Abstract
Background:
CD40 ligand (CD40L) expression on platelets is mediated by agonists, but the underlying mechanism is still unclear.
Methods and results:
CD40L expression was measured in platelets from healthy subjects both with and without the addition of antioxidants or a phospholipase A2 (PLA2) inhibitor and in platelets from 2 patients with an inherited deficiency of gp91phox. Immunoprecipitation analysis was also performed to determine whether normal platelets showed gp91phox expression. Unlike catalase and mannitol, superoxide dismutase inhibited agonist-induced platelet CD40L expression in healthy subjects. Immunoprecipitation analysis also showed that platelets from healthy subjects expressed gp91phox. In 2 male patients with inherited gp91phox deficiency, collagen-, thrombin-, and arachidonic acid-stimulated platelets showed an almost complete absence of superoxide anion (O(2)(-)) and CD40L expression. Incubation of platelets from healthy subjects with a PLA2 inhibitor almost completely prevented agonist-induced O(2)(-) and CD40L expression.
Conclusions:
These data provide the first evidence that platelet CD40L expression occurs via arachidonic acid-mediated gp91phox activation.
MeSH terms
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Adult
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Antioxidants / pharmacology
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Arachidonic Acid / metabolism*
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Arachidonic Acids / pharmacology
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Aspirin / pharmacology
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Blood Platelets / drug effects
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Blood Platelets / metabolism*
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CD40 Ligand / biosynthesis*
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CD40 Ligand / blood
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CD40 Ligand / genetics
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Catalase / pharmacology
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Collagen / pharmacology
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Granulomatous Disease, Chronic / blood
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Granulomatous Disease, Chronic / enzymology
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Humans
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Male
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Mannitol / pharmacology
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Membrane Glycoproteins / deficiency
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Membrane Glycoproteins / genetics
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Membrane Glycoproteins / physiology*
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NADPH Oxidase 2
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NADPH Oxidases / deficiency
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NADPH Oxidases / genetics
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NADPH Oxidases / physiology*
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Phospholipases A / antagonists & inhibitors
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Phospholipases A2
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Platelet Activation / drug effects
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Platelet Aggregation Inhibitors / pharmacology
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Reactive Oxygen Species / metabolism*
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Superoxide Dismutase / pharmacology
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Superoxides / metabolism
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Thrombin / pharmacology
Substances
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Antioxidants
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Arachidonic Acids
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Membrane Glycoproteins
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Platelet Aggregation Inhibitors
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Reactive Oxygen Species
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arachidonyltrifluoromethane
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Superoxides
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CD40 Ligand
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Arachidonic Acid
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Mannitol
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Collagen
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Catalase
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Superoxide Dismutase
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CYBB protein, human
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NADPH Oxidase 2
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NADPH Oxidases
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Phospholipases A
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Phospholipases A2
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Thrombin
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Aspirin