title: Peroxiredoxins play a major role in protecting Trypanosoma cruzi against macrophage- and endogenously-derived peroxynitrite.
abstract: There is increasing evidence that Trypanosoma cruzi antioxidant enzymes play a key immune evasion role by protecting the parasite against macrophage-derived reactive oxygen and nitrogen species. Using T. cruzi transformed to overexpress the peroxiredoxins TcCPX (T. cruzi cytosolic tryparedoxin peroxidase) and TcMPX (T. cruzi mitochondrial tryparedoxin peroxidase), we found that both cell lines readily detoxify cytotoxic and diffusible reactive oxygen and nitrogen species generated in vitro or released by activated macrophages. Parasites transformed to overexpress TcAPX (T. cruzi ascorbate-dependent haemoperoxidase) were also more resistant to H2O2 challenge, but unlike TcMPX and TcCPX overexpressing lines, the TcAPX overexpressing parasites were not resistant to peroxynitrite. Whereas isolated tryparedoxin peroxidases react rapidly (k=7.2 x 10(5) M(-1) x s(-1)) and reduce peroxynitrite to nitrite, our results demonstrate that both TcMPX and TcCPX peroxiredoxins also efficiently decompose exogenous- and endogenously-generated peroxynitrite in intact cells. The degree of protection provided by TcCPX against peroxynitrite challenge results in higher parasite proliferation rates, and is demonstrated by inhibition of intracellular redox-sensitive fluorescence probe oxidation, protein 3-nitrotyrosine and protein-DMPO (5,5-dimethylpyrroline-N-oxide) adduct formation. Additionally, peroxynitrite-mediated over-oxidation of the peroxidatic cysteine residue of peroxiredoxins was greatly decreased in TcCPX overexpressing cells. The protective effects generated by TcCPX and TcMPX after oxidant challenge were lost by mutation of the peroxidatic cysteine residue in both enzymes. We also observed that there is less peroxynitrite-dependent 3-nitrotyrosine formation in infective metacyclic trypomastigotes than in non-infective epimastigotes. Together with recent reports of up-regulation of antioxidant enzymes during metacyclogenesis, our results identify components of the antioxidant enzyme network of T. cruzi as virulence factors of emerging importance.
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
authors.forename: Lucía
authors.initials: L
authors.lastname: Piacenza
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Peluffo
authors.forename: María Noel
authors.initials: MN
authors.lastname: Alvarez
authors.forename: John M
authors.initials: JM
authors.lastname: Kelly
authors.forename: Shane R
authors.initials: SR
authors.lastname: Wilkinson
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
mesh_terms: D000818:Animals; D014355:Chagas Disease / Q000453:epidemiology / Q000517:prevention & control; D006801:Humans; D007700:Kinetics; D007843:Latin America / Q000453:epidemiology; D008264:Macrophages / Q000469:parasitology / Q000502:physiology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D054464:Peroxiredoxins / Q000235:genetics / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000494:pharmacology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014344:Trypanocidal Agents / Q000494:pharmacology*; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000201:enzymology*; D014774:Virulence
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; D014344:Trypanocidal Agents; D030421:Peroxynitrous Acid; D054464:Peroxiredoxins