Age-related loss of CpG methylation in the tumour necrosis factor promoter

Abstract

Background: Dysregulated production of TNF has been implicated in the pathogenesis and severity of inflammatory rheumatic diseases, many of which show age-related increased incidence. Ageing is also associated with changes in the immune system including higher systemic levels of pro-inflammatory cytokines. Methylation of DNA is an important regulator of gene expression and changes with age.Objective: In this study we investigated whether the DNA methylation status of the TNF promoter changed with age in peripheral blood leucocytes and macrophages.Methods and results: Using pyrosequencing assays we detected age-related demethylation of CpG motifs (−304, −245 and −239) in the TNF promoter in human peripheral blood cells from 312 healthy controls (0.8% per decade, confidence interval (CI)=0.44–1.13%, p=1×10−5) and primary monocyte-derived macrophages (MDM) from a separate population of 78 healthy controls (1.4% per decade, CI=0.79–2.13%, p=7×10−5). Methylation a TNF promoter fragment (−345–+154) resulted in 78% reduction of reporter gene activity compared with the unmethylated promoter construct.Conclusions: These data suggest a potential role of accrued changes in DNA methylation in the development of age-related inflammatory diseases, such as rheumatoid arthritis and polymyalgia rheumatica, in which TNF is a pivotal mediator.