关键词: SIRT1-mTOR, 大黄素, 骨关节炎, 软骨细胞, 增殖凋亡, 氧化应激

Abstract: BACKGROUND: Previous studies have shown that silent mating-type information regulator 2 homolog 1 (SIRT1)-mechanistic target of rapamycin (mTOR) signaling plays an important role in the progression of osteoarthritis. Emodin has a protective effect on osteoarthritic chondrocytes.
OBJECTIVE: To investigate the effects of emodin on the proliferation, apoptosis and oxidative stress of osteoarthritic chondrocytes based on the SIRT1-mTOR signaling. 
METHODS: Rat chondrocytes were isolated and cultured in vitro. Osteoarthritic chondrocyte model in vitro was induced by 10 ng/mL interleukin-1β. Cell counting kit-8 method was used to determine the viability of rat chondrocytes treated with 0, 20, 40, 80, 120, 160 µmol/L emodin, and the appropriate concentration of emodin was selected. Rat chondrocytes isolated and cultured in vitro were randomly divided into control group, model group, low-dose emodin group, high-dose emodin group, EX527 group, and high-dose emodin+EX527 group. In vitro osteoarthritis model was constructed by induction of 10 ng/mL interleukin 1β in all groups except the control group. The cells in the latter four groups were correspondingly treated with emodin or/and EX527. The proliferation and apoptosis of chondrocytes in each group were detected by cell counting kit-8, Edu staining and flow cytometry respectively. The relative content of reactive oxygen species and the levels of malondialdehyde, superoxide dismutase, catalase, and glutathione peroxidase in chondrocytes of rats in each group were measured with the kit. The expression of proteins related to cell matrix degradation, apoptosis and the SIRT1-mTOR pathway-related proteins in each group were detected by western blot. 
RESULTS AND CONCLUSION: Compared with the control group, the survival rate of chondrocytes, the positive rate of Edu, the levels of superoxide dismutase, catalase, and glutathione peroxidase, and the expression of Bcl-2 and SIRT1 proteins in the model group were decreased, while the apoptosis rate, the relative content of reactive oxygen species, the level of malondialdehyde, the expression of Bax, matrix metalloproteinase 3, matrix metalloproteinase 9 proteins, and p-mTOR/mTOR were increased (P < 0.05). Compared with the model group, the survival rate of chondrocytes, the positive rate of Edu, the levels of superoxide dismutase, catalase, and glutathione peroxidase, and the expression of Bcl-2 and SIRT1 proteins in the low- and high-dose emodin groups were increased, while the apoptosis rate, the relative content of reactive oxygen species, the level of malondialdehyde, the expression of Bax, matrix metalloproteinase 3, matrix metalloproteinase 9 proteins, and p-mTOR/mTOR were decreased (P < 0.05). Compared with the low- and high-dose emodin groups, the indexes of EX527 group showed the opposite trend (P < 0.05). Compared with the high-dose emodin group, the survival rate of chondrocytes, the positive rate of Edu, the levels of superoxide dismutase, catalase, and glutathione peroxidase, and the expression of Bcl-2 and SIRT1 proteins in the high-dose emodin+EX527 group were decreased, while the apoptosis rate, the relative content of reactive oxygen species, the level of malondialdehyde, the expression of Bax, matrix metalloproteinase 3, matrix metalloproteinase 9 proteins, and p-mTOR/mTOR were increased (P < 0.05). To conclude, emodin can inhibit oxidative stress of osteoarthritic chondrocytes by activating the SIRT1-mTOR signaling, thereby promoting chondrocyte proliferation and reducing apoptosis.

Key words: SIRT1-mTOR, emodin, osteoarthritis, chondrocyte, proliferation and apoptosis, oxidative stress