Inhibition of host Lactate dehydrogenase A by a small-molecule limitsMycobacterium tuberculosisgrowth and potentiates bactericidal activity of isoniazid

Abstract

13Lactate dehydrogenase A (LDHA) mediates interconversion of pyruvate and lactate. Increased 14 lactate turnover is shared by malignant and immune cells. Hypoxic lung granuloma in 15 Mycobacterium tuberculosis-infected animals present elevated levels of Ldha and lactate. Such 16 alteration in metabolic milieu could influence the outcome of interactions between M. 17 tuberculosis and its infected immune cells. Given the central role of LDHA for tumorigenicity, 18 targeting lactate metabolism is a promising approach for cancer therapy. Here, we sought to 19 determine the importance of LDHA for Tuberculosis (TB) disease progression and its potential as 20 a host-directed therapeutic target. To this end, we administered FX11, a small-molecule NADH-21 competitive LDHA inhibitor, to M. tuberculosis infected C57BL/6J mice and Nos2 -/mice with 22 hypoxic necrotizing lung TB lesions mimicking human pathology more closely. FX11 did not 23 inhibit M. tuberculosis growth in aerobic/hypoxic liquid culture, but modestly reduced the 24 pulmonary bacterial burden in C57BL/6J mice. Intriguingly, FX11 administration limited M. 25 tuberculosis replication and onset of necrotic lesions in Nos2 -/mice. In this model, Isoniazid 26 (INH) monotherapy has been known to exhibit biphasic killing kinetics owing to the probable 27 selection of an INH-tolerant subpopulation. This adverse effect was corrected by adjunct FX11 28 treatment and augmented the INH-derived bactericidal effect against M. tuberculosis. Our 29findings therefore support LDHA as a potential target for host-directed adjunctive TB therapy 30 and encourage further investigations into the underlying mechanism. 31 IMPORTANCE 32Tuberculosis (TB) continues to be a global health threat of critical dimension. 33Standard TB drug treatment is prolonged and cumbersome. Inappropriate treatment or non-34 compliance results in emergence of drug-resistant Mycobacterium tuberculosis strains (MDR-35 3 TB) that render current treatment options ineffective. Targeting the host immune system as 36 adjunct therapy to augment bacterial clearance is attractive as it is also expected to be effective 37 against MDR-TB. Here, we provide evidence that pharmaceutical blockade of host lactate 38 dehydrogenase A (LDHA) by a small-molecule limits M. tuberculosis growth and reduces 39 pathology. Notably, LDHA inhibition potentiates the effect of Isoniazid, a first-line anti-TB 40 drug. Hence, its implications of our findings for short-term TB treatment are profound. In sum, 41 our findings establish murine LDHA as a potential target for host-directed TB therapy. 42Untargeted metabolite analysis has identified elevated levels of lactate in necrotic 59 granuloma of M. tuberculosis-infected guinea pigs (9). Generation of lactate from pyruvate, a 60 terminal glycolytic step, is catalyzed by lactate dehydrogenase A (LDHA), whose functions 61 depend on hypoxia-inducible factors (HIFs) (10). Both LDHA and HIF1-α transcripts have been 62 found to be significantly induced in M. tuberculosis-infected m...