Objective To investigate the effect of dexmedetomidine(Dex)on bone loss in tail-suspended rats and primarily explore its regulatory mechanism on bone metabolism.Methods A total of 30 male rats were randomly divided into a control group,a model group,and a Dex group,with 10 animals in each group.Rat model of osteoporosis was established by hind limb suspension for 4 weeks.Dex at a dose of 10 μg/kg was given intraperitoneally,once every other day from the day of tail suspension.And equal amount of normal saline was given to the control and model group.Bone histological staining was used to observe the trabecular bone area fraction.Biomechanical three-point bending test was employed to measure the maximum load,stiffness,and fracture energy.Dual calcein/alizarin red fluorescence labeling and tartrate resistant acid phosphatase(TRAP)staining were applied respectively to detect the mineral apposition rate and bone formation rate as well as the number of osteoclasts on bone surfaces.Secondly,after primary osteoblasts were isolated from the tibiae of tail-suspended rats and then treated with 1 nmol/L Dex,the proportion of alkaline phosphatase(ALP)-positive osteoblasts and the activity of the enzyme were detected by ALP staining and activity test.qRT-PCR was applied to measure the expression of osteogenic activity-related factors,including osteocalcin(Ocn),Runt related transcription factor 2(Runx2),Osterix protein(Osx),and type 1 collagen(Col1).Results The animal experiments revealed that Dex treatment significantly increased the tibial trabecular bone area fraction,inhibited the decrease in bone mechanical strength,and enhanced the mineralization deposition rate and new bone formation rate of trabecular bone in the tail-suspended rats(all P＜0.001).The in vitro experiments showed that Dex treatment obviously improved ALP activity and the number of ALP-positive osteoblasts in primary osteoblasts isolated from tail-suspended rats(P＜0.01),and up-regulated the expression levels of osteogenic differentiation-related genes,such as Ocn,Runx2,Osx and Col1(P＜0.01).Conclusion Dex exerts anti-bone loss effect in tail-suspended rats,which may be associated with its stimulation on osteoblast-mediated bone formation.

Objective To delineate the expressions of ubiquitin-specific proteinase 49 (USP49)and FK506 binding protein 51 (FKBP51) in the spinal dorsal horns and their roles in rats with diabetic neuropathic pain (DNP).Methods Male SD rats were fed with high glucose and high fat diet with an intraperitoneal injection of 1％ streptozocin to establish DNP rat models.DNP rats were allocated into DNP group,control shRNA group (KC group) and knockdown USP49 group (KD group,n=10);saline,Ad-scrambled shRNA (3×108 PFU/mL) and Ad-USP49-shRNA (3×108 PFU/mL) were intrathecally injected into the rats of the three groups.Another 10 normal rats were chosen as control group (C group).Thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were measured one d before model establishment,one and 7 d after model establishment,one,three and 7 d after intrathecal injection.The mRNA and protein expressions of USP49,FKBP51 and glucocorticoid receptor α (GRα)in dorsal horn neurons were detected by real time-PCR and Western blotting.Results (1) TWL showed no significant difference among the four groups one d before model establishment (P＞0.05);three and 7 d after intrathecal injection,TWL in KD group was significantly prolonged as compared with that in the DNP group,and significantly shortened as compared with that in C group (P＜0.05).(2) MWT showed no significant difference among the four groups one d before model establishment (P＞0.05);three and 7 d after intrathecal injection,MWT in KD group was significantly higher as compared with that in the DNP group,and significantly lower as compared with that in C group (P＜0.05).(3) As compared with DNP group,KD group had significantly decreased mRNA expressions of USP49 and FKBP51,and statistically increased mRNA GRα expression (P＜0.05).(4) As compared with DNP group,KD group had significantly decreased protein expressions of USP49 and FKBP51,and statistically increased protein GRα expression (P＜0.05).Conclusion Specific knockdown of USP49 expression is associated with improvement of heat hyperalgesia and mechanical hyperalgesia in DNP rats,which may be attributed to the de-ubiquitination ofFKBP51 by USP49.