Wnt1/β-catenin signaling up-regulates spinal VGLUT2 expression to maintain neuropathic pain in mice / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE The present study was aimed to investigate the role of Wnt/β-catenin sig-naling in spinal VGLUT2 regulation and neuropathic pain. METHODS To elucidate the association be-tween VGLUT2 and neuropathic pain,we determined the expression and distribution characteristics of VGLUT2 in mice subjected to spared nerve injury(SNI),and then observed the effects of two VGLUT2 targeting shRNAs on mechanical allodynia and glutamate release.The effects of Wnt/β-catenin signal-ing on VGLUT2 expression and pain behavior were investigated by using Wnt agonist,Wnt1,and Wnt/β-catenin pathway inhibitor XAV939 in SNI mice.RESULTS SNI surgery induced significant up-regula-tion of VGLUT2 on postoperative days 7,14,and 21.Double immunofluorescence labeling of VGLUT2 with NeuN,MAP2,Iba-1,or GFAP showed that VGLUT2 was mainly expressed in neurons in the dor-sal horn of the spinal cord after SNI(NeuN,MAP2).Intrathecal administration of VGLUT2 shRNAs be-fore or after SNI surgery significantly decreased mechanical allodynia and glutamate release. Mean-while,Wnt1/β-catenin signaling increased significantly after SNI surgery.Over-expression of β-catenin in PC12 cells increased VGLUT2 protein level,intrathecal administration of Wnt agonist or Wnt1 signifi-cantly increased VGLUT2 protein expression in spinal cord, while Wnt/β-catenin pathway inhibitor XAV939 decreased VGLUT2 expression in PC12 cells and spinal cord.Additionally,intrathecal admin-istration of XAV939 7 days after SNI significantly attenuated mechanical allodynia in mice, which was in accordance with down-regulation of VGLUT2 protein levels.VGLUT2 shRNAs significantly attenuat-ed Wnt agonist or Wnt1 induced mechanical allodynia. CONCLUSION Wnt1/β-catenin signaling path-way up-regu-lates the spinal VGLUT2 expression,and this regulation is involved in neuropathic pain behavior.