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

Mediators Inflamm. 2014:2014:143450. doi: 10.1155/2014/143450. Epub 2014 Sep 10.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bradykinin / analogs & derivatives
  • Bradykinin / metabolism*
  • Bradykinin / pharmacology
  • Bradykinin B2 Receptor Antagonists / pharmacology
  • Cricetinae
  • Humans
  • Kininogens / metabolism*
  • Kinins / metabolism
  • Leishmania major / immunology
  • Leishmania major / metabolism*
  • Leishmania major / pathogenicity
  • Leukocyte Elastase / metabolism
  • Macrophages / drug effects*
  • Macrophages / metabolism
  • Male
  • Phagocytosis / drug effects*
  • Receptor, Bradykinin B1 / metabolism*
  • Receptor, Bradykinin B2 / metabolism*
  • Serine Proteinase Inhibitors / pharmacology*

Substances

  • Bradykinin B2 Receptor Antagonists
  • Kininogens
  • Kinins
  • Receptor, Bradykinin B1
  • Receptor, Bradykinin B2
  • Serine Proteinase Inhibitors
  • icatibant
  • Leukocyte Elastase
  • Bradykinin