RESUMO
Infection with protozoan parasite Trypanosoma cruzi results in activation of nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs). NLR activation leads to inflammasome formation, the activation of caspase-1, and the subsequent cleavage of IL-1ß and IL-18. Considering that inflammasome activation and IL-1ß induction by macrophages are key players for an appropriate T cell response, we investigated the relevance of NLR pyrin domain-containing 3 (NLRP3) and caspase-1/11 to elucidate their roles in the induction of different T cell phenotypes and the relationship with parasite load and hepatic inflammation during T. cruzi-Tulahuen strain acute infection. We demonstrated that infected nlrp3-/- and C57BL/6 wild type (WT) mice exhibited similar parasitemia and survival, although the parasite load was higher in the livers of nlrp3-/- mice than in those of WT mice. Increased levels of transaminases and pro-inflammatory cytokines were found in the plasma of WT and nlrp3-/- mice indicating that NLRP3 is dispensable to control the parasitemia but it is required for a better clearance of parasites in the liver. Importantly, we have found that NLRP3 and caspase-1/11-deficient mice differentially modulate T helper (Th1, Th2, and Th17) and cytotoxic T lymphocyte phenotypes. Strikingly, caspase-1/11-/- mice showed the most dramatic reduction in the number of IFN-γ- and IL-17-producing CD4+ and CD8+ T cells associated with higher parasitemia and lower survival. Additionally, caspase-1/11-/- mice demonstrated significantly reduced liver inflammation with the lowest alanine aminotransferase (ALT) levels but the highest hepatic parasitic load. These results unequivocally demonstrate that caspase-1/11 pathway plays an important role in the induction of liver adaptive immunity against this parasite infection as well as in hepatic inflammation.
Assuntos
Caspase 1/imunologia , Caspases/imunologia , Doença de Chagas/imunologia , Inflamassomos/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/imunologia , Doença Aguda , Animais , Caspase 1/genética , Caspases/genética , Caspases Iniciadoras , Citocinas/imunologia , Interleucina-1beta/imunologia , Fígado/parasitologia , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Carga Parasitária , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Linfócitos T/imunologia , Transaminases/sangue , Trypanosoma cruziRESUMO
BACKGROUND: The immune mechanisms underlying experimental non-alcoholic steatohepatitis (NASH), and more interestingly, the effect of T. cruzi chronic infection on the pathogenesis of this metabolic disorder are not completely understood. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated immunological parameters in male C57BL/6 wild type and TLR4 deficient mice fed with a standard, low fat diet, LFD (3% fat) as control group, or a medium fat diet, MFD (14% fat) in order to induce NASH, or mice infected intraperitoneally with 100 blood-derived trypomastigotes of Tulahuen strain and also fed with LFD (I+LFD) or MFD (I+MFD) for 24 weeks. We demonstrated that MFD by itself was able to induce NASH in WT mice and that parasitic infection induced marked metabolic changes with reduction of body weight and steatosis revealed by histological studies. The I+MFD group also improved insulin resistance, demonstrated by homeostasis model assessment of insulin resistance (HOMA-IR) analysis; although parasitic infection increased the triglycerides and cholesterol plasma levels. In addition, hepatic M1 inflammatory macrophages and cytotoxic T cells showed intracellular inflammatory cytokines which were associated with high levels of IL6, IFNγ and IL17 plasmatic cytokines and CCL2 chemokine. These findings correlated with an increase in hepatic parasite load in I+MFD group demonstrated by qPCR assays. The recruitment of hepatic B lymphocytes, NK and dendritic cells was enhanced by MFD, and it was intensified by parasitic infection. These results were TLR4 signaling dependent. Flow cytometry and confocal microscopy analysis demonstrated that the reactive oxygen species and peroxinitrites produced by liver inflammatory leukocytes of MFD group were also exacerbated by parasitic infection in our NASH model. CONCLUSIONS: We highlight that a medium fat diet by itself is able to induce steatohepatitis. Our results also suggest a synergic effect between damage associated with molecular patterns generated during NASH and parasitic infection, revealing an intense cross-talk between metabolically active tissues, such as the liver, and the immune system. Thus, T. cruzi infection must be considered as an additional risk factor since exacerbates the inflammation and accelerates the development of hepatic injury.
Assuntos
Doença de Chagas/complicações , Hepatopatia Gordurosa não Alcoólica/parasitologia , Espécies Reativas de Oxigênio/metabolismo , Trypanosoma cruzi , Animais , Peso Corporal , Doença de Chagas/imunologia , Doença de Chagas/patologia , Quimiocina CCL2/metabolismo , Colesterol/sangue , Dieta , Resistência à Insulina/fisiologia , Interferon gama/metabolismo , Interleucina-17/metabolismo , Interleucina-6/metabolismo , Fígado/parasitologia , Fígado/patologia , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Hepatopatia Gordurosa não Alcoólica/imunologia , Hepatopatia Gordurosa não Alcoólica/patologia , Estresse Oxidativo , Fatores de Risco , Transdução de Sinais , Linfócitos T Citotóxicos/imunologia , Receptor 4 Toll-Like/genética , Triglicerídeos/sangueRESUMO
Myeloid-derived suppressor cells (MDSCs) are key players in the immune suppressive network. During acute infection with the causative agent of Chagas disease, Trypanosoma cruzi, BALB/c mice show less inflammation and better survival than C57BL/6 (B6) mice. In this comparative study, we found a higher number of MDSCs in the spleens and livers of infected BALB/c mice compared with infected B6 mice. An analysis of the two major MDSCs subsets revealed a greater number of granulocytic cells in the spleens and livers of BALB/c mice when compared with that in B6 mice. Moreover, splenic MDSCs purified from infected BALB/c mice inhibited ConA-induced splenocyte proliferation. Mechanistic studies demonstrated that ROS and nitric oxide were involved in the suppressive activity of MDSCs, with a higher number of infected CD8(+) T cells suffering surface-nitration compared to uninfected controls. An upregulation of NADPH oxidase p47 phox subunit and p-STAT3 occurred in MDSCs and infected IL-6 KO mice showed less recruitment of MDSCs and impaired survival. Remarkably, in vivo depletion of MDSCs led to increased production of IL-6, IFN-γ, and a Th17 response with very high parasitemia and mortality. These findings demonstrate a new facet of MDSCs as crucial regulators of inflammation during T. cruzi infection.