The Leishmaniasis is an infectious disease caused by parasites of the Leishmania genus and are distributed in different parts of the world. This pathology manifests in several clinical forms: Visceral leishmaniasis (VL), cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL). The Leishmania parasite presents two evolutionary forms: promastigote form, free life parasite, and amastigotes, intracellular binding, present mainly in the mononuclear phagocytic cells. The growth inhibition or destruction of parasites within the host cell is an essential to break the infection mechanism. Inhibition of macrophage leishmanicidal effect appears to be related to the ability of some species to inhibit the nitric oxide (NO) production. Recent studies have shown that some species of Leishmania have the ability to produce NO by the constitutive form of nitric oxide synthase (cNOS). This work aims to detect and locate the cNOS enzyme present in Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis promastigotes. For this reason, this study used flow cytometry, which allowed to quantify NO production in parasites, indicating the increased activity of the cNOS enzyme in Leishmania (Leishmania) amazonensis compared with Leishmania (Viannia) braziliensis species. We performed immunostaining of promastigotes with anti-cNOS antibody to watch the ultrastructural localization of the enzyme by transmission electron microscopy (TEM), then co-labeling with anti-cNOS and anti-GAPDH antibody to confirm the probable compartmentalization this enzyme in glycossomal organelles. The results suggest that NO production by different strains of Leishmania is a process located in the glycossomal organelles capturing L-arginine from the host cell, the substrate depletion deprives the host to synthesize the harmful exogenous NO to the parasite. This modulation suggests another escape mechanism that trypanosomatid protozoa present in the complex host-parasite interaction.
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