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Aryl hydrocarbon receptor (AhR) plays an important role in inflammation and immunity as a new therapeutic target for infectious disease and sepsis. Punicalagin (PUN) is a Chinese herbal monomer extract of pomegranate peel that has beneficial anti-inflammatory, antioxidant and anti-infective effects. However, whether PUN is a ligand of AhR, its effect on AhR expression, and its signaling pathway remain poorly understood. In this study, we found that PUN was a unique polyphenolic compound that upregulated AhR expression at the transcriptional level, and regulated the AhR nongenomic pathway. AhR expression in lipopolysaccharide-induced macrophages was upregulated by PUN in vitro and in vivo in a time- and dose-dependent manner. Using specific inhibitors and siRNA, induction of AhR by PUN depended on sequential phosphorylation of 90-kDa ribosomal S6 kinase (p90RSK), which was activated by the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and phosphoinositide-dependent protein kinase (PDK)1 pathways. PUN promoted p90RSK-mediated activator protein-1 (AP-1) activation. AhR knockout or inhibitors reversed suppression of interleukin (IL)-6 and IL-1β expression by PUN. PUN decreased Listeria load and increased macrophage survival via AhR upregulation. In conclusion, we identified PUN as a novel selective AhR modulator involved in AhR expression via the MEK/ERK and PDK1 pathways targeting p90RSK/AP-1 in inflammatory macrophages, which inhibited macrophage inflammation and promoted bactericidal activity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Tapinarof is a non‐steroidal, topical, aryl hydrocarbon receptor agonist. We evaluated the efficacy and safety of tapinarof cream (1%) in Japanese patients aged ≥18 years with plaque psoriasis in two phase 3 trials, ZBA4‐1 and ZBA4‐2. ZBA4‐1 (N = 158) consisted of a 12‐week, double‐blind, vehicle‐controlled treatment period (period 1) and a 12‐week extension treatment period (period 2). Patients were randomized 2:1 to tapinarof or vehicle in period 1; subsequently, all patients who were enrolled in period 2 received tapinarof. ZBA4‐2 (N = 305) was a 52‐week, open‐label, uncontrolled trial in which all patients received tapinarof. In period 1 of ZBA4‐1, the proportion of patients who achieved a Physician Global Assessment (PGA) score of 0 (clear) or 1 (almost clear) with ≥2‐grade improvement from baseline at week 12 (PGA treatment success, the primary endpoint) was 20.06% in the tapinarof group and 2.50% in the vehicle group (p = 0.0035). The proportion of patients with ≥75% improvement from baseline in the Psoriasis Area and Severity Index (PASI) score at week 12 (PASI75 response, a key secondary endpoint) was 37.7% in the tapinarof group and 3.8% in the vehicle group (p < 0.0001). In ZBA4‐2, PGA treatment success rate was 30.0% at week 12, 51.3% at week 24, and 56.3% at week 52, and PASI75 response rate was 50.4% at week 12, 77.5% at week 24, and 79.9% at week 52, indicating that efficacy responses improved over time and were maintained over 52 weeks. Across the two trials, most adverse events (AEs) were mild or moderate; common AEs included folliculitis and contact dermatitis. In summary, tapinarof cream (1%) was efficacious and generally safe for up to 52 weeks of treatment in Japanese patients with plaque psoriasis. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (S. aureus) commonly reside on human skin in residents in long‐term care facilities, yet its colonization and impact on the skin of hemodialysis (HD) patients have yet to be studied. The aim of the present study was to investigate the colonization of S. aureus on the skin of pruritic and non‐pruritic HD patients, and the influence of S. aureus and S. aureus‐secreted α‐toxin on skin barrier function‐related protein expression. In this study, a higher relative S. aureus count in pruritic HD patients compared to non‐pruritic HD patients and healthy subjects were revealed by real‐time polymerase chain reaction. S. aureus and α‐toxin decreased mRNA and protein expression levels of aryl hydrocarbon receptor (AHR), ovo‐like transcriptional repressor 1 (OVOL1), and filaggrin (FLG) in keratinocytes. In addition, anti‐alpha‐hemolysin (anti‐hla) was used as an α‐toxin neutralizer, and it successfully abrogated S. aureus‐induced AHR, OVOL1, and FLG mRNA and protein expression downregulation. Mechanistically, α‐toxin could decrease FLG activity by preventing the recruitment of AHR to the FLG promoter region. In conclusion, pruritic HD patients had higher S. aureus colonization, with S. aureus‐secreted α‐toxin suppressing FLG expression through the AHR‐FLG axis. [ABSTRACT FROM AUTHOR]

Due to the expanding oil-related activities, the arctic and sub-arctic marine environments are increasingly vulnerable to oil-related pollution such as accidental oil spills. These cold-water ecosystems harbor many fish species that are both ecologically and economically important such as the pelagic polar cod (Boreogadus saida), capelin (Mallotus villosus), and benthic long rough dab (Hippoglossoides platessoides). The latter two are much less studied and it is crucial to characterize their responses to oil-related contaminants and develop molecular biomarkers and genomic resources for future monitoring. In this study, liver slice preparation and culture methods were used to characterize the transcriptome responses (using RNA-seq) in capelin and long rough dab to exposures of the polycyclic aromatic hydrocarbon (PAH) compound benzo[a] pyrene (BaP). The liver slice culture and exposure experiments were performed onboard a research vessel in the Barents Sea. Strong up-regulation of genes involved in biotransformation, particularly the aryl hydrocarbon receptor signaling pathway was observed in both species. A comparison of the number of differentially expressed genes (DEGs) with previously published polar cod exposures indicates that the latter respondedmore strongly (higher number of genes), suggesting higher uptake and bioconcentration of BaP in the fatty liver tissue, although other factors such as differences in clearance rate could potentially affect the responses. This study provides new genomic resources and gene expression biomarkers in capelin and long rough dab, enhancing our understanding of their response mechanism to oil-related contaminants. [ABSTRACT FROM AUTHOR]

Uric acid (UA) is the end product of purine metabolism. In recent years, UA has been found to be associated with the prognosis of clinical cancer patients. However, the intricate mechanisms by which UA affects the development and prognosis of tumor patients has not been well elucidated. In this study, we explored the role of UA in breast cancer, scrutinizing its impact on breast cancer cell function by treating two types of breast cancer cell lines with UA. The role of UA in the cell cycle and proliferation of tumors and the underlying mechanisms were further investigated. We found that the antioxidant effect of UA facilitated the scavenging of reactive oxygen species (ROS) in breast cancer, thereby reducing aryl hydrocarbon receptor (AhR) expression and affecting the breast cancer cell cycle, driving the proliferation of breast cancer cells through the AhR/p27Kip1/cyclin E1 pathway. Moreover, in breast cancer patients, the expression of AhR and its downstream genes may be closely associated with cancer progression in patients. Therefore, an increase in UA could promote the proliferation of breast cancer cells through the AhR/p27Kip1/cyclin E1 pathway axis. [ABSTRACT FROM AUTHOR]

Background: Intake of dietary fiber is associated with a reduced risk of inflammatory bowel disease. β-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. BsYQ6kaZHXkFsG8eqgZ27E Video Abstract [ABSTRACT FROM AUTHOR]

Tertiary lymphoid tissues (TLTs) are adaptive immune structures that develop during chronic inflammation and may worsen or lessen disease outcomes in a context-specific manner. Immune cell activity governing TLT formation in the intestines is dependent on immune cell aryl hydrocarbon receptor (AhR) activation. Homeostatic immune cell activity in the intestines is further dependent on ligand activation of AhR in intestinal epithelial cells (IECs), yet whether AhR activation and signaling in IECs influences the formation of TLTs in the presence of dietary AhR ligands is not known. To this end, we used IEC-specific AhR deletion coupled with a mouse model of dextran sodium sulfate (DSS)-induced colitis to understand how dietary AhR ligand 3, 3′-diindolylmethane (DIM) influenced TLT formation. DIM consumption increased the size of TLTs and decreased T-cell aggregation to TLT sites in an IEC-specific manner. In DSS-exposed female mice, DIM consumption increased the expression of genes implicated in TLT formation (Interleukin-22, Il-22; CXC motif chemokine ligand 13, CXCL13) in an IEC AhR-specific manner. Conversely, in female mice without DSS exposure, DIM significantly reduced the expression of Il-22 or CXCL13 in iAhRKO mice, but this effect was not observed in WT animals. Our findings suggest that DIM affects the immunological landscape of TLT formation during DSS-induced colitis in a manner contingent on AhR expression in IECs and biological sex. Further investigations into specific immune cell activity, IEC-specific AhR signaling pathways, and dietary AhR ligand-mediated effects on TLT formation are warranted. [ABSTRACT FROM AUTHOR]

In previous studies, using transcriptomic analysis, we observed higher levels of aryl hydrocarbon receptor (AHR) gene expression in the peripheral blood cells of centenarians compared to octogenarians. This suggests the potential significance of this receptor in maintaining physiological balance and promoting healthy aging, possibly linked to its critical role in detoxifying xenobiotics. In our current study, we confirmed that AHR expression is indeed higher in centenarians. We employed C. elegans as a model known for its suitability in longevity studies to explore whether the AHR pathway has a significant impact on lifespan and healthspan. Our survival assays revealed that two different mutants of AHR-1 exhibited lower longevity. Additionally, we used a mouse model to examine whether supplementation with pomegranate extract modulates the expression of AHR pathway genes in the liver. Furthermore, we studied a nutritional strategy based on pomegranate extract administration to investigate its potential modulation of life- and healthspan in worms. [ABSTRACT FROM AUTHOR]

Introduction: Increasing evidence shows that hyperactive aryl hydrocarbon receptor (AHR) signalling is involved in renal disease. However, no currently available intervention strategy is effective in halting disease progression by targeting the AHR signalling. Our previous study showed that barleriside A (BSA), a major component of Plantaginis semen, exhibits renoprotective effects. Methods: In this study, we determined the effects of BSA on AHR expression in 5/ 6 nephrectomized (NX) rats. We further determined the effect of BSA on AHR, nuclear factor kappa B (NF-κB), and the nuclear factor erythroid 2-related factor 2 (Nrf2) signalling cascade in zymosan-activated serum (ZAS)-stimulated MPC5 cells. Results: BSA treatment improved renal function and inhibited intrarenal nuclear AHR protein expression in NX-treated rats. BSA mitigated podocyte lesions and suppressed AHR mRNA and protein expression in ZAS-stimulated MPC5 cells. BSA inhibited inflammation by improving the NF-κB and Nrf2 pathways in ZASstimulated MPC5 cells. However, BSA did not markedly upregulate the expression of podocyte-specific proteins in the ZAS-mediated MPC5 cells treated with CH223191 or AHR siRNA compared to untreated ZAS-induced MPC5 cells. Similarly, the inhibitory effects of BSA on nuclear NF-κB p65, Nrf2, and AHR, as well as cytoplasmic cyclooxygenase-2, heme oxygenase-1, and AHR, were partially abolished in ZAS-induced MPC5 cells treated with CH223191 or AHRsiRNA compared with untreated ZAS-induced MPC5 cells. These results indicated that BSA attenuated the inflammatory response, partly by inhibiting AHR signalling. Discussion: Both pharmacological and siNRA findings suggested that BSA mitigated podocyte lesions by improving the NF-κB and Nrf2 pathways via inhibiting AHR signalling. Therefore, BSA is a high-affinity AHR antagonist that abolishes oxidative stress and inflammation. [ABSTRACT FROM AUTHOR]

Retention of metabolic end‐products in the bodily fluids of patients with chronic kidney disease (CKD) may lead to uremia. The uremic toxin indoxyl sulfate (IS), a tryptophan metabolite, is an endogenous ligand of aryl hydrocarbon receptor (AhR). It is clarified that the upregulation and activation of AhR by IS in tubular epithelial cells (TECs) promote renal senescence and fibrosis. Renal TEC‐specific knockout of AhR attenuates renal senescence and fibrosis, as well as the suppression of PGC1α‐mediated mitochondrial biogenesis in ischemia reperfusion (IR)‐ or IS‐treated CKD mice kidneys. Overexpression of peroxisome proliferator‐activated receptor gamma coactivator 1‐α (PGC1α) attenuates IS‐induced cell senescence and extracellular matrix production in cultured TECs. Mechanistically, AhR is able to interact with PGC1α and promotes the ubiquitin degradation of PGC1α via its E3 ubiquitin ligase activity. In summary, the elevation and activation of AhR by the accumulated uremic toxins in the progression of CKD accelerate renal senescence and fibrosis by suppressing mitochondrial biogenesis via promoting ubiquitination and proteasomal degradation of PGC1α. [ABSTRACT FROM AUTHOR]

The maternal–fetal interface is composed of the placenta, which is affiliated with the fetus, and the maternal decidua. During pregnancy, the placenta is mainly responsible for nutrient transport and immune tolerance maintenance, which plays a key role in fetal growth and development and pregnancy maintenance. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that exists in various cell types at the maternal–fetal interface and is involved in multiple cellular processes. Recent studies have highlighted the role of AhR in regulating various physiological processes, including glucose and lipid metabolism, as well as tryptophan metabolism and immune responses, within non-pregnant tissues. This review shifts focus towards understanding how AhR modulation impacts metabolism and immune regulation at the maternal-fetal interface. This may implicate the development of pregnancy-related complications and the potential target of the AhR pathway for therapeutic strategies against poor pregnancy outcomes. • AhR during pregnancy is spatio-temporal specific at the maternal-fetal interface. • AhR plays a role in immunity and metabolism at the maternal-fetal interface. • AhR may be a potential therapeutic target. [ABSTRACT FROM AUTHOR]

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 (AhRΔRorc) which depletes this receptor in immune cells involved in production of IL-22. Colitis was induced in wildtype (WT), AhRΔRorc, and littermate (LM) mice with or without I3C treatment. Results: Results showed AhRΔRorc 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 AhRΔRorc 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. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AhR) is a versatile environmental sensor and transcription factor found throughout the body, responding to a wide range of small molecules originating from the environment, our diets, host microbiomes, and internal metabolic processes. Increasing evidence highlights AhR's role as a critical regulator of numerous biological functions, such as cellular differentiation, immune response, metabolism, and even tumor formation. Typically located in the cytoplasm, AhR moves to the nucleus upon activation by an agonist where it partners with either the aryl hydrocarbon receptor nuclear translocator (ARNT) or hypoxia-inducible factor 1β (HIF-1β). This complex then interacts with xenobiotic response elements (XREs) to control the expression of key genes. AhR is notably present in various crucial immune cells, and recent research underscores its significant impact on both innate and adaptive immunity. This review delves into the latest insights on AhR's structure, activating ligands, and its multifaceted roles. We explore the sophisticated molecular pathways through which AhR influences immune and lymphoid cells, emphasizing its emerging importance in managing inflammatory diseases. Furthermore, we discuss the exciting potential of developing targeted therapies that modulate AhR activity, opening new avenues for medical intervention in immune-related conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

After birth, the development of secondary lymphoid tissues (SLTs) in the colon is dependent on the expression of the aryl hydrocarbon receptor (AhR) in immune cells as a response to the availability of AhR ligands. However, little is known about how AhR activity from intestinal epithelial cells (IECs) may influence the development of tertiary lymphoid tissues (TLTs). As organized structures that develop at sites of inflammation or infection during adulthood, TLTs serve as localized centers of adaptive immune responses, and their presence has been associated with the resolution of inflammation and tumorigenesis in the colon. Here, we investigated the effect of the conditional loss of AhR activity in IECs in the formation and immune cell composition of TLTs in a model of acute inflammation. In females, loss of AhR activity in IECs reduced the formation of TLTs without significantly changing disease outcomes or immune cell composition within TLTs. In males lacking AhR expression in IECs, increased disease activity index, lower expression of functional-IEC genes, increased number of TLTs, increased T-cell density, and lower B- to Tcell ratio were observed. These findings may represent an unfavorable prognosis when exposed to dextran sodium sulfate (DSS)-induced epithelial damage compared with females. Sex and loss of IEC AhR also resulted in changes in microbial populations in the gut. Collectively, these data suggest that the formation of TLTs in the colon is influenced by sex and AhR expression in IECs. NEW & NOTEWORTHY This is the first research of its kind to demonstrate a clear connection between biological sex and the development of tertiary lymphoid tissues (TLT) in the colon. In addition, the research finds that in a preclinical model of inflammatory bowel disease, the expression of the aryl hydrocarbon receptor (AhR) influences the development of these structures in a sex-specific manner [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: Aryl hydrocarbon receptor (AHR), a crucial molecular marker associated with glioma, is a potential therapeutic target. We aimed to establish a non-invasive predictive model for AHR through radiomics. Methods: Contrast-enhanced T1-weighted (T1W) MRI and the corresponding and clinical variables of glioblastoma patients from The Cancer Genome Atlas (TCGA) and The Cancer Imaging Archive (TCIA) were obtained for analysis. KM curves and Cox regression analyses were used to assess the prognostic value of AHR expression. The radiomics features were screened by Max-Relevance and Min-Redundancy (mRMR) and recursive feature elimination (RFE), followed by the construction of two predictive models using logistic regression (LR) and a support vector machine (SVM). Results: The expression levels of AHR in tumour patients were significantly higher than those in the control group, and higher AHR expression was associated with worse prognosis (P<0.05). AHR remained a risk factor for poor prognosis in glioblastoma after multivariate adjustment (HR: 1.61, 95% CI: 1.085–2.39, P<0.05). The radiomics models constructed using LR and SVM based on three selected features achieved area under the curve (AUC) values of 0.887 and 0.872, respectively. Radiomics score emerged as a key factor influencing overall survival (OS) after multivariate adjustment in the Cox model (HR: 3.931, 95% CI: 1.272–12.148, P < 0.05). Conclusion: The radiomics models could effectively distinguish the expression levels of AHR and predict prognosis in patients with glioblastoma, which may serve as a powerful tool to assist clinical assessment and precision treatment. [ABSTRACT FROM AUTHOR]

The kynurenine pathway (KP) of tryptophan degradation generates several metabolites such as kynurenine (KYN) or kynurenic acid (KA) that serve as endogenous ligands of the aryl hydrocarbon receptor (AHR). Due to its distinct biological roles particularly modulating the immune system, the AHR is a current therapeutic target across different inflammation-related diseases. Here, we show an acute exercise-induced increase in AHR ligand availability on a systemic level and a kynurenine pathway activation in peripheral blood mononuclear cells (PBMCs). Concurrently, the AHR is activated in PBMCs following acute exercise. Exercise effects on both, kynurenic acid and AHR activation in PBMCs were greater in response to high-intensity interval exercise (HIIE) (50 min, six 3-min intervals at 90% V̇ o 2peak, and 3-min intervals at 50% V̇ o 2peak in between) compared with workload-matched moderate-intensity continuous exercise (MICE) (50 min). In conclusion, these data indicate a novel mechanistic link in how exercise modulates the immune system through the kynurenine pathway-AHR axis, potentially underlying exercise-induced benefits in various chronic diseases. NEW & NOTEWORTHY: The findings of this study show that acute endurance exercise activates a receptor that has been described to integrate metabolic signals into the immune system. We uncover a potential mechanistic link on how exercise modulates the immune system through the kynurenine pathway-AHR axis, potentially underlying exercise-induced benefits in various chronic diseases and of relevance for other cell types. [ABSTRACT FROM AUTHOR]

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women. This study aimed to investigate the therapeutic effects and mechanism of Jujuboside A on PCOS using a dehydroepiandrosterone (DHEA)-induced PCOS mouse model. Estrogen and androgen homeostasis was evaluated in serum from both clinical samples and PCOS mice. The stages of the estrous cycle were determined based on vaginal cytology. The ovarian morphology was observed by stained with hematoxylin and eosin. Moreover, we analyzed protein expression of cytochrome P450 1A1 (CYP1A1), cytochrome P450 1A2 (CYP1A2) and aryl hydrocarbon receptor (AhR) in ovary and KGN cells. Molecular docking, immunofluorescence, and luciferase assay were performed to confirm the activation of AhR by Jujuboside A. Jujuboside A effectively alleviated the disturbance of estrogen homeostasis and restored ovarian function, leading to an improvement in the occurrence and progression of PCOS. Furthermore, the protective effect of JuA against PCOS was dependent on increased CYP1A2 levels regulated by AhR. Our findings suggest that Jujuboside A improves estrogen disorders and may be a potential therapeutic agent for the treatment of PCOS. [ABSTRACT FROM AUTHOR]

Intestinal eosinophils express the aryl hydrocarbon receptor (AHR), an environmental sensor and ligand-activated transcription factor that responds to dietary or environmental ligands. AHR regulates tissue adaptation, survival, adhesion, and immune functions in intestinal eosinophils. The AHR repressor (AHRR) is itself induced by AHR and believed to limit AHR activity in a negative feedback loop. We analyzed gene expression in intestinal eosinophils from wild-type and AHRR knockout mice and found that AHRR did not suppress most AHR-dependent genes. Instead, AHRR limited the expression of a distinct small set of genes involved in the innate immune response. These included S100 proteins, antimicrobial proteins, and alpha-defensins. Using bone marrow–derived eosinophils, we found that AHRR knockout eosinophils released more reactive oxygen species upon stimulation. This work shows that the paradigm of AHRR as a repressor of AHR transcriptional activity does not apply to intestinal eosinophils. Rather, AHRR limits the expression of innate immune response and antimicrobial genes, possibly to maintain an anti-inflammatory phenotype in eosinophils when exposed to microbial signals in the intestinal environment. [ABSTRACT FROM AUTHOR]

Hawke's Bay in New Zealand was impacted by Cyclone Gabrielle in 2023, experiencing intense weather conditions and rainfall. Rivers and streams surged beyond their banks, displacing large amounts of sediment. The sewage treatment plant and industries in the Waitangi catchment, south of the city of Napier, were heavily impacted, making them potential sources of contaminants. The aim of this study was to investigate the risk of displaced sediments deposited south of Napier City, using bioassays and chemical analysis methods. Sediment samples were collected across a gradient between the coastline and the Waitangi Stream. The toxicity of chemically extracted or elutriate samples was assessed by Microtox®, mussel embryo–larval development, and aryl hydrocarbon and constitutive androstane receptor yeast two-hybrid assays. Targeted chemical analysis and automated identification and quantification system (AIQS-GC) methods were used to identify contaminants. The elutriates showed low toxicity and the yeast assays showed levels of activity like those previously reported. Chemical methods confirmed historical contamination by DDT and its metabolites DDE and DDD, as well as by plant sterols. Overall, the toxicity and chemicals detected are what would be expected from a typical agricultural soil. The risk posed by the displaced sediment in the Waitangi catchment can be considered low. Combining chemical and bioanalytical methods was an effective approach to investigate the potential risks of post-disaster contamination. [ABSTRACT FROM AUTHOR]

Abstract Aryl hydrocarbon receptor (AhR) plays an important role in inflammation and immunity as a new therapeutic target for infectious disease and sepsis. Punicalagin (PUN) is a Chinese herbal monomer extract of pomegranate peel that has beneficial anti-inflammatory, antioxidant and anti-infective effects. However, whether PUN is a ligand of AhR, its effect on AhR expression, and its signaling pathway remain poorly understood. In this study, we found that PUN was a unique polyphenolic compound that upregulated AhR expression at the transcriptional level, and regulated the AhR nongenomic pathway. AhR expression in lipopolysaccharide-induced macrophages was upregulated by PUN in vitro and in vivo in a time- and dose-dependent manner. Using specific inhibitors and siRNA, induction of AhR by PUN depended on sequential phosphorylation of 90-kDa ribosomal S6 kinase (p90RSK), which was activated by the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and phosphoinositide-dependent protein kinase (PDK)1 pathways. PUN promoted p90RSK-mediated activator protein-1 (AP-1) activation. AhR knockout or inhibitors reversed suppression of interleukin (IL)-6 and IL-1β expression by PUN. PUN decreased Listeria load and increased macrophage survival via AhR upregulation. In conclusion, we identified PUN as a novel selective AhR modulator involved in AhR expression via the MEK/ERK and PDK1 pathways targeting p90RSK/AP-1 in inflammatory macrophages, which inhibited macrophage inflammation and promoted bactericidal activity.

Yiqiong Zhang,1,2,&ast; Shanshan Li,1,2,&ast; Xiaojuan Fan,1 Yue Wu1,2 1Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, People’s Republic of China; 2Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi’an Jiaotong University, Xi’an, Shaanxi, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Xiaojuan Fan; Yue Wu, Email colors727@163.com; yue.wu@xjtu.edu.cnBackground: Patients with sepsis frequently develop septic cardiomyopathy, which is known to be closely related to excessive inflammatory responses. Indole-3-propionic acid (IPA) is a tryptophan metabolite with anti-inflammatory properties that have been demonstrated in various studies. In this study, we investigated the underlying mechanisms and therapeutic role of IPA in septic cardiomyopathy.Methods: To investigate the role of IPA in septic cardiomyopathy, we constructed a lipopolysaccharide (LPS)-induced rat model of septic cardiomyopathy, and treated rats with IPA. Inflammatory factors and the NF-κB/NLRP3 pathway were evaluated in myocardial tissues and cells after IPA treatment using RT-qPCR, ELISA, Western blotting, and immunohistochemistry. To further elucidate the role of the aryl hydrocarbon receptor (AhR), we detected changes in inflammatory mediators and the NF-κB/NLRP3 pathway in in vivo and in vitro models of septic cardiomyopathy, which were treated with the AhR antagonist CH-223191 and/or AhR agonist FICZ.Results: IPA supplementation improved cardiac dysfunction in rats with septic cardiomyopathy. IPA reduced inflammatory cytokine release and inhibited NF-κB/NLRP3 signaling pathway in myocardial tissue and in H9c2 cells. CH-223191 impaired the anti-inflammatory effect of IPA in LPS-treated cells, whereas FICZ exerted the same effect as IPA. IPA also exhibited anti-inflammatory activity by binding to the AhR. Our results indicated that IPA attenuated septic cardiomyopathy in rats via AhR/NF-κB/NLRP3 signaling.Conclusion: Our study revealed that IPA improved left heart dysfunction and myocardial inflammation caused by sepsis via AhR/NF-κB/NLRP3 signaling, suggesting that IPA is a potential therapy for septic cardiomyopathy.Keywords: Indole-3-propionic acid, septic cardiomyopathy, cardiac function, inflammation, aryl hydrocarbon receptor

Background: Uremic toxin indoxyl sulfate (IS) induces vascular inflammation, a crucial event in renal failure, and vascular complications in patients with chronic kidney disease (CKD). In endothelial cells, IS increases the production of inflammatory cytokines partially via the activation of the aryl hydrocarbon receptor (AhR), and several food flavonoids have been reported to act as antagonists of AhR. Objective: This study aimed to investigate whether antagonistic flavonoids can attenuate IS-induced inflammatory responses in vascular endothelial cells in vitro and renal failure in vivo. Design: Human umbilical vein endothelial cells (HUVECs) pretreated with the flavones apigenin, chrysin, or luteolin were stimulated with IS. Expression levels of genes involved in AhR signaling, inflammatory cytokine production, and reactive oxygen species (ROS) production were analyzed. Uninephrectomized mice were orally administered chrysin and received daily intraperitoneal injections of IS for 4 weeks. Results: In HUVECs, IS upregulated the mRNA expression of AhR-targeted genes (CYP1A1 and AhRR), and genes involved in inflammation (NOX4, MCP-1, IL-6, and COX2) and monocyte invasion/adhesion (ICAM1). All three flavones attenuated the IS-induced increase in the expression of these mRNAs. They also suppressed the IS-induced nuclear translocation of AhR and intracellular ROS production. Furthermore, IS-induced phosphorylation of the signal transducer and activator of transcription 3 (STAT3) was inhibited by treatment with these flavones. The results of in-vivo experiments showed that administration with chrysin attenuated the elevation of blood urea nitrogen levels and AhR-target gene expression and the pathological impairment of renal tissues in mice, regardless of higher serum levels of IS. Conclusions: Natural food flavones antagonizing AhR exerted protective effects against IS-induced inflammation through the inhibition of the AhR–STAT3 pathway in HUVECs. Moreover, chrysin ameliorated IS-induced renal dysfunction in a mouse model of CKD. These flavonoids could be a therapeutic strategy for vascular inflammation in CKD.

Objective To investigate the mechanism of autoinducer-2(AI-2) in relieving intestinal injury in neonatal mouse model of necrotizing enterocolitis (NEC). Methods Thirty-six 7-day-old C57BL/6J mice were randomly divided into Control group (fed by mother mice), NEC group (NEC model induced by formula+lipopolysaccharide administration, hypoxia and cold stress), and NEC+AI-2 group (AI-2 solution added to the modeled formula milk), with 12 mice in each group.The body weight and survival rate of each group were recorded during the modeling period.In 3 d after modeling, the mice were euthanized, and the histopathological changes in the terminal ileum were observed using HE staining.The mRNA expression levels of aryl hydrocarbon receptor (AHR), cytochrome P450 1A1(CYP1A1), TNF-α, IL-6 and IL-22 in intestinal tissue were detected with RT-qPCR.The protein levels of AHR and CYP1A1 in intestinal tissues were measured with Western blotting.The contents of TNF-α, IL-6 and IL-22 in intestinal tissues were detected using enzyme-linked immunosorbent assay (ELISA). Results The survival rate of neonatal rats was significantly higher in the NEC+AI-2 group than the NEC group (91.7%vs 66.7%, P < 0.05).The NEC+AI-2 group had obviously lower intestinal pathological injury score (1.33±0.21 vs 2.67±0.33, P < 0.05), increased mRNA and protein levels of AHR and CYP1A1 in intestinal tissues (P < 0.05), decreased expression levels of pro-inflammatory factors TNF-α and IL-6 in intestinal tissues (P < 0.05), while increased expression level of anti-inflammatory factor IL-22(P < 0.05) when compared with the NEC group.Furthermore, the expression and activation of intestinal AHR were negatively correlated with the intestinal pathological injury score (P < 0.001). Conclusion AI-2 alleviates intestinal injury in neonatal mice with NEC by activating AHR to regulate inflammatory response.

Abstract The membrane-delimited receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), angiotensin-converting enzyme 2 (ACE2), which is expressed in the intestine, collaborates with broad neutral amino acid transporter 1 (B0AT1). Tryptophan (Trp) is transported into intestinal epithelial cells by ACE2 and B0AT1. However, whether ACE2 and its binding protein B0AT1 are involved in Trp-mediated alleviation of intestinal injury is largely unknown. Here, we used weaned piglets and IPEC-J2 cells as models and found that ACE2/B0AT1 alleviated lipopolysaccharide (LPS)-induced diarrhea and promoted intestinal barrier recovery via transport of Trp. The levels of the aryl hydrocarbon receptor (AhR) and mechanistic target of rapamycin (mTOR) pathways were altered by ACE2. Dietary Trp supplementation in LPS-treated weaned piglets revealed that Trp alleviated diarrhea by promoting ACE2/B0AT1 expression, and examination of intestinal morphology revealed that the damage to the intestinal barrier was repaired. Our study demonstrated that ACE2 accompanied by B0AT1 mediated the alleviation of diarrhea by Trp through intestinal barrier repair via the mTOR pathway.

Objective To analyze the effects and molecular mechanisms of AhR signaling pathway in the treatment of scleroderma with Bushen Yijing Decoction. Methods The active ingredients of Bushen Yijing Decoction and its target genes, AhR signaling pathway genes and the genes related to scleroderma were searched through TCMSP and other databases, and LC-MS results. Target gene network diagram of scleroderma, AhR pathway and the key active ingredients in Bushen Yijing Decoction were constructed. The protein-protein interaction network was constructed with STRING database, and GO and Genome KEGG were also performed. Finally, the molecular docking of the active ingredients and AhR were verified. Results Ferulic acid, quercetin, kaempferol, isoferulic acid and luteolin were key active ingredients in Bushen Yijing Decoction for the treatment of scleroderma by targeting AhR signaling pathway. These active ingredients possibly regulated AhR signaling pathway molecules, including IL-6, CTNNB1, HSP90AA1, TNF and PTGS2, which were involved in the pathogenesis of scleroderma. Molecular docking showed that the binding energies of ferulic acid, kaempferol, quercetin, isoferulic acid and luteolin with AhR were lower than -6.0 kcal/mol, indicating a good binding activity. Conclusions The mechanisms by which Bushen Yijing Decoction treats scleroderma can be attributed to the active ingredients such as ferulic acid, quercetin, kaempferol, isoferulic acid, luteolin, which target AhR signaling pathway and regulate core targets, including IL-6, CTNNB1, HSP90AA1, TNF and PTGS2.

Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are mycotoxins widely found as cereal contaminants, and their co-consumption is associated with liver cancer. Both are immunotoxic, but their interactions have been little studied. This work was aimed to evaluate in mouse spleen mononuclear cells (SMC) the effects of the exposure to AFB1 (5–50 µM), FB1 (25–250 µM), and AFB1–FB1 mixtures (MIX) on the in vitro differentiation of regulatory T cells (Treg and Tr1-like) and Th17 cells, as well as elucidate the contribution of aryl hydrocarbon receptor (Ahr) in such effects. AFB1 and mainly MIX induced cytotoxicity in activated CD4 cells via Ahr signaling. AFB1 (5 µM) increased the Treg cell differentiation, but its combination with FB1 (25 µM) also reduced Th17 cell expansion by Ahr-dependent mechanisms. Therefore, this mixture could enhance the Treg/Th17 cell ratio and favor immunosuppression and escape from tumor immunosurveillance to a greater extent than individual mycotoxins. Whereas, AFB1-FB1 mixtures at medium–high doses inhibited the Tr1-like cell expansion induced by the individual mycotoxins and affected Treg and Th17 cell differentiation in Ahr-independent and dependent manners, respectively, which could alter anti-inflammatory and Th17 immune responses. Moreover, individual FB1 altered regulatory T and Th17 cell development independently of Ahr. In conclusion, AFB1 and FB1 interact by modifying Ahr signaling, which is involved in the immunotoxicity as well as in the alteration of the differentiation of Treg, Tr1-like, and Th17 cells induced by AFB1-FB1 mixtures. Therefore, Ahr is implicated in the regulation of the anti- and pro-inflammatory responses caused by the combination of AFB1 and FB1. [ABSTRACT FROM AUTHOR]

Circadian clocks maintain diurnal rhythms of sleep–wake cycle of 24 h that regulate not only the metabolism of an organism but also many other periodical processes. There is substantial evidence that circadian regulation is impaired in Alzheimer's disease. Circadian clocks regulate many properties known to be disturbed in Alzheimer's patients, such as the integrity of the blood–brain barrier (BBB) as well as the diurnal glymphatic flow that controls waste clearance from the brain. Interestingly, an evolutionarily conserved transcription factor, that is, aryl hydrocarbon receptor (AhR), impairs the function of the core clock proteins and thus could disturb diurnal rhythmicity in the BBB. There is abundant evidence that the activation of AhR signalling inhibits the expression of the major core clock proteins, such as the brain and muscle arnt‐like 1 (BMAL1), clock circadian regulator (CLOCK) and period circadian regulator 1 (PER1) in different experimental models. The expression of AhR is robustly increased in the brains of Alzheimer's patients, and protein level is enriched in astrocytes of the BBB. It seems that AhR signalling inhibits glymphatic flow since it is known that (i) activation of AhR impairs the function of the BBB, which is cooperatively interconnected with the glymphatic system in the brain, and (ii) neuroinflammation and dysbiosis of gut microbiota generate potent activators of AhR, which are able to impair glymphatic flow. I will examine current evidence indicating that activation of AhR signalling could disturb circadian functions of the BBB and impair glymphatic flow and thus be involved in the development of Alzheimer's pathology. [ABSTRACT FROM AUTHOR]

Difamilast, a phosphodiesterase 4 (PDE4) inhibitor, has been shown to be effective in the treatment of atopic dermatitis (AD), although the mechanism involved remains unclear. Since IL-33 plays an important role in the pathogenesis of AD, we investigated the effect of difamilast on IL-33 activity. Since an in vitro model of cultured normal human epidermal keratinocytes (NHEKs) has been utilized to evaluate the pharmacological potential of adjunctive treatment of AD, we treated NHEKs with difamilast and analyzed the expression of the suppression of tumorigenicity 2 protein (ST2), an IL-33 receptor with transmembrane (ST2L) and soluble (sST2) isoforms. Difamilast treatment increased mRNA and protein levels of sST2, a decoy receptor suppressing IL-33 signal transduction, without affecting ST2L expression. Furthermore, supernatants from difamilast-treated NHEKs inhibited IL-33-induced upregulation of TNF-α, IL-5, and IL-13 in KU812 cells, a basophil cell line sensitive to IL-33. We also found that difamilast activated the aryl hydrocarbon receptor (AHR)–nuclear factor erythroid 2-related factor 2 (NRF2) axis. Additionally, the knockdown of AHR or NRF2 abolished the difamilast-induced sST2 production. These results indicate that difamilast treatment produces sST2 via the AHR–NRF2 axis, contributing to improving AD symptoms by inhibiting IL-33 activity. [ABSTRACT FROM AUTHOR]

Cyprodinil, a globally utilized broad-spectrum pyrimidine amine fungicide, has been observed to elicit cardiac abnormality. Resveratrol (RSV), a naturally occurring polyphenolic compound, showcases remarkable defensive properties in nurturing cardiac development. To investigate whether RSV could protect against cyprodinil-induced cardiac defects, we exposed zebrafish embryos to cyprodinil (500 μg/L) in the presence or absence of RSV (1 μM). Our results showed that RSV significantly mitigated the decrease of survival rate and embryo movement and the hatching delay induced by cyprodinil. In addition, RSV also improved cyprodinil-induced zebrafish cardiac developmental toxicity, including pericardial edema and cardiac function impairment. In mechanism, RSV attenuated the cyprodinil-induced changes in mRNA expression involved in cardiac development, such as myh6, myl7, tbx5, and gata4, and calcium ion channels, such as ncx1h, slc8a4a, and atp2a2b. We further showed that RSV might inhibit the activity of aryl hydrocarbon receptor (AhR) signaling pathways induced by cyprodinil. In summary, our findings establish that the protective effects of RSV against the cardiac developmental toxicity are induced by cyprodinil due to its remarkable ability to inhibit AhR activity. Our findings not only shed light on a new avenue for regulating and ensuring the safe utilization of cyprodinil but also presents a novel concept to promote its responsible use. [ABSTRACT FROM AUTHOR]

Macrophages play an essential role in the innate immune system by differentiating into functionally diverse subsets in order to fight infection, repair damaged tissues, and regulate inappropriate immune responses. This functional diversity stems from their ability to adapt and respond to signals in the environment, which is in part mediated through aryl hydrocarbon receptor (AHR)-signaling. AHR, an environmental sensor, can be activated by various ligands, ranging from environmental contaminants to microbially derived tryptophan metabolites. This review discusses what is currently known about how AHR-signaling influences macrophage differentiation, polarization, and function. By discussing studies that are both consistent and divergent, our goal is to highlight the need for future research on the mechanisms by which AHR acts as an immunological switch in macrophages. Ultimately, understanding the contexts in which AHR-signaling promotes and/or inhibits differentiation, proinflammatory functions, and immunoregulatory functions, will help uncover functional predictions of immunotoxicity following exposure to environmental chemicals as well as better design AHR-targeted immunotherapies. [ABSTRACT FROM AUTHOR]

Tryptophan metabolism dysregulation has been observed in vitiligo. However, drawing a mechanistic linkage between this metabolic disturbance and vitiligo pathogenesis remains challenging. Aim to reveal the characterization of tryptophan metabolism in vitiligo and investigate the role of tryptophan metabolites in vitiligo pathophysiology. LC-MS/MS, dual-luciferase reporter assay, ELISA, qRT-PCR, small interfering RNA, western blotting, and immunohistochemistry were employed. Kynurenine pathway activation and KYAT enzyme-associated deviation to kynurenic acid (KYNA) in the plasma of stable non-segmental vitiligo were determined. Using a public microarray dataset, we next validated the activation of kynurenine pathway was related with inflammatory-related genes expression in skin of vitiligo patients. Furthermore, we found that KYNA induced CXCL10 upregulation in keratinocytes via AhR activation. Moreover, the total activity of AhR agonist was increased while the AhR concentration per se was decreased in the plasma of vitiligo patients. Finally, higher KYAT, CXCL10, CYP1A1 and lower AhR expression in vitiligo lesional skin were observed by immunohistochemistry staining. This study depicts the metabolic and genetic characterizations of tryptophan metabolism in vitiligo and proposes that KYNA, a tryptophan-derived AhR ligand, can enhance CXCL10 expression in keratinocytes. • The tryptophan metabolism pattern in the peripheral blood of stable vitiligo patients was depicted. • Kynurenine pathway activation and KYAT enzyme-associated deviation to kynurenic acid were determined in vitiligo patients. • Inflammatory-related genes were associated with the activation of the kynurenine pathway in vitiligo skin samples. • Kynurenic acid upregulated CXCL10 expression via canonical AhR signaling in human keratinocytes. • Circulating upregulation of AhR agonists while concomitant downregulation of AhR per se was revealed in vitiligo patients. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that has wide-ranging roles, including regulation of inflammation and homeostasis. AhR is not a cell surface receptor; rather, it exists in a cytoplasmic complex that responds to a wide variety of structurally dissimilar endogenous, microbial, and environmental ligands. The ubiquitous expression of AhR, its ability to be activated by a wide range of ligands, and its capacity to act as a master regulator for gene expression and homeostasis make it a promising new therapeutic target. Clinical trials of tapinarof cream have now validated AhR agonism as a therapeutic approach that can deliver significant efficacy for treating inflammatory skin diseases, including psoriasis and atopic dermatitis. Tapinarof 1% cream is a first-in-class, nonsteroidal, topical, AhR agonist with a pharmacokinetic profile that results in localized exposure at sites of disease, avoiding systemic safety concerns, drug interactions, or off-target effects. Psoriasis and atopic dermatitis both involve epidermal inflammation, cellular immune responses, dysregulation of skin barrier protein expression, and oxidative stress. On the basis of the clinical effectiveness of tapinarof cream for treating inflammatory skin diseases, we review how targeting AhR may offer a significant opportunity in other conditions that share key aspects of pathogenesis, including asthma, inflammatory bowel disease, eosinophilic esophagitis, ophthalmic, and nervous system diseases. [ABSTRACT FROM AUTHOR]

Introduction: Dioxins represent a category of enduring environmental contaminants that possess the capability to elicit endocrine disruptions and a spectrum of ailments, most notably encompassing malignancies, immunological impairments, and nervous system impairments. These chemical compounds incite the generation of Reactive Oxygen Species (ROS), consequently instigating cellular toxicity through the activation of the Aryl Hydrocarbon Receptor (AHR). Given the significant noxiousness associated with dioxins, it is imperative to implement decisive actions aimed at mitigating ongoing ambient exposure. In spite of advancements in comprehending the origin and fundamental mechanisms of persistent environmental pollutants, the development of efficacious interventions has remained an elusive endeavor. Objectives: This investigation focuses on the distinct pharmacological mechanisms inherent in polyphenolic constituents that have been hitherto explored in relation to various dioxin-induced toxicities, both in in vivo and in vitro models. Materials and Methods: Preclinical studies were identified through systematic searches of PubMed, Embase, and the Cochrane Library, while clinical trials were retrieved from ClinicalTrials.gov and PubMed databases. Results: Preclinical research unveils the significant efficacy of phytochemicals in mitigating dioxin toxicity. Conversely, clinical findings exhibit a mixed spectrum of outcomes, but hold promise for the use of phytochemicals as adjuncts to conventional therapies for diverse dioxin-induced toxicities. These outcomes suggest that polyphenols may exert substantial influence on disease-related mechanisms such as oxidative stress, inflammation, apoptosis, and gene regulation. Conclusion: In our assessment, this represents the inaugural comprehensive review encompassing in vitro and in vivo investigations concerning the molecular-level interactions between various environmental contaminants and polyphenols. Furthermore, additional clinical investigations are warranted, with a focus on the appropriate patient populations, identification of relevant toxicity biomarkers, and elucidation of the impact of phytochemicals on these parameters. [ABSTRACT FROM AUTHOR]

Objectives Materials and Methods Results Conclusions The purpose of this study was to determine whether indoxyl sulfate (IS) is involved in alveolar bone deterioration and to elucidate the mechanism underlying alveolar bone loss in chronic kidney disease (CKD) patients.Mice were divided into the control group, CP group (ligature‐induced periodontitis), CKD group (5/6 nephrectomy), and CKD + CP group. The concentration of IS in the gingival crevicular fluid (GCF) was determined by HPLC. The bone microarchitecture was evaluated by micro‐CT. MC3T3‐E1 cells were stimulated with IS, and changes in mitochondrial morphology and ferroptosis‐related factors were detected. RT‐PCR, western blotting, alkaline phosphatase activity assays, and alizarin red S staining were utilized to assess how IS affects osteogenic differentiation.Compared with that in the other groups, alveolar bone destruction in the CKD + CP group was more severe. IS accumulated in the GCF of mice with CKD. IS activated the aryl hydrocarbon receptor (AhR) in vitro, inhibited MC3T3‐E1 cell osteogenic differentiation, caused changes in mitochondrial morphology, and activated the SLC7A11/GPX4 signaling pathway. An AhR inhibitor attenuated the aforementioned changes induced by IS.IS activated the AhR/SLC7A11/GPX4 signaling pathway, inhibited osteogenesis in MC3T3‐E1 cells, and participated in alveolar bone resorption in CKD model mice through ferroptosis. [ABSTRACT FROM AUTHOR]

Background: Allergen-specific immunotherapy (AIT) is able to restore immune tolerance to allergens in allergic patients. However, some patients do not or only poorly respond to current treatment protocols. Therefore, there is a need for deeper mechanistic insights and further improvement of treatment strategies. The relevance of the aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor, has been investigated in several inflammatory diseases, including allergic asthma. However, its potential role in AIT still needs to be addressed. Methods: Amurinemodel of AIT in ovalbumin-induced allergic airway inflammation was performed in AhR-deficient (AhR-/-) and wild-type mice. Furthermore, AIT was combined with the application of the high-affinity AhR agonist 10-chloro-7Hbenzimidazo[2,1-a]benzo[de]iso-quinolin-7-one (10-Cl-BBQ) as an adjuvant to investigate the effects of AhR activation on therapeutic outcome. Results: Although AhR-/- mice suffer stronger allergic responses than wild-type mice, experimental AIT is comparably effective in both. Nevertheless, combining AIT with the administration of 10-Cl-BBQ improved therapeutic effects by an AhRdependent mechanism, resulting in decreased cell counts in the bronchoalveolar fluid, decreased pulmonary Th2 and Th17 cell levels, and lower sIgE levels. Conclusion: This study demonstrates that the success of AIT is not dependent on the AhR. However, targeting the AhR during AIT can help to dampen inflammation and improve tolerogenic vaccination. Therefore, AhR ligands might represent promising candidates as immunomodulators to enhance the efficacy of AIT. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AhR) is a transcription factor that regulates the immune system through complicated transcriptional programs. Genistein, an AhR ligand, exhibits anti-inflammatory properties. However, its role in modulating immune responses via the AhR signaling pathway remains unclear. In this study, 360 male Arbor Acre broilers (1-day-old) were fed a basal diet supplemented with 40 or 80 mg/kg genistein and infected with or without Clostridium perfringens (Cp). Our results demonstrated that genistein ameliorated Cp-induced intestinal damage, as reflected by the reduced intestinal lesion scores and improved intestinal morphology and feed-to-gain ratio. Moreover, genistein increased intestinal sIgA, TGF-β, and IL-10, along with elevated serum IgG, IgA, and lysozyme levels. Genistein improved intestinal AhR and cytochrome P450 family 1 subfamily A member 1 (CYP1A1) protein levels and AhR+ cell numbers in Cp-challenged broilers. The increased number of AhR+CD163+ cells in the jejunum suggested a potential association between genistein-induced AhR activation and anti-inflammatory effects mediated through M2 macrophage polarization. In IL-4-treated RAW264.7 cells, genistein increased the levels of AhR, CYP1A1, CD163, and arginase (Arg)-1 proteins, as well as IL-10 mRNA levels. This increase was attenuated by the AhR antagonist CH223191. In summary, genistein activated the AhR signaling pathway in M2 macrophages, which enhanced the secretion of anti-inflammatory cytokines and attenuated intestinal damage in Cp-infected broilers Cp. [ABSTRACT FROM AUTHOR]

Maternal obesity and/or Western diet (WD) is associated with an increased risk of metabolic dysfunction-associated steatotic liver disease (MASLD) in offspring, driven, in part, by the dysregulation of the early life microbiome. Here, using a mouse model of WD-induced maternal obesity, we demonstrate that exposure to a disordered microbiome from WD-fed dams suppressed circulating levels of endogenous ligands of the aryl hydrocarbon receptor (AHR; indole, indole-3-acetate) and TMAO (a product of AHR-mediated transcription), as well as hepatic expression of Il10 (an AHR target), in offspring at 3 weeks of age. This signature was recapitulated by fecal microbial transfer from WD-fed pregnant dams to chow-fed germ-free (GF) lactating dams following parturition and was associated with a reduced abundance of Lactobacillus in GF offspring. Further, the expression of Il10 was downregulated in liver myeloid cells and in LPS-stimulated bone marrow-derived macrophages (BMDM) in adult offspring, suggestive of a hypo-responsive, or tolerant, innate immune response. BMDMs from adult mice lacking AHR in macrophages exhibited a similar tolerogenic response, including diminished expression of Il10. Overall, our study shows that exposure to maternal WD alters microbial metabolites in the offspring that affect AHR signaling, potentially contributing to innate immune hypo-responsiveness and progression of MASLD, highlighting the impact of early life gut dysbiosis on offspring metabolism. Further investigations are warranted to elucidate the complex interplay between maternal diet, gut microbial function, and the development of neonatal innate immune tolerance and potential therapeutic interventions targeting these pathways. [ABSTRACT FROM AUTHOR]

The membrane-delimited receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), angiotensin-converting enzyme 2 (ACE2), which is expressed in the intestine, collaborates with broad neutral amino acid transporter 1 (B0AT1). Tryptophan (Trp) is transported into intestinal epithelial cells by ACE2 and B0AT1. However, whether ACE2 and its binding protein B0AT1 are involved in Trp-mediated alleviation of intestinal injury is largely unknown. Here, we used weaned piglets and IPEC-J2 cells as models and found that ACE2/B0AT1 alleviated lipopolysaccharide (LPS)-induced diarrhea and promoted intestinal barrier recovery via transport of Trp. The levels of the aryl hydrocarbon receptor (AhR) and mechanistic target of rapamycin (mTOR) pathways were altered by ACE2. Dietary Trp supplementation in LPS-treated weaned piglets revealed that Trp alleviated diarrhea by promoting ACE2/B0AT1 expression, and examination of intestinal morphology revealed that the damage to the intestinal barrier was repaired. Our study demonstrated that ACE2 accompanied by B0AT1 mediated the alleviation of diarrhea by Trp through intestinal barrier repair via the mTOR pathway. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators. [ABSTRACT FROM AUTHOR]

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD) is a persistent environmental contaminant and high affinity ligand for the aryl hydrocarbon receptor (AhR). In animal models, AhR activation by TCDD generally inhibits antibody secretion. However, it is less clear if this translates to human antibody production. Using a human Burkitt lymphoma B-cell line (CL-01) that can be stimulated to secrete Ig and undergo class switch recombination to other Ig isotypes, the current study evaluated the effects of AhR activation or antagonism on the human Ig isotypic expression profile with CD40L+IL-4 stimulation. Our results suggest that AhR agonists (TCDD and indirubin) have little to no effect on IgM or IgA secretion, which were also not induced with stimulation. However, AhR activation significantly inhibited stimulation-induced IgG secretion, an effect reversed by the AhR antagonist CH223191. Evaluation of Ig heavy chain (IgH) constant region gene expression (ie Cμ, Cγ1-4, Cα1-2, and Cε that encode for IgM, IgG1-4, IgA1-2, and IgE, respectively) demonstrated differential effects. While Cμ and Cα2 transcripts were unaffected by stimulation or AhR agonists, AhR activation significantly inhibited stimulation-induced Cγ2-4 and Cε mRNA transcripts, which was reversed by AhR antagonism. Notably, AhR antagonism in the absence of exogenous AhR ligands significantly increased IgG and IgA secretion as well as the expression of Cγ2-4 and Cε. These results suggest that modulation of AhR activity differentially alters the IgH isotypic expression profile and antibody secretion that may be partly dependent on cellular stimulation. Since a variety of chemicals from anthropogenic, industrial, pharmaceutical, dietary, and bacterial sources bind the AhR, the ability of environmental exposures to alter AhR activity (i.e. activate or inhibit) may have a direct influence on immune function and antibody-relevant disease conditions. [ABSTRACT FROM AUTHOR]

Tryptophan is an essential amino acid transformed by host and gut microbial enzymes into metabolites that regulate mucosal homeostasis through aryl hydrocarbon receptor (AhR) activation. Alteration of tryptophan metabolism has been associated with chronic inflammation; however, whether tryptophan supplementation affects the metabolite repertoire and AhR activation under physiological conditions in humans is unknown. We performed a randomized, double blind, placebo-controlled, crossover study in 20 healthy volunteers. Subjects on a low tryptophan background diet were randomly assigned to a 3-wk l -tryptophan supplementation (3 g/day) or placebo, and after a 2-wk washout switched to opposite interventions. We assessed gastrointestinal and psychological symptoms by validated questionnaires, AhR activation by cell reporter assay, tryptophan metabolites by liquid chromatography and high-resolution mass spectrometry, cytokine production in isolated monocytes by ELISA, and microbiota profile by 16S rRNA Illumina technique. Oral tryptophan supplementation was well tolerated, with no changes in gastrointestinal or psychological scores. Compared with placebo, tryptophan increased AhR activation capacity by duodenal contents, but not by feces. This was paralleled by higher urinary and plasma kynurenine metabolites and indoles. Tryptophan had a modest impact on fecal microbiome profiles and no significant effect on cytokine production. At the doses used in this study, oral tryptophan supplementation in humans induces microbial indole and host kynurenine metabolic pathways in the small intestine, known to be immunomodulatory. The results should prompt tryptophan intervention strategies in inflammatory conditions of the small intestine where the AhR pathway is impaired. NEW & NOTEWORTHY: We demonstrate that in healthy subjects, orally administered tryptophan activates microbial indole and host kynurenine pathways in the small intestine, the primary metabolic site for dietary components, and the richest source of immune cells along the gut. This study provides novel insights in how to optimally activate immunomodulatory AhR pathways and indole metabolism in the small intestine, serving as basis for future therapeutic trials using l -tryptophan supplementation in chronic inflammatory conditions affecting the small intestine. [ABSTRACT FROM AUTHOR]

Obesity has become a pandemic, as currently more than half a billion people worldwide are obese. The etiology of obesity is multifactorial, and combines a contribution of hereditary and behavioral factors, such as nutritional inadequacy, along with the influences of environment and reduced physical activity. Two types of adipose tissue widely known are white and brown. While white adipose tissue functions predominantly as a key energy storage, brown adipose tissue has a greater mass of mitochondria and expresses the uncoupling protein 1 (UCP1) gene, which allows thermogenesis and rapid catabolism. Even though white and brown adipocytes are of different origin, activation of the brown adipocyte differentiation program in white adipose tissue cells forces them to transdifferentiate into "beige" adipocytes, characterized by thermogenesis and intensive lipolysis. Nowadays, researchers in the field of small molecule medicinal chemistry and gene therapy are making efforts to develop new drugs that effectively overcome insulin resistance and counteract obesity. Here, we discuss various aspects of white-to-beige conversion, adipose tissue catabolic re-activation, and non-shivering thermogenesis. [ABSTRACT FROM AUTHOR]

For the past 70 years, the dopamine hypothesis has been the key working model in schizophrenia. This has contributed to the development of numerous inhibitors of dopaminergic signaling and antipsychotic drugs, which led to rapid symptom resolution but only marginal outcome improvement. Over the past decades, there has been limited research on the quantifiable pathological changes in schizophrenia, including premature cellular/neuronal senescence, brain volume loss, the attenuation of gamma oscillations in electroencephalograms, and the oxidation of lipids in the plasma and mitochondrial membranes. We surmise that the aberrant activation of the aryl hydrocarbon receptor by toxins derived from gut microbes or the environment drives premature cellular and neuronal senescence, a hallmark of schizophrenia. Early brain aging promotes secondary changes, including the impairment and loss of mitochondria, gray matter depletion, decreased gamma oscillations, and a compensatory metabolic shift to lactate and lactylation. The aim of this narrative review is twofold: (1) to summarize what is known about premature cellular/neuronal senescence in schizophrenia or schizophrenia-like disorders, and (2) to discuss novel strategies for improving long-term outcomes in severe mental illness with natural senotherapeutics, membrane lipid replacement, mitochondrial transplantation, microbial phenazines, novel antioxidant phenothiazines, inhibitors of glycogen synthase kinase-3 beta, and aryl hydrocarbon receptor antagonists. [ABSTRACT FROM AUTHOR]

The environmental factor aryl hydrocarbon receptor (AhR), a key protein connecting the external environmental signals (e.g., environmental endocrine disruptor TCDD) to internal cellular processes, is involved in the activation of peripheral macrophages and inflammatory response in human body. Thus, there is widespread interest in finding compounds to anti‐inflammatory response in macrophages by targeting human AhR. Here, ensemble docking based‐virtual screening was first used to screen a library (~200,000 compounds) against human AhR ligand binding domain (LBD) and 25 compounds were identified as potential inhibitors. Then, 9 out of the 25 ligands were found to down‐regulate the mRNA expression of CYP1A1 (a downstream gene of AhR signaling) in AhR overexpressing macrophages. The most potent compound AE‐411/41415610 was selected for further study and found to reduce both mRNA and protein expressions level of CYP1A1 in mouse peritoneal macrophage. Moreover, protein chip signal pathway analysis indicated that AE‐411/41415610 play a role in regulating JAK–STAT and AKT–mTOR pathways. In sum, the discovered hits with novel scaffolds provided a starting point for future design of more effective AhR‐targeted lead compounds to regulate CYP1A1 expression of inflammatory peritoneal macrophages. [ABSTRACT FROM AUTHOR]

Background: Wildfires are a global concern due to their wide-ranging environmental, economic, and public health impacts. Climate change contributes to an increase in the frequency and intensity of wildfires making smoke exposure a more significant and recurring health concern for individuals with airway diseases. Some of the most prominent effects of wildfire smoke exposure are asthma exacerbations and allergic airway sensitization. Likely due to the delayed recognition of its health impacts in comparison with cigarette smoke and industrial or traffic-related air pollution, research on the composition, the mechanisms of toxicity, and the cellular/molecular pathways involved is poor or non-existent. Summary: This review discusses potential underlying pathological mechanisms of wildfire-smoke-related allergic airway disease and asthma. We focused on major gaps in understanding the role of wildfire smoke composition in the development of airway disease and the known and potential mechanisms involving cellular and molecular players of oxidative injury at the epithelial barrier in airway inflammation. We examine how PM2.5, VOCs, O3, endotoxin, microbes, and toxic gases may affect oxidative stress and inflammation in the respiratory mucosal barrier. We discuss the role of AhR in mediating smoke's effects in alarmin release and IL-17A production and how glucocorticoid responsiveness may be impaired by IL-17A-induced signaling and epigenetic changes leading to steroid-resistant severe airway inflammation. Key Message: Effective mitigation of wildfire-smoke-related respiratory health effects would require comprehensive research efforts aimed at a better understanding of the immune regulatory effects of wildfire smoke in respiratory health and disease. [ABSTRACT FROM AUTHOR]

FICZ (6-formylindolo[3,2-b]carbazole) is a potent aryl hydrocarbon receptor agonist that has a poorly understood function in the regulation of inflammation. In this study, we investigated the effect of aryl hydrocarbon receptor activation by FICZ in a murine model of autoimmune hepatitis induced by concanavalin A. High-throughput sequencing techniques such as single-cell RNA sequencing and assay for transposase accessible chromatin sequencing were used to explore the mechanisms through which FICZ induces its effects. FICZ treatment attenuated concanavalin A–induced hepatitis, evidenced by decreased T-cell infiltration, decreased circulating alanine transaminase levels, and suppression of proinflammatory cytokines. Concanavalin A revealed an increase in natural killer T cells, T cells, and mature B cells upon concanavalin A injection while FICZ treatment reversed the presence of these subsets. Surprisingly, concanavalin A depleted a subset of CD55+ B cells, while FICZ partially protected this subset. The immune cells showed significant dysregulation in the gene expression profiles, including diverse expression of migratory markers such as CCL4 , CCL5 , and CXCL2 and critical regulatory markers such as Junb. Assay for transposase accessible chromatin sequencing showed more accessible chromatin in the CD3e promoter in the concanavalin A–only group as compared to the naive and concanavalin A–exposed, FICZ-treated group. While there was overall more accessible chromatin of the Adgre1 (F4/80) promoter in the FICZ-treated group, we observed less open chromatin in the Itgam (CD11b) promoter in Kupffer cells, supporting the ability of FICZ to reduce the infiltration of proinflammatory cytokine producing CD11b+ Kupffer cells. Taken together, these data demonstrate that aryl hydrocarbon receptor activation by FICZ suppresses liver injury through the limitation of CD3+ T-cell activation and CD11b+ Kupffer cell infiltration. [ABSTRACT FROM AUTHOR]

Aryl hydrocarbon receptor (AhR) is a ligand‐dependent transcription factor. We previously reported spontaneous ileocecal tumorigenesis in AhR‐deficient mice after the age of 10 weeks, which originated in the confined area between ileum and cecum. This study aimed to investigate the underlying mechanism that causes tumor development at this particular location. To observe mucosal architecture in detail, tissues of ileocecal region were stained with methylene blue. Gene expression profile in the ileocecal tissue was compared with cecum. Immunohistochemical analysis was performed with ileocecal tissues using antibodies against ileum‐specific Reg3β or cecum‐specific Pitx2. In AhR+/+ mice and AhR+/− mice, that do not develop lesions, methylene blue staining revealed the gradually changing shape and arrangement of villi from ileum to cecum. It was also observed in AhR‐deficient mice before developing lesions. Microarray‐based analysis revealed abundant antimicrobial genes, such as Reg3, in the ileocecal tissue while FGFR2 and Pitx2 were specific to cecum. Immunohistochemical analysis of AhR‐deficient mice indicated that lesions originated from the ileocecal junction, a boundary area between different epithelial types. Site‐specific gene expression analysis revealed higher expression of IL‐1β at the ileocecal junction compared with the ileum or cecum of 9–11‐week‐old AhR‐deficient mice. These findings indicate that AhR plays a vital function in the ileocecal junction. Regulating AhR activity can potentially manage the stability of ileocecal tissue possessing cancer‐prone characteristics. This investigation contributes to understanding homeostasis in different epithelial transitional tissues, frequently associated with pathological states. [ABSTRACT FROM AUTHOR]