The Antiplatelet Aggregation Effects Of Nitric Oxide-releasing Aspirin

Objective: Excessive accumulation of platelets at sites ofatherosclerotic plaque is a crucial pathogenic event that isresponsible for the development of the acute coronarysyndromes, stroke and the ischaemic complications ofperipheral vascular disease. Progress in the understanding of thecentral importance of platelets in cardiovascular and strokedisease, combined with the development of new classes ofantiplatelet agents, has dramatically altered the landscape interms of the clinical management of vascular disease. Untilrecently, aspirin was the only antiplatelet agent in widespreadclinical use for cardiovascular disease. The mechanism throughwhich ASA produces these beneficial effects is related to itsability to irreversibly inhibit thromboxane production by platelet.There is convincing evidence for the efficacy of aspirin inlong-term prophylaxis of myocardial infarction and stroke. But,long-term inhibition of this regulatory pathway by aspirinwouldhave an increased risk of serious gastrointestinal complications,such as bleeding, perforation, or other adverse events resultingin hospitalization or death. Following with the development ofnew classes of antiplatelet agents, ADP-raceptorantagonists andphosphodiesterase(PDE) inhibitors are increasingly recognizedas important therapeutic options in high risk patientpopulations.The recent emergence of antagonists of theglycoprotein(GP) GPIIb-IIIa has heralded a new era inantiplatelet therapy and provided clinical confirmation of theimportmance of platelets in cardiovascular and strokedisease.Nitric oxide-releasing aspirins are new chemical entitiesobtained by adding a nitric oxide-releasing moiety to aspirin.NCX-4016 is the prototype of this family of molecules. Bothaspirin and nitric oxide moieties of NCX-4016 contribute to itseffectiveness, the latter occurring via both cyclic guanosylmonophosphate-dependent and -independent mechanisms. Invitro studies have shown that NCX-4016 inhibits plateletaggregation induced by aspirin-sensitive (arachidonic acid) andaspirin-insensitive (thrombin) agonist. In contrast to aspirin,NCX-4016 exerts a multilevel regulation of inflammatory target,including caspase-1 and NF-kB. This broad spectrum ofactivities translates to an increased potency of this drug inmodulating cardiovascular inflammation. Animal and Humanstudies have shown, that while nitric oxide-aspirin maintains itsanti-thrombotic activity, it spares the gastrointestinal tract.Indeed, a 7-day course of NCX-4016 results in 90% reduction ofgastric damage caused by equimolar doses of aspirin.BPI-1095,BPI-1096 is an kind of nitric oxide-releasing aspirinwith new type of substitution radical. The difference with othersis that it can perform its organism action and undemond ofesterase hydrolysis. So it can releasing NO molecul effectivelyand did not interference with aspirin's effectiveness.The aim ofthe present study was to test the antiplatelet active of BPI-1095and BPI-1096 by estimate the platelet antiaggregating inducedby arachidonic acid, adnephrin,restocetin, ADP,and PAF in vitro.Methods: venous blood samples(40ml) were collectedfrom healthy adult volunteers who had not previously beentaking any drugs for at least 3 weeks. 3.8% Sodium citrate wasused as anticoagulation .PRP was obtained by low speedcentrifugation(1000g for 10 minut) at room temperature. Therest of blood samples was centrifugated(3000g for 10 minut) forPPP at room temperature. Platelaet was counted using oxalicacid ammonia assay. A final concentration of 250~300×109platelet/L was obtained by dilution by PPP. Platelet aggregationwas estimated by a standard nephelometric technique in wich300ul of platelet suspension were incubated at 370C in afour-channel aggregometer. The antiaggregant effects ofBPI-1095 and BPI-1096 were tested incubating the drug withplatelet at 370C for 10minut before the addition of the agonist.For comparison ,we also tested the antiaggregant effects ofaspirin and DMSO. The cells were kept at room temperature andused withen 2 hours.Results: 1 Ris-induced aggregation of platelet wasinhibited by BPI-1096 at concentration 20 and 50uM, but didnot affect the platelet aggregation at concentration 150uM.Atconcentration 20 and 50uM BPI-1096 displayed inhibitoryeffects similar to ASA,while at concentration 150uM hadsignificantly less effects than ASA.BPI-1095 did not have anyeffects on platelet aggregation in every concentration. 2BPI-1096 inhibited adnephrin-induced platelet aggregation atconcentration 50 and 150uM, but did not affect the plateletaggregation at concentration 20uM.At concentration 20 and50uM BPI-1096 displayed inhibitory effects similar toASA,while at concentration 150uM had significantly less effectsthan ASA.BPI-1095 just inhibited adnephrin-induced plateletaggregation at concentration 50uM. 3 BPI-1096 inhibitedPAF-induced platelet aggregation at concentration 20 and150uM, but did not affect the platelet aggregation atconcentration 50uM.At every concentration BPI-1096 displayedinhibitory effects similar to ASA.BPI-1095 did not have anyeffects on platelet aggregation in every concentration. 4BPI-1096 inhibited ADP-induced platelet aggregation at everyconcentration and displayed similary inhibitory effects to ASA.BPI-1095 did not have any effects on platelet aggregation inevery concentration. 5 BPI-1095 and BPI-1096 did not showany effects on platelet aggregation induced by AA in everyconcentration. At 20 and 50uM concentration of BPI-1096 havethe same inhibitory efficiency as ASA while showed significientless inhibitory efficiency than ASA.Conclusion: 1 BPI-1096 can inhibit each inducer inducedplatelet aggregation at every concentration.2 BPI-1096 did notshow stronger inhibitory effect as more as the increased...