High Cholesterol-Induced Bone Loss Is Attenuated by Arctiin via an Action in Osteoclasts

High cholesterol-induced bone loss is highly associated with oxidative stress, which leads to the generation of oxysterols, such as 7-ketocholesterol (7-KC). Here, we conducted in vivo and in vitro experiments to determine whether arctiin prevents high cholesterol diet-induced bone loss by decreasing oxidative stress. First, arctiin was orally administered to atherogenic diet (AD)-fed C57BL/6J male mice at a dose of 10 mg/kg for 6 weeks. Micro-computerized tomography (μCT) analysis showed that arctiin attenuated AD-induced boss loss. For our in vitro experiments, the anti-oxidant effects of arctiin were evaluated in 7-KC-stimulated osteoclasts (OCs). Arctiin decreased the number and activity of OCs and inhibited autophagy by disrupting the nuclear localization of transcription factor EB (TFEB) and downregulating the oxidized TFEB signaling pathway in OCs upon 7-KC stimulation. Furthermore, arctiin decreased the levels of reactive oxygen species (ROS) by enhancing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), catalase, and heme oxygenase 1 (HO-1), all of which affected OC differentiation. Conversely, silencing of Nrf2 or HO-1/catalase attenuated the effects of arctiin on OCs. Collectively, our findings suggested that arctiin attenuates 7-KC-induced osteoclastogenesis by increasing the expression of ROS scavenging genes in the Nrf2/HO-1/catalase signaling pathway, thereby decreasing OC autophagy. Moreover, arctiin inhibits the oxidation and nuclear localization of TFEB, thus protecting mice from AD-induced bone loss. Our findings thus demonstrate the therapeutic potential of arctiin for the prevention of cholesterol-induced bone loss.