Red Blood Cell Research Group, Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, CH-8057 Zurich, Switzerland.
Department of Medical Oncology and Hematology, University Hospital and University of Zurich, CH-8091 Zurich, Switzerland.
Cells. 2024 Aug 16;13(16):1363. doi: 10.3390/cells13161363.
Density reversal of senescent red blood cells has been known for a long time, yet the identity of the candidate ion transporter(s) causing the senescent cells to swell is still elusive. While performing fractionation of RBCs from healthy individuals in Percoll density gradient and characterization of the separated fractions, we identified a subpopulation of cells in low-density fraction (1.02% ± 0.47) showing signs of senescence such as loss of membrane surface area associated with a reduction in band 3 protein abundance, and Phosphatidylserine (PS) exposure to the outer membrane. In addition, we found that these cells are overloaded with Na and Ca. Using a combination of blockers and activators of ion pumps and channels, we revealed reduced activity of Plasma membrane Ca ATPase and an increase in Ca and Na leaks through ion channels in senescent-like cells. Our data revealed that Ca overload in these cells is a result of reduced PMCA activity and facilitated Ca uptake via a hyperactive Piezo1 channel. However, we could not exclude the contribution of other Ca-permeable ion channels in this scenario. In addition, we found, as a universal mechanism, that an increase in intracellular Ca reduced the initially high selectivity of Piezo1 channel for Ca and allowed higher Na uptake, Na accumulation, and swelling.
衰老的红细胞密度逆转早已为人所知，但导致衰老细胞肿胀的候选离子转运体（s）的身份仍难以捉摸。在对健康个体的 RBC 进行 Percoll 密度梯度分离并对分离的各部分进行特征分析的过程中，我们在低密度部分（1.02%±0.47）发现了一个具有衰老特征的细胞亚群，例如与带 3 蛋白丰度降低相关的膜表面积损失，以及磷脂酰丝氨酸（PS）暴露于外膜。此外，我们发现这些细胞中 Na 和 Ca 超载。通过离子泵和通道的阻滞剂和激活剂的组合，我们发现衰老样细胞中质膜 Ca ATP 酶的活性降低，并且通过过活跃的 Piezo1 通道增加 Ca 和 Na 泄漏。我们的数据表明，这些细胞中的 Ca 超载是 PMCA 活性降低的结果，并且通过过度活跃的 Piezo1 通道促进 Ca 摄取。然而，我们不能排除在这种情况下其他 Ca 渗透性离子通道的贡献。此外，我们发现，作为一种普遍机制，细胞内 Ca 的增加降低了 Piezo1 通道最初对 Ca 的高选择性，并允许更高的 Na 摄取、Na 积累和肿胀。
