Quercetin protects against iron overload-induced osteoporosis through activating the Nrf2/HO-1 pathway

Aims: Eucommia is the tree bark of Eucommia japonica, family Eucommiaceae. In traditional Chinese medicine, Eucommia is often used to treat osteoporosis. Quercetin (QUE), a major flavonoid extract of Eucommia japonica, has been reported to have anti-osteoporosis effects. However, there are no studies reporting the mechanism of QUE in the treatment of iron overload-induced osteoporosis. This study set out to investigate the therapeutic effects of QUE against iron overload-induced bone loss and its potential molecular mechanisms. Materials and methods: In vitro, MC3T3-E1 cells were used to study the effects of QUE on osteogenic differen-tiation, anti-apoptosis and anti-oxidative stress damage in an iron overload environment (FAC 200 mu M). In vivo, we constructed an iron overload mouse model by injecting iron dextrose intraperitoneally and assessed the osteoprotective effects of QUE by Micro-CT and histological analysis. Key findings: In vitro, we found that QUE increased the ALP activity of MC3T3-E1 cells in iron overload envi-ronment, promoted the formation of bone mineralized nodules and upregulated the expression of Runx2 and Osterix. In addition, QUE was able to reduce FAC-induced apoptosis and ROS production, down-regulated the expression of Caspase3 and Bax, and up-regulated the expression of Bcl-2. In further studies, we found that QUE activated the Nrf2/HO-1 signaling pathway and attenuated FAC-induced oxidative stress damage. The results of the in vivo study showed that QUE was able to reduce iron deposition induced by iron dextrose and attenuate bone loss. Significance: Our results suggested that QUE protects against iron overload-induced osteoporosis by activating the Nrf2/HO-1 signaling pathway.