Lifetime study in mice after acute low-dose ionizing radiation: a multifactorial study with special focus on cataract risk.

Because of the increasing application of ionizing radiation in medicine, quantitative data on effects of low-dose radiation are needed to optimize radiation protection, particularly with respect to cataract development. Using mice as mammalian animal model, we applied a single dose of 0, 0.063, 0.125 and 0.5 Gy at 10 weeks of age, determined lens opacities for up to 2 years and compared it with overall survival, cytogenetic alterations and cancer development. The highest dose was significantly associated with increased body weight and reduced survival rate. Chromosomal aberrations in bone marrow cells showed a dose-dependent increase 12 months after irradiation. Pathological screening indicated a dose-dependent risk for several types of tumors. Scheimpflug imaging of the lens revealed a significant dose-dependent effect of 1% of lens opacity. Comparison of different biological end points demonstrated long-term effects of low-dose irradiation for several biological end points.

Effects of ionizing radiation on telomere length and telomerase activity in cultured human lens epithelium cells.

PURPOSE: To investigate the effects of ionizing radiation on telomere length and telomerase activity in human lens epithelial cells. There are studies suggesting evidence of telomere length in association with opacity of the lens; however, these studies have been conducted on Canine Lens cells. Our study was designed to understand further the effects of different doses of ionizing radiation on telomere length and telomerase activity in cultured human lens epithelium cells from three Donors. MATERIALS AND METHODS: For this study, embryonic human lens epithelial (HLE) cells from three donors, obtained commercially were cultured. Telomere length and telomerase activity were measured after each passage until cells stopped growing in culture. This was repeated on irradiated (0.001 Gy, 0.01 Gy, 0.02 Gy, 0.1 Gy, 1 Gy and 2 Gy) cells. DNA damage response using the H2AX and telomere dysfunction foci assays were also examined at 30 mins, 24 hours, 48 hours and 72 hours postirradiation. RESULTS AND CONCLUSION: We have demonstrated genetic changes in telomere length and oxidative stress, which may be relevant to cataractogenesis. Our study shows that in control cells telomere length increases as passage increases. We have also demonstrated that telomere length increases at higher doses of 1.0 Gy and 2.0 Gy. However, telomerase activity decreases dose dependently and as passages increase. These results are not conclusive and further studies ex vivo measuring lens opacity and telomere length in the model would be beneficial in a bigger cohort, hence confirming a link between telomere length, cataractogenesis and genetic factors.