The role of cyclooxygenase and lipoxygnase 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 −5M, 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 A 2 and prostaglandin B 2 which significantly suppressed adhesion at 10 −5M. Of the synthetic analogs tested, 6α-carbaprostacyclin I 2, (5Z)-9β-ethynyl-calcium salt (U-64,567E) was inhibitory at 10 −5M. The cyclooxygenase inhibitors acetylsalicylic acid, indomethacin and ibuprofen were inactive. Products of the lipoxygenase pathways, leukotriene B 4 (LTB 4), 5-hydroxyeicosatetraenoic acid (5-HETE) and 15-hydroperoxyeicosatetraenoic acid (15-HPETE) exhibited variable inhibitory activity at 10 −5M 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 −5M. The dual cyclooxygenase-lipoxygenase inhibitor, BW755C was inactive. Bovine PMNs did not respond chemotactically to LTB 4 although they were able to synthesize the 5-lipoxygenase products LTB 4 and 5-HETE. It is concluded that the relative lack of arachidonic acid metabolism via cyclooxygenase and lipoxygenase pathways in the adhesive interaction between bovine PMN Leukocytes and bovine vascular endothelial cells is a reflection of the species studied. Moreover, we are convinced that an awareness of the derivation of cell types will tend to abrogate the confusion that currently exists with respect to the involvement of arachidonic metabolism in cellular interactions.