低能量代谢诱导HeLa细胞及SD大鼠的辐射保护作用

Radioprotective effect of calorie restriction in Hela cells and SD rats

目的探讨低能量代谢状态对受照后子宫颈癌HeLa细胞存活的影响，并研究饥饿状态下大鼠受照后抗氧化损伤指标的变化情况。方法四甲基偶氮唑盐（MTT）比色法检测不同浓度葡萄糖对HeLa细胞生长的影响；克隆形成法检测浓度分别为t、5、10和25mmol／L的葡萄糖对HeLa细胞辐射敏感性的影响；不同浓度葡萄糖联合6Gy的x射线处理后，流式细胞术检测细胞周期的变化，AnnexinV—FITC法检测细胞凋亡。动物实验采用SD雄性大鼠60只，采用随机表法将大鼠随机分为6组，每组10只，其中每两组分别给予正常饮食、饥饿24h和饥饿48h处理，每种处理方式中一组不照射，另一组给予11Gy的X射线照射。照射后2h采集大鼠静脉血液，采用ELISA试剂盒检测血中超氧化物歧化酶（SOD）、总抗氧化能力（T—AOC）的水平。结果葡萄糖浓度≤25mmol/L可增加HeLa细胞的存活率，而〉25mmol／L却使HeLa细胞的存活率降低。在25mmol／L以下，随着葡萄糖浓度的下降，HeLa细胞的辐射敏感性也逐渐降低，25、10、5mmol／L相对于1mmoL／L组，辐射增敏比（SER）分别为1．23、1．10和1．07。相比于高糖（25mmol／L）联合6Gy的x射线处理组，低糖（1mmol／L）联合组降低了G：／M期及s期细胞比例[G：／M期（49．68±1．88）％和（35．54±1．45）％，s期（16．88±1．22）％和（10．23±1．65）％，t=10．42和5．61，P〈0．05]，而且使细胞早期凋亡明显减少[（25．50±0．95）％和（7．56±1．07）％，t=21．72，P〈0．05]。与正常饮食组比较，照射后饥饿48 h处理组的大鼠血中SOD、T—AOC含量明显增加（t=40．32和42．78，P〈0．05）。结论无论在细胞水平还是在动物整体水平上，低能量代谢状态均具有一定的辐射防护作用，而高能量代谢状态则增加其辐射敏感性。

Objective To explore the effect of low calorie metabolism on the survival of HeLa cells exposed to X-rays, and the influence of starvation on the antioxidative factors in the blood of rats after irradiation. Methods MTT method was used to evaluate the impact of different concentration glucose on the proliferation of HeLa cells. Colony formation assay was employed to detect the influence of glucose （ 1, 5, 10 and 25 mmol/L） on radiosensitivity of HeLa cells. Flow cytometry assay was used to analyze distribution of cell cycle and apoptosis. 60 male SD rats were randomly divided into 6 groups with 10 rats each. Rats in every two groups were fed ad libitum, fasted for 24 h and fasted for 48 h, respectively. Rats in one group of each approach were respectively exposed to whole-body X-rays at 11 Gy. At 2 h after irradiation, all of rats were sacrificed and their venous blood was collected. Elisa kits were used to detect uperoxide dismutase （SOD） and total antioxidant capacity （T-AOC）. Results An increased viability was observed in HeLa cells treated with the glucose at low concentration （ 〈25 mmol/L）, while HeLa cell growth was inhibited by glucose at doses of 〉25 mmol/L. Relevant to cells treated with 1 mmol/L glucose, SERs （sensitive enhancement ratio） in cells exposed to 5, 10 and 25 mmol/L glucose were 1.07, 1.10 and 1.23, respectively. A reduction of G2/M and S arrests and apoptosis caused by 6 Gy X-rayirradiation were observed [ （49.68 ± 1.88） % and （35.54 ± 1.45 ） % at G2/M phase, （ 16.88 ± 1.22） % and （10.23 ±1.65）% at S phase, t= 10.42, 5.61, P〈0.05]and in the cells treated with 1 mmol/L glucose compared with cells treated with 25 mmol/L glucose [ （25.50 ± 0.95 ） % and （7.56±l. 07 ） % , t = 21.72, P 〈 0. 05 ]. Without irradiation, calorie restriction exhibited a negligible influence on SOD and T-AOC in rats. However, after 11 Gy irradiation, compared with rats fed ad libitum, the levels of SOD and T-AOC were significantly increased in rats with calorie restriction （ t = 40. 32, 42.78, P 〈 0. 05 ）. Conclusions Calorie restriction has a certain radioprotective effect in vivo and in vitro.