Multifaceted remodeling by vitamin C boosts sensitivity of Mycobacterium tuberculosis subpopulations to combination treatment by anti-tubercular drugs

Abstract

Bacterial dormancy is a major impediment to the eradication of tuberculosis (TB), because currently used drugs primarily target actively replicating bacteria. Therefore, decoding of the critical survival pathways in dormant tubercle bacilli is a research priority to formulate new approaches for killing these bacteria. Employing a network-based gene expression analysis approach, we demonstrate that redox active vitamin C (vit C) triggers a multifaceted and robust adaptation response in Mycobacterium tuberculosis (Mtb) involving ~ 67% of the genome. Vit C-adapted bacteria display well-described features of dormancy, including growth stasis and progression to a viable but non-culturable (VBNC) state, loss of acid-fastness and reduction in length, dissipation of reductive stress through triglyceride (TAG) accumulation, protective response to oxidative stress, and tolerance to first line TB drugs. VBNC bacteria are reactivatable upon removal of vit C and they recover drug susceptibility properties. Vit C synergizes with pyrazinamide, a unique TB drug with sterilizing activity, to kill dormant and replicating bacteria, negating any tolerance to rifampicin and isoniazid in combination treatment in both in-vitro and intracellular infection models. Finally, the vit C multi-stress redox models described here also offer a unique opportunity for concurrent screening of compounds/combinations active against heterogeneous subpopulations of Mtb. These findings suggest a novel strategy of vit C adjunctive therapy by modulating bacterial physiology for enhanced efficacy of combination chemotherapy with existing drugs, and also possible synergies to guide new therapeutic combinations towards accelerating TB treatment.

Can vitamin C help in managing tuberculosis associated with diabetes mellitus?

“…4 Vitamin C possibly has both pro-oxidant and antioxidant activities regarding mycobacteria (Table 1). [5][6][7][8][9][10] Biologically plausible hypotheses pertaining to the modulation of anti-TB drug efficacy by these activities are summarized as follows. The former activity might help in bacillary killing through the oxidative burst, 1,5 and the latter activity possibly in limiting the size of Mtb persister population, through inhibition of mycobacterial dormancy-related pathways 5-7 that likely include guanosine pentaphosphate ((p)ppGpp) signalling, as there is a structural analogy of vitamin C and guanosine diphosphate, the substrate for (p)ppGpp synthesis.…”

Reactive nitrogen and oxygen species: Friend or foe in the tuberculosis fight

“…We have read with great joy the letter to the editor, written by Yew et al, which analyzes and compares several recent articles [1][2][3][4] showing the intimate relationship between Mycobacterium tuberculosis' (Mtb) redox status -mainly due to the presence of Reactive Nitrogen and Oxygen Species (RNOS) -and tubercular drug efficacy. Given the fact that tuberculosis (TB) is an infectious disease for which there is a limited arsenal of effective drugs, it is crucial to find new drugs or to somehow enhance pre-existing treatments.…”

Redox‐guided small molecule antimycobacterials

“…Recently, similar results were shown by the same group that Vitamin C has dichotomous role in modulating antibiotic activity. It was found that co‐treatment of Vitamin C with INH and RIF leads to drug tolerance which increased their Minimum Inhibitory Concentration (MIC) by 32‐ to 128‐fold, but on the contrary, increased the cidal activity of PZA by fourfold . These findings suggest that the combination of Vitamin C with PZA significantly improves killing of Vitamin C‐induced dormant bacteria, and also efficiently negates Vitamin C‐induced tolerance to INH and RIF in both axenic culture and intracellular models.…”