The effect of inorganic nitrate and antiplatelet drugs on NO metabolites and platelet reactivity in patients with stable coronary artery disease

P2Y12 antagonists are commonly prescribed in coronary artery disease (CAD) patients undergoing coronary intervention, however non-P2Y12 mediated effects have also been observed. The thienopyridine-Clopidogrel, for example, forms S-nitrosothiols (RSNO) at low pH, in the presence of nitrite in-vitro but it is unclear whether this occurs substantially in-vivo. It is unknown whether the newer class of non-thienopyridine antiplatelets(ticagrelor) has similar properties. Dietary sources of inorganic nitrate (NO3-) are also known to provide alternative pathways for NO production. This thesis investigates the effect of dietary nitrate supplement with or without clopidogrel therapy on NO metabolites and platelet inhibition in CAD patients and explores the potential role of ticagrelor in RSNO biosynthesis. In vitro studies demonstrate dietary NO3- (in the form of SIS®-Go+ and Beet-It®) gets converted to nitrite via bacterial nitrate reductase and thereby readily formed S-nitrosothiols in the simulated acidic gastric medium with and without clopidogrel. In CAD patients, dietary NO3- (SIS® Go+) along with or without clopidogrel therapy results in a significant rise in plasma nitrate, nitrite and RSNO levels. NO3- + clopidogrel therapy caused significantly more inhibition of TRAP mediated platelet activation with patients receiving clopidogrel with little change in the ADP mediated platelet inhibition, suggesting a non-ADP mediated effect due to RSNO. Concomitant PPI therapy has no effect. Importantly, Ticagrelor has the ability to form RSNO in vitro and in-vivo. RSNO increased significantly in patients following a loading dose of Ticagrelor. However, elevated RSNO are not sustained in patients receiving a maintenance dose of Ticagrelor. In conclusion, dietary NO3- therapy significantly augments RSNO level with or without clopidogrel in CAD. Ticagrelor exhibits RSNO formation in-vitro and in CAD patients. Augmented RSNO may explain the P2Y12 independent effects seen with these agents and represents a novel therapeutic approach in future management of CAD

Dietary nitrate supplementation reduces circulating platelet-derived extracellular vesicles in coronary artery disease patients on clopidogrel therapy: a randomised, double-blind, placebo-controlled study

Extracellular vesicles (EVs) are implicated in the pathogenesis of cardiovascular disease (CVD). Specifically, platelet-derived EVs are highly pro-coagulant, promoting thrombin generation and fibrin clot formation. Nitrate supplementation exerts beneficial effects in CVD, via an increase in nitric oxide (NO) bioavailability. Clopidogrel is capable of producing NO-donating compounds, such as S-nitrosothiols (RSNO) in the presence of nitrite and low pH. The aim of this study was to assess the effect of nitrate supplementation with versus without clopidogrel therapy on circulating EVs in coronary artery disease (CAD) patients. In this randomized, double-blind, placebo-controlled study, CAD patients with (n = 10) or without (n = 10) clopidogrel therapy received a dietary nitrate supplement (SiS nitrate gel) or identical placebo. NO metabolites and platelet activation were measured using ozone-based chemiluminescence and multiple electrode aggregometry. EV concentration and origin were determined using nanoparticle tracking analysis and time-resolved fluorescence. Following nitrate supplementation, plasma RSNO was elevated (4.7 ± 0.8 vs 0.2 ± 0.5 nM) and thrombin-receptor mediated platelet aggregation was reduced (−19.9 ± 6.0 vs 4.0 ± 6.4 U) only in the clopidogrel group compared with placebo. Circulating EVs were significantly reduced in this group (−1.183e11 ± 3.15e10 vs −9.93e9 ± 1.84e10 EVs/mL), specifically the proportion of CD41+ EVs (−2,120 ± 728 vs 235 ± 436 RFU [relative fluorescence unit]) compared with placebo. In vitro experiments demonstrated clopidogrel–SNO can reduce platelet-EV directly (6.209e10 ± 4.074e9 vs 3.94e11 ±  1.91e10 EVs/mL). In conclusion, nitrate supplementation reduces platelet-derived EVs in CAD patients on clopidogrel therapy, increasing patient responsiveness to clopidogrel. Nitrate supplementation may represent a novel approach to moderating the risk of thrombus formation in CAD patients

Early Clinical Experience with a Polymer-Free Biolimus A9 Drug-Coated Stent in DES-Type Patients Who Are Poor Candidates for Prolonged Dual Anti-Platelet Therapy.

INTRODUCTION:Prolonged dual anti-platelet therapy (DAPT) may cause excess bleeding in certain patients. The biolimus-A9 drug-coated stent (BA9-DCS) has a rapid drug-elution profile allowing shortened DAPT. Data were gathered on the early experience implanting this stent in drug-eluting stent eligible patients deemed to be at high risk of bleeding. BACKGROUND AND METHODS:The demographics, procedural data and clinical outcomes were gathered prospectively for 249 patients treated with a BA9-DCS stent at 2 UK centres, and compared to a cohort of patients treated in the same period with drug-eluting stents (PCI-DES). RESULTS:Operator-defined BA9-DCS indications included warfarin therapy, age, and anaemia. Patients receiving a BA9-DCS were older (71.6±11.8 vs. 64.8±11.6yrs, p<0.001), more often female (38.2 vs. 26.8%, P<0.001), and more likely to have comorbidity including chronic kidney disease or poor LV function than PCI-DES patients. The baseline Mehran bleed risk score was also significantly higher in the BA9-DCS group (19.4±8.7 vs. 13.1±5.8, p<0.001). Of the BA9-DCS cohort, 95.5% of patients demonstrated disease fitting NICE criteria for DES placement. The number of lesions treated (1.81±1.1 vs. 1.58±0.92, p = 0.003), total lesion length (32.1±21.7 vs. 26.1±17.6mm, p<0.001), number of stents used (1.93±1.11 vs. 1.65±1.4, p = 0.007) and total stent length (37.5±20.8 vs. 32.4±20.3, p<0.01) were greater for BA9-DCS patients. DAPT was prescribed for 3.3±3.9 months for BA9-DCS patients and 11.3±2.4 months for PCI-DES patients (p<0.001). At follow up of 392±124 days despite the abbreviated DAPT course stent related event were infrequent with ischemia-driven restenosis PCI (2.8 vs. 3.4%, p = 0.838), and stent thrombosis (1.6 vs. 2.1%, p = 0.265) rates similar between the BA9-DCS ad PCI-DES groups. After propensity scoring all clinical end-points were similar between both cohorts. CONCLUSIONS:This early experience using polymer-free BA9 drug-coated stents in drug-eluting stent type patients at risk of bleeding are encouraging. Further studies are warranted

Baseline demographics of patients treated with a BA9 drug-coated stent vs. PCI-DES population.

<p>Baseline demographics of patients treated with a BA9 drug-coated stent vs. PCI-DES population.</p

Adjusted clinical outcomes after propensity scoring in patients treated with a BA9 drug-coated stent vs. PCI-DES population.

<p>Adjusted clinical outcomes after propensity scoring in patients treated with a BA9 drug-coated stent vs. PCI-DES population.</p

Procedural data for patients treated with a BA9 drug-coated stent vs. PCI-DES population.

<p>Procedural data for patients treated with a BA9 drug-coated stent vs. PCI-DES population.</p