Natural killer cell effector function is critical for host defense against alcohol-associated bacterial pneumonia.

Alcohol use is an independent risk factor for the development of bacterial pneumonia due, in part, to impaired mucus-facilitated clearance, macrophage phagocytosis, and recruitment of neutrophils. Alcohol consumption is also known to reduce peripheral natural killer (NK) cell numbers and compromise NK cell cytolytic activity, especially NK cells with a mature phenotype. However, the role of innate lymphocytes, such as NK cells during host defense against alcohol-associated bacterial pneumonia is essentially unknown. We have previously shown that indole supplementation mitigates increases in pulmonary bacterial burden and improves pulmonary NK cell recruitment in alcohol-fed mice, which were dependent on aryl hydrocarbon receptor (AhR) signaling. Employing a binge-on-chronic alcohol-feeding model we sought to define the role and interaction of indole and NK cells during pulmonary host defense against alcohol-associated pneumonia. We demonstrate that alcohol dysregulates NK cell effector function and pulmonary recruitment via alterations in two key signaling pathways. We found that alcohol increases transforming growth factor beta (TGF-ß) signaling while suppressing AhR signaling. We further demonstrated that NK cells isolated from alcohol-fed mice have a reduced ability to kill Klebsiella pneumoniae. NK cell migratory capacity to chemokines was also significantly altered by alcohol, as NK cells isolated from alcohol-fed mice exhibited preferential migration in response to CXCR3 chemokines but exhibited reduced migration in response to CCR2, CXCR4, and CX3CR1 chemokines. Together this data suggests that alcohol disrupts NK cell-specific TGF-ß and AhR signaling pathways leading to decreased pulmonary recruitment and cytolytic activity thereby increasing susceptibility to alcohol-associated bacterial pneumonia.

Bacteroides uniformis degrades ß-glucan to promote Lactobacillus johnsonii improving indole-3-lactic acid levels in alleviating colitis.

BACKGROUND: Intake of dietary fiber is associated with a reduced risk of inflammatory bowel disease. ß-Glucan (BG), a bioactive dietary fiber, has potential health-promoting effects on intestinal functions; however, the underlying mechanism remains unclear. Here, we explore the role of BG in ameliorating colitis by modulating key bacteria and metabolites, confirmed by multiple validation experiments and loss-of-function studies, and reveal a novel bacterial cross-feeding interaction. RESULTS: BG intervention ameliorates colitis and reverses Lactobacillus reduction in colitic mice, and Lactobacillus abundance was significantly negatively correlated with the severity of colitis. It was confirmed by further studies that Lactobacillus johnsonii was the most significantly enriched Lactobacillus spp. Multi-omics analysis revealed that L. johnsonii produced abundant indole-3-lactic acid (ILA) leading to the activation of aryl hydrocarbon receptor (AhR) responsible for the mitigation of colitis. Interestingly, L. johnsonii cannot utilize BG but requires a cross-feeding with Bacteroides uniformis, which degrades BG and produces nicotinamide (NAM) to promote the growth of L. johnsonii. A proof-of-concept study confirmed that BG increases L. johnsonii and B. uniformis abundance and ILA levels in healthy individuals. CONCLUSIONS: These findings demonstrate the mechanism by which BG ameliorates colitis via L. johnsonii-ILA-AhR axis and reveal the important cross-feeding interaction between L. johnsonii and B. uniformis. Video Abstract.

The aryl hydrocarbon receptor and FOS mediate cytotoxicity induced by Acinetobacter baumannii.

Acinetobacter baumannii is a pathogenic and multidrug-resistant Gram-negative bacterium that causes severe nosocomial infections. To better understand the mechanism of pathogenesis, we compare the proteomes of uninfected and infected human cells, revealing that transcription factor FOS is the host protein most strongly induced by A. baumannii infection. Pharmacological inhibition of FOS reduces the cytotoxicity of A. baumannii in cell-based models, and similar results are also observed in a mouse infection model. A. baumannii outer membrane vesicles (OMVs) are shown to activate the aryl hydrocarbon receptor (AHR) of host cells by inducing the host enzyme tryptophan-2,3-dioxygenase (TDO), producing the ligand kynurenine, which binds AHR. Following ligand binding, AHR is a direct transcriptional activator of the FOS gene. We propose that A. baumannii infection impacts the host tryptophan metabolism and promotes AHR- and FOS-mediated cytotoxicity of infected cells.

Tryptophan regulates the expression of IGFBP1 in bovine endometrial epithelial cells in vitro via the TDO2-AHR pathway.

BACKGROUND: This study aimed to identify the roles of L-tryptophan (Trp) and its rate-limiting enzymes on the receptivity of bovine endometrial epithelial cells. Real-time PCR was conducted to analyze the differential expression of genes between different groups of bovine endometrial epithelial cells. Western blot was performed to detect Cyclooxygenase-2 (COX2) expression after treatment with Trp or kynurenine (the main metabolites of Trp). The kynurenine assay was used to examine if Trp or prostaglandin E2 (PGE2) can increase the production of kynurenine in the bovine endometrial epithelial cells. RESULTS: Trp significantly stimulates insulin growth factor binding protein 1 (IGFBP1) expression, a common endometrial marker of conceptus elongation and uterus receptivity for ruminants. When bovine endometrial epithelial cells are treated with Trp, tryptophan hydroxylase-1 remains unchanged, but tryptophan 2,3-dioxygenase 2 (TDO2) is significantly increased, suggesting tryptophan is mainly metabolized through the kynurenine pathway. Kynurenine significantly stimulates IGFBP1 expression. Furthermore, Trp and kynurenine significantly increase the expression of aryl hydrocarbon receptor (AHR). CH223191, an AHR inhibitor, abrogates the induction of Trp and kynurenine on IGFBP1. PGE2 significantly induces the expression of TDO2, AHR, and IGFBP1. CONCLUSIONS: The regulation between Trp / kynurenine and PGE2 may be crucial for the receptivity of the bovine uterus.

Regulation of Bacteroides acidifaciens by the aryl hydrocarbon receptor in IL-22-producing immune cells has sex-dependent consequential impact on colitis.

Introduction: Colitis is an inflammatory bowel disease (IBD) characterized by immune cell dysregulation and alterations in the gut microbiome. In our previous report, we showed a natural product in cruciferous vegetables and ligand of the aryl hydrocarbon receptor (AhR), indole-3-carbinol (I3C), was able to reduce colitis-induced disease severity and microbial dysbiosis in an interleukin-22 (IL-22) dependent manner. Methods: In the current study, we performed single-cell RNA sequencing (scRNAseq) from colonocytes during colitis induction and supplementation with I3C and show how this treatment alters expression of genes involved in IL-22 signaling. To further define the role of IL-22 signaling in I3C-mediated protection during colitis and disease-associated microbial dysbiosis, we generated mice with AhR deficiency in RAR-related orphan receptor c (Rorc)-expressing cells (AhR ΔRorc ) which depletes this receptor in immune cells involved in production of IL-22. Colitis was induced in wildtype (WT), AhR ΔRorc , and littermate (LM) mice with or without I3C treatment. Results: Results showed AhR ΔRorc mice lost the efficacy effects of I3C treatment which correlated with a loss of ability to increase IL-22 by innate lymphoid type 3 (ILC3s), not T helper 22 (Th22) cells. 16S rRNA microbiome profiling studies showed AhR ΔRorc mice were unable to regulate disease-associated increases in Bacteroides, which differed between males and females. Lastly, inoculation with a specific disease-associated Bacteroides species, Bacteroides acidifaciens (B. acidifaciens), was shown to exacerbate colitis in females, but not males. Discussion: Collectively, this report highlights the cell and sex-specific role of AhR in regulating microbes that can impact colitis disease.

Mesenchymal stromal cells restrain the Th17 cell response via L-amino-acid oxidase within lymph nodes.

Mesenchymal stromal/stem cells (MSC) have emerged as a promising therapeutic avenue for treating autoimmune diseases, eliciting considerable interest and discussion regarding their underlying mechanisms. This study revealed the distinctive ability of human umbilical cord MSC to aggregate within the lymph nodes of mice afflicted with autoimmune diseases, but this phenomenon was not observed in healthy mice. The specific distribution is driven by the heightened expression of the CCL21-CCR7 axis in mice with autoimmune diseases, facilitating the targeted homing of MSC to the lymph nodes. Within the lymph nodes, MSC exhibit a remarkable capacity to modulate Th17 cell function, exerting a pronounced anti-inflammatory effect. Transplanted MSC stimulates the secretion of L-amino-acid oxidase (LAAO), a response triggered by elevated levels of tumor necrosis factor-α (TNF-α) in mice with autoimmune diseases through the NF-κB pathway. The presence of LAAO is indispensable for the efficacy of MSC, as it significantly contributes to the inhibition of Th17 cells. Furthermore, LAAO-derived indole-3-pyruvic acid (I3P) serves as a potent suppressor of Th17 cells by activating the aryl hydrocarbon receptor (AHR) pathway. These findings advance our understanding of the global immunomodulatory effects exerted by MSC, providing valuable information for optimizing therapeutic outcomes.

Association of Estrogen Receptor-α and Aryl Hydrocarbon Receptor Gene Polymorphisms with Ischemic Stroke in an Egyptian Population: A Pilot Study.

Stroke is the second leading cause of death and a major contributor to disability worldwide, with the highest prevalence in developing countries. Ischemic stroke (IS) is a complex disease resulting from genetic and environmental interactions. The present work is a pilot study exploring the association of estrogen receptor-α (ESR1) and aryl hydrocarbon receptor (AHR) SNPs with IS in a small Egyptian population of IS patients. Sixty IS patients and 60 matched healthy controls were included in this case-control study. Genotyping of ESR1 PvuII (rs2234693), ESR1 XbaI (rs9340799), and AHR rs2066853 SNPs was performed using real-time PCR. ESR1 PvuII TC and CC genotypes were associated with IS (odds ratio (OR) = 2.821, 95% confidence interval (CI) = 1.204-6.609, p = 0.017, and OR = 9.455, 95% CI = 2.222-40.237, p = 0.002, respectively), and TC genotype in female IS (OR = 4.018, 95% CI = 1.117-14.455, p = 0.033). Additionally, ESR1 XbaI GA and GG genotypes were associated with IS (OR = 2.833, 95% CI = 1.190-6.749, p = 0.019, and OR = 34.000, 95% CI = 6.965-165.980, p < 0.001, respectively), and the AG and GG genotypes in male IS (OR = 3.378, 95% CI = 1.103-10.347, p = 0.033 and OR = 22.8, 95% CI = 2.580-201.488, p = 0.005, respectively) and the GG genotype in female IS (95% CI = 7.259-1115.914, p < 0.001). ESR1 PvuII and XbaI haplotypes C-A, T-G, and C-A increased the risk of IS in both genders, in male IS, and in female IS apart from C-A. The AG genotype of AHR rs2066853 was associated with male IS (OR = 6.900, 95% CI = 2.120-22.457 p = 0.001). ESR1 PvuII, ESR1 XbaI, and AHR rs2066853 SNPs are associated with IS in Egyptians. However, this is a small sample, and the findings should be replicated in a larger population.

Lactobacillus-derived indole derivatives ameliorate intestinal barrier damage in rat pups with complementary food administration.

The consumption of complementary foods can bring about diarrhea and intestinal barrier dysfunction in infants. In this study, three different Lactobacillus strains combined with L-tryptophan (Trp) were administered to rat pups with complementary foods. Complementary food feeding caused inflammatory cell infiltration, crypt structure irregularity and goblet cell reduction in the colon tissues of the rat pups. However, the oral administration of Trp combined with Lactiplantibacillus plantarum DPUL-S164 or Limosilactobacillus reuteri DPUL-M94 significantly restored the pathological changes in the colon tissues and inhibited the expression of pro-inflammatory cytokines in the colon and ileum of the rat pups. M94 or S164 combined with Trp intervention could promote the expression of cell differentiation genes and tight junction proteins, and restore the intestinal barrier damage caused by complementary foods in rat pups by activating the aryl hydrocarbon receptors (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In addition, the indole-3-lactic acid (ILA), indole-3-propionic acid (IPA), or indole-3-carbaldehyde (I3C) level in the cecal contents of the rat pups increased after intervention of Trp combined with S164 or M94, which may account for the amelioration of intestinal barrier damage in rat pups administered with complementary foods. Furthermore, S164 or M94 combined with Trp intervention up-regulated the relative abundance of f_Lactobacillaceae, f_Akkermansiaceae, g_Lactobacillus, and g_Akkermansia in the intestinal tract of the rat pups. In conclusion, S164 or M94 combined with Trp intervention can ameliorate complementary food-induced intestinal barrier damage and gut flora disorder in rat pups by producing ILA, IPA, or I3C, which are AhR ligands.

Disturbances of the gut microbiota-derived tryptophan metabolites as key actors in vagotomy-induced mastitis in mice.

Previous studies have demonstrated that gut microbiota dysbiosis promotes the development of mastitis. The interaction of the vagus nerve and gut microbiota endows host homeostasis and regulates disease development, but whether the vagus nerve participates in the pathogenesis of mastitis is unclear. Here, vagotomized mice exhibit disruption of the blood-milk barrier and mammary gland inflammation. Notably, mastitis and barrier damage caused by vagotomy are dependent on the gut microbiota, as evidenced by antibiotic treatment and fecal microbiota transplantation. Vagotomy significantly alters the gut microbial composition and tryptophan metabolism and reduces the 5-hydroxyindole acetic acid (5-HIAA) level. Supplementation with 5-HIAA alleviates vagotomy-induced mastitis, which is associated with the activation of the aryl hydrocarbon receptor (AhR) and subsequent inhibition of the NF-κB pathway. Collectively, our findings indicate the important role of the vagus-mediated gut-mammary axis in the pathogenesis of mastitis and imply a potential strategy for the treatment of mastitis by targeting the vagus-gut microbiota interaction.

Benvitimod upregulates filaggrin, involucrin and loricrin expressions via aryl hydrocarbon receptor-OVO-like 1 axis.

Benvitimod has been successfully used in the treatment of psoriasis and atopic dermatitis (AD). However, the mechanism remains to be clarified. We aim to assess the effects of benvitimod on MC903-induced dermatitis in mice and to investigate the effects of benvitimod on filaggrin (FLG), involucrin (IVL), and loricrin (LOR) expressions and possible mechanism. MC903-induced mouse AD model was used to evaluate the effects of benvitimod. Filaggrin, involucrin, and loricrin protein and mRNA expressions in lesions of mice dermatitis were measured by Western blot and quantitative real-time PCR. In vitro, normal human epidermal keratinocytes (NHEKs) were cultured and benvitimod was used to treat NHEKs primed with IL-4 and IL-13. Then AHR and OVOL1 in NHEKs were knocked down to evaluate the role of AHR and OVOL1 in the effects of benvitimod. Topical treatment of benvitimod repaired skin barrier and alleviated skin inflammation in mouse AD model. This effect was inhibited by pretreatment with an AHR antagonist. Benvitimod upregulated the filaggrin, involucrin, and loricrin expressions in lesions of mouse AD model. In addition, benvitimod upregulated the filaggrin, involucrin, and loricrin expressions in NHEKs. Knockdown of AHR or OVO-like (OVOL)1 abrogated the upregulation of filaggrin, involucrin, and loricrin induced by benvitimod. Benvitimod attenuated MC903-induced mouse dermatitis and upregulated filaggrin, involucrin, and loricrin expressions via AHR-OVOL1 axis.

Modulation of Ceramide-Induced Apoptosis in Enteric Neurons by Aryl Hydrocarbon Receptor Signaling: Unveiling a New Pathway beyond ER Stress.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a persistent organic pollutant and a potent aryl hydrocarbon receptor (AHR) ligand, causes delayed intestinal motility and affects the survival of enteric neurons. In this study, we investigated the specific signaling pathways and molecular targets involved in TCDD-induced enteric neurotoxicity. Immortalized fetal enteric neuronal (IM-FEN) cells treated with 10 nM TCDD exhibited cytotoxicity and caspase 3/7 activation, indicating apoptosis. Increased cleaved caspase-3 expression with TCDD treatment, as assessed by immunostaining in enteric neuronal cells isolated from WT mice but not in neural crest cell-specific Ahr deletion mutant mice (Wnt1Cre+/-/Ahrb(fl/fl)), emphasized the pivotal role of AHR in this process. Importantly, the apoptosis in IM-FEN cells treated with TCDD was mediated through a ceramide-dependent pathway, independent of endoplasmic reticulum stress, as evidenced by increased ceramide synthesis and the reversal of cytotoxic effects with myriocin, a potent inhibitor of ceramide biosynthesis. We identified Sptlc2 and Smpd2 as potential gene targets of AHR in ceramide regulation by a chromatin immunoprecipitation (ChIP) assay in IM-FEN cells. Additionally, TCDD downregulated phosphorylated Akt and phosphorylated Ser9-GSK-3ß levels, implicating the PI3 kinase/AKT pathway in TCDD-induced neurotoxicity. Overall, this study provides important insights into the mechanisms underlying TCDD-induced enteric neurotoxicity and identifies potential targets for the development of therapeutic interventions.

From farm to pharma: Investigation of the therapeutic potential of the dietary plants Apium graveolens L., Coriandrum sativum, and Mentha longifolia, as AhR modulators for Immunotherapy.

Autoimmune diseases represent a complex array of conditions where the body's immune system mistakenly attacks its own tissues. These disorders, affecting millions worldwide, encompass a broad spectrum of conditions ranging from rheumatoid arthritis and multiple sclerosis to lupus and type 1 diabetes. The Aryl hydrocarbon receptor (AhR) translocator, expressed across immune and other cell types, plays crucial roles in immune disorders and inflammatory diseases. With a realm towards natural remedies in modern medicine for disease prevention, this study investigates the electronic properties and behaviors of bioactive compounds from dietary sources, including Apium graveolens L. (Celery), Coriandrum sativum seeds (Coriander), and Mentha longifolia, as AhR modulators. Through comprehensive analysis (HOMO-LUMO, ESP, LOL, and ELF), electron-rich and -poor regions, electron localization, and delocalization are identified, contrasting these compounds with the toxic AhR ligand, TCDD. Evaluation of Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) properties reveals favorable pharmacokinetics without blood-brain barrier penetration, indicating drug-like characteristics. Molecular docking demonstrates stronger interactions of dietary flavonoid ligands with AhR transcription compared to TCDD. Molecular dynamics simulations confirm the stability of complexes and the sustainability of interactions formed. This research underscores the potential of natural compounds as effective AhR modulators for therapeutic interventions in immune-related disorders.

[The involvement and underlying mechanism of the aryl hydrocarbon receptor (AhR) in the impairment of male mammalian fertility induced by environmental pollutants].

In recent decades, there has been a consistent decline in semen quality across the globe, with environmental pollution emerging as the predominant factor. Persistent organic pollutants (POPs) have garnered considerable attention due to their potent biological toxicity and resistance to natural degradation. Within this class of pollutants, polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic hydrocarbons (HAHs) have been identified as detrimental agents that can disrupt cellular physiological functions by activating aryl hydrocarbon receptor (AhR). However, the precise role of AhR in the adverse effects of environmental pollutants on male mammalian fertility remains incompletely understood. This article provides a comprehensive review of the impact of various environmental pollutants, specifically PAHs such as benzo[a]pyrene, 3-methylcholanthrene, and 7,12-dimethylbenzo[a]anthracene, HAHs including 2,3,7,8-tetrachlorodibenzo-p-dioxins, polychlorinated biphenyls, polybrominated diphenyl ethers, and the pollutant complex PM2.5, as well as cigarette smoke condensates, on male mammalian reproductive function. Additionally, this review focuses on the role of the AhR in mediating these effects. The objective of this review is to elucidate the involvement of AhR in the regulation of male mammalian fertility, thereby offering insights for prospective investigations into the interplay between AhR and male reproductive function, as well as the etiology of idiopathic male infertility in clinic.

Indoxyl Sulfate Inhibits Osteogenesis in Bone Marrow Mesenchymal Stem Cells through the AhR/Hes1 Pathway.

Uremic toxins cause bone disorders in patients with chronic kidney disease (CKD). These disorders are characterized by low turnover osteodystrophy and impaired bone formation in the early stages of CKD. Evidence indicates that the aryl hydrocarbon receptor (AhR) mediates signals that suppress early osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs). However, whether the AhR mediates the effects of indoxyl sulfate (IS), a uremic toxin, on BMSC osteogenesis remains unclear. We investigated whether IS affects osteogenesis through the AhR/Hes1 pathway. Expression levels of osteogenesis genes (Runx2, Bmp2, Alp, and Oc), AhR, and Hes1 were measured in mouse BMSCs (D1 cells). At concentrations of 2-50 µM, IS significantly reduced mineralization, particularly in the early stages of BMSC osteogenesis. Furthermore, IS significantly downregulated the expression of Runx2, Bmp2, Oc, and Alp. Notably, this downregulation could be prevented using an AhR antagonist and through Ahr knockdown. Mechanistically, IS induced the expression of Hes1 through AhR signaling, thereby suppressing the transcription of Runx2 and Bmp2. Our findings suggest that IS inhibits early osteogenesis of BMSCs through the AhR/Hes1 pathway, thus suppressing the transcription of Runx2 and Bmp2. Our findings may guide new therapeutic strategies against CKD-related bone disorders.

Multi-omics insights into anti-colitis benefits of the synbiotic and postbiotic derived from wheat bran arabinoxylan and Limosilactobacillus reuteri.

Exploring nutritional therapies that manipulate tryptophan metabolism to activate AhR signaling represents a promising approach for mitigating chronic colitis. Arabinoxylan is a bioactive constituent abundant in wheat bran. Here, we comprehensively investigated anti-colitis potentials of wheat bran arabinoxylan (WBAX), its synbiotic and postbiotic derived from WBAX and Limosilactobacillus reuteri WX-94 (i.e., a probiotic strain exhibiting tryptophan metabolic activity). WBAX fueled L. reuteri and promoted microbial conversion of tryptophan to AhR ligands during in vitro fermentation in the culture medium and in the fecal microbiota from type 2 diabetes. The WBAX postbiotic outperformed WBAX and its synbiotic in augmenting efficacy of tryptophan in restoring DSS-disturbed serum immune markers, colonic tight junction proteins and gene profiles involved in amino acid metabolism and FoxO signaling. The WBAX postbiotic remodeled gut microbiota and superiorly enhanced AhR ligands (i.e., indole metabolites and bile acids), alongside with elevation in colonic AhR and IL-22. Associations between genera and metabolites modified by the postbiotic and colitis in human were verified and strong binding capacities between metabolites and colitis-related targets were demonstrated by molecular docking. Our study advances the novel perspective of WBAX in manipulating tryptophan metabolism and anti-colitis potentials of WBAX postbiotic via promoting gut microbiota-dependent AhR signaling.

The Aryl Hydrocarbon Receptor Regulates Invasiveness and Motility in Acute Myeloid Leukemia Cells through Expressional Regulation of Non-Muscle Myosin Heavy Chain IIA.

Acute myeloid leukemia (AML) is the most prevalent type of hematopoietic malignancy. Despite recent therapeutic advancements, the high relapse rate associated with extramedullary involvement remains a challenging issue. Moreover, therapeutic targets that regulate the extramedullary infiltration of AML cells are still not fully elucidated. The Aryl Hydrocarbon Receptor (AHR) is known to influence the progression and migration of solid tumors; however, its role in AML is largely unknown. This study explored the roles of AHR in the invasion and migration of AML cells. We found that suppressed expression of AHR target genes correlated with an elevated relapse rate in AML. Treatment with an AHR agonist on patient-derived AML cells significantly decreased genes associated with leukocyte trans-endothelial migration, cell adhesion, and regulation of the actin cytoskeleton. These results were further confirmed in THP-1 and U937 AML cell lines using AHR agonists (TCDD and FICZ) and inhibitors (SR1 and CH-223191). Treatment with AHR agonists significantly reduced Matrigel invasion, while inhibitors enhanced it, regardless of the Matrigel's stiffness. AHR agonists significantly reduced the migration rate and chemokinesis of both cell lines, but AHR inhibitors enhanced them. Finally, we found that the activity of AHR and the expression of NMIIA are negatively correlated. These findings suggest that AHR activity regulates the invasiveness and motility of AML cells, making AHR a potential therapeutic target for preventing extramedullary infiltration in AML.

Hydroquinone impairs trophoblast migration and invasion via AHR-twist-IFITM1 axis.

INTRODUCTION: Embryo implantation is a tightly regulated process, critical for a successful pregnancy. After attachment of the blastocyst to the surface epithelium of the endometrium trophoblast migrate from the trophectoderm and invade into the stromal component of endometrium. Alterations on either process will lead to implantation failure or miscarriage. Volatile organic compounds (VOCs) such as benzene induce pregnancy complications, including preterm birth and miscarriages. The mechanism of this effect is unknown. The objective of this study was to elucidate the impact of benzene metabolite, Hydroquinone, on trophoblast function. We tested the hypothesis that Hydroquinone activates the Aryl hydrocarbon receptor (AhR) pathway modulating trophoblast migration and invasion. METHODS: First-trimester trophoblast cells (Sw.71) were treated with hydroquinone (6 and 25 µM). Trophoblast migration and invasion was evaluated using a 3D invasion/migration model. Gene expression was quantified by q-PCR and Western blot analysis. RESULTS: Hydroquinone impairs trophoblast migration and invasion. This loss is associated with the activation of the AhR pathway which reduced the expression of Twist1and IFITM1. IFITM1 overexpression can rescue impaired trophoblast migration. DISCUSSION: Our study highlights that hydroquinone treatment induces the activation of the AhR pathway in trophoblast cells, which impairs trophoblast invasion and migration. We postulate that activation of the AhR pathway in trophoblast suppress Twist1 and a subsequent IFITM1. Thus, the AhR-Twist1-IFITM1 axis represent a critical pathway involved in the regulation of trophoblast migration and it is sensitive to benzene exposure. These findings provide crucial insights into the molecular mechanisms underlying pregnancy complications induced by air pollution.

Microbiome-derived indole-3-lactic acid reduces amyloidopathy through aryl-hydrocarbon receptor activation.

Alzheimer's disease (AD) pathogenesis has been associated with the gut microbiome and its metabolites, though the specific mechanisms have remained unclear. In our study, we used a multi-omics approach to identify specific microbial strains and metabolites that could potentially mitigate amyloidopathy in 5xFAD mice, a widely used model for AD research. Among the microbial strains tested, three showed promising results in reducing soluble amyloid-beta (Aß) levels. Plasma metabolomics analysis revealed an enrichment of tryptophan (Trp) and indole-3-lactic acid (ILA) in mice with reduced soluble Aß levels, suggesting a potential preventative role. The administration of a combined treatment of Trp and ILA prevented both Aß accumulation and cognitive impairment in the 5xFAD mice. Our investigation into the mechanism revealed that ILA's effect on reducing Aß levels was mediated through the activation of microglia and astrocytes, facilitated by the aryl hydrocarbon receptor (AhR) signaling pathway. These mechanisms were verified through experiments in 5xFAD mice that included an additional group with the administration of ILA alone, as well as in vitro experiments using an AhR inhibitor. Clinical data analysis revealed a greater abundance of Lactobacillus reuteri in the gut of healthy individuals compared to those at early stages of Aß accumulation or with mild cognitive impairment. Additionally, human post-mortem brain analyses showed an increased expression of genes associated with the AhR signaling pathway in individuals without AD, suggesting a protective effect against AD progression. Our results indicate that ILA from gut microbes could inhibit the progression of amyloidopathy in 5xFAD mice through activation of AhR signaling in the brain.

Aryl hydrocarbon receptor confers protection against macrophage pyroptosis and intestinal inflammation through regulating polyamine biosynthesis.

Rationale: The aryl hydrocarbon receptor (AhR) functions in the regulation of intestinal inflammation, but knowledge of the underlying mechanisms in innate immune cells is limited. Here, we investigated the role of AhR in modulating the functions of macrophages in inflammatory bowel disease pathogenesis. Methods: The cellular composition of intestinal lamina propria CD45+ leukocytes in a dextran sulfate sodium (DSS)-induced mouse colitis model was determined by single-cell RNA sequencing. Macrophage pyroptosis was quantified by analysis of lactate dehydrogenase release, propidium iodide staining, enzyme-linked immunosorbent assay, western blot, and flow cytometry. Differentially expressed genes were confirmed by RNA-seq, RT-qPCR, luciferase assay, chromatin immunoprecipitation, and immunofluorescence staining. Results: AhR deficiency mediated dynamic remodeling of the cellular composition of intestinal lamina propria (LP) CD45+ immune cells in a colitis model, with a significant increase in monocyte-macrophage lineage. Mice with AhR deficiency in myeloid cells developed more severe dextran sulfate sodium induced colitis, with concomitant increased macrophage pyroptosis. Dietary supplementation with an AhR pre-ligand, indole-3-carbinol, conferred protection against colitis while protection failed in mice lacking AhR in myeloid cells. Mechanistically, AhR signaling inhibited macrophage pyroptosis by promoting ornithine decarboxylase 1 (Odc1) transcription, to enhance polyamine biosynthesis. The increased polyamine, particularly spermine, inhibited NLRP3 inflammasome assembly and subsequent pyroptosis by suppressing K+ efflux. AHR expression was positively correlated with ODC1 in intestinal mucosal biopsies from patients with ulcerative colitis. Conclusions: These findings suggest a functional role for the AhR/ODC1/polyamine axis in maintaining intestinal homeostasis, providing potential targets for treatment of inflammatory bowel disease.

Effects of Early Life Exposures to the Aryl Hydrocarbon Receptor Ligand TCDF on Gut Microbiota and Host Metabolic Homeostasis in C57BL/6J Mice.

BACKGROUND: Exposure to persistent organic pollutants (POPs) and disruptions in the gastrointestinal microbiota have been positively correlated with a predisposition to factors such as obesity, metabolic syndrome, and type 2 diabetes; however, it is unclear how the microbiome contributes to this relationship. OBJECTIVE: This study aimed to explore the association between early life exposure to a potent aryl hydrocarbon receptor (AHR) agonist and persistent disruptions in the microbiota, leading to impaired metabolic homeostasis later in life. METHODS: This study used metagenomics, nuclear magnetic resonance (NMR)- and mass spectrometry (MS)-based metabolomics, and biochemical assays to analyze the gut microbiome composition and function, as well as the physiological and metabolic effects of early life exposure to 2,3,7,8-tetrachlorodibenzofuran (TCDF) in conventional, germ-free (GF), and Ahr-null mice. The impact of TCDF on Akkermansia muciniphila (A. muciniphila) in vitro was assessed using optical density (OD 600), flow cytometry, transcriptomics, and MS-based metabolomics. RESULTS: TCDF-exposed mice exhibited lower abundances of A. muciniphila, lower levels of cecal short-chain fatty acids (SCFAs) and indole-3-lactic acid (ILA), as well as lower levels of the gut hormones glucagon-like peptide 1 (GLP-1) and peptide YY (PYY), findings suggestive of disruption in the gut microbiome community structure and function. Importantly, microbial and metabolic phenotypes associated with early life POP exposure were transferable to GF recipients in the absence of POP carry-over. In addition, AHR-independent interactions between POPs and the microbiota were observed, and they were significantly associated with growth, physiology, gene expression, and metabolic activity outcomes of A. muciniphila, supporting suppressed activity along the ILA pathway. CONCLUSIONS: These data obtained in a mouse model point to the complex effects of POPs on the host and microbiota, providing strong evidence that early life, short-term, and self-limiting POP exposure can adversely impact the microbiome, with effects persisting into later life with associated health implications. https://doi.org/10.1289/EHP13356.