Ionizing radiation-induced microRNA expression changes in cultured RGC-5 cells

Treatment of hepatotoxicity induced by γ-radiation using platelet-rich plasma and/or low molecular weight chitosan in experimental rats

Background and aim: Platelet-rich plasma (PRP) is rich in growth factors and plays an important role in tissue healing and cytoprotection. Also, it has been proved that low molecular weight chitosan (LMC) possesses many outstanding health benefits. The aim of this study was to assess the possibility of using PRP and/or fungal LMC to treat hepatotoxicity induced by γ-radiation in albino rats.Materials and methods: Forty-eight adult male albino rats were randomly divided into eight groups. Group I (control), Group II (PRP alone), Group III (LMC alone), Group IV (PRP + LMC), Group V (γ-irradiated alone), Group VI (γ-irradiated + PRP), Group VII (γ-irradiated + LMC), and Group VIII (γ-irradiated + PRP + LMC). The irradiated rats were whole body exposed to γ-radiation (8 Gy) as fractionated doses (2 Gy) twice a week for 2 consecutive weeks. The treated groups received PRP (0.5 mL/kg body weight, s.c.) and/or LMC (10 mg/kg body weight, s.c.) 2 days a week 1 h after every dose of γ-radiation and continued for another week after the last dose of radiation. Serum alanine transaminase (ALT) and aspartate transaminase (AST) activities, as well as reduced glutathione (GSH) content, malondialdehyde (MDA), total antioxidant capacity (TAC), and nuclear factor erythroid 2-related factor 2 (Nrf2) levels in the liver tissue and relative expression of microRNA-21 (miR-21) in serum were measured, in addition to histopathological examination.Results: Exposure of rats to γ-radiation resulted in a significant increase in serum ALT and AST activities, hepatic MDA levels, and serum miR-21 relative expression, along with a significant decrease in hepatic GSH content, TAC, and Nrf2 levels. Treatment with PRP and/or fungal LMC after exposure to γ-radiation ameliorated these parameters and improved the histopathological changes induced by γ-radiation.Conclusions: The results demonstrated that PRP and/or LMC inhibited γ-radiation-induced hepatotoxicity and using both of them together seems more effective. They can be a candidate to be studied toward the development of a therapeutic strategy for liver diseases.

Radiation-induced Chromosome Instability: The Role of Dose and Dose Rate

Nontargeted effects include radiation-induced genomic instability (RIGI) which is observed in the progeny of cells exposed to ionizing radiation and can be manifested in different ways, including chromosomal instability and micronucleus (MN) formation. Since genomic instability is commonly observed in tumors and has a role in tumor progression, RIGI has the potential of being an important mechanism for radiation-induced cancer. The work presented explores the role of dose and dose rate on RIGI, determined using a MN assay, in normal primary human fibroblast (HF19) cells exposed to either 0.1 Gy or 1 Gy of X-rays delivered either as an acute (0.42 Gy/min) or protracted (0.0031 Gy/min) exposure. While the expected increase in MN was observed following the first mitosis of the irradiated cells compared to unirradiated controls, the results also demonstrate a significant increase in MN yields in the progeny of these cells at 10 and 20 population doublings following irradiation. Minimal difference was observed between the two doses used (0.1 and 1 Gy) and the dose rates (acute and protracted). Therefore, these nontargeted effects have the potential to be important for the low-dose and dose-rate exposure. The results also show an enhancement of the cellular levels of reactive oxygen species after 20 population doublings, which suggests that ionising radiation (IR) could potentially perturb the homeostasis of oxidative stress and so modify the background rate of endogenous DNA damage induction. In conclusion, the investigations have demonstrated that normal primary human fibroblast (HF19) cells are susceptible to the induction of early DNA damage and RIGI, not only after a high dose and high dose rate exposure to low linear energy transfer, but also following low dose, low dose rate exposures. The results suggest that the mechanism of radiation induced RIGI in HF19 cells can be correlated with the induction of reactive oxygen species levels following exposure to 0.1 and 1 Gy low-dose rate and high-dose rate x-ray irradiation.

Emergence of miR-34a in radiation therapy

Expressions of many microRNAs (miRNAs) in response to ionizing radiation (IR) have already been investigated and some of them seem to play an important role in the tumor radioresistance, normal tissue radiotoxicity or as predictive biomarkers to radiation. miR-34a is an emerging miRNA in recent radiobiology studies. Here, we review this miR-34 family member by detailing its different roles in radiation response and we will discuss about the role that it can play in radiation treatment. Thus, we will show that IR regulates miR-34a by increasing its expression. We will also highlight different biological processes involved in cellular response to IR and regulated by miR-34a in order to demonstrate the role it can play in tumor radio-response or normal tissue radiotoxicity as a radiosensitizer or radioprotector. miR-34a is poised to assert itself as an important player in radiobiology and should become more and more important in radiation therapy management.

Changes of MicroRNA-1, -15b and -21 Levels in Irradiated Rat Hearts After Treatment With Potentially Radioprotective Drugs

The aim of this study was to measure expression levels of microRNAs (miRNAs) (miRNA-1, -15b and -21) in the rat myocardium after a single dose of ionizing radiation (6-7 Gy/min, total 25 Gy). The rats were treated with selected drugs (Atorvastatin, acetylsalicylic acid (ASA), Tadalafil, Enbrel) for six weeks after irradiation. MiRNAs levels were measured by RT-qPCR. Irradiation down-regulated miRNA-1 in irradiated hearts. In Tadalafil- and Atorvastatin-treated groups, miRNA-1 expression levels were further decreased compared with irradiated controls. However, Enbrel increased miRNA-1 level in irradiated hearts similarly to that in non-irradiated untreated group. Increase of miRNA-15b is pro-apoptotic in relationship with ischemia. Irradiation caused down-regulation of miRNA-15b. Administration of ASA in the irradiated group resulted in the increase of miRNA-15b expression compared to non-treated controls without irradiation. After Enbrel administration, miRNA-15b levels were overexpressed compared to non-treated normal group. MiRNA-21 belongs to the most markedly up-regulated miRNAs in response to cardiogenic stress. MiRNA-21 was increased nearly 2-fold compared to non-treated hearts whereas Tadalafil reduced miRNA-21 levels (about 40 %). Our study suggests that Enbrel and Tadalafil changed miRNAs expression values of the irradiated rats to the values of non-irradiated controls, thus they might be helpful in mitigation of radiation-induced toxicity.