Objective To investigate the effect of curcumin on the apoptosis in spinal cord and dorsal root ganglion neurons in a rat model of diabetic neuropathic pain (DNP) . Methods One hundred and eight male SD rats weighing 200-230 g were randomly divided into 4 groups ( n = 27 each): control group (group C), DNP group, solvent control group (group SC) and curcumin group (group Cur) . Diabetes was induced with intraperitoneal streptozocin 70 mg/kg. Successful induction of diabetes was defined as blood glucose ＞ 16.7 mmol/L. Curcumin and com oil 100 mg/kg (23 mg/ml) were given intraperitoneally once a day for 14 consecutive days starting from 14 days after administration of streptozocin in Cur and SC groups respectively. Mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured 2 d before and 14 d after streptozocin injection and 3, 7 and 14 d after curcumin injection. The pain threshold measured at 14 d after administration of streptozocin decreased by more than 15% of the baseline in all the rats. The expression of caspase-3 and Bcl-2 in spinal cord and dorsal root ganglion was determined at 3, 7 and 14 d after curcumin injection by immuno-histochemistry and Western blot, and the neuronal apoptosis rate was determined by TUNEL. Results Compared with group C, MWT and Bcl-2 expression were significantly decreased, TWL was significantly shortened, the neurona lapoptosis rate and caspase-3 expression were significantly increased in DNP, SC and Cur groups ( P ＜ 0.05).Compared with group DNP, MWT and Bcl-2 expression were significantly increased, TWL was significantly prolonged, the neuronal apoptosis rate and caspase-3 expression were significantly decreased in Cur group ( P ＜0.05) . There was no significant difference in the parameters mentioned above between DNP and SC groups ( P ＞0.05). Conclusion Curcumin can attenuate DNP by inhibiting the apoptosis in spinal dorsal hom and dorsal root ganglion neurons in rats, and the inhibition of caspase-3 expression and increase in Bcl-2 expression are involved in the mechanism.

ObjectiveTo investigate the effects of curcumin on type 2 diabetic neuropathic pain (DNP)and expression of inositol-requiring enzyme 1α (IRE1α) in spinal dorsal horn and dorsal root ganglia (DRG) in rats.MethodsType 2 diabetes mellitus was induced by high-fat and high-sucrose diet and intraperitoneal streptozotocin (STZ) 35 mg/kg,and confirmed by fasting blood glucose level ＞ 16.7 mmol/L in male SD rats.Type 2 DNP was confirmed by the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWI.) measured on day 14 after STZ administration ＜ 80％ of the baseline value.The rats were then randomly divided into 3 groups ( n =27 each):DNP group,curcumin group (group Cur) and solvent control group (group SC).Curcumin and corn oil 100 mg/kg (25 mg/ml) were given intraperitoneally once a day for 14 consecutive days starting from 14 days after administration of streptozocin in Cur and SC groups respectively.Another 27 rats were chosen and served as control group (group C) and fed with common fodders.MWT and TWL were measured at 3,7 and 14 day after curcumin administration.The expression of IRE1α in spinal dorsal horn and DRG was detected by Western blot.ResultsCompared with group C,MWT was significantly decreased and TWL was significantly shortened,and the expression of IRE1α was up-regulated in DNP,Cur,and SC groups (P ＜ 0,05),Compared with group DNP,MWT were significantly increased,TWL was significantly prolonged,and the expression of IRE1α in spinal dorsal horn and DRG was down-regulated in group Cur (P ＜ 0.05).There was no significantdifference in the parameters mentioned above between DNP and SC groups (P ＞ 0.05).ConclusionCurcumin can attenuate type 2 1)NP and inhibition of the expression of IRE1α in spinal dorsal horn and DRG is involved in the mechanism.