The epidemiological studies confirm an increased risk of cardiovascular disease in multiple sclerosis, especially prothrombotic events directly associated with abnormal platelet activity. The aim of our study was to investigate the level of blood platelet activation in the circulation of patients with chronic phase of multiple sclerosis (SP MS) and their reactivity in response to typical platelets’ physiological agonists. We examined 85 SP MS patients diagnosed according to the revised McDonald’s criteria and 50 healthy volunteers as a control group. The platelet activation and reactivity were assessed using flow cytometry analysis of the following: P-selectin expression (CD62P), activation of GP IIb/IIIa complex (PAC-1 binding), and formation of platelet microparticles (PMPs) and platelet aggregates (PA) in agonist-stimulated (ADP, collagen) and unstimulated whole blood samples. Furthermore, we measured the level of soluble P-selectin (sP-selectin) in plasma using ELISA method, to evaluate the in vivo level of platelet activation, both in healthy and SP MS subjects. We found a statistically significant increase in P-selectin expression, GP IIb/IIIa activation, and formation of PMPs and PA, as well as in unstimulated and agonist-stimulated (ADP, collagen) platelets in whole blood samples from patients with SP MS in comparison to the control group. We also determined the higher sP-selectin level in plasma of SP MS subjects than in the control group. Based on the obtained results, we might conclude that during the course of SP MS platelets are chronically activated and display hyperreactivity to physiological agonists, such as ADP or collagen.

Dandelion (Taraxacum officinale L.) roots, leaves, and flowers have a long history of use in traditional medicine. Compared to the above organs, dandelion fruits are the least known and used. Hence, the present paper was aimed at the phytochemical analysis of T. officinale fruit extract and estimating its antiradical, antiplatelet, and antioxidant properties related to hemostasis. Methanolic extract of fruits (E1), enriched with polyphenols (188 mg gallic acid equivalents (GAE)/g), was successfully separated into cinnamic acids (E2; 448 mg GAE/g) and flavonoids (E3; 377 mg GAE/g) extracts. Flavonoid extract was further divided into four fractions characterized by individual content: A (luteolin fraction; 880 mg GAE/g), B (philonotisflavone fraction; 516 mg GAE/g), C (flavonolignans fraction; 384 mg GAE/g), and D (flavone aglycones fraction; 632 mg GAE/g). High DPPH radical scavenging activity was evaluated for fractions A and B (A > B > Trolox), medium for extracts (Trolox > E3 > E2 > E1), and low for fractions C and D. No simple correlation between polyphenol content and antiradical activity was observed, indicating a significant influence of qualitative factor, including higher anti-oxidative effect of flavonoids with B-ring catechol system compared to hydroxycinnamic acids. No cytotoxic effect on platelets was observed for any dandelion preparation tested. In experiments on plasma and platelets, using several different parameters (lipid peroxidation, protein carbonylation, oxidation of thiols, and platelet adhesion), the highest antioxidant and antiplatelet potential was demonstrated by three fruit preparations–hydroxycinnamic acids extract (E2), flavonoid extract (E3), and luteolin fraction (A). The results of this paper provide new information on dandelion metabolites, as well as their biological potential and possible use concerning cardiovascular diseases.

Polyphenolic compounds of plant origin are well known to be beneficial to human health: they exert protective effects on haemostasis and have a particular influence on blood platelets. However, the anti-platelet properties of polyphenolic compounds observed so far have not been weighed against their potential cytotoxic action against platelets. The aim of this study was to demonstrate that anti-platelet and cytotoxic effects on blood platelets may interfere and therefore, may often lead to confusion when evaluating the properties of plant extracts or other agents towards blood platelets. The anti-platelet and cytotoxic in vitro effects of plant extracts obtained from the husks of walnuts (J. regia) and flowers of arnica (A. montana) on platelet reactivity and viability were examined. Platelet function was assessed using standard methods (flow cytometry: P-selectin expression, activation of GPIIbIIIa complex, vasodilator-stimulated phosphoprotein, VASP index; turbidimetric and impedance aggregometry) and newly set assays (flow cytometric monitoring of platelet cytotoxicity). The results reveal that none of the studied plant extracts demonstrated cytotoxicity towards blood platelets. The phenolic acid-rich extract of A. montana (7.5 and 15 µg/ml) significantly reduced the ADP-induced aggregation in both whole blood and PRP, and decreased the platelet reactivity index (PRI; VASP phosphorylation) in whole blood, while showing excellent antioxidant capacity. The extract of J. regia husks significantly reduced ADP-induced platelet aggregation in whole blood when applied at 7.5 µg/ml, and only slightly decreased the PRI at 15 µg/ml. Both examined extracts suppressed platelet hyper-reactivity, and such influence did not interfere with cytotoxic effects of the extracts. Thus, its high polyphenol content, excellent antioxidant capacity and distinct anti-platelet properties, in combination with its lack of toxicity, make the extract of A. montana flowers a possible candidate as an anti-platelet agent or a compounding diet supplement.

Multiple sclerosis (MS) is the autoimmune disease of the central nervous system with complex pathogenesis, different clinical courses and recurrent neurological relapses and/or progression. Despite various scientific papers that focused on early stage of MS, our study targets selective group of late stage secondary progressive MS patients. The presented work is concerned with the reactivity of blood platelets in primary hemostasis in SP MS patients. 50 SP MS patients and 50 healthy volunteers (never diagnosed with MS or other chronic diseases) were examined to evaluate the biological activity of blood platelets (adhesion, aggregation), especially their response to the most important physiological agonists (thrombin, ADP, and collagen) and the effect of oxidative stress on platelet activity. We found that the blood platelets from SP MS patients were significantly more sensitive to all used agonists in comparison with control group. Moreover, the platelet hemostatic function was advanced in patients suffering from SP MS and positively correlated with increased production ofO2-∙in these cells, as well as with Expanded Disability Status Scale. We postulate that the increased oxidative stress in blood platelets in SP MS may be primarily responsible for the altered haemostatic properties of blood platelets.

The blood platelets are crucial for the coagulation physiology to maintain haemostatic balance and are involved in various pathologies such as atherosclerosis and thrombosis. The studies of recent years have shown that anucleated platelets are able to succeed protein synthesis. Additionally, mRNA translation in blood platelets is regulated by miRNA molecules. Recent works postulate the possibility of using miRNAs as biomarkers of atherosclerosis and ischemic episodes. This review article describes clinical studies that presented blood platelets miRNAs expression profile changes in different thrombotic states, which suggest use of these molecules as predictive biomarkers.

Platelets are anucleated cells that upon activation by agonists or during storage may develop apoptotic events. The role of peroxynitrite and its reactive intermediates in apoptotic process in blood platelets is unknown. In order to study the appearance of biomarkers of apoptosis in platelets after treatment with peroxynitrite and with thrombin different markers were chosen: annexin V binding (phosphatidylserine exposure), platelet microparticle formation, mitochondrial membrane depolarization, caspase-3 activation and P-selectin expression. In gel-filtrated platelets treated with different concentrations of peroxynitrite (0.01, 0.1, 1.0 mM, 10 minute, 37°C) a significant increase of phosphatidylserine exposure (about 36% at the highest concentration, p < 0.01) and the platelet microparticle formation were observed. Peroxynitrite caused a dose-dependent caspase-3 activation and depolarization of mitochondrial potential. The same apoptotic markers were appeared in thrombin-activated platelets. Dose-dependent tyrosine nitration in platelet proteins caused by peroxynitrite was reduced in the presence of (−)-epicatechin. Moreover, (−)-epicatechin distinctly reduced the level of apoptotic markers. The obtained results indicate that peroxynitrite responsible for oxidative/nitrative stress and changes in platelet function may promote in vitro apoptotic events in human gel-filtrated platelets via intrinsic pathway. Nitration of tyrosine seems to be partly associated with the appearance of apoptotic markers in platelets.