Distinct activation mechanisms trigger the trypanocidal activity of DNA damaging prodrugs

Abstract

SummaryQuinone‐based compounds have been exploited to treat infectious diseases and cancer, with such chemicals often functioning as inhibitors of key metabolic pathways or as prodrugs. Here, we screened an aziridinyl 1,4‐benzoquinone (ABQ) library against the causative agents of trypanosomiasis, and cutaneous leishmaniasis, identifying several potent structures that exhibited EC50 values of <100 nM. However, these compounds also displayed significant toxicity towards mammalian cells indicating that they are not suitable therapies for systemic infections. Using anti‐T. brucei ABQs as chemical probes, we demonstrated that these exhibit different trypanocidal modes of action. Many functioned as type I nitroreductase (TbNTR) or cytochrome P450 reductase (TbCPR) dependent prodrugs that, following activation, generate metabolites which promote DNA damage, specifically interstrand crosslinks (ICLs). Trypanosomes lacking TbSNM1, a nuclease that specifically repairs ICLs, are hypersensitive to most ABQ prodrugs, a phenotype exacerbated in cells also engineered to express elevated levels of TbNTR or TbCPR. In contrast, ABQs that contain substituent groups on the biologically active aziridine do not function as TbNTR or TbCPR‐activated prodrugs and do not promote DNA damage. By unravelling how ABQs mediate their activities, features that facilitate the desired anti‐parasitic growth inhibitory effects could be incorporated into new, safer compounds targeting these neglected tropical diseases.

Unraveling the antitrypanosomal mechanism of benznidazole and related 2‐nitroimidazoles: From prodrug activation to DNA damage

“…Controls assessing the susceptibility of wild type and recombinant T . brucei towards nonnitroheterocyclic compounds (e.g., tetracycline, melarsprol, G418, and eflornithine) or DNA damaging agents (e.g., UV light, mechlorethamine, phleomycin, hydroxyurea, and methyl methanesulfonate) have been previously reported (Bot et al., 2013; Dattani & Wilkinson, 2019; Meredith et al., 2017; Wilkinson et al., 2008).…”

“…Where appropriate, protein expression was induced by adding tetracycline (1 μg/ml). reported (Bot et al, 2013;Dattani & Wilkinson, 2019;Meredith et al, 2017;Wilkinson et al, 2008).…”

Genome-scale RNAi screens in African trypanosomes

“…Identification of the mitochondrial nitroreductase, NTR, known to metabolise nifurtimox and benznidazole, provided early proof-of-principle for RIT-seq screening in this respect [16]. Indeed, further DNA-damaging nitro prodrugs were subsequently also found, by RNAi screening, to be activated by NTR [39]. This class of prodrugs has had a major impact in treating infections with South American [40] and African trypanosomes [26] over many decades, while fexinidazole, a drug recently approved for sleeping sickness [41], is also activated by NTR [42].…”

Cherchez l'Electron

“…Meredith et al . investigate the action of aziridinyl 1,4‐benzoquinones (ABQ) against the “Tritryp” parasites Trypanosoma brucei , Trypanosoma cruzi and Leishmania major (Meredith et al ., ). Quinones, in contrast to nitro compounds, are ubiquitous in nature (and even the bombardier beetle uses 1,4‐benzoquinone to fend off aggressors).…”