The Protective Effect Of Dexmedetomidine On Lipopolysaccharide-induced Neuroinflammation In Aged Mice And Its Relationship With Brain Iron Metabolism

Objective:To evaluate the protective effect of dexmedetomidine on lipopolysaccharide-induced neuroinflammation in aged mice and its relationship with brain iron metabolism.Methods:Forty SPF KM mice,12 months old,weighing 45-65 g,were randomly divided into 4 groups?n=10?:Normal saline group?group N?,Dexmedetomidine group?group D?,Lipopolysaccharide group?group LPS?,Dexmedetomidine+Lipopolysaccharide group?group D+LPS?.The mice in group Dwere given dexmedetomidine,injected intraperitoneally at a dose of 10 ml/kg?200?g/kg?.The mice in group LPS were given LPS,10 ml/kg?5 mg/kg?by intraperitoneal injection.The mice in the D+LPS group were given dexmedetomidine 10 ml/kg.After2 h,LPS,10 ml/kg,was injected.At the same time,mice in group N were given equal normal saline by intraperitoneal injection.After 24 h of normal feeding,all mice were injected intraperitoneally with pentobarbital sodium?1 ml/100 g?until disappearance of righting reflex.The mice were fixed in supine position and the abdominal wall were cut along the midline of abdomen to open the chest,exposing the heart.Cardiacperfusionwasperformedwithpre-cooled0.9%saline.Immediately,the heads of the mice were cut off,and the cranium was dissected.The brain completely were peeled,with the cortex and hippocampusseparated.The expression of IL-6 in hippocampus and iron-related protein,FTL and TfR1,were detected by Western Blot.Protein bands were obtained using a chemiluminescence imaging system and analyzed using Image J software.The target protein expression was reflected by the ratio of the gray level of the target protein to the gray value of the?-actin band.Real-time RT-PCR was used to determine the hippocampal hepcidin mRNA level in each group,calculated by2^-??CT.The level of ROS in hippocampus of mice in each group was measured by reactive oxygen species?ROS?test kit,and expressed as the ratio of fluorescence value/mg protein.SPSS 21.0 software was used for statistical analysis.The measurement data of normal distribution were expressed as mean±standard deviation?x±s?.One-way ANOVA was used to compare among groups.P<0.05 was considered statistically significant.Results:1.Western blot results showed that compared with group N,the expression of FTL and TfR1 in mice hippocampus were no significant differences in group D?P>0.05?;IL-6,FTL and TfR1 levels in group LPS were up-regulated?P<0.05?.Compared with group LPS,the expression of IL-6,FTL and TfR1 in mice hippocampus of group D+LPS were significantly down-regulated.?P<0.05?.2.RT-PCR results showed that compared with group N,the level of hepcidin mRNA in hippocampus of group D were no significant differences?P>0.05?;the level of hepcidin mRNA in hippocampus of group LPS increased?P<0.05?.Compared with group LPS,the level of hepcidin mRNA in hippocampus of group D+LPS decreased?P<0.05?.3.ROS detection results showed that compared with group N,the level of ROS in hippocampus of group D decreased?P<0.05?;the level of ROS of group LPS increased significantly?P<0.05?.Compared with group LPS,the level of ROS in hippocampus of group D+LPS decreased?P<0.05?.Conclusion:Dexmedetomidine has no effect on brain iron metabolism in aged mice,while pre-administration of dexmedetomidine can improve neuroinflammatory-induced brain iron metabolism disorders,playing a neuroprotective role.