SIRT1 and SIRT3 impact host mitochondrial function and host- Salmonella pH balance during infection

Mitochondria are an important organelle regulating energy homeostasis. Mitochondrial health and dynamics are crucial determinants of the outcome of several bacterial infections. SIRT3, a major mitochondrial sirtuin, along with SIRT1 regulates key mitochondrial functions. This led to considerable interest in understanding the role of SIRT1 and SIRT3 in governing mitochondrial functions during Salmonella infection. Here, we show that loss of SIRT1 and SIRT3 function either by shRNA-mediated knockdown or inhibitor treatment led to increased mitochondrial dysfunction with alteration in mitochondrial bioenergetics alongside increased mitochondrial superoxide generation in the Salmonella-infected macrophages. Consistent with dysfunctional mitochondria, mitophagy was induced along with altered mitochondrial fusion-fission dynamics in S. Typhimurium-infected macrophages. Additionally, the mitochondrial bioenergetic alteration promotes acidification of the infected macrophage cytosolic pH. This host cytosolic pH imbalance skewed the intra-phagosomal and intra- bacterial pH in the absence of SIRT1 and SIRT3, resulting in decreased SPI-2 gene expression. Our results suggest a novel role of SIRT1 and SIRT3 in maintaining the intracellular Salmonella niche by modulating the mitochondrial bioenergetics and dynamics in the infected macrophages. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/557159v2_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@486cbaorg.highwire.dtl.DTLVardef@da2fb0org.highwire.dtl.DTLVardef@70cd46org.highwire.dtl.DTLVardef@1b4d0bd_HPS_FORMAT_FIGEXP M_FIG C_FIG