Neutrophil apoptosis is delayed by trauma patients' plasma via a mechanism involving proinflammatory phospholipids and protein kinase C.
BACKGROUND
Delayed apoptosis of primed neutrophils (PMNs) may facilitate PMN-mediated tissue injury leading to multiple organ failure (MOF). We previously reported delayed apoptosis and priming of PMNs in severely injured patients at risk for MOF. Our in vitro and in vivo data have implicated phospholipids in PMN cytotoxicity following trauma and shock. The phospholipid signaling pathway remains to be elucidated, but may involve protein kinase C (PKC). We hypothesized that circulating platelet-activating factor (PAF) and PAF-like proinflammatory phospholipids mediate delayed postinjury PMN apoptosis and that PKC is integral to the signaling pathway.


METHODS
Blood was drawn from severely injured patients (n = 6; mean injury severity score = 21 and transfusion = 10 units) at 6 h postinjury. The plasma fraction was isolated and incubated (5% CO(2), 37 degrees C, 24 h) with PMNs harvested from healthy volunteers. Some PMNs were preincubated with a PAF receptor antagonist (WEB 2170, 400 microM) or a PKC inhibitor (Bis I, 1 microM). Apoptotic index (% PMNs undergoing apoptosis) was assessed morphologically.


RESULTS
Trauma patients' plasma delayed PMN apoptosis compared with plasma from controls. The PMN apoptotic index was not altered by WEB 2170 or Bis I alone; however, WEB 2170 or Bis I pretreatment abrogated delayed PMN apoptosis in response to trauma patients' plasma.


CONCLUSIONS
Trauma patients' plasma delays apoptosis of PMNs. Our data implicate PAF-like phospholipids in this effect, and PKC appears to be integral in the signaling process. Further elucidation of specific lipids and signaling pathways may reveal clinically accessible therapeutic targets to prevent PMN-mediated hyperinflammation.
Biffl
W L
WL
Department of Surgery, Denver Health Medical Center and University of Colorado Health Sciences Center, Denver, CO, USA. wlbiffl@usasurg.org
West
K E
KE
Moore
E E
EE
Gonzalez
R J
RJ
Carnaggio
R
R
Offner
P J
PJ
Silliman
C C
CC
D000293:Adolescent; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D001381:Azepines / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D015601:Injury Severity Score; D008301:Maleimides / Q000494:pharmacology; D008875:Middle Aged; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D010743:Phospholipids / Q000276:immunology*; D010949:Plasma / Q000187:drug effects / Q000276:immunology*; D010972:Platelet Activating Factor / Q000187:drug effects / Q000276:immunology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000187:drug effects / Q000276:immunology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013997:Time Factors; D014230:Triazoles / Q000494:pharmacology; D014947:Wounds and Injuries / Q000276:immunology*
D001381:Azepines; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D010743:Phospholipids; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D014230:Triazoles; C063964:bepafant; D011493:Protein Kinase C; C070515:bisindolylmaleimide I