Objective:Gut-derived serotonin strongly inhibits bone formation by inhibiting osteoblast proliferation.Our previous study demonstrated that the lignan-rich fraction prepared from Sambucus willimasii Hance,a folk herbal medicine used to treat bone fractures and joint diseases in China,exerted bone-protective effects,and its actions were modulated by suppressing the synthesis of gut-derived serotonin via the inhibition of intestinal tryptophan hydroxylase 1(TPH-1).However,there is no direct evidence for the action of lignans on TPH-1.This study aimed to verify the direct action of lignans on the TPH-1 and its influence on serotonin synthesis and bone properties.Methods:Molecular docking and surface plasmon resonance were performed to determine the affinities of lignans to TPH-1.The cell viability and the protein activity and expression of TPH-1 were measured in RBL2H3 cells.The serum serotonin level and bone mineral density upon lignan treatment in ovariectomized mice were determined.Result:The lignans showed high binding scores and binding affinities to TPH-1,inhibited the activity and protein expression of TPH-1,suppressed the serum serotonin levels in ovariectomized mice as well as promoted bone mineral density.Conclusion:This is the first study to report that lignans are novel TPH-1 inhibitors and that these lignans could be potential agents for the management of serotonin-related diseases,including osteoporosis.
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