Banca de QUALIFICAÇÃO: ANA LÚCIA ESTEVAM DOS SANTOS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA LÚCIA ESTEVAM DOS SANTOS
DATE: 21/02/2025
TIME: 14:00
LOCAL: Google Meet
TITLE:

EVALUATION OF THE LEISHMANICIDAL ACTIVITY OF THE LECTIN OBTAINED FROM THE SEEDS OF Canavalia ensiformis (ConA) ON STRAINS OF Leishmania infantum

KEY WORDS:

Parasites. Leishmaniasis. Concanavalin A. Synergism.

PAGES: 73
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

Leishmaniasis encompasses a group of diseases caused by protozoa of the genus Leishmania. It manifests in three main clinical forms: visceral leishmaniasis (VL), cutaneous leishmaniasis (CL), and mucocutaneous leishmaniasis (MCL). The first-line drugs for leishmaniasis treatment are pentavalent antimonials, which have adverse effects and high toxicity. In this context, new therapies have been explored, including plant lectins. Lectins are proteins found in all organisms that can specifically and reversibly bind to free carbohydrates or glycoproteins and glycolipids. The lectin extracted from Canavalia ensiformis seeds, called concanavalin A (ConA), specifically binds to mannose/glucose, and studies have shown that ConA can modulate immune responses, protecting cells against microbial infections. Therefore, this study aims to evaluate the leishmanicidal effect and analyze the possible mechanisms of action of ConA against Leishmania infantum strains. ConA (12–0.37 µM) was incubated with L. infantum (C8) promastigote cultures for 24, 48, and 72 hours, and cell viability was assessed by counting in a Neubauer chamber. The role of the carbohydrate recognition domain (CRD) was subsequently evaluated by associating ConA (5 μM) with 0.1 M α-methyl-mannoside. Fluorescence assays using 2',7'-dichlorodihydrofluorescein diacetate (DCFH2-DA) and propidium iodide (PI) were conducted to investigate the mechanisms of cell death. Scanning electron microscopy (SEM) was used to examine ultrastructural changes induced by ConA. Additionally, synergism and modulation analyses between ConA and amphotericin B (AmB) were performed. Cytotoxicity on RAW 264.7 macrophages was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. ConA exhibited leishmanicidal activity at most tested concentrations in a concentration- and time-dependent manner. The inhibitory concentrations required to eliminate 50% of L. infantum strains were: IC50/24h = 5 μM; IC50/48h = 4 μM; IC50/72h = 3 μM. The α-methyl-mannoside assay demonstrated that the inhibition of promastigote growth caused by ConA was partially reversed, indicating that the lectin's activity is associated with CRD-mediated carbohydrate interactions on the Leishmania membrane. The results showed that ConA can induce the production of reactive oxygen species (ROS) and cause damage to cell membrane integrity, in addition to promoting morphological alterations in parasite membranes. The combination of ConA with AmB was more effective than either compound alone; the association exhibited a synergistic to additive effect (0.57 μM AmB plus 34.5 μM ConA induced 95% growth inhibition), leading to an almost twofold reduction in the required dose of amphotericin B when used alone. Furthermore, at subinhibitory concentrations, ConA was able to modulate AmB activity at all tested concentrations. Cytotoxicity analyses revealed that neither ConA alone nor in combination with AmB exhibited toxicity in RAW 264.7 cells. Instead, an increase in cell proliferation was observed. These findings suggest that ConA has antipromastigote potential and a possible synergistic interaction with amphotericin B against L. infantum strains, highlighting its potential as a promising candidate for improving leishmaniasis treatment.

COMMITTEE MEMBERS:
Externa à Instituição - RAQUEL GUIMARÃES BENEVIDES - UFC
Presidente - CLAUDENER SOUZA TEIXEIRA
Externa à Instituição - DAIANY ALVES RIBEIRO
Interna - JACQUELINE COSMO ANDRADE PINHEIRO