Giardia duodenalis is a flagellated unicellular eukaryotic microorganism that commonly causes diarrheal disease throughout the world. Treatment of giardiasis is limited to nitroheterocyclic compounds as metronidazole and benzimidazoles as albendazole, where remarkably treatment failure is relatively common. Consequently, the need for new options to treat this disease is underscored. We predicted by a bioinformatic approach that nicotinamide inhibits Giardia sirtuins by the nicotinamide exchange pathway, and since sirtuins are involved in cell cycle control, they could be related with arrest and decrease of viability. When trophozoites were treated with nicotinamide (NAM), a strong arrest of Giardia trophozoites in G2 phase was observed and at the same time changes in transcriptional expression of sirtuins were produced. Interestingly, the G2 arrest is not related to double-strand breaks, which strengthens the role of sirtuins in the control of the Giardia cell cycle. Results with NAM-treated trophozoites as predicted demonstrate antigiardial effects and thus open new options for the treatment of giardiasis, either with the combination of nicotinamide with another antigiardial drug, or with the design of specific inhibitors for Giardia sirtuins.
Keywords: DNA double-strand breaks; GdSir2.1–2.5; Giardiasis; Metronidazole; NAM.
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