerative colitis (UC) induced chemically by exposure of mice to various concentrations of DSS, we obtained an optimum animal PGF model of acute UC manifested by mucin depletion, epithelial degeneration and necrosis, leading to the disappearance of epithelial cells, infiltration of lamina propria and submucosa with neutrophils, cryptitis, and accompanied by decreased viability of intestinal microbiota, loss of body weight, dehydration, moderate rectal bleeding, and a decrease in the selected markers of cellular proliferation and apoptosis. The obtained PGF model did not exhibit changes that could contribute to inflammation by means of alteration of the metabolic status and the induced dysbiosis did not serve as a bearer of pathogenic microorganisms participating in development of ulcerative colitis. The inflammatory process was induced particularly by exposure to DSS and its toxic action on compactness and integrity of mucosal barrier in the large intestine. This offers new possibilities of the use of this animal model in studies with or without participation of pathogenic microbiota in IBD pathogenesis.

Acute Intestinal Inflammation Depletes/Recruits Histamine-Expressing Myeloid Cells From the Bone Marrow Leading to Exhaustion of MB-HSCs

BACKGROUND & AIMS

Histidine decarboxylase (HDC), the histamine-synthesizing enzyme, is expressed in a subset of myeloid cells but also marks quiescent myeloid-biased hematopoietic stem cells (MB-HSCs) that are activated upon myeloid demand injury. However, the role of MB-HSCs in dextran sulfate sodium (DSS)-induced acute colitis has not been addressed.

METHODS

We investigated HDC+ MB-HSCs and myeloid cells by flow cytometry in acute intestinal inflammation by treating HDC-green fluorescent protein (GFP) male mice with 5% DSS at various time points. HDC+ myeloid cells in the colon also were analyzed by flow cytometry and immunofluorescence staining. Knockout of the HDC gene by using HDC-/-; HDC-GFP and ablation of HDC+ myeloid cells by using HDC-GFP; HDC-tamoxifen-inducible recombinase Cre system; diphtheria toxin receptor (DTR) mice was performed. The role of H2-receptor signaling in acute colitis was addressed by treatment of DSS-treated mice with the H2 agonist dimaprit dihydrochloride. Kaplan-Meier survival analysis was performed to assess the effect on survival.

RESULTS

In acute colitis, rapid activation and expansion of MB-HSC from bone marrow was evident early on, followed by a gradual depletion, resulting in profound HSC exhaustion, accompanied by infiltration of the colon by increased HDC+ myeloid cells. Knockout of the HDC gene and ablation of HDC+ myeloid cells enhance the early depletion of HDC+ MB-HSC, and treatment with H2-receptor agonist ameliorates the depletion of MB-HSCs and resulted in significantly increased survival of HDC-GFP mice with acute colitis.

CONCLUSIONS

Exhaustion of bone marrow MB-HSCs contributes to the progression of DSS-induced acute colitis, and preservation of quiescence of MB-HSCs by the H2-receptor agonist significantly enhances survival, suggesting the potential for therapeutic utility.

Anti-Inflammatory and Intestinal Microbiota Modulation Properties of Jinxiang Garlic (Allium sativum L.) Polysaccharides toward Dextran Sodium Sulfate-Induced Colitis

Garlic polysaccharides are great potential agents because of their anti-inflammation, antioxidation, and immunomodulation properties. However, few studies have reported their anti-inflammatory effects on improving the colon system and corresponding intestinal microbiota. Herein, a water-soluble garlic polysaccharide (WSGP) was extracted from Jinxiang garlic to evaluate its effects on ameliorating dextran sulfate sodium (DSS)-induced colitis in a mouse model. The results showed that (1) after administration of the WSGP (200 or 400 mg/kg/day), the feed intake, body weight, and colon length of colitic mice were increased, while the disease activity index and the histological score of colitic mice were decreased; (2) the WSGP reduced the colonic tissue damage and inhibited the expression of inflammatory factors (interleukin 6, interleukin 1 beta , and tumor necrosis factor alpha); and (3) the WSGP enhanced the production of short-chain fatty acids and improved the composition of intestinal microbiota. The key microorganisms, including Muribaculaceae, Lachnospiraceae, Lachnospiraceae_NK4A136_group, Mucispirillum, Helicobacter, Ruminococcus_1, and Ruminiclostridium_5, were identified to be associated with inflammatory bowel diseases. Taken together, this study proved that WSGP supplementation could alleviate DSS-induced colitis by improving mucosal barriers, blocking proinflammatory cytokines, and modulating gut microbiota.

Cyclosporine protects from intestinal epithelial injury by modulating butyrate uptake via upregulation of membrane monocarboxylate transporter 1 levels

Background and aims

A relationship between treatment outcomes and intestinal microbiota in patients with inflammatory bowel diseases has been demonstrated. Cyclosporine treatment leads to rapid improvement in severe ulcerative colitis. We hypothesized that the potent effects of cyclosporine would be exerted through relationships between intestinal epithelial cells (IECs) and the host microbiota. The present study was designed to elucidate the effects of cyclosporine on monocarboxylate transporter 1 (MCT1) regulation and butyrate uptake by IECs.

Methods

Colitis was induced in C57BL6 mice via the administration of 4% dextran sulfate sodium in drinking water, following which body weights, colon lengths, and histological scores were evaluated. To examine the role of butyrate in the protective effects of cyclosporine, MCT1 inhibitor and an antibiotic cocktail was administered and tributyrin (TB; a prodrug of butyrate) was supplemented; MCT1 protein expression and acetylated histone 3 (AcH3) signals in IECs, as well as the MCT1-membrane fraction of Caco-2 cells, were evaluated. To explore butyrate uptake, as s butyrate derivatives, 3-bromopyruvic acid (3-BrPA) and 1-pyrenebutyric acid were used.

Results

Treatment with cyclosporine inhibited body weight loss and colon length shortening. However, treatment with MCT1 inhibitor and the antibiotic cocktail negated the efficacy of cyclosporine, whereas TB supplementation restored its protective effect. Furthermore, cyclosporine upregulated MCT1 expression in the membrane and the AcH3 signal in IECs, while also inducing higher anti-inflammatory cytokine production compared to that in the vehicle-treated mice. The transcription level of MCT1 mRNA in IECs and Caco-2 cells did not increase with cyclosporine treatment; however, cyclosporine treatment increased membrane MCT1 expression in these cells and uptake of butyrate derivative.

Conclusion

Cyclosporine treatment modulates butyrate uptake via the post-transcriptional upregulation of membrane MCT1 levels in IECs.

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The protective effect of cyclosporine needs microbiota-derived butyrate.

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Cyclosporine increased the fraction of MCT1 at the cell membrane.

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Cyclosporine enhanced butyrate uptake and regulatory cytokine expression.

Microbiota-derived metabolite promotes HDAC3 activity in the gut

The coevolution of mammalian hosts and their beneficial commensal microbes has led to development of symbiotic host-microbiota relationships1. Epigenetic machinery permits mammalian cells to integrate environmental signals2; however, how these pathways are fine-tuned by diverse cues from commensal bacteria is not well understood. Here we reveal a highly selective pathway through which microbiota-derived inositol phosphate regulates histone deacetylase 3 (HDAC3) activity in the intestine. Despite the abundant presence of HDAC inhibitors such as butyrate in the intestine, we found that HDAC3 activity was sharply increased in intestinal epithelial cells of microbiota-replete mice compared with germ-free mice. This divergence was reconciled by the finding that commensal bacteria, including Escherichia coli, stimulated HDAC activity through metabolism of phytate and production of inositol-1,4,5-trisphosphate (InsP3). Both intestinal exposure to InsP3 and phytate ingestion promoted recovery following intestinal damage. Of note, InsP3 also induced growth of intestinal organoids derived from human tissue, stimulated HDAC3-dependent proliferation and countered butyrate inhibition of colonic growth. Collectively, these results show that InsP3 is a microbiota-derived metabolite that activates a mammalian histone deacetylase to promote epithelial repair. Thus, HDAC3 represents a convergent epigenetic sensor of distinct metabolites that calibrates host responses to diverse microbial signals.

Sesamol Supplementation Attenuates DSS-Induced Colitis via Mediating Gut Barrier Integrity, Inflammatory Responses, and Reshaping Gut Microbiome

Sesamol, a liposoluble lignan extract, has already been proved to possess potent anti-inflammatory properties, and it could also regulate gut dysfunction. The purpose of the present research is to explore the protective effect of sesamol on colitis mice. In the current research, sesamol treatment (100 mg/kg bodyweight/day) for 6 weeks inhibited the dextran sulphate sodium (DSS)-induced bodyweight loss of mice. Transmission electron microscopy and hematoxylin and eosin staining results showed that the DSS-induced histopathological changes of mice were also recovered by sesamol supplementation. In addition, DSS-induced inflammatory responses were inhibited by sesamol supplementation via the NF-κB signaling pathway in mice colon. Moreover, sesamol treatment prevented gut barrier damages by enhancing the expression of tight junction proteins (occludin, claudin-1, and ZO-1) and recovering the loss of gut mucus layer. Furthermore, sesamol supplementation also increased the short-chain fatty acid (SCFAs) contents of acetate, propionate, and butyrate. Furthermore, sesamol supplementation changed the gut microbiome structure by enhancing the relative abundance of Coprococcuscus, Butyricicoccus, Odoribacter, and AF12 in colitis mice. In conclusion, sesamol could effectively ameliorate DSS-induced colitis by promoting gut microecology.

Dietary Fructose Alters the Composition, Localization, and Metabolism of Gut Microbiota in Association With Worsening Colitis

BACKGROUND & AIMS

The incidence of inflammatory bowel diseases has increased over the last half century, suggesting a role for dietary factors. Fructose consumption has increased in recent years. Recently, a high fructose diet (HFrD) was shown to enhance dextran sodium sulfate (DSS)-induced colitis in mice. The primary objectives of the current study were to elucidate the mechanism(s) underlying the pro-colitic effects of dietary fructose and to determine whether this effect occurs in both microbially driven and genetic models of colitis.

METHODS

Antibiotics and germ-free mice were used to determine the relevance of microbes for HFrD-induced worsening of colitis. Mucus thickness and quality were determined by histologic analyses. 16S rRNA profiling, in situ hybridization, metatranscriptomic analyses, and fecal metabolomics were used to determine microbial composition, spatial distribution, and metabolism. The significance of HFrD on pathogen and genetic-driven models of colitis was determined by using Citrobacter rodentium infection and Il10-/- mice, respectively.

RESULTS

Reducing or eliminating bacteria attenuated HFrD-mediated worsening of DSS-induced colitis. HFrD feeding enhanced access of gut luminal microbes to the colonic mucosa by reducing thickness and altering the quality of colonic mucus. Feeding a HFrD also altered gut microbial populations and metabolism including reduced protective commensal and bile salt hydrolase-expressing microbes and increased luminal conjugated bile acids. Administration of conjugated bile acids to mice worsened DSS-induced colitis. The HFrD also worsened colitis in Il10-/- mice and mice infected with C rodentium.

CONCLUSIONS

Excess dietary fructose consumption has a pro-colitic effect that can be explained by changes in the composition, distribution, and metabolic function of resident enteric microbiota.

Prescription Opioids induce Gut Dysbiosis and Exacerbate Colitis in a Murine Model of Inflammatory Bowel Disease

BACKGROUND AND AIMS

Opioids are the most prescribed analgesics for pain in inflammatory bowel diseases [IBD]; however, the consequences of opioid use on IBD severity are not well defined. This is the first study investigating consequences of hydromorphone in both dextran sodium sulphate [DSS]-induced colitis and spontaneous colitis (IL-10 knockout [IL-10-/-]) mouse models of IBD.

METHODS

To determine the consequences of opioids on IBD pathogenesis, wild-type [WT] mice were treated with clinically relevant doses of hydromorphone and colitis was induced via 3% DSS in drinking water for 5 days. In parallel we also determined the consequences of opioids in a spontaneous colitis model.

RESULTS

Hydromorphone and DSS independently induced barrier dysfunction, bacterial translocation, disruption of tight junction organisation and increased intestinal and systemic inflammation, which were exacerbated in mice receiving hydromorphone in combination with DSS. Hydromorphone + DSS-treated mice exhibited significant microbial dysbiosis. Predictive metagenomic analysis of the gut microbiota revealed high abundance in the bacterial communities associated with virulence, antibiotic resistance, toxin production, and inflammatory properties. Hydromorphone modulates tight junction organisation in a myosin light chain kinase [MLCK]-dependent manner. Treatment with MLCK inhibitor ML-7 ameliorates the detrimental effects of hydromorphone on DSS-induced colitis and thus decreases severity of IBD. Similarly, we demonstrated that hydromorphone treatment in IL-10-/- mice resulted in accelerated clinical manifestations of colitis compared with control mice.

CONCLUSIONS

Opioids used for pain management in IBD accelerate IBD progression by dysregulation of the gut microbiota, leading to expansion of pathogenic bacteria, translocation of bacteria, immune deregulation and sustained inflammation.

Proline-Rich Acidic Protein 1 (PRAP1) Protects the Gastrointestinal Epithelium From Irradiation-Induced Apoptosis

BACKGROUND & AIMS

The intestinal epithelium must be resilient to physiochemical stress to uphold the physiological barrier separating the systemic compartment from the microbial and antigenic components of the gut lumen. Identifying proteins that mediate protection and enhancing their expression is therefore a clear approach to promote intestinal health. We previously reported that oral ingestion of the probiotic Lactobacillus rhamnosus GG not only induced the expression of several recognized cytoprotective factors in the murine colon, but also many genes with no previously described function, including the gene encoding proline-rich acidic protein 1 (PRAP1). PRAP1 is a highly expressed protein in the epithelium of the gastrointestinal tract and we sought to define its function in this tissue.

METHODS

Purified preparations of recombinant PRAP1 were analyzed biochemically and PRAP1 antisera were used to visualize localization in tissues. Prap1-/- mice were characterized at baseline and challenged with total body irradiation, then enteroids were generated to recapitulate the irradiation challenge ex vivo.

RESULTS

PRAP1 is a 17-kilodalton intrinsically disordered protein with no recognizable sequence homology. PRAP1 expression levels were high in the epithelia of the small intestine. Although Prap1-/- mice presented only mild phenotypes at baseline, they were highly susceptible to intestinal injury upon challenge. After irradiation, the Prap1-/- mice showed accelerated death with a significant increase in apoptosis and p21 expression in the small intestinal epithelium.

CONCLUSIONS

PRAP1 is an intrinsically disordered protein highly expressed by the gastrointestinal epithelium and functions at exposed surfaces to protect the barrier from oxidative insult.

Abnormal gut microbiota composition contributes to cognitive dysfunction in streptozotocin-induced diabetic mice

Both diabetes and Alzheimer’s disease are age-related disorders, and numerous studies have demonstrated that patients with diabetes are at an increased risk of cognitive dysfunction (CD) and Alzheimer’s disease, suggesting shared or interacting pathomechanisms. The present study investigated the role of abnormal gut microbiota in diabetes-induced CD and the potential underlying mechanisms. An intraperitoneal injection of streptozotocin administered for 5 consecutive days was used for establishing a diabetic animal model. Hierarchical cluster analysis of Morris water maze (MWM) performance indices (escape latency and target quadrant crossing) was adopted to classify the diabetic model mice into CD and Non-CD phenotypes. Both β-diversity and relative abundance of several gut bacteria significantly differed between the CD and Non-CD groups. Further, fecal bacteria transplantation from Non-CD mice, but not from CD mice, into the gut of pseudo-germ-free mice significantly improved host MWM performance, an effect associated with alterations in β-diversity and relative abundance of host gut bacteria. Collectively, these findings suggest that abnormal gut microbiota composition contributes to the onset of diabetes-induced CD and that improving gut microbiota composition is a potential therapeutic strategy for diabetes and related comorbidities.

Anti-Inflammatory and Gut Microbiota Modulatory Effect of Lactobacillus rhamnosus Strain LDTM 7511 in a Dextran Sulfate Sodium-Induced Colitis Murine Model

Inflammatory bowel disease (IBD) is a group of conditions involving chronic relapsing-remitting inflammation of the gastrointestinal tract with an unknown etiology. Although the cause-effect relationship between gut microbiota and IBD has not been clearly established, emerging evidence from experimental models supports the idea that gut microbes play a fundamental role in the pathogenesis of IBD. As microbiome-based therapeutics for IBD, the beneficial effects of probiotics have been found in animal colitis models and IBD patients. In this study, based on the dextran sulfate sodium (DSS)-induced colitis mouse model, we investigated Lactobacillus rhamnosus strain LDTM 7511 originating from Korean infant feces as a putative probiotic strain for IBD. The strain LDTM 7511 not only alleviated the release of inflammatory mediators, but also induced the transition of gut microbiota from dysbiotic conditions, exhibiting the opposite pattern in the abundance of DSS colitis-associated bacterial taxa to the DSS group. Our findings suggest that the strain LDTM 7511 has the potential to be used as a probiotic treatment for IBD patients in comparison to L. rhamnosus GG (ATCC 53103), which has been frequently used for IBD studies.

Sucralose Promotes Colitis-Associated Colorectal Cancer Risk in a Murine Model Along With Changes in Microbiota

Sucralose is a calorie-free high-intensity artificial sweetener that is widely used in thousands of foods and beverages all over the world. Although it was initially regarded as a safe, inert food additive, its adverse effect on gut microbiota and health has drawn more and more attention as evidence accumulates. Studies by us and others revealed that sucralose exacerbated gut damage and inflammation in animal models for inflammatory bowel disease (IBD), including those for both ulcerative colitis, and Crohn's disease. Our study demonstrated that sucralose greatly aggravated dextran sulfate sodium (DSS)-induced colitis along with causing changes in gut microbiota, the gut barrier and impaired inactivation of digestive proteases mediated by deconjugated bilirubin. It is well-documented that IBD greatly increases the risk of colorectal cancer (CRC), the globally third-most-common cancer, which, like IBD, has a high rate in the developed countries. Azoxymethane (AOM)/DSS has been the most commonly used animal model for CRC. In this study, we further explored the effect of sucralose on tumorigenesis and the possible mechanism involved using the AOM/DSS mouse model. First, 1.5 mg/ml sucralose was included in the drinking water for 6 weeks to reach a relatively stable phase of impact on gut microbiota. Then, 10 mg/kg AOM was administered through intraperitoneal injection. Seven days later, 2.5% DSS was put in the drinking water for 5 days, followed by 2 weeks without DSS. The 5 days of DSS was then repeated, and the mice were sacrificed 6 weeks after AOM injection. The results showed that sucralose caused significant increases in the number and size of AOM/DSS-induced colorectal tumors along with changes in other parameters such as body and spleen weight, pathological scores, mortality, fecal β-glucuronidase and digestive proteases, gut barrier molecules, gut microbiota, inflammatory cytokines and pathways (TNFα, IL-1β, IL-6, IL-10, and TLR4/Myd88/NF-κB signaling), and STAT3/VEGF tumor-associated signaling pathway molecules. These results suggest that sucralose may increase tumorigenesis along with dysbiosis of gut microbiota, impaired inactivation of digestive protease, damage to the gut barrier, and exacerbated inflammation.

Abnormal gut microbiota composition is associated with experimental autoimmune prostatitis-induced depressive-like behaviors in mice

BACKGROUND

Depressive symptoms are found in approximately 78% of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) patients, but the pathological mechanisms remain unknown. Increasing evidence suggests that abnormal gut microbiota may play an important role in depression. Thus, we aimed to investigate whether gut microbiota contributes to CP/CPPS-associated depression by using a mouse model of experimental autoimmune prostatitis (EAP).

METHODS

Male nonobese diabetic mice were immunized twice by subcutaneous injection of prostate antigen and adjuvant. Behavioral tests consisted of an open field test, sucrose preference test, forced swimming tests, and tail suspension test was used to confirm the depression-like symptoms that were induced by EAP. Then, fecal samples were collected, and 16S ribosomal RNA gene sequencing was performed to detect differences in gut microbiota composition between control and EAP group. Additionally, fecal bacteria from the control and EAP mice were transplanted into antibiotics-induced pseudo-germ-free mice to investigate the effects on host behaviors and the composition of gut bacteria.

RESULTS

EAP was successfully established and exhibited depressive-like behaviors in mice. The 16S rRNA analysis of fecal samples indicated the abnormal composition of gut microbiota in the EAP mice compared to the control mice. In the fecal microbiota transplant study, antibiotics-treated pseudo-germ-free mice presented depressive states as compared to naïve mice. Fecal bacteria transplant from EAP mice, but not from control mice, into the pseudo-germ-free mice, significantly exaggerated host depression-like behaviors. Moreover, fecal bacteria transplants from control and EAP mice induced distinct alterations in α-diversity and β-diversity indices. In all, 24 bacteria at six phylogenetic levels were remarkably changed by the fecal bacteria transplantation.

CONCLUSIONS

Abnormal gut microbiota composition after EAP induction may contribute to the development of depression in mice. A therapeutic strategy that targets gut microbiota may provide an alternative treatment for alleviating this condition.

Fucose Ameliorate Intestinal Inflammation Through Modulating the Crosstalk Between Bile Acids and Gut Microbiota in a Chronic Colitis Murine Model

BACKGROUND

Recurrent intestinal inflammation is frequently associated with aberrant bile acid profiles and microbial community. Fucose exerts a protective effect on commensal bacteria in the case of intestinal pathogen infection. We speculated that fucose might also have certain impact on the microbial ecosystem under the chronic colitis setting.

METHODS

To validate our hypothesis, multi-omics examination was performed in combination with microbiomics and metabonomics in a chronic dextran sulfate sodium (DSS) murine model in the presence or absence of fucose. The 16S RNA sequencing was carried out to determine the ileum and colon microbiota. Primary and secondary bile acids, together with the respective taurine and glycine conjugates, were quantified through ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-MS). Moreover, enzymes involved in regulating bile acid synthesis were also detected. Finally, an experiment was carried out on the antibiotic-treated mice to examine the role of gut microbiota.

RESULTS

Administration of exogenous-free fucose markedly alleviated the inflammatory response in colitis mice. In addition, excessive intestinal bile acid accumulated in DSS mice was decreased in the presence of fucose, along with the restoration of the compromised regulation on hepatic bile acid synthesis. Moreover, the shifts in bile acid profiles were linked with the improved gut microbiome dysbiosis. However, the protective effects of fucose were abolished in mice treated with antibiotic cocktail, indicating that microbiota played a pivotal role.

CONCLUSIONS

Findings in this study suggest that fucose ameliorates colitis through restoring the crosstalk between bile acid and gut microbiota.

Epithelial Toll-like receptors and their role in gut homeostasis and disease

The human gastrointestinal tract is colonized by trillions of microorganisms that interact with the host to maintain structural and functional homeostasis. Acting as the interface between the site of the highest microbial burden in the human body and the richest immune compartment, a single layer of intestinal epithelial cells specializes in nutrient absorption, stratifies microorganisms to limit colonization of tissues and shapes the responses of the subepithelial immune cells. In this Review, we focus on the expression, regulation and functions of Toll-like receptors (TLRs) in the different intestinal epithelial lineages to analyse how epithelial recognition of bacteria participates in establishing homeostasis in the gut. In particular, we elaborate on the involvement of epithelial TLR signalling in controlling crypt dynamics, enhancing epithelial barrier integrity and promoting immune tolerance towards the gut microbiota. Furthermore, we comment on the regulatory mechanisms that fine-tune TLR-driven immune responses towards pathogens and revisit the role of TLRs in epithelial repair after injury. Finally, we discuss how dysregulation of epithelial TLRs can lead to the generation of dysbiosis, thereby increasing susceptibility to colitis and tumorigenesis.

Platelet activating factor receptor acts to limit colitis-induced liver inflammation

Liver inflammation is a common extraintestinal manifestation in inflammatory bowel disease (IBD), yet, the mechanisms driving gut-liver axis inflammation remain poorly understood. IBD leads to a breakdown in the integrity of the intestinal barrier causing an increase in portal and systemic gut-derived antigens, which challenge the liver. Here, we examined the role of platelet activating factor receptor (PAFR) in colitis-associated liver damage using dextran sulfate sodium (DSS) and anti-CD40-induced colitis models. Both DSS and anti-CD40 models exhibited liver inflammation associated with colitis. Colitis reduced global PAFR protein expression in mouse livers causing an exclusive re-localization of PAFR to the portal triad. The global decrease in liver PAFR was associated with increased sirtuin 1 while relocalized PAFR expression was limited to Kupffer cells (KCs) and co-localized with toll-like receptor 4. DSS activated the NLRP3-inflammasome and increased interleukin (IL)-1β in the liver. Antagonism of PAFR amplified the inflammasome response by increasing NLRP3, caspase-1, and IL-1β protein levels in the liver. LPS also increased NLRP3 response in human hepatocytes, however, overexpression of PAFR restored the levels of NLPR3 and caspase-1 proteins. Interestingly, KCs depletion also increased IL-1β protein in mouse liver after DSS challenge. These data suggest a protective role for PAFR-expressing KCs during colitis and that regulation of PAFR is important for gut-liver axis homeostasis.

Perivascular localization of macrophages in the intestinal mucosa is regulated by Nr4a1 and the microbiome

While the ontogeny and recruitment of the intestinal monocyte/macrophage lineage has been studied extensively, their precise localization and function has been overlooked. Here we show by imaging the murine small and large intestines in steady-state that intestinal CX3CR1⁺ macrophages form an interdigitated network intimately adherent to the entire mucosal lamina propria vasculature. The macrophages form contacts with each other, which are disrupted in the absence of microbiome, monocyte recruitment (Ccr2^−/−), or monocyte conversion (Nr4a1^−/−). In dysbiosis, gaps exist between the perivascular macrophages correlating with increased bacterial translocation from the lamina propria into the bloodstream. The recruitment of monocytes and conversion to macrophages during intestinal injury is also dependent upon CCR2, Nr4a1 and the microbiome. These findings demonstrate a relationship between microbiome and the maturation of lamina propria perivascular macrophages into a tight anatomical barrier that might function to prevent bacterial translocation. These cells are also critical for emergency vascular repair.

Lamina propria macrophages are at the frontline of defense against intestinal pathogens. Here the authors reveal that CCR2 and NR4A1-dependent CX3CR1+ macrophages form a dense network around the vessels in the lamina propria, and implicate this anatomical structure into prevention of systemic bacterial dissemination.