The Research For Effects And Its Underlying Mechanism Of PIC On Osteoclasts

The bone homeostasis is maintained by the precise balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption.Excessive bone resorption occurs when osteoclasts are present in elevated numbers and/or exhibit enhanced activity,which eventually leads to a series of bone diseases such as osteoporosis,rheumatoid arthritis and myeloma.Osteoclast is the only cell responsible for bone resorption,thus,targeting inhibition of osteoclast formation and bone resorption is considered to be one of the most effective ways to deal with these diseases.At present,drugs for treating bone diseases are less and also with many side effects.Therefore,it is very necessary to develop new drugs with less side effects.Piceatannol has a variety of biological functions,including antioxidant,anti-inflammatory,anti-cancer,anti-diabetic,cardioprotective,neuroprotective and immunomodulatory properties.However,there are few reports on the treatment of bone diseases by piceatannol.Although studies have shown that piceatannol inhibits osteoclast formation,the precise mechanism of piceatannol to inhibit osteoclast formation and whether piceatannol can promote the apoptosis of mature osteoclasts have not been reported.In this study,we focus on piceatannol.CCK-8 was used to detect cytotoxicity.The detection of TRAP staining and TRAP activity confirmed that piceatannol inhibited RANKL-induced osteoclast formation in a concentration-dependent manner.Toluidine blue staining and Scanning Electron Microscope(SEM)were used to detect the bone resorptive area.We confirmed that piceatannol inhibited RANKL-induced bone resorption in a dose-dependent manner.We confirmed that piceatannol inhibited the expression of osteoclast-specific genes by Real-time qPCR.Western Blot analysis demonstrated that piceatannol inhibited RANKL-induced osteoclast formation and bone resorption by suppressing NF-?B,JNK,ERK and AKT signaling pathways.However,piceatannol had no effect on p38 signaling pathway.Notably,we demonstrated that piceatannol promoted apoptosis of mature osteoclasts via caspase-3 signaling pathways by several experiments,such as TRAP staining,LDH release assay,Hoechst staining,caspase-3 activity assay and caspase-3 protein expression assay.In conclusion,this study confirmed the inhibitory effect and the underlying mechanism of piceatannol on osteoclast formation and bone resorption through systematic in vitro experiments.We also proposed for the first time that piceatannol promotes apoptosis of mature osteoclasts.Our findings may contribute to the treatment of bone diseases characterized by excessive bone resorption.