Docking study and antiosteoporosis effects of a dibenzylbutane lignan isolated from Litsea cubeba targeting Cathepsin K and MEK1

Litsea cubeba (Lour.) Pers. (Lauraceae family) has been used as a folk prescription in China for the treatment of rheumatic diseases for a long time. Previous studies of our laboratory have indicated that 9′-O-di-(E)-feruloyl-meso-5, 5′-dimethoxy-secoisolariciresinol (FCL) which is a dibenzylbutane lignan enriched in L. cubeba displayed anti-inflammatory activity in LPS induced RAW264.7 cells. The present study was aimed to investigate anti-osteoporosis/anti-rheumatoid arthritis (RA) properties of FCL and explore its potential molecular targets. The anti-RA and anti-osteoporosis properties were evaluated by determination of cell proliferation, alkaline phosphatase (ALP) activity and calcium deposition formation on osteoblasts. Meanwhile, the Tartaric Resistnt Acid Phosphatase (TRAP) inhibitory activity of FCL was evaluated on the macrophage colony-stimulating factor (M-CSF) and soluble receptor activator of nuclear factor kappa-B ligand (sRANKL) induced bone marrow cells (BMCs). Furthermore, molecular docking was carried out to predict the molecular targets of FCL, and cellular thermal shift assay (CETSA) was carried out to verify the in silico molecular docking results. The present results revealed that FCL promoted osteoblastogenesis and bone formation whereas suppressed osteoclastogenesis, and importantly, FCL showed strong binding activities to the cathepsin K and mitogen-activated proteinkinase kinase 1 (MEK1) based on the results of molecular docking and CETSA. Taken together, our results indicated that FCL may possess the anti-osteoporosis potential through acting on the targets of cathepsin K and MEK1.