Pérez M del Rosario, Dubner D, Michelin S, Leteurtre F, Carosella E D, Gisone P A
Autoridad Regulatoria Nuclear, Gerencia de Apoyo Científico, Laboratorio de Radiopatología, Av del Libertador 8250, CP 1429 Buenos Aires, Argentina.
Int J Radiat Biol. 2002 Dec;78(12):1175-83. doi: 10.1080/0955300021000013812.
To examine the influence of dose, dose-rate and radiation quality on telomerase activity (TA) in the KG1a hematopoietic cell line.
KG1a cells were irradiated with gamma-rays (0.5-5 Gy) at 0.025 Gy/min, 0.30 Gy/min and 1.57 Gy/min and with a neutron/gamma-ray field (5 Gy). Cell viability was determined by trypan blue exclusion. Apoptosis and cell cycle distribution were evaluated by flow cytometry. Proliferative capacity was studied by MTS assay and TA by PCR. Following 3Gy gamma-irradiation, the expression of hTERT, hTR and TP1 genes was evaluated by RT-PCR.
Dose- and dose-rate-dependent telomerase activation with an increase in hTERT mRNA and a drop in hTP1 mRNA were observed after irradiation. Down-regulation of telomerase activity occurred in a dose-dependent manner. Although non-significant changes in short-term survival were observed after irradiation, late apoptosis became evident after G2/M arrest. Early repression of TA preceded telomerase activation in samples irradiated with a neutron/gamma-ray field, in which short-term survival was affected.
Radiation-induced telomerase activation depends on dose-rate. High-LET and low-LET irradiations induce similar changes in TA that differ mainly in their kinetics and their magnitude. Changes in TA are not related to cell-cycle redistribution nor to the induction of cell death; they are the consequence of specific regulatory responses to ionizing radiation. Mechanisms including both transcriptional and post-translational control may be involved in this regulation.
研究剂量、剂量率和辐射质量对KG1a造血细胞系端粒酶活性（TA）的影响。
用γ射线（0.5 - 5 Gy）分别以0.025 Gy/min、0.30 Gy/min和1.57 Gy/min的剂量率照射KG1a细胞，并用中子/γ射线场（5 Gy）照射。通过台盼蓝拒染法测定细胞活力。通过流式细胞术评估细胞凋亡和细胞周期分布。通过MTS法研究增殖能力，通过PCR研究端粒酶活性。在3 Gy γ射线照射后，通过RT-PCR评估hTERT、hTR和TP1基因的表达。
照射后观察到剂量和剂量率依赖性的端粒酶激活，hTERT mRNA增加，hTP1 mRNA下降。端粒酶活性的下调呈剂量依赖性。虽然照射后短期存活无显著变化，但在G2/M期阻滞后期凋亡变得明显。在受到中子/γ射线场照射的样本中，端粒酶活性的早期抑制先于端粒酶激活，其中短期存活受到影响。
辐射诱导的端粒酶激活取决于剂量率。高传能线密度和低传能线密度照射诱导端粒酶活性发生类似变化，主要区别在于其动力学和幅度。端粒酶活性的变化与细胞周期重新分布和细胞死亡诱导无关；它们是对电离辐射的特定调节反应的结果。包括转录和翻译后控制在内的机制可能参与了这种调节。
