New Insights into the Pro-Inflammatory Activities of Ang1 on Neutrophils: Induction of MIP-1β Synthesis and Release.

Elizabeth Dumas,Martin G Sirois,Michel White,Patrick P Mcdonald,Paul-Eduard Neagoe,Bruno Lourenco Diaz

doi:10.1371/journal.pone.0163140

Elizabeth Dumas, Martin G Sirois + Show 4 more

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https://doi.org/10.1371/journal.pone.0163140

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Abstract

We reported the expression of angiopoietin Tie2 receptor on human neutrophils and the capacity of angiopoietins (Ang1 and Ang2) to induce pro-inflammatory activities, such as platelet-activating factor synthesis, β2-integrin activation and neutrophil migration. Recently, we observed differential effects between both angiopoietins, namely, the capacity of Ang1, but not Ang2, to promote rapid interleukin-8 synthesis and release, as well as neutrophil viability. Herein, we addressed whether Ang1 and/or Ang2 could modulate the synthesis and release of macrophage inflammatory protein-1β (MIP-1β) by neutrophils. Neutrophils were isolated from blood of healthy volunteers; intracellular and extracellular MIP-1β protein concentrations were assessed by ELISA. After 24 hours, the basal intracellular and extracellular MIP-1β protein concentrations were ≈500 and 100 pg/106 neutrophils, respectively. Treatment with Ang1 (10 nM) increased neutrophil intracellular and extracellular MIP-1β concentrations by 310 and 388% respectively. Pretreatment with PI3K (LY294002), p38 MAPK (SB203580) and MEK (U0126) inhibitors completely inhibited Ang1-mediated increase of MIP-1β intracellular and extracellular protein levels. Pretreatment with NF-κB complex inhibitors, namely Bay11-7085 and IKK inhibitor VII or with a transcription inhibitor (actinomycin D) and protein synthesis inhibitor (cycloheximide), did also abrogate Ang1-mediated increase of MIP-1β intracellular and extracellular protein levels. We validated by RT-qPCR analyses the effect of Ang1 on the induction of MIP-1β mRNA levels. Our study is the first one to report Ang1 capacity to induce MIP-1β gene expression, protein synthesis and release from neutrophils, and that these effects are mediated by PI3K, p38 MAPK and MEK activation and downstream NF-κB activation.

Highlights

Angiogenesis is a critical process to many biological conditions, such as physiological somatic growth and vascular repair, and to pathological cancer and rheumatoid arthritis [1]
This study addresses for the first time the capacity of angiopoietins to modulate the expression of macrophage inflammatory protein-1β (MIP-1β) mRNA, its protein synthesis and release by the neutrophils
We report that only Ang1 has the capacity to induce MIP-1β synthesis and release by the neutrophils while Ang2 has no such effect

Summary

Introduction

Angiogenesis is a critical process to many biological conditions, such as physiological somatic growth and vascular repair, and to pathological cancer and rheumatoid arthritis [1]. Three majors growth factors have been described for their participation in the angiogenic process: namely, the vascular endothelial growth factor (VEGF), which induces the formation of new blood vessels; angiopoietin-1 (Ang1), which contributes to the stabilization of the neovessels; and angiopoietin-2 (Ang2), which disrupts pre-existing vasculature [3] In addition to their participation to pro-angiogenic activities, we and other groups reported that these growth factors can induce several pro-inflammatory activities mainly in endothelial cells (ECs) and in leukocytes. We and other groups have reported that both angiopoietins in a Tie2-dependent manner are capable to recruit neutrophils and eosinophils as well as to promote neutrophil adhesion onto human extracellular matrix [11,12,13,14] Both Ang and Ang induce neutrophil migration and potentiate interleukin-8 (IL-8) chemotactic activity [12, 14]. Ang has the capacity to induce IL-1β synthesis and IL-1RA release, while Ang has no such effects [15,16,17]

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