Mechanism And Influence Of High Mobility Group Box1on Neuronal Injury And P-glycoprotein Expression In Epileptic Rats

Background:Previous studies have demonstrated that brain inflammation is involved in epilepsy occurrence, development, and closely related to neuronal injury caused by seizure. Drug transporter P-glycoprotein (P-gp) is considered as one of the important mechanisms leading to drug-resistant epilepsy (DRE), and associated with inflammatory transcription factor nuclear factor kappa B (NF-κB) activation. Recent studies report that epileptic brain can produce numerous high mobility group box1(HMGB1), which is a member of damage-associated molecular patterns (DAMPs), have an effect on the pattern recognition receptor (PRR) mediate inflammation and regulate the activity of NF-κB. Our previous study found that epileptic brain overexpression of P-gp was related to NF-kB activation, inhibition of NF-κB activity downregulated P-gp expression, then, whether HMGB1can regulate P-gp expression?Objective:This study was aimed to observe the behaviour of seizure, the neuronal damage and astrocyte activation in epileptic, rats with HMGB1antagonizing, to investigate whether P-gp expression is affected by HMGB1via activation of NF-κB in epileptic rat brain.Methods:Male SD rats were divided into sham operation group (n=5), epilepsy model group (EP group, n=8),1400ng BoxA pretreated epilepsy group (B1400group, n=8),140ng BoxA pretreated epilepsy group (B140group, n=8),14ng BoxA pretreated epilepsy group (B14group, n=8). BoxA were administrated to the rats by intracerebroventricular injection, the sham operation group and EP group were only treated with NS. To make epileptic rat model by inject kainic acid (KA) into hippocampus15min after BoxA intervention, NS instead of KA in sham group. We observed the rats’behavior during seizure and recorded the seizure onset time (SOT) to stage III, as an indicator to assess the seizure susceptibility. Rat brain were collected24h after KA treating, observe the brain insult generally by H.E. staining, to test the extent of neuronal damage by neuronal nuclei (NeuN) staining, to evaluate activation of astrocytes by glial fibrillary acidic protein(GFAP) staining. HMGB1, p-NF-KB-p65, P-gp expression were also examed by immunohistochemistry method.Main results:(1) The BoxA pretreated groups showed prolonged SOT than the EP group (P <0.05).(2) The BoxA pretreated groups showed lighter brain damage and less loss of neuron than the EP group (P<0.05).(3) The EP group showed astrocyte swelling. GFAP expression of the BoxA pretreated groups were less than the EP group (P<0.05).(4) Overall comparison between the five groups, the differences of HMGB1expression level were not statistically significant. In the EP group HMGB1expression was not found in hippocampal neurons, but increased expression couled be found in non-neuronal cells (glial, endothelial cells, etc.). Neurons in the BoxA pretreated groups expressed different levels of HMGB1, the expression in non-neuronal cells was less than the EP group.(6) P-gp expression in the BoxA pretreated groups was less than the EP group (P <0.05).(3) P-NF-κB-p65expression in B1400group and B140group were significantly less than the EP group (P<0.05), B14group had a similar trend, but there was no statistical significance.Conclusion:Antagonizing HMGB1with BoxA can reduce seizure susceptibility in rats, decrease neuronal injury, ease astrocyte swelling, activating, showed neuroprotective effect and inhibit activation of NF-κB, reduce the expression of P-gp. Combined with our previous studies, BoxA potentially reduce NF-κB activation and its downstream P-gp expression induced by HMGB1.