The Role Of Oxidative Stress In The Mitochondrial Damage Of The Lung Tissue Of BALB/c Mice Induced By Radon And Its Progeny

Objective:Radon has become the second major pathogenic factor of lung cancer after smoking.At present,a large number of studies mainly focus on the epidemiological investigation of radon-induced lung cancer,but the related experimental animal experiments and molecular mechanism studies is still very scarce.To establish an animal model of radon exposure and observe the adverse effects of radon and its daughters on mitochondria of lung tissue in mice,so as to provide experimental data for elucidating the mechanism of lung tissue damage induced by radon and its daughters.Methods:Male BALB/c mice aged 6-8 weeks were fed adaptively for one week.Animals were randomly divided into 7 groups(10 mice in each group).Radon was inhaled through HD-3 radon chamber for 8 hours a day.After exposure dosage reached 6,12,18,60,120,180 WLM,mice were sacrificed after 12 hours of vertebral dislocation on an empty stomach.Pathology of lung tissue of mice(control and radon-exposed groups)was examined by HE staining;trachea-bronchus of mice in control and radon-exposed groups were taken for enzymatic digestion and cell identification.Flow cytometry(FCM)was used to detect intracell reactive oxygen species(ROS),mitochondrial membrane potential(MMP)and cell apoptosis of trachea-bronchia epithelial cell of mice.The activity of SOD(superoxide dismutase)in lung tissues was detected by WST-8 method.The content of MDA(malondialdehyde)was detected by thiobarbituric acid method(TBA),the expression of Cyt-C?COX-2 and mitochondrial DNA copy number was detected by Real-time PCR,and the change of ATP level was detected by enzyme labeling instrument.Male BALB/c mice were divided into four groups(10 mice in each group):control group(control),180 WLM,melatonin group(Mel)and 180 WLM+Mel group.According to the above detection methods,the changes of lung tissues were measured after melatonin treatment.Immunohistochemical method was used to detect the expression of autophagy-related protein p62 and LC3B and the expression of apoptotic factor caspase-3 in lung tissues in control group,melatonin(Mel)group,60WLM,180WLM and 180WLM+Mel group.The level of mRNA expression of p62,LC3B,caspase-3 in lung tissues of each group was detected by Real-time PCR.Results:HE staining results of lung tissues indicatesthere was no significant difference between low dose group and control group.With the increase of exposure dose,alveolar septum became thicker,alveolar wall ruptured seriously,epithelial cells in bronchial cavity exfoliated and inflammatory cells infiltrated under bronchial mucosa increased in high dose group.Compared with 180 WLM radon-exposed group,the thickness of alveolar septum increased,epithelial cells of bronchial wall decreased,inflammatory cells infiltrated under bronchial mucosa decreased,foreign bodies in bronchial cavity decreased and cilia arranged neatly in 180 WLM+Mel group.With the increase of exposure dose,the level of reactive oxygen species,MDA and apoptosis of trachea-bronchus of mice increased significantly,the level of mitochondrial membrane potential,SOD,Cyt-C,COX-2,MtDNA copy number and ATP of lung issue decreased significantly.Compared with the 180 WLM radon-exposed group,the level of ROS,apoptotic,MDA of trachea-bronchus of mice in 180 WLM+Mel group decreased,the level of MMP,SOD,Cyt-C,COX-2,ATP and MtDNA copy number of lung tissue increased.Immunohistochemical results showed that,compared with control group,with the increase of exposure dose,the positive number of caspase-3,p62,LC3B,the expression of caspase-3 mRNA,autophagy marker protein p62,LC3B mRNA increased.Meanwhile,compared with 180WLM dosage group,the positive number of caspase-3,p62,LC3B,the expression of caspase-3 mRNA,autophagy marker protein P62,Lc3B mRNA decreased in 180WLM+Mel dosage group.Conclusion:(1)Long-term low dose radon exposure may lead to lung tissue damage through oxidative stress.(2)Melatonin can protect lung tissue from radon exposure by reducing oxidative stress.(3)Radon and its daughters may induce autophagy and apoptosis through the ROS pathway.