• Ying Wang, Qulian Guo, Jianqin Yan, Minghua Yang, Yan Lin, and Zhiping Lin.
• Department of Anesthesiology, Teaching Hospital of Fujian Medical University/Fujian Cancer Hospital, Fuzhou 350014, China.
• Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2016 Jun 28; 41 (6): 578-85.

ObjectiveTo explore the role of DNA methyltransferases (DNMTs) in the pathogenesis of neuropathic pain (NPP) in rats following sciatic nerve chronic constriction injury (CCI).
MethodsA total of 27 adult male Sprague-Dawley rats with successful implantation of lumbar intrathecal catheter were randomly divided into 3 groups: a sham + normal saline group (sham+NS group), a CCI+NS group, and a CCI+5-azacytidine group (CCI+5-AZA group) (n=9 in each group). The rats in the Sham+NS group and the CCI+NS group received NS, while the rats in the CCI+5-AZA group received 10 μmol/L of 5-AZA (a DNMTs inhibition) once a day through spinal injection from the 3th day to 14th day after CCI surgery. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of ipsilateral hinds in the 3 groups were measured before or at the 3th, 5th, 7th, 10th or 14th day after CCI surgery. At the end of experiments, all rats were killed under deep anesthesia and their lumbar spinal cords were dissected to examine the DNMT1, DNMT3a and DNMT3b expression by RT-PCR, Western blot and immunohistochemistry, respectively.
ResultsCompared with the sham+NS group, the MWT and TWL in the CCI+NS group were obviously reduced from the 3th day to the 14th day after surgery (both P<0.05). Compared with the CCI+NS group, the MWT and TWL in the CCI+5-AZA group were obviously increased from the 5th day to the 14th day after surgery (both P<0.05), but they were still reduced compared with the sham+NS group (both P<0.05). The DNMT1, DNMT3a and DNMT3b were highly expressed in the lumbar spinal dorsal horn in all rats, and the positive signals were mainly located in the nucleus. The DNMT1, DNMT3a and DNMT3b levels in the CCI+NS group were increased significantly compared with that in the sham+NS group on the 14th day after surgery (all P<0.05). The DNMT1, DNMT3a and DNMT3b expressions in the CCI+ 5-AZA group were decreased significantly compared with that in the CCI+NS group (all P<0.05), but they still increased compared with that in the sham+NS group (all P<0.05). 
ConclusionUp-regulation of DNMTs in the lumbar spinal may play an important role in the pathogenesis of NPP in CCI rats. DNMTs inhibitors (5-AZA) could reduce expression of DNMTs and attenuate CCI-induced NPP, which might be a potential therapeutic drug for NPP.

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