Effect of Iron Uptake on Expression of Cytosolic Fe-S Cluster Machinery Proteins in Leishmania donovani
Parasites of genus Leishmania are the causative agents of complex neglected diseases called Leishmaniasis, and are a significant global health concern. They are unicellular, kinetoplastid, dimorphic protozoan parasites that exist in the motile promastigote form in sandflies, and the amastigote form within infected mammalian macrophages. Although most microbes are destroyed in the harsh environment of phagocytes, Leishmania have developed an adaptive mechanism that allows them to survive inside macrophages. Acquisition of essential elements is an important evolutionary adaptation gained by the parasite, in which iron is one such element. The utility of iron resides in its redox potential ability (Fe2+/Fe3+switch), and thus functions in the biological systems by its incorporation into the proteins, in order to impart stability and catalytic potential; e.g. cofactor Fe-S clusters, oxygen sensing and transport, cellular and energy metabolism. Iron acquisition is essential for survival, but the parasites are also vulnerable to its toxicity. Ferrous (Fe2+) iron is the biologically active form of iron and can be transported across membranes. However, the redox potential of ferrous iron also generates cellular toxicity. Thus, ferrous iron is stored either as a complex with proteins, or is oxidized to a less toxic ferric form. We aim to explore the effect of ferrous sulphate (FeSO4) as a source of Fe2+ ion in various concentrations in Leshmania donovani, the causative organism of Visceral Leishmaniasis. We found that at lower concentrations like 100 µM, 250 µM and 500 µM, the growth rate and declining phase of the parasite is faster than the control, and the growth and survival is lesser at a higher concentration like 1mM, 2mM, 3mM, 5mM, 10mM and 15mM. 20mM is found to be highly toxic because the parasites do not show any growth after 2 days. An assay of Reactive Oxygen Species (ROS) confirms that the amount of ROS increases more in lower concentrations of, and less in higher concentrations.
Keywords: Leishmania growth, viability, FeSO4 concentrations, ROS level, Iron toxicity