Abstract
Platelets play a pivotal role in coagulation, or clot formation, resulting in haemostasis, after endothelium injury. Disturbance of platelet activation may lead to pathologic thrombosis. Platelet activation and aggregation are common factors in atherothrombotic events, critical in the atherothrombotic process, and cardiovascular diseases. Several drugs are being used for antiplatelet therapy to prevent and/or treat atherosclerosis and cardiovascular diseases. Synthetic antiplatelet drugs hold possible undesired health consequences (cardiovascular diseases, carcinogenicity, etc.), advocating their replacement with natural, effective, and non-toxic compounds. Many phenolic compounds are created as secondary metabolites of plants, are found in many fruits and vegetables, and constitute a wide family of high-added-value molecules. Their biological activities include antioxidant, anti-platelet, and anti-inflammatory action. Based on the above, we examined five phenolic compounds (ellagic acid, ferulic acid, gallic acid, quercetin, and kaempferol) for their effect on platelet reactivity in whole blood samples using flow cytometry.
 Quantification of activated platelet marker CD62-P by flow cytometry showed that all five compounds inhibited platelet activation in vitro, induced by adenosine diphosphate (ADP) and collagen. Interestingly, based on the IC50 values obtained for expression of CD62-P, among ellagic, ferulic, and gallic acid, gallic acid showed significantly higher inhibition than the other two. Kaempferol found to be a more potent inhibitor than quercetin, following previously reported results from aggregometry. Results obtained from our flow cytometry screening indicate antiplatelet activity from novel phenolic compounds and their potential use as drugs for thrombosis and cardiovascular diseases.
Highlights
Haemostasis is an important physiological process, wherein activated platelets adhere to the injured vessel wall, form aggregates to stop bleeding and create a barrier for infections
Of the anticoagulants investigated so far, the selective thrombin inhibitor hirudin is considered as the most suitable anticoagulant for studies of platelet aggregation in vitro in whole blood [12], [13]. As it has been reported adenosine diphosphate (ADP)- and collagen-induced aggregation was significantly lower in citrated blood compared to hirudin-treated blood, reflecting the importance of extracellular calcium for platelet function [12]
Aspirin reduces ischaemic stroke and in parallel may cause haemorrhagic stroke and bleeding. These methods can be divided into two groups: platelet aggregation tests, which measure the extent of platelet aggregation in response to AA and ADP [4]-[6], and flow cytometry, which determines the surface expression of platelet activation markers after the addition of agonists (ADP, collagen)
Summary
Haemostasis is an important physiological process, wherein activated platelets adhere to the injured vessel wall, form aggregates to stop bleeding and create a barrier for infections. Adenosine diphosphate (ADP), epinephrine, serotonin, thromboxane A2 and thrombin facilitate platelet activation [1]. They recruit platelets from circulation, platelets change shape and release several pro-inflammatory molecules as P-selectin and CD40 ligand, convert GPIb/IIIa complex (a central platelet receptor mediating platelet aggregation) into its active form, which allows platelet aggregation. In arterial thrombosis, increased platelet activation can be measured indirectly, through quantification of activation markers on their cell surface These platelet biomarkers are of great importance, as they may predict thrombotic situations. Estimation of surface-bound CD62P alone or/in combination with CD63 or CD40L, by flow cytometric analysis is widely used for diagnosis of platelet activation state in ex vivo patientderived samples. The effect of these five phenolic compounds was examined on platelet reactivity by flow cytometric analysis in an attempt to gain further insight on their antiplatelet impact
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