Investigation of underlying mechanisms of platelet activation by oxidized collagen

Abstract

The production of reactive oxygen species (ROS) leads to the oxidation of proteins that generate damage present in chronic diseases, such as cardiovascular diseases. An important component of cardiovascular diseases associated with exacerbated ROS production is platelet hyperactivity, found in patients with risk factors for ischemic events. Platelets are important to prevent excessive bleeding, however, when overactivated they can lead to thrombus formation. An important platelet agonist, present in the vascular subendothelium and relevant to cardiovascular diseases, is collagen, which has a long half-life. It is possible that vascular collagen is oxidized over time and is present in the arteries of patients with cardiovascular disease. In fact, a recent study demonstrated the presence of oxidized collagen after acute myocardial infarction in mice. Although there are studies on the role of ROS in platelet function, and the presence of oxidized collagen in cardiovascular diseases, it is not known whether collagen oxidation contributes to platelet hyperactivation. Therefore, our hypothesis is that collagen oxidation by hydrogen peroxide (H2O2) can alter platelet function, which would be relevant to understand ischemic events in patients at risk. Preliminary data from our group indicate that platelets aggregate more when in contact with oxidized collagen. In this project we will seek to understand the signaling pathways relevant to the platelet effect of oxidized collagen. We will do this using specific inhibitors of proteins relevant to the collagen pathway (namely, Src kinase), as well as platelet-activating collateral pathways, such as CD36, ADP, and cyclooxygenases. We will investigate both platelet aggregation and the global signaling of these platelets using immunoblotting assays in the presence or absence of inhibitors. Finally, we anticipate that data from this work will contribute to the understanding of the pathophysiology of platelet hyperactivity in scenarios of oxidative stress, such as that found in patients with chronic cardiovascular diseases.