Capsaicin inhibits arginine kinase and exerts anti-Trypanosoma cruzi activity
Trypanosoma cruzi is the causative agent of Chagas disease, considered within the list of twenty neglected diseases according to the World Health Organization. There are only two therapeutic drugs for Chagas disease, both of them unsuitable for the chronic phase, therefore the development of new drugs is a priority. T. 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 from our laboratory, possible TcAK inhibitors were identified through computer simulations, resulting in the best-scoring compounds cyanidin derivatives and capsaicin. Considering these results, in this work we evaluate the effect of capsaicin on TcAK activity and its trypanocidal effect. Although capsaicin produced a weak inhibition on the recombinant TcAK activity (IC50 {approx} 800 {micro}M), it had a strong trypanocidal effect on epimastigotes and trypomastigotes (IC50 = 6.26 {micro}M and 0.26 {micro}M, respectively) being 20-fold more active on trypomastigotes than mammalian cells. Epimastigotes that overexpress TcAK were 37% more resistant to capsaicin than wild type parasites, suggesting that trypanocidal activity could be due, in part, to the enzyme inhibition. However, the difference between the concentrations at which the enzyme is inhibited and the parasite death is caused implies the presence of other targets. In this sense, the prohibitin-2 and calmodulin were identified as other possible capsaicin targets. Capsaicin is a strong and selective trypanocidal agent active in nanomolar concentrations, with an IC50 57-fold lower than benznidazole, the drug currently used for treating Chagas disease.