Up-regulation of TFF expression by PPARgamma ligands in gastric epithelial cells

An active protein from Dendrobium officinale residue: Protects the gastric mucosa and stabilized in the gastrointestinal tract

A large number of by-products generated in the food industry is discarded as waste, especially the residue left after extracting plant resources, which is typically repurposed as fertilizer. In this study, we extracted and purified a new protein, DOP1, from the residue of Dendrobium officinale Kimura & Migo (D. officinale), and explored the protective effect of DOP1 on alcohol-induced gastric mucosal injury. Its amino acid composition and the stability of secondary structure were measured by amino acid analysis and various spectroscopic methods. The microscopic morphology of DOP1 was observed by electron microscopy and its particle distribution was determined to be in the range of 3.7-5.5 nm. In addition, DOP1 was found to exhibit excellent protective activity against alcohol-induced gastric mucosal injury, as well as anti-inflammatory and antioxidant activities by in vitro and in vivo activity assays, which may be related to the upregulation of TFF2 through the activation of PPARγ. Intriguingly, DOP1 does not degrade and remains active after being digested by the gastrointestinal tract. From an economic and sustainable perspective, the discovery of DOP1 will provide new opportunities for the enhanced utilization and sustainable development of D. officinale resources.

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.

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.

Quantitative analysis of the effect of Helicobacter pylori on the expressions of SOX2, CDX2, MUC2, MUC5AC, MUC6, TFF1, TFF2, and TFF3 mRNAs in human gastric carcinoma cells

OBJECTIVE

To investigate the phenotypic characters of carcinoma cells and the response of gastric epithelial cells to Helicobacter pylori (H. pylori) infection using the gastric carcinoma cell lines.

MATERIAL AND METHODS

Real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the effect of H. pylori infection on mRNA levels of transcription factors (SOX2 and CDX2), mucin core proteins (MUC2, MUC5AC, and MUC6), and trefoil factor family peptides (TFF) (TFF1, TFF2, and TFF3) in gastric carcinoma cells (AGS, MKN45, and KATO III cells). H. pylori ATCC 43504 and its isogenic cag pathogenicity island (PAI) deleted mutant were used.

RESULTS

These cell lines expressed mixed gastric and intestinal phenotypes. The intestinal phenotype predominated in AGS cells and gastric phenotypes in MKN45 and KATO III cells. In all three cell lines, H. pylori infection inhibited SOX2 mRNA expression, but induced the three TFFs mRNAs. In AGS cells, H. pylori induced cag PAI-dependent mRNA expression of CDX2, MUC2, MUC5AC, and MUC6. mRNA expressions of CDX2, MUC5AC, and MUC6 were inhibited in KATO III cells, whereas MUC2 mRNA expression was unchanged. In MKN45 cells, H. pylori induced the three MUCs mRNAs but inhibited CDX2 mRNA expression.

CONCLUSIONS

This study provides a useful platform for selecting appropriate cell lines to model H. pylori-related changes in the gastric epithelium that mirror the changes seen in vivo. The outcome of H. pylori infection may reflect changes in the mucus gel layer caused by altered expression of mucins and TFF peptides.

Up-regulation of TFF1 (pS2) expression by TNF-alpha in gastric epithelial cells

BACKGROUND AND AIM

TFF1 (pS2) is expressed at a high level in gastric epithelial cells and plays an important role in protecting the gastric mucosa. However, the regulatory mechanisms of TFF1 expression are not fully understood. The aim of this study was to investigate the effect of TNF-alpha, a representative proinflammatory cytokine, on TFF1 expression.

METHODS

MKN45 and AGS cells, derived from human gastric carcinoma, were used. Endogenous TFF1 mRNA expression was analyzed by real-time quantitative RT-PCR. The sequences of the human TFF1 promoter were cloned into the pGL3-basic vector and reporter gene assays were performed. Nuclear factor (NF)-kappaB activity was monitored using a reporter vector that contained multiple copies of NF-kappaB responsive element upstream of the luciferase gene. Interaction between NF-kappaB and TFF1 cis-element was examined by electophoretic mobility shift assay (EMSA).

RESULTS

TNF-alpha activated NF-kappaB and up-regulated endogenous TFF1 mRNA expression as well as the transcription of the TFF1 reporter genes in a dose-dependent manner. IL-1beta, another proinflammatory cytokine, also up-regulated TFF1 expression. TNF-alpha responsive element was mapped between -342 and -147 of the human TFF1 promoter and a putative NF-kappaB binding site was identified at -231. When this element was deleted, the reporter genes became almost insensitive to TNF-alpha treatment. EMSA showed binding of NF-kappaB to this element.

CONCLUSIONS

Inflammatory stimuli that activate NF-kappaB appear to up-regulate TFF1 expression in gastric epithelial cells. This mechanism may aid in the protection of the gastric mucosa under inflammatory conditions.

Regulation of TFF3 expression by homeodomain protein CDX2

Although trefoil factor family 3 (TFF3) plays an important role in protecting the intestinal mucosa, the regulatory mechanisms of its expression are not fully understood. Since homeodomain protein CDX2 has been reported to be critically involved in the development and differentiation of intestinal epithelium, we examined whether CDX2 affects the expression of TFF3. The transcription of human TFF3 reporter genes was significantly up-regulated by the transient overexpression of CDX2 in COS-7 cells and AGS gastric cells. Electrophoretic mobility shift assay revealed the presence of at least two CDX-binding sites within the human TFF3 promoter. Deletion analysis showed the relative importance of the proximal CDX-binding site at -63. We also detected the up-regulation of endogenous TFF3 mRNA expression in AGS cells stably transfected with CDX2 expression vectors. These results suggest that CDX2 plays a key role in the expression of TFF3 in the intestine and perhaps in intestinal metaplasia of the stomach.

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Peroxisome proliferator-activated receptor gamma (PPARgamma) regulates trefoil factor family 2 (TFF2) expression in gastric epithelial cells

Although trefoil factor family 2 (TFF2) plays a critical role in the defense and repair of gastric mucosa, the regulatory mechanism of TFF2 expression is not fully understood. In this study, we investigated the regulation of TFF2 expression by peroxisome proliferator-activated receptor gamma (PPARgamma) in gastric epithelial cells. MKN45 gastric cells were used. TFF2 mRNA expression was analyzed by real-time quantitative RT-PCR. The promoter sequence of the human TFF2 gene was cloned into pGL3-basic vector for reporter gene assays. Ciglitazone was mainly used as a specific PPARgamma ligand. MKN45 cells expressed functional PPARgamma proteins. Endogenous TFF2 mRNA expression and TFF2 reporter gene transcription was significantly up-regulated by ciglitazone in a dose-dependent manner. Reporter gene assays showed that two distinct cis-elements are involved in the response to PAPRgamma activation. Within one of these element (nucleotides -558 to -507), we identified a functional peroxisome proliferator responsive element (PPRE) at -522 (5'-GGGACAAAGGGCA-3'). Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay confirmed the binding of PPARgamma to this sequence. Another element (nucleotides -407 to -358) appeared to be a composite enhancer element indirectly regulated by PPARgamma and a combination of these two cis-elements was required for the full response of the human TFF2 gene expression to PPARgamma. These data demonstrate that human TFF2 gene is a direct target of PPARgamma in gastric epithelial cells. Since TFF2 is a critical gastroprotective agent, PPARgamma may be involved in the gastric mucosal defense through regulating TFF2 expression in humans.

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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.

PPARgamma mediates NSAIDs-induced upregulation of TFF2 expression in gastric epithelial cells

Trefoil factor family (TFF) is a group of peptides that play critical roles in maintaining gastric mucosal integrity. In real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) and reporter gene assays, we show that indomethacin and aspirin upregulate TFF2 expression in MKN45 gastric cells. These drugs also activated peroxisome proliferator-activated receptor gamma (PPARgamma) at concentration ranges that increase TFF2 expression, and upregulated TFF2 expression was suppressed by GW9662, a specific inhibitor of PPARgamma. These results suggest that indomethacin and aspirin upregulate gastric expression of TFF2 through activation of PPARgamma. This mechanism may be important in reducing the extent of gastric mucosal injury caused by the administration of non-steroidal anti-inflammatory drugs (NSAIDs).