Mitochondrial superoxide radicals mediate programmed cell death in Trypanosoma cruzi: cytoprotective action of mitochondrial iron superoxide dismutase overexpression

Abstract

Trypanosoma cruzi undergo PCD (programmed cell death) under appropriate stimuli, the mechanisms of which remain to be established. In the present study, we show that stimulation of PCD in T. cruzi epimastigotes by FHS (fresh human serum) results in rapid (<1 h) externalization of phosphatidylserine and depletion of the low molecular mass thiols dihydrotrypanothione and glutathione. Concomitantly, enhanced generation of oxidants was established by EPR and immuno-spin trapping of radicals using DMPO (5,5-dimethylpyrroline-N-oxide) and augmentation of the glucose flux through the pentose phosphate pathway. In the early period (<20 min), changes in mitochondrial membrane potential and inhibition of respiration, probably due to the impairment of ADP/ATP exchange with the cytosol, were observed, conditions that favour the generation of O2*-. Accelerated rates of mitochondrial O2*- production were detected by the inactivation of the redox-sensitive mitochondrial aconitase and by oxidation of a mitochondrial-targeted probe (MitoSOX). Importantly, parasites overexpressing mitochondrial FeSOD (iron superoxide dismutase) were more resistant to the PCD stimulus, unambiguously indicating the participation of mitochondrial O2*- in the signalling process. In summary, FHS-induced PCD in T. cruzi involves mitochondrial dysfunction that causes enhanced O(2)(*-) formation, which leads to cellular oxidative stress conditions that trigger the initiation of PCD cascades; moreover, overexpression of mitochondrial FeSOD, which is also observed during metacyclogenesis, resulted in cytoprotective effects.

Iron metabolism in trypanosomatids, and its crucial role in infection

“…death mirrors the mechanism shown in T. cruzi for complement-induced programmed cell death of epimastigotes, which is mediated by mitochondrial O 2 .x (Piacenza et al 2007). Thus, the drug-induced death of Leishmania may involve activation of their cell death programme at the mitochondrial level.…”

Antagonic activities of Trypanosoma cruzi metacaspases affect the balance between cell proliferation, death and differentiation

“…The filled arrowhead shows that cells with a high content of TcMCA3-eGFP remain arrested in the DNA synthesis phase row). 23,26 These cells are clearly progressing through the cell cycle as about 80% of them had duplicated the DNA content 9 h after HU removal. In contrast, a dissimilar behaviour can be observed in the induced population (Figure 4e, second row), depending on the TcMCA3-eGFP levels.…”

Cytochrome c-mediated oxidation of hydroethidine and mito-hydroethidine in mitochondria: Identification of homo- and heterodimers

“…Moreover, recent research suggests that mitochondrial cytochromes could also oxidize HE to a dimeric product [8]. The probe (MitoSOX ™ Red) is being used in the detection and quantitation of mitochondria-generated superoxide [9][10][11]. As mitochondria are enriched with cyt c 3+ (0.1 to 5 mM) [12,13] within the intermembrane compartment, we decided to investigate this reaction in detail.…”