DNA methylation of TH1/TH2 cytokine genes affects sensitization and progress of experimental asthma

Epigenetic changes in DNA methylation have recently been demonstrated to be involved in effector T-cell polarization, resulting in differential secretion of TH1 and TH2 cytokines. However, the contribution to the development of a chronic inflammatory phenotype remains still unclear. We sought to investigate changes in DNA methylation in marker genes of T-cell subsets during allergen sensitization/challenge and their influence on the development of an allergic airway inflammatory response. The relationship between changes in DNA methylation and phenotype development were examined in a well-established model of experimental asthma. DNA methylation was investigated at genomic loci associated with TH1 (IFNG promoter) or TH2 (conserved noncoding sequence 1 [CNS1]) cytokine production by using bisulfite pyrosequencing. Analysis of CD4+ T cells revealed a significant increase in DNA methylation at the IFNG promoter after allergen sensitization/challenge, which correlated with decreased IFN-γ cytokine expression, whereas only minor changes were observed at the CNS1 locus. Furthermore, the increase in DNA methylation at the IFNG promoter could be reversed with a DNA methyltransferase (DNMT) inhibitor in vitro and in vivo with beneficial effects on sensitization status and allergic phenotype. The specific importance of the DNA methylation status in CD4+ T cells could be confirmed by using adoptive transfer experiments. We here report the novel finding that epigenetic regulation in T cells contributes to the development of experimental asthma and can be targeted pharmacologically.