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BACKGROUND: Apoptosis is involved in the formation of degenerative joint diseases. Therefore, anti-chondrocyte apoptosis may be an effective way to treat osteoarthritis. Neferine has a wide range of pharmacological activities including anti-inflammatory, anti-tumor and anti-apoptotic activities, and its effect on OBJECTIVE: To investigate the effect of neferine on chondrocyte apoptosis induced by interleukin-1β and elucidate its possible mechanism. METHODS: (1) The rat chondrocytes at logarithmical stage were taken and intervened in five groups. The control group was cultured routinely. The model group was routinely cultured for 24 hours after treatment with interleukin-1β for 2 hours. The low-, medium-, and high-dose groups were treated with interleukin-1β for 2 hours and then cultured with 5, 10, and 20 μmol/L neferine for 24 hours, respectively. At the end of culture, cell apoptosis, chondroglycoprotein 39 and type II collagen levels in cell supernatants, mRNA and protein expression of apoptosis-related proteins, and mRNA and protein expression of proteins related to the protein kinase R-like endoplasmic reticulum kinase (PERK)/activating transcription factor 4 (ATF4) signaling pathway were detected. (2) Rat chondrocytes at logarithmic growth period were taken and divided into four groups: control group and model group were treated with the same intervention as above, drug group was treated with interleukin-1β for 2 hours and then cultured with 20 μmol/L neferine for 24 hours, and activator group was treated with interleukin1β for 2 hours and then cultured with 20 μmol/L neferine and CCT020312, an activator of PERK/ATF4 signaling pathway, for 24 hours. At the end of culture, cell proliferation was detected by cell counting kit-8 assay, apoptosis was detected by flow cytometry, and mRNA and protein expressions of apoptosis-related proteins and PERK/ATF4 signaling pathway-related proteins were detected. RESULTS AND CONCLUSION: (1) Compared with the control group, the model group showed increased apoptosis (P < 0.05), decreased proliferative activity (P < 0.05), increased level of chondroglycoprotein 39 (P < 0.05), decreased level of type II collagen (P < 0.05), decreased mRNA and protein expression of Bcl-2 protein (P < 0.05), increased mRNA and protein expression of Bax protein, increased caspase-3 mRNA expression, increased Cleaved-caspase-3 protein expression (P < 0.05), increased mRNA expression of PERK, ATF4, and C/EBP homologous protein (P < 0.05), and increased protein expression of p-PERK, ATF4, and C/EBP homologous protein (P < 0.05). Compared with the model group, neferine reversed the above effects of interleukin-1β on chondrocytes in a concentration-dependent manner. (2) Compared with the drug group, the activator group showed increased apoptosis (P < 0.05), decreased proliferative activity (P < 0.05), elevated mRNA expression of caspase-3, ATF4, and C/EBP homologous protein (P < 0.05), and elevated protein expression of Cleavedcaspase-3, ATF4, and C/EBP homologous protein (P < 0.05). (3) To conclude, neferine inhibits interleukin-1β-induced chondrocyte apoptosis and enhances cell proliferation activity, and the mechanism of action may be related to blocking the PERK/ATF4 signaling pathway in the endoplasmic reticulum. [ABSTRACT FROM AUTHOR]

BACKGROUND: Curcumin has been shown to play antioxidative, anti-inflammatory and anti-apoptotic roles in osteoarthritis, but the underlying mechanisms remain unclear. OBJECTIVE: To investigate the effects of curcumin on apoptosis and proliferation of chondrocytes induced by lipopolysaccharide, and to explore the potential mechanisms, so as to provide new ideas for the treatment of osteoarthritis. METHODS: Chondrocytes were isolated from the 4-week-old Sprague-Dawley rats, cultured, and identified by toluidine blue staining. The chondrocyte inflammation model in vitro was established by lipopolysaccharide induction. The cells were divided into five groups: control group (common medium); model group (medium with 5 µg/L lipopolysaccharide); low-dose group (medium with 5 µg/L lipopolysaccharide + 5 µmol/L curcumin); medium-dose group (medium with 5 µg/L lipopolysaccharide + 10 µmol/L curcumin); high-dose group (medium with 5 µg/L lipopolysaccharide + 20 µmol/L curcumin). After 24 hours, the expression levels of interleukin 1β and transforming growth factor α in the cellular supernatant were detected by ELISA method. The apoptotic cells were detected by flow cytometry. Cell proliferation was tested by MTT assay. The expression levels of autophagy-related proteins and extracellular regulated protein kinases 1/2 were determined by western blot assay. RESULTS AND CONCLUSION: The levels of interleukin 1β and transforming growth factor α in the supernatant of chondrocytes induced by lipopolysaccharide were significantly higher than those in the control group (P < 0.01). The levels of interleukin 1β and transforming growth factor α in the supernatant treated with curcumin were lower than those in the model group, which was on a dose-dependent manner (P < 0.05, P < 0.01). After 24 hours of treatment, apoptotic rate of cells in the model group was significantly higher than that in the control group (P < 0.01). Compared with the model group, the cell apoptotic rate in each curcumin group was decreased, especially the high-dose group (P < 0.01). MTT assay showed that the cell proliferation ability in the model group was significantly lower than that in the control group (P < 0.01). Compared with the model group, the cell proliferation ability in each curcumin group was restored, and the effect was the best in the high-dose group. The results of western blot showed that the autophagic ability and the levels of autophagy marker (LC3-II) and autophagy related protein (Beclin-1) were significantly increased in each curcumin group compared with the model group(P < 0.05, P < 0.01), and the expression level of p-ERK1/2 protein was significantly increased (P < 0.05). Our findings suggest that 20 µmol/L curcumin cannot only inhibit apoptosis and relieve inflammatory of chondrocytes induced by lipopolysaccharide, but also has a certain antagonistic effect on lipopolysaccharide- induced inhibition of inflammatory chondrocyte proliferation, which may be via regulating the ERK1/2 pathway-activated autophagy. [ABSTRACT FROM AUTHOR]