Inhibitory Effects of 1',2'-Dihydrorotenone on Osteoclast Differentiation and Bone Resorption In Vitro and In Vivo

It is important to identify therapeutic compounds with no adverse effects for use in the chemotherapy of patients with bone-related diseases. The aim of this study was to identify a new compound that inhibits osteoclast differentiation and bone resorption. Herein, we examined the effects of 1’,2’-dihydrorotenone on osteoclast differentiation and bone resorption in vitro and in vivo. 1’,2’-dihydrorotenone inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation of cultured bone marrow macrophages (BMMs) in a dosedependent manner. However, 1’,2’-dihydrorotenone did not exert cytotoxic effect on BMMs. 1’,2’-dihydrorotenone suppressed the expression of c-fos and NFATc1 as well as osteoclast-specific genes in BMMs treated with RANKL. Treatment with RANKL inhibited the expression of inhibitors of differentiation/DNA binding (Id)1, 2, and 3; however, in the presence of 1’,2’-dihydrorotenone, RANKL did not suppress the expression of Id1, 2, and 3. Furthermore, 1’,2’-dihydrorotenone inhibited bone resorption and considerably attenuated the erosion of trabecular bone induced by lipopolysaccharide treatment. Taken together, these results suggest that 1’,2’-dihydrorotenone has the potential to be applied in therapies for bone-related diseases.