The role of cyclooxygenase and lipoxygenase pathways in the adhesive interaction between bovine polymorphonuclear leukocytes and bovine endothelial cells

Abstract

The effects of arachidonic acid metabolites, analogues and cyclooxygenase/lipoxygenase inhibitors were tested on an "in vitro" bovine model of endothelial cell (EC)-polymorphonuclear leukocyte (PMN) adhesion. Arachidonic acid blocked adhesion at 10(-5)M, a dose which also induced aggregation of PMN. Lower doses did not affect either EC-PMN adhesion or PMN aggregation. Various cyclooxygenase pathway metabolites were inactive in the EC-PMN adhesion assay, with the exception of prostaglandin A2 and prostaglandin B2 which significantly suppressed adhesion at 10(-5)M. Of the synthetic analogs tested, 6 alpha-carbaprostacyclin I2, (5Z)-9 beta-ethynyl-calcium salt (U-64,567E) was inhibitory at 10(-5)M. The cyclooxygenase inhibitors acetylsalicylic acid, indomethacin and ibuprofen were inactive. Products of the lipoxygenase pathways, leukotriene B4 (LTB4), 5-hydroxyeicosatetraenoic acid (5-HETE) and 15-hydroperoxyeicosatetraenoic acid (15-HPETE) exhibited variable inhibitory activity at 10(-5)M only. Paradoxical effects were observed with the putative lipoxygenase inhibitors 4,7,10,13-eicosatetraynoic acid (4,7,10,13 ETYA), 5,8,11,14-eicosatetraynoic acid (5,8,11,14 ETYA) and nordihydroguairetic acid (NDGA), which also suppressed EC-PMN adhesion at 10(-5)M. The dual cyclooxygenase-lipoxygenase inhibitor, BW755C was inactive. Bovine PMNs did not respond chemotactically to LTB4 although they were able to synthesize the 5-lipoxygenase products LTB4 and 5-HETE.