Wnt/β-Catenin Signal Pathway Involved In The Treatment Of Neuropathic Pain By Electroacupuncture

Objective:1.The CCI（Chronic constrictive injury）model was performed to evaluate the therapeutic effect of electroacupuncture（EA）in neuropathic pain（NP）;2.The expression of Wnt3a/β-catenin and the activation of astrocytes in L4-5 spinal cord of CCI rats were observed,so as to verify whether the Wnt/β-catenin signal pathway participate in activation of spinal astrocytes and elucidate the possible pathogenesis of NP.3.Moreover,observing the expression of Wnt3a/β-catenin and the activation of astrocytes after electroacupuncture treatment,so as to explore the possible mechanism of electroacupuncture treatment of NP.Methods:1.A total of 195 SD rats weighing 220²50g were selected as research subjects.According to the random number table method,rats were randomly divided into three groups,sham operation group（S group,n=65）,model group（M group,n=65）,and electroacupuncture group（D group,n=65）.2.M Group:the right sciatic nerve was isolated and ligated with 4-0 silk thread;In S group,only the right sciatic nerve trunk was isolated without ligation.In D group,based on CCI operation,two acupoints of"Huantiao"and"Weizhong"were stimulated with 2HZ/1mA electroacupuncture for 15min daily.3.The mechanical withdrawal threshold（MWT）and thermal withdrawal threshold（TWL）of the right foot in each group were measured at preoperative（T0）,postoperative 3days（T1）,postoperative 7 days（T2）,and postoperative 14 days（T3）respectively.The L4-5 spinal segments were removed after perfusion of normal saline into the heart,and the expressions of Wnt3a,β-catenin,GFAP and wnt3a mRNA andβ-catenin mRNA in L4-5 tissues were detected by Western blot and qPCR.In addition,the expressions of IL-18in the L4-5 were detected by ELISA.5.Deep anesthesia was performed at the end of the behavioral test at T3,the chest was opened to expose the heart,perfused with 4%paraformaldehyde,and immunohistochemical assay were used to observe the activation of astrocytes.Results:1).MWT:rats in M group and D group were lower than those in group S at T₁、T₂、T₃（P<0.05）.At T₁、T₂、T₃,rats in D group were higher than M group（P<0.05）;TWL:rats in M group and D group were lower than those in group S at T₁、T₂、T₃（P<0.05）.At T₁、T₂、T₃,rats in D group were higher than M group（P<0.05）.2)IL-18 concentration in L4-5:the concentration of IL-18 in M group and D group began to increase at T₁,which was different from T₀（P<0.05）,at T₁、T₂、T₃,the concentration of IL-18 in M group and D group were significantly higher than that in group S（P<0.05）.The concentration of IL-18 in group D decreased at T₁、T₂、T₃,obviously lower than that in M group（P<0.05）.3).Expressions of wnt3a mRNA andβ-catenin mRNA in L4-5 spinal cord tissues of rat in three groups:the expression of wnt3a mRNA andβ-catenin mRNA in M group and D group began to increase at T₁,which was different from that of T0;Compared with S group,M group and D group increased at T₁、T₂、T₃（P<0.05）.At T₁、T₂、T₃,D group were significantly lower than group M（P<0.05）.4).The expressions of wnt3a andβ-catenin in the L4-5spinal cord tissues of the three groups:the expression of wnt3a andβ-catenin in the M group and the D group began to increase in T₁,which was different from that in T₀;Compared with group S,group M and group D increased at T₁、T₂、T₃（P<0.05）.At T₁、T₂、T₃,D group were significantly lower than M group（P<0.05）.5).The activation of astrocytes in L4-5 spinal cord tissues of the three groups:compared with the activation of astrocytes in S group,the expression of GFAP in group M and group D was significantly higher than that in group S at T₃（P<0.05）.The activation degree of astrocytes in group D was significantly lower than that in group M,and the expression of GFAP was significantly lower than that in group M（P<0.05）.Conclusion:1.CCI model induced the NP-associated hyperalgesia and prompted the activation of astrocytes and the release the proinflammtory cytokine IL-18 in spinal cord;2.Wnt/β-catenin signal pathway may mediate the activation of astrocytes thus promote the central sensitization of neuropathic pain;3.Electroacupuncture could inhibit the activation of Wnt/β-catenin pathway,thereby inhibiting the activation of astrocytes and blocking the further development of NP.