Mycobacterium tuberculosis induces metabolic reprogramming in macrophages like the Warburg effect. This enhances antimicrobial performance at the expense of increased inflammation, which may promote a pathogen-permissive host environment. Since the NAD(+)-dependent protein deacetylase Sirtuin 3 (SIRT3) is an important regulator of mitochondrial metabolism and cellular redox homeostasis, we hypothesized that SIRT3 modulation mediates M. tuberculosis-induced metabolic reprogramming. Infection of immortalized and primary murine macrophages resulted in reduced levels of SIRT3 mRNA and protein and perturbation of SIRT3-regulated enzymes in the tricarboxylic acid cycle, electron transport chain, and glycolytic pathway. These changes were associated with increased reactive oxygen species and reduced antioxidant scavenging, thereby triggering mitochondrial stress and macrophage cell death. Relevance to tuberculosis disease in vivo was indicated by greater bacterial burden and immune pathology in M. tuberculosis-infected Sirt3 (-/-) mice. CD11b(+) lung leukocytes isolated from infected Sirt3(-/-) mice showed decreased levels of enzymes involved in central mitochondrial metabolic pathways, along with increased reactive oxygen species. Bacterial burden was also greater in lungs of LysM(cre)Sirt3(L2/L2) mice, demonstrating the importance of macrophage-specific SIRT3 after infection. These results support the model of SIRT3 as a major upstream regulatory factor, leading to metabolic reprogramming in macrophages by M. tuberculosis IMPORTANCE Tuberculosis, the disease caused by the bacterium M. tuberculosis, remains one of the top 10 causes of death worldwide. Macrophages, the first cells to encounter M. tuberculosis and critical for defense against infection, are hijacked by M. tuberculosis as a protected growth niche. M. tuberculosis-infected macrophages undergo metabolic reprogramming where key mitochondrial pathways are modulated, but the mechanisms driving this metabolic shift is unknown. Our study demonstrates that M. tuberculosis downregulates Sirtuin 3 (SIRT3), an important regulator of mitochondrial metabolism, leading to SIRT3-dependent transcriptional downregulation of mitochondrial metabolic proteins, which is followed by oxidative stress and macrophage necrosis. This study identifies SIRT3 modulation as a key event in M. tuberculosis-induced metabolic reprograming in macrophages that defend against tuberculosis.

Mycobacterium tuberculosis (Mtb) executes a plethora of immune-evasive mechanisms, which contribute to its pathogenesis, limited efficacy of current therapy, and the emergence of drug-resistant strains. This has led to resurgence in attempts to develop new therapeutic strategies/targets against tuberculosis (TB). We show that Mtb down-regulates sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, in monocytes/macrophages, TB animal models, and TB patients with active disease. Activation of SIRT1 reduced intracellular growth of drug-susceptible and drug-resistant strains of Mtb and induced phagosome-lysosome fusion and autophagy in a SIRT1-dependent manner. SIRT1 activation dampened Mtb-mediated persistent inflammatory responses via deacetylation of RelA/p65, leading to impaired binding of RelA/p65 on the promoter of inflammatory genes. In Mtb-infected mice, the use of SIRT1 activators ameliorated lung pathology, reduced chronic inflammation, and enhanced efficacy of anti-TB drug. Mass cytometry-based high-dimensional analysis revealed that SIRT1 activation mediated modulation of lung myeloid cells in Mtb-infected mice. Myeloid cell-specific SIRT1 knockout mice display increased inflammatory responses and susceptibility to Mtb infection. Collectively, these results provide a link between SIRT1 activation and TB pathogenesis and indicate a potential of SIRT1 activators in designing an effective and clinically relevant host-directed therapies for TB.