Takahashi Shinichi, Ushida Miho, Komine Risa, Shimodaira Aya, Uchida Toshihiro, Ishihara Hiroaki, Shibano Toshiro, Watanabe Gentaro, Ikeda Yasuo, Murata Mitsuru
The Keio-Daiichi Project on Genetics of Thrombosis, Keio University, Tokyo 160-8582, Japan.
Thromb Res. 2008;121(4):509-17. doi: 10.1016/j.thromres.2007.05.017. Epub 2007 Jul 13.
Aspirin's inhibitory effect on platelet function has been shown to be highly heterogeneous. However, due to the considerable individual variation in pharmacokinetics after aspirin intake, it has been difficult to investigate the mechanism of aspirin resistance empirically. Our objective was to examine whether platelet responsiveness to in vitro aspirin treatment could be affected by cyclooxygenase (COX)-1/2 protein levels in platelets or single-nucleotide polymorphisms (SNPs), which could possibly change specific activity of enzymes and/or aspirin susceptibility. Collagen/epinephrine closure time (CEPI-CT) of PFA-100 in blood from 178 healthy males was assessed with/without aspirin. Platelet COX-1 protein levels and the sequences of COX-1 gene exons were examined in three groups categorized by CEPI-CT: PR (Poor responders to aspirin), 10 people showing the shortest CEPI-CT under aspirin; GR-High or GR-Low (good responders to aspirin with high or low platelet basal reactivity), 10 people showing CEPI-CT over 300 s under aspirin and having the shortest or longest basal CEPI-CT, respectively. We analyzed the three groups, representing phenotypic extremes, aiming to increase statistical power to investigate the possible relevance of COXs to platelet response to aspirin. Western blot analysis revealed that COX-1 was abundantly expressed in platelets at comparable levels among the three groups, whereas COX-2 was undetectable. The frequencies of nonsynonymous COX-1/2 SNPs were unlikely to explain the difference in aspirin responsiveness considering the observed genotype frequencies and wide individual variation in platelet response. These results suggest that heterogeneity in platelet responsiveness to in vitro aspirin is independent of COX-1/2 protein levels and SNPs.
阿司匹林对血小板功能的抑制作用已被证明具有高度异质性。然而，由于服用阿司匹林后药代动力学存在相当大的个体差异，很难通过实证研究阿司匹林抵抗的机制。我们的目的是研究血小板对体外阿司匹林治疗的反应性是否会受到血小板中环氧化酶（COX）-1/2蛋白水平或单核苷酸多态性（SNP）的影响，这些因素可能会改变酶的比活性和/或阿司匹林敏感性。对178名健康男性血液中PFA-100的胶原/肾上腺素封闭时间（CEPI-CT）在有/无阿司匹林的情况下进行了评估。根据CEPI-CT将三组人群的血小板COX-1蛋白水平和COX-1基因外显子序列进行了检测：PR组（阿司匹林反应不佳者），10人在服用阿司匹林时CEPI-CT最短；GR-High或GR-Low组（血小板基础反应性高或低的阿司匹林反应良好者），10人在服用阿司匹林时CEPI-CT超过300秒，且基础CEPI-CT分别最短或最长。我们分析了这三组代表表型极端的人群，旨在提高统计效力以研究COX与血小板对阿司匹林反应的可能相关性。蛋白质印迹分析显示，COX-1在血小板中大量表达，三组水平相当，而COX-2未检测到。考虑到观察到的基因型频率和血小板反应的广泛个体差异，非同义COX-1/2 SNP的频率不太可能解释阿司匹林反应性的差异。这些结果表明，血小板对体外阿司匹林反应的异质性与COX-1/2蛋白水平和SNP无关。
