Transcriptional Regulation of CYP2E1: Promoter Methylation in In Vitro Models and Human Liver Disease Samples

Background/Objectives: DNA methylation is a critical epigenetic mechanism involved in gene expression regulation. This study examines promoter methylation of CYP2E1 in healthy liver, intestinal mucosa, as well as pathological liver samples, alongside in in vitro cell models. Methods: First, in tissue samples from the liver, duodenum, jejunum, and colon of healthy organ donors, CYP2E1 promoter methylation was quantified using the EpiTect Methyl II PCR System, while gene expression was determined by quantitative real-time PCR. Then, in vitro experiments were performed using HepG2 and Caco-2 cell lines. Cells were treated with 5-Aza-2'-deoxycytidine to induce demethylation, with subsequent analysis of CYP2E1 mRNA levels. Subsequently, promoter methylation was assessed via pyrosequencing, while gene expression was quantified using quantitative real-time PCR. Results: The analysis revealed statistically significant differences in the methylation patterns of the CYP2E1 promoter between healthy liver and gastrointestinal tissues. In cell lines, treatment with 5-Aza-2'-deoxycytidine resulted in increased CYP2E1 mRNA levels and demonstrated a strong negative correlation between promoter methylation and gene expression. However, in liver disease samples, differential methylation did not consistently translate into decreased CYP2E1 expression. Conclusions: Although in vitro experiments support a regulatory role of promoter methylation in controlling CYP2E1 expression, the clinical data indicate that additional factors may contribute to gene regulation in liver pathology.