SIRT1 and SIRT3 mediated immune-metabolic switch is crucial for the establishment of Salmonella pathogenicity of infection.

Abstract

Salmonella continues to be a threat to the human population by taking a toll on the lives of about 20,000 individuals globally per year. Host sirtuins or NAD+-dependent deacetylases are the major players in host immuno-metabolic regulation. However, the role of sirtuins in the modulation of the immune metabolism pertaining to Salmonellosis is largely unknown. Here, we investigated the role of SIRT1 and SIRT3 in mediating immuno-metabolic switch along the progression of Salmonella infection. Gene profiling (Nanostring) data along with flow cytometric analysis indicated the ability of the wildtype Salmonella Typhimurium to skew the polarization state of the macrophages from a pro-inflammatory M1 state toward an immunosuppressive M2 state along its course of infection. Further, using shRNA-mediated knockdown studies and catalytic inhibitor treatment, we showed that SIRT1 and SIRT3 play a crucial role in mediating the immuno-metabolic switch that governs macrophage polarization in Salmonella-infected macrophages. SIRT1 or SIRT3 knockdown or inhibition led to decreased expression of M2 surface markers such as CD206 and showed increased production of pro-inflammatory cytokines and ROS generation which together resulted in attenuated bacterial intracellular proliferation within the infected RAW264.7 macrophages. Alongside immunological functions by modulating p65 NF-kappaB acetylation, SIRT1, and SIRT3 knockdown or inhibition also skews Salmonella-induced host metabolic shift towards increased fatty acid oxidation by regulating acetylation status of HIF-1alpha and PDHA1 which in turn impacts the metabolism of Salmonella within the infected macrophages. In vivo mice-model infection studies highlighted the role of SIRT1 and SIRT3 in controlling bacterial burden and dissemination.