Osthole Inhibits M1 Macrophage Polarization and Attenuates Osteolysis in a Mouse Skull Model

Excessive bone resorption due to increased inflammatory factors is a common feature of inflammatory lytic bone diseases. This group of diseases is effectively treated with drugs. In recent years, many studies have reported that traditional Chinese medicine herbs have substantial effects on inflammation, osteoclast differentiation and maturation, and bone destruction. Herein, we investigated the effects of osthole (OST) on lipopolysaccharide- (LPS-) induced macrophage polarization, inflammatory responses, and osteolysis. In vitro, we used immunofluorescence and quantitative real-time polymerase chain reaction assays to confirm whether bone marrow-derived macrophages showed an increased expression of inflammatory factors, such as interleukin-6, iNOS, CCR7, and CD86, in the presence of LPS. However, we found that such expression was suppressed and that the M2 macrophage expression increased in the presence of OST. OST reduced LPS- and RANKL-induced intracellular reactive oxygen species production in the bone marrow-derived macrophages. Further, it potently suppressed osteoclast differentiation and osteoclast-specific gene expression by suppressing the P38/MAPK and NF-κB pathways. Consistent with the in vitro observations, OST greatly ameliorated LPS-induced bone resorption and modulated the ratio of macrophages at the site of osteolysis. Taken together, OST has great potential for use in the management of osteolytic diseases.