Amyloid Peptide 1-42 Induces Integrin IIb3 Activation, Platelet Adhesion, and Thrombus Formation in a NADPH Oxidase-Dependent Manner.

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 amyloid peptides on the function of platelets, the cells driving haemostasis. Amyloid peptide 1-42 (A1-42), A1-40, and A25-35 were tested in static adhesion experiments, and it was found that platelets preferentially adhere to A1-42 compared to other A peptides. In addition, significant platelet spreading was observed over A1-42, while A1-40, A25-35, and the scA1-42 control did not seem to induce any platelet spreading, which suggested that only A1-42 activates platelet signalling in our experimental conditions. A1-42 also induced significant platelet adhesion and thrombus formation in whole blood under venous flow condition, while other A peptides did not. The molecular mechanism of A1-42 was investigated by flow cytometry, which revealed that this peptide induces a significant activation of integrin IIb3, but does not induce platelet degranulation (as measured by P-selectin membrane translocation). Finally, A1-42 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 A1-42-dependent platelet adhesion in static conditions, thrombus formation in physiological flow conditions, integrin IIb3 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 1-42. The molecular mechanisms described in this manuscript may play an important role in the neurovascular impairment observed in Alzheimer's patients.