Dephosphorelation of Bad and upregulation of Bcl-2 in hippocampus of rats following limbic seizure induced by kainic acid injection into amygdaloid nucleus / 生理学报

ABSTRACT

The purpose of the present study was to explore the seizure-induced changes in Bad (Bcl-2-associated death protein), 14-3-3, phosphoBad, Bcl-2 and Bcl-XL expression in the rat model of focal limbic seizure. Unilateral intra-amygdaloid injection of kainic acid (KA) was made to induce seizure. Electroencephalogram (EEG) and regional cerebral flow (r-CBF) were monitored continuously. Diazepam (30 mg/kg) was administered to terminate the seizure. The apoptotic and surviving neurons in the hippocampus were observed by terminal deoxynucleotidyl transferrase-mediated dUTP nick end labeling (TUNEL) and cresyl violet staining, the expression of Bad, 14-3-3, phosphoBad, Bcl-2 and Bcl-XL were detected with immunofluorescence, Western blot and immunoprecipitation. The results showed that TUNEL-positive neurons appeared at 8 h and reached maximum at 24 h following seizure cessation within the ipsilateral CA3 subfield of the hippocampus. Seizure induced the dephosphorylation of Bad and the dissociation of Bad from its chaperone protein 14-3-3 and subsequent dimerization of Bad with Bcl-XL. The expression of phosphoBad decreased and Bcl-2 increased. There was little change in r-CBF after the seizure. These results suggest that seizure leads to a dephosphorylation of Bad and an upregulation of Bcl-2. Dephosphorylation of Bad may be injurious while the upregulation of Bcl-2 may be protective to the brain damage induced by seizures, but not related with r-CBF.