Unraveling the Immune Metabolic Epigenetic Axis to Improve Tuberculosis Therapy

Tuberculosis is caused by the bacteria Mycobacterium tuberculosis (Mtb), which mainly affects the lungs. Macrophages (MΦ) are critical innate immune cells that phagocytize and kill Mtb. Prior studies have shown that the metabolic enzymes of the tricarboxylic acid cycle (TCA) “moonlight” in the nucleus and regulate cell function and fate by acting as epigenetic switches to regulate cell phenotype. We have evaluated if the moonlighting of TCA enzymes regulates MΦ immune phenotype. MΦ can develop “trained” phenotypes with improved anti-mycobacterial immunity while “tolerant” MΦ develops phenotypes with detrimental anti-mycobacterial immunity. We hypothesized that both “trained” and “Tolerant” MΦ phenotypes are dependent upon TCA moonlighting. Using monocyte-derived macrophages (MDMΦ) and standard protocols to induce trained or tolerant MΦ, we implemented confocal microscopy to quantify TCA moonlighting and used flow cytometry to measure to cytokine production. Median fluorescent intensity (MFI) of Isocitrate dehydrogenase3 (IDH3) and citrate synthase (CS) in the nuclei of MDMΦ was determined. The effect on phenotype and TCA moonlighting by inhibitors of multiple pathways were evaluated. Both trained and tolerant protocols induced TCA moonlighting of IDH3 and CS (p<0.05). Trained phenotype exhibited an increase in cytokine production, while the tolerant phenotype demonstrated a decrease in cytokine production. This project was completed with contributions from Tomoki Nishiguchi and Andrew R. DiNardo from Baylor College of Medicine.