Lasting Effects of Low to Non-Lethal Radiation Exposure during Late Gestation on Offspring's Cardiac Metabolism and Oxidative Stress

In utero exposure to ionizing radiation and metabolic regulation: perspectives for future multi- and trans-generation effects studies

PURPOSE

The radiation protection community has been particularly attentive to the risks of delayed effects on offspring from low dose or low dose-rate exposures to ionizing radiation. Despite this, the current epidemiologic studies and scientific data are still insufficient to provide the necessary evidence for improving risk assessment guidelines. This literature review aims to inform future studies on multigenerational and transgenerational effects. It primarily focuses on animal studies involving in utero exposure and discusses crucial elements for interpreting the results. These elements include in utero exposure scenarios relative to the developmental stages of the embryo/fetus, and the primary biological mechanisms responsible for transmitting heritable or hereditary effects to future generations. The review addresses several issues within the contexts of both multigenerational and transgenerational effects, with a focus on hereditary perspectives.

CONCLUSIONS

Knowledge consolidation in the field of Developmental Origins of Health and Disease (DOHaD) has led us to propose a new study strategy. This strategy aims to address the transgenerational effects of in utero exposure to low dose and low dose-rate radiation. Within this concept, there is a possibility that disruption of epigenetic programming in embryonic and fetal cells may occur. This disruption could lead to metabolic dysfunction, which in turn may cause abnormal responses to future environmental challenges, consequently increasing disease risk. Lastly, we discuss methodological limitations in our studies. These limitations are related to cohort size, follow-up time, model radiosensitivity, and analytical techniques. We propose scientific and analytical strategies for future research in this field.

Absence of Depressive and Anxious Behavior with Genetic Dysregulation in Adult C57Bl/6J Mice after Prenatal Exposure to Ionizing Radiation

The exposure of ionizing radiation during early gestation often leads to deleterious and even lethal effects; however, few extensive studies have been conducted on late gestational exposures. This research examined the behavior al effects of C57Bl/6J mouse offspring exposed to low dose ionizing gamma irradiation during the equivalent third trimester. Pregnant dams were randomly assigned to sham or exposed groups to either low dose or sublethal dose radiation (50, 300, or 1000 mGy) at gestational day 15. Adult offspring underwent a behavioral and genetic analysis after being raised under normal murine housing conditions. Our results indicate very little change in the behavioral tasks measuring general anxiety, social anxiety, and stress-management in animals exposed prenatally across the low dose radiation conditions. Quantitative real-time polymerase chain reactions were conducted on the cerebral cortex, hippocampus, and cerebellum of each animal; results indicate some dysregulation in markers of DNA damage, synaptic activity, reactive oxygen species (ROS) regulation, and methylation pathways in the offspring. Together, our results provide evidence in the C57Bl/6J strain, that exposure to sublethal dose radiation (<1000 mGy) during the last period of gestation leads to no observable changes in behaviour when assessed as adults, although some changes in gene expression were observed for specific brain regions. These results indicate that the level of oxidative stress occurring during late gestation for this mouse strain is not sufficient for a change in the assessed behavioral phenotype, but results in some modest dysregulation of the genetic profile of the brain.

Effects of low-dose oxygen ions on cardiac function and structure in female C57BL/6J mice

PURPOSE

Astronauts in space vehicles beyond low-Earth orbit will be exposed to high charge and energy (HZE) ions, and there is concern about potential adverse effects on the cardiovascular system. Thus far, most animal studies that assess cardiac effects of HZE particles have included only males. This study assessed the effects of oxygen ions (¹⁶O) as a representative ion of the intravehicular radiation environment on the heart of female mice.

MATERIALS AND METHODS

Female C57BL/6 J mice at 6 months of age were exposed to ¹⁶O (600 MeV/n) at 0.25-0.26 Gy/min to a total dose of 0, 0.1, or 0.25 Gy. Cardiac function and abdominal aorta blood velocity were measured with ultrasonography at 3, 5, 7, and 9 months after irradiation. At 2 weeks, 3 months, and 9 months, cardiac tissue was collected to assess collagen deposition and markers of immune cells.

RESULTS

Ultrasonography revealed increased left ventricle mass, diastolic volume and diameter but there was no change in the abdominal aorta. There was no indication of cardiac fibrosis however, a 75 kDa peptide of left ventricular collagen type III and α-smooth muscle cell actin were increased suggesting some remodeling had occurred. Left ventricular protein levels of the T-cell marker CD2 was significantly increased at all time points, while the neutrophil marker myeloperoxidase was decreased at 2 weeks and 9 months.

CONCLUSIONS

These results taken together suggest ¹⁶O ion exposure did not result in cardiac fibrosis or cardiac dysfunction in female mice. However, it does appear mild cardiac remodeling occurs in response to HZE radiation.