A novel model of the small intestinal epithelium in co-culture with 'gut-like' dendritic cells.

Cross-talk between dendritic cells (DCs) and the intestinal epithelium is important in the decision to mount a protective immune response to a pathogen or to regulate potentially damaging responses to food antigens and the microbiota. Failures in this decision-making process contribute to the development of intestinal inflammation, making the molecular signals that pass between DCs and intestinal epithelial cells potential therapeutic targets. Until now, models with sufficient complexity to understand these interactions have been lacking.

Modelling the Gastrointestinal Carriage of Klebsiella pneumoniae Infections.

Klebsiella pneumoniae is a leading cause of nosocomial and community acquired infections, making K. pneumoniae the pathogen that is associated with the second largest number of deaths attributed to any antibiotic resistant infection. K.

Loss of interleukin-10 receptor disrupts intestinal epithelial cell proliferation and skews differentiation towards the goblet cell fate.

Intestinal epithelial cells (IEC) are crucial for maintaining proper digestion and overall homeostasis of the gut mucosa. IEC proliferation and differentiation are tightly regulated by well described pathways, however, relatively little is known about how cytokines shape these processes. Given that the anti-inflammatory cytokine interleukin (IL)-10 promotes intestinal barrier function, and insufficient IL-10 signaling increases susceptibility to intestinal diseases like inflammatory bowel disease, we hypothesized that IL-10 signaling modulates processes underlying IEC proliferation and differentiation.

Microbiota-derived butyrate dynamically regulates intestinal homeostasis through regulation of actin-associated protein synaptopodin.

The intestinal mucosa exists in dynamic balance with trillions of luminal microbes. Disruption of the intestinal epithelial barrier, commonly observed in mucosal inflammation and diseases such as inflammatory bowel diseases (IBDs), is often associated with dysbiosis, particularly decreases in species producing short-chain fatty acids (SCFAs), such as butyrate. It remains unclear to what extent microbiota-derived factors contribute to the overall maintenance of intestinal homeostasis.

Epithelial HIF-1α/claudin-1 axis regulates barrier dysfunction in eosinophilic esophagitis.

Epithelial barrier dysfunction is a significant factor in many allergic diseases, including eosinophilic esophagitis (EoE). Infiltrating leukocytes and tissue adaptations increase metabolic demands and decrease oxygen availability at barrier surfaces. Understanding of how these processes impact barrier is limited, particularly in allergy.

Oral vitamin B supplement is delivered to the distal gut, altering the corrinoid profile and selectively depleting in C57BL/6 mice.

Vitamin B is a critical nutrient for humans as well as microbes. Due to saturable uptake, high dose oral B supplements are largely unabsorbed and reach the distal gut where they are available to interact with the microbiota. The aim of this study was to determine if oral B supplementation in mice alters 1) the concentration of B and related corrinoids in the distal gut, 2) the fecal microbiome, 3) short chain fatty acids (SCFA), and 4) susceptibility to experimental colitis.

The Hematopoietic Oxidase NOX2 Regulates Self-Renewal of Leukemic Stem Cells.

The NADPH-dependent oxidase NOX2 is an important effector of immune cell function, and its activity has been linked to oncogenic signaling. Here, we describe a role for NOX2 in leukemia-initiating stem cell populations (LSCs). In a murine model of leukemia, suppression of NOX2 impaired core metabolism, attenuated disease development, and depleted functionally defined LSCs.

Control and dysregulation of redox signalling in the gastrointestinal tract.

Redox signalling in the gastrointestinal mucosa is held in an intricate balance. Potent microbicidal mechanisms can be used by infiltrating immune cells, such as neutrophils, to protect compromised mucosae from microbial infection through the generation of reactive oxygen species. Unchecked, collateral damage to the surrounding tissue from neutrophil-derived reactive oxygen species can be detrimental; thus, maintenance and restitution of a breached intestinal mucosal barrier are paramount to host survival.

Neutrophils as sources of dinucleotide polyphosphates and metabolism by epithelial ENPP1 to influence barrier function via adenosine signaling.

Extracellular adenosine signaling is established as a protective component in mucosal inflammatory responses. The sources of extracellular adenosine include enzymatic processing from nucleotides, such as ATP and AMP, that can be liberated from a variety of cell types, including infiltrating leukocytes. Here we demonstrate that activated human neutrophils are a source of diadenosine triphosphate (Ap3A), providing an additional source of nucleotides during inflammation.

Microbiota-Derived Indole Metabolites Promote Human and Murine Intestinal Homeostasis through Regulation of Interleukin-10 Receptor.

Interactions between the gut microbiota and the host are important for health, where dysbiosis has emerged as a likely component of mucosal disease. The specific constituents of the microbiota that contribute to mucosal disease are not well defined. The authors sought to define microbial components that regulate homeostasis within the intestinal mucosa.

MyD88 is an essential component of retinoic acid-induced differentiation in human pluripotent embryonal carcinoma cells.

We have previously reported that myeloid differentiation primary response gene 88 (MyD88) is downregulated during all-trans retinoic acid (RA)-induced differentiation of pluripotent NTera2 human embryonal carcinoma cells (hECCs), whereas its maintained expression is associated with RA differentiation resistance in nullipotent 2102Ep hECCs. MyD88 is the main adapter for toll-like receptor (TLR) signalling, where it determines the secretion of chemokines and cytokines in response to pathogens. In this study, we report that loss of MyD88 is essential for RA-facilitated differentiation of hECCs.

Neutrophils as Components of Mucosal Homeostasis.

Inflammatory responses in the intestinal mucosa inevitably result in the recruitment of neutrophils (polymorphonuclear leukocytes [PMNs]). Epithelial cells that line the mucosa play an integral role in the recruitment, maintenance, and clearance of PMNs at sites of inflammation. The consequences of such PMN-epithelial interactions often determine tissue responses and, ultimately, organ function.

Oxygen metabolism and innate immune responses in the gut.

Epithelial cells of the mucosa provide a first line of defense to prevent the inappropriate translocation of luminal antigens, and therefore contribute significantly to nonspecific innate immunity. In the gastrointestinal (GI) tract, barrier is provided by multiple components of the mucosa, including mucus production, epithelial junctional complexes, and the production of antimicrobial molecules. In recent years, it is better appreciated that tissue oxygen metabolism is key to homeostasis in the mucosa.

Perturbation of neddylation-dependent NF-κB responses in the intestinal epithelium drives apoptosis and inhibits resolution of mucosal inflammation.

Recent work has revealed a central role for neddylation (the conjugation of a Nedd8-moiety to Cullin proteins) in the fine tuning of the NF-κB response (via Cullin-1). In the present study, we investigated the contribution of Cullin-1 neddylation and NF-κB signaling to mucosal inflammatory responses in vitro and in vivo. Initial in vitro studies using cultured intestinal epithelial cells revealed that the neddylation inhibitor MLN4924 prominently induces the deneddylation of Cullin-1.

Neutrophils and the inflammatory tissue microenvironment in the mucosa.

The interaction of neutrophils (PMNs) and epithelial cells are requisite lines of communication during mucosal inflammatory responses. Consequences of such interactions often determine endpoint organ function, and for this reason, much interest has developed around defining the constituents of the tissue microenvironment of inflammatory lesions. Physiologic in vitro and in vivo models have aided in the discovery of components that define the basic inflammatory machinery that mold the inflammatory tissue microenvironment.

Imaging Inflammatory Hypoxia in the Murine Gut.

The inflammatory bowel diseases (IBD), including Crohn's disease and ulcerative colitis, result in chronic inflammation to the gastrointestinal tract. In ulcerative colitis, inflammation tends to be more superficial and restricted to the colon; contrastingly, Crohn's disease presents as patchy, more penetrative inflammation that can occur throughout the gastrointestinal tract. Other differences between these diseases include the nature of their respective immune responses-Crohn's disease presents as a Th1 and ulcerative colitis as a Th2-type inflammation.

Hypoxia and Mucosal Inflammation.

Sites of inflammation are defined by significant changes in metabolic activity. Recent studies have suggested that O2 metabolism and hypoxia play a prominent role in inflammation so-called "inflammatory hypoxia," which results from a combination of recruited inflammatory cells (e.g.

Hypercapnia Suppresses the HIF-dependent Adaptive Response to Hypoxia.

Molecular oxygen and carbon dioxide are the primary gaseous substrate and product of oxidative metabolism, respectively. Hypoxia (low oxygen) and hypercapnia (high carbon dioxide) are co-incidental features of the tissue microenvironment in a range of pathophysiologic states, including acute and chronic respiratory diseases. The hypoxia-inducible factor (HIF) is the master regulator of the transcriptional response to hypoxia; however, little is known about the impact of hypercapnia on gene transcription.

Hypoxia-recruited angiogenic neutrophils.

In this issue of Blood, Massena et al identify a novel CD49d+CXCR4highVEGFR1high population of neutrophils that specifically migrate to sites of hypoxia and enhance angiogenesis.

HIF-dependent regulation of claudin-1 is central to intestinal epithelial tight junction integrity.

Intestinal epithelial cells (IECs) are exposed to profound fluctuations in oxygen tension and have evolved adaptive transcriptional responses to a low-oxygen environment. These adaptations are mediated primarily through the hypoxia-inducible factor (HIF) complex. Given the central role of the IEC in barrier function, we sought to determine whether HIF influenced epithelial tight junction (TJ) structure and function.

Crosstalk between Microbiota-Derived Short-Chain Fatty Acids and Intestinal Epithelial HIF Augments Tissue Barrier Function.

Interactions between the microbiota and distal gut are fundamental determinants of human health. Such interactions are concentrated at the colonic mucosa and provide energy for the host epithelium through the production of the short-chain fatty acid butyrate. We sought to determine the role of epithelial butyrate metabolism in establishing the austere oxygenation profile of the distal gut.

Neutrophils and inflammatory metabolism in antimicrobial functions of the mucosa.

In this mini-review, we will discuss recent findings that implicate neutrophil infiltration and function in establishing a metabolic environment to facilitate efficient pathogen clearance. For decades, neutrophils have been regarded as short lived, nonspecific granulocytes, equipped with toxic antimicrobial factors and a respiratory burst generating ROS. Recent findings demonstrate the importance of HIF signaling in leukocytes and surrounding tissues during inflammation.

Stabilization of HIF through inhibition of Cullin-2 neddylation is protective in mucosal inflammatory responses.

There is interest in understanding post-translational modifications of proteins in inflammatory disease. Neddylation is the conjugation of the molecule neural precursor cell expressed, developmentally down-regulated 8 (NEDD8) to promote protein stabilization. Cullins are a family of NEDD8 targets important in the stabilization and degradation of proteins, such as hypoxia-inducible factor (HIF; via Cullin-2).

Transmigrating neutrophils shape the mucosal microenvironment through localized oxygen depletion to influence resolution of inflammation.

Acute intestinal inflammation involves early accumulation of neutrophils (PMNs) followed by either resolution or progression to chronic inflammation. Based on recent evidence that mucosal metabolism influences disease outcomes, we hypothesized that transmigrating PMNs influence the transcriptional profile of the surrounding mucosa. Microarray studies revealed a cohort of hypoxia-responsive genes regulated by PMN-epithelial crosstalk.

IFN-γ-mediated induction of an apical IL-10 receptor on polarized intestinal epithelia.

Cytokines secreted at sites of inflammation impact the onset, progression, and resolution of inflammation. In this article, we investigated potential proresolving mechanisms of IFN-γ in models of inflammatory bowel disease. Guided by initial microarray analysis, in vitro studies revealed that IFN-γ selectively induced the expression of IL-10R1 on intestinal epithelia.