Activation of human platelets by misfolded proteins.

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Herczenik E, Bouma B, Korporaal SJ, Strangi R, Zeng Q, Gros P, Van Eck M, Van Berkel TJ, Gebbink MF, Akkerman JW

Activation of human platelets by misfolded proteins.

Arterioscler Thromb Vasc Biol. 2007 Jul;27(7):1657-65. Epub 2007 May 17.

PubMed ID

17510465 [ View in PubMed

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Abstract

OBJECTIVE: Protein misfolding diseases result from the deposition of insoluble protein aggregates that often contain fibrils called amyloid. Amyloids are found in Alzheimer disease, atherosclerosis, diabetes mellitus, and systemic amyloidosis, which are diseases where platelet activation might be implicated. METHODS AND RESULTS: We induced amyloid properties in 6 unrelated proteins and found that all induced platelet aggregation in contrast to fresh controls. Amyloid-induced platelet aggregation was independent of thromboxane A2 formation and ADP secretion but enhanced by feedback stimulation through these pathways. Treatments that raised cAMP (iloprost), sequestered Ca2+ (BAPTA-AM) or prevented amyloid-platelet interaction (sRAGE, tissue-type plasminogen activator [tPA]) induced almost complete inhibition. Modulation of the function of CD36 (CD36-/- mice), p38(MAPK) (SB203580), COX-1 (indomethacin), and glycoprotein Ib alpha (Nk-protease, 6D1 antibody) induced approximately 50% inhibition. Interference with fibrinogen binding (RGDS) revealed a major contribution of alphaIIb beta3-independent aggregation (agglutination). CONCLUSIONS: Protein misfolding resulting in the appearance of amyloid induces platelet aggregation. Amyloid activates platelets through 2 pathways: one is through CD36, p38(MAPK), thromboxane A2-mediated induction of aggregation; the other is through glycoprotein Ib alpha-mediated aggregation and agglutination. The platelet stimulating properties of amyloid might explain the enhanced platelet activation observed in many diseases accompanied by the appearance of misfolded proteins with amyloid.

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Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Iloprost	Tissue-type plasminogen activator	Protein	Humans	Unknown	Other/unknown	Details