Summary
The lipoxygenase metabolites of arachidonic acid have an important role in lymphocyte activation. We used a specific 5-lipoxygenase inhibitor, A-63162, to examine the role of 5-lipoxygenase (5-lo) in equine blood mononuclear cell (bmc) proliferation and leukotriene B4 (ltb4) synthesis after stimulation with mitogen (phytohemagglutinin, pha) or calcium ionophore (A23187). The A-63162 inhibited pha-induced equine bmc proliferation and, at the same concentration, also inhibited A23187-induced ltb4 synthesis. The presence of exogenous interleukin 2 (il-2) or the cyclooxygenase inhibitor indomethacin, failed to reverse the immunosuppression caused by A-63162. Further, we found that A-63162, at the concentration that inhibited bmc proliferation and ltb4 synthesis, had no effect on bmc viability. The addition of the specific protein kinase C inhibitor, H-7, did not inhibit A23187-induced ltb4 synthesis. Results indicate that 5-lipoxygenase metabolites may have an important role in equine lymphocyte activation and that protein kinase C has no role in regulating ltb4 production after A23187 stimulation.
