FÁRMACOS ANTILEISHMANIAIS: ENSAIOS DE ATIVIDADE ANTILEISHMANIA E MECANISMOS DE AÇÃO DE COMPLEXOS DE USNATO COM ÍONS LANTANÍDEOS E DROGAS DE REFERÊNCIA

Abstract

Leishmaniases are a group of infectious, parasitic diseases caused by parasites of the genus Leishmania sp. These diseases are endemic in several countries, including Brazil, where they pose a significant public health threat. The complexity of the disease, characterized by its diverse clinical manifestations, poses a substantial challenge in the diagnosis and treatment of leishmaniasis. Adherence to treatment regimens is hindered by adverse reactions to medications, which can lead to therapeutic failure, recurrent infections, and even fatal outcomes. Leishmania (L.) amazonensis, a prominent species in the American continent, exhibits diverse infectivity phenotypes, manifesting as anything from localised cutaneous lesions (Cutaneous Leishmaniasis, CL) to disseminated lesions, and, in more severe cases, visceralization. Previous studies using usnic acid have shown effective and promising results against species of Leishmania sp. The aim of this study was to evaluate the anti-leishmanial action of sodium usnate (soluble form of usnic acid - SAU) complexed with the lanthanide ions lanthanum - La(III), neodymium - Nd(III), gadolinium - Gd(III), terbium - Tb(III), europium - Eu(III) and samarium - Sa(III) and to clarify their possible mechanisms of leishmanicidal action. In addition, the aim was to analyse the in vitro behaviour of three strains of L. amazonensis against the reference drugs used in clinical practice, two strains isolated from patients - one from a case of CL and the other from a clinical case of visceral leishmaniasis (VL) - and one reference strain. The lanthanide complexes were highly active against promastigote forms (IC50 < 1.50 µM) and intracellular amastigotes (IC50 < 7.52 µM). The EuL3-3H2O (IC50 =2.98 µM; selectivity index, SI=6.73) and NdL3-3H2O (IC50 =2.83 µM; SI=6.97) complexes showed the highest activities, with greater selectivity in amastigote forms. In the course of investigating the mechanism of leishmanicidal action, an increase in the release of nitric oxide (NO) was detected in cells infected with L. amazonensis and treated with EuL3·3H2O (6.25 µg/mL). This finding suggests that this may be one of the mechanisms involved. Furthermore, alterations in mitochondrial membrane potential were evident in parasites exposed to SmL3-4H2O and GdL3-2H2O, suggesting that lanthanides complexed with sodium usnate can enhance their anti-leishmania activity, with the parasite's mitochondria serving as the primary target. With respect to the efficacy of the reference drugs on the various strains of L. amazonensis, it is noteworthy that Amphotericin B exhibited high activity against both evolutionary forms of the parasites. Pentamidine demonstrated notable activity against the MHOM/BR/2022/LV045_22 strain (IC50 = 0.0429 µM), which was isolated from a patient with visceral leishmaniasis (VL), underscoring the potential of pentamidine in the development of technologies aimed at mitigating adverse effects to enhance treatment efficacy.