Protective Effect Of Glycyrrhizic Acid On Brain Injury After Convulsion In Developing Rats And Its Mechanism

Objective:The purpose of this experiment was to investigate whether pretreatment with GA(glycyrrhizic acid)could reduce convulsions in developing rats by inhibiting hippocampal neuronal death,microglia activation,BBB destruction and down-regulating the expressions of RAGE,VEGF,ERK,and TNF-α.The hindbrain injury has a protective effect.Methods:Forty-eight SD male rats,aged 21 days,were randomly divided into: control(normal saline)group,PTZ(pentylenetetrazole)group,20 mg/kg GA+PTZ group,and 40 mg/kg GA+PTZ group,n=12.The developmental rat model of convulsion was made by intraperitoneal injection of pentylenetetrazole(PTZ),modeling success criteria should reach the Racine score IV-V.GA was administered by intraperitoneal injection 2 h before PTZ-induced convulsions.24 h after the seizure,the rats were sacrificed to take the brain tissue,and the time,grade and latency of the seizure were recorded;the pathological changes of brain tissue were observed by hematoxylin-eosin(HE)staining;immunofluorescence(IF)staining was used to observe the activation of hippocampal microglia;blood-brain barrier permeability was detected by Evans blue(EB)penetration test;the protein expressions of RAGE,VEGF,ERK and TNF-α in hippocampus were detected by Western blotting(WB).The expression of RAGE,VEGF,ERK and TNF-α m RNA in hippocampus was detected by real-time quantitative PCR(q RT-PCR).Results:1.Compared with the PTZ group,the 40 mg/kg GA+PTZ group had significantly longer convulsive seizure latency(P<0.05);2.Compared with the PTZ group,the time of convulsion in the GA group was significantly shortened(P<0.05);the time of convulsion in the GA group was statistically significant(P<0.05);3.Compared with the PTZ group,the 40mg/kg GA+PTZ group had a significantly lower level of convulsions(P<0.05);4.HE staining results showed that the PTZ group had hyperchromatic nucleus,pyknosis,cell loosening,and edema;the GA group had neuronal hyperstaining,pyknosis,cell loosening,and edema decreased;5.IF staining results showed that compared with the control group,the number of activated microglia in the PTZ group was significantly increased(P<0.05);compared with the PTZ group,the number of activated microglia in the GA group was significantly decreased(P<0.05);6.The results of EB staining showed that compared with the control group,the content of Evans blue in the brain tissue of the PTZ group was significantly increased(P<0.05);compared with the PTZ group,the content of Evans blue in the brain tissue of the GA group was significantly decreased(P<0.05);7.Western Bolt: Compared with the control group,the protein expressions of RAGE,VEGF,ERK2 and TNF-α in the PTZ group were significantly increased(P<0.05);compared with the PTZ group,the protein expressions of RAGE in the GA group were significantly decreased(P<0.05),the protein expressions of VEGF,ERK2 and TNF-αwere also significantly decreased in the 40 mg/kg GA+PTZ group(P<0.05);8.q RT-PCR: Compared with the control group,the m RNA expressions of RAGE,VEGF,ERK2 and TNF-α in the PTZ group were significantly increased(P<0.05);compared with the PTZ group,the m RNA expressions of RAGE,VEGF,ERK2 and TNF-α in the GA group were significantly decreased(P<0.05);compared with the 20mg/kg GA+PTZ group,the 40mg/kg GA+PTZ group significantly enhanced the inhibitory effect on the expression of RAGE and TNF-α m RNA(P<0.05).Conclusions:1.GA pretreatment can reduce the severity of convulsions and prolong the latency of seizures.2.GA pretreatment has protective effect on post-convulsive brain injury in developing rats,which may be related to the inhibition of hippocampal neuronal death,microglia activation,BBB destruction and down-regulation of the expressions of RAGE,VEGF,ERK and TNF-α.