Adebodun F, Post J F
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555-0653.
J Cell Physiol. 1995 Apr;163(1):80-6. doi: 10.1002/jcp.1041630109.
The levels of intracellular free Ca(II) and Zn(II) during dexamethasone (dex)-induced apoptosis in CEM cell lines were determined by 19F nuclear magnetic resonance (NMR), using the fluorinated intracellular chelator 1,2-bis-(2- amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid (5-FBAPTA). The effects of these divalent metal ions on growth rate and DNA degradation were evaluated. Measurements were done on one dex-sensitive (CEM-C7) and three different dex-resistant variants (CEM-C1, CEM-4R4, and CEM-ICR27). Dex caused a continuous increase in the Ca(II) level in dex-sensitive CEM-C7 cells, while in CEM-C1 cells dex caused an initial increase in the Ca(II) level which in approximately 36 h was restored to its normal value. The intracellular Ca(II) level in CEM-4R4 cells was not significantly affected by dex, while that of CEM-ICR27 cells decreased after dex incubation. Only the dex-sensitive CEM-C7 cells showed dex-induced DNA degradation. An intracellular free Zn(II) level of approximately 1 nM was measured for the dex-resistant CEM-C1 cells. No detectable level of intracellular Zn(II) was found in the other cell lines. Incubation with < 100 microM Zn(II) did not inhibit dex-induced apoptosis in CEM-C7 cells (e.g., DNA degradation). Treatment with approximately 250 microM Zn(II) caused significant decrease in growth rate in all cell lines and prevented dex-induced DNA degradation in CEM-C7 cells. A calibrated amount of Ca(II) ionophore (A23187), used to increase Ca(II) concentrations up to the dex-induced levels, did not induce DNA degradation in CEM-C7 or CEM-C1 cells. While elevation of intracellular Ca(II) by itself is not sufficient to initiate apoptosis in CEM-C7 cells, the results reported here suggest that Ca(II) is involved in the killing mechanism as a secondary factor. The combination of dex and ionophore caused significant DNA degradation in CEM-C1 cells, which normally showed resistance to each compound individually. The combination of dex and the Zn(II) chelator phenanthroline also caused extensive DNA degradation in the normally dex-resistant CEM-C1 cells, suggesting that Zn(II) plays a role in the dex resistance of these cells.
使用氟化细胞内螯合剂1,2-双（2-氨基-5-氟苯氧基）乙烷-N,N,N',N'-四乙酸（5-FBAPTA），通过19F核磁共振（NMR）测定地塞米松（dex）诱导CEM细胞系凋亡过程中细胞内游离Ca（II）和Zn（II）的水平。评估了这些二价金属离子对生长速率和DNA降解的影响。对一种对地塞米松敏感的细胞系（CEM-C7）和三种不同的对地塞米松耐药的变体（CEM-C1、CEM-4R4和CEM-ICR27）进行了测量。地塞米松使对地塞米松敏感的CEM-C7细胞中的Ca（II）水平持续升高，而在CEM-C1细胞中，地塞米松使Ca（II）水平最初升高，约36小时后恢复到正常值。地塞米松对CEM-4R4细胞中的细胞内Ca（II）水平没有显著影响，而地塞米松孵育后CEM-ICR27细胞中的细胞内Ca（II）水平降低。只有对地塞米松敏感的CEM-C7细胞显示出地塞米松诱导的DNA降解。对地塞米松耐药的CEM-C1细胞的细胞内游离Zn（II）水平约为1 nM。在其他细胞系中未检测到细胞内Zn（II）水平。用<100μM Zn（II）孵育不会抑制CEM-C7细胞中地塞米松诱导的凋亡（如DNA降解）。用约250μM Zn（II）处理导致所有细胞系的生长速率显著降低，并阻止CEM-C7细胞中地塞米松诱导的DNA降解。用于将Ca（II）浓度提高到地塞米松诱导水平的校准量的Ca（II）离子载体（A23187），在CEM-C7或CEM-C1细胞中未诱导DNA降解。虽然细胞内Ca（II）本身升高不足以引发CEM-C7细胞凋亡，但此处报道的结果表明Ca（II）作为次要因素参与了杀伤机制。地塞米松和离子载体的组合在通常对每种化合物单独耐药的CEM-C1细胞中导致显著的DNA降解。地塞米松和Zn（II）螯合剂菲咯啉的组合也在通常对地塞米松耐药的CEM-C1细胞中导致广泛的DNA降解，表明Zn（II）在这些细胞的地塞米松耐药中起作用。
