Oral arsenic administration to humanizedUDP-glucuronosyltransferase1 neonatal mice induces UGT1A1 through a dependence on Nrf2 and PXR.

Inorganic arsenic (iAs) is an environmental toxicant that can lead to severe health consequences, which can be exacerbated if exposure occurs early in development. Here, we evaluated the impact of oral iAs treatment on UDP-glucuronosyltransferase 1A1 (UGT1A1) expression and bilirubin metabolism in humanized UGT1 (hUGT1) mice. We found that oral administration of iAs to neonatal hUGT1 mice that display severe neonatal hyperbilirubinemia leads to induction of intestinal UGT1A1 and a reduction in total serum bilirubin values. Oral iAs administration accelerates neonatal intestinal maturation, an event that is directly associated with UGT1A1 induction. As a reactive oxygen species producer, oral iAs treatment activated the Keap-Nrf2 pathway in the intestinal tract and liver. When Nrf2-deficient hUGT1 mice (hUGT1/Nrf2-/-) were treated with iAs, it was shown that activated Nrf2 contributed significantly toward intestinal maturation and UGT1A1 induction. However, hepatic UGT1A1 was not induced upon iAs exposure. We previously demonstrated that the nuclear receptor PXR represses liver UGT1A1 in neonatal hUGT1 mice. When PXR was deleted in hUGT1 mice (hUGT1/Pxr-/-), derepression of UGT1A1 was evident in both liver and intestinal tissue in neonates. Furthermore, when neonatal hUGT1/Pxr-/- mice were treated with iAs, UGT1A1 was superinduced in both tissues, confirming PXR release derepressed key regulatory elements on the gene that could be activated by iAs exposure. With iAs capable of generating reactive oxygen species in both liver and intestinal tissue, we conclude that PXR deficiency in neonatal hUGT1/Pxr-/- mice allows greater access of activated transcriptional modifiers such as Nrf2 leading to superinduction of UGT1A1.

The role of soluble epoxide hydrolase in the intestine.

The soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) is an α/ß hydrolase fold protein that is, widely distributed throughout the body. Recent studies have highlighted that sEH, in the metabolism of polyunsaturated fatty acids, plays a part in the pathogenesis of various diseases, including cardiovascular disease, Alzheimer's disease and intestine-associated disease. This review discusses the current findings on the role of sEH in the development of intestine- and intestine-associated diseases, including colitis, colorectal cancer, and other intestinal diseases, as well as the potential underlying mechanisms involved.

The role of hypoxia-inducible factor 1-alpha in inflammatory bowel disease.

Inflammatory bowel disease (IBD) develops as a result of a combination of genetic predisposition, dysbiosis of the gut microbiota, and environmental influences, which is mainly represented by ulcerative colitis (UC) and Crohn's disease (CD). IBDs can result in inflammatory hypoxia by causing intestinal inflammation and vascular damage. The hypoxia-inducible factor 1-alpha (HIF-1α), as a transcription factor, can regulate the cellular adaptation to low oxygen levels and support the development and function of the gut barrier. HIF-αplays its functions through translocating into the nucleus, dimerizing with HIF-1ß, and binding to hypoxia-responsive elements of HIF-1 target genes. So far, most studies have addressed the function of HIF-1α in murine models of IBD. In this review, we aim to outline the major roles of HIF-1α in the IBD.

Modeling Intestinal Stem Cell Function with Organoids.

Intestinal epithelial cells (IECs) are crucial for the digestive process and nutrient absorption. The intestinal epithelium is composed of the different cell types of the small intestine (mainly, enterocytes, goblet cells, Paneth cells, enteroendocrine cells, and tuft cells). The small intestine is characterized by the presence of crypt-villus units that are in a state of homeostatic cell turnover. Organoid technology enables an efficient expansion of intestinal epithelial tissue in vitro. Thus, organoids hold great promise for use in medical research and in the development of new treatments. At present, the cholinergic system involved in IECs and intestinal stem cells (ISCs) are attracting a great deal of attention. Thus, understanding the biological processes triggered by epithelial cholinergic activation by acetylcholine (ACh), which is produced and released from neuronal and/or non-neuronal tissue, is of key importance. Cholinergic signaling via ACh receptors plays a pivotal role in IEC growth and differentiation. Here, we discuss current views on neuronal innervation and non-neuronal control of the small intestinal crypts and their impact on ISC proliferation, differentiation, and maintenance. Since technology using intestinal organoid culture systems is advancing, we also outline an organoid-based organ replacement approach for intestinal diseases.

Mutual regulation between butyrate and hypoxia-inducible factor-1α in epithelial cell promotes expression of tight junction proteins.

Inflammatory bowel disease is a kind of multi-aetiological chronic disease that is driven by multidimensional factors. Hypoxia-inducible factor-1α (HIF-1α) plays an important role in anti-inflammatory and cellular responses to hypoxia. Previous studies have found that B or T-cell-specific HIF-1α knock out mice exhibit severe colonic inflammation. However, we know very little about other functions of HIF-1α in intestinal epithelial cells (IECs). In our study, HIF-1αΔIEC mice were used to study the function of HIF-1α in IECs. HIF-1α was knocked down in Caco-2 cells by transfection with a small interfering (si) RNA. Immunohistochemical staining and western blotting were used to detect the expression of zonula occluden-1 (ZO-1) and Occludin. The content of colon was harvested for high-performance liquid chromatography analysis to examine the levels of butyrate in the gut. Our research found that HIF-1α played a protective role in dextran sulphate sodium-induced colitis, which was partly due to its regulation of tight junction (TJ) protein expression. Further study revealed that HIF-1α mediated TJ proteins levels by moderating the content of butyrate. Moreover, we found that butyrate regulated TJ protein expression, which is dependent on HIF-1α. These results indicated that there is a mutual regulatory mechanism between butyrate and HIF-1α, which has an important role in the maintenance of barrier function of the gastrointestinal tract.

Inflammasomes of the intestinal epithelium.

While the functional importance of inflammasomes in blood-derived cell types is well established, it remains poorly understood how inflammasomes in nonhematopoietic cells contribute to mucosal immunity. Recent studies have revealed functional roles of inflammasomes - particularly NAIP/NLRC4, NLRP6, and noncanonical caspase-4 (caspase-11) - within epithelial cells of the gut in mucosal immune defense, inflammation, and tumorigenesis. Here, we review and discuss these findings in the broader context of tissue compartment-specific mucosal immunity. We propose several models whereby activities of the intestinal epithelial inflammasomes converge on mechanisms to remove compromised epithelial cells, maintain host-microbiota mutualism, and communicate with immune cells of the underlying lamina propria.

Interferon Lambda in the Pathogenesis of Inflammatory Bowel Diseases.

Interferon λ (IFN-λ) is critical for host viral defense at mucosal surfaces and stimulates immunomodulatory signals, acting on epithelial cells and few other cell types due to restricted IFN-λ receptor expression. Epithelial cells of the intestine play a critical role in the pathogenesis of Inflammatory Bowel Disease (IBD), and the related type II interferons (IFN-γ) have been extensively studied in the context of IBD. However, a role for IFN-λ in IBD onset and progression remains unclear. Recent investigations of IFN-λ in IBD are beginning to uncover complex and sometimes opposing actions, including pro-healing roles in colonic epithelial tissues and potentiation of epithelial cell death in the small intestine. Additionally, IFN-λ has been shown to act through non-epithelial cell types, such as neutrophils, to protect against excessive inflammation. In most cases IFN-λ demonstrates an ability to coordinate the host antiviral response without inducing collateral hyperinflammation, suggesting that IFN-λ signaling pathways could be a therapeutic target in IBD. This mini review discusses existing data on the role of IFN-λ in the pathogenesis of inflammatory bowel disease, current gaps in the research, and therapeutic potential of modulating the IFN-λ-stimulated response.

Polysaccharide extracts of Astragalus membranaceus and Atractylodes macrocephala promote intestinal epithelial cell migration by activating the polyamine-mediated K+ channel.

Astragalus membranaceus (Radix Astragali, RA) and Atractylodes macrocephala (Rhizoma Atractylodis Macrocephalae, RAM) are often used to treat gastrointestinal diseases. In the present study, we determined the effects of polysaccharides extracts from these two herbs on IEC-6 cell migration and explored the potential underlying mechanisms. A migration model with IEC-6 cells was induced using a single-edged razor blade along the diameter of cell layers in six-well polystyrene plates. The cells were grown in control media or media containing spermidine (5 µmol·L-1, SPD), alpha-difluoromethylornithine (2.5 mmol·L-1, DFMO), 4-Aminopyridine (40 µmol·L-1, 4-AP), the polysaccharide extracts of RA or RAM (50, 100, or 200 mg·L-1), DFMO plus SPD, or DFMO plus polysaccharide extracts of RA or RAM for 12 or 24 h. Next, cytosolic free Ca2+ ([Ca2+]cyt) was measured using laser confocal microscopy, and cellular polyamine content was quantified with HPLC. Kv1.1 mRNA expression was assessed using RT-qPCR and Kv1.1 and RhoA protein expressions were measured with Western blotting analysis. A cell migration assay was carried out using Image-Pro Plus software. In addition, GC-MS was introduced to analyze the monosaccharide composition of both polysaccharide extracts. The resutls showed that treatment with polysaccharide extracts of RA or RAM significantly increased cellular polyamine content, elevated [Ca2+]cyt and accelerated migration of IEC-6 cells, compared with the controls (P < 0.01). Polysaccharide extracts not only reversed the inhibitory effects of DFMO on cellular polyamine content and [Ca2+]cyt, but also restored IEC-6 cell migration to control level (P < 0.01 or < 0.05). Kv1.1 mRNA and protein expressions were increased (P < 0.05) after polysaccharide extract treatment in polyamine-deficient IEC-6 cells and RhoA protein expression was increased. Molar ratios of D-ribose, D-arabinose, L-rhamnose, D-mannose, D-glucose, and D-galactose was 1.0 : 14.1 : 0.3 : 19.9 : 181.3 : 6.3 in RA and 1.0 : 4.3 : 0.1 : 5.7 : 2.8 : 2.2 in RAM. In conclusion, treatment with RA and RAM polysaccharide extracts stimulated migration of intestinal epithelial cells via a polyamine-Kv1.1 channel activated signaling pathway, which facilitated intestinal injury healing.

Intrinsic Autophagy Is Required for the Maintenance of Intestinal Stem Cells and for Irradiation-Induced Intestinal Regeneration.

Autophagy is a lysosomal degradation pathway with important roles in physiological homeostasis and disease. However, the role of autophagy in intestinal stem cells (ISCs) is unclear. Here, we show that intrinsic autophagy in ISCs is important for ISC homeostasis. Mice lacking autophagy protein 5 (ATG5) in intestinal epithelial cells (iECs) (Villin-Cre: Atg5fl/fl, hereafter Atg5ΔIEC mice) or in all iECs except Paneth cells (Ah-Cre: Atg5fl/fl mice) had significantly fewer ISCs than did control mice and showed impaired ISC-dependent intestinal recovery after irradiation. Crypt ISCs from Atg5ΔIEC mice had significantly higher reactive oxygen species (ROS) levels than did those from control mice. A ROS-inducing reagent decreased the ISC number and impaired ISC regenerative capacity ex vivo, and treating Atg5ΔIEC mice with an antioxidant rescued their defects. Our results show that intrinsic autophagy supports ISC maintenance by reducing excessive ROS. Optimizing autophagy may lead to autophagy-based therapies for intestinal injuries.

ErbB3 binding protein 1 (EBP1) participates in the regulation of intestinal inflammation via mediating Akt signaling pathway.

ErbB3 binding protein-1 (EBP1) belongs to a family of DNA/RNA binding proteins implicated in cell growth, differentiation and apoptosis. Previous data demonstrated that EBP1 regulates phosphorylation of Akt to drive tumor progress. However, the expression and biological functions of EBP1 in ulcerative colitis (UC) remain unclear. In this study, we reported for the first time that EBP1 was down-regulated in intestinal epithelial cell (IECs) of patients with UC. In DSS-induced colitis, we observed the down-regulation of EBP1 accompanied with the elevated levels of proinflammatory cytokines (IL-1ß, IL-6 and IL-8) and Akt activation indicators (phosphorylated Akt) in colitis IECs, indicating the possible involvement of EBP1 in regulation of intestinal inflammation via mediating Akt in UC. Employing the TNF-α-treated HT-29 cells as an IEC inflammatory model, we confirmed the negative correlation of EBP1 with Akt activation and Akt-dependent inflammation progress in vitro. EBP1 knocking down and over-expression significantly regulated TNF-α-induced Akt activation and proinflammatory cytokines expression in HT-29 cells. Taken together, our data suggested that EBP1 participates in the regulation of intestinal inflammation via mediating Akt signaling pathway.

Advanced application of porcine intestinal epithelial cells for the selection of immunobiotics modulating toll-like receptor 3-mediated inflammation.

PURPOSE: In this study, we aimed to characterize toll-like receptor (TLR)-3-mediated inflammatory immune response in porcine intestinal epithelial (PIE) cells and in PIE-immune cell co-cultures and, to evaluate if these in vitro systems are useful for selecting immunomodulatory lactic acid bacteria. RESULTS: We demonstrated that these systems are valuable tools for the in vitro study of the inflammatory response triggered by TLR3 in intestinal epithelial cells (IECs) and of the interaction between IECs and immune cells. In addition, we showed that PIE cells could be used for the selection of immunobiotic lactobacilli strains with anti-inflammatory activities. We found that Lactobacillus casei MEP221114 is an immunobiotic candidate for modulation of TLR3-mediated inflammatory responses. CONCLUSION: The present study deepened our understanding of the mechanisms of immunobiotic action by demonstrating that the interaction between some lactobacilli strains and IECs can up-regulate the mRNA expression of TLR negative regulators and that this effect could help to regulate the production of inflammatory mediators during the generation of a TLR3-mediated immune response.