Isolation and characterization of putative trefoil peptide receptors

Tff3 Deficiency Differentially Affects the Morphology of Male and Female Intestines in a Long-Term High-Fat-Diet-Fed Mouse Model

Trefoil factor family protein 3 (Tff3) protects the gastrointestinal mucosa and has a complex mode of action in different tissues. Here, we aimed to determine the effect of Tff3 deficiency on intestinal tissues in a long-term high-fat-diet (HFD)-fed model. A novel congenic strain without additional metabolically relevant mutations (Tff3-/-/C57Bl6NCrl strain, male and female) was used. Wild type (Wt) and Tff3-deficient mice of both sexes were fed a HFD for 36 weeks. Long-term feeding of a HFD induces different effects on the intestinal structure of Tff3-deficient male and female mice. For the first time, we found sex-specific differences in duodenal morphology. HFD feeding reduced microvilli height in Tff3-deficient females compared to that in Wt females, suggesting a possible effect on microvillar actin filament dynamics. These changes could not be attributed to genes involved in ER and oxidative stress, apoptosis, or inflammation. Tff3-deficient males exhibited a reduced cecal crypt depth compared to that of Wt males, but this was not the case in females. Microbiome-related short-chain fatty acid content was not affected by Tff3 deficiency in HFD-fed male or female mice. Sex-related differences due to Tff3 deficiency imply the need to consider both sexes in future studies on the role of Tff in intestinal function.

The Forms of the Lectin Tff2 Differ in the Murine Stomach and Pancreas: Indications for Different Molecular Functions

The lectin TFF2 belongs to the trefoil factor family (TFF). This polypeptide is typically co-secreted with the mucin MUC6 from gastric mucous neck cells, antral gland cells, and duodenal Brunner glands. Here, TFF2 fulfills a protective function by forming a high-molecular-mass complex with the MUC6, physically stabilizing the mucus barrier. In pigs and mice, and slightly in humans, TFF2 is also synthesized in the pancreas. Here, we investigated the murine stomach, pancreas, and duodenum by fast protein liquid chromatography (FPLC) and proteomics and identified different forms of Tff2. In both the stomach and duodenum, the predominant form is a high-molecular-mass complex with Muc6, whereas, in the pancreas, only low-molecular-mass monomeric Tff2 was detectable. We also investigated the expression of Tff2 and other selected genes in the stomach, pancreas, and the proximal, medial, and distal duodenum (RT-PCR analysis). The absence of the Tff2/Muc6 complex in the pancreas is due to a lack of Muc6. Based on its known motogenic, anti-apoptotic, and anti-inflammatory effects, we propose a protective receptor-mediated function of monomeric Tff2 for the pancreatic ductal epithelium. This view is supported by a report that a loss of Tff2 promotes the formation of pancreatic intraductal mucinous neoplasms.

Defects in the expression of colonic host defense factors associate with barrier dysfunction induced by a high-fat/high-cholesterol diet

The effect of Western diets in the gastrointestinal system is largely mediated by their ability to promote alterations in the immunity and physiology of the intestinal epithelium, and to affect the composition of the commensal microbiota. To investigate the response of the colonic epithelium to high-fat/high-cholesterol diets (HFHCDs), we evaluated the synthesis of host defense factors involved in the maintenance of the colonic homeostasis. C57BL/6 mice were fed an HFHCD for 3 weeks and their colons were evaluated for histopathology, gene expression, and microbiota composition. In addition, intestinal permeability and susceptibility to Citrobacter rodentium were also studied. HFHCD caused colonic hyperplasia, loss of goblet cells, thinning of the mucus layer, moderate changes in the composition of the intestinal microbiota, and an increase in intestinal permeability. Gene expression analyses revealed significant drops in the transcript levels of Muc1, Muc2, Agr2, Atoh1, Spdef, Ang4, Camp, Tff3, Dmbt1, Fcgbp, Saa3, and Retnlb. The goblet cell granules of HFHCD-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. In correspondence with these defects, colonic bacteria were in close contact with, and invading the epithelium. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHCD-fed animals accompanied by increased epithelial damage. Collectively, our results show that HFHCD perturbs the synthesis of colonic host defense factors, which associate with alterations in the commensal microbiota, the integrity of the intestinal barrier, and the host's susceptibility to enteric infections.

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.

Trefoil Factor Family Member 2: From a High-Fat-Induced Gene to a Potential Obesity Therapy Target

Obesity has its epidemiological patterns continuously increasing. With controlling both diet and exercise being the main approaches to manage the energy metabolism balance, a high-fat (HF) diet is of particular importance. Indeed, lipids have a low satiety potential but a high caloric density. Thus, focusing on pharmacologically targetable pathways remains an approach with promising therapeutic potential. Within this context, trefoil factor family member 2 (Tff2) has been characterized as specifically induced by HF diet rather than low-fat diet. TFF2 has also been linked to diverse neurological mechanisms and metabolic patterns suggesting its role in energy balance. The hypothesis is that TFF2 would be a HF diet-induced signal that regulates metabolism with a focus on lipids. Within this review, we put the spotlight on key findings highlighting this line of thought. Importantly, the hypothetical mechanisms pointed highlight TFF2 as an important contributor to obesity development via increasing lipids intestinal absorption and anabolism. Therefore, an outlook for future experimental activities and evaluation of the therapeutic potential of TFF2 inhibition is given. Indeed, its knockdown or downregulation would contribute to an antiobesity phenotype. We believe this work represents an addition to our understanding of the lipidic molecular implications in obesity, which will contribute to develop therapies aiming to manage the lipidic metabolic pathways including the absorption, storage and metabolism via targeting TFF2-related pathways. We briefly discuss important relevant concepts for both basic and clinical researchers.

Trefoil Factor Family (TFF) Peptides and Their Links to Inflammation: A Re-evaluation and New Medical Perspectives

Trefoil factor family peptides (TFF1, TFF2, TFF3), together with mucins, are typical exocrine products of mucous epithelia. Here, they act as a gastric tumor suppressor (TFF1) or they play different roles in mucosal innate immune defense (TFF2, TFF3). Minute amounts are also secreted as endocrine, e.g., by the immune and central nervous systems. As a hallmark, TFF peptides have different lectin activities, best characterized for TFF2, but also TFF1. Pathologically, ectopic expression occurs during inflammation and in various tumors. In this review, the role of TFF peptides during inflammation is discussed on two levels. On the one hand, the expression of TFF1-3 is regulated by inflammatory signals in different ways (upstream links). On the other hand, TFF peptides influence inflammatory processes (downstream links). The latter are recognized best in various Tff-deficient mice, which have completely different phenotypes. In particular, TFF2 is secreted by myeloid cells (e.g., macrophages) and lymphocytes (e.g., memory T cells), where it modulates immune reactions triggering inflammation. As a new concept, in addition to lectin-triggered activation, a hypothetical lectin-triggered inhibition of glycosylated transmembrane receptors by TFF peptides is discussed. Thus, TFFs are promising players in the field of glycoimmunology, such as galectins and C-type lectins.

Trefoil Factor Family (TFF) Peptides and Their Diverse Molecular Functions in Mucus Barrier Protection and More: Changing the Paradigm

Trefoil factor family peptides (TFF1, TFF2, TFF3) are typically co-secreted together with mucins. Tff1 represents a gastric tumor suppressor gene in mice. TFFs are also synthesized in minute amounts in the immune and central nervous systems. In mucous epithelia, they support rapid repair by enhancing cell migration ("restitution") via their weak chemotactic and anti-apoptotic effects. For a long time, as a paradigm, this was considered as their major biological function. Within recent years, the formation of disulfide-linked heterodimers was documented for TFF1 and TFF3, e.g., with gastrokine-2 and IgG Fc binding protein (FCGBP). Furthermore, lectin activities were recognized as enabling binding to a lipopolysaccharide of Helicobacter pylori (TFF1, TFF3) or to a carbohydrate moiety of the mucin MUC6 (TFF2). Only recently, gastric TFF1 was demonstrated to occur predominantly in monomeric forms with an unusual free thiol group. Thus, a new picture emerged, pointing to diverse molecular functions for TFFs. Monomeric TFF1 might protect the gastric mucosa as a scavenger for extracellular reactive oxygen/nitrogen species. Whereas, the TFF2/MUC6 complex stabilizes the inner layer of the gastric mucus. In contrast, the TFF3-FCGBP heterodimer (and also TFF1-FCGBP) are likely part of the innate immune defense of mucous epithelia, preventing the infiltration of microorganisms.

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.

Odyssey of trefoil factors in cancer: Diagnostic and therapeutic implications

Trefoil factors 1, 2, and 3 (TFFs) are a family of small secretory molecules involved in the protection and repair of the gastrointestinal tract (GI). TFFs maintain and restore epithelial structural integrity via transducing key signaling pathways for epithelial cell migration, proliferation, and invasion. In recent years, TFFs have emerged as key players in the pathogenesis of multiple diseases, especially cancer. Initially recognized as tumor suppressors, emerging evidence demonstrates their key role in tumor progression and metastasis, extending their actions beyond protection. However, to date, a comprehensive understanding of TFFs' mechanism of action in tumor initiation, progression and metastasis remains obscure. The present review discusses the structural, functional and mechanistic implications of all three TFF family members in tumor progression and metastasis. Also, we have garnered information from studies on their structure and expression status in different organs, along with lessons from their specific knockout in mouse models. In addition, we highlight the emerging potential of using TFFs as a biomarker to stratify tumors for better therapeutic intervention.

Different Forms of TFF2, A Lectin of the Human Gastric Mucus Barrier: In Vitro Binding Studies

Trefoil factor family 2 (TFF2) and the mucin MUC6 are co-secreted from human gastric and duodenal glands. TFF2 binds MUC6 as a lectin and is a constituent of the gastric mucus. Herein, we investigated human gastric extracts by FPLC and identified mainly high- but also low-molecular-mass forms of TFF2. From the high-molecular-mass forms, TFF2 can be completely released by boiling in SDS or by harsh denaturing extraction. The low-molecular-mass form representing monomeric TFF2 can be washed out in part from gastric mucosa specimens with buffer. Overlay assays with radioactively labeled TFF2 revealed binding to the mucin MUC6 and not MUC5AC. This binding is modulated by Ca²⁺ and can be blocked by the lectin GSA-II and the monoclonal antibody HIK1083. TFF2 binding was also inhibited by Me-β-Gal, but not the α anomer. Thus, both the α1,4GlcNAc as well as the juxtaperipheral β-galactoside residues of the characteristic GlcNAcα1→4Galβ1→R moiety of human MUC6 are essential for TFF2 binding. Furthermore, there are major differences in the TFF2 binding characteristics when human is compared with the porcine system. Taken together, TFF2 appears to fulfill an important role in stabilizing the inner insoluble gastric mucus barrier layer, particularly by its binding to the mucin MUC6.

Commercial Porcine Gastric Mucin Preparations, also Used as Artificial Saliva, are a Rich Source for the Lectin TFF2: In Vitro Binding Studies

Mucous gels (mucus) cover internal body surfaces. The secretory mucins MUC5AC and MUC6 and the protective peptide TFF2 are characteristic constituents of gastric mucus; TFF2 is co-secreted with MUC6. Herein, we investigated two commercial mucin preparations by FPLC and proteomics, because they are model systems for studying the rheology of gastric mucins. One preparation is also used as a saliva substitute, for example, after radiation therapy. We show that both preparations contain TFF2 (≈0.6 to 1.1 %, w/w). The majority of TFF2 is strongly bound noncovalently to mucin in a manner that is resistant to boiling in SDS. First overlay assays with ¹²⁵ I-labeled porcine TFF2 revealed that mucin binding is modulated by Ca²⁺ and can be blocked by the lectin GSA-II and the antibody HIK1083, both recognizing the peripheral GlcNAcα1→4Galβ1→R moiety of MUC6. TFF2 binding was also inhibited in the presence of Me-β-Gal but less so by the α anomer. TFF2 may play a role in the oligomerization and secretion of MUC6, the rheology of gastric mucus, and the adherence of gastric microbiota. TFF2 in artificial saliva may be of benefit. TFF2 might also interact with the sugar moiety of various receptors.

Increased expression of deleted in malignant brain tumors (DMBT1) gene in precancerous gastric lesions: Findings from human and animal studies

Helicobacter pylori infection triggers a cascade of inflammatory stages that may lead to the appearance of non-atrophic gastritis, multifocal atrophic, intestinal metaplasia, dysplasia, and cancer. Deleted in malignant brain tumors 1 (DMBT1) belongs to the group of secreted scavenger receptor cysteine-rich proteins and is considered to be involved in host defense by binding to pathogens. Initial studies showed its deletion and loss of expression in a variety of tumors but the role of this gene in tumor development is not completely understood. Here, we examined the role of DMBT1 in gastric precancerous lesions in Caucasian, African American and Hispanic individuals as well as in the development of gastric pathology in a mouse model of H. pylori infection. We found that in 3 different populations, mucosal DMBT1 expression was significantly increased (2.5 fold) in individuals with dysplasia compared to multifocal atrophic gastritis without intestinal metaplasia; the increase was also observed in individuals with advanced gastritis and positive H. pylori infection. In our animal model, H. pylori infection of Dmbt1-/- mice resulted in significantly higher levels of gastritis, more extensive mucous metaplasia and reduced Il33 expression levels in the gastric mucosa compared to H. pylori-infected wild type mice. Our data in the animal model suggest that in response to H. pylori infection DMBT1 may mediate mucosal protection reducing the risk of developing gastric precancerous lesions. However, the increased expression in human gastric precancerous lesions points to a more complex role of DMBT1 in gastric carcinogenesis.

DMBT1 expression in biliary carcinogenesis with correlation of clinicopathological data

AIMS

Deleted in malignant brain tumours 1 (DMBT1) exerts functions in the regulation of epithelial differentiation and inflammation and has been proposed as a tumour suppressor. Because chronic inflammation is a hallmark of cholangiocarcinogenesis, the aim of this study was to investigate the expression of DMBT1 in biliary tract cancer (BTC) and to correlate this expression with clinicopathological data.

METHODS AND RESULTS

The expression of DMBT1 protein was examined immunohistochemically in 157 BTC patients [41 intrahepatic (ICC), 60 extrahepatic cholangiocarcinomas (ECC) and 56 adenocarcinomas of the gallbladder (GBAC)]. Additionally, 56 samples of high-grade biliary intraepithelial neoplasia (BilIN 3) and 92 corresponding samples of histological non-neoplastic biliary tract tissues were included. DMBT1 expression was increased significantly in BilIN 3 compared to normal tissue (P < 0.0001) and BTC (P < 0.0001). BTC showed no significant difference in DMBT1 expression compared to non-neoplastic biliary tissue (P = 0.315). Absent DMBT1 expression in non-neoplastic biliary tissue of BTC patients was associated with poorer survival (P = 0.027). DMBT1 expression was correlated significantly with patients' age (P < 0.001).

CONCLUSION

DMBT1 is expressed differently in cholangiocarcinogenesis and poorer patients' survival rates are associated with absent DMBT1 expression in non-neoplastic biliary tissue, suggesting a tumour-suppressive role of DMBT1 in early cholangiocarcinogenesis.

Trefoil Factor Peptides and Gastrointestinal Function

Trefoil factor (TFF) peptides, with a 40-amino acid motif and including six conserved cysteine residues that form intramolecular disulfide bonds, are a family of mucin-associated secretory molecules mediating many physiological roles that maintain and restore gastrointestinal (GI) mucosal homeostasis. TFF peptides play important roles in response to GI mucosal injury and inflammation. In response to acute GI mucosal injury, TFF peptides accelerate cell migration to seal the damaged area from luminal contents, whereas chronic inflammation leads to increased TFF expression to prevent further progression of disease. Although much evidence supports the physiological significance of TFF peptides in mucosal defenses, the molecular and cellular mechanisms of TFF peptides in the GI epithelium remain largely unknown. In this review, we summarize the functional roles of TFF1, 2, and 3 and illustrate their action mechanisms, focusing on defense mechanisms in the GI tract.

SALSA: A Regulator of the Early Steps of Complement Activation on Mucosal Surfaces

Complement is present mainly in blood. However, following mechanical damage or inflammation, serous exudates enter the mucosal surfaces. Here, the complement proteins interact with other endogenous molecules to keep microbes from entering the parenteral tissues. One of the mucosal proteins known to interact with the early complement components of both the classical and the lectin pathway is the salivary scavenger and agglutinin (SALSA). SALSA is also known as deleted in malignant brain tumors 1 and gp340. It is found both attached to the epithelium and secreted into the surrounding fluids of most mucosal surfaces. SALSA has been shown to bind directly to C1q, mannose-binding lectin, and the ficolins. Through these interactions SALSA regulates activation of the complement system. In addition, SALSA interacts with surfactant proteins A and D, secretory IgA, and lactoferrin. Ulcerative colitis and Crohn's disease are examples of diseases, where complement activation in mucosal tissues may occur. This review describes the latest advances in our understanding of how the early complement components interact with the SALSA molecule. Furthermore, we discuss how these interactions may affect disease propagation on mucosal surfaces in immunological and inflammatory diseases.

Trefoil factor family peptides – friends or foes?

Trefoil factor family (TFF) peptides are a group of molecules bearing a characteristic three-loop trefoil domain. They are mainly secreted in mucous epithelia together with mucins but are also synthesized in the nervous system. For many years, TFF peptides were only known for their wound healing and protective function, e.g. in epithelial protection and restitution. However, experimental evidence has emerged supporting a pivotal role of TFF peptides in oncogenic transformation, tumorigenesis and metastasis. Deregulated expression of TFF peptides at the gene and protein level is obviously implicated in numerous cancers, and opposing functions as oncogenes and tumor suppressors have been described. With regard to the regulation of TFF expression, epigenetic mechanisms as well as the involvement of various miRNAs are new, promising aspects in the field of cancer research. This review will summarize current knowledge about the expression and regulation of TFF peptides and the involvement of TFF peptides in tumor biology and cancerogenesis.

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.

TFF2, a MUC6-binding lectin stabilizing the gastric mucus barrier and more (Review)

The peptide TFF2 (formerly 'spasmolytic polypeptide'), a member of the trefoil factor family (TFF) containing two TFF domains, is mainly expressed together with the mucin MUC6 in the gastric epithelium and duodenal Brunner's glands. Pathologically, TFF2 expression is observed ectopically during stone diseases, chronic inflammatory conditions and in several metaplastic and neoplastic epithelia; most prominent being the 'spasmolytic polypeptide-expressing metaplasia' (SPEM), which is an established gastric precancerous lesion. TFF2 plays a critical role in maintaining gastric mucosal integrity and appears to restrain tumorigenesis in the stomach. Recently, porcine TFF2 has been shown to interact with the gastric mucin MUC6 and thus stabilize the gastric mucus barrier. On the one hand, TFF2 binds to MUC6 via non-covalent lectin interactions with the glycotope GlcNAcα1→4Galβ1→R. On the other hand, TFF2 is probably also covalently bound to MUC6 via disulfide bridges. Thus, implications for the complex multimeric assembly, cross-linking, and packaging of MUC6 as well as the rheology of gastric mucus are discussed in detail in this review. Furthermore, TFF2 is also expressed in minor amounts in the immune and nervous systems. Thus, similar to galectins, its lectin activity would perfectly enable TFF2 to form multivalent complexes and cross-linked lattices with a plethora of transmembrane glycoproteins and thus modulate different signal transduction processes. This could explain the multiple and diverse biological effects of TFF2 [e.g., motogenic, (anti)apoptotic, and angiogenic effects]. Finally, a function during fertilization is also possible for TFF domains because they occur as shuffled modules in certain zona pellucida proteins.

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.

Kinetic characterization of an intestinal trefoil factor receptor

Objective

To determine whether intestinal epithelial cells have a receptor for intestinal trefoil factor and characterize receptor-ligand binding kinetics.

Methods

Radioligand binding assays were performed to characterize the binding kinetics between [¹²⁵I]-labeled ITF and IEC-6, HT-29, Caco2 and HaCaT cells. The K_d, B_max and other kinetic variables describing the interaction between ITF and its potential receptors were determined.

Results

Radioligand binding assays performed at 4°C showed that the K_d value for the association between [¹²⁵I]-ITF and IEC-6, HT-29, and Caco2 cells were 1.99±0.12×10⁻⁹ M, 3.89±0.42×10⁻⁹ M, and 2.04±0.17×10⁻⁹ M, respectively. B_max values were 1.17±0.04×10¹¹, 3.97±0.29×10¹¹, and 2.03±0.08×10¹¹ sites/cell, respectively. The K_i values for the interaction between IEC-6, HT-29, and Caco2 cells and non-labeled ITF were 20.98±0.57 nM, 36.87±3.35 nM, and 21.38±0.93 nM, respectively, and the IC₅₀ values were 25.21±0.39 nM, 40.68±0.27 nM, and 23.61±0.25 nM, respectively. Radioligand binding kinetic results showed the association rate constants (k₊₁) for IEC-6, HT-29, and Caco2 cells were 0.22±0.04 min⁻¹, 0.29±0.04 min⁻¹, and 0.26±0.05 min⁻¹, respectively, and the dissociation rate constants (k_-1) were 0.06±0.02 min⁻¹, 0.03±0.01 min⁻¹, and 0.04±0.01 min⁻¹, respectively. For the HaCaT cells, the K_d was 4.86±0.28×10⁻⁸ M and B_max was 5.81±0.15×10⁸ sites/cell, the very low specific binding between [¹²⁵I]-ITF and these cells made it impossible to calculate binding kinetic parameters.

Conclusions

An ITF-specific receptor appears to be present on the three types of intestinal epithelial cells (IEC-6, HT-29, and Caco-2), and there may be no ITF receptor on epidermal cells.

Trefoil factor family member 2 (Tff2) KO mice are protected from high-fat diet-induced obesity

INTRODUCTION

Trefoil factor family member 2 (Tff2) is a small gut peptide, mainly known for its protective and healing functions. As previously demonstrated, high-fat (HF) feeding can rapidly and specifically modulate Tff2 transcription in key tissues of mice, including the duodenum and mesenteric adipose tissue, therefore suggesting a novel role for this gene in energy balance.

DESIGN AND METHODS

To explore whether and how Tff2 can influence feeding behavior and energy metabolism, Tff2 knock-out (KO) mice were challenged with HF diet for 12 weeks, hence food and energy intakes, body composition, as well as energy excretion and serum lipid and hormonal levels were analyzed. Finally, energy efficiency was estimated.

RESULTS

Tff2 KO mice showed a greater appetite and higher energy intake compared to wild-type (WT). Consistently, they presented lower levels of serum leptin, and increased transcription of agouti-related protein (Agrp) in the hypothalamus. Though energy and triglyceride fecal excretion were augmented in Tff2 KO mice, digestible energy intake was superior. However, KO mice were finally protected from HF diet-induced obesity, and accumulated less weight and fat depots than WT animals, while keeping a normal lean mass. Energy efficiency was lower in HF-KO mice, while energy expenditure and locomotor activity were globally increased.

CONCLUSIONS

The present work demonstrates previously unsuspected roles for Tff2 and suggests it to be a mastermind in the control of energy balance and a promising therapeutic target for obesity.

A variant form of the human deleted in malignant brain tumor 1 (DMBT1) gene shows increased expression in inflammatory bowel diseases and interacts with dimeric trefoil factor 3 (TFF3)

The protein deleted in malignant brain tumors (DMBT1) and the trefoil factor (TFF) proteins have all been proposed to have roles in epithelial cell growth and cell differentiation and shown to be up regulated in inflammatory bowel diseases. A panel of monoclonal antibodies was raised against human DMBT1^gp340. Analysis of lung washings and colon tissue extracts by Western blotting in the unreduced state, two antibodies (Hyb213-1 and Hyb213-6) reacted with a double band of 290 kDa in lung lavage. Hyb213-6, in addition, reacted against a double band of 270 kDa in colon extract while Hyb213-1 showed no reaction. Hyb213-6 showed strong cytoplasmic staining in epithelial cells of both the small and large intestine whereas no staining was seen with Hyb213-1. The number of DMBT1^gp340 positive epithelial cells, stained with Hyb213-6, was significantly up regulated in inflammatory colon tissue sections from patients with ulcerative colitis (p<0.0001) and Crohn’s disease (p = 0.006) compared to normal colon tissue. Immunohistochemical analysis of trefoil factor TFF1, 2 and 3 showed that TFF1 and 3 localized to goblet cells in both normal colon tissue and in tissue from patients with ulcerative colitis or Crohn’s disease. No staining for TFF2 was seen in goblet cells in normal colon tissue whereas the majority of tissue sections in ulcerative colitis and Crohn’s disease showed sparse and scattered TFF2 positive goblet cells. DMBT1 and TFF proteins did therefore not co-localize in the same cells but localized in adjacent cells in the colon. The interaction between DMBT1^gp340 and trefoil TFFs proteins was investigated using an ELISA assay. DMBT1^gp340 bound to solid-phase bound recombinant dimeric TFF3 in a calcium dependent manner (p<0.0001) but did not bind to recombinant forms of monomeric TFF3, TFF2 or glycosylated TFF2. This implies a role for DMBT1 and TFF3 together in inflammatory bowel disease.

Human gastric TFF2 peptide contains an N-linked fucosylated N,N'-diacetyllactosediamine (LacdiNAc) oligosaccharide

In the human stomach, the peptide trefoil factor family 2 (TFF2) is secreted together with the mucin MUC6 by mucous neck cells (MNCs) and antral gland cells. TFF2 is strongly associated with the gastric mucus and promotes gastric restitution. Here, TFF2 was purified from the human corpus and antrum, respectively, by size-exclusion chromatography, and the N-linked glycan structure at N-15 of the mature peptide was determined. As a hallmark, the unusual monofucosylated N,N'-diacetylhexosediamine (tentatively assigned as GalNAcβ1 → 4GlcNAc, LacdiNAc) modification was detected as the terminal structure of a bi-antennary complex type N-glycan exhibiting also core fucosylation. Replicate analyses did not show microheterogeneities in the fraction of peptide-N-glycosidase F cleaved and permethylated N-glycans when analyzed by matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). On the glycopeptide level, a minor glycan microheterogeneity was evident in liquid chromatography-electrospray ionization (ESI)-MS, demonstrating the presence of underfucosylated species. The tryptic TFF2 N-glycopeptide p34-39 (LSPHNR N-glycosylated with Fuc3Hex3HexNAc6) was identified by both ESI-tandem mass spectrometry and MALDI-post-source decay analysis. Lectin analyses with the Wisteria floribunda agglutinin indicated the potential presence of LacdiNAc terminating glycans and revealed minor differences between TFF2 from fundic units, i.e. MNCs, and antral units, i.e. antral gland cells. Strikingly, on the level of the primary structure, there was no indication that the formation of the proposed LacdiNAc structure is cis-controlled by a peptidic determinant related to the published sequences.

High trefoil factor 1 (TFF1) expression in human retinoblastoma cells correlates with low growth kinetics, increased cyclin-dependent kinase (CDK) inhibitor levels and a selective down-regulation of CDK6

Trefoil factor family (TFFs) peptides facilitate epithelial restitution, but also effect cell proliferation and apoptosis of normal and various cancer cell lines. In a recent study by our group, TFF2 expression was demonstrated in the murine retina, where it exhibits pro-proliferative and pro-apoptotic effects. In the present study, we investigated the expression and function of TFF peptides in eight human retinoblastoma cell lines. TFF1 was the only TFF peptide expressed at detectable levels in immunoblots of retinoblastoma cells. TFF1 expression levels were highly variable in different retinoblastoma cell lines and negatively correlated with cell growth curves. Recombinant human TFF1 had a negative effect on cell viability and caused a reduction in cell proliferation. Retinoblastoma cell lines with high TFF1 expression levels exhibited a selective down-regulation of cyclin-dependent kinase (CDK) 6, whereas CDK4 and CDK2 seem to be unaffected by TFF1 expression. In immunocytochemical studies, we observed a nuclear co-localization of TFF1 and CDK2 in Cajal bodies (CBs). In high TFF1 expressing human retinoblastoma cell lines CBs were smaller and higher in number compared to retinoblastoma lines with low TFF1 expression, indicating differences in cell cycle status between the different retinoblastoma cell lines. Our data further support the notion for a potential tumor suppressor function of TFF1. The nuclear localization of TFF1 in CBs--considered to play a role in cell cycle progression, potentially acting as a platform for CDK-cyclin function-offers a new impetus in the ongoing search for potential TFF1 interacting proteins.

The salivary scavenger and agglutinin binds MBL and regulates the lectin pathway of complement in solution and on surfaces

The salivary scavenger and agglutinin (SALSA), also known as gp340, salivary agglutinin and deleted in malignant brain tumor 1, is a 340-kDa glycoprotein expressed on mucosal surfaces and secreted into several body fluids. SALSA binds to a broad variety of microbes and endogenous ligands, such as complement factor C1q, surfactant proteins D and A, and IgA. Our search for novel ligands of SALSA by direct protein-interaction studies led to the identification of mannan-binding lectin (MBL) as a new binding partner. We observed that surface-associated SALSA activates complement via binding of MBL. On the other hand, soluble SALSA was found to inhibit Candida albicans-induced complement activation. Thus, SALSA has a dual complement activation modifying function. It activates the lectin pathway when bound to a surface and inhibits it when free in the fluid phase. These activities are mediated via a direct interaction with MBL. This suggests that SALSA could target the innate immune responses to certain microorganisms and simultaneously limit complement activation in the fluid phase.

The conserved scavenger receptor cysteine-rich superfamily in therapy and diagnosis

The scavenger receptor cysteine-rich (SRCR) superfamily of soluble or membrane-bound protein receptors is characterized by the presence of one or several repeats of an ancient and highly conserved protein module, the SRCR domain. This superfamily (SRCR-SF) has been in constant and progressive expansion, now up to more than 30 members. The study of these members is attracting growing interest, which parallels that in innate immunity. No unifying function has been described to date for the SRCR domains, this being the result of the limited knowledge still available on the physiology of most members of the SRCR-SF, but also of the sequence versatility of the SRCR domains. Indeed, involvement of SRCR-SF members in quite different functions, such as pathogen recognition, modulation of the immune response, epithelial homeostasis, stem cell biology, and tumor development, have all been described. This has brought to us new information, unveiling the possibility that targeting or supplementing SRCR-SF proteins could result in diagnostic and/or therapeutic benefit for a number of physiologic and pathologic states. Recent research has provided structural and functional insight into these proteins, facilitating the development of means to modulate the activity of SRCR-SF members. Indeed, some of these approaches are already in use, paving the way for a more comprehensive use of SRCR-SF members in the clinic. The present review will illustrate some available evidence on the potential of well known and new members of the SRCR-SF in this regard.

Trefoil factor family peptide 2 acts pro-proliferative and pro-apoptotic in the murine retina

Although expression of trefoil factor family (TFF) peptides has been reported in the brain, nothing is known about TFF expression in the retina. The aim of this study was to test whether TFF peptides are expressed in the murine retina and have any function here. In contrast to most tissues studied, where TFF1 and TFF3 are the predominant peptides, TFF2 is the only peptide expressed in the murine retina. Immunohistochemical studies on murine retinal sections indicate that cells of the ganglion cell layer are the retinal source for murine TFF2 (Tff2). In organotypic murine retina cell cultures recombinant TFF2 exerted a strong pro-apoptotic and pro-proliferative rather than an anti-apoptotic and anti-proliferating effect described in most human cancer cell lines investigated so far. In blockage experiments we were able to demonstrate that the pro-apoptotic effect of TFF2 is caspase-dependent. Western blot analysis of TFF2 treated retinal wholemount homogenates revealed significant reductions in the phosphorylation level of ERK and STAT3 proteins compared to basal conditions, suggesting that in the developing murine retina survival mechanism are down-regulated upon TFF2 administration. Our results suggest that during retinal cell death periods, requiring a tightly regulated balance between cell survival and cell death, TFF2 acts pro-proliferative and pro-apoptotic at least in developing mouse retinae cultured in vivo.

Downregulation of trefoil factor 3 gene expression in the colon of the senescence-accelerated mouse (SAM)-P6 revealed by oligonucleotide microarray analysis

Global comparison of the colonic gene expression profiles between 14-month-old senescenceaccelerated mouse (SAM)-P6 mice and SAM-R1 mice, a wild-type control, was conducted with an oligonucleotide microarray containing more than 5,000 mouse genes. Eight genes were upregulated more than two-fold and 94 genes were downregulated more than two-fold in SAM-P6 mice. The three cell defense genes intelectin1 (Itln1), trefoil factor 3 (intestinal) (Tff3) and "deleted in malignant brain tumors 1" (Dmbt1) were among those extensively downregulated. Quantitative RT-PCR analysis confirmed that Itln1 mRNA was almost undetectable in SAM-P6 colon, whereas it was readily detected in SAM-R1 colon. Colonic expression of both Tff3 and Dmbt1 mRNA was also substantially decreased, to one third and two thirds of the levels in SAM-R1 mice, respectively. A 14 kDa Tff3 dimer was detected by Western blotting in the colon of all three SAM-R1 mice, but was not present in three SAM-P6 mice. No upregulation of 3 cell defense genes was detected in 3-month-old SAM-R1 as well as SAM-P6 mice. These results suggest that a diminution of the intestinal trefoil factor system may be involved in the acceleration of aging in SAM-P6 mice.

Morphological and functional changes in the colon after massive small bowel resection

PURPOSE

Anecdotal evidence suggests that the colon plays an important role after small bowel resection (SBR). However, colonic changes have not previously been studied. The aim of this study was to characterize morphological and functional changes within the colon after SBR and elucidate the influence of diet complexity on adaptation.

METHOD

In study 1, 4-week-old piglets underwent a 75% SBR or sham operation and were studied at 2, 4, and 6 weeks postoperation to allow analysis of early and late adaptation responses. Piglets received a polymeric infant formula (PIF). In study 2, SBR piglets received an elemental diet and were studied at 6 weeks postoperation and compared with SBR + PIF piglets from study 1. For both studies, immunohistochemistry was used to quantitate intestinal cell types. Changes in functional proteins were measured by Western blot, enteroendocrine/peptide YY (PYY), enterocyte/liver fatty acid binding protein (L-FABP), and goblet cells/trefoil factor 3 (TFF3).

RESULTS

In study 1, early and late adaptation-related changes were observed after SBR. Early adaptation included increased numbers of enterocytes (P = .0001), whereas late adaptation included increased proliferative cell numbers (P = .02). Enteroendocrine, goblet, and apoptotic cells numbers were significantly elevated in the resected group at all time-points studied (P < .05). Functional changes included increased levels of L-FABP (P = .04) and PYY (P = .03). There was no change in TFF3 expression. In study 2, feeding with an elemental diet resulted in suboptimal adaptation as evidenced by reduced rate of weight gain and significant reductions in total cell numbers (P = .0001), proliferative (P = .0001) and apoptotic cells (P = .04), enteroendocrine cells (P = .001), and PYY expression (P .004).

CONCLUSION

These findings indicate that significant morphological and functional changes occur in the colon after massive SBR and that these occur as early and late adaptation responses. Elemental diet was associated with suboptimal adaptation suggesting an effect of diet complexity on colonic adaptation.

Review: Gp-340/DMBT1 in mucosal innate immunity

Deleted in Malignant Brain Tumour 1 (DMBT1) is a gene that encodes alternatively spliced proteins involved in mucosal innate immunity. It also encodes a glycoprotein with a molecular mass of 340 kDa, and is referred to as gp-340 (DMBT1(gp340)) and salivary agglutinin (DMBT1(SAG)). DMBT1(gp340) is secreted into broncho-alveolar surface lining fluid whereas DMBT(SAG) is present in the saliva. The two molecules were shown to be identical and both interact with and agglutinate several Gram-negative and Gram-positive bacteria including Streptococcus mutans, a bacterium responsible for caries in the oral cavity. DMBT1(gp340) interacts with surfactant proteins A and D (SP-D). DMBT1(gp340) and SP-D can individually and together interact and agglutinate influenza A virus. DMBT1(gp340) also binds to HIV-1 and facilitates transcytosis of the virus into epithelial cells. DMBT1 binds to a variety of other host proteins, including serum and secretory IgA, C1q, lactoferrin, MUC5B and trefoil factor 2 (TFF2), all molecules with involvement in innate immunity and/or wound-healing processes. Recent generation of Dmbt1-deficient mice has provided the research field of DMBT1 with a model that allows research to progress from in vitro studies to in vivo functional studies of the multifunctional proteins encoded by the DMBT1 gene.

Signal transduction and gene transcription induced by TFF3 in oral keratinocytes

Trefoil factor family 3 (TFF3) is secreted in saliva. The peptide improves the mechanical and chemical resistance of mucins, and it may act as a motility signal for oral keratinocytes during wound healing. This study aimed to identify novel functions of TFF3 in oral keratinocytes. To achieve this, we used phosphoprotein and messenger RNA (mRNA) arrays to compare TFF3-treated and untreated oral keratinocytes. Analysis of the phosphoprotein array indicated that TFF3 signals through the mitogen-activated protein kinases (MAPKs) c-Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK1/2), and through the phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB) pathway. Microarray analysis of mRNA showed that TFF3 stimulation induced changes in the expression of genes functionally related to cell death/survival, cell growth and proliferation, and cell movement. The reverse transcription-polymerase chain reaction (RT-PCR) results indicated that the transcription of some immediate-early genes (IEGs) was downregulated, whereas the IEGs FBJ osteosarkoma oncogene (FOS) and C-MYC binding protein (MYCBP2) were transiently upregulated by TFF3 stimulation. Together, the results of the arrays indicate that TFF3 is a modifying factor in pathways regulating cell survival, cell growth and proliferation, and cell migration of oral keratinocytes. Trefoil factor family 3 may therefore promote oral wound healing and it should be considered for the treatment of oral ulcerating diseases, or of other diseases.

Secreted trefoil factor 2 activates the CXCR4 receptor in epithelial and lymphocytic cancer cell lines

The secreted trefoil factor family 2 (TFF2) protein contributes to the protection of the gastrointestinal mucosa from injury by strengthening and stabilizing mucin gels, stimulating epithelial restitution, and restraining the associated inflammation. Although trefoil factors have been shown to activate signaling pathways, no cell surface receptor has been directly linked to trefoil peptide signaling. Here we demonstrate the ability of TFF2 peptide to activate signaling via the CXCR4 chemokine receptor in cancer cell lines. We found that both mouse and human TFF2 proteins (at approximately 0.5 microm) activate Ca2+ signaling in lymphoblastic Jurkat cells that could be abrogated by receptor desensitization (with SDF-1alpha) or pretreatment with the specific antagonist AMD3100 or an anti-CXCR4 antibody. TFF2 pretreatment of Jurkat cells decreased Ca2+ rise and chemotactic response to SDF-1alpha. In addition, the CXCR4-negative gastric epithelial cell line AGS became highly responsive to TFF2 treatment upon expression of the CXCR4 receptor. TFF2-induced activation of mitogen-activated protein kinases in gastric and pancreatic cancer cells, KATO III and AsPC-1, respectively, was also dependent on the presence of the CXCR4 receptor. Finally we demonstrate a distinct proliferative effect of TFF2 protein on an AGS gastric cancer cell line that expresses CXCR4. Overall these data identify CXCR4 as a bona fide signaling receptor for TFF2 and suggest a mechanism through which TFF2 may modulate immune and tumorigenic responses in vivo.

Developmental pathways during in vitro progression of human islet neogenesis

Islet neogenesis, or the differentiation of islet cells from precursor cells, is seen in vitro and in vivo both embryonically and after birth. However, little is known about the differentiation pathways during embryonic development for human pancreas. Our previously reported in vitro generation of islets from human pancreatic tissue provides a unique system to identify potential markers of neogenesis and to determine the molecular mechanisms underlying this process. To this end, we analyzed the gene expression profiles of three different stages during in vitro islet generation: the Initially Adherent, Expanded, and Differentiated stages. Samples from four human pancreases were hybridized to Affymetrix U95A GeneChips, and data analyzed using GeneSpring 7.0/9.0 software. Using scatter plots we selected genes with a 2-fold or greater differential expression. Of the 12,000 genes/ESTs present on these arrays, 295 genes including 38 acinar-enriched genes were selectively lost during the progression from the Initially Adherent stage to the Expanded stage; 468 genes were increased in this progression to Expanded tissue; and 529 genes had a two-fold greater expression in the Differentiated stage than in the Expanded tissue. Besides the expected increases in insulin, glucagon, and duct markers (mucin 6, aquaporin 1 and 5), the beta cell auto-antigen IA-2/phogrin was increased 5-fold in Differentiated. In addition, developmentally important pathways, including notch/jagged, Wnt/frizzled, TGFbeta superfamily (follistatin, BMPs, and SMADs), and retinoic acid (COUP-TFI, CRABP1, 2, and RAIG1) were differentially regulated during the expansion/differentiation. Two putative markers for islet precursor cells, UCHL1/PGP9.5 and DMBT1, were enhanced during the progression to differentiated cells, but only the latter could be a marker of islet precursor cells. We suggest that appropriate manipulation of these differentiation-associated pathways will enhance the efficiency of differentiation of insulin-producing beta-cells in this in vitro model.

Rodent IRR-219 (IgGFcgammaBP) and rTFF3, expressed mainly in the intestinal mucosa, depleted during dextran sulfate sodium-induced colitis

IgGFcgammaBP and TFF3 are related with adaptation during injury, mucosal defense, and epithelial healing. In this work, we produced the polyclonal antibodies for rat IgGFcgammaBP or TFF3 and assessed their tissue distributions in adult and prenatal rats, rTFF3 molecular patterns under reduced and nonreduced condition, involvement of IgGFcgammaBP, and TFF3 in dextran sulfate sodium (DSS)-induced colitis. Polyclonal antibodies of rat IgGFcgammaBP or TFF3 were produced with their synthetic polypeptide. Rat TFF3 was detected in the scraped intestinal mucosa by SDS/PAGE and Western blotting. Immunohistochemical stainings of rat IgGFcgammaBP or TFF3 were performed in different tissues, mainly in mucin-producing tissues, of adult rat and prenatal rat intestine. Rat IgGFcgammaBP and TFF3 were immunohistochemically detected in the distal colon of rat colitis model induced with 7% DSS. IgGFcgammaBP and TFF3 were mainly expressed in the intestinal mucosa with different distribution patterns. The scattered staining was also found in the epithelium of bile duct. There was strong expression of IgGFcgammaBP and TFF3 in rat embryonic intestine. There were two kinds of rTFF3 complexes existed with different molecular weights, 250 and 55 kDa, under nonreduced conditions, but shifted to 6 kDa under reduced conditions. In the DSS-induced colitis model, IgGFcgammaBP and TFF3 were significantly decreased in the distal colon mucosa at the onset and active phases comparing with the normal control, partially recovered at the regenerative phase. Based on these findings,IgGFcgammaBP and TFF3 were widely expressed in the intestinal mucosa, depleted during DSS-induced colitis. Rat TFF3 existed mainly in two complexes with 250 and 55 kDa molecular weights. The present findings indicate they are two important goblet cell-derived components possibly related to the pathogenesis of DSS-induced colitis, a rat model of ulcerative colitis.

Regulation of DMBT1 via NOD2 and TLR4 in intestinal epithelial cells modulates bacterial recognition and invasion

Mucosal epithelial cell layers are constantly exposed to a complex resident microflora. Deleted in malignant brain tumors 1 (DMBT1) belongs to the group of secreted scavenger receptor cysteine-rich proteins and is considered to be involved in host defense by pathogen binding. This report describes the regulation and function of DMBT1 in intestinal epithelial cells, which form the primary immunological barrier for invading pathogens. We report that intestinal epithelial cells up-regulate DMBT1 upon proinflammatory stimuli (e.g., TNF-alpha, LPS). We demonstrate that DMBT1 is a target gene for the intracellular pathogen receptor NOD2 via NF-kappaB activation. DMBT1 is strongly up-regulated in the inflamed intestinal mucosa of Crohn's disease patients with wild-type, but not with mutant NOD2. We show that DMBT1 inhibits cytoinvasion of Salmonella enterica and LPS- and muramyl dipeptide-induced NF-kappaB activation and cytokine secretion in vitro. Thus, DMBT1 may play an important role in the first line of mucosal defense conferring immune exclusion of bacterial cell wall components. Dysregulated intestinal DMBT1 expression due to mutations in the NOD2/CARD15 gene may be part of the complex pathophysiology of barrier dysfunction in Crohn's disease.

Transplacental exposure to inorganic arsenic at a hepatocarcinogenic dose induces fetal gene expression changes in mice indicative of aberrant estrogen signaling and disrupted steroid metabolism

Exposure to inorganic arsenic in utero in C3H mice produces hepatocellular carcinoma in male offspring when they reach adulthood. To help define the molecular events associated with the fetal onset of arsenic hepatocarcinogenesis, pregnant C3H mice were given drinking water containing 0 (control) or 85 ppm arsenic from day 8 to 18 of gestation. At the end of the arsenic exposure period, male fetal livers were removed and RNA isolated for microarray analysis using 22K oligo chips. Arsenic exposure in utero produced significant (p<0.001) alterations in expression of 187 genes, with approximately 25% of aberrantly expressed genes related to either estrogen signaling or steroid metabolism. Real-time RT-PCR on selected genes confirmed these changes. Various genes controlled by estrogen, including X-inactive-specific transcript, anterior gradient-2, trefoil factor-1, CRP-ductin, ghrelin, and small proline-rich protein-2A, were dramatically over-expressed. Estrogen-regulated genes including cytokeratin 1-19 and Cyp2a4 were over-expressed, although Cyp3a25 was suppressed. Several genes involved with steroid metabolism also showed remarkable expression changes, including increased expression of 17beta-hydroxysteroid dehydrogenase-7 (HSD17beta7; involved in estradiol production) and decreased expression of HSD17beta5 (involved in testosterone production). The expression of key genes important in methionine metabolism, such as methionine adenosyltransferase-1a, betaine-homocysteine methyltransferase and thioether S-methyltransferase, were suppressed. Thus, exposure of mouse fetus to inorganic arsenic during a critical period in development significantly alters the expression of various genes encoding estrogen signaling and steroid or methionine metabolism. These alterations could disrupt genetic programming at the very early life stage, which could impact tumor formation much later in adulthood.

Differentiation of columnar epithelia: the hensin pathway

Epithelia, the most common variety of cells in complex organisms exist in many shapes. They are sheets of polarized cells that separate two compartments and selectively transport materials from one to the other. After acquiring these general characteristics, they differentiate to become specialized types such as squamous columnar or transitional epithelia. High density seeding converts a kidney-derived cell line from flat ;generic' epithelial cells to columnar cells. The cells acquire all the characteristics of differentiated columnar cells, including microvilli, and the capacity for apical endocytosis. The high seeding density induces the deposition of a new protein termed hensin and polymerization of hensin is the crucial event that dictates changes in epithelial phenotype. Hensin is widely expressed in most epithelia. Its deletion in mice leads to embryonic lethality at the time of generation of the first columnar epithelium, the visceral endoderm. Moreover many human cancers have deletions in the hensin gene, which indicates that it is a tumor suppressor.

Cellular localization, binding sites, and pharmacologic effects of TFF3 in experimental colitis in mice

Trefoil factors (TFFs) are essential for protection and restitution of the gastrointestinal mucosa but many aspects of TFF biology are unclear. Our aim was to compare the localization of endogenous TFFs and binding sites for injected TFF3 in the colon of healthy and colitic mice and to study the effect of TFF3 on dextrane sulfate sodium (DSS)-induced colitis in mice. Expression of endogenous TFF1-3 was examined by in situ hybridization and immunohistochemistry, and the distribution of intravenously, intraperitoneally, and subcutaneously administered (125)I-TFF3 by autoradiography and gamma-counting. The effect of systemically administered TFF3 on DSS-induced colitis was assessed. We found increased expression of endogenous TFF3 and increased binding of injected (125)I-TFF3 in the colon of animals with DSS-induced colitis. The distribution of intraperitoneally and subcutaneously administered (125)I-TFF3 was comparable. Systemic administration of the peptides reduced the severity of colitis. Expression of endogenous TFF3 and binding of systemically administered TFF3 are increased in DSS-induced colitis. Systemic administration of TFF3 attenuates the disease. These findings suggest a role of TFF3 in mucosal protection.

Molecular forms of trefoil factor 1 in normal gastric mucosa and its expression in normal and abnormal gastric tissues

AIM: To study the molecular forms of trefoil factor 1 (TFF1) in normal gastric mucosa and its expression in normal and abnormal gastric tissues (gastric carcinoma, atypical hyperplasia and intestinalized gastric mucosa) and the role of TFF1 in the carcinogenesis and progression of gastric carcinoma and its molecular biological mechanism underlying gastric mucosa protection.

METHODS: The molecular forms of TFF1 in normal gastric mucosa were observed by Western blot. The expression of TFF1 in normal and abnormal gastric tissues (gastric carcinoma, atypical hyperplasia and intestinalized gastric mucosa) was also assayed by immunohistochemical method. The average positive AO was estimated by Motic Images Advanced 3.0 software.

RESULTS: Three patterns of TFF1 were found in normal gastric mucosa: monomer, dimmer, and TFF1 compound whose molecular weight is about 21 kDa. The concentration of TFF1 compound was the highest among these three patterns. TFF1 was expressed mainly in epithelial cytoplasm of the mucosa in gastric body and antrum, especially around the nuclei. The closer the TFF1 to the lumen, the higher the expression of TFF1. The expression of TFF1 in peripheral tissue of gastric carcinoma (0.51 ± 0.07) was higher than that in normal gastric mucosa (0.44 ± 0.06, P < 0.001). The expression of TFF1 in gastric adenocarcinoma was positively related to the differentiation of adenocarcinoma. The lower the differentiation of adenocarcinoma was, the weaker the expression of TFF1. No TFF1 was expressed in poorly-differentiated adenocarcinoma. The expression of TFF1 in moderately-well differentiated adenocarcinoma (0.45 ± 0.07) was a little lower than that in normal mucosa (P > 0.05). The expression of TFF1 in gastric mucosa with atypical hyperplasia (0.57 ± 0.03) was significantly higher than that in normal gastric mucosa (P < 0.001). No TFF1 was expressed in intestinalized gastric mucosa. There was no statistically significant difference between the expressions of TFF1 in gastric mucosa around the intestinalized tissue (0.45 ± 0.07) and normal gastric mucosa (P > 0.05).

CONCLUSION: TFF1 is expressed mainly in epithelial cytoplasm of the mucosa in gastric body and antrum. Its main pattern is TFF1 compound, which may have a greater biological activity than monomer and dimer. The expression of TFF1 in peripheral mucosa of gastric ulcer is higher than that in mucosa 5 cm beyond the ulcer, indicating that TFF1 plays an important part in protection and restitution of gastric mucosa. The expression of TFF1 is increased in peripheral tissues of gastric carcinoma and gastric mucosa with atypical hyperplasia, but is decreased in cancer tissues, implying that TFF1 may be related to suppression and differentiation of carcinoma. The weaker expression of TFF1 in poorly-differentiated carcinoma may be related to the destruction of glands and cells in cancer tissues and the decrease in secretion of TFF1.

Therapeutic drug delivery by genetically modified Lactococcus lactis

Food-grade bacteria have been consumed throughout history without associated pathologies and are, therefore, absolutely safe to ingest. Unexpectedly, Lactococcus lactis (L. lactis), known from cheese production, can be genetically engineered to constantly secrete satisfactory amounts of bioactive cytokines. Both of these features enabled the development of a new kind of topical delivery system: topical and active delivery of therapeutic proteins by genetically modified micro-organisms. The host organism's record inspired the development of applications that target intestinal diseases. In a variety of mouse models, chronic colon inflammation can be successfully treated with (interleukin) IL-10-secreting L. lactis. Trefoil factor (TFF) producer strains have also been shown to be very effective in the treatment of acute colitis. Such novel therapeutic strains are textbook examples of genetically modified (GM) organisms. There are legitimate concerns with regard to the deliberate release of GM micro-organisms. On development of these applications, therefore, we have engineered these bacteria in such a way that biological containment is guaranteed. The essential gene thyA, encoding thymidylate synthase, has been exchanged for IL-10. This makes the GM strain critically dependent on thymidine. Lack of thymidine, for example, resulting from thymidine consumption by thyA-deficient strains-will irreversibly lead to induced "thymidine-less death." This accomplishment has created the possibility of using this strategy for application in human medicine.

Molecular characterization of the porcine deleted in malignant brain tumors 1 gene (DMBT1)

The human gene deleted in malignant brain tumors 1 (DMBT1) is considered to play a role in tumorigenesis and pathogen defense. It encodes a protein with multiple scavenger receptor cysteine-rich (SRCR) domains, which are involved in recognition and binding of a broad spectrum of bacterial pathogens. The SRCR domains are encoded by highly homologous repetitive exons, whose number in humans may vary from 8 to 13 due to genetic polymorphism. Here, we characterized the porcine DMBT1 gene on the mRNA and genomic level. We assembled a 4.5 kb porcine DMBT1 cDNA sequence from RT-PCR amplified seminal vesicle RNA. The porcine DMBT1 cDNA contains an open reading frame of 4050 nt. The transcript gives rise to a putative polypeptide of 1349 amino acids with a calculated mass of 147.9 kDa. Compared to human DMBT1, it contains only four N-terminal SRCR domains. Northern blotting revealed transcripts of approximately 4.7 kb in size in the tissues analyzed. Analysis of ESTs suggested the existence of secreted and transmembrane variants. The porcine DMBT1 gene spans about 54 kb on chromosome 14q28-q29. In contrast to the characterized cDNA, the genomic BAC clone only contained 3 exons coding for N-terminal SRCR domains. In different mammalian DMBT1 orthologs large interspecific differences in the number of SRCR exons and utilization of the transmembrane exon exist. Our data suggest that the porcine DMBT1 gene may share with the human DMBT1 gene additional intraspecific variations in the number of SRCR-coding exons.