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

Abstract

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-β on induction of PKR-promoter activity. The observed effects required the engagement of TLR2. TLR2-KO macrophages expressed low IFN-β 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.

SOD1 Plasma Level as a Biomarker for Therapeutic Failure in Cutaneous Leishmaniasis

“…The extremely long (mean disease duration [±SD], 10.9 ± 2.1 years) uncontrolled parasite replication in patients with DCL might have led to selection of SOD-overexpressing parasite clones [7, 8]. Alternatively, increased systemic levels of SOD1 in patients with LCL and those with DCL might reflect a parasite escape mechanism from host leishmanicidal activity mediated by type I IFN, as suggested by our previous work [9] and recently confirmed in murine and human macrophages [14]. In agreement with this hypothesis, we found a significant positive correlation between SOD1 mRNA and total IFN-α/β mRNA levels, using in situ transcriptomics (nCounter; Supplementary Figure 2 A ).…”

Leishmania infantum Induces Mild Unfolded Protein Response in Infected Macrophages

“…amazonensis (belonging to L . mexicana complex which causes cutaneous leishmaniasis) suppresses NO production by repressing the iNOS expression via the NF-kB transcription factor [33] and reduces ROS accumulation by inducing SOD-1 [34] in human and mouse cells. Moreover, it has been shown that L .…”

Human Dendritic Cells Exhibit a Pronounced Type I IFN Signature following Leishmania major Infection That Is Required for IL-12 Induction

“…We recently demonstrated that L. major induces IFNβ expression (4 hrs post infection) in human DCs, and that early production of this type I IFN may act in autocrine dependent manner to subsequently drive IDO induction (31). In human macrophages, it has been reported that type I IFNs impair anti-leishmanicidal activity (45) through a SOD1/PKR signaling mechanisms that that become activated downstream of TLR2 engagement (46). Our pathway analysis revealed the type I IFN pathway was significantly enriched during L. major infection, and we therefore evaluated the applicability of these findings by examining the role of this pathway in our DC model system.…”