KCNN4 Promotes Inflammatory Pain By Inducing The Activation Of Neurons In Anterior Cingulate Cortex

Background: Pain is one of the most serious diseases affecting the living standard of humanbeings,and there is no complete cure so far.Inflammatory pain is a common type of clinical pain,and its occurrence is related to the increased excitability of nervous system caused by central and peripheral sensitization.The change of the neuronal excitability involves in a variety of factors,among which ion channels are a common factor.KCNN4 can alter membrane action potentials by modulating calcium ion and calcium-dependent post-hyperpolarizing current,it can also affect neuronal excitability.ACC is a highly connected cortical area of the rostral part of the corpus callosum.As one of the largest part in the limbic system of the brain,ACC has been confirmed by many studies to be involved in the processing of somatic pain and negative emotions when pain occurs,but the specific mechanism of its occurrence is unclear.Objective: The purpose of this experiment was to investigate the role of KCNN4 in the activation of neurons in ACC when inflammatory pain occurs.Methods: C57BL/6J mice（8-12 week old）were divided into sham operation group（Sham）,inflammatory pain group（CFA）,negative virus group（CFA+NC-LV）,interference virus group（CFA+KCNN4-LV）and sham-operated interference virus control group（Sham+KCNN4-LV）,each group with 7 mice.The mice in the LV group were injected with virus in ACC area.To construct inflammatory pain model,the CFA group were injected with complete Freund’s adjuvant on the 7th day after the injection of virus.The Sham group were injected with an equal volum of normal saline.The Paw withdrawal mechanical threshold（PWT）of mice in each group was measured 1 day before modeling and 1,3,5,7 days after modeling.The expression of KCNN4 and the activation of neurons in ACC were detected by RT-PCR,Western blot and immunohistochemistry in each group.Result:1.The immunohistochemistry indicated that KCNN4 co-localized with neurons in the ACC;compared with the sham operation group,the expression of KCNN4 in the ACC of the inflammatory pain group was up-regulated,and the cfos immunofluorescence labeling indicated that the activation of neurons in ACC was up-regulated;after using interference virus to knockdown the expression of KCNN4,anti-KCNN4 and anti-MAP2 immunofluorescence labeling was reduced.2.The results of PWT indicated that there was no significance difference in the basal pain threshold of the five groups of mice before modeling.On the 1,3,5,7 days after modeling,compared with the sham-operated group,the mechanical pain threshold of mice in the inflammatory pain group was apparently reduced（P<0.05）.After knocking down the expression of KCNN4 with the interference virus,the mechanical pain threshold of inflammatory pain mice was increased（P<0.05）.3.The results of RT-PCR and Western blot indicated that compared with the shamoperated group,the m RNA and protein expression of KCNN4 in the ACC of the inflammatory pain group was increased（P<0.05）;after knockdown by the interfering virus,its expression was decreased（P<0.05）.Conclusion: KCNN4 can promote the occurrence of inflammatory pain by inducing the activation of ACC neurons.