mp7b00719_si_001.pdf (5.87 MB)
Insights on the Mechanism of Action of INH‑C10 as an Antitubercular Prodrug
journal contribution
posted on 2017-11-01, 00:00 authored by Diogo Vila-Viçosa, Bruno L. Victor, Jorge Ramos, Diana Machado, Miguel Viveiros, Jacek Switala, Peter C. Loewen, Ruben Leitão, Filomena Martins, Miguel MachuqueiroTuberculosis
remains one of the top causes of death worldwide,
and combating its spread has been severely complicated by the emergence
of drug-resistance mutations, highlighting the need for more effective
drugs. Despite the resistance to isoniazid (INH) arising from mutations
in the katG gene encoding the catalase-peroxidase
KatG, most notably the S315T mutation, this compound is still one
of the most powerful first-line antitubercular drugs, suggesting further
pursuit of the development of tailored INH derivatives. The N′-acylated INH derivative with a long alkyl chain
(INH-C10) has been shown to be more effective than INH
against the S315T variant of Mycobacterium tuberculosis, but the molecular details of this activity enhancement are still
unknown. In this work, we show that INH N′-acylation
significantly reduces the rate of production of both isonicotinoyl
radical and isonicotinyl–NAD by wild type KatG, but not by
the S315T variant of KatG mirroring the in vivo effectiveness
of the compound. Restrained and unrestrained MD simulations of INH
and its derivatives at the water/membrane interface were performed
and showed a higher preference of INH-C10 for the lipidic
phase combined with a significantly higher membrane permeability rate
(27.9 cm s–1), compared with INH-C2 or
INH (3.8 and 1.3 cm s–1, respectively). Thus, we
propose that INH-C10 is able to exhibit better minimum
inhibitory concentration (MIC) values against certain variants because
of its better ability to permeate through the lipid membrane, enhancing
its availability inside the cell. MIC values of INH and INH-C10 against two additional KatG mutations (S315N and D735A)
revealed that some KatG variants are able to process INH faster than
INH-C10 into an effective antitubercular form (wt and S315N), while others show similar reaction rates
(S315T and D735A). Altogether, our results highlight the potential
of increased INH lipophilicity for treating INH-resistant strains.