Syringaresinol inhibits ferroptosis and ameliorates glucocorticoid-induced MC3T3-E1 osteoporosis by modulating the Nrf2/SLC7A11/GPX4 pathway

Background: Osteoporosis (OP) is closely related to osteoblast damage and abnormal activation of ferroptosis. Aims: To investigate whether natural polyphenolic compound syringaresinol (Syr) improves OP by activating the Nrf2/solute carrier family 7 member 11 (SLC7A11)/glutathione peroxidase 4 (GPX4) pathway. Methods: A dexamethasone (DEX)-induced osteoblast injury model of MC3T3-E1 was established and the impacts of Syr on cell viability were assessed using Cell Counting Kit-8 and lactate dehydrogenase (LDH) assay. Osteogenic differentiation of MC3T3-E1 cells was assessed by alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining and different kits. Oxidative stress factors and Fe2+ content were examined by flow cytometry and different kits. The levels of bone formation, ferroptosis and Nrf2/SLC7A11/GPX4 pathway-related proteins were examined through western blot. Results: Syr at concentrations of 25, 50, and 100 ?M did not negatively impact MC3T3-E1 cell viability, and was able to enhance the viability of DEX-treated MC3T3-E1 cells and inhibit LDH release. Syr effectively increased ALP activity and ARS stained area and up-regulated bone formation marker proteins in MC3T3-E1 cells. Additionally, Syr inhibited oxidative stress and decreased ferroptosis-related protein levels. Notably, Syr activated Nrf2/SLC7A11/GPX4 pathway. Silencing Nrf2 impaired the ameliorative impact of Syr on osteogenic function and caused oxidative stress and ferroptosis. Conclusion: Syr inhibits ferroptosis, promotes osteogenesis in MC3T3-E1 cells and ameliorates DEX-induced OP by activating Nrf2/SLC7A11/GPX4 pathway.