Reduction of cAMP and cGMP inhibitory effects in human platelets by MRP4-mediated transport
Reduction of cAMP and cGMP inhibitory effects in human platelets by MRP4-mediated transport
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DOI：
10.1160/th12-04-0232
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发表时间：
2012-11-01
影响因子：
6.7
通讯作者：
Pulcinelli, Fabio Maria
中科院分区：
文献类型：
--
作者：
Borgognone, Alessandra;Pulcinelli, Fabio Maria
环核苷酸依赖性血小板抑制是限制血栓形成的最重要的生理途径。血小板cAMP和cGMP增加是内皮细胞产生前列环素和一氧化氮的结果，分别通过PKA和PKG起作用。血小板中环核苷酸的胞浆浓度受AC和gc依赖性合成和pde依赖性降解的调节。在一些细胞中，环核苷酸也通过mrp4 /5/8依赖性外排被消除。由于只有MRP4在血小板中以致密颗粒的高水平表达，我们确定了其在血小板细胞质中消除环核苷酸的作用。我们研究了MRP4抑制对血小板cAMP/cGMP效应的影响。cAMP和cgmp升高剂对血小板聚集的环核苷酸抑制作用被MRP4抑制强烈增强，共同底物VASP的环核苷酸依赖性磷酸化也是如此。MRP4抑制降低了血小板颗粒中的cAMP浓度，cAMP和cGMP都与MRP4的既定底物（fluo-cAMP）竞争进入颗粒。在这里，我们提供了MRP4介导的环核苷酸转运作为其在人血小板中消除的生理机制的一部分的第一个证据，这可能代表了增加环核苷酸依赖性抑制的新靶点。
Cyclic nucleotide-dependent inhibition of platelets represents the most important physiological way to limit thrombus formation. cAMP and cGMP increase in platelets as a consequence of prostacyclin and nitric oxide production by endothelial cells and act through PKA and PKG, respectively. The cytosolic concentration of cyclic nucleotides in platelets is regulated by AC- and GC-dependent synthesis and PDE-dependent degradation. In some cells cyclic nucleotides are eliminated also through MRP4/5/8-dependent efflux. As only MRP4 is expressed in platelets, at high levels in dense granules, we determined its role in the elimination of cyclic nucleotides from platelet cytosol. We studied the effects of MRP4 inhibition on cAMP/cGMP effects in platelets. Cyclic nucleotide inhibitory effects triggered by cAMP and cGMP-elevating agents on platelet aggregation are strongly enhanced by MRP4 inhibition and so is cyclic nucleotide-dependent phosphorylation of the common substrate VASP. MRP4 inhibition decreases cAMP concentration in platelet granules and both cAMP and cGMP compete with an established substrate of MRP4 (fluo-cAMP) for entrance in granules. Here we provide the first evidence of the transport of cyclic nucleotides mediated by MRP4 as part of their physiological mechanism of elimination in human platelets, which might represent a novel target to increase cyclic nucleotide-dependent inhibition.