Impacto da utilização de diferentes formas evolutivas de Trypanosoma cruzi no processo de screening de novos fármacos

Abstract

T. cruzi is a parasite that presents different evolutionary stages in its life cycle and all can be used in screening for trypanosomal molecules. The objective of this work was to evaluate the impact of the use of different evolutionary forms of T. cruzi in determining the activity of products of natural origin and synthetic drugs. The study was carried out using two strategies: systematic review of the literature and experimental evaluation. The search strategy was carried out in accordance with PRISMA and included the construction of specific filters for retrieving articles in the PubMed, Web of Science and Scopus databases. Information on the parasite strain, experimental protocol, reference drug(s) and in vivo outcome, when applicable, was extracted from each article. 226 full articles were included in the review. The results showed a notable growth in the number of publications in the last decade, compared to other periods. The results indicated great heterogeneity related to the use of evolutionary forms, strains of the parasite and protocols for determining activity. Epimastigote was the evolutionary form most frequently used in studies involving natural products (75%), while for synthetic and semi-synthetic substances the use of the three forms was similar. Significant changes in the EC-50 values were identified among amastigotes, epimastigotes and trypomastigotes, however, due to the heterogeneity of the experimental protocols used, it was not possible to measure the impact of using one or the other way on the translational value of the screening. For the experimental evaluation, two groups of substances were used: (i) products of natural origin that present or not some evidence of anti-T activity. cruzi already reported (red propolis, geopropolis and 11 extracts of endophytic fungi isolated from the Dalbergia ecastaphyllus plant); (ii) drugs that have anti- T.cruzi activity (nitroimidazoles and azoles). After studying toxicity in Vero cells, non-toxic concentrations of natural products were used to screen for trypanosomicidal activity on the different evolutionary forms of strain Y. No anti-epimastigote activity was detected for any products of natural origin and azoles, while for these same groups of molecules maximum levels of 50% mortality on trypomastigotes were observed. A different profile was observed for amastigotes, with percentages of inhibition ranging from 60% to 90% for propolis and extracts of endophytic fungi. Dose-effect curves were then evaluated on amastigotes for three of the fungi extracts, in addition to the propolis, resulting in similar mean EC-50 values (approximately 6 μg / mL), except for one of the extracts, whose EC-50 was 9 , 76 ± 0.89 μg / mL. Regarding the reference molecules of the nitroimidazole group, the level of activity on the different evolutionary forms was similar. The data obtained demonstrated that the evolutionary form of the parasite can influence the response profile of the parasite to treatment. Due to the heterogeneity of protocols referred to in the literature, it was not possible to infer about the translational value of the models used in experimental in vitro chemotherapy. In this sense, the harmonization of experimental strategies is essential to define viable, reproducible screening strategies and select promising trypanosomicidal molecules more assertively.