Department of Transfusion Medicine, Huashan Hospital, Fudan University, Shanghai, China; Department of Transfusion Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Department of Transfusion Medicine, Huashan Hospital, Fudan University, Shanghai, China.
Thromb Res. 2024 Aug;240:109056. doi: 10.1016/j.thromres.2024.109056. Epub 2024 May 31.
Platelet apoptosis is irreversible under current storage conditions in blood banks. Studies have shown that programmed cell death ligand 1 (PD-L1) in tumour cells is required for neoplastic progression, tumour recurrence and metastasis by regulating apoptosis. However, whether PD-L1 is involved in storage-induced apoptosis in platelets remains poorly understood. In this study, we explored whether PD-L1 on platelets participated in the regulation of storage-induced apoptosis under blood bank conditions, as well as the underlying mechanism. Several apoptotic events in platelets from humans and PD-L1-knockout mice during storage under blood bank conditions were measured. The mechanism by which storage-induced apoptosis was regulated by platelet-intrinsic PD-L1 signalling was further investigated. Our results showed that PD-L1 in platelets progressively decreased. There was a strong negative correlation between platelet PD-L1 expression and the phosphatidylserine (PS) externalization rate and cleaved caspase-3 level and a positive correlation with anti-apoptosis protein Bcl-xl. Ex vivo, PD-L1-/- platelets stored at 22 °C showed rapid apoptosis via an intrinsic mitochondria-dependent pathway over time. Likewise, inhibiting PD-L1 signalling with BMS-1166 accelerated apoptosis by intrinsic mitochondria-dependent pathway. Coimmunoprecipitation analysis revealed that PD-L1 could bind AKT in platelets, and the binding capacity of both showed a progressive decrease with time. Finally, the decrease in PD-L1 expression levels during storage could be attributed to a complex process of progressive secretion. Therefore, platelet PD-L1 inhibits storage-induced apoptosis by sustaining activation of the AKT signalling pathway, which is expected to become a target for alleviating platelet storage lesions (PSLs) under current blood bank conditions.
在当前血库的储存条件下，血小板凋亡是不可逆的。研究表明，肿瘤细胞中的程序性细胞死亡配体 1（PD-L1）通过调节细胞凋亡，对于肿瘤的进展、复发和转移是必需的。然而，PD-L1 是否参与血小板的储存诱导凋亡仍知之甚少。在本研究中，我们探讨了 PD-L1 是否参与了血库条件下储存诱导的血小板凋亡的调节，以及潜在的机制。测量了人类和 PD-L1 敲除小鼠血小板在血库条件下储存过程中的几种凋亡事件。进一步研究了血小板内在 PD-L1 信号调节储存诱导凋亡的机制。我们的结果表明，血小板中的 PD-L1 逐渐减少。血小板 PD-L1 表达与磷脂酰丝氨酸（PS）外翻率和裂解的 caspase-3 水平呈强烈负相关，与抗凋亡蛋白 Bcl-xl 呈正相关。在体，PD-L1-/-血小板在 22°C 储存时，通过内在的线粒体依赖性途径，随着时间的推移迅速发生凋亡。同样，用 BMS-1166 抑制 PD-L1 信号也会通过内在的线粒体依赖性途径加速凋亡。共免疫沉淀分析表明，PD-L1 可以与血小板中的 AKT 结合，两者的结合能力随时间呈逐渐下降趋势。最后，储存过程中 PD-L1 表达水平的降低可归因于一个渐进的分泌复杂过程。因此，血小板 PD-L1 通过维持 AKT 信号通路的激活来抑制储存诱导的凋亡，这有望成为缓解当前血库条件下血小板储存损伤（PSLs）的靶点。
