| Radon is an inert radioactive gas that exists naturally in the air, and it's a respiratory radioactive contaminants can't be ignored. According to the report by UNSCEAR in 2000, the radioactive dose from radon and its decay products account for 54% of the total annual absorbed dose in normal living environment. Indoor radon problem has been the focus of the radiation protection. The World Health Organization launched the Global Residential Radon Project(IRP)in 2005 and made the natural radionuclide of radon as the preferred global burden of disease nuclides evaluation. Radon is the second largest risk factor that cause lung cancer besides smoking. Epidemiological surveys showed that when miners worked in the environment of higher level of radon for a long time,the risk of lung cancer would be increased. Ignoring smoking,with the increasing of radon-exposure the incidence of lung cancer increased significantly.In recent years, with the economic development,mining,geothermal and nuclear power,underground radioactive material is transferred to the surface, forming a number of new contaminated areas and high radon areas.Recently lots extremely high rodon springs were discovered in RUOERGAI County, Sichuan Province.Our preliminary investigations revealed that the concentration of radon in indoor and outdoor living areas were up to 201164Bq/m3 and 699 Bq/m3,respectively. It is a high radon and high radiation areas in the world.Therefore, The health effects of the residents in the region need to be studied. Meanwhile we selected Tibetan residents who live in the same altitude area, have the same lifestyle but not in contact with radon spring's as the control.Radon can increase chromosome aberrations in human peripheral blood lymphocytes. The results showed that:fragments,chromatid break and the sum of chromatid aberration in high radon group were higher than the control (P>0.05); "dic+r" in high radon group and the control were 0.18±0.03(%) and 0.12±0.04(%),respectively. No significant differences were found between the two groups but both nuch higher than the average spontaneous rate of chromosome of the healthy people at home and abroad (0.03%). When the subjects in high radon group were grouped by baths,we found that "dic+r" rate increased with the number of baths after excluding an exception value in "0～" group.Both chromosome-type and chromatid-type aberration in female were higher than men,no significant difference(P >0.05). Chromatid-type aberration in high radon group were increased with age (P> 0.05). In addition,micronucleus and micronucleus cells in high radon group were significantly higher than control(P< 0.05). Cytogenetic studies showed that, compared with the control,high radon group population had certain radiation damage.In order to understand the molecular changes, we detected the lung cancer related genes (p53, p16 and k-ras) using real-time PCR and detected the p53,pl6 and k-ras proteins expression by Western blotting. The reslts show that:compared with the control, p53, p16 and k-ras gene in high radon group were 0.97,1.5 and 1.33 times;p53,p16 and k-ras proteins in high radon group were 0.7,1.7 and 1.23 times.MicroRNAs widespread in the biosphere and are highly conserved. They widely involved in cell differentiation and development, apoptosis,tumorigenesis and other aspects of gene expression.In this study, we focused on several cancer-related microRNAs, including let-7a,miR-34a/b and miR-145.Real-time PCR results showed that compared with the control,let-7a and miR-145 downregulated,were 0.61 times and 0.64 times,respectively,no significant difference. MiR-34a/b expression were significantly increased,15.7 times and 351.24 times higher than the control respectively. miR-34a/b in high radon group showed abnormally high expression, suggesting that miR-34a/b may be an early marker for radiation damage,and provide research biomarker clues for the further development of radon induced lung cancer. In this paper we have drew the preliminary conclusion that radon-induced lung injury as well as lung cancer is a multi-gene complex multi-step biological process. P53,p16,k-ras and microRNAs have play roles in this process. Therefore,further studies need to be more to study related genes,and provide a theoretical basis.for the early diagnosis of lung cancer caused by radon. |
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