Influence of low doses microwave radiation on activities of antioxidative enzymes of Isatis indigotica seedlings exposed to enhanced UV-B radiation

IEECAS SKLLQG

Survivin expressions in human hepatoma HepG2 cells exposed to ionizing radiation of different LET

Survivin is a member of the inhibitors of apoptosis (IAP) protein family that interferes with post-mitochondrial events including activation of caspases. To examine the regulation of survivin expression in response to irradiation with different linear energy transfer (LET), human hepatoma HepG2 cells were irradiated in vitro with X-rays and carbon ions. Cellular sensitivities to low- and high-LET radiation were determined by colony formation. Survivin expression at mRNA and protein level were measured with RT-PCR and Western blot analyses, respectively. Radiation-induced cell cycle arrest and apoptosis were investigated with flow cytometry. We found that low-LET X-rays induced dose-dependent increases in survivin expression. After exposure to high-LET carbon ions, survivin expression gradually increased from 0 to 4 Gy, and then declined at 6 Gy. More pronounced survivin expression, stronger G(2)/M phase arrest was observed after exposure to carbon ions in comparison with X-rays at doses from 0 to 4 Gy. These observations indicate that there is a differential survivin expression in response to different LET radiations and the cycle arrest mechanism may be associated with it. In addition, our data on induction of apoptosis are compatible with the assumption that survivin expression induced by low-LET X-rays radiation may play a critical role in inhibiting apoptosis. However, after irradiation with ions, an anti-apoptotic function of survivin is not evident, possibly because of the serious damage produced by densely ionizing radiation.

A correlation between radiation sensitivity and initial chromatid breaks in cancer cell lines revealed by Calyculin A-induced premature condensation

Three human malignancy cell lines were irradiated with Co-60 gamma-rays. Initial chromatid breaks were measured by using the chemically induced premature chromosome condensation technique. Survival curves of cells exposed to gamma rays was linear-quadratic while the efficiency of Calyculin A in inducing PCC of G(2) PCC was about five times more than G(1) PCC. A dose-dependent increase in radiation-induced chromatid/isochromatid breaks was observed in G(1) and G(2) phase PCC and a nearly positive linear correlation was found between cell survival and chromatin breaks. This study implies that low LET radiation-induced chromatid/isochromatid breaks can potentially be used to predict the radiosensitivity of tumor cells either in in vitro experimentation or in in vivo clinical radiotherapy.

Adenovirus-mediated p53 gene transfer sensitizes hepatocellular carcinoma cells to heavy-ion radiation

Background. The purpose of this study was to investigate whether adenovirus-mediated p53 transfer could sensitize hepatocellular carcinoma to heavy-ion irradiation. Methods. HepG2 cells were preexposed to a C-12(6+) beam, and then infected with replication-deficient adenovirus recombinant vectors containing human wild-type p53 (AdCMV-p53) (C-12(6+) irradiation + AdCMV-p53 infection). The survival fraction was determined by clonogenic assay. The cell cycle, cell apoptosis, and p53 expression were monitored by flow cytometric analysis. Results. p53 expression in C-12(6+) irradiation + AdCMV-p53 infection groups was markedly higher than that in C-12(6+) irradiation only groups (P < 0.05), suggesting that the preexposure to the C-12(6+) beam promoted the expression of exogenous p53 in HepG2 cells infected with AdCMV-p53 only. The G(1)-phase arrest and cell apoptosis in the C-12(6+) irradiation + AdCMV-p53 infection groups were significantly more than those in the C-12(6+) irradiated groups (P < 0.05). The survival fractions of the C-12(6+) irradiation + AdCMV-p53 infection groups decreased by 30%-49% compared with those of the C-12(6+) beam-irradiated only groups (P < 0.05). Conclusions. Adenovirus-mediated p53 gene transfer can promote G(1)-phase arrest and cell apoptosis, thus sensitizing hepatocellular carcinoma cells to heavy-ion irradiation.

Potential role of DNA-dependent protein kinase in cellular resistance to ionizing radiation

In this paper, we study the ability of DNA-PK-deficient (M059J) and -proficient (M059K) cells to undergo the rate of cellular proliferation, cell cycle distribution and apoptosis after 10 Gy X-ray irradiation, and the role of DNA-PK in radiosensitivity. The results showed that M059J cells exhibited hyper-radiosensitivity compared with M059K cells. A strong G2 phase arrest was observed in M059J cells post irradiation. Significant accumulation in the G2 phase in M059J cells was accompanied by apoptosis at 12 h. Altogether, the data suggested that DNA-PK may have two roles in mammalian cells after DNA damage, a role in DNA DSB repair and a second role in DNA-damaged cells to traverse a G2 checkpoint, by which DNA-PK may affect cellular sensitivity to ionizing radiation. 地址: [Li Ning; Zhang Hong; Wang Yanling; Hao Jifang] Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Peoples R China; [Li Ning; Zhang Hong; Wang Yanling; Hao Jifang] Key Lab Heavy Ion Radiat Med Gansu Prov, Lanzhou 730000, Peoples R China; [Li Ning; Wang Yanling] Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China; [Wang Xiaohu] Gansu Tumor Hosp, Dept Radiotherapy, Lanzhou 730050, Peoples R China

High-efficiency transfer and expression of AdCMV-p53 in human hepatocellular carcinoma cells induced by low-dose carbon-ion radiation

Objective To investigate whether the irradiation with C-beam could enhance adenovirus-mediated transfer and expression of p53 in human hepatocellular carcinoma. Materials and methods HepG2 cells were exposed to C-beam or gamma-ray and then infected with replicationdeficient adenovirus recombinant vectors containing human wild-type p53 or green fluorescent protein, respectively. The transfer efficiency and expression level of the exogenous gene were detected by flow cytometric analysis. Cell survival fraction was detected by clonogenic assay. Results The transfer frequency in C-beam or gamma-irradiated groups increased by 50-83% and 5.7-38.0% compared with the control, respectively (P < 0.05). Compared with C-beam alone, p53 alone, and gamma-ray with p53, the percentages of p53 positive cells for 1 Gy C-beam with p53 increased by 56.0-72.0%, 63.5-82.0%, and 31.3-72.5% on first and third day after the treatments, respectively (P < 0.05). The survival fractions for the 2Gy C-bearn and AdCMV-p53 infection groups decreased to similar to 2%. Conclusion C-beam irradiation could significantly promote AdCMV-green fluorescent protein transfer and expression of p53.

抑制survivin表达增强人肝癌HepG2细胞对高线性能量转移射线的辐射敏感性；Inhibiting Survivin Expression Increases The Radiosensitivity of Human Hepatoma HepG2 Cells to High-LET Radiation

探讨了肿瘤细胞中survivin的表达对高线性能量转移(LET)射线辐射敏感性的影响.根据Gen Bank提供的survivin序列,合成特异性survivin-siRNA寡核苷酸,转染人肝癌HepG2细胞,抑制survivin的表达.发现siRNA转染后诱导了HepG2细胞G2/M期阻滞,增加了自发性和辐射诱导的细胞凋亡.在高线性能量转移(LET)碳离子辐照后,siRNA转染细胞的克隆存活率明显下降.这些结果表明survivin表达是HepG2细胞产生对高LET射线辐射抗性的关键因素.

小肠电离辐射损伤研究进展；Advances in Small Intestinal Ionizing Radiation Injury Research

肠道的电离辐射损伤是腹部及盆腔肿瘤放射治疗过程中的剂量限制因素。综述了小肠电离辐射损伤的临床症状、小肠上皮及粘膜下层基质改变、信号分子表达变化、组织学变化和超微结构变化。简介了中国科学院近代物理研究所重离子束辐射生物医学重点实验室正在进行的有关小肠重离子辐射损伤及防护方面的研究工作。

空间辐射生物学研究进展；Research Progress on Space Radiation Biology

空间电离辐射尤其是高能带电粒子辐射可造成生物机体的严重损伤,是载人航天飞行的关键性限制因素之一。研究表明,带电粒子的生物学效应与其性质、剂量以及不同生物学终点有关;此外,微重力环境可能会影响空间辐射生物学效应。从多年来的空间搭载实验研究和地基模拟实验研究两个方面,综述了空间辐射的生物损伤效应及其与微重力环境复合作用的生物效应。

Survivin表达在高LET射线诱导细胞凋亡中作用机理的初步研究；A Preliminary Study on Action Mechanisms of Survivin Expression in Cell Apoptosis Induced by High-LET Radiation

先前的研究表明,肿瘤细胞中survivin的高表达与细胞对高传能线密度(LET)射线的辐射抗性相关。研究了survivin表达在高LET射线诱导的细胞凋亡中的作用,发现抑制survivin表达对高LETC离子辐射诱导的Bcl-2和Bax表达没有明显的影响。在高LET射线辐照中,survivin可能通过抑制caspase-3和-9活性的途径,抑制了细胞凋亡。

Inhibiting Survivin Expression Increases The Radiosensitivity of Human Hepatoma HepG2 Cells to High-LET Radiation

The influence of survivin expression on the radiosensitivity of tumor cells to high linear energy transfer (LET) radiation is investigated. Survivin-specific short-interfering RNA (siRNA) oligonucleotides were synthesized based on the survivin sequence provided by GenBank. Human hepatoma HepG2 cells were transfected with survivin-specific siRNA to inhibit its expressions. It was found that the transfection with surviving-specific siRNA increased the levels of G2/M arrest and the apoptotic rates induced by radiation in HepG2 cells. After exposure to high-LET carbon ions, a reduced clonogenic survival effect was observed in the cells treated with siRNA. These results show that survivin plays a key role in mediating the radioresistance of cells to high-LET radiation.

Effect of gamma-ray radiation on physiological, morphological characters and chromosome aberrations of minitubers in Solanum tuberosum L.

Purpose: To investigate the effects of gamma-ray radiation on the physiological, morphological characters and chromosome aberrations of minitubers. Materials and methods: Minitubers of one potato cultivar, 'Shepody', were irradiated with 8 doses of gamma-rays (0, 10, 20, 30, 40, 50, 60, 70 and 80 Gy [Gray]) to investigate the effects of radiation on emergence ability, plant height and root length, morphological variations, chromosome aberrations, M-1 (first generation mutants) tuber number and size of minituber plants. Results: Compared with the non-irradiated controls, the whole period of emergence was prolonged by 10-15 days for minitubers treated with gamma-ray radiation, but low doses of radiation (10, 20 and 30 Gy) promoted the emergence percentage of minitubers. With an increase in radiation dose, the emergence percentage, plant height and root length of minituber plants were significantly inhibited at 40 and 50 Gy. No emergence occurred at 60 Gy and higher doses. After radiation, a series of morphological variations and chromosome aberrations appeared in minituber plants. Radiation with 20 Gy promoted tuber formation, and the average number and diameter of M-1 tubers per plant were significantly increased over the control by 71% and 34%, respectively. Conclusion: Low doses of radiation (10-30 Gy) might be used as a valuable parameter to study the improvement of minitubers by gamma-ray radiation treatment.