title: Overexpression of activated protein C is detrimental during severe experimental gram-negative sepsis (melioidosis).
abstract: OBJECTIVE
  The interplay between inflammation and blood coagulation is an essential part of host defense during severe pneumosepsis. Melioidosis, instigated by the Gram-negative bacterium Burkholderia pseudomallei, is a frequent cause of pneumosepsis in Southeast Asia. Patients with severe pneumosepsis, including melioidosis, have decreased circulating levels of protein C. Activated protein C has anticoagulant and anti-inflammatory properties. In this study, we aimed to investigate the effect of sustained elevated activated protein C levels on the host response during melioidosis.
  
  
  METHODS
  Animal study.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Wild type and activated protein C overexpressing C57BL/6 mice.
  
  
  METHODS
  Mice were intranasally infected with viable B. pseudomallei and killed after 24, 48, or 72 hours for harvesting of lungs, liver, spleen, and blood. Additionally, survival studies were performed.
  
  
  RESULTS
  Plasma activated protein C concentrations in activated protein C overexpressing mice (median 18.1 ng/mL) were in the same range as previously measured in patients treated with recombinant human activated protein C. Activated protein C overexpressing mice demonstrated enhanced susceptibility to B. pseudomallei infection compared with wild type mice as evidenced by a strongly increased mortality accompanied by enhanced bacterial loads in the lungs, blood, and distant organs 48 hours after infection. Additionally, at this time point, activated protein C overexpressing mice showed elevated levels of proinflammatory cytokines in lungs and plasma, together with increased pulmonary histopathology scores and neutrophil influx. At 72 hours postinfection, decreased levels of thrombin-antithrombin complexes, reflecting inhibition of coagulation, were measured in lungs of activated protein C overexpressing mice.
  
  
  CONCLUSIONS
  Constitutively enhanced expression of activated protein C impairs host defense during severe Gram-negative sepsis caused by B. pseudomallei.
authors.affiliation: 1Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, the Netherlands. 2Center for Experimental and Molecular Medicine (CEMM), Academic Medical Center, Amsterdam, the Netherlands. 3Department of Internal Medicine, Academic Medical Center, Amsterdam, the Netherlands. 4Department of Pathology, Academic Medical Center, Amsterdam, the Netherlands. 5Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands. 6Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands. 7Department of Clinical Chemistry and Pathobiochemistry, Otto-von-Guericke University, Magdeburg, Germany.
authors.forename: Liesbeth M
authors.initials: LM
authors.lastname: Kager
authors.forename: W Joost
authors.initials: WJ
authors.lastname: Wiersinga
authors.forename: Joris J T H
authors.initials: JJ
authors.lastname: Roelofs
authors.forename: Onno J
authors.initials: OJ
authors.lastname: de Boer
authors.forename: Joost C M
authors.initials: JC
authors.lastname: Meijers
authors.forename: Berend
authors.initials: B
authors.lastname: Isermann
authors.forename: Cornelis
authors.initials: C
authors.lastname: van't Veer
authors.forename: Tom
authors.initials: T
authors.lastname: Van der Poll
mesh_terms: D000818:Animals; D001778:Blood Coagulation Disorders / Q000097:blood* / Q000382:microbiology; D016957:Burkholderia pseudomallei; D016207:Cytokines / Q000097:blood; D008168:Lung / Q000382:microbiology; D008554:Melioidosis / Q000097:blood* / Q000401:mortality; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D011486:Protein C / Q000032:analysis / Q000378:metabolism*; D012720:Severity of Illness Index
chemical_list: D016207:Cytokines; D011486:Protein C