On the Nature of Murine Radiation-Induced Subcapsular Cataracts: Optical Coherence Tomography-Based Fine Classification, In Vivo Dynamics and Impact on Visual Acuity

Individual response of the ocular lens to ionizing radiation

PURPOSE

Cataract (opacification of the ocular lens) is a typical tissue reaction (deterministic effect) following ionizing radiation exposure, for which prevention dose limits have been recommended in the radiation protection system. Manifestations of radiation cataracts can vary among individuals, but such potential individual responses remain uncharacterized. Here we review relevant literature and discuss implications for radiation protection. This review assesses evidence for significant modification of radiation-induced cataractogenesis by age at exposure, sex and genetic factors based on current scientific literature.

CONCLUSIONS

In addition to obvious physical factors (e.g. dose, dose rate, radiation quality, irradiation volume), potential factors modifying individual responses for radiation cataracts include sex, age and genetics, with comorbidity and coexposures also having important roles. There are indications and preliminary data identifying such potential modifiers of radiation cataract incidence or risk, although no firm conclusions can yet be drawn. Further studies and a consensus on the evidence are needed to gain deeper insights into factors determining individual responses regarding radiation cataracts and the implications for radiation protection.

Aged Nrf2-Null Mice Develop All Major Types of Age-Related Cataracts

Purpose

Age-related cataracts affect the majority of older adults and are a leading cause of blindness worldwide. Treatments that delay cataract onset or severity have the potential to delay cataract surgery, but require relevant animal models that recapitulate the major types of cataracts for their development. Unfortunately, few such models are available. Here, we report the lens phenotypes of aged mice lacking the critical antioxidant transcription factor Nfe2l2 (designated as Nrf2 −/−).

Methods

Three independent cohorts of Nrf2 −/− and wild-type C57BL/6J mice were evaluated for cataracts using combinations of slit lamp imaging, photography of freshly dissected lenses, and histology. Mice were fed high glycemic diets, low glycemic diets, regular chow ad libitum, or regular chow with 30% caloric restriction.

Results

Nrf2 −/− mice developed significant opacities between 11 and 15 months and developed advanced cortical, posterior subcapsular, anterior subcapsular, and nuclear cataracts. Cataracts occurred similarly in male mice fed high or low glycemic diets, and were also observed in 21-month male and female Nrf2 −/− mice fed ad libitum or 30% caloric restriction. Histological observation of 18-month cataractous lenses revealed significant disruption to fiber cell architecture and the retention of nuclei throughout the cortical region of the lens. However, fiber cell denucleation and initiation of lens differentiation was normal at birth, with the first abnormalities observed at 3 months.

Conclusions

Nrf2 −/− mice offer a tool to understand how defective antioxidant signaling causes multiple forms of cataract and may be useful for screening drugs to prevent or delay cataractogenesis in susceptible adults.

Complex Long-term Effects of Radiation on Adult Mouse Behavior

We have shown previously that a single radiation event (0.063, 0.125 or 0.5 Gy, 0.063 Gy/min) in adult mice (age 10 weeks) can have delayed dose-dependent effects on locomotor behavior 18 months postirradiation. The highest dose (0.5 Gy) reduced, whereas the lowest dose (0.063 Gy) increased locomotor activity at older age independent of sex or genotype. In the current study we investigated whether higher doses administered at a higher dose rate (0.5, 1 or 2 Gy, 0.3 Gy/min) at the same age (10 weeks) cause stronger or earlier effects on a range of behaviors, including locomotion, anxiety, sensorimotor and cognitive behavior. There were clear dose-dependent effects on spontaneous locomotor and exploratory activity, anxiety-related behavior, body weight and affiliative social behavior independent of sex or genotype of wild-type and Ercc2S737P heterozygous mice on a mixed C57BL/6JG and C3HeB/FeJ background. In addition, smaller genotype- and dose-dependent radiation effects on working memory were evident in males, but not in females. The strongest dose-dependent radiation effects were present 4 months postirradiation, but only effects on affiliative social behaviors persisted until 12 months postirradiation. The observed radiation-induced behavioral changes were not related to alterations in the eye lens, as 4 months postirradiation anterior and posterior parts of the lens were still normal. Overall, we did not find any sensitizing effect of the mutation towards radiation effects in vivo.

ZNF219 protects human lens epithelial cells against H2O2-induced injury via targeting SOX9 through activating AKT/GSK3β pathway

Opacity of the lens caused by cataracts could lead to severe visual impairment and even blindness. Oxidative stress caused by exposure of lens epithelial cells to hydrogen peroxide (H₂O₂) can lead to DNA damage and impair cell function. Therefore, how to prevent lens epithelial cells from being harmed by H₂O₂ is an urgent problem. The ZNF219 gene belongs to the Kruppel like zinc finger gene family, which is involved in a variety of biological processes. In this study, we found the low expression of ZNF219 in H₂O₂-induced HLE-B3 cells. We further noticed ZNF219 could improve the survival rate of H₂O₂-induced HLE-B3 cells, and inhibit the apoptosis and oxidative stress response. Mechanically, ZNF219 protected human lens epithelial cells against H₂O₂-induced injury via targeting SOX9 through activating AKT/GSK3β pathway. We therefore thought ZNF219 was a key protective protein in the oxidative damage of human lens epithelial cells and the pathogenesis of cataract.