Division of Pediatric Hematology, Taichung Veterans General Hospital, No.160, Sec.3, Chung-Kang Rd., Taichung City 40705, Taiwan.
Thromb Res. 2010 Oct;126(4):311-8. doi: 10.1016/j.thromres.2010.06.023. Epub 2010 Aug 13.
The pathogenesis of childhood chronic immune thrombocytopenic purpura (ITP) is mainly mediated by antiplatelet autoantibodies, which have been shown to induce platelet apoptosis in murine models. Decreased CXCR4 expression, which can regulate apoptotic pathway, has been described in platelet disorders. The present study aims to determine whether platelet apoptosis is increased in pediatric patients with chronic ITP and whether there is any involvement of the CXCR4 chemokines axis. Twenty-one patients and 12 controls were studied. Using flow cytometry, we investigated apoptotic markers of platelets including annexin V, caspase 3, and mitochondrial inner transmembrane potential depolarization. The percentage of the platelets with apoptosis-positive markers was not increased in chronic ITP patients. CXCR4 expression was higher in the patients as detected by flow cytometric (P=0.001) and western blotting analysis (P=0.013). The results also revealed that CXCR4 downstream proteins, Akt phosphorylation was more frequent in chronic ITP patients than controls. Plasma stromal cell-derived factor 1 levels analyzed by enzyme-linked immunosorbent assay were decreased in patients (P=0.001) and inversely correlated to CXCR4 expression (r=-0.62, P<0.001). In conclusion, the study shows platelet apoptosis resistance existing in pediatric patients with chronic ITP. It may be associated with enhanced CXCR4 expression and Akt activation.
儿童慢性免疫性血小板减少性紫癜(ITP)的发病机制主要由抗血小板自身抗体介导,该抗体已被证明可在鼠模型中诱导血小板凋亡。在血小板疾病中,已经描述了 CXCR4 表达减少,其可以调节凋亡途径。本研究旨在确定儿童慢性 ITP 患者的血小板凋亡是否增加,以及 CXCR4 趋化因子轴是否有任何参与。研究了 21 名患者和 12 名对照。使用流式细胞术,我们研究了包括膜联蛋白 V、半胱天冬酶 3 和线粒体内膜电位去极化在内的血小板凋亡标志物。在慢性 ITP 患者中,未发现血小板凋亡阳性标志物的百分比增加。通过流式细胞术(P=0.001)和 Western blot 分析(P=0.013)检测到患者的 CXCR4 表达更高。结果还表明,慢性 ITP 患者的 CXCR4 下游蛋白 Akt 磷酸化比对照组更频繁。通过酶联免疫吸附试验分析的血浆基质细胞衍生因子 1 水平在患者中降低(P=0.001),并与 CXCR4 表达呈负相关(r=-0.62,P<0.001)。总之,该研究表明,儿科慢性 ITP 患者存在血小板凋亡抵抗。这可能与增强的 CXCR4 表达和 Akt 激活有关。
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