抗血小板成分KW-7之作用機轉探討

The Action Mechanism of An Antiplatelet Compound, KW-7

王薇雅(Wei-Ya Wang)

指導教授 ： 吳志中 ； 吳永昌

高雄醫學大學/藥學院/天然藥物研究所碩士班/碩士(2003年)

摘要

在本研究中，我們針對40個新合成且具有benzylisoquinoline化學結構衍生物進行抗血小板凝集活性篩選的試驗，其中以8,9-dimethoxyl-1-(4-methoxy-phenyl)-5,6-dihydro-pyrrolo [2,1-a] isoquinoline-2,3-dione (KW-7)具有最強效的抗血小板凝集活性，我們乃進一步探討KW-7抗血小板凝集的作用機轉。在兔子血小板懸浮液中，KW-7以濃度有關的方式抑制由arachidonic acid (100 μM)、collagen (10 μg/ml)、thrombin (0.1 U/ml)及PAF (1 ng/ml) 所引起的血小板凝集，其抑制凝集反應的IC50值分別依序為10.4 ± 0.1 μM，10.9 ± 2.0 μM，32.7 ± 0.4 μM，及32.9 ± 1.8 μM。此外，KW-7對於已經形成的血小板凝集塊，也能明顯的引起去凝集作用。KW-7可以抑制上述血小板刺激劑引發之thromboxane A2的形成，以及細胞內鈣離子上升作用。在完整的血小板中，KW-7可以分別增加cAMP與cGMP含量，其cAMP增加的含量大於cGMP所增加的含量。當KW-7 (10 μM)與PGE1 (1 μM)或SNP (1 μM)共置時，可協同增進PGE1或SNP的效果使cAMP與cGMP含量上升。而KW-7 (10 μM)與IBMX (100 μM)共置時，發現並不會對血小板內的cyclic nucleotides有進一步促進的現象。在兔子血小板均質液中，KW-7 (1-50 μM)以濃度有關的方式抑制cAMP phosphodiesterase 與cGMP phosphodiesterase的活性，其IC50分別為7.8 ± 0.8 μM 與14.5 ± 5.1 μM。SQ22536 (80 μM)可完全抑制KW-7引起之血小板cAMP 含量增加作用，並明顯逆轉其血小板凝集抑制作用。 反之，ODQ (2 μM)雖可完全抑制KW-7引起之血小板cGMP 含量增加，卻不能影響KW-7的抗血小板凝集作用。由上述結果顯示，KW-7為一新型之cyclic nucleotide phosphodiesterase抑制劑，且其抗血小板凝集作用主要來自提高血小板cAMP 含量，繼而抑制血小板的凝集作用。

關鍵字

血小板 ； 磷酯脢抑制劑 ； 抗血小板凝集

並列摘要

In the search of new antiplatelet agents, forty newly synthetic benzylisoquinoline derivatives were tested for antiplatelet activities. Among them, 8,9-dimethoxyl-1-(4-methoxy-phenyl)-5,6-dihydro-pyrrolo- [2,1-a] isoquinoline-2,3-dione (KW-7) showed the most potent inhibitory effect on platelet aggregation elicited by various platelet stimulators. In the present study, the mechanism of action of KW-7 was further investigated. KW-7 concentration- dependently inhibited platelet aggregation caused by arachidonic acid (100 μM), collagen (10 μg/ml), thrombin (0.1 U/ml) and PAF (1 ng/ml) with IC50 values of 10.4 ± 0.1 μM, 10.9 ± 2.0 μM, 32.7 ± 0.4 μM, and 32.9 ± 1.8 μM, respectively. Also, addition of KW-7 to platelets that had been aggregated caused a rapid disaggregation. KW-7 prevented intracellular calcium mobilization and thromboxane formation elicited by the inducers. KW-7 alone induced a substantial increase in cAMP levels and a less increase in GMP levels in platelets. Moreover, KW-7 potentiated the antiaggregatory effect of prostaglandin E1 and sodium nitroprusside associated with elevating of platelet cAMP and cGMP levels. In contrast, the combination of KW-7 and IBMX had no additional effects on platelet cyclic nucleotide levels. In platelet homogenates, KW-7 inhibited both cAMP- and cGMP- phosphodiesterase in a concentration- dependent manner with IC50 values of 7.8 ± 0.8 μM and 14.5 ± 5.1 μM, respectively. The antiplatelet effect of KW-7 was reversed by SQ22536 (80 μM) and H89 (20 μM) but not by ODQ (2 μM). These data indicate that KW-7 is an inhibitor of phosphodiesterase and its antiplatelet effect is mainly mediated by elevation of cAMP levels.

並列關鍵字

blood platelets ； phosphodiesterase inhibitor ； antiplatelets ； cAMP/ cGMP

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