The Regulatory Mechanism Of The BRD4 Signaling Pathway In Anterior Cingulate Cortex Of Rats With Neuropathic Pain And Anxiety-like Behavior

Objective:The purpose of this study was to investigate whether the BRD4 signaling pathway in anterior cingulate cortex is involved in the regulation of neuropathic pain and its regulatory mechanism,so as to provide a new target for the study of neuropathic pain.Methods:CCI was chosen to build the neuropathic pain model,the rats were ligated and compressed on one side of the sciatic nerve.Forty five healthy adult male SD rats,,weighing 250-350 g,were randomly divided into three groups(n=15):Normal group(N group),sham group(S group)and model group(CCI group,C group).In sham operation group,only free sciatic nerve without ligation.In the model group,the mechanical withdrawal threshold(MWT)of the rat lateral foot was reduced by 40% as the successful modeling criteria for screening.At the same time,30 rats were randomly divided into 2 groups(n=15),control group(CCI+ Saline,C+S group)and pentoxifyllie treatment group(CCI+PTX,C+P group)after successful establishment of CCI model.PTX was an inhibitor of TNF-α,rats in the C+P group received intraperitoneal injection of PTX 100mg/kg and rats in the C+S group received the same dose of normal saline.All rats were sacrificed 14 days after the operation,and the anterior cingulate cortex was taken.After modeling,the changes of pain threshold in rats were recorded and the anxiety expression of rats caused by pain was observed by open field experiment before sampling.The content of TNF-α in the anterior cingulate cortex of each group was determined by ELISA,and the change of BRD4 expression in ACC was observed by Western blot and immunohistochemistry.Results: 1.After modeling,there was no significant change in pain threshold of rats in group S,while the mechanical withdrawal threshold and the paw withdrawal latency of rats in group C were significantly decreased(P<0.001);2.Rats in group S showed no anxiety in the open-field experiment compared with rats in group N,and rats in group C showed anxiet-like behavior expression:(1)Compared with rats in group N and group S,rats in group C entered the central area of the open-field area significantly less(P<0.01 or P<0.05);(2)Compared with rats in group N and Group S,rats in group C had significantly reduced residence time in the central area of the open field(P<0.05);3.Compared with group N,TNF-α content in ACC of rats in group S showed no significant change,while TNF-α content in ACC of rats in group C increased significantly compared with that of rats in group S and N(P<0.01);4.Compared with group N,BRD4 expression in ACC of rats in group S showed no significant change,while BRD4 expression in ACC of rats in group C increased significantly compared with group N and group S(P<0.01 or P<0.05);5.The mechanical withdrawal threshold and the paw withdrawal latency thermal of rats in group C+P were significantly higher than that of rats in group C+S(P<0.05);6.Compared with group C+S,anxiety behaviors of rats in group C+P were improved:(1)Rats in group C+P entered the central area of open field more often than rats in group C+S(P<0.05);(2)Rats in group C+P spent more time in the central area of the open field than rats in group C+S(P<0.05);7.Compared with group C+S,the content of TNF-α in ACC of group C+P increased(P<0.05);8.Compared with group C+S,BRD4 expression was increased in ACC of group C+P(P<0.05).Conclusion:The BRD4 signaling pathway in anterior cingulate cortex is involved in the regulation of neuropathic pain,and inhibiting TNF-α in ACC can effectively reduce the BRD4 expression in ACC,relieve pain,and improve the anxiety caused by pain.