Effect Of Dexmedetomidine On Septic Mice Neuroinflammation Induced By Lipopolysaccharide

Objective:To investigate the neuroprotective molecular mechanism of Dexmedetomidine by observing the changes of micro RNA-223 and NLRP3 inflammasome by the use of dexmedetomidine（Dex）in Lipopolysaccharide（LPS）-induced sepsis mice.Methods:A tolal of 224 healthy ICR male mice were randomly divided into four groups,including the normal saline group（group C）,LPS+dexmedetomidine group（group LD）,LPS+Atipamezole+dexmedetomidine group（group LT）.Nomal saline 0.5 ml was administered in group C,after 30 minutes nomal saline 0.5 ml was administered in group C every two hours for three times.Intraperitoneal injection of LPS 12 mg/kg used to build septic mice model,after 30 minutes nomal saline 0.5 ml was administered in group L every two hours for three times.Dexmedetomidine 40μg/kg add nomal saline to 0.5 ml was administered every two hours for three times after building septic mice model 30 minutes in group LD.Theα₂-adrenoceptor antagonist Atipamezole（Ati）750μg/kg add nomal saline to 0.5 ml was immediately administered every two hours for three times prior to the administration of dexmedetomidine after building septic mice model 30 minutes in group LT.The experiment was divided into two parts.In the first part of experiment,after building septic mice model 24 hours,morris water maze test was to observe the escape latency at day 2,3,4,5,6 and the times of crossing the platform at day 7,the Kaplan-meier method was used to analyze the survival rate of mice.The step-through latency at day2,3,4 and the number of errors within 5 min were observed to evaluate the memory retrieval ability of mice in the passive avoidance experiment.In the second part of experiment,the concentration of IL-18 and IL-1βin hippocampal tissue were determined by enzyme-linked immune sorbent assay（ELISA）.The expression of micro RNA-223,NLRP3,Caspase-1,ASC in hippocampal tissue were detected by RT-PCR.Western Blot method was used to detect the protein content of NLRP3、Caspase-1 p20 and ASC in hippocampus tissue.Hematoxylin eosin staining was used to observe the pathological structure damage of hippocampus.Another mice were fixed for in situ terminal staining（TUNEL staining）in each group to detect the percentage of apoptotic neurons in hippocampus 24 hours after the establishment of septic mice model.Results:In the first part of experiment,Compared with group C,the escape lantency time at day 4,5,6 was significantly prolonged（P<0.05）and the number of crossing platforms at day 7 were decreased（P<0.05）in group L and group LT in the Morris Water Maze Test,the step-through latency in group L and LT at day 2,3,4 was significantly shortened（P<0.05）,and the number of errors was significantly increased in the Passive Avoidance Experiment（P<0.05）.Compared with group L,the escape lantency time at day 4,5,6 in group LD was significantly shortened（P<0.05）,the number of crossing platforms at day 7 were increased in the Morris Water Maze Test（P<0.05）,the step-through latency in group LD was significantly prolonged at day 2,3,4（P<0.05）,the number of errors decreased significantly in the Passive Avoidance Experiment（P<0.05）;Compared with group LD,the escape lantency time at day 4,5,6 in group LT was significantly prolonged（P<0.05）,the number of crossing platforms at day 7 were decreased in the Morris Water Maze Test（P<0.05）,the step-through latency was significantly shortened on day 2,3,4 in group LT（P<0.05）,the number of errors decreased significantly in the Passive Avoidance Experiment（P<0.05）.After the establishment of the model,there were no mice died in group C,the 48-hour mortality rate of mice in group L,group LD and group LT was 30%,12%and 20%respectively.In the second part of experiment,Compared with group C,the content of IL-1βand IL-18 in hippocampus were significantly increased after 24 hours in group L,group LD and group LT（P<0.05）,the genes expression and protein content of NLRP3,Caspase-1/Caspase-1 p20,ASC in hippocampal tissue were significantly increased after 24 hours in group L and group LT（P<0.05）,the genes expression of micro RNA-223 in hippocampal tissue were significantly decreased after 24 hours in group L and group LT（P<0.05）,the percentage of apoptotic cells in hippocampal neurons of group L and group LT was significantly increased after 24 hours（P<0.05）.Compared with group L,the content of IL-1βand IL-18 in hippocampus were significantly decreased after 24 hours in group LD（P<0.05）,the genes expression and protein content of NLRP3,Caspase-1/Caspase-1 p20 and ASC in hippocampal tissue were significantly decreased after 24 hours in group LD（P<0.05）,the genes expression of micro RNA-223 in hippocampal tissue were significantly increased after24 hours in group LD（P<0.05）,the percentage of apoptotic cells in hippocampal neurons of group LD was significantly decreased after 24 hours（P<0.05）.Compared with group LD,the content of IL-1βand IL-18 in hippocampus were significantly increased after 24 hours in group LT（P<0.05）,the genes expression and protein content of NLRP3,Caspase-1/Caspase-1 p20,ASC in hippocampal tissue were significantly increased after 24 hours in group LT（P<0.05）,the genes expression of micro RNA-223 in hippocampal tissue were significantly decreased after 24 hours in group LT（P<0.05）,the percentage of apoptotic cells in hippocampal neurons of group LT was significantly increased after 24 hours（P<0.05）.Conclusions:Dexmedetomidine alleviates septic mice neuroinflammatory injury induced by lipopolysaccharide throughα2 adrenergic receptor,and reduces the concentration of inflammatory factors,and reduces the apoptosis rate of hippocampal neurons,which may be related to the reduction of NLRP3 inflammasome activiation by inhibiting miRNA-223/NLRP3 axis.