Exposure to a mixture of 23 chemicals associated with unconventional oil and gas operations alters immune response to challenge in adult mice.

The prevalence of unconventional oil and gas (UOG) operations raises concerns regarding the potential for adverse health outcomes following exposure to water tainted by mixtures of UOG associated chemicals. The potential effects that exposure to complex chemical mixtures has on the immune system have yet to be fully evaluated. In this study, effects on the immune system of adult mice exposed to a mixture of 23 chemicals that have been associated with water near active UOG operations were investigated. Female and male mice were exposed to the mixture via their drinking water for at least 8 weeks. At the end of the exposure, cellularity of primary and secondary immune organs, as well as an immune system function, were assessed using three different models of disease, i.e. house dust mite (HDM)-induced allergic airway disease, influenza A virus infection, and experimental autoimmune encephalomyelitis (EAE). The results indicated exposures resulted in different impacts on T-cell populations in each disease model. Furthermore, the consequences of exposure differed between female and male mice. Notably, exposure to the chemical mixture significantly increased EAE disease severity in females, but not in male, mice. These findings indicated that direct exposure to this mixture leads to multiple alterations in T-cell subsets and that these alterations differ between sexes. This suggested to us that direct exposure to UOG-associated chemicals may alter the adult immune system, leading to dysregulation in immune cellularity and function.

DNA Methylation Patterns in CD4+ T Cells of Naïve and Influenza A Virus-Infected Mice Developmentally Exposed to an Aryl Hydrocarbon Receptor Ligand.

BACKGROUND: Early life environmental exposures can have lasting effects on the function of the immune system and contribute to disease later in life. Epidemiological studies have linked early life exposure to xenobiotics that bind the aryl hydrocarbon receptor (AhR) with dysregulated immune responses later in life. Among the immune cells influenced by developmental activation of the AhR are CD4+ T cells. Yet, the underlying affected cellular pathways via which activating the AhR early in life causes the responses of CD4+ T cells to remain affected into adulthood remain unclear. OBJECTIVE: Our goal was to identify cellular mechanisms that drive impaired CD4+ T-cell responses later in life following maternal exposure to an exogenous AhR ligand. METHODS: C57BL/6 mice were vertically exposed to the prototype AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), throughout gestation and early postnatal life. The transcriptome and DNA methylation patterns were evaluated in CD4+ T cells isolated from naïve and influenza A virus (IAV)-infected adult mice that were developmentally exposed to TCDD or vehicle control. We then assessed the influence of DNA methylation-altering drug therapies on the response of CD4+ T cells from developmentally exposed mice to infection. RESULTS: Gene and protein expression showed that developmental AhR activation reduced CD4+ T-cell expansion and effector functions during IAV infection later in life. Furthermore, whole-genome bisulfite sequencing analyses revealed that developmental AhR activation durably programed DNA methylation patterns across the CD4+ T-cell genome. Treatment of developmentally exposed offspring with DNA methylation-altering drugs alleviated some, but not all, of the impaired CD4+ T-cell responses. DISCUSSION: Taken together, these results indicate that skewed DNA methylation is one of the mechanisms by which early life exposures can durably change the function of T cells in mice. Furthermore, treatment with DNA methylation-altering drugs after the exposure restored some aspects of CD4+ T-cell functional responsiveness. https://doi.org/10.1289/EHP7699.

The Ancestral Environment Shapes Antiviral CD8+ T cell Responses across Generations.

Recent studies have linked health fates of children to environmental exposures of their great grandparents. However, few studies have considered whether ancestral exposures influence immune function across generations. Here, we report transgenerational inheritance of altered T cell responses resulting from maternal (F0) exposure to the aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Since F0 exposure to TCDD has been linked to transgenerational transmission of reproductive problems, we asked whether maternal TCDD exposure also caused transgenerational changes in immune function. F0 exposure caused transgenerational effects on the CD8+ T cell response to influenza virus infection in females but not in males. Outcrosses showed changes were passed through both parental lineages. These data demonstrate that F0 exposure to an aryl hydrocarbon receptor (AHR) agonist causes durable changes to immune responses that can affect subsequent generations. This has broad implications for understanding how the environment of prior generations shapes susceptibility to pathogens and antiviral immunity in later generations.

Early life exposures shape the CD4+ T cell transcriptome, influencing proliferation, differentiation, and mitochondrial dynamics later in life.

Early life environmental exposures drive lasting changes to the function of the immune system and can contribute to disease later in life. One of the ways environmental factors act is through cellular receptors. The aryl hydrocarbon receptor (AHR) is expressed by immune cells and binds numerous xenobiotics. Early life exposure to chemicals that bind the AHR impairs CD4+ T cell responses to influenza A virus (IAV) infection in adulthood. However, the cellular mechanisms that underlie these durable changes remain poorly defined. Transcriptomic profiling of sorted CD4+ T cells identified changes in genes involved in proliferation, differentiation, and metabolic pathways were associated with triggering AHR during development. Functional bioassays confirmed that CD4+ T cells from infected developmentally exposed offspring exhibit reduced proliferation, differentiation, and cellular metabolism. Thus, developmental AHR activation shapes T cell responsive capacity later in life by affecting integrated cellular pathways, which collectively alter responses later in life. Given that coordinated shifts in T cell metabolism are essential for T cell responses to numerous challenges, and that humans are constantly exposed to many different types of AHR ligands, this has far-reaching implications for how AHR signaling, particularly during development, durably influences T cell mediated immune responses across the lifespan.

Conditional deletion of Ahr alters gene expression profiles in hematopoietic stem cells.

The aryl hydrocarbon receptor (AHR) is a ligand activated bHLH transcription factor that belongs to the Per-Arnt-Sim (PAS) superfamily of proteins involved in mediating responses to cellular environment regulating normal physiological and developmental pathways. The AHR binds a broad range of naturally derived and synthetic compounds, and plays a major role in mediating effects of certain environmental chemicals. Although our understanding of the physiological roles of the AHR in the immune system is evolving, there is little known about its role in hematopoiesis and hematopoietic diseases. Prior studies demonstrated that AHR null (AHR-KO) mice have impaired hematopoietic stem cell (HSC) function; they develop myeloproliferative changes in peripheral blood cells, and alterations in hematopoietic stem and progenitor cell populations in the bone marrow. We hypothesized mice lacking AHR expression only within hematopoietic cells (AHRVav1 mice) would develop similar changes. However, we did not observe a complete phenocopy of AHR-KO and AHRVav1 animals at 2 or 18 months of age. To illuminate the signaling mechanisms underlying the alterations in hematopoiesis observed in these mice, we sorted a population of cells highly enriched for HSC function (LSK cells: CD34-CD48-CD150+) and performed microarray analyses. Ingenuity Pathway and Gene Set Enrichment Analyses revealed that that loss of AHR within HSCs alters several gene and signaling networks important for HSC function. Differences in gene expression networks among HSCs from AHR-KO and AHRVav1 mice suggest that AHR in bone marrow stromal cells also contributes to HSC function. In addition, numerous studies have suggested a role for AHR in both regulation of hematopoietic cells, and in the development of blood diseases. More work is needed to define what these signals are, and how they act upon HSCs.

Developmental Exposure to a Mixture of 23 Chemicals Associated With Unconventional Oil and Gas Operations Alters the Immune System of Mice.

Chemicals used in unconventional oil and gas (UOG) operations have the potential to cause adverse biological effects, but this has not been thoroughly evaluated. A notable knowledge gap is their impact on development and function of the immune system. Herein, we report an investigation of whether developmental exposure to a mixture of chemicals associated with UOG operations affects the development and function of the immune system. We used a previously characterized mixture of 23 chemicals associated with UOG, and which was demonstrated to affect reproductive and developmental endpoints in mice. C57Bl/6 mice were maintained throughout pregnancy and during lactation on water containing two concentrations of this 23-chemical mixture, and the immune system of male and female adult offspring was assessed. We comprehensively examined the cellularity of primary and secondary immune organs, and used three different disease models to probe potential immune effects: house dust mite-induced allergic airway disease, influenza A virus infection, and experimental autoimmune encephalomyelitis (EAE). In all three disease models, developmental exposure altered frequencies of certain T cell sub-populations in female, but not male, offspring. Additionally, in the EAE model disease onset occurred earlier and was more severe in females. Our findings indicate that developmental exposure to this mixture had persistent immunological effects that differed by sex, and exacerbated responses in an experimental model of autoimmune encephalitis. These observations suggest that developmental exposure to complex mixtures of water contaminants, such as those derived from UOG operations, could contribute to immune dysregulation and disease later in life.

Summary of the 2017 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

On June 24, 2017, the 22nd annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held as a satellite conference during the annual Research Society on Alcoholism (RSA) Scientific Meeting in Denver, Colorado. The 2017 meeting focused broadly on mechanisms that link alcohol to tissue injury and inflammation, and how this research can be translated to improve human health. Two plenary sessions composed the meeting, which first explored the association between alcohol and trauma/tissue injury, and finished with a discussion of alcohol and mucosal inflammation. The presentations encompassed diverse areas of alcohol research, from effects on the brain, to airway and pulmonary systems, to gut barrier disruption. The discussions also thoughtfully highlighted how current laboratory and clinical research can be used to prevent or treat alcohol-related morbidity and mortality.

Aryl hydrocarbon receptor signaling modulates antiviral immune responses: ligand metabolism rather than chemical source is the stronger predictor of outcome.

The aryl hydrocarbon receptor (AHR) offers a compelling target to modulate the immune system. AHR agonists alter adaptive immune responses, but the consequences differ across studies. We report here the comparison of four agents representing different sources of AHR ligands in mice infected with influenza A virus (IAV): TCDD, prototype exogenous AHR agonist; PCB126, pollutant with documented human exposure; ITE, novel pharmaceutical; and FICZ, degradation product of tryptophan. All four compounds diminished virus-specific IgM levels and increased the proportion of regulatory T cells. TCDD, PCB126 and ITE, but not FICZ, reduced virus-specific IgG levels and CD8+ T cell responses. Similarly, ITE, PCB126, and TCDD reduced Th1 and Tfh cells, whereas FICZ increased their frequency. In Cyp1a1-deficient mice, all compounds, including FICZ, reduced the response to IAV. Conditional Ahr knockout mice revealed that all four compounds require AHR within hematopoietic cells. Thus, differences in the immune response to IAV likely reflect variances in quality, magnitude, and duration of AHR signaling. This indicates that binding affinity and metabolism may be stronger predictors of immune effects than a compound's source of origin, and that harnessing AHR will require finding a balance between dampening immune-mediated pathologies and maintaining sufficient host defenses against infection.

Summary of the 2016 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

On November 18, 2016 the 21st annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at the Center for Translational Research and Education at Loyola University Chicago's Health Sciences Campus in Maywood, IL. The 2016 meeting focused broadly on alcohol and inflammation, epigenetics, and the microbiome. The four plenary sessions of the meeting were Alcohol, Inflammation, and Immunity; Alcohol and Epigenetics; Alcohol, Transcriptional Regulation, and Epigenetics; and Alcohol, Intestinal Mucosa, and the Gut Microbiome. Presentations in all sessions of the meeting explored putative underlying causes for chronic diseases and mortality associated with alcohol consumption, shedding light on future work and potential therapeutic targets to alleviate the negative effects of alcohol misuse.

Inflammaging and the Lung.

With the coming of the "silver tsunami," expanding the knowledge about how various intrinsic and extrinsic factors affect the immune system in the elderly is timely and of immediate clinical need. The global population is increasing in age. By the year 2030, more than 20% of the population of the United States will be older than 65 years of age. This article focuses on how advanced age alters the immune systems and how this, in turn, modulates the ability of the aging lung to deal with infectious challenges from the outside world and from within the host.

Alcohol, aging, and innate immunity.

The global population is aging: in 2010, 8% of the population was older than 65 y, and that is expected to double to 16% by 2050. With advanced age comes a heightened prevalence of chronic diseases. Moreover, elderly humans fair worse after acute diseases, namely infection, leading to higher rates of infection-mediated mortality. Advanced age alters many aspects of both the innate and adaptive immune systems, leading to impaired responses to primary infection and poor development of immunologic memory. An often overlooked, yet increasingly common, behavior in older individuals is alcohol consumption. In fact, it has been estimated that >40% of older adults consume alcohol, and evidence reveals that >10% of this group is drinking more than the recommended limit by the National Institute on Alcohol Abuse and Alcoholism. Alcohol consumption, at any level, alters host immune responses, including changes in the number, phenotype, and function of innate and adaptive immune cells. Thus, understanding the effect of alcohol ingestion on the immune system of older individuals, who are already less capable of combating infection, merits further study. However, there is currently almost nothing known about how drinking alters innate immunity in older subjects, despite innate immune cells being critical for host defense, resolution of inflammation, and maintenance of immune homeostasis. Here, we review the effects of aging and alcohol consumption on innate immune cells independently and highlight the few studies that have examined the effects of alcohol ingestion in aged individuals.

Developmental Activation of the AHR Increases Effector CD4+ T Cells and Exacerbates Symptoms in Autoimmune Disease-Prone Gnaq+/- Mice.

Perinatal environmental exposures are potentially important contributors to the increase in autoimmune diseases. Yet, the mechanisms by which these exposures increase self-reactive immune responses later in life are poorly understood. Autoimmune diseases require CD4(+) T cells for initiation, progression, and/or clinical symptoms; thus, developmental exposures that cause durable changes in CD4(+) T cells may play a role. Early life activation of the aryl hydrocarbon receptor (AHR) causes persistent changes in the response of CD4(+) T cells to infection later in life but whether CD4(+) T cells are affected by developmental exposure in the context of an autoimmune disease is unknown. Gnaq(+/-) mice develop symptoms of autoimmune disease similar to those measured clinically, and therefore can be used to evaluate gene-environment interactions during development on disease progression. Herein, we examined the effect of AHR activation in utero and via lactation, or solely via lactation, on disease onset and severity in adult Gnaq(+/-) offspring. Developmental activation of the AHR-accelerated disease in Gnaq(+/-) mice, and this correlates with increases in effector CD4(+) T-cell populations. Increased symptom onset and cellular changes due to early life AHR activation were more evident in female Gnaq(+/-) mice compared with males. These observations suggest that developmental AHR activation by pollutants, and other exogenous ligands, may increase the likelihood that genetically predisposed individuals will develop clinical symptoms of autoimmune disease later in life.

Activation of the aryl hydrocarbon receptor during development enhances the pulmonary CD4+ T-cell response to viral infection.

Respiratory infections are a threat to health and economies worldwide, yet the basis for striking variation in the severity of infection is not completely understood. Environmental exposures during development are associated with increased severity and incidence of respiratory infection later in life. Many of these exposures include ligands of the aryl hydrocarbon receptor (AHR), a transcription factor expressed by immune and nonimmune cells. In adult animals, AHR activation alters CD4(+) T cells and changes immunopathology. Developmental AHR activation impacts CD4(+) T-cell responses in lymphoid tissues, but whether skewed responses are also present in the infected lung is unknown. To determine whether pulmonary CD4(+) T-cell responses are modified by developmental AHR activation, mice were exposed to the prototypical AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin during development and infected with influenza virus as adults. Lungs of exposed offspring had greater bronchopulmonary inflammation compared with controls, and activated, virus-specific CD4(+) T cells contributed to the infiltrating leukocytes. These effects were CD4(+) T cell subset specific, with increases in T helper type 1 and regulatory T cells, but no change in the frequency of T helper type 17 cells in the infected lung. This is in direct contrast to prior reports of suppressed conventional CD4(+) T-cell responses in the lymph node. Using adoptive transfers and manipulating the pathogen properties, we determined that developmental exposure influenced factors intrinsic and extrinsic to CD4(+) T cells and may involve developmentally induced changes in signals from infected lung epithelial cells. Thus developmental exposures lead to context-dependent changes in pulmonary CD4(+) T-cell subsets, which may contribute to differential responses to respiratory infection.

Effects of developmental activation of the AhR on CD4+ T-cell responses to influenza virus infection in adult mice.

BACKGROUND: Epidemiological and animal studies indicate that maternal exposure to pollutants that bind the aryl hydrocarbon receptor (AhR) correlates with poorer ability to combat respiratory infection and lower antibody levels in the offspring. These observations point to an impact on CD4+ T cells. Yet, the consequence of developmental exposure to AhR ligands on the activation and differentiation of CD4+ T cells has not been directly examined. OBJECTIVES: Our goal was to determine whether maternal exposure to an AhR ligand directly alters CD4+ T cell differentiation and function later in life. METHODS: C57BL/6 mice were exposed to a prototypical AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), in utero and via suckling. We then measured CD4+ T-cell activation and differentiation into distinct effector populations in adult offspring that were infected with influenza A virus (IAV). Reciprocal adoptive transfers were used to define whether modifications in CD4+ T-cell responses resulted from direct effects of developmental TCDD exposure on CD4+ T cells. RESULTS: Developmental exposure skewed CD4+ T-cell responses to IAV infection. We observed fewer virus-specific, activated CD4+ T cells and a reduced frequency of conventional CD4+ effector-cell subsets. However, there was an increase in regulatory CD4+ T cells. Direct effects of AhR activation on CD4+ T cells resulted in impaired differentiation into conventional effector subsets; this defect was transferred to mice that had not been developmentally exposed to TCDD. CONCLUSIONS: Maternal exposure to TCDD resulted in durable changes in the responsive capacity and differentiation of CD4+ T cells in adult C57BL/6 mice.