The aryl hydrocarbon receptor: a perspective on potential roles in the immune system

Deoxynivalenol exposure during pregnancy has adverse effects on placental structure and immunity in mice model

Deoxynivalenol (DON), a highly prevalent food contaminant, is known to induce reproductive and immunotoxicity in humans upon exposure. The present study focused on the consequences of exposure to DON during pregnancy for placental barrier and immune function, as well as fetal survival. Female mice received diets contaminated with DON (6.25 and 12.5 mg/kg of diet), starting immediately after mating until the end of the experiment. On day 17 of pregnancy the animals were killed, and maternal and fetal samples were collected for further analysis. Feeding on DON-contaminated diets decreased fetal survival, and DON was detected at significant levels in the fetus. Placentae from DON-exposed mice revealed a reduction in expression of junctional proteins, ZO-1, E-cadherin and claudins, upregulation of AHR mRNA expressions, and increase in IFN-ꝩ, IL-6 and IL-4 production. In conclusion, results of this study demonstrate harmful effects of DON on the course of pregnancy and fetal survival, which might be due to immunological changes in maternal immune organs and placenta. Altogether, these data underline the importance of the quality of maternal diet during pregnancy as they clearly demonstrate the potential harmful effects of a commonly present food-contaminant.

Exposure to the Dioxin-like Pollutant PCB 126 Afflicts Coronary Endothelial Cells via Increasing 4-Hydroxy-2 Nonenal: A Role for Aldehyde Dehydrogenase 2

Exposure to environmental pollutants, including dioxin-like polychlorinated biphenyls (PCBs), play an important role in vascular inflammation and cardiometabolic diseases (CMDs) by inducing oxidative stress. Earlier, we demonstrated that oxidative stress-mediated lipid peroxidation derived 4-hydroxy-2-nonenal (4HNE) contributes to CMDs by decreasing the angiogenesis of coronary endothelial cells (CECs). By detoxifying 4HNE, aldehyde dehydrogenase 2 (ALDH2), a mitochondrial enzyme, enhances CEC angiogenesis. Therefore, we hypothesize that ALDH2 activation attenuates a PCB 126-mediated 4HNE-induced decrease in CEC angiogenesis. To test our hypothesis, we treated cultured mouse CECs with 4.4 µM PCB 126 and performed spheroid and aortic ring sprouting assays, the ALDH2 activity assay, and Western blotting for the 4HNE adduct levels and real-time qPCR to determine the expression levels of Cyp1b1 and oxidative stress-related genes. PCB 126 increased the gene expression and 4HNE adduct levels, whereas it decreased the ALDH2 activity and angiogenesis significantly in MCECs. However, pretreatment with 2.5 µM disulfiram (DSF), an ALDH2 inhibitor, or 10 µM Alda 1, an ALDH2 activator, before the PCB 126 challenge exacerbated and rescued the PCB 126-mediated decrease in coronary angiogenesis by modulating the 4HNE adduct levels respectively. Finally, we conclude that ALDH2 can be a therapeutic target to alleviate environmental pollutant-induced CMDs.

Novel Insights on Dietary Polyphenols for Prevention in Early-Life Origins of Hypertension: A Review Focusing on Preclinical Animal Models

Polyphenols are the largest group of phytochemicals with health benefits. Early life appears to offer a critical window of opportunity for launching interventions focused on preventing hypertension, as increasing evidence supports the supposition that hypertension can originate in early life. Although polyphenols have antihypertensive actions, knowledge of the potential beneficial action of the early use of polyphenols to avert the development of hypertension is limited. Thus, in this review, we first provide a brief summary of the chemistry and biological function of polyphenols. Then, we present the current epidemiological and experimental evidence supporting the early-life origins of hypertension. We also document animal data on the use of specific polyphenols as an early-life intervention to protect offspring against hypertension in adulthood and discuss underlying mechanisms. Continued research into the use of polyphenols to prevent hypertension from starting early in life will have far-reaching implications for future health.

Discrete Biochemical Systems Theory

Almost every biomedical systems analysis requires early decisions regarding the choice of the most suitable representations to be used. De facto the most prevalent choice is a system of ordinary differential equations (ODEs). This framework is very popular because it is flexible and fairly easy to use. It is also supported by an enormous array of stand-alone programs for analysis, including many distinct numerical solvers that are implemented in the main programming languages. Having selected ODEs, the modeler must then choose a mathematical format for the equations. This selection is not trivial as nearly unlimited options exist and there is seldom objective guidance. The typical choices include ad hoc representations, default models like mass-action or Lotka-Volterra equations, and generic approximations. Within the realm of approximations, linear models are typically successful for analyses of engineered systems, but they are not as appropriate for biomedical phenomena, which often display nonlinear features such as saturation, threshold effects or limit cycle oscillations, and possibly even chaos. Power-law approximations are simple but overcome these limitations. They are the key ingredient of Biochemical Systems Theory (BST), which uses ODEs exclusively containing power-law representations for all processes within a model. BST models cover a vast repertoire of nonlinear responses and, at the same time, have structural properties that are advantageous for a wide range of analyses. Nonetheless, as all ODE models, the BST approach has limitations. In particular, it is not always straightforward to account for genuine discreteness, time delays, and stochastic processes. As a new option, we therefore propose here an alternative to BST in the form of discrete Biochemical Systems Theory (dBST). dBST models have the same generality and practicality as their BST-ODE counterparts, but they are readily implemented even in situations where ODEs struggle. As a case study, we illustrate dBST applied to the dynamics of the aryl hydrocarbon receptor (AhR), a signal transduction system that simultaneously involves time delays and stochasticity.

Rosmarinus officinalis L. Leaf Extracts and Their Metabolites Inhibit the Aryl Hydrocarbon Receptor (AhR) Activation In Vitro and in Human Keratinocytes: Potential Impact on Inflammatory Skin Diseases and Skin Cancer

Aryl hydrocarbon receptor (AhR) activation by environmental agents and microbial metabolites is potentially implicated in a series of skin diseases. Hence, it would be very important to identify natural compounds that could inhibit the AhR activation by ligands of microbial origin as 6-formylindolo[3,2-b]carbazole (FICZ), indirubin (IND) and pityriazepin (PZ) or the prototype ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Five different dry Rosmarinus officinalis L. extracts (ROEs) were assayed for their activities as antagonists of AhR ligand binding with guinea pig cytosol in the presence of [³H]TCDD. The methanolic ROE was further assayed towards CYP1A1 mRNA induction using RT-PCR in human keratinocytes against TCDD, FICZ, PZ, and IND. The isolated metabolites, carnosic acid, carnosol, 7-O-methyl-epi-rosmanol, 4′,7-O-dimethylapigenin, and betulinic acid, were assayed for their agonist and antagonist activity in the presence and absence of TCDD using the gel retardation assay (GRA). All assayed ROE extracts showed similar dose-dependent activities with almost complete inhibition of AhR activation by TCDD at 100 ppm. The methanol ROE at 10 ppm showed 99%, 50%, 90%, and 85% inhibition against TCDD, FICZ, IND, and PZ, respectively, in human keratinocytes. Most assayed metabolites exhibited dose-dependent antagonist activity. ROEs inhibit AhR activation by TCDD and by the Malassezia metabolites FICZ, PZ, and IND. Hence, ROE could be useful for the prevention or treatment of skin diseases mediated by activation of AhR.

Hypertension of Developmental Origins: Consideration of Gut Microbiome in Animal Models

Hypertension is the leading cause of global disease burden. Hypertension can arise from early life. Animal models are valuable for giving cogent evidence of a causal relationship between various environmental insults in early life and the hypertension of developmental origins in later life. These insults consist of maternal malnutrition, maternal medical conditions, medication use, and exposure to environmental chemicals/toxins. There is a burgeoning body of evidence on maternal insults can shift gut microbiota, resulting in adverse offspring outcomes later in life. Emerging evidence suggests that gut microbiota dysbiosis is involved in hypertension of developmental origins, while gut microbiota-targeted therapy, if applied early, is able to help prevent hypertension in later life. This review discusses the innovative use of animal models in addressing the mechanisms behind hypertension of developmental origins. We will also highlight the application of animal models to elucidate how the gut microbiota connects with other core mechanisms, and the potential of gut microbiota-targeted therapy as a novel preventive strategy to prevent hypertension of developmental origins. These animal models have certainly enhanced our understanding of hypertension of developmental origins, closing the knowledge gap between animal models and future clinical translation.

What If Not All Metabolites from the Uremic Toxin Generating Pathways Are Toxic? A Hypothesis

The topic of uremic toxicity has received broad attention from the nephrological community over the past few decades. An aspect that is much less often considered is the possibility that the metabolic pathways that generate uremic toxins also may produce molecules that benefit body functions. Here, we discuss this dualism based on the example of tryptophan-derived metabolites, which comprise elements that are mainly toxic, such as indoxyl sulfate, kynurenine and kynurenic acid, but also beneficial compounds, such as indole, melatonin and indole-3-propionic acid, and ambivalent (beneficial for some aspects and harmful for others) compounds such as serotonin. This dualism can also be perceived at the level of the main receptor of the tryptophan-derived metabolites, the aryl hydrocarbon receptor (AHR), which has also been linked to both harm and benefit. We hypothesize that these beneficial effects are the reason why uremic toxin generation remained preserved throughout evolution. This duality is also not unique for the tryptophan-derived metabolites, and in this broader context we discuss the remote sensing and signaling theory (RSST). The RSST proposes that transporters (e.g., organic anion transporter 1—OAT1; ATP-binding cassette transporter G—ABCG2) and drug metabolizing enzymes form a large network of proteins interacting to promote small molecule remote communication at the inter-organ (e.g., gut–liver–heart–brain–kidney) and inter-organismal (e.g., gut microbe–host) levels. These small molecules include gut microbe-derived uremic toxins as well as beneficial molecules such as those discussed here. We emphasize that this positive side of uremic metabolite production needs more attention, and that this dualism especially needs to be considered when assessing and conceiving of therapeutic interventions. These homeostatic considerations are central to the RSST and suggest that interventions be aimed at preserving or restoring the balance between positive and negative components rather than eliminating them all without distinction.

Aryl hydrocarbon receptor as a DNA methylation reader in the stress response pathway

The aryl hydrocarbon receptor (AhR) mediates various cellular responses upon exposure to exogenous and endogenous stress factors. In these responses, AhR plays a dual role as a stress sensor for detecting various AhR ligands and as a transcription factor that upregulates the expression of downstream effector genes, such as those encoding drug-metabolizing enzymes. As a transcription factor, it selectively binds to the unmethylated form of a specific sequence called the xenobiotic responsive element (XRE). We suggest that AhR is a novel DNA methylation reader, unlike classical methylation readers, such as methyl-CpG-binding protein 2, which binds to methylated sequences. Under physiological conditions of continuous exposure to endogenous AhR ligands, such as kynurenine, methylation states of the individual target XREs must be strictly regulated to select and coordinate the expression of downstream genes responsible for maintaining homeostasis in the body. In contrast, long-term exposure to AhR ligands frequently leads to changes in the methylation patterns around the XRE sequence. These data indicate that AhR may contribute to the adaptive cellular response to various stresses by modulating DNA methylation. Thus, the DNA methylation profile of AhR target genes should be dynamically controlled through a balance between robustness and flexibility under both physiological and stress conditions. AhR is a pivotal player in the regulation of stress response as it shows versatility by functioning as a stress sensor, methylation reader, and putative methylation modulator.

Gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin primes cortical microglia to tissue injury

Recent studies have shown that the aryl hydrocarbon receptor (AhR) is expressed in the brain's native immune cells, known as microglia. However, while the impact of exposure to AhR ligands is well studied in the peripheral immune system, the impact of such exposure on immune function in the brain is less well defined. Microglia serve dual roles in providing synaptic and immunological support for neighboring neurons and in mediating responses to environmental stimuli, including exposure to environmental chemicals. Because of their dual roles in regulating physiological and pathological processes, cortical microglia are well positioned to translate toxic stimuli into defects in cortical function via aberrant synaptic and immunological functioning, mediated either through direct microglial AhR activation or in response to AhR activation in neighboring cells. Here, we use gene expression studies, histology, and two-photon in vivo imaging to investigate how developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a high-affinity and persistent AhR agonist, modulates microglial characteristics and function in the intact brain. Whole cortical RT-qPCR analysis and RNA-sequencing of isolated microglia revealed that gestational and lactational TCDD exposure produced subtle, but durable, changes in microglia transcripts. Histological examination and two-photon in vivo imaging revealed that while microglia density, distribution, morphology, and motility were unaffected by TCDD exposure, exposure resulted in microglia that responded more robustly to focal tissue injury. However, this effect was rectified with depletion and repopulation of microglia. These results suggest that gestational and lactational exposure to AhR ligands can result in long-term priming of microglia to produce heightened responses towards tissue injury which can be restored to normal function through microglial repopulation.

Immune sensing of microbial metabolites: Action at the tumor

The microbiome affects establishment and growth of tumors as well as response to immune-based therapies. In this issue of Immunity, Hezaveh et al. (2022) reveal that metabolites of dietary tryptophan generated by the gut microbiota activate the aryl hydrocarbon receptor in myeloid cells, promoting an immune suppressive tumor microenvironment and facilitating pancreatic ductal adenocarcinoma growth.

Current understandings and perspectives of petroleum hydrocarbons in Alzheimer's disease and Parkinson's disease: a global concern

Over the last few decades, the global prevalence of neurodevelopmental and neurodegenerative illnesses has risen rapidly. Although the aetiology remains unclear, evidence is mounting that exposure to persistent hydrocarbon pollutants is a substantial risk factor, predisposing a person to neurological diseases later in life. Epidemiological studies correlate environmental hydrocarbon exposure to brain disorders including neuropathies, cognitive, motor and sensory impairments; neurodevelopmental disorders like autism spectrum disorder (ASD); and neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). Particulate matter, benzene, toluene, ethylbenzene, xylenes, polycyclic aromatic hydrocarbons and endocrine-disrupting chemicals have all been linked to neurodevelopmental problems in all class of people. There is mounting evidence that supports the prevalence of petroleum hydrocarbon becoming neurotoxic and being involved in the pathogenesis of AD and PD. More study is needed to fully comprehend the scope of these problems in the context of unconventional oil and natural gas. This review summarises in vitro, animal and epidemiological research on the genesis of neurodegenerative disorders, highlighting evidence that supports inexorable role of hazardous hydrocarbon exposure in the pathophysiology of AD and PD. In this review, we offer a summary of the existing evidence gathered through a Medline literature search of systematic reviews and meta-analyses of the most important epidemiological studies published so far.

The Aryl Hydrocarbon Receptor (AHR): A Novel Therapeutic Target for Pulmonary Diseases?

The aryl hydrocarbon receptor (AHR) is a cytoplasmic transcription factor that is well-known for regulating xenobiotic metabolism. Studies in knockout and transgenic mice indicate that the AHR plays a vital role in the development of liver and regulation of reproductive, cardiovascular, hematopoietic, and immune homeostasis. In this focused review on lung diseases associated with acute injury and alveolar development, we reviewed and summarized the current literature on the mechanistic role(s) and therapeutic potential of the AHR in acute lung injury, chronic obstructive pulmonary disease, and bronchopulmonary dysplasia (BPD). Pre-clinical studies indicate that endogenous AHR activation is necessary to protect neonatal and adult lungs against hyperoxia- and cigarette smoke-induced injury. Our goal is to provide insight into the high translational potential of the AHR in the meaningful management of infants and adults with these lung disorders that lack curative therapies.

Low Blue Dose Photodynamic Therapy with Porphyrin-Iron Oxide Nanoparticles Complexes: In Vitro Study on Human Melanoma Cells

The purpose of this study was to investigate the effectiveness in photodynamic therapy of iron oxide nanoparticles (γ-Fe2O3 NPs), synthesized by laser pyrolysis technique, functionalized with 5,10,15,20-(Tetra-4-sulfonatophenyl) porphyrin tetraammonium (TPPS) on human cutaneous melanoma cells, after only 1 min blue light exposure. The efficiency of porphyrin loading on the iron oxide nanocarriers was estimated by using absorption and FTIR spectroscopy. The singlet oxygen yield was determined via transient characteristics of singlet oxygen phosphorescence at 1270 nm both for porphyrin functionalized nanoparticles and rose bengal used as standard. The irradiation was performed with a LED (405 nm, 1 mW/cm2) for 1 min after melanoma cells were treated with TPPS functionalized iron oxide nanoparticles (γ-Fe2O3 NPs_TPPS) and incubated for 24 h. Biological tests revealed a high anticancer effect of γ-Fe2O3 NPs_TPPS complexes indi-cated by the inhibition of tumor cell proliferation, reduction of cell adhesion, and induction of cell death through ROS generated by TPPS under light exposure. The biological assays were combined with the pharmacokinetic prediction of the porphyrin.

Genetic variation in CYP1A1 and AHRR genes increase the risk of systemic lupus erythematosus and exacerbate disease severity in smoker patients

BACKGROUND

Genetic variations of aryl hydrocarbon receptor (AHR) pathway genes could influence the imbalanced immune response to xenobiotics. Therefore, we aimed to investigate the polymorphism of AHR pathway genes in systemic lupus erythematosus (SLE) patients in association with smoking.

METHODS

Genomic DNA from patients (N = 107) and controls (N = 105) of a population from northeast of Iran was used for genotyping of CYP1A1 T>C (rs4646903) and AHRR C>G (rs2292596) variants. The SLEDAI score and smoking status of the patients were registered. The AHR activity was estimated by CYP1A1 and CYP1B1 gene expression in peripheral blood mononuclear cells (PBMC).

RESULTS

The C allele in rs4646903 (odds ratio [OR] = 2.67) and G allele in rs2292596 (OR = 1.79) SNPs were significantly associated with the increased risk of SLE. The AHR pathway was more active in high-risk CYP1A1/AHRR: C/G haplotype. The most severe disease was observed in smoker patients with high-risk haplotype and both smoking (Exp (β) = 9.5) and high-risk CYP1A1/AHRR (C/G) haplotype (Exp (β) = 3.7) can significantly increase the likelihood of having severe (SLEDAI ≥ 20) SLE disease activity.

CONCLUSION

Our findings indicated the association of xenobiotic-metabolizing genes (CYP1A1, AHRR) polymorphisms with the susceptibility to SLE and disease severity regarding the smoking background, suggesting the interaction of gene and environmental risk factors in SLE pathogenesis.

Epithelial Aryl Hydrocarbon Receptor Protects From Mucus Production by Inhibiting ROS-Triggered NLRP3 Inflammasome in Asthma

Background

Despite long-standing recognition in the significance of mucus overproduction in asthma, its etiology remains poorly understood. Muc5ac is a secretory mucin that has been associated with reduced pulmonary function and asthma exacerbations.

Objectives

We sought to investigate the immunological pathway that controls Muc5ac expression and allergic airway inflammation in asthma.

Methods

Cockroach allergen-induced Muc5ac expression and aryl hydrocarbon receptor (AhR) signaling activation was examined in the human bronchial epithelial cells (HBECs) and mouse model of asthma. AhR regulation of Muc5ac expression, mitochondrial ROS (Mito-ROS) generation, and NLRP3 inflammasome was determined by AhR knockdown, the antagonist CH223191, and AhR-/- mice. The role of NLRP3 inflammasome in Muc5ac expression and airway inflammation was also investigated.

Results

Cockroach allergen induced Muc5ac overexpression in HBECs and airways of asthma mouse model. Increased expression of AhR and its downstream genes CYP1A1 and CYP1B1 was also observed. Mice with AhR deletion showed increased allergic airway inflammation and MUC5AC expression. Moreover, cockroach allergen induced epithelial NLRP3 inflammasome activation (e.g., NLRP3, Caspase-1, and IL-1β), which was enhanced by AhR knockdown or the antagonist CH223191. Furthermore, AhR deletion in HBECs led to enhanced ROS generation, particularly Mito-ROS, and inhibition of ROS or Mito-ROS subsequently suppressed the inflammasome activation. Importantly, inhibition of the inflammasome with MCC950, a NLRP3-specifc inhibitor, attenuated allergic airway inflammation and Muc5ac expression. IL-1β generated by the activated inflammasomes mediated cockroach allergen-induced Muc5ac expression in HBECs.

Conclusions

These results reveal a previously unidentified functional axis of AhR-ROS-NLRP3 inflammasome in regulating Muc5ac expression and airway inflammation.

Toxic Effects of Indoxyl Sulfate on Osteoclastogenesis and Osteoblastogenesis

Uremic toxins, such as indoxyl sulfate (IS) and kynurenine, accumulate in the blood in the event of kidney failure and contribute to further bone damage. To maintain the homeostasis of the skeletal system, bone remodeling is a persistent process of bone formation and bone resorption that depends on a dynamic balance of osteoblasts and osteoclasts. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates the toxic effects of uremic toxins. IS is an endogenous AhR ligand and is metabolized from tryptophan. In osteoclastogenesis, IS affects the expression of the osteoclast precursor nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) through AhR signaling. It is possible to increase osteoclast differentiation with short-term and low-dose IS exposure and to decrease differentiation with long-term and/or high-dose IS exposure. Coincidentally, during osteoblastogenesis, through the AhR signaling pathway, IS inhibits the phosphorylation of ERK, and p38 reduces the expression of the transcription factor 2 (Runx2), disturbing osteoblastogenesis. The AhR antagonist resveratrol has a protective effect on the IS/AhR pathway. Therefore, it is necessary to understand the multifaceted role of AhR in CKD, as knowledge of these transcription signals could provide a safe and effective method to prevent and treat CKD mineral bone disease.

Construction and Validation of a Novel Immunosignature for Overall Survival in Uveal Melanoma

Objectives

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, and immune infiltration plays a crucial role in the prognosis of UM. This study aimed to generate an immunological marker-based predictive signature for the overall survival (OS) of UM patients.

Methods

Single-sample gene-set enrichment analysis (ssGSEA) was used to profile immune cell infiltration in 79 patients with UM from The Cancer Genome Atlas (TCGA) database. Univariate and multivariate least absolute shrinkage and selection operator (LASSO) Cox regressions were used to determine the prognostic factors for UM and construct the predictive immunosignature. Receiver operating characteristic (ROC) curves, decision curve analysis (DCA), and calibration curves were performed to evaluate the clinical ability and accuracy of the model. In addition, the predictive accuracy was compared between the immunosignature and the Tumor, Node, Metastasis (TNM) staging system of American Joint Committee on Cancer (AJCC). We further analyzed the differences in clinical characteristics, immune infiltrates, immune checkpoints, and therapy sensitivity between high- and low-risk groups characterized by the prognostic model.

Results

Higher levels of immune cell infiltration in UM were related to a lower survival rate. Matrix metallopeptidase 12 (MMP12), TCDD inducible poly (ADP-ribose) polymerase (TIPARP), and leucine rich repeat neuronal 3 (LRRN3) were identified as prognostic signatures, and an immunological marker-based prognostic signature was constructed with good clinical ability and accuracy. The immunosignature was developed with a concordance index (C-index) of 0.881, which is significantly better than that of the TNM staging system (p < 0.001). We further identified 1,762 genes with upregulated expression and 798 genes with downregulated expression in the high-risk group, and the differences between the high- and low-risk groups were mainly in immune-related processes. In addition, the expression of most of the immune checkpoint-relevant and immune activity-relevant genes was significantly higher in the high-risk group, which was more sensitive to therapy.

Conclusion

We developed a novel immunosignature constructed by MMP12, TIPARP, and LRRN3 that could effectively predict the OS of UM.

Cytotoxicity and chemical composition of women's personal PM2.5 exposures from rural China

Personal exposure PM samples aid in determining the sources and chemical composition of real-world exposures, particularly in settings with household air pollution. However, their use in toxicological research is limited, despite uncertainty regarding health effects in these settings and evidence of differential toxicity among PM_2.5 sources and components. This study used women's PM_2.5 exposure samples collected using personal exposure monitoring in rural villages in three Chinese provinces (Beijing, Shanxi, and Sichuan) during summer and winter. Water-soluble organic carbon, ions, elements, and organic tracers (e.g. levoglucosan and polycyclic aromatic hydrocarbons [PAHs]) were quantified in water and organic PM_2.5 extracts. Human lung epithelial cells (A549) were exposed to the extracts. Cell death, reactive oxygen species (ROS), and gene expression were measured. Biomass burning contributions were higher in Sichuan samples than in Beijing or Shanxi. Some PM characteristics (total PAHs and coal combustion source contributions) and biological effects of organic extract exposures (cell death, ROS, and cytokine gene expression) shared a common trend of higher levels and effects in winter than in summer for Shanxi and Beijing but no seasonal differences in Sichuan. Modulation of phase I/AhR-related genes (cyp1a1 and cyp1b1) and phase II/oxidative stress-related genes (HO-1, SOD1/2, NQO-1, and catalase) was either low or insignificant, without clear trends between samples. No significant cell death or ROS production was observed for water extract treatments among all sites and seasons, even at possible higher concentrations tested. These results support organic components, particularly PAHs, as essential drivers of biological effects, which is consistent with some other evidence from ambient PM_2.5.

Direct measurement with personal samplers captures the chemical complexity of PM_2.5 exposures better than fixed monitors. To investigate biological effects, lung cells were exposed to extracts of exposure PM_2.5 samples.

The toxic impacts of microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) on haematic parameters in a marine bivalve species and their potential mechanisms of action

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) are universally detected in the marine ecosystem and may exert adverse impacts on marine species. Although under realistic pollution scenarios, PAH pollution usually occurs as a mixture of different PAH compounds, the toxic impacts of PAH mixtures on marine organisms remain largely unknown to date, including their interactions with other emergent pollutants such as MPs. In this study, the single and combined toxic impacts of polystyrene MPs and a mixture of PAHs (standard mix of 16 representative PAHs) on haematic parameters were evaluated in the blood clam Tegillarca granosa. Our data demonstrated that blood clams treated with the pollutants examined led to decreased total haemocyte count (THC), changed haematic composition, and inhibited phagocytosis of haemocytes. Further analyses indicated that MPs and a mixture of PAHs may exert toxic impacts on haematic parameters by elevating the intracellular contents of reactive oxygen species (ROS), giving rise to lipid peroxidation (LPO) and DNA damage, reducing the viability of haemocytes, and disrupting important molecular signalling pathways (indicated by significantly altered expressions of key genes). In addition, compared to clams treated with a single type of pollutant, coexposure to MPs and a mixture of PAHs exerted more severe adverse impacts on all the parameters investigated, indicating a significant synergistic effect of MPs and PAHs.

Generation of an Allelic Series at the Ahr Locus Using an Edited Recombinant Approach

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor and a member of the PER-ARNT-SIM (PAS) superfamily of environmental sensors. The AHR is involved in a series of biological processes including adaptive metabolism of xenobiotics, toxicity of certain environmental pollutants, vascular development, fertility, and immune function. Mouse models, including the Ahr null and Ahr conditional null (Ahrfx) mice, are widely used for the study of AHR-mediated biology and toxicity. The Ahr conditional null mouse harbors the low-affinity Ahrd allele that exhibits approximately a 10-fold lower binding affinity for certain xenobiotic AHR ligands than the widely used C57BL/6 mouse that harbors the higher affinity Ahrb1 allele. Here, we report a novel mouse model that introduces a V375A polymorphism that converts the low-affinity allele into a high-affinity allele, offering a more sensitive conditional model. In the generation of this novel conditional allele, two additional mutants arose, including a 3-bp deletion in the PAS-B domain (AhrNG367R) and an early termination codon in the PAS-B domain (AhrTer383). The AhrNG367R allele presents as a phenocopy of the null and the AhrTer383 allele presents as an antimorph when assessing for the ductus venosus and liver lobe weight endpoints. These new models represent a series of tools that will be useful in further characterizing AHR biology.

Commensal microbiota regulates skin barrier function and repair via signaling through the aryl hydrocarbon receptor

The epidermis forms a barrier that defends the body from desiccation and entry of harmful substances, while also sensing and integrating environmental signals. The tightly orchestrated cellular changes needed for the formation and maintenance of this epidermal barrier occur in the context of the skin microbiome. Using germ-free mice, we demonstrate the microbiota is necessary for proper differentiation and repair of the epidermal barrier. These effects are mediated by microbiota signaling through the aryl hydrocarbon receptor (AHR) in keratinocytes, a xenobiotic receptor also implicated in epidermal differentiation. Mice lacking keratinocyte AHR are more susceptible to barrier damage and infection, during steady-state and epicutaneous sensitization. Colonization with a defined consortium of human skin isolates restored barrier competence in an AHR-dependent manner. We reveal a fundamental mechanism whereby the microbiota regulates skin barrier formation and repair, which has far-reaching implications for the numerous skin disorders characterized by epidermal barrier dysfunction.

Gill and liver transcriptomic responses of Achirus lineatus (Neopterygii: Achiridae) exposed to water-accommodated fraction (WAF) of light crude oil reveal an onset of hypoxia-like condition

Crude oil is one of the most widespread pollutants released into the marine environment, and native species have provided useful information about the effect of crude oil pollution in marine ecosystems. We consider that the lined sole Achirus lineatus can be a useful monitor of the effect of crude oil in the Gulf of Mexico (GoM) because this flounder species has a wide distribution along the GoM, and its response to oil components is relevant. The objective of this study was to compare the transcriptomic changes in liver and gill of adults lined sole fish (Achirus lineatus) exposed to a sublethal acute concentration of water-accommodated fraction (WAF) of light crude oil for 48 h. RNA-Seq was performed to assess the transcriptional changes in both organs. A total of 1073 differentially expressed genes (DEGs) were detected in gills; 662 (61.69%) were upregulated, and 411 (38.30%) were downregulated whereas in liver, 515 DEGs; 306 (59.42%) were upregulated, and 209 (40.58%) were downregulated. Xenobiotic metabolism and redox metabolism, along with DNA repair mechanisms, were activated. The induction of hypoxia-regulated genes and the generalized regulation of multiple signaling pathways support the hypothesis that WAF exposition causes a hypoxia-like condition.

Interleukin-20 exacerbates acute hepatitis and bacterial infection by downregulating IκBζ target genes in hepatocytes

BACKGROUND & AIMS

Interleukin (IL)-20 and IL-22 belong to the IL-10 family. IL-10 is a well-documented anti-inflammatory cytokine while IL-22 is well known for epithelial protection and its antibacterial function, showing great therapeutic potential for organ damage; however, the function of IL-20 remains largely unknown.

METHODS

Il20 knockout (Il20-/-) mice and wild-type littermates were generated and injected with Concanavalin A (ConA) and Klebsiella pneumoniae (K.P.) to induce acute hepatitis and bacterial infection, respectively.

RESULTS

Il20-/- mice were resistant to acute hepatitis and exhibited selectively elevated levels of the hepatoprotective cytokine IL-6. Such selective inhibition of IL-6 by IL-20 was due to IL-20 targeting hepatocytes that produce high levels of IL-6 but a limited number of other cytokines. Mechanistically, IL-20 upregulated NAD(P)H: quinone oxidoreductase 1 (NQO1) expression and subsequently promoted the protein degradation of transcription factor IκBζ, resulting in selective downregulation of the IκBζ-dependent gene Il6 as well several other IκBζ-dependent genes including lipocalin-2 (Lcn2). Given the important role of IL-6 and LCN2 in limiting bacterial infection, we examined the effect of IL-20 on bacterial infection and found Il20-/- mice were resistant to K.P. infection and exhibited elevated levels of hepatic IκBζ-dependent antibacterial genes. Moreover, IL-20 upregulated hepatic NQO1 by binding to IL-22R1/IL-20R2 and activating ERK/p38MAPK/NRF2 signaling pathways. Finally, the levels of hepatic IL1B, IL20, and IκBζ target genes were elevated, and correlated with each other, in patients with severe alcoholic hepatitis.

CONCLUSIONS

IL-20 selectively inhibits hepatic IL-6 production rather than exerting IL-10-like broad anti-inflammatory properties. Unlike IL-22, IL-20 aggravates acute hepatitis and bacterial infection. Thus, anti-IL-20 therapy could be a promising option to control acute hepatitis and bacterial infection.

LAY SUMMARY

Several interleukin (IL)-20 family cytokines have been shown to play important roles in controllimg inflammatory responses, infection and tissue damage, but the role of IL-20 remains unclear. Herein, we elucidated the role of IL-20 in liver disease and bacterial infection. We show that IL-20 can aggravate hepatitis and bacterial infection; thus, targeting IL-20 holds promise for the treatment of patients with liver disease.

[Aryl hydrocarbon receptor modulates airway inflammation in mice with cockroach allergen-induced asthma by regulating Th17/Treg differentiation]

OBJECTIVE

To investigate whether aryl hydrocarbon receptor (AhR) modulates cockroach allergen (CRE)-induced asthma by regulating Th17/Treg differentiation.

OBJECTIVE

Mouse models of CRE-induced asthma established by sensitizing and challenging the mice with CRE were randomized into asthma model group, AhR agonist group treated with TCDD (10 μg/ kg), and AhR antagonist group treated with TCDD and CH223191 (10 mg/kg) (n=5), with 5 mice without CRE challenge as the control group. The expressions of AhR, Cyp1a1 and Cyp1b1 mRNA in the lung tissues of the mice were detected using RT-PCR, and pulmonary inflammation was evaluated with immumohistochemical staining. The expressions of inflammatory cytokines in the lungs were detected using ELISA, and the expression of Treg in the lung tissues and pulmonary lymph nodes was analyzed with flow cytometry.

OBJECTIVE

Both TCDD and CH223191 were capable of modulating pulmonary expressions of AhR and its downstream genes Cyp1a1 and Cyp1b1 in asthmatic mice (P < 0.002). TCDD treatment significantly decreased inflammatory cells and mucus production in the lungs of asthmatic mice, and BALFs from TCDD-treated mice with CRE challenge contained lowered levels of the proinflammatory factors including IL-4, IL-13 and IL-17A (P < 0.001) but increased anti-inflammatory factors including IL-10, IL-22 and TGF-β1 (P < 0.001). All these changes were significantly reversed by treatment with CH223191 to the levels comparable with those in the asthma model group (P>0.05). More importantly, TCDD treatment significantly increased the number of Tregs cells and FOXP3 expression and lowered RORγt mRNA expression in the lungs and pulmonary lymph nodes in asthmatic mice (P < 0.001); inhibition of AhR with CH223191, as compared with TCDD, significantly decreased the expression of CD4⁺CD25⁺Foxp3⁺Treg cells in the lungs and pulmonary lymph nodes and the expression of FOXP3 mRNA in lymphocytes and increased RORγt mRNA expression (P < 0.001) to the levels comparable with those in asthma model group (P>0.05).

OBJECTIVE

AhR activation modulates airway inflammation in mice with CRE-induced asthma by modulating the differentiation of Th17/Treg.

Amino Acid Trp: The Far Out Impacts of Host and Commensal Tryptophan Metabolism

Tryptophan (Trp) is an essential amino acid primarily derived from the diet for use by the host for protein synthesis. The intestinal tract is lined with cells, both host and microbial, that uptake and metabolize Trp to also generate important signaling molecules. Serotonin (5-HT), kynurenine and its downstream metabolites, and to a lesser extent other neurotransmitters are generated by the host to signal onto host receptors and elicit physiological effects. 5-HT production by neurons in the CNS regulates sleep, mood, and appetite; 5-HT production in the intestinal tract by enterochromaffin cells regulates gastric motility and inflammation in the periphery. Kynurenine can signal onto the aryl hydrocarbon receptor (AHR) to elicit pleiotropic responses from several cell types including epithelial and immune cells, or can be further metabolized into bioactive molecules to influence neurodegenerative disease. There is a remarkable amount of cross-talk with the microbiome with regard to tryptophan metabolites as well. The gut microbiome can regulate the production of host tryptophan metabolites and can use dietary or recycled trp to generate bioactive metabolites themselves. Trp derivatives like indole are able to signal onto xenobiotic receptors, including AHR, to elicit tolerogenic effects. Here, we review studies that demonstrate that tryptophan represents a key intra-kingdom signaling molecule.

Aryl Hydrocarbon Receptors in Indole Derivative Treated Mice: Neuropharmacological Perspectives

Aim/objective. When applied in pharmacological doses, the indole derivative melatonin exhibits neuroactive and neuroprotective effects. Indoles and their metabolites, such as kynurenine, are ligands of aryl hydrocarbon receptors (AhR). This study aimed to evaluate the antiepileptic and analgesic activity of melatonin and two synthetic melatonin derivatives. The possible involvement of AhR and kynurenine in their neuropharmacological effects were also tested.

Methods. The tested substances were: melatonin, two melatonin derivatives bearing aryl hydrocarbon moiety with either furyl or thienyl substitute (3e and 3f), and alpha naphthoflavone (ANF), an antagonist of AhR. After intraperitoneal injection of 30, 100, or 300 mg/kg of the tested agents for seven days, male mice ICR (25-30 g) were subjected to a corneal kindling seizure model. Two tests for analgesia, i.e., the hot plate test and the formalin test, were also applied. AhR and kynurenine concentrations were evaluated in brain homogenates.

Results. Substances 3e and 3f demonstrated an antiepileptic activity comparable to that of melatonin. Some analgesic activity was also shown, albeit lower than that of melatonin in equivalent doses. For melatonin and 3f treated mice, dose-dependent increases in AhR and kynurenine levels in brain homogenates were recorded. The antagonist ANF neither blocks the antiseizure activity of the tested indoles, nor demonstrated analgesic activity.

Conclusion. Melatonin and the two tested melatonin-aroylhydrazone derivatives bearing either furyl or thienyl substitute exhibit antiepileptic and analgesic activity. Our results did not support the involvement of AhR in the demonstrated neurobiological activity. Further studies are needed to elucidate their exact molecular mechanisms.

Gene coexpression networks reveal molecular interactions underlying cichlid jaw modularity

Background

The oral and pharyngeal jaw of cichlid fishes are a classic example of evolutionary modularity as their functional decoupling boosted trophic diversification and contributed to the success of cichlid adaptive radiations. Most studies until now have focused on the functional, morphological, or genetic aspects of cichlid jaw modularity. Here we extend this concept to include transcriptional modularity by sequencing whole transcriptomes of the two jaws and comparing their gene coexpression networks.

Results

We show that transcriptional decoupling of gene expression underlies the functional decoupling of cichlid oral and pharyngeal jaw apparatus and the two units are evolving independently in recently diverged cichlid species from Lake Tanganyika. Oral and pharyngeal jaw coexpression networks reflect the common origin of the jaw regulatory program as there is high preservation of gene coexpression modules between the two sets of jaws. However, there is substantial rewiring of genetic architecture within those modules. We define a global jaw coexpression network and highlight jaw-specific and species-specific modules within it. Furthermore, we annotate a comprehensive in silico gene regulatory network linking the Wnt and AHR signalling pathways to jaw morphogenesis and response to environmental cues, respectively. Components of these pathways are significantly differentially expressed between the oral and pharyngeal jaw apparatus.

Conclusion

This study describes the concerted expression of many genes in cichlid oral and pharyngeal jaw apparatus at the onset of the independent life of cichlid fishes. Our findings suggest that – on the basis of an ancestral gill arch network—transcriptional rewiring may have driven the modular evolution of the oral and pharyngeal jaws, highlighting the evolutionary significance of gene network reuse. The gene coexpression and in silico regulatory networks presented here are intended as resource for future studies on the genetics of vertebrate jaw morphogenesis and trophic adaptation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01787-9.

Targeting Dietary and Microbial Tryptophan-Indole Metabolism as Therapeutic Approaches to Colon Cancer

Tryptophan metabolism, via the kynurenine (Kyn) pathway, and microbial transformation of tryptophan to indolic compounds are fundamental for host health; both of which are altered in colon carcinogenesis. Alterations in tryptophan metabolism begin early in colon carcinogenesis as an adaptive mechanism for the tumor to escape immune surveillance and metastasize. The microbial community is a key part of the tumor microenvironment and influences cancer initiation, promotion and treatment response. A growing awareness of the impact of the microbiome on tryptophan (Trp) metabolism in the context of carcinogenesis has prompted this review. We first compare the different metabolic pathways of Trp under normal cellular physiology to colon carcinogenesis, in both the host cells and the microbiome. Second, we review how the microbiome, specifically indoles, influence host tryptophan pathways under normal and oncogenic metabolism. We conclude by proposing several dietary, microbial and drug therapeutic modalities that can be utilized in combination to abrogate tumorigenesis.

Typical organic pollutant-protein interactions studies through spectroscopy, molecular docking and crystallography: A review

With the development of industry and human society, more attention was paid for the toxic effects of organic pollutants that are closely related to human daily life. Previous studies mainly focused on the dose-response relationship and cytotoxic effects of pollutants to organisms，while little research focused on pollutant-protein interactions at molecular level. However, the binding of organic pollutants to biomolecules, especially proteins like transporters, membrane receptor and nuclear receptors, is often the first step of toxic effects. It can make a series of endocrine disrupting and genotoxic effects through cell signaling pathway by binding specific target proteins including serum albumin, thyroid transporter, estrogen receptor, androgen receptor, and aryl hydrocarbon receptor. Thus, the research of interactions between organic pollutants and proteins is helpful and necessary to understand the distribution, metabolism and toxicity mechanism of compounds in organisms at the molecular level. This paper reviewed the latest research progress of the interaction types of persistent organic pollutants (POPs), emerging pollutants and some other pollutants with targeted proteins. In addition, we summarized several main experimental techniques for studying pollutant-protein interactions including ultraviolet/visible absorption spectrometry (UV-vis), fluorescence, infrared spectrometry, circular dichroic spectra (CD), molecular docking and X-ray crystallography. This review contributes to the molecular mechanism of the interaction between organic pollutants and biomolecules.

Genetics-Based Approach to Identify Novel Genes Regulated by the Aryl Hydrocarbon Receptor in Mouse Liver

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor in the Per-Arnt-Sim superfamily of environmental sensors that is linked to several metabolic diseases, including nonalcoholic fatty liver disease. Much remains unknown regarding the impact of genetic variation in AHR-driven disease, as past studies have focused on a small number of inbred strains. Recently, the presence of a wide range of interindividual variability amongst humans was reported in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototypical ligand of the AHR. In this study, a panel of 14 diverse mouse strains was exposed to TCDD for 10 days to characterize the AHR-mediated response across genetic backgrounds. Responses to TCDD are heavily dependent on genetic background. Although mice carry 1 of 4 Ahr alleles known to impact the affinity to AHR-ligands, we observed significant intra-allelic variability suggesting the presence of novel genetic modifiers of AHR signaling. A regression-based approach was used to scan for genes regulated by the AHR and/or associated with TCDD-induced phenotypes. The approach identified 7 genes, 2 of which are novel, that are likely regulated by the AHR based on association with hepatic TCDD burden (p ≤ .05). Finally, we identified 1 gene, Dio1, which was associated with change in percent body fat across the diverse set of strains (p ≤ .05). Overall, the results in this study exemplify the power of genetics-based approaches in identifying novel genes that are putatively regulated by the AHR.

Aryl hydrocarbon receptor: Its roles in physiology

Aryl hydrocarbon receptor (AHR) was initially discovered as a cellular protein involved in mediating the detoxification of xenobiotic compounds. Extensive research in the past two decades has identified several families of physiological ligands and uncovered important functions of AHR in normal development and homeostasis. Deficiency in AHR expression disrupts major signaling systems and transcriptional programs, which appear to be responsible for the development of numerous developmental abnormalities including cardiac hypertrophy and epidermal hyperplasia. This mini review primarily summarizes recent advances in our understanding of AHR functions in normal physiology with an emphasis on the cardiovascular, gastrointestinal, integumentary, nervous, and immunomodulatory systems.

AhR Ligands Differentially Regulate miRNA-132 Which Targets HMGB1 and to Control the Differentiation of Tregs and Th-17 Cells During Delayed-Type Hypersensitivity Response

Aryl hydrocarbon receptor (AhR), is a transcription factor and an environmental sensor that has been shown to regulate T cell differentiation. Interestingly, AhR ligands exert varying effects from suppression to exacerbation of inflammation through induction of Tregs and Th-17 cells, respectively. In the current study, we investigated whether the differential effects of AhR ligands on T cell differentiation are mediated by miRNA during delayed-type hypersensitivity (DTH) reaction against methylated Bovine Serum Albumin (mBSA). Treatment of C57BL/6 mice with TCDD attenuated mBSA-mediated DTH response, induced Tregs, decreased Th-17 cells, and caused upregulation of miRNA-132. TCDD caused an increase in several Treg subsets including inducible peripheral, natural thymic, and Th3 cells. Also, TCDD increased TGF-β and Foxp3 expression. In contrast, treating mice with FICZ exacerbated the DTH response, induced inflammatory Th17 cells, induced IL-17, and RORγ. Analysis of miRNA profiles from draining lymph nodes showed that miR-132 was upregulated in the TCDD group and downregulated in the FICZ group. Transfection studies revealed that miRNA-132 targeted High Mobility Group Box 1 (HMGB1). Downregulation of HMGB1 caused an increase in FoxP3+ Treg differentiation and suppression of Th-17 cells while upregulation of HMGB1 caused opposite effects. Moreover, TCDD was less effective in suppressing DTH response and induction of Tregs in mice that were deficient in miR-132. In summary, this study demonstrates that TCDD and FICZ have divergent effects on DTH response and T cell differentiation, which is mediated through, at least in part, regulation of miRNA-132 that targets HMGB1.

Cigarette smoke-induced alterations in blood: A review of research on DNA methylation and gene expression

Worldwide, smoking remains a threat to public health, causing preventable diseases and premature mortality. Cigarette smoke is a powerful inducer of DNA methylation and gene expression alterations, which have been associated with negative health consequences. Here, we review the current knowledge on smoking-related changes in DNA methylation and gene expression in human blood samples. We identified 30 studies focused on the association between active smoking, DNA methylation modifications, and gene expression alterations. Overall, we identified 1,758 genes with differentially methylated sites (DMS) and differentially expressed genes (DEG) between smokers and nonsmokers, of which 261 were detected in multiple studies (≥4). The most frequently (≥10 studies) reported genes were AHRR, GPR15, GFI1, and RARA. Functional enrichment analysis of the 261 genes identified the aryl hydrocarbon receptor repressor and T cell pathways (T helpers 1 and 2) as influenced by smoking status. These results highlight specific genes for future mechanistic and translational research that may be associated with cigarette smoke exposure and smoking-related diseases. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The Notch signaling pathway involvement in innate lymphoid cell biology

The role of Notch in the immune system was first described in the late 90s. Reports revealed that Notch is one of the most conserved developmental pathways involved in diverse biological processes such as the development, differentiation, survival and functions of many immune populations. Here, we provide an extended view of the pleiotropic effects of the Notch signaling on the innate lymphoid cell (ILC) biology. We review the current knowledge on Notch signaling in the regulation of ILC differentiation, plasticity and functions in diverse tissue types and at both the fetal and adult developmental stages. ILCs are early responder cells that secrete a large panel of cytokines after stimulation. By controlling the abundance of ILCs and the specificity of their release, the Notch pathway is also implicated in the regulation of their functions. The Notch pathway is therefore an important player in both ILC cell fate decision and ILC immune response.

Developmental Programming and Reprogramming of Hypertension and Kidney Disease: Impact of Tryptophan Metabolism

The concept that hypertension and chronic kidney disease (CKD) originate in early life has emerged recently. During pregnancy, tryptophan is crucial for maternal protein synthesis and fetal development. On one hand, impaired tryptophan metabolic pathway in pregnancy impacts fetal programming, resulting in the developmental programming of hypertension and kidney disease in adult offspring. On the other hand, tryptophan-related interventions might serve as reprogramming strategies to prevent a disease from occurring. In the present review, we aim to summarize (1) the three major tryptophan metabolic pathways, (2) the impact of tryptophan metabolism in pregnancy, (3) the interplay occurring between tryptophan metabolites and gut microbiota on the production of uremic toxins, (4) the role of tryptophan-derived metabolites-induced hypertension and CKD of developmental origin, (5) the therapeutic options in pregnancy that could aid in reprogramming adverse effects to protect offspring against hypertension and CKD, and (6) possible mechanisms linking tryptophan metabolism to developmental programming of hypertension and kidney disease.

Immunotherapy of COVID-19 with poly (ADP-ribose) polymerase inhibitors: starting with nicotinamide

COVID-19 induces a proinflammatory environment that is stronger in patients requiring intensive care. The cytokine components of this environment may determine efficacy or otherwise of glucocorticoid therapy. The immunity modulators, the aryl hydrocarbon receptor (AhR) and the nuclear NAD+-consuming enzyme poly (ADP-ribose) polymerase 1 (PARP 1) may play a critical role in COVID-19 pathophysiology. The AhR is overexpressed in coronaviruses, including COVID-19 and, as it regulates PARP gene expression, the latter is likely to be activated in COVID-19. PARP 1 activation leads to cell death mainly by depletion of NAD+ and adenosine triphosphate (ATP), especially when availability of these energy mediators is compromised. PARP expression is enhanced in other lung conditions: the pneumovirus respiratory syncytial virus (RSV) and chronic obstructive pulmonary disease (COPD). I propose that PARP 1 activation is the terminal point in a sequence of events culminating in patient mortality and should be the focus of COVID-19 immunotherapy. Potent PARP 1 inhibitors are undergoing trials in cancer, but a readily available inhibitor, nicotinamide (NAM), which possesses a highly desirable biochemical and activity profile, merits exploration. It conserves NAD+ and prevents ATP depletion by PARP 1 and Sirtuin 1 (silent mating type information regulation 2 homologue 1) inhibition, enhances NAD+ synthesis, and hence that of NADP+ which is a stronger PARP inhibitor, reverses lung injury caused by ischaemia/reperfusion, inhibits proinflammatory cytokines and is effective against HIV infection. These properties qualify NAM for therapeutic use initially in conjunction with standard clinical care or combined with other agents, and subsequently as an adjunct to stronger PARP 1 inhibitors or other drugs.

Harnessing In Silico, In Vitro, and In Vivo Data to Understand the Toxicity Landscape of Polycyclic Aromatic Compounds (PACs)

Polycyclic aromatic compounds (PACs) are compounds with a minimum of two six-atom aromatic fused rings. PACs arise from incomplete combustion or thermal decomposition of organic matter and are ubiquitous in the environment. Within PACs, carcinogenicity is generally regarded to be the most important public health concern. However, toxicity in other systems (reproductive and developmental toxicity, immunotoxicity) has also been reported. Despite the large number of PACs identified in the environment, research attention to understand exposure and health effects of PACs has focused on a relatively limited subset, namely polycyclic aromatic hydrocarbons (PAHs), the PACs with only carbon and hydrogen atoms. To triage the rest of the vast number of PACs for more resource-intensive testing, we developed a data-driven approach to contextualize hazard characterization of PACs, by leveraging the available data from various data streams (in silico toxicity, in vitro activity, structural fingerprints, and in vivo data availability). The PACs were clustered on the basis of their in silico toxicity profiles containing predictions from 8 different categories (carcinogenicity, cardiotoxicity, developmental toxicity, genotoxicity, hepatotoxicity, neurotoxicity, reproductive toxicity, and urinary toxicity). We found that PACs with the same parent structure (e.g., fluorene) could have diverse in silico toxicity profiles. In contrast, PACs with similar substituted groups (e.g., alkylated-PAHs) or heterocyclics (e.g., N-PACs) with varying ring sizes could have similar in silico toxicity profiles, suggesting that these groups are better candidates for toxicity read-across analysis. The clusters/regions associated with certain in silico toxicity, in vitro activity, and structural fingerprints were identified. We found that genotoxicity/carcinogenicity (in silico toxicity) and xenobiotic homeostasis and stress response (in vitro activity), respectively, dominate the toxicity/activity variation seen in the PACs. The "hot spots" with enriched toxicity/activity in conjunction with availability of in vivo carcinogenicity data revealed regions of either data-poor (hydroxylated-PAHs) or data-rich (unsubstituted, parent PAHs) PACs. These regions offer potential targets for prioritization of further in vivo assessment and for chemical read-across efforts. The analysis results are searchable through an interactive web application (https://ntp.niehs.nih.gov/go/pacs_tableau), allowing for alternative hypothesis generation.

Resveratrol Rescue Indoxyl Sulfate-Induced Deterioration of Osteoblastogenesis via the Aryl Hydrocarbon Receptor /MAPK Pathway

Indoxyl sulfate (IS), a uremic toxin derived from dietary tryptophan metabolism by the gut microbiota, is an endogenous aryl hydrocarbon receptor (AhR) agonist and a key player in bone remodeling. Resveratrol (RSV), an AhR antagonist, plays a protective role in shielding against AhR ligands. Our study explored the impact of IS on osteoblast differentiation and examined the possible mechanism of IS in controlling the expression of osteoblastogenesis markers through an in-depth investigation of AhR signaling. In vivo, we found histological architectural disruption of the femoral bones in 5/6 nephrectomies of young adult IS exposed mice, including reduced Runx2 antigen expression. RSV improved the diaphysis architecture, Runx2 expression, and trabecular quality. In vitro data suggest that IS at 500 and 1000 μM disturbed osteoblastogenesis through suppression of the ERK and p38 mitogen-activated protein kinase (MAPK) pathways, which were found to be downstream of AhR. RSV proved to ameliorate the anti-osteoblastogenic effects of IS through the inhibition of AhR and downstream signaling. Taken together, we demonstrated that the IS/AhR/MAPK signaling pathway plays a crucial role in the inhibition of osteoblastogenesis, and RSV has a potential therapeutic role in reversing the IS-induced decline in osteoblast development and suppressing abnormal bone turnover in chronic kidney disease patients.

Aryl hydrocarbon receptor expression in serum, peripheral blood mononuclear cells, and skin lesions of patients with atopic dermatitis and its correlation with disease severity

Background

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor, which is critically involved in the pathogenesis of a variety of skin diseases. The aim of this study was to detect AhR and its downstream regulators including cytochrome P450 (CYP1A1), AhR nuclear translocation (ARNT), and aryl hydrocarbon receptor repressor (AhRR) in serum, peripheral blood mononuclear cells (PBMCs), and skin lesions in patients with atopic dermatitis (AD).

Methods

Twenty-nine AD patients defined according to the criteria of Hanifin and Rajka and Chinese criteria of AD were included. Subjects without allergic and chronic diseases were recruited as controls. Patients and controls were selected from the dermatology outpatient clinic of Peking University People's Hospital from August 1 to December 31 in 2018. Enzyme-linked immunosorbent assay was performed to detect serum AhR level. The mRNA of AhR, AhRR, ARNT, and CYP1A1 in PBMCs were measured by real-time quantitative polymerase chain reaction. AhR expression in skin lesions was measured by immunohistochemistry.

Results

AhR was significantly higher expressed in serum (41.26 ± 4.52 vs. 33.73 ± 2.49 pmol/L, t = 6.507, P < 0.001) and skin lesions (0.191 ± 0.041 vs. 0.087 ± 0.017, t = 10.036, P < 0.001) of AD patients compared with those of controls. The mRNA levels of AhR (1.572 ± 0.392 vs. 1.000 ± 0.173, t = 6.819, P < 0.001), AhRR (2.402 ± 1.716 vs. 1.000 ± 0.788, t = 3.722, P < 0.001), CYP1A1 (2.258 ± 1.598 vs. 1.000 ± 0.796, t = 3.400, P = 0.002) in PBMCs of AD patients were higher compared with those of controls. The difference in mRNA levels of ARNT was not statistically significant between the patients and controls (1.383 ± 0.842 vs. 1.000 ± 0.586, t = 1.653, P = 0.105). AhR mRNA levels in PBMCs positively correlated with eczema area and severity index score and serum interleukin-6 levels.

Conclusion

AhR and its downstream regulators were highly expressed in serum, PBMCs, and skin of AD patients, which might contribute to the pathogenesis of AD.

In silico toxicity evaluation of Salubrinal and its analogues

This paper reports on a comprehensive in silico toxicity assessment of Salubrinal and its analogues containing a cinnamic acid residue or quinoline ring using the online servers admetSAR, ADMETlab, ProTox, ADVERPred, Pred-hERG and Vienna LiverTox. Apart from rare exceptions, in all 55 studied structures, mild or practical absence of acute toxicity was predicted for rats (III or IV toxicity class). Cardiotoxic, hepatotoxic and immunotoxic effects were predicted for Salubrinal and its analogues. We constructed models of the main predicted anti-targets hERG, BSEP, MRP3, MRP4 and AhR using the principle of homologous modeling. Molecular docking studies were carried out with the obtained models. We carried out molecular docking for all targets using AutoDock Vina, implemented in the PyRx 0.8 software package. According to the results of molecular docking, the compounds analyzed are potential moderate or weak hERG blockers. Induction of cholestasis and, as a consequence, liver damage by these drugs, directly related to inhibition of BSEP, MRP3 and MRP4, most likely will not be observed. Interaction with AhR for the studied compounds is impossible for steric reasons and, as a consequence, toxic effects on the immune and other organ systems associated with the activation of the AhR signaling pathway are excluded.

Selectively targeting key inflammatory pathways in cystic fibrosis

Cystic fibrosis (CF) is a rare genetic disorder caused by a defect in the ion channel Cystic Fibrosis Transmembrane conductance Regulator (CFTR), resulting in ionic imbalance of surface fluid. Although affecting multiple organs, the progressive deterioration of respiratory function by recurrent infections and chronic inflammation represents the main cause of morbidity and mortality in CF patients. The development of modulators targeting the basic defect of CFTR has represented a major breakthrough in CF therapy, but the impact on inflammation has remained enigmatic. The emerging scenario taking hold in the field points to inflammation as a major, somehow missed, therapeutic target for prevention of lung decline. Not surprisingly, the development of anti-inflammatory drugs is taking its share in the drug development pipeline. But the path is not straightforward and targeting inflammation should be balanced with the increased risk of infection. The strategy to restore the homeostatic regulation of inflammation to efficiently respond to infection while preventing lung damage needs to be based on identifying and targeting endogenous immunoregulatory pathways that are defective in CF. We herein provide an overview of anti-inflammatory drugs currently approved or under investigation in CF patients, and present our recent studies on how the knowledge on defective immune pathways in CF may translate into innovative and selective anti-inflammatory therapeutics. Through the discovery of naturally occurring molecules or their synthetic mimics, this review emphasizes the critical importance of selectively targeting key inflammatory pathways to preserve immunocompetence in CF patients.

Immunotoxicity of petroleum hydrocarbons and microplastics alone or in combination to a bivalve species: Synergic impacts and potential toxication mechanisms

Both the frequent occurrence of accidental petroleum spills and the ubiquitous presence of microplastics (MPs) in the sea may pose severe threats to marine species. However, the immunotoxic impacts of these two types of pollutants and the underlying toxication mechanisms still remain largely unknown in sessile filter-feeding bivalve mollusks. Therefore, the impacts of exposure to petroleum hydrocarbons and MPs alone or in combination on the total count, cell type composition, and phagocytic activity of hemocytes were investigated in the blood clam, Tegillarca granosa. In addition, the intracellular ROS content, cell viability, degree of DNA damage, and expression levels of genes from immune-, apoptosis-, and immunotoxicity-related pathways were analyzed to reveal the potential toxication mechanisms. The results demonstrated that exposure to petroleum hydrocarbons and MPs alone or in combination at environmentally realistic concentrations could exert significant immunotoxic impacts on the blood clam, which may be caused by alterations in a series of physiological and molecular processes. In addition, the immunotoxicity of petroleum hydrocarbons could be significantly aggravated by the copresence of MPs, which suggests that coexposure to these two pollutants deserves closer attention.

New immunotherapeutic drugs in advanced non-small cell lung cancer (NSCLC): from preclinical to phase I clinical trials

INTRODUCTION

The development of immune checkpoint inhibitors (ICI) has represented a revolution in the treatment of non-small cell lung cancer (NSCLC) and has established a new standard of care for different settings. However, through adaptive changes, cancer cells can develop resistance mechanisms to these drugs, hence the necessity for novel immunotherapeutic agents.

AREAS COVERED

This paper explores the immunotherapeutics currently under investigation in phase I clinical trials for the treatment of NSCLC as monotherapies and combination therapies. It provides two comprehensive tables of phase I agents which are listed according to target, drug, drug class, mechanism of action, setting, trial identifier, and trial status. A comprehensive literature search was carried out to identify eligible studies from MEDLINE/PubMed and ClinicalTrials.gov.

EXPERT OPINION

A key hurdle to success in this field is our limited understanding of the synergic interactions of the immune targets in the context of the TME. While we can recognize the links between inhibitors and some particularly promising new targets such as TIM-3 and LAG3, we continue to develop approaches to exploit their interactions to enhance the immune response of the patient to tumor cells.

Kynurenines in the Pathogenesis of Multiple Sclerosis: Therapeutic Perspectives

Over the past years, an increasing amount of evidence has emerged in support of the kynurenine pathway’s (KP) pivotal role in the pathogenesis of several neurodegenerative, psychiatric, vascular and autoimmune diseases. Different neuroactive metabolites of the KP are known to exert opposite effects on neurons, some being neuroprotective (e.g., picolinic acid, kynurenic acid, and the cofactor nicotinamide adenine dinucleotide), while others are toxic to neurons (e.g., 3-hydroxykynurenine, quinolinic acid). Not only the alterations in the levels of the metabolites but also disturbances in their ratio (quinolinic acid/kynurenic acid) have been reported in several diseases. In addition to the metabolites, the enzymes participating in the KP have been unearthed to be involved in modulation of the immune system, the energetic upkeep of neurons and have been shown to influence redox processes and inflammatory cascades, revealing a sophisticated, intertwined system. This review considers various methods through which enzymes and metabolites of the kynurenine pathway influence the immune system, the roles they play in the pathogenesis of neuroinflammatory diseases based on current evidence with a focus on their involvement in multiple sclerosis, as well as therapeutic approaches.

The aryl hydrocarbon receptor pathway controls matrix metalloproteinase-1 and collagen levels in human orbital fibroblasts

Thyroid eye disease (TED) affects 25–50% of patients with Graves’ Disease. In TED, collagen accumulation leads to an expansion of the extracellular matrix (ECM) which causes destructive tissue remodeling. The purpose of this study was to investigate the therapeutic potential of activating the aryl hydrocarbon receptor (AHR) to limit ECM accumulation in vitro. The ability of AHR to control expression of matrix metalloproteinase-1 (MMP1) was analyzed. MMP1 degrades collagen to prevent excessive ECM. Human orbital fibroblasts (OFs) were treated with the pro-scarring cytokine, transforming growth factor beta (TGFβ) to induce collagen production. The AHR ligand, 6-formylindolo[3,2b]carbazole (FICZ) was used to activate the AHR pathway in OFs. MMP1 protein and mRNA levels were analyzed by immunosorbent assay, Western blotting and quantitative PCR. MMP1 activity was detected using collagen zymography. AHR and its transcriptional binding partner, ARNT were depleted using siRNA to determine their role in activating expression of MMP1. FICZ induced MMP1 mRNA, protein expression and activity. MMP1 expression led to a reduction in collagen 1A1 levels. Furthermore, FICZ-induced MMP1 expression required both AHR and ARNT, demonstrating that the AHR-ARNT transcriptional complex is necessary for expression of MMP1 in OFs. These data show that activation of the AHR by FICZ increases MMP1 expression while leading to a decrease in collagen levels. Taken together, these studies suggest that AHR activation could be a promising target to block excessive collagen accumulation and destructive tissue remodeling that occurs in fibrotic diseases such as TED.

Particulate Matter Toxicity Is Nrf2 and Mitochondria Dependent: The Roles of Metals and Polycyclic Aromatic Hydrocarbons

Particulate matter (PM), an important component of air pollution, induces significant adverse health effects. Many of the observed health effects caused by inhaled PM are associated with oxidative stress and inflammation. This association has been linked in particular to the particles’ chemical components, especially the inorganic/metal and the organic/polycyclic aromatic hydrocarbon (PAH) fractions, and their ability to generate reactive oxygen species in biological systems. The transcription factor NF-E2 nuclear factor erythroid-related factor 2 (Nrf2) is activated by redox imbalance and regulates the expression of phase II detoxifying enzymes. Nrf2 plays a key role in preventing PM-induced toxicity by protecting against oxidative damage and inflammation. This review focuses on specific PM fractions, particularly the dissolved metals and PAH fractions, and their roles in inducing oxidative stress and inflammation in cell and animal models with respect to Nrf2 and mitochondria.

Effects of high-fat diet and intestinal aryl hydrocarbon receptor deletion on colon carcinogenesis

Consumption of a high-fat diet has been associated with an increased risk of developing colorectal cancer (CRC). However, the effects of the interaction between dietary fat content and the aryl hydrocarbon receptor (AhR) on colorectal carcinogenesis remain unclear. Mainly known for its role in xenobiotic metabolism, AhR has been identified as an important regulator for maintaining intestinal epithelial homeostasis. Although previous research using whole body AhR knockout mice has revealed an increased incidence of colon and cecal tumors, the unique role of AhR activity in intestinal epithelial cells (IECs) and modifying effects of fat content in the diet at different stages of sporadic CRC development are yet to be elucidated. In the present study, we have examined the effects of a high-fat diet on IEC-specific AhR knockout mice in a model of sporadic CRC. Although loss of AhR activity in IECs significantly induced the development of premalignant lesions, in a separate experiment, no significant changes in colon mass incidence were observed. Moreover, consumption of a high-fat diet promoted cell proliferation in crypts at the premalignant colon cancer lesion stage and colon mass multiplicity as well as β-catenin expression and nuclear localization in actively proliferating cells in colon masses. Our data demonstrate the modifying effects of high-fat diet and AhR deletion in IECs on tumor initiation and progression.NEW & NOTEWORTHY Through the use of an intestinal-specific aryl hydrocarbon receptor (AhR) knockout mouse model, this study demonstrates that the expression of AhR in intestinal epithelial cells is required to reduce the formation of premalignant colon cancer lesions. Furthermore, consumption of a high-fat diet and the loss of AhR in intestinal epithelial cells influences the development of colorectal cancer at various stages.

In utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure exacerbates urinary dysfunction in hormone-treated C57BL/6J mice through a non-malignant mechanism involving proteomic changes in the prostate that differ from those elicited by testosterone and estradiol

A recent study directed new focus on the fetal and neonatal environment as a risk factor for urinary dysfunction in aging males. Male mice were exposed in utero and via lactation (IUL) to the persistent environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and then administered slow-release, subcutaneous implants of testosterone and estradiol (T+E2) as adults to mimic the hormonal environment of aging men. IUL TCDD exposure worsened T+E2-induced voiding dysfunction. Mice in the previous study were genetically prone to prostatic neoplasia and it was therefore unclear whether TCDD exacerbates voiding dysfunction through a malignant or non-malignant mechanism. We demonstrate here that IUL TCDD exposure acts via a non-malignant mechanism to exacerbate T+E2-mediated male mouse voiding dysfunction characterized by a progressive increase in spontaneous void spotting. We deployed a proteomic approach to narrow the possible mechanisms. We specifically tested whether IUL TCDD exacerbates urinary dysfunction by acting through the same prostatic signaling pathways as T+E2. The prostatic protein signature of TCDD/T+E2-exposed mice differed from that of mice exposed to T+E2 alone, indicating that the mechanism of action of TCDD differs from that of T+E2. We identified 3641 prostatic proteins in total and determined that IUL TCDD exposure significantly changed the abundance of 102 proteins linked to diverse molecular and physiological processes. We shed new light on the mechanism of IUL TCDD-mediated voiding dysfunction by demonstrating that the mechanism is independent of tumorigenesis and involves molecular pathways distinct from those affected by T+E2.