Prostaglandin E1 inhibits N-formyl-methionyl-leucyl-phenylalanine-mediated depolarization responses by decreasing the proportion of responsive cells without affecting chemotaxin-induced forward light scatter changes.
Hypaque-Ficoll-purified human polymorphonuclear neutrophils (PMN) equilibrated with the membrane potential-sensitive probe 3,3'dipentyloxacarbocyanine [di-O-C(5)(3)] were incubated with buffer or cytochalasin B (cyto B) followed by incubation with prostaglandin E1 (PGE1) (0 to 10(-5) M) for 5 min at 37 degrees C. The cells were then stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP) (0 to 10(-5) M). Changes in forward light scatter (FWD-SC), 90 degrees scatter (90 degrees -SC), and fluorescence intensity were measured by flow cytometry to determine the effects of PGE1 on FMLP-induced shape change, secretion, and membrane potential responses, respectively. In other experiments, the effects of PGE1 preincubation on FMLP +/- cyto B and phorbol myristate acetate-induced (O2) production were measured by superoxide dismutase-inhibitable cyto c reduction. PGE1 had no direct effects on the FWD-SC, 90 degrees-SC, or resting potential fluorescence of unstimulated or cyto B-pretreated PMN. PGE1 produced a dose-dependent inhibition of the proportion of depolarizing PMN in response to FMLP, which was maximal at 10(-6) M (42.1 +/- 6.9% inhibition, p less than 0.005), but was apparent at 10(-8) M. The PGE1-induced inhibition was maximal after 30 sec of incubation at 37 degrees C and was caused by a decrease in the maximal percentage of depolarizing PMN without a significant change in the FMLP dose-response curve (Km = 2.43 vs 3.62 X 10(-8) M, control vs PGE1-treated) or an inhibition in the degree of depolarization by the responding subpopulation. PGE1 also inhibited the loss of 90 degrees-SC induced by FMLP in cyto B-pretreated cells (secretion response) (46.2 +/- 16.5% inhibition of the maximal 90 degrees-SC loss, n = 5, p less than 0.005), but did not affect the increase in FWD-SC seen with FMLP-induced PMN activation or the ability of cyto B to recruit more PMN to depolarize. PGE1 also inhibited FMLP +/- cyto B-induced O2 production in a dose-dependent fashion; phorbol myristate acetate-induced O2 production was also slightly inhibited, but only at high PGE1 concentrations. The data indicate that PGE1 inhibits FMLP-induced cell activation by a mechanism that involves a step distal to the recruitment of unresponsive PMN by cyto B, and that PGE1 is capable of inhibiting depolarization responses without affecting FMLP-induced shape change, providing more support for a dissociation between the two activation pathways.
Department of Internal Medicine, University of California, Davis, School of Medicine 95616.
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Fletcher
D000527:Alprostadil / Q000494:pharmacology*; D003571:Cytochalasin B / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors*; D009391:Nephelometry and Turbidimetry; D009504:Neutrophils / Q000187:drug effects* / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D003571:Cytochalasin B; D009240:N-Formylmethionine Leucyl-Phenylalanine; D000527:Alprostadil; D013755:Tetradecanoylphorbol Acetate