Alteration Of NF-κB/TFAM/mtDNA Pathway In Radon-induced Lung Injury

Objective: To explore the role of NF-κB/TFAM/mt DNA pathway in lung and human bronchial epithelial cells injury induced by radon.Methods:(1) Balb/c mice were exposed to radon and its progeny in a multifunction ecological radon room at a constant radiation level of 100,000Bq/m3. A survey of ATP level in sample of lung tissue was performed for mice for model group and control group. Pathology of lung tissue of mice was examined by HE staining. The protein expression of TFAM, NF-κB p65 and COXⅡ was detected by immunohistochemistry and Western Blot. The mRNA level of TFAM, NF-κB p65 and COXⅡ genes was detected by Real-time PCR.(2) Human bronchial epithelial cell line(HBE) was applied and exposed to radon gas. Flow cytometry(FCM) was used to detect intracellular reactive oxygen species(ROS), mitochondrial membrane potential(MMP) and cell cycle. The protein expression of TFAM, NF-κB p65 and COXⅡ was detected by immunohistochemistry and Western Blot. The mRNA level of TFAM, NF-κB p65 and COXⅡ genes was detected by Real-time PCR.(3) The NF-κB p65 overexpression plasmid and siRNA were transfected into the HR10 cells. The expression of TFAM and mtDNA was detected by Western Blot and Real-time PCR, The TFAM overexpression plasmid was transfected into HR10 cells to detect the change in mtDNA copy number.Results:(1) Pathological observation revealed the thickening of alveolar walls and inflammatory cell infiltration in lung tissue, with airway smooth muscle hyperplasia and thickening. The expressions of TFAM, NF-κB p65 and COXⅡ increased with cumulative doses of radon exposure. ATP level has no obvious change.(2) In HBE cells exposed to radon, the level of ROS decreased and that of MMP increased. The cell cycle was restrained in G1 phase. And ATP levels rised obviously. The expressions of TFAM, NF-κB p65 and COXⅡ also increased with cumulative doses of radon exposure.(3) The expression of TFAM was significantly higher in the NF-κB p65 overexpressed cells and significantly lower in the siRNA cells. In cells with overexpression and inhibition of TFAM and NF-κB, the mtDNA copy number increased or decreased accordingly.Conclusions:(1) The mouse and HBE cell models with radon-exposure were established and alterations in gene and protein expressions induced by radon were revealed.(2) The NF-κB/TFAM/mtDNA pathway was confirmed to take part in the damage process of mouse lung and HBE cells induced by radon exposure.