The signaling pathway PI3K/Akt is involved in IL-6 production, TLR2 expression and survival of cardiomyocytes during Trypanosoma cruzi infection

AOKI MP; CARRERA-SILVA AE; PELLEGRINI AV; GUIÑAZÚ NL; CANO RC; GEA S

Rio de Janeiro. Brasil

Congreso; 13th International Congress of Immunology; 2007

Pathogen recognition receptors from the TLR family are crucial for the generation of effective immunity but are also involved in mammalian cell survival. Little is known about the innate immunity of cardiomyocytes and parasite infection. We previously demonstrated that T. cruzi infection as well as cruzipain, a major parasite antigen, protected isolated cardiac cells against apoptosis induced by growth factor deprivation. The anti-apoptotic effect was mediated by PI3K/Akt and MEK1/ERK signaling pathways. Here we analyzed the interplay between the cardiomyocyte innate immune response and T. cruzi infection. Neonatal BALB/c mouse myocytes were cultured with cruzipain or infected with different doses of trypomastigotes from Tulahuen strain. We found that parasite infection as well as cruzipain strongly up-regulate the membrane expression and mRNA of TLR2 but not TLR4 evaluated by flow cytometry, immunocytochemistry and RT-PCR respectively. Employing ELISA assays, we observed that both stimuli strongly increase the release of the pro-inflammatory cytokine IL-6 (medium 950.8±120.2pg/ml; cruzipain 4748.3±920.2pg/ml; trypomastigotes 3107.9±980.2pg/ml) but not IL-4 anti-inflammatory cytokine. In addition, NF-kB transcription factor translocates to the cardiac cell nucleus after T. cruzi infection indicating that it is activated by the parasite. The pharmacological inhibition of NF-kB with TPCK (25 µM) or PI3K with Ly294002 (25 µM) lead to a complete abrogation of cruzipain induced anti-apoptosis, IL-6 release and TLR2 up-regulation. These results strongly suggest the existence of a very tight link among cardiomyocyte innate immunity and its response to T. cruzi infection.