Activation of genes for spasmolytic peptide, transforming growth factor alpha and for cyclooxygenase (COX)-1 and COX-2 during gastric adaptation to aspirin damage in rats

Trefoil Factor Family Member 2 (TFF2) as an Inflammatory-Induced and Anti-Inflammatory Tissue Repair Factor

Trefoil factor family member 2 (TFF2) is known for its involvement in mucosal repair. Whereas it is overexpressed during inflammatory processes, adding TFF2 leads to an anti-inflammatory effect that would contribute to create the microenvironment required for tissue repair. These properties present TFF2 with a homeostatic pattern during inflammatory processes as illustrated by selected examples.

Trefoil factor 2 activation of CXCR4 requires calcium mobilization to drive epithelial repair in gastric organoids

KEY POINTS

Determining the signalling cascade of epithelial repair, using murine gastric organoids, allows definition of regulatory processes intrinsic to epithelial cells, at the same time as validating and dissecting the signalling cascade with more precision than is possible in vivo Following single cell damage, intracellular calcium selectively increases within cells adjacent to the damage site and is essential for promoting repair. Trefoil factor 2 (TFF2) acts via chemokine C-X-C receptor 4 and epidermal growth factor receptor signalling, including extracellular signal-regulated kinase activation, to drive calcium mobilization and promote gastric repair. Sodium hydrogen exchanger 2, although essential for repair, acts downstream of TFF2 and calcium mobilization.

ABSTRACT

The gastric mucosa of the stomach is continually exposed to environmental and physiological stress factors that can cause local epithelial damage. Although much is known about the complex nature of gastric wound repair, the stepwise process that characterizes epithelial restitution remains poorly defined. The present study aimed to determine the effectors that drive gastric epithelial repair using a reductionist culture model. To determine the role of trefoil factor 2 (TFF2) and intracellular calcium (Ca2+ ) mobilization in gastric restitution, gastric organoids were derived from TFF2 knockout (KO) mice and yellow Cameleon-Nano15 (fluorescent calcium reporter) transgenic mice, respectively. Inhibitors and recombinant protein were used to determine the upstream and downstream effectors of gastric restitution following photodamage (PD) to single cells within the gastric organoids. Single cell PD resulted in parallel events of dead cell exfoliation and migration of intact neighbouring cells to restore a continuous epithelium in the damage site. Under normal conditions following PD, Ca2+ levels increased within neighbour migrating cells, peaking at ∼1 min, suggesting localized Ca2+ mobilization at the site of cell protrusion/migration. TFF2 KO organoids exhibit delayed repair; however, this delay can be rescued by the addition of exogenous TFF2. Inhibition of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK)1/2 or a TFF2 receptor, chemokine C-X-C receptor 4 (CXCR4), resulted in significant delay and dampened Ca2+ mobilization. Inhibition of sodium hydrogen exchanger 2 (NHE2) caused significant delay but did not affect Ca2+ mobilization. A similar delay was observed in NHE2 KO organoids. In TFF2 KO gastric organoids, the addition of exogenous TFF2 in the presence of EGFR or CXCR4 inhibition was unable to rescue repair. The present study demonstrates that intracellular Ca2+ mobilization occurs within gastric epithelial cells adjacent to the damage site to promote repair by mechanisms that involve TFF2 signalling via CXCR4, as well as activation of EGFR and ERK1/2. Furthermore NHE2 is shown to be important for efficient repair and to operate via a mechanism either downstream or independent of calcium mobilization.

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.

Difficult establishment of a chronic nonsteroidal anti-inflammatory drugs induced gastric inflammation rat model due to gastric adaptation and small bowel damage

BACKGROUND/AIMS

The prevalence of peptic ulcer disease has not decreased mainly due to an increase in the use of NSAIDs. This study was conducted in order to determine whether a chronic NSAID-induced gastric inflammation model could be established by repeated administration of NSAID.

METHODS

Indomethacin (10 mg/kg) was administered once per week for six weeks in 8- and 26-week rats and animals were sacrificed every week after administration. Gross ulcer index, histologic damage index, myeloperoxidase (MPO) activity, and mucus (glucosamine) levels were measured. Small bowel damage was also evaluated.

RESULTS

Gross gastric damage index showed a peak level at three weeks and then decreased slowly in the 26-week indomethacin group. Gastric mucosal glucosamine level increased in both the 8-week (p=0.038) and 26-week groups (p=0.007). In addition, gastric mucosal MPO level decreased in the 8-week group (p=0.018) but did not show a decrease in the 26-week group. Small bowel damage began to occur at three weeks during the schedule and eight of 36 rats (22.2%) died due to perforation or peritonitis of the small bowel in the 8- and 26-week indomethacin groups, respectively.

CONCLUSIONS

Due to gastric adaptation and small bowel damage, repeated administration of NSAID to experimental animals may not be an adequate method for establishment of the chronic gastric inflammation model.

EXPRESSION OF REG1Α, GAST AND TGFB1 GENES IN CONDITIONS OF STRESSINDUCED GASTRIC MUCOUS LESIONS DEVELOPMENT AND HEALING IN RATS

Analysis of Reg1a gene expression in rat gastric mucosa under development and healing of stress-induced lesions was carried out. Increased expression of Reg1a was observed after 1 hour of stressor impact - 2,1 times, and achieved the maximum level expression after 3 hours of stress exposure - 3,5 times, that occurred on the background of lipid peroxidation intensification and antioxidant system dysfunction. The sharp decrease in 1,6 and 2 times of Reg1a gene expression was shown in 12 and 24 hours respectively after termination of the stressor action. Analysis of Gast gene expression did not confirm that gastrin stimulated Reg1a expression in gastric mucosa under water immersion restraint stress. The positive correlation between Reg1a and Tgfb1 genes expression was determined in the dynamics of stress-induced gastric lesions’ development and healing, which may indicate the involvement of Tgfb1 to acceleration of lesion’s healing.

Reactive increase in gastric mucus secretion is an adaptive defense mechanism against low-dose aspirin-induced gastropathy

BACKGROUND

Gastric mucus is considered to play an essential role in gastric mucosal defense mechanisms, especially when irritants are present in the stomach.

AIM

To investigate the relationship between low-dose aspirin-induced gastropathy and gastric secretory function, especially gastric mucus secretion, in healthy volunteers.

METHODS

Thirty male, asymptomatic, Helicobacter pylori pylori-negative healthy volunteers were asked to take 100 mg of enteric-coated aspirin (Bayaspirin) once a day for 10 days. Endoscopic examination was performed before and 3 and 10 days after drug administration. The extent of endoscopically assessed gastric mucosal injury was semi-quantitatively evaluated according to the modified Lanza score. The pentagastrin-stimulated gastric juice was collected for 10 min during the endoscopic examination and subjected to analysis for gastric acid (mEq/10 min) or mucus (mg hexose/10 min) output.

RESULTS

Overall, the 10-day aspirin treatment significantly increased gastric mucus secretion from 0.8 (interquartile range 1.7) to 1.6 (1.6) mg hexose/10 min (P < 0.05), with a concomitant and significant decrease in the gastric acid/mucus ratio from 4.3 (5.2) to 2.9 (4.7) (P < 0.01). Subsequent analysis of two subgroups of volunteers categorized according to their endoscopic status ("severe gastropathy" vs. "modest gastropathy") revealed that changes in gastric secretory parameters occurred exclusively in those subjects without severe gastric injury; there was no alteration in these parameters in subjects with severe gastric injury.

CONCLUSIONS

The results of this study suggest that the reactive increase in gastric mucus secretion is an adaptive defense mechanism against low-dose aspirin-induced gastropathy. In some individuals, such a response may be insufficient to prevent the development of severe mucosal injury and even ulcers and their complications.

Association of gastric acid and mucus secretion level with low-dose aspirin-induced gastropathy

BACKGROUND

Low-dose aspirin is known to cause upper gastrointestinal complications. The mechanism by which the aspirin disrupts gastric mucosal integrity remains to be clarified. In this study we investigated the temporal association of gastric secretory parameters (acid and mucus) with aspirin-induced gastropathy.

METHODS

In 42 long-term low-dose aspirin-takers and the same number of sex- and age-matched controls, pentagastrin-stimulated gastric juice was collected for 10 min during endoscopic examination. The collected gastric juice was divided and half was submitted to analysis for gastric acid (mEq/10 min) and the other half was analyzed for mucin (mg hexose/10 min) output. The grade of gastric mucosal injury was assessed endoscopically according to the modified Lanza score, and a score of more than 4 was defined as the presence of severe gastropathy.

RESULTS

While gastric acid secretion did not differ significantly between aspirin-takers and controls, gastric mucus secretion, in terms of mucin output, was significantly increased in aspirin-takers compared to controls (4.1 (SD 4.8) vs. 2.3 (1.4) mg hexose/10 min, P < 0.05). Consequently, the acid/mucin ratio was significantly decreased in aspirin-takers compared to controls (1.2 (1.0) vs. 1.7 (1.4), P < 0.05). In the subanalysis of 25 aspirin-takers without severe gastropathy, gastric mucus secretion was increased and the acid/mucus ratio was decreased compared with controls, but there was no such association in the remaining 17 aspirin-takers with severe gastropathy.

CONCLUSION

Overall, gastric mucus secretion is increased in aspirin-takers, suggesting a functional adaptive response to long-term administration of the drug. However, it is possible that the adaptive response is impaired in some aspirin takers, who might be susceptible to severe upper gastrointestinal complication.

Cyclooxygenase-2 expression in chronic hepatitis C and the effect of interferon alpha treatment

BACKGROUND AND AIM

Cyclooxygenase-2 (COX-2), a target of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), is upregulated in chronic hepatitis B and may have a role in hepatocellular carcinoma. Little is known about the expression of COX-2 in chronic hepatitis C (HCV) infection. The aim the present study was to evaluate the extent of COX-2 expression in liver biopsies in patients with HCV infection and to determine the effect of treatment with interferon alpha (IFN).

METHODS

Percutaneous liver biopsy specimens were retrieved. Following formalin fixation and paraffin embedding, the biopsies were histologically evaluated for inflammation and fibrosis. The extent of COX-2 expression was measured by the avidin biotin immunohistochemical technique using a monoclonal COX-2 antibody. The extent of COX-2 expression was graded according to the number of hepatocytes expressing COX-2. Data were analyzed using Student's t-test.

RESULTS

Liver biopsies from 10 patients before and after treatment with IFN were obtained and compared with nine normal liver biopsies. All of the liver biopsies showed some COX-2 expression. COX-2 expression was confined to hepatocytes and bile duct epithelium and was not detected in vascular endothelium or inflammatory cells. The extent of COX-2 expression was greater in hepatitis C infected liver biopsies than in normal biopsies. Following treatment with IFN, there was a greater than threefold reduction in COX-2 expression (P < 0.01). This result was independent of the sustained virological response.

CONCLUSION

In this small pilot study we have shown that COX-2 is overexpressed in liver biopsies infected with HCV and COX-2 expression is reduced following treatment with IFN.

In vitro antiproliferative activity against human colon cancer cell lines of representative 4-thiazolidinones. Part I

The characterization of two cyclooxygenase isoforms (COX), the rate-limiting enzyme for the synthesis of prostaglandins (PGs) from arachidonic acid, has allowed the development of COX-2 selective inhibitors as non-steroidal anti-inflammatory drugs (NSAIDs) with significant gastric tolerability. However, PGs are also important in cancer pathogenesis. Thus, there is an increasing interest in studying COX-2 inhibitors as potential drugs aimed at the prevention and treatment of cancer, especially colorectal cancer. The purpose of this study was to determine the inhibitory effects of some representative 4-thiazolidinones, already widely investigated as potential NSAIDs, on the growth of five human colon carcinoma cell lines with a different COX-2 expression, and to correlate them with COX-2 inhibitory properties. Our results preliminarily revealed that 2-phenylimino derivative 3 and 2,4-thiazolidindione 4 were the most active compounds. In particular, 3 mainly inhibited the HT29 cell line characterized by a high COX-2 expression, whereas 4 showed antiproliferative properties on all tested cell lines, suggesting molecular targets other than COX-2 inhibition.

Cyclooxygenase 2, pS2, inducible nitric oxide synthase and transforming growth factor alpha in gastric adaptation to stress

AIM

To determine the role of mucosal gene expression of cyclooxygenase 2 (COX-2), pS2 (belongs to trefoil peptides), inducible nitric oxide synthase (iNOS) and transforming growth factor alpha (TGFalpha) in gastric adaptation to water immersion and restraint stress (WRS) in rats.

METHODS

Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 d. Gastric mucosal blood flow (GMBF) was measured by laser Doppler flowmeter-3. The extent of gastric mucosal lesions were evaluated grossly and histologically and expressions of COX-2, pS2,iNOS and TGFalpha were determined by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot.

RESULTS

The damage to the surface of gastric epithelium with focal areas of deep haemorrhagic necrosis was induced by repeated WRS. The adaptative cytoprotection against stress was developed with activation of cell proliferation in the neck regions of gastric glands. The ulcer index (UI) in groups II, III and IV was markedly reduced as compared with group I (I: 47.23+/-1.20; IV: 10.39+/-1.18,P<0.01). GMBF significantly decreased after first exposure to WRS with an adaptive increasement of GMBF in experimental groups after repetitive challenges with WRS. After the 4th WRS, the value of GMBF almost restored to normal level (I: 321.87+/-8.85; IV: 455.95+/-11.81, P<0.01). First WRS significantly decreased the expression of pS2 and significantly increased the expressions of COX-2, iNOS and TGFalpha. After repeated WRS, pS2 and TGFalpha expressions gradually increased (pS2: I: 0.37+/-0.02; IV: 0.77+/-0.01; TGFalpha: I: 0.86+/-0.01; IV: 0.93+/-0.03, P<0.05) with a decrease in the expressions of COX-2 and iNOS (COX-2: I: 0.45+/-0.02; IV: 0.22+/-0.01; iNOS: I: 0.93+/-0.01; IV: 0.56+/-0.01, P<0.01). Expressions of pS2, COX-2, iNOS and TGFalpha showed regular changes with a good relationship among them.

CONCLUSION

Gastric adaptation to WRS injury involves enhanced cell proliferation, increased expression of pS2 and TGFalpha, and reduced expression of COX-2 and iNOS. These changes play an important role in adaptation of gastric mucosa after repeated WRS.

Indometacin up-regulates TFF2 expression in gastric epithelial cells

BACKGROUND

Trefoil factor family peptides are expressed in gastrointestinal epithelial cells and play a critical role in maintaining mucosal integrity. Although non-steroidal anti-inflammatory drugs (NSAIDs) are important causative agents of gastric mucosal lesions, few data are available about the effect of NSAIDs on trefoil family peptides in gastric mucosa.

AIM

To examine whether indometacin, a widely used NSAID, affects trefoil factor family expression in gastric epithelial cells.

METHODS

MKN45, a cell line derived from human gastric cancer, was used. TFF1, TFF2, and TFF3 mRNA expression was assessed by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). TFF2 gene transcription was also examined by luciferase reporter gene assay.

RESULTS

Relative expression level of TFF1, TFF2, TFF3 mRNA was 616: 12: 1 in unstimulated MKN45 cells. Although indometacin (1-250 micro mol/L) had no significant effect on the expression of TFF1 and TFF3 mRNA, it up-regulated TFF2 mRNA expression in a dose- and time-dependent manner. Luciferase reporter gene assay confirmed the up-regulation of TFF2 gene transcription by indometacin. Indometacin-induced up-regulation of TFF2 expression was not antagonized by externally applied prostaglandin E2.

CONCLUSION

These results suggest that indometacin up-regulates gastric epithelial cell TFF2 expression through a COX-independent mechanism. Since TFF peptides play an important role in gastric mucosal protection, indometacin-induced TFF2 may reduce the degree of gastric mucosal damage induced by indometacin.

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.

Inhibition of rat mammary gland carcinogenesis by simultaneous targeting of cyclooxygenase-2 and peroxisome proliferator-activated receptor gamma

We examined the effect of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, and N-(9-fluorenyl-methyloxycarbonyl)-L-leucine (F-L-Leu), a peroxisome proliferator-activated receptor gamma (PPAR gamma) agonist, separately and combined, on the development of methylnitrosourea (MNU)-induced rat mammary gland carcinogenesis. Celecoxib and F-L-Leu significantly reduced tumor incidence and multiplicity (P < 0.05). Combining both agents exerted higher (synergistic) cancer inhibition than separate treatments (P < 0.05). The effects of the test drugs on COX-2 and PPAR gamma expression and on the synthesis of prostaglandin E(2) (PGE(2)) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) were examined in rat mammary normal (MNU-untreated), uninvolved, and tumor (MNU-treated) tissues. Celecoxib and F-L-Leu, separately, inhibited COX-2 and up-regulated PPAR gamma expression. These effects were paralleled by inhibition of PGE(2) synthesis and up-regulation of 15d-PGJ(2). Combined treatment resulted in higher alterations in COX-2 and PPAR gamma transcripts and PG synthesis compared with separate administrations. The effect of the test agents on Bcl(2), BAX, and protein kinase C alpha expression levels were examined in the rat mammary gland and the pro-(BAX:Bcl(2)) and anti-[PKC alpha*(Bcl(2)/BAX)] apoptotic ratios were evaluated. Each drug increased the proapoptotic ratio by 2- to 7-fold and reduced the antiapoptotic ratio by 2- to >8-fold in all tissues. Combined treatment, however, resulted in >9- to 14-fold up-regulation in the proapoptotic processes and 15- to >30-fold down-regulation in the antiapoptotic ones. Analyses were also carried out on the drug-induced modulation of cell cycle regulators and proliferation markers (cyclin-dependent kinase 1 and proliferating cell nuclear antigen). F-L-Leu and celecoxib each reduced the cyclin-dependent kinase 1 and proliferating cell nuclear antigen expression in the tumor. Higher down-regulation was attained in all tissues by combined treatment where cyclin-dependent kinase 1 and proliferating cell nuclear antigen almost retained the expression levels observed in the normal glands. In conclusion, simultaneous targeting of COX-2 and PPAR gamma may inhibit mammary cancer development more effectively than targeting each molecule alone. COX-2 inhibitors and PPAR gamma agonists coordinately mediate their anticancer effect via both COX-dependent (inhibition of COX-2, activation of PPAR gamma, and modulation PG synthesis) and COX-independent (induction of proapoptotic factors and inhibition of cell proliferation) pathways.

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).

Role of TFF in healing of stress-induced gastric lesions

AIM: To determine the changes of pS2 and ITF of TFF expression in gastric mucosa and the effect on ulcer healing of pS2, ITF to Water-immersion and restraint stress (WRS) in rats.

METHODS: Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 days.Gastric mucosal blood flow (GMBF) was measured by LDF-3 flowmeter and the extent of gastric mucosal lesions were evaluated grossly and histologically. Expression of pS2 and ITF mRNA was determined by RT-PCR. Immunohistochemistry was used to further detect the expression of pS2 and ITF.

RESULTS: WRS applied once produced numerous gastric mucosal erosions, but the number of these lesions gradually declined and GMBF restored at 2, 4, 8 h after stress. The area of gastric mucosal lesion was reduced by 64.9% and GMBF was increased by 89.8% at 8 h. The healing of stress-induced ulcerations was accompanied by increased expression of pS2 (0.51 ± 0.14 vs 0.77 ± 0.11, P < 0.01) and ITF (0.022 ± 0.001vs 0.177 ± 0.010, P < 0.01). The results were demonstrated further by immunohistochemistry of pS2 (0.95 ± 0.11 vs 1.41 ± 0.04, P < 0.01) and ITF (0.134 ± 0.001 vs 0.253 ± 0.01,P < 0.01). With repeated WRS, adaptation to this WRS developed, the area of gastric mucosal lesions was reduced by 22.0% after four consecutive WRS. This adaptation to WRS was accompanied by increased GMBF (being increased by 94.2%), active cell proliferation in the neck region of gastric glands, and increased expression of pS2 (0.37 ± 0.02 vs 0.77 ± 0.01, P < 0.01) and ITF (0.040 ± 0.001vs 0.372 ± 0.010, P < 0.01). The result was demonstrated further by immunohistochemistry of pS2 (0.55 ± 0.04 vs 2.46 ± 0.08, P < 0.01) and ITF (0.134 ± 0.001vs 0.354 ± 0.070, P < 0.01).

CONCLUSION: TFF may not only participate in the early phase of epithelial repair known as restitution(maked by increased cell migration),but also play an important role in the subsequent,protracted phase of glandular renewal(made by cell proliferation).

Role of the ITF in repairing of stress-induced gastric lesions

AIM

To determine the changes of ITF (intestinal trefoil peptides) expression in gastric mucosal and the effect on ulcer healing of ITF to WRS in rats.

METHODS

Wistar rats were exposed to single or multiple WRS for 4 h every other day for up to 6 days. Gastric mucosal blood flow(GMBF) was measured by LDF-3 Flow meter and the extent of gastric mucosal lesions were evaluated grossly and histologically. Expression of ITF mRNA was determined by RT-PCR. Immunohistochemistry was used to further detect the expression of ITF.

RESULTS

Single time of WRS produced numerous gastric mucosal erosions, but the number of these lesions gradually declined and GMBF restorated at 2, 4, 8 h after stress; the area of gastric mucosal lesion was reduced by 64.9% and GMBF was increased by 89.8% at 8 h, the healing of stress-induced ulcerations was accompanied by increased expression of ITF (0.022±0.001 vs 0.177±0.010 P<0.01), the results were demonstrated further by immunohistoch- emistry (0.134±0.001 vs 0.253±0.01, P<0.01). With repeated WRS, the adaptation to this WRS developed, the area of gastric mucosal lesions was reduced by 22.0% after four consecutive WRS, this adaptation to WRS was accompanied by increased GMBF(94.2%) and active cell proliferation in the neck region of gastric glands and by increased expression of ITF (0.040±0.001 vs 0.372±0.010 P<0.01), the result were demonstrated further by immunohistochemistry (0.134±0.001 vs 0.354±0.070, P<0.01).

CONCLUSION

ITF may participate in the early phase of epithelial repair known as restitution, but also may play an important role in the subsequent, protracted phase of glandular renewal.

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.

Gastric toxicity of racemic ketoprofen and its enantiomers in rat: oxygen radical generation and COX-expression

OBJECTIVE AND DESIGN

The gastric toxicity of racemic-ketoprofen and its enantiomers (S(+)- and R(-)-ketoprofen), oxygen free radical generation and neutrophil infiltration in response to damage were evaluated in rats. Changes in prostaglandin synthesis, cyclooxygenase expression and glutathione metabolism were also studied.

MATERIALS AND METHODS

Studies were performed in Wistar rats. Drugs were given by oral administration: racemic-ketoprofen (100, 50 and 25 mg/kg body weight); S(+) and R(-)-ketoprofen (50, 25 and 12.5 mg/kg body weight). Determinations were made of gastric mucosal injury, lipid peroxidation, xanthine oxidase, myeloperoxidase and superoxide dismutase activities, glutathione levels, glutathione peroxidase and glutathione reductase activities, gastric prostaglandin synthesis (PGE2 levels) and COX-expression.

RESULTS

Racemic-ketoprofen dose-dependently exhibited the highest toxicity. In contrast, S(+)-ketoprofen at half the dose of the racemic compound proved to be less ulcerogenic. R(-)-ketoprofen was also less ulcerogenic, but when administered as the racemate exacerbated gastric ulceration caused by S(+)-ketoprofen. Drug administration produced significant increases in lipid peroxidation levels and xanthine-oxidase and a decrease in superoxide dismutase activity. Nevertheless the racemate induced the highest disturbances in oxidative metabolism. No changes in myeloperoxidase values and glutathione metabolism were found. Cyclooxygenase-1 immunoreactivity was observed and did not differ from that in control rats. Cyclooxygenase-2 could also be expressed after treatments.

CONCLUSIONS

R(-)-ketoprofen and S(+)-ketoprofen have a comparable gastric toxicity and they both have a better gastric toxicity profile as compared to the racemate. In addition to inhibition of prostaglandin synthesis, damage resulted in an increase of cyclooxygenase-2 protein expression. Oxygen radicals, including superoxide anions, could also be implicated.

Aspirin effects on gastric epithelial cell proliferation and cytokine expression

Aspirin is known to cause gastric injury and to delay ulcer healing. The effects of aspirin on gastric epithelial cell function are heterogeneous; in contrast to injuring the mucosa, aspirin may also act beneficially by inducing adaptation; a mechanism that is poorly understood. We aimed to document the effects of different doses of aspirin on gastric epithelial cell function defined as proliferation, and secretion as well as mRNA expression of cytokines. Furthermore, we studied the effects of aspirin pretreatment on cytokine secretion as a potential element of gastric adaptation. The proliferative activity of three different gastric epithelial cell lines (AGS, KATO III, RGM-1) was assessed by (3)H-thymidine incorporation; secretion of growth factors PDGF-AB and VEGF into culture supernatant was documented by ELISA. mRNA transcripts of both cytokines were quantified by real time RT-PCR. Low doses of aspirin did not alter the proliferative dynamics in two of the three studied cell lines; high doses abolished proliferation. Secretion of PDGF-AB and VEGF increased during the first days of low dose aspirin exposition; higher concentrations led to a depletion of cytokines after an initial liberation in the case of VEGF, mRNA of which was also dose-dependently increased by aspirin. Seven-day pretreatment with low amounts of aspirin did not alter the secretory response of the epithelia caused by higher doses of this drug. The secretion of cytokines and proliferation of gastric epithelial cells are adversely effected by aspirin in a similarly dose-dependent fashion as the intended effects of this drug on platelet function and pain relief.

Aspirin promotes TFF2 gene activation in human gastric cancer cell lines

Trefoil factor family (TFF) peptides promote cell migration, heal the mucosa and may suppress tumor growth. In reporter gene assays we show that aspirin (1-12 mM) evokes a six-fold up-regulation of TFF2, but not TFF1 and TFF3 transcription in human gastrointestinal cell lines. 6 h after application up-regulation of endogenous TFF2 mRNA was observed. TFF2 transcription was enhanced by indomethacin and arachidonic acid but repressed by staurosporine, suggesting mediation via protein kinase C. We mapped an aspirin responding element -546 to -758 bp upstream of TFF2. Up-regulation of TFF2 by aspirin may partially explain the chemopreventive potential of low dose aspirin in gastrointestinal carcinogenesis.

Gastroprotective and ulcer healing effects of nitric oxide-releasing non-steroidal anti-inflammatory drugs

BACKGROUND & AIM

New class of nitric oxide-releasing non-steroidal anti-inflammatory drugs was shown to inhibit cyclooxygenase and prostaglandin generation without causing mucosal damage but whether these agents are capable of affecting gastric mucosal damage induced by strong irritants and healing of chronic gastric ulcers remains to be studied. In this investigation, effects of nitric oxide-releasing aspirin and nitric oxide-releasing naproxen were compared with those of native agents on gastric lesions provoked by 100% ethanol and on healing of chronic acetic acid ulcers.

RESULTS

Both, nitric oxide-releasing aspirin and naproxen dose-dependently attenuated ethanol-induced damage and produced a significant rise in gastric blood flow but did not delay healing of gastric ulcers while native aspirin and naproxen had no influence on ethanol-induced gastric damage but significantly prolonged ulcer healing, reduced gastric blood flow and suppressed mucosal generation of prostaglandin E2. The gastroprotective and hyperaemic effects of both nitric oxide-non-steroidal anti-inflammatory drugs were completely abolished by ODQ, an inhibitor of guanylyl cyclase-cGMP system but not influenced by suppression of nitric oxide-synthase with L-NNA. The damaging effects of native acetyl salicylate acid or naproxen were aggravated by acidification of these non-steroidal anti-inflammatory drugs but the exogenous acid added to nitric oxide-acetyl salicylate acid or nitric oxide-naproxen failed to influence their effect. Despite inhibiting of PGE2 generation, both nitric oxide-releasing derivatives and native aspirin and naproxen failed to affect expression of cyclooxygenase-1 mRNA but upregulated the cyclooxygenase-2 mRNA. Concurrent inhibition of cyclooxygenase-2 by selective inhibitor NS-398 which by itself delayed ulcer healing and attenuated the gastric blood flow at ulcer margin, significantly worsened the effects of these nitric oxide-non-steroidal anti-inflammatory drugs and their parent drugs on ulcer healing and the gastric blood flow at the ulcer margin.

CONCLUSIONS

1) Coupling of nitric oxide to aspirin or naproxen attenuates ethanol-induced damage, possibly due to an increase in gastric microcirculation mediated by excessive release and action of nitric oxide that probably compensates for PG deficiency induced by non-steroidal anti-inflammatory drugs; and 2) nitric oxide-non-steroidal anti-inflammatory drug, unlike classic non-steroidal anti-inflammatory drugs, does not affect intact gastric mucosa and fails to delay the healing of pre-existing ulcers.

Effect of naproxen on the hamster gastric antrum: ulceration, adaptation and efficacy of anti-ulcer drugs

BACKGROUND

Various animal models of non-steroidal anti-inflammatory drug (NSAID)-induced gastric ulceration exist. These models have limitations, which make them less relevant to the human situation.

AIM

: To develop a more simple and more relevant model of NSAID-induced gastric ulceration and adaptation.

METHODS

Gastric ulceration was evaluated following the orogastric administration of naproxen (80 mg/kg b.d.) to hamsters. The effects of misoprostol and famotidine on gastric acid secretion and ulceration were also determined. Gastric adaptation was evaluated by proliferating cell nuclear antigen (PCNA) immunohistochemistry, in hamsters given naproxen for 3 weeks. Antral resistance to acute injury by NSAIDs and ethanol was also determined in these animals.

RESULTS

Naproxen caused primarily gastric antral ulceration, which decreased from day 3 to day 21. This gastric adaptation was accompanied by an increase in PCNA positive cells, particularly on days 7 and 14. The adapted gastric antral mucosa was resistant to acute damage by various agents. Misoprostol (1 or 100 microg/kg) prevented antral ulceration, without affecting gastric acid secretion. Despite decreasing acid output by> 90%, famotidine (30 mg/kg) failed to prevent ulceration.

CONCLUSION

The administration of naproxen (80 mg/kg b.d.) to hamsters is a simple, reliable and relevant method for evaluating NSAID-induced gastric antral ulceration and adaptation.