Delay the progression of glucocorticoid‐induced osteoporosis: Fraxin targets ferroptosis via the Nrf2/GPX4 pathway

Glucocorticoid-induced osteoporosis (GIOP) commonly accelerates bone loss, increasing the risk of fractures and osteonecrosis more significantly than traditional menopausal osteoporosis. The extracellular environment influenced by glucocorticoids heightens fracture and osteonecrosis risks. Fraxin (Fra), a key component of the traditional Chinese herbal remedy Cortex Fraxini, is known for its wide-ranging pharmacological effects, but its impact on GIOP remains unexplored. This investigation aims to delineate the effects and underlying mechanisms of Fra in combating dexamethasone (Dex)-induced ferroptosis and GIOP. We established a mouse model of GIOP via intraperitoneal injections of Dex and cultured osteoblasts with Dex treatment for in vitro analysis. We evaluated the impact of Fra on Dex-treated osteoblasts through assays such as C11-BODIPY and FerroOrange staining, mitochondrial functionality tests, and protein expression analyses via Western blot and immunofluorescence. The influence of Fra on bone microarchitecture of GIOP in mice was assessed using microcomputerized tomography, hematoxylin and eosin staining, double-labeling with Calcein-Alizarin Red S, and immunohistochemistry at imaging and histological levels. Based on our data, Fra prevented Dex-induced ferroptosis and bone loss. In vitro, glutathione levels increased and malondialdehyde, lipid peroxidation, and mitochondrial reactive oxygen species decreased. Fra treatment also increases nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione peroxidase 4 (GPX4), and COL1A1 expression and promotes bone formation. To delve deeper into the mechanism, the findings revealed that Fra triggered the activation of Nrf2/GPX4 signaling. Moreover, the use of siRNA-Nrf2 blocked the beneficial effect of Fra in osteoblasts cultivated with Dex. Fra effectively combats GIOP by activating the Nrf2/GPX4 signaling pathway to inhibit ferroptosis.