Mechanism Study Of Caprin-1 Mediates Chronic Pain Via Regulating The Expression Of Camkiiα

Objective:Pain is a kind of unpleasant subjective feeling caused by the injury of tissue stimulation.It is an urgent scientific problem to reveal the mechanism of pain and to find effective therapeutic targets.The local regulation of Ca MKIIαexpression is a key factor in determining the efficiency of excitatory synaptic transmission,which plays an important role in the process of nociceptive transmission.The up-regulation of Ca MKIIαexpression at the synaptic site promotes the formation of pain sensitization.Caprin-1 is a major RNA-binding protein in RNA granules in neurons,and plays an important role in mediating the transport and localization of dendritic Ca MKIIαm RNA in neurons.However,the regulation of Ca MKIIαexpression by Caprin-1 and its role in the occurrence and development of chronic pain remain unclear.Therefore,this study aims to explore the role and mechanism of caprin-1 regulating Ca MKIIαexpression in chronic pain.Methods:C57BL/6J mice（8 weeks of age）were divided into inflammatory pain group（CFA）and Sham operation group（Sham）,with 5 mice in each group.Paw Withdrawal Mechanical Threshold（PWT）of mice in each group was determined at 0,1,3,5 and 7 days after establishment of the animal model.Western blot and RT-PCR were used to detect the expression levels of Caprin-1 and Ca MKIIαin the spinal cord lumbar enlargement segment of mice in each group,Combined with behavioral analysis to determine whether Caprin-1 and Ca MKIIαwere involved in the formation of inflammatory pain.F0 passage Nestin ^{Cre ERT2}mice were hybridized with caprin-1^flox/floxmice to obtain genotype of Nestin^{Cre ERT2};Caprin-1^flox/+F1 passage.Then backcrossing them with the genotype of Caprin-1^flox/floxF0 passage mice to get genotypes of Nestin ^{Cre ERT2};Caprin-1^flox/floxinducible conditional knock-out mice.The experiment mice were divided into three groups:wild type control group（WT）,Nestin ^{Cre ERT2};Caprin-1^flox/floxsolvent control group（SC）and Caprin-1 knockout group（KO）with 15 mice in each group.Mice in WT group and KO group were intraperitoneally injected with tamoxifen,and mice in SC group were given control solvent for 5 consecutive days.The PWT of each group was determined after 10 days.Western blot,RT-PCR and IHC were used to detect the expression and distribution of Caprin-1 and Ca MKIIαin spinal cord lumbar enlargement segment.Result:1.PWT was decreased and the expression of Caprin-1 and Ca MKIIαwere upregulated in mice with inflammatory pain.2.Caprin-1 and Ca MKIIαwere co-labeled in mouse spinal dorsal horn neurons.3.Inducible conditional gene knockout mice with genotype Nestin ^{Cre ERT2};Caprin-1^flox/floxwas obtained by two and three generation of breeding.4.After caprin-1 knockout induced by tamoxifen,PWT increased in KO group mice compared with WT and SC group mice（P<0.05）.Caprin-1 and Ca MKIIαwere down-regulated in mouse spinal dorsal horn neurons.Conclusion:1.Tamoxifen continuous injection induced adult mice(Nestin ^{Cre ERT2};Caprin-1^flox/flox)Caprin-1 gene knockout.2.Caprin-1 mediates the development and progression of chronic pain by regulating Ca MKIIαexpression.