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Leishmania amazonensis promastigotes induce and are killed by neutrophil extracellular traps.

ABSTRACT: Neutrophils are short-lived leukocytes that die by apoptosis, necrosis, and NETosis. Upon death by NETosis, neutrophils release fibrous traps of DNA, histones, and granule proteins named neutrophil extracellular traps (NETs), which can kill bacteria and fungi. Inoculation of the protozoan Leishmania into the mammalian skin causes local inflammation with neutrophil recruitment. Here, we investigated the release of NETs by human neutrophils upon their interaction with Leishmania parasites and NETs' ability to kill this protozoan. The NET constituents DNA, elastase, and histones were detected in traps associated to promastigotes by immunofluorescence. Electron microscopy revealed that Leishmania was ensnared by NETs released by neutrophils. Moreover, Leishmania and its surface lipophosphoglycan induced NET release by neutrophils in a parasite number- and dose-dependent manner. Disruption of NETs by DNase treatment during Leishmania-neutrophil interaction increased parasite survival, evidencing NETs' leishmanicidal effect. Leishmania killing was also elicited by NET-rich supernatants from phorbol 12-myristate 13-acetate-activated neutrophils. Immunoneutralization of histone during Leishmania-neutrophil interaction partially reverted Leishmania killing, and purified histone killed the parasites. Meshes composed of DNA and elastase were evidenced in biopsies of human cutaneous leishmaniasis. NET is an innate response that might contribute to diminish parasite burden in the Leishmania inoculation site.

SUBMITTER: Guimaraes-Costa AB

PROVIDER: S-EPMC2672475 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Leishmania amazonensis promastigotes induce and are killed by neutrophil extracellular traps.

Guimarães-Costa Anderson B AB Nascimento Michelle T C MT Froment Giselle S GS Soares Rodrigo P P RP Morgado Fernanda N FN Conceição-Silva Fátima F Saraiva Elvira M EM

Proceedings of the National Academy of Sciences of the United States of America 20090403 16

Neutrophils are short-lived leukocytes that die by apoptosis, necrosis, and NETosis. Upon death by NETosis, neutrophils release fibrous traps of DNA, histones, and granule proteins named neutrophil extracellular traps (NETs), which can kill bacteria and fungi. Inoculation of the protozoan Leishmania into the mammalian skin causes local inflammation with neutrophil recruitment. Here, we investigated the release of NETs by human neutrophils upon their interaction with Leishmania parasites and NETs ...[more]

PMID: 19346483

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Project description:B-1 cells are considered an innate-like B cell population that participates in effective innate and adaptive responses to pathogens. B-1 cells produce immunoglobulins, cytokines, chemokines, migrate to inflammatory sites, and differentiate into mononuclear phagocyte-like cells. Murine B-1 cells phagocytosed Leishmania in vitro and in vivo and participate in immunity against Leishmania. Our group showed that B-1 cells or their extracellular vesicles (EVs) led to a resistance to experimental infection by L. amazonensis. However, the B-1 cells' responses to Leishmania or EVs isolated from parasites are still poorly characterized. Studying the activation and differentiation of B-1 cells in vivo can contribute to a better understanding of how these cells participate in immunity to L. amazonensis. Thus, we evaluated the expression of myeloid (M-csfr, G-csfr, Spi-1) and lymphoid (EBF, E2A, IL-7R) lineage commitment factors, Toll-like receptors (TLRs), activation cell surface markers, nitric oxide (NO) and reactive oxygen species (ROS) production in murine peritoneal B-1 cells collected after 24 or 48 h post-infection with Leishmania (Leishmania) amazonensis promastigotes or EVs released by the parasites. Our results demonstrated that L. amazonensis infection did not stimulate the expression of CD40, CD80, CD86, F4/80, and MHC II in B-1 cells, but a significant decrease in the production of NO and ROS was observed. The infection induced a significantly higher arginase expression in B-1 cells, but the stimulation with EVs led to a decrease in this gene expression. TLR-2 and TLR-6 had significantly higher expression in B-1 cells from mice intraperitoneally stimulated with the parasite. The TLR-9 expression was higher in animals infected or stimulated for 48 h with EVs. Interestingly, in B-1 cells the stimulus with L. amazonensis led to a substantial increase in the expression of myeloid restricted transcription factors. Thus, our study suggests that the parasites or EVs differently modulated the activation and differentiation of B-1 cells.

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Leishmania amazonensis promastigotes induce and are killed by neutrophil extracellular traps.

Publications

Leishmania amazonensis promastigotes induce and are killed by neutrophil extracellular traps.

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