Changes in ionizing radiation dose rate affect cell cycle progression in adipose derived stem cells

Mechanisms of Antitumor Activity of Low Doses of Radiation Associated with Activation of Cells' Defense System

BACKGROUND

The effects of ionizing radiation (IR) involve a highly orchestrated series of events in cells, including DNA damage and repair, cell death, and changes in the level of proliferation associated with the stage of the cell cycle. A large number of existing studies in literature have examined the activity of genes and their regulators in mammalian cells in response to high doses of ionizing radiation. Although there are many studies, the research in effect of low doses of ionizing radiation remains limited. Though much progress has been made in understanding the basic principles of effects of low doses of radiation on individual components of biological systems, less is known about how low doses affect target molecules and regulate the cellular networks (e.g., activation of the immune system, genes and their regulators in the phenomenon of hormesis, and the formation of an adaptive response). These observations determined the purpose of the work: to investigate the activity of genes and non-coding RNAs (long non-coding RNAs and microRNAs) in various organs of mice with transplanted Lewis carcinoma after low-dose radiation.

MATERIALS AND METHODS

Twenty-four female C57Bl/6 mice were transplanted subcutaneously with Lewis carcinoma cells (105 cells in 0.2 mL of Hanks' solution). Total 4-fold X-ray irradiation with an interval of 4 days at a dose of 0.075 Gy (0.85 Gy/min) was performed on the RUST M1 from 6 days after transplantation; the tumor size was measured daily. The mice were divided into the following groups: "Biocontrol", "Biocontrol + irradiation", "Tumor" and "Tumor + irradiation". On the 19th day from the beginning of the experiment, the mice were euthanized. The expression profiles of mRNA genes, long non-coding RNAs, and microRNAs controlling the response to radiation were determined in the bone marrow, thymus, spleen, and tumor of mice.

RESULTS

Fractionated low-dose irradiation of mice with transplanted Lewis carcinoma caused a growth decrease of implanted tumor cells compared to the similar group without irradiation. At the same time, there was an activation of oncosuppressors and a decrease in the activity of oncogenes in the thymus and spleen of mice with tumor and irradiation. In the "Tumor" group, without irradiation, the number of activated oncogenes prevailed over the number of inactivated ones.

CONCLUSIONS

Thus, the low-dose radiation exposure led to the activation of antitumor immunity in mice, which manifested itself in slowing tumor growth in animals and the induction of oncosuppressors and inhibition of oncogene expression.

Low-dose radiation exaggerates HFD-induced metabolic dysfunction by gut microbiota through PA-PYCR1 axis

Co-exposure of High-fat-diet (HFD) behavior and environmental low-dose radiation (LDR) is common among majority occupational workers, but the synergism of this co-exposure in metabolic health is poorly understood. This study aimed to investigate the impact of gut microbiota and its metabolites on the regulation of HFD accompanied by LDR-associated with metabolic dysfunction and insulin resistance. Here, we reported that Parasutterella was markedly elevated in the gut microbiota of mice in co-exposure of HFD and LDR, accompanied by increased pyrrolidinecarboxylic acid (PA) level in both intestine and plasma. Transplantation of fecal microbiota from mice with co-exposure HFD and LDR with metabolic dysfunction resulted in increased disruption of metabolic dysfunction, insulin resistance and increased PYCR1 (Pyrroline-5-carboxylate reductase 1) expression. Mechanistically, intestinal barrier was damaged more serious in mice with co-exposure of HFD and LDR, leading high PA level in plasma, activating PYCR1 expression to inhibit insulin Akt/mTOR (AKT kinase-transforming protein/Serine threonine-protein kinase) signaling pathway to aggravate HFD-induced metabolic impairments. This study suggests a new avenue for interventions against western diet companied with low dose radiation exposure-driven metabolic impairments.

Genomic Changes Driven by Radiation-Induced DNA Damage and Microgravity in Human Cells

The space environment consists of a complex mixture of different types of ionizing radiation and altered gravity that represents a threat to humans during space missions. In particular, individual radiation sensitivity is strictly related to the risk of space radiation carcinogenesis. Therefore, in view of future missions to the Moon and Mars, there is an urgent need to estimate as accurately as possible the individual risk from space exposure to improve the safety of space exploration. In this review, we survey the combined effects from the two main physical components of the space environment, ionizing radiation and microgravity, to alter the genetics and epigenetics of human cells, considering both real and simulated space conditions. Data collected from studies on human cells are discussed for their potential use to estimate individual radiation carcinogenesis risk from space exposure.