The Antioxidant Effect Induced By Low-dose Radiation In Human Bronchial Epithelial Cell And Its Mechanism

Background and objective:Lung cancer is the world’s most malignant tumor. As air pollution and population aging,the incidence of lung cancer increases year by year. In addition, the malignant degree of lungcancer is high and the lifetime is short, looking for effective treatment is becoming more andmore attention. Radiotherapy is an important means for lung cancer treatment, but oxidationdamage seriously hindered the increase of radiation dose in order to improve curative effect.Current researches have find low-dose radiation (LDR) can improve antioxidant effect, butthe mechanism has not yet been elucidated.In the recent years, the nuclear factor E2related factor2(Nrf2) has been proved to bekey factor of adjusting intracellular antioxidants. PKC, MAPK and PI3K/AKT proteinkinase pathway were proved to be involved in regulating the activation of Nrf2-ARE signaltransduction pathways and its gene expression regulation.The objective of this study was to clarify the antioxidant mechanism of low-doseradiation.Methods:1. LDR induced HBE cells against oxidative damage mechanism(1) First of all, with low doses of radiation processing HBE cells, dose effect and timeeffect experiment, respectively with Western blot method to detect the nucleus nrf2level, soas to select HBE cells induced oxidative damage of dose and the best processing time.(2) The ROS kit to detect the ROS level induced by low doses of radiation on HBE andNrf2siRNA HBE cells, to clear relationship among LDR, Nrf2and anti-oxidative stress.2. LDR induced HBE cells Nrf2nuclear transfer mechanismWith Western blot method to observe different blockers (U0126, LY294002) can blockHBE cells nrf2nuclear transfer. And verify that LDR can activate the MAPK/ERK,PI3K/Akt signaling pathway.Results:1. Low doses of radiation induced oxidative damage HBE cells optimal dose and timerespectively is25mGy and24h. 2.25mGy LDR24h causeγ-GCS mRNA levels are significantly higher than thenormal control group3, LDR group was lower than normal control group, of which75mGy ROS level thelowest dose group, and500mGy high doses of radiation caused by ROS levels aresignificantly higher than the normal control group, shows that low doses of radiation candecrease the level of free radicals in cells, thereby producing antioxidant effect.4. After transfection Nrf2siRNA HBE cells LDR ROS levels in the cell, and LDR Nrf2HBE cells induced with nuclear transfer, to reduce the level of ROS and anti-oxidativestress.5. After low-dose radiation, via ERK phosphorylation inhibitor U0126the HBE Nrf2levels in the nuclei of processing, and cell total Nrf2level unchanged, shows that low dosesof radiation can be through the MAPK/ERK induced Nrf2nuclear transfer.6. After low-dose radiation, the Akt phosphorylation inhibitors LY294002processingHBE Nrf2levels in the nuclei of the cells in total Nrf2level unchanged, shows that lowdoses of radiation can be induced by PI3K/Akt Nrf2nuclear transfer.Conclusion:1. LDR induces the nuclear transfer of Nrf2in HBE cells, reduces ROS level, andexerts antioxidant effect.2. LDR induces the nuclear transfer of Nrf2in HBE cells through activation ofMAPK/ERK and PI3K/Akt signaling pathways, and plays antioxidant activity.