Immunomodulation By Subchronic Low Dose 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in Experimental Autoimmune Encephalomyelitis in the Absence of Pertussis Toxin

Oxytocin and Vasopressin Gene Expression in the Brain as Potential Biomarkers for Cannabidiol Therapeutic Efficacy

Over the last several years, there has been increased interest in cannabidiol (CBD) to treat various ailments such as pain, anxiety, insomnia, and inflammation. The potential for CBD as an anti-inflammatory therapy has come, in part, from its demonstrated ability to suppress neuroinflammation in autoimmune diseases, such as the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). The increased use of CBD strongly suggests that more research is necessary to elucidate its safety and efficacy and determine the mechanisms by which it acts. Thus, we conducted two separate studies. In the first, RNA sequencing (RNA-Seq) analysis of brains of female mice undergoing EAE in the presence and absence of CBD was conducted to identify potential genes that mediated its neuroprotective effects when efficacious. In the second, we assessed some of the same genes in male and female mice treated with CBD in the absence of an immune stimulus. Together, these data showed that CBD modestly increased oxytocin (Oxt) and arginine vasopressin (vasopressin, Avp) gene expression in the brains of mice, regardless of whether there was active inflammation. Overall, these data suggest that Oxt and Avp might act as biomarkers for CBD exposure.

Mild Disease Course of Experimental Autoimmune Encephalomyelitis without Pertussis Toxin: Brain Transcriptome Analysis Reveals Similar Signaling to Active Lesions in Multiple Sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a powerful model to study multiple sclerosis (MS). One of the approaches for EAE is to actively immunize with myelin-derived peptides with immune adjuvants. One of the commonly used immune adjuvants is pertussis toxin (PTx), without which EAE disease is mild with relatively longer onset. However, pertussis toxin can also inhibit G protein-coupled receptor (GPCR) signaling so it can confound investigations into the role of GPCRs in EAE or therapies designed to target GPCRs. Since EAE via active immunization without PTx results in a relatively mild disease state, we wanted to confirm that appropriate signaling molecules for the disease were being induced in one target tissue (i.e., brain). RNA-Seq analysis of whole brain tissue demonstrated that the MS signaling pathway was strongly activated in symptomatic mice. In addition, there was activation of Th1 (IFN signaling), Th2 (IL-4 signaling), and Th17 (IL-17 signaling). In comparing canonical pathways from our mouse mild EAE brains with a human MS atlas, EAE shared the most pathways with active and inactive lesions. An advantage of this approach is that disease induction is slower to develop and results in modest clinical signs, which likely more closely mimic human disease onset.

Endocrine-disrupting chemicals and autoimmune diseases

Endocrine-disrupting chemicals (EDCs) widely exist in people's production and life which have great potential to damage human and animal health. Over the past few decades, growing attention has been paid to the impact of EDCs on human health, as well as immune system. So far, researchers have proved that EDCs (such as bisphenol A (BPA), phthalate, tetrachlorodibenzodioxin (TCDD), etc.) affect human immune function and promotes the occurrence and development of autoimmune diseases (ADs). Therefore, in order to better understand how EDCs affect ADs, we summarized the current knowledge about the impact of EDCs on ADs, and elaborated the potential mechanism of the impact of EDCs on ADs in this review.

Potential for TCDD to induce regulatory functions in B cells as part of the mechanism for T cell suppression in EAE

Part of the mechanism by which 2,3,7.8-tetrachlorodibenzo-p-dioxin (TCDD) suppresses immune function involves induction of regulatory T cells and suppression of effector T cells. The goal of this project was to examine whether TCDD's suppression of effector T cells was due in part to inducing B regulatory cells (Bregs). TCDD's potential to increase the percentage and/or function of CD24+CD38+ B cells was assessed in response to lipopolysaccharide (LPS) + interleukin (IL)-4 in vitro and in a mild model of experimental autoimmune encephalomyelitis (EAE) in vivo. In vitro, TCDD did not consistently increase the percentage of CD19+CD24+CD38+ cells using splenocytes, purified B cells or bone marrow (BM) cells. However, TCDD increased IL-10 in all three culture preparations, and TCDD increased the percentage of CD5+CD24+CD38+ cells producing IL-10. In EAE, TCDD did not affect the percentage of the CD24+CD38+ cell population in CD19, B220 or CD5 B cells in splenocytes (SPLC), lymph nodes (LN) nor BM cells at end-stage disease. On the other hand, TCDD increased the CD19+CD24+CD38+ percentage in the spinal cord (SC) in EAE. Moreover, TCDD-treated B cells isolated from spleens or TCDD-treated BM cells in EAE mice modestly reduced the ability of naïve effector T cells to express interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Together these data show that TCDD can induce regulatory functions in B cells, although it was not obvious simply by examining the expression of regulatory markers but by assessing function by cytokine production or mixed lymphocyte responses.

Prophylactic and Therapeutic Effect of Kynurenine for Experimental Autoimmune Encephalomyelitis (EAE) Disease

Background

The essential amino acid, tryptophan, is predominantly metabolised through the kynurenine pathway (KP) to generate kynurenine, an aryl-hydrocarbon receptor (AhR) pro-ligand that exerts its effects in a ligand-dependent manner. Interaction between kynurenine and the AhR is an effector mechanism of immunosuppression. We previously found that the KP is involved in multiple sclerosis (MS) disease progression. We postulated that AhR activation by kynurenine might be neuroprotective by encouraging differentiation of Tregs. In this study, we assess both the prophylactic and therapeutic efficiency of kynurenine on disease severity and progression in mice with experimental autoimmune encephalomyelitis (EAE), an MS model.

Methods

Myelin oligodendrocyte glycoprotein induced EAE mice (n = 6 per group) were treated with 200 mg/kg L-kynurenine once daily for 10 days beginning on either day 1 of EAE induction (prophylactic) or once they demonstrated motor weakness (therapeutic). Clinical disease severity measured by disease score, time on rotarod, and body weight.

Results

The prophylactic kynurenine treatment significantly (P < .0001) prevented the development of a more severe disease course with mice demonstrating diminished relapse rate and improved clinical and behavioural outcomes. However, therapeutic kynurenine did not significantly (P = .4463) decrease the clinical signs until 36 days following induction of disease; after 36 days, it also significantly (P = .0479) reduced disease relapse. Mean body weight measurements only correlated with time on rotarod (r = -.6410; P = .0007) but not clinical scores (r = .1925; P = .3674).

Conclusions

Kynurenine ameliorates EAE disease progression prophylactically and reduces relapses therapeutically. Further investigations are needed to elucidate the molecular mechanism explaining the therapeutic role of kynurenine for MS.

EDC-induced mechanisms of immunotoxicity: a systematic review

Endocrine-disrupting chemicals (EDCs) refer to a group of chemicals that cause adverse effects in human health, impairing hormone production and regulation, resulting in alteration of homeostasis, reproductive, and developmental, and immune system impairments. The immunotoxicity of EDCs involves many mechanisms altering gene expression that depend on the activation of nuclear receptors such as the aryl hydrocarbon receptor (AHR), the estrogen receptor (ER), and the peroxisome proliferator-activated receptor (PPAR), which also results in skin and intestinal disorders, microbiota alterations and inflammatory diseases. This systematic review aims to review different mechanisms of immunotoxicity and immunomodulation of T cells, focusing on T regulatory (Treg) and Th17 subsets, B cells, and dendritic cells (DCs) caused by specific EDCs such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), bisphenols (BPs) and polyfluoroalkyl substances (PFASs). To achieve this objective, a systematic study was conducted searching various databases including PubMed and Scopus to find in-vitro, in-vivo, and biomonitoring studies that examine EDC-dependent mechanisms of immunotoxicity. While doing the systematic review, we found species- and cell-specific outcomes and a translational gap between in-vitro and in-vivo experiments. Finally, an adverse outcome pathway (AOP) framework is proposed, which explains mechanistically toxicity endpoints emerging from different EDCs having similar key events and can help to improve our understanding of EDCs mechanisms of immunotoxicity. In conclusion, this review provides insights into the mechanisms of immunotoxicity mediated by EDCs and will help to improve human health risk assessment.

TCDD Inhibition of IgG1 Production in Experimental Autoimmune Encephalomyelitis (EAE) and In Vitro

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) is a ligand for the aryl hydrocarbon receptor (AhR). TCDD is well-characterized to produce immunotoxicity, including suppression of antibody production. Previously we showed that TCDD inhibited myelin oligodendrocyte glycoprotein (MOG) peptide-specific IgG and attenuated disease in experimental autoimmune encephalomyelitis (EAE) model in mice. Thus, the purpose of this study was to characterize the effects of TCDD on IgG subclasses in EAE and in vitro and assess effects in B cells derived from various tissues. TCDD modestly suppressed intracellular IgG expression in splenocytes (SPLC), but not bone marrow (BM) or lymph node (LN) cells. To further understand TCDD's effects on IgG, we utilized LPS and LPS + IL-4 in vitro to stimulate IgG3 and IgG1 production, respectively. TCDD preferentially suppressed IgG1+ cell surface expression, especially in SPLC. However, TCDD was able to suppress IgG1 and IgG3 secretion from SPLC and B cells, but not BM cells. Lastly, we revisited the EAE model and determined that TCDD suppressed MOG-specific IgG1 production. Together these data show that the IgG1 subclass of IgG is a sensitive target of suppression by TCDD. Part of the pathophysiology of EAE involves production of pathogenic antibodies that can recruit cytolytic cells to destroy MOG-expressing cells that comprise myelin, so inhibition of IgG1 likely contributes to TCDD's EAE disease attenuation.

Isolation of Transcriptomic-Quality Total RNA from Mouse Spinal Cords

Assessing cells, proteins, and total RNA in the spinal cord is vital for advancing our understanding of neuroinflammation and neurodegenerative diseases. For instance, immune cells infiltrate the spinal cord in the experimental autoimmune encephalomyelitis (EAE) model, commonly used to study multiple sclerosis. Thus, it is valuable to assess total RNA to determine the neuronal and inflammatory profiles in the spinal cord. Further, RNA profiles are useful for deciphering the effects of drugs or chemicals on neuroinflammation and neurodegenerative diseases such as EAE. The purpose of this protocol and the online video illustrating it is to describe and demonstrate the expulsion of the spinal cord from the mouse spinal column and homogenization of the spinal cord using liquid nitrogen for optimal RNA isolation. Although we present this method with spinal cords from EAE mice, the technique is broadly applicable, including RNA isolation from the spinal cords of healthy mice. Proper performance of these steps is critical to achieving a sufficient yield of transcriptomic-quality spinal cord RNA when combined with final isolation using commercially available kits. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Isolation of the spinal cord from the spinal column Support Protocol: Preparation of blunt-end needle for spinal cord isolation Basic Protocol 2: Spinal cord homogenization using liquid nitrogen Basic Protocol 3: Assessment of RNA purity, quantification, and integrity.

Targeting AhR as a Novel Therapeutic Modality against Inflammatory Diseases

For decades, activation of Aryl Hydrocarbon Receptor (AhR) was excluded from consideration as a therapeutic approach due to the potential toxic effects of AhR ligands and the induction of the cytochrome P450 enzyme, Cyp1a1, following AhR activation. However, it is now understood that AhR activation not only serves as an environmental sensor that regulates the effects of environmental toxins, but also as a key immunomodulator where ligands induce a variety of cellular and epigenetic mechanisms to attenuate inflammation. Thus, the emergence of further in-depth research into diverse groups of compounds capable of activating this receptor has prompted reconsideration of its use therapeutically. The aim of this review is to summarize the body of research surrounding AhR and its role in regulating inflammation. Specifically, evidence supporting the potential of targeting this receptor to modulate the immune response in inflammatory and autoimmune diseases will be highlighted. Additionally, the opportunities and challenges of developing AhR-based therapies to suppress inflammation will be discussed.

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin potential impacts on peripheral blood mononuclear cells of endometriosis women

Endometriosis happens following the implantation of endometrial-derived tissues outside the uterine cavity. It has been suggested that 2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is involved in endometriosis development. Furthermore, aryl hydrocarbon receptor (AHR), as a TCDD receptor, has been demonstrated to regulate immune responses. Nonetheless, data regarding the mechanisms, through which TCDD influences the immune system in endometriosis, are still inconclusive. Therefore, frequency of regulatory T cells (Tregs) and the expression of FOXP3, AHR and indoleamine 2, 3-dioxygenase 1 (IDO1) from endometriosis and non-endometriosis individuals were investigated in the absence and presence of TCDD; also, the concentration of IL-6 and kynurenine in the supernatant of cultures was assessed. The impact of TCDD-treated PBMCs on the migration capacity of menstrual blood-derived stromal stem cells (MenSCs) and monocyte chemoattractant protein-1 (MCP-1) and IL-6 production was determined. Here, we found that AHR and IDO1 expression levels were lower in endometriosis PBMCs; however, TCDD treatment increased AHR, FOXP3, IDO1, IL-6, and Treg levels in the endometriosis group (P ≤ 0.05-0.0001). TCDD-treated PBMCs increased the migration capacity of MenSCs and up-regulated MCP-1 and IL-6 levels in the PBMCs/MenSCs co-culture (P ≤ 0.01-0.0001). In conclusion, these results shed light on the probable mechanisms, through which AHR activation by chemical toxicants can impact inflammatory immune mediators involved in the development of endometriosis; also, these data support the idea that TCDD could promote endometriosis progression.

Effects of endocrine disrupting chemicals on myelin development and diseases

In the central and peripheral nervous systems, myelin is essential for efficient conduction of action potentials. During development, oligodendrocytes and Schwann cells differentiate and ensure axon myelination, and disruption of these processes can contribute to neurodevelopmental disorders. In adults, demyelination can lead to important disabilities, and recovery capacities by remyelination often decrease with disease progression. Among environmental chemical pollutants, endocrine disrupting chemicals (EDCs) are of major concern for human health and are notably suspected to participate in neurodevelopmental and neurodegenerative diseases. In this review, we have combined the current knowledge on EDCs impacts on myelin including several persistent organic pollutants, bisphenol A, triclosan, heavy metals, pesticides, and nicotine. Besides, we presented several other endocrine modulators, including pharmaceuticals and the phytoestrogen genistein, some of which are candidates for treating demyelinating conditions but could also be deleterious as contaminants. The direct impacts of EDCs on myelinating cells were considered as well as their indirect consequences on myelin, particularly on immune mechanisms associated with demyelinating conditions. More studies are needed to describe the effects of these compounds and to further understand the underlying mechanisms in relation to the potential for endocrine disruption.

TCDD attenuates EAE through induction of FasL on B cells and inhibition of IgG production

Previously we demonstrated that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suppressed experimental autoimmune encephalomyelitis (EAE), a model to study multiple sclerosis (MS), through induction of regulatory T cells (Tregs) and suppression of effector T cell function in the spleen. Since B cells and specifically regulatory B cells (Bregs) have been shown to be so critical in the pathology associated with EAE and MS, we wanted to determine whether TCDD could also induce Bregs. We specifically hypothesized that a Fas ligand (FasL)+ Breg population would be induced by TCDD in EAE thereby triggering apoptosis in Fas-expressing effector T cells as one mechanism to account for inhibition of T cell function by TCDD. TCDD (0.1-2.5 μg/kg/day administered orally for 12 days) modestly increased the percentage of FasL + B cells in the spleen and spinal cord in TCDD-treated EAE mice. However, we did not detect significant increases in percentages of FasL + B cells using TCDD in vitro in mouse splenocytes or human peripheral blood mononuclear cells (PBMCs). Part of the modest effect by TCDD was likely related to the localized expression of FasL; for instance, in the spleen, FasL was more highly expressed by IgM^hiIgD^lo marginal zone (MZ) B cells, but IgM^loIgD^hi follicular (FO) B cells were more responsive to TCDD. Consistent with our observation of modest upregulation of FasL, we also observed modest changes in mitochondrial membrane potential in T cells co-cultured with isolated total B cells or IgM-depleted (i.e., FO-enriched) B cells from TCDD-treated EAE mice. These data suggest that while small microenvironments of apoptosis might be occurring in T cells in response to TCDD-treated B cells, it is not a major mechanism by which T cell function is compromised by TCDD in EAE. TCDD did robustly suppress IgG production systemically and in spleen and spinal cord B cells at end stage disease. Thus, these studies show that TCDD's primary effect on B cells in EAE is compromised IgG production but not FasL + Breg induction.

The ameliorative effects of capsidiol isolated from elicited Capsicum annuum on mouse splenocyte immune responses and neuroinflammation

Capsidiol, is an anti-fungal phytoalexin produced by plants of Solanaceae. Capsidiol was examined in cultures of primary splenocytes (SPLCs) isolated from healthy C57BL/6 mice and from those with induced experimental autoimmune encephalomyelitis (EAE) as a mouse model for autoimmune neurodegenerative multiple sclerosis (MS). We also examined the impact of capsidiol in IFN-γ-stimulated mouse BV2 microglial cells. Capsidiol resulted in a significant reduction in the anti-CD3/CD28 (αCD3/CD28)-induced IFN-γ⁺ CD4⁺ (Th1) and IFN-γ⁺ CD8⁺ (Tc1) populations as well as in the production of cytokines (IFN-γ, IL-17A, IL-6, IL-2, TNF-α, and IP-10). Specifically, the CD4⁺ and CD8⁺ populations (T-bet⁺ IFN-γ^- , T-bet⁺ IFN-γ⁺ , and T-bet^- IFN-γ⁺ ) and cytokine production mediated by Th1/Tc1 polarization were diminished by 25 μM capsidiol. MOG_35-55 restimulation of SPLCs from EAE mice resulted in an increase in antigen-specific T cells, including Th1, IL-17A⁺ CD4⁺ (Th17), and IL-17A⁺ CD8⁺ (Tc17) populations. By contrast, capsidiol resulted in a decrease in the proportions of Th17 and Tc17 cells; MOG_35-55 -specific cytokine production was also diminished by capsidiol. Capsidiol treatment resulted in diminished levels of IFN-γ-induced nitric oxide and IL-6; expression of iNOS and COX-2 were suppressed by 50 μM capsidiol in IFN-γ-stimulated BV2 cells. This is the first report of capsidiol-mediated immunomodulatory and antineuroinflammatory activities that may serve to prevent neurodegeneration.

Novel Endogenous Ligands of Aryl Hydrocarbon Receptor Mediate Neural Development and Differentiation of Neuroblastoma

Aryl hydrocarbon receptor (AHR) signaling has been suggested to play roles in various physiological functions independent of its xenobiotic activity, including cell cycle regulation, immune response, and embryonic development. Several endogenous ligands were also identified by high-throughput screening techniques. However, the mechanism by which these molecules mediate AHR signaling in certain functions is still elusive. In this study, we investigated the possible pathway through which AHR and its endogenous ligands regulate neural development. We first identified two neuroactive steroids, 3α,5α-tetrahydrocorticosterone and 3α,5β-tetrahydrocorticosterone (5α- and 5β-THB), as novel AHR endogenous ligands through the use of an ultrasensitive dioxin-like compound bioassay and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS). We then treated zebrafish embryos with 5α- and 5β-THB, which enhance the expression of neurogenesis marker HuC. Furthermore, 5α- and 5β-THB both enhanced the expression of myelinating glial cell markers, sex determining region Y-box 10 (Sox10), and myelin-associated proteins myelin basic protein (Mbp) and improved the mobility of zebrafish larvae via the Ahr2 pathway. These results indicated that AHR mediates zebrafish neurogenesis and gliogenesis, especially the differentiation of oligodendrocyte or Schwann cells. Additionally, we showed that these molecules may induce neuroblastoma (NB) cell differentiation suggesting therapeutic potential of 5α- and 5β-THB in NB treatment. In summary, our results reveal that 5α- and 5β-THB are endogenous ligands of AHR and have therapeutic potential for NB treatment. By the interaction with THB, AHR signaling regulates various aspects of neural development.

Ethanol extract of Glycyrrhizae Radix modulates the responses of antigen-specific splenocytes in experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disorder resulting in paralysis, and the responses of reactive T cells against self-antigens are hallmarks. Glycyrrhizae Radix (GR) has been used for detoxification and reducing inflammation. However, very few reports have described the effects of GR on MS.

PURPOSE

The immunomodulatory effects of GR extract on autoimmune responses were evaluated through in vitro, ex vivo, and in vivo assays using primary mouse splenocytes (SPLC), mouse microglia BV2 cell line, and a mouse model of experimental autoimmune encephalomyelitis (EAE).

STUDY DESIGN

Ethanol extract of GR was used in vitro with primary SPLC in the condition of anti-CD3/CD28 stimulation and interferon (IFN)-γ-producing CD4+ (TH1)/CD8+ (TC1) polarization as well as IFN-γ-stimulated BV2 cells. For EAE induction, female C57BL/6 mice were immunized with 200 μg of myelin oligodendrocyte glycoprotein (MOG)35-55 without pertussis toxin. EAE SPLC (ex vivo) and EAE mice (in vivo) were treated with GR extract to evaluate the changes in antigen-specific responses. SPLC media containing antigen-specific responses were used to stimulate BV2 cells.

RESULTS

GR extract effectively modulated the responses of reactive splenic T cells through the reduction in IFN-γ+ T cell populations, the expressions of cell adhesion molecules (CAMs), and secretions of cytokines containing IFN-γ and a chemokine IFN-γ-induced protein 10 (IP-10) in vitro. In addition, GR extract significantly decreased nitric oxide production and secretion of tumor necrosis factor (TNF)-α and IP-10 in IFN-γ-stimulated BV2 cells. The antigen-specific TH1 and TC1 populations were decreased following administration of 100 mg/kg of GR extract, whereas CD8+IL-17A+ (TC17) population was increased on day 36 after EAE induction. Moreover, IFN-γ, which showed the highest secretion among examined cytokines, and IP-10 decreased on day 36. SPLC media derived from 100 mg/kg GR extract-administered EAE mice revealed the ameliorative effects on BV2 cell stimulation.

CONCLUSION

This is the first report on the immunomodulatory effects of GR extract on antigen-specific SPLC responses in EAE. These results could be helpful for the discovery of drug candidates for MS by focusing on IFN-γ-related autoimmune responses.

Neuroinflammation and B-Cell Phenotypes in Cervical and Lumbosacral Regions of the Spinal Cord in Experimental Autoimmune Encephalomyelitis in the Absence of Pertussis Toxin

OBJECTIVES

The active experimental autoimmune encephalomyelitis (EAE) model is often initiated using myelin oligodendrocyte glycoprotein (MOG) immunization followed by pertussis toxin (PTX) to study multiple sclerosis. However, PTX inactivates G protein-coupled receptors, and with increasing knowledge of the role that various G protein-coupled receptors play in immune homeostasis, it is valuable to establish neuroimmune endpoints for active EAE without PTX.

METHODS

Female C57BL/6 mice were immunized with MOG35-55 peptide in Complete Freund's Adjuvant and neuroinflammation, including central nervous system B-cell infiltration, was compared to saline-injected mice. Since it was anticipated that disease onset would be slower and less robust than EAE in the presence of PTX, both cervical and lumbosacral sections of the spinal cord were evaluated.

RESULTS

Immunohistochemical analysis showed that EAE without PTX induced immune infiltration, CCL2 and VCAM-1 upregulation. Demyelination in the cervical region correlated with the infiltration of CD19+ B cells in the cervical region. There was upregulation of IgG, CD38, and PDL1 on B cells in cervical and lumbosacral regions of the spinal cord in EAE without PTX. Interestingly, IgG was expressed predominantly by CD19- cells.

CONCLUSIONS

These data demonstrate that many neuroimmune endpoints are induced in EAE without PTX and although clinical disease is mild, this can be used as an autoimmune model when PTX inactivation of G protein-coupled receptors is not desired.

The Aryl Hydrocarbon Receptor and the Nervous System

The aryl hydrocarbon receptor (or AhR) is a cytoplasmic receptor of pollutants. It translocates into the nucleus upon binding to its ligands, and forms a heterodimer with ARNT (AhR nuclear translocator). The heterodimer is a transcription factor, which regulates the transcription of xenobiotic metabolizing enzymes. Expressed in many cells in vertebrates, it is mostly present in neuronal cell types in invertebrates, where it regulates dendritic morphology or feeding behavior. Surprisingly, few investigations have been conducted to unravel the function of the AhR in the central or peripheral nervous systems of vertebrates. In this review, we will present how the AhR regulates neural functions in both invertebrates and vertebrates as deduced mainly from the effects of xenobiotics. We will introduce some of the molecular mechanisms triggered by the well-known AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which impact on neuronal proliferation, differentiation, and survival. Finally, we will point out the common features found in mice that are exposed to pollutants, and in AhR knockout mice.

Evaluation of Marijuana Compounds on Neuroimmune Endpoints in Experimental Autoimmune Encephalomyelitis

Cannabinoid compounds refer to a group of more than 60 plant-derived compounds in Cannabis sativa, more commonly known as marijuana. Exposure to marijuana and cannabinoid compounds has been increasing due to increased societal acceptance for both recreational and possible medical use. Cannabinoid compounds suppress immune function, and while this could compromise one's ability to fight infections, immune suppression is the desired effect for therapies for autoimmune diseases. It is critical, therefore, to understand the effects and mechanisms by which cannabinoid compounds alter immune function, especially immune responses induced in autoimmune disease. Therefore, this unit will describe induction and assessment of the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS), and its potential alteration by cannabinoid compounds. The unit includes three approaches to induce EAE, two of which provide correlations to two forms of MS, and the third specifically addresses the role of autoreactive T cells in EAE. © 2018 by John Wiley & Sons, Inc.

Role of AhR in positive regulation of cell proliferation and survival

The aryl hydrocarbon receptor (AhR) is an important nuclear transcription factor that is best known for mediating toxic responses by adjusting numbers of metabolism-related enzymes, including CYP1A1 and CYP1B1. Previous findings have revealed that, in addition to negatively regulating cell proliferation and survival, AhR may also positively regulate these pathways. Here, we review these findings and summarize distinct mechanisms by which AhR promotes cell proliferation and survival, including modulation of receptor expression, growth factor signalling and apoptosis, regulating the cell cycle and promoting cytokine expression. This review will aid better understanding the role of AhR in positive regulation of cell proliferation and survival.

Divergent Ah Receptor Ligand Selectivity during Hominin Evolution

We have identified a fixed nonsynonymous sequence difference between humans (Val381; derived variant) and Neandertals (Ala381; ancestral variant) in the ligand-binding domain of the aryl hydrocarbon receptor (AHR) gene. In an exome sequence analysis of four Neandertal and Denisovan individuals compared with nine modern humans, there are only 90 total nucleotide sites genome-wide for which archaic hominins are fixed for the ancestral nonsynonymous variant and the modern humans are fixed for the derived variant. Of those sites, only 27, including Val381 in the AHR, also have no reported variability in the human dbSNP database, further suggesting that this highly conserved functional variant is a rare event. Functional analysis of the amino acid variant Ala381 within the AHR carried by Neandertals and nonhuman primates indicate enhanced polycyclic aromatic hydrocarbon (PAH) binding, DNA binding capacity, and AHR mediated transcriptional activity compared with the human AHR. Also relative to human AHR, the Neandertal AHR exhibited 150-1000 times greater sensitivity to induction of Cyp1a1 and Cyp1b1 expression by PAHs (e.g., benzo(a)pyrene). The resulting CYP1A1/CYP1B1 enzymes are responsible for PAH first pass metabolism, which can result in the generation of toxic intermediates and perhaps AHR-associated toxicities. In contrast, the human AHR retains the ancestral sensitivity observed in primates to nontoxic endogenous AHR ligands (e.g., indole, indoxyl sulfate). Our findings reveal that a functionally significant change in the AHR occurred uniquely in humans, relative to other primates, that would attenuate the response to many environmental pollutants, including chemicals present in smoke from fire use during cooking.