Avaliação do potencial leishmanicida in vitro dos polissacarídeos sulfatados das algas marinhas vermelhas Asparagopsis armata e Gracilaria cornea

Abstract

Pharmacotherapy for the treatment of leishmaniosis presents a series of severe side effects, in addition to increasing drug resistance. Therefore, it is necessary to prospect for new alternative therapies that are effective, safe, and acceptable. Total Sulfated Polysaccharides (TSP) from the red seaweed Asparagopsis armata and Gracilaria cornea possess various biological effects, such as antinociceptive and anti-inflammatory effects, and are therefore considered promising natural sources for application in the treatment of different diseases. However, there are no studies on the leishmanicidal potential of those species so far. In view of the above, this study aimed to evaluate the leishmanicidal potential, in vitro, against Leishmania braziliensis and

cytotoxic potential of TSP of the seaweed species A. armata (Aa-TSP) and G. cornea (Gc- TSP). To this end, TSP were obtained through proteolytic digestion of those algae using papain

(60°C, 6h), yielding 11,29% and 14,63% for Aa-TSP and Gc-TSP, respectively. Regarding the contents of soluble carbohydrates and free sulfate, Aa-TSP presented yields of 47,54% and 33,44%, respectively, and Gc-TSP presented yields of 69,40% and 11,14%. Regarding the

determination of soluble protein levels, they were found to be absent. To evaluate the anti- promastigote effect, the TSP were added to a suspension of promastigotes for 24 and 48h, and

the effect was assessed through microscopic analysis using Trypan Blue. J774 lineage macrophages were infected with L. braziliensis and treated or untreated with the TSPs (5, 10, 25, 50 and 100 g/mL) for the analysis of parasite load, cytokine, and NO levels, after 24 and

48h. Futhermore, TSP cytotoxicity was assessed using the MTT essay. After evaluation, Gc- TSP presented the smallest reduction in cell viability, not reaching 50% reduction (at 24 and

48h). Only the concentration of 100 g/mL of Aa-TSP caused a significant reduction in promastigote survival after 24h (45,96% ± 11,89%). However, Aa-TSP and Gc-TSP caused significant reduction in intracellular parasite load, exhibiting the greatest reduction at 100 g/mL (98,62% ± 0,27% and 92,02% ± 0,46%, respectively) respectively after 48h. An increase in NO was observed in response to Aa-TSP after 24h, and in TNF-a production following treatment with Aa-TSP and Gc-TSP after 48h. A decrease in IL-10 levels occurred after 24h, although not at all concentrations. In view of these results, Aa-TSP and Gc-TSP exhibited a promising in vitro effect in J744 macrophages infected with L. braziliensis, reducing the parasite load and suggesting immunomodulatory potential. However, further studies are required to better investigate the mechanisms of action of these TSP in macrophages and in

other experimental models, considering the possible involvement of additional signaling pathways that may have contributed intracellularly to the observed leishmanicidal effect.