Human cutaneous leishmaniasis: interferon-dependent expression of double-stranded RNA-dependent protein kinase (PKR) via TLR2

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-beta on induction of PKR-promoter activity. The observed effects required the engagement of TLR2. TLR2-KO macrophages expressed low IFN-beta 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/IFN1-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.-De Carvalho Vivarini, A., Pereira, R. M. S., Dias Teixeira, K. L., Calegari-Silva, T. C., Bellio, M., Laurenti, M. D., Corbett, C. E. P., de Castro Gomes, C. M., Soares, R. P., Mendes Silva, A., Silveira, F. T., Lopes, U. G. Human cutaneous leish-maniasis: interferon-dependent expression of double-stranded RNA-kinase (PKR) via TLR2. FASEB J. 25, 4162-4173 (2011). www.fasebj.org