Formation of lipoxins and leukotrienes during receptor-mediated interactions of human platelets and recombinant human granulocyte/macrophage colony-stimulating factor-primed neutrophils

The generation of lipoxygenase products of arachidonic acid is considered an important event in inflammation. This study demonstrates the levels of both lipoxins and leukotrienes (LTC4, LTD4, LTB4, and omega-oxidized LTB4) generated from endogenous sources of arachidonate by PMN primed with recombinant human granulocyte/macrophage colony- stimulating factor and in coincubations with platelets (1:1 to 1:100 ratio). Upon exposure to receptor-mediated stimuli (FMLP and thrombin), the levels of lipoxins generated were within the range of both LTB4 and LTC4. Co-incubation of [1-14C]arachidonate-labeled platelets with primed polymorphonuclear leukocytes (PMN) followed by addition of thrombin and FMLP led to the formation of both 5- and 15-LO products that carried 14C label. Thus, in addition to the transcellular conversion of LTA4 to platelet-derived lipoxins and LTC4, PMN can use platelet-derived arachidonate to generate lipoxygenase products. These results are the first to document the relationship between the levels of lipoxins and leukotrienes generated by receptor-mediated activation of cytokineprimed PMN interacting with platelets. Moreover, they indicate that PMN-platelet interactions utilize bidirectional transcellular routes to contribute to lipoxin formation.