X射线诱导人肺腺癌A549细胞凋亡及线粒体DNA基因表达下调

目的 研究不同剂量X线对人肺腺癌A549细胞增殖及凋亡的影响，并检测其线粒体DNA（mtDNA）基因的差异表达。方法 以同步培养的未受照细胞为对照，8MVX线分别以2、4、6和8Gy的吸收剂量照射A549细胞，MTT比色法分析细胞增殖曲线；并于照射后24h，流式细胞仪测定细胞周期分布和凋亡率，电镜观察细胞超微结构，人mtDNA基因表达谱芯片检测靶基因的表达变化。结果X射线抑制A549细胞增殖，以4Gv为显著；随着照射剂量的增加，细胞凋亡率增加，G2／M期细胞比率增加，6和8Gy组表现出G2／M期阻滞，透射电镜下4Gy组可见凋亡的形态改变，8Gy组细胞近碎裂；X射线照射后mtDNA编码基因呈普遍下调表达，包括2Gy组的3种tRNA基因、4Gy组的2种tRNA基因和4种mRNA基因、6Gy组的6种tRNA基因和1种rRNA基因，8Gy组的2种tRNA基因。结论X射线可抑制A549细胞增殖，诱导细胞凋亡及mtDNA编码基因的普遍下调表达。随着辐射剂量的增加，剂量依赖性效应逐步减弱而解除。4Gy为体外研究的相对高效、安全剂量。

Apoptosis and down-regulated expression of mitochondrial DNA genes in A549 cells induced by X-ray irradiation

Objective To investigate the apoptotic effect and differential expression of mitochondrial DNA(mtDNA) genes in A549 human lung adenocarcinoma at different doses of X-ray irradiation. Methods A549 cells were irradiated with 8 MV X rays at the absorbed doses of 2,4,6 or 8 Gy, and then cultured for 24 h. Cell proliferation was detected by MTT assay. Cell cycle distribution and apoptotic rates were determined by flow cytometry (FCM). The apoptotic morphology was observed by transmission electron microscope (TEM). The differential expression of mtDNA genes were detected with mtDNA oligonucleotide microarray. Results The proliferation of A549 cells was inhibited by X irradiation,especially at 4 Gy. Dose-dependent apoptosis and cell percentage increase of G₂/M phase were displayed,while the apoptotic morphological characters were observed at 4 Gy group. Down_regulation of Expression of 3 tRNA genes, 2 tRNA genes and 4 mRNA genes, 6 tRNA genes and 1 rRNA gene,2 tRNA genes, which were all encoded by mtDNA, were identified at groups 2,4,6 and 8 Gy, respectively. Conclusions After exposure to X-ray, proliferative inhibition and apoptosis, as well as down-regulated expression of mitochondrial DNA genes were observed in A549 cells and 4 Gy may be regarded as an effective and safe dose in vitro.