Differences in sustained alterations in protein expression between livers of mice exposed to high-dose-rate and low-dose-rate radiation

Multiple radiations and its effect on biological system - a review on in vitro and in vivo mechanisms

PURPOSE

We are exposed to different types of radiation from natural sources or for biomedical diagnostic and therapeutic purposes at different doses or times. The dose, duration, and number of exposures can cause multiple effects both in vivo and in vitro. Several researchers have explored the effects of ionizing and non-ionizing radiation in cell lines and animal models. Macromolecules, such as DNA, RNA, and proteins, are the primary targets of damage and can lead to several diseases, including cancer and even cell death. Chronic low-dose exposure of cells to radiation can cause alterations in gene expression and can be deleterious to the fate of the cells. We aim to discuss the implications of multiple radiations on different biological systems, including how nanotechnology can facilitate the effects of radiation in therapeutics.

CONCLUSION

In this review, we discuss the in vitro and in vivo changes that occur due to exposure to different types of radiation used in diagnosis, therapeutics, and other means, such as radiation equipment operators and patients being exposed. The effects of ionizing and non-ionizing radiation have been discussed separately. We have also mentioned in detail about the human-caused accidents of Hiroshima and Chernobyl in this article. The application of nanotechnology in facilitating the effects of radiation in the therapy and management of radioresistance of cells has also been discussed. The radio resistance and method to improve the radiosensitivity have also been mentioned. This review article can reflect the recent developments in the various uses of ionizing and non-ionizing radiation in biomedical field and will open up new avenues to utilize radiation in a more prudent way. The role of nanotechnology in reducing the harmful effects of radiation is also discussed.

Autophagy-related genes analysis reveals potential biomarkers for prediction of the impaired walking capacity of peripheral arterial disease

BACKGROUND

The role of autophagy and autophagy-related genes in peripheral arterial disease (PAD) remains unknown and may be of diagnostic and prognostic value. The aim of this study is to investigate the relationship between autophagy and PAD, and identify potential diagnostic or prognostic biomarkers for medical practice.

METHODS

Differentially expressed autophagy-related genes in PAD were explored from GSE57691 and validated in our WalkByLab registry participants by quantitative real-time polymerase chain reaction (qRT-PCR). The level of autophagy in peripheral blood mononuclear cells (PBMCs) of WalkByLab participants was assessed by analyzing autophagic marker proteins (beclin-1, P62, LC3B). Single sample gene set enrichment analysis (ssGSEA) was used to evaluate the immune microenvironment within the artery wall of PAD patients and healthy persons. Chemokine antibody array and enzyme-linked immunosorbent assay were used to assess the chemokines in participants' plasma. Treadmill testing with Gardner protocol was used to evaluate participants' walking capacity. Pain-free walking distance, maximum walking distance, and walking time were recorded. Finally, a nomogram model based on logistic regression was built to predict impaired walking performance.

RESULTS

A total of 20 relevant autophagy-related genes were identified, and these genes were confirmed to be expressed at low levels in our PAD participants. Western blotting demonstrated that the expression of autophagic marker proteins beclin-1 and LC3BII were significantly reduced in PAD patients' PBMCs. ssGSEA revealed that most of the autophagy-related genes were strongly correlated with immune function, with the largest number of associated genes showing interaction between cytokine-and-cytokine receptors (CCR). In this context, the chemokines growth-related oncogene (GRO) and neutrophil activating protein2 (NAP2) are highly expressed in the plasma of WalkByLab PAD patients and were significantly negatively correlated with the walking distance assessed by Gardner treadmill testing. Finally, the plasma NAP2 level (AUC: 0.743) and derived nomogram model (AUC: 0.860) has a strong predictive potential to identify a poor walking capacity.

CONCLUSIONS

Overall, these data highlight both the important role of autophagy and autophagy-related genes in PAD and link them to vascular inflammation (expression of chemokines). In particular, chemokine NAP2 emerged as a novel biomarker that can be used to predict the impaired walking capacity in PAD patients.

Molecular and cellular basis of the dose-rate-dependent adverse effects of radiation exposure in animal models. Part II: Hematopoietic system, lung and liver

While epidemiological data have greatly contributed to the estimation of the dose and dose-rate effectiveness factor (DDREF) for human populations, studies using animal models have made significant contributions to provide quantitative data with mechanistic insights. The current article aims at compiling the animal studies, specific to rodents, with reference to the dose-rate effects of cancer development. This review focuses specifically on the results that explain the biological mechanisms underlying dose-rate effects and their potential involvement in radiation-induced carcinogenic processes. Since the adverse outcome pathway (AOP) concept together with the key events holds promise for improving the estimation of radiation risk at low doses and low dose-rates, the review intends to scrutinize dose-rate dependency of the key events in animal models and to consider novel key events involved in the dose-rate effects, which enables identification of important underlying mechanisms for linking animal experimental and human epidemiological studies in a unified manner.

LOW DOSE-RATE RADIATION-SPECIFIC ALTERATIONS FOUND IN A GENOME-WIDE GENE EXPRESSION ANALYSIS OF THE MOUSE LIVER

Life span shortening and increased incidences of cancer and non-cancer diseases were observed in B6C3F1 mice irradiated with gamma-rays at a low dose-rate (LDR) of 20 mGy/d for 400 d. A genome-wide gene expression profiling of livers from mice irradiated at a LDR (20 mGy/d, 100-400 d) was performed. LDR radiation affected specific pathways such as those related to lipid metabolism, e.g. 'Cholesterol biosynthesis' and 'Adipogenesis' in females irradiated for 200 and 300 d at 20 mGy/d, with increased expression of genes encoding cholesterol biosynthesis enzymes (Cyp51, Sqle, Fdps) as age and radiation dose increased. No significant alterations in the expression of these genes were observed in male mice exposed similarly. However, the genes encoding adipogenesis regulators, Srebf1 and Pparg, increased with age and radiation dose in both sexes. Comparison between LDR-irradiated and medium dose-rate (400 mGy/d) male mice revealed quite different gene expression profiles. These results seem to be consistent with the increased incidence of fatty liver and obesity in female mice exposed to LDR radiation and suggest that metabolism is an important target of LDR radiation.

Effects of chronic exposure to low levels of IR on Medaka (Oryzias latipes): a proteomic and bioinformatic approach

PURPOSE

Chronic exposure to ionizing radiation (IR) at low doses (<100 mGy) has been insufficiently studied to understand fully the risk to health. Relatively little knowledge exists regarding how species and healthy tissues respond at the protein level to chronic exposure to low doses of IR, and mass spectrometric-based profiling of protein expression is a powerful tool for studying changes in protein abundance.

MATERIALS AND METHODS

SDS gel electrophoresis, LC-MS/MS mass spectrometry-based approaches and bioinformatic data analytics were used to detect proteomic changes following chronic exposure to moderate/low doses of radiation in adults and normally developed Medaka fish (Oryzias latipes).

RESULTS

Significant variations in the abundance of proteins involved in thyroid hormone signaling and lipid metabolism were detected, which could be related to the gonadal regression phenotype observed after 21.04 mGy and 204.3 mGy/day exposure. The global proteomic change was towards overexpression of proteins in muscle and skin, while the opposite effect was observed in internal organs.

CONCLUSION

The present study provides information on the impacts of biologically relevant low doses of IR, which will be useful in future research for the identification of potential biomarkers of IR exposure and allow for a better assessment of radiation biosafety regulations.

Effects of low dose and low dose rate low linear energy transfer radiation on animals - review of recent studies relevant for carcinogenesis

Purpose: Carcinogenic effects of radiation are often assumed to be universally understood, more often than, for example, carcinogenic effects of many different chemicals. This in turn leads to an assumption that any dose of radiation, delivered at any dose rate, poses a serious health challenge. This remains an issue of dispute and low dose radiation research is focused on understanding whether these exposures contribute to cancer incidence. This review is focused on the low linear energy transfer (low LET) radiation exposures for which the data is the most abundant in recent years. Materials and methods: Review of the literature between 2008 and today, highlighting some of the most diverse studies in low dose research. Results: Low dose and low dose rate, low LET ionizing radiation animal studies suggest that the effects of exposure very much depend on animal genotype and health status.Conclusions: Only the integration of all of the data from different models and studies will lead to a fuller understanding of low dose radiation effects. Therefore, we hope to see an increase in international archival efforts and exchange of raw data information opening the possibilities for new types of meta analyses.

Life-Shortening Effect of Chronic Low-Dose-Rate Irradiation in Calorie-Restricted Mice

Calorie restriction is known to influence several physiological processes and to alleviate the late effects of radiation exposure such as neoplasm induction and life shortening. However, earlier related studies were limited to acute radiation exposure. Therefore, in this study we examined the influence of chronic low-dose-rate irradiation on lifespan. Young male B6C3F1/Jcl mice were divided randomly into two groups, which were fed either a low-calorie (65 kcal/ week) or high-calorie (95 kcal/week) diet. The latter is comparable to ad libitum feeding. The animals in the irradiated group were continuously exposed to gamma rays for 400 days at 20 mGy/day, resulting in a total dose of 8 Gy. Exposure and calorie restriction were initiated at 8 weeks of age and the diets were maintained for life. The life-shortening effects from chronic whole-body irradiation were compared between the groups. Body weights were reduced in calorie-restricted mice irrespective of radiation treatment. Radiation induced a shortened median lifespan in both groups, but to a greater extent in the calorie-restricted mice. These results suggest that calorie restriction may sensitize mice to chronic low-dose-rate radiation exposure to produce a life-shortening effect rather than alleviating the effects of radiation.

Re-evaluation of the linear no-threshold (LNT) model using new paradigms and modern molecular studies

The linear no-threshold (LNT) model is currently used to estimate low dose radiation (LDR) induced health risks. This model lacks safety thresholds and postulates that health risks caused by ionizing radiation is directly proportional to dose. Therefore even the smallest radiation dose has the potential to cause an increase in cancer risk. Advances in LDR biology and cell molecular techniques demonstrate that the LNT model does not appropriately reflect the biology or the health effects at the low dose range. The main pitfall of the LNT model is due to the extrapolation of mutation and DNA damage studies that were conducted at high radiation doses delivered at a high dose-rate. These studies formed the basis of several outdated paradigms that are either incorrect or do not hold for LDR doses. Thus, the goal of this review is to summarize the modern cellular and molecular literature in LDR biology and provide new paradigms that better represent the biological effects in the low dose range. We demonstrate that LDR activates a variety of cellular defense mechanisms including DNA repair systems, programmed cell death (apoptosis), cell cycle arrest, senescence, adaptive memory, bystander effects, epigenetics, immune stimulation, and tumor suppression. The evidence presented in this review reveals that there are minimal health risks (cancer) with LDR exposure, and that a dose higher than some threshold value is necessary to achieve the harmful effects classically observed with high doses of radiation. Knowledge gained from this review can help the radiation protection community in making informed decisions regarding radiation policy and limits.

Radiation-Induced Reactions in The Liver - Modulation of Radiation Effects by Lifestyle-Related Factors

Radiation has a wide variety of effects on the liver. Fibrosis is a concern in medical fields as one of the acute effects of high-dose irradiation, such as with cancer radiotherapies. Cancer is also an important concern following exposure to radiation. The liver has an active metabolism and reacts to radiations. In addition, effects are modulated by many environmental factors, such as high-calorie foods or alcohol beverages. Adaptations to other environmental conditions could also influence the effects of radiation. Reactions to radiation may not be optimally regulated under conditions modulated by the environment, possibly leading to dysregulation, disease or cancer. Here, we introduce some reactions to ionizing radiation in the liver, as demonstrated primarily in animal experiments. In addition, modulation of radiation-induced effects in the liver due to factors such as obesity, alcohol drinking, or supplements derived from foods are reviewed. Perspectives on medical applications by modulations of radiation effects are also discussed.

Experimental studies on the biological effects of chronic low dose-rate radiation exposure in mice: overview of the studies at the Institute for Environmental Sciences

This review summarizes the results of experiments conducted in the Institute for Environmental Sciences for the past 21 years, focusing on the biological effects of long-term low dose-rate radiation exposure on mice. Mice were chronically exposed to gamma rays at dose-rates of 0.05, 1 or 20 mGy/day for 400 days to total doses of 20, 400 or 8000 mGy, respectively. The dose rate 0.05 mGy/day is comparable to the dose limit for radiation workers. The parameters examined were lifespan, neoplasm incidence, antineoplasm immunity, body weight, chromosome aberration(s), gene mutation(s), alterations in mRNA and protein levels and trans-generational effects. At 20 mGy/day, all biological endpoints were significantly altered except neoplasm incidence in the offspring of exposed males. Slight but statistically significant changes in lifespan, neoplasm incidences, chromosome abnormalities and gene expressions were observed at 1 mGy/day. Except for transient alterations in the mRNA levels of some genes and increased liver neoplasm incidence attributed to radiation exposure, the remaining biological endpoints were not influenced after exposure to 0.05 mGy/day. Results suggest that chronic low dose-rate exposure may induce small biological effects.