ABSTRACT
A Th1 response is required for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The role of pro-Th1 IL-12 in malaria is complex and controversial. In this study, we addressed the role of IL-12Rß2 in ECM development. C57BL/6 mice deficient for IL-12Rß2, IL-12p40, or IL-12p35 were analyzed for ECM development after blood-stage PbA infection in terms of ischemia and blood flow by noninvasive magnetic resonance imaging and angiography, T cell recruitment, and gene expression. Without IL-12Rß2, no neurologic sign of ECM developed upon PbA infection. Although wild-type mice developed distinct brain microvascular pathology, ECM-resistant, IL-12Rß2-deficient mice showed unaltered cerebral microcirculation and the absence of ischemia after PbA infection. In contrast, mice deficient for IL-12p40 or IL-12p35 were sensitive to ECM development. The resistance of IL-12Rß2-deficient mice to ECM correlated with reduced recruitment of activated T cells and impaired overexpression of lymphotoxin-α, TNF-α, and IFN-γ in the brain after PbA infection. Therefore, IL-12Rß2 signaling is essential for ECM development but independent from IL-12p40 and IL-12p35. We document a novel link between IL-12Rß2 and lymphotoxin-α, TNF-α, and IFN-γ expression, key cytokines for ECM pathogenesis.
Subject(s)
Interleukin-12 Receptor beta 2 Subunit/metabolism , Malaria, Cerebral/immunology , Plasmodium berghei/immunology , Th1 Cells/immunology , Animals , Brain/metabolism , Brain/microbiology , Brain/pathology , CD8-Positive T-Lymphocytes/immunology , Interferon-gamma/biosynthesis , Interleukin-12 Receptor beta 2 Subunit/deficiency , Interleukin-12 Receptor beta 2 Subunit/genetics , Interleukin-12 Subunit p35/deficiency , Interleukin-12 Subunit p35/genetics , Interleukin-12 Subunit p35/immunology , Interleukin-12 Subunit p40/deficiency , Interleukin-12 Subunit p40/genetics , Interleukin-12 Subunit p40/immunology , Lymphocyte Activation/immunology , Lymphotoxin-alpha/biosynthesis , Malaria, Cerebral/parasitology , Malaria, Cerebral/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout , Plasmodium berghei/growth & development , Plasmodium berghei/pathogenicity , Signal Transduction/immunology , Tumor Necrosis Factor-alpha/biosynthesisABSTRACT
The generation of reactive oxygen species (ROS) is inherent to immune responses. ROS are crucially involved in host defense against pathogens by promoting bacterial killing, but also as signaling agents coordinating the production of cytokines. Transient Receptor Potential Melastatin 2 (TRPM2) is a Ca(2+)-permeable channel gated via binding of ADP-ribose, a metabolite formed under conditions of cellular exposure to ROS. Here, we show that TRPM2-deficient mice are extremely susceptible to infection with Listeria monocytogenes (Lm), exhibiting an inefficient innate immune response. In a comparison with IFNγR-deficient mice, TRPM2(-/-) mice shared similar features of uncontrolled bacterial replication and reduced levels of inducible (i)NOS-expressing monocytes, but had intact IFNγ responsiveness. In contrast, we found that levels of cytokines IL-12 and IFNγ were diminished in TRPM2(-/-) mice following Lm infection, which correlated with their reduced innate activation. Moreover, TRPM2(-/-) mice displayed a higher degree of susceptibility than IL-12-unresponsive mice, and supplementation with recombinant IFNγ was sufficient to reverse the unrestrained bacterial growth and ultimately the lethal phenotype of Lm-infected TRPM2(-/-) mice. The severity of listeriosis we observed in TRPM2(-/-) mice has not been reported for any other ion channel. These findings establish an unsuspected role for ADP-ribose and ROS-mediated cation flux for innate immunity, opening up unique possibilities for immunomodulatory intervention through TRPM2.
