Epigenetic dysregulation of mrna expression in rat prefrontal cortex following acute PCP administration
Author
Henriksen, Josephine Holm
Term
4. term
Publication year
2011
Submitted on
2011-06-01
Pages
53
Abstract
Skizofreni er en alvorlig psykisk lidelse, som rammer op til 2% af befolkningen globalt. Mænd får typisk debut i sen ungdom eller tidlig voksenalder og ofte mere alvorligt end kvinder. Symptomer deles ofte i tre grupper: positive (fx hallucinationer), negative (fx social tilbagetrækning) og kognitive (fx opmærksomheds- og hukommelsesproblemer). Behandlingen er primært antipsykotika, som inddeles i første generation (FGA) og anden generation (SGA). FGA kan give ekstrapyramidale bivirkninger, og derfor foretrækkes ofte SGA med mildere bivirkningsprofil. Årsagerne og sygdomsmekanismerne er stadig uklare, men skizofreni anses generelt for at være en multifaktoriel, neurodevelopmental tilstand påvirket af genetiske, epigenetiske og miljømæssige faktorer. Foreslåede sammenhænge omfatter fødested og -tid, parasitinfektioner, lav IQ, moderens ernæring og obstetriske komplikationer. Epigenetiske mekanismer som DNA-methylering, regulering af genudtryk og histonmodifikationer antages at spille en rolle. Muligt involverede gener omfatter Arc (aktivitetsreguleret cytoskelet-associeret protein), cfos og brain-derived neurotrophic factor (BDNF). Denne undersøgelse havde til formål at: (1) vurdere, hvordan en akut dosis phencyclidin (PCP, 10 mg/kg) over tid påvirker mRNA-udtryk (et mål for genaktivitet) af Arc, cfos og BDNF i præfrontal cortex (PFC) hos voksne rotter, (2) måle niveauet af H4-acetylering ved promotorerne (geners kontrolregioner) for disse gener efter PCP, (3) måle niveauet af H3 fosfo-acetylering ved de samme promotorer, og (4) undersøge om der er sammenhæng mellem PCP-induceret mRNA-udtryk i Arc, cfos og BDNF og H4-acetylering samt H3 fosfo-acetylering ved de tilsvarende promotorer. Studiet omfattede PFC-væv fra 30 unge, voksne han-rotter (Sprague-Dawley). Rotterne blev inddelt i to kontrolgrupper og fem forsøgsgrupper med akut PCP-administration. mRNA for Arc, cfos og BDNF blev kvantificeret med qRT-PCR ved 60, 120, 240, 360 minutter og 24 timer efter PCP; β-actin blev brugt som housekeeping-gen. Variationer i histon H4-acetylering og histon H3 fosfo-acetylering blev målt på isoleret kromatin med en ChIP-assay, som registrerer kemiske “mærker” på DNA-pakkende proteiner tæt ved specifikke gener. Sammenlignet med kontrolgrupperne var Arc-mRNA signifikant øget 240 minutter efter PCP. cfos-mRNA var signifikant øget 60 og 120 minutter efter PCP, og BDNF-mRNA var signifikant øget 240 og 360 minutter efter PCP. Der sås øget H4-acetylering ved promotorerne for cfos og BDNF 360 minutter efter PCP, mens der ikke blev fundet forskelle i H3 fosfo-acetylering for Arc, cfos eller BDNF. For BDNF korrelerede mRNA-stigningen med øget H4-acetylering ved den tilsvarende BDNF-promotor I, som også toppede i 360-minuttersgruppen. Konklusion: En enkelt, akut PCP-dosis gav tidsafhængige, midlertidige stigninger i genaktivitet for Arc, cfos og BDNF i rotternes PFC, samt øget H4-acetylering ved cfos- og BDNF-promotorer. For BDNF fulgte H4-acetyleringen ved promotor I samme tidsmønster som mRNA-stigningen, hvilket tyder på transkriptionsregulering af BDNF gennem H4-acetylering.
Schizophrenia is a serious mental disorder that affects up to 2% of the global population. Men typically develop symptoms earlier, in late adolescence or early adulthood, and often more severely than women. Symptoms are commonly grouped as positive (e.g., hallucinations), negative (e.g., social withdrawal), and cognitive (e.g., attention and memory problems). Treatment relies mainly on antipsychotics, categorized as first-generation (FGAs) and second-generation (SGAs). FGAs can cause extrapyramidal side effects, so SGAs are often preferred due to a milder side-effect profile. The causes and mechanisms remain unclear, but schizophrenia is generally viewed as a multifactorial neurodevelopmental condition shaped by genetic, epigenetic, and environmental factors. Proposed links include place and time of birth, parasitic infections, low IQ, maternal nutrition, and obstetric complications. Epigenetic processes such as DNA methylation, regulation of gene expression, and histone modifications are thought to play roles. Genes suggested to be involved include Arc (activity-regulated cytoskeleton-associated protein), cfos, and brain-derived neurotrophic factor (BDNF). This study aimed to: (1) test how a single acute dose of phencyclidine (PCP, 10 mg/kg) over time affects mRNA expression (a measure of gene activity) of Arc, cfos, and BDNF in the prefrontal cortex (PFC) of adult rats; (2) measure levels of H4 acetylation at the promoters (gene control regions) of these genes after PCP; (3) measure levels of H3 phospho-acetylation at the same promoters; and (4) examine whether PCP-induced changes in mRNA for Arc, cfos, and BDNF correlate with H4 acetylation and H3 phospho-acetylation at their corresponding promoters. The study used PFC tissue from 30 young adult male Sprague-Dawley rats, divided into two control groups and five PCP-treated groups. mRNA for Arc, cfos, and BDNF was quantified by qRT-PCR at 60, 120, 240, and 360 minutes, and 24 hours after PCP; β-actin served as the housekeeping gene. Variations in histone H4 acetylation and histone H3 phospho-acetylation were assessed on isolated chromatin using a ChIP assay, which detects chemical “tags” on DNA-packaging proteins near specific genes. Compared with controls, Arc mRNA was significantly increased 240 minutes after PCP. cfos mRNA was significantly increased at 60 and 120 minutes, and BDNF mRNA was significantly increased at 240 and 360 minutes. H4 acetylation was elevated at the cfos and BDNF promoters at 360 minutes after PCP, while no differences were found in H3 phospho-acetylation for Arc, cfos, or BDNF. For BDNF, the mRNA increase correlated with higher H4 acetylation at the corresponding BDNF promoter I, which also peaked in the 360-minute PCP group. Conclusion: A single acute PCP dose produced time-dependent, transient increases in Arc, cfos, and BDNF gene activity in the rat PFC, along with increased H4 acetylation at the cfos and BDNF promoters. For BDNF, H4 acetylation at promoter I matched the timing of the mRNA rise, suggesting transcriptional regulation of BDNF via H4 acetylation.
[This abstract was generated with the help of AI]
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