Phospholipase A(2)-derived neutral lipids from posthemorrhagic shock mesenteric lymph prime the neutrophil oxidative burst

Background. Our previous work identified posthemorrhagic shock mesenteric l ymph (PHSML) lipids as key elements in polymorphonuclear neutrophil (PMN)-p rovoked acute lung injury. We hypothesize that gut phospholipase A(2) (PLA( 2)) is responsible for the generation of proinflammatory lipids in PHSML th at primes circulating PMNs for enhanced oxidative burst. Methods. Mesenteric lymph was collected from rats (n = 5) before (preshock) , during the induction of hemorrhagic shock (mean arterial pressure, 40 min Hg x 30 minutes), and at resuscitation (shed blood + 2x lactated Ringer's solution). PLA(2) inhibition (quinacrine, 10 mg/kg, intravenously) was give n before shock was induced. Extracted lipids were separated by normal phase high-pressure liquid chromatography and resuspended in albumin. PMNs were exposed to a 5% vol:vol concentration of eluted lipids and activated with N -formyl-methionyl-leucyl-phenylalanine (1 mu mol/L). Superoxide production was assessed by cytochrome C reduction. Results. High-pressure liquid chromatography-extracted neutral lipids of ly mph collected before hemorrhagic shock did not prime the PMN oxidase, where as isolated neutral lipids of postshock lymph primed PMNs 2.6-+/-0.32-fold above baseline (P<.05). PLA(2) inhibition returned PHSML neutral lipid prim ing to baseline levels. Conclusions. PLA(2) inhibition before hemorrhagic shock abrogates the neutr ophil priming effects of PHSML through reduction of the accumulation of pro inflammatory neutral lipids. Identification of these PLA(2)-dependent lipid s provides a mechanistic link that may have therapeutic implications for po stshock acute lung injury.