Effect of rebamipide on prostaglandin EP4 receptor gene expression in rat gastric mucosa

[Epithelial protective therapy in comorbid diseases. Practical Guidelines for Physicians]

This document was produced with the support of the National Medical Association for the Study of Comorbidities (NASС). In 2021 the first multidisciplinary National Consensus on the pathophysiological and clinical aspects of Increased Epithelial Permeability Syndrome was published. The proposed guidelines are developed on the basis of this Consensus, by the same team of experts. Twenty-eight Practical Guidelines for Physicians statements were adopted by the Expert Council using the "delphic" method. Such main groups of epithelial protective drugs as proton pump inhibitors, bismuth drugs and probiotics are discussed in these Guidelines from the positions of evidence-based medicine. The clinical and pharmacological characteristics of such a universal epithelial protector as rebamipide, acting at the preepithelial, epithelial and subepithelial levels, throughout gastrointestinal tract, are presented in detail.

Effect of Polymers and Storage Relative Humidity on Amorphous Rebamipide and Its Solid Dispersion Transformation: Multiple Spectra Chemometrics of Powder X-Ray Diffraction and Near-Infrared Spectroscopy

This study aimed to investigate the effect of polymers and storage relative humidity on amorphous rebamipide (RB) and its solid dispersion phase transformation using chemometrics based on multiple datasets. The amorphous RB was prepared using particle mixture and grinding methods with hydroxypropyl cellulose, polyvinylpyrrolidone, and sodium dodecyl sulfate. Prepared amorphous RB and solid dispersion samples were stored under a relative humidity of 30% and 75% for four weeks. Infrared spectra of the dispersion samples suggested that the hydrogen bond network was constructed among quinolinone, carbonyl acid, and amide of RB and other polymers. The dataset combining near-infrared (NIR) spectra and powder X-ray diffractograms were applied to principal component analysis (PCA). The relationship between diffractograms and NIR spectra was evaluated using loadings and the PCA score. The multiple spectra analysis is useful for evaluating model amorphous active pharmaceutical ingredients without a standard sample.

New Prospects of Cytoprotection in the Treatment and Prevention of Gastric and Intestinal Diseases (Resolution of an Expert Council and Literature Review)

Aim. To generalize up-to-date information on the possibilities of cytoprotection in the treatment and prevention of gastric and intestinal diseases, as well as to present the materials of an Expert Council meeting held on February 8, 2020 in Moscow under the support of the Alium company.

General provisions. The conducted Expert Council meeting was aimed at discussing the importance of improving the cytoprotective properties of the gastric and intestinal mucous membrane in the treatment of its lesions. It was shown that Rebamipide exhibits positive effects on various parts of the protective barrier of the gastrointestinal tract (GIT), primarily due to its stimulating action on the production of prostaglandins playing a key role in maintaining the cytoprotective properties of the gastrointestinal mucosa. The possibilities of applying Rebamipide for the treatment and prevention of erosive and ulcerative gastrointestinal lesions caused by non-steroidal anti-inflammatory (NSAIDs) and antithrombotic drugs were demonstrated. In the treatment of gastroesophageal reflux disease, Rebamipide is recommended for patients refractory to therapy with proton pump inhibitors (PPIs) and for those with non-acid reflux. The efficacy of Rebamipide in the treatment of Helicobacter pylori (H. pylori) infection, as well as functional dyspepsia and chronic gastritis, was confirmed.

Conclusions. Rebamipid is a highly effective drug positively affecting various cytoprotection links, thus being suitable for the treatment and prevention of erosive and ulcerative lesions of the gastrointestinal tract, as well as gastroenterological diseases of various etiologies.

Conflict of interest: The Expert Council meeting was supported by the Alium company.

Mucus reduction promotes acetyl salicylic acid-induced small intestinal mucosal injury in rats

BACKGROUND

Acetyl salicylic acid (ASA) is a useful drug for the secondary prevention of cerebro-cardiovascular diseases, but it has adverse effects on the small intestinal mucosa. The pathogenesis and prophylaxis of ASA-induced small intestinal injury remain unclear. In this study, we focused on the intestinal mucus, as the gastrointestinal tract is covered by mucus, which exhibits protective effects against various gastrointestinal diseases.

MATERIALS AND METHODS

ASA was injected into the duodenum of rats, and small intestinal mucosal injury was evaluated using Evans blue dye. To investigate the importance of mucus, Polysorbate 80 (P80), an emulsifier, was used before ASA injection. In addition, rebamipide, a mucus secretion inducer in the small intestine, was used to suppress mucus reduction in the small intestine of P80-administered rats.

RESULTS

The addition of P80 reduced the mucus and exacerbated the ASA-induced small intestinal mucosal injury. Rebamipide significantly suppressed P80-reduced small intestinal mucus and P80-increased intestinal mucosal lesions in ASA-injected rats, demonstrating that mucus is important for the protection against ASA-induced small intestinal mucosal injury. These results provide new insight into the mechanism of ASA-induced small intestinal mucosal injury.

CONCLUSION

Mucus secretion-increasing therapy might be useful in preventing ASA-induced small intestinal mucosal injury.

Protective Effects of Genipin on Gastrointestinal Disorders

Genipin, an aglycone of geniposide, is a major component of gardeniae fructus, and has been used to treat jaundice, various inflammatory disorders, and liver disease, and has also been used as a natural cross-linking agent. The authors conducted several experiments to evaluate the protective effects of genipin on gastrointestinal disorders, such as, gastritis and gastric ulcers. Genipin showed inhibitory effects against HCl·ethanol-induced acute gastritis and indomethacin-induced gastric ulcers in rats and increased prostaglandin E₂ (PGE₂) in AGS gastric cancer cell. Genipin had significant effects on aggressive factors, acid-neutralization, and gastric secretion, and inhibited H⁺/K⁺-ATPase (a proton pump), which secretes gastric acid. The results obtained indicate that genipin has significant gastroprotective effects and might be useful for treating and preventing gastric lesions.

Rebamipide retards CCl4-induced hepatic fibrosis in rats: Possible role for PGE2

Prostaglandin E2 (PGE2) is a potent physiological suppressor of liver fibrosis. Because the anti-ulcer drug rebamipide can induce the formation of endogenous PGE2, this study investigated the potential effects of rebamipide on development of a hepatic fibrosis that was inducible by carbon tetrachloride (CCl4). Groups of Wistar rats received intraperitoneal (IP) injections of CCl4 (0.45 ml/kg [0.72 g CCl4/kg]) over the course of for 4 weeks. Sub-sets of CCl4-treated rats were also treated concurrently with rebamipide at 60 or 100 mg/kg. At 24 h after the final treatments, liver function and oxidative stress were indirectly assessed. The extent of hepatic fibrosis was evaluated using two fibrotic markers, hyaluronic acid (HA) and pro-collagen-III (Procol-III); isolated liver tissues underwent histology and were evaluated for interleukin (IL)-10 and PGE2 content. The results indicated that treatment with rebamipide significantly inhibited CCl4-induced increases in serum ALT and AST and also reduced oxidative stress induced by CCl4. Fibrotic marker assays revealed that either dose of rebamipide decreased the host levels of Procol-III and HA that had become elevated due to the CCl4. At the higher dose tested, rebamipide appeared to be able to permit the hosts to have a normal liver histology and to minimize any CCl4-induced collagen precipitation in the liver. Lastly, the use of rebamipide was seen to be associated with significant increases in liver levels of both PGE2 and the anti-inflammatory cytokine IL-10. Based on these findings, it is concluded that rebamipide can retard hepatic fibrosis induced by CCl4 and that this effect may, in part, be mediated by an induction of PGE2 and IL-10 in the liver itself.

Rebamipide delivered by brushite cement enhances osteoblast and macrophage proliferation

Many of the bioactive agents capable of stimulating osseous regeneration, such as bone morphogenetic protein-2 (BMP-2) or prostaglandin E2 (PGE2), are limited by rapid degradation, a short bioactive half-life at the target site in vivo, or are prohibitively expensive to obtain in large quantities. Rebamipide, an amino acid modified hydroxylquinoline, can alter the expression of key mediators of bone anabolism, cyclo-oxygenase 2 (COX-2), BMP-2 and vascular endothelial growth factor (VEGF), in diverse cell types such as mucosal and endothelial cells or chondrocytes. The present study investigates whether Rebamipide enhances proliferation and differentiation of osteoblasts when delivered from brushite cement. The reactive oxygen species (ROS) quenching ability of Rebampide was tested in macrophages as a measure of bioactivity following drug release incubation times, up to 14 days. Rebamipide release from brushite occurs via non-fickian diffusion, with a rapid linear release of 9.70% ± 0.37% of drug per day for the first 5 days, and an average of 0.5%-1% per day thereafter for 30 days. Rebamipide slows the initial and final cement setting time by up to 3 and 1 minute, respectively, but does not significantly reduce the mechanical strength below 4% (weight percentage). Pre-osteoblast proliferation increases by 24% upon exposure to 0.4 uM Rebamipide, and by up to 73% when Rebamipide is delivered via brushite cement. Low doses of Rebamipide do not adversely affect peak alkaline phosphatase activity in differentiating pre-osteoblasts. Rebamipide weakly stimulates proliferation in macrophages at low concentrations (118 ± 7.4% at 1 uM), and quenches ROS by 40-60%. This is the first investigation of Rebamipide in osteoblasts.

The prostanoid EP4 receptor and its signaling pathway

The EP4 prostanoid receptor is one of four receptor subtypes for prostaglandin E2. It belongs to the family of G protein-coupled receptors. It was originally identified, similar to the EP2 receptor as a G(s)α-coupled, adenylyl cyclase-stimulating receptor. EP4 signaling plays a variety of roles through cAMP effectors, i.e., protein kinase A and exchange protein activated by cAMP. However, emerging evidence from studies using pharmacological approaches and genetically modified mice suggests that EP4, unlike EP2, can also be coupled to G(i)α, phosphatidylinositol 3-kinase, β-arrestin, or β-catenin. These signaling pathways constitute unique roles for the EP4 receptor. EP4 is widely distributed in the body and thus plays various physiologic and pathophysiologic roles. In particular, EP4 signaling is closely related to carcinogenesis, cardiac hypertrophy, vasodilation, vascular remodeling, bone remodeling, gastrointestinal homeostasis, renal function, and female reproductive function. In addition to the classic anti-inflammatory action of EP4 on mononuclear cells and T cells, recent evidence has shown that EP4 signaling contributes to proinflammatory action as well. The aim of this review is to present current findings on the biologic functions of the EP4 receptor. In particular, we will discuss its diversity from the standpoint of EP4-mediated signaling.

Rebamipide ameliorates indomethacin-induced small intestinal injury in rats via the inhibition of matrix metalloproteinases activity

BACKGROUND AND AIM

The pathogenesis of non-steroidal anti-inflammatory drugs (NSAIDs)-induced small intestinal lesions remains unclear, although it is considered to be quite different from that of upper gastrointestinal tract ulcers due to the absence of acid and the presence of bacteria and bile in the small intestine. The aim of this study was to characterize specific gene expression profiles of intestinal mucosa in indomethacin-induced small intestinal injury, and to investigate the effects of rebamipide on the expression of these genes.

METHODS

Intestinal injury was induced in male Wistar rats by subcutaneous administration of indomethacin. Total RNA of the intestinal mucosa was extracted 24 h after indomethacin administration, gene expression was investigated using microarray analysis, and the identified genes were confirmed by real-time polymerase chain reaction (PCR). In addition, we investigated whether the treatment with rebamipide altered the expression of these identified genes.

RESULTS

The administration of indomethacin induced small intestine injuries, and these lesions were significantly inhibited by the treatment with rebamipide. Microarray analysis showed that the genes for several matrix metalloproteinases (MMPs) and several chemokine-related genes were significantly upregulated, and metallothionein 1a (MT1a) was downregulated in the intestinal mucosa after administration of indomethacin. The expressions of these genes were reversed by the treatment with rebamipide.

CONCLUSION

These data suggest that MMPs, chemokines, and MT1a may play an important role in the intestinal mucosal injury induced by indomethacin. In particular, the inhibition of MMP genes and chemokine-related genes by rebamipide may be important for the therapeutic effect against NSAIDs-induced small intestinal injury.

A study on the efficacy of rebamipide for patients with proton pump inhibitor-refractory non-erosive reflux disease

BACKGROUND AND AIM

Reflux symptoms in patients with non-erosive reflux disease (NERD) cannot be easily controlled by treatment with proton pump inhibitors (PPI). The anti-inflammatory function of rebamipide may be effective for protecting the esophageal mucosa. This prospective randomized multicenter placebo-controlled study was performed to clarify the efficacy of rebamipide for NERD patients whose reflux symptoms were refractory to PPI treatment.

METHODS

One hundred forty-nine patients were enrolled on the basis of a QUEST score of over 6 and absence of endoscopically proven esophageal mucosal breaks. All the patients were initially administered 15 mg of lansoprazole for 4 weeks, and the symptoms were then assessed using QUEST and GSRS. PPI-refractory patients were randomly assigned to administration of rebamipide or placebo t.i.d. for 4 weeks.

RESULTS

Three of the 149 patients were lost to follow-up, and 60 among the remaining 146 patients were found to be PPI-refractory. Among these PPI-refractory patients, 31 were randomly assigned to a rebamipide group and 29 to a placebo group. At the end of drug administration, the QUEST and GSRS scores did not differ between the rebamipide and placebo groups, although a significantly higher proportion of patients in the rebamipide group showed amelioration of abdominal pain and diarrhea.

CONCLUSION

Administration of rebamipide cannot effectively control reflux symptoms in NERD patients whose symptoms are refractory to PPI therapy.

Rebamipide increases the mucin-like glycoprotein production in corneal epithelial cells

PURPOSE

Dry eye is a multifactorial disease of tears and the ocular surface due to tear deficiency or excessive tear evaporation. Tear film instability is due to a disturbance in ocular surface mucin leading to a dysfunction of mucin, resulting in dry eye. In this study, we examined the effect of rebamipide, an anti-ulcer agent, on glycoconjugate production, as an indicator of mucin-like glycoprotein in cultured corneal epithelial cells. Further, we investigated the effect of rebamipide on the gene expression of membrane-associated mucins.

METHODS

Confluent cultured human corneal epithelial cells were incubated with rebamipide for 24 h. The glycoconjugate content in the supernatant and the cell extracts was measured by wheat germ agglutinin-enzyme-linked lectin assay combined gel-filtration method. In the experiment on mucin gene expression, cultured human corneal epithelial cells were collected at 0, 3, 6, and 12 h after administration of rebamipide. Real-time quantitative polymerase chain reaction was used to analyze the quantity of MUC1, MUC 4, and MUC16 gene expression.

RESULTS

Rebamipide significantly increased the glycoconjugate contents in the supernatant and cell extract. In the mucin gene expression in the cells, rebamipide increased MUC1 and MUC4 gene expression, but did not increase MUC16 gene expression.

CONCLUSIONS

Rebamipide promoted glycoconjugate, which has a property as a mucin-like glycoprotein, in human corneal epithelial cells. The increased production was mediated by MUC1 and MUC4 gene expression.

Treating ocular surface disease: new agents in development

This paper reviews recent advances and investigation in the treatment of ocular surface pathology. There is significant investment in this area, paralleling the growing demand for more effective alternatives to current treatments. Clinicians are becoming more aware of surface pathology, yet the ability to treat the most common forms of ocular pathology are still limited to the few medications approved by the US Food and Drug Administration. Medicines and devices currently under investigation are very promising. It is absolutely critical to understand the emerging options and think of their role in the treatment paradigm.

Rebamipide suppresses TLR-TBK1 signaling pathway resulting in regulating IRF3/7 and IFN-α/β reduction

TANK-binding kinase 1 (TBK1) regulates the interferon regulatory factor (IRF) 3 and IRF7 activation pathways by double strand RNA (dsRNA) via Toll-like receptor (TLR) 3 and by lipopolysaccharide (LPS) via TLR4. Rebamipide is useful for treating inflammatory bowel disease (IBD). Although IBD is associated with nuclear factor-κB (NF-κB), any association with the TBK1-IRF pathway remains unknown. How rebamipide affects the TBK1-IRF pathway is also unclear. We analyzed the relationship between IBD (particularly ulcerative colitis; UC) and the TLR-TBK1-IRF3/7 pathway using human colon tissue, a murine model of colitis and human colonic epithelial cells. Inflamed colonic mucosa over-expressed TKB1, NAP1, IRF3, and IRF7 mRNA compared with normal mucosa. TBK1 was mainly expressed in inflammatory epithelial cells of UC patients. The expression of TBK1, IRF3, IRF7, IFN-α and IFN-β mRNA was suppressed in mice given oral dextran sulfate-sodium (DSS) and daily rectal rebamipide compared with mice given only DSS. Rebamipide reduced the expression of TBK1, IRF3 and IRF7 mRNA induced by LPS/dsRNA, but not of NF-κB mRNA in colonic epithelial cells. Rebamipide might suppress the TLR-TBK1 pathway, resulting in IRF3/7-induction of IFN-α/β and inflammatory factors. TBK1 is important in the induction of inflammation in patients with UC. If rebamipide represses the TLR-TBK1 pathway, then rectal administration should suppress inflammation of the colonic mucosa in patients with UC.

Management of recurrence of symptoms of gastroesophageal reflux disease: synergistic effect of rebamipide with 15 mg lansoprazole

BACKGROUND

Proton pump inhibitors (PPIs) are effective in healing reflux esophagitis and relieving the symptoms of gastroesophageal reflux disease (GERD). Prevention of recurrence of symptoms has become a therapeutic aim in patients with these conditions.

AIMS

We investigated the effects of rebamipide, a mucosal protective anti-ulcer agent, on recurrence of reflux symptoms during PPI maintenance therapy.

METHODS

Patients with esophagitis of Los Angeles classification A or B were treated with PPIs for 8 weeks. Patients with relief of symptoms were enrolled for further study. Forty-one patients were randomized to maintenance therapy with 15 mg of lansoprazole daily or 15 mg of lansoprazole and 300 mg rebamipide daily, and recurrence of symptoms was monitored over 12 months. In some patients, concentration of rebamipide and interleukin(IL)-8 expression in the esophageal mucosa were estimated.

RESULTS

During the 12-month period, 11/20 patients (52.4%) taking lansoprazole 15 mg daily suffered recurrence of symptoms, compared to 4/20 patients (20%) treated with lansoprazole 15 mg and rebamipide 300 mg daily (P < 0.05). Rebamipide was detected in the esophageal mucosa 90-180 min after oral administration. IL-8 mRNA expression in the esophageal mucosa of patients with rebamipide was significantly decreased compared with that of patients without rebamipide.

CONCLUSIONS

Combination therapy with rebamipide and lansoprazole appears to be highly effective in preventing recurrence of symptoms during long-term maintenance treatment for GERD.

Rebamipide: a gastrointestinal protective drug with pleiotropic activities

Rebamipide, a gastroprotective drug, was developed in Japan and was proven to be superior to cetraxate, the former most prescribed drug of the same category, in 1989 in the treatment for gastric ulcers. The initially discovered basic mechanisms of action of rebamipide included its action as a prostaglandin inducer and oxygen free-radical scavenger. In the last 5 years, several basic and clinical studies have been performed for functional dyspepsia, chronic gastritis, NSAID-induced gastrointestinal injuries, gastric ulcer following eradication therapy for Helicobacter pylori, gastric ulcer after endoscopic surgery and ulcerative colitis. In addition, several molecules have been identified as therapeutic targets of rebamipide to explain its pleiotropic pharmacological actions. The aim of this article is to provide an update on the pharmacological and clinical profile of rebamipide and to explore further possibilities for additional indications.

Rebampide enema therapy as a treatment for patients with chronic radiation proctitis: initial treatment or when other methods of conservative management have failed

INTRODUCTION

Radiation proctitis is a common complication following radiation therapy for pelvic malignancies. There have been no formal trials of treatment for radiation proctitis and a variety of methods are currently used. We assessed the efficacy of rebamipide enema to control symptoms and proctoscopic findings from radiation proctitis.

MATERIALS AND METHODS

Fifteen patients with radiation proctitis were enrolled. Enemas containing 150 mg rebamipide per dosing were administered after morning bowel movement, and always prior to bedtime, twice daily for 4 weeks. The efficacy of treatment was assessed from clinical symptoms (Subjective Objective Management Analysis Scale for Rectal Toxicity) and endoscopic findings.

RESULTS

The mean bleeding score improved from 2.67 to 0.53 (P < 0.01). The mean symptom scores improved in those patients who had pain (0.40 to 0.13), tenesmus (0.40 to 0.20), and stool frequency (0.27 to 0.13). The mean improvement in telangiectasia scores (2.13 to 0.80, P < 0.01), bleeding point scores (1.80 to 0.27, P < 0.01), and friable mucosa scores (1.33 to 0.20, P < 0.01) were all statistically significant. No side effects were noted in any patients.

CONCLUSION

Rebamipide enema therapy for radiation proctitis is a safe and effective treatment of radiation proctitis. We suggest the value of rebamipide enema in the treatment of radiation proctitis when other conservative management or first treatment has failed.

Prophylactic effect of rebamipide on aspirin-induced gastric lesions and disruption of tight junctional protein zonula occludens-1 distribution

Aspirin and nonsteroidal anti-inflammatory agents are known to induce gastroduodenal complications such as ulcer, bleeding, and dyspepsia. In this study, we examined the prophylactic effect of rebamipide, an anti-ulcer agent with free-radical scavenging and anti-inflammatory effect, on acidified aspirin-induced gastric mucosal injury in rats. In addition, we investigated the mucosal barrier functions disrupted by aspirin. Oral administration of acidified aspirin resulted in linear hemorrhagic erosions with increasing myeloperoxidase activity and thiobarbituric acid-reactive substance concentrations in the gastric mucosa. Rebamipide suppressed these acidified aspirin-induced gastric lesions and inflammatory changes significantly, and its protective effect was more potent in the case of repeated (twice daily for 3 days) treatment than single treatment before aspirin administration. Immunostaining of zonula occludens (ZO)-1, one of the tight junctional proteins, was strengthened in rat gastric mucosa after repeated administration of rebamipide. In addition, aspirin induced the increasing transport of fluorescine isothiocyanate-labeled dextrans with localized disruption and decreased expression of ZO-1 protein on rat gastric mucosal cell line RGM-1. Rebamipide effectively prevented aspirin-induced permeability changes and disruption of ZO-1 distribution. These results suggest that rebamipide protects against aspirin-induced gastric mucosal lesions by preserving gastric epithelial cell-to cell integrity in addition to the anti-inflammatory effects.

Effect of OPC-12759 on EGF receptor activation, p44/p42 MAPK activity, and secretion in conjunctival goblet cells

The purpose of the study was to determine if OPC-12759 stimulates secretion from conjunctival goblet cells in culture and if it activates the EGF receptor (EGFR) and p44/p42 mitogen-activated protein kinase (MAPK) to cause mucin secretion. Conjunctival goblet cells were cultured from pieces of male rat conjunctiva. OPC-12759 was added at increasing concentrations and for varying times to the cultured cells. The cholinergic agonist carbachol was used as a positive control. In selected experiments an inhibitor of the EGFR, AG1478, or an inhibitor of the kinase that activates MAPK, U0126, were added before OPC-12759. Goblet cell secretion of high molecular weight glycoconjugates was measured by an enzyme-linked lectin assay using the lectin UEA-1. Activation of the EGFR and MAPK were determined with Western blotting analysis using antibodies specific to the phosphorylated and the total amounts of these proteins. We found that OPC-12759 induced goblet cell secretion in a time- and concentration-dependent manner. Inhibition of the EGFR with AG1478 blocked secretion stimulated by OPC-12759. Inhibition of MAPK with U0126 also blocked secretion stimulated by OPC-12759. OPC-12759 increased the phosphorylation of the EGFR and MAPK in a time-dependent manner. We concluded that OPC-12759 stimulates secretion from cultured conjunctival goblet cells by activating the EGFR, which then induces MAPK activity.

Effect of a gastro-protective agent, rebamipide, on symptom improvement in patients with functional dyspepsia: a double-blind placebo-controlled study in Japan

BACKGROUND AND AIM

Although mucosal protective agents have been used frequently for treatment of symptomatic gastritis, there has been no well-controlled study of functional dyspepsia. The aim of this study was to assess the efficacy of a 4-week treatment with rebamipide for the relief of overall dyspeptic symptoms and the improvement in quality of life from an untreated baseline in Japanese patients with functional dyspepsia.

METHODS

In a double-blinded, randomized, placebo-controlled, single-center study, 81 patients with functional dyspepsia were recruited and treated with rebamipide (100 mg, t.i.d.) or placebo for 4 weeks. Symptoms were assessed at baseline and at the end of the study period by a symptom questionnaire. Quality of life was evaluated by the QPD 32.

RESULTS

Data was analyzed for symptoms from 38 patients who received rebamipide and 33 patients who received placebo treatment. Overall symptoms were significantly improved in both the rebamipide and placebo treatment groups from the untreated baseline after 4 weeks of treatment, and the mean changes in overall symptoms were not significantly different between the groups. However, the improvement in symptom score was significantly greater in the treatment arm than in the placebo arm for three items, which were bloating, belching, and pain or discomfort that was relieved after a meal. Regarding quality of life, social restriction and pain intensity were significantly improved in the rebamipide treatment group in per-protocol analysis (P = 0.048 and P = 0.031, respectively).

CONCLUSIONS

Although rebamipide was not significantly better than placebo in reducing overall symptoms by 4 weeks' treatment, it may partially improve the symptoms. It may also be beneficial in improvement of quality of life in Japanese patients with functional dyspepsia.

Bone biomechanical properties in EP4 knockout mice

Among the four prostaglandin E receptor subtypes, EP(4) has been implicated as an important regulator of both bone formation and bone resorption; however, the integrated activities of this receptor on bone biomechanical properties have not been examined previously. This study compared the bone biomechanical properties of EP(4) knockout (KO) transgenic mice to strain-matched wild-type (WT) controls. We examined two groups of adult female mice: WT (n = 12) and EP(4) KO (n = 12). Femurs were tested in three-point bending and the lumbar-4 (L4) vertebral body by compression. Distal femur and vertebral body trabecular bone architecture were quantified using micro-computed tomography. Biomechanical structural parameters (ultimate/yield load, stiffness) were measured and apparent material parameters (ultimate/yield stress, modulus) calculated. Body weights and bone sizes were not different between EP(4) KO and WT mice (P > 0.05, Student's t-test). EP(4) KO mice exhibited reduced structural (ultimate/yield load) and apparent material (ultimate/yield stress) strength in the femoral shaft and vertebral body compared to WT (P < 0.05). Vertebral body stiffness and femoral neck ultimate load (structural strength) were marginally lower in EP(4) KO than that in WT mice (P < 0.1). In addition, EP(4) KO mice have smaller distal femur and vertebral bone volume to total volume (BV/TV) trabecular thickness than WT mice (P < 0.05). These results suggest that the prostaglandin receptor EP(4) has an important role in determining biomechanical competence in the mouse skeleton. Despite similar bone size, the absence of an EP(4) receptor may have removed a necessary link for bone adaptation pathways, which resulted in relatively weaker bone properties.

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Rebamipide enema is effective for treatment of experimental dextran sulfate sodium induced colitis in rats

We investigated therapeutic efficacy of rebamipide using dextran sulfate sodium (DSS) induced colitis model in rats. Three percent DSS solution was given to rats for 9 days. After that, we evaluated the drug efficacy on colitis sustained with continuous drinking of 1% DSS. Twice-daily treatment with 0.3% or 1% rebamipide for 14 days significantly ameliorated the stool abnormality in the colitis model, preferentially suppressed hematochezia. The colonic mucosal lesion, determined by Alcian blue staining on day 24, was significantly reduced by rebamipide enema in a dose-dependent manner. Either rebamipide or 5-aminosalycilic acid (5-ASA) enema treated once daily significantly ameliorated colitis. The minimum effective dose of rebamipide was 0.3% in once-daily treatment, and that of 5-ASA was 10%. In a mechanistic study, the epithelial cell sheet formation of the T84 colon cancer cell was measured as an increase in generation of trans-epithelial electrical resistance in vitro. Rebamipide accelerated the increase, while 5-ASA conversely suppressed it. These results suggest that rebamipide enema is effective for treatment of experimental ulcerative colitis (UC).

15th anniversary of rebamipide: looking ahead to the new mechanisms and new applications

Rebamipide, a gastro-protective drug, was developed in Japan for the treatment of peptic ulcer disease. It was proven superior to the former same category drug cetraxate in a randomized, controlled, double-blind, comparative clinical study in 1989. Rebamipide's mechanisms of actions are different from anti-secretory drugs; it accelerates and improves the quality of ulcer healing and reduces ulcer recurrence rate. Numerous studies have been conducted to explain the mechanisms responsible for these actions, 37 papers were published by 1998. Major properties of rebamipide include: stimulation of prostaglandin and mucus glycoprotein synthesis, inhibition of reactive oxygen species, inflammatory cytokines and chemokines, and inhibition of neutrophils activation. Since 1998, 107 papers were published, clarifying further effects of rebamipide on cyclooxygenase-2, prostaglandin E receptors, growth factors (i.e., HGF, EGF, and VEGF), heat-shock proteins, nitric oxide, adhesion molecules, neutrophils, and Helicobacter pylori- and NSAID-related pathology. Moreover, inhibitory action of rebamipide on gastric cancer growth has also been shown. In this issue we reviewed recent advances in understanding of rebamipide's mechanism of action and its newest clinical applications.

Rebamipide, a gastro-protective drug, inhibits indomethacin-induced apoptosis in cultured rat gastric mucosal cells: association with the inhibition of growth arrest and DNA damage-induced 45 alpha expression

Rebamipide, a gastromucosal protective drug, suppresses indomethacin-induced gastropathy in humans and rodents. Effects of rebamipide on gene expression in indomethacin-treated gastric mucosal cells (RGM1) were investigated using high-density oligonucleotide arrays. Indomethacin induced apoptosis in RGM1 cells in a dose-dependent manner. Rebamipide pretreatment significantly reduced indomethacin-induced apoptosis. We used gene expression profiling on high-density oligonucleotide probe arrays to characterize the transcriptional response of RGM1 cells to indomethacin treatment for 6 hr. Of the 8,799 probes examined, 717 (8.1%) were induced (400 probes) or repressed (317 probes) at least 1.5-fold. Among the 158 genes that were induced by indomethacin at least 2.0-fold, four genes that were down-regulated by rebamipide at least 2.0-fold are listed: growth arrest and DNA-damage-inducible 45 alpha (GADD 45 alpha), golgi SNAP receptor complex member 1, iodothyronine deiodinases, and transcription factor 8. Real time-PCR confirmed GADD 45 alpha expression and its inhibition by rebamipide. Inhibition of apoptosis-related genes is possibly important for the cytoprotective effect of rebamipide against indomethacin-induced gastric mucosal cell injury.

Role of prostaglandins in maintaining gastric mucus-cell permeability against acid exposure

Regulation of gastric epithelial permeability is important in the protection of the gastric mucosa from secreted acid. However, the mechanism(s) for this regulation in gastric mucus cells remains unknown. In this study, we evaluated gastric epithelial-cell permeability in response to acid exposure by monitoring trans-epithelial electrical resistance (TEER) and paracellular permeability with carbon 14-labeled mannitol. We also examined the role of prostaglandins on gastric epithelial permeability. Rat gastric epithelial cells (RGM-1) were plated on 8-microm-pore tissue-culture inserts. Cells were exposed to solutions of differing pH (3-7.4), with and without the nonsteroidal antiinflammatory drug (NSAID) indomethacin (10(-7) mol/L), for 60 to 120 minutes. Transepithelial permeability was measured on the basis of TEER and the diffusion rate of [(14)C]mannitol. Prostaglandin E(2) (PGE(2)) was administered in some experiments with NSAIDs. After acid exposure (pH 3.0-5.0), TEER rapidly and significantly increased, peaking in 5 minutes. Diffusion of [(14)C]mannitol was blocked during the period when TEER increased. Pretreatment with the cyclooxygenase (COX) inhibitor indomethacin blocked the rapid acid-induced increase in TEER. A specific COX-2 inhibitor had no effect on this rapid increase in TEER. The blockade by indomethacin was eliminated by the addition of PGE(2). These findings suggest that when gastric-surface mucus cells are exposed to acid, gastric epithelial permeability decreases rapidly to inhibit acid back-diffusion. Prostaglandins play an important role in this protective response to acid exposure. COX inhibitors such as indomethacin may inhibit the regulation of epithelial permeability by reducing the concentration of PGE(2).

Efficacy of rebamipide as adjunctive therapy in the treatment of recurrent oral aphthous ulcers in patients with Behçet's disease: a randomised, double-blind, placebo-controlled study

BACKGROUND

Behçet's disease (BD) is a recurrent inflammatory disease involving chronic recurrent oral aphthous ulcers (aphthae), uveitis, skin lesions and genital ulcers. We prospectively investigated the efficacy of rebamipide, a gastroprotective drug, against oral aphthous ulcers in BD patients.

METHODS

In a multicentre, double-blind, placebo-controlled study, 35 patients with BD, having as the main symptom oral aphthosis, were randomised to receive rebamipide 300 mg/day or placebo for 12 to 24 weeks between August 1994 and December 1996. Oral aphthosis must have occurred within 4 weeks prior to enrolment and must have been visible for at least 7 days during that time. Oral aphthae count and pain scores were recorded daily in a diary by the patients themselves. Monthly aphthae count and pain scores were defined as the sum of aphthae count and pain scores for a month, respectively. Investigators rated the global improvement in aphthae count and pain using a 6-point scale. The rate of change in monthly aphthae count and pain scores in the first 3 and last 3 months of treatment were assessed in patients with more severe symptoms whose aphthae count and pain score were >28 at baseline (trial entry).

RESULTS

The rate of moderate or marked improvement in aphthae count and pain was 36% (5 of 14 subjects) in the placebo group and 65% (11 of 17 subjects) in the rebamipide group. During months 2 to 6 of treatment, aphthae count tended to increase and reached a peak at month 4 in the placebo group but decreased in the rebamipide group. Pain score decreased to the same extent in both groups for the first 3 months of treatment; however, in the fourth to sixth months of treatment, the pain score tended to increase in the placebo group but decreased in the rebamipide group. In patients with a monthly aphthae pain score >28 at baseline, pain and count scores decreased throughout the 6 months of rebamipide treatment but increased during the last 3 months of treatment in the placebo group (p < 0.01 for the between-group comparisons).

CONCLUSIONS

Rebamipide is well tolerated and improves the aphthae count and pain score in BD patients. It may therefore be useful in the treatment and prevention of frequently recurrent oral aphthous ulcers (not restricted to BD). Administration of rebamipide is not cumbersome, and it does not cause any discomfort, which corticosteroid ointments for example may do; furthermore, there are no specific adverse drug reactions. Rebamipide is therefore recommended as a long-term treatment for recurrent oral aphthous ulcers.

Expression of midkine and receptor-like protein tyrosine phosphatase (RPTP)-beta genes in the rat stomach and the influence of rebamipide

BACKGROUND

Midkine has been reported to bind to receptor-like protein tyrosine phosphatase (RPTP)-beta and to play important roles in growth and differentiation of various cells. Midkine is expressed in rat stomach during experimental ulcer healing, suggesting that the midkine-RPTP-beta system has some physiological functions in the stomach. Rebamipide is a mucoprotective drug used for the treatment of gastric ulcers. We have tested the hypothesis that the ulcer healing mechanism stimulated by rebamipide is linked physiologically to the gastric midkine-RPTP-beta system.

MATERIALS AND METHODS

Seven-week-old-male Wistar rats were used. Midkine and RPTP-beta gene expression in rat stomach was investigated by laser capture microdissection coupled with the reverse transcription-polymerase chain reaction (RT-PCR). The effects of rebamipide on midkine and RPTP-beta expression in rat stomach and the gastric epithelial cell line RGM1 were evaluated by RT-PCR and Northern blot analyses.

RESULTS

Midkine and RPTP-beta expression was detected in the gastric mucosal, submucosal and muscle layers. Rebamipide stimulated both midkine and RPTP-beta expression in rat stomach and RGM1 cells.

CONCLUSION

Rebamipide may protect the gastric mucosa by regulating midkine and RPTP-beta expression.

Rebamipide binds to iNOS-positive cells in acetic acid-treated but not in ethanol-treated rat gastric mucosa

BACKGROUND

Rebamipide is a gastroprotective agent to stimulate prostaglandin generation in gastric mucosa and attenuate the activity of neutrophils, but direct evidence for the effector sites of this agent has remained to be clarified.

AIM

The present study was undertaken to show the effector sites of rebamipide in control and ulcer-provoked rats.

METHODS

The rats were divided into control, acetic acid- and ethanol-treated rats. In the acetic acid-treated group, 100% acetic acid was attached to the serosal surface of the stomach for 30 s, 7 days before the experiments. In the ethanol-treated group, a dose of 0.5 mL/100 g body weight of 50% ethanol was administered through orogastric intubation 2 h before the experiments. Using the unfixed cryostat sections, aqueous solution of 3H-rebamipide was applied and the localization of the binding sites of rebamipide was investigated by autoradiography.

RESULTS

In the control rats, rebamipide was found to bind to the surface epithelial cells. In the ethanol-treated group, few binding sites were observed in the damaged gastric mucosa. In the acetic acid-treated group, the marked accumulation of the binding sites of 3H-rebamipide was observed in the mesenchymal cells in the lamina propria mucosae between the regenerated gastric epithelial cells. Combination of autoradiography and immunohistochemistry has revealed that iNOS-immunoreactive cells had the strong binding of rebamipide in the acetic acid-treated group. Some of these cells were CD68-positive macrophages, while others were CD68-negative, corresponding to polymorphonuclear leucocytes. In the ethanol-treated acute gastric mucosal injury group, few binding sites were observed in the damaged gastric mucosa.

CONCLUSIONS

Autoradiography has made it clear that rebamipide binds to iNOS-positive cells in the gastric mucosa 7 days after acetic acid-treatment.

Endogenous cyclo-oxygenase activity regulates mouse gastric surface pH

In the stomach, production of prostaglandins by cyclo-oxygenase (COX) is believed to be important in mucosal defence. We tested the hypothesis that endogenous COX activity is required for protective gastric surface pH control. Intact stomachs of anaesthetized mice were perfused with a weakly buffered solution (150 mM NaCl + 4 mM Homopipes) at pH values from 2.5 to 7.0. Gastric effluents were collected to measure pH and estimate amounts of acid or alkali secretion in nanomoles secreted per minute. A switch from net acid to net alkali secretion was seen in response to acidifying luminal pH with an apparent 'set point' between pH 4 and 5. At luminal pH 3, the net alkali secretion (12.7 +/- 2.8 nmol OH(-) equivalents min(-1)) was abolished (2.2 +/- 1.7 nmol OH(-) min(-1)) by the non-specific COX inhibitor indomethacin (5 mg kg(-1) I.P.). Similar inhibition was observed using a COX-1 inhibitor (SC-560; 10 mg kg(-1) I.P.), but not a COX-2 inhibitor (NS-398; 10 mg kg(-1) I.P.). Subsequent treatment with 16,16-dimethyl prostaglandin E(2) (dm-PGE(2); 1 mg kg(-1) I.P.) rescued the alkali secretion (21.8 +/- 2.7 nmol OH(-) min(-1)). In either the absence or presence of the H(+),K(+)-ATPase inhibitor omeprazole (60 mg kg(-1) I.P.), indomethacin blocked similar amounts of net alkali secretion (10.5 +/- 2.7 and 16.4 +/- 3.4 nmol OH(-) min(-1), respectively). We also used in vivo confocal microscopy to examine pH near the mucosal surface. The gastric mucosal surface of anaesthetized mice was exposed and mucosal surface pH was imaged using the fluorescence intensity ratio of Cl-NERF as a pH indicator. Results showed a switch from a continuous net acid to net alkali secretion by the stomach in response to changing superfusate pH from 5 to 3. At luminal pH 3, the relatively alkaline surface pH (4.3 +/- 0.1) was acidified (3.6 +/- 0.2) by indomethacin, and subsequent dm-PGE(2) restored surface pH (4.2 +/- 0.2). We conclude that the pre-epithelial alkaline layer is regulated by endogenous COX activity.

Prostanoid receptor subtypes

Prostanoids are a group of lipid mediators that include the prostaglandins (PG) and thromboxanes (TX). Upon cell stimulation, prostanoids are synthesized from arachidonic acid via the cyclooxygenase (COX) pathway and released outside the cells to exert various physiological and pathological actions in a variety of tissues and cells. The activities of prostanoids are mediated by specific G protein-coupled receptors, which have been classified on the basis of pharmacological experiments into eight types and subtypes according to their responsiveness to selective agonists and antagonists. These prostanoid receptors have been cloned from various species including human, and their distinct binding properties and signal transduction pathways have been characterized by analyses of cells expressing each receptor. Furthermore, the distribution patterns of prostanoid receptor mRNAs have been determined in tissues and cells for various species. This information is useful for understanding the molecular basis of the pathophysiological actions of prostanoids.

Effects of prostaglandins on spontaneous apoptosis in gastric mucosal cells

Prostaglandins have cytoprotective effects on gastric mucosa via the influence of various mechanisms. The purpose of this study is to examine the effects of prostaglandins on maturation-dependent spontaneous apoptosis in gastric mucosal cells in vitro, which mimics the apoptosis of gastric mucosal cells related with a rapid cell turnover rate in vivo. Both prostaglandin E1 and E2 inhibited spontaneous apoptosis in a dose-dependent manner and increased the viability of gastric mucosal cells in culture. A number of antiulcer drugs presently in clinical use were shown to increase the concentrations of prostaglandins in cells. All of the drugs tested clearly inhibited the spontaneous apoptosis in a dose-dependent manner. Based on these results, we propose that the cytoprotective effects of prostaglandins on gastric mucosa in vivo can be partially explained by an increase in the number of gastric mucosal cells present as a result of the inhibition of maturation-dependent spontaneous apoptosis.

Gastric secretion

The influence of central and peripheral stimuli on gastric acid secretion is mediated via activation of histaminergic, gastrinergic, and cholinergic pathways coupled to intracellular second-messenger systems that determine the trafficking and activity of H+ K+-ATPase, the proton pump of the parietal cell. Histamine, released from enterochromaffin-like cells stimulates the parietal cell directly via H-2 receptors coupled to generation of cAMP. Gastrin, acting via cholecystokinin-2 receptors on enterochromaffin-like cells coupled to an increase in intracellular calcium, stimulates the parietal cell indirectly by activating histidine decarboxylase, releasing histamine, and inducing enterochromaffin-like cell hypertrophy and hyperplasia. Acetylcholine, released from gastric postganglionic intramural neurons, stimulates the parietal cell directly via M-3 receptors coupled to intracellular calcium release and calcium entry. The second-messenger systems activated in the parietal cell converge on H+ K+-ATPase that catalyzes the exchange of luminal K+ for cytoplasmic H+ and is responsible for gastric luminal acidification. The main inhibitor of acid secretion is somatostatin which, acting via sst2 receptors, exerts a tonic inhibitory influence on parietal, enterochromaffin-like, and gastrin cells. Acute infection with Helicobacter pylori results in hypochlorhydria, whereas chronic infection may be associated with either hypo- or hyperchlorhydria. Although prostaglandins are thought to play a physiologic role in the regulation of acid secretion and maintenance of gastric mucosal integrity, the precise roles of cyclooxygenase-1 and cyclooxygenase-2 in these processes still eludes us.

Characterization and application of a gastric surface mucous cell line GSM06 established from temperature-sensitive simian virus 40 large T-antigen transgenic mice

It has been indicated that transgenic mouse harboring a temperature-sensitive simian virus 40 large T-antigen gene is useful for establishing cell lines from tissues that have proved difficult to culture in vitro. The gastric surface mucous cell line GSM06 was established from a primary culture of gastric fundic mucosal cells of the transgenic mice. GSM06 cells showed temperature-sensitive growth in culture and expressed large T-antigen at a permissive temperature (33 degrees C) but not at a nonpermissive temperature (39 degrees C). At 39 degrees C, the cells produced periodic acid-Schiff positive glycoconjugates that formed a mucous sheet like the gastric surface mucosa in the stomach. Insulin markedly increased the production of glycoconjugates. In addition, proprotein-processing endoprotease furin suppression retarded cell growth, but accelerated cell differentiation. An air-liquid interface promoted the differentiation of GSM06 cells in a reconstruction culture with nitrocellulose membrane and collagen gel. The gastric surface mucous cell line GSM06 with unique characteristics, therefore, should be useful as an in vitro model of the gastric mucosa for physiological and pharmacological investigations. Moreover, experiments using immortalized cells established in vitro and having specific functions may offer an alternative to experiments using living animals and thereby offer a solution to this ethical issue.