RESUMO
Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7.
Assuntos
Animais , Humanos , Masculino , Camundongos , Nitrorredutases/efeitos dos fármacos , Tiadiazóis , Triazóis , Tripanossomicidas , Trypanosoma brucei brucei/efeitos dos fármacos , Trypanosoma brucei brucei/enzimologia , Ensaio Cometa , Dano ao DNA/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Nitrorredutases/metabolismo , Testes de Sensibilidade Parasitária , Relação Estrutura-Atividade , Tiadiazóis/química , Tiadiazóis/metabolismo , Tiadiazóis/farmacologia , Tiadiazóis/toxicidade , Triazóis/química , Triazóis/metabolismo , Triazóis/farmacologia , Triazóis/toxicidade , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Tripanossomicidas/toxicidade , Trypanosoma cruzi/efeitos dos fármacosRESUMO
The kinetoplast genetic code deviates from the universal code in that 90 percent of mitochondrial tryptophans are specified by UGA instead of UGG codons. A single nucleus-encoded tRNA Trp(CCA) is used by both nuclear and mitochondria genes, since all kinetoplast tRNAs are imported into the mitochondria from the cytoplasm. To allow decoding of the mitochondrial UGA codons as tryptophan, the tRNA Trp(CCA) anticodon is changed to UCA by an editing event. Two tryptophanyl tRNA synthetases (TrpRSs) have been identified in Trypanosoma brucei: TbTrpRS1 and TbTrpRS2 which localize to the cytoplasm and mitochondria respectively. We used inducible RNA interference (RNAi) to assess the role of TbTrpRSs. Our data validates previous observations of TrpRS as potential drug design targets and investigates the RNAi effect on the mitochondria of the parasite.
Assuntos
Animais , Interferência de RNA , RNA de Protozoário/metabolismo , RNA de Transferência/metabolismo , Trypanosoma brucei brucei/enzimologia , Triptofano-tRNA Ligase/metabolismo , Expressão Gênica , RNA de Protozoário/genética , RNA de Transferência/genética , Fatores de Tempo , Trypanosoma brucei brucei/citologia , Trypanosoma brucei brucei/genética , Triptofano-tRNA Ligase/genéticaRESUMO
The study of Trypanosoma cruzi type II DNA-topoisomerase should provide new clues for the rational development of new drugs for the chemotherapy of Chagas' disease. This enzyme is very likely involved in the processes leading to T. cruzi replication and differentiation since both processes are blocked by bacterial type II DNA topoisomerase inhibitors. In this article, we review and discuss our recent data related to the cloning, sequencing, and expression of T. cruzi type II topoisomerase