The survival of cadiomyocytes induced by Trypanosoma cruzi experimental infection is dependent on TLR2 signalling, IL6 production and STAT3 activation

PONCE NE; CANO R; CARRERA SILVA A; GEA S

Bs As

Congreso; First french-Argentine Immunology Congress FAIC 2010; 2010

Sociedad Argentina de Inmunologia

Local innate immunity plays a central role in defense response and homeostasis in the heart. Previously, we have reported that T. cruzi infection protects isolated cardiomyocytes from apoptosis. Our objective was to elucidate cardiomyocyte innate immune response to T. cruzi infection and its possible role in the cytoprotection. We found that TLR2 expression, but not TLR4, was strongly increased by the parasite in BALB/c neonatal cardiomyocyte cultures. Among the cytokines tested (IL6, TNFá, IL1b, IL17, IL10 and IL4), we detected a rapid and sustained production of IL6 (P<0.02), and NF-kB-dependent (P<0.001), regardless of the cell:parasite ratio used. In order to test the involvement of TLR2 in the inhibition of apoptosis, primary cultures were transfected with a dominant-negative TLR2 (dnTLR2) plasmid or its control vector (CV), followed by incubation with T. cruzi (Tulahuen 1:1) or the TLR2 agonist PAM3CSK4 (PAM3) and then, were subjected to serum starvation for 48h. FACS analysis showed that overexpression of dnTLR2 blocked the parasite- and PAM3-induced cytoprotective effect, whereas in cultures transfected with CV both stimulus decreased the apoptotic rate (P<0.001). Besides, infection induced IL6 production in CV-transfected cells (P<0.05), but it was blocked in infected cultures transfected with dnTLR2. To investigate whether IL6 released in response to parasite plays a role in the cardiomyocyte survival, this cytokine was depleted using neutralizing antibody. The treatment abolished the parasite-induced cytoprotection (P<0.02). In addition, we found that IL6 production strikingly increased the STAT3 phosphorylation in primary cultures incubated with supernatants from infected monolayers. Our results strongly suggest that the triggering of TLR2 signalling, followed by IL6 production and STAT3 activation, play a key role in T. cruzi-induced cardiomyocyte protection.