Abstract
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.
Keywords
extracellular vesicles - clopidogrel - nitrate - nitrite - nitric oxide