Deletion of the
            <i>Trypanosoma brucei</i>
            Superoxide Dismutase Gene
            <i>sodb1</i>
            Increases Sensitivity to Nifurtimox and Benznidazole

Prathalingham, S. Radhika; Wilkinson, Shane R.; Horn, David; Kelly, John M.

doi:10.1128/aac.01360-06

Cited by 40 publications

(34 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…validated as a drug target using small molecule inhibitors (32), and TbSODB-null parasites show increased sensitivity to the superoxide-generating molecules paraquat and nifurtimox (27). In our experiments, an increased susceptibility to OSU-40 was observed upon knockdown of either TbTryS or TbSODB, consistent with the hypothesis that antitrypanosomal dihydroquinolines induce oxidative stress in the parasite.…”

Section: Discussionsupporting

confidence: 77%

“…For these experiments, we used an inducible RNAi system to independently knock down the ROS-detoxifying enzymes TbTryS and TbSODB, thus creating parasites with a compromised ROS detoxification system. We selected these enzymes on the basis of their proven essentiality using both chemical and genetic approaches (1,7,27,32,40,41). TbTryS has been RNAi was initiated and maintained for at least 2 days prior to susceptibility assays.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Induction of Oxidative Stress in Trypanosoma brucei by the Antitrypanosomal Dihydroquinoline OSU-40

Dayton

Kuppusamy

et al. 2012

Antimicrob Agents Chemother

View full text Add to dashboard Cite

In the present study, we sought to provide further support for the hypothesis that OSU-40 kills trypanosomes through oxidative stress. Inducible RNA interference (RNAi) was applied to downregulate key enzymes in parasite antioxidant defense, including T. brucei trypanothione synthetase (TbTryS) and superoxide dismutase B (TbSODB). Both TbTryS RNAi-induced and TbSODB RNAi-induced cells showed impaired growth and increased sensitivity toward OSU-40 by 2.4-fold and 3.4-fold, respectively. Decreased expression of key parasite antioxidant enzymes was thus associated with increased sensitivity to OSU-40, consistent with the hypothesis that OSU-40 acts through oxidative stress. Finally, the dose-dependent formation of free radicals was observed after incubation of T. brucei with OSU-40 utilizing electron spin resonance (ESR) spectroscopy. These data support the notion that the mode of antitrypanosomal action for this class of compounds is to induce oxidative stress. H uman African trypanosomiasis (HAT) is a vector-borne parasitic disease caused by the Trypanosoma brucei subspecies T. b. rhodesiense and T. b. gambiense.The trypanosome proliferates in the host's hemolymphatic system during the first stage of HAT and invades the central nervous system in the second stage. Transmitted by the tsetse fly, the disease mainly affects rural populations in sub-Saharan Africa and is fatal if untreated. Although according to the World Health Organization the number of new cases has dropped to just over 7,000 during 2010 (39), very few drugs are available to treat HAT (2, 4, 42). Pentamidine and suramin, both developed in the first half of the 20th century, are used against first-stage disease, while melarsoprol and eflornithine are used to treat second-stage disease. These drugs are far from satisfactory due to limitations such as severe toxicity, poor efficacy, acquired resistance, rising failure rates, and lack of availability (2, 4, 42). With high efficacy and a good safety profile, nifurtimox-eflornithine combination therapy (NECT) was introduced as a first-line treatment for second-stage HAT caused by T. b. gambiense in 2009 (4, 22, 42). However, administration of NECT is relatively complicated, and its efficacy toward T. b. rhodesiense is still questionable (4, 42). Thus, new drugs are needed against HAT that are safe, affordable, easy to administer, active against first-and second-stage disease, and effective against both subspecies of T. brucei (4, 42).From a previous synthetic medicinal chemistry study, we discovered several N1-substituted 1,2-dihydroquinoline-6-ols displaying nanomolar 50% inhibitory concentrations (IC 50 s) in vitro against T. b. rhodesiense and selectivity indexes (SI) up to Ͼ18,000 (11). OSU-40 (1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate) (Fig. 1) showed a potency (IC 50 , 0.014 M; SI, 1,700) close to that of melarsoprol (IC 50 , 0.008 M; SI, 1,000) against T. b. rhodesiense STIB900 in vitro. In an early treatment mouse model of acute African trypanosomiasis, OSU-40 prolonged the life s...

show abstract

Section: Discussionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Induction of Oxidative Stress in Trypanosoma brucei by the Antitrypanosomal Dihydroquinoline OSU-40

Dayton

Kuppusamy

et al. 2012

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…Several trypanosomal enzymes, including cytochrome P450 reductases and trypanothione reductase, have been shown to mediate this reaction in vitro, appearing to confirm earlier findings (18)(19)(20); this idea gained strength following reports that trypanosomes had a limited enzymatic capacity to metabolize reactive oxygen species (21). To date, the only functional evidence for the involvement of superoxide anions in nifurtimox toxicity is indirect, coming from studies on the superoxide dismutase B1 isoform, where T. brucei SODB1 (TbSODB1) null mutants and T. cruzi SODB1 (TcSODB1)-overexpressing cells are more susceptible to the nitrofuran than are wild-type cells (22,23). Genetic manipulation of T. brucei or T. cruzi engineered to express altered levels of oxygen-sensitive NTR activators-for example, cytochrome P450 reductase, trypanothione reductase, or other components of the trypanosomal oxidative defense system-generates parasites that display the same susceptibilities to nifurtimox as control cells (24,25).…”

supporting

confidence: 49%

Evaluating 5-Nitrofurans as Trypanocidal Agents

Bot

Hall

Álvarez

et al. 2013

Antimicrob Agents Chemother

Self Cite

View full text Add to dashboard Cite

“…Indirect evidence for this pathway stems from functional studies of SODB1, a trypanosomal superoxide dismutase isoform located in the cytosol and glycosome (7,52). T. cruzi and T. brucei parasites with genetically altered levels of SODB1 were shown previously to be more susceptible to benznidazole than controls, demonstrating that any perturbation of this enzyme leads to an imbalance of superoxide anion metabolism that is toxic to the parasite (35,42). This peculiarity in toxicity and SODB1 levels presumably arises as cells with no or low levels of SODB1 activity are killed by superoxide anions, whereas parasites with elevated levels of the enzyme are affected by H 2 O 2 , the product of this dismutation reaction.…”

mentioning

confidence: 99%

Activation of Benznidazole by Trypanosomal Type I Nitroreductases Results in Glyoxal Formation

Hall

Wilkinson

2012

Antimicrob Agents Chemother

Self Cite

195

180

View full text Add to dashboard Cite

Benznidazole, a 2-nitroimidazole, is the front-line treatment used against American trypanosomiasis, a parasitic infection caused by Trypanosoma cruzi. Despite nearly 40 years of use, the trypanocidal activity of this prodrug is not fully understood. It has been proposed that benznidazole activation leads to the formation of reductive metabolites that can cause a series of deleterious effects, including DNA damage and thiol depletion. Here, we show that the key step in benznidazole activation involves an NADH-dependent trypanosomal type I nitroreductase. This catalyzes an oxygen-insensitive reaction with the interaction of enzyme, reductant, and prodrug occurring through a ping-pong mechanism. Liquid chromatography/mass spectrometry (LC/MS) analysis of the resultant metabolites identified 4,5-dihydro-4,5-dihydroxyimidazole as the major product of a reductive pathway proceeding through hydroxylamine and hydroxy intermediates. The breakdown of this product released the reactive dialdehyde glyoxal, which, in the presence of guanosine, generated guanosine-glyoxal adducts. These experiments indicate that the reduction of benznidazole by type I nitroreductase activity leads to the formation of highly reactive metabolites and that the expression of this enzyme is key to the trypanocidal properties displayed by the prodrug.

show abstract

Deletion of the Trypanosoma brucei Superoxide Dismutase Gene sodb1 Increases Sensitivity to Nifurtimox and Benznidazole

Cited by 40 publications

References 26 publications

Induction of Oxidative Stress in Trypanosoma brucei by the Antitrypanosomal Dihydroquinoline OSU-40

Induction of Oxidative Stress in Trypanosoma brucei by the Antitrypanosomal Dihydroquinoline OSU-40

Evaluating 5-Nitrofurans as Trypanocidal Agents

Activation of Benznidazole by Trypanosomal Type I Nitroreductases Results in Glyoxal Formation

Contact Info

Product

Resources

About