Effects of fluoride exposure on autophagy and AMPK/mTOR/ULK1 pathway in NG108-15 cells / 中华地方病学杂志

ABSTRACT

Objective:To investigate the effects of fluoride exposure on autophagy and the expression levels of adenosine monophosphate activated protein kinase (AMPK), mammalian target of rapamycin (mTOR) and Unc-51-like kinase 1 (ULK1) in mouse neuroblastoma and rat glioma fusion cells (NG108-15 cells).Methods:NG108-15 cells were cultured in vitro and divided into control group (0 mg/L), low fluoride group (20 mg/L), medium fluoride group (40 mg/L) and high fluoride group (80 mg/L) according to the final concentration of sodium fluoride, and the cells were collected after 24 h of treatment for standby. NG108-15 cells autophagy was detected by immunofluorescence/immunocytochemistry (IF/ICC method, the autophagy positive control group was treated with chloroquine phosphate); the mRNA expression levels of AMPK, mTOR and ULK1 in each group were detected by real-time fluorescent quantitative polymerase chain reaction (qRT-PCR); the protein expression levels of autophagy related protein microtubule-associated protein 1 light chain 3B (LC3B), AMPK, mTOR, ULK1, phosphorylation (p)-AMPK, p-mTOR, p-ULK1 in each group were detected by Western blotting. Results:No autophagosome was detected in the control group, and autophagosomes were detected in all the fluoride groups. The protein expression level of LC3B in the low, medium and high fluoride groups (1.80 ± 0.59, 2.16 ± 0.60, 2.30 ± 0.57) was significantly higher than that in the control group (1.00 ± 0.29, P < 0.05). The results of qRT-PCR showed that compared with the control group, the mRNA expression levels of AMPK in medium and high fluoride groups were higher (2.30 ± 0.57, 4.41 ± 1.05 vs 1.00 ± 0.01, P < 0.05); the mRNA expression levels of mTOR in the low, medium and high fluoride groups were lower (0.79 ± 0.04, 0.76 ± 0.09, 0.64 ± 0.10 vs 1.00 ± 0.01, P < 0.05), and the mRNA expression levels of ULK1 were higher (1.81 ± 0.39, 1.96 ± 0.35, 4.22 ± 1.03 vs 1.00 ± 0.01, P < 0.05). The results of Western blotting showed that compared with the control group, the protein expression levels of AMPK (1.21 ± 0.05, 1.20 ± 0.04, 1.30 ± 0.07 vs 1.00 ± 0.03), p-AMPK (1.12 ± 0.05, 1.20 ± 0.06, 1.49 ± 0.07 vs 1.00 ± 0.02), ULK1 (1.16 ± 0.05, 1.26 ± 0.05, 1.15 ± 0.05 vs 1.00 ± 0.04) and p-ULK1 (1.19 ± 0.04, 1.17 ± 0.02, 1.24 ± 0.05 vs 1.00 ± 0.05) in the low, medium and high fluoride groups were higher ( P < 0.05), and the protein expression levels of mTOR were lower (0.77 ± 0.03, 0.60 ± 0.03, 0.55 ± 0.04 vs 1.00 ± 0.04, P < 0.05); the protein expression levels of p-mTOR in the medium and high fluoride groups were lower (0.93 ± 0.05, 0.48 ± 0.02 vs 1.00 ± 0.02, P < 0.05). Conclusion:Fluoride exposure can induce autophagy in NG108-15 cells, and the expression of AMPK and ULK1 are up-regulated, while the expression of mTOR is down-regulated.