PanethcellTNF-signalinginducesbacterialsepsis: PC transcriptome 15h ater TNF in IFNARKO mice

Paneth Cells (PCs) are secretory cells located in the crypts of Lieberkühn of the small intestine. They produce antimicrobial peptides (AMPs) and are thought to keep the microbiome under control. The cytokine TNF, which functions mainly via its TNF receptor 1 (TNFR1 or P55), is a driving force in many inflammatory bowel disease (IBD) patients, but its impact on PCs is poorly known. We have generated PC-specific P55 knockout mice (P55Paneth KO) and found that these mice are protected against lethal TNF-induced systemic inflammatory response syndrome (SIRS). The impact of TNF on PCs is characterized by morphological changes and by intestinal bacterial translocation into organs, such as liver, in which these bacteria induce expression of numerous genes, associated with typical sepsis signatures. The presence of these bacteria cause lethality of the mice. Based on bulk RNA-SEQ on pure PCs, P55 signaling stimulated mainly a type-I IFN response in the PCs, which drives the bacterial translocation and lethality via IFNAR1. Interestingly, based on ER stress reporter mice, PCs constitutively have high amounts of spliced XBP1 (XBP1s) protein, presumably to support their secretion of AMPs, and TNF eradicates this XBP1s production, leading to failure of the unfolded protein response (UPR). This causes reduced antimicrobial activity in PCs, in a P55 and IFNAR1-dependent way. Our data suggest a novel axis induced by TNF in PCs, leading to interferon-induced UPR failure causing lethal bacterial translocation to the liver (and other organs)