| Objective: Bone cancer pain(BCP)is pain caused by primary bone cancer or tumor metastasis.Increasing evidence and our previous studies indicate that mammalian silencing information regulator 2 homolog 1(SIRT1)is involved in peripheral sensitization and central sensitization of BCP.The potential mechanism of SIRT1 in bone cancer pain may provide clues for pain treatment.Dynamics-related protein 1(Drp1)is an important regulator of mitochondrial fission.Methods: Twenty-seven female SD rats were randomly divided into Sham group,BCP group,and BCP+SRT1720 group.MRMT-1 rat breast cancer cells were injected into the left tibia to establish a model of metastatic breast cancer-induced bone pain.Sham group was injected with an equal volume of Hank’s Balanced Salt Solution(HBSS)at the same location.The degree of bone destruction in the BCP group was observed by X-ray film of the tibia and HE staining,and the mechanical pain test was used for verification.Twelve days after modeling,SRT1720 was injected intrathecally in the BCP+SRT1720 group,and the same volume of DMSO + normal saline(volume ratio 1: 1)was injected in the Sham group and the BCP group.The 50% paw withdrawal threshold(PWT)was determined at 0,1,3,5,7,12,18,and 24 h after administration in each group.The levels of related proteins in each group were examined by Western Blot,immunofluorescence,and ELISA.Apoptosis was determined by terminal deoxynucleotidyl transferase(TdT)-mediated dUTP nick end labeling(TUNEL).In in vitro experiments,SHSY5 Y cells were used as experimental models.SRT1720 was administrated at concentrations of 0,1,and 10 μM,respectively.Western Blot,immunofluorescence,ELISA,and other experimental methods were used to test the expression of related proteins.Cell proliferation was assessed by EdU method in each group Mitochondrial membrane potential at the cell level was determined using the Mitochondrial Membrane Potential Detection Kit(JC-1).Results:(1)Compared with the Sham group,BCP rats exhibited marked bone destruction and showed sensitive mechanical pain.BCP rats exhibited an increase in the infiltration and apoptosis of inflammatory cells and expression of Drp1,and a reduction in the expression of SIRT1 protein in the spinal cord(p <0.05).(2)Compared with the BCP group without SRT1720 injection,the BCP+SRT1720 group exhibited increased SIRT1 phosphorylation,attenuated expression of Drp1,and improved pain behavior(p <0.05)after intrathecal injection of the SIRT1 agonist SRT1720.SRT1720 also downregulated the apoptotic index BAX/Bcl-2 and the expression of proapoptotic gene caspase-3,inhibited the apoptosis of the spinal cord,and reduced the proportion of Drp1-positive cells and the expression of Drp1 in BCP rats(p <0.05).(3)In in vitro studies,SRT1720 treatment reduced the expression of Drp1 in a dose-dependent manner(p <0.05),blocked CCCP-induced changes in mitochondrial membrane potential,thereby reducing apoptosis and promoting proliferation.Conclusion: These data suggest that SRT1720-triggered activation of SIRT1 reduces bone cancer pain by preventing Drp1-mediated mitochondrial fission.The results provide a novel therapeutic target for the treatment of bone cancer pain. |
