Modulation of monocyte function by activated protein C, a natural anticoagulant

J Immunol. 2006 Aug 15;177(4):2115-22. doi: 10.4049/jimmunol.177.4.2115.

Abstract

Activated protein C is the first effective biological therapy for the treatment of severe sepsis. Although activated protein C is well established as a physiological anticoagulant, emerging data suggest that it also exerts anti-inflammatory and antiapoptotic effects. In this study, we investigated the ability of activated protein C to modulate monocyte apoptosis, inflammation, phagocytosis, and adhesion. Using the immortalized human monocytic cell line THP-1, we demonstrated that activated protein C inhibited camptothecin-induced apoptosis in a dose-dependent manner. The antiapoptotic effect of activated protein C requires its serine protease domain and is dependent on the endothelial cell protein C receptor and protease-activated receptor-1. In primary blood monocytes from healthy individuals, activated protein C inhibited spontaneous apoptosis. With respect to inflammation, activated protein C inhibited the production of TNF, IL-1beta, IL-6, and IL-8 by LPS-stimulated THP-1 cells. Activated protein C did not influence the phagocytic internalization of Gram-negative and Gram-positive bioparticles by THP-1 cells or by primary blood monocytes. Activated protein C also did not affect the expression of adhesion molecules by LPS-stimulated blood monocytes nor the ability of monocytes to adhere to LPS-stimulated endothelial cells. We hypothesize that the protective effect of activated protein C in sepsis reflects, in part, its ability to prolong monocyte survival in a manner that selectively inhibits inflammatory cytokine production while maintaining phagocytosis and adherence capabilities, thereby promoting antimicrobial properties while limiting tissue damage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Apoptosis / immunology
  • Apoptosis Regulatory Proteins / antagonists & inhibitors
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis Regulatory Proteins / physiology
  • Blood Coagulation / immunology*
  • Cell Adhesion / immunology
  • Cell Line, Transformed
  • Cell Survival / immunology
  • Cells, Cultured
  • Enzyme Activation / immunology
  • Humans
  • Inflammation Mediators / antagonists & inhibitors
  • Inflammation Mediators / metabolism
  • Inflammation Mediators / physiology
  • Lipopolysaccharides / pharmacology
  • Monocytes / immunology*
  • Monocytes / metabolism*
  • Monocytes / microbiology
  • Phagocytosis / immunology
  • Protein C / metabolism
  • Protein C / physiology*

Substances

  • Apoptosis Regulatory Proteins
  • Inflammation Mediators
  • Lipopolysaccharides
  • Protein C