2023, Vol. 27 ›› Issue (26): 4147-4153

Protective effect of metformin against lipopolysaccharide-induced chondrocyte injury by activating nuclear factor E2 and its relevant signaling pathway

Wang Xudong1, Han Junzhu1, Wang Wenrui2, Xia Qixin1, Guo Cheng1   

Abstract: BACKGROUND: Previous studies have shown that the nuclear factor E2-related factor 2/heme oxygenase 1 signaling pathway is crucial for the development of osteoarthritis, and metformin has a certain protective effect on chondrocytes.
OBJECTIVE: To investigate the protective effect and mechanism of metformin on chondrocyte injury induced by lipopolysaccharide.
METHODS: Sprague-Dawley rat chondrocytes were isolated, cultured, and identified in vitro. Passage 3 chondrocytes were selected and treated with different concentrations of lipopolysaccharide (0, 10, 50, 100, 500, 1 000, and 5 000 μg/L) and metformin (0, 50, 100, 500, 1 000, 5 000, and 10 000 μmol/L) for 24 hours. Cell viability was then detected by cell counting kit-8 method, and the optimal mass concentrations of lipopolysaccharide and metformin were screened. According to different treatment factors, the chondrocytes were divided into blank group, lipopolysaccharide (5 000 μg/L) induced group, and 5 000 μg/L lipopolysaccharide +1 000 μmol/L group. Cell apoptosis was detected by flow cytometry. Oxidative stress was detected by reactive oxygen species, malondialdehyde, and superoxide dismutase kits. The mRNA and protein expressions of interleukin-1β, cyclooxygenase 2, type II collagen, nuclear factor E2-related factor 2, and heme oxygenase were detected by RT-PCR and western blot, respectively.
RESULTS AND CONCLUSION: Lipopolysaccharide reduced the activity of chondrocytes and induced apoptosis of chondrocytes, while metformin increased the activity of chondrocytes and decreased the apoptosis rate. The levels of reactive oxygen species and malondialdehyde were increased and the activity of superoxide dismutase was decreased in lipopolysaccharide-induced chondrocytes, while treatment with metformin decreased the levels of reactive oxygen species and malondialdehyde and increased the activity of superoxide dismutase in lipopolysaccharide-induced chondrocytes. Lipopolysaccharide increased the expressions of interleukin-1β and cyclooxygenase-2 in chondrocytes, and decreased the expressions of type II collagen, nuclear factor E2-related factor 2, and heme oxygenase 1 in chondrocytes. After metformin intervention, the expressions of interleukin-1β and cyclooxygenase-2 were decreased, and the expression of type II collagen, nuclear factor E2-related factor 2, and heme oxygenase 1 were increased. To conclude, metformin can inhibit lipopolysaccharide-induced chondrocyte injury, possibly through the activation of nuclear factor E2-related factor 2/heme oxygenase 1 signaling pathway

Key words: metformin, osteoarthritis, oxidative damage, Nrf2/HO-1 pathway