Trypanosoma cruzi Induces the Reactive Oxygen Species-PARP-1-RelA Pathway for Up-regulation of Cytokine Expression in Cardiomyocytes

In this study, we demonstrate that human cardiomyocytes (AC16) produce reactive oxygen species (ROS) and inflammatory cytokines in response to Trypanosoma cruzi. ROS were primarily produced by mitochondria, some of which diffused to cytosol of infected cardiomyocytes. These ROS resulted in an increase in 8-hydroxyguanine lesions and DNA fragmentation that signaled PARP-1 activation evidenced by poly(ADP-ribose) ( PAR) modification of PARP-1 and other proteins in infected cardiomyocytes. Phenyl-alpha-tert-butylnitrone blocked the mitochondrial ROS (mtROS) formation, DNA damage, and PARP-1 activation in infected cardiomyocytes. Further inhibition studies demonstrated that ROS and PARP-1 signaled TNF-alpha and IL-1 beta expression in infected cardiomyocytes. ROS directly signaled the nuclear translocation of RelA (p65), NF-kappa B activation, and cytokine gene expression. PARP-1 exhibited no direct interaction with p65 and did not signal its translocation to nuclei in infected cardiomyocytes. Instead, PARP-1 contributed to PAR modification of p65-interacting nuclear proteins and assembly of the NF-kappa B transcription complex. PJ34 (PARP-1 inhibitor) also prevented mitochondrial poly(ADP-ribosyl)ation (PARylation) and ROS formation. We conclude that T. cruzimediated mtROS provide primary stimulus for PARP-1-NF-kappa B activation and cytokine gene expression in infected cardiomyocytes. PAR modification of mitochondrial membranes then results in a feedback cycle of mtROS formation and DNA damage/PARP-1 activation. ROS, either through direct modulation of cytosolic NF-kappa B, or via PARP-1-dependent PAR modification of p65-interacting nuclear proteins, contributes to cytokine gene expression. Our results demonstrate a link between ROS and inflammatory responses in cardiomyocytes infected by T. cruzi and provide a clue to the pathomechanism of sustained inflammation in Chagas disease.