Feijge Marion A H, Ansink Karin, Vanschoonbeek Kristof, Heemskerk Johan W M
Department of Biochemistry, University of Maastricht, P.O. Box 616, Maastricht, MD 6200, The Netherlands.
Biochem Pharmacol. 2004 Apr 15;67(8):1559-67. doi: 10.1016/j.bcp.2003.12.028.
Prostaglandin-induced cAMP elevation restrains key signaling pathways in platelet activation including Ca(2+) mobilization and integrin alphaIIbbeta3 affinity regulation. We investigated how cAMP turnover by cyclic nucleotide phosphodiesterases (PDEs) regulates platelet activation. In washed human platelets, inhibition of all PDEs and also specific inhibition of PDE3 but not of PDE5 suppressed thrombin-induced Ca(2+) responses. The effect of general PDE or PDE3 inhibition was accompanied by an increase in cAMP, and potentiated by Gs stimulation with prostaglandin E(1). In platelet-rich plasma, general or PDE3 inhibition blocked platelet aggregation, integrin activation, secretion and thrombin generation. In contrast, inhibition of PDE5 increased the cGMP level, but without significant influence on aggregation, alphaIIbbeta3 activation, secretion or procoagulant activity. Nitroprusside (nitric oxide) potentiated the effect of PDE5 inhibition in elevating cGMP. Nitroprusside inhibited platelet responses, but this was accompanied by elevation of cAMP. Together, these results indicate that cAMP is persistently formed in platelets, independently of agonist-induced Gs stimulation. PDE3 thus functions to keep cAMP at a low equilibrium level and reduce the cAMP-regulated threshold for platelet activation. This crucial role of PDE3, but not of PDE5, extends to all major processes in thrombus formation: assembly of platelets into aggregates, secretion of autocrine products, and procoagulant activity.
前列腺素诱导的环磷酸腺苷（cAMP）升高可抑制血小板活化中的关键信号通路，包括钙离子动员和整合素αIIbβ3亲和力调节。我们研究了环核苷酸磷酸二酯酶（PDEs）介导的cAMP周转如何调节血小板活化。在洗涤后的人血小板中，抑制所有PDEs以及特异性抑制PDE3而非PDE5可抑制凝血酶诱导的钙离子反应。一般PDE或PDE3抑制的作用伴随着cAMP的增加，并通过前列腺素E1刺激Gs而增强。在富含血小板的血浆中，一般或PDE3抑制可阻断血小板聚集、整合素活化、分泌和凝血酶生成。相反，抑制PDE5可增加环磷酸鸟苷（cGMP）水平，但对聚集、αIIbβ3活化、分泌或促凝活性无显著影响。硝普钠（一氧化氮）增强了PDE5抑制在升高cGMP方面的作用。硝普钠抑制血小板反应，但这伴随着cAMP的升高。总之，这些结果表明血小板中持续形成cAMP，与激动剂诱导的Gs刺激无关。因此，PDE3的作用是将cAMP维持在低平衡水平，并降低cAMP调节的血小板活化阈值。PDE3而非PDE5的这一关键作用延伸至血栓形成的所有主要过程：血小板聚集成聚集体、自分泌产物的分泌以及促凝活性。
