Effect of inflammatory cytokines on DNA methylation and demethylation

Philadelphia

Objective: To determine the effects of inflammatory cytokines and mediators on expression of DNMT and TETenzymes in human gingival fibroblasts isolated from patients with periodontitis as well as normal and transformed cell lines.Methods: Expression levels of DNA methylatransferase (DNMT1 and 3a) and demethylase (TET1) were examined by RT-PCR in cells treated for up to 24 hours with IL-1, IL-6 or prostaglandin E2. The role of PGE2 in IL-1 suppression of DNMT3a expression was assessed by treating cells with IL-1 in the presence and absence of NS-398. Global levels of DNA methylation following treatment with IL-1 were measured in an ELISA-like assay.Results: Treatment of HGF with IL-1 caused a three-fold increase in levels of DNMT1 mRNA over 24 hours, but a two-fold decrease in DNMT3a mRNA in the same samples. Global levels of 5mC were increased in HGF treated with IL-1 for 72 hours relative to untreated controls. PGE2 caused a dose-dependent decrease in levels of DNMT3asimilar to IL-1, but also slightly decreased levels of DNMT1. Conclusion: These data are consistent with the hypothesis that exposure to inflammatory cytokines or PGE2 alters levels and/or activity of enzymes involved in DNA methylation, resulting in global and possibly gene-specific changes which can lead to changes in cellular characteristics over time. Further experiments will be aimed at testing the effects of these cytokines on expression of DNMT and TET enzymes in normal and transformedelucidating mechanisms involved in cytokine regulation of these enzymes.