Avaliação da atividade anti-promastigota da lectina obtida das sementes de Luetzelburgia auriculata (Allemão) Ducke sobre Leishmania major

Abstract

Leishmaniasis is an infectious disease that interferes in patients quality of life and can be classified into Visceral Leishmaniasis (LV), when there is organ involvement, and Tegumentary Leishmaniasis (LT), when there is integument involvement. TL is most often caused by the species L. braziliensis, L. guyanensis and L. amazonensis on the American continent, and by L. major, L. tropica and L. aethiopica on the European, African and Asian continents. On their cell surface, leishmanias have a large amount of glycoconjugates that perform important functions for the parasite throughout its life cycle. Among these glycoconjugates, Lipophosphoglycans (LPGs) are in greatest quantity. L. major's LPG is a polymer that contains mostly galactose. The treatment of leishmaniasis is based on the administration of glucantime and amphotericin B, which, although effective, have limitations stimulating the search for therapeutic alternatives. In this context, lectins stand out due to their already known ability to interact with glycans of various pathogens. The agglutinin obtained from Luetzelburgia auriculata (LAA) seeds has binding affinity for galactose and lactose. Based on these findings, the research evaluated the in vitro anti-promastigote potential of LAA in L. major strain. Promastigotes were incubated with different concentrations of LAA (320 – 5 μg/mL) and cell viability determined by Neubauer chamber counting. After determining the IC50/24h of the LAA, the participation of the carbohydrate recognition domain (CRD) in lectin activity was evaluated. Fluorescence assays with 2’,7’-dichlorodihydrofluorescein diacetate (DCFH2-DA) and Propidium Iodide (PI) were performed in order to verify the possible mechanisms of action of lectin. Scanning electron microscopy was used to evaluate the possible morphological changes induced by LAA in promastigote forms. The effect of the association between LAA and Amphotericin B and glucantime on promastigote forms was also evaluated. LAA inhibited the growth of promastigote forms of L. major in a time and concentration-dependent manner, with IC50/24h values = 82 μg/mL; IC50/48h = 25 μg/mL; IC50/72h = 20 μg/mL. The data obtained showed that lectin activity is related to its ability to recognize and bind to glycans present in L. major and that treatment with LAA is capable of inducing ROS production, damage to cell membrane integrity and morphological changes in parasites. LAA has also been shown to have a modulatory effect when associated with amphotericin B, improving the activity of this drug. Our results present LAA as a promising alternative in the treatment of cutaneous leishmaniasis caused by L. major, requiring in vivo studies that can elucidate its mechanisms of action in a biological system.