GENE EXPRESSION RESPONDED TO FAS STIMULATION IN TRAYPANOSOMA CRUZI INFECTED HOST CELLS USING DNA MICROARRAY TECHNIQUE

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Thypanosoma cruzi the protozoan parasite that causes Chagas' disease in Latin America. We reported that T.cruzi infection inhibits Fas-mediated apoptosis in host cells, and this inhibition is thought to be a defense strategy for the parasite to escape from host immune responses. To elucidate a molecular mechanism of the inhibition, we determined the time courses of transcriptional changes in uninfected (control) and T.cruzi infected cells using DNA microarray technology. Human fibrosarcoma cells were infected with T.cruzi, cultured for 3-4 days and stimulated by anti-Fas antibody. Total RNA was extracted and converted to first-strand cDNA: cDNA was labeled with Cy5-dUTP (control) or Cy3-dUTP (infected) and hybridized to human apoptosis chips consisting of 164 apoptosis related genes. Apoptosis inhibitory genes (apoptosis inhibitor 1 and c-FLLIP) and caspases (caspase-1, -4, and -7) showed higher expression levels in T.cruzi infected than in control cells at 10 to 30 mm after Fas stimulation. Further, the fluorescence intensities of I-kB, bcl-W and cell cycle related genes were higher in infected cells at 2 to 24 h after the induction. To determine the consequences of a T.cruzi infection on apoptosis in vivo, we infected Wistar rats with either the T.cruzi Sylvio-X10/7 clone or the Sylvio-X10/4 clone to simulate an acute (lethal) or chronic disease model, respectively. At predetermined times post-infection, paraffin sections of the rats' hearts were processed using the TUNEL reaction to detect apoptotic cells. In the lethal disease model, inflammatory lymphocytes were found around T.cruzi-infected muscle cells at 7 days post-infection. Surprisingly, however, although some of the lymphocytes were TUNEL positive, T.cruzri-infected muscle cells were TUNEL negative. Furthermore, in the chronic disease model it was difficult to find either T.cruzi infected cells or apoptotic cells in the heart sections.