Gut bacteria interact directly with colonic mast cells in a humanized mouse model of IBS

Altered gut metabolites and metabolic reprogramming involved in the pathogenesis of colitis-associated colorectal cancer and the transition of colon "inflammation to cancer"

Colitis-associated colorectal cancer (CAC) is fatal and can develop spontaneously or as a complication of inflammatory bowel diseases. Although co-administration of azoxymethane/dextran sulfate sodium (AOM/DSS) is a classic method for CAC modeling, its limitations need to be addressed. Accordingly, we aimed to optimize the AOM/DSS model to study CAC extensively and further investigate its pathogenic mechanisms relative to microbiota and metabolism. We optimized the CAC model via a single or enhanced injection of AOM combined with different administration modes and varying DSS concentrations. Subsequently, the fecal-microbiota composition was examined using 16S RNA sequencing, and fecal-colon-metabolome profiles were evaluated via ultra-high performance liquid chromatography-mass spectrometry. Two interval injections of AOM combined with 1.5 % DSS-free drinking resulted in a high tumor formation rate, uniform tumor formation, and low mortality. Based on this model, we innovatively divided the pathogenesis of CAC into three stages, namely inflammation induction, proliferation initiation, and tumorigenesis, and examined the pathological characteristics in each stage. Gut microbial dysbiosis and metabolic alteration drove colorectal tumorigenesis by aggravating inflammation while promoting cell proliferation and carcinogenesis in mice. For the first time, we dynamically demonstrated the process of colon "inflammation to cancer" transformation and provided novel insights to clarify the role of amino acid metabolism in the formation of CAC.

Dandruff lesional scalp skin exhibits epidermal T cell infiltration and a weakened hair follicle immune privilege

OBJECTIVE

Dandruff is characterised by the presence of perivascular leukocytes and mild inflammation; however, the immune microenvironment of dandruff-affected scalp skin and the potential changes to the hair follicle's (HF) physiological immune privilege (HF IP) remain unknown. Here, we characterised the HF immune microenvironment and immune privilege status in dandruff-affected scalp skin.

METHODS

We assessed relevant key parameters in healthy versus dandruff-affected human scalp biopsies using quantitative immunohistomorphometry, laser capture microdissection, and RNA sequencing.

RESULTS

The number of epidermal CD4+ and CD8+ T cells was increased in lesional dandruff scalp skin, while the number of MHC class II+/CD1a+ Langerhans cells was decreased in the infundibulum. The number of intrafollicular and perifollicular CD4+ T cells and CD8+ T cells, perifollicular CD68+ macrophages, and tryptase+ mast cells remained unchanged. Interestingly, MHC class Ia and ß2-microglobulin protein expression were significantly increased specifically in the suprabulbar outer root sheath (ORS) compartment of dandruff-associated HFs. RNAseq analysis of laser capture micro-dissected suprabulbar ORS compartment revealed antigen presentation pathway as the top regulated canonical pathway, along with the upregulation of HF-IP genes such as HLA-C, HLA-DP, and TAP1, which are normally down-regulated in healthy HFs. Intrafollicular protein expression of known HF IP guardians (CD200 and α-MSH) and 'danger signals' (MICA and CXCL10) remained unaltered at the IP sites of dandruff lesional HFs compared to non-lesional and healthy HFs. Instead, the expression of macrophage migration inhibiting factor (MIF), another HF IP guardian, was reduced.

CONCLUSION

Together, this work shows that dandruff is associated with epidermal T-cell infiltration and a weakened HF IP in the suprabulbar ORS of HFs in dandruff lesional scalp.

Traditional Chinese medicine for functional gastrointestinal disorders and inflammatory bowel disease: narrative review of the evidence and potential mechanisms involving the brain-gut axis

Functional gastrointestinal disorders (FGIDs) and inflammatory bowel disease (IBD) are common clinical disorders characterized by recurrent diarrhea and abdominal pain. Although their pathogenesis has not been fully clarified, disruptions in intestinal motility and immune function are widely accepted as contributing factors to both conditions, and the brain-gut axis plays a key role in these processes. Traditional Chinese Medicine (TCM) employs a holistic approach to treatment, considers spleen and stomach impairments and liver abnormality the main pathogenesis of these two diseases, and offers a unique therapeutic strategy that targets these interconnected pathways. Clinical evidence shows the great potential of TCM in treating FGIDs and IBD. This study presents a systematic description of the pathological mechanisms of FGIDs and IBD in the context of the brain-gut axis, discusses clinical and preclinical studies on TCM and acupuncture for the treatment of these diseases, and summarizes TCM targets and pathways for the treatment of FGIDs and IBD, integrating ancient wisdom with contemporary biomedical insights. The alleviating effects of TCM on FGID and IBD symptoms are mainly mediated through the modulation of intestinal immunity and inflammation, sensory transmission, neuroendocrine-immune network, and microbiota and their metabolism through brain-gut axis mechanisms. TCM may be a promising treatment option in controlling FGIDs and IBD; however, further high-quality research is required. This review provides a reference for an in-depth exploration of the interventional effects and mechanisms of TCM in FGIDs and IBD, underscoring TCM's potential to recalibrate the dysregulated brain-gut axis in FGIDs and IBD.

Da-Jian-Zhong decoction alleviates diarrhea-predominant irritable bowel syndrome via modulation of gut microbiota and Th17/Treg balance

ETHNOPHARMACOLOGICAL RELEVANCE

Da-Jian-Zhong decoction (DJZD) is a herbal formula clinically used for abdominal pain and diarrhea induced by spleen-Yang deficiency syndrome. Recently, treatment of diarrhea-predominant irritable bowel syndrome (IBS-D) with DJZD has received increasing attention, but the underlying mechanism of action remains elusive.

AIM OF THE STUDY

We aimed to evaluate the therapeutic effect of DJZD on IBS-D rats and to elucidate the underlying mechanisms.

MATERIALS AND METHODS

An IBS-D rats model was constructed using a two-factor superposition method of neonatal maternal separation and Senna folium aqueous extract lavage. Moreover, the effect of DJZD was evaluated based on the body weight, rectal temperature, abdominal withdrawal reflex (AWR), and Bristol stool scale score (BSS). The factors that regulate the DJZD effects on IBS-D were estimated using whole microbial genome, transcriptome sequencing (RNA-Seq), flow cytometry, and quantitative reverse transcription polymerase chain reaction (RT-qPCR) analyses.

RESULTS

We found that DJZD alleviated the symptoms of IBS-D rats, with the low-dose (2.4 g/kg) as the better ones, as shown by the higher body weight and lower AWR score and BSS. At the phylum level, the relative abundance of Bacteroidetes was obviously increased, and at the genus level, Lactobacillus and Parabacteroides were increased, while that of Firmicutes_bacterium_424 and Ruminococcus gnavus was decreased in DJZD group. Furthermore, the significantly enriched GO terms after treatment with DJZD mainly included the immune response, positive regulation of activated T cell proliferation, and positive regulation of interleukin-17 (IL-17) production. Importantly, flow cytometry analysis further revealed that the T helper cell type 17/regulatory T cell (Th17/Treg) balance contributed to the DJZD-induced alleviation of IBS-D symptoms, as DJZD downregulated Th17/Treg ratio and Th17 cell-related cytokines IL-17 and IL-6 levels in the colon.

CONCLUSIONS

These results demonstrated that DJZD has a good therapeutic effect on IBS-D rats, probably by maintaining the homeostasis of gut microbiota and regulating Th17/Treg balance and its related inflammatory factors.

Butyrate promotes visceral hypersensitivity in IBS model via mast cell-derived DRG neuron lincRNA-01028-PKC-TRPV1 pathway

Emerging evidence indicates that gut dysbiosis is involved in the pathogenesis of visceral hypersensitivity (VH). However, how gut microbiota contributes to the development of VH is unknown. Here, we sought to examine the signal transduction pathways from gut to dorsal root ganglion (DRG) responsible for this. Therefore, abdominal withdrawal reflex (AWR) scores, fecal output, fecal water content, and total gastrointestinal transit time (TGITT) were assessed in Con rats, VH rats, rats treated with NaB, and VH rats treated with VSL#3. Fecal microbiota and its metabolite (short-chain fatty acids, SCFAs), mast cell degranulation in colon, lincRNA-01028, miR-143, and protease kinase C (PKC) and TRPV1 expression in DRGs were further detected. VH rats showed an increased fecal water content, a shortened TGITT, an increased abundance of Clostridium sensu stricto 1 and increased butyrate in fecal samples, an increased mast cell degranulation, an increased expression of lincRNA-01028, PKC, and TRPV1, and a decreased expression of miR-143 in DRGs compared with control rats, which could be restored by the application of probiotic VSL#3. The above-mentioned detection in rats treated with butyrate was similar to that of VH rats. We further confirm whether butyrate sensitized DRG neurons by a lincRNA-01028, miR-143, and PKC-dependent mechanism via mast cell in vitro. In co-cultures, MCs treated with butyrate elicited a higher TRPV1 current, a higher expression of lincRNA-01028, PKC, and a lower expression of miR-143 in DRG neurons, which could be inhibited by a lincRNA-01028 inhibitor. These findings indicate that butyrate promotes visceral hypersensitivity via mast cell-derived DRG neuron lincRNA-01028-PKC-TRPV1 pathway.IMPORTANCEIrritable bowel syndrome (IBS), characterized by visceral hypersensitivity, is a common gastrointestinal dysfunction syndrome. Although the gut microbiota plays a role in the pathogenesis and treatment of irritable bowel syndrome (IBS), the possible underlying mechanisms are unclear. Therefore, it is of critical importance to determine the signal transduction pathways from gut to DRG responsible for this in vitro and in vivo assay. This study demonstrated that butyrate sensitized TRPV1 in DRG neurons via mast cells in vivo and in vitro by a lincRNA-01028, miR-143, and PKC-dependent mechanism. VH rats similarly showed an increased abundance of Clostridium sensu stricto 1, an increased fecal butyrate, an increased mast cell degranulation, and increased expression of TRPV1 compared with control rats, which could be restored by the application of VSL#3. In conclusion, butyrate produced by the altered intestinal microbiota is associated with increased VH.

Small intestinal bacterial overgrowth in diabetic gastroenteropathy

BACKGROUND

Although diabetic gastroenteropathy (DGE) is associated with small intestinal bacterial overgrowth (SIBO), most studies have evaluated SIBO with a hydrogen breath test, which may be affected by altered transit in DGE. The risk factors for the consequences of SIBO in DGE are poorly understood. We aimed to evaluate the prevalence of, risk factors for, and gastrointestinal symptoms associated with SIBO in patients with DGE.

METHODS

In 75 patients with DGE and dyspepsia, we tested for SIBO (≥105 colony forming units /mL of aerobic and/or anaerobic bacteria in a duodenal aspirate) and assessed gastric emptying (GE) of solids, symptoms during a GE study and during an enteral lipid challenge (300 kcal/2 h), and daily symptoms with a Gastroparesis Cardinal Symptom Index diary for 2 weeks. Symptoms and GE were compared in patients with versus without SIBO.

KEY RESULTS

Of 75 patients, 34 (45%) had SIBO, which was not associated with the use of proton pump inhibitors, daily symptoms, GE, or symptoms during a GE study. During enteral lipid challenge, severe nausea (p = 0.006), fullness (p = 0.02) and bloating (p = 0.009) were each associated with SIBO. Twenty patients (59%) with versus 13 (32%) without SIBO had at least one severe symptom during the lipid challenge (p = 0.006).

CONCLUSIONS & INFERENCES

Among patients with DGE 45% had SIBO, which was associated with symptoms during enteral lipid challenge but not with delayed GE, symptoms during a GE study, or daily symptoms. Perhaps bacterial products and even fatty acids are recognized by and activate mast cells that drive the increased lipid sensitivity in SIBO.

Antihyperalgesic properties of gut microbiota: Parabacteroides distasonis as a new probiotic strategy to alleviate chronic abdominal pain

ABSTRACT

The potential role of gut microbiota in pain modulation is arousing an emerging interest since recent years. This study investigated neuromodulatory properties of gut microbiota to identify next-generation probiotics to propose alternative therapies for visceral pain management. Neuromodulation ability of 10 bacterial strains isolated from a healthy donor was assessed both on ND7/23 immortalized cell line and primary neuronal cells from rat dorsal root ganglia. This screening highlighted the neuroinhibitory property of Parabacteroides distasonis (F1-2) strain, supported both by its intracellular content and membrane fraction, which was further investigated in visceral pain mouse models. Oral administration of F1-2 resulted in a significant decrease of colonic hypersensitivity (CHS) in dextran sulfate sodium (0.5%) model associated with low-grade inflammation and a significant decrease of CHS in Citrobacter rodentium postinfectious models. No effect of F1-2 oral administration on CHS was observed in a neonatal maternal separation stress model. Antihyperalgesic effect unlikely involved modulation of inflammatory processes or restoration of intestinal barrier. Exploration of direct dialogue mechanisms between this strain and nervous system, assessed by calcium imaging experiments, revealed that F1-2 interacts directly with nociceptors by reducing activation level on capsaicin, inflammatory soup, and bradykinin stimulations. Our study provides new insights about bacteria-host interaction and places P distasonis as a potential therapeutic strategy in the treatment of visceral pain observed in leaky gut-associated pathologies.

Gut microbiota and intestinal immunity-A crosstalk in irritable bowel syndrome

Irritable bowel syndrome (IBS), one of the most prevalent functional gastrointestinal disorders, is characterized by recurrent abdominal pain and abnormal defecation habits, resulting in a severe healthcare burden worldwide. The pathophysiological mechanisms of IBS are multi-factorially involved, including food antigens, visceral hypersensitivity reactions, and the brain-gut axis. Numerous studies have found that gut microbiota and intestinal mucosal immunity play an important role in the development of IBS in crosstalk with multiple mechanisms. Therefore, based on existing evidence, this paper elaborates that the damage and activation of intestinal mucosal immunity and the disturbance of gut microbiota are closely related to the progression of IBS. Combined with the application prospect, it also provides references for further in-depth exploration and clinical practice.

The gut microbiome in disorders of gut-brain interaction

Functional gastrointestinal disorders (FGIDs), chronic disorders characterized by either abdominal pain, altered intestinal motility, or their combination, have a worldwide prevalence of more than 40% and impose a high socioeconomic burden with a significant decline in quality of life. Recently, FGIDs have been reclassified as disorders of gut-brain interaction (DGBI), reflecting the key role of the gut-brain bidirectional communication in these disorders and their impact on psychological comorbidities. Although, during the past decades, the field of DGBIs has advanced significantly, the molecular mechanisms underlying DGBIs pathogenesis and pathophysiology, and the role of the gut microbiome in these processes are not fully understood. This review aims to discuss the latest body of literature on the complex microbiota-gut-brain interactions and their implications in the pathogenesis of DGBIs. A better understanding of the existing communication pathways between the gut microbiome and the brain holds promise in developing effective therapeutic interventions for DGBIs.

Apigenin attenuates visceral hypersensitivity in water avoidance stress rats by modulating the microbiota-gut-brain axis and inhibiting mast cell activation

Visceral hypersensitivity (VH) and gut microbiota dysbiosis significantly contribute to the occurrence and development of irritable bowel syndrome (IBS), exacerbated by stress. Apigenin, a natural flavonoid derived from plants, possesses a range of beneficial properties. However, additional research is necessary to investigate its potential in alleviating symptoms of IBS and elucidating its underlying mechanisms of action. Our study confirms that apigenin effectively reverses mast cell and microglial activation, regulates the composition and abundance of the gut microbiota, improves intestinal barrier function in rats induced with water-avoidance stress, and mitigates VH and colonic hypermotility. Furthermore, in vitro studies suggest a potential role of dysbiotic gut microbiota in activating mast cells at the cellular level. Notably, apigenin inhibits mast cell degranulation through the toll-like receptor 4 (TLR4) / myeloid differentiation primary response gene 88 (MyD88) / nuclear factor-kappa B (NF-κB) pathway. In conclusion, this study discusses the potential therapeutic effects of apigenin in alleviating VH and modulating the gut-brain axis in water-avoidance stress rats, providing a novel or alternative treatment approach for IBS.

IMOVNN: incomplete multi-omics data integration variational neural networks for gut microbiome disease prediction and biomarker identification

The gut microbiome has been regarded as one of the fundamental determinants regulating human health, and multi-omics data profiling has been increasingly utilized to bolster the deep understanding of this complex system. However, stemming from cost or other constraints, the integration of multi-omics often suffers from incomplete views, which poses a great challenge for the comprehensive analysis. In this work, a novel deep model named Incomplete Multi-Omics Variational Neural Networks (IMOVNN) is proposed for incomplete data integration, disease prediction application and biomarker identification. Benefiting from the information bottleneck and the marginal-to-joint distribution integration mechanism, the IMOVNN can learn the marginal latent representation of each individual omics and the joint latent representation for better disease prediction. Moreover, owing to the feature-selective layer predicated upon the concrete distribution, the model is interpretable and can identify the most relevant features. Experiments on inflammatory bowel disease multi-omics datasets demonstrate that our method outperforms several state-of-the-art methods for disease prediction. In addition, IMOVNN has identified significant biomarkers from multi-omics data sources.

Human milk oligosaccharides: potential therapeutic aids for allergic diseases

Childhood allergy, including asthma, eczema, and food allergies, is a major global health burden, with prevalence increasing dramatically and novel interventions needed. Emerging research suggests that human milk oligosaccharides (HMOs), complex glycans found in breastmilk, have allergy-protective properties, indicating exciting therapeutic potential. This review evaluates current literature on the role of HMOs in allergy, assesses underlying immunological mechanisms, and discusses future research needed to translate findings into clinical implications. HMOs may mediate allergy risk through multiple structure-specific mechanisms, including microbiome modification, intestinal barrier maturation, immunomodulation, and gene regulation. Findings emphasize the importance of breastfeeding encouragement and HMO-supplemented formula milk for high allergy-risk infants. Although further investigation is necessary to determine the most efficacious structures against varying allergy phenotypes and their long-term efficacy, HMOs may represent a promising complementary tool for childhood allergy prevention.

Histamine-producing bacteria and their role in gastrointestinal disorders

INTRODUCTION

Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine.

AREAS COVERED

This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023.

EXPERT OPINION

The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Role of CD34 in inflammatory bowel disease

Inflammatory bowel disease (IBD) is caused by a variety of pathogenic factors, including chronic recurrent inflammation of the ileum, rectum, and colon. Immune cells and adhesion molecules play an important role in the course of the disease, which is actually an autoimmune disease. During IBD, CD34 is involved in mediating the migration of a variety of immune cells (neutrophils, eosinophils, and mast cells) to the inflammatory site, and its interaction with various adhesion molecules is involved in the occurrence and development of IBD. Although the function of CD34 as a partial cell marker is well known, little is known on its role in IBD. Therefore, this article describes the structure and biological function of CD34, as well as on its potential mechanism in the development of IBD.

Diet-microbial cross-talk underlying increased visceral perception

Visceral hypersensitivity, a fundamental mechanism of chronic visceral pain disorders, can result from both central or peripheral factors, or their combination. As an important regulator of normal gut function, the gut microbiota has been implicated as a key peripheral factor in the pathophysiology of visceral hypersensitivity. Patients with chronic gastrointestinal disorders, such as irritable bowel syndrome, often present with abdominal pain secondary to adverse reactions to dietary components. As both long- and short-term diets are major determinants of gut microbiota configuration that can result in changes in microbial metabolic output, it is becoming increasingly recognized that diet-microbiota interactions play an important role in the genesis of visceral sensitivity. Changes in pain signaling may occur via diet-induced changes in secretion of mediators by both the microbiota and/or host cells. This review will examine the peripheral influence of diet-microbiota interactions underlying increased visceral sensitivity.

Multi-omics for biomarker approaches in the diagnostic evaluation and management of abdominal pain and irritable bowel syndrome: what lies ahead

Reliable biomarkers for common disorders of gut-brain interaction characterized by abdominal pain, including irritable bowel syndrome (IBS), are critically needed to enhance care and develop individualized therapies. The dynamic and heterogeneous nature of the pathophysiological mechanisms that underlie visceral hypersensitivity have challenged successful biomarker development. Consequently, effective therapies for pain in IBS are lacking. However, recent advances in modern omics technologies offer new opportunities to acquire deep biological insights into mechanisms of pain and nociception. Newer methods for large-scale data integration of complementary omics approaches have further expanded our ability to build a holistic understanding of complex biological networks and their co-contributions to abdominal pain. Here, we review the mechanisms of visceral hypersensitivity, focusing on IBS. We discuss candidate biomarkers for pain in IBS identified through single omics studies and summarize emerging multi-omics approaches for developing novel biomarkers that may transform clinical care for patients with IBS and abdominal pain.