Effect of curcumin on expression of MMP-2 and MMP-9 in spinal dorsal horn and dorsal root ganglion of rats with type 2 diabetic neuropathic pain

Abstract

Objective To evaluate the effect of curcumin on the expression of MMP-2 and MMP-9 in the spinal dorsal horn and dorsal root ganglion (DRG) of rats with type 2 diabetic neuropathic pain (DNP).Methods Type 2 diabetes mellitus was induced by high-fat and high-sucrose diet and intraperitoneal streptozotocin 35 mg/kg,and confirmed by fasting blood glucose level ≥ 16.7 mmol/L in male Sprague-Dawley rats.Type 2 DNP was confirmed by the mechanical paw withdrawal threshold (MWT) and thermal paw withdraw latency (TWL) measured on day 14 after streptozotocin administration ＜ 80％ of the baseline value.The rats were then randomly divided into 3 groups (n =27 each):type 2 DNP group (group DNP); curcumin group (group Cur); solvent control group (group SC).In Cur and SC groups,curcumin 100 mg/kg and corn oil 4 ml/kg were injected intraperitonally,respectively,once a day for 14 consecutive days starting from day 14 after streptozotocin administration.Another 27 normal Sprague-Dawley male rats served as control group (group C) and were fed with normal forage.MWT and TWL were measured before type 2 DNP was induced,after type 2 DNP was induced,and at 3,7 and 14 days after curcumin injection(T1-5).The rats were sacrificed after MWT and TWL were measured at T3-5,and the lumbar segments of the spinal cord and DRG (L4-6) were removed for determination of the expression of MMP-2 and MMP-9 by Western blot.Results Compared with group C,MWT was significantly decreased and TWL was shortened,and MMP-2 and MMP-9 expression in the spinal dorsal horn and DRG was up-regulated in DNP,Cur and SC groups.Compared with DNP group,MWT was significantly increased and TWL was prolonged,and MMP-2 and MMP-9 expression in the spinal dorsal horn and DRG was down-regulated in Cur group,and no significant changes were found in the parameters mentioned above in SC group.Conclusion The mechanism by which curcumin attenuates type 2 DNP may be related to up-regulation of the expression of MMP-2 and MMP-9 in the spinal dorsal horns and DRG of rats. Key words: Curcumin ; Diabetes mellitus, type 2 ; Neuralgia; Spinal cord ; Ganglia, spinal Matrix metalloproteinase 2; Matrix metalloproteinase 9