RESUMO
We investigated the type I interferon (IFN-1)/PKR axis in the outcome of the Leishmania (Leishmania) amazonensis infection, along with the underlying mechanisms that trigger and sustain this signaling pathway. Reporter assays of cell extracts from RAW-264.7 macrophages infected with L. (L.) amazonensis or HEK-293T cells cotransfected with TLR2 and PKR promoter constructions were employed. Primary macrophages of TLR2-knockout (KO) or IFNR-KO mice were infected, and the levels of PKR, IFN-1, and superoxide dismutase 1 (SOD1) transcript levels were investigated and compared. Immunohistochemical analysis of human biopsy lesions was evaluated for IFN-1 and PKR-positive cells. Leishmania infection increased the expression of PKR and IFN-ß on induction of PKR-promoter activity. The observed effects required the engagement of TLR2. TLR2-KO macrophages expressed low IFN-ß and PKR levels postinfection with a reduced parasite load. We also revealed the requirement of PKR signaling for Leishmania-induced IFN-1 expression, responsible for sustaining PKR expression and enhancing infection. Moreover, during infection, SOD1 transcripts increased and were also enhanced when IFN-1 was added to the cultures. Remarkably, SOD1 expression was abrogated in infected, dominant-negative PKR-expressing cells. Finally, lesions of patients with anergic diffuse cutaneous leishmaniasis exhibited higher levels of PKR/IFN-1-expressing cells compared to those with single cutaneous leishmaniasis. In summary, we demonstrated the mechanisms and relevance of the IFN-1/PKR axis in the Leishmania infection.
Assuntos
Interferon Tipo I/metabolismo , Leishmania mexicana , Leishmaniose Cutânea/enzimologia , Leishmaniose Cutânea/imunologia , Receptor 2 Toll-Like/metabolismo , eIF-2 Quinase/metabolismo , Animais , Glicoesfingolipídeos/imunologia , Interações Hospedeiro-Parasita , Humanos , Leishmania mexicana/imunologia , Leishmania mexicana/patogenicidade , Leishmaniose Cutânea/genética , Leishmaniose Tegumentar Difusa/enzimologia , Leishmaniose Tegumentar Difusa/genética , Leishmaniose Tegumentar Difusa/imunologia , Macrófagos Peritoneais/enzimologia , Macrófagos Peritoneais/imunologia , Macrófagos Peritoneais/parasitologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , Regiões Promotoras Genéticas , Transdução de Sinais , Superóxido Dismutase/genética , Superóxido Dismutase-1 , Receptor 2 Toll-Like/deficiência , Receptor 2 Toll-Like/genética , Transfecção , eIF-2 Quinase/genéticaRESUMO
Cytokine-inducible (or type 2) nitric oxide synthase (iNOS) is indispensable for the resolution of Leishmania major or Leishmania donovani infections in mice. In contrast, little is known about the expression and function of iNOS in human leishmaniasis. Here, we show by immunohistological analysis of skin biopsies from Mexican patients with local (LCL) or diffuse (DCL) cutaneous leishmaniasis that the expression of iNOS was most prominent in LCL lesions with small numbers of parasites whereas lesions with a high parasite burden (LCL or DCL) contained considerably fewer iNOS-positive cells. This is the first study to suggest an antileishmanial function of iNOS in human Leishmania infections in vivo.