Study On The Effect Of Polymyxin B On Focal Cerebral Ishemia And Reperfusion In Rats And Its Mechanism

Objective The effects of polymyxin B on the model of focal cerebral ischemiareperfusion(I / R)were analyzed by neurobehavioral score,water content of cerebral infarction,infiltration of inflammatory cells,interleukin(Interleukin,IL)-1 β,intestinal permeability and the peripheral blood lipopolysaccharides(LPS).Methods According to the random principle,120 healthy 10-week-old male clean grade sprague-dawley(SD)rats were divided into three groups:sham operation group(sham-operated group),middle cerebral artery occlusion/reperfusion model group(middle cerebral artery occlusion/reperfusion model group),and Polymyxin B group(40 rats in each group).The MCAO/R model on the right side was prepared by the improved Longa bolt method[1].The Longa neural function defect rating scale was used to score>1 points,and the modeling was considered successful.The following operations were carried out immediately after successful modeling:PMB group was injected intraperitoneally with PMB solution(2.5g /g)using a 1m L syringe[2],and sham group and MCAO/R group were given a considerable volume of normal saline.MCAO/R group and PMB group in ischemia-reperfusion in rats after 24 H after the sham group at corresponding time points,use Bederson neural function defect scale neurobehavioral scores,the use of dry wet weight method to calculate the right hemisphere brain tissue water content,the use of hematoxylin-eosin staining dye(H-E)observed the pathological histology rat hippocampus CA1 area on the right side,reverse transcription polymerase chain reaction technology is used to measure the rats on the right side of hippocampal CA1 area IL-1β m RNA expression,Peripheral blood concentrations of luciferin isothiocyanate-Dextran(fitc-dextran-4kd,FD4)were measured by fluorescence spectrophotometry,and peripheral blood LPS concentrations were measured by limulus reagent end-point coloration method.The data were recorded as mean±standard deviation(± s),and the normality and homogeneity of variance were analyzed.Variance analysis and t test were used to compare different groups.The data were statistically analyzed using SPSS 21.0.P<0.05 was statistically significant.Results 1.Bederson score was used to evaluate the neurological impairment in rats:no neurological impairment was found in sham group;Compared with sham group,MCAO/R group showed significant neurological impairment symptoms and significantly increased neurological function score(P<0.01).Compared with MCAO/R group,PMB group showed a significant decrease in neurological function score(P<0.05).2.Dry and wet specific gravity method was used to measure the water content of brain tissue:compared with sham group,the water content of brain tissue in MCAO/R group increased significantly(P<0.01).Compared with MCAO/R group,the brain water content of PMB group was significantly reduced(P<0.01).3.H-E staining was used to observe the histopathological changes of brain tissues:the cells in the CA1 area of the hippocampus in sham group had normal morphology,without edema and necrosis.In the MCAO/R group,nerve cells in the CA1 area of the hippocampus in the infarcted area were concentrated,arranged in a disordered manner,the intercellular space was widened,and the intercellular interstitium was loose and swollen.The concentration of nerve cells and the degree of interstitial swelling in the CA1 area of the hippocampus in the PMB group were significantly reduced,and the arrangement was relatively orderly.4.RT-PTR technique was used to measure the expression of IL-1β m RNA in the hippocampal CA1 region of the brain tissue.Compared with sham group,the expression level of IL-1β m RNA in MCAO/R group was significantly increased(P<0.01).Compared with the MCAO/R group,the expression level of IL-1β m RNA in the PMB group decreased significantly(P<0.01),but was still higher than that in the Sham group(P<0.01).5.Fluorescence spectrophotometer was used to measure FD4 concentration in peripheral blood of rats:compared with sham group,the concentration of FD4 in peripheral blood of MCAO/R group was significantly increased(P<0.01).Compared with MCAO/R group,the concentration of FD4 in PMB group decreased significantly(P<0.01).6.The concentration of LPS in peripheral blood of rats was measured by limulus lysate end point coloration method:compared with Sham group,the concentration of LPS in other groups was increased to different degrees.Compared with MCAO/R group,the peripheral blood LPS concentration of PMB group was significantly reduced(P<0.01).Conclusion 1.PMB can reduce the neurological deficit score and brain tissue edema in the model of focal brain I/R injury in rats.2.PMB can improve the intestinal permeability of the model of focal brain I/R injury in rats,reduce the concentration of LPS in peripheral blood,so as to reduce the cell damage in the ischemic region of hippocampal CA1 and downregulate the expression of IL-1β m RNA in the hippocampal CA1.3.PMB can reduce the damage of the hippocampal CA1 area after brain I/R by reducing the concentration of peripheral blood LPS,so as to reduce brain edema and neurological function score.