Entry of gut lymph into the circulation primes rat neutrophil respiratory burst in hemorrhagic shock

Objective. Endothelial cell injury by polymorphonuclear neutrophil (neutrophil [PMN]) respiratory burst after trauma and hemorrhagic shock (T/HS) predisposes subjects to acute respiratory distress syndrome and multiple organ failure. T/HS mesenteric lymph injures endothelial cell and lymph duct ligation (LDL) before T/HS prevents pulmonary injury. We investigated the role of mesenteric lymph in PMN priming by T/HS. Design: Prospective experiment in rats. Setting. University hospital laboratory. Subjects: Adult male rats. Interventions: Mesenteric lymph was obtained from rats undergoing T/HS (30 mm Hg, 90 mins) or sham shock (T/SS). Plasma was harvested from uninstrumented control (UC), T/HS, T/SS, and T/HS+LDL rats. PMNs were isolated from UC, T/HS, and T/HS+LDL rats. Measurements and Main Results: PMNs from UC rats were incubated in buffer, 1% T/HS lymph, and 1% T/SS lymph. PMNs from UC rats were incubated in UG, T/HS, T/SS, and T/HS+LDL plasma. PMN respiratory burst was initiated by using macrophage inflammatory protein (MIP)-2/platelet-aggregating factor (PAF) or phorbol myristate acetate. Cytosolic calcium ([Ca2+](i)) responses to MIP-2/PAF were assayed in PMN from UG, T/HS, and T/HS+LDL rats. PMN preincubated in T/HS lymph showed significant elevations in MIP/PAF-elicited respiratory burst compared with T/HS lymph or buffer only (p < .05; analysis of variance/Tukey's test). T/HS lymph incubation also increased (p < .05) phorbol myristate acetate elicited respiratory burst compared with buffer or T/SS. Preincubation in T/HS plasma increased MIP-2/PAF-elicited respiratory burst (p < .05) compared with UC or T/SS plasma. LDL blocked T/HS priming of respiratory burst. Control PMN [Ca 2+]i responses to MIP-2 and PAF were low. T/SS PMN were significantly more responsive, but the T/HS PMN showed still higher responses (p < .01). LDL reversed the priming of [Ca2+](i) responses by T/HS (p < .01). Conclusions: PMNs are primed by T/HS lymph but not T/SS lymph and by T/HS plasma but not T/SS plasma. LDL before shock prevents T/HS plasma from priming PMN. The magnitude of respiratory burst found here paralleled the [Ca2+](i) responses seen to receptor dependent initiating agonists. Mesenteric lymph is both necessary and sufficient to prime PMN after T/HS in the rat, and it primes PMN in part by enhancing [Ca2+](i) responses to G-protein coupled chemoattractants. Mesenteric lymph mediates postshock PMN dysfunction.