Modifiers of radiation effects in the eye

Effect of adenosine treatment on ionizing radiation toxicity in zebrafish early life stages

The danger of ionizing radiation exposure to human health is a concern. Since its wide use in medicine and industry, the development of radioprotectors has been very significant. Adenosine exerts anti-inflammatory actions and promotes tissue protection and repair, by activating the P1 receptors (A1, A2A, A2B, and A3). Zebrafish (Danio rerio) is an appropriate tool in the fields of toxicology and pharmacology, including the evaluation of radiobiological outcomes and in the search for radioprotector agents. This study aims to evaluate the effect of adenosine in the toxicity induced by radiation in zebrafish. Embryos were treated with 1, 10, or 100 µM adenosine, 30 min before the exposure to 15 Gy of gamma radiation. Adenosine potentiated the effects of radiation in heart rate, body length, and pericardial edema. We evaluated oxidative stress, tissue remodeling and inflammatory. It was seen that 100 µM adenosine reversed the inflammation induced by radiation, and that A2A2 and A2B receptors are involved in these anti-inflammatory effects. Our results indicate that P1R activation could be a promising pharmacological strategy for radioprotection.

Caffeic acid phenethyl ester: A review on its pharmacological importance, and its association with free radicals, COVID-19, and radiotherapy

Caffeic acid phenethyl ester (CAPE), a main active component of propolis and a flavonoid, is one of the natural products that has attracted attention in recent years. CAPE, which has many properties such as anti-cancer, anti-inflammatory, antioxidant, antibacterial and anti-fungal, has shown many pharmacological potentials, including protective effects on multiple organs. Interestingly, molecular docking studies showed the possibility of binding of CAPE with replication enzyme. In addition, it was seen that in order to increase the binding security of the replication enzyme and CAPE, modifications can be made at three sites on the CAPE molecule, which leads to the possibility of the compound working more powerfully and usefully to prevent the proliferation of cancer cells and reduce its rate. Also, it was found that CAPE has an inhibitory effect against the main protease enzyme and may be effective in the treatment of SARS-CoV-2. This review covers in detail the importance of CAPE in alternative medicine, its pharmacological value, its potential as a cancer anti-proliferative agent, its dual role in radioprotection and radiosensitization, and its use against coronavirus disease 2019 (COVID-19).

Discovery of the radio-protecting effect of Ecliptae Herba, its constituents and targeting p53-mediated apoptosis in vitro and in vivo

Radiation protection drugs are often accompanied by toxicity, even amifostine, which has been the dominant radio-protecting drug for nearly 30 years. Furthermore, there is no therapeutic drug for radiation-induced intestinal injury (RIII). This paper intends to find a safe and effective radio-protecting ingredient from natural sources. The radio-protecting effect of Ecliptae Herba (EHE) was discovered preliminarily by antioxidant experiments and the mouse survival rate after ¹³⁷Cs irradiation. EHE components and blood substances in vivo were identified through UPLC‒Q-TOF. The correlation network of "natural components in EHE-constituents migrating to blood-targets-pathways" was established to predict the active components and pathways. The binding force between potential active components and targets was studied by molecular docking, and the mechanism was further analyzed by Western blotting, cellular thermal shift assay (CETSA), and ChIP. Additionally, the expression levels of Lgr5, Axin2, Ki67, lysozyme, caspase-3, caspase-8,8-OHdG, and p53 in the small intestine of mice were detected. It was found for the first time that EHE is active in radiation protection and that luteolin is the material basis of this protection. Luteolin is a promising candidate for RⅢ. Luteolin can inhibit the p53 signaling pathway and regulate the BAX/BCL2 ratio in the process of apoptosis. Luteolin could also regulate the expression of multitarget proteins related to the same cell cycle.

Biological Protection in Deep Space Missions

During deep space missions, astronauts are exposed to highly ionizing radiation, incl. neutrons, protons and heavy ions from galactic cosmic rays (GCR), solar wind (SW) and solar energetic particles (SEP). This increase the risks for cancerogenisis, damages in central nervous system (CNS), cardiovascular diseases, etc. Large SEP events can even cause acute radiation syndrome (ARS). Long term manned deep space missions will therefor require unique radiation protection strategies. Since it has been shown that physical shielding alone is not sufficient, this paper propose pre-flight screening of the aspirants for evaluation of their level of adaptive responses. Methods for boosting their immune system, should also be further investigated, and the possibility of using radiation effect modulators are discussed. In this paper, especially, the use of vitamin C as a promising non-toxic, cost-effective, easily available radiation mitigator (which can be used hours after irradiation), is described. Although it has previously been shown that vitamin C can decrease radiation-induced chromosomal damage in rodents, it must be further investigated before any conclusions about its radiation mitigating properties in humans can be concluded.

BRAIN AND EYE AS POTENTIAL TARGETS FOR IONIZING RADIATION IMPACT: PART II - RADIATION CEREBRO/OPHTALMIC EFFECTS IN CHILDREN, PERSONS EXPOSED IN UTERO, ASTRONAUTS AND INTERVENTIONAL RADIOLOGISTS

BACKGROUND

Ionizing radiation (IR) can affect the brain and the visual organ even at low doses, while provoking cognitive, emotional, behavioral, and visual disorders. We proposed to consider the brain and the visual organ as potential targets for the influence of IR with the definition of cerebro-ophthalmic relationships as the «eye-brain axis».

OBJECTIVE

The present work is a narrative review of current experimental, epidemiological and clinical data on radiation cerebro-ophthalmic effects in children, individuals exposed in utero, astronauts and interventional radiologists.

MATERIALS AND METHODS

The review was performed according to PRISMA guidelines by searching the abstract and scientometric databases PubMed/MEDLINE, Scopus, Web of Science, Embase, PsycINFO, Google Scholar, published from 1998 to 2021, as well as the results of manual search of peer-reviewed publications.

RESULTS

Epidemiological data on the effects of low doses of IR on neurodevelopment are quite contradictory, while data on clinical, neuropsychological and neurophysiological on cognitive and cerebral disorders, especially in the left, dominant hemisphere of the brain, are nore consistent. Cataracts (congenital - after in utero irradiation) and retinal angiopathy are more common in prenatally-exposed people and children. Astronauts, who carry out longterm space missions outside the protection of the Earth's magnetosphere, will be exposed to galactic cosmic radiation (heavy ions, protons), which leads to cerebro-ophthalmic disorders, primarily cognitive and behavioral disorders and cataracts. Interventional radiologists are a special risk group for cerebro-ophthalmic pathology - cognitivedeficits, mainly due to dysfunction of the dominant and more radiosensitive left hemisphere of the brain, andcataracts, as well as early atherosclerosis and accelerated aging.

CONCLUSIONS

Results of current studies indicate the high radiosensitivity of the brain and eye in different contingents of irradiated persons. Further research is needed to clarify the nature of cerebro-ophthalmic disorders in different exposure scenarios, to determine the molecular biological mechanisms of these disorders, reliable dosimetric support and taking into account the influence of non-radiation risk factors.

The Protective Effect of Estrogen Against Radiation Cataractogenesis is Dependent Upon the Type of Radiation

Astronauts participating in prolonged space missions constitute a population of individuals who are at an increased risk for cataractogenesis due to exposure to densely ionizing charged particles. Using a rat model, we have previously shown that after irradiation of eyes with either low-linear energy transfer (LET) 60Co γ rays or high-LET 56Fe particles, the rate of progression of anterior and posterior subcapsular cataracts was significantly greater in ovariectomized females implanted with 17-β-estradiol (E2) compared to ovariectomized or intact rats. However, our additional low-LET studies indicated that cataractogenesis may be a modifiable late effect, since we have shown that the modulation of cataractogenesis is dependent upon the timing of administration of E2. Interestingly, we found that E2 protected against cataractogenesis induced by low-LET radiation, but only if administered after the exposure; if administered prior to and after irradiation, for the entire period of observation, then E2 enhanced progression and incidence of cataracts. Since most radioprotectors tested to date are unsuccessful in protecting against the effects of high-LET radiation, we wished to determine whether the protection mediated by E2 against radiation cataractogenesis induced by low-LET radiation would also be observed after high-LET irradiation. Female 56-day-old Sprague-Dawley rats were treated with E2 at various times relative to the time of single-eye irradiation with 2 Gy of 56Fe ions. We found that administration of E2 before irradiation and throughout the lifetime of the rat enhanced cataractogenesis compared to ovariectomized animals. The enhancing effect was slightly reduced when estrogen was removed after irradiation. However, in contrast to what we observed after γ-ray irradiation, there was no inhibition of cataractogenesis if E2 was administered only after 56Fe-ion irradiation. We conclude that protection against cataractogenesis by estrogen is dependent upon the type and ionization density of radiation that the lens was exposed to. The lack of inhibition of radiation cataractogenesis in rats that receive E2 treatment after high-LET irradiation may be attributed to the qualitative differences in the types of DNA damage induced with high-LET radiation compared to low-LET radiation or how damage may be modified at the DNA or tissue level after irradiation.

1,4-Dithiothreitol treatment ameliorates hematopoietic and intestinal injury in irradiated mice: Potential application of a treatment for acute radiation syndrome

Radiation exposure poses a significant threat to public health, which can lead to acute hematopoietic system and intestinal system injuries due to their higher radiation sensitivity. Hence, antioxidants and thiol-reducing agents could have a potential protective effect against this complication. The dithiol compound 1,4-dithiothreitol (DTT) has been used in biochemistry, peptide/protein chemistry and clinical medicine. However, the effect of DTT on ionizing radiation (IR)-induced hematopoietic injury and intestinal injury are unknown. The current investigation was designed to evaluate the effect of DTT as a safe and clinically applicable thiol-radioprotector in irradiated mice. DTT treatment improved the survival of irradiated mice and ameliorated whole body irradiation (WBI)-induced hematopoietic injury by attenuating myelosuppression and myeloid skewing, increasing self-renewal and differentiation of hematopoietic progenitor cells/hematopoietic stem cells (HPCs/HSCs). In addition, DTT treatment protected mice from abdominal irradiation (ABI)-induced changes in crypt-villus structures and function. Furthermore, treatment with DTT significantly enhanced the ABI-induced reduction in Olfm4 positive cells and offspring cells of Lgr5⁺ stem cells, including lysozyme⁺ Paneth cells and Ki67⁺ cells. Moreover, IR-induced DNA strand break damage, and the expression of proapoptotic-p53, Bax, Bak protein and antiapoptotic-Bcl-2 protein were reversed in DTT treated mice, and DTT also promoted small intestine repair after radiation exposure via the p53 intrinsic apoptotic pathway. In general, these results demonstrated the potential of DTT for protection against hematopoietic injury and intestinal injury after radiation exposure, suggesting DTT as a novel effective agent for radioprotection.

Development of a novel artifact-free eye shield based on silicon rubber-lead composition in the CT examination of the head

The aim of this work was to develop a novel artifact-free eye shield and evaluate its effect on the dose received by the eye lens and the resulting image quality in the CT examination of the head. A new material for an eye shield was synthesised from silicon rubber (SR) and lead (Pb) using a simple method. The percentage of Pb was varied from 0 to 5% wt. An anthropomorphic head phantom was scanned with and without the SR-Pb eye shield, and compared with a tungsten paper (WP) eye shield. The distance from the eye shield and head was varied from 0 to 5 cm. The dose to the eye lens was measured using photo-luminescence detectors (PLDs). The presence of artifacts was determined by measuring CT numbers at different eye lens locations and by subtracting images with and without the eye shield. The dose reduction increases with increasing Pb content in the SR-Pb eye shield. A 5% wt SR-Pb eye shield reduced the eye lens dose by up to 50%, whereas the WP eye shield reduced the dose by up to 86%. The CT numbers in images with the SR-Pb eye shield in the regions of both eyes and the center of the head phantom is similar to those without the eye shield, indicating that there is no artifact in the resulting image. Using the WP eye shield, there is considerable artifact with the CT number increasing by up to 700% in the regions of both eyes and the center of the head. It is found that the distance between the SR-Pb eye shield and the head does not affect either the dose or the resulting images. A SR-Pb-based eye shield can be applied in clinical environments and should be placed directly above the eye surface for dose optimisation.