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Regulated cell death is an integral part of life, and has broad effects on organism development and homeostasis.sup.1. Malfunctions within the regulated cell death process, including the clearance of dying cells, can manifest in diverse pathologies throughout various tissues including the gastrointestinal tract.sup.2. A long appreciated, yet elusively defined relationship exists between cell death and gastrointestinal pathologies with an underlying microbial component.sup.3-6, but the direct effect of dying mammalian cells on bacterial growth is unclear. Here we advance a concept that several Enterobacteriaceae, including patient-derived clinical isolates, have an efficient growth strategy to exploit soluble factors that are released from dying gut epithelial cells. Mammalian nutrients released after caspase-3/7-dependent apoptosis boosts the growth of multiple Enterobacteriaceae and is observed using primary mouse colonic tissue, mouse and human cell lines, several apoptotic triggers, and in conventional as well as germ-free mice in vivo. The mammalian cell death nutrients induce a core transcriptional response in pathogenic Salmonella, and we identify the pyruvate formate-lyase-encoding pflB gene as a key driver of bacterial colonization in three contexts: a foodborne infection model, a TNF- and A20-dependent cell death model, and a chemotherapy-induced mucositis model. These findings introduce a new layer to the complex host-pathogen interaction, in which death-induced nutrient release acts as a source of fuel for intestinal bacteria, with implications for gut inflammation and cytotoxic chemotherapy treatment. Intestinal microorganisms exploit nutrients released by apoptotic gut epithelial cells for growth., Author(s): Christopher J. Anderson [sup.1] [sup.2] , Christopher B. Medina [sup.3] , Brady J. Barron [sup.3] , Laura Karvelyte [sup.1] , Tania Løve Aaes [sup.1] [sup.2] , Irina Lambertz [sup.1] [...]

Caspase-dependent apoptosis accounts for approximately 90% of homeostatic cell turnover in the body.sup.1, and regulates inflammation, cell proliferation, and tissue regeneration.sup.2-4. How apoptotic cells mediate such diverse effects is not fully understood. Here we profiled the apoptotic metabolite secretome and determined its effects on the tissue neighbourhood. We show that apoptotic lymphocytes and macrophages release specific metabolites, while retaining their membrane integrity. A subset of these metabolites is also shared across different primary cells and cell lines after the induction of apoptosis by different stimuli. Mechanistically, the apoptotic metabolite secretome is not simply due to passive emptying of cellular contents and instead is a regulated process. Caspase-mediated opening of pannexin 1 channels at the plasma membrane facilitated the release of a select subset of metabolites. In addition, certain metabolic pathways continued to remain active during apoptosis, with the release of only select metabolites from a given pathway. Functionally, the apoptotic metabolite secretome induced specific gene programs in healthy neighbouring cells, including suppression of inflammation, cell proliferation, and wound healing. Furthermore, a cocktail of apoptotic metabolites reduced disease severity in mouse models of inflammatory arthritis and lung-graft rejection. These data advance the concept that apoptotic cells are not inert cells waiting for removal, but instead release metabolites as 'good-bye' signals to actively modulate outcomes in tissues. Apoptotic cells communicate with neighbouring cells by the regulated release of specific metabolites, and a cocktail of select apoptotic metabolites reduces disease severity in mouse models of inflammatory arthritis and lung transplant rejection., Author(s): Christopher B. Medina [sup.1] [sup.2] , Parul Mehrotra [sup.3] , Sanja Arandjelovic [sup.1] [sup.2] , Justin S. A. Perry [sup.1] [sup.2] , Yizhan Guo [sup.4] , Sho Morioka [sup.1] [...]