Redox metabolism as a key driver of metacyclic promastigote to amastigote transition in Leishmania infantum.

Leishmania is a protozoan parasite causing leishmaniasis, a disease affecting millions globally. It is transmitted through bites from infected sand-flies, primarily of the Phlebotomus spp. or Lutzomyia spp. The parasite has two main life stages: the promastigote, found in the insect vector, and the amastigote, residing in the macrophages of the host. The mechanisms behind stage differentiation are not well understood. This study shows that redox metabolism modulations are crucial for the life cycle of Leishmania infantum, influencing stage transitions. Inhibiting redox metabolism caused significant morphological changes, from flagellated promastigotes to amastigote-like forms. These changes were evidenced by transcriptomic and metabolomic analyses. RNA sequencing indicated that redox inhibition affected several genes, including one for an iron transporter, LINF_310039600. Using CRISPR-Cas9, knockout mutants of this gene were created, revealing upregulation of amastin, a marker of the amastigote form, underscoring the role of redox metabolism in stage differentiation.