Toll-like receptors (TLRs) are a family of signal transducing molecules which are critical for the induction of innate immunity. They have been associated with cardiomyocyte survival and parasite control. Previously, we demonstrated that cardiomyocytes infected with T. cruzi or treated with cruzipain (Cz), in medium serum deprived, displayed an increase in cell viability.
We investigated the modulation of TLR2 expression and PI3K and MAPKs signaling pathways induced by T. cruzi infection or cruzipain treatment in the cardiomyocyte survival.
Neonatal BALB/c mouse myocytes were cultured with Cz or T. cruzi infected.
The cultures were pre-treatment with pharmacologic inhibitors for each pathway. We observed that Ly294002 (PI3K) and PD098059 (MEK1) but not JNK or p38 MAPK inhibitors (SP600125 or SB203580) increased the apoptotic rate of cardiomyocytes treated with Cz (P<0.01) evaluated through Annexin V/ propidium iodide.
Phosphorylation of Akt and ERK1/2 by Western blot were observed after Cz treatment or T. cruzi infection
Furthermore, Cz up-regulated the TLR2-mRNA, Bcl-2, Bcl- xL and p-Bad expression and diminished the caspase-3 cleavage. Changes in TLR2, Bcl-2 and Bcl-xL expression and phosphorylation of Akt and MAPKs were analyzed by Western blotting. Bad phosphorylation was determined by immunocytochemistry and TLR2-mRNA by RT-PCR
We conclude that T. cruzi infection and Cz treatment of cardiomyocytes activate PI3K/Akt and MEK1/ERK1/2 signaling pathways and are able to modulate TLR2 expression.
