Inhibition of Neuron Restrictive Silencing Factor (REST/NRSF) Chromatin Binding Attenuates Epileptogenesis

Abstract

The mechanisms by which brain insults lead to subsequent epilepsy remain unclear. Insults including trauma, stroke, infections and long seizures (status epilepticus; SE) increase the nuclear expression and chromatin binding of the neuronal restrictive silencing factor / RE-1 silencing transcription factor (NRSF/REST). REST/NRSF orchestrates major disruption of the expression of key neuronal genes, including ion channels and neurotransmitter receptors, potentially contributing to epileptogenesis. Accordingly, transient interference with REST/NRSF chromatin binding after an epilepsy-provoking SE suppressed spontaneous seizures for the 12- day duration of a prior study. However, whether the onset of epileptogenesis was suppressed or only delayed has remained unresolved. The current experiments determined if transient interference with REST/NRSF chromatin binding prevented epileptogenesis enduringly, or, alternatively, slowed epilepsy onset.Epileptogenesis was elicited in adult male rats via systemic kainic acid-induced SE (KA-SE). We then determined if decoy, NRSF-binding-motif oligodeoxynucleotides (NRSE-ODNs), given twice following KA-SE (a) prevented REST/NRSF binding to chromatin, using chromatin immunoprecipitation; (b) prevented the onset of spontaneous seizures, measured with chronic digital video-EEG.Blocking NRSF function transiently after KA-SE significantly lengthened the latent period to a first spontaneous seizure. Whereas this intervention did not influence the duration and severity of spontaneous seizures, total seizure number and seizure burden were lower in the NRSE- ODN compared with scrambled-ODN cohorts.Transient interference with REST/NRSF function after KA-SE delays and moderately attenuates insult-related hippocampal epilepsy, but does not abolish it. Thus, the anticonvulsant and antiepileptogenic actions of NRSF are but one of the multifactorial mechanisms generating epilepsy in the adult brain.Significance Statement The mechanisms by which brain insults can lead to subsequent epilepsy remain unclear. Insults may influence neuronal functions by enduringly changing their gene expression programs, often via changes in master regulators such as transcription factors (TFs). The TF REST/NRSF is activated by insults, alters gene expression selectively, and thus promotes aberrant neuronal function and connectivity. Previously, blocking REST/NRSF function transiently in developing brain prevented cognitive problems that accompany SE-induced epilepsy. Here, blocking REST/NRSF DNA binding transiently following SE in adult rats delayed and attenuated epileptogenesis, but did not abolish it.