Radiation-induced ophthalmic risks of long duration spaceflight: Current investigations and interventions

Potential Risks of Ocular Molecular and Cellular Changes in Spaceflight

PURPOSE

Many fundamental cellular and molecular changes are known to occur in biological systems during spaceflight, including oxidative stress, DNA damage, mitochondrial damage, epigenetic factors, telomere lengthening, and microbial shifts. We can apply the consequences of these molecular changes in ocular cells, such as the retinal ganglion cells and corneal epithelium, to identify ophthalmologic risks during spaceflight. This review aims to discuss the potential molecular changes in greater detail and apply the principles to ocular cells and ophthalmic disease risk in astronauts.

METHODS

A targeted, relevant search of the literature on the topic and related topics of ocular surface and spaceflight was conducted with scholarly databases PubMed, Web of Science, and Embase from inception to July2024 with search terms "oxidative stress"; "DNA damage"; "Mitochondrial Dysfunction"; "Epigenetics"; "Telomeres"; "Microbiome"; "ocular cells"; "spaceflight"; "microgravity"; "radiation."

RESULTS

A total of 115 articles were included following screening and eligibility assessment. Key findings include molecular changes and their contributions to ophthalmic diseases like cataracts, spaceflight-associated neuro-ocular syndrome, and dry eye syndrome.

CONCLUSION

This review provides a comprehensive overview of risks to vision associated with long-duration spaceflight missions beyond low Earth orbit (LEO). Further investigation into targeted countermeasures is imperative to mitigate vision-threatening sequelae in astronauts undertaking deep-space exploration.

Nanotechnology meets radiobiology: Fullerenols and Metallofullerenols as nano-shields in radiotherapy

Despite significant advances in the development of radioprotective measures, the clinical application of radioprotectors and radiomitigators remains limited due to insufficient efficacy and high toxicity of most agents. Additionally, in oncological radiotherapy, these compounds may interfere with the therapeutic effectiveness. Recent progress in nanotechnology highlights fullerenols (FulOHs) and metallofullerenols (Me@FulOHs) as promising candidates for next-generation radioprotectors. These nanostructures possess unique antioxidant properties, demonstrating greater efficacy in rediucing oxidative stress compared to conventional agents. Moreover, their potential to minimize pro-oxidative risks depends on the precise identification of cellular environments and irradiation conditions that optimize their radioprotective effects. In parallel, Me@FulOHs serve as powerful theranostic tools in oncology. Their strong imaging signals enable high-resolution PET and MRI, facilitating early detection and accurate localization of pathogenic alterations. This dual functionality positions Me@FulOHs as key components in advanced radiotherapy. By integrating these nanomaterials with modern theranostic approaches, it is possible to enhance the precision of treatment while minimizing side effects, addressing a critical need in contemporary oncology. This review emphasizes the importance of systematic evaluation of context-dependent effects of Me@FulOHs, particularly in pre- and post-irradiation scenarios, to optimize their clinical relevance. The dual role of Me@FulOHs as both radioprotectors and diagnostic agents distinguishes them from traditional compounds, paving the way for innovative practical applications. Their use in radiotherapy represents a significant step toward the development of safer and more effective strategies in radiation protection and cancer treatment. We also review ionizing radiation effects, classifications, cancer radiotherapy applications, and countermeasures.

Exploring Angiotensin II and Oxidative Stress in Radiation-Induced Cataract Formation: Potential for Therapeutic Intervention

Radiation-induced cataracts (RICs) represent a significant public health challenge, particularly impacting individuals exposed to ionizing radiation (IR) through medical treatments, occupational settings, and environmental factors. Effective therapeutic strategies require a deep understanding of the mechanisms underlying RIC formation (RICF). This study investigates the roles of angiotensin II (Ang II) and oxidative stress in RIC development, with a focus on their combined effects on lens transparency and cellular function. Key mechanisms include the generation of reactive oxygen species (ROS) and oxidative damage to lens proteins and lipids, as well as the impact of Ang II on inflammatory responses and cellular apoptosis. While the generation of ROS from water radiolysis is well established, the impact of Ang II on RICs is less understood. Ang II intensifies oxidative stress by activating type 1 receptors (AT1Rs) on lens epithelial cells, resulting in increased ROS production and inflammatory responses. This oxidative damage leads to protein aggregation, lipid peroxidation, and apoptosis, ultimately compromising lens transparency and contributing to cataract formation. Recent studies highlight Ang II's dual role in promoting both oxidative stress and inflammation, which accelerates cataract development. RICs pose a substantial public health concern due to their widespread prevalence and impact on quality of life. Targeting Ang II signaling and oxidative stress simultaneously could represent a promising therapeutic approach. Continued research is necessary to validate these strategies and explore their efficacy in preventing or reversing RIC development.

Safety protocols, precautions, and countermeasures aboard the International Space Station to prevent ocular injury

The International Space Station (ISS) is a $100 billion epicenter of human activity in the vacuum of space that displays mankind's collective endeavor to explore the cosmic frontier. Even within the marvels of technological sophistication aboard the ISS, the human eye remains a highly vulnerable structure. In the absence of multiple layers of protection and risk assessments, crewmembers would face a substantial increase in vulnerability to ocular injury. Aside from stringent preflight screening criteria for astronauts, the ISS is equipped with ophthalmic medications, environmental control and life support systems (e.g., humidity regulation, carbon dioxide removal, pressurized device regulators), and radiation protection to reduce ocular injury. Moreover, additional countermeasures are currently being developed to mitigate the effects of spaceflight-associated neuro-ocular syndrome (SANS) and lunar dust toxicity for the Artemis Program missions. The success of future endeavors hinges not only on continued technological innovation, but also respecting the intricate interplay between human physiology and the extraterrestrial environments. Establishing habitations on the Moon and Mars, as well as NASA's Gateway Program (humanity's first space station around the Moon), will introduce a new set of challenges, underscoring the necessity for continuous insights into ocular health in space. We discuss the safety protocols, precautions, and countermeasures implemented on the ISS to prevent ocular injury - an aspect often overshadowed by the grandeur of space exploration.

Coordinated lunar time (LTC): Implications of a lunar-centric time zone on astronaut health and space medicine

Lunar exploration offers an exciting opportunity for humanity to advance scientific knowledge and future potential economic growth and possibly allow humans to become a multi-planetary species. On April 2, 2024 the US Office of Science and Technology Policy released a memorandum outlining the current Biden-Harris Administration's policy on the need to establish time standards at celestial bodies other than Earth. This memorandum also introduced the need for Coordinated Lunar Time (CLT), the concept of having a reference time for the moon. The establishment of CLT would provide a multitude of benefits for astronaut health, from expedition planning, to maintaining a sense of order in an austere environment. International agreements and collaboration will be required prior to the recognition of CLT.