Maternal exposure of mice to glyphosate induces depression- and anxiety-like behavior in the offspring via alterations of the gut-brain axis.

The past decade has been characterized by increased awareness and de-stigmatization of mental health issues, in particular the most common neuropsychiatric disorders depression and anxiety. Further, with growing understanding of neurodevelopmental disorders such as attention deficit and hyperactivity disorder and autism spectrum disorder, the number of diagnosed patients has increased. The pathogenesis of these behavioral disorders is multifactorial and early-life exposure to environmental chemicals has been proposed to be a relevant risk factor that might mediate these effects by disturbances on the gut-brain-axis. However, for glyphosate, the most widely used pesticide worldwide, there are only limited and inconsistent findings that link chronic low-dose exposure in particular during early life to neurobehavioral disorders. Here, we explored the impact of maternal oral glyphosate exposure (0.5 and 50 mg/kg body weight/day) during pregnancy and the lactational period on offspring's behavior, brain gene expression and gut microbiota using a cross-generational mouse model. Behavioral analyses revealed a depression- and anxiety-like behavior as well as social deficits most notably in adult female offspring of glyphosate-exposed dams. Furthermore, the expression of tryptophan hydroxylase 2, an enzyme discussed to be linked to behavioral problems, was reduced in the hippocampus of female offspring and correlated to a glyphosate-induced DNA hypermethylation of the gene. Moreover, maternal glyphosate exposure significantly altered the gut microbiota in the female offspring including a decreased abundance of Akkermansia and increased abundance of Alistipes and Blautia, bacteria involved in tryptophan metabolism and associated with depression- and anxiety-like disorders. Our results suggest that glyphosate might influence the gut-brain axis crosstalk following in-utero and lactational exposure. This study underlines the importance of understanding the impact of exposure to pesticides on the gut-brain axis and further emphasizes the need for microbiome analyses to be compulsorily included in health risk assessments of pesticides.

Glyphosate differentially affects the allergic immune response across generations in mice.

Exposure to environmental pollutants via food, particularly during the prenatal and early postnatal periods, has been linked to adverse effects on the immune system. Among these pollutants, the widely used pesticide glyphosate has been associated with endocrine disruption, autism, and cancer. Occupational high exposure to glyphosate has also been shown to influence immune function and exacerbate allergic asthma. However, there are no studies investigating the effect of a common low-dose glyphosate exposure on the allergic immune response - neither directly nor across generations. We therefore explored the impact of oral low-dose glyphosate exposure (0.5 and 50 mg/kg body weight/day) on airway inflammation in dams (F0) and the offspring (F1 and F2 generations) using a murine multi-generational asthma model. While exposure to 50 mg/kg glyphosate induced a mild eosinophilic infiltration in the bronchoalveolar lavage and TH2 cytokine production in the dams, the F1 offspring developed a reduced immune response after maternal exposure to 0.5 mg/kg glyphosate. In particular, decreased lung inflammation, HDM-specific IgE levels, and asthma-relevant cytokine production were primarily observed in the female F1 offspring. However, not only the TH2 cytokines IL-13 and IL-5 but also the TH17 cytokine IL-17 and TH1 cytokine IFN-γ were reduced indicating a more general immunosuppressive function. Notably, the dampened immune response was no longer observed in the female F2 generation. Furthermore, female F1 offspring showed an increased abundance of bacteria in the gut, which have been associated with probiotic-mediated reduced allergic immune responses. Our results suggest a potential immunosuppressive effect of low-dose maternal glyphosate exposure in the F1 offspring that might be mediated by an altered microbiota composition. Further studies are needed to explore if this type of immune response modulation might also be associated with impairments in immune defense upon infectious diseases or even cancer pathology.

Effects of exposure to single and multiple parabens on asthma development in an experimental mouse model and a prospective cohort study.

Parabens are widely used preservatives present in consumer products like cosmetics and food. Although several epidemiological studies suggest that early-life exposure to parabens might alter the immune response and allergy risk in childhood, the evidence with respect to asthma is not clear. Therefore, we investigated the effect of paraben exposure on asthma development in mice and humans. Using a murine asthma model the experimental data show both, an asthma-reducing effect after direct exposure of adult mice to n-butyl paraben (nBuP) as well as an asthma-promoting effect after maternal exposure to ethyl paraben (EtP) in the female offspring. Interestingly, exposure of mice to a mixture of EtP and nBuP starting prenatally until the end of asthma induction in the adult offspring was without effect on allergic airway inflammation. In addition, parabens were determined within the German prospective mother-child cohort LINA and their single and mixture effect on asthma development in children within the first 10 years of life was estimated by logistic and Bayesian kernel machine regression (BKMR). Both approaches revealed no adverse effects of parabens on children's asthma development, neither when stratified for being at risk due to a positive family history of atopy nor when analysed separately for sex specificity. Therefore, we conclude that although single parabens might differentially impact asthma development, an adverse effect could not be seen in a multiple paraben exposure setting. Consequently, not only the time point of exposure but also multiple exposure scenarios to parabens should be considered in the evaluation of individuals' specific disease risk.

Mold, Mycotoxins and a Dysregulated Immune System: A Combination of Concern?

Fungi represent one of the most diverse and abundant eukaryotes on earth. The interplay between mold exposure and the host immune system is still not fully elucidated. Literature research focusing on up-to-date publications is providing a heterogenous picture of evidence and opinions regarding the role of mold and mycotoxins in the development of immune diseases. While the induction of allergic immune responses by molds is generally acknowledged, other direct health effects like the toxic mold syndrome are controversially discussed. However, recent observations indicate a particular importance of mold/mycotoxin exposure in individuals with pre-existing dysregulation of the immune system, due to exacerbation of underlying pathophysiology including allergic and non-allergic chronic inflammatory diseases, autoimmune disorders, and even human immunodeficiency virus (HIV) disease progression. In this review, we focus on the impact of mycotoxins regarding their impact on disease progression in pre-existing immune dysregulation. This is complemented by experimental in vivo and in vitro findings to present cellular and molecular modes of action. Furthermore, we discuss hypothetical mechanisms of action, where evidence is missing since much remains to be discovered.

Wood emissions and asthma development: Results from an experimental mouse model and a prospective cohort study.

BACKGROUND: Increased use of renewable resources like sustainably produced wood in construction or for all sorts of long-lived products is considered to contribute to reducing society's carbon footprint. However, as a natural, biological material, wood and wood products emit specific volatile organic compounds (VOCs). Therefore, the evaluation of possible health effects due to wood emissions is of major interest. OBJECTIVES: We investigated the effects of an exposure to multiple wood-related VOCs on asthma development. METHODS: A murine asthma model was used to evaluate possible allergic and inflammatory effects on the lung after short- or long-term and perinatal exposure to pinewood or oriented strand board (OSB). In addition, wood-related VOCs were measured within the German prospective mother-child cohort LINA and their joint effect on early wheezing or asthma development in children until the age of 10 was estimated by Bayesian kernel machine regression (BKMR) stratifying also for family history of atopy (FHA). RESULTS: Our experimental data show that neither pinewood nor OSB emissions even at high total VOC levels and a long-lasting exposure period induce significant inflammatory or asthma-promoting effects in sensitized or non-sensitized mice. Moreover, an exposure during the vulnerable time window around birth was also without effect. Consistently, in our mother-child cohort LINA, an exposure to multiple wood-related VOCs during pregnancy or the first year of life was not associated with early wheezing or asthma development in children independent from their FHA. CONCLUSION: Our findings indicate that emissions from wood and wood products at levels commonly occurring in the living environment do not exert adverse effects concerning wheezing or asthma development.

Phthalate Exposure During the Prenatal and Lactational Period Increases the Susceptibility to Rheumatoid Arthritis in Mice.

The prenatal and early postnatal period is highly sensitive to environmental exposures that may interfere with the developmental programming of the immune system leading to an altered disease risk in later life. To clarify the role of early influences in activation or exacerbation of autoimmune diseases like rheumatoid arthritis (RA) we investigated the effect of maternal exposure during the prenatal and lactational period of DBA/1 mice to the plasticizer benzyl butyl phthalate (BBP) on the development of RA in the offspring. Using a mild collagen-induced arthritis (CIA) model, maternal BBP-exposure increased both the prevalence and the severity of RA in the progeny compared to un-exposed dams. Additionally, maternal BBP exposure led to elevated serum IgG1 and IgG2a level in the offspring and increased the IFN-γ and IL-17 release from collagen-re-stimulated spleen cells. Transcriptome analysis of splenocytes isolated from 3-week-old pups before RA-induction revealed considerable changes in gene expression in the offspring from BBP-exposed dams. Among them were regulator of G-protein signaling 1 (rgs1), interleukin-7 receptor (il-7r) and CXC chemokine 4 (cxcr4), all genes that have previously been described as associated with RA pathology. In summary, our results demonstrate that perinatal exposure to BBP increases the susceptibility of the offspring to RA, probably via a phthalate-induced disturbed regulation of RA-relevant genes or signaling pathways.

Maternal paraben exposure triggers childhood overweight development.

Parabens are preservatives widely used in consumer products including cosmetics and food. Whether low-dose paraben exposure may cause adverse health effects has been discussed controversially in recent years. Here we investigate the effect of prenatal paraben exposure on childhood overweight by combining epidemiological data from a mother-child cohort with experimental approaches. Mothers reporting the use of paraben-containing cosmetic products have elevated urinary paraben concentrations. For butyl paraben (BuP) a positive association is observed to overweight within the first eight years of life with a stronger trend in girls. Consistently, maternal BuP exposure of mice induces a higher food intake and weight gain in female offspring. The effect is accompanied by an epigenetic modification in the neuronal Pro-opiomelanocortin (POMC) enhancer 1 leading to a reduced hypothalamic POMC expression. Here we report that maternal paraben exposure may contribute to childhood overweight development by altered POMC-mediated neuronal appetite regulation.

MEST mediates the impact of prenatal bisphenol A exposure on long-term body weight development.

Background: Exposure to endocrine-disrupting chemicals can alter normal physiology and increase susceptibility to non-communicable diseases like obesity. Especially the prenatal and early postnatal period is highly vulnerable to adverse effects by environmental exposure, promoting developmental reprogramming by epigenetic alterations. To obtain a deeper insight into the role of prenatal bisphenol A (BPA) exposure in children's overweight development, we combine epidemiological data with experimental models and BPA-dependent DNA methylation changes. Methods: BPA concentrations were measured in maternal urine samples of the LINA mother-child-study obtained during pregnancy (n = 552), and BPA-associated changes in cord blood DNA methylation were analyzed by Illumina Infinium HumanMethylation450 BeadChip arrays (n = 472). Methylation changes were verified by targeted MassARRAY analyses, assessed for their functional translation by qPCR and correlated with children's body mass index (BMI) z scores at the age of 1 and 6 years. Further, female BALB/c mice were exposed to BPA from 1 week before mating until delivery, and weight development of their pups was monitored (n ≥ 8/group). Additionally, human adipose-derived mesenchymal stem cells were treated with BPA during the adipocyte differentiation period and assessed for exposure-related epigenetic, transcriptional and morphological changes (n = 4). Results: In prenatally BPA-exposed children two CpG sites with deviating cord blood DNA-methylation profiles were identified, among them a hypo-methylated CpG in the promoter of the obesity-associated mesoderm-specific transcript (MEST). A mediator analysis suggested that prenatal BPA exposure was connected to cord blood MEST promoter methylation and MEST expression as well as BMI z scores in early infancy. This effect could be confirmed in mice in which prenatal BPA exposure altered Mest promoter methylation and transcription with a concomitant increase in the body weight of the juvenile offspring. An experimental model of in vitro differentiated human mesenchymal stem cells also revealed an epigenetically induced MEST expression and enhanced adipogenesis following BPA exposure. Conclusions: Our study provides evidence that MEST mediates the impact of prenatal BPA exposure on long-term body weight development in offspring by triggering adipocyte differentiation.

Spray-Dried Nanoparticle-in-Microparticle Delivery Systems (NiMDS) for Gene Delivery, Comprising Polyethylenimine (PEI)-Based Nanoparticles in a Poly(Vinyl Alcohol) Matrix.

Nucleic acid-based therapies rely on efficient formulations for nucleic acid protection and delivery. As nonviral strategies, polymeric and lipid-based nanoparticles have been introduced; however, biological efficacy and biocompatibility as well as poor storage properties due to colloidal instability and their unavailability as ready-to-use systems are still major issues. Polyethylenimine is the most widely explored and promising candidate for gene delivery. Polyethylenimine-based polyplexes and their combination with liposomes, lipopolyplexes, are efficient for DNA or siRNA delivery in vitro and in vivo. In this study, a highly potent spray-dried nanoparticle-in-microparticle delivery system is presented for the encapsulation of polyethylenimine-based polyplexes and lipopolyplexes into poly(vinyl alcohol) microparticles, without requiring additional stabilizing agents. This easy-to-handle gene delivery device allows prolonged nanoparticle storage and protection at ambient temperature. Biological analyses reveal further advantages regarding profoundly reduced cytotoxicity and enhanced transfection efficacies of polyethylenimine-based nanoparticles from the nanoparticle-in-microparticle delivery system over their freshly prepared counterparts, as determined in various cell lines. Importantly, this nanoparticle-in-microparticle delivery system is demonstrated as ready-to-use dry powder to be an efficient device for the inhalative delivery of polyethylenimine-based lipopolyplexes in vivo, as shown by transgene expression in mice after only one administration.

Maternal phthalate exposure promotes allergic airway inflammation over 2 generations through epigenetic modifications.

BACKGROUND: Prenatal and early postnatal exposures to environmental factors are considered responsible for the increasing prevalence of allergic diseases. Although there is some evidence for allergy-promoting effects in children because of exposure to plasticizers, such as phthalates, findings of previous studies are inconsistent and lack mechanistic information. OBJECTIVE: We investigated the effect of maternal phthalate exposure on asthma development in subsequent generations and their underlying mechanisms, including epigenetic alterations. METHODS: Phthalate metabolites were measured within the prospective mother-child cohort Lifestyle and Environmental Factors and Their Influence on Newborns Allergy Risk (LINA) and correlated with asthma development in the children. A murine transgenerational asthma model was used to identify involved pathways. RESULTS: In LINA maternal urinary concentrations of mono-n-butyl phthalate, a metabolite of butyl benzyl phthalate (BBP), were associated with an increased asthma risk in the children. Using a murine transgenerational asthma model, we demonstrate a direct effect of BBP on asthma severity in the offspring with a persistently increased airway inflammation up to the F2 generation. This disease-promoting effect was mediated by BBP-induced global DNA hypermethylation in CD4+ T cells of the offspring because treatment with a DNA-demethylating agent alleviated exacerbation of allergic airway inflammation. Thirteen transcriptionally downregulated genes linked to promoter or enhancer hypermethylation were identified. Among these, the GATA-3 repressor zinc finger protein 1 (Zfpm1) emerged as a potential mediator of the enhanced susceptibility for TH2-driven allergic asthma. CONCLUSION: These data provide strong evidence that maternal BBP exposure increases the risk for allergic airway inflammation in the offspring by modulating the expression of genes involved in TH2 differentiation through epigenetic alterations.

Mold metabolites drive rheumatoid arthritis in mice via promotion of IFN-gamma- and IL-17-producing T cells.

Environmental factors have been discussed as triggers for autoimmune diseases like rheumatoid arthritis (RA). However, the role of chemical exposures in activation or exacerbation of RA is not clarified yet. Exposure of DBA/1 mice to the mold metabolites ochratoxin A (OTA) or deoxynivalenol (DON) increased the prevalence and the clinical severity of RA compared to un-exposed mice using an experimental collagen-induced arthritis model. Mycotoxin-exposed mice showed enhanced serum IgG1 and IgG2a levels and an elevated production of IL-1ß and IL-6 in inflamed joints and of IFN-γ and IL-17 in splenocytes. Additionally, OTA and DON increased the release of the pro-inflammatory cytokines IL-1ß, IL-6 and TNF-α in activated murine macrophages and supported the differentiation of naïve T cells into Th1 cells, while treatment of CD4+T cells with the supernatant from mycotoxin-exposed macrophages induced IL-17 production. Furthermore, exposure of mice to OTA or DON enhanced the gene expression of Stat1, Stat3 and Stat4 in the spleen while the collagen-induced increase of Socs1 and Socs3 was abolished. Our results demonstrate that mycotoxins increase the susceptibility to develop RA via an enhanced stimulation of macrophages and promotion of Th1/Th17 cell differentiation by induction of Stat signalling pathways and down-regulation of the Socs-mediated feedback inhibition.

Syndecan-1 regulates dendritic cell migration in cutaneous hypersensitivity to haptens.

In human dendritic cells (DCs), we previously demonstrated in vitro that syndecan-1 (SDC1) is downregulated during maturation correlating with enhanced motility. We investigated the effects of SDC1 on DC migration in vivo during TNCB(2,4,6-trinitro-1-chlorobenzene)-induced cutaneous hypersensitivity reaction (CHS) in mice. We show that DC in SDC1-deficient mice migrated faster and at a higher rate to lymph nodes draining the hapten-painted skin. Adoptive transfer of SDC1-deficient hapten- and fluorochrome-labelled DC into wild-type (WT) mice led to increased and faster migration of DC to paracortical lymph nodes, and to a stronger CHS compared to WT DC. In SDC1-/- mice, CCR7 remains longer on the DC surface within the first 15-minutes maturation (after LPS-induced maturation). In addition, a time-dependent upregulation of CCL2, CCL3, VCAM1 and talin was found during maturation in SDC1-/- DC. However, no difference in T-cell-stimulating capacity of SDC1-deficient DC was found compared to WT DC. Mechanistically, SDC1-deficient DC showed enhanced migration towards CCL21 and CCL19. This may result from functional overexpression of CCR7 in SDC1-/- DC. Increased and accelerated migration of otherwise functionally intact SDC1-deficient DC leads to an exacerbated CHS. Based on our results, we conclude that SDC1 on DC negatively regulates DC migration.

From the exposome to mechanistic understanding of chemical-induced adverse effects.

The exposome encompasses an individual's exposure to exogenous chemicals, as well as endogenous chemicals that are produced or altered in response to external stressors. While the exposome concept has been established for human health, its principles can be extended to include broader ecological issues. The assessment of exposure is tightly interlinked with hazard assessment. Here, we explore if mechanistic understanding of the causal links between exposure and adverse effects on human health and the environment can be improved by integrating the exposome approach with the adverse outcome pathway (AOP) concept that structures and organizes the sequence of biological events from an initial molecular interaction of a chemical with a biological target to an adverse outcome. Complementing exposome research with the AOP concept may facilitate a mechanistic understanding of stress-induced adverse effects, examine the relative contributions from various components of the exposome, determine the primary risk drivers in complex mixtures, and promote an integrative assessment of chemical risks for both human and environmental health.

Allergen-Induced IL-6 Regulates IL-9/IL-17A Balance in CD4+ T Cells in Allergic Airway Inflammation.

IL-9-secreting Th9 cells have been considered to play a pivotal role in the pathogenesis of atopic diseases. To what extent IL-9-producing cells are induced or regulated by sensitization with naturally occurring allergens is not yet clear. Naturally occurring allergens are capable of inducing IL-6 production in dendritic cells (DCs). Whether allergen-induced IL-6 supports a Th9 subtype by increasing IL-9 production, as observed in in vitro studies, or rather favors Th17 differentiation is not finally resolved. Therefore, in the present study we have investigated the impact of IL-6 on the Th9/Th17 balance depending on the predominant cytokine milieu and, additionally, in vivo using a DC-driven murine asthma model. In vitro, IL-6 increases Th9 cells under strong IL-4 and TGF-ß activation, whereas under moderate IL-4 and TGF-ß activation the presence of IL-6 shifts naive CD4(+) cells to Th17 cells. To induce allergic airway inflammation, OVA-pulsed DCs from IL-6-deficient or wild-type donors were adoptively transferred into BALB/c mice. Recipients receiving IL-6-producing wild-type DCs showed a significant decrease of Th9- and IL-4-producing Th2 cells but an increase of Th17 cells in lung tissue in comparison with recipients sensitized with IL-6-deficient DCs. Our data suggest that the IL-6-mediated reduction of Th2-related IL-4 leads to a decline of the Th9 immune response and allows Th17 differentiation.

Environment-induced epigenetic reprogramming in genomic regulatory elements in smoking mothers and their children.

Epigenetic mechanisms have emerged as links between prenatal environmental exposure and disease risk later in life. Here, we studied epigenetic changes associated with maternal smoking at base pair resolution by mapping DNA methylation, histone modifications, and transcription in expectant mothers and their newborn children. We found extensive global differential methylation and carefully evaluated these changes to separate environment associated from genotype-related DNA methylation changes. Differential methylation is enriched in enhancer elements and targets in particular "commuting" enhancers having multiple, regulatory interactions with distal genes. Longitudinal whole-genome bisulfite sequencing revealed that DNA methylation changes associated with maternal smoking persist over years of life. Particularly in children prenatal environmental exposure leads to chromatin transitions into a hyperactive state. Combined DNA methylation, histone modification, and gene expression analyses indicate that differential methylation in enhancer regions is more often functionally translated than methylation changes in promoters or non-regulatory elements. Finally, we show that epigenetic deregulation of a commuting enhancer targeting c-Jun N-terminal kinase 2 (JNK2) is linked to impaired lung function in early childhood.

Critical role for syndecan-4 in dendritic cell migration during development of allergic airway inflammation.

Syndecan-4 (SDC4), expressed on dendritic cells (DCs) and activated T cells, plays a crucial role in DC motility and has been shown as a potential target for activated T-cell-driven diseases. In the present study, we investigate the role of SDC4 in the development of T-helper 2 cell-mediated allergic asthma. Using SDC4-deficient mice or an anti-SDC4 antibody we show that the absence or blocking of SDC4 signalling in ovalbumin-sensitized mice results in a reduced asthma phenotype compared with control animals. Most importantly, even established asthma is significantly decreased using the anti-SDC4 antibody. The disturbed SDC4 signalling leads to an impaired motility and directional migration of antigen-presenting DCs and therefore, to a modified sensitization leading to diminished airway inflammation. Our results demonstrate that SDC4 plays an important role in asthma induction and indicate SDC4 as possible target for therapeutic intervention in this disease.

The G protein-coupled receptor P2Y14 influences insulin release and smooth muscle function in mice.

UDP sugars were identified as extracellular signaling molecules, assigning a new function to these compounds in addition to their well defined role in intracellular substrate metabolism and storage. Previously regarded as an orphan receptor, the G protein-coupled receptor P2Y14 (GPR105) was found to bind extracellular UDP and UDP sugars. Little is known about the physiological functions of this G protein-coupled receptor. To study its physiological role, we used a gene-deficient mouse strain expressing the bacterial LacZ reporter gene to monitor the physiological expression pattern of P2Y14. We found that P2Y14 is mainly expressed in pancreas and salivary glands and in subpopulations of smooth muscle cells of the gastrointestinal tract, blood vessels, lung, and uterus. Among other phenotypical differences, knock-out mice showed a significantly impaired glucose tolerance following oral and intraperitoneal glucose application. An unchanged insulin tolerance suggested altered pancreatic islet function. Transcriptome analysis of pancreatic islets showed that P2Y14 deficiency significantly changed expression of components involved in insulin secretion. Insulin secretion tests revealed a reduced insulin release from P2Y14-deficient islets, highlighting P2Y14 as a new modulator of proper insulin secretion.

Lifetime-dependent effects of bisphenol A on asthma development in an experimental mouse model.

BACKGROUND: Environmental factors are thought to contribute significantly to the increase of asthma prevalence in the last two decades. Bisphenol A (BPA) is a xenoestrogen commonly used in consumer products and the plastic industry. There is evidence and an ongoing discussion that endocrine disruptors like BPA may affect human health and also exert alterations on in the immune system. The aim of this study was to investigate age-dependent effects of BPA on the asthma risk using a murine model to explain the controversial results reported till date. METHODS: BALB/c mice were exposed to BPA via the drinking water for different time periods including pregnancy and breastfeeding. To induce an asthma phenotype, mice were sensitized to ovalbumin (OVA), followed by an intrapulmonary allergen challenge. RESULTS: BPA exposure during pregnancy and breastfeeding had no significant effect on asthma development in the offspring. In contrast, lifelong exposure from birth until the last antigen challenge clearly increased eosinophilic inflammation in the lung, airway hyperreactivity and antigen-specific serum IgE levels in OVA-sensitized adult mice compared to mice without BPA exposure. Surprisingly, BPA intake during the sensitization period significantly reduced the development of allergic asthma. This effect was reversed in the presence of a glucocorticoid receptor antagonist. CONCLUSIONS: Our results demonstrate that the impact of BPA on asthma risk is strongly age-dependent and ranges from asthma-promoting to asthma-reducing effects. This could explain the diversity of results from previous studies regarding the observed health impact of BPA.

Generation of IL-8 and IL-9 producing CD4⁺ T cells is affected by Th17 polarizing conditions and AHR ligands.

The T helper cell subsets Th1, Th2, Th17, and Treg play an important role in immune cell homeostasis, in host defense, and in immunological disorders. Recently, much attention has been paid to Th17 cells which seem to play an important role in the early phase of the adoptive immune response and autoimmune disease. When generating Th17 cells under in vitro conditions the amount of IL-17A producing cells hardly exceeds 20% while the nature of the remaining T cells is poorly characterized. As engagement of the aryl hydrocarbon receptor (AHR) has also been postulated to modulate the differentiation of T helper cells into Th17 cells with regard to the IL-17A expression we ask how far do Th17 polarizing conditions in combination with ligand induced AHR activation have an effect on the production of other T helper cell cytokines. We found that a high proportion of T helper cells cultured under Th17 polarizing conditions are IL-8 and IL-9 single producing cells and that AHR activation results in an upregulation of IL-8 and a downregulation of IL-9 production. Thus, we have identified IL-8 and IL-9 producing T helper cells which are subject to regulation by the engagement of the AHR.