Inhibition of the macrophage demethylase LSD1 reverses Leishmania amazonensis-induced transcriptomic changes and causes a decrease in parasite load

Intracellular pathogens exploit host cell functions to favor their own survival. In recent years, the subversion of epigenetic regulation has emerged as a key microbial strategy to modify host cell gene expression and evade antimicrobial immune responses. Using the protozoan parasite Leishmania as a model system, we have recently demonstrated that infection causes histone H3 hypomethylation, which is associated with the establishment of an anti-inflammatory phenotype, suggesting that host cell demethylases may play a role in the intracellular survival of these parasites. In this study, we employed a combination of pharmacological, RNA sequencing and interaction studies to investigate the role of the macrophage lysine demethylase LSD1 (KDM1a) in Leishmania intracellular infection in vitro . Treatment of infected macrophages with two validated LSD1-specific inhibitors resulted in a significant reduction in parasite burden. We confirmed the impact of these inhibitors on LSD1 activity within macrophage nuclear extracts using an in vitro demethylase assay and established their LSD1 target engagement in situ by cellular thermal shift assay. RNA-seq analysis of infected and inhibitor-treated macrophages linked parasite killing to a partial reversion of infection-dependent expression changes, restoring the macrophage anti-microbial response and limiting cholesterol biosynthesis. While we ruled out any impact of Leishmania on LSD1 expression or localization, we uncovered significant alterations in LSD1 complex formation within infected macrophages, involving unique interactions with host proteins as well as interactions with Leishmania proteins that appear to be secreted into the macrophage nucleus. Our study sheds important new light on the epigenetic mechanisms of macrophage immuno-metabolic subversion by intracellular Leishmania and identifies LSD1 as a potential candidate for host-directed, anti-leishmanial therapy. ### Competing Interest Statement The authors have declared no competing interest.