| Background:Surgery and trauma can cause immune stress in the body,and immune stress can lead to inflammatory reactions,especially the central nervous system(CNS)inflammatory response often leads to postoperative CNS complications.CNS inflammation is one of the main causes of postoperative operative cognitive dysfunction(POCD).Interleukin-1beta(IL-1β)is one of the important inflammatory factors that cause CNS inflammation.IL-1β leads to neuronal cell dysfunction and apoptosis.Microglia(MI)acts as an immune cell of the CNS,and its activation plays an important role in the occurrence and development of CNS inflammation.Surgical trauma can induce MI secretion of IL-1β in the CNS,especially in the Hippocampal.,which leads to an inflammatory reaction.In recent years,it has been found that after activation of NOD-like receptor 3(NLRP3),apoptosis-associated speck-like protein(ASC)and caspase activation are recruited.-1(cysteinyl aspartate specific proteinase-1,Caspase-1)processing interleukin-1beta Precursors(pro-IL-1β)into IL-1β,an inflammatory pathway that is key for the synthesis and secretion of IL-1β way.Many studies have found that the use of dexmedetomidine(Dex)has the effect of inhibiting multiple inflammatory factors,but its molecular mechanism remains unclear.Therefore,this paper intends to simulate rat CNS inflammation as an animal model by establishing a laparotomy to verify whether Dex can reduce the synthesis and secretion of inflammatory mediator IL-1β and reduce the inflammatory response of CNS by inhibiting the activation of NLRP3 in the hippocampus.It provides a reference for Dex to inhibit the CNS inflammatory response.Purpose:In this experiment,a rat laparotomy model was established to simulate rat CNS inflammation and treated with Dex.Immunohistochemistry(IHC),Western blot(WB),Immunofluorescence(IF)and other methods were used to study whether Dex could inhibit NLRP3 inflammatory bodies in MI of hippocampus,reduce the production of inflammatory factor IL-1beta,thereby reducing the inflammatory response of CNS caused by surgical injury.The research includes: 1.The effect of Dex on MI activation in the hippocampus of rat laparotomy exploration model;2.The effect of Dex on the expression of IL-1 beta protein in the hippocampus of rat laparotomy exploration model;3.The effect of Dex on NLRP3,apoptosis-associated speck-like protein(ASC)and cysteine in the hippocampus of rats after laparotomy exploration.The expression of cysteinyl aspartate specific proteinase-1(Caspase-1)and the expression of NLRP3 in the cytoplasm of MI in hippocampus.Method:A laparotomy model was established by exploratory laparotomy.A total of 84 male SD rats: sham-operated group A,operation group B,D1(intraperitoneal injection of 5μg/kg Dex),D2(intraperitoneal injection of 10μg/kg Dex).Dex was injected intraperitoneally before the establishment of exploratory laparotomy model.Group D1 and Group D2 received additional Dex doses every 6 hours.After 12 hours of anesthesia,the rats were sacrificed and lavaged with PBS solution(WB test only with normal saline)and the hippocampus tissue was collected.The number of activated MI labeled by Iba-1 in hippocampal CA1 region of rats was detected by immunohistochemistry.The expression of IL-1beta,NLRP3,ASC and Caspase-1 protein was detected by immunoblotting.The change of NLRP3 in cytoplasm was detected by immunofluorescence assay.Results:1.Dex can reduce the activation of MI in hippocampus of rat laparotomy model.Immunohistochemistry was used to detect the activated MI in hippocampus.The results showed that compared with group A,the number of activated MI in group B increased significantly(P < 0.01).Compared with group B,the number of activated MI in group D1 decreased significantly(P < 0.01).Compared with group D1,the number of activated MI in group D2 decreased significantly(P < 0.01).Compared with group A,the number of activated MI increased in group D2(P < 0.05).2.Dex can reduce IL-1β production in hippocampus of rat laparotomy model.WB results showed that the expression of IL-1 beta protein in group A was significantly less than that in group B(P < 0.01).After Dex treatment,the expression of IL-1 beta protein in group D1(5μg/kg Dex)was significantly less than that in group B.The expression of IL-1 beta protein in group D2(10μg/kg Dex)was less than that in group D1(5μg/kg Dex)(P < 0.05).3.Dex can reduce the production of NLRP3,ASC and Caspase-1 in hippocampus of rat laparotomy model.NLRP3: group A was significantly less than group B(P < 0.01).After Dex treatment,D1(5μg/kg Dex)group was significantly less than group B(P < 0.01).After increasing Dex dose,group D2(10μg/kg Dex)was less than group D1(5μg/kg Dex)(P < 0.05).ASC: Group A was significantly less than Group B(P < 0.01).After Dex treatment,group D1(5μg/kg Dex)was significantly less than Group B(P < 0.01).After increasing Dex dosage,group D2(10μg/kg Dex)was less than Group D1(5μg/kg Dex)(P < 0.05).Caspase-1: group A was significantly less than B group(P < 0.01).After Dex treatment,group D1(5μg/kg Dex)was less than group B(P < 0.05).After increasing Dex dose,group D2(10μg/kg Dex)was less thangroup D1(5μg/kg Dex)(P < 0.05).The results of immunofluorescence experiment suggest that Dex may decrease the activation of NLRP3 in MI cytoplasm of POCD model rats by laparotomy.Conclusion:Dex attenuates the inflammatory response of CNS after laparotomy in rats by inhibiting MI activation,which may be related to inhibition of NLRP3 activation in MI cytoplasm and subsequent reduction of IL-1β production. |
