The C4 sterol demethylation step of Trypanosoma cruzi: activity of new candidate inhibitors on parasite growth.

CAEIRO, L; COSENTINO, R; TEKIEL, V; AGUERO, F

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias.; 2017

SAIB-SAP-SAIC-SAi, etc

THE C4 STEROL DEMETHYLATION STEP OF Trypanosoma cruzi: ACTIVITY OF NEW CANDIDATE INHIBITORS ON PARASITE GROWTHIn Trypanosoma cruzi the sterol biosynthesis pathways is a validated target for chemotherapeutic intervention. Humans and trypanosomes share many of the enzymes leading to essential isoprenoid and sterol precursors. However, there are also key differences in these pathways. Whereas the main sterol in mammals is cholesterol, T. cruzi (and yeast/fungi) have ergosterol as their main sterol. Hence, while similar, the pathways also show a number of key steps that differ and that could be exploited to selectively affect parasite enzymes (Cosentino RO et al, 2014). During their synthesis, sterol precursors become functional only after removal of the two methyl groups at C4 by a membrane-bound multienzymatic complex. Intriguingly, enzymes and inhibitors of the C4 demethylation step have remained poorly characterized. In this study, we report the identification of a number of candidate inhibitors of steroid C4-demethylation, based on computational and literature searches. As part of these searches, we have identified 5 compounds associated with inhibition of C4-sterol demethylation at either of these enzymatic steps in different organisms. These are: APB (2-(pentylsulfanyl)-1,3-benzothiazol-6-amine); Fenhexamid; Totarol; NCE-893, and FR171456. We tested them for inhibition of intracellular amastigote replication using transgenic T. cruzi parasites expressing a β-galactosidase reporter gene, and benznidazole as a positive control. Briefly, we treated infected cells and measured β-galactosidase activity with CPRG after 72hs. Except for totarol (which was toxic), all other drugs were active in the assay, with EC50s ranging from 30 µM (fenhexamid) to 0.1 µM (FR171456). Using FR171456, we observed an altered morphology of amastigotes by SEM. In conclusion, these data suggest that the C4-demethylation step of the ergosterol biosynthetic pathway of T. cruzi is also a valid target for development of new drugs for Chagas Disease. Supported by PICTO-Glaxo-2013-0067