RESUMO
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an abnormal CAG repeat expansion in the huntingtin gene coding for a protein with an elongated polyglutamine sequence. HD patients present choreiform movements, which are caused by the loss of neurons in the striatum and cerebral cortex. Previous reports indicate that the absence of the aryl hydrocarbon receptor (AhR) protects mice from excitotoxic insults and increases the transcription of neurotrophic factors. Based on these data, we evaluated the effects of the lack of the AhR on a mice model of HD, generating a double transgenic mouse, expressing human mutated huntingtin (R6/1 mice) and knockout for the AhR. Our results show that the body weight of 30-week-old double transgenic mice is similar to that of R6/1 mice; however, feet clasping, an indicative of neuronal damage in the R6/1 animals, was not observed. In addition, motor coordination and ambulatory behavior in double transgenic mice did not deteriorate over time as occur in the R6/1 mice. Moreover, the anxiety behavior of double transgenic mice was similar to wild type mice. Interestingly, astrogliosis is also reduced in the double transgenic mice. The present data demonstrate that the complete loss of the AhR reduces the motor and behavioral deterioration observed in R6/1 mice, suggesting that the pharmacological modulation of the AhR could be a therapeutic target in HD.
Assuntos
Comportamento Animal/fisiologia , Gliose/fisiopatologia , Proteína Huntingtina/genética , Doença de Huntington/metabolismo , Doença de Huntington/fisiopatologia , Atividade Motora/fisiologia , Receptores de Hidrocarboneto Arílico/fisiologia , Animais , Modelos Animais de Doenças , Doença de Huntington/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , FenótipoRESUMO
AhR is a ligand-activated transcription factor that plays an important role in the innate and adaptive immune responses. In infection models, it has been associated with host responses that promote or inhibit disease progression. In pulmonary paracoccidioidomycosis, a primary fungal infection endemic in Latin America, immune protection is mediated by Th1/Th17 cells and disease severity with predominant Th2/Th9/Treg responses. Because of its important role at epithelial barriers, we evaluate the role of AhR in the outcome of a pulmonary model of paracoccidioidomycosis. AhR-/- mice show increased fungal burdens, enhanced tissue pathology and mortality. During the infection, AhR-/- mice have more pulmonary myeloid cells with activated phenotype and reduced numbers expressing indoleamine 2,3 dioxygenase 1. AhR-deficient lungs have altered production of cytokines and reduced numbers of innate lymphoid cells (NK, ILC3 and NCR IL-22). The lungs of AhR-/- mice showed increased presence Th17 cells concomitant with reduced numbers of Th1, Th22 and Foxp3+ Treg cells. Furthermore, treatment of infected WT mice with an AhR-specific antagonist (CH223191) reproduced the main findings obtained in AhR-/- mice. Collectively our data demonstrate that in pulmonary paracoccidioidomycosis AhR controls fungal burden and excessive tissue inflammation and is a possible target for antifungal therapy.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Paracoccidioidomicose/imunologia , Receptores de Hidrocarboneto Arílico/fisiologia , Células Th17/imunologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Indolamina-Pirrol 2,3,-Dioxigenase/metabolismo , Pulmão/imunologia , Pulmão/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Hidrocarboneto Arílico/genética , Células Th17/patologiaRESUMO
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in controlling several aspects of immune responses, including the activation and differentiation of specific T cell subsets and antigen-presenting cells, thought to be relevant in the context of experimental Trypanosoma cruzi infection. The relevance of AhR for the outcome of T. cruzi infection is not known and was investigated here. We infected wild-type (WT) mice and AhR knockout (AhR KO) mice with T. cruzi (Y strain) and determined levels of parasitemia, myocardial inflammation and fibrosis, expression of AhR/cytokines/suppressor of cytokine signaling (SOCS) (spleen/heart), and production of nitric oxide (NO), reactive oxygen species (ROS), and peroxynitrite (ONOO(-)) (spleen). AhR expression was increased in the heart of infected WT mice. Infected AhR KO mice displayed significantly reduced parasitemia, inflammation, and fibrosis of the myocardium. This was associated with an anticipated increased immune response characterized by increased levels of inflammatory cytokines and reduced expression of SOCS2 and SOCS3 in the heart. In vitro, AhR deficiency caused impairment in parasite replication and decreased levels of ROS production. In conclusion, AhR influences the development of murine Chagas disease by modulating ROS production and regulating the expression of key physiological regulators of inflammation, SOCS1 to -3, associated with the production of cytokines during experimental T. cruzi infection.
Assuntos
Doença de Chagas/fisiopatologia , Citocinas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptores de Hidrocarboneto Arílico/fisiologia , Trypanosoma cruzi/fisiologia , Animais , Cardiomiopatia Chagásica/metabolismo , Cardiomiopatia Chagásica/patologia , Doença de Chagas/metabolismo , Doença de Chagas/patologia , Modelos Animais de Doenças , Camundongos , Camundongos Knockout , Miocardite/metabolismo , Miocardite/patologia , Óxido Nítrico/metabolismo , Ácido Peroxinitroso/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Baço/metabolismo , Proteínas Supressoras da Sinalização de Citocina/metabolismoRESUMO
AIMS: The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxicity of environmental pollutants. It is also implicated in the regulation of the immune system. Ahr-null macrophages overproduce several proinflammatory cytokines following LPS-mediated stimulation, suggesting that AHR affects the balance between the inflammatory M1 and anti-inflammatory M2 phenotypes. Therefore, the present study aimed to examine whether the loss of AHR modifies macrophage polarization. MATERIALS AND METHODS: Peritoneal macrophages from wild-type and Ahr-null mice were differentiated into M1 or M2 phenotype by treatment with LPS/IFNγ or IL-4, and several M1 and M2 markers were determined by qPCR and ELISA assays. Macrophage phagocytic capacity was determined through phagocytosis of yeast and Leishmania major infection assays. Nitric oxide (NO) and urea production, and arginase activity were also determined. KEY FINDINGS: When macrophages were polarized to the M1 phenotype, Ahr-null cells presented a mixed response; higher levels of IL-1ß, IL-6, IL-12, and TNFα were observed after IFNγ- and LPS-mediated activation. However, Ahr-null cells also exhibited decreased NO production and phagocytic capacity. When macrophage was polarized to the M2 phenotype, Ahr-null cells exhibited lower levels of Fizz1, Ym1, and IL-10. In contrast, arginase activity was increased when compared to wild-type macrophages. In addition, macrophages from Ahr-null mice were more susceptible to L. major infection. SIGNIFICANCE: Disruption of the Ahr gene alters macrophage polarization when compared to WT macrophage. These changes may affect the development and resolution of several diseases such as bacterial or parasitic infections.
Assuntos
Arginina/biossíntese , Polaridade Celular/fisiologia , Macrófagos Peritoneais/citologia , Óxido Nítrico/biossíntese , Receptores de Hidrocarboneto Arílico/fisiologia , Animais , Células Cultivadas , Macrófagos Peritoneais/imunologia , Masculino , Camundongos , Camundongos Knockout , Fagocitose , Receptores de Hidrocarboneto Arílico/genéticaRESUMO
The aryl hydrocarbon receptor (AHR) is a major transcription factor regulated by different mechanisms. The classical view of AHR activation by xenobiotics needs to be amended by recent findings on the regulation of AHR by endogenous ligands and by crosstalk with other signaling pathways. In the cytosol the AHR recruits a large number of binding partners, including HSP90, p23, XAP2 and the ubiquitin ligases cullin 4B and CHIP. Furthermore, XAP2 binds the cyclic nucleotide phosphodiesterases PDE2A and PDE4A5. PDE2A inhibits nuclear translocation of AHR suggesting an important regulatory role of cyclic nucleotides in AHR trafficking. Signaling involving cAMP is organized in subcellular compartments and a distinct cAMP compartment might be required for proper AHR mobility and function. We conclude that the AHR complex integrates ligand binding and cyclic nucleotide signaling to generate an adequate transcriptional response.
Assuntos
Nucleotídeos Cíclicos/metabolismo , Diester Fosfórico Hidrolases/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Transdução de Sinais , Animais , Humanos , Ligantes , Nucleotídeos Cíclicos/fisiologia , Diester Fosfórico Hidrolases/fisiologia , Ligação Proteica , Receptores de Hidrocarboneto Arílico/fisiologiaRESUMO
The aryl hydrocarbon receptor (AHR) mediates toxic responses to environmental contaminants and plays pivotal physiological roles in various biological processes as well, particularly in ovarian function. It is well documented that expression and function of the AHR is negatively regulated by transforming growth factor-beta (TGF-beta) in many cell types. In addition, several studies indicate that AHR activity inhibits TGF-beta expression and function in some systems. However, the interplay between these two signals is highly dependent upon the cell type being studied, precluding a generalization about the outcome of such interaction. Therefore, the goal of the present study was to determine the effect of TGF-beta on AHR expression and activation in granulosa cells, an ovarian cell type where the growth factor is mitogenic and AHR activation has been associated with promotion of proliferation as well. In addition, we conducted experiments aimed at evaluating the effect of AHR ligands on TGF-beta action in our system. Results presented herein demonstrate that AHR expression is not regulated by TGF-beta in rat granulosa cells, neither at the mRNA level nor at the protein level. Moreover, we find that the growth factor does not alter the transcriptional function of the AHR. Conversely, we show that activation of AHR by an agonist deregulates TGF-beta function in granulosa cells, inhibiting its transcriptional activity and its mitogenic action. The described one-sided interplay between TGF-beta and AHR signaling pathway may help provide a mechanistic explanation to some of the physiological outcomes of AHR or TGF-beta activation in granulosa cells.
Assuntos
Células da Granulosa/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Transdução de Sinais/fisiologia , Fator de Crescimento Transformador beta/metabolismo , Animais , Células Cultivadas , Feminino , Células da Granulosa/citologia , Células da Granulosa/fisiologia , Ratos , Ratos Sprague-Dawley , Receptores de Hidrocarboneto Arílico/fisiologia , Ovinos , Suínos , Fator de Crescimento Transformador beta/fisiologiaRESUMO
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates toxicity of environmental pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin. The exposure to AhR agonists results in profound suppression of cellular and humoral immune responses and compromises host to infectious disease. Therefore, to define the role of AhR in the immune response, spleen cells from ovalbumin (OVA)-immunized and naïve mice were removed and stimulated in vitro with either OVA or mitogen concanavalin-A (Con A), respectively. Proliferation, CD19+, F4/80+, CD4+ and CD8+ T cells expansion and cytokines production were measured in C57BL/6-AhR-/- mice (AhR-/-) and compared with immune response in similarly immunized age-matched wild type (AhR+/+) mice. In response to OVA immunization, AhR-/- mice had similar levels of serum OVA-specific IgG2a, IgG1, and IgG2b compared with AhR+/+ animals. However, AhR-/- mice showed splenomegalia and an increase in B cells. No changes were observed on proliferation and IL-4 secretion, although AhR-/- cells produced more IFN-gamma and IL-12 than AhR+/+ cells. Similar results were observed with Con A stimulation, a decrease on IL-5 and no change on IL-2 secretion were observed on AhR-/- cells compared with AhR+/+ cells in response to Con A stimulation. High levels of IFN-gamma mRNA were detected in AhR-/- lymphocytes, but IL-4 mRNA levels in AhR-/- cells were similar to those in AhR+/+ mice. These data suggest that AhR may play an important role in the normal development and function of immune system by down-regulating IFN-gamma and IL-12 expression.