Avaliação da atividade antileishmanial do extrato de cianobactéria Nostoc sp. e sensibilidade à fármacos em isolados clínicos de Leishmania (L.) infantum

Abstract

In Brazil, the main drugs adopted for the treatment of visceral leishmaniasis are pentavalent antimony (Glucantime®) and the antifungal Amphotericin B (AmB), both with high toxicity and occurrences of therapeutic failures reported worldwide, which is a complex and multifactorial phenomenon, related with the host-parasite interaction, as well as the response of the parasite to drugs, measured by their sensitivity to drugs. Considering the scarcity of drugs and even phenomena such as drug resistance, identifying new natural compounds with antileishmanial action has been the focus of much research. In this sense, cyanobacteria are photosynthetic organisms, responsible for the production of bioactive compounds with antiparasitic activity. Thus, the present study aimed to test the antileishmanial activity of the cyanobacteria extract Nostoc sp. and to evaluate drug sensitivity in clinical isolates of Leishmania (L.) infantum obtained from patients with VL in the state of Maranhão. To verify the sensitivity of the promastigote forms, the isolates were submitted to cell viability test, using MTT, against trivalent Antimony and Amphotericin B, verifying an EC50 variation from 66.2 ± 9.8 to 155 ± 3.6 μM and 118.9 ± 14.7 nM to 243.5 ± 21.3 nM, respectively. In the intracellular amastigote forms in peritoneal macrophages, evaluated by direct counting, the EC50 values for pentavalent antimony and amphotericin B ranged from 16.1 to 39.3 μM and 0.09 to 0.18 μM, respectively. Furthermore, both in the intracellular promastigote and amastigote forms, a greater tolerance of clinical isolates to antimony was observed, in the tri- or pentavalent forms. In parallel, when evaluating the antileishmanial activity of promastigotes of the reference strain of L. (L.) infantum against the crude extract of cyanobacteria of the genus Nostoc sp. GBBB01, by direct counting, there was a statistically significant difference in concentrations from 500 to 31.25ug/mL in relation to the untreated control, however when the analysis was performed by flow cytometry, these differences were not found. In the intracellular amastigote forms, the crude extract of cyanobacteria of the genus Nostoc sp showed antileishmanial activity, being possible to calculate the IC50, only for one of the clinical isolates (MHOM/BR/2018/ASFF- MA) evaluated. Furthermore, the crude cyanobacteria extract also did not induce cytotoxic effect on peritoneal macrophages under the conditions tested. Thus, it can be stated that there is an intraspecific variability in the sensitivity to traditional drugs (Antimonium and Amphotericin B) in clinical isolates from this highly endemic area for VL, and that the crude extract of cyanobacteria of the genus Nostoc sp. GBBB01 presented antileishmanial activity, which needs to be better explored due to the divergence of results between analysis techniques, the need for new tests, considering that even for the cyanobacteria extract there is variation in this activity depending on the strain of L. infantum evaluated.