PARP1-cGAS-NF-kappaB pathway of proinflammatory macrophage activation by extracellular vesicles released during Trypanosoma cruzi infection and Chagas disease.

Trypanosoma cruzi (T. cruzi) is the etiological agent of Chagas cardiomyopathy. In the present study, we investigated the role of extracellular vesicles (Ev) in shaping the macrophage (Mphi) response in progressive Chagas disease (CD). We purified T. cruzi Ev (TcEv) from axenic parasite cultures, and T. cruzi-induced Ev (TEv) from the supernatants of infected cells and plasma of acutely and chronically infected wild-type and Parp1-/- mice. Cultured (Raw 264.7) and bone-marrow Mphi responded to TcEV and TEv with a profound increase in the expression and release of TNF-alpha, IL-6, and IL-1beta cytokines. TEv produced by both immune (Mphi) and non-immune (muscle) cells were proinflammatory. Chemical inhibition or genetic deletion of PARP1 (a DNA repair enzyme) significantly depressed the TEv-induced transcriptional and translational activation of proinflammatory Mphi response. Oxidized DNA encapsulated by TEv was necessary for PARP1-dependent proinflammatory Mphi response. Inhibition studies suggested that DNA-sensing innate immune receptors (cGAS>>TLR9) synergized with PARP1 in signaling the NFkappaB activation, and inhibition of PARP1 and cGAS resulted in >80% inhibition of TEv-induced NFkappaB activity. Histochemical studies showed intense inflammatory infiltrate associated with profound increase in CD11b+CD68+TNF-alpha+ Mphi in the myocardium of CD wild-type mice. In comparison, chronically infected Parp1-/- mice exhibited low-to-moderate tissue inflammation, >80% decline in myocardial infiltration of TNF-alpha+ Mphi, and no change in immunoregulatory IL-10+ Mphi. We conclude that oxidized DNA released with TEv signal the PARP1-cGAS-NF-kappaB pathway of proinflammatory Mphi activation and worsens the chronic inflammatory pathology in CD. Small molecule antagonists of PARP1-cGAS signaling pathway would potentially be useful in reprogramming the Mphi activation and controlling the chronic inflammation in CD.