RESUMO
Studies performed in vitro suggest that activation of Toll-like receptors (TLRs) by parasite-derived molecules may initiate inflammatory responses and host innate defense mechanisms against Trypanosoma cruzi. Here, we evaluated the impact of TLR2 and myeloid differentiation factor 88 (MyD88) deficiencies in host resistance to infection with T. cruzi. Our results show that macrophages derived from TLR2 (-/-) and MyD88(-/-) mice are less responsive to GPI-mucin derived from T. cruzi trypomastigotes and parasites. In contrast, the same cells from TLR2(-/-) still produce TNF-alpha, IL-12, and reactive nitrogen intermediates (RNI) upon exposure to live T. cruzi trypomastigotes. Consistently, we show that TLR2(-/-) mice mount a robust proinflammatory cytokine response as well as RNI production during the acute phase of infection with T. cruzi parasites. Further, deletion of the functional TLR2 gene had no major impact on parasitemia nor on mortality. In contrast, the MyD88(-/-) mice had a diminished cytokine response and RNI production upon acute infection with T. cruzi. More importantly, we show that MyD88(-/-) mice are more susceptible to infection with T. cruzi as indicated by the higher parasitemia and accelerated mortality, as compared with the wild-type mice. Together, our results indicate that T. cruzi parasites elicit an alternative inflammatory pathway independent of TLR2. This pathway is partially dependent on MyD88 and necessary for mounting optimal inflammatory and RNI responses that control T. cruzi replication during the early stages of infection.
Assuntos
Antígenos de Diferenciação/genética , Doença de Chagas/imunologia , Citocinas/biossíntese , Mediadores da Inflamação/metabolismo , Receptores Imunológicos/deficiência , Receptores Imunológicos/genética , Trypanosoma cruzi/imunologia , Doença Aguda , Proteínas Adaptadoras de Transdução de Sinal , Animais , Antígenos de Diferenciação/fisiologia , Células Cultivadas , Doença de Chagas/genética , Doença de Chagas/parasitologia , Citocinas/antagonistas & inibidores , Regulação para Baixo/genética , Regulação para Baixo/imunologia , Imunidade Inata/genética , Mediadores da Inflamação/antagonistas & inibidores , Interferon gama/antagonistas & inibidores , Interferon gama/biossíntese , Interleucina-12/antagonistas & inibidores , Interleucina-12/biossíntese , Macrófagos Peritoneais/imunologia , Macrófagos Peritoneais/metabolismo , Macrófagos Peritoneais/parasitologia , Masculino , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 88 de Diferenciação Mieloide , Espécies Reativas de Nitrogênio/biossíntese , Receptores de Superfície Celular/deficiência , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/fisiologia , Receptores Imunológicos/fisiologia , Receptor 2 Toll-Like , Receptores Toll-Like , Trypanosoma cruzi/crescimento & desenvolvimento , Trypanosoma cruzi/patogenicidade , Fator de Necrose Tumoral alfa/antagonistas & inibidores , Fator de Necrose Tumoral alfa/biossínteseRESUMO
Pretreatment of macrophages with Toll-like receptor (TLR)2 or TLR4 agonists leads to a stage of cell hyporesponsiveness to a second stimulation with TLR agonists. This tolerance state is accompanied by the repression of IL-1 receptor-associated kinase-1, mitogen-activated protein kinases, and IkappaB phosphorylation and expression of genes encoding proinflammatory cytokines, like IL-1beta and TNF-alpha. In this report, we demonstrated that mucin-like glycoprotein (tGPI-mucin) of Trypanosoma cruzi trypomastigotes (TLR2 agonist) and LPS (TLR4 agonist) induce cross-tolerance in macrophages and we addressed the role of phosphatase activity in this process. Analysis of the kinetic of phosphatase activity induced by tGPI-mucin or LPS revealed maximum levels between 12 and 24 h, which correlate with the macrophage hyporesponsiveness stage. The addition of okadaic acid, an inhibitor of phosphatase activity, reversed macrophage hyporesponsiveness after exposure to either LPS or tGPI-mucin, allowing phosphorylation of IL-1R-associated kinase-1, mitogen-activated protein kinases, and IkappaB and leading to TNF-alpha gene transcription and cytokine production. Furthermore, pretreatment with either the specific p38/stress-activated protein kinase-2 inhibitor (SB203580) or the NF-kappaB translocation inhibitor (SN50) prevented the induction of phosphatase activity and hyporesponsiveness in macrophage, permitting cytokine production after restimulation with LPS. These results indicate a critical role of p38/stress-activated protein kinase-2 and NF-kappaB-dependent phosphatase in macrophage hyporesponsiveness induced by microbial products that activate TLR2 and TLR4.