Regulation of Intestinal Stem Cell Stemness by the Aryl Hydrocarbon Receptor and Its Ligands

Chlorpyrifos Inhibits Intestinal Stem Cell Proliferation and Differentiation at the Acceptable Daily Intake and Disrupts Immune Responses at High Doses

The acceptable daily intake (ADI) and maximum residue limits in food for chlorpyrifos (CPF), a widely used organophosphorus pesticide, may damage the intestine. Here, we evaluated damage to the intestine by CPF at the ADI (0.01 mg/kg bodyweight/day) and at 10 times the ADI (10ADI; 0.1 mg/kg bodyweight/day) in mice after 8 weeks of exposure and evaluated the resulting immune response to an enterotoxigenic Escherichia coli (ETEC) infection. CPF at the ADI dose significantly disrupted the intestinal integrity and intestinal stem cell functionality, which may be associated with reduced indole-3-propionic acid levels. However, mice in the 10ADI group exhibited only elevated pro-inflammatory cell and cytokine levels. During ETEC infection, intestinal mucosal immunity was activated by the 10ADI dose, as indicated by increased regulatory T cells and IL-10 levels, which were associated with decreased fecal butyric acid content. Our study demonstrated that the effects of pesticide residues appear to be dose-specific, bringing attention to the health risk at the ADI level.

Integration of Multi-Omics and Network Pharmacology Analysis Reveals the Mechanism of Qingchang Huashi Jianpi Bushen Formula in Repairing the Epithelial Barrier of Ulcerative Colitis

Purpose

Derivation of Qingchang Huashi formula, named Qingchang Huashi Jianpi Bushen (QCHS_JPBS) formula, has shown significant therapeutic effect on patients with ulcerative colitis (UC). In this study, the potential mechanism of QCHS_JPBS formula in repairing mucosal damage was explored from the perspective of intestinal stem cell (ISCs) differentiation, and potential targets of the QCHS_JPBS formula to improve UC were predicted using network pharmacology analysis.

Methods

The therapeutic efficacy of QCHS_JPBS formula was evaluated in a mouse model of 2.5% dextran sulfate sodium (DSS) induced colitis. The effect of this formula on the ISC differentiation was evaluated using tissue transmission electron microscopy, immunofluorescence, and RT-qPCR. The cecal contents were subjected to 16s RNA sequencing analysis and non-target metabolomics analysis using LC-MS/MS. The fecal microbiota transplantation method verified the essential role of gut microbiota in promoting ISC differentiation and repairing mucosal damage.

Results

The results indicated that QCHS_JPBS formula suppressed the inflammatory response and repaired the damaged intestinal epithelial barrier in DSS-induced colitis mice. QCHS_JPBS formula promoted ISC differentiation, particularly in the direction of goblet cells. QCHS_JPBS formula restored gut dysbiosis and regulated metabolic disorders in DSS-induced colitis mice. And then, the results of fecal microbiota transplantation indicated that QCHS_JPBS formula promoted differentiation of intestinal stem cells to repair mucosal damage through gut microbiota. Finally, a total of 79 active ingredients of QCHS_JPBS formula were identified based on LC-MS analysis and EGFR, STAT3, SRC, AKT1, and HSP90AA1 were considered as potential therapeutic UC targets of QCHS_JPBS formula based on network pharmacology analysis.

Conclusion

The present study demonstrated that QCHS_JPBS formula promoted the differentiation of ISCs through gut microbiota to repair the damaged intestinal epithelial barrier in UC mice.

Drosophila AHR limits tumor growth and stem cell proliferation in the intestine

Background

The aryl hydrocarbon receptor (AHR) plays important roles in intestinal homeostasis, limiting tumour growth and promoting differentiation in the intestinal epithelium. Spineless, the Drosophila homolog of AHR, has only been studied in the context of development but not in the adult intestine.

Methods

The role of Spineless in the Drosophila midgut was studied by overexpression or inactivation of Spineless in infection and tumour models and RNA sequencing of sorted midgut progenitor cells.

Results

We show that spineless is upregulated in the adult intestinal epithelium after infection with Pseudomonas entomophila ( P. e.). Spineless inactivation increased stem cell proliferation following infection-induced injury. Spineless overexpression limited intestinal stem cell proliferation and reduced survival after infection. In two tumour models, using either Notch RNAi or constitutively active Yorkie, Spineless suppressed tumour growth and doubled the lifespan of tumour-bearing flies. At the transcriptional level it reversed the gene expression changes induced in Yorkie tumours, counteracting cell proliferation and altered metabolism.

Conclusions

These findings demonstrate a new role for Spineless in the adult Drosophila midgut and highlight the evolutionarily conserved functions of AHR/Spineless in the control of proliferation and differentiation of the intestinal epithelium.

Aryl Hydrocarbon Receptor (AHR) Suppresses Arsenic (As3+)-Induced Malignant Transformation by Antagonizing TOX Expression

Environmental arsenic (As³⁺) exposure poses a significant public health concern due to its carcinogenic potential. Our previous research suggests that As³⁺-induced carcinogenesis is mediated by inhibition of the aryl hydrocarbon receptor (AHR). However, the precise role of AHR in As³⁺-induced malignant transformation as well as cancer stem-like cell (CSC) formation, along with its underlying mechanisms, remains unclear. In this study, we used BEAS-2B cells with CRISPR-Cas9 gene editing, RNA sequencing, and immunoprecipitation to examine AHR's role in As³⁺-induced CSC development. Our findings reveal that AHR suppresses CSC formation triggered by low-dose As³⁺ (0.5 μM) via transcriptional repression of TOX, a high mobility group box DNA binding protein that play a critical role in T cell exhaustion within tumor immunology. TOX knockdown inhibited CSC formation, while its overexpression enhanced cMYC, a CSC-associated transcription factor. TOX interactome analysis identified associations with proteins such as KCTD10, TRIM21, HMGA1, FLOT1, and FLOT2, which may regulate TOX's stability and activity. Enrichment analyses highlighted their involvement in cancer-related pathways, supporting the role of TOX in promoting CSC formation during As³⁺-induced carcinogenesis. Notably, this study identifies TOX as an oncogenic factor in non-immunological contexts and underscores AHR's tumor-suppressive function through TOX repression, offering novel insights into the mechanisms underlying As³⁺-induced carcinogenesis.

Mulberry Leaf-Derived Morin Activates β-Catenin by Binding to Frizzled7 to Promote Intestinal Stem Cell Expansion upon Heat-Stable Enterotoxin b Injury

Intestinal stem cells (ISCs) sustain epithelial renewal by dynamically altering behaviors of proliferation and differentiation in response to various nutrition and stress inputs. However, how ISCs integrate bioactive substance morin cues to protect against heat-stable enterotoxin b (STb) produced by Escherichia coli remains an uncertain question with implications for treating bacterial diarrhea. Our recent work showed that oral mulberry leaf-derived morin improved the growth performance in STb-challenged mice. Furthermore, morin supplementation reinstated the impaired small-intestinal epithelial structure and barrier function by stimulating ISC proliferation and differentiation as well as supporting intestinal organoid expansion ex vivo. Importantly, the Wnt/β-catenin pathway, an ISC fate commitment signal, was reactivated by morin to restore the jejunal crypt-villus architecture in response to STb stimulation. Mechanically, the extracellular morin-initiated β-catenin axis is dependent or partially dependent on the Wnt membrane receptor Frizzled7 (FZD7). Our data reveal an unexpected role of leaf-derived morin, which represents molecular signaling targeting the FZD7 platform instrumental for controlling ISC regeneration upon STb injury.

Lactobacillus rhamnosus GG Stimulates Dietary Tryptophan-Dependent Production of Barrier-Protecting Methylnicotinamide

BACKGROUND & AIMS

Lacticaseibacillus rhamnosus GG (LGG) is the world's most consumed probiotic but its mechanism of action on intestinal permeability and differentiation along with its interactions with an essential source of signaling metabolites, dietary tryptophan (trp), are unclear.

METHODS

Untargeted metabolomic and transcriptomic analyses were performed in LGG monocolonized germ-free mice fed trp-free or -sufficient diets. LGG-derived metabolites were profiled in vitro under anaerobic and aerobic conditions. Multiomic correlations using a newly developed algorithm discovered novel metabolites tightly linked to tight junction and cell differentiation genes whose abundances were regulated by LGG and dietary trp. Barrier-modulation by these metabolites were functionally tested in Caco2 cells, mouse enteroids, and dextran sulfate sodium experimental colitis. The contribution of these metabolites to barrier protection is delineated at specific tight junction proteins and enterocyte-promoting factors with gain and loss of function approaches.

RESULTS

LGG, strictly with dietary trp, promotes the enterocyte program and expression of tight junction genes, particularly Ocln. Functional evaluations of fecal and serum metabolites synergistically stimulated by LGG and trp revealed a novel vitamin B3 metabolism pathway, with methylnicotinamide (MNA) unexpectedly being the most robust barrier-protective metabolite in vitro and in vivo. Reduced serum MNA is significantly associated with increased disease activity in patients with inflammatory bowel disease. Exogenous MNA enhances gut barrier in homeostasis and robustly promotes colonic healing in dextran sulfate sodium colitis. MNA is sufficient to promote intestinal epithelial Ocln and RNF43, a master inhibitor of Wnt. Blocking trp or vitamin B3 absorption abolishes barrier recovery in vivo.

CONCLUSIONS

Our study uncovers a novel LGG-regulated dietary trp-dependent production of MNA that protects the gut barrier against colitis.

Regulation Mechanism and Potential Value of Active Substances in Spices in Alcohol-Liver-Intestine Axis Health

Excessive alcohol intake will aggravate the health risk between the liver and intestine and affect the multi-directional information exchange of metabolites between host cells and microbial communities. Because of the side effects of clinical drugs, people tend to explore the intervention value of natural drugs on diseases. As a flavor substance, spices have been proven to have medicinal value, but they are still rare in treating hepatointestinal diseases caused by alcohol. This paper summarized the metabolic transformation of alcohol in the liver and intestine and summarized the potential value of various perfume active substances in improving liver and intestine diseases caused by alcohol. It is also found that bioactive substances in spices can exert antioxidant activity in the liver and intestine environment and reduce the oxidative stress caused by diseases. These substances can interfere with fatty acid synthesis, promote sugar and lipid metabolism, and reduce liver injury caused by steatosis. They can effectively regulate the balance of intestinal flora, promote the production of SCFAs, and restore the intestinal microenvironment.

Synbiotic Combination between Lactobacillus paracasei VL8 and Mannan-Oligosaccharide Repairs the Intestinal Barrier in the Dextran Sulfate Sodium-Induced Colitis Model by Regulating the Intestinal Stem Cell Niche

Previously, Lactobacillus paracasei VL8, a lactobacillus strain isolated from the traditional Finnish fermented dairy product Viili, demonstrated immunomodulatory and antibacterial effects. The prebiotic mannan-oligosaccharide (MOS) further promoted its antibacterial activity and growth performance, holding promise for maintaining intestinal health. However, this has not been verified in vivo. In this study, we elucidated the process by which L. paracasei VL8 and its synbiotc combination (SYN) with MOS repair the intestinal barrier function in dextran sodium sulfate (DSS)-induced colitis mice. SYN surpasses VL8 or MOS alone in restoring goblet cells and improving the tight junction structure. Omics analysis on gut microbiota reveals SYN's ability to restore Lactobacillus spp. abundance and promote tryptophan metabolism. SYN intervention also inhibits the DSS-induced hyperactivation of the Wnt/β-catenin pathway. Tryptophan metabolites from Lactobacillus induce intestinal organoid differentiation. Co-housing experiments confirm microbiota transferability, replicating intestinal barrier repair. In conclusion, our study highlights the potential therapeutic efficacy of the synbiotic combination of Lactobacillus paracasei VL8 and MOS in restoring the damaged intestinal barrier and offers new insights into the complex crosstalk between the gut microbiota and intestinal stem cells.

Microbiota-derived tryptophan metabolites indole-3-lactic acid is associated with intestinal ischemia/reperfusion injury via positive regulation of YAP and Nrf2

BACKGROUND

Lactobacillus has been demonstrated to serve a protective role in intestinal injury. However, the relationship between Lactobacillus murinus (L. murinus)-derived tryptophan metabolites and intestinal ischemia/reperfusion (I/R) injury yet to be investigated. This study aimed to evaluate the role of L. murinus-derived tryptophan metabolites in intestinal I/R injury and the underlying molecular mechanism.

METHODS

Liquid chromatograph mass spectrometry analysis was used to measure the fecal content of tryptophan metabolites in mice undergoing intestinal I/R injury and in patients undergoing cardiopulmonary bypass (CPB) surgery. Immunofluorescence, quantitative RT-PCR, Western blot, and ELISA were performed to explore the inflammation protective mechanism of tryptophan metabolites in WT and Nrf2-deficient mice undergoing intestinal I/R, hypoxia-reoxygenation (H/R) induced intestinal organoids.

RESULTS

By comparing the fecal contents of three L. murinus-derived tryptophan metabolites in mice undergoing intestinal I/R injury and in patients undergoing cardiopulmonary bypass (CPB) surgery. We found that the high abundance of indole-3-lactic acid (ILA) in the preoperative feces was associated with better postoperative intestinal function, as evidenced by the correlation of fecal metabolites with postoperative gastrointestinal function, serum I-FABP and D-Lactate levels. Furthermore, ILA administration improved epithelial cell damage, accelerated the proliferation of intestinal stem cells, and alleviated the oxidative stress of epithelial cells. Mechanistically, ILA improved the expression of Yes Associated Protein (YAP) and Nuclear Factor erythroid 2-Related Factor 2 (Nrf2) after intestinal I/R. The YAP inhibitor verteporfin (VP) reversed the anti-inflammatory effect of ILA, both in vivo and in vitro. Additionally, we found that ILA failed to protect epithelial cells from oxidative stress in Nrf2 knockout mice under I/R injury.

CONCLUSIONS

The content of tryptophan metabolite ILA in the preoperative feces of patients is negatively correlated with intestinal function damage under CPB surgery. Administration of ILA alleviates intestinal I/R injury via the regulation of YAP and Nrf2. This study revealed a novel therapeutic metabolite and promising candidate targets for intestinal I/R injury treatment.

Transcriptional Regulation of Math1 by Aryl Hydrocarbon Receptor: Effect on Math1+ Progenitor Cells in Mouse Small Intestine

The physiological roles of aryl hydrocarbon receptor (AhR) in the small intestine have been revealed as immunomodulatory and barrier functions. However, its contributions to cell fate regulation are incompletely understood. The Notch-activated signaling cascade is a central component of intestinal cell fate determinations. The lateral inhibitory mechanism governed by Notch directs cell fates toward distinct cell lineages (i.e., absorptive and secretory cell lineages) through its downstream effector, mouse atonal homolog 1 (MATH1). An investigation employing cell lines and intestinal crypt cells revealed that AhR regulates Math1 expression in a xenobiotic response element (XRE)-dependent manner. The AhR-Math1 axis was further addressed using intestinal organoids, where AhR-Math1 and HES1-Math1 axes appeared to coexist within the underlying Math1 transcriptional machinery. When the HES1-Math1 axis was pharmacologically suppressed, β-naphthoflavone-mediated AhR activation increased the number of goblet and Math1+ progenitor cells in the organoids. The same pharmacological dissection of the AhR-Math1 axis was applied in vivo, demonstrating an enhanced number of Math1+ progenitor cells in the small intestine following AhR activation. We report here that AhR-Math1 is a direct transcriptional axis with effects on Math1+ progenitor cells in the small intestine, highlighting a novel molecular basis for fine-tuning Notch-mediated cell fate regulation.

From Nucleus to Organs: Insights of Aryl Hydrocarbon Receptor Molecular Mechanisms

The aryl hydrocarbon receptor (AHR) is a markedly established regulator of a plethora of cellular and molecular processes. Its initial role in the detoxification of xenobiotic compounds has been partially overshadowed by its involvement in homeostatic and organ physiology processes. In fact, the discovery of its ability to bind specific target regulatory sequences has allowed for the understanding of how AHR modulates such processes. Thereby, AHR presents functions in transcriptional regulation, chromatin architecture modifications and participation in different key signaling pathways. Interestingly, such fields of influence end up affecting organ and tissue homeostasis, including regenerative response both to endogenous and exogenous stimuli. Therefore, from classical spheres such as canonical transcriptional regulation in embryonic development, cell migration, differentiation or tumor progression to modern approaches in epigenetics, senescence, immune system or microbiome, this review covers all aspects derived from the balance between regulation/deregulation of AHR and its physio-pathological consequences.

A Novel Probiotic Bacillus subtilis Strain Confers Cytoprotection to Host Pig Intestinal Epithelial Cells during Enterotoxic Escherichia coli Infection

Enteric infections caused by enterotoxic Escherichia coli (ETEC) negatively impact the growth performance of piglets during weaning, resulting in significant economic losses for the producers. With the ban on antibiotic usage in livestock production, probiotics have gained a lot of attention as a potential alternative. However, strain specificity and limited knowledge on the host-specific targets limit their efficacy in preventing ETEC-related postweaning enteric infections. We recently isolated and characterized a novel probiotic Bacillus subtilis bacterium (CP9) that demonstrated antimicrobial activity. Here, we report anti-ETEC properties of CP9 and its impact on metabolic activity of swine intestinal epithelial (IPEC-J2) cells. Our results showed that pre- or coincubation with CP9 protected IPEC-J2 cells from ETEC-induced cytotoxicity. CP9 significantly attenuated ETEC-induced inflammatory response by reducing ETEC-induced nitric oxide production and relative mRNA expression of the Toll-like receptors (TLRs; TLR2, TLR4, and TLR9), proinflammatory tumor necrosis factor alpha, interleukins (ILs; IL-6 and IL-8), augmenting anti-inflammatory granulocyte-macrophage colony-stimulating factor and host defense peptide mucin 1 (MUC1) mRNA levels. We also show that CP9 significantly (P < 0.05) reduced caspase-3 activity, reinstated cell proliferation and increased relative expression of tight junction genes, claudin-1, occludin, and zona occludens-1 in ETEC-infected cells. Finally, metabolomic analysis revealed that CP9 exposure induced metabolic modulation in IPEC J2 cells with the greatest impact seen in alanine, aspartate, and glutamate metabolism; pyrimidine metabolism; nicotinate and nicotinamide metabolism; glutathione metabolism; the citrate cycle (TCA cycle); and arginine and proline metabolism. Our study shows that CP9 incubation attenuated ETEC-induced cytotoxicity in IPEC-J2 cells and offers insight into potential application of this probiotic for ETEC infection control. IMPORTANCE ETEC remains one of the leading causes of postweaning diarrhea and mortality in swine production. Due to the rising concerns with the antibiotic use in livestock, alternative interventions need to be developed. In this study, we analyzed the cytoprotective effect of a novel probiotic strain in combating ETEC infection in swine intestinal cells, along with assessing its mechanism of action. To our knowledge, this is also the first study to analyze the metabolic impact of a probiotic on intestinal cells. Results from this study should provide effective cues in developing a probiotic intervention for ameliorating ETEC infection and improving overall gut health in swine production.

Stem-Cell Theory of Cancer: Implications for Antiaging and Anticancer Strategies

A stem-cell theory of cancer predicates that not only does the cell affect the niche, the niche also affects the cell. It implicates that even though genetic makeup may be supreme, cellular context is key. When we attempt to solve the mystery of a long cancer-free life, perhaps we need to search no further than the genetics and epigenetics of the naked mole-rat. When we try to unlock the secrets in the longevity and quality of life, perhaps we need to look no further than the lifestyle and habits of the super centenarians. We speculate that people with Down's syndrome and progeria age faster but have fewer cancers, because they are depleted of stem cells, and, as a consequence, have fewer opportunities for stem cell defects that could predispose them to the development of cancer. We contemplate whether these incredible experiments of nature may provide irrefutable evidence that cancer is a stem-cell disease-fewer aberrant stem cells, fewer cancers; no defective stem cells, no cancer. In this perspective, we investigate a stem-cell origin of aging and cancer. We elaborate an intriguing inverse relationship between longevity and malignancy in the naked mole-rat, in Down's syndrome, and in progeria. We postulate that stem-cell pools and stemness factors may affect aging and dictate cancer. We propose that a healthy microbiome may protect and preserve stem cell reserves and provide meaningful antiaging effects and anticancer benefits.

Targeting AhR as a Novel Therapeutic Modality against Inflammatory Diseases

For decades, activation of Aryl Hydrocarbon Receptor (AhR) was excluded from consideration as a therapeutic approach due to the potential toxic effects of AhR ligands and the induction of the cytochrome P450 enzyme, Cyp1a1, following AhR activation. However, it is now understood that AhR activation not only serves as an environmental sensor that regulates the effects of environmental toxins, but also as a key immunomodulator where ligands induce a variety of cellular and epigenetic mechanisms to attenuate inflammation. Thus, the emergence of further in-depth research into diverse groups of compounds capable of activating this receptor has prompted reconsideration of its use therapeutically. The aim of this review is to summarize the body of research surrounding AhR and its role in regulating inflammation. Specifically, evidence supporting the potential of targeting this receptor to modulate the immune response in inflammatory and autoimmune diseases will be highlighted. Additionally, the opportunities and challenges of developing AhR-based therapies to suppress inflammation will be discussed.