The protein disulphide isomerase inhibitor CxxCpep modulates oxidative burst and mitochondrial function in platelets

BACKGROUND

We have previously described CxxCpep, a peptide with anti-platelet properties that inhibits peri/epicellular protein disulphide isomerase (pecPDI) by forming a mixed disulfide bond with Cys400 within the pecPDI active site.

OBJECTIVES

Here we sought to determine if pecPDI targeted by CxxCpep is relevant to redox mechanisms downstream of the collagen receptor GPVI in platelets.

METHODS AND RESULTS

Restriction of effects of CxxCpep to the platelet surface was confirmed by LC-MS/MS following cell fractionation. Platelet aggregation was measured in platelet-rich plasma (PRP) incubated with 30 μM CxxCpep or vehicle. CxxCpep inhibited collagen-induced platelet aggregation but exerted no effect in TRAP-6-stimulated platelets. PRP was incubated with DCFDA to measure oxidative burst upon platelet adhesion to collagen. Results showed that CxxCpep decreased oxidative burst in platelets adhered to immobilized collagen while the number of adherent cells was unaffected. Furthermore, flow cytometry studies using a FITC-maleimide showed that the GPVI agonist CRP stimulated an increase in free thiols on the platelet outer membrane, which was inhibited by CxxCpep. Finally, CxxCpep inhibited platelet mitochondrial respiration upon activation with collagen, but not with thrombin.

CONCLUSIONS

Our data suggest that pecPDI is a potential modulator of GPVI-mediated redox regulation mechanisms and that CxxCpep can be further exploited as a template for new antiplatelet compounds.

Platelet Function Monitoring Performed after Carotid Stenting during Endovascular Stroke Treatment Predicts Outcome

OBJECTIVES

Many studies showed that platelet reactivity testing can predict ischemic events after carotid stenting or ischemic stroke. The aim of our study was to assess the role of early platelet function monitoring in predicting 90-days functional outcome, stent thrombosis and hemorrhagic transformation in patients with ischemic stroke treated with endovascular procedures requiring emergent extracranial stenting.

MATERIALS AND METHODS

We performed a retrospective study on consecutive patients with acute anterior circulation stroke admitted to our hospital between January 2015 and March 2020, in whom platelet reactivity testing was performed within 10 days from stenting. Patients were divided according to validated cutoffs in acetylsalicylic acid and Clopidogrel responders and not responders. Group comparison and regression analyses were performed to identify differences between groups and outcome predictors.

RESULTS

We included in the final analysis 54 patients. Acetylsalicylic acid resistance was an independent predictor of poor 90 days outcome (OR for modified Rankin scale (mRS) ≤ 2: 0.10 95% CI: 0.02 - 0.69) whereas Clopidogrel resistance was an independent predictor of good outcome (OR for mRS ≤ 2: 7.09 95%CI: 1.33 - 37.72). Acetylsalicylic acid resistance was also associated with increased 90-days mortality (OR: 18.42; 95% CI: 1.67 - 203.14).

CONCLUSION

We found a significant association between resistance to acetylsalicylic acid and poor 90-days functional outcome and between resistance to Clopidogrel and good 90-days functional outcome. If confirmed, our results might improve pharmacological management after acute carotid stenting.

A novel purine analogue bearing nitrate ester prevents platelet activation by ROCK activity inhibition

Natural purines like ATP, ADP and adenosine have crucial roles in platelet physiology. This knowledge has been significant in drug development and today ADP receptor antagonists are widely used for prevention of thrombotic events following myocardial infarction and ischaemic stroke. Recent studies have shown that a purine analogue bearing nitrate ester group (denoted MK128) has anti-inflammatory effects probably due to its ability to donate nitric oxide (NO). However, other pharmacological mechanisms may contribute to the observed effect. The aim of the present study was to establish the anti-platelet activity and elucidate the underlying molecular mechanism(s) of the purine analogue MK128. We found that MK128 reduced aggregation and secretion induced by the thrombin receptor agonist SFLLRN and nearly abolished aggregation and secretion induced by thromboxane A2 (TxA2) and collagen receptor agonists. The inhibition took place despite blockage of the NO/cGMP signalling system. Furthermore, interaction between MK128 and platelet purinergic receptors did not explain the observed inhibition. Instead, we found that MK128 concentration-dependently inhibited Rho-associated kinase (ROCK), which led to decreased ROCK-dependent myosin phosphatase target subunit (MYPT)-1 phosphorylation and suppression of platelet functional responses.

Preoperative antithrombotic therapy and risk of blood transfusion and mortality following hip fracture surgery: a Danish nationwide cohort study

Hip fracture surgery is associated with high risk of bleeding and mortality. The patients often have cardiovascular comorbidity, which requires antithrombotic treatment. This study found that preoperative use of oral anticoagulants was not associated with transfusion or mortality following hip fracture surgery, whereas increased risk may exist for antiplatelet drugs.

INTRODUCTION

Hip fracture surgery is associated with high bleeding risk and mortality; however, data on operative outcomes of hip fracture patients admitted while on antithrombotic therapy is sparse. We examined if preoperative antithrombotic treatment was associated with increased use of blood transfusion and 30-day mortality following hip fracture surgery.

METHODS

Using data from the Danish Multidisciplinary Hip Fracture Registry, we identified 74,791 hip fracture surgery patients aged ≥ 65 years during 2005-2016. Exposure was treatment with non-vitamin K antagonist oral anticoagulant (NOAC), vitamin K antagonists (VKA), or antiplatelet drugs at admission for hip fracture. Outcome was blood transfusion within 7 days postsurgery and death within 30 days.

RESULTS

A 45.3% of patients received blood transfusion and 10.6% died. Current NOAC use was associated with slightly increased risk of transfusion (adjusted relative risk (aRR) 1.07, 95% confidence interval (CI) 1.01-1.14), but similar mortality risk (adjusted hazard ratio (aHR) 0.88, 95% CI 0.75-1.03) compared with non-users. The pattern remained when restricting to patients with short surgical delay (< 24 h). VKA users did not have increased risk of transfusion or mortality. The risks of transfusion (aRR 1.15 95% CI 1.12-1.18) and 30-day mortality (aHR 1.18 95% CI 1.14-1.23) were increased among antiplatelet users compared with non-users.

CONCLUSIONS

In an observational setting, neither preoperative NOAC nor VKA treatments were associated with increased risk of 30-day postoperative mortality among hip fracture patients. NOAC was associated with slightly increased risk of transfusion. Preoperative use of antiplatelet drugs was associated with increased risk of transfusion and mortality.

Relevance of Antiplatelet Therapy Duration After Stent-Assisted Coil Embolization for Unruptured Intracranial Aneurysms

BACKGROUND

The optimal duration of dual-antiplatelet therapy (DAPT) for preventing delayed thromboembolic events (DTEs) remains unclear. We aimed to determine whether longer DAPT provides improved protection against delayed DTEs.

METHODS

This retrospective cohort study included 507 stent-assisted coil embolization procedures using a single stent for unruptured intracranial aneurysms. We performed coarsened exact matching according to the duration of maintenance DAPT. DTEs were defined as any neurologic symptoms concerning the stented vascular territory and occurring at 1 month or later after the procedure. After stratification according to DAPT duration (short-term, <9 months; long-term, ≥9 months), the log-rank test and Z-analysis were performed to evaluate the efficacy of long-term DAPT for preventing DTEs.

RESULTS

Of 507 treated patients (median follow-up, 44 months), 25 (4.9%) experienced DTEs at 1 month after the procedure. Among all DTEs, 9 (1.8%) were infarctions confirmed on magnetic resonance imaging. Permanent neurologic deficit (modified Rankin Scale score ≥2) occurred in 2 (0.4%) patients. On procedure-to-event analysis, long-term DAPT was not superior for preventing DTEs. Most events occurred within 1 month of switching from DAPT to single-antiplatelet therapy, regardless of DAPT duration. The longest time from the procedure to DTE occurrence was 22 months. Age older than 54.5 years was identified as independent risk factor for DTE-stroke.

CONCLUSIONS

Compared with short-term DAPT, long-term DAPT delays the occurrence of DTEs but does not lower their incidence. Longer-term DAPT (>9 months) should be considered after stent-assisted coil embolization for unruptured intracranial aneurysms, although its efficacy remains to be clarified.

Anti Xa oral anticoagulants inhibit in vivo platelet activation by modulating glycoprotein VI shedding

Anti Xa non-vitamin K oral anticoagulants (anti Xa NOACs) seem to possess antiplatelet effect in vitro, but it is unclear if this occurs also in vivo. Aim of the study was to compare the effect on platelet activation of two anti Xa NOACs, namely apixaban and rivaroxaban, to warfarin, and to investigate the potential underlying mechanism by evaluating soluble glycoprotein GPVI (sGPVI), a protein involved in platelet activation. We performed a cross-sectional including AF patients treated with warfarin (n=30), or apixaban 10mg/day (n=40), or rivaroxaban 20mg/day (n=40). Patients were balanced for sex, age and cardiovascular risk factors. Platelet activation by urinary excretion of 11-dehydro-thromboxane (Tx) B₂ and soluble GPVI (sGPVI) were analysed at baseline and after 3 months of treatment. Baseline TxB₂ value was 155.2±42.7ng/mg creatinine. The 3 months-variation of urinary excretion of TxB₂ was -6.5% with warfarin (p=0.197), -29% with apixaban (p<0.001) and -31% with rivaroxaban (p<0.001). Use of anti Xa NOACs was independently associated to the variation of urinary TxB₂ (B: -0.469, p<0.001), after adjustment for clinical characteristics; sGPVI was significantly lower in patients treated with NOACs at 3 months (p<0.001), while only a trend for the warfarin group (p=0.116) was observed. The variation of sGPVI was correlated with that of TxB₂ in the NOACs group (Rs: 0.527, p<0.001). In 15 patients (5 per each group) platelet recruitment was significantly lowered at 3 months by NOACs (p<0.001), but not by warfarin. The study provides evidence that anti Xa NOACs significantly inhibit urinary TxB₂ excretion compared to warfarin, suggesting that NOACs possess antiplatelet property.

High On-Treatment Platelet Reactivity in Peripheral Arterial Disease: A Pilot Study to Find the Optimal Test and Cut Off Values

OBJECTIVE

Restenosis and stent thrombosis after endovascular intervention in patients with peripheral arterial disease (PAD) can potentially be tackled by more intensive antiplatelet therapy, such as dual antiplatelet therapy (DAPT) consisting of aspirin and P2Y12 inhibitor. Despite clopidogrel treatment, some patients still display high platelet reactivity (HCPR). Tailored antiplatelet therapy, based on platelet reactivity testing, might overcome HCPR. However, more data are warranted regarding the proportion of patients with HCPR in the PAD population, different platelet reactivity tests, their correlation, and the optimal timing for these tests as a stepping stone for a future trial investigating the potential benefit of tailored antiplatelet therapy in PAD patients.

METHODS

Thirty patients on DAPT after percutaneous transluminal angioplasty underwent platelet reactivity testing by VerifyNow, vasodilator-stimulated phosphoprotein (VASP) and platelet activation assay, and CYP2C19-polymorphism testing.

RESULTS

The proportion of patients with HCPR measured by VerifyNow varied between 43.3% and 83.3%, depending on the cut off values used. Testing within 24 hours of initiation of DAPT gave a higher proportion of HCPR than testing after more than 24 hours. According to DNA testing, 14.8% were CYP2C19*2 homozygote, 22.2% heterozygote, and 63% CYP2C19*2 negative. VASP assay revealed 24% HCPR. The highest HCPR rate was found with a VerifyNow cut off of less than 40% inhibition, whereas the lowest HCPR rate was found with the VASP assay. There was a low correlation between the tests.

CONCLUSION

HCPR is present in PAD patients and research on HCPR is needed in this population; timing of tests is relevant and standardisation of tests is needed. The optimal conditions for platelet function testing should be determined.

YY-39, a tick anti-thrombosis peptide containing RGD domain

Ticks are obligatory blood feeding ectoparasites, which continuously attach to their hosts for 1-2 weeks. There are many biologically active compounds in tick salivary glands interfering host haemostatic system and to successfully obtain blood meal. Several platelet aggregation inhibitors have been identified from ticks. A family of conserved peptides, which were identified from transcriptome analysis of many tick salivary glands, were found to contain unique primary structure including predicted mature peptides of 39-47 amino acid residues in length and a Pro/Glu(P/E)-Pro/His(P/H)-Lys-Gly-Asp(RGD) domain. Given their unique structure and RGD domain, they are considered a novel family of disintegrins that inhibit platelet aggregation. One of them (YY-39) was tested for its effects on platelets and thrombosis in vivo. YY-39 was found effectively to inhibit platelet aggregation induced by adenosine diphosphate (ADP), thrombin and thromboxane A2 (TXA2). Furthermore, YY-39 blocked platelet adhesion to soluble collagen and bound to purified GPIIb/IIIa in a dose-dependent manner. In in vivo experiments, YY-39 reduced thrombus weight effectively in a rat arteriovenous shunt model and inhibited thrombosis in a carrageenan-induced mouse tail thrombosis model. Combined with their prevalence in ticks and platelet inhibitory functions, this family of peptides might be conserved tick anti-haemostatic molecules.

A potent anti-thrombosis peptide (vasotab TY) from horsefly salivary glands

Vasotab TY is a KGD (Lys-Gly-Asp)-containing peptide identified from salivary glands of the horsefly of Tabanus yao. We have previously reported that vasotab TY showed a strong vasodilator activity. In the present study, vasotab TY was found to inhibit platelet aggregation effectively. It completely inhibited platelet aggregation induced by adenosine diphosphate (ADP) at the concentration of 9.6μg/ml. Vasotab TY significantly reduced thrombus weight in rat arteriovenous shunt model and inhibited thrombosis in carrageenan-induced mouse tail thrombosis model in vivo. Vasotab TY competitively bound to glycoprotein IIb/IIIa (GPIIb/IIIa) with eptifibatide, a well-known KGD-containing cyclic heptapeptide containing high specificity and high affinity for GPIIb/IIIa, suggesting that it is an antagonist of the fibrinogen receptor GPIIb/IIIa on the surface of platelet. The KGD motif in vasotab TY may facilitate the binding of it to GPIIb/IIIa. Vasotab TY showed a half-life of more than 1h in vivo. It showed little side effects including little bleeding, no hemolytic activity on human blood red cells and no cytotoxicity on human keratinocyte and THP-1 cells. Combined its vasodilator and platelet inhibitory functions, vasotab TY might be an excellent candidate for the development of clinical anti-thrombosis medicines.

Combining antiplatelet and antithrombotic therapy (triple therapy): what are the risks and benefits?

Most patients with mechanical heart valves and many patients with atrial fibrillation will require long-term anticoagulation therapy. For patients with mechanical prosthetic valves, only warfarin is indicated. However, for patients with nonvalvular atrial fibrillation who are at increased risk for embolic stroke, one of the newer antithrombotic medications, such as rivaroxaban, dabigatran, and apixaban, also can be used. Patients with indications for antithrombotic therapy often will have coexisting vascular disease, such as coronary artery disease, requiring concomitant antiplatelet therapy with aspirin alone or more commonly with a dual antiplatelet regimen, aspirin and clopidogrel, or prasugrel or ticagrelor. The risks and benefits of this approach are still not well defined, and current guidelines have included recommendations based primarily on expert opinion.