TFF3 and EGF induce different migration patterns of intestinal epithelial cells in vitro and trigger increased internalization of E-cadherin

Pathological and therapeutic roles of bioactive peptide trefoil factor 3 in diverse diseases: recent progress and perspective

Trefoil factor 3 (TFF3) is the last small-molecule peptide found in the trefoil factor family, which is mainly secreted by intestinal goblet cells and exerts mucosal repair effect in the gastrointestinal tract. Emerging evidence indicated that the TFF3 expression profile and biological effects changed significantly in pathological states such as cancer, colitis, gastric ulcer, diabetes mellitus, non-alcoholic fatty liver disease, and nervous system disease. More importantly, mucosal protection would no longer be the only effect of TFF3, it gradually exhibits carcinogenic activity and potential regulatory effect of nervous and endocrine systems, but the inner mechanisms remain unclear. Understanding the molecular function of TFF3 in specific diseases might provide a new insight for the clinical development of novel therapeutic strategies. This review provides an up-to-date overview of the pathological effects of TFF3 in different disease and discusses the binding proteins, signaling pathways, and clinical application.

Integrity of the Intestinal Barrier: The Involvement of Epithelial Cells and Microbiota-A Mutual Relationship

Simple Summary

The gastrointestinal tract is a complex organization of various types of epithelial cells forming a single layer of the mucosal barrier, the host mucosal immune system, and microorganisms termed as gut microbiota inhabiting this area. The mucosal barrier, including physical and chemical factors, spatially segregates gut microbiota and the host immune system preventing the development of immune response directed towards non-pathogenic commensals and dietary antigens. However, for the maintenance of the integrity of the mucosal surfaces, cross-talk between epithelial cells and microbiota is required. The microbiome and the intestinal epithelium developed a complex dependence necessary for sustaining intestinal homeostasis. In this review, we highlight the role of specific epithelial cell subtypes and their role in barrier arrangement, the mechanisms employed by them to control intestinal microbiota as well as the mechanisms utilized by the microbiome to regulate intestinal epithelial function. This review will provide information regarding the development of inflammatory disorders dependent on the loss of intestinal barrier function and composition of the intestinal microbiota.

Abstract

The gastrointestinal tract, which is constantly exposed to a multitude of stimuli, is considered responsible for maintaining the homeostasis of the host. It is inhabited by billions of microorganisms, the gut microbiota, which form a mutualistic relationship with the host. Although the microbiota is generally recognized as beneficial, at the same time, together with pathogens, they are a permanent threat to the host. Various populations of epithelial cells provide the first line of chemical and physical defense against external factors acting as the interface between luminal microorganisms and immunocompetent cells in lamina propria. In this review, we focus on some essential, innate mechanisms protecting mucosal integrity, thus responsible for maintaining intestine homeostasis. The characteristics of decisive cell populations involved in maintaining the barrier arrangement, based on mucus secretion, formation of intercellular junctions as well as production of antimicrobial peptides, responsible for shaping the gut microbiota, are presented. We emphasize the importance of cross-talk between gut microbiota and epithelial cells as a factor vital for the maintenance of the homeostasis of the GI tract. Finally, we discuss how the imbalance of these regulations leads to the compromised barrier integrity and dysbiosis considered to contribute to inflammatory disorders and metabolic diseases.

Salivary Trefoil Factor Family (TFF) Peptides and Their Roles in Oral and Esophageal Protection: Therapeutic Potential

Human saliva is a complex body fluid with more than 3000 different identified proteins. Besides rheological and lubricating properties, saliva supports wound healing and acts as an antimicrobial barrier. TFF peptides are secreted from the mucous acini of the major and minor salivary glands and are typical constituents of normal saliva; TFF3 being the predominant peptide compared with TFF1 and TFF2. Only TFF3 is easily detectable by Western blotting. It occurs in two forms, a disulfide-linked homodimer (Mr: 13k) and a high-molecular-mass heterodimer with IgG Fc binding protein (FCGBP). TFF peptides are secretory lectins known for their protective effects in mucous epithelia; the TFF3 dimer probably has wound-healing properties due to its weak motogenic effect. There are multiple indications that FCGBP and TFF3-FCGBP play a key role in the innate immune defense of mucous epithelia. In addition, homodimeric TFF3 interacts in vitro with the salivary agglutinin DMBT1^gp340. Here, the protective roles of TFF peptides, FCGBP, and DMBT1^gp340 in saliva are discussed. TFF peptides are also used to reduce radiotherapy- or chemotherapy-induced oral mucositis. Thus, TFF peptides, FCGBP, and DMBT1^gp340 are promising candidates for better formulations of artificial saliva, particularly improving wound healing and antimicrobial effects even in the esophagus.

Chemical Synthesis of TFF3 Reveals Novel Mechanistic Insights and a Gut-Stable Metabolite

TFF3 regulates essential gastro- and neuroprotective functions, but its molecular mode of action remains poorly understood. Synthetic intractability and lack of reliable bioassays and validated receptors are bottlenecks for mechanistic and structure–activity relationship studies. Here, we report the chemical synthesis of TFF3 and its homodimer via native chemical ligation followed by oxidative folding. Correct folding was confirmed by NMR and circular dichroism, and TFF3 and its homodimer were not cytotoxic or hemolytic. TFF3, its homodimer, and the trefoil domain (TFF3_10-50) were susceptible to gastrointestinal degradation, revealing a gut-stable metabolite (TFF3_7-54; t_1/2 > 24 h) that retained its trefoil structure and antiapoptotic bioactivity. We tried to validate the putative TFF3 receptors CXCR4 and LINGO2, but neither TFF3 nor its homodimer displayed any activity up to 10 μM. The discovery of a gut-stable bioactive metabolite and reliable synthetic accessibility to TFF3 and its analogues are cornerstones for future molecular probe development and structure–activity relationship studies.

Structure, Function, and Therapeutic Potential of the Trefoil Factor Family in the Gastrointestinal Tract

Trefoil factor family peptides (TFF1, TFF2, and TFF3) are key players in protecting, maintaining, and repairing the gastrointestinal tract. Accordingly, they have the therapeutic potential to treat and prevent a variety of gastrointestinal disorders associated with mucosal damage. TFF peptides share a conserved motif, including three disulfide bonds that stabilize a well-defined three-loop-structure reminiscent of a trefoil. Although multiple functions have been described for TFF peptides, their mechanisms at the molecular level remain poorly understood. This review presents the status quo of TFF research relating to gastrointestinal disorders. Putative TFF receptors and protein partners are described and critically evaluated. The therapeutic potential of these peptides in gastrointestinal disorders where altered mucosal biology plays a crucial role in the underlying etiology is discussed. Finally, areas of investigation that require further research are addressed. Thus, this review provides a comprehensive update on TFF literature as well as guidance toward future research to better understand this peptide family and its therapeutic potential for the treatment of gastrointestinal disorders.

Extracellular production of recombinant sus scrofa trefoil factor 3 by Brevibacillus choshinensis

Trefoil factor 3 (TFF3) is involved in cell adhesion, motility and apoptosis, regulates mucosal immunity and maintains the functional integrity of intestinal epithelia. The upregulation of TFF3 expression in the weaning rat intestine attracted our interest. The present study hypothesized that TFF3 may serve a role in preventing diarrhea in weaning piglets, which is an important consideration in the pig farming industry. Previous recombinant TFF3 protein expression yields obtained from Escherichia coli were too low and the bioactivity of the protein was poor. Hence, this expression system was unsuitable for industrial applications. The present study explored the production of recombinant sus scrofa TFF3 in a Brevibacillus choshinensis (B. choshinensis) expression system, aiming to enhance the expression level of bioactive protein. To achieve this, the sus scrofa TFF3-encoding gene fragment was fused into an E. coli-Brevibacillus shuttle vector pNCMO2. High levels of TFF3 (30 mg/l) were produced and secreted into the B. choshinensis culture medium in soluble form with a molecular mass of 13.6 kDa and high immunoreactivity in western blotting. Thus, Brevibacillus may be used to produce useful mucosal factors for biochemical analyses and mucosal protection, and in industrial applications to produce novel inhibitors of diarrhea.

Different Forms of TFF3 in the Human Saliva: Heterodimerization with IgG Fc Binding Protein (FCGBP)

The peptide TFF3 is a member of a family of secretory lectins, and is typically synthesized by mucous epithelia together with mucins. It is mainly released from intestinal goblet cells as a high-molecular mass heterodimer with IgG Fc binding protein (FCGBP). Herein, we investigated human saliva by fast protein liquid chromatography (FPLC) and proteomics and identified high- and low-molecular-mass forms of TFF3. Whereas the high-molecular-mass forms represent a heterodimer with FCGBP, the low-molecular-mass forms represent homodimeric TFF3 forms. Proteomic analysis also revealed a C-terminally truncated form of TFF3. We hypothesize that salivary TFF3-FCGBP might play a role in the innate immune defense of the oral cavity and that TFF3 might also bind to microbial glycans. The known interaction of TFF3 with the agglutinin DMBT-1, a typical constituent of human saliva, further supports this protective role.

Trefoil Factor 3 (TFF3) Is Involved in Cell Migration for Skeletal Repair

The aim of the study was to explore the possible role of Trefoil Factor Family peptide 3 (TFF3) for skeletal repair. The expression of TFF3 was analyzed in human joint tissues as well as in a murine bone fracture model. Serum levels of TFF3 following a defined skeletal trauma in humans were determined by ELISA. The mRNA expression of TFF3 was analyzed under normoxia and hypoxia. Expression analysis after stimulation of human mesenchymal progenitor cells (MPCs) with TFF3 was performed by RT² Profiler PCR Array. The effect of recombinant human (rh)TFF3 on MPCs was analysed by different migration and chemotaxis assays. The effect on cell motility was also visualized by fluorescence staining of F-Actin. TFF3 was absent in human articular cartilage, but strongly expressed in the subchondral bone and periosteum of adult joints. Strong TFF3 immunoreactivity was also detected in murine fracture callus. Serum levels of TFF3 were significantly increased after skeletal trauma in humans. Expression analysis demonstrated that rhTFF3 significantly decreased mRNA of ROCK1. Wound healing assays showed increased cell migration of MPCs by rhTFF3. The F-Actin cytoskeleton was markedly influenced by rhTFF3. Cell proliferation was not increased by rhTFF3. The data demonstrate elevated expression of TFF3 after skeletal trauma. The stimulatory effects on cell motility and migration of MPCs suggest a role of TFF3 in skeletal repair.

Morphology and dynamics of tumor cell colonies propagating in epidermal growth factor supplemented media

The epidermal growth factor (EGF) plays a key role in physiological and pathological processes. This work reports on the influence of EGF concentration (c _EGF) on the modulation of individual cell phenotype and cell colony kinetics with the aim of perturbing the colony front roughness fluctuations. For this purpose, HeLa cell colonies that remain confluent along the whole expansion process with initial quasi-radial geometry and different initial cell populations, as well as colonies with initial quasi-linear geometry and large cell population, are employed. Cell size and morphology as well as its adhesive characteristics depend on c _EGF. Quasi-radial colonies (QRC) expansion kinetics in EGF-containing medium exhibits a complex behavior. Namely, at the first stages of growth, the average QRC radius evolution can be described by a t ^1/2 diffusion term coupled with exponential growth kinetics up to a critical time, and afterwards a growth regime approaching constant velocity. The extension of each regime depends on c _EGF and colony history. In the presence of EGF, the initial expansion of quasi-linear colonies (QLCs) also exhibits morphological changes at both the cell and the colony levels. In these cases, the cell density at the colony border region becomes smaller than in the absence of EGF and consequently, the extension of the effective rim where cell duplication and motility contribute to the colony expansion increases. QLC front displacement velocity increases with c _EGF up to a maximum value in the 2-10 ng ml^-1 range. Individual cell velocity is increased by EGF, and an enhancement in both the persistence and the ballistic characteristics of cell trajectories can be distinguished. For an intermediate c _EGF, collective cell displacements contribute to the roughening of the colony contours. This global dynamics becomes compatible with the standard Kardar-Parisi-Zhang growth model, although a faster colony roughness saturation in EGF-containing medium than in the control medium is observed.

Colonization of the cervicovaginal space with Gardnerella vaginalis leads to local inflammation and cervical remodeling in pregnant mice

The role of the cervicovaginal (CV) microbiome in regulating cervical function during pregnancy is poorly understood. Gardnerella vaginalis (G. vaginalis) is the most common bacteria associated with the diagnosis of bacterial vaginosis (BV). While BV has been associated with preterm birth (PTB), clinical trials targeting BV do not decrease PTB rates. It remains unknown if G. vaginalis is capable of triggering molecular, biomechanical and cellular events that could lead to PTB. The objective of this study was to determine if cervicovaginal colonization with G. vaginalis, in pregnant mice, induced cervical remodeling and modified cervical function. CD-1 timed-pregnant mice received a 5X10⁸ CFU/mL intravaginal inoculation of G. vaginalis or control on embryonic day 12 (E12) and E13. On E15, the mice were sacrificed and cervicovaginal fluid (CVF), amniotic fluid (AF), cervix, uterus, placentas and fetal membranes (FM) were collected. Genomic DNA was isolated from the CVF, placenta, uterus and FM and QPCR was performed to confirm colonization. IL-6 was measured in the CVF and AF and soluble e-cadherin (seCAD) was assessed in the CVF by ELISA. RNA was extracted from the cervices to evaluate IL-10, IL-8, IL-1β, TNF-α, Tff-1, SPINK-5, HAS-1 and LOX expression via QPCR. Mucicarmine and trichrome staining was used to assess cervical mucin and collagen. Biomechanical properties of the cervix were studied using quasi-static tensile load-to-failure biomechanical tests. G. vaginalis successfully colonized the CV space. This colonization induced immune responses (increased IL-6 levels in CVF and AF, increased mRNA expression of cervical cytokines), altered the epithelial barrier (increased seCAD in the CVF), induced cervical remodeling (increased mucin production, altered collagen) and altered cervical biomechanical properties (a decrease in biomechanical modulus and an increase in maximum strain). The ability of G. vaginalis to induce these molecular, immune, cellular and biomechanical changes suggests that this bacterium may play a pathogenic role in premature cervical remodeling leading to PTB.

Deciphering the Complex Signaling Systems That Regulate Intestinal Epithelial Cell Death Processes and Shedding

Intestinal epithelial cells play a fundamental role in maintaining homeostasis. Shedding of intestinal cells in a controlled manner is critical to maintenance of barrier function. Barrier function is maintained during this shedding process by a redistribution of tight junctional proteins to facilitate closure of the gap left by the shedding cell. However, despite the obvious importance of epithelial cell shedding to gut health, a central question is how the extrusion of epithelial cells is achieved, enabling barrier integrity to be maintained in the healthy gut and restored during inflammation remains largely unanswered. Recent studies have provided evidence that excessive epithelial cell shedding and loss of epithelial barrier integrity is triggered by exposure to lipopolysaccharide or tumor necrosis factor alpha. Subsequent studies have provided evidence of the involvement of specific cellular components and signaling mechanisms as well as the functionality of microbiota that can be either detrimental or beneficial for intestinal barrier integrity. This review will focus on the evidence and decipher how the signaling systems through which the mucosal immune system and microbiota can regulate epithelial cell shedding and how these mechanisms interact to preserve the viability of the epithelium.

Disruption of the epithelial barrier during intestinal inflammation: Quest for new molecules and mechanisms

The intestinal epithelium forms a key protective barrier that separates internal organs from the harmful environment of the gut lumen. Increased permeability of the gut barrier is a common manifestation of different inflammatory disorders contributing to the severity of disease. Barrier permeability is controlled by epithelial adherens junctions and tight junctions. Junctional assembly and integrity depend on fundamental homeostatic processes such as cell differentiation, rearrangements of the cytoskeleton, and vesicle trafficking. Alterations of intestinal epithelial homeostasis during mucosal inflammation may impair structure and remodeling of apical junctions, resulting in increased permeability of the gut barrier. In this review, we summarize recent advances in our understanding of how altered epithelial homeostasis affects the structure and function of adherens junctions and tight junctions in the inflamed gut. Specifically, we focus on the transcription reprogramming of the cell, alterations in the actin cytoskeleton, and junctional endocytosis and exocytosis. We pay special attention to knockout mouse model studies and discuss the relevance of these mechanisms to human gastrointestinal disorders.

Trefoil factors: Gastrointestinal-specific proteins associated with gastric cancer

Trefoil factor family (TFF), composed of TFF1, TFF2, and TFF3, is a cluster of secreted peptides characterized by trefoil domain (s) and C-terminal dimerization domain. TFF1, a gastric tumor suppressor, is a single trefoil peptide originally detected in breast cancer cell lines but expressed mainly in the stomach; TFF2, a candidate of gastric cancer suppressor with two trefoil domains, is abundant in the stomach and duodenal Brunner's glands; and TFF3 is another single trefoil peptide expressed throughout the intestine which can promote the development of gastric carcinoma. According to multiple studies, TFFs play a regulatory function in the mammals' digestive system, namely in mucosal protection and epithelial cell reconstruction, tumor suppression or promotion, signal transduction and the regulation of proliferation and apoptosis. Action mechanisms of TFFs remain unresolved, but the recent demonstration of a GKN (gastrokine) 2-TFF1 heterodimer implicates structural and functional interplay with gastrokines. This review aims to encapsulate the structural and biological characteristics of TFF.

Trefoil Factor 3 (TFF3) Is Regulated by Food Intake, Improves Glucose Tolerance and Induces Mucinous Metaplasia

Trefoil factor 3 (TFF3), also called intestinal trefoil factor or Itf, is a 59 amino acid peptide found as a homodimer predominantly along the gastrointestinal tract and in serum. TFF3 expression is elevated during gastrointestinal adenoma progression and has been shown to promote mucosal wound healing. Here we show that in contrast to other trefoil factor family members, TFF1 and TFF2, TFF3 is highly expressed in mouse duodenum, jejunum and ileum and that its expression is regulated by food intake. Overexpression of TFF3 using a recombinant adeno-associated virus (AAV) vector, or daily administration of recombinant TFF3 protein in vivo improved glucose tolerance in a diet-induced obesity mouse model. Body weight, fasting insulin, triglyceride, cholesterol and leptin levels were not affected by TFF3 treatment. Induction of mucinous metaplasia was observed in mice with AAV-mediated TFF3 overexpression, however, no such adverse histological effect was seen after the administration of recombinant TFF3 protein. Altogether these results suggest that the therapeutic potential of targeting TFF3 to treat T2D may be limited.

Generation of Lactococcus lactis capable of coexpressing epidermal growth factor and trefoil factor to enhance in vitro wound healing

Epidermal growth factor (EGF) and trefoil factor 3 (TFF3) are peptides that actively support the restitution and repair of mucosal epithelial barriers. Previous studies have shown that TFF3 enhanced EGF effect in wound healing, suggesting that the combined application of the two factors may be advantageous in clinical tissue repair. Expression of multiple proteins in a single host is a desirable approach in a biotechnological process, allowing to reduce cost and increase production efficiency. The aim of the present study was to study the feasibility of coexpressing EGF and TFF3 in food grade bacteria, Lactococcus lactis (L. lactis). Using an expression construct allowing simultaneous translation of two separate recombinant peptides, we generated a L. lactis that coexpressed and secreted EGF and TFF3 dually (LL-ET). Western blot analysis revealed that LL-ET secreted 45-54 % more total recombinant peptides (EGF+TFF3) per flask fermentation and 21-37 % more total recombinant proteins in bioreactor fermentation compared to their single factor expressing L. lactis counterparts (LL-EGF and LL-TFF3, respectively). The resulted recombinant EGF and TFF3 showed enhancement in wound healing activity in vitro. Our data suggest that the dual expression and secretion of EGF and TFF3 by L. lactis effectively accelerated cell migration, demonstrating potential future oral application of L. lactis fermentation product containing dual factors or a cocktail of factors to potentially treat intestinal damage and inflammation.

From cell membrane to the nucleus: an emerging role of E-cadherin in gene transcriptional regulation

E-cadherin is a well-known mediator of cell–cell adherens junctions. However, many other functions of E-cadherin have been reported. Collectively, the available data suggest that E-cadherin may also act as a gene transcriptional regulator. Here, evidence supporting this claim is reviewed, and possible mechanisms of action are discussed. E-cadherin has been shown to modulate the activity of several notable cell signalling pathways, and given that most of these pathways in turn regulate gene expression, we proposed that E-cadherin may regulate gene transcription by affecting these pathways. Additionally, E-cadherin has been shown to accumulate in the nucleus where documentation of an E-cadherin fragment bound to DNA suggests that E-cadherin may directly regulate gene transcription. In summary, from the cell membrane to the nucleus, a role for E-cadherin in gene transcription may be emerging. Studies specifically focused on this potential role would allow for a more thorough understanding of this transmembrane glycoprotein in mediating intra- and intercellular activities.

Intestinal trefoil factor activates the PI3K/Akt signaling pathway to protect gastric mucosal epithelium from damage

Intestinal trefoil factor (ITF, also named as trefoil factor 3, TFF3) is a member of the TFF-domain peptide family, which plays an essential role in the regulation of cell survival, cell migration and maintains mucosal epithelial integrity in the gastrointestinal tract. However, the underlying mechanisms and associated molecules remain unclear. The aim of this study was to explore the protective effects of ITF on gastric mucosal epithelium injury and its possible molecular mechanisms of action. In the present study, we show that ITF was able to promote the proliferation and migration of GES-1 cells via a mechanism that involves the PI3K/Akt signaling pathway. Western blot results indicated that ITF induced a dose- and time-dependent increase in the Akt signaling pathway. ITF also plays an essential role in the restitution of GES-1 cell damage induced by lipopolysaccharide (LPS). LPS induced the apoptosis of GES-1 cells, decreased cell viability significantly (P<0.01) and led to epithelial tight junction damage, which is attenuated via ITF treatment. The protective effect of ITF on the integrity of GES-1 was abrogated by inhibition of the PI3K/Akt pathway. Taken together, our results demonstrate that ITF promotes the proliferation and migration of gastric mucosal epithelial cells and preserves gastric mucosal epithelial integrity after damage is mediated by activation of the PI3K/Akt signaling pathway. This study suggested that the PI3K/Akt pathway could act as a key intracellular pathway in the gastric mucosal epithelium that may serve as a therapeutic target to preserve epithelial integrity during injury.

Inflammatory signals that regulate intestinal epithelial renewal, differentiation, migration and cell death: Implications for necrotizing enterocolitis

Necrotizing enterocolitis is a disease entity with multiple proposed pathways of pathogenesis. Various combinations of these risk factors, perhaps based on genetic predisposition, possibly lead to the mucosal and epithelial injury that is the hallmark of NEC. Intestinal epithelial integrity is controlled by a tightly regulated balance between proliferation and differentiation of epithelium from intestinal epithelial stem cells and cellular loss by apoptosis. various signaling pathways play a key role in creating and maintaining this balance. The aim of this review article is to outline intestinal epithelial barrier development and structure and the impact of these inflammatory signaling and regulatory pathways as they pertain to the pathogenesis of NEC.

Dynamics and regulation of epithelial adherens junctions: recent discoveries and controversies

Adherens junctions (AJs) are evolutionarily conserved plasma-membrane structures that mediate cell-cell adhesions in multicellular organisms. They are organized by several types of adhesive integral membrane proteins, most notably cadherins and nectins that are clustered and stabilized by a number of cytoplasmic scaffolds. AJs are key regulators of tissue architecture and dynamics via control of cell proliferation, polarity, shape, motility, and survival. They are absolutely critical for normal tissue morphogenesis and their disruption results in pathological abnormalities in different tissues. Although the field of adherens-junction research dramatically progressed in recent years, a number of important questions remain controversial and poorly understood. This review outlines basic principles that regulate organization of AJs in mammalian epithelia and discusses recent advances and standing controversies in the field. A special attention is paid to the regulation of AJs by vesicle trafficking and the intracellular cytoskeleton as well as roles and mechanisms of adherens-junction disruption during tumor progression and tissue inflammation.

Trefoil factor 3 peptide regulates migration via a Twist-dependent pathway in gastric cell

Trefoil factor 3 (TFF3) is a member of the TFF-domain peptide family and essential in regulating cell migration and maintaining mucosal integrity in gastrointestinal tract. However, the role of TFF3 and its downstream regulating mechanisms in cancer cell migration remain unclear. We previously reported that TFF3 prolonged the up-regulation of Twist protein to modulate IL-8 secretion in intestinal epithelial cells. In this study, we investigated the role of Twist protein in TFF3-induced migration of SGC7901 cells. While Twist was activated by TFF3, siRNA-mediated knockdown of Twist abolished TFF3-induced cell migration. Furthermore, the migration related marker CK-8 as well as ZO-1 and MMP-9 was also regulated by TFF3 via a Twist-dependent mechanism. Our study suggests that Twist, as an important potential downstream effector, plays a key role in TFF3-modulated metastasis in gastric cancer and can be a promising therapeutic target against intestinal-type gastric cancer.

The role of growth factors in intestinal regeneration and repair in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease resulting in major neonatal morbidity and mortality. The pathology is poorly understood, and the means of preventing and treating NEC are limited. Several endogenous growth factors have been identified as having important roles in intestinal growth as well as aiding intestinal repair from injury or inflammation. In this review, we will discuss several growth factors as mediators of intestinal regeneration and repair as well as potential therapeutic agents for NEC.

Mucosal healing in ulcerative colitis: pathophysiology and pharmacology

Ulcerative colitis (UC) is a colonic inflammatory condition with a substantial impact on the quality of life of affected persons. The disease carries a cumulative risk of need of colectomy of 20-30% and an estimated cumulative risk of colorectal cancer of 18% after 30 years of disease duration. With the introduction of the tumor necrosis factor-alpha inhibitors for the treatment of UC, it has become increasingly evident that the disease course is influenced by whether or not the patient achieves mucosal healing. Thus, patients with mucosal healing have fewer flare-ups, a decreased risk of colectomy, and a lower probability of developing colorectal cancer. Understanding the mechanisms of mucosal wound formation and wound healing in UC, and how they are affected therapeutically is therefore of importance for obtaining efficient treatment strategies holding the potential of changing the disease course of UC. This review is focused on the pathophysiological mechanism of mucosal wound formation in UC as well as the known mechanisms of intestinal wound healing. Regarding the latter topic, pathways of both wound healing intrinsic to epithelial cells and the wound-healing mechanisms involving interaction between epithelial cells and other cells of the mucosa are discussed. The biochemistry of wound healing in UC provides the basis for the subsequent description of how these pathways are affected by the current medications, and what can be learnt on how to design future treatment regimens for UC based on targeting mucosal healing.

Regulatory function of trefoil peptides (TFF) on intestinal cell junctional complexes

Abstract Trefoil peptides (TFF) are constitutively expressed in the gastrointestinal tract and are involved in gastrointestinal defence and repair by promoting epithelial restitution. Although there is a general consensus regarding the pro-motogenic activity of trefoil peptides, the cellular mechanisms through which they mediate these processes are not completely understood. Pertubation of the E-cadherin/catenin complex at intercellular junctions appears to be a functional pathway through which TFF2 and TFF3 promote cell migration. Tight junction complexes seal the paracellular spaces between cells and contribute to epithelial barrier function. TFF3 peptide stimulation stabilises these junctions through upregulation of the tightening protein claudin-1 and redistribution of ZO-1 from the cytoplasm to the intercellular membrane with an increase in binding to occludin. Modulation of the functional activity and subcellular localisation of epithelial junctional adhesion molecules represent important mechanisms by which trefoil peptides may promote migration of intestinal epithelial cells in vitro and healing of mucosal damage in vivo.

Milk fat globule-epidermal growth factor 8 is decreased in intestinal epithelium of ulcerative colitis patients and thereby causes increased apoptosis and impaired wound healing

Milk fat globule-epidermal growth factor 8 (MFG-E8) plays an important role in maintaining intestinal barrier homeostasis and accelerating intestinal restitution. However, studies of MFG-E8 expression in humans with ulcerative colitis are lacking. We examined MFG-E8 expression in colonic mucosal biopsies from ulcerative colitis patients and healthy controls (n = 26 each) by real-time quantitative polymerase chain reaction (PCR), Western blot analysis and immunohistochemistry. MFG-E8 mRNA and protein expression was lower in ulcerative colitis patients than in controls. MFG-E8 expression was inversely correlated with mucosal inflammatory activity and clinical disease activity in patients. MFG-E8 was present in human intestinal epithelial cells both in vivo and in vitro. Apoptosis induction was also detected in the intestinal epithelium of ulcerative colitis patients by terminal-deoxynucleoitidyl transferase mediated nick-end labeling assay. We used lentiviral vectors encoding human MFG-E8 targeting short hairpin RNA to obtain MFG-E8 knockdown intestinal epithelia cell clones. MFG-E8 knockdown could promote apoptosis in intestinal epithelial cell lines, accompanied by a decrease in level of the antiapoptotic protein B-cell lymphoma 2 (BCL-2) and induction of the proapoptotic protein BCL2-associated protein X (BAX). The addition of recombinant human MFG-E8 led to decreased BAX and cleaved caspase-3 levels and induction of BCL-2 level in intestinal epithelia cells. MFG-E8 knockdown also attenuated wound healing on scratch assay of intestinal epithelial cells. The mRNA level of intestinal trefoid factor 3, a pivotal factor in intestinal epithelial cell migration and restitution, was downregulated with MFG-E8 knockdown. In conclusion, we demonstrated that decreased colonic MFG-E8 expression in patients with ulcerative colitis may be associated with mucosal inflammatory activity and clinical disease activity through basal cell apoptosis and preventing tissue healing in the pathogenesis of ulcerative colitis.

E-cadherin is critical for collective sheet migration and is regulated by the chemokine CXCL12 protein during restitution

Chemokines and other immune mediators enhance epithelial barrier repair. The intestinal barrier is established by highly regulated cell-cell contacts between epithelial cells. The goal of these studies was to define the role for the chemokine CXCL12 in regulating E-cadherin during collective sheet migration during epithelial restitution. Mechanisms regulating E-cadherin were investigated using Caco2(BBE) and IEC-6 model epithelia. Genetic knockdown confirmed a critical role for E-cadherin in in vitro restitution and in vivo wound repair. During restitution, both CXCL12 and TGF-β1 tightened the monolayer by decreasing the paracellular space between migrating epithelial cells. However, CXCL12 differed from TGF-β1 by stimulating the significant increase in E-cadherin membrane localization during restitution. Chemokine-stimulated relocalization of E-cadherin was paralleled by an increase in barrier integrity of polarized epithelium during restitution. CXCL12 activation of its cognate receptor CXCR4 stimulated E-cadherin localization and monolayer tightening through Rho-associated protein kinase activation and F-actin reorganization. These data demonstrate a key role for E-cadherin in intestinal epithelial restitution.

Selective non-steroidal glucocorticoid receptor agonists attenuate inflammation but do not impair intestinal epithelial cell restitution in vitro

Introduction

Despite the excellent anti-inflammatory and immunosuppressive action of glucocorticoids (GCs), their use for the treatment of inflammatory bowel disease (IBD) still carries significant risks in terms of frequently occurring severe side effects, such as the impairment of intestinal tissue repair. The recently-introduced selective glucocorticoid receptor (GR) agonists (SEGRAs) offer anti-inflammatory action comparable to that of common GCs, but with a reduced side effect profile.

Methods

The in vitro effects of the non-steroidal SEGRAs Compound A (CpdA) and ZK216348, were investigated in intestinal epithelial cells and compared to those of Dexamethasone (Dex). GR translocation was shown by immunfluorescence and Western blot analysis. Trans-repressive effects were studied by means of NF-κB/p65 activity and IL-8 levels, trans-activation potency by reporter gene assay. Flow cytometry was used to assess apoptosis of cells exposed to SEGRAs. The effects on IEC-6 and HaCaT cell restitution were determined using an in vitro wound healing model, cell proliferation by BrdU assay. In addition, influences on the TGF-β- or EGF/ERK1/2/MAPK-pathway were evaluated by reporter gene assay, Western blot and qPCR analysis.

Results

Dex, CpdA and ZK216348 were found to be functional GR agonists. In terms of trans-repression, CpdA and ZK216348 effectively inhibited NF-κB activity and IL-8 secretion, but showed less trans-activation potency. Furthermore, unlike SEGRAs, Dex caused a dose-dependent inhibition of cell restitution with no effect on cell proliferation. These differences in epithelial restitution were TGF-β-independent but Dex inhibited the EGF/ERK1/2/MAPK-pathway important for intestinal epithelial wound healing by induction of MKP-1 and Annexin-1 which was not affected by CpdA or ZK216348.

Conclusion

Collectively, our results indicate that, while their anti-inflammatory activity is comparable to Dex, SEGRAs show fewer side effects with respect to wound healing. The fact that SEGRAs did not have a similar effect on cell restitution might be due to a different modulation of EGF/ERK1/2 MAPK signalling.

IL-6/STAT3/TFF3 signaling regulates human biliary epithelial cell migration and wound healing in vitro

Interleukin-6 (IL-6), through activation of the signal transducer and activator of transcription 3 (STAT3) and trefoil factor family 3 (TFF3), has been implicated in the promotion of mouse biliary epithelial cell (BEC) proliferation and migration. However, it is still unclear whether the IL-6/STAT3/TFF3 signaling had similar effects on human BECs. Here, we showed that exposure of human BECs to recombinant IL-6 resulted in STAT3 phosphorylation and increased the expression of TFF3 at both mRNA and protein levels. Moreover, inhibition of STAT3 using RNA interference significantly abrogated IL-6-induced TFF3 expression. In an in-vitro wound healing model, IL-6 facilitated human BEC migration. This promotion of cell migration by IL-6 was blocked when STAT3 was knocked down. Interestingly, the addition of exogenous TFF3 could rescue the cell migration defects caused by STAT3 silencing. In conclusion, our data indicate that STAT3 plays a critical role in IL-6-induced TFF3 expression in human BECs and the IL-6/STAT3/TFF3 signaling is involved in human BEC migration and wound healing.

Relationship between TFF3 expression and gastric cardiac carcinogenesis

AIM: To explore the relationship between the expression of trefoil factor 3 (TFF3) protein and the evolution of gastric cardiac adenocarcinoma.

METHODS: The streptavidin-peroxidase immunohistochemistry method was used to detect TFF3 protein expression in 24 cardiac gastritis specimens, 52 intestinal metaplasia specimens, 65 specimens of intestinal metaplasia with dysplasia and 35 gastric cardiac adenocarcinoma specimens from a high incidence area of gastric cardiac adenocarcinoma in Henan.

RESULTS: TFF3 protein is predominantly expressed in the striated border of the columnar cells in cardiac gastritis and intestinal metaplasia tissues, and in the cytoplasm in dysplasia and carcinoma tissues. The positive rates of TFF3 protein in cardiac gastritis, intestinal metaplasia, dysplasia, and carcinoma tissues were 20.8%, 44.2%, 46.2% and 54.3%, respectively. The expression of TFF3 was correlated well with the pathological grade of the lesions (r = 0.232, P < 0.05). The location of TFF3 expression was correlated with the pathological types of the lesions (Kappa = 0.490).

CONCLUSION: Overexpression of TFF3 protein in the cytoplasm is involved in gastric cardiac carcinogenesis and might be one of important risk factors for gastric cardiac adenocarcinoma.

Phase II, randomized, double-blind, placebo-controlled study of recombinant human intestinal trefoil factor oral spray for prevention of oral mucositis in patients with colorectal cancer who are receiving fluorouracil-based chemotherapy

PURPOSE

This study evaluated the safety and efficacy of recombinant human intestinal trefoil factor (rhITF) administered as topical oral spray for prevention and treatment of chemotherapy-induced oral mucositis (OM).

PATIENTS AND METHODS

Ninety-nine patients with colorectal cancer who had moderate to severe OM (WHO grade >or= 2) in the first cycle of chemotherapy were randomly assigned to receive either placebo, rhITF 10 mg/mL (ie, low dose), or rhITF 80 mg/mL (ie, high dose) by oral spray (300 microL, eight times each day) for 14 consecutive days in the second chemotherapy cycle. Patients were assessed on days 1, 3, 5, 7, 10, 12, 14, and 21 (+/- 2 days for the last assessment) for safety and for OM incidence and severity.

RESULTS

Treatment of patients at high risk for developing OM with low- or high-dose rhITF significantly reduced the amount of incidence (75% to 81%; low-dose rhITF P < .001; high-dose rhITF P = .002). Frequencies of WHO grade >or= 2 OM in the placebo, low-dose rhITF, and high-dose rhITF groups were 48.5%, 9.1%, and 12.1%, respectively. Assessment of the area under the curve revealed statistically significant reductions in OM severity in the rhITF-treated groups versus placebo. Only a minority of patients (6.1%) reported treatment-emergent adverse events (TEAEs), all of which were mild to moderate in intensity and resolved without sequelae. The incidence of TEAEs was not significantly different among treatment groups.

CONCLUSION

rhITF oral spray formulation was safe and effective when used for the reduction of chemotherapy-associated OM in patients with colorectal cancer. Patients exhibited high compliance in dosing administration. Future clinical study is planned to develop this drug for use in OM management in patients with cancer.

Beneficial effect of 3,4,5,6-tetrahydroxyxanthone on dyslipidemia in apolipoprotein E-deficient mice

Previous investigations have shown that decreased expression of angiopoietin-like protein 3 (Angptl3) is protective against dyslipidemia in atherosclerosis. The present study was conducted to test the effect of 3,4,5,6-tetrahydroxyxanthone, a xanthone compound, on dyslipidemia in apolipoprotein E-deficient (ApoE-/-) mice. Forty mice were randomly divided into 4 groups (n = 10): control group (C57BL/6J mice), ApoE-/-mice group, and two groups of ApoE-/- mice treated with 3,4,5,6-tetrahydroxyxanthone (10 or 30 mg/kg per day). Eight weeks after treatment, lipid levels in the blood and liver, expression of hepatic Angptl3, and adipose tissue lipoprotein lipase (LPL) were determined. Treatment with 3,4,5,6-tetrahydroxyxanthone (10 or 30 mg/kg) significantly decreased plasma and hepatic total cholesterol and triglyceride concentrations, increased plasma high-density lipoprotein cholesterol, and significantly downregulated expression of Angptl3 mRNA and protein concomitantly with upregulated expression of LPL mRNA. In addition, T0901317 (a liver X receptor ligand) caused elevated expression of hepatic Angptl3 mRNA and protein, and the effect of T0901317 was also abrogated by 3,4,5,6-tetrahydroxyxanthone in vivo and in vitro. The present results suggest that the beneficial effect of 3,4,5,6-tetrahydroxyxanthone on dyslipidemia may be related to reduced expression of Angptl3.

Advance in relationship between TFF3 and gastric cancer

Trefoil factor family (TFF) consists of three members, including TFF1, TFF2 and TFF3. TFF has such functions as maintaining gut mucosal integrity, promoting epithelial cell restitution, as well as cell signal transduction, modulating apoptosis and enhancing invasion. Therefore, TFF plays crucial roles in the process of inflammation and tumorigenesis. Researches recently have indicated that TFF3 plays an important role in gastric cancer, especially in intestinal gastric carcinoma.

Advances in research of trefoil factor 3

As one of important defensive factors, trefoil factor 3 (TFF3) has considerable relation to the lesion, recovery, proliferation and malignancy of gastrointestinal mucosa. Furthermore, the correlation between TFF3 and tumor, including its pathogenesis, progress and prognosis, has been reported remarkably. However, the binding proteins of TFF3 remains to be confirmed and the research of TFF3 on the mechanism of action and signal transduction pathway is just initial. This article reviewed the progress in TFF3 research.

Intestinal trefoil factor/TFF3 promotes re-epithelialization of corneal wounds

Disorders of wound healing characterized by impaired or delayed re-epithelialization are a serious medical problem. These conditions affect many tissues, are painful, and are difficult to treat. In this study using cornea as a model, we demonstrate the importance of trefoil factor 3 (TFF3, also known as intestinal trefoil factor) in re-epithelialization of wounds. In two different models of corneal wound healing, alkali- and laser-induced corneal wounding, we analyzed the wound healing process in in vivo as well as in combined in vivo/in vitro model in wild type (Tff3(+)(/)(+)) and Tff3-deficient (Tff3(-)(/)(-)) mice. Furthermore, we topically applied different concentrations of recombinant human TFF3 (rTFF3) peptide on the wounded cornea to determine the efficacy of rTFF3 on corneal wound healing. We found that Tff3 peptide is not expressed in intact corneal epithelium, but its expression is extensively up-regulated after epithelial injury. Re-epithelialization of corneal wounds in Tff3(-/-) mice is significantly prolonged in comparison to Tff3(+/+) mice. In addition, exogenous application of rTFF3 to the alkali-induced corneal wounds accelerates significantly in in vivo and in combined in vivo/in vitro model wound healing in Tff3(+/+) and Tff3(-/-) mice. These findings reveal a pivotal role for Tff3 in corneal wound healing mechanism and have broad implications for developing novel therapeutic strategies for treating nonhealing wounds.