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Gut hepcidin: a key regulator of inflammation

ABSTRACT: Hepcidin is demonstrated to be the key iron regulatory hormone, produced by the liver. Here we show an unexpected role of hepcidin as a master initiator of the local and systemic inflammatory response. We found that hepcidin was highly expressed in the colon of two major idiopathic inflammatory bowel diseases : Crohn's disease (CD) and ulcerative colitis (UC). Thanks to the generation of intestinal specific hepcidin KO mice (Hepc{delta}int), we found in a DSS-induced colitis model that hepcidin mediated the induction of key inflammatory cytokines and was protective against intestinal injury. In a model of LPS-induced acute inflammation, intestinal hepcidin expression was increased through a TLR4 dependent pathway andwas required for intestinal neutrophil infiltration and inflammation. Strikingly, intestinal hepcidin was absolutely required for the systemic production of key inflammatory cytokines (IL-6, CXCL1, TNF-alpha ...) as well as for the setting of the hypoferremia of inflammation. In a sepsis model, Hepc{delta}int mice were protected against LPS-induced mortality. Mechanistically, we showed that hepcidin was a direct neutrophil chemoattractant and a proinflammatory molecule in macrophages through a Myd88 dependent pathway. Altogether, we demonstrated that Hepcidin is a key new essential component of the immune system and may be a promising target in many inflammatory diseases.

ORGANISM(S): Mus musculus

PROVIDER: GSE71073 | GEO | 2019/02/14

SECONDARY ACCESSION(S): PRJNA290309

REPOSITORIES: GEO

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Project description:Neutrophil accumulation in crypt abscesses is a pathological hallmark of ulcerative colitis. Based on recent evidence that mucosal metabolic changes influence disease outcomes, we hypothesized that transmigrating neutrophils influence the transcriptional profile of intestinal epithelia. Microarray studies revealed a cohort of hypoxia-responsive genes regulated by neutrophil-epithelial crosstalk. Real-time O2 sensing indicated that transmigrating neutrophils rapidly deplete microenvironmental O2 sufficient enough to stabilize intestinal epithelial cell hypoxia-inducible factor (HIF). Utilizing HIF reporter mice in a TNBS colitis model, we investigated the relative contribution of neutrophils and the respiratory burst to M-bM-^@M-^\inflammatory hypoxiaM-bM-^@M-^] in vivo. Gp91phox-null mice, which mirror human chronic granulomatous disease, developed accentuated colitis compared to control with exaggerated neutrophil infiltration and diminished inflammatory hypoxia. In conclusion, transcriptional imprinting of host tissue by infiltrating neutrophils modulates the host response to inflammation. Likewise, the respiratory burst contributes fundamentally to localized O2 depletion, resultant microenvironmental hypoxia and effective inflammatory resolution. Two models were employed, direct and indirect. The M-bM-^@M-^\DirectM-bM-^@M-^] migration model entailed establishing a chemotactic gradient (using fMLP) across monolayers of T84 intestinal epithelial cells grown on the underside of permeable supports (3um pore). Neutrophils (PMN) were induced to migrate in the physiologically relevant the physiologically relevant basolateral-to-apical direction. Following migration, T84s were rested in complete media and 2hrs later harvested for RNA isolation. In the Indirect model, PMN were applied to T84s as with the direct model. After migration, conditioned supernatants were collected, cells pelleted and supernatants filtered through 0.2um pore. Conditioned supernatants were transferred to naive T84 monolayers for 2hrs, followed by RNA harvest. Each model was exposed to neutrophils (PMN) or not. All monolayers contained chemotactic peptide fMLP on the apical side. Total of 12 samples, 4 conditions in triplicate: Direct migration without neutrophils (T84 +fMLP -PMN), Direct migration with neutrophils (T84 +fMLP +PMN), Indirect migration without neutrophils (T84 +fMLP -PMN), Indirect migration with neutrophils (T84 +fMLP +PMN)

Project description:To investigate the detailed molecular mechanisms for the regulatory role of HIF-2α in experimental colitis, microarray gene expression analysis was performed on colon RNA isolated from 6- to 8-week-old Hif-2αF/F, Hif-2αlΔIE mice treated with 3%DSS for 3 days. Background & Aims: Hypoxic inflammation is characterized by decreased oxygen tension in inflammatory foci, and is a notable feature in inflammatory bowel disease (IBD). Hypoxic response is mediated by transcription factors hypoxia-inducible factor (HIF)-1α and HIF-2α, both of which are highly induced in IBD. HIF-1α is a protective factor that limits intestinal barrier dysfunction during inflammation. However, the role of HIF-2α has not been assessed in hypoxic inflammation and IBD. Methods: A hypoxia reporter mouse model was used to test the presence of hypoxia and HIF-2α in dextran sulfate sodium (DSS) and Citrobacter rodentium (C.rod)-induced colitis. The role of HIF-2α in these mouse models of colitis was further assessed in mice with an intestinal epithelium-specific gain- and loss-of-function of HIF-2α. Results: Induction of hypoxia and HIF-2α was confirmed in both murine experimental colitis models and human IBD samples. Disruption of HIF-2α attenuated colonic inflammation whereas stabilization of HIF-2α potentiated inflammation in mouse models of colitis. Interestingly, intestine specific overexpression of HIF-2α but not HIF-1α leads to spontaneous colitis and premature death in mice. Further mechanistic analysis showed that HIF-2α is a driver for pro-inflammatory response and is critical regulator of intestinal epithelial-derived tumor necrosis factor (TNF)-α. Blocking TNF-α completely ameliorated HIF-2α potentiated intestinal inflammation. Conclusions: These data demonstrate that HIF-2α is a critical transcription factor essential in intestinal epithelium elicited inflammatory response. Global gene expression profiling in colon RNAs isolated from 7-week-old Hif-2αF/F (n=6, Shah 007) and Hif-2αΔIE (n=5, Shah 008).

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Gut hepcidin: a key regulator of inflammation

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