Effects of α-Particle Radiation on MicroRNA Responses in Human Cell-Lines

MicroRNAs Responding to Space Radiation

High-energy and high-atom-number (HZE) space radiation poses an inevitable potential threat to astronauts on deep space exploration missions. Compared with low-LET radiation, high-energy and high-LET radiation in space is more efficient in inducing clustered DNA damage with more serious biological consequences, such as carcinogenesis, central nervous system injury and degenerative disease. Space radiation also causes epigenetic changes in addition to inducing damage at the DNA level. Considering the important roles of microRNAs in the regulation of biological responses of radiation, we systematically reviewed both expression profiling and functional studies relating to microRNAs responding to space radiation as well as to space compound environment. Finally, the directions for improvement of the research related to microRNAs responding to space radiation are proposed. A better understanding of the functions and underlying mechanisms of the microRNAs responding to space radiation is of significance to both space radiation risk assessment and therapy development for lesions caused by space radiation.

Radon in indoor air of primary schools: determinant factors, their variability and effective dose

Radon is a radioactive gas, abundant in granitic areas, such as in the city of Porto at the north-east of Portugal. This gas is a recognized carcinogenic agent, being appointed by the World Health Organization as the leading cause of lung cancer after smoking. The aim of this preliminary survey was to determine indoor radon concentrations in public primary schools, to analyse the main factors influencing their indoor concentration levels and to estimate the effective dose in students and teachers in primary schools. Radon concentrations were measured in 45 classrooms from 13 public primary schools located in Porto, using CR-39 passive radon detectors for about 2-month period. In all schools, radon concentrations ranged from 56 to 889 Bq/m(3) (mean = 197 Bq/m(3)). The results showed that the limit of 100 Bq/m(3) established by WHO IAQ guidelines was exceeded in 92 % of the measurements, as well as 8 % of the measurements exceeded the limit of 400 Bq/m(3) established by the national legislation. Moreover, the mean annual effective dose was calculated as 1.25 mSv/y (ranging between 0.58 and 3.07 mSv/y), which is below the action level (3-10 mSv). The considerable variability of radon concentration observed between and within floors indicates a need to monitor concentrations in several rooms for each floor. A single radon detector for each room can be used, provided that the measurement error is considerably lower than variability of radon concentration between rooms. The results of the present survey will provide useful baseline data for adopting safety measures and dealing effectively with radiation emergencies. In particular, radon remediation techniques should be used in buildings located in the highest radon risk areas of Portugal. The results obtained in the current study concerning radon levels and their variations will be useful to optimize the design of future research surveys.

Gene expression responses in human lung fibroblasts exposed to alpha particle radiation

This study examined alpha (α-) particle radiation effects on global changes in gene expression for the purposes of identifying potential signaling pathways that may be involved in Radon ((222)Rn) gas exposure and lung carcinogenesis. Human lung fibroblast cells were exposed to α-particle radiation at a dose range of 0-1.5Gy. Twenty-four hours post-exposure, transcript modulations were monitored using microarray technology. A total of 208 genes were shown to be dose-responsive (FDR adjusted p<0.05, Fold change>|2|) of which 32% were upregulated and 68% downregulated. Fourteen of the high expressing genes (>|4| fold) were further validated using alternate technology and among these genes, GDF15 and FGF2 were assessed at the protein level. GDF15, a known marker of lung injury, had expression levels 3-fold higher in exposed cell culture media, 24h post-irradiation as detected by ELISA. Further, pathway analysis of the dose-responsive transcripts showed them to be involved in biological processes related to cell cycle control/mitosis, chromosome instability and cell differentiation. This panel of genes with particular focus on GDF15 may merit further analysis to determine their specific role in mechanisms leading to α-particle induced lung carcinogenesis.