Post-hemorrhagic shock mesenteric lymph lipids prime neutrophils for enhanced cytotoxicity via phospholipase A(2)

Hemorrhagic shock induced mesenteric hypoperfusion has long been implicated as a key event in the pathogenesis of the adult respiratory distress syndr ome (ARDS) and multiple organ failure (MOF). Previous work links post-hemor rhagic shock mesenteric lymph (PHSML) lipids and neutrophil (PMN) priming i n the pathogenesis of ARDS. We hypothesize that gut phospholipase A(2)(PLA( 2)) liberates proinflammatory lipids following hemorrhagic shock, which are responsible for enhanced PMN cytotoxicity. Mesenteric lymph was collected from rats (n greater than or equal to 5) before hemorrhagic shock, during h emorrhagic shock (MAP 40 mm Hg x 30 min), and after resuscitation (shed blo od + 2x lactated Ringers). PMNs were incubated with physiologic concentrati ons (1-5%, v:v) of (a) buffer control, (b) sham (c) pre-shock lymph, (c) PH SML, (d) PHSML lipid extracts, (e) heat-denatured PSHML, and (f)PHSML harve sted after IV pretreatment with a known PLA(2) inhibitor (quinacrine,10 mg/ kg). PMNs were activated with fMLP (1 pmol), and the maximal rate of supero xide production measured by reduction of cytochrome c. Gut morphology was a ssessed histologically using hematoxalin and eosin (HE) staining. PHSML and PHSML lipid extracts (5%, v:v) primed for enhanced superoxide production c ompared to buffer controls (2.5-fold and 3.6-fold), sham (2.5-fold) and pre -shock lymph (2.0-fold). Lymph collected after systemic PLA(2) inhibition, in contrast, abrogated the PMN priming response. Gut mucosal morphology, at end-resuscitation, was intact on HE staining both with and without PLA(2) inhibition. Heat denaturing the PHSML (eliminating cytokines and complement ), on the other hand, did not reduce PMN priming. Physiologic concentration s of PHSML lipids prime the PMN respiratory burst. Lymph priming is diminis hed with systemic PLA(2) inhibition, implicating gut PLA(2) as a source of proinflammatory lipids that may be central in the pathogenesis of hemorrhag ic shock induced ARDS/MOF.