Rebamipide inhibits indomethacin-induced small intestinal injury: possible involvement of intestinal microbiota modulation by upregulation of α-defensin 5

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

The effect of rebamipide on non-steroidal anti-inflammatory drug-induced gastro-enteropathy: a multi-center, randomized pilot study

BACKGROUND/AIMS

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly-used medications, and ailments such as arthritis or heart disease, require long-term use of these drugs, which can induce gastroenteropathy with bleeding and ulcers. This study investigated the associations between efficacy, safety, and gastrointestinal symptoms linked to rebamipide and proton pump inhibitor administration in patients requiring long-term NSAID use.

METHODS

This study was a multi-center, randomized, open-labeled, pilot design.

RESULTS

Thirty-three patients were included. Of these, 15 were included in the study group and 18 were in the control group. NSAID-induced gastric ulcers, which were the primary outcome of this study, did not occur in either the study or control group. Changes in the number of small bowel erosions and ulcers were -0.6 ± 3.06 in the study group and 1.33 ± 4.71 in the control group. The number of subjects with mucosal breaks (defined as multiple erosions and/or ulcers) was three (20%) in the study group and six (40%) in the control group (p = 0.427). No serious adverse events occurred in either group. However, dyspepsia and skin rashes occurred in six patients (31.58%) in the study group and 13 (65%) in the control group (p = 0.036).

CONCLUSION

Although statistically significant differences were not generated, possibly as a result of the small sample size, mucosal breaks observed via capsule endoscopy revealed that rebamipide was likely to be more effective than lansoprazole in preventing small intestine damage caused by NSAIDs. Furthermore, fewer side-effects emerged with rebamipide.

The Role of Gut Microbiota in Some Liver Diseases: From an Immunological Perspective

Gut microbiota is a microecosystem composed of various microorganisms. It plays an important role in human metabolism, and its metabolites affect different tissues and organs. Intestinal flora maintains the intestinal mucosal barrier and interacts with the immune system. The liver is closely linked to the intestine by the gut-liver axis. As the first organ that comes into contact with blood from the intestine, the liver will be deeply influenced by the gut microbiota and its metabolites, and the intestinal leakage and the imbalance of the flora are the trigger of the pathological reaction of the liver. In this paper, we discuss the role of gut microbiota and its metabolites in the pathogenesis and development of autoimmune liver diseases((including autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis), metabolic liver disease such as non-alcoholic fatty liver disease, cirrhosisits and its complications, and liver cancer from the perspective of immune mechanism. And the recent progress in the treatment of these diseases was reviewed from the perspective of gut microbiota.

Preventive effect of rebamipide on NSAID-induced lower gastrointestinal tract injury using FAERS and JADER

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for their antipyretic, analgesic, and anti-inflammatory properties. However, various aspects of NSAID-induced lower gastrointestinal tract injury remain unclear, and effective prophylaxis has not been established. Based on its pharmacological effect and clinical trials, rebamipide may prevent lower gastrointestinal tract injury, although this evidence is limited by the small scale of trials. The present study used the FDA Adverse Event Reporting System (FAERS) and the Japanese Adverse Event Reporting Database (JADER) to assess the efficacy of rebamipide in combination with loxoprofen and diclofenac in preventing NSAID-induced lower gastrointestinal tract injury. The calculated reporting odds ratio and 95% confidence interval (CI) for rebamipide in combination with loxoprofen and diclofenac were 1.15 (95% CI 0.88–1.51) and 1.28 (95% CI 0.82–2.01) for FAERS, and 0.50 (95% CI 0.35–0.71) and 0.43 (95% CI 0.27–0.67) for JADER, respectively. No signal was detected when combining drugs. These results suggest a prophylactic effect of rebamipide on NSAID-induced lower gastrointestinal tract injury.

Erosive and ulcerative lesions of the digestive tract: optimization of diagnosis and management tactics

Erosive and ulcerative lesions of the digestive tract are one of the most pressing problems in the clinic of internal diseases due to the extremely widespread prevalence, the presence of severe complications, often fatal, diagnostic difficulties due to the presence of a large number of asymptomatic pathologies and difficulties in the rational choice of therapy. Particularly noteworthy is the data that during the global pandemic of Covid-19 infection, it is capable, quite often, of causing the development of erosive and ulcerative lesions of the gastrointestinal tract. In this regard, it seems important to use drugs that can not only prevent the occurrence of erosive and ulcerative lesions and strictures throughout the gastrointestinal tract, but also effectively achieve epithelialization of injuries to the mucous membrane of the oral cavity, esophagus, stomach, small and large intestine. One of them is Rebamipid-CZ, which has a fairly high safety and efficacy profile. It seems important to consider the issues of optimizing the prevention and treatment of erosive and ulcerative lesions of various parts of the gastrointestinal tract of various etiologies, taking into account the possibility of using rebamipide both as part of complex therapy and in isolation.

Functional gastrointestinal disorders. Overlap syndrome Clinical guidelines of the Russian Scientific Medical Society of Internal Medicine and Gastroenterological Scientific Society of Russia

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Research progress of non-steroidal anti-inflammatory drug-induced small intestinal injury

Non-steroidal anti-inflammatory drugs (NSAIDs) are used widely around the world because of their anti-inflammatory, analgesic, and antiplatelet activity. However, long-term application of NSAIDs can lead to complications. Previously, the clinical attention was dedicated to the NSAID-induced upper gastrointestinal complications. Recently, the detection rate of small intestinal damage related to NSAIDs has increased due to the wide use of endoscopes such as capsule endoscopy and double-balloon colonoscopy. Although the majority of patients have no significant symptoms, there are still a small percentage of patients who develop obvious symptoms or complicated ulcers that require therapeutic intervention. Despite significant advances in our understanding of NSAIDs, the treatment modality and regimen for NSAID-induced small intestinal damage have remained relatively unclear. This article will provide a comprehensive overview of NSAID-induced small intestinal damage with regard to the epidemiology, clinical manifestations, diagnosis, risk factors, pathogenesis, and treatment, in order to provide informative evidence for clinical practice.

Protective role of resolvin D1, a pro-resolving lipid mediator, in nonsteroidal anti-inflammatory drug-induced small intestinal damage

Resolvin D1, a specialized pro-resolving lipid mediator produced from docosahexaenoic acid by 15- and 5-lipoxygenase, exerts anti-inflammatory effects driving to the resolution of inflammation. The present study aimed to elucidate its role in small intestinal damage induced by nonsteroidal anti-inflammatory drug (NSAID). Indomethacin was administered orally to C57BL/6J male mice, which were sacrificed 24 h later to collect small intestine specimens. Before administration of indomethacin, mice were subjected to intraperitoneal treatment with resolvin D1 or oral administration of baicalein, a 15-lipoxygenase inhibitor. Small intestinal damage induced by indomethacin was attenuated by pretreatment with resolvin D1. Furthermore, resolvin D1 reduced the gene expression levels of interleukin-1β, tumor necrosis factor-α, and CXCL1/keratinocyte chemoattractant. Conversely, the inhibition of 15-lipoxygenase activity by baicalein increased the expression of genes coding for these inflammatory cytokines and chemokine, leading to exacerbated small intestinal damage, and reduced the concentration of resolvin D1 in the small intestinal tissue. Exogenous treatment with resolvin D1 negated the deleterious effect of baicalein. 15-lipoxygenase was mainly expressed in the epithelium and inflammatory cells of the small intestine, and its gene and protein expression was not affected by the administration of indomethacin. Inhibition of the resolvin D1 receptor, lipoxin A4 receptor /formyl peptide receptor 2, by its specific inhibitors Boc-1 and WRW4 aggravated indomethacin-induced small intestinal damage. Collectively, these results indicate that resolvin D1 produced by 15-lipoxygenase contributes to mucoprotection against NSAID-induced small intestinal damage through its anti-inflammatory effect.

Influence of proton pump inhibitor or rebamipide use on gut microbiota of rheumatoid arthritis patients

OBJECTIVE

Patients with RA commonly use gastrointestinal (GI) protective drugs for treatment and prevention of drug-associated GI injuries. However, how these drugs affect the gut microbiota in RA patients remains unknown. The objective of this study was to examine the gut microbiota of RA patients according to use of GI protective drugs such as proton pump inhibitors (PPIs), histamine 2-receptor antagonists and rebamipide.

METHODS

Faecal samples were obtained from 15 healthy controls and 32 RA patients who were receiving PPI, histamine 2-receptor antagonist or rebamipide. Bacterial DNA was extracted from the faecal samples and 16S rRNA sequencing was performed. Microbial composition and function were analysed using Quantitative Insights Into Microbial Ecology and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States.

RESULTS

RA patients exhibited reduced diversity and altered composition of the gut microbiota compared with healthy controls. The gut microbiota of RA patients receiving acid-suppressing drugs, particularly PPIs, was distinct from that of RA patients receiving rebamipide (PPI vs rebamipide, P = 0.005). Streptococcus was enriched in RA patients receiving PPI, while Clostridium bolteae was enriched in RA patients receiving rebamipide. The gut microbiota of PPI users was abundant with microbial functional pathway involved in the production of virulence factors. This featured microbial function was positively correlated with relative abundance of Streptococcus, the differentially abundant taxa of PPI users.

CONCLUSION

The gut microbiota of RA patients receiving PPIs was distinguishable from that of those receiving rebamipide. The enriched virulent function in the gut microbiota of PPI users suggests that inappropriate PPI use may be harmful in RA patients.

Potential Strategies in the Prevention of Nonsteroidal Anti-inflammatory Drugs-Associated Adverse Effects in the Lower Gastrointestinal Tract

With the increasing use of nonsteroidal anti-inflammatory drugs (NSAIDs), the incidence of lower gastrointestinal (GI) complications is expected to increase. However, unlike upper GI complications, the burden, pathogenesis, prevention and treatment of NSAID-associated lower GI complications remain unclear. To date, no cost-effective and safe protective agent has been developed that can completely prevent or treat NSAID-related lower GI injuries. Selective COX-2 inhibitors, misoprostol, intestinal microbiota modulation, and some mucoprotective agents have been reported to show protective effects on NSAID-induced lower GI injuries. This review aims to provide an overview of the current evidence on the prevention of NSAID-related lower GI injuries.

Rebamipide ameliorates indomethacin-induced small intestinal damage and proton pump inhibitor-induced exacerbation of this damage by modulation of small intestinal microbiota

Non-steroidal anti-inflammatory drugs (NSAIDs) induce small intestinal damage. It has been reported that rebamipide, a mucoprotective drug, exerts a protective effect against NSAID-induced small intestinal damage; however, the underlying mechanism remains unknown. In this study, we investigated the significance of the small intestinal microbiota in the protective effect of rebamipide against indomethacin-induced small intestinal damage in mice. A comprehensive analysis of the 16S rRNA gene sequencing revealed an alteration in the composition of the small intestinal microbiota at the species level, modulated by the administration of rebamipide and omeprazole. The transplantation of the small intestinal microbiota of the mice treated with rebamipide suppressed the indomethacin-induced small intestinal damage. Omeprazole, a proton pump inhibitor, exacerbated the indomethacin-induced small intestinal damage, which was accompanied by the alteration of the small intestinal microbiota. We found that the transplantation of the small intestinal microbiota of the rebamipide-treated mice ameliorated indomethacin-induced small intestinal damage and the omeprazole-induced exacerbation of the damage. These results suggest that rebamipide exerts a protective effect against NSAID-induced small intestinal damage via the modulation of the small intestinal microbiota, and that its ameliorating effect extends also to the exacerbation of NSAID-induced small intestinal damage by proton pump inhibitors.

Protective effect and mechanism of rebamipide on NSAIDs associated small bowel injury

PURPOSE

To investigate the protective effect and mechanism of rebamipide on NSAIDs associated intestinal injury.

METHODS

Intestinal injury was induced in Sprague Dawley rats by intragastric administration of diclofenac with rebamipide intervention, and LPS and TAK-242 were given intraperitoneally respectively. The expression of TLR4/NF-κB and the related proteins in the intestinal mucosa were detected. 55 patients taking NSAIDs and diagnosed as NSAIDs associated small intestinal injury were recruited as NSAIDs group. Another 55 patients without NSAIDs and no obvious abnormality in the small bowel served as the control group.

RESULTS

The macroscopic and histological scores of the small intestinal mucosa in the rebamipide pretreatment group were significantly lower compared to the diclofenac group (p < 0.01). The expressions of Tollip, ZO-1 and Claudin-1 in the diclofenac group were down-regulated compared with that in the control group, while they increased significantly in the rebamipide pretreatment group (p < 0.01). The expressions of TLR4/NF-κBp65, IL-1β, IL-6, IL-8, and TNF-α significantly increased in the model group while they were down-regulated in the rebamipide pretreatment group (p < 0.05). Administration of LPS 1 h after diclofenac aggravated small intestinal damage, and increased expression of IL-1β, IL-6, IL-8 and TNF-α. Administration of rebamipide did not effectively reverse intestinal injury induced by diclofenac and LPS. In contrast, pretreatment with TAK-242 significantly inhibited damage and prevented the increased expression of the cytokines. The expression of TLR4 and NF-κBp65 in the patients with NSAIDs associated intestinal injury was significantly higher than that in the control group (p < 0.01), while the expression of Tollip was decreased (p < 0.01).

CONCLUSION

Rebamipide effectively alleviated intestinal mucosa injury by probably suppressing the TLR4/NF-κB signaling pathway and the decreasing of ZO-1 and Claudin-1 induced by diclofenac.

Gut Microbiota in NSAID Enteropathy: New Insights From Inside

As a class of the commonly used drugs in clinical practice, non-steroidal anti-inflammatory drugs (NSAIDs) can cause a series of adverse events including gastrointestinal injuries. Besides upper gastrointestinal injuries, NSAID enteropathy also attracts attention with the introduction of capsule endoscopy and double balloon enteroscopy. However, the pathogenesis of NSAID enteropathy remains to be entirely clarified. Growing evidence from basic and clinical studies presents that gut microbiota is a critical factor in NSAID enteropathy progress. We have reviewed the recent data about the interplay between gut microbiota dysbiosis and NSAID enteropathy. The chronic medication of NSAIDs could change the composition of the intestinal bacteria and aggravate bile acids cytotoxicity. Meanwhile, NSAIDs impair the intestinal barrier by inhibiting cyclooxygenase and destroying mitochondria. Subsequently, intestinal bacteria translocate into the mucosa, and then lipopolysaccharide released from gut microbiota combines to Toll-like receptor 4 and induce excessive production of nitric oxide and pro-inflammatory cytokines. Intestinal injuries present in the condition of intestinal inflammation and oxidative stress. In this paper, we also have reviewed the possible strategies of regulating gut microbiota for the management of NSAID enteropathy, including antibiotics, probiotics, prebiotics, mucosal protective agents, and fecal microbiota transplant, and we emphasized the adverse effects of proton pump inhibitors on NSAID enteropathy. Therefore, this review will provide new insights into a better understanding of gut microbiota in NSAID enteropathy.

Current knowledge on non-steroidal anti-inflammatory drug-induced small-bowel damage: a comprehensive review

Recent advances in small-bowel endoscopy such as capsule endoscopy have shown that non-steroidal anti-inflammatory drugs (NSAIDs) frequently damage the small intestine, with the prevalence rate of mucosal breaks of around 50% in chronic users. A significant proportion of patients with NSAIDs-induced enteropathy are asymptomatic, but some patients develop symptomatic or complicated ulcers that need therapeutic intervention. Both inhibition of prostaglandins due to the inhibition of cyclooxygenases and mitochondrial dysfunction secondary to the topical effect of NSAIDs play a crucial role in the early process of injury. As a result, the intestinal barrier function is impaired, which allows enterobacteria to invade the mucosa. Gram-negative bacteria and endogenous molecules coordinate to trigger inflammatory cascades via Toll-like receptor 4 to induce excessive expression of cytokines such as tumor necrosis factor-α and to activate NLRP3 inflammasome, a multiprotein complex that processes pro-interleukin-1β into its mature form. Finally, neutrophils accumulate in the mucosa, resulting in intestinal ulceration. Currently, misoprostol is the only drug that has a proven beneficial effect on bleeding small intestinal ulcers induced by NSAIDs or low-dose aspirin, but its protection is insufficient. Therefore, the efficacy of the combination of misoprostol with other drugs, especially those targeting the innate immune system, should be assessed in the next step.

Novel self-nanomicellizing formulation based on Rebaudioside A: A potential nanoplatform for oral delivery of naringenin

In the study described here, we strove to develop an orally administered novel self-nanomicellizing formulation based on Rebaudioside A (RA) for delivering naringenin (NAR) with improved bioavailability and therapeutic efficacy. Our research found that RA and naringenin (NAR) could be formulated into self-assembling nanomicelles (RA-NAR) using a simple ethanol dissolution-evaporation method. We found that the RA-NAR self-assemblies comprised ultra-small micelles (5.234 ± 0.311 nm) in a uniform dispersion state (the polydispersity index was 0.243 ± 0.039) with a near-neutral surface charge (-[2.268 ± 0.729] mV). We also found that RA-NAR had a well-storage stability at 4 °C with light protection. In addition, we observed that RA-NAR exhibited enhanced apparent solubility, in-vitro permeability, and antioxidant activity. After we administered RA-NAR to rats orally, we observed an increase in area under the curve (AUC_0→t) to 19,500.82 ng/mL/h versus 9324.47 ng/mL/h observed with free NAR and an increase of maximum concentration (Cmax) to 27,326.10 ng/mL from the free-NAR Cmax level of 2549.04 ng/mL. The tissue distribution assessments further demonstrated that RA-NAR could effectively increase the NAR concentration in all tested intestinal segments. Our mouse model results showed as well that oral administration of RA-NAR could efficiently protect against small intestine injuries induced by indomethacin, and the mechanisms by inhibiting proinflammatory cytokines and oxidative stress were involved in its therapeutic effect. Taken together, these findings indicate that a self-nanomicellizing formulation based on RA has great potential as a novel oral nano-drug delivery system for NAR.

Pharmacological and clinical feature of rebamipide: new therapeutic targets

Rebamipide is a cytoprotector developed in Japan where it has been successfully used for the treatment of stomach diseases for 30 years. Initially discovered effects of the drug included the induction of prostaglandins and the elimination of free oxygen radicals. Recent studies discovered new therapeutic targets of the drug, its new forms that made possible using rebamipid for the treatment of such diseases as NSAID enteropathy, ulcerative colitis, radiation colitis, pouchitis, enteropathy with impaired membrane digestion. It is used in endoscopy, ophthalmology, chemotherapy, rheumatology. The aim of this review is to present current information about the pharmacological and clinical feature of rebamipide and to study its therapeutic potential.

Prostaglandin E2 accelerated recovery of chemotherapy-induced intestinal damage by increasing expression of cyclin D

Intestinal stem cells (ISCs) play a crucial role in maintaining intestinal homeostasis upon chemotherapy and radiotherapy. It has been documented that prostaglandin E2 (PGE2) treatment improved hematopoietic stem cell function in vitro and in vivo, while the relationship between PGE2 and intestinal stem cells remains unclear. Presently, mice were exposed to PGE1, dmPGE2 and indomethacin. Numbers and function of ISCs were assessed by analyzing Olfm4⁺ ISCs. Intestinal protection of dmPGE2 was investigated on a 5-fluorouracil (5FU)-induced intestinal damage mouse model. The results showed that dmPGE2 treatment, but not PGE1, increased numbers of Olfm4⁺ ISCs in dose- and time-dependent manners. Indomethacin treatment decreased numbers of Olfm4⁺ ISCs. The beneficial effects of short-term dmPGE2 treatment on intestine were supported in a 5FU-induced intestinal damage model. Our data showed that 5FU treatment significantly decreased numbers of Olfm4⁺ ISCs and goblet cells in intestine, which could be ameliorated by dmPGE2 treatment. dmPGE2 treatment accelerated the recovery of 5FU-induced ISC injury via increasing expression of cyclin D1 and D2 in intestine. Furthermore, dmPGE2 treatment-induced expression of cyclin D1 and D2 might be mediated by up-regulation of FOXM1 expression in intestine. These findings feature PGE2 as an effective protector against chemotherapy-induced intestinal damage.

NSAID-Gut Microbiota Interactions

Nonsteroidal anti-inflammatory drugs (NSAID)s relieve pain, inflammation, and fever by inhibiting the activity of cyclooxygenase isozymes (COX-1 and COX-2). Despite their clinical efficacy, NSAIDs can cause gastrointestinal (GI) and cardiovascular (CV) complications. Moreover, NSAID use is characterized by a remarkable individual variability in the extent of COX isozyme inhibition, therapeutic efficacy, and incidence of adverse effects. The interaction between the gut microbiota and host has emerged as a key player in modulating host physiology, gut microbiota-related disorders, and metabolism of xenobiotics. Indeed, host-gut microbiota dynamic interactions influence NSAID disposition, therapeutic efficacy, and toxicity. The gut microbiota can directly cause chemical modifications of the NSAID or can indirectly influence its absorption or metabolism by regulating host metabolic enzymes or processes, which may have consequences for drug pharmacokinetic and pharmacodynamic properties. NSAID itself can directly impact the composition and function of the gut microbiota or indirectly alter the physiological properties or functions of the host which may, in turn, precipitate in dysbiosis. Thus, the complex interconnectedness between host-gut microbiota and drug may contribute to the variability in NSAID response and ultimately influence the outcome of NSAID therapy. Herein, we review the interplay between host-gut microbiota and NSAID and its consequences for both drug efficacy and toxicity, mainly in the GI tract. In addition, we highlight progress towards microbiota-based intervention to reduce NSAID-induced enteropathy.

Gastric acid inhibitor aggravates indomethacin-induced small intestinal injury via reducing Lactobacillus johnsonii

Proton pump inhibitors (PPIs) alter the composition of the intestinal microbiome, exacerbating indomethacin (IND)-induced small intestinal damage. Vonoprazan fumarate inhibits gastric acid secretion using a different mechanism from PPIs. We investigated the effects of both drugs on the intestinal microbiome and IND-induced small intestinal damage. We sought to clarify whether PPI-induced dysbiosis and worsening of the damage were due to a specific drug class effect of PPIs. Rabeprazole administration increased operational taxonomic unit numbers in the small intestines of C57BL/6 J mice, whereas the difference was not significant in the vonoprazan-treated group but exhibited a trend. Permutational multivariate analysis of variance of the unweighted UniFrac distances showed significant differences between vehicle- and vonoprazan- or rabeprazole-treated groups. L. johnsonii was the predominant microbial species, and the population ratio decreased after vonoprazan and rabeprazole administration. The vonoprazan- and rabeprazole-treated groups showed increased IND-induced damage. This high sensitivity to IND-induced damage was evaluated by transplantation with contents from the small intestine of mice treated with either vonoprazan or rabeprazole. Supplementation of L. johnsonii orally in mice treated with rabeprazole and vonoprazan prevented the increase in IND-induced small intestinal damage. In conclusion, both rabeprazole and vonoprazan aggravated NSAID-induced small intestinal injury by reducing the population of L. johnsonii in the small intestine via suppressing gastric acid secretion.

NSAIDs disrupt intestinal homeostasis by suppressing macroautophagy in intestinal epithelial cells

Small intestinal damage induced by nonsteroidal anti-inflammatory drugs (NSAIDs) remains an under-recognized clinical disorder. The incomplete understanding of the pathophysiology has hampered the development of prevention and treatment strategies leading to the high morbidity and mortality rates. NSAIDs are known to modulate macroautophagy, a process indispensable for intestinal homeostasis. Whether NSAIDs stimulate or repress macroautophagy and how this correlates with the clinical manifestations of NSAID enteropathy, however, remains unknown. The objectives of this study were to determine whether NSAIDs impaired macroautophagy and how this affects macroautophagy-regulated intestinal epithelial cell (IEC) processes essential for intestinal homeostasis (i.e., clearance of invading pathogens, secretion and composition of mucus building blocks, and inflammatory response). We show that NSAID treatment of IECs inhibits macroautophagy in vitro and in vivo. This inhibition was likely attributed to a reduction in the area and/or distribution of lysosomes available for degradation of macroautophagy-targeted cargo. Importantly, IEC regulatory processes necessary for intestinal homeostasis and dependent on macroautophagy were dysfunctional in the presence of NSAIDs. Since macroautophagy is essential for gastrointestinal health, NSAID-induced inhibition of macroautophagy might contribute to the severity of intestinal injury by compromising the integrity of the mucosal barrier, preventing the clearance of invading microbes, and exacerbating the inflammatory response.

NSAID-induced small intestinal mucosal injury: Mechanism, prevention and treatment

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in clinical practice. It was well known in the past that the main side effect of NSAIDs was gastric mucosal injury. However, with the advancement of the diagnostic and therapeutic technology, NSAIDs have been found to cause much more severe damage to the small intestinal mucosa than we expected in recent years. Therefore, it is of great significance to elucidate the mechanism for NSAIDs to cause small intestinal mucosal injury to aid the clinical prevention and treatment of this condition. This paper aims to review the progress in the research of the mechanism, prevention, and treatment of NSAID-induced small intestinal mucosal injury.

Involvement of gliadin, a component of wheat gluten, in increased intestinal permeability leading to non-steroidal anti-inflammatory drug-induced small-intestinal damage

Gliadin, a component of wheat gluten known to be an important factor in the etiology of celiac disease, is related to several other diseases through its enhancing effect on intestinal paracellular permeability. We investigated the significance of gliadin in non-steroidal anti-inflammatory drug (NSAID)-induced small-intestinal damage in mice. 7-week-old C57BL/6 male mice were divided into the following groups: standard diet group, in which mice were fed with wheat-containing standard rodent diet (CE-2); gluten-free diet group, in which mice were fed with gluten-free diet (AIN-76A); and gliadin-administered group, in which mice fed with gluten-free diet were administered with gliadin (~250 mg/kg BW). Each group was subdivided into negative, healthy control group and NSAID-treated group. To some mice fed with gluten-free diet and administered with gliadin, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor was administered for clarification of the significance of EGFR in NSAID-induced small intestinal damage and intestinal permeability. In mice fed with a gluten-free diet, indomethacin or diclofenac induced very mild mucosal damage in the small intestine compared with that in mice fed with a wheat-containing standard diet. Gliadin exacerbated the NSAID-induced small-intestinal damage in mice fed with a gluten-free diet. With the administration of indomethacin, MPO activity, a marker of neutrophil infiltration into the mucosa and mRNA expression level of tumor necrosis factor α and interleukin-1β in the small intestine were higher in the gliadin-administered mice. Gliadin increased the intestinal paracellular permeability without indomethacin administration (4.3-fold) and further increased the permeability after indomethacin administration (2.1-fold). Gliadin induced phosphorylation of epidermal growth factor receptor (EGFR) in small-intestinal tissues, and erlotinib (an EGFR tyrosine kinase inhibitor) attenuated the indomethacin-induced intestinal damage and permeability exacerbated by gliadin, accompanied by inhibition of EGFR phosphorylation. These results suggest that gliadin plays an important role in the induction and exacerbation of NSAID-induced small-intestinal damage, and that increase in intestinal permeability via the EGFR signalling pathway is involved in its mechanism.

Human Defensin-5 Blocks Ethanol and Colitis-Induced Dysbiosis, Tight Junction Disruption and Inflammation in Mouse Intestine

Alcohol consumption has been shown to cause dysbiosis, but the mechanism involved in it is unknown. Recurrent colitis is known to induce expression of α-defensins in the colon, but the effect of alcohol consumption on it is not known. We investigated the effect of ethanol on α-defensin expression in the small intestine and colitis-induced expression in colon in mice. Furthermore, we evaluated the effect of human defensin-5 (HD5) on ethanol and colitis-induced gut barrier dysfunction and mucosal damage. Recurrent colitis was induced by feeding dextran sulfate sodium (DSS), 3 cycles of 5-days each with 15 days intervals, followed by 30-days remission. Ethanol was fed during the intervals and recovery in a liquid diet with or without HD5. Expression of α-defensins, tight junction (TJ) integrity and cytokine/chemokine expression were analyzed. Chronic ethanol feeding reduced α-defensin expression in the small intestine and colitis-induced defensin expression in the colon. HD5 attenuated the growth of enterotoxigenic Bacteriodes fragilis and E. coli, but had no effect on non-toxigenic Bacteriodes fragilis or probiotics, the Lactobacilli. Ethanol and colitis elevated Enterobacteriaceae, Firmicutes and Firmicutes to Bacteriodetes ratio in colonic mucosa. HD5 feeding attenuated ethanol and colitis-induced dysbiosis, disruption of intestinal epithelial TJ, mucosal inflammation, expression of pro-inflammatory cytokines and chemokines in the small intestine and colon, and endotoxemia. These results demonstrate that ethanol suppresses intestinal α-defensin expression, leading to dysbiosis, barrier dysfunction, inflammation and endotoxemia. HD5 feeding attenuates intestinal injury caused by ethanol and colitis, indicating that defensin expression is a potential target for treatment of alcoholic tissue injury and colitis.

Microbiota Plays a Key Role in Non-Steroidal Anti-Inflammatory Drug-Induced Small Intestinal Damage

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) damage the small intestine by causing multiple erosions and ulcers. However, to date, no established therapies and prophylactic agents are available to treat such damages. We reviewed the role of intestinal microbiota in NSAID-induced intestinal damage and identified potential therapeutic candidates.

SUMMARY

The composition of the intestinal microbiota is an important factor in the pathophysiology of NSAID-induced small intestinal damage. Once mucosal barrier function is disrupted due to NSAID-induced prostaglandin deficiency and mitochondrial malfunction, lipopolysaccharide from luminal gram-negative bacteria and high mobility group box 1 from the injured epithelial cells activate toll-like receptor 4-signaling pathway and nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 inflammasome; this leads to the release of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-1β. Proton pump inhibitors (PPIs) are often used for the prevention of NSAID-induced injuries to the upper gastrointestinal tract. However, several studies indicate that PPIs may induce dysbiosis, which may exacerbate the NSAID-induced small intestinal damage. Our recent research suggests that probiotics and rebamipide could be used to prevent NSAID-induced small intestinal damage by regulating the intestinal microbiota. Key Messages: Intestinal microbiota plays a key role in NSAID-induced small intestinal damage, and modulating the composition of the intestinal microbiota could be a new therapeutic strategy for treating this damage.

Determination of the adequate dosage of rebamipide, a gastric mucoprotective drug, to prevent low-dose aspirin-induced gastrointestinal mucosal injury

Small intestinal mucosal injury caused by low-dose aspirin is a common cause of obscure gastrointestinal bleeding. We aimed to investigate the protective effects and optimal dose of rebamipide for low-dose aspirin-induced gastrointestinal mucosal injury. In this prospective randomized trial, 45 healthy volunteers (aged 20–65 years) were included and divided into three groups. The groups received enteric-coated aspirin 100 mg (low-dose aspirin) plus omeprazole 10 mg (Group A: proton pump inhibitor group), low-dose aspirin plus rebamipide 300 mg (Group B: standard-dose group), or low-dose aspirin plus rebamipide 900 mg (Group C: high-dose group). Esophagogastroduodenoscopy and video capsule endoscopy were performed, and the fecal occult blood reaction and fecal calprotectin levels were measured before and two weeks after drug administration. Although the fecal calprotectin levels increased significantly in Group A, they did not increase in Groups B and C. The esophagogastroduodenoscopic and video capsule endoscopic findings and the fecal occult blood test findings did not differ significantly among the three groups. In conclusion, standard-dose rebamipide is sufficient for preventing mucosal injury of the small intestine induced by low-dose aspirin, indicating that high-dose rebamipide is not necessary.

Effects of heat-killed Lactobacillus kunkeei YB38 on human intestinal environment and bowel movement: a pilot study

It is well known that lactic acid bacteria supplementation is beneficial for intestinal conditions such as microbiota; however, the effects of killed-lactic acid bacteria on intestinal conditions are largely unclear. This study aimed to evaluate the effect of heat-killed Lactobacillus kunkeei YB38 (YB38) at a dose of approximately 10 mg/day on human intestinal environment and bowel movement. This single-blind study enrolled 29 female subjects with a low defecation frequency who consumed heat-killed YB38 at four increasing dosage levels: 0 (placebo), 2, 10, and 50 mg. Each dose was consumed daily for two weeks, with a two-week baseline period preceding the dosing-period and a two-week washout period ending the study. Observed levels of Bacteroides fragilis group significantly decreased with intake of heat-killed YB38 at ≥10 mg/day compared with levels during placebo intake (P<0.01). Faecal pH significantly decreased with 10 and 50 mg/day intake (P<0.01 and 0.05, respectively). Acetic acid levels tended to increase in faeces at the 50 mg/day dose (P<0.1). Bowel movement tended to increase in all heat-killed YB38 intake periods (P<0.1). In conclusion, heat-killed YB38 altered human intestinal microbiota at doses of ≥10 mg/day and tended to increase bowel movement at ≥2 mg/day. This is the first study to show the intestinal microbiota-altering effect of L. kunkeei and to report the bowel movement-improving effect of heat-killed lactic acid bacteria.

Reduction of prostaglandin transporter predicts poor prognosis associated with angiogenesis in gastric adenocarcinoma

BACKGROUND AND AIM

Prostaglandin (PG) E2 promotes gastrointestinal carcinogenesis and tumor progression. The total amount of biologically active PGE2 in tissues is determined by a balance of PG biosynthesis and degradation pathways, which involve the PG transporter (PGT). We investigated PGT in gastric adenocarcinoma by determining its expression pattern and examining associations of PGT with prognosis and tumor angiogenesis.

METHODS

PGT expression was determined by immunohistochemistry in advanced gastric adenocarcinoma specimens obtained from 96 patients who underwent surgical resection. Correlations between PGT expression level and clinicopathological factors were statistically analyzed. Angiogenesis in the tumor tissue was evaluated by counting the number of microvessels. The role of PGT in mRNA and protein expression of vascular endothelial growth factor (VEGF) was examined in gastric cancer cells stimulated by PGE2 .

RESULTS

Based on multivariate and Kaplan-Meier analyses, negativity for PGT expression was an independent poor prognostic factor. There were more microvessels in PGT-negative tumors than in PGT-positive tumors. Transfection of AGS and MKN7 gastric cancer cells with PGT-specific siRNA led to increased VEGF mRNA and protein expression accompanied by increased PGE2 in the culture media.

CONCLUSIONS

PGT expression is an independent predictor of poor survival and is associated with tumor angiogenesis in gastric adenocarcinoma.

Administration of Non-Absorbable Antibiotics to Pregnant Mice to Perturb the Maternal Gut Microbiota Is Associated with Alterations in Offspring Behavior

There is increasing evidence that the gut microbiota plays a major role in host health and disease. In this study, we examined whether perturbation of the maternal gut microbiota during pregnancy, induced by administration of non-absorbable antibiotics to pregnant dams, influences the behavior of offspring. Terminal restriction fragment length polymorphism analyses of fecal bacterial composition showed that the relative abundance of the bacterial order Lactobacillales was lower in offspring born from antibiotic-treated dams (20.7±3.4%) than in control offspring (42.1±6.2%) at P24, while the relative abundance of the bacterial family Clostridium subcluster XIVa was higher in offspring born from antibiotic-treated dams (34.2±5.0%) than in control offspring (16.4±3.3%). Offspring born from antibiotic-treated dams exhibited low locomotor activity in both familiar and novel environments, and preferred to explore in the peripheral area of an unfamiliar field at postnatal week 4. At postnatal weeks 7–8, no difference was observed in the level of locomotor activity between control offspring and offspring from antibiotic-treated dams, while the tendency for the offspring from antibiotic-treated dams to be less engaged in exploring the inside area was still observed. The behavioral phenotypes of the offspring from antibiotic-treated dams at postnatal week 4 could be rescued to a considerable extent through fostering of these offspring by normal dams from postnatal day 1. Although the detailed underlying mechanisms are not fully elucidated, the present results suggest that administration of non-absorbable antibiotics to pregnant dams to perturb the maternal gut microbiota during pregnancy leads to alterations in the behavior of their offspring.

Bidirectional interactions between indomethacin and the murine intestinal microbiota

The vertebrate gut microbiota have been implicated in the metabolism of xenobiotic compounds, motivating studies of microbe-driven metabolism of clinically important drugs. Here, we studied interactions between the microbiota and indomethacin, a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenases (COX) -1 and -2. Indomethacin was tested in both acute and chronic exposure models in mice at clinically relevant doses, which suppressed production of COX-1- and COX-2-derived prostaglandins and caused small intestinal (SI) damage. Deep sequencing analysis showed that indomethacin exposure was associated with alterations in the structure of the intestinal microbiota in both dosing models. Perturbation of the intestinal microbiome by antibiotic treatment altered indomethacin pharmacokinetics and pharmacodynamics, which is probably the result of reduced bacterial β-glucuronidase activity. Humans show considerable inter-individual differences in their microbiota and their responses to indomethacin - thus, the drug-microbe interactions described here provide candidate mediators of individualized drug responses.

Hesperetin Modifies the Composition of Fecal Microbiota and Increases Cecal Levels of Short-Chain Fatty Acids in Rats

There has been particular interest in the prebiotic-like effects of commonly consumed polyphenols. This study aimed to evaluate the effects of hesperidin (HD) and its aglycone hesperetin (HT), major flavonoids in citrus fruits, on the structure and activity of gut microbiota in rats. Rats ingested an assigned diet (a control diet, a 0.5% HT diet, or a 1.0% HD diet) for 3 weeks. Terminal restriction fragment length polymorphism analysis revealed that the proportion of Clostridium subcluster XIVa in the feces collected at the third week of feeding was significantly reduced by the HT diet: 19.8 ± 4.3% for the control diet versus 5.3 ± 1.5% for the HT diet (P < 0.01). There was a significant difference in the cecal pool of short-chain fatty acids (SCFA), the sum of acetic, propionic, and butyric acids, between the control diet (212 ± 71 μmol) and the HT diet (310 ± 51 μmol) (P < 0.05), whereas the HD diet exhibited no effects (245 ± 51 μmol). Interestingly, dietary HT resulted in a significant increase in the excretion of starch in the feces. HT, but not HD, might reduce starch digestion, and parts of undigested starch were utilized to produce SCFA by microbial fermentation in the large intestine.

Rebamipide Alters the Esophageal Microbiome and Reduces the Incidence of Barrett's Esophagus in a Rat Model

BACKGROUND

Barrett's esophagus (BE) is characterized by a distinct Th2-predominant cytokine profile. However, antigens that shift the immune response toward the Th2 profile are unknown.

AIM

We examined the effects of rebamipide on the esophageal microbiome and BE development in a rat model.

METHODS

BE was induced by esophagojejunostomy in 8-week-old male Wistar rats. Rats were divided into control and rebamipide-treated group receiving either a normal or a 0.225 % rebamipide-containing diet, respectively, and killed 8, 16, 24, and 32 weeks after the operation. PCR-amplified 16S rDNAs extracted from esophageal samples were examined by terminal-restriction fragment length polymorphism (T-RFLP) analysis to assess microbiome composition. The dynamics of four bacterial genera (Lactobacillus, Clostridium, Streptococcus, and Enterococcus) were analyzed by real-time PCR.

RESULTS

The incidences of BE in the control and rebamipide group at 24 and 32 weeks were 80 and 100, and 20 and 33 %, respectively. T-RFLP analysis of normal esophagus revealed that the proportion of Clostridium was 8.3 %, while that of Lactobacillales was 71.8 %. The proportions of Clostridium increased and that of Lactobacillales decreased at 8 weeks in both groups. Such changes were consistently observed in the control but not in the rebamipide group. Clostridium and Lactobacillus expression was lower and higher, respectively, in the rebamipide group than in the control group.

CONCLUSIONS

Rebamipide reduced BE development and altered the esophageal microbiome composition, which might play a role in BE development.

Rebamipide Promotes the Regeneration of Aspirin-Induced Small-Intestine Mucosal Injury through Accumulation of β-Catenin

BACKGROUND

The effect of rebamipide on repairing intestinal mucosal damage induced by nonsteroidal anti-inflammatory drugs and its mechanism remain unclear. In this study, we sought to explore the mechanism whereby rebamipide could promote the regeneration of aspirin-induced intestinal mucosal damage.

METHODS

BALB/c mice were administered aspirin (200 mg/kg/d) for 5 days to induce acute small intestinal injury (SII). Subsequently, SII mice were treated with rebamipide (320 mg/kg/d) for 5 days. The structure of intestinal barrier was observed with transmission electron microscope, and Zo-1 and occludin expressions were detected. The proliferative index was indicated by the percentage of proliferating cell nuclear antigen positive cells. The prostaglandin E2 (PGE2) levels in the small intestine tissues were measured by an enzyme immunoassay. The mRNA and protein expression levels of cyclooxygenase (COX) and β-catenin signal were detected in the small intestine using quantitative PCR and Western blot, respectively.

RESULTS

COX expression was significantly down-regulated in aspirin induced SII (P < 0.05). In SII mice treated with rebamipide, histopathological findings of aspirin-induced intestinal inflammation were significantly milder and tight junctions between intestinal epithelial cells were improved significantly. The proliferative index increased after rebamipide treatment when compared with that in the control mice. The expressions of COX-2, β-catenin, and c-myc and the PGE2 concentrations in small intestinal tissues were significantly increased in mice with rebamipide treatments (P < 0.05).

CONCLUSION

Rebamipide administration in aspirin-induced SII mice could improve the intestinal barrier structure and promote the regeneration of small intestinal epithelial injury through up-regulating COX-2 expression and the accumulation of β-catenin.

Effect of hyperglycemia on hepatocellular carcinoma development in diabetes

Compared with other cancers, diabetes mellitus is more closely associated with hepatocellular carcinoma (HCC). However, whether hyperglycemia is associated with hepatic carcinogenesis remains uncertain. In this study, we investigate the effect of hyperglycemia on HCC development. Mice pretreated with 7,12-dimethylbenz (a) anthracene were divided into three feeding groups: normal diet (Control), high-starch diet (Starch), and high-fat diet (HFD) groups. In addition, an STZ group containing mice that were fed a normal diet and injected with streptozotosin to induce hyperglycemia was included. The STZ group demonstrated severe hyperglycemia, whereas the Starch group demonstrated mild hyperglycemia and insulin resistance. The HFD group demonstrated mild hyperglycemia and severe insulin resistance. Multiple HCC were macroscopically and histologically observed only in the HFD group. Hepatic steatosis was observed in the Starch and HFD groups, but levels of inflammatory cytokines, interleukin (IL)-6, tumor necrosis factor-α, and IL-1β, were elevated only in the HFD group. The composition of gut microbiota was similar between the Control and STZ groups. A significantly higher number of Clostridium cluster XI was detected in the feces of the HFD group than that of all other groups; it was not detectable in the Starch group. These data suggested that hyperglycemia had no effect on hepatic carcinogenesis. Different incidences of HCC between the Starch and HFD groups may be attributable to degree of insulin resistance, but diet-induced changes in gut microbiota including Clostridium cluster XI may have influenced hepatic carcinogenesis. In conclusion, in addition to the normalization of blood glucose levels, diabetics may need to control insulin resistance and diet contents to prevent HCC development.

A multicenter, randomized, double-blind, placebo-controlled trial of high-dose rebamipide treatment for low-dose aspirin-induced moderate-to-severe small intestinal damage

BACKGROUND

Low-dose aspirin (LDA) frequently causes small bowel injury. While some drugs have been reported to be effective in treating LDA-induced small intestinal damage, most studies did not exclude patients with mild damage thought to be clinically insignificant.

AIM

We conducted a multicenter, randomized, double-blind, placebo-controlled trial to assess the efficacy of a high dose of rebamipide, a gastroprotective drug, for LDA-induced moderate-to-severe enteropathy.

METHODS

We enrolled patients who received 100 mg of enteric-coated aspirin daily for more than 3 months and were found to have more than 3 mucosal breaks (i.e., erosions or ulcers) in the small intestine by capsule endoscopy. Eligible patients were assigned to receive either rebamipide 300 mg (triple dose) 3 times daily or placebo for 8 weeks in a 2:1 ratio. Capsule endoscopy was then repeated. The primary endpoint was the change in the number of mucosal breaks from baseline to 8 weeks. Secondary endpoints included the complete healing of mucosal breaks at 8 weeks and the change in Lewis score (an endoscopic score assessing damage severity) from baseline to 8 weeks.

RESULTS

The study was completed by 38 patients (rebamipide group: n = 25, placebo group: n = 13). After 8 weeks of treatment, rebamipide, but not placebo, significantly decreased the number of mucosal breaks (p = 0.046). While the difference was not significant (p = 0.13), the rate of complete mucosal break healing in the rebamipide group (32%, 8 of 25) tended to be higher than that in the placebo group (7.7%, 1 of 13). Rebamipide treatment significantly improved intestinal damage severity as assessed by the Lewis score (p = 0.02), whereas placebo did not. The triple dose of rebamipide was well tolerated.

CONCLUSIONS

High-dose rebamipide is effective for the treatment of LDA-induced moderate-to-severe enteropathy.

TRIAL REGISTRATION

UMIN Clinical Trials Registry UMIN000003463.

Effect of bifidobacterium on defensin-5 expression in intestinal injury of preweaning rats

AIM: To investigate the protective effect of bifidobacterium in endotoxin-induced intestinal injury in preweaning rats.

METHODS: Preweaning rats were randomly divided into three groups (n = 40 for each): a control group (group C), a model group (group E) and a treatment group (group T). Both groups E and T were intraperitoneally injected with lipopolysaccharide (LPS) at a dose of 5 mg/kg (5 mg/L in normal saline), and group T was intragastrically administrated with bifidobacterium suspension (2.0 × 10⁹ CFU/mL, 0.5 mL each time, twice a day, until the end of the experiment) 7 d before LPS administration. Group C was intraperitoneally injected with normal saline. After intraperitoneal injection and intragastric administration, the rats were placed back to the initial cage to receive breast feeding. The rats were killed at 2, 6, 12, 24 or 72 h, respectively, after endotoxin or physiological saline injection to collect serum and ileal tissue samples. Myeloperoxidase (MPO) contents in serum and ileum were detected at different times, and expression of ileal defensin-5 mRNA was evaluated by reverse transcription-polymerase chain reaction.

RESULTS: Serum and ileal MPO contents in group E were significantly higher than those in group C (serum contents: 107.50 ± 17.70 vs 157.14 ± 24.67, P < 0.05; ileal contents: 1.03 ± 0.21 vs 1.57 ± 0.33, P < 0.05), which peaked at 12 h and 6 h, respectively. MPO contents in group T were significantly lower than those in group E (serum contents: 114.38 ± 24.56 vs 145.25 ± 23.62, P < 0.05; ileal contents: 1.25 ± 0.24 vs 1.57 ± 0.33, P < 0.05). The expression of defensin-5 mRNA in group E was significantly higher than that in group C (0.953 ± 0.238 vs 0.631 ± 0.146, P < 0.05), which peaked at 2 h, and then decreased gradually. The expression of defensin-5 mRNA in group T was significantly lower than that in group E (0.487 ± 0.149 vs 0.758 ± 0.160, P < 0.05) apparently in 24 h. The expression of defensin-5 mRNA at 2 h in group T was significantly higher than that in group C (0.824 ± 0.158 vs 0.631 ± 0.146, P < 0.05).

CONCLUSION: MPO and defensin-5 mRNA increase in preweaning rats with LPS-induced intestinal injury. Bifidobacterium protects the gut by inhibiting MPO activity, not by increasing defensin-5 secretion.

Rebamipide protects small intestinal mucosal injuries caused by indomethacin by modulating intestinal microbiota and the gene expression in intestinal mucosa in a rat model

The effect of rebamipide, a mucosal protective drug, on small intestinal mucosal injury caused by indomethacin was examined using a rat model. Indomethacin administration (10 mg/kg, p.o.) induced intestinal mucosal injury was accompanied by an increase in the numbers of intestinal bacteria particularly Enterobacteriaceae in the jejunum and ileum. Rebamipide (30 and 100 mg/kg, p.o., given 5 times) was shown to inhibit the indomethacin-induced small intestinal mucosal injury and decreased the number of Enterococcaceae and Enterobacteriaceae in the jejunal mucosa to normal levels. It was also shown that the detection rate of segmented filamentous bacteria was increased by rebamipide. PCR array analysis of genes related to inflammation, oxidative stress and wound healing showed that indomethacin induced upregulation and downregulation of 14 and 3 genes, respectively in the rat jejunal mucosa by more than 5-fold compared to that of normal rats. Rebamipide suppressed the upregulated gene expression of TNFα and Duox2 in a dose-dependent manner. In conclusion, our study confirmed that disturbance of intestinal microbiota plays a crucial role in indomethacin-induced small intestinal mucosal injury, and suggests that rebamipide could be used as prophylaxis against non-steroidal anti-inflammatory drugs -induced gastrointestinal mucosal injury, by modulating microbiota and suppressing mucosal inflammation in the small intestine.

Specific changes of gut commensal microbiota and TLRs during indomethacin-induced acute intestinal inflammation in rats

BACKGROUND AND AIMS

Gut microbiota is a contributing factor in the development and maintenance of intestinal inflammation, although precise cause-effect relationships have not been established. We assessed spontaneous changes of gut commensal microbiota and toll-like receptors (TLRs)-mediated host-bacterial interactions in a model of indomethacin-induced acute enteritis in rats.

METHODS

Male Spague-Dawley rats, maintained under conventional conditions, were used. Enteritis was induced by systemic indomethacin administration. During the acute phase of inflammation, animals were euthanized and ileal and ceco-colonic changes evaluated. Inflammation was assessed through disease activity parameters (clinical signs, macroscopic/microscopic scores and tissue levels of inflammatory markers). Microbiota (ileal and ceco-colonic) was characterized using fluorescent in situ hybridization (FISH) and analysis of 16s rDNA polymorphism. Host-bacterial interactions were assessed evaluating the ratio of bacterial adherence to the intestinal wall (FISH) and expression of TLRs 2 and 4 (RT-PCR).

RESULTS

After indomethacin, disease activity parameters increased, suggesting an active inflammation. Total bacterial counts were similar in vehicle- or indomethacin-treated animals. However, during inflammation the relative composition of the microbiota was altered. This dysbiotic state was characterized by an increase in the counts of Bacteroides spp., Enterobacteriaceae (in ileum and cecum-colon) and Clostridium spp. (in ileum). Bacterial wall adherence significantly increased during inflammation. In animals with enteritis, TLR-2 and -4 were up-regulated both in the ileum and the ceco-colonic region.

CONCLUSIONS

Gut inflammation implies qualitative changes in GCM, with simultaneous alterations in host-bacterial interactions. These observations further support a potential role for gut microbiota in the pathophysiology of intestinal inflammation.

A simple high performance liquid chromatography method for determination of rebamipide in rat urine

Rebamipide is a mucoprotective agent commonly used to prevent nonsteriodal anti-inflammatory drug-induced gastrointenstinal side effects [1]. Human plasma and urine analysis of rebamipide utilizing high performance liquid chromatography (HPLC) have been reported [2]. Recently, we reported on the plasma levels of rebamipide in presense or absence of celecoxib or diclofenac in rats [3] using a modified HPLC method of detection developed by Jeoung et al. [4]. To tailor the method towards use in urinary rebamipide extraction and analysis, the following modifications were made:•

To compensate for high concentrations of rebamipide found in urine, a new rebamipide stock solution was prepared with a final concentration of 50,000 ng/mL.

•

Rat urine calibration standards were obtained within the range of 50–1000 ng/mL and 1000–50,000 ng/mL.

•

Plasma samples were replaced with urine samples.