Amyloid Peptide<i>β</i>1-42 Induces Integrin<i>α</i>IIb<i>β</i>3 Activation, Platelet Adhesion, and Thrombus Formation in a NADPH Oxidase-Dependent Manner

Abstract

The progression of Alzheimer's dementia is associated with neurovasculature impairment, which includes inflammation, microthromboses, and reduced cerebral blood flow. Here, we investigate the effects of <i>β</i> amyloid peptides on the function of platelets, the cells driving haemostasis. Amyloid peptide <i>β</i>1-42 (A<i>β</i>1-42), A<i>β</i>1-40, and A<i>β</i>25-35 were tested in static adhesion experiments, and it was found that platelets preferentially adhere to A<i>β</i>1-42 compared to other A<i>β</i> peptides. In addition, significant platelet spreading was observed over A<i>β</i>1-42, while A<i>β</i>1-40, A<i>β</i>25-35, and the scA<i>β</i>1-42 control did not seem to induce any platelet spreading, which suggested that only A<i>β</i>1-42 activates platelet signalling in our experimental conditions. A<i>β</i>1-42 also induced significant platelet adhesion and thrombus formation in whole blood under venous flow condition, while other A<i>β</i> peptides did not. The molecular mechanism of A<i>β</i>1-42 was investigated by flow cytometry, which revealed that this peptide induces a significant activation of integrin <i>α</i>IIb<i>β</i>3, but does not induce platelet degranulation (as measured by P-selectin membrane translocation). Finally, A<i>β</i>1-42 treatment of human platelets led to detectable levels of protein kinase C (PKC) activation and tyrosine phosphorylation, which are hallmarks of platelet signalling. Interestingly, the NADPH oxidase (NOX) inhibitor VAS2870 completely abolished A<i>β</i>1-42-dependent platelet adhesion in static conditions, thrombus formation in physiological flow conditions, integrin <i>α</i>IIb<i>β</i>3 activation, and tyrosine- and PKC-dependent platelet signalling. In summary, this study highlights the importance of NOXs in the activation of platelets in response to amyloid peptide <i>β</i>1-42. The molecular mechanisms described in this manuscript may play an important role in the neurovascular impairment observed in Alzheimer's patients.