小鼠胸腺淋巴细胞辐射损伤与修复的分子机理研究

摘要

目的探讨细胞凋亡在小鼠胸腺淋巴细胞辐射损伤中的作用，为阐明淋巴细胞辐射损伤特点和机理以及急性放射病的防治提供重要依据。方法应用原位末端标记、DNA电泳和免疫组化技术观察经2、4、6和8 Gy不同剂量γ-线整体照射后，小鼠胸腺淋巴细胞凋亡的动态变化过程和Bax、Bcl-2蛋白在其中的作用。结果　(1)照射后早期淋巴细胞凋亡率迅速增加，如6 Gy照后4 h和1天凋亡率分别为对照值的3.6和9.3倍；凋亡率还还随照射剂量的增加而迅速升高。(2)胸腺和外周血淋巴细胞数在照射后急剧减少与淋巴细胞凋亡成相反趋势，提示凋亡可能是急性照射后淋巴细胞减少的主要途径之一。(3)透射电镜观察表明，6Gy γ-线照射后，小鼠胸腺淋巴细胞出现早、中、晚期典型凋亡细胞的形态学特征。(4)DNA凝胶电泳显示2～6Gy照后4和8 h，胸腺淋巴细胞出现特征的DNA梯形谱。(5)照射后Bax、Bcl-2蛋白的异常表达证实二者在淋巴细胞凋亡的调控中起重要作用。结论　细胞凋亡在不鼠胸腺淋巴细胞辐射损伤全过程中起重要作用，而Bax和Bcl-2蛋白参与了淋巴细胞凋亡的调控。%Objectives To investigate the role of apoptosis in radiation-induced mouse thymus lymphocyte damage and repair and provide the basis for understanding the molecular mechanism of radiation-induced lymphocyte damage and repair as well as the prevention and treatment of acute radiation sickness.Methods We studied the dynamic changes of apoptosis of mouse thymus lymphocytes and the expression of bax and bcl-2 gene products after 2, 4, 6 and 8 Gy of whole body γ-irradiation using in situ terminal labeling, DNA electrophoresis and immunohistochemical techniques. Results At the early stage after irradiation, the percentage of apoptotic lymphocytes increased rapidly in accordance with the increasing of radiation doses, while the counts of the thymus and peripheral lymphocytes decreased sharply, showing an opposite change to lymphocyte apoptosis. After 6 Gy γ-irradiation, typical morphological characteristics of thymus apoptotic lymphocytes in early, middle and late stages were found by transmission electron microscopy. The thymus lymphocytes displayed characteristic DNA ladders 4hr and 8hr after 2-6 Gy γ-irradiation, using DNA gel electrophoresis techniques. Abnormal expression of bcl-2 and bax gene products were shown in irradiated lymphocytes.Conclusions Apoptosis plays an important role in the process of radiation-induced mouse thymus lymphocyte damage and repair. Bcl-2 and Bax proteins may regulate the process of lymphocyte apoptosis.