title: Leishmania inhibitor of serine peptidase 2 prevents TLR4 activation by neutrophil elastase promoting parasite survival in murine macrophages.
abstract: Leishmania major is a protozoan parasite that causes skin ulcerations in cutaneous leishmaniasis. In the mammalian host, the parasite resides in professional phagocytes and has evolved to avoid killing by macrophages. We identified L. major genes encoding inhibitors of serine peptidases (ISPs), which are orthologs of bacterial ecotins, and found that ISP2 inhibits trypsin-fold S1A family peptidases. In this study, we show that L. major mutants deficient in ISP2 and ISP3 (Δisp2/3) trigger higher phagocytosis by macrophages through a combined action of the complement type 3 receptor, TLR4, and unregulated activity of neutrophil elastase (NE), leading to parasite killing. Whereas all three components are required to mediate enhanced parasite uptake, only TLR4 and NE are necessary to promote parasite killing postinfection. We found that the production of superoxide by macrophages in the absence of ISP2 is the main mechanism controlling the intracellular infection. Furthermore, we show that NE modulates macrophage infection in vivo, and that the lack of ISP leads to reduced parasite burdens at later stages of the infection. Our findings support the hypothesis that ISPs function to prevent the activation of TLR4 by NE during the Leishmania-macrophage interaction to promote parasite survival and growth.
authors.affiliation: Instituto de Biofisica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, Brazil.
authors.forename: Marilia S
authors.initials: MS
authors.lastname: Faria
authors.forename: Flavia C G
authors.initials: FC
authors.lastname: Reis
authors.forename: Ricardo L
authors.initials: RL
authors.lastname: Azevedo-Pereira
authors.forename: Lesley S
authors.initials: LS
authors.lastname: Morrison
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Mottram
authors.forename: Ana Paula C A
authors.initials: AP
authors.lastname: Lima
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006790:Host-Parasite Interactions / Q000276:immunology; D007424:Intracellular Fluid / Q000201:enzymology / Q000276:immunology / Q000469:parasitology*; D018320:Leishmania major / Q000201:enzymology* / Q000254:growth & development* / Q000276:immunology; D019272:Leukocyte Elastase / Q000037:antagonists & inhibitors / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000201:enzymology / Q000276:immunology / Q000469:parasitology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018384:Oxidative Stress / Q000276:immunology; D015842:Serine Proteinase Inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015843:Serpins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000378:metabolism*
chemical_list: D015842:Serine Proteinase Inhibitors; D015843:Serpins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C434683:serpin-2; D019272:Leukocyte Elastase