Dai Jiawen, Itahana Koji, Baskar Rajamanickam
Molecular Radiobiology Laboratory, Division of Cellular and Molecular Research, Singapore.
Cancer and Stem Cell Biology Program, Duke-NUS Graduate Medical School, Singapore.
Biochem Biophys Res Commun. 2015 Feb 27;458(1):104-9. doi: 10.1016/j.bbrc.2015.01.076. Epub 2015 Jan 28.
Cells in many organs exist in both proliferating and quiescent states. Proliferating cells are more radio-sensitive, DNA damage pathways including p53 pathway are activated to undergo either G1/S or G2/M arrest to avoid entering S and M phase with DNA damage. On the other hand, quiescent cells are already arrested in G0, therefore there may be fundamental difference of irradiation response between proliferating and quiescent cells, and this difference may affect their radiosensitivity. To understand these differences, proliferating and quiescent human normal lung fibroblasts were exposed to 0.10-1 Gy of γ-radiation. The response of key proteins involved in the cell cycle, cell death, and metabolism as well as histone H2AX phosphorylation were examined. Interestingly, p53 and p53 phosphorylation (Ser-15), as well as the cyclin-dependent kinase inhibitors p21 and p27, were induced similarly in both proliferating and quiescent cells after irradiation. Furthermore, the p53 protein half-life, and expression of cyclin A, cyclin E, proliferating cell nuclear antigen (PCNA), Bax, or cytochrome c expression as well as histone H2AX phosphorylation were comparable after irradiation in both phases of cells. The effect of radioprotection by a glycogen synthase kinase 3β inhibitor on p53 pathway was also similar between proliferating and quiescent cells. Our results showed that quiescence does not affect irradiation response of key proteins involved in stress and DNA damage at least in normal fibroblasts, providing a better understanding of the radiation response in quiescent cells, which is crucial for tissue repair and regeneration.
许多器官中的细胞都处于增殖和静止两种状态。增殖细胞对辐射更敏感，包括p53途径在内的DNA损伤通路被激活，从而使细胞发生G1/S或G2/M期阻滞，以避免在DNA损伤的情况下进入S期和M期。另一方面，静止细胞已停滞在G0期，因此增殖细胞和静止细胞之间的辐射反应可能存在根本差异，而这种差异可能会影响它们的放射敏感性。为了了解这些差异，将增殖和静止的人正常肺成纤维细胞暴露于0.10 - 1 Gy的γ辐射下。检测了细胞周期、细胞死亡和代谢相关关键蛋白的反应以及组蛋白H2AX的磷酸化情况。有趣的是，照射后增殖细胞和静止细胞中p53及其磷酸化（Ser-15）以及细胞周期蛋白依赖性激酶抑制剂p21和p27的诱导情况相似。此外，照射后两个阶段细胞中p53蛋白的半衰期、细胞周期蛋白A、细胞周期蛋白E、增殖细胞核抗原（PCNA）、Bax或细胞色素c的表达以及组蛋白H2AX的磷酸化情况均相当。糖原合酶激酶3β抑制剂对p53途径的辐射防护作用在增殖细胞和静止细胞之间也相似。我们的结果表明，至少在正常成纤维细胞中，静止状态不会影响应激和DNA损伤相关关键蛋白的辐射反应，这有助于更好地理解静止细胞中的辐射反应，而这对于组织修复和再生至关重要。
