Origin of monocytes/macrophages contributing to chronic inflammation in chagas disease: Sirt1 inhibition of fak-nfκb-dependent proliferation and proinflammatory activation of macrophages

Background: Trypanosoma cruzi (Tc) causes Chagas disease (CD) that is the most frequent cause of heart failure in Latin America. TNF-α⁺ monocytes/macrophages (Mo/Mϕ) are associated with inflammatory pathology in chronic CD. In this study, we determined the progenitor lineage of Mo/Mϕ contributing to inflammation and examined the regulatory role of SIRT1 in modulating the Mo/Mϕ response in Chagas disease. Methods and Results: C57BL/6 mice were infected with Tc, treated with SIRT1 agonist (SRT1720) after control of acute parasitemia, and monitored during chronic phase (150 days post-infection). Flow cytometry studies showed an increase in maturation of bone marrow hematopoietic stem cell (HSC)-derived Mo of proinflammatory and anti-inflammatory phenotype in acutely-and chronically-infected mice; however, these cells were not increased in splenic compartment of infected mice. Instead, yolk-sac-derived CD11b⁺ F4/80⁺ Mo/Mϕ were increased in sinusoidal compartment of Chagas mice. The splenic CD11b⁺ F4/80⁺ Mo/Mϕ of Chagas (vs. control) mice exhibited increased mRNA, protein, and surface expression of markers of proinflammatory phenotype (CD80⁺/CD64⁺ > CD200⁺/CD206⁺) associated with proinflammatory cytokines response (IL-6+TNF-α >> Arg-1+IL-10), and these were also detected in the myocardium of chronically infected mice. Infected mice treated with SRT1720 (vs. infected/untreated) exhibited decreased splenic expansion and myocardial infiltration of proinflammatory Mo/Mϕ. SRT1720 did not alter the inherent capability of splenic Mo/Mϕ of Chagas mice to respond to pathogen stimulus. Instead, SRT1720 dampened the Tc-induced increase in the expression and/or phosphorylation of focal adhesion kinase (FAK) and downstream transcription factors (Pu.1, c-Myb, and Runx1) involved in Mϕ proliferation and migration and Notch1 involved in functional activation. Studies in cultured Mϕ confirmed the agonistic effects of SIRT1 in controlling the Tc-induced, FAK-dependent increase in the expression of transcription factors and showed that SIRT1 agonist and FAK inhibitor abrogated the NF-κB transcriptional activity and inflammatory cytokine gene expression in Tc-infected Mϕ. Conclusions: The proinflammatory Mo/Mϕ of yolk sac origin drive the splenic and tissue inflammatory response in chronic CD. SRT1720 reprogrammed the Tc-induced FAK-dependent transcription factors involved in Mϕ proliferation and proinflammatory activation in Chagas disease.