^137Csγ射线诱导人外周血线粒体DNA缺失的时间和剂量-效应关系

Time-and dose-effect of mitochondrial DNA deletions in γ-ray irradiated human peripheral blood

目的研究^137Csγ 射线诱导的人外周血线粒体DNA4934bp和4977bp缺失的时间和剂量一效应，并探讨其在电离辐射受照者剂量估算中的应用意义。方法采集5名健康成人外周血进行 ^137Csγ 射线离体照射，取其中1份血样给予5Gy照射后分别培养2、24、48和72h，另4份血样均经6等分后分别给予0、0．5、1、2、5和10Gy照射，孵养2h后采用实时荧光定量PCR方法和凝胶电泳，检测人外周血线粒体DNA4934bp（mtDNA4934bp）和4977bp（mtDNA4977bp）缺失的表达水平，并用CurveExpert1．4软件拟合剂量一效应曲线。结果^137Csγ射线照射离体人血后，诱发的mtDNA4934bp缺失和mtDNA4977bp缺失在照后2h即升高，mtDNA4934bp缺失水平在照后2h和48h有相对表达高点（t=10．782和8．966，P〈0．05）；而mtDNA4977bp缺失水平在照后48h表达最高（t=7．433，P〈0．05）。0．5～10Gy的”’cs1射线照射诱发的mtDNA4934bp缺失（t=2．895～8．105，P〈0．05）和mtDNA4977bp缺失（t=3．006～7．715，P〈0．05）均随照射剂量增加。其中，mtDNA4977bp缺失在相同照射剂量下变化更大，尤其是在10Gy剂量照射时，二者差异更明显（t=2．919，P〈0．05），即对于大剂量照射，mtDNA4977bp缺失可能更为灵敏，但是个体差异较mtDNA4934bp缺失大。拟合的剂量．效应曲线回归方程分别为P．=1．178＋0．1219D（R。=0．9269，mtDNA4934bp缺失）和t=1．2578＋0．1933D（R2=0．9016，mtDNA4977bp缺失）。结论^137Csγ 射线诱发的线粒体DNA片段缺失与辐射剂量有良好的数学回归关系，有可能为照射后生物剂量快速估算和预后评估提供依据。

Objective To study the time-and dose-effect of mitochondrial DNA （mtDNA） 4934 bp and 4977 bp deletions in the human peripheral blood irradiated by ^137 Cs γ-rays, and to evaluate its implication in biological dosimetry. Methods The peripheral blood from five healthy adults was collected and irradiated with γ-rays. The peripheral blood of one healthy aduh was irradiated with 5 Gy and cultured for 2, 24, 48 and 72 h after irradiation. The peripheral blood from the other four healthy adults was cultured for 2 h after 0, 0. 5, 1, 2, 5 and 10 Gy irradiation. The peripheral blood mtDNA 4934 bp and 4977 bp deletions were detected by real-time polymerase chain reaction and gel electrophoresis. The dose- effect curves were fitted using Curve Expert 1.4 Software. Results mtDNA 4934 bp and 4977 bp deletions were induced at 2 h post-irradiation and the mtDNA 4934 bp deletion had relative high levels at 2 h and 48 h after radiation （ t = 10. 782 and 8. 966, P 〈 0. 05 ） , and mtDNA 4977 bp deletion reached the highest level at 48 h after radiation （t=7.433, P〈0.05）. mtDNA4934 bp （t=2.895-8.105, P〈0.05） and 4977 bp deletion （t = 3. 006 - 7. 715, P 〈 0.05） irradiated at 0.5 - 10 Gy increased with a dose- dependent manner. The incidence of mtDNA 4977 bp deletion was higher than that of 4934 bp deletion for those samples exposed with same close of irradiation, especially at 10 Gy （ t = 2. 919, P 〈 0. 05 ） , whichsuggested that 4977 bp deletion might be more sensitive than 4934 bp deletion at high dose. But larger individual differences were found in 4977 bp deletion compared with 4934 bp deletion. The dose-effect equations for 4934 bp deletion and 4977 bp deletion were Y1 = 1. 178 ＋0. 1219D （R2 =0. 9269） and Y2 = 1. 2578 ＋ 0. 1933D （R2 = 0. 9016） ,respeetively. Conclusions The induction of mtDNA deletion was correlated with radiation dose, and thus it may be a available method for biological dose estimation and prognostic evaluation.