Platelet particle formation by anti GPIIIa49-66 Ab, Ca2+ ionophore A23187, and phorbol myristate acetate is induced by reactive oxygen species and inhibited by dexamethasone blockade of platelet phospholipase A2, 12-lipoxygenase, and NADPH oxidase.
An HIV antibody (Ab) against platelet integrin GPIIIa49-66 induces complement-independent platelet particle formation by the elaboration of reactive oxygen species (ROS) downstream of the activation of the platelet NADPH oxidase by the 12-lipoxygenase (12-LO) product 12(S)-HETE. To determine whether other inducers of platelet particle formation also function via the induction of ROS, we examined the effects of the Ca(2+) ionophore A23187 and phorbol myristate acetate (PMA). Both agents induced oxidative platelet particle formation in an identical fashion as Ab, requiring Ca(2+) flux and 12(S)-HETE production as well as intact NADPH oxidase and 12-LO pathways. Since HIV-ITP patients with this Ab correct their platelet counts with dexamethasone (Dex), we examined the role of this steroid in this unique autoimmune disorder. Dex at therapeutic concentrations inhibited Ab-, A23187-, or PMA-induced platelet particle formation by inhibiting platelet PLA(2), 12-LO, and NADPH oxidase. The operational requirement of translocation of PLA(2), 12-LO, and NADPH oxidase components (p67 phox) from cytosol to membrane for induction of ROS was both inhibited and partially reversed by Dex in platelets. We conclude that (1) platelet particle formation can be induced by the generation of ROS; and (2) platelet PLA(2), 12-LO, NADPH oxidase, and cytosol membrane translocation, requirements for ROS production, are inhibited by Dex.
Nardi
Michael A
MA
Department of Pediatrics, Center for Molecular Therapeutics, Columbia College of Physicians and Surgeons, New York, NY, USA.
Gor
Yelena
Y
Feinmark
Steven J
SJ
Xu
Fang
F
Karpatkin
Simon
S
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D001792:Blood Platelets / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology*; D002273:Carcinogens / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D054513:Group IV Phospholipases A2; D006801:Humans; D039661:Integrin beta3 / Q000276:immunology / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010084:Oxidation-Reduction; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000378:metabolism; D054467:Phospholipases A2; D021381:Protein Transport; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013921:Thrombocytopenia / Q000378:metabolism / Q000473:pathology / Q000821:virology
D000893:Anti-Inflammatory Agents; D000911:Antibodies, Monoclonal; D002273:Carcinogens; D039661:Integrin beta3; D007476:Ionophores; D016859:Lipoxygenase Inhibitors; D017382:Reactive Oxygen Species; D000001:Calcimycin; D003907:Dexamethasone; D001092:Arachidonate 12-Lipoxygenase; D019255:NADPH Oxidases; D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054467:Phospholipases A2; D013755:Tetradecanoylphorbol Acetate