Secretion of the trefoil factor TFF3 from the isolated vascularly perfused rat colon

Tiron ameliorates acetic acid-induced colitis in rats: Role of TGF-β/EGFR/PI3K/NF-κB signaling pathway

BACKGROUND

Ulcerative colitis (UC), an ongoing inflammatory disorder of the colon, is marked by persistent mucosal surface irritation extending from the rectum to the near-proximal colon. Tiron is a synthetic analogue of vitamin E which is known to have antioxidant and anti-inflammatory effects in various animal models, so the goal of this study was to find out whether Tiron had any preventive impacts on UC inflicted by acetic acid (A.A) exposure in rats.

METHOD

Tiron (235 and 470 mg/kg) was administered intra-peritoneally for 2 weeks, and A.A (2 ml, 3 % v/v) was injected intra-rectally to cause colitis. Colon tissues and blood samples were then collected for measurement of various inflammatory and oxidative stress biomarkers.

RESULTS

Tiron administration significantly diminished lactate dehydrogenase (LDH), C-reactive protein (CRP), colon weight, and the weight/length ratio of the colon as compared to A.A-injected rats. Additionally, Tiron attenuated oxidative stress biomarkers. Tiron also enforced the levels of Glucagon-like peptide-1 (GLP-1) and trefoil factor-3 (TFF-3), while it greatly lowered the expression of nuclear factor kappa B (NF-κB), interleukin-6 (IL-6), interferon-γ (IFN-γ), and transforming growth factor-1(TGF-β1), phosphorylated epidermal growth factor receptor (P-EGFR), phosphatidylinositol-3-kinase (PI3K) and protein kinase B (AKT) expression in colonic cellular structures. Furthermore, colonichistopathologic damages, revealed by hematoxylin and eosin (H&E) and Alcian Blue stain, were significantly decreased upon Tiron administration.

CONCLUSION

Tiron prevented A.A-induced colitis in rats via modulating inflammatory pathway TGF-β1/P-EGFR/PI3K/AKT/NF-κB, alongside managing the oxidant/antioxidant equilibrium, and boosting the reliability of the intestinal barrier.

Guardians of the gut: influence of the enteric nervous system on the intestinal epithelial barrier

The intestinal mucosal surface forms one of the largest areas of the body, which is in direct contact with the environment. Co-ordinated sensory functions of immune, epithelial, and neuronal cells ensure the timely detection of noxious queues and potential pathogens and elicit proportional responses to mitigate the threats and maintain homeostasis. Such tuning and maintenance of the epithelial barrier is constantly ongoing during homeostasis and its derangement can become a gateway for systemic consequences. Although efforts in understanding the gatekeeping functions of immune cells have led the way, increasing number of studies point to a crucial role of the enteric nervous system in fine-tuning and maintaining this delicate homeostasis. The identification of immune regulatory functions of enteric neuropeptides and glial-derived factors is still in its infancy, but has already yielded several intriguing insights into their important contribution to the tight control of the mucosal barrier. In this review, we will first introduce the reader to the current understanding of the architecture of the enteric nervous system and the epithelial barrier. Next, we discuss the key discoveries and cellular pathways and mediators that have emerged as links between the enteric nervous, immune, and epithelial systems and how their coordinated actions defend against intestinal infectious and inflammatory diseases. Through this review, the readers will gain a sound understanding of the current neuro-immune-epithelial mechanisms ensuring intestinal barrier integrity and maintenance of intestinal homeostasis.

The enteric nervous system

Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.

Roles of gastrointestinal polypeptides in intestinal barrier regulation

The intestinal barrier is a dynamic entity that is organized as a multilayer system and includes various intracellular and extracellular elements. The gut barrier functions in a coordinated manner to impede the passage of antigens, toxins, and microbiome components and simultaneously preserves the balanced development of the epithelial barrier and the immune system and the acquisition of tolerance to dietary antigens and intestinal pathogens.Numerous scientific studies have shown a significant association between gut barrier damage and gastrointestinal and extraintestinal diseases such as inflammatory bowel disease, celiac disease and hepatic fibrosis. Various internal and external factors regulate the intestinal barrier. Gastrointestinal peptides originate from enteroendocrine cells in the luminal digestive tract and are critical gut barrier regulators. Recent studies have demonstrated that gastrointestinal peptides have a therapeutic effect on digestive tract diseases, enhancing epithelial barrier activity and restoring the gut barrier. This review demonstrates the roles and mechanisms of gastrointestinal polypeptides, especially somatostatin (SST) and vasoactive intestinal peptide (VIP), in intestinal barrier regulation.

Neurons and Glia in the Enteric Nervous System and Epithelial Barrier Function

The intestinal epithelial barrier is the largest exchange surface between the body and the external environment. Its functions are regulated by luminal, and also internal, components including the enteric nervous system. This review summarizes current knowledge about the role of the digestive "neuronal-glial-epithelial unit" on epithelial barrier function.

Epithelial cell types and their proposed roles in maintaining the mucosal barrier in human chagasic-megacolonic mucosa

Patients suffering from chagasic megacolon must have an intact mucosal barrier as they survive this chronic disease for decades. A key structure of the mucosal barrier are epithelial cells. Vasoactive-intestinal-peptide (VIP)-positive nerve fibres are involved in influencing, e.g., epithelial cell proliferation, mucus secretion (e.g., mucin 2 and trefoil factor 3 of goblet cells) and inflammation or autoimmunity, all putative and/or known factors altered in chagasic megacolon. We analyzed qualitatively and quantitatively goblet cells, their specific markers, such as mucin 2 (MUC2) and trefoil factor 3 (TFF3) and enterocytes, the relation of VIP-immunoreactive nerve fibres to the epithelia, the distribution of gelsolin, a protein involved in chronic inflammation processes in the epithelia, and the proliferation rate of epithelial cells by combined 4',6-diamidino-2-phenylindole (DAPI) and phosphohistone-H3 (PHH3) staining. Goblet cells were the dominating epithelial cell type. They accounted for 38.4% of all epithelial cells in controls and changed to 58.9% in the megacolonic parts. In contrast to the overall expression in goblet cells of control epithelia, TFF3 was confined to goblet cells at the base of the crypts whereas MUC2 was found only in luminal goblet cells. Gelsolin-positive goblet cells were predominantly recognized within the controls. Finally, the mean value of mitosis increased from 1.5% within the controls up to 2.6% in the anal parts of the chagasic sepcimens. Taken together, increased cell proliferation, preponderance of goblet cells, differential MUC 2, and TFF 3 expression might all be factors maintaining an intact mucosal barrier within chagasic megacolon.

Vasoactive intestinal polypeptide promotes intestinal barrier homeostasis and protection against colitis in mice

Inflammatory bowel disease is a chronic gastrointestinal inflammatory disorder associated with changes in neuropeptide expression and function, including vasoactive intestinal peptide (VIP). VIP regulates intestinal vasomotor and secretomotor function and motility; however, VIP's role in development and maintenance of colonic epithelial barrier homeostasis is unclear. Using VIP deficient (VIPKO) mice, we investigated VIP's role in epithelial barrier homeostasis, and susceptibility to colitis. Colonic crypt morphology and epithelial barrier homeostasis were assessed in wildtype (WT) and VIPKO mice, at baseline. Colitic responses were evaluated following dinitrobenzene sulfonic acid (DNBS) or dextran-sodium sulfate (DSS) exposure. Mice were also treated with exogenous VIP. At baseline, VIPKO mice exhibited distorted colonic crypts, defects in epithelial cell proliferation and migration, increased apoptosis, and altered permeability. VIPKO mice also displayed reduced goblet cell numbers, and reduced expression of secreted goblet cell factors mucin 2 and trefoil factor 3. These changes were associated with reduced expression of caudal type homeobox 2 (Cdx2), a master regulator of intestinal function and homeostasis. DNBS and DSS-induced colitis were more severe in VIPKO than WT mice. VIP treatment rescued the phenotype, protecting VIPKO mice against DSS colitis, with results comparable to WT mice. In conclusion, VIP plays a crucial role in the development and maintenance of colonic epithelial barrier integrity under physiological conditions and promotes epithelial repair and homeostasis during colitis.

Reprint of: Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Quantitative measurements of trefoil factor family peptides: possibilities and pitfalls

The trefoil factor family (TFF) peptides TFF1, TFF2, and TFF3 are produced and secreted by mucous membranes throughout the body. Their importance for the protection and repair of epithelial surfaces is well established, and the three peptides are present in various amounts in mucosal secretions as well as in the circulation. They have been linked to both inflammatory diseases and to various types of cancer, and serum concentrations of TFF3 show a more than 47-fold increase during pregnancy. Several both commercial and in-house immunoassays exist, but a number of methodological issues remain unresolved. This review describes methodological challenges in the measurement of the peptides in humans, and summarizes current knowledge concerning the occurrence and possible significance of the peptides in human health and disease.

Human intestinal TFF3 forms disulfide-linked heteromers with the mucus-associated FCGBP protein and is released by hydrogen sulfide

TFF3 is a secretory peptide belonging to the trefoil factor family with a predicted size of 59 amino acid residues containing seven cysteine residues. It is predominantly expressed in intestinal goblet cells where it plays a key role in mucosal regeneration and repair processes. In the course of these studies, human colonic TFF3 was shown to exist mainly as a high molecular weight heteromer. Purification of this heteromer and characterization by LC-ESI-MS/MS analysis identified the IgG Fc binding protein (FCGBP) as the disulfide-linked partner protein of TFF3. FCGBP is a constituent of intestinal mucus secreted by goblet cells. Furthermore, low amounts of TFF3/monomer and only little TFF3/dimer were detected in human colonic extracts. Here, we show that these TFF3 forms can be released from the purified TFF3-FCGBP heteromer complex in vitro by reduction with hydrogen sulfide (H(2)S). Such a mechanism would be in line with the high H(2)S concentrations reported to occur in the lumen of the colon. Of special note, this points to intestinal mucus as a reservoir for a biologically active peptide. Also proteolytic processing of FCGBP was observed which is in line with multiple autocatalytic cleavages as proposed earlier by Johansson et al. (J. Proteome Res. 2009 , 8 , 3549 - 3557).

The intestinal trefoil factor (Tff3), also expressed in the inner ear, interacts with peptides contributing to apoptosis

The 3 members of the mammalian trefoil factor family (TFF) are expressed and secreted as cytoprotective peptides along the entire length of the normal gastrointestinal tract. More recently, they were shown to display multifunctional properties. Goblet cells of the small and large intestine constitute a major source for the synthesis of the third family member, TFF3 (formerly intestinal trefoil factor, ITF). TFF3, like the other family members, is rapidly up-regulated in response to physical wounding of the digestive tract. In addition, Tff3 was also detected in the posterior pituitary gland. Apart from this Tff3 function as a neuropeptide, also presence of Tff3 in the mouse cochlea was noted and Tff3-deficient animals display hearing impairment and accelerated presbyacusis. To elucidate Tff3's mode of function and its unexpected contribution to the hearing process, we strived to determine Tff3's interacting partners and to establish the functional network. To this end, we used a protein-protein binding assay based on a specific transcriptional regulation in yeast cells (the yeast-two-hybrid assay). We looked for interacting partners of Tff3 in a mouse cochlea cDNA library (from donors aged 3-15 days, P3-P15). Our data show that several binding candidates exist and that they could contribute to the known involvement of the trefoil peptides to apoptosis.

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.

Lack of Tff3 peptide results in hearing impairment and accelerated presbyacusis

Tff peptides are secreted mainly by the gastrointestinal epithelial cells and their primary role is maintaining normal structure and function of mucous epithelia. Ongoing studies on their expression pattern have disclosed other sites of their synthesis thus revealing additional physiological functions in the organism. Here we present new data about Tff3 expression in the cochlea of the rodent inner ear. On the basis of RT-PCR we describe the presence of Tff3 transcripts in both, a mouse cDNA library isolated from whole cochleae from postnatal days 3-15 (P3-P15), and also in cochlear tissue. By using a riboprobe for the fragment containing exon 1, 2 and 3 of Tff3, in situ hybridization, localized Tff3 signals in neurons of spiral ganglion and vestibular organ. We did not observe any abnormalities in the middle ear of Tff3 knock-out mice, neither did histological examination of the inner ear indicate any gross morphological changes in the cochlea. However, ABR (auditory evoked brain stem responses) audiograms revealed that the Tff3 knock-out animals show an accelerated presbyacusis and a hearing loss of about 15 dB at low frequencies increasing to 25 dB loss at higher frequencies. These findings suggest that Tff3 could play a role in neurosensory signaling. Further studies are needed to clarify this new function in the auditory system.

Human pancreatic polypeptide has a marked diurnal rhythm that is affected by ageing and is associated with the gastric TFF2 circadian rhythm

Normal circadian variations in vasoactive intestinal polypeptide, somatostatin, cholecystokinin and pancreatic polypeptide were measured to determine if these alter with aging and to identify gastrointestinal regulatory hormones that might control the dramatic diurnal variation in the gastric cytoprotective trefoil protein TFF2. Plasma pancreatic polypeptide concentrations showed a marked diurnal rhythm (p < 0.0001). Basal and postprandial pancreatic polypeptide concentrations increased with age (p < 0.01). The timing of the diurnal rhythm was consistent with pancreatic polypeptide inhibiting TFF2 secretion and there was a negative association between pancreatic polypeptide and TFF2 concentrations (p < 0.002). The much higher pancreatic polypeptide concentrations in older people will induce increased satiety that may contribute to 'anorexia of ageing'. These results identify potential therapies for treatment of gastric mucosal morbidity and age-associated loss of appetite.

Effects of topical treatment of sodium butyrate and 5-aminosalicylic acid on expression of trefoil factor 3, interleukin 1beta, and nuclear factor kappaB in trinitrobenzene sulphonic acid induced colitis in rats

BACKGROUND AND AIMS

Butyrate enemas have been shown to be effective in treatment of ulcerative colitis, but the mechanism of the effects of butyrate is not totally known. This study evaluates effects of topical treatment of sodium butyrate (NaB) and 5-aminosalicylic acid (5-ASA) on the expression of trefoil factor 3 (TFF3), interleukin 1beta (IL1beta), and nuclear factor kappaB (NFkappaB) in trinitrobenzene sulphonic acid (TNBS) induced colitis in rats.

METHODS

Distal colitis was induced in male Wistar rats by colonic administration of TNBS and colonically treated with NaB, 5-ASA, combination of NaB and 5-ASA, and normal saline for 14 consecutive days. Colonic damage score, tissue myeloperoxidase (MPO) activity, TFF3 mRNA expression, serum IL1beta production, and tissue NFkappaB expression were determined, respectively.

RESULTS

Treatment of NaB, 5-ASA, and the combination improved diarrhoea, colonic damage score, and MPO activities, increased TFF3 mRNA expression, and decreased serum IL1beta production and tissue NFkappaB expression. The combination therapy of NaB and 5-ASA had better effects than any other single treatment.

CONCLUSIONS

The combination of topical treatment of NaB and 5-ASA was effective for relieving and repairing colonic inflammation and the effects were related to stimulation of TFF3 mRNA expression and down-regulation of IL1beta production and NFkappaB expression.

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Expression of human TFF3 in relation to growth of HT-29 cell subpopulations: involvement of PI3-K but not STAT6

The trefoil factor family (TFF) peptides 1 and 2 (TFF1 and 2) are expressed in mucus cells of the stomach, whereas TFF3 is localized in goblet cells of the intestine. In the present study, we aimed to determine whether phosphatidylinositol 3-kinase (PI3-K) or signal transducer and activator of transcription protein 6 (STAT6) is involved in the expression of goblet cell specific markers. TFF3 expression was analyzed by RT-PCR, Northern blot, and radioimmunoassay (RIA) in relation to cell growth in subclones of HT-29 cells including the CL.16E and methotrexate (MTX) cell lines, which both exhibit a phenotype of mucus-secreting intestinal cells. A 30-fold increase in TFF3 mRNA levels and a 10-fold increase in TFF3-cell content were observed between the early proliferative and the late confluency states. The levels of MUC2 and MUC3 mRNA were also increased in the course of the differentiation process. A three to fourfold increase in PI3-K and Akt activities was observed in early post-confluent cells as compared with pre-confluent cells. Exposure of pre- and post-confluent cells to LY294002, a specific PI3-K inhibitor, for 1-4 days profoundly reduced TFF3 and MUC2 expression. A marked reduction in mucin granules content was also observed in LY-treated cells. Inhibition of the mitogen-activated protein (MAP) kinase kinase (MEK) with PD98059 did not modify the course of differentiation of the goblet cell lines. Moreover, stable transfection of HT-29 CL.16E cells with a dominant negative form of STAT6 had no effect on TFF3 induction. Together, these data indicate that PI3-K promotes the expression of TFF3 and MUC2 and that the PI3-K/Akt pathway may play a pivotal role in intestinal goblet cell differentiation.

TFF3 modulates NF-{kappa}B and a novel negative regulatory molecule of NF-{kappa}B in intestinal epithelial cells via a mechanism distinct from TNF-{alpha}

Trefoil factor 3 (intestinal trefoil factor) is a cytoprotective factor in the gut. Herein we compared the effect of trefoil factor 3 with tumor necrosis factor-alpha on 1) activation of NF-kappaB in intestinal epithelial cells; 2) expression of Twist protein (a molecule essential for downregulation of nuclear factor-kappaB activity in vivo); and 3) production of interleukin-8. We showed that Twist protein is constitutively expressed in intestinal epithelial cells. Tumor necrosis factor-alpha induced persistent degradation of Twist protein in intestinal epithelial cells via a signaling pathway linked to proteasome, which was associated with prolonged activation of NF-kappaB. In contrast to tumor necrosis factor, trefoil factor 3 triggered transient activation of NF-kappaB and prolonged upregulation of Twist protein in intestinal epithelial cells via an ERK kinase-mediated pathway. Unlike tumor necrosis factor-alpha, transient activation of NF-kappaB by trefoil factor 3 is not associated with induction of IL-8 in cells. To examine the role of Twist protein in intestinal epithelial cells, we silenced the Twist expression by siRNA. Our data showed that trefoil factor 3 induced interleukin-8 production after silencing Twist in intestinal epithelial cells. Together, these observations indicated that 1) trefoil factor 3 triggers a diverse signal from tumor necrosis factor-alpha on the activation of NF-kappaB and its associated molecules in intestinal epithelial cells; and 2) trefoil factor 3-induced Twist protein plays an important role in the modulation of inflammatory cytokine production in intestinal epithelial cells.

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IL-4 and IL-13 up-regulate intestinal trefoil factor expression: requirement for STAT6 and de novo protein synthesis

The development of intestinal goblet cell hyperplasia/hypertrophy during nematode infection involves the Th2 cytokines IL-4 and IL-13 via STAT6 activation. This is thought to play an important role in host protective immunity against the infection. In this study we demonstrate that IL-4 and IL-13 up-regulate the specific goblet cell product trefoil factor-3 (TFF3) from the mucus-producing HT-29 CL.16E and HT-29 cells selected by adaptation to methotrexate. Up-regulation of TFF3 mRNA and protein levels occurred in a time- and dose-dependent fashion and was accompanied by up-regulation of the goblet cell product mucin 2 (MUC2). Addition of actinomycin D before IL-4/IL-13 stimulation led to decreases in TFF3 mRNA levels similar to those observed in controls without IL-4/IL-13. Furthermore, IL-4-mediated increased TFF3 transcription required de novo protein synthesis. Stable transfection of HT-29 CL.16E cells with a truncated dominant-negative form of STAT6 produced a cell line that was unresponsive to IL-4/IL-13. Although only one consensus STAT6 binding site is contained in the TFF3 gene, located in the intron 1, it did not operate as an enhancer in the context of an SV40 promoter/luciferase construct. Thus, STAT6 activation mediates a transcriptional enhancement of TFF3 by induction of de novo synthesized protein in goblet cells.

Trefoil factor family (TFF) peptides and cancer progression

TFF peptides are involved in mucosal maintenance and repair through motogenic and antiapoptotic activities. These peptides are overexpressed during inflammatory processes and cancer progression. They also function as scatter factors, proinvasive and angiogenic agents. Such a divergence is related to the pathophysiological state of tissues submitted to persistent aggressive situations during digestive processes in the normal gastrointestinal tract, inflammatory and neoplastic diseases. In agreement with this model, TFF peptides are connected with multiple oncogenic pathways. As a consequence, the TFF signaling pathways may serve as potential targets in the control of chronic inflammation and progression of human solid tumors.

Cell type specific expression of secretory TFF peptides: colocalization with mucins and synthesis in the brain

The "TFF domain" is an ancient cysteine-rich shuffled module forming the basic unit for the family of secretory TFF peptides (formerly P-domain peptides and trefoil factors). It is also an integral component of mosaic proteins associated with mucous surfaces. Three mammalian TFF peptides are known (i.e., TFF1-TFF3); however, in Xenopus laevis the pattern is more complex (xP1, xP4.1, xP4.2, and xP2). TFF peptides are typical secretory products of a variety of mucin-producing epithelial cells (e.g., the conjunctiva, the salivary glands, the gastrointestinal tract, the respiratory tract, and the uterus). Each TFF peptide shows an unique expression pattern and different mucin-producing cells are characterized by their specific TFF peptide/secretory mucin combinations. TFF peptides have a pivotal role in maintaining the surface integrity of mucous epithelia in vivo. They are typical constituents of mucus gels, they modulate rapid mucosal repair ("restitution") by their motogenic and their cell scattering activity, they have antiapoptotic effects, and they probably modulate inflammatory processes. Pathological expression of TFF peptides occurs as a result of chronic inflammatory diseases or certain tumors. TFF peptides are also found in the central nervous system, at least in mammals. In particular, TFF3 is synthesized from oxytocinergic neurons of the hypothalamus and is released from the posterior pituitary into the bloodstream.