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Abstract: Trypanosoma cruzi arginine kinase is a key enzyme in cell energy management and is also involved in pH and nutritional stress response mechanisms. T. cruzi epimastigotes treated with hydrogen peroxide presented a time-dependent increase in arginine kinase expression, up to 10-fold, when compared with untreated parasites. Among other oxidative stress-generating compounds tested, only nifurtimox produced more than 2-fold increase in arginine kinase expression. Moreover, parasites overexpressing arginine kinase showed significantly increased survival capability during hydrogen peroxide exposure. These findings suggest the participation of arginine kinase in oxidative stress response systems. [Copyright &y& Elsevier]

Abstract: Adenylate kinases supply energy routes in cellular energetic homeostasis. In this work, we identified and characterized the adenylate kinase activity in extracts from the flagellated parasite Trypanosoma cruzi, the causative agent of Chagas'' disease. Adenylate kinase activity was detected in different subcellular fractions and the cytosolic isoform was biochemically characterized. Cytosolic adenylate kinase specific activity increases continuously during the epimastigote growth and is down-regulated when other soluble phosphotransferase, arginine kinase, is overexpressed. Six different genes of adenylate kinase isoforms were identified and the mRNA expression was confirmed by RT-PCR and Northern Blot. Three open reading frames coding for different enzyme isoforms named TzADK1, TzADK2 and TzADK5 were cloned and functionally expressed in E. coli. This work reports an unusually large number of genes of adenylate kinases and suggests a coordinated regulation of phosphotransferase-mediated ATP regenerating pathways in the unicellular parasite Trypanosoma cruzi. [Copyright &y& Elsevier]

Trypanosoma cruzi is the causative agent of Chagas disease. There are only two approved treatments, both of them unsuitable for the chronic phase, therefore the development of new drugs is a priority. Trypanosoma cruzi arginine kinase (TcAK) is a promising drug target since it is absent in humans and it is involved in cellular stress responses. In a previous study, possible TcAK inhibitors were identified through computer simulations resulting the best compounds capsaicin and cyanidin derivatives. Here, we evaluate the effect of capsaicin on TcAK activity and its trypanocidal effect. Although capsaicin produced a weak enzyme inhibition, it had a strong trypanocidal effect on epimastigotes and trypomastigotes (IC50 = 6.26 µM and 0.26 µM, respectively) being 20-fold more active on trypomastigotes than mammalian cells. Capsaicin was also active on the intracellular cycle reducing by half the burst of trypomastigotes at approximately 2 µM. Considering the difference between the concentrations at which parasite death and TcAK inhibition occur, other possible targets were predicted. Capsaicin is a selective trypanocidal agent active in nanomolar concentrations, with an IC50 57-fold lower than benznidazole, the drug currently used for treating Chagas disease. [ABSTRACT FROM AUTHOR]

Arginine kinase catalyzes the reversible transphosphorylation between ADP and phosphoarginine which plays a critical role in the maintenance of cellular energy homeostasis. Arginine kinase from the protozoan parasite Trypanosoma cruzi , the etiologic agent of Chagas disease, meets the requirements to be considered as a potential therapeutic target for rational drug design including being absent in its mammalian hosts. In this study a group of polyphenolic compounds was evaluated as potential inhibitors of arginine kinase using molecular docking techniques. Among the analyzed compounds with the lowest free binding energy to the arginine kinase active site (<−6.96 kcal/mol), resveratrol was chosen for subsequent assays. Resveratrol inhibits 50% of recombinant arginine kinase activity at 325 μM. The trypanocidal effect of resveratrol was evaluated on the T. cruzi trypomastigotes bursting from infected CHO K1 cells, with IC 50 = 77 μM. Additionally epimastigotes overexpressing arginine kinase were 5 times more resistant to resveratrol compared to controls. Taking into account that: (1) resveratrol is considered as completely nontoxic; (2) is easily accessible due to its low market price; and (3) has as a well-defined target enzyme which is absent in the mammalian host, it is a promising compound as a trypanocidal drug for Chagas disease. [ABSTRACT FROM AUTHOR]