Activation of the G2 cell cycle checkpoint enhances survival of epithelial cells exposed to hyperoxia
Activation of the G2 cell cycle checkpoint enhances survival of epithelial cells exposed to hyperoxia
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DOI：
10.1152/ajplung.00299.2002
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发表时间：
2003-02-01
影响因子：
4.9
通讯作者：
Keng, PC
中科院分区：
文献类型：
--
作者：
O'Reilly, MA;Staversky, RJ;Keng, PC
在高氧损伤DNA过程中产生的活性氧，通过p53依赖的p21激活（Cip1/WAF1/Sdi1）抑制G1期细胞增殖，并杀死细胞。由于检查点激活保护细胞免受遗传毒性应激，我们研究了高氧期间小鼠II型上皮细胞系MLE 15的细胞增殖和存活。之所以选择这些细胞进行研究，是因为它们表达猿猴大T抗原和小T抗原，这些抗原通过破坏p53依赖的G1检查点来部分转化细胞。细胞计数、5-溴-2'-脱氧尿苷标记和流式细胞术显示，高氧在一次复制后减慢细胞周期进程，导致72 h明显的G2期阻滞。加入咖啡因，使G2检查点失活，减少了G2中高氧细胞的百分比，增加了亚G1和G1的百分比。G2检查点的取消与增强的氧诱导的DNA链断裂和细胞死亡相关。咖啡因不影响DNA的完整性或细胞暴露于室内空气的活力。同样，咖啡因废除了G2检查点在高氧A549上皮细胞和增强氧诱导的毒性。这些数据表明，高氧在一个细胞周期后迅速抑制增殖，并且G2检查点对于限制DNA损伤和细胞死亡至关重要。
Reactive oxygen species produced during hyperoxia damage DNA, inhibit proliferation in G1-through p53-dependent activation of p21(Cip1/WAF1/Sdi1), and kill cells. Because checkpoint activation protects cells from genotoxic stress, we investigated cell proliferation and survival of the murine type II epithelial cell line MLE15 during hyperoxia. These cells were chosen for study because they express Simian large and small-T antigens, which transform cells in part by disrupting the p53-dependent G1 checkpoint. Cell counts, 5-bromo-2'-deoxyuridine labeling, and flow cytometry revealed that hyperoxia slowed cell cycle progression after one replication, resulting in a pronounced G2 arrest by 72 h. Addition of caffeine, which inactivates the G2 checkpoint, diminished the percentage of hyperoxic cells in G2 and increased the percentage in sub-G1 and G1. Abrogation of the G2 checkpoint was associated with enhanced oxygen-induced DNA strand breaks and cell death. Caffeine did not affect DNA integrity or viability of cells exposed to room air. Similarly, caffeine abrogated the G2 checkpoint in hyperoxic A549 epithelial cells and enhanced oxygen-induced toxicity. These data indicate that hyperoxia rapidly inhibits proliferation after one cell cycle and that the G2 checkpoint is critical for limiting DNA damage and cell death.