Disulfiram Inhibits M. tuberculosis Growth by Altering Methionine Pool, Redox Status and Host-Immune Response

Abstract

Methionine biosynthetic pathway, essential for the growth of Mycobacterium tuberculosis (Mtb) in the host, represents an attractive target for the development of novel anti-tuberculars. Here, we have biochemically characterized homoserine acetyl transferase (HSAT viz. MetA) of Mtb, which catalyses the first committed step of methionine and S-adenosylmethionine (SAM) biosynthesis. High-throughput screening of a 2300 compound library resulted in identification of thiram, an anti-fungal organosulfur compound, as the most potent MetA inhibitor. Further analysis of thiram analogs led to the identification of orally bioavailable disulfiram (DIS, an anti-alcoholism FDA approved drug) as a novel inhibitor of MetA. Both thiram and DIS restricted the growth of drug-sensitive and drug-resistant Mtb strains in a bactericidal manner. ThermoFlour assay demonstrated direct binding of DIS with MetA. Metabolomic and transcriptomic studies showed DIS mediated perturbation of methionine and redox homeostasis, respectively, in Mtb. In concordance, the effect of DIS on Mtb growth was partially rescued by supplementation with either L-methionine as well as N-acetyl cysteine, suggesting a multi-target killing mechanism. In Mtb-infected mice, DIS administration restricted bacterial growth, increased efficacy of isoniazid, ameliorated lung pathology, modulated lung immune cell landscape and protective immune response. Taken together, our results demonstrate that DIS can be repurposed for designing an effective anti-tubercular therapy. Funding Statement: The research fellowship to D.C. and T.P.G. from Department of Biotechnology, Govt. of India is acknowledged. Ava.S. fellowship was supported by the University of Grants commission. R.B. acknowledges Department of Science and Technology India and FICCI for providing C.V. Raman International fellowship. R.S. acknowledge THSTI, and Department of Biotechnology, Govt. of India (BT/PR29075/BRB/10/1699/2018) for funding. This research was supported by SIgN A*STAR, A*STAR JCO-CDA grant (#1518251030), and Singapore-India Joint grant (#1518224018) to A.S. Declaration of Interests: None. Ethics Approval Statement: The proposed animal experiments were approved by the institutional animal ethics committee of Defence Science Organization (DSO), Singapore.