Regulation of Epigenetic Modifiers Including KDM6B, by Interferon-γ and Interleukin-4 in Human Macrophages

Background: Interferon-gamma (IFN-gamma) or interleukin-4 (IL-4) drives widely different transcriptional programs in macrophages. However, how IFN-gamma and IL-4 alter expression of histone-modifying enzymes involved in epigenetic regulation and how this affects the resulting phenotypic polarization is incompletely understood. Methods and results: We investigated steady-state messenger RNA levels of 84 histone-modifying enzymes and related regulators in colony-stimulating factor-1 differentiated primary human macrophages using quantitative polymerase chain reaction. IFN-gamma or IL-4 treatment for 6-48h changed 11 mRNAs significantly. IFN-gamma increased CIITA, KDM6B, and NCOA1, and IL-4 also increased KDM6B by 6h. However, either cytokine decreased AURKB, ESCO2, SETD6, SUV39H1, and WHSC1, whereas IFN-gamma alone decreased KAT2A, PRMT7, and SMYD3 mRNAs only after 18h, which coincided with decreased cell proliferation. Rendering macrophages quiescent by growth factor starvation or adenovirus-mediated overexpression of p27(kip1) inhibited expression of AURKB, ESCO2, SUV39H1, and WHSC1, and mRNA levels were restored by overexpressing the S-phase transcription factor E2F1, implying their expression, at least partly, depended on proliferation. However, CIITA, KDM6B, NCOA1, KAT2A, PRMT7, SETD6, and SMYD3 were regulated independently of effects on proliferation. Silencing KDM6B, the only transcriptional activator upregulated by both IFN-gamma and IL-4, pharmacologically or with short hairpin RNA, blunted a subset of responses to each cytokine. Conclusion: These findings demonstrate that IFN-gamma or IL-4 can regulate the expression of histone acetyl transferases and histone methyl transferases independently of effects on proliferation and that upregulation of the histone demethylase, KDM6B, assists phenotypic polarization by both cytokines.