Region-specific vulnerability to endoplasmic reticulum stress-induced neuronal death in rat brain after status epilepticus

Abstract

We sought to clarify the involvement and the intra-cerebral distribution variability of C/EBP homologous protein (CHOP), a representative molecule related to endoplasmic reticulum (ER) stress-induced cell death signalling pathways, in neuronal death resulting from status epilepticus in rats. The expression patterns of CHOP and glucose-regulated protein (GRP) 78, a good marker of ER stress, were assessed by Western blotting, real-time PCR, Hoechst and immunohistochemistry in the hippocampus, cortex and striatum on a status epilepticus (SE) model. Double-fluorescent staining of CHOP and the terminal deoxynucleotidyl transferase-mediated DNA nick-end labelling (TUNEL) method were performed to clarify the involvement of CHOP in cell death. SE resulted in a timedependent increase in the expression of GRP78 and CHOP. The expression of GRP78 protein was increased at 3, 6 and 12 h after SE and no brain region variability was found. The expression of CHOP protein was also increased, reached its peak at 24 h and remained high at 48 h. CHOP protein expression, however, showed brain region variability with highest expression noted in the hippocampus followed by the striatum, and lowest in the cortex. The up-regulation of CHOP occurring at the transcriptional level was demonstrated by real-time PCR. Double fluorescence showed that CHOP expression strongly correlated with neurons undergoing apoptosis. The results indicated that SE compromises the function of the ER and that the hippocampus is more vulnerable than the cortex and the striatum.