Banca de DEFESA: BÁRBARA DE SOUZA CARDOSO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : BÁRBARA DE SOUZA CARDOSO
DATE: 11/07/2025
TIME: 10:00
LOCAL: Instituto de Química, sala 49
TITLE:
The Role of the NADPH Oxidases Inhibitors VAS2870, Setanaxib and GKT in the Activities of the LFR1 of Leishmania amazonensis and Possible Influence on Infection and Differentiation of the Parasite
KEY WORDS:
Leishmania amazonensis, NADPH oxidases, LFR1.
PAGES: 75
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Orgânica
SPECIALTY: Estrutura, Conformação e Estereoquímica
SUMMARY:
The species Leishmania amazonensis occurs in various parts of Brazil and is the causative agent of Cutaneous Leishmaniasis, transmitted by phlebotomine insect vectors to vertebrate hosts. During the parasite’s life cycle, there is an alternation between the promastigote forms, present in the vector, and the intracellular infective amastigote forms, which arise from the differentiation of metacyclic promastigotes within the mammalian host. Recently, it has been described that the ferric reductase enzyme (LFR1) of L. amazonensis, when activated by heme, can also function as a NADPH oxidase (NOX). This bifunctional enzyme appears to be involved in the parasite’s differentiation process and may constitute a new pharmacological target. NOXs are involved in various pathologies such as cancer, cardiac, and neurodegenerative diseases; therefore, there is an intense search for drugs that inhibit the activity of these enzymes. Some of these inhibitors are commercially available, such as Setanaxib, GKT136901, and VAS2870. In this context, in order to investigate whether LFR1 could be a target for drug therapy against leishmaniasis, this study aims to analyze the effect of Setanaxib, GKT136901, and VAS2870 on the activities of LFR1 from L. amazonensis and to assess their effects on the proliferation, differentiation, and infectivity of the parasites, as well as to perform an in silico analysis of the interaction of these inhibitors with LFR1. Preliminary results using the Amplex Red® reagent to measure heme-dependent H2O2 production showed that Setanaxib at 15 µM, GKT136901 at 2.5 µM, and VAS2870 at concentrations as low as 1 µM were able to completely abolish NOX activity. The cytotoxic effect of these inhibitors against promastigote forms was also evaluated through the MTT assay, in which only VAS2870 exhibited toxic effects, showing a loss of 20% and 90% in cell viability in the presence of 10 µM of the inhibitor after 24 h and 72 h, respectively. Regarding the ferric reductase activity of LFR1, measured through a colorimetric method with the (K3Fe(CN)6) reagent, the promising inhibitor VAS2870 at 1 µM did not show a significant inhibitory effect but inhibited this activity at concentrations above 5 µM. The in silico study, which aimed to demonstrate the possible interaction between VAS2870 and the dehydrogenase domain of LFR1 modeled comparatively, showed that this inhibitor interacts covalently and stably with the enzyme’s active site. In axenic cultures that stimulate promastigote-to-amastigote differentiation, VAS2870 appears to act by inhibiting this process at non-cytotoxic concentrations, although it did not exert an effect on L. amazonensis infection in murine macrophages. These results suggest that VAS2870 can act on both activities of LFR1, exerting effects on the life cycle of L. amazonensis. Furthermore, the possibility of deeper studies regarding the effects of these and other NOX inhibitors on LFR1 is not excluded.
COMMITTEE MEMBERS:
Presidente - 3145590 - DANIELA COSENTINO GOMES
Interno - 2582213 - MARCO ANDRE ALVES DE SOUZA
Interno - 1058758 - MARCO EDILSON FREIRE DE LIMA
Externa à Instituição - MICHELLE TANNY CUNHA DO NASCIMENTO - UFRJ
Externa à Instituição - SUZETE ARAUJO OLIVEIRA GOMES - UFF