title: Ischemic insults promote epigenetic reprogramming of mu opioid receptor expression in hippocampal neurons.
abstract: Transient global ischemia is a neuronal insult that induces delayed, selective death of hippocampal CA1 pyramidal neurons. A mechanism underlying ischemia-induced cell death is activation of the gene silencing transcription factor REST (repressor element-1 silencing transcription factor)/NRSF (neuron-restrictive silencing factor) and REST-dependent suppression of the AMPA receptor subunit GluR2 in CA1 neurons destined to die. Here we show that REST regulates an additional gene target, OPRM1 (mu opioid receptor 1 or MOR-1). MORs are abundantly expressed by basket cells and other inhibitory interneurons of CA1. Global ischemia induces a marked decrease in MOR-1 mRNA and protein expression that is specific to the selectively vulnerable area CA1, as assessed by quantitative real-time RT-PCR, Western blotting, and ChIP. We further show that OPRM1 gene silencing is REST-dependent and occurs via epigenetic modifications. Ischemia promotes deacetylation of core histone proteins H3 and H4 and dimethylation of histone H3 at lysine-9 (H3-K9) over the MOR-1 promoter, an signature of epigenetic gene silencing. Acute knockdown of MOR-1 gene expression by administration of antisense oligodeoxynucleotides to hippocampal slices in vitro or injection of the MOR antagonist naloxone to rats in vivo affords protection against ischemia-induced death of CA1 pyramidal neurons. These findings implicate MORs in ischemia-induced death of CA1 pyramidal neurons and document epigenetic remodeling of expression of OPRM1 in CA1 inhibitory interneurons.
authors.affiliation: Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Luigi
authors.initials: L
authors.lastname: Formisano
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Noh
authors.forename: Takahiro
authors.initials: T
authors.lastname: Miyawaki
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mashiko
authors.forename: Michael V L
authors.initials: MV
authors.lastname: Bennett
authors.forename: R Suzanne
authors.initials: RS
authors.lastname: Zukin
mesh_terms: D000818:Animals; D002470:Cell Survival; D044127:Epigenesis, Genetic; D006624:Hippocampus / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D007511:Ischemia / Q000378:metabolism; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
chemical_list: D006657:Histones; D009292:Narcotic Antagonists; C485765:Oprm1 protein, rat; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D009270:Naloxone