Mycobacterium tuberculosis reduces global histone acetylation in human macrophages which is restored by Sirtuin inhibitors

Abstract

Abstract Mycobacterium tuberculosis (Mtb) infects and grows in human macrophages unless they are activated earlier using IFN-γ. IFN-γ polarized M1-Macrophages (MΦs) and IL-4 driven M2-MΦs respectively kill Mtb or are permissive. Mtb infected M1-MΦs showed an increased expression of iNOS and autophagy-regulating ATGs compared to M2-MΦs. Despite increased bactericidal function, M1-MΦs were unable to eradicate Mtb. Hypothesis Because M1- and M2-MΦs differentially expressed Sirtuin1, 2, 3 and Sirt5, we hypothesized that, Sirtuin-dependent histone deacetylation would affect gene expression and bactericidal function Methods M0 (naive), M1 or M2-MΦs were treated with inhibitors of Sirtuin1, Sirt2, Sirt3 and Sirt5 followed by Mtb infection, and evaluation of histone modifications using a novel triomics approach. Viability of Mtb was measured before and after Sirtuin blockade and correlated to mRNA expression for iNOS and ATG5 using qPCR. Results a) Relative to uninfected M0-MΦs, M1-MΦs showed higher levels of histone acetylation followed by M2-MΦs. b) Mtb infection reduced global histone acetylation in all three MΦ phenotypes, with an concurrent increase in histone methylation. c) Blockade of Sirt1, 2, 3 but not Sirt5 led to a dramatic restoration of histone acetylation in all three phenotypes, although M2-MΦs were still resistant to Sirt3 inhibitors. d) M0, M1- and M2-MΦs killed Mtb more effectively after Sirt2 blockade compared to Sirt1, 3 and 5 inhibition, which was associated with an increase in mRNA for iNOS and ATG5. Conclusion We conclude that Mtb decreases histone acetylome of human MΦs and Sirtuin inhibitors provide a new epigenetic mechanism to restore macrophage bactericidal function against tuberculosis. Supported by NIH NIAID RO1 AI-122070 and AI-161015.