title: The effect of phenobarbital on gene expression levels of p53 and Dnmt1 in the liver of Wistar rats.
abstract: BACKGROUND
  Our previous studies have shown that short-term treatment with phenobarbital (PB) resulted in cytosine methylation of CpG sites on the p53 gene promoter in male Wistar rats' liver. Furthermore, PB induced DNA-methyltransferases (DNMTs) activity was also demonstrated; being the enzymes that catalyze methyl group transfer to cytosine in CpG dinucleotides.
  
  
  OBJECTIVE
  Since DNA methylation is involved in regulating gene transcription and that DNMT1 is implicated in regulating DNA methylation, this study assessed whether PB-induced hypermethylation of the p53 promoter region was associated with an altered expression of p53 and Dnmt1 genes.
  
  
  METHODS
  Male Wistar rats received PB in three daily oral doses (at 24-h intervals) of 92,8 mg/kg b.w. x day-1. Levels of mRNA for p53 and Dnmt1 and levels of relevant proteins were respectively examined by Real-Time PCR and Western blot analysis.
  
  
  RESULTS
  Gene expression analysis revealed that exposure of Wistar rats to PB caused statistically significant alternations in the expression of tested genes. We found that both mRNA and protein expression of p53 was down-regulated, whereas expression of Dnmt1 (both mRNA and protein) was up-regulated after PB treatment.
  
  
  CONCLUSIONS
  Suppression of p53 mRNA and protein expression, which is probably a result of epigenetic changes, (in particular aberrant p53 promoter hypermethylation), can be associated with tumour promoting activity of phenobarbital.
authors.affiliation: Department of Toxicology and Risk Assessment, National Institute of Public Health-National Institute of Hygiene, Warsaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Urbanek-Olejnik
authors.forename: Monika
authors.initials: M
authors.lastname: Liszewska
authors.forename: Grażyna
authors.initials: G
authors.lastname: Kostka
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000927:Anticonvulsants / Q000633:toxicity*; D019175:DNA Methylation; D004261:DNA Replication / Q000187:drug effects; D016158:Genes, p53 / Q000187:drug effects*; D008099:Liver / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D010634:Phenobarbital / Q000633:toxicity*; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000927:Anticonvulsants; D010634:Phenobarbital