Leukocyte mediated vein injury and thrombosis is reduced by a lipoxygenase inhibitor

We have previously demonstrated an in vivo model of deep vein thrombosis which suggests that the neutrophil promotes vascular injury and thrombosis following blood flow stasis. Since leukotrienes are potent mediators of vascular injury and neutrophil (PMN) chemotaxis, we wished to determine if in vivo inhibition of 5-lipoxygenase would reduce neutrophil mediated events in our model. Lipoxygenase was inhibited in vivo with 2,3-diethyl-4-methoxy,1-naphthalenol acetate (U-66,855). The in vivo activity of U-66,855 was demonstrated in 4 cats. Each animal was treated with 5 mg/kg of U-66,855 intravenously. Blood cell leukotriene B4 (LTB4) and thromboxane A2, via its metabolite thromboxane B2 (TBX2) was assessed before and 30, 60, and 120 min after dosing. Blood cell LTB4 and TBX2 production was stimulated by A23187 (24 microM) and assayed by radioimmunoassay. We exposed and isolated a 3-cm segment of the jugular veins from 10 additional cats 5 of which were treated with U-66,855 (5 mg/kg, iv). In order to assess the effect of stasis, the jugular veins were ligated at the thoracic inlet for 2 hr after which the veins were perfused, fixed in 2.5% glutaraldehyde, and prepared for electron microscopy. U-66,855 reduced LTB4 production significantly (P less than 0.01), but not TBX2. In untreated cats, PMNs adhered to and migrated underneath the venous endothelium. Additionally, platelets, fibrin and formed thrombi were found on the basement membrane exposed by the migrating neutrophils. In contrast, we observed significantly reduced PMN adhesion as well as no fibrin deposition in veins obtained from cats treated with U-66,855. The results suggest that 5-lipoxygenase inhibition can significantly reduce undesirable neutrophil/vessel wall interactions.