Audifás-Salvador Matus-Meza

Trypanosoma cruzi is a protozoan parasite that causes Chagas disease in humans. The current antichagasic drugs nifurtimox and benznidazole have inconveniences of toxicity; therefore, the search for alternative therapeutic strategies is necessary. The present study reports the synthesis, drug-likeness predictions, and in vitro anti-trypanosome activity of a series of 14 quinazoline 2,4,6-triamine derivatives. All compounds were tested against T. cruzi (epimastigotes and trypomastigotes) and in HFF1 human foreskin fibroblasts. The bioassays showed that compounds 2–4 containing nitrobenzoyl substituents at 6-position of the quinazoline 2,4,6-triamine nucleus were the most potent on its antiprotozoal activity. The effect was observed at 24 h and it was preserved for at least 5 days. Also, compounds 2–4 were not toxic to the human control cells, showing high selectivity index. The quinazoline nitro derivatives have potential use as antichagasic agents.

Recently, we published that the monoclonal antibody (D12 mAb) recognizes gp63 of L. mexicana, and it is responsible for COX activity. This D12 mAb exhibited cross-reactivity with Trypanosoma cruzi, Entamoeba histolytica, Acanthamoeba castellanii, and Naegleria fowleri. COX activity assays performed in these parasites suggested the potential presence of such enzymatic activity. In our investigation, we confirmed that wild-type recombinant gp63 exhibits COX-like activity, in contrast to a mutated recombinant gp63 variant. Consequently, our objective was to identify sequences orthologous to gp63 and subsequently analyze the binding of arachidonic acid (AA) to the putative active sites of these proteins. Given the absence of a crystallized structure for this protein in the Protein Data Bank (PDB), it was imperative to first obtain a three-dimensional structure by homology modeling, using leishmanolysin from Leishmania major (PDB ID: LML1) as a template in the Swiss model database. The results obtained through molecular docking simulations revealed the primary interactions of AA close to the Zinc atom present in the catalytic site of gp63-like molecules of several parasites, predominantly mediated by hydrogen bonds with HIS264, HIS268 and HIS334. Furthermore, COX activity was evaluated in commensal species such as E. dispar and during the encystment process of E. invadens.

Linearolactone (1) and kaempferol (2) have amebicidal activity in in vitro studies. The type of cell death induced by 1 and 2 and their effects on the virulence of E. histolytica were analyzed by transmission and confocal electron microscopy, reactive oxygen species (ROS) production, and apoptosis, detected by flow cytometry with dichlorofluorescein 2′,7′-diacetate and annexin-V binding, respectively, and confirmed by TUNEL. The interaction of 1 and 2 with actin was analyzed by docking, and the in vivo amoebicidal activity was established with the Mesocricetus auratus model; amebic liver abscess (ALA) development was evaluated by magnetic resonance (MR) and validated post mortem. In vitro, compounds 1 and 2 caused chromatin condensation, intracellular ROS, and loss of actin structures. Coupling analysis showed that they bind to the allosteric and catalytic sites of actin with binding energies of −11.30 and −8.45 kcal/mol, respectively. Treatments with 1 and 2 induced a decrease in ALA formation without toxic effects on the liver and kidney. Thus, compound 1, but not 2, was able to induce apoptosis-like effects in E. histolytica trophozoites by intracellular production of ROS that affected the actin cytoskeleton structuration. In vivo, compound 1 was more active than compound 2 to reduce the development of ALA.