Priming of the neutrophil cytotoxic response is central to the pathogenesis of early postinjury multiple organ failure (MOF). Platelet-activating factor (PAF) has been implicated as a key inflammatory mediator in postinjury neutrophil priming and requires p38 MAPK signaling to produce its biologic effects. Hypertonic saline (HTS) resuscitation decreases the postinjury inflammatory response following shock in animals and decreases receptor-mediated neutrophil (PMN) cytotoxic functions in vitro. We hypothesized that HTS attenuates PAF priming of the PMN cytotoxic response by interfering with PAF-mediated p38 MAPK signal transduction. Isolated PMNs were preincubated in isotonic buffer or HTS (Na+ = 180 mM), then primed with PAF. Neutrophil CD11b/CD18 expression was measured by flow cytometry. Receptor-dependent (fMLP), N-formyl-methionyl-leucyl-phenylalanine, fMLP) and receptor-independent (PMA) O2− production was measured by reduction of cytochrome c in resting and PAF primed PMNs. Total p38 MAPK protein PAF-mediated p38 MAPK activation was assessed by western blot of PMN lysates. Clinically relevant levels of HTS attenuated PAF-mediated β2-integrin expression. While HTS attenuated receptor-dependent (fMLP and PAF/fMLP) O2− production, receptor-independent (PMA) O2− production was unaffected. Conversely, HTS attenuated PAF priming of PMA-mediated O2− production. PAF and HTS did not alter total cellular p38 MAPK content. Clinically relevant levels of HTS alone did not activate p38 MAPK but inhibited PAF mediated p38 MAPK activation. HTS attenuates PAF priming of the PMN cytotoxic response by altering intracellular signal transduction. Therefore, HTS resuscitation may attenuate postinjury PMN priming and ultimately the risk of developing MOF.
*Department of Surgery, Denver Health Medical Center, University of Colorado Health Sciences Center, Denver, Colorado and †Bonfils Blood Center and the Department of Pediatrics, University of Colorado Health Sciences Center, Denver, Colorado
Resident Research Award.
Presented at the 20th Annual Meeting of the Surgical Infection Society, April 27-29, 2000, Providence, RI.
Supported in part by National Institutes of Health grants P50GM4922 and T32GM08315.
Address reprint requests to Ernest E. Moore, MD, Chief Department of Surgery, Denver Health Medical Center, 777 Bannock Street, Denver, CO 80204.
Received 27 Apr 2000; first review completed 2 May 2000; accepted in final form 15 Jun 2000
©2000The Shock Society