Validation of the organic electrochemical transistor for in vitro toxicology

Background

The gastrointestinal epithelium provides a physical and biochemical barrier to the passage of ions and small molecules; however this barrier may be breached by pathogens and toxins. The effect of individual pathogens/toxins on the intestinal epithelium has been well characterized: they disrupt barrier tissue in a variety of ways, such as by targeting tight junction proteins, or other elements of the junctions between adjacent cells. A variety of methods have been used to characterize disruption in barrier tissue, such as immunofluorescence, permeability assays and electrical measurements of epithelia resistance, but these methods remain time consuming, costly and ill-suited to diagnostics or high throughput toxicology.

Methods

The advent of organic electronics has created a unique opportunity to interface the worlds of electronics and biology, using devices such as the organic electrochemical transistor (OECT), whose low cost materials and potential for easy fabrication in high throughput formats represent a novel solution for assessing epithelial tissue integrity.

Results

In this study, OECTs were integrated with gastro-intestinal cell monolayers to study the integrity of the gastrointestinal epithelium, providing a very sensitive way to detect minute changes in ion flow across the cell layer due to inherent amplification by the transistor.

Major conclusions

We validate the OECT against traditional methods by monitoring the effect of toxic compounds on epithelial tissue. We show a systematic characterization of this novel method, alongside existing methods used to assess barrier tissue function.

General significance

The toxic compounds induce a dramatic disruption of barrier tissue, and the OECT measures this disruption with increased temporal resolution and greater or equal sensitivity when compared with existing methods. This article is part of a Special Issue entitled Organic Bioelectronics — Novel Applications in Biomedicine.     

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying tissue compartments, restricting the transport of smaller molecules across the epithelium and almost completely prohibiting epithelial macromolecular transport. This selectivity is determined by the mucous gel layer, which limits the transport of lipophilic molecules and both the apical receptors and tight junctional protein complexes of the epithelium. In vitro cell culture models of the epithelium are convenient, but as a model, they lack the complexity of interactions between the microbiota, mucous-gel, epithelium and immune system. On the other hand, in vivo assessment of intestinal absorption or permeability may be performed, but these assays measure overall gastrointestinal absorption, with no indication of site specificity. Ex vivo permeability assays using "intestinal sacs" are a rapid and sensitive method of measuring either overall intestinal integrity or comparative transport of a specific molecule, with the added advantage of intestinal site specificity. Here we describe the preparation of intestinal sacs for permeability studies and the calculation of the apparent permeability (P_app)of a molecule across the intestinal barrier. This technique may be used as a method of assessing drug absorption, or to examine regional epithelial barrier dysfunction in animal models of gastrointestinal disease.     

Multivalent Adhesion Molecule 7 Clusters Act as Signaling Platform for Host Cellular GTPase Activation and Facilitate Epithelial Barrier Dysfunction

Vibrio parahaemolyticus is an emerging bacterial pathogen which colonizes the gastrointestinal tract and can cause severe enteritis and bacteraemia. During infection, V. parahaemolyticus primarily attaches to the small intestine, where it causes extensive tissue damage and compromises epithelial barrier integrity. We have previously described that Multivalent Adhesion Molecule (MAM) 7 contributes to initial attachment of V. parahaemolyticus to epithelial cells. Here we show that the bacterial adhesin, through multivalent interactions between surface-induced adhesin clusters and phosphatidic acid lipids in the host cell membrane, induces activation of the small GTPase RhoA and actin rearrangements in host cells. In infection studies with V. parahaemolyticus we further demonstrate that adhesin-triggered activation of the ROCK/LIMK signaling axis is sufficient to redistribute tight junction proteins, leading to a loss of epithelial barrier function. Taken together, these findings show an unprecedented mechanism by which an adhesin acts as assembly platform for a host cellular signaling pathway, which ultimately facilitates breaching of the epithelial barrier by a bacterial pathogen.     

How are the expression patterns of gut antimicrobial peptides modulated by human gastrointestinal diseases? A bridge between infectious,inflammatory, and malignant diseases

The human gut barrier is the tissue exposed to the highest load of microorganisms, harbouring 100 trillion bacteria. In addition, the gut's renewal rate outruns that of any other human tissue. Antimicrobial peptides (AMPs) are highly optimized defense molecules in the intestinal barrier optimized to maintain gastrointestinal homeostasis. Alterations in AMPs activity can lead to or result from human gastrointestinal diseases. In this review, unique, conserved, or otherwise regular alterations in the expression patterns of human AMPs across gastrointestinal inflammatory and infectious diseases were analyzed for pattern elucidation. Human gastrointestinal diseases are associated with alterations in gut AMPs' expression patterns in a peptide‐specific, disease‐specific, and pathogen‐specific way, modulating human gastrointestinal functioning. Across diseases, there is a (i) marked reduction in otherwise constitutively expressed AMPs, leading to increased disease susceptibility, and a (ii) significant increase in the expression of inducible AMPs, leading to tissue damage and disease severity. Infections and inflammatory conditions are associated with altered gene expression in the gut, whose patterns may favour cellular metaplasia, mucosal dysfunction, and disease states. Altered expression of AMPs can thus thrive disease severity and evolution since its early stages. Nevertheless, the modulation of AMP expression patterns unveils promising therapeutic targets.     

The role of the gastrointestinal tract in the development of burn sepsis.

Conceptualization of the gastrointestinal tract as the "motor" that drives sepsis and multiple-system organ failure has only recently been appreciated. Most of the investigation into the pathophysiology of gut-derived sepsis involves using animal models; however, some of the findings are already being corroborated in human studies. The gastrointestinal tract is a dynamic organ whose function as a front-line defense against infection needs to be appreciated. The development of lethal sepsis is a function of the microbial load and virulence, the status of the gastrointestinal barrier, and the magnitude of the host defense response. In assuming care of a critically ill patient, we must be judicious in the use of antibiotics in order to prevent intestinal overgrowth of potential pathogens. Providing proper nutrition by an enteral route (when possible) not only satisfies caloric needs but regulates the microflora and maintains the integrity of the mucosal barrier. Burn patients should receive enteral nutrition early, the first day if possible. This not only will protect the intestinal mucosa but also will blunt the hypermetabolic response following thermal injury. Lastly, the patient should not receive an excessive amount of narcotic or sedative, for these drugs have an inhibitory effect on gastrointestinal motility, encouraging bacterial overgrowth. In the near future, new therapeutic modalities may soon become available to protect and treat the compromised gastrointestinal barrier. These modalities may include, but certainly are not limited to, the use of glutamine and xanthine oxidase inhibitors to prevent stress-related injury to the gastrointestinal mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacterial population and innate immunity-related genes in rat gastrointestinal tract are altered by vitamin A-deficient diet

Vitamin A and its derivatives have been shown to regulate the growth and differentiation of gastrointestinal epithelial cells; in addition, vitamin A deficiency has been convincingly shown to be associated with increased susceptibility to infection. The gastrointestinal mucosal barrier, which is a component of the innate immune system, is considered the first line of defense, as it provides a barrier between the external environment and the internal milieu. A disturbance in the integrity of the intestinal epithelium is one of the main factors involved in increased incidence of infections during vitamin A deficiency. In this study, the effects of vitamin A deficiency on microbial ecology and the expression of genes related to the intestinal mucosa's innate immunity were examined in a rat model. Using the 16s rDNA method, we demonstrate that a vitamin A-deficient (VAD) diet increases the total amount of bacteria in the gastrointestinal tract and alters the intestinal microflora. Results show a decrease in the relative proportion of Lactobacillus spp. and the simultaneous appearance of Escherichia coli strains. Lack of vitamin A significantly changed mucin (MUC) dynamics, as reflected by the enlarged goblet-cell "cup" area relative to controls; decreased MUC2 mRNA expression in the jejunum, ileum and colon of VAD rats and increased MUC3 mRNA expression in the ileum and colon of these rats. In addition, vitamin A deficiency down-regulated defensin 6 mRNA expression while up-regulating toll-like receptors 2 and 5 mRNA expressions. The current study indicates that vitamin A deficiency interferes with the integrity of the gastrointestinal mucosal barrier.     

Knockdown of aquaporin 3 is involved in intestinal barrier integrity impairment

AQP3 is a water/glycerol transporter expressed at the basolateral membrane of colonic epithelial cells. Although AQPs are expressed in the gastrointestinal tract, their effect on intestinal barrier has not been clear. Here, we showed that knockdown of AQP3 caused a dramatic, dose-dependent increase in E. coli C25 translocation, with the reduction of TEER and increasing LY permeability. Western blots revealed that expression of Claudin-1 and Occludin were significantly decreased in the AQP3 knockdown group, demonstrating that this treatment enhances paracellular permeability via an opening of the tight junction complex. These data not only describe the correlation between transcellular and paracellular pathways in human intestines, but also show that targeted knockdown of AQP3 might impair the intestinal barrier integrity.     

Histamine selectively interrupts VE-cadherin adhesion independently of capacitive calcium entry

Histamine is an important agent of innate immunity, transiently increasing the flux of immune-competent molecules from the vascular space to the tissues and then allowing rapid restoration of the integrity of the endothelial barrier. In previous work we found that histamine alters the endothelial barrier by disrupting cell-cell adhesion and identified VE-cadherin as an essential participant in this process. The previous work did not determine whether histamine directly interrupted VE-cadherin adhesion, whether the effects of histamine were selective for cadherin adhesion, or whether capacitive calcium flux across the cell membrane was necessary for the effects of histamine on cell-cell adhesion. In the current work we found that histamine directly interrupts adhesion of L cells expressing the type 1 histamine (H1) receptor and VE-cadherin to a VE-cadherin-Fc fusion protein. In contrast, integrin-mediated adhesion to fibronectin of the same L cells expressing the H1 receptor was not affected by histamine, demonstrating that the effects of histamine are selective for cadherin adhesion. Some of the effects of many edemagenic agonists on endothelium are dependent on the capacitive flux of calcium across the endothelial cell membrane. Blocking capacitive calcium flux with LaCl3 did not prevent histamine from interrupting VE-cadherin adhesion of transfected L cells, nor did it prevent histamine from interrupting cell-cell adhesion of human umbilical vein endothelial cells. These data support the contentions that histamine directly and selectively interrupts cadherin adhesion and this effect on cadherin adhesion is independent of capacitive calcium flux.     

肠黏膜屏障与肠道菌群的相互关系

摘要：人类肠道中微生物群与肠道环境相互作用以维持机体健康。肠黏膜屏障主要由黏液层、肠道菌群、肠道免疫系统和肠上皮细胞本身的完整性等构成。肠道作为直接与大量菌群接触的器官,其屏障功能在肠道健康中的作用尤为显著。肠道菌群与肠道屏障相互作用,保持肠道菌群与肠道屏障相对稳定,肠道菌群参与肠道免疫反应的建立,共同建立机体天然防御系统,在保持肠道免疫的动态平衡中具有重要作用。当两者之间的平衡被打破时,可诱发功能性胃肠病（如肠易激综合征）及免疫相关性疾病（如炎症性肠病）。本文主要阐述肠黏膜屏障与肠道菌群之间的相互关系以及与肠道屏障功能障碍相关的肠道疾病。     

Procyanidins protect Caco-2 cells from bile acid- and oxidant-induced damage

Procyanidins can exert cytoprotective, anti-inflammatory, and anticarcinogenic actions in the gastrointestinal tract. Previous evidence has shown that procyanidins can interact with synthetic membranes and protect them from oxidation and disruption. Thus, in this study we investigated the capacity of a hexameric procyanidin fraction (Hex) isolated from cocoa to protect Caco-2 cells from deoxycholic (DOC)-induced cytotoxicity, cell oxidant increase, and loss of monolayer integrity. Hex interacted with the cell membranes without affecting their integrity, as evidenced by a Hex-mediated increase in the transepithelial electrical resistance, and inhibition of DOC-induced cytotoxicity. DOC induced an increase in cell oxidants, alterations in the paracellular transport, and redistribution of the protein ZO-1 from cell-cell contacts into the cytoplasm. Hex partially inhibited all these events at concentrations ranging from 2.5 to 20 microM. Similarly, Hex (5-10 microM) inhibited the increase in cell oxidants, and the loss of integrity of polarized Caco-2 cell monolayers induced by a lipophilic oxidant (2,2'-azobis (2,4-dimethylvaleronitrile). Results show that the assayed procyanidin fraction can interact with cell membranes and protect Caco-2 cells from DOC-induced cytotoxicity, oxidant generation, and loss of monolayer integrity. At the gastrointestinal tract, large procyanidins may exert beneficial effects in pathologies such us inflammatory diseases, alterations in intestinal barrier permeability, and cancer.     

Damaged Intestinal Epithelial Integrity Linked to Microbial Translocation in Pathogenic Simian Immunodeficiency Virus Infections

The chronic phase of HIV infection is marked by pathological activation of the immune system, the extent of which better predicts disease progression than either plasma viral load or CD4⁺ T cell count. Recently, translocation of microbial products from the gastrointestinal tract has been proposed as an underlying cause of this immune activation, based on indirect evidence including the detection of microbial products and specific immune responses in the plasma of chronically HIV-infected humans or SIV-infected Asian macaques. We analyzed tissues from SIV-infected rhesus macaques (RMs) to provide direct in situ evidence for translocation of microbial constituents from the lumen of the intestine into the lamina propria and to draining and peripheral lymph nodes and liver, accompanied by local immune responses in affected tissues. In chronically SIV-infected RMs this translocation is associated with breakdown of the integrity of the epithelial barrier of the gastrointestinal (GI) tract and apparent inability of lamina propria macrophages to effectively phagocytose translocated microbial constituents. By contrast, in the chronic phase of SIV infection in sooty mangabeys, we found no evidence of epithelial barrier breakdown, no increased microbial translocation and no pathological immune activation. Because immune activation is characteristic of the chronic phase of progressive HIV/SIV infections, these findings suggest that increased microbial translocation from the GI tract, in excess of capacity to clear the translocated microbial constituents, helps drive pathological immune activation. Novel therapeutic approaches to inhibit microbial translocation and/or attenuate chronic immune activation in HIV-infected individuals may complement treatments aimed at direct suppression of viral replication.     

Role of cadherin-17 in oncogenesis and potential therapeutic implications in hepatocellular carcinoma

Cadherin is an important cell adhesion molecule that plays paramount roles in organ development and the maintenance of tissue integrity. Dysregulation of cadherin expression is often associated with disease pathology including tissue dysplasia, tumor formation, and metastasis. Cadherin-17 (CDH17), belonging to a subclass of 7D-cadherin superfamily, is present in fetal liver and gastrointestinal tract during embryogenesis, but the gene becomes silenced in healthy adult liver and stomach tissues. It functions as a peptide transporter and a cell adhesion molecule to maintain tissue integrity in epithelia. However, recent findings from our group and others have reported aberrant expression of CDH17 in major gastrointestinal malignancies including hepatocellular carcinoma (HCC), stomach and colorectal cancers, and its clinical association with tumor metastasis and advanced tumor stages. Furthermore, alternative splice isoforms and genetic polymorphisms of CDH17 gene have been identified in HCC and linked to an increased risk of HCC. CDH17 is an attractive target for HCC therapy. Targeting CDH17 in HCC can inhibit tumor growth and inactivate Wnt signaling pathway in concomitance with activation of tumor suppressor genes. Further investigation on CDH17-mediated oncogenic signaling and cognate molecular mechanisms would shed light on new targeting therapy on HCC and potentially other gastrointestinal malignancies.     

UT-B1 Mediates Transepithelial Urea Flux in the Rat Gastrointestinal Tract

The process of urea nitrogen salvaging plays a vital role in the symbiotic relationship between mammals and their intestinal bacteria. The first step in this process requires the movement of urea from the mammalian bloodstream into the gastrointestinal tract lumen via specialized proteins known as facilitative urea transporters. In this study, we examined both transepithelial urea fluxes and urea transporter protein abundance along the length of the rat gastrointestinal tract. Urea flux experiments that used rat gastrointestinal tissues showed significantly higher transepithelial urea transport was present in caecum and proximal colon (P < 0.01, n = 8, analysis of variance [ANOVA]). This large urea flux was significantly inhibited by 1,3,dimethylurea (P < 0.001, n = 8, ANOVA) and thiourea (P < 0.05, n = 6, unpaired t-test), both known blockers of facilitative urea transporters. Immunoblotting analysis failed to detect any UT-A protein within rat gastrointestinal tissue protein samples. In contrast, a 30-kDa UT-B1 protein was strongly detected in both caecum and proximal colon samples at significantly higher levels compared to the rest of the gastrointestinal tract (P < 0.01, n = 4, ANOVA). We therefore concluded that UT-B1 mediates the transepithelial movement of urea that occurs in specific distal regions of the rat gastrointestinal tract.     

Mucosal mast cells of the rat intestine: a re-evaluation of fixation and staining properties, with special reference to protein blocking and solubility of the granular glycosaminoglycan

Mucosal mast cells of the gastrointestinal tract constitute a separate cell line within the mast cell system of the rat, differing in several respects from the classical connective tissue mast cells and, unlike the latter, requiring special fixation techniques for their demonstration. We have examined some histochemical properties of mucosal mast cells of the duodenum and compared them with connective tissue mast cells of the tongue or skin. The results indicate that the structural integrity of the granules of both types of mast cell is partly dependent on ionic linkages between glycosaminoglycan and protein. The so far unidentified glycosaminoglycan of mucosal mast cells appears to be more soluble than the heparin of connective tissue mast cells. The strongly fluorescent binding of Berberine to the granules of connective tissue mast cells and, depending on their content, of heparin is absent from mucosal mast cells, confirming previous findings which suggested that they contain a glycosaminoglycan with a lower degree of sulphation. Aldehyde fixation by routine procedures reversibly blocks the cationic dye binding of mucosal mast cell granules. The dye binding groups may be unmasked by trypsination or by long staining times of the order of several days. The results suggest that the blocking of staining by aldehydes is caused by a diffusion barrier of a protein nature. Mucosal and connective tissue mast cells thus differ with respect to the spatial arrangement of glycosaminoglycan and protein in their granules. As a result of the study a modified method for the demonstration of mucosal mast cells in tissue sections is described, based on normal formaldehyde fixation and staining in Toluidine Blue for a long time. It has some advantages over previous methods and preserves the structure of mucosal and connective tissue mast cells equally well.     

Low speed preparation of microsomes: a comparative study

Microsomal fractions were isolated from hepatic tissue, housefly abdomen and southern armyworm midgut, either by centrifugation of post-mitochondrial supernatant for 1 h at 105 000×g or by calcium sedimentation and low speed centrifugation. A comparison of the two methods of isolation were made on the basis of: NADPH oxidase activity, O-demethylation of p-nitroanisole, spectral parameters of cytochrome P-450, and integrity of ultrastructural constituents. The method of isolation did not effect these parameters appreciably for microsomes isolated from hepatic tissue. Calcium sedimentation of insect microsomes resulted in a reduction of enzyme activity and an apparent decrease in cytochrome P-450. Ultrastructural integrity did not appear to be influenced by the method of sedimentation.     

MIND the gap: an astroglial perspective on barrier regulation

The blood-brain barrier (BBB) is a specialized tissue interface that provides an important homeostatic and immunosurveillance role in the CNS. Unlike most microvascular tissues, which readily promote paracellular passage of solutes and macromolecules, the BBB is more analogous to polarized mucosal epithelia that restrict such permeability in order to prevent disease onset. Recent transgenic ablation studies have demonstrated that the BBB and mucosal tissues also share a requirement for astroglial-regulated barrier integrity. This review highlights the emerging concept that astroglia regulate barrier function at markedly different tissue interfaces. It also explores possible lessons that might be learnt by adopting epithelial model paradigms of the BBB. For example, novel glial-derived S-nitrosylation signals that regulate intestinal permeability in the digestive tract might provide new mechanistic insights into the function of the BBB. A better understanding of such universal mechanisms for barrier regulation will facilitate novel therapeutic strategies that target permeability disorders at CNS and mucosal tissue interfaces.     

Distribution of CD4pos -, CD8pos – and Regulatory T Cells in the Upper and Lower Gastrointestinal Tract in Healthy Young Subjects

The gastrointestinal immune system is involved in the development of several autoimmune-mediated diseases, including inflammatory bowel disease, multiple sclerosis, and type 1 diabetes mellitus. Alterations in T-cell populations, especially regulatory T cells (Tregs), are often evident in patients suffering from these diseases. To be able to detect changes in T-cell populations in diseased tissue, it is crucial to investigate T-cell populations in healthy individuals, and to characterize their variation among different regions of the gastrointestinal (GI) tract. While limited data exist, quantitative data on biopsies systematically drawn from various regions of the GI tract are lacking, particularly in healthy young humans. In this report, we present the first systematic assessment of how T cells—including Tregs—are distributed in the gastrointestinal mucosa throughout the GI tract of healthy young humans by means of multi-parameter FACS analysis. Gastroduodenoscopy and colonoscopy were performed on 16 healthy volunteers aged between 18 and 32. Biopsies were drawn from seven GI regions, and were used to determine the frequencies of CD8⁺-, CD4⁺- and Tregs in the gastrointestinal mucosa by means of multi-parameter FACS analysis. Our data show that there is significant variation in the baseline T-cell landscape along the healthy human gastrointestinal tract, and that mucosal T-cell analyses from a single region should not be taken as representative of the entire gastrointestinal tract. We show that certain T-cell subsets in the gastrointestinal mucosa vary significantly among regions; most notably, that Tregs are enriched in the appendiceal orifice region and the ascending colon, and that CD8^pos T cells are enriched in the gastric mucosa.     

A two-barrier compartment model for volume flow across amphibian skin

The amphibian skin has long been used as a model tissue for the study of ion transport and osmotic water movement across tight epithelia. To understand the mechanism of water uptake across amphibian skin, we model the skin as a well-stirred compartment bounded by an apical barrier and a tissue barrier. The compartment represents the lateral intercellular space between cells in the stratum granulosum. The apical barrier represents the stratum corneum, the principal/mitochondria-rich cells, and the junctional area between cells. This barrier is hypothesized to have the ability to actively transport solutes through Na+-K+-ATPase. The actively transported solute flux is assumed to satisfy the Michaelis-Menten relationship. The tissue barrier represents a composite barrier comprising the stratum spinosum, the stratum germinativum, the basal lamina, and the dermis. Our model shows that 1) the predicted rehydration rates from apical bathing solutions are in good agreement with the experiment results in Hillyard and Larsen (J Comp Physiol 171: 283-292, 2001); 2) under their experimental conditions, there is a substantial volume flux coupled to the active solute flux and this coupled volume flux is nearly constant when the osmolality of the apical bathing solution is >100 mosmol/kgH2O; 3) the molar ratio of the actively transported solute flux to the coupled water flux is about 1:160, which is the same as that reported in Nielsen (J Membr Biol 159: 61-69, 1997).     

Isolation and characterization of a cDNA encoding a novel member of the human regenerating protein family: Reg IV

Human Reg and Reg-related genes constitute a multi-gene family belonging to the calcium (C-type) dependent lectin superfamily. Regenerating gene family members are expressed in the proximal gastrointestinal (GI) tract and ectopically at other sites in the setting of tissue injury. By high-throughput sequence analysis of a large inflammatory bowel disease library, two cDNAs have been isolated which encode a novel member of this multigene family. Based on primary sequence homology, tissue expression profiles, and shared exon-intron junction genomic organization, we assign this gene to the regenerating gene family. Specific protein structural differences suggest that the current three regenerating gene subtypes should be expanded to four. We demonstrate that Reg IV has a highly restricted tissue expression pattern, with prominent expression in the gastrointestinal tract. Reg IV mRNA expression is significantly up-regulated by mucosal injury from active Crohn's disease or ulcerative colitis.     

Ghrelin reverts intestinal stem cell loss associated with radiation-induced enteropathy by activating Notch signaling

BackgroudExposure to high-dose radiation, such as after a nuclear accident or radiotherapy, elicits severe intestinal damage and is associated with a high mortality rate. In treating patients exhibiting radiation-induced intestinal dysfunction, countermeasures to radiation are required. In principle, the cellular event underlying radiation-induced gastrointestinal syndrome is intestinal stem cell (ISC) apoptosis in the crypts. High-dose irradiation induces the loss of ISCs and impairs intestinal barrier function, including epithelial regeneration and integrity. Notch signaling plays a critical role in the maintenance of the intestinal epithelium and regulates ISC self-renewal. Ghrelin, a hormone produced mainly by enteroendocrine cells in the gastrointestinal tract, has diverse physiological and biological functions.PurposeWe investigate whether ghrelin mitigates radiation-induced enteropathy, focusing on its role in maintaining epithelial function.MethodsTo investigate the effect of ghrelin in radiation-induced epithelial damage, we analyzed proliferation and Notch signaling in human intestinal epithelial cell. And we performed histological analysis, inflammatory response, barrier functional assays, and expression of notch related gene and epithelial stem cell using a mouse model of radiation-induced enteritis.ResultsIn this study, we found that ghrelin treatment accelerated the reversal of radiation-induced epithelial damage including barrier dysfunction and defective self-renewing property of ISCs by activating Notch signaling. Exogenous injection of ghrelin also attenuated the severity of radiation-induced intestinal injury in a mouse model.ConclusionThese data suggest that ghrelin may be used as a potential therapeutic agent for radiation-induced enteropathy.