The Hormesis Effect Of BDE-47in HepG₂Cells And The Potential Molecular Mechanism

Polybrominated diphenyl ethers （PBDEs）, as additive flame retardants, are widespread used in electrical equipment, wire, furniture, and textile. PBDEs havecharacters of high liposolubility, chemical stability, low degradation, and lowevaporability which contribute to environmental persistence and bioamplification bythe way of physical leakage and chemical binding. At present the production and useof PBDEs has been restricted, but PBDEs exist in all the places in the earth biospheresuch as air, water, soil, each kind of sediments, as well as wild animal, fish,domesticated fowl and in humanity’s organism. PBDEs present a potential risk to theenvironment and human health. To date, some in vitro and in vivo studies hadreported that the functionary target organs of PBDEs are mainly the fatty tissue, thethyroid gland, the reproduction growth and the central nervous system. PBDEspossess neurotoxicity, hepatotoxicity, immunotoxicity, reproduction toxicology,endocrine disrupting, and carcinogenicity.After synthetically analyze all the announced monitoring results from the globalcrowd, some researchers reported that BDE-47was one kind of the closest PBDEshomolog to the crowd and BDE-47was also one of the most main homologs. Peopleexposed to low concentrations of PBDE-47in normal life. The purpose of this studyis to investigate the effect of low-dose BDE-47on HepG₂cells to confirm if it cancause hormesis and to explore its possible mechanism.We used CCK-8test to detect the proliferation in HepG₂cells treated withBDE-47（10-14,10-13,10-12,10-11,10-10,10-9,10-8,10-7,10-6,10-5M and20,40,60,80,100μM） for1,2and3days. At the same time, observing whether BDE-47couldinduce HepG₂cells to cause hormesis and determined its dose range （Hormetie Zone）.Then we detected the reactive oxygen species （ROS） level and measured activities oftwo antioxidants （SOD, GSH） in different times. Single cell gel electrophoresis wasused to observe whether PBDE-47in the zone can lead to DNA damage in HepG₂cells. Cell cycle was assayed by flow cytometer, and protein level of PCNA, Cydlin D1, AKT, DNA-PKcs were observed using Western blot.The results showed that low dose of BDE-47（10-10,10-9and10-8M） couldpromote cell proliferation, increase cell survival and induce production of ROS in atime-dependent manner, but could not cause DNA damage and cell apoptosis.Moreover the activity of SOD and GSH do not change. Low dose of BDE-47significantly up-regulated the expression of DNA-PKcs and phosphorylation of Akt inthe HepG₂cells. Cell cycle analysis showed a significant decrease in G1phase afterexposure to BDE-47, and the expression level of Cyclin D1elevated. However, inDNA-PKcs inhibited cells, the overexpression level of Cyclin D1also was observed.We also found that the pre-expose to low dose BDE-47could relieve the negativeeffect of high dose （50μM） exposure on cells. These results suggested that low doseBDE-47has hormesis effect in HepG₂cells and PI3K/Akt pathway may be involvedin regulation of cell growth and survival.