Role of spinal cord mitochondrial autophagy in alleviation of diabetic neuropathic pain by curcumin in mice / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of spinal cord mitochondrial autophagy in alleviation of diabetic neuropathic pain (DNP) by curcumin in mice.Methods:SPF healthy male C57BL/6 mice, aged 2 months, weighing 20-25 g, in which DNP model was established by intraperitoneal injection of streptozotocin (STZ) 130 mg/kg, were used in this study.A total of 36 mice with successfully established DNP model were divided into 3 groups ( n=12 each) using the random number table method: DNP group, DNP + curcumin group (DPR group), and DNP + curcumin + cyclosporine A group (DRC group). Another 12 C57BL/6 mice were selected and served as normal control group (NC group), and the equal volume of normal saline was intraperitoneally injected.In group DPR, curcumin 200 mg/kg was administered by intragastric gavage, once a day, for 7 consecutive days.In group DRC, the mitochondrial autophagy inhibitor cyclosporine A 10 mg/kg was intrathecally injected once a day for 7 consecutive days before each administration of curcumin.The equal volume of normal saline was administered by intragastric gavage at the same time point, once a day, for 7 consecutive days in group NC and group DNP.The mechanical paw withdrawal threshold (MWT) was measured before intragastric gavage and at 1, 3, 5 and 7 days after intragastric gavage.After the last behavioral testing, the L 4-6 spinal cord tissues were removed for determination of the mitochondrial membrane potential and ROS content (by JC-1 and DCFH-DA combined with flow cytometry), expression of microtubule-associated protein light chain 3 (LC3), Beclin1 and P62 (by Western blot), and mitochondrial autophagosomes (by transmission electron microscopy) and for microscopic examination of the co-expression of LC3-Ⅱwith mitochondrial translocase outer membrane protein 20 (TOM20) (using immunofluorescence double-labeling technique). Results:Compared with group NC, the MWT and mitochondrial membrane potential were significantly decreased, the ROS content and LC3-Ⅱ/Ⅰ ratio were increased, the expression of Beclin1 was up-regulated, the expression of P62 was down-regulated ( P<0.05), the number of mitophagosomes developed was increased, and the co-expression of LC3-Ⅱwith TOM20 was increased in group DNP.Compared with group DNP, the MWT and mitochondrial membrane potential were significantly increased, the ROS content was decreased, and LC3-Ⅱ/Ⅰ ratio was increased, the expression of Beclin1 was up-regulated, the expression of P62 was down-regulated ( P<0.05), the number of mitophagosomes developed was increased, and the co-expression of LC3-Ⅱwith TOM20 was increased in group DPR.Compared with group DPR, the MWT and mitochondrial membrane potential were significantly decreased, the ROS content was increased, LC3-Ⅱ/Ⅰ ratio was decreased, the expression of Beclin1 was down-regulated, the expression of P62 was up-regulated ( P<0.05), the number of mitophagosomes developed was decreased, and the co-expression of LC3-Ⅱ with TOM20 was decreased in group DRC. Conclusions:The mechanism by which curcumin reduces DNP may be related to the up-regulation of mitochondrial autophagy in the spinal cord and improvement in mitochondrial function in mice.