Department of Emergency and Disaster Medicine, Gifu University Graduate School of Medicine, Gifu, Japan.
Int J Mol Med. 2013 Jun;31(6):1291-7. doi: 10.3892/ijmm.2013.1345. Epub 2013 Apr 11.
It has been shown that thrombopoietin (TPO) amplifies agonist-induced platelet activation. However, the precise mechanism of action of TPO has not yet been fully elucidated. We have previously reported that the adenosine diphosphate (ADP)‑induced phosphorylation of heat shock protein 27 (HSP27) via the p38 mitogen-activated protein (MAP) kinase pathway correlates with the ADP-induced platelet-derived growth factor (PDGF)-AB secretion and the release of soluble CD40 ligand (sCD40L) from human platelets. In the present study, we investigated the effects of TPO on platelet activation induced by ADP. We examined the effects of TPO on ADP-induced platelet activation under different treatments: TPO was administered 15 min prior to stimulation with ADP (pre-treatment); TPO and ADP were simultaneously administered (simultaneous treatment); and TPO was administered 2 min following stimulation with ADP (post-treatment). TPO, which alone had no effect on platelet aggregation, synergistically enhanced the ADP (1 mM)-induced platelet aggregation only when it was administered prior to stimulation with ADP. Pre-treatment with TPO significantly increased the secretion of PDGF-AB and the release of sCD40L, and markedly enhanced the ADP-induced phosphorylation of p38 MAP kinase and HSP27 in the platelets. However, simultaneous treatment with TPO or TPO post-treatment failed to affect the ADP-induced platelet aggregation, the secretion of PDGF-AB, the release of sCD40L and the phosphorylation p38 MAP kinase or HSP27. These results strongly suggest that pre-treatment with TPO significantly amplifies ADP-induced HSP27 phosphorylation via the p38 MAP kinase pathway in human platelets.
已证实，血小板生成素（TPO）可放大激动剂诱导的血小板激活。然而，TPO 的确切作用机制尚未完全阐明。我们之前曾报道，通过 p38 丝裂原激活蛋白（MAP）激酶途径，二磷酸腺苷（ADP）诱导的热休克蛋白 27（HSP27）磷酸化与 ADP 诱导的血小板衍生生长因子（PDGF）-AB 分泌和人血小板中可溶性 CD40 配体（sCD40L）的释放相关。在本研究中，我们研究了 TPO 对 ADP 诱导的血小板激活的影响。我们在不同处理条件下检查了 TPO 对 ADP 诱导的血小板激活的影响：在刺激 ADP 前 15 分钟给予 TPO（预处理）；TPO 和 ADP 同时给予（同时处理）；以及在刺激 ADP 后 2 分钟给予 TPO（后处理）。TPO 单独对血小板聚集没有影响，但仅当在刺激 ADP 前给予 TPO 时，TPO 才可协同增强 ADP（1mM）诱导的血小板聚集。TPO 预处理可显著增加 PDGF-AB 的分泌和 sCD40L 的释放，并显著增强 ADP 诱导的血小板中 p38 MAP 激酶和 HSP27 的磷酸化。然而，TPO 同时处理或 TPO 后处理均不能影响 ADP 诱导的血小板聚集、PDGF-AB 的分泌、sCD40L 的释放以及 p38 MAP 激酶或 HSP27 的磷酸化。这些结果强烈表明，TPO 预处理可通过人血小板中的 p38 MAP 激酶途径显著放大 ADP 诱导的 HSP27 磷酸化。
