Persistent oxidative stress and gene expression changes in radiation-induced genomic instability

Radiation Effects of Normal B-Lymphoblastoid Cells after Exposing Them to Low-Dose-Rate Irradiation from Tritium β-rays

The effects of tritium at low doses and low dose rates have received increasing attention due to recent developments in fusion energy and the associated risks of tritium releases into the environment. Mitochondria have been identified as a potential candidate for studying the effects of low-dose/low-dose-rate radiation, with extensive experimental results obtained using X-ray irradiation. In this study, irradiation experiments were conducted on normal B-lymphoblastoid cells using HTO at varying doses. When compared to X-ray irradiation, no significant differences in cell viability induced by different doses were observed. However, the results of ATP levels showed a significant difference between the irradiated sample at a dose of 500 mGy by tritium beta-rays and the sham-irradiated sample, while the levels obtained with X-ray irradiation were almost identical to the sham-irradiated sample. In contrast, ATP levels for both tritium beta-rays and X-rays at a dose of 1.0 Gy showed minimal differences compared to the sham-irradiated sample. Furthermore, distinct effects at 500 mGy were also confirmed in both ROS levels and apoptosis results obtained through tritium beta-ray irradiation. This suggests that mitochondria might be a potential sensitive target for investigating the effects of tritium beta-ray irradiation.

Non-targeted effects of radiation: a personal perspective on the role of exosomes in an evolving paradigm

PURPOSE

Radiation-induced non-targeted effects (NTE) have implications in a variety of areas relevant to radiation biology. Here we evaluate the various cargo associated with exosomal signalling and how they work synergistically to initiate and propagate the non-targeted effects including Genomic Instability and Bystander Effects.

CONCLUSIONS

Extra cellular vesicles, in particular exosomes, have been shown to carry bystander signals. Exosome cargo may contain nucleic acids, both DNA and RNA, as well as proteins, lipids and metabolites. These cargo molecules have all been considered as potential mediators of NTE. A review of current literature shows mounting evidence of a role for ionizing radiation in modulating both the numbers of exosomes released from affected cells as well as the content of their cargo, and that these exosomes can instigate functional changes in recipient cells. However, there are significant gaps in our understanding, particularly regarding modified exosome cargo after radiation exposure and the functional changes induced in recipient cells.

Parental gamma irradiation induces reprotoxic effects accompanied by genomic instability in zebrafish (Danio rerio) embryos

Gamma radiation represents a potential health risk to aquatic and terrestrial biota, due to its ability to ionize atoms and molecules in living tissues. The effects of exposure to ⁶⁰Co gamma radiation in zebrafish (Danio rerio) were studied during two sensitive life stages: gametogenesis (F0: 53 and 8.7mGy/h for 27 days, total doses 31 and 5.2Gy) and embryogenesis (9.6mGy/h for 65h; total dose 0.62Gy). Progeny of F0 exposed to 53mGy/h showed 100% mortality occurring at the gastrulation stage corresponding to 8h post fertilization (hpf). Control and F0 fish exposed to 8.7mGy/h were used to create four lines in the first filial generation (F1): control, G line (irradiated during parental gametogenesis), E line (irradiated during embryogenesis) and GE line (irradiated during parental gametogenesis and embryogenesis). A statistically significant cumulative mortality of GE larva (9.3%) compared to controls was found at 96 hpf. E line embryos hatched significantly earlier compared to controls, G and GE (48-72 hpf). The deformity frequency was higher in G and GE, but not E line compared to controls at 72 hpf. One month after parental irradiation, the formation of reactive oxygen species (ROS) was increased in the G line, but did not significantly differ from controls one year after parental irradiation, while at the same time point it was significantly increased in the directly exposed E and GE lines from 60 to 120 hpf. Lipid peroxidation (LPO) was significantly increased in the G line one year after parental irradiation, while significant increase in DNA damage was detected in both the G and GE compared to controls and E line at 72 hpf. Radiation-induced bystander effects, triggered by culture media from tissue explants and observed as influx of Ca²⁺ ions through the cellular membrane of the reporter cells, were significantly increased in 72 hpf G line progeny one month after irradiation of the parents. One year after parental irradiation, the bystander effects were increased in the E line compared to controls, but not in progeny of irradiated parents (G and GE lines). Overall, this study showed that irradiation of parents can result in multigenerational oxidative stress and genomic instability in irradiated (GE) and non-irradiated (G) progeny of irradiated parents, including increases in ROS formation, LPO, DNA damage and bystander effects. The results therefore highlight the necessity for multi- and transgenerational studies to assess the environmental impact of gamma radiation.

Salvianic acid A protects L-02 cells against γ-irradiation-induced apoptosis via the scavenging of reactive oxygen species

Salvianic acid A (SAA) is the main hydrophilic active ingredient of Salvia miltiorrhiza bunge, which has long been used to treat liver and heart disease in China. In the present study, we investigated the radioprotective effects of SAA against γ-radiation-induced apoptosis in cultured human embryo liver L-02 cells. The results demonstrated that SAA markedly inhibited γ-radiation induced apoptosis, decreased DNA damage, and increased the intracellular antioxidative ability of the L-02 cells. SAA exhibited radioprotection by decreasing the generation of reactive oxygen species, inhibiting the release of mitochondrial cytochrome C, blocking the activation of caspase-3, and down regulating the expression of Bax and P53 and up regulating the expression of Bcl-2. This indicated that SAA pretreatment inhibited the caspase-dependent mitochondria apoptosis pathway. The radioprotection of the SAA pretreatment was also evidenced by an increased survival ratio, maintaining the antioxidant enzyme levels in the liver, inhibition of oxidative stress, and relative low liver and renal toxicity compared with estriol exposure. In conclusion, SAA may be an effective radioprotector against γ-radiation induced apoptosis in L-02 cells and damage in mice, the antioxidant potency of SAA might be correlated with the beneficial radioprotectant effects observed.

Investigation of the radioprotective efficacy of hesperidin against gamma-radiation induced cellular damage in cultured human peripheral blood lymphocytes

The present study was aimed to evaluate the radioprotective efficacy of hesperidin (HN), a flavonone glycoside against gamma-radiation-induced cellular damage in cultured human peripheral blood lymphocytes. Different concentrations of HN (3.27, 6.55, 9.83, 13.10, 16.38 and 19.65 microM) were pre-incubated with lymphocytes for 30 min prior to gamma-irradiation [4 Gy] and the micronuclei (MN) scoring, dicentric aberration and comet assay were performed to fix the effective dose of HN against gamma-irradiation induced cellular damage. The results indicated that among all the concentrations, 16.38 microM concentration of HN showed optimum protection by effectively decreasing the MN frequencies, dicentric aberrations and comet attributes. Based on the above results, 16.38 microM concentration of HN was fixed as the effective dose to further investigate its radioprotective efficacy which was then carried out by pre-incubating lymphocytes with 16.38 microM concentration of HN, exposing the lymphocytes to different doses (1, 2, 3 and 4 Gy) of radiation and investigating radiation induced genetic damage (MN, dicentric aberration, comet assay, DNA fragmentation assay) and biochemical changes (changes in the level of enzymic and non-enzymic antioxidants, lipid peroxidation). The results indicated a dose dependent increase in both genetic damage and thiobarbituric acid reactive substances (TBARS), accompanied by a significant decrease in the antioxidant status compared to HN treated groups which modulated the toxic effects through its antioxidant potential. Thus the current study shows HN to be an effective radioprotector against gamma-radiation induced in-vitro cellular damage in lymphocytes.

Voltammetric determination of gamma radiation-induced DNA damage

Homopolydeoxyribonucleotides, poly[dGuo], poly[dAdo], poly[dThd], and poly[dCyd], and calf thymus single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) aqueous solutions previously exposed to gamma radiation doses between 2 and 35 Gy, were studied by differential pulse voltammetry using a glassy carbon electrode. The interpretation of the voltammetric data was also supported by the electrophoretic migration profile obtained for the same ssDNA and dsDNA gamma-irradiated samples by nondenaturing agarose gel electrophoresis. The generation of 8-oxo-7,8-dihydroguanine, 2,8-dihydroxyadenine, 5-formyluracil, base-free sites, and single- and double-stranded breaks in the gamma-irradiated DNA samples was detected voltammetrically, with the amount depending on the irradiation time. It was found that the current peaks obtained for 8-oxoguanine increase linearly with the radiation dose applied to the nucleic acid sample, and values between 8 and 446 8-oxo-7,8-dihydroguanine (8-oxoGua) per 10(6) guanines per Gy were obtained according to the nucleic acid sample. The results showed that voltammetry can be used for monitoring and simultaneously characterizing different kinds of DNA damage caused by gamma radiation exposure.