PI3K/AKT/Nrf2 signalling pathway is involved in the ameliorative effects of xanthohumol on amyloid β-induced oxidative damage and bone loss

Xanthohumol (XAN), a natural isoflavone from Humulus lupulus L., possesses biological activities on relieving oxidative stress and osteoporosis (OP). This study aimed to evaluate the antioxidative and osteoprotective effect of XAN on Aβ-injured osteoblasts, and explore its underlying mechanism. Osteoblasts were pretreated with XAN followed by stimulation with Aβ1-42. Cell proliferation, ALP activity, bone mineralization and bone formation index were measured. Apoptosis and reactive oxygen species (ROS) were analysed with flow cytometer. PI3K inhibitor LY294002 or siRNA-Nrf2 was added and transfected in osteoblasts, to further confirm whether the pathway participated in the regulation of XAN-induced cytoprotection. XAN markedly improved the proliferation, differentiation and mineralization of Aβ-injured osteoblasts. Additionally, XAN reduced cell apoptosis rate and ROS level, and increased the expression of p-AKT, Nrf2, NQO1, HO-1 and SOD-2. More importantly, LY294002 or siNrf2 abolished the beneficial effect of XAN on osteoblasts activity and decreased the PI3K expression and inhibited its downstream proteins, indicating XAN activated PI3K/AKT/Nrf2 pathway in Aβ-injured osteoblasts. It was the first time to reveal the antioxidative and osteoprotective effect of XAN through regulating PI3K/AKT/Nrf2 pathway in Aβ-injured osteoblasts, which provides reference for the clinical application of XAN in the prevention and treatment of OP.