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

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.

Redefining Autoimmune Disorders' Pathoetiology: Implications for Mood and Psychotic Disorders' Association with Neurodegenerative and Classical Autoimmune Disorders

Although previously restricted to a limited number of medical conditions, there is a growing appreciation that 'autoimmune' (or immune-mediated) processes are important aspects of a wide array of diverse medical conditions, including cancers, neurodegenerative diseases and psychiatric disorders. All of these classes of medical conditions are associated with alterations in mitochondrial function across an array of diverse cell types. Accumulating data indicate the presence of the mitochondrial melatonergic pathway in possibly all body cells, with important consequences for pathways crucial in driving CD8⁺ T cell and B-cell 'autoimmune'-linked processes. Melatonin suppression coupled with the upregulation of oxidative stress suppress PTEN-induced kinase 1 (PINK1)/parkin-driven mitophagy, raising the levels of the major histocompatibility complex (MHC)-1, which underpins the chemoattraction of CD8⁺ T cells and the activation of antibody-producing B-cells. Many factors and processes closely associated with autoimmunity, including gut microbiome/permeability, circadian rhythms, aging, the aryl hydrocarbon receptor, brain-derived neurotrophic factor (BDNF) and its receptor tyrosine receptor kinase B (TrkB) all interact with the mitochondrial melatonergic pathway. A number of future research directions and novel treatment implications are indicated for this wide collection of poorly conceptualized and treated medical presentations. It is proposed that the etiology of many 'autoimmune'/'immune-mediated' disorders should be conceptualized as significantly determined by mitochondrial dysregulation, with alterations in the mitochondrial melatonergic pathway being an important aspect of these pathoetiologies.

Evolutive emergence and divergence of an Ig regulatory node: An environmental sensor getting cues from the aryl hydrocarbon receptor?

One gene, the immunoglobulin heavy chain (IgH) gene, is responsible for the expression of all the different antibody isotypes. Transcriptional regulation of the IgH gene is complex and involves several regulatory elements including a large element at the 3' end of the IgH gene locus (3'RR). Animal models have demonstrated an essential role of the 3'RR in the ability of B cells to express high affinity antibodies and to express different antibody classes. Additionally, environmental chemicals such as aryl hydrocarbon receptor (AhR) ligands modulate mouse 3'RR activity that mirrors the effects of these chemicals on antibody production and immunocompetence in mouse models. Although first discovered as a mediator of the toxicity induced by the high affinity ligand 2,3,7,8-tetracholordibenzo-p-dioxin (dioxin), understanding of the AhR has expanded to a physiological role in preserving homeostasis and maintaining immunocompetence. We posit that the AhR also plays a role in human antibody production and that the 3'RR is not only an IgH regulatory node but also an environmental sensor receiving signals through intrinsic and extrinsic pathways, including the AhR. This review will 1) highlight the emerging role of the AhR as a key transducer between environmental signals and altered immune function; 2) examine the current state of knowledge regarding IgH gene regulation and the role of the AhR in modulation of Ig production; 3) describe the evolution of the IgH gene that resulted in species and population differences; and 4) explore the evidence supporting the environmental sensing capacity of the 3'RR and the AhR as a transducer of these cues. This review will also underscore the need for studies focused on human models due to the premise that understanding genetic differences in the human population and the signaling pathways that converge at the 3'RR will provide valuable insight into individual sensitivities to environmental factors and antibody-mediated disease conditions, including emerging infections such as SARS-CoV-2.

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.