Stem Cells in the Intestine: Possible Roles in Pathogenesis of Irritable Bowel Syndrome

Environmentally relevant concentrations of benzophenones exposure disrupt intestinal homeostasis, impair the intestinal barrier, and induce inflammation in mice

The aim of this study is to investigate the adverse effects of benzophenones (BPs) on the intestinal tract of mice and the potential mechanism. F1-generation ICR mice were exposed to BPs (benzophenone-1, benzophenone-2, and benzophenone-3) by breastfeeding from birth until weaning, and by drinking water after weaning until maturity. The offspring mice were executed on postnatal day 56, then their distal colons were sampled. AB-PAS staining, HE staining, immunofluorescence, Transmission Electron Microscope, immunohistochemistry, Western Blot and RT-qPCR were used to study the effects of BPs exposure on the colonic tissues of offspring mice. The results showed that colonic microvilli appeared significantly deficient in the high-dose group, and the expression of tight junction markers Zo-1 and Occludin was significantly down-regulated and the number of goblet cells and secretions were reduced in all dose groups, and the expression of secretory cell markers MUC2 and KI67 were decreased, as well as the expression of intestinal stem cell markers Lgr5 and Bmi1, suggesting that BPs exposure caused disruption of intestinal barrier and imbalance in the composition of the intestinal stem cell pool. Besides, the expression of cellular inflammatory factors such as macrophage marker F4/80 and tumor necrosis factor TNF-α was elevated in the colonic tissues of all dose groups, and the inflammatory infiltration was observed, which means the exposure of BPs caused inflammatory effects in the intestinal tract of F1-generation mice. In addition, the contents of Notch/Wnt signaling pathway-related genes, such as Dll-4, Notch1, Hes1, Ctnnb1and Sfrp2 were significantly decreased in each high-dose group (P < 0.05), suggesting that BPs may inhibit the regulation of Notch/Wnt signaling pathway. In conclusion, exposure to BPs was able to imbalance colonic homeostasis, disrupt the intestinal barrier, and trigger inflammation in the offspring mice, which might be realized through interfering with the Notch/Wnt signaling pathway.

Genetics of irritable bowel syndrome: shifting gear via biobank-scale studies

The pathophysiology of irritable bowel syndrome (IBS) is multifactorial and probably involves genetic predisposition and the effect of environmental factors. Unlike other gastrointestinal diseases with a heritable component, genetic research in IBS has been scarce and mostly characterized by small underpowered studies, leading to inconclusive results. The availability of genomic and health-related data from large international cohorts and population-based biobanks offers unprecedented opportunities for long-awaited, well-powered genetic studies in IBS. This Review focuses on the latest advances that provide compelling evidence for the importance of genes involved in the digestion of carbohydrates, ion channel function, neurotransmitters and their receptors, neuronal pathways and the control of gut motility. These discoveries have generated novel information that might be further refined for the identification of predisposed individuals and selection of management strategies for patients. This Review presents a conceptual framework, the advantages and potential limitations of modern genetic research in IBS, and a summary of available evidence.

Role of IL-22 in intestinal microenvironment and potential targeted therapy through diet

IL-22 is a type 2 receptor cytokine in IL-10 family. IL-22 is usually secreted by innate and adaptive immune cells and takes its effects on non-hematopoietic cells. Through activate STAT3 pathway, IL-22 plays an important role in infection clearance and tissue regeneration, which is critical for barrier integrate and homeostasis. Abnormal activation of IL-22 signal was observed in inflammation diseases, autoimmune diseases, and cancers. We review the recent discoveries about the mechanism and regulation of IL-22 signal pathway from the perspective of intestinal micro-environment. Diet-based IL-22 target therapeutic strategies and their potential clinical significance will also be discussed.

Bisphenol chemicals disturb intestinal homeostasis via Notch/Wnt signaling and induce mucosal barrier dysregulation and inflammation

Emerging evidence has shown that bisphenol A (BPA) can exert adverse effects on intestinal barrier in rodents, but little is known about its underlying mechanisms. We previously found BPA and its substitute bisphenol F (BPF) disrupted Notch signaling and altered intestinal histological structures in Xenopus laevis tadpoles. The present study aimed to determine whether BPA and BPF could affect intestinal homeostasis via Notch/Wnt signaling and induce intestinal barrier dysregulation in adult mammals, given the fundamental roles of the two conserved signaling pathways in intestinal homeostasis and regulation of intestinal barrier. We found that following 7-day administration with BPA or BPF through drinking water at the reference dose of 50 μg/kg/d and no observed adverse effect level of 5 mg/kg/d (NOAEL) of BPA, adult male mice displayed no alterations at histological and cellular levels in colons, but high dose of both BPA and BPF downregulated the expression of Notch- and Wnt-related genes as well as key genes responsible for intestinal homeostasis. When administration was extended to 14 days, all treatments significantly suppressed the expression of all tested Notch- and Wnt-related genes; correspondingly, administrated colons exhibited downregulated expression of key genes responsible for intestinal homeostasis and reduced cell proliferation in crypts. Importantly, all treatments suppressed secretory cell differentiation, reduced mucin protein levels and downregulated expression of tight junction markers, implicating mucosal barrier dysregulation. Furthermore, inflammatory cell infiltration and upregulated expression of inflammatory cytokine genes in colons, coupled with increased serum inflammatory cytokine levels, were observed in all treatments. All results show that both BPA and BPF at the reference dose disrupted Notch/Wnt signaling and intestinal homeostasis, thereby leading to mucosal barrier dysregulation and intestinal inflammation in mice. This is the first study revealing the adverse influences of BPF on mammal intestines and underlying mechanisms for bisphenol-caused intestinal injury.

The relationship between hidradenitis suppurativa and irritable bowel syndrome: a cross-sectional study

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which one experiences abdominal pain, tension, cramping, bloating, and changes in the form and frequency of defecation, without an underlying organic disease. Many skin diseases have been reported to be more common in people with functional bowel disease. To our knowledge, however, no previous study investigated the potential relationship between hidradenitis suppurativa (HS) and IBS. In this study, we aimed to examine the potential association between IBS and HS.

METHODS

Patients with HS and healthy subjects were enrolled in this cross-sectional study. All participants were assessed for the presence of IBS. ROME IV criteria were used to identify IBS cases. Hurley staging, modified Sartorius score, and physician's global assessment score were applied to define clinical severity and staging of HS.

RESULTS

According to the Rome IV diagnostic criteria, 54 (67.50%) of 80 HS patients and 23 (28.75%) of 80 control group were diagnosed with IBS. The frequency of IBS was statistically significantly higher in the patient group than in the control group (P < 0.001). No statistically significant difference was found between the two groups in terms of abnormal stool frequency and family history of IBS (P = 0.28, P = 0.862, respectively). Abnormal stool form, mucus in stool, abdominal distension, feeling of incomplete evacuation were statistically significantly higher in HS patients compared to the controls (P = 0.01, P = 0.02, P < 0.001, P = 0.001, respectively).

STW 5 Herbal Preparation Modulates Wnt3a and Claudin 1 Gene Expression in Zebrafish IBS-like Model

AIM

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by chronic abdominal pain and stool irregularities. STW 5 has proven clinical efficacy in functional gastrointestinal disorders, including IBS, targeting pathways that suppress inflammation and protect the mucosa. Wnt signaling is known to modulate NF-kβ-dependent inflammatory cytokine production. This sparked the idea of evaluating the impact of STW 5 on the expression of inflammatory-response and Wnt/β catenin-target genes in an IBS-like model.

MAIN METHODS

We used zebrafish and dextran sodium sulfate (DSS) treatment to model IBS-like conditions in vivo and in vitro and examined the effects of subsequent STW 5 treatment on the intestines of DSS-treated fish and primary cultured intestinal and neuronal cells. Gross gut anatomy, histology, and the expression of Wnt-signaling and cytokine genes were analyzed in treated animals and/or cells, and in controls.

KEY FINDINGS

DSS treatment up-regulated the expression of interleukin-8, tumor necrosis factor-α, wnt3a, and claudin-1 in explanted zebrafish gut. Subsequent STW 5 treatment abolished both the macroscopic signs of gut inflammation, DSS-induced mucosecretory phenotype, and normalized the DSS-induced upregulated expression of il10 and Wnt signaling genes, such as wnt3a and cldn1 in explanted zebrafish gut. Under inflammatory conditions, STW 5 downregulated the expression of the pro-inflammatory cytokine genes il1β, il6, il8, and tnfα while it upregulated the expression of the anti-inflammatory genes il10 and wnt3a in enteric neuronal cells in vitro.

SIGNIFICANCE

Wnt signaling could be a novel target for the anti-inflammatory and intestinal permeability-restoring effects of STW 5, possibly explaining its clinical efficacy in IBS.

Dietary modulation of gut microbiota for the relief of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a frequently diagnosed gastrointestinal (GI) disorder characterized by recurrent abdominal pain, bloating, and changes in the stool form or frequency without any structural changes and overt inflammation. It is not a life-threatening condition but causes a considerable level of discomfort and distress. Among the many pathophysiologic factors, such as altered GI motility, visceral hypersensitivity, and low-grade mucosal inflammation, as well as other immunologic, psychologic, and genetic factors, gut microbiota imbalance (dysbiosis), which is frequently found in IBS, has been highlighted as an etiology of IBS. Dysbiosis may affect gut mucosal homeostasis, immune function, metabolic regulation, and even visceral motor function. As diet is shown to play a fundamental role in the gut microbiota profile, this review discusses the influence of diet on IBS occurring through the modulation of gut microbiota. Based on previous studies, it appears that dietary modulation of the gut microbiota may be effective for the alleviation of IBS symptoms and, also an effective IBS management strategy based on the underlying mechanism; especially because, IBS currently has no specific treatment owing to its uncertain etiology.

Gut microbiota composition and functional prediction in diarrhea-predominant irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is common and difficult to treat and its pathogenesis is closely related to gut microbiota. However, differences in gut microbiota of patients in different regions make it more difficult to elucidate the mechanism of IBS. We performed an analysis of gut microbiota composition and functional prediction in Chinese patients with diarrhea-predominant IBS (IBS-D).

METHODS

Fecal samples were obtained from 30 IBS-D patients and 30 healthy controls (HCs) in Nanchang, China. Using 16S gene sequence profiles, we analyzed the abundance of dominant microbiota at different taxonomy levels. Based on 16S information, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to predicting the function of gut microbiota.

RESULTS

Compared to HCs, gut microbiota richness but not diversity was decreased in IBS-D patients. The abundant phyla Firmicutes, Fusobacteria and Actinobacteria decreased significantly, and Proteobacteria increased significantly in IBS-D patients. PICRUSt indicated that function expression of gut microbiota in IBS-D patients was up-regulated in metabolism of cofactors and vitamins, xenobiotics biodegradation and metabolism, and down-regulated in environmental adaptation, cell growth and death.

CONCLUSIONS

Compared with the normal population in China, IBS-D patients are characterized by complex and unstable gut microbiota, which may influence inflammation and metabolism of the host.

Effect of Listeria monocytogenes on intestinal stem cells in the co-culture model of small intestinal organoids

Listeria monocytogenes is a foodborne pathogen that causes systemic infections by crossing the intestinal barrier. However, in vitro analysis of the interaction of L. monocytogenes and small intestinal epithelium has yet to be fully elucidated. To study host responses from intestinal epithelium during L. monocytogenes infection, we used the co-culture model of small intestinal organoids and L. monocytogenes. Results showed that L. monocytogenes mediated damage to intestinal epithelium, especially intestinal stem cells. L. monocytogenes was found to reduce budding rate and increase mortality of organoids. Moreover, it affected the proliferation of epithelial cells and numbers of secretory cells. In addition, it was demonstrated that L. monocytogenes stimulated a reduction in the number of Lgr5+ stem cells. Furthermore, L. monocytogenes affected the expression of Hes1, Math1 and Sox9 to interfere with the differentiation of intestinal stem cells. Collectively, our findings reveal the effects of L. monocytogenes infection on intestinal stem cells and demonstrate that small intestinal organoid is a suitable experimental model for studying intestinal epithelium-pathogen interactions.

Enterochromaffin cell hyperplasia in the gut: Factors, mechanism and therapeutic clues

Enterochromaffin (EC) cell is the main cell type that responsible for 5-hydroxytryptamine (5-HT) synthesis, storage and release of the gut. Intestinal 5-HT play a key role in visceral sensation, intestinal motility and permeability, EC cell hyperplasia and increased 5-HT bioavailability in the gut have been found to be involved in the symptoms generation of irritable bowel syndrome and inflammatory bowel disease. EC cells originate from intestinal stem cells, the interaction between proliferation and differentiation signals on intestinal stem cells enable EC cell number to be regulated in a normal level. This review focuses on the impact factors, pathogenesis mechanisms, and therapeutic clues for intestinal EC cells hyperplasia, and showed that EC cell hyperplasia was observed under the condition of physiological stress, intestinal infection or intestinal inflammation, the disordered proliferation and/or differentiation of intestinal stem cells as well as their progenitor cells all contribute to the pathogenesis of intestinal EC cell hyperplasia. The altered intestinal niche, i.e. increased corticotrophin releasing factor (CRF) signal, elevated nerve growth factor (NGF) signal, and Th2-dominant cytokines production, has been found to have close correlation with intestinal EC cell hyperplasia. Currently, CRF receptor antagonist, nuclear factor-κB inhibitor, and NGF receptor neutralizing antibody have been proved useful to attenuate intestinal EC cell hyperplasia, which may provide a promising clue for the therapeutic strategy in EC cell hyperplasia related diseases.

Effect of moxibustion on the expression of GDNF and its receptor GFRα3 in the colon and spinal cord of rats with irritable bowel syndrome

BACKGROUND

Moxibustion treatment has been found to ameliorate clinical symptoms including abdominal pain, diarrhoea and constipation in patients with irritable bowel syndrome (IBS). Herein we investigated the mechanisms underlying the use of moxibustion in a rat model of IBS.

METHODS

In our study, an IBS model was established in rats by colorectal distension (CRD) stimulus and mustard oil enema. The rats were randomly divided into a normal group, model group, mild moxibustion group, electroacupuncture group, probiotic group and dicetel group. Abdominal withdrawal reflex (AWR) scores were determined within 90 min of the last treatment. The expression of GDNF/GFRα3 protein and mRNA in the colon and spinal cord were detected by immunohistochemistry and quantitative real-time-PCR, respectively.

RESULTS

The IBS model rats had significantly higher AWR scores than the normal group (P<0.01). After mild moxibustion treatment, the AWR score was significantly reduced (20 mm Hg, P<0.05; 40 mm Hg, 60 mm Hg and 80 mm Hg, P<0.01). The model group showed significantly more colonic glial cell line-derived neurotrophic factor (GDNF/GFRα3 (GDNF family receptor α3) protein and mRNA expression in the colon and spinal cord than the normal group (P<0.01). Compared with the model group, the expression of GDNF/GFRα3 protein and mRNA in the colon and spinal cord of the rats were significantly decreased in the mild moxibustion group (colon: GDNF and GFRα3 protein, P<0.01; GDNF and GFRα3 mRNA, P<0.01; spinal cord: GDNF and GFRα3 protein, P<0.01; GDNF mRNA, P<0.05, GFRα3 mRNA, P<0.01).

CONCLUSIONS

Our data suggest that moxibustion therapy may mitigate CRD-induced increases in the expression of GDNF and its receptor GFRα3 in the colon and spinal cord in a rat model of IBS.

Progress in understanding relationship between bile acid metabolic disorder and gut diseases

There are a large number of microorganisms in the human intestine, which rely on the nutrition in the digestive tract to survive. At the same time, they affect the intestinal neuro-immune function through the metabolism substances produced by themselves. The enteric neuro-immune system regulates the functions of digestion and absorption so as to maintain the homeostasis in the intestine. Intestinal bile acid metabolism disorder might induce gut dysfunction or intestinal immune imbalance. This review describes the effect of intestinal microbes on the enteric nervous system or other signal molecules of the bile acid pathway linked to some intestinal disorders, with an aim to provide a theoretical basis for clinical treatment of the related diseases.

Gut microbiota was modulated by moxibustion stimulation in rats with irritable bowel syndrome

Background

The pathogenesis of irritable bowel syndrome (IBS) is closely related to intestinal dysbacteriosis and can be controlled by moxibustion treatment. However, the mechanism underlying the therapeutic value of moxibustion in IBS treatment remains unknown.

Methods

An IBS rat model was established by colorectal distention (CRD) stimulus and mustard oil clyster. Sixty-five male rats were randomly divided into six groups: normal, IBS model, moxibustion, electroacupuncture (EA), Bifid-triple Viable Capsule (BTVC) and Pinaverium Bromide (PB) groups. The moxibustion group was treated with mild moxibustion at the bilateral Tianshu (ST25) and Shangjuxu (ST37) for 10 min/day for 7 days, the EA group was given EA at ST25 and ST37 once daily for 7 days, while the BTVC group and PB groups received Bifid-triple Viable Capsule and Pinaverium Bromide solution (at the proportion of 1:0.018) respectively by gavage once daily for 7 days. After the treatment, abdominal withdrawal reflex (AWR) scores were determined based on CRD stimulus, gut microbiota profiling was conducted by 16S rRNA high-throughput sequencing.

Results

Irritable bowel syndrome model rats had significantly increased AWR scores at all intensities (20, 40, 60 and 80 mmHg) compared with the normal group. Moxibustion treatment significantly reduced AWR scores compared with the IBS model group at all intensities. Across all groups the most abundant phyla were Bacteroidetes and Firmicutes followed by Proteobacteria and Candidatus Saccharibacteria. At genus level IBS model rats had a higher abundance of Prevotella, Bacteroides and Clostridium XI and a lower abundance of Lactobacillus and Clostridium XIVa compared with normal rats. These changes in microbiota profiles could however be reversed by moxibustion treatment. Alpha diversity was decreased in IBS model rats compared with normal rats, yet significantly increased in moxibustion- and PB-treated rats compared with IBS rats.

Conclusion

Our findings suggest that moxibustion treats IBS by modulating the gut microbiota.

Small Maf functions in the maintenance of germline stem cells in the Drosophila testis

Reactive oxygen species (ROS) are byproducts generated during normal cellular metabolism, and redox states have been shown to influence stem cell self-renewal and lineage commitment across phyla. However, the downstream effectors of ROS signaling that control stem cell behavior remain largely unexplored. Here, we used the Drosophila testis as an in vivo model to identify ROS-induced effectors that are involved in the differentiation process of germline stem cells (GSCs). In the Affymetrix microarray analysis, 152 genes were either upregulated or downregulated during GSC differentiation induced by elevated levels of ROS, and a follow-up validation of the gene expression by qRT-PCR showed a Spearman's rho of 0.9173 (P<0.0001). Notably, 47 (31%) of the identified genes had no predicted molecular function or recognizable protein domain. These suggest the robustness of this microarray analysis, which identified many uncharacterized genes, possibly with an essential role in ROS-induced GSC differentiation. We also showed that maf-S is transcriptionally downregulated by oxidative stress, and that maf-S knockdown promotes GSC differentiation but Maf-S overexpression conversely results in an over-growth of GSC-like cells by promoting the mitotic activity of germ cell lineage. Together with the facts that Maf-S regulates ROS levels and genetically interacts with Keap1/Nrf2 in GSC maintenance, our study suggests that Maf-S plays an important role in the Drosophila testis GSC maintenance by participating in the regulation of redox homeostasis.

Applications of Fuzi Lizhong decoction in digestive system diseases

Fuzi Lizhong decoction came from "Treatise on Three Categories of Pathogenic Factors", and it can nourish the spleen and stomach and treat middle Jiao deficiency or Yang deficiency of the spleen and kidney. Although Fuzi Lizhong decoction is famous for warming middle Jiao to dispel cold, it was rarely used alone to treat digestive system diseases. Modern physicians often combine Fuzi Lizhong decoction with traditional Chinese medicine or Western medicine to treat digestive system diseases, such as irritable bowel syndrome, drug-induced liver injury, chronic gastritis, ulcerative colitis, functional dyspepsia, chronic diarrhea and so on, with significant effects observed. This reflects the philosophy of treatment based on syndrome differentiation and same treatment for different diseases for traditional Chinese medicine. We recommend that in future research and clinical applications, Fuzi Lizhong decoction should be combined with emotional therapy based on the experience of traditional Chinese medicine to better exploit the unique advantages of traditional Chinese medicine in the treatment of digestive diseases.