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

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

UA influences the progression of breast cancer via the AhR/p27Kip1/cyclin E pathway.

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.

Efferocytosis drives a tryptophan metabolism pathway in macrophages to promote tissue resolution.

Macrophage efferocytosis prevents apoptotic cell (AC) accumulation and triggers inflammation-resolution pathways. The mechanisms linking efferocytosis to resolution often involve changes in macrophage metabolism, but many gaps remain in our understanding of these processes. We now report that efferocytosis triggers an indoleamine 2,3-dioxygenase-1 (IDO1)-dependent tryptophan (Trp) metabolism pathway that promotes several key resolution processes, including the induction of pro-resolving proteins, such interleukin-10, and further enhancement of efferocytosis. The process begins with upregulation of Trp transport and metabolism, and it involves subsequent activation of the aryl hydrocarbon receptor (AhR) by the Trp metabolite kynurenine (Kyn). Through these mechanisms, macrophage IDO1 and AhR contribute to a proper resolution response in several different mouse models of efferocytosis-dependent tissue repair, notably during atherosclerosis regression induced by plasma low-density lipoprotein (LDL) lowering. These findings reveal an integrated metabolism programme in macrophages that links efferocytosis to resolution, with possible therapeutic implications for non-resolving chronic inflammatory diseases, notably atherosclerosis.

Novel AHR ligand AGT-5 ameliorates type 1 diabetes in mice through regulatory cell activation in the early phase of the disease.

Type 1 diabetes (T1D) is an autoimmune disease with a strong chronic inflammatory component. One possible strategy for the treatment of T1D is to stimulate the regulatory arm of the immune response, i.e. to promote the function of tolerogenic dendritic cells (tolDC) and regulatory T cells (Treg). Since both cell types have been shown to be responsive to the aryl hydrocarbon receptor (AHR) activation, we used a recently characterized member of a new class of fluorescent AHR ligands, AGT-5, to modulate streptozotocin-induced T1D in C57BL/6 mice. Prophylactic oral administration of AGT-5 reduced hyperglycemia and insulitis in these mice. Phenotypic and functional analysis of cells in the pancreatic infiltrates of AGT-5-treated mice (at the early phase of T1D) revealed a predominantly anti-inflammatory environment, as evidenced by the upregulation of tolDC and Treg frequency, while CD8+ cell, Th1 and Th17 cells were significantly reduced. Similarly, AGT-5 enhanced the proportion of Treg and tolDC in small intestine lamina propria and suppressed the activation status of antigen-presenting cells through down-regulation of co-stimulatory molecules CD40, CD80 and CD86. The expression levels of Cyp1a1, controlled by the AHR, were increased in CD4+, CD8+ and Treg, confirming the AHR-mediated effect of AGT-5 in these cells. Finally, AGT-5 stimulated the function of regulatory cells in the pancreatic islets and lamina propria by upregulating indoleamine 2,3-dioxigenase 1 (IDO1) in tolDC. These findings were supported by the abrogation of AGT-5-mediated in vitro effects on DC in the presence of IDO1 inhibitor. AGT-5 also increased the expression of CD39 or CD73 ATP-degrading ectoenzymes by Treg. The increase in Treg is further supported by the upregulated frequency of IL-2-producing type 3 innate lymphoid cells (ILC3) in the lamina propria. Anti-inflammatory effects of AGT-5 were also validated on human tonsil cells, where in vitro exposure to AGT-5 increased the proportion of immunosuppressive dendritic cells and ILC3. These results suggest that AGT-5, by stimulating AHR, may promote a general immunosuppressive environment in the pancreas and small intestine lamina propria at the early phase of disease, and thereby inhibit the severity of T1D in mice.

1,4-Diol Hq (TBHQ) vs 1,4-dithiol (TBDT); simulation of safe antioxidant with a lower carcinogenic activity.

OBJECTIVES: tert-Butylhydroquinone (TBHQ) is an antioxidant and preservative used in unsaturated vegetable oils and processed foods. However, when consumed in higher doses daily, it may pose a threat to public health by potentially increasing the risk of cancer, as it has an affinity with both the aryl hydrocarbon receptor (AhR) and the estrogen receptor alpha (ERα). METHODS: This study aimed to examine the impact of substituting the 1,4-diol of TBHQ with 1,4-dithiol, referred to as TBDT, on the carcinogenic and antioxidant systems using computational methods. The binding affinity of TBHQ and TBDT to the two carcinogenic receptors, AhR and ERα, as well as to the antioxidant receptor Keap1 alone and in connection with Nrf2 (Nrf2-Keap1) was investigated through docking analysis. RESULTS: The results indicated a decrease in TBDT's binding strength to ERα and AhR when assessed using Molegro Virtual Docker (P-value: 0.0001 and 0.00001, respectively), AutoDock Vina (P-value: 0.0001 and 0.0001), and the online server Fast DRH (P-value: 0.0001 and 0.0001). However, TBDT's binding affinity to Keap1 was predicted to be significantly stronger than TBHQ's by both MVD and AutoDock Vina (P-value: 0.0001 and 0.04), while its binding to Nrf2-Keap1 assessed to be stronger only by MVD (P-value: 0.0001). CONCLUSION: These findings suggest that TBDT not only exhibits higher antioxidant activity as a better ligand for the antioxidant system but also shows lower affinity with the AhR and ERα receptors. Therefore, TBDT can be considered a safer compound than TBHQ.

Kynurenine Attenuates Ulcerative Colitis Mediated by the Aryl Hydrocarbon Receptor.

The higher prevalence of ulcerative colitis (UC) and the side effects of its therapeutic agents contribute to finding novel treatments. This study aimed to investigate whether kynurenine (KYN), a tryptophan metabolite, has the possibility of alleviating UC and further clarifying the underlying mechanism. The effect of KYN on treating UC was evaluated by intestinal pathology, inflammatory cytokines, and tight-junction proteins in colitis mice and LPS-stimulated Caco-2 cells. Our results revealed that KYN relieved pathological symptoms of UC, improved intestinal barrier function, enhanced AhR expression, and inhibited NF-κB signaling pathway activation in the colon of colitis mice. Moreover, the improved intestinal barrier function, the decreased inflammasome production, and the inhibited activation of the NF-κB signaling pathway by KYN were dependent on AhR in Caco-2 cells. KYN could trigger AhR activation, inactivate the NF-κB signaling pathway, and inhibit NLRP3 inflammasome production, thus alleviating intestinal epithelial barrier dysfunction and reducing intestinal inflammation. In conclusion, the present study reveals that KYN ameliorates UC by improving the intestinal epithelial barrier and activating the AhR-NF-κB-NLRP3 signaling pathway, and it can be a promising therapeutic agent and dietary supplement for alleviating UC.

The Aryl Hydrocarbon Receptor and Its Crosstalk: A Chemopreventive Target of Naturally Occurring and Modified Phytochemicals.

The aryl hydrocarbon receptor (AhR) is an environmentally sensitive transcription factor (TF) historically associated with carcinogenesis initiation via the activation of numerous carcinogens. Nowadays, the AhR has been attributed to multiple endogenous functions to maintain cellular homeostasis. Moreover, crosstalk, often reciprocal, has been found between the AhR and several other TFs, particularly estrogen receptors (ERs) and nuclear factor erythroid 2-related factor-2 (Nrf2). Adequate modulation of these signaling pathways seems to be an attractive strategy for cancer chemoprevention. Several naturally occurring and synthetically modified AhR or ER ligands and Nrf2 modulators have been described. Sulfur-containing derivatives of glucosinolates, such as indole-3-carbinol (I3C), and stilbene derivatives are particularly interesting in this context. I3C and its condensation product, 3,3'-diindolylmethane (DIM), are classic examples of blocking agents that increase drug-metabolizing enzyme activity through activation of the AhR. Still, they also affect multiple essential signaling pathways in preventing hormone-dependent cancer. Resveratrol is a competitive antagonist of several classic AhR ligands. Its analogs, with ortho-methoxy substituents, exert stronger antiproliferative and proapoptotic activity. In addition, they modulate AhR activity and estrogen metabolism. Their activity seems related to a number of methoxy groups introduced into the stilbene structure. This review summarizes the data on the chemopreventive potential of these classes of phytochemicals, in the context of AhR and its crosstalk modulation.

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

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

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

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

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

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

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

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

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

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

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

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

Assessment of receptor-mediated activity (AhR and ERα), mutagenicity, and teratogenicity of metal shredder wastes in Wallonia, Belgium.

In this study, hazardous wastes including fluff, dust, and scrubbing sludge were sampled in 2019 from two metal shredding facilities located in Wallonia, Belgium. To assess the extent of the contamination, a global approach combining chemical and biological techniques was used, to better reflect the risks to health and the environment. The samples investigated induced significant in vitro aryl hydrocarbon receptor (AhR) agonistic bioactivities and estrogenic receptor (ERα) (ant)agonistic bioactivities in the respective CALUX (chemical activated luciferase gene expression) bioassays. The mutagenicity of the samples was investigated with the bacterial reverse gene mutation test using the Salmonella typhimurium TA98 and TA100 strains. Except for the sludge sample (site 3), all samples induced a mutagenic response in the TA98 strain (± S9 metabolic fraction) whereas in the TA100 strain (+ S9 metabolic fraction), only the sludge sample (site 2) showed a clear mutagenic effect. The in vivo toxicity/teratogenicity of the shredder wastes was further evaluated with zebrafish embryos. Except for the dust sample (site 2), all samples were found to be teratogenic as they returned teratogenic indexes (TIs) > 1. The high levels of contamination, the mutagenicity, and the teratogenicity of these shredder wastes raise significant concerns about their potential negative impacts on both human health and environment.

In Silico Exploration of AHR-HIF Pathway Interplay: Implications for Therapeutic Targeting in ccRCC.

The oxygen-sensing pathway is a crucial regulatory circuit that defines cellular conditions and is extensively exploited in cancer development. Pathogenic mutations in the von Hippel-Lindau (VHL) tumour suppressor impair its role as a master regulator of hypoxia-inducible factors (HIFs), leading to constitutive HIF activation and uncontrolled angiogenesis, increasing the risk of developing clear cell renal cell carcinoma (ccRCC). HIF hyperactivation can sequester HIF-1ß, preventing the aryl hydrocarbon receptor (AHR) from correctly activating gene expression in response to endogenous and exogenous ligands such as TCDD (dioxins). In this study, we used protein-protein interaction networks and gene expression profiling to characterize the impact of VHL loss on AHR activity. Our findings reveal specific expression patterns of AHR interactors following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and in ccRCC. We identified several AHR interactors significantly associated with poor survival rates in ccRCC patients. Notably, the upregulation of the androgen receptor (AR) and retinoblastoma-associated protein (RB1) by TCDD, coupled with their respective downregulation in ccRCC and association with poor survival rates, suggests novel therapeutic targets. The strategic activation of the AHR via selective AHR modulators (SAhRMs) could stimulate its anticancer activity, specifically targeting RB1 and AR to reduce cell cycle progression and metastasis formation in ccRCC. Our study provides comprehensive insights into the complex interplay between the AHR and HIF pathways in ccRCC pathogenesis, offering novel strategies for targeted therapeutic interventions.

Involvement of Aryl Hydrocarbon Receptor in Longevity and Healthspan: Insights from Humans, Mice, and C. elegans.

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.

Involvement of Intestinal Epithelium Aryl Hydrocarbon Receptor Expression and 3, 3'-Diindolylmethane in Colonic Tertiary Lymphoid Tissue Formation.

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.

PFOS and PFOSA induce oxidative stress-mediated cardiac defects in zebrafish via PPARγ and AHR pathways, respectively.

Perfluorooctane sulfonate (PFOS) and its precursor, perfluorooctane sulfonamide (PFOSA), are widespread in the environment. Evidence suggests a strong link between maternal exposure to PFOS/PFOSA and congenital heart diseases in the offspring, but the underlying mechanisms remain unclear. We hypothesized that PFOS and PFOSA induce cardiac defects through the peroxisome proliferator-activated receptor gamma (PPARγ) and aryl hydrocarbon receptor (AHR) pathways, respectively. In this study, we demonstrated that exposing zebrafish embryos to either PFOSA or PFOS caused cardiac malformations and dysfunction. Both PFOS and PFOSA induced reactive oxygen species (ROS) overproduction, mitochondrial damage, and apoptosis in zebrafish larvae hearts. Blockade of PPARγ through either pharmaceutical inhibition or genetic knockdown only attenuated the changes caused by PFOS, but not those elicited by PFOSA. Conversely, inhibition of AHR alleviated the adverse effects induced by PFOSA but not by PFOS. Both PFOSA and PFOS exhibited similar binding affinities to AHR using molecular docking techniques. The varying ability of PFOS and PFOSA to induce AHR activity in zebrafish embryonic hearts can be attributed to their different capabilities for activating PPARγ. In summary, our findings indicate that PFOS and PFOSA induce excessive ROS production in zebrafish larvae via the PPARγ and AHR pathways, respectively. This oxidative stress in turn causes mitochondrial damage and apoptosis, leading to cardiac defects.

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

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