Endotoxin-induced monocytic microparticles have contrasting effects on endothelial inflammatory responses

PLoS One. 2014 Mar 19;9(3):e91597. doi: 10.1371/journal.pone.0091597. eCollection 2014.

Abstract

Septic shock is a severe disease state characterised by the body's life threatening response to infection. Complex interactions between endothelial cells and circulating monocytes are responsible for microvasculature dysfunction contributing to the pathogenesis of this syndrome. Here, we intended to determine whether microparticles derived from activated monocytes contribute towards inflammatory processes and notably vascular permeability. We found that endotoxin stimulation of human monocytes enhances the release of microparticles of varying phenotypes and mRNA contents. Elevated numbers of LPS-induced monocytic microparticles (mMP) expressed CD54 and contained higher levels of transcripts for pro-inflammatory cytokines such as TNF, IL-6 and IL-8. Using a prothrombin time assay, a greater reduction in plasma coagulation time was observed with LPS-induced mMP than with non-stimulated mMP. Co-incubation of mMP with the human brain endothelial cell line hCMEC/D3 triggered their time-dependent uptake and significantly enhanced endothelial microparticle release. Unexpectedly, mMP also modified signalling pathways by diminishing pSrc (tyr416) expression and promoted endothelial monolayer tightness, as demonstrated by endothelial impedance and permeability assays. Altogether, these data strongly suggest that LPS-induced mMP have contrasting effects on the intercellular communication network and display a dual potential: enhanced pro-inflammatory and procoagulant properties, together with protective function of the endothelium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brain / cytology
  • Brain / drug effects
  • Brain / metabolism
  • Cell Line
  • Cell-Derived Microparticles / chemistry*
  • Cell-Derived Microparticles / metabolism
  • Coculture Techniques
  • Endothelial Cells / cytology
  • Endothelial Cells / drug effects
  • Endothelial Cells / metabolism*
  • Gene Expression
  • Humans
  • Inflammation / metabolism
  • Inflammation / pathology
  • Intercellular Adhesion Molecule-1 / genetics
  • Intercellular Adhesion Molecule-1 / metabolism
  • Interleukin-6 / genetics
  • Interleukin-6 / metabolism
  • Interleukin-8 / genetics
  • Interleukin-8 / metabolism
  • Lipopolysaccharides / pharmacology*
  • Monocytes / cytology
  • Monocytes / drug effects
  • Monocytes / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Signal Transduction
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • IL6 protein, human
  • Interleukin-6
  • Interleukin-8
  • Lipopolysaccharides
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • Intercellular Adhesion Molecule-1

Grant support

This work was supported by grants from the National Health Medical Research Council # 570771, 571014, 1009914, 1028241 and the Rebecca L. Cooper Medical Research Foundation. The support of the University of Sydney Bridging Support Grant and funding from the Al Kerr Bequest, Sydney Medical School is also gratefully acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.