title: Ecotin-like ISP of L. major promastigotes fine-tunes macrophage phagocytosis by limiting the pericellular release of bradykinin from surface-bound kininogens: a survival strategy based on the silencing of proinflammatory G-protein coupled kinin B2 and B1 receptors.
abstract: Inhibitors of serine peptidases (ISPs) expressed by Leishmania major enhance intracellular parasitism in macrophages by targeting neutrophil elastase (NE), a serine protease that couples phagocytosis to the prooxidative TLR4/PKR pathway. Here we investigated the functional interplay between ISP-expressing L. major and the kallikrein-kinin system (KKS). Enzymatic assays showed that NE inhibitor or recombinant ISP-2 inhibited KKS activation in human plasma activated by dextran sulfate. Intravital microscopy in the hamster cheek pouch showed that topically applied L. major promastigotes (WT and Δisp2/3 mutants) potently induced plasma leakage through the activation of bradykinin B2 receptors (B2R). Next, using mAbs against kininogen domains, we showed that these BK-precursor proteins are sequestered by L. major promastigotes, being expressed at higher % in the Δisp2/3 mutant population. Strikingly, analysis of the role of kinin pathway in the phagocytic uptake of L. major revealed that antagonists of B2R or B1R reversed the upregulated uptake of Δisp2/3 mutants without inhibiting macrophage internalization of WT L. major. Collectively, our results suggest that L. major ISP-2 fine-tunes macrophage phagocytosis by inhibiting the pericellular release of proinflammatory kinins from surface bound kininogens. Ongoing studies should clarify whether L. major ISP-2 subverts TLR4/PKR-dependent prooxidative responses of macrophages by preventing activation of G-protein coupled B2R/B1R.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21990-400 Rio de Janeiro, RJ, Brazil.
authors.forename: Erik
authors.initials: E
authors.lastname: Svensjö
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21990-400 Rio de Janeiro, RJ, Brazil.
authors.forename: Larissa
authors.identifier: 0000-0003-2974-433X
authors.initials: L
authors.lastname: Nogueira de Almeida
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21990-400 Rio de Janeiro, RJ, Brazil.
authors.forename: Lucas
authors.initials: L
authors.lastname: Vellasco
authors.affiliation: Escola Paulista de Medicina, Universidade Federal de São Paulo, 04044-020 São Paulo, SP, Brazil.
authors.forename: Luiz
authors.identifier: 0000-0002-5589-2822
authors.initials: L
authors.lastname: Juliano
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21990-400 Rio de Janeiro, RJ, Brazil.
authors.forename: Julio
authors.initials: J
authors.lastname: Scharfstein
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D065094:Bradykinin B2 Receptor Antagonists / Q000494:pharmacology; D006224:Cricetinae; D006801:Humans; D007704:Kininogens / Q000378:metabolism*; D007705:Kinins / Q000378:metabolism; D018320:Leishmania major / Q000276:immunology / Q000378:metabolism* / Q000472:pathogenicity; D019272:Leukocyte Elastase / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010587:Phagocytosis / Q000187:drug effects*; D043783:Receptor, Bradykinin B1 / Q000378:metabolism*; D043782:Receptor, Bradykinin B2 / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*
chemical_list: D065094:Bradykinin B2 Receptor Antagonists; D007704:Kininogens; D007705:Kinins; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D015842:Serine Proteinase Inhibitors; C065679:icatibant; D019272:Leukocyte Elastase; D001920:Bradykinin