title: Isoliquiritigenin enhances radiosensitivity of HepG2 cells via disturbance of redox status.
abstract: Redox balance plays an important role in the maintenance of cell growth and survival. Disturbance of this equilibrium can alter normal cellular processes. Excessive reactive oxygen species (ROS) are often found in cancer cells. However, cancer cells have an efficient antioxidant system to counteract the increased generation of ROS. This high antioxidant capacity also favors resistance to drugs and radiation. Here, we show that isoliquiritigenin (ISL), a natural antioxidant, effectively decreased ROS in HepG2 cells in a time-dependant manner at 0.5, 1, and 2 h of treatment. The decreased ROS caused redox imbalance and reductive stress. To adapt to this state, nuclear factor erythroid-2-related factor 2, which regulates the antioxidant enzyme system, was significantly decreased. Antioxidant enzymes reached their lowest level at 6 h after ISL treatment. Endogenous ROS were still being generated so after 6 h of ISL treatment, ROS were clearly higher than before ISL treatment, causing redox imbalance in the HepG2 cells which changed from reductive to oxidative stress. At this stage, cells were irradiated with X-rays. The excess ROS induced serious oxidative stress, resulting in radiosensitization. Therefore, we concluded that ISL induced oxidative stress by disturbing the redox status and ultimately enhancing the radiosensitivity of HepG2 cells.
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Sun
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiao-fei
authors.initials: XF
authors.lastname: Ma
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.forename: Lu
authors.initials: L
authors.lastname: Gan
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Liu
authors.forename: Zhen-hua
authors.initials: ZH
authors.lastname: Wang
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D047188:Chalcones / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008315:Malondialdehyde / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects*; D011839:Radiation, Ionizing; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
chemical_list: D000975:Antioxidants; D047188:Chalcones; D051267:NF-E2-Related Factor 2; D017382:Reactive Oxygen Species; D008315:Malondialdehyde; C040920:isoliquiritigenin; D002374:Catalase; D005978:Glutathione