Inhibition of DNA methylation in proliferating human lymphoma cells by immune cell oxidants

Abstract

Excessive generation of oxidants by immune cells results in acute tissue damage. One mechanism by which oxidant exposure could have long-term impact is through modulation of epigenetic pathways. We hypothesized that methylation of newly synthesized DNA in proliferating cells can be altered by oxidants that target DNA methyltransferase (DNMT) activity or deplete its substrate, the methyl donor SAM. To this end, we investigated the impact of two oxidants produced by neutrophils, hydrogen peroxide (H2O2) and glycine chloramine, on maintenance DNA methylation in Jurkat T-lymphoma cells. Using cell synchronization and MS-based analysis, we measured heavy deoxycytidine isotope incorporation into newly synthesized DNA and observed that a sub-lethal bolus of glycine chloramine, but not H2O2, significantly inhibited DNA methylation. Both oxidants inhibited DNMT1 activity, but only the chloramine depleted SAM, suggesting that removal of substrate was the most effective means of inhibiting DNA methylation. These results indicate that immune cell–derived oxidants generated during inflammation have the potential for impacting the epigenome of neighboring cells.