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目的低剂量照射(low-dose radiation,LDR)可调节细胞信号传导,通过各种基因和蛋白的表达改变其分子生物学效应,由此产生了多样复杂且不同于大剂量照射的生物效应。用LDR及LDR联合大剂量照射(high-dose radiation,HDR)人红白血病细胞系K562(CML),探讨LDR对K562细胞周期进程及凋亡的影响。方法按照K562细胞照射剂量不同分为4组,对照组(0Gy)、LDR组(0.08、0.50Gy)、HDR组(6Gy)及LDR联合HDR组(0.08/6Gy、0.50/6Gy,LDR/HDR组)。采用6 MV X射线照射,LDR与HDR间隔8h;照射后按不同时间点收集细胞,流式细胞仪检测细胞周期变化与凋亡并分析细胞DNA倍体变化。结果 LDR后6h各组S期比例增加,对照组与LDR各组分别为55.38±2.22 vs 71.91±7.30、73.13±4.09(Z=-2.428,P=0.022;Z=-3.987,P<0.001);12hG2/M期细胞比例增加,出现G2/M阻滞,24h达峰值,对照组与LDR各组分别为17.81±1.27 vs 26.61±7.82、29.02±2.76(Z=-3.684,P<0.001;Z=-2.928,P<0.001);48h各组G0/G1细胞增多,72h达峰值,对照组与LDR各组分别为27.07±1.19 vs52.32±2.42、44.06±1.90(Z=-2.351,P=0.020;Z=-2.172,P=0.032)。LDR/HDR后6hS期细胞比例增多,且G2/M期比例增加,即G2/M期阻滞,12h达峰值并持续至24h,12h HDR组与LDR/HDR各组G2/M期分别为26.98±2.15 vs 56.27±1.57、69.31±2.51(Z=-2.564,P=0.021;Z=-7.759,P<0.001)。LDR后48h凋亡率增加,96h达峰值,对照组与LDR各组分别为1.82±0.12 vs 3.21±0.20、6.28±0.30(Z=-3.959,P=0.003;Z=-9.705,P<0.001);LDR/HDR照射后24h凋亡率增加,120h达峰值,HDR组与LDR/HDR各组分别为14.21±0.61 vs 17.38±0.92、27.91±1.07(Z=-2.986,P=0.027;Z=-6.973,P<0.001)。LDR后6h各组四倍体及八倍体细胞增加,且随照射剂量增大而增多,对照组与LDR各组八倍体细胞分别为2.41±0.15 vs 4.84±0.46、7.83±0.59,差异有统计学意义,H值分别为5.956和7.200,P值分别为0.025和0.001;LDR/HDR后6h各组四倍体及八倍体细胞增加,亦随LDR剂量增大而增多,HDR组与LDR/HDR各组八倍体细胞分别为6.49±1.05 vs 10.80±1.23、13.77±0.79,差异有统计学意义,H值分别为5.600和7.200,P值分别为0.05和0.001。结论 LDR能诱导K562凋亡,并能增强随后HDR对K562凋亡作用;LDR能诱导S/M期解偶联及G2/M期阻滞等细胞周期进程改变;LDR诱导K562凋亡可能与S/M期解偶联及G2/M期阻滞等改变细胞周期进程有关。
Objective Low-dose radiation (LDR) regulates cellular signaling and alters its molecular biological effects through the expression of various genes and proteins, resulting in a diverse and diverse biological effect that is different from high-dose irradiation. LDR and LDR combined with high-dose radiation (HDR) human erythroleukemia cell line K562 (CML) to investigate the effects of LDR on the cell cycle progression and apoptosis of K562 cells. Methods The K562 cells were divided into 4 groups: control group (0Gy), LDR group (0.08,0.50Gy), HDR group (6Gy) and LDR group (0.08 / 6Gy, 0.50 / 6Gy, LDR / HDR group) ). Using 6 MV X-ray irradiation, the interval between LDR and HDR was 8h. Cells were harvested at different time points after irradiation. Cell cycle changes and apoptosis were detected by flow cytometry and DNA ploidy changes were analyzed. Results Six days after LDR, the proportion of S phase in each group increased, while that in control group and LDR group was 55.38 ± 2.22 vs 71.91 ± 7.30 and 73.13 ± 4.09 respectively (Z = -2.428, P = 0.022; Z = -3.987, P <0.001) The proportion of cells in 12hG2 / M phase increased, the G2 / M block appeared and reached the peak value at 24h, which was 17.81 ± 1.27 vs 26.61 ± 7.82 and 29.02 ± 2.76 respectively (Z = -3.684, P <0.001; Z = -2.928, P <0.001). The number of G0 / G1 cells in each group increased at 72h and peaked at 72h, and the control group and LDR groups were 27.07 ± 1.19 vs 52.32 ± 2.42 and 44.06 ± 1.90 respectively (Z = -2.351, P = 0.020 ; Z = -2.172, P = 0.032). HDR and HDR increased the proportion of cells in 6hS and the proportion of G2 / M increased (G2 / M phase arrest, peaked at 12h and continued to 24h, respectively. ± 2.15 vs 56.27 ± 1.57, 69.31 ± 2.51 (Z = -2.564, P = 0.021; Z = -7.759, P <0.001). The apoptotic rate increased 48h after LDR and reached the peak value at 96h. The difference was 1.82 ± 0.12 vs 3.21 ± 0.20 and 6.28 ± 0.30 respectively (Z = -3.959, P = 0.003; Z = -9.705, P <0.001) The apoptosis rate increased at 24h after LDR / HDR irradiation and reached the peak at 120h. The HDR and LDR / HDR groups were 14.21 ± 0.61 vs 17.38 ± 0.92 and 27.91 ± 1.07 respectively (Z = -2.986, P = 0.027; Z = 6.973, P <0.001). The levels of tetraploid and octaploid cells in each group increased 6 h after LDR, and increased with the increase of irradiation dose. The levels of octapods in control and LDR groups were 2.41 ± 0.15 vs 4.84 ± 0.46 and 7.83 ± 0.59, respectively Statistical significance, H values were 5.956 and 7.200, P values were 0.025 and 0.001; LDR / HDR 6h after each group of tetraploid and octaploid cells increased, also increased with the increase of LDR dose, HDR group and LDR / HDR octoploid cells in each group were 6.49 ± 1.05 vs 10.80 ± 1.23,13.77 ± 0.79, the difference was statistically significant, H values were 5.600 and 7.200, P values were 0.05 and 0.001. Conclusions LDR can induce apoptosis of K562 cells and enhance the subsequent apoptosis of K562 cells induced by HDR. LDR can induce S / M phase transition and G2 / M arrest, and the apoptosis of K562 cells induced by LDR may be related to S / M phase uncoupling and G2 / M arrest and other changes in cell cycle progression.