A Minireview on Gastrointestinal Microbiota and Radiosusceptibility

Mitigating effects of sublethal and lethal whole-body gamma irradiation in a mouse model with soluble melanin

The field of radiation countermeasures is growing, however, currently there are no effective and non-toxic compounds which could be administered orally to the individuals post exposure to high doses of ionising radiation. The pigment melanin is ubiquitous through all kingdoms of life and provides selective advantage under radiation stress through its role as a chemical and physical shield, and its capacity to respond and react to exposures. Soluble allomelanin was administered to mice following whole-body exposure to lethal or sublethal doses of gamma radiation to determine its capacity to mitigate the effects of acute radiation syndrome, and its utility as a radiation countermeasure. Allomelanin has shown a trend to improve survival post an 8 Gy sublethal radiation exposure when administered up to 48 h post-irradiation. Furthermore, it improved median and overall survival to a 10 Gy lethal radiation exposure, specifically when administered at 24 h post-irradiation. Histological analysis on the jejunum region of the small intestine of this treatment group indicated that alterations of the mucosal and submucosal architecture, and disruption of the lymphatic system associated with lethal radiation exposure were mitigated when allomelanin was administered at 24 h post-irradiation. Based on this work soluble allomelanin derived from a fungal source could serve as an easily sourced, cost-effective, and viable countermeasure to accidental radiation exposure and merits further investigation.

Modifying the Microbiome as a Potential Mechanism of Photobiomodulation: A Case Report

Objective: The objective of this case study was to elucidate the effect of photobiomodulation (PBM) on the microbiome. Background: The gut microbiome has been identified as a key component of health, with gut dysbiosis, characterized by decreased microbial diversity and an altered microbial composition, being recognized as instrumental in many diseases and disorders. Previous research has suggested that the gut microbiome can be favorably altered in animal models using PBM. Materials and methods: The participant had their microbiome tested on nine occasions, three times before any treatment, three times after radiotherapy and commencement of immunotherapy for breast cancer, and three times after PBM treatment. The PBM treatment consisted of infrared laser treatment (904 nm; 700 Hz pulse frequency, 861.3 total joules) to the abdomen three times per week for 11 weeks. Results: The microbiome of the participant showed significant changes in diversity after PBM treatment, but not after cancer therapy, with an increase in the number of known beneficial bacteria (Akkermansia, Faecalibacterium, and Roseburia) and decrease in the number of potentially pathogenic genera. Conclusions: The results suggested the possibility that PBM may alter the microbiome and thus it represents a therapeutic avenue for chronic diseases with otherwise limited treatment options.

Mitigation of Iron Irradiation-Induced Genotoxicity and Genomic Instability by Postexposure Dietary Restriction in Mice

Background and Purpose. Postexposure onset of dietary restriction (DR) is expected to provide therapeutic nutritional approaches to reduce health risk from exposure to ionizing radiation (IR) due to such as manned space exploration, radiotherapy, or nuclear accidents as IR could alleviate radiocarcinogenesis in animal models. However, the underlying mechanisms remain largely unknown. This study is aimed at investigating the effect from postexposure onset of DR on genotoxicity and genomic instability (GI) induced by total body irradiation (TBI) in mice. Materials and Methods. Mice were exposed to 2.0 Gy of accelerated iron particles with an initial energy of 500 MeV/nucleon and a linear energy transfer (LET) value of about 200 keV/μm. After TBI, mice were either allowed to free access to a standard laboratory chow or treated under DR (25% cut in diet). Using micronucleus frequency (MNF) in bone marrow erythrocytes, induction of acute genotoxicity and GI in the hematopoietic system was, respectively, determined 1 and 2 months after TBI. Results and Conclusions. TBI alone caused a significant increase in MNF while DR alone did not markedly influence the MNF. DR induced a significant decrease in MNF compared to the treatment by TBI alone. Results demonstrated that postexposure onset of DR could relieve the elevated MNF induced by TBI with high-LET iron particles. These findings indicated that reduction in acute genotoxicity and late GI may be at least a part of the mechanisms underlying decreased radiocarcinogenesis by DR.