Effect of mild moxibustion on pain and expression of LC3 and Bax in spinal cord in cervical spondylotic radiculopathy rats

Abstract

To observe the effect of mild moxibustion (Moxi) at "Dazhui" (GV14) on neuropathic pain, expression of autophagy and apoptosis factor LC3 and Bax proteins and mRNAs in the spinal cord tissue in rats with cervical spondylotic radiculopathy (CSR), so as to explore its underlying mechanism underlying relief of CSR-induced pain. Forty rats (half male half female) were randomly divided into blank control, model, Moxi, Moxi+autophagy inhibitor 3-methyladenine (3-MA, Moxi+3-MA) groups, with 10 rats in each group. The CSR model was established by loose ligature of the local cervical nerve roots. Three days after modeling, mild Moxi was applied to GV14 for 10 min, once daily for 7 days. Rats of the Moxi+3-MA group received intraperitoneal injection of 3-MA(1 mL, 15 mg/kg+ saline) before Moxi, once daily for 7 consecutive days. Rats of the model and Moxi groups were also given normal saline (i.p., 1 mL), once daily for 7 days. The gait behavior score (1-3 points) was scaled according to the rats' pain reaction and foot paw contracture produced walking disorder and the mechanical pain threshold (MPT) was detected before and after the treatment. The expression of spinal cord LC3 and Bax proteins and mRNAs were detected by immunohistochemistry and quantitative RT-PCR, respectively. Compared with the blank control group, the gait disorder score, and percentage of Bax positive cells and expression of Bax mRNA were significantly increased (P<0.01, P<0.05), and MPT was markedly decreased in the model group (P<0.01). After the treatment, the gait disorder score, percentage of Bax positive cells and Bax mRNA expression were significantly down-regulated (P<0.01, P<0.05), while the MPT and percentage of LC3 positive cells and LC3 mRNA expression were considerably increased (P<0.01, P<0.05) in both Moxi and Moxi+3-MA groups. The therapeutic effects of mild Moxi were remarkably superior to those of Moxi+3-MA in downregulating gait disorder score, Bax positive cell percentage and Bax mRNA expression, and in up-regulating MPT, LC3 positive cell percentage and LC3 mRNA expression (P<0.05), suggesting a reduction of the function of mild Moxi after administration of 3-MA. Mild Moxi at GV14 can relieve neuropathic pain in CSR rats, which may be related to its functions in up-regulating LC3 autophagy, thereby inhibiting the expression of Bax pro-apoptotic protein in spinal cord to reduce apoptosis and to repair nerve injury.