长期低剂量γ照射对人B淋巴母细胞辐射敏感性的影响

Effects of long-term low-doseγ-rays exposure on radiosensitivity of human B lymphoblast cells

目的探讨长期低剂量（LDR）γ辐射对人B淋巴母细胞HMy2．CIR（HMy）辐射敏感性的影响及其机制。方法实验将HMy细胞分为对照组和长期LDR组，其中长期LDR组选用可以显著促进细胞增殖的低剂量γ射线对HMy细胞每周照射3次，每次0．032Gy，连续照射4周，在长期LDR处理结束后分别对部分对照组和长期LDR组细胞进行2Gy照射。以CCK-8[内含WST-8，即2-（2-甲氧基-4-硝基苯基）-3-（4-硝基苯基）-5-（2，4-二磺酸苯）-2H-四唑单钠盐]法检测细胞增殖和辐射敏感性，流式细胞术检测细胞凋亡率和γ-H2AX表达，RT—PCR法检测细胞周期相关基因cyclinD1、细胞增殖核抗原PCNA，以及凋亡相关基因bcl-2和bax的表达。结果长期LDR可以显著提高细胞的增殖率（t=9．607，P〈0．01），增加cyclinD1和PCNA基因表达（t=6．869、9．229，P〈0．01），增加抗凋亡基因bcl-2表达（t=2．662，P〈0．05），降低抑凋亡基因bax的表达（t=19．908，P〈0．01）。同时，受长期LDR照射的细胞对攻击剂量（2Gy）产生适应性，使得细胞辐射敏感性显著降低（t=8．896，P〈0．01）；与单纯2Gy照射组相比，LDR＋2Gy组细胞γ—H2AX表达量（t=10．264，P〈0．01）和细胞凋亡率（t=4．762，P〈0．01）均显著降低。结论长期LDR辐射可通过促进周期相关基因表达从而促进细胞增殖，并通过减少细胞凋亡来降低其辐射敏感性。

Objective To investigate the effects of long-term low-dose radiation （LDR） of γ-rays on the proliferation and radiosensitivity of human lymphoblast cells HMy2. CIR （HMy） and to elucidate the underlying mechanism. Methods HMy cells were divided into control group and long-term LDR group. For the long-term LDR treatment, HMy cells were fractionally exposed to a low dose of γ-rays, which could enhance cell proliferation, 3 times per week for 4 weeks. After the long-term LDR exposure, part of the control and long-term LDR exposed cells were further irradiated with a challenging dose （2 Gy） of γ-rays. Then cell proliferation and radiosensitivity were assayed by CCK-8 kit, cell apoptosis, and γ-H2AX formation was measured by flow eytometry. Gene expressions of cyclinD1, PCNA, bcl-2 and bax were detected by RT-PCR. Results The long-term LDR significantly increased cell proliferation （t = 9. 607, P 〈 0.01 ） accompanied with up-regulation of cell cycle regulation gene eyclinD1 （ t = 6. 869, P 〈 0.01 ） , proliferation regulation gene PCNA （proliferating cell nuclear antigen） （ t = 9. 229, P 〈 0. 01 ） and bcl-2 gene （ t = 2. 662, P 〈 0. 05 ） , but decreased the expression of pro-apoptotic gene bax （ t = 19. 908, P 〈 0.01 ） in HMy cells. Compared to untreated cells, the long-term LDR decreased cell radiosensitivity （t = 8. 896,P〈0.01）, including apoptosis induction （t =4.762,P 〈0.01） and γ-H2AX formation （t = 10. 264, P 〈 0.01 ）. Conclusions The long-term LDR promoted cell proliferation by up-regulating cell cycle related genes, while it reduced the radiosensitivity of HMy cells with acquisition of apoptotic resistance.