Mitochondrial superoxide radicals mediate programmed cell death in Trypanosoma cruzi: cytoprotective action of mitochondrial iron superoxide dismutase overexpression.
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.
Piacenza
Lucía
L
Departamento de Bioquímica, Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
Irigoín
Florencia
F
Alvarez
María Noel
MN
Peluffo
Gonzalo
G
Taylor
Martin C
MC
Kelly
John M
JM
Wilkinson
Shane R
SR
Radi
Rafael
R
D000818:Animals; D017209:Apoptosis; D045304:Cytochromes c / Q000378:metabolism; D019610:Cytoprotection; D015971:Gene Expression Regulation, Enzymologic; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism; D007150:Immunohistochemistry; D008928:Mitochondria / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D018384:Oxidative Stress; D013095:Spermidine / Q000031:analogs & derivatives / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*
D013481:Superoxides; D045304:Cytochromes c; C044809:trypanothione; D013482:Superoxide Dismutase; D009247:NADH, NADPH Oxidoreductases; C049608:trypanothione reductase; D005978:Glutathione; D013095:Spermidine