Investigations into effects of 12-lipoxygenase and NADPH oxidase on platelet activity, and influences of dietary dark chocolate

Abstract

Platelets play a pivotal role in both normal hemostasis and pathological bleeding and importantly also contribute to the development of atherothrombosis. Even though platelet function tests traditionally are utilised mainly for the diagnosis and management of patients presenting with bleeding problems rather than thrombosis, new and improved platelet function tests are now increasingly used to monitor anti-platelet therapy in patients and to identify patients at risk of arterial disease. Based on light transmission traditional aggregometry, this thesis reports data from a new model of platelet aggregation using a modified 96-well plate format. This method allows examination of many agonists at a range of concentrations at the same time. Thus, more information can be collated about different aspects of platelet function and smaller assay volumes can be used while still obtaining reliable results. To further utilise this method, agonist combinations were used in the 96-well plate approach that resemble the actions of machines such as the PFA-100, which uses combined agonists within a cartridge, but at much lower cost. Platelet cyclooxygenase has been widely studied; however, the functions of platelet 12-lipoxygenase and NADPH oxidase in platelets are still generally not understood. Data presented here demonstrate that both pathways are partly essential in platelet activation following exposure to stimulatory agonists. To further explore the relationship between dietary intake and the risk of atherothrombosis, an in vivo study was performed to observe the antiplatelet effects following from consumption of dark chocolate in baseline hypertensive patients. Based on findings in this thesis, it can be 4 concluded that this new method of evaluating platelet aggregation and adhesion in a 96-well plate format is very useful, and that new observations into influences on platelets of pathways other than cyclooxygenase may be beneficial in the development of new antiplatelet drugs.