Acute bilirubin ditaurate exposure attenuates ex vivo platelet reactive oxygen species production, granule exocytosis and activation.

BACKGROUND: Bilirubin, a by-product of haem catabolism, possesses potent endogenous antioxidant and platelet inhibitory properties. These properties may be useful in inhibiting inappropriate platelet activation and ROS production; for example, during storage for transfusion. Given the hydrophobicity of unconjugated bilirubin (UCB), we investigated the acute platelet inhibitory and ROS scavenging ability of a water-soluble bilirubin analogue, bilirubin ditaurate (BRT) on ex vivo platelet function to ascertain its potential suitability for inclusion during platelet storage. METHODS: The inhibitory potential of BRT (10-100 µM) was assessed using agonist induced platelet aggregation, dense granule exocytosis and flow cytometric analysis of P-selectin and GPIIb/IIIa expression. ROS production was investigated by analysis of H2DCFDA fluorescence following agonist simulation while mitochondrial ROS production investigated using MitoSOX™ Red. Platelet mitochondrial membrane potential and viability was assessed using TMRE and Zombie Green™ respectively. RESULTS: Our data shows ≤35 µM BRT significantly inhibits both dense and alpha granule exocytosis as measured by ATP release and P-selectin surface expression, respectively. Significant inhibition of GPIIb/IIIa expression was also reported upon ≤35 µM BRT exposure. Furthermore, platelet exposure to ≤10 µM BRT significantly reduces platelet mitochondrial ROS production. Despite the inhibitory effect of BRT, platelet viability, mitochondrial membrane potential and agonist induced aggregation were not perturbed. CONCLUSIONS: These data indicate, for the first time, that BRT, a water-soluble bilirubin analogue, inhibits platelet activation and reduces platelet ROS production ex vivo and may, therefore, may be of use in preserving platelet function during storage.

Implications for maintaining vascular access device patency and performance: Application of science to practice.

INTRODUCTION: Vascular access devices are commonly inserted devices that facilitate the administration of fluids and drugs, as well as blood sampling. Despite their common use in clinical settings, these devices are prone to occlusion and failure, requiring replacement and exposing the patient to ongoing discomfort/pain, local vessel inflammation and risk of infection. A range of insertion and maintenance strategies are employed to optimize device performance; however, the evidence base for many of these mechanisms is limited and the mechanisms contributing to the failure of these devices are largely unknown. AIMS/OBJECTIVES: (1) To revisit existing understanding of blood, vessel physiology and biological fluid dynamics; (2) develop an understanding of the implications that different clinical practices have on vessel health, and (3) apply these understandings to vascular access device research and practice. METHOD: Narrative review of biomedical and bioengineering studies related to vascular access practice. RESULTS/OUTCOMES: Current vascular access device insertion and maintenance practice and policy are variable with limited clinical evidence to support the theoretical assumptions underpinning these regimens. This review demonstrates the physiological response to vascular access device insertion, flushing and infusion on the vein, blood components and blood flow. These appear to be associated with changes in intravascular fluid dynamics. Variable forces are at play that impact blood componentry and the endothelium. These may explain the mechanisms contributing to vascular access failure. CONCLUSION: This review provides an update to our current knowledge and understanding of vascular physiology and the hemodynamic response, challenging some previously held assumptions regarding vascular access device maintenance, which require further investigation.

Potential of Anthocyanin to Prevent Cardiovascular Disease in Diabetes.

Context • Type 2 diabetes mellitus is an independent precipitating factor for cardiovascular disease (CVD). Heart disease is one of the leading causes of mortality in patients with diabetes, mainly due to macrovascular complications, such as atherosclerosis. Although aspirin is a frequently used therapy for the inhibition of platelet hyperactivity, many studies suggest that aspirin resistance is rising. Objective • The study intended to investigate the benefits of anthocyanin (AC) as an antioxidant with inhibitory effects on platelets and, consequently, its potential usefulness as complementary antiplatelet therapy to attenuate the negative effects of atherosclerosis and CVD in patients with diabetes. Design • The research team performed a literature review. The team conducted a database search from 2007 to 2017 using Library of Congress, LISTA, PubMed, and Web of Science Core Collection databases, using the following keywords: anthocyanins, platelet, cardiovascular disease, and diabetes. Setting • The study took place at the School of Medical Sciences at Griffith University's Gold Coast campus (Southport, Australia). Results • Platelets have a major pathophysiological role of atherosclerosis and consequently CVD in diabetes. Antiplatelet drugs have a potent inhibitory effect of thrombotic and CVD risks in diabetes. Dietary antioxidants including ACs have a potential platelet inhibitory effect. Hence, ACs may act as complementary therapy to reduce CVD in diabetes. Conclusions • Although antiplatelet drugs such as aspirin provide significant action in the management of CVD, aspirin has limited benefits in diabetes. An AC antioxidant has a potential effect as an antiplatelet agent that subsequently can prevent atherosclerosis and CVD and, therefore, AC may be an alternative to other antiplatelet drugs such as aspirin. However, more interventional studies and large-scale clinical trials are necessary to prove the efficiency of AC as an alternative to other platelet-inhibitory drugs.

Thrombotic and cardiovascular risks in type two diabetes; Role of platelet hyperactivity.

One of the most commonly identified chronic illnesses in many countries is type 2 diabetes mellitus (T2DM). T2DM denotes an independent risk factor for cardiovascular disease (CVD). Heart disease is one of the causes of mortality in patients with diabetes, mainly due to the macrovascular complications. One of these macrovascular complications in diabetes is atherosclerosis, which involves a complicated pathophysiological process. Besides hyperglycemia, oxidative stress plays a significant role in the pathogenesis of diabetes and its associated risk of CVD. There are many other factors including molecular, metabolic, lipid, fibrinolytic, and platelet function disorders precipitate to thrombotic and CVD risks in T2DM. Also, Platelets have an increased response to procoagulants in patients with diabetes. Platelet hyperactivity, in the presence of oxidative stress, has a major effect on the progression of thrombotic and CVD events. This review will discuss the impact of the above factors and the potential effects of platelet hyperactivity on thrombotic and cardiovascular risks.

The flavonols quercetin and 3',4'-dihydroxyflavonol reduce platelet function and delay thrombus formation in a model of type 1 diabetes.

Diabetes is associated with increased cardiovascular risk. We have recently shown that the naturally occurring flavonol quercetin (Que) or the synthetic flavonol 3',4'-dihydroxyflavonol (DiOHF) inhibits platelet function and delays thrombus formation in healthy mice. Therefore, the aim of this study was to investigate the effect of Que or DiOHF treatment on platelet function and ferric chloride-induced carotid artery thrombosis in a mouse model of type 1 diabetes. Diabetic mice treated with Que or DiOHF maintained blood flow at a significantly higher level than untreated diabetic mice at the end of the recording period. In addition, treatment with Que or DiOHF significantly reduced diabetes-induced platelet hyper-aggregability in response to platelet agonist stimulation. Furthermore, treatment with Que or DiOHF significantly inhibited dense, but not alpha, granule exocytosis in diabetic and control mice. Our demonstration that flavonols delay thrombus formation in diabetes suggests a potential clinical role for these compounds in anti-platelet therapy.

Inhibition of platelet-mediated arterial thrombosis and platelet granule exocytosis by 3',4'-dihydroxyflavonol and quercetin.

Flavonols are polyphenolic compounds with broad-spectrum kinase inhibitory, as well as potent anti-oxidant and anti-inflammatory properties. Anti-platelet potential of quercetin (Que) and several related flavonoids have been reported; however, few studies have assessed the ability of flavonols to inhibit exocytosis of different platelet granules or to inhibit thrombus formation in vivo. 3',4'-Dihydroxyflavonol (DiOHF) is a flavonol which is structurally related to Que and has been shown to have greater anti-oxidant capacity and to improve the endothelial function in the context of diabetes and ischaemia/reperfusion injury. While the structural similarity to Que suggests DiOHF may have a potential to inhibit platelet function, no studies have assessed the anti-platelet potential of DiOHF. We therefore investigated platelet granule inhibition and potential to delay arterial thrombosis by Que and DiOHF. Both Que and DiOHF showed inhibition of collagen, adenosine diphosphate and arachidonic acid stimulated platelet aggregation, agonist-induced GPIIb/IIIa activation as demonstrated by PAC-1 and fibrinogen binding. While both flavonols inhibited agonist-induced granule exocytosis, greater inhibition of dense granule exocytosis occurred with DiOHF as measured by both ATP release and flow cytometry. In contrast, while Que inhibited agonist-induced P-selectin expression, as measured by both platelet surface P-selectin expression and upregulation of surface GPIIIa expression, inhibition by DiOHF was not significant for either parameter. C57BL/6 mice treated with 6 mg kg(-1) IV Que or DiOHF maintained greater blood flow following FeCl3-induced carotid artery injury when compared to the vehicle control. We provide evidence that Que and DiOHF improve blood flow following arterial injury in part by attenuating platelet granule exocytosis.