Negative Modulation of Bystander DNA Repair Potential by X-Ray Targeted Tissue Volume in Arabidopsis thaliana

The role of signaling systems of plant in responding to key astrophysical factors: increased ionizing radiation, near-null magnetic field and microgravity

Plants will form the basis of artificial ecosystems in space exploration and the creation of bases on other planets. Astrophysical factors, such as ionizing radiation (IR), magnetic fields (MF) and gravity, can significantly affect the growth and development of plants beyond Earth. However, to date, the ways in which these factors influence plants remain largely unexplored. The review shows that, despite the lack of specialized receptors, plants are able to perceive changes in astrophysical factors. Potential mechanisms for perceiving changes in IR, MF and gravity levels are considered. The main pathway for inducing effects in plants is caused by primary physicochemical reactions and change in the levels of secondary messengers, including ROS and Ca2+. The presence of common components, including secondary messengers, in the chain of responses to astrophysical factors determines the complex nature of the response under their combined action. The analysis performed and the proposed hypothesis will help in planning space missions, as well as identifying the most important areas of research in space biology.

From Classical Radiation to Modern Radiation: Past, Present, and Future of Radiation Mutation Breeding

Radiation mutation breeding has been used for nearly 100 years and has successfully improved crops by increasing genetic variation. Global food production is facing a series of challenges, such as rapid population growth, environmental pollution and climate change. How to feed the world's enormous human population poses great challenges to breeders. Although advanced technologies, such as gene editing, have provided effective ways to breed varieties, by editing a single or multiple specific target genes, enhancing germplasm diversity through mutation is still indispensable in modern and classical radiation breeding because it is more likely to produce random mutations in the whole genome. In this short review, the current status of classical radiation, accelerated particle and space radiation mutation breeding is discussed, and the molecular mechanisms of radiation-induced mutation are demonstrated. This review also looks into the future development of radiation mutation breeding, hoping to deepen our understanding and provide new vitality for the further development of radiation mutation breeding.

Bystander effect and abscopal effect in recurrent thymic carcinoma treated with carbon-ion radiation therapy: A case report

BACKGROUND

Although the bystander effect and abscopal effect are familiar in medicine, they are relatively rare in clinical practice. Herein, we report the case of a patient who demonstrated an obvious bystander effect and abscopal effect response following carbon-ion irradiation for recurrent thymic carcinoma.

CASE SUMMARY

A 44-year-old female presented with shortness of breath. Eleven years prior, she was diagnosed with athymic tumor located in the anterosuperior mediastinum. She underwent extensive tumor resection, and the postoperative pathologic diagnosis was thymic carcinoma. She was administered 50 Gy/25 Fx of postoperative radiation. In 2019, she was diagnosed with a recurrence of thymic carcinoma, with multiple recurrent nodules and masses in the left thoracic chest and peritoneal cavity, the largest of which was in the diaphragm pleura proximal to the pericardium, with a size of 6.7 cm × 5.3 cm × 4.8 cm. She received carbon-ion radiotherapy. After carbon-ion radiotherapy treatment, the treated masses and the untreated masses were observed to have noticeably shrunk on the day of carbon-ion radiotherapy completion and on follow-up imaging. We followed the CARE Guidelines for consensus-based clinical case reporting guideline development and completed the CARE Checklist of information to report this case.

CONCLUSION

This report is the first of obvious abscopal and bystander effects following carbon-ion irradiation in a human patient, and further research is needed to better elucidate the mechanisms of bystander and abscopal effects.

Quantitative modeling of multigenerational effects of chronic ionizing radiation using targeted and nontargeted effects

Stress response signals can propagate between cells damaged by targeted effects (TE) of ionizing radiation (e.g. energy depositions and ionizations in the nucleus) and undamaged "bystander" cells, sometimes over long distances. Their consequences, called non-targeted effects (NTE), can substantially contribute to radiation-induced damage (e.g. cell death, genomic instability, carcinogenesis), particularly at low doses/dose rates (e.g. space exploration, some occupational and accidental exposures). In addition to controlled laboratory experiments, analysis of observational data on wild animal and plant populations from areas contaminated by radionuclides can enhance our understanding of radiation responses because such data span wide ranges of dose rates applied over many generations. Here we used a mechanistically-motivated mathematical model of TE and NTE to analyze published embryonic mortality data for plants (Arabidopsis thaliana) and rodents (Clethrionomys glareolus) from the Chernobyl nuclear power plant accident region. Although these species differed strongly in intrinsic radiosensitivities and post-accident radiation exposure magnitudes, model-based analysis suggested that NTE rather than TE dominated the responses of both organisms to protracted low-dose-rate irradiation. TE were predicted to become dominant only above the highest dose rates in the data. These results support the concept of NTE involvement in radiation-induced health risks from chronic radiation exposures.

REVIEW OF QUANTITATIVE MECHANISTIC MODELS OF RADIATION-INDUCED NON-TARGETED EFFECTS (NTE)

Quantitative mechanistic modeling of the biological effects of ionizing radiation has a long rich history. Initially, it was dominated by target theory, which quantifies damage caused by traversal of cellular targets like DNA by ionizing tracks. The discovery that mutagenesis, death and/or altered behavior sometimes occur in cells that were not themselves traversed by any radiation tracks but merely interacted with traversed cells was initially seen as surprising. As more evidence of such 'non-targeted' or 'bystander' effects accumulated, the importance of their contribution to radiation-induced damage became more recognized. Understanding and modeling these processes is important for quantifying and predicting radiation-induced health risks. Here we review the variety of mechanistic mathematical models of nontargeted effects that emerged over the past 2-3 decades. This review is not intended to be exhaustive, but focuses on the main assumptions and approaches shared or distinct between models, and on identifying areas for future research.