Search Results (441)

Kynurenic acid (KYNA), a tryptophan metabolite, possesses immunomodulatory properties, although the molecular mechanism of this action has not yet been resolved. In the present study, the effects of KYNA on the secretion of selected cytokines and chemokines by macrophages derived from the human THP-1 cell line are investigated. Furthermore, the involvement of the aryl hydrocarbon receptor (AhR) and the G protein-coupled receptor 35 (GPR35) in mediating the effects of KYNA was examined. In lipopolysaccharide (LPS)-stimulated THP-1-derived macrophages, KYNA significantly reduced IL-6 and CCL-2, but increased IL-10 and M-CSF levels. AhR antagonist CH-223191 reduced the KYNA influence on IL-6, CCL-2, and M-CSF production, while the GPR35 antagonist, ML-145, blocked KYNA-induced IL-10 production. Furthermore, it was shown that THP-1 derived macrophages were capable of synthesizing and releasing KYNA and that its production was increased in the presence of LPS. These findings suggest that THP-1-derived macrophages are a source of KYNA and that KYNA modulates inflammatory responses predominantly through AhR and GPR35 receptors. Our study provides further evidence for the involvement of macrophages in immunomodulatory processes that are dependent on AhR and GPR35 receptors, as well as the potential role of KYNA in these phenomena. Full article

The intestinal barrier governs organismal health through nutrient absorption, microbial homeostasis, and immune surveillance. While calorie restriction (CR) enhances metabolic health, the molecular mechanisms underlying its beneficial effects on gut integrity remain unclear. Here, we demonstrate that the aryl hydrocarbon receptor (AHR), a conserved xenobiotic sensor and metabolic regulator, is essential for CR-mediated improvements in intestinal function. Using Caenorhabditis elegans (C. elegans), we subjected wild-type (N2) and AHR-deficient strains (CZ2485 and ZG24) to ad libitum feeding (AL), intermittent fasting (IF), or complete food deprivation (FD). In wild-type animals, intermittent fasting markedly reduced intestinal permeability and bacterial burden while enhancing mitochondrial function and reducing reactive oxygen species. Complete food deprivation conferred modest benefits. Remarkably, these protective effects were severely compromised in AHR mutants, which exhibited increased gut leakage, bacterial colonization, and mitochondrial oxidative stress under fasting conditions. These findings establish AHR as a critical mediator of fasting-induced intestinal resilience, revealing a previously unrecognized regulatory axis linking metabolic sensing to gut barrier homeostasis. Our work illuminates fundamental mechanisms through which calorie restriction promotes gastrointestinal health and identifies AHR-dependent pathways as promising therapeutic targets for metabolic and inflammatory distress affecting the gut–systemic interface. Full article

Enteroendocrine cells (EECs) are specialized secretory cells in the gut epithelium that differentiate from intestinal stem cells (ISCs). Mature EECs secrete incretin hormones that stimulate pancreatic insulin secretion and regulate appetite. Decreased EEC numbers and impaired secretion of the incretin glucagon-like peptide-1 (GLP1) have been implicated in obesity-associated metabolic complications. Gut microbial metabolites of dietary tryptophan (TRP) were recently shown to modulate ISC proliferation and differentiation. However, their specific effects on EEC differentiation are not known. We hypothesized that the gut microbial metabolites of dietary tryptophan counteract impaired GLP1 production and function in obesity by stimulating EEC differentiation from ISCs. We utilized complementary models of human and rat intestines to determine the effects of obesity or TRP metabolites on EEC differentiation. EEC differentiation was assessed by the EEC marker chromogranin A (CHGA) levels in the intestinal mucosa of normal versus obese rats. The effects of TRP metabolites on EEC differentiation were determined in human intestinal organoids treated with indole, a primary TRP metabolite, or the culture supernatant of Lactobacillus acidophilus grown in TRP media (LA-CS-TRP). Our results showed that the mRNA and protein levels of CHGA, the EEC marker, were significantly decreased (~60%) in the intestinal mucosa of high-fat-diet-induced obese rat intestines. The expression of the transcription factors that direct the ISC differentiation towards the EEC lineage was also decreased in obesity. In human organoids, treatment with indole or LA-CS-TRP significantly increased (more than 2-fold) CHGA levels, which were blocked by the aryl hydrocarbon receptor (AhR) antagonist CH-223191. Thus, the stimulation of EEC differentiation by colonic microbial metabolites highlights a novel therapeutic role of TRP metabolites in obesity and associated metabolic disorders. Full article

The scientific community’s interest in natural compounds with antiviral properties has considerably increased after the emergence of the severe acute respiratory syndrome coronavirus (SARS-CoV-2), especially for their potential use in the treatment of the COVID-19 infection. From this perspective, bovine coronavirus (BCoV), member of the genus β-CoV, represents a valuable virus model to study human β-CoVs, bypassing the risks of handling highly pathogenic and contagious viruses. Pimarane diterpenes are a significant group of secondary metabolites produced by phytopathogenic fungi, including several Diplodia species. Among the members of this class of natural products, sphaeropsidin A (SphA) and its analog sphaeropsidin B (SphB) are well known for their bioactivities, such as antimicrobial, insecticidal, herbicidal, and anticancer. In this study, the antiviral effects of SphA and SphB were evaluated for the first time on bovine (MDBK) cells infected with BCoV. Our findings showed that both sphaeropsidins significantly increased cell viability in infected cells. These substances also caused substantial declines in the virus yield and in the levels of the viral spike S protein. Interestingly, during the treatment, a cellular defense mechanism was detected in the downregulation of the aryl hydrocarbon receptor (AhR) signaling, which is affected by BCoV infection. We also observed that the presence of SphA and SphB determined the deacidification of the lysosomal environment in infected cells, which may be related to their antiviral activities. In addition, in silico investigations have been performed to elucidate the molecular mechanism governing the recognition of bovine AhR (bAhR) by Sphs. Molecular docking studies revealed significant insights into the structural determinants driving the bAhR binding by the examined compounds. Hence, in vitro and in silico results demonstrated that SphA and SphB are promising drug candidates for the development of efficient therapies able to fight a β-CoV-like BCoV during infection. Full article

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure has long been associated with reproductive dysfunction in males and females even at miniscule levels, which can persist across generations. Given the continued industrial use and detection of other aryl hydrocarbon receptor (AhR) agonists in the general population and the demonstrated heritable phenotypes of TCDD exposure, further work is justified to elucidate reproductive pathologies and minimize exposure risk. In females, multi- and transgenerational subfertility has been demonstrated in a zebrafish (Danio rerio) model exposed to 50 pg/mL TCDD once at 3 and 7 weeks post fertilization (wpf). We further characterize the histopathologic, hormonal and transcriptomic outcomes of the mature female zebrafish ovary following early-life TCDD exposure. Exposure was associated with significantly increased ovarian atresia in the F0 and F1, but not F2 generation. Other oocyte staging and vitellogenesis were unaffected in all generations. Exposed F0 females showed increased levels of whole-body triiodothyronine (T3) and 17β-estradiol (E2) levels, but not vitellogenin (Vtg), 11-ketotestosterone (11-KT), cortisol, thyroxine (T4), or testosterone (T). Ovarian transcriptomics were most dysregulated in the F2. Both F0 and F2, but not F1, showed changes in epigenetic-related gene expression. Rho signaling was the top pathway for both F0 and F2. Full article

Industrial development has increased environmental dioxin concentrations, sparking concern about human health impacts. Examining dioxin neurotoxicity has highlighted associations with cognitive impairment and behavioral abnormality. Dioxins are ligands of the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor; it is speculated that dioxin-induced AHR activation is pivotal for toxic effects. Accurate AHR-expressing cell identification is therefore indispensable for understanding the molecular and cellular mechanisms of dioxin toxicity. Herein, current knowledge regarding AHR expression in the mammalian brain is summarized, and dioxin neurotoxicity mechanisms are discussed. Histological studies show AHR-expressing neurons in multiple brain regions, including the hippocampus and cerebral cortex. Dopaminergic and noradrenergic neurons exhibit AHR expression, suggesting possible roles in the monoaminergic system. AHR overactivation evokes dendritic arborization atrophy, whereas its deficiency increases complexity, implying that AHR-mediated signaling is crucial for neuronal growth and maturation. AHR is also involved in neurogenesis and neuronal precursor migration. Collectively, these findings support the notion that dioxin-induced AHR overactivation in individual neurons disrupts neural circuit structure, ultimately leading to impaired brain function. However, as AHR downstream signaling is intertwined with various molecules and pathways, the precise mechanisms remain unclear. Further studies on the expression, signaling, and roles of AHR are needed to clarify dioxin neurotoxicity. Full article

Matrix metalloproteinase-9 (MMP-9) and lipopolysaccharide (LPS) levels are known to be elevated in obesity and contribute to metabolic dysfunction. 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), an endogenous ligand of the aryl hydrocarbon receptor (AhR), has been implicated in the regulation of inflammatory responses. This study aimed to determine whether ITE can inhibit LPS-induced MMP-9 expression in monocytic cells and to explore the underlying signaling mechanisms involved. Human monocytic THP-1 cells and primary human monocytes were treated with LPS in the presence or absence of ITE. MMP-9 mRNA and protein levels were assessed using quantitative real-time PCR and ELISA, respectively, while gelatin zymography was employed to evaluate MMP-9 enzymatic activity. Chromatin immunoprecipitation followed by qPCR (ChIP-qPCR) was performed to assess NF-κB and AP-1 binding to the MMP-9 promoter region. Our findings demonstrate that ITE significantly suppresses LPS-induced MMP-9 gene and protein expression. This suppression is associated with a marked reduction in LPS-induced NF-κB and AP-1 transcriptional activity. ChIP-qPCR confirmed that ITE attenuates the recruitment of NF-κB and AP-1 to the MMP-9 promoter, thereby inhibiting its transcription. In summary, ITE downregulates LPS-induced MMP-9 expression by interfering with NF-κB/AP-1 signaling, suggesting a potential anti-inflammatory mechanism that could be relevant in the context of MMP-9-driven inflammatory conditions. Full article

Metabolic dysfunction-associated fatty liver disease (MAFLD) represents a global health burden, however, therapeutic advancements remain hindered by incomplete insights on mechanisms and suboptimal clinical interventions. This review focused on the transcription factors (TFs) associated with the gut–liver axis, emphasizing their roles as molecular interpreters of systemic crosstalk in MAFLD. We delineate how TF networks integrate metabolic, immune, and gut microbial signals to manage hepatic steatosis, inflammation, and fibrosis. For instance, metabolic TFs such as peroxisome proliferator-activated receptor α (PPARα) and farnesoid X receptor (FXR) are responsible for regulating lipid oxidation and bile acid homeostasis, while immune-related TFs like signal transducer and activator of transcription 3 (STAT3) modulate inflammatory cascades involving immune cells. Emerging evidence highlights microbiota-responsive TFs, like hypoxia-inducible factor 2α (HIF2α) and aryl hydrocarbon receptor (AHR), linking microbial metabolite signaling to hepatic metabolic reprogramming. Critically, TF-centric therapeutic strategies, including selective TF-agonists, small molecules targeted to degrade TF, and microbiota modulation, hold considerable promise for treating MAFLD. By synthesizing these insights, this review underscores the necessity to dissect TF-mediated interorgan communication and proposes a roadmap for translating mechanism discoveries into precision therapies. Future research should prioritize the use of multi-omics approaches to map TF interactions and validate their clinical relevance to MAFLD. Full article

Environmental pollutants like PM2.5 contribute to chronic rhinosinusitis (CRS). The aryl hydrocarbon receptor (AhR), a contaminant sensor linked to tryptophan metabolites, is regulated by IL4I. However, how PM2.5 stimulation via IL4I1 influences AhR activation and CRS pathogenesis remains unclear. This study explored the IL4I1-AhR pathway in CRS using patient tissues, HNEpCs, and murine models. Methods included IHC, qRT-PCR, and WB under PM2.5 exposure, with further investigation into downstream effects on CYP1B1 and epithelial–mesenchymal transition (EMT). Significant upregulation of IL4I1, AhR, and CYP1B1 was observed in CRS tissues, with higher expression levels in CRS patients. Exposure to PM2.5 activated the IL4I1-AhR pathway, leading to decreased E-cadherin, increased N-cadherin and vimentin, and impaired nasal mucosal barrier function. In vitro experiments demonstrated that PM2.5-induced EMT in HNEpCs was mediated by IL4I1-dependent AhR activation. CH223191 reduced cell migration and EMT, while IL4I1 knockdown attenuated AhR activation and EMT marker expression. Murine models further confirmed that PM2.5 exacerbated nasal polyp formation and tissue remodeling via the IL4I1-AhR pathway. This study underscores the critical role of the IL4I1-AhR signaling pathway in PM2.5-induced nasal mucosal barrier dysfunction and EMT in CRS. IL4I1, as an upstream regulator of AhR, promotes EMT and nasal mucosal barrier disruption. Full article

Latent tuberculosis infection (LTBI) is prevalent in patients with type 2 diabetes. We aimed to examine the relationship between serum levels of aryl hydrocarbon receptor (AhR) and LTBI in patients with type 2 diabetes. In this cross-sectional study, patients with type 2 diabetes were screened for LTBI using the QuantiFERON-TB (QFT) test. Of 543 patients screened for LTBI, 133 (24.5%) were QFT-positive. The QFT-positive patients had higher AhR levels than the QFT-negative patients (44.6 [interquartile range: 25.4–58.6] pg/mL vs. 37.8 [interquartile range: 17.4–55.0] pg/mL; p = 0.004). According to the receiver operating characteristic curve, the area under the curve was 0.584 (95% confidence interval: 0.528–0.639; p = 0.004) and the optimal cutoff value for serum AhR levels was of 37.7 pg/mL for differentiating a QFT-positive result. By a multivariable logistic regression analysis, the patients with high AhR levels had a greater risk of being QFT positive than those with low AhR levels (odds ratio = 1.902, 95% confidence interval: 1.254–2.886; p = 0.003). In conclusion, in patients with type 2 diabetes, a high serum AhR level was associated with LTBI. Full article

Psoriasis is a chronic inflammatory skin disease characterised by increased oxidative stress, the overproliferation of keratinocytes, the accumulation of inflammatory mediators, and skin barrier damage. Although a number of therapeutic options are available, finding long-term treatments that are well-tolerated and patient-friendly treatments remains a challenge. Tapinarof is a new type of aryl hydrocarbon receptor (AhR) modulator that has recently attracted attention as a promising non-steroidal alternative. However, its application may be limited by its poor water solubility and low degree of skin penetration. Nanotechnology-based drug carriers, specially nanogels, offer new opportunities to overcome these limitations by combining the advantages of targeted drug delivery and enhanced skin penetration. Furthermore, nanogel formulations can improve skin hydration and support the restoration of skin barrier function, which are important in the treatment of psoriasis. This review focuses on current and emerging therapeutic approaches, with particular emphasis on the potential of incorporating tapinarof into nanogel formulations as a novel alternative to topical psoriasis treatment. Full article

Polycyclic aromatic hydrocarbons (PAHs), prevalent aquatic contaminants, arise from burning fossil fuels, a major source of greenhouse gases driving global warming. PAHs and warmer temperatures individually exert diverse negative effects on aquatic organisms. However, the effects of PAH exposure and/or rising temperature remain largely unknown. Liver in vitro models, like the rainbow trout (Oncorhynchus mykiss) RTL-W1 liver cell line, have been employed to unravel PAH-exposure effects, primarily on cell viability and enzymatic activity. Here, monolayer-cultured (2D) RTL-W1 cells were used to assess the co-exposure effects of temperature (18 and 21 °C) and two PAHs, benzo[a]pyrene (B[a]P) and benzo[k]fluoranthene (B[k]F), at 10 and 100 nM. After a 72 h exposure, the cell density and viability were evaluated using the trypan blue and LDH assays. The mRNA levels of the detoxification-associated genes aryl hydrocarbon receptor (AhR), cytochrome P450 (CYP)1A, CYP3A27, glutathione S-transferase omega 1 (GSTO1), uridine diphosphate–glucuronosyltransferase (UGT), catalase (CAT), and multidrug resistance-associated protein 2 (MRP2) were measured by RT-qPCR. Temperature influenced cell viability and LDH leakage. Both PAHs reduced the cell density and upregulated the mRNA levels of AhR, CYP1A, CYP3A27, and UGT, while GSTO1 and MRP2 were only augmented after the higher B[k]F concentration. Temperature influenced CAT and UGT expression. There was no interaction between temperature and the PAHs. Overall, the results show that B[k]F has more effects on detoxification targets than B[a]P, whereas a temperature increase mildly affects gene expression. The RTL-W1 in 2D seems useful for unravelling not only the liver effects of PAH but also the impact of temperature stress. Full article

Background: Particulate matter (PM) is a major environmental pollutant that induces oxidative stress, inflammation, and extracellular matrix (ECM) degradation, leading to skin damage and accelerated aging. Xanthorrhizol (XAN), a bioactive compound derived from Curcuma xanthorrhiza Roxb., exhibits anti-inflammatory and antioxidative properties, making it a promising candidate for protecting against PM-induced skin damage. This study investigated the protective effects of XAN and C. xanthorrhiza supercritical extract (CXSE) on PM-exposed skin cells. Methods: A 3D-reconstructed skin model and HaCaT human keratinocytes were exposed to PM (100 µg/mL) with or without CXSE or XAN. Histological analysis, enzyme-linked immunosorbent assay (ELISA), Western blot, reverse transcription-polymerase chain reaction (RT-PCR), and reporter gene assays were performed to assess the ECM integrity, inflammatory cytokine production, aryl hydrocarbon receptor (AhR) activation, and oxidative stress responses. Results: PM exposure activates AhR and mitogen-activated protein kinases (MAPK) signaling, increases reactive oxygen species (ROS) levels, and upregulates matrix metalloproteinases (MMPs) and inflammatory cytokines. CXSE and XAN suppresses AhR-mediated transcriptional activity and downregulates the expression of AhR target genes. Additionally, CXSE and XAN reduces ROS production by upregulating antioxidant enzyme-related genes. Conclusions: CXSE and XAN protect against PM-induced skin damage by inhibiting oxidative stress, inflammation, and ECM degradation, highlighting their potential as natural anti-pollution skincare ingredients. Full article

Background/Objectives: Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic hepatic condition marked by lipid buildup, lipotoxicity, and inflammation. Prior research indicates that 3,3′-Diindolemethane (DIM), a natural indole-type phytochemical that is abundant in brassicaceae vegetables, has been reported to reduce body weight and improve lipid metabolism in mice subjected to a high-fat diet (HFD). The aryl hydrocarbon receptor (AhR), a nuclear receptor implicated in lipid metabolism and immune regulation, serves as a functional receptor for DIM. However, the underlying signaling pathways that regulate MAFLD remain elusive. Our objective is to ascertain the beneficial impact of DIM on MAFLD and the associated mechanisms. Methods: Hematoxylin and eosin staining, together with Oil Red O staining, were utilized to assess the pathological changes and lipid deposition in the liver. Biochemical analysis was employed to measure levels of triglyceride (TG), total cholesterol (TC), free fatty acid (FFA), aspartate transaminase (AST), alanine transaminase (ALT), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). The cell survival rate of HepG2 cells treated with palmitic acid (PA) and DIM was assessed using the CCK-8 assay. Flow cytometry was employed to measure the fluorescence intensity emitted by lipid droplets within cells. Western blotting analysis was performed to assess AhR pathway and fatty acid transporter expression levels in hepatic tissue. Results: Our results showed that DIM significantly attenuated body weight gain and hepatic injury brought on by HFD, decreased lipid droplet accumulation in HepG2 cells, and effectively suppressed the phosphorylation of p38 MAPK and the protein expression levels of fatty acid transporters CD36 and FATP4. Conclusions: DIM reduced lipid accumulation by activating AhR and suppressing p38 MAPK phosphorylation, thereby inhibiting fatty acid transport and inflammatory responses. These findings suggest that DIM may represent a promising therapeutic candidate for MAFLD, warranting further exploration for clinical applications. Full article

Disruption in macrophage polarization is linked to inflammatory diseases and metabolic disorders. Our study aimed to investigate how AHR activation by I3C and TCDD could impact glucose transporters and macrophage phenotypes and functions in human macrophages. Human monocyte-derived macrophages (hMDMs) and THP-1 cell-derived macrophage-like cells were treated for 24 h with 100 ng/mL LPS, 100 nM TCDD, and 10 ng/µL I3C. CYP1A1 and CYP1B1 expression was significantly increased in the I3C and TCDD treatments, with CYP1B1 showing a higher fold change in I3C compared to TCDD. The AHRR expression was the highest in the TCDD group. For macrophage polarization, I3C significantly elevated CD163 expression while reducing CD16 and CD86, indicative of M2-like polarization. Additionally, I3C promoted ARG1 expression and reduced NOS2 levels, while TCDD increased NOS2. A cytokine analysis revealed I3C-induced upregulation of IL-10 and TGF-β, while TCDD significantly elevated TNF-α and IL-12. I3C upregulated glucose transporter genes (GLUT1, GLUT3, GLUT6), in contrast to the downregulation observed in TCDD-treated cells. Our findings demonstrated that I3C distinctly modulates AHR activation genes, macrophage polarization, cytokine expression, and glucose transporter levels in THP-1 cells compared to the TCDD and LPS treatments. Our findings suggest that I3C favors an anti-inflammatory M2-like macrophage polarization coupled with enhanced metabolic activity. Full article