Search Results (208)

Kynurenic acid (KYNA), a small molecule derived from the tryptophan–kynurenine pathway, can readily diffuse across biological membranes and act as an endogenous ligand for receptors such as the aryl hydrocarbon receptor (Ahr). While KYNA dysregulation is implicated in neurodegenerative disorders, the role of the KYNA–Ahr-IL-6 axis in MSC proliferation and differentiation remains poorly defined. We investigated the impact of KYNA on murine bone marrow-derived MSCs (BM-MSCs) at various concentrations (10–200 μM) and time points (8–48 h). The BM-MSC phenotype was assessed via flow cytometry; proliferation, via cell counting; and the gene expression of Ahr, Cyp1a1, Cyp1b1, and Il-6, via quantitative real-time PCR. Multipotency was evaluated through adipogenic, osteogenic, and chondrogenic differentiation assays with histochemical confirmation. KYNA significantly upregulated Ahr mRNA expression. Among the tested concentrations, 100 μM KYNA induced the highest Ahr expression (~19.1 ± 1.5-fold greater than that of the untreated controls, p < 0.005). Notably, 10 and 50 μM KYNA caused moderate induction, whereas compared with 100 μM KYNA, 200 μM did not further increase expression. In addition, KYN treatment increased Cyp1a1, Cyp1b1, and Il-6 expression, with increases of ~64.6 ± 4.5-fold, ~43.6 ± 2.3-fold, and ~41.6 ± 1.2-fold, respectively. Compared with no treatment, 100 µM KYNA enhanced BM-MSC proliferation by 1.210 ± 0.02, 1.189 ± 0.03, and 1.242 ± 0.02-fold across passages P3, P4, and P5, respectively (p < 0.05), without altering Sca-1, CD90, or CD45 expression or impairing trilineage differentiation potential. KYNA may activate the AHR–IL-6 signaling axis to promote BM-MSC expansion. This controlled proliferative effect, without loss of phenotypic or functional integrity, highlights the pharmacological potential of KYNA as a small-molecule modulator for stem cell-based therapies. Full article

Metabolic-dysfunction-associated fatty liver disease (MAFLD) is a chronic liver disease characterized by abnormal lipid metabolism. The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor involved in regulating multiple physiological processes. Recent studies have demonstrated that AHR exerts a multifaceted regulatory role in liver diseases by integrating metabolic and immune signaling pathways; however, the specific role of AHR in MAFLD is not clear. In our work, a rat model of MAFLD was established by feeding wild-type (WT) and AHR knockout (AHR^−/−) rats with a high-fat, high-fructose, and high-cholesterol diet (HFHFrHCD) for 10 weeks, and then the liver injury markers, lipid-related biochemical indices and liver histopathology were examined to elucidate the effect of AHR on MAFLD progression. We discovered that AHR deficiency can elevate plasma transaminase levels, increase hepatic triglyceride (TG) and total cholesterol (TC), and exacerbate insulin resistance (IR) under an overnutrition environment. Subsequently, liver transcriptome and RT-qPCR were performed to investigate the underlying mechanism, which revealed that the hepatic bile acid synthesis was inhibited because of lower Cytochrome P450 Family 7 Subfamily A Member 1 (CYP7A1) expression in the liver when AHR was knockout. Additionally, intestinal flora dysbiosis occurred in AHR^−/− rats fed with HFHFrHCD, which might also contribute to the hepatic cholesterol accumulation. Taken together, our results suggested that AHR might play an important role in regulating cholesterol metabolism by inhibiting bile acid synthesis and breaking the steady state of the gut microbiota during the MAFLD progression. Full article

Environmental allergens trigger epithelial reactive oxygen species (ROS) production and cellular senescence, contributing to airway inflammation. The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor responsive to environmental stimuli, may modulate this process. Single-cell transcriptomics from allergen-challenged bronchoalveolar brushings of allergic asthma and non-asthmatic allergic control subjects were analyzed for ROS, senescence, and AhR activity. Club cell-specific p16 knockout (p16^ΔScgb1a1) and AhR-deficient (AhR^ΔScgb1a1) mice were used to assess epithelial senescence and AhR function. Single-cell analysis revealed epithelial senescence as a hallmark of allergen-induced asthma. p16^ΔScgb1a1 mice exhibited reduced ROS levels and airway inflammation. Single-cell analysis also demonstrated increased AhR activity and ROS generation in airway epithelial cells of allergen-treated asthmatics, and ROS correlated positively with AhR activity and senescence. It was documented that the regulation of AhR on senescence was attenuated by VAF347, whereas AhR deficiency exacerbated ROS generation and inflammation in AhR^ΔScgb1a1 mice. RNA-seq identified senescence as a key AhR-regulated pathway, implicating c-Myc, TGF-β2, and SERPINE1 as major targets. AhR binding to the c-Myc promoter was confirmed by ChIP-PCR, and pharmacologic inhibition of c-Myc with EN4 reduced allergen-induced ROS, senescence, and inflammation. These findings demonstrate that epithelial AhR suppresses allergen-induced ROS generation and cellular senescence via direct regulation of c-Myc. Full article

Osteoporosis is a systemic skeletal disease that severely impairs the health of the elderly population. The interaction between the receptor activator of the NF-κB ligand (RANKL) and its receptor RANK is critical for osteoclast differentiation and function. Therefore, targeting the RANKL/RANK interaction represents a promising strategy for osteoporosis. In this study, we employed a newly established yeast two-hybrid system based on RANKL/RANK interaction and identified IMB-R38, a novel benzamide compound that dose-dependently blocked RANKL/RANK interaction by inhibiting the growth of AH109 cells harboring pAD-RANKL/pBD-RANK plasmids in quadruple-dropout medium. IMB-R38 significantly suppressed osteoclast differentiation, disrupted F-actin ring formation, and downregulated the expression of osteoclast-specific genes, including NFATc1 and MMP9 in RANKL-induced RAW264.7 macrophages. IMB-R38 also promoted osteoblast differentiation by upregulating the expression of osteogenic genes. Importantly, in a dexamethasone (DXM)-induced osteoporotic zebrafish model, IMB-R38 significantly increased bone mineralization, with anti-osteoporosis efficacy superior to that of alendronate sodium (Alen). RT-qPCR assays showed that IMB-R38 significantly upregulated the mRNA expression of osteogenesis genes (Bmp2, Runx2a, Runx2b, Sp7, Alp, and Oc) while markedly downregulating that of the osteoclastogenesis genes (Mmp9, Mmp13, and Mmp2) compared with the DXM group. Mechanistically, an SPR assay confirmed that IMB-R38 directly binds with RANK but not RANKL to disrupt RANKL/RANK interaction. Furthermore, Asp168 of RANK was identified as a key amino acid that mediates both RANKL interaction and IMB-R38 binding. The inhibition of RANKL/RANK by IMB-R38 suppressed JNK phosphorylation and, consequently, osteoclast differentiation and function. Collectively, our findings identify IMB-R38 as a novel RANKL/RANK inhibitor with therapeutic potential for osteoporosis through its regulation of bone metabolism. Full article

The emergence of multidrug-resistant Staphylococcus aureus underscores the urgent need for novel therapeutic agents targeting essential bacterial pathways. The lipoteichoic acid synthase (LtaS) is crucial for the synthesis of lipoteichoic acid in the cell wall of Gram-positive bacteria and represents a promising and vulnerable target for antimicrobial drug development. This study employed a comprehensive computational pipeline to identify potent inhibitors of the LtaS enzyme. A library of natural compounds was retrieved from the COCONUT database and screened against the crystal structure of the extracellular domain of LtaS (eLtaS) (PDB ID: 2W5R, obtained from the Protein Data Bank) through a multi-stage molecular docking strategy. This process started with High-Throughput Virtual Screening (HTVS), followed by Standard Precision (SP) docking, and culminated in Extra Precision (XP) docking to refine the selection of hits. The top-ranking compounds from XP docking were subsequently subjected to MM-GBSA binding free energy calculations for further filtration. The stability and dynamic behavior of the resulting candidate complexes were then evaluated using 100 ns molecular dynamics (MD) simulations, which confirmed the structural integrity and binding stability of the ligands. Density Functional Theory calculations revealed that screened ligands exhibit improved electronic stabilization and charge-transfer characteristics compared to a reference compound, suggesting enhanced reactivity and stability relevant for hit identification. Finally, ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) profiling was conducted to assess the drug-likeness and pharmacokinetic safety of the lead compounds. These findings support them as promising orally active leads for further optimization. Our integrated approach shortlisted eight initial hits (A–H) that showed interesting scaffold diversity and finally identified two compounds, herein referred to as Compound A and Compound B, which demonstrated stable binding, favorable free energy, and an acceptable Absorption, Distribution, Metabolism, and Excretion, and Toxicity (ADMET) profile. These candidates emerge as promising starting points for developing novel anti-staphylococcal agents targeting the LtaS enzyme that cand be further proved by experimental validation. Full article

Pharmacological compounds can disrupt glucose homeostasis, leading to impaired glucose tolerance, hyperglycemia, or newly diagnosed diabetes, as well as worsening glycemic control in patients with pre-existing diabetes. Traditional risk factors alone cannot explain the rapidly growing global incidence of diabetes. Therefore, prevention of insulin resistance could represent an effective strategy. Achieving this goal requires a deeper understanding of the mechanisms underlying the development of insulin resistance, with particular attention to the aryl hydrocarbon receptor (AhR). AhR, a transcription factor functioning as a xenobiotic sensor, plays a key role in various molecular pathways regulating normal homeostasis, organogenesis, and immune function. Activated by a range of exogenous and endogenous ligands, AhR is involved in the regulation of glucose and lipid metabolism as well as insulin sensitivity. However, current findings remain contradictory regarding whether AhR activation exerts beneficial or detrimental effects. This narrative review summarizes recent studies exploring the role of the AhR pathway in insulin secretion and glucose homeostasis across different tissues, and discusses molecular mechanisms involved in this process. Considering that several drugs act as AhR ligands, the review also compares how these ligands affect metabolic pathways of glucose and lipid metabolism and insulin sensitivity, producing either positive or negative effects. Full article

Anti-TNF-α therapy is widely used for inflammatory bowel disease (IBD), but response rates vary, and long-term efficacy declines in many patients. Given the limitations of existing treatments, novel therapeutic strategies are needed. This study investigates whether Lactobacillus murinus (L. murinus) attenuates tumor necrosis factor alpha (TNF-α)-induced pro-inflammatory responses in a human intestinal epithelial cell model of colitis by modulating the aryl hydrocarbon receptor (AHR). An in vitro model was established using Caco-2 cell monolayers treated with TNF-α to simulate intestinal inflammation. Cells were pre-treated with L. murinus or known AHR ligands, and the effects on AHR activation, barrier integrity, and inflammatory response were assessed via transepithelial electrical resistance (TEER) and IL-8 quantifications. As CYP1A1 is a well-established transcriptional target of AHR, its mRNA expression was used as a surrogate marker of AHR modulation in this model. TNF-α stimulation significantly disrupted epithelial barrier integrity and increased IL-8 secretion in a dose-dependent manner. L. murinus pre-treatment enhanced CYP1A1 expression and was associated with reduced TNF-α-induced barrier disruption and IL-8 secretion. Notably, the beneficial effects of L. murinus on epithelial integrity were not replicated by synthetic AHR ligands, suggesting ligand-selective differences in AHR related responses. These findings suggest that AHR-associated signaling induced by L. murinus may contribute to mitigation of TNF-α-induced epithelial barrier dysfunction and inflammation. This study identifies a potential probiotic-associated mechanism that warrants further investigation, including studies designed to establish a causal role of AHR dependency in the observed effects. In addition, future studies are needed to identify the specific L. murinus metabolites responsible for inducing CYP1A1 expression and activating the AHR pathway. Full article

Background: Pruritus is burdensome across dermatoses. Beyond Staphylococcus, broader components of the cutaneous microbiome—bacteria, fungi, and viruses—and their products shape itch via barrier disruption, immune polarization, and direct neurosensory activation. Methods: We conducted a narrative review of human and translational studies. PubMed/MEDLINE, Scopus, and Web of Science were searched from inception to 27 August 2025 using terms for itch, skin microbiome, bacteriotherapy, proteases, PAR, TRP channels, IL-31, Malassezia, and AHR ligands. English and Italian records were screened; randomized trials, systematic reviews, and mechanistic studies were prioritized; and unsupported single case reports were excluded. Results: Beyond Staphylococcus aureus, microbial drivers include secreted proteases activating PAR-2/4; pore-forming peptides and toxins engaging MRGPRs and sensitizing TRPV1/TRPA1; and metabolites, especially tryptophan-derived AHR ligands, that recalibrate barrier and neuro-immune circuits. Commensal taxa can restore epidermal lipids, tight junctions, and antimicrobial peptides. Early studies of topical live biotherapeutics—Roseomonas mucosa and Staphylococcus hominis A9—report reductions in disease severity and itch. Fungal communities, particularly Malassezia, contribute via lipases and bioactive metabolites with context-dependent effects. Across studies, heterogeneous itch metrics, small samples, and short follow-up limit certainty. Conclusions: The cutaneous microbiome actively contributes to itch and is targetable. Future studies should prioritize standardized itch endpoints, responder stratification, and robust safety for live biotherapeutics. Full article

Food allergies are rising globally, posing a multifactorial public health challenge driven by complex interactions among diet, immune development, and environmental exposures. This review highlights emerging insights into the cellular and molecular mechanisms by which specific dietary components, particularly vitamin A, fibre, indole compounds, and proteins, promote intestinal homeostasis. These nutrients act through both microbiota-dependent and -independent pathways, primarily in the small intestine, enhancing epithelial barrier integrity and supporting tolerogenic immune responses. Two key signalling axes, mediated by retinoic acid (RA) and aryl hydrocarbon receptor (AhR) ligands, converge to regulate RORγt-expressing immune cells, including group 3 innate lymphoid cells, TCRγδ⁺CD8αα⁺ intraepithelial lymphocytes (IELs), and Th17 cells, which are essential for secondary lymphoid organ development and barrier reinforcement. RA and AhR also guide the homing and specialization of diverse regulatory T cell subsets and CD4⁺ IELs, which collectively sustain peripheral tolerance to dietary antigens. Recent findings implicate RORγt⁺ antigen-presenting cells in the induction of peripheral Tregs during early life, particularly at weaning, underscoring a critical window for tolerance establishment. Microbial metabolites and commensal-derived signals further shape these immune pathways, reflecting the intricate interplay between host, diet, and microbiota in the regulation of oral tolerance. Full article

The intestinal epithelium constitutes a critical barrier that protects the host from luminal toxins. Persistent organic pollutants (POPs), including dioxins and dioxin-like polychlorinated biphenyls, are ubiquitous aryl hydrocarbon receptor (AhR) ligands. However, their effects on intestinal barrier integrity remain poorly understood. We examined representative POPs in vitro (using human Caco-2 monolayers) and in vivo (using a mouse jejunal loop model). Measurements of transepithelial electrical resistance, fluorescein isothiocyanate–dextran permeability, and cytotoxicity revealed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) impaired barrier function at non-cytotoxic concentrations. This effect was accompanied by increased ethoxyresorufin-O-deethylase activity and subsequently reversed by the AhR antagonist CH223191, indicating AhR dependence. Mechanistically, TCDD suppressed claudin-1, claudin-4, and zonula occludens-1 expression while upregulating the transcription factor Slug, consistent with junctional remodeling. In vivo, TCDD enhanced systemic dextran leakage and reduced claudin-4 expression in jejunal epithelia. These findings identify intestinal barrier disruption as a sensitive toxicological endpoint of POP exposure and provide mechanistic insight into the link between environmental pollutants and gastrointestinal dysfunction. Full article

Background/Objectives: Targeting Hsp90β with isoform-selective inhibitors offers a promising therapeutic strategy with reduced toxicity compared to pan-Hsp90 inhibition. However, mechanisms of resistance to Hsp90β-selective inhibition remain poorly defined. This study aimed to identify molecular determinants of Hsp90β dependency and pharmacologic resistance across cancer types. Methods: We integrated gene dependency, transcriptomic, proteomic, metabolomic, and drug sensitivity data from the Cancer Cell Line Encyclopedia with in vitro validation using the Hsp90β-selective inhibitor, NDNB-25. Comparative and correlation analyses were performed to identify resistance-associated pathways, followed by network and combination drug testing to validate functional interactions. Results: Resistant cell lines exhibited extensive rewiring of Rho GTPase signaling, cytoskeletal remodeling, and metabolic adaptation, including mitochondrial dysfunction and redox imbalance. Integrated analyses linked these phenotypes to aryl hydrocarbon receptor (AHR) activation and compensatory Hsp90α expression. Experimental validation confirmed increased kynurenine levels, a known endogenous AHR ligand, in NDNB-25–acquired resistant cells. Gene–drug network integration revealed collateral sensitivity to carboplatin, which synergized with Hsp90β inhibition in resistant models. Conclusions: This study defines the molecular features and adaptive programs underlying resistance to Hsp90β-selective inhibition and identifies therapeutic vulnerabilities that can be exploited to overcome it. The findings establish a systems-level framework for predicting Hsp90β inhibitor response and support rational combination strategies, including carboplatin co-treatment, for future preclinical development. Full article

The aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, plays a crucial role in regulating immune homeostasis, inflammatory responses, and intestinal barrier function. Indole compounds and their derivatives are ligands of AHR, which can activate the AHR signal transduction pathway and show significant regulatory potential in various inflammatory and immune diseases. Cystic fibrosis (CF) is a life-threatening autosomal recessive genetic disorder. Cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction affects multiple systems throughout the body. The core of its pathological process is chronic infection, abnormal inflammation, and tissue damage caused by mucus accumulation. Exploring alternative or adjunctive therapeutic strategies targeting pathological pathways downstream of CFTR is of significant importance. The aim of the present study is to explore the multiple beneficial effects that indole compounds may exert in regulating pulmonary infection and inflammation, repairing intestinal barrier function, and regulating immune homeostasis in CF patients by activating the AHR signaling pathway. Additionally, this study discusses the risks and challenges associated with developing indole compounds as CF drugs, offering a novel research approach distinct from traditional CFTR modulators for creating new CF therapeutics. Full article

Carcinogenesis is a complex process characterized by the uncontrolled proliferation of abnormal cells, influenced by environmental, genetic, and epigenetic factors. Chronic inflammation is undoubtedly one of the key contributors to carcinogenesis. Inflammatory bowel disease (IBD) is associated with an increased risk of colorectal cancer (CRC) due to persistent inflammation resulting from continuous immune system activation and excessive immune cell recruitment. IBD is also linked to certain nutritional deficiencies, primarily due to dietary modifications necessitated by the disease’s pathophysiology. Consequently, individualized nutritional supplementation appears to be a rational approach to addressing these deficiencies. The use of functional foods, including anti-inflammatory nutraceuticals, in individuals with IBD may play a crucial role in modulating cellular pathways that inhibit the release of inflammatory mediators. Thus, the regulation of the aryl hydrocarbon receptor (AhR) and G protein-coupled receptor 35 (GPR35) through dietary ligands appears to be of significant importance not only in the treatment of IBD and maintenance of remission but also in the prevention of tumorigenic transformation, particularly in genetically predisposed individuals. This narrative review was conducted using PubMed, Scopus, and Web of Science databases. The search covered literature published between January 2000 and June 2024. Keywords included ‘inflammatory bowel disease’, ‘colorectal cancer’, ‘AhR’, ‘aryl hydrocarbon receptor’, ‘GPR35’, ‘cytochrome P450’, ‘nutraceuticals’, ‘probiotics’, and ‘superfoods’. Only English-language articles were included. The selection focused on studies investigating mechanistic pathways and the role of dietary ligands in AhR and GPR35 activation in IBD and CRC. The SANRA guidelines for narrative reviews were followed to ensure transparency and minimize bias. Full article

In recent years, gut–brain axis signaling has been recognized as an essential factor modifying behavior, mood, cognition, and cellular viability under physiological and pathological conditions. Consequently, the intestinal microbiome has become a potential therapeutic target in neurological and psychiatric disorders. The microbiota-derived metabolite of tryptophan (Trp), indole-3-propionic acid (IPA), was discovered to target a number of molecular processes and to impact brain function. In this review, we outline the key mechanisms by which IPA may affect neuronal activity and survival and provide an update on the evidence supporting the neuroprotective action of the compound in various experimental paradigms. Accumulating data indicates that IPA is a free radical scavenger, a ligand of aryl hydrocarbon receptors (AhR) and pregnane X receptors (PXR), and an anti-inflammatory molecule. IPA decreases the synthesis of the proinflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), tumor necrosis factor-α (TNF-α), and other cytokines, reduces the generation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome, and enhances the synthesis of neurotrophic factors. Furthermore, produced in the gut, or administered orally, IPA boosts the central levels of kynurenic acid (KYNA), a neuroprotective metabolite of Trp. IPA reduces the release of proinflammatory molecules in the gut, breaking the gut–inflammation–brain vicious cycle, which otherwise leads to neuronal loss. Moreover, as a molecule that easily enters central compartment, IPA may directly impact brain function and cellular survival. Overall, the gathered data confirms neuroprotective features of IPA, and supports its potential use in high-risk populations, in order to delay the onset and ameliorate the course of neurodegenerative disorders and cognitive impairment. Clinical trials evaluating IPA as a promising therapeutic add-on, able to slow down the progress of neurodegenerative disorders such as Alzheimer’s or Parkinson’s disease and to limit the morphological and behavioral consequences of ischemic stroke, are urgently needed. Full article

Exposure to persistent organic pollutants such as 2,3,7,8-tetrachlorodibenzodioxin (TCDD) increases metabolic disorder risk. In this study, we show that a single intraperitoneal injection of TCDD (10 μg/kg) in C57BL/6J mice induced body weight gain, lipid accumulation in the liver and adipose tissue, macrophage infiltration, and elevated hepatic and serum triglyceride levels after 12 weeks. Despite serum aryl hydrocarbon receptor (AhR) ligand levels normalizing by 12 weeks, the persistent effects suggest TCDD sequestration in fat tissue. TCDD inhibited the expression of mitochondrial proteins (COX1, TOM20, TFAM, H2AX) and reduced mitochondrial oxygen consumption. Liver-specific AhR knockout ameliorated TCDD-induced mitochondrial dysfunction, lipid accumulation, and macrophage infiltration. Mechanistically, TCDD-induced hepatic plasminogen activator inhibitor-1 (PAI-1) promoted adipocyte hypertrophy. In the liver, PAI-1 disrupted the interaction between tissue-type plasminogen activator (tPA) and apolipoprotein B (ApoB), thereby enhancing very-low-density lipoprotein (VLDL) assembly. These findings reveal that hepatocyte-derived circulating PAI-1, upregulated via hepatic AhR activation, contributes to adipocyte hypertrophy and hepatosteatosis through the intracellular modulation of the tPA–PAI-1 axis. Thus, hepatic AhR activation drives mitochondrial dysfunction and obesity, even after a single TCDD exposure. Full article