Auranofin Targets Thioredoxin Reductases in Trichomonas vaginalis

Trichomonas vaginalis is an anaerobic, parasitic protozoan, responsible for trichomoniasis, the world’s most common, non-viral sexually transmitted infection. Lacking many of the defenses present in other organisms to combat oxidative stress, Trichomonas vaginalis relies extensively on the thioredoxin system—NADPH, thioredoxin reductase, and thioredoxin—as a means to protect against exposure to excess oxygen. Current trichomoniasis treatment relies exclusively on the 5-nitroimidazole drugs, but fear of drug-resistant strains and allergic reactions to 5-nitroimidazole treatment necessitate the discovery of a new treatment method for trichomoniasis. Previous research has shown that auranofin, an FDA-approved drug, was effective at inhibiting activity of one of Trichomonas vaginalis’ isoforms of thioredoxin reductase (of which the organism has five total). Our research showed that only two of the isoforms were transcribed and expressed at high levels, and that both of these isoforms were susceptible to auranofin treatment. Not only that, these two isoforms were also shown to be susceptible to various auranofin analogs, having comparable or lower IC50 values. Further tests on these analogs might show that they are actually better treatment candidates if they exhibit less symptoms than auranofin. Experiments examining how mRNA and protein levels were modulated in response to two different concentrations of auranofin treatment showed that while some isoforms show increased levels, no one isoform experienced any drastic changes. Together, this data suggests that further studies should focus on these two most highly expressed isoforms of thioredoxin reductase