title: Platelets induce apoptosis during sepsis in a contact-dependent manner that is inhibited by GPIIb/IIIa blockade.
abstract: OBJECTIVE
  End-organ apoptosis is well-described in progressive sepsis and Multiple Organ Dysfunction Syndrome (MODS), especially where platelets accumulate (e.g. spleen and lung). We previously reported an acute sepsis-induced cytotoxic platelet phenotype expressing serine protease granzyme B. We now aim to define the site(s) of and mechanism(s) by which platelet granzyme B induces end-organ apoptosis in sepsis.
  
  
  METHODS
  End-organ apoptosis in murine sepsis (i.e. polymicrobial peritonitis) was analyzed by immunohistochemistry. Platelet cytotoxicity was measured by flow cytometry following 90 minute ex vivo co-incubation with healthy murine splenocytes. Sepsis progression was measured via validated preclinical murine sepsis score.
  
  
  RESULTS
  There was evident apoptosis in spleen, lung, and kidney sections from septic wild type mice. In contrast, there was a lack of TUNEL staining in spleens and lungs from septic granzyme B null mice and these mice survived longer following induction of sepsis than wild type mice. In co-incubation experiments, physical separation of septic platelets from splenocytes by a semi-permeable membrane reduced splenocyte apoptosis to a rate indistinguishable from negative controls. Chemical separation by the platelet GPIIb/IIIa receptor inhibitor eptifibatide decreased apoptosis by 66.6±10.6% (p = 0.008). Mice treated with eptifibatide in vivo survived longer following induction of sepsis than vehicle control mice.
  
  
  CONCLUSIONS
  In sepsis, platelet granzyme B-mediated apoptosis occurs in spleen and lung, and absence of granzyme B slows sepsis progression. This process proceeds in a contact-dependent manner that is inhibited ex vivo and in vivo by the platelet GPIIb/IIIa receptor inhibitor eptifibatide. The GPIIb/IIIa inhibitors and other classes of anti-platelet drugs may be protective in sepsis.
authors: Division of Critical Care Medicine, Children's National Medical Center, Washington, DC, United States of America.
authors: Matthew
authors: M
authors: Sharron
authors: Claire E
authors: CE
authors: Hoptay
authors: Andrew A
authors: AA
authors: Wiles
authors: Lindsay M
authors: LM
authors: Garvin
authors: Mayya
authors: M
authors: Geha
authors: Angela S
authors: AS
authors: Benton
authors: Kanneboyina
authors: K
authors: Nagaraju
authors: Robert J
authors: RJ
authors: Freishtat
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001792:Blood Platelets / Q000187:drug effects* / Q000473:pathology*; D020169:Caspases / Q000378:metabolism; D018450:Disease Progression; D000077542:Eptifibatide; D053804:Granzymes / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000276:immunology; D008214:Lymphocytes / Q000187:drug effects; D008297:Male; D051379:Mice; D010455:Peptides / Q000494:pharmacology* / Q000627:therapeutic use; D054353:Perforin / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018805:Sepsis / Q000097:blood* / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D013154:Spleen / Q000187:drug effects / Q000276:immunology
chemical_list: D010455:Peptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D054353:Perforin; D053804:Granzymes; D020169:Caspases; D000077542:Eptifibatide