Beneficial effect of a platelet-activating factor antagonist, WEB 2086, on endotoxin-induced lung injury

We tested the hypothesis that platelet-activating factor plays an important role in promoting endotoxin-induced lung injury by studying the effect of WEB 2086, a specific platelet-activating factor receptor antagonist, on lung vascular leak in endotoxin-treated rats. Intraperitoneal injection of Salmonella enteritidis endotoxin (2 mg/kg) increased the extravascular leakage of 125I-labeled albumin in perfused lungs at 30 min, 2 h, 6 h, and 48 h. Treatment with WEB 2086 (10 mg/kg ip) either 20 min before or 30 min after endotoxin injection significantly reduced lung injury at 2 h after endotoxin (leak index: control 0.74 +/- 0.03, endotoxin 1.79 +/- 0.14, endotoxin + pretreated WEB 1.23 +/- 0.09, endotoxin + posttreated WEB 1.21 +/- 0.13). In addition, posttreatment with WEB 2086 starting at 90 min after endotoxin injection markedly reduced lung leak at 6 h (control 0.74 +/- 0.03, endotoxin 1.29 +/- 0.14, endotoxin + WEB 0.71 +/- 0.06). The protective effect of WEB 2086 was not the result of cyclooxygenase blockade because the release of thromboxane B2 by endotoxin-treated lungs was not affected by WEB 2086. Furthermore, neither pretreatment nor posttreatment with WEB 2086 significantly reduced the endotoxin-induced increase in plasma glutathione disulfide, a marker of in vivo oxidative stress. In rats given a lethal dose of endotoxin (20 mg/kg ip), posttreatment with WEB 2086, starting at 2 h after endotoxin, significantly improved survival compared with vehicle treatment. We conclude that WEB 2086 ameliorated endotoxin-induced lung injury without reducing oxidative stress in the rat and suggest that blockade of platelet-activating factor receptor may be an important therapeutic consideration in sepsis-induced acute lung vascular injury.