Bacterial lipopolysaccharide priming of P388D₁ macrophage-like cells for enhanced arachidonic acid metabolism. Platelet-activating factor receptor activation and regulation of phospholipase A₂

P388D₁ cells are stimulated by platelet-activating factor (PAF) to release arachidonic acid metabolites (Lister, M.D., Glaser, K.B., Ulevitch, R.J., and Dennis, E.A. (1989) J. Biol. Chem. 264, 8520-8528). While the release of prostaglandin E₂ (PGE₂) in response to PAF is only two to three times the constitutive PGE₂ production, bacterial lipopolysaccharides (LPS) are able to prime P388D₁ cells for enhanced arachidonic metabolism, increasing PAF-stimulating PGE₂ production to 9-12 times the constitutive PGE₂ production. The extent and rate of [³H]arachidonic acid release from prelabeled P388D₁ cells are also increased in primed cells relative to unprimed cells in response to PAF-stimulation. LPS from either Salmonella Re595 or Escherichia coli 0111:B4 prime P388D₁ cells in a concentration-dependent manner but have themselves no ability to stimulate arachidonic acid metabolism. LPS priming is sensitive to inhibition by actinomycin D, while primed PAF-stimulation of PGE₂ production is blocked by cyclohexamide which implicates a protein which is rapidly turning over. Primed PAF stimulation is also inhibited by the phospholipase A₂ inhibitor manoalogue and the tyrosine-specific protein kinase inhibitor genistein, but not by the kinase inhibitor H-7. These results suggest that priming amplifies signal transduction pathways for PAF, which results in increased arachidonate availability. The multiple levels at which primed PAF-stimulated PGE₂ production appears to be regulated are discussed.