The Role And Mechanism Of High Mobility Group Box 1 In Cortical Dysplasia-associated Epilepsy

Focal cortical dysplasia(FCD)is one of the most common causes of intractable epilepsy,with poor treatment and prognosis.Previous research showed that neuroinflammation may play a vital role in FCD-associated epilepsy.High mobility group box 1(HMGB1),as an important pro-inflammatory factor,is activated in FCD,but its role and mechanism in the development of FCD-associated epilepsy are still unclear.Therefore,in this study,an FCD epilepsy model was established by intrauterine freezing injury in rats,and techniques such as monoclonal antibody drugs,electrophysiology,reverse transmonosynaptic virus neural tracing,and immunohistochemistry were used to study the role and the mechanism of HMGB1 involved in neural circuit reorganization in FCD-associated epilepsy.In this study,the FCD model was first established in rats in the third trimester of pregnancy(17-18 days of pregnancy)by intrauterine freezing injury modeling.It was found that in the subthreshold pentylenetetrazol-induced seizure model of adult FCD rats,the seizure stage and generalized seizure duration increased,and the focal seizure as well as generalized seizure latency decreased,suggesting an increased susceptibility to epilepsy.Further,we used immunohistochemical analysis to find that the expression level and the translocation rate of HMGB1 increased in microglia in puberty FCD rats(P16)and in neurons,astrocytes and microglia in adult FCD rats(P50).In the epileptogenic focus samples of clinical FCD patients,the translocation rate of HMGB1 in neurons and astrocytes also increased,suggesting that there is a continuous activation of HMGB1 in FCD-associated epilepsy with cell specificity.To verify the role of HMGB1 in FCD-associated epileptogenesis,we first injected HMGB1 recombinant protein in the cortex of adult and puberty FCD rats.It was found that it had no significant change in the susceptibility to epilepsy.But the injection of HMGB1 recombinant protein into the hippocampus could aggravate epilepsy,and the seizure-promoting effect of injection in puberty was more obvious than that in adults.At the same time,we found that the anti-seizure effect of anti-HMGB1 monoclonal antibody injection into the tail vein of puberty FCD rats was more obvious than that of adult injection,indicating that the increase of HMGB1 in the hippocampus in the early stage of FCD may play a key role in the formation of subsequent epilepsy susceptibility.To further explore the mechanism by which early HMGB1 mediates increased susceptibility to epilepsy,we used isolated brain slices to electrophysiologically record neuronal excitability in different subregions of the hippocampus.It was found that the excitability of granule cells in DG increased significantly,and the excitatory input they received increased while the inhibitory input did not change significantly.Golgi staining analysis revealed that the granule cells in DG had a large number of increased dendritic spines,and reverse transmonosynaptic virus tracing also showed that the granule cells in DG received more upstream projections,mainly from the medial septum.We found that anti-HMGB1 monoclonal antibody intervention in the early stage can reverse the reorganization of neural circuits in FCD rats,and the mechanism may be related to reversing the abnormal activation of microglia in FCD rats.To sum up,this topic reveals for the first time the key role of HMGB1 in the hippocampus in the early stage of FCD-associated epileptogenesis,and initially reveals the related mechanism of its regulation of hippocampal neural circuit reorganization.The study provides an experimental basis for the neuroinflammation theory of FCDassociated epilepsy,and suggests that HMGB1 is a potential new drug target for antiFCD-associated epilepsy.