Role of inorganic nitrate and nitrite in driving nitric oxide-GMP-mediated inhibition of platelet aggregation in vitro and in vivo
Role of inorganic nitrate and nitrite in driving nitric oxide-GMP-mediated inhibition of platelet aggregation in vitro and in vivo
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DOI：
10.1111/jth.12711
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发表时间：
2014-11-01
影响因子：
10.4
通讯作者：
Emerson, M.
中科院分区：
文献类型：
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作者：
Apostoli, G. L.;Solomon, A.;Emerson, M.
背景一氧化氮(Nitric Oxide，NO)是一种重要的血小板负性调节因子，参与血栓性疾病的病理过程。血小板产生一氧化氮，但一氧化氮合酶(NOS)在血小板中的存在及其功能意义尚不清楚。无机硝酸盐/亚硝酸盐被认为是生物活性NO的一种来源，尽管它在健康和血管功能障碍中对血小板的调节作用尚不完全清楚。方法采用已建立的评估体内和体外血小板聚集的方法，研究了NO-cGMP信号事件在血小板中的功能意义和上游来源，并评估了内皮型一氧化氮合酶(ENOS)缺乏时无机硝酸盐向亚硝酸盐的生物转化。结果磷酸二酯酶5(PDE5)抑制剂西地那非体外抑制人血小板聚集。这种抑制作用可被鸟苷酸环化酶抑制剂和NO清除剂消除，但不受NOS抑制的影响。与野生型小鼠相比，体内血栓栓塞型放射性标记小鼠的血小板聚集与血浆亚硝酸盐浓度升高相关。结论与野生型小鼠相比，血小板在NO下游产生短暂的内源性cGMP信号，这种信号主要独立于一氧化氮合酶，并可通过抑制PDE5而增强。此外，亚硝酸盐可以在血小板内产生瞬时的NO-cGMP信号。体内注射硝酸盐后，内皮型一氧化氮合酶的缺失导致血浆亚硝酸盐水平升高，对血小板功能产生负面影响。我们的数据表明，无机硝酸盐在eNOS缺乏时发挥抗血小板作用，并且，潜在地，饮食硝酸盐可能减少内皮功能障碍时的血小板过度活动。
BackgroundNitric oxide (NO) is a critical negative regulator of platelets that is implicated in the pathology of thrombotic diseases. Platelets generate NO, but the presence and functional significance of NO synthase (NOS) in platelets is unclear. Inorganic nitrate/nitrite is increasingly being recognized as a source of bioactive NO, although its role in modulating platelets during health and vascular dysfunction is incompletely understood.MethodsWe investigated the functional significance and upstream sources of NO-cGMP signaling events in platelets by using established methods for assessing invitro and invivo platelet aggregation, and assessed the bioconversion of inorganic nitrate to nitrite during deficiency of endothelial NOS (eNOS).ResultsThe phosphodiesterase5 (PDE5) inhibitor sildenafil inhibited human platelet aggregation invitro. This inhibitory effect was abolished by a guanylyl cyclase inhibitor and NO scavengers, but unaffected by NOS inhibition. Inorganic nitrite drove cGMP-mediated inhibition of human platelet aggregation invitro and nitrate inhibited platelet function in eNOS(-/-) mice invivo in a model of thromboembolic radiolabeled platelet aggregation associated with an enhanced plasma nitrite concentration as compared with wild-type mice.ConclusionsPlatelets generate transient, endogenous cGMP signals downstream of NO that are primarily independent of NOS and may be enhanced by inhibition of PDE5. Furthermore, nitrite can generate transient NO-cGMP signals in platelets. The absence of eNOS leads to enhanced plasma nitrite levels following nitrate administration invivo, which negatively impacts on platelet function. Our data suggest that inorganic nitrate exerts an antiplatelet effect during eNOS deficiency, and, potentially, that dietary nitrate may reduce platelet hyperactivity during endothelial dysfunction.