Virulent Trypanosoma cruzi strains express high levels of antioxidant enzymes

LUCÍA PIACENZA, M. PAOLA ZAGO, GONZALO PELUFFO, JOHN M KELLY, SHANE R WILKINSON, MIGUEL BASOMBRIO AND RAFAEL RADI

Montevideo, Uruguay

Congreso; V Meeting of SFRBM-South American Group. V International Conference on Peroxynitrite and Reactive Nitrogen Species; 2007

Society for Free Radical Biology and Medicine- South American Group

The overexpression of antioxidant enzymes in Trypanosoma cruzi, including mitochondrial (TcMPX) and cytosolic (TcCPX) tryparedoxin peroxidases, ascorbate peroxidase (TcAPX) and iron-containing superoxide dismutases (Fe-SODs) is  being revealed as a key mechanism for immune evasion and defense against macrophage-derived reactive oxygen and nitrogen species. Increased levels of TcMPX, TcAPX and Fe-SODA have been found in the infective metacyclic-trypomastigote of T.cruzi compared to the non-infective epimastigote. Moreover, release Fe-SOD during infection and increase expression of Fe-SOD in benznidazole-resistant strains, places the antioxidant enzyme network of T. cruzi as an emerging virulence factor. We evaluated the sensitivity of T.cruzi strains towards biologically-relevant oxidants (hydrogen peroxide, H2O2 and peroxynitrite, ONOO-). We used several isolates that belongs to two major phylogenetic lineages TCI and TCII characterized by different virulence behavior in mice, ranging from highly aggressive to extremely attenuated at the histopathology level. Epimastigotes of highly virulent T. cruzi populations were more resistant to H2O2 and ONOO- challenge as evaluated by the [3H]-Thymidine incorporation assay. In the same line, ONOO--dependent protein 3-nitrotyrosine formation was lower in the virulent strains. We also analyzed mRNA levels of TcMPX, TcCPX, TcAPX and Fe-SOD by RT-PCR. We found a positive correlation between mRNA levels of TcAPX, TcCPX and Fe-SODA with strain virulence, which is in agreement with the higher resistance observed against H2O2 and ONOO- challenge.  Levels of antioxidant enzymes were also elevated in trypomastigotes when compared to epimastigotes. Our data strongly support the hypothesis that the parasite antioxidant enzyme armamentarium present at the onset of macrophage invasion plays a central role in parasite-host cell interactions and in the establishment of the infection.