Susceptibility of Leishmania amazonensis Axenic Amastigotes to the Calpain Inhibitor MDL28170

Leishmaniasis encompasses a group of neglected diseases caused by flagellated protozoa belonging to the Leishmania genus, associated with high morbidity and mortality. The search for compounds with anti-Leishmania activity that exhibit lower toxicity and can overcome the emergence of resistant strains remains a significant goal. In this context, the calpain inhibitor MDL28170 has previously demonstrated deleterious effects against promastigote forms of Leishmania amazonensis, which led us to investigate its role on axenic amastigote forms. The calpain inhibitor MDL28170 was able to decrease the viability of amastigotes in a typically dose-dependent manner. The treatment with the IC₅₀ dose (13.5 μM) for 72 h led to significant amastigote lysis and increased cell-to-cell aggregation. Ultrastructural analysis revealed several cellular alterations, including disruption of the trans-Golgi network and the formation of autophagosomes when treated with MDL28170 at ½ × IC₅₀ dose. Additionally, mitochondrial swelling and the formation of concentric membranous structures inside the mitochondrion were observed after incubation with the IC₅₀ dose. These results reinforce the potential application of the calpain inhibitor MDL28170 against L. amazonensis, highlighting its effectiveness and possible mechanism of action against the parasite.