Cytosolic Fe-superoxide dismutase safeguardsTrypanosoma cruzifrom macrophage-derived superoxide radical

Abstract

Trypanosoma cruzi, the causative agent of Chagas disease (CD), contains exclusively Fe-dependent superoxide dismutases (Fe-SODs). During T. cruzi invasion to macrophages, superoxide radical (O2•−) is produced at the phagosomal compartment toward the internalized parasite via NOX-2 (gp91-phox) activation. In this work, T. cruzi cytosolic Fe-SODB overexpressers (pRIBOTEX–Fe-SODB) exhibited higher resistance to macrophage-dependent killing and enhanced intracellular proliferation compared with wild-type (WT) parasites. The higher infectivity of Fe-SODB overexpressers compared with WT parasites was lost in gp91-phox−/− macrophages, underscoring the role of O2•− in parasite killing. Herein, we studied the entrance of O2•− and its protonated form, perhydroxyl radical [(HO2•); pKa = 4.8], to T. cruzi at the phagosome compartment. At the acidic pH values of the phagosome lumen (pH 5.3 ± 0.1), high steady-state concentrations of O2•− and HO2• were estimated (∼28 and 8 µM, respectively). Phagosomal acidification was crucial for O2•− permeation, because inhibition of the macrophage H+-ATPase proton pump significantly decreased O2•− detection in the internalized parasite. Importantly, O2•− detection, aconitase inactivation, and peroxynitrite generation were lower in Fe-SODB than in WT parasites exposed to external fluxes of O2•− or during macrophage infections. Other mechanisms of O2•− entrance participate at neutral pH values, because the anion channel inhibitor 5-nitro-2-(3-phenylpropylamino) benzoic acid decreased O2•− detection. Finally, parasitemia and tissue parasite burden in mice were higher in Fe-SODB–overexpressing parasites, supporting the role of the cytosolic O2•−-catabolizing enzyme as a virulence factor for CD.

Functions of ROS in Macrophages and Antimicrobial Immunity

“…Since no ROS measurements in Nox2- or Nox4-deficient cells were performed, the location (T.g.-containing phagosome or other cellular organelles) and the function (directly or indirectly antiparasitic) of Nox4-derived ROS remained elusive. The ability of Toxoplasma parasites to detoxify phagosomal ROS was demonstrated with the evolutionary related Toxoplasma cruzii in phagosomes of J774A.1 macrophage-like cells (J774) and BMDM [ 283 ]. No ROS measurements with classical probes were performed, but elegant and technically challenging direct measurements of O 2 ●− in the parasitic cytosol and the phagosomes were performed in WT and Nox2-deficient J774 cells.…”

Boronate-Based Probes for Biological Oxidants: A Novel Class of Molecular Tools for Redox Biology

“…Because erythrocytes contain a large amount of hemoglobin, they serve as a sink/scavenger of • NO, preventing it from reacting with Nox2-derived . Fl-B was also instrumental in demonstrating that Trypanosoma cruzi uses the Fe-superoxide dismutase enzyme to resist being killed by macrophages via removing phagosomal (Nox2-derived) and limiting ONOO − formation (Martinez et al, 2019 ).…”

Redox Balance Keepers and Possible Cell Functions Managed by Redox Homeostasis in Trypanosoma cruzi

“…cytotoxic oxidants (Piacenza et al, 2008;Arias et al, 2013;Martínez et al, 2019). The expression levels of cTXNPx as well as of mTXNPx are increased in infective and intracellular stages of the parasite (Zago et al, 2016); these two enzymes work in concert to control the cytosolic and mitochondrial oxidative stress (De Figueiredo Peloso et al, 2011), and are extensively studied for the design of anti-parasite therapies.…”