Ephrinb3 modulates hippocampal neurogenesis and the reelin signaling pathway in a pilocarpineinduced model of epilepsy

Abstract

EphrinB3 is important in the regulation of cell proliferation, differentiation and migration via cellcell contact, and can activate the reelin pathway during brain development. However, the effect of ephrinB3 on hippocampal neurogenesis and the reelin pathway in epilepsy remains to be fully elucidated. In the present study, the expression of ephrinB3 in pilocarpineinduced status epilepticus (SE) rats was investigated. SYBR Greenbased reverse transcriptionquantitative polymerase chain reaction analysis, immunohistochemical labeling and western blot analysis were used to detect the gene and protein expression levels of ephrinB3 and reelin pathway proteins. Immunofluorescence staining of doublecortin (DCX) was utilized to analyze hippocampal neurogenesis. The data revealed that the mRNA and protein expression levels of ephrinB3 in the hippocampus decreased during the spontaneous seizure period. Of note, the expression of reelin and its downstream phosphorylation disabled 1 (pDab1) were also notably decreased during the spontaneous seizure period, which showed similar dynamic changes as in the expression of ephrinB3. In addition, it was found that the number of DCXlabeled neuronal progenitor cells was increased in the hippocampus following pilocarpineinduced SE. To further clarify the role of ephrinB3 in neurogenesis and the reelin pathway in epilepsy, an exogenous ephrinB3 clustering stimulator, EphB3Fc, was infused into the bilateral hippocampus of the rats postSE. Following EphB3Fc injection, it was found that the expression levels of reelin and pDab1 were significantly increased in the epileptic rats following EphB3Fc injection. The number of DCXlabeled neuronal progenitor cells was reduced in the hippocampus of the epileptic rats. Furthermore, the intensity and frequency of spontaneous recurrent seizures and electroencephalographic seizures were attenuated in the epileptic rats postinjection. These results demonstrated the critical role of ephrinB3 in regulation of the reelin pathway and hippocampal neurogenesis in epilepsy, providing experimental evidence that ephrinB3 functions as a potential protective factor in epilepsy, at least in animals.