Adebodun F, Post J F
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555-0653.
J Cell Physiol. 1993 Jan;154(1):199-206. doi: 10.1002/jcp.1041540123.
The induction of apoptosis in leukemic cells by dexamethasone is well known, but the mechanism of this type of cell death and of dexamethasone resistance by some variants is still poorly understood. Apoptotic cell death is preceded by many changes in cellular properties, such as glucose metabolism, cell size, cell density, and others. In this study, 19F-NMR has been used to characterize changes in cell membrane potential and intracellular accessible volume during dexamethasone induced apoptosis. One dex-sensitive (CEM-C7) and three dex-resistant variants (CEM-C1, CEM-ICR27, and CEM-4R4) were examined. We have observed separate intracellular and extracellular resonances for trifluoroacetate and trifluoroacetamide added to suspended leukemic cells. From the equilibrium distribution of these fluoro-compounds between intra and extracellular spaces, the changes in membrane potential and intracellular accessible volume were calculated. The membrane potential for CEM-C7 cells was found to significantly decrease in the presence of dexamethasone (9-mV decrease within 18 h of dexamethasone treatment), while that of CEM-ICR27 was found in some samples to increase on dexamethasone incubation. The membrane potential for CEM-C1 decreased slightly, while that of CEM-4R4 was not appreciably affected by dexamethasone. The reduction of membrane potential seems to be an early step in the mechanism of dexamethasone induced apoptosis. Although the intracellular volume varied with cell type and dexamethasone incubation (for CEM-C7), the fractional intracellular volume (alpha = Vin/Vcell) was found to be the same (0.82 +/- 0.06) for all the cell lines in the presence and absence of dexamethasone.
地塞米松诱导白血病细胞凋亡是众所周知的，但这种细胞死亡类型以及某些变体产生地塞米松耐药性的机制仍知之甚少。凋亡性细胞死亡之前会出现许多细胞特性的变化，如葡萄糖代谢、细胞大小、细胞密度等。在本研究中，19F-NMR已被用于表征地塞米松诱导凋亡过程中细胞膜电位和细胞内可及体积的变化。研究了一种对地塞米松敏感的细胞系（CEM-C7）和三种对地塞米松耐药的变体（CEM-C1、CEM-ICR27和CEM-4R4）。我们观察到添加到悬浮白血病细胞中的三氟乙酸盐和三氟乙酰胺在细胞内和细胞外有单独的共振信号。根据这些含氟化合物在细胞内和细胞外空间的平衡分布，计算了膜电位和细胞内可及体积的变化。发现地塞米松存在时，CEM-C7细胞的膜电位显著降低（地塞米松处理18小时内降低9 mV），而在一些样本中，发现CEM-ICR27细胞在孵育地塞米松时膜电位增加。CEM-C1细胞的膜电位略有下降，而CEM-4R4细胞的膜电位不受地塞米松的明显影响。膜电位的降低似乎是地塞米松诱导凋亡机制中的早期步骤。尽管细胞内体积随细胞类型和地塞米松孵育情况而变化（对于CEM-C7细胞），但在有和没有地塞米松的情况下，所有细胞系的细胞内体积分数（α = Vin/Vcell）均相同（0.82±0.06）。
