Alterations of epithelial permeability by Helicobacter and IL-1beta in vitro: protective effect of rebamipide

BPC 157 Rescued NSAID-cytotoxicity Via Stabilizing Intestinal Permeability and Enhancing Cytoprotection

The stable gastric pentadecapeptide BPC 157 protects stomach cells, maintains gastric integrity against various noxious agents such as alcohol, nonsteroidal anti-inflammatory drugs (NSAIDs), and exerts cytoprotection/ adaptive cytoprotection/organoprotection in other epithelia, that is, skin, liver, pancreas, heart, and brain. Especially BPC 157 counteracts gastric endothelial injury that precedes and induces damage to the gastric epithelium and generalizes "gastric endothelial protection" to protection of the endothelium of other vessels including thrombosis, prolonged bleeding, and thrombocytopenia. In this background, we put the importance of BPC 157 as a possible way of securing GI safety against NSAIDs-induced gastroenteropathy since still unmet medical needs to mitigate NSAIDs-induced cytotoxicity are urgent. Furthermore, gastrointestinal irritants such as physical or mental stress, NSAIDs administration, surfactants destroyer such as bile acids, alcohol can lead to leaky gut syndrome through increasing epithelial permeability. In this review article, we described the potential rescuing actions of BPC 157 against leaky gut syndrome after NSAIDs administration for the first time.

Additive Effects of Rebamipide Plus Proton Pump Inhibitors on the Expression of Tight Junction Proteins in a Rat Model of Gastro-Esophageal Reflux Disease

Background/Aims

The aim of this study was to investigate the effects of rebamipide on tight junction proteins in the esophageal mucosa in a rat model of gastroesophageal reflux disease (GERD).

Methods

GERD was created in rats by tying the proximal stomach. The rats were divided into a control group, a proton pump inhibitor (PPI) group, and a PPI plus rebamipide (PPI+R) group. Pantoprazole (5 mg/kg) was administered intraperitoneally to the PPI and PPI+R groups. An additional dose of rebamipide (100 mg/kg) was administered orally to the PPI+R group. Mucosal erosions, epithelial thickness, and leukocyte infiltration into the esophageal mucosa were measured in isolated esophagi 14 days after the procedure. A Western blot analysis was conducted to measure the expression of claudin-1, -3, and -4.

Results

The mean surface area of mucosal erosions, epithelial thickness, and leukocyte infiltration were lower in the PPI group and the PPI+R group than in the control group. Western blot analysis revealed that the expression of claudin-3 and -4 was significantly higher in the PPI+R group than in the control group.

Conclusions

Rebamipide may exert an additive effect in combination with PPI to modify the tight junction proteins of the esophageal mucosa in a rat model of GERD. This treatment might be associated with the relief of GERD symptoms.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Alkali burn treated with 2% rebamipide ophthalmic suspension: a case report

A 47-year-old man presented at the Ophthalmology Department of Saku City Asama General Hospital complaining of hyperemia and pain after industrial sodium hydroxide (approx. 40% concentration) had entered his left eye. With an epithelial defect of the bulbar and palpebral conjunctiva, ischemia of the inferior third of the limbal conjunctiva, a total corneal epithelial defect and mild corneal stromal opacity, the damage was determined as Roper-Hall grade III. 2% rebamipide ophthalmic suspension, which is used for dry eye disease, was administered 4 times a day followed by conventional treatment for serious alkali injury. The corneal epithelial defect was resolved, and there were no side effects. The effectiveness of 2% rebamipide ophthalmic suspension in both the repair and improvement of the damage in the conjunctival and corneal epithelia, and its anti-inflammatory effect suggest that it may be an effective treatment not only for dry eye disease but also for alkali ocular damage.

Rebamipide increases barrier function and attenuates TNFα-induced barrier disruption and cytokine expression in human corneal epithelial cells

BACKGROUND

Disruption of corneal epithelial barrier function by inflammation may contribute to the development of dry eye. The effects of rebamipide, a drug used for the treatment of dry eye, on barrier function and cytokine expression in a human corneal epithelial (HCE) cell line were examined.

METHODS

Barrier function of HCE cells was evaluated by measurement of transepithelial electrical resistance (TER). The subcellular localisation of the tight junction protein zonula occludens (ZO)-1 was examined by immunofluorescence analysis. The release of cytokines was determined with ELISAs, and the intracellular abundance of cytokine mRNAs was quantitated by reverse transcription and real-time PCR analysis. Degradation of the nuclear factor-κB inhibitor IκBα was detected by immunoblot analysis.

RESULTS

Rebamipide increased TER of HCE cells in a concentration-dependent manner as well as attenuating the loss of TER and the disappearance of ZO-1 from the cell surface induced by tumour necrosis factor α (TNFα). Rebamipide also suppressed TNFα-induced expression of interleukin-6 and interleukin-8 at the mRNA and protein levels and inhibited the TNFα-induced degradation of IκBα.

CONCLUSIONS

The upregulation of barrier function and the anti-inflammatory effects of rebamipide, together with its mucin secretagogue activity, may contribute to the effectiveness of this drug for the treatment of dry eye.

Rebamipide suppresses diclofenac-induced intestinal permeability via mitochondrial protection in mice

AIM: To investigate the protective effect and mechanism of rebamipide on small intestinal permeability induced by diclofenac in mice.

METHODS: Diclofenac (2.5 mg/kg) was administered once daily for 3 d orally. A control group received the vehicle by gavage. Rebamipide (100 mg/kg, 200 mg/kg, 400 mg/kg) was administered intragastrically once a day for 3 d 4 h after diclofenac administration. Intestinal permeability was evaluated by Evans blue and the FITC-dextran method. The ultrastructure of the mucosal barrier was evaluated by transmission electron microscopy (TEM). Mitochondrial function including mitochondrial swelling, mitochondrial membrane potential, mitochondrial nicotinamide adenine dinucleotide-reduced (NADH) levels, succinate dehydrogenase (SDH) and ATPase activities were measured. Small intestinal mucosa was collected for assessment of malondialdehyde (MDA) content and myeloperoxidase (MPO) activity.

RESULTS: Compared with the control group, intestinal permeability was significantly increased in the diclofenac group, which was accompanied by broken tight junctions, and significant increases in MDA content and MPO activity. Rebamipide significantly reduced intestinal permeability, improved inter-cellular tight junctions, and was associated with decreases in intestinal MDA content and MPO activity. At the mitochondrial level, rebamipide increased SDH and ATPase activities, NADH level and decreased mitochondrial swelling.

CONCLUSION: Increased intestinal permeability induced by diclofenac can be attenuated by rebamipide, which partially contributed to the protection of mitochondrial function.

The Role of Th17 in Neuroimmune Disorders: Target for CAM Therapy. Part II

Decades of research went into understanding the role that Th1 autoreactive T-cells play in neuroinflammation. Here we describe another effector population, the IL-17-producing T-helper lineage (Th17), which drives the inflammatory process. Through the recruitment of inflammatory infiltration neutrophils and the activation of matrix metalloproteinases, IL-17, a cytokine secreted by Th17 cells, contributes to blood-brain barrier breakdown and the subsequent attraction of macrophages and monocytes into the nervous system. The entry of cells along with the local production of inflammatory cytokines leads to myelin and axonal damage. This activation of the inflammatory response system is induced by different pathogenic factors, such as gut bacterial endotoxins resulting in progressive neurodegeneration by Th17 cells. Through the understanding of the role of bacterial endotoxins and other pathogenic factors in the induction of autoimmune diseases by Th17 cells, CAM practitioners will be able to design CAM therapies targeting IL-17 activity. Targeted therapy can restore the integrity of the intestinal and blood-brain barriers using probiotics, N-acetyl-cysteine, α-lipoic acid, resveratrol and others for their patients with autoimmunities, in particular those with neuroinflammation and neurodegeneration.

Mechanism of IL-1beta-induced increase in intestinal epithelial tight junction permeability

The IL-1beta-induced increase in intestinal epithelial tight junction (TJ) permeability has been postulated to be an important mechanism contributing to intestinal inflammation of Crohn's disease and other inflammatory conditions of the gut. The intracellular and molecular mechanisms that mediate the IL-1beta-induced increase in intestinal TJ permeability remain unclear. The purpose of this study was to elucidate the mechanisms that mediate the IL-1beta-induced increase in intestinal TJ permeability. Specifically, the role of myosin L chain kinase (MLCK) was investigated. IL-1beta caused a progressive increase in MLCK protein expression. The time course of IL-1beta-induced increase in MLCK level correlated linearly with increase in Caco-2 TJ permeability. Inhibition of the IL-1beta-induced increase in MLCK protein expression prevented the increase in Caco-2 TJ permeability. Inhibition of the IL-1beta-induced increase in MLCK activity also prevented the increase in Caco-2 TJ permeability. Additionally, knock-down of MLCK protein expression by small interference RNA prevented the IL-1beta-induced increase in Caco-2 TJ permeability. The IL-1beta-induced increase in MLCK protein expression was preceded by an increase in MLCK mRNA expression. The IL-1beta-induced increase in MLCK mRNA transcription and subsequent increase in MLCK protein expression and Caco-2 TJ permeability was mediated by activation of NF-kappaB. In conclusion, our data indicate that the IL-1beta increase in Caco-2 TJ permeability was mediated by an increase in MLCK expression and activity. Our findings also indicate that the IL-1beta-induced increase in MLCK protein expression and Caco-2 TJ permeability was mediated by an NF-kappaB-dependent increase in MLCK gene transcription.

Rebamipide, anti-gastric ulcer drug, up-regulates the induction of iNOS in proinflammatory cytokine-stimulated hepatocytes

Nitric oxide (NO) generated from inducible NO synthase (iNOS) during hepatic injury has been reported to contribute to cytoprotection or cellular damage. Rebamipide, anti-gastric ulcer drug, has protective effects in a variety of tissue and organ injury. However, it remains unknown whether rebamipide is involved in the regulation of iNOS gene expression under pathological conditions. We examined whether rebamipide influences the induction of iNOS in hepatocytes exposed to pro-inflammatory cytokine. Primary cultured rat hepatocytes were treated with interleukin (IL)-1beta in the presence or absence of rebamipide. Pretreatment of cells with rebamipide resulted in up-regulation of iNOS induction by IL-1beta, followed by increased NO production. Rebamipide enhanced the degradation of IkappaBalpha and the activation of NF-kappaB. Further, rebamipide super-induced the up-regulation of type I IL-1 receptor (IL-1RI), which is essential for iNOS induction in addition to the IkappaB/NF-kappaB pathway. Transfection experiments revealed that rebamipide increased the transactivation of iNOS promoter and the stability of iNOS mRNA. In the latter, rebamipide increased the antisense-transcript corresponding to the 3'-UTR of iNOS mRNA, which stabilizes iNOS mRNA by interacting with the 3'-UTR and RNA-binding proteins. These findings demonstrate that rebamipide up-regulates iNOS by iNOS promoter activation through NF-kappaB, and by its mRNA stabilization presumably through the super-induction of IL-1RI and antisense-transcript. Rebamipide may contribute to a novel potentiated treatment in liver injuries.

Effect of rebamipide on the colonic barrier in interleukin-10-deficient mice

Our aim was to study the effect of a mucosal protective agent, rebamipide, on the colonic barrier and the immune response in colitis-prone interleukin-10-deficient (IL-10-/-) C57BL/6 mice infected with Helicobacter hepaticus. After sacrifice, in all mice, control, or previously infected with H. hepaticus, or previously infected and treated with rebamipide enema, a histological examination of colonic samples was performed, intestinal permeability was studied in Ussing chamber, and mesenteric lymph node proliferation and cytokine secretion were measured. Mice treated with rebamipide presented a reinforcement of the distal colonic epithelial barrier, an increase of mesenteric lymph node cells proliferation, and of IFNgamma and IL-12 secretion. These results indicate that in IL-10-/- mice with mild colitis, rectally administered rebamipide reinforces the distal colonic barrier and has a slight Th1 immuno-stimulatory effect on mesenteric lymph node cells. These properties could be helpful in the management of some inflammatory bowel diseases.

Rebamipide enemas-new effective treatment for patients with corticosteroid dependent or resistant ulcerative colitis

In this study we investigated the effect of rebamipide enema in patients with steroid-resistant and/or dependent ulcerative colitis. Rebamipide enemas were administered twice daily for a 12-week period; this treatment was further continued longer in patients who requested this. Disease activity index as reflecting the clinical condition and endoscopic index with histological grading were determined before and after the treatment period. Nine of 11 (81.8%) patients on 12-week treatment with rebamipide approved and were classified as colitis in remission. Moreover, seven of 11 patients requested long-term medication, the longest medication term being 80 weeks. These results medicated that rebamipide enemas may be effective in patients with steroid-resistant and/or dependent ulcerative colitis.

The role of enterocytes in the intestinal barrier function and antigen uptake

The intestinal epithelium is a critical interface between the organism and its environment. The cell polarity and structural properties of the enterocytes, limiting the amount of antigen reaching the epithelial surface, form the basis of the integrity of the epithelium. However, apart from their participation in digestive processes, the enterocytes perform more than just a passive barrier function. The resistance of the tight junctions regulates the paracellular transport of antigens. Furthermore, the enterocytes take up and process antigens, involving two functional pathways. In the major pathway, enzymes in the lysosomes degrade the antigens. In the minor direct transcytotic pathway, the antigens are not degraded and are released into the interstitial space. Moreover, the enterocytes can present processed antigens directly to T cells and are often directly involved in immune processes. In inflammatory conditions, the properties of the epithelial barrier and the outcome of the immune response to luminal antigens can be changed.

Dual infection with Helicobacter bilis and Helicobacter hepaticus in p-glycoprotein-deficient mdr1a-/- mice results in colitis that progresses to dysplasia

Patients with inflammatory bowel disease (IBD) are at increased risk for developing high-grade dysplasia and colorectal cancer. Animal IBD models that develop dysplasia and neoplasia may help elucidate the link between inflammation and colorectal cancer. Mdr1a-/- mice lack the membrane efflux pump p-glycoprotein and spontaneously develop IBD that can be modulated by infection with Helicobacter sp: H. bilis accelerates development of colitis while H. hepaticus delays disease. In this study, we determined if H. hepaticus infection could prevent H. bilis-induced colitis. Unexpectedly, a proportion of dual-infected mdr1a-/- mice showed IBD with foci of low- to high-grade dysplasia. A group of dual-infected mdr1a-/- animals were maintained long term (39 weeks) by intermittent feeding of medicated wafers to model chronic and relapsing disease. These mice showed a higher frequency of high-grade crypt dysplasia, including invasive adenocarcinoma, possibly because H. hepaticus, in delaying the development of colitis, allows time for transformation of epithelial cells. Colonic epithelial preparations from co-infected mice showed increased expression of c-myc (5- to 12-fold) and interleukin-1alpha/beta (600-fold) by real-time polymerase chain reaction relative to uninfected wild-type and mdr1a-/- animals. This animal model may have particular relevance to human IBD and colorectal cancer because certain human MDR1 polymorphisms have been linked to ulcerative colitis and increased risk for colorectal cancer.

Neutrophils augment recovery of porcine ischemia-injured ileal mucosa by an IL-1beta- and COX-2-dependent mechanism

Polymorphonuclear neutrophils (PMNs) play a critical role in intestinal mucosal injury and repair. To study effects of PMNs on acutely injured mucosa, we applied PMNs isolated from circulation or peritoneal fluid from animals with chemically induced peritonitis to ischemia-injured porcine ileal mucosa. In preliminary experiments, PMNs enhanced recovery of transepithelial electrical resistance (TER), and this action was inhibited by pretreatment with the nonselective cyclooxygenase (COX) inhibitor indomethacin. Because COX-2 is upregulated by inflammatory mediators such as IL-1beta, which is released by PMNs, we postulated that PMNs enhance recovery of ischemia-injured mucosa by a pathway involving IL-1beta and COX-2. Application of 5 x 10(6) PMNs to the serosal surface of ischemia-injured mucosa significantly enhanced recovery of TER (P < 0.05), an effect that was inhibited by the selective COX-2 inhibitor NS-398 (5 microM) and by an IL-1beta receptor antagonist (0.1 mg/ml). Addition of 10 ng/ml IL-1beta to the serosal surface of injured tissues caused a significant increase in TER (P < 0.05) that was inhibited by pretreatment with NS-398. Western blot analysis of mucosal homogenates revealed dramatic upregulation of COX-2 in response to IL-1beta or peritoneal PMNs, and the latter was inhibited by an IL-1beta receptor antagonist. Real-time PCR revealed that increased mRNA COX-2 expression preceded increased COX-2 protein expression in response to IL-1beta. We concluded that PMNs augment recovery of TER in ischemia-injured ileal mucosa via IL-1beta-dependent upregulation of COX-2.

Vagal afferent input from the acid-challenged rat stomach to the brainstem: Enhancement by interleukin-1β

Exposure of the gastric mucosa to back-diffusing concentrations of HCl (0.25 M, pH 0.51) stimulates vagal afferent input to the brainstem. Here we have examined whether pretreatment of rats with the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha causes sensitization of vagal afferent pathways to HCl. Rats were pretreated i.p. with interleukin-1beta, tumor necrosis factor-alpha (10 microg/kg) or their vehicle (sterile saline) 24, 48 and 96 h before intragastric administration of HCl (0.25 M, 1 ml/100 g). Activation of neurons in the nucleus tractus solitarii was visualized by c-Fos immunohistochemistry 2 h after the HCl challenge. I.p. administration of interleukin-1beta and tumor necrosis factor-alpha alone induced c-Fos in the brainstem, an effect that was gone after 24 h. At this time, however, the effect of HCl to cause expression of c-Fos in the nucleus tractus solitarii was significantly enhanced by pretreatment with interleukin-1beta and tumor necrosis factor-alpha. The sensitizing effect of i.p.-administered interleukin-1beta was sustained for more than 48 h and prevented by the interleukin-1 receptor antagonist anakinra. Intracisternal administration of interleukin-1beta and tumor necrosis factor-alpha (100 ng) failed to amplify the HCl-evoked expression of c-Fos in the brainstem. These results show that peripheral administration of the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha induces prolonged sensitization of vagal afferent pathways to gastric HCl challenge. This effect seems to arise from a peripheral action on vagal afferents and may be of relevance to gastric chemonociception.

Gastric Helicobacter infection inhibits development of oral tolerance to food antigens in mice

The increase in the transcellular passage of intact antigens across the digestive epithelium infected with Helicobacter pylori may interfere with the regulation of mucosal immune responses. The aim of this work was to study the capacity of Helicobacter infection to inhibit the development of oral tolerance or to promote allergic sensitization and the capacity of a gastro-protective agent, rebamipide, to interfere with these processes in mice. Oral tolerance to ovalbumin (OVA) was studied in 48 C3H/He 4-week-old mice divided into four groups: (i) OVA-sensitized mice; (ii) OVA-"tolerized" mice (that is, mice that were rendered immunologically tolerant); (iii) H. felis-infected, OVA-tolerized mice; (iv) and H. felis-infected, OVA-tolerized, rebamipide-treated mice. Oral sensitization to hen egg lysozyme (HEL) was studied in 48 mice divided into four groups: (i) controls; (ii) HEL-sensitized mice; (iii) H. felis-infected, HEL-sensitized mice; and (iv) H. felis-infected, HEL-sensitized, rebamipide-treated mice. Specific anti-OVA or anti-HEL immunoglobulin E (IgE) and IgG1/IgG2a serum titers were measured by enzyme-linked immunosorbent assay. Additionally, the capacity of rebamipide to interfere with antigen presentation and T-cell activation in vitro, as well as absorption of rebamipide across the epithelial monolayer, was tested. H. felis infection led to the inhibition of oral tolerance to OVA, but rebamipide prevented this inhibitive effect of H. felis. H. felis infection did not enhance the sensitization to HEL, but rebamipide inhibited the development of this sensitization. Moreover, rebamipide inhibited in a dose-dependent manner antigen presentation and T-cell activation in vitro and was shown to be able to cross the epithelium at a concentration capable of inducing this inhibitory effect. We conclude that H. felis can inhibit the development of oral tolerance to OVA in mice and that this inhibition is prevented by rebamipide.

Review article: rebamipide and the digestive epithelial barrier

Rebamipide exerts a positive effect on the digestive epithelial barrier by reinforcing its integrity in normal and in inflammatory conditions, and by normalizing the macromolecular transport across this barrier, increased by Helicobacter infection. Moreover, in mice, rebamipide is capable of diminishing allergic sensitization and of counteracting the inhibitory effect of Helicobacter pylori on oral tolerance to dietary antigens. These properties of rebamipide could explain its anti-inflammatory activity with respect to the digestive mucosa and could provide protection against allergic sensitization to foreign antigens in susceptible individuals.

Review article: the role of rebamipide in the management of inflammatory disease of the gastrointestinal tract

Rebamipide stimulates the generation of endogenous prostaglandins in the gastric mucosa and is reported to accelerate ulcer healing. This review discusses whether rebamipide can prevent Helicobacter pylori infection, reduce inflammation, accelerate healing after eradication, promote ulcer healing, and prevent progression of preneoplastic lesions. Furthermore, we evaluate its usefulness in other inflammatory conditions of the gastrointestinal tract. We conclude that rebamipide is an important candidate for long-term suppression of gastro-intestinal inflammation, particularly if reducing the complications of H. pylori infection without eradicating the organism becomes accepted. If its ability to accelerate mucosal normalization is confirmed, rebamipide could be added to eradication regimens. Little information exists on whether such therapy could help limit the development of pre-neoplastic lesions. In light of the dearth of effective drugs to control inflammation in idiopathic inflammatory bowel disease, the potential of any promising new and safe compound deserves to be fully explored. The next step is to devise a targeted plan of translational research, so that results from the bench may be used to design rigorously controlled international clinical trials.

In-vitro transfer of nitazoxanide across the intestinal epithelial barrier

Nitazoxanide is a thiazolide compound that exhibits antimicrobial properties against helminths, protozoa, anaerobic bacteria and also Helicobacter pylori. The mucosal diffusion of this new drug has not been studied. The aim of this study was to examine the transport of radiolabelled nitazoxanide across the epithelial barrier according to the mode (mucosal or serosal) of drug administration. HT29-19A intestinal epithelial cells, grown as monolayers on microporous filters, were used as an epithelial model. In a short-term (100 min) transport study, the apical to basal and the basal to apical transport of nitazoxanide across the monolayers was studied in an Ussing chamber. In a long-term (24 h) study, the transport of the drug and its intracellular accumulation were studied in filter-grown epithelial monolayers kept in culture plates. In the short-term transport study, both the apical and basal fluxes achieved a steady state after 70 min and there was no significant difference between the apical to basal (3991+/-1001 ng h(-1) cm(-2)) and the basal to apical (4246+/-856 ng h(-1) cm(-2)) nitazoxanide fluxes. In the long-term transport study, after apical or basal drug application, a gradual increase in the drug concentration in the opposite compartment was noted, which reached similar values for apical and basal fluxes (2497+/-125 and 2309+/-81 ng mL(-1), respectively) after 24 h. Moreover, a rapid, although transitory, intracellular accumulation of nitazoxanide was observed at 10 min after apical (299+/-25 ng/10(6) cells) and basal (124+/-10 ng/10(6) cells) drug application, but decreased thereafter. There is an important transepithelial transport of nitazoxanide across the digestive epithelial monolayer with a rapid intracellular accumulation of the drug. No difference between the apical to basal and basal to apical fluxes of the drug was observed, suggesting that both topical and systemic modes of action of this antibiotic are successful.

Omeprazole increases permeability across isolated rat gastric mucosa pre-treated with an acid secretagogue

Triple therapy using proton-pump inhibitors (PPIs) in combination with oral antibiotics for the treatment of Helicobacter pylori-associated gastritis has shown increased efficacy for reasons that are still poorly understood. Possible explanations include a direct antibacterial effect of the PPIs or a PPI-mediated increase in bacterial susceptibility to antibiotics. Using an in-vitro model of rat gastric mucosa, we examined fluxes of a radiolabelled marker molecule through the interepithelial tight junctions under normal conditions and under the influence of an acid secretagogue (50 microM histamine) and a PPI (100 microM omeprazole). Paracellular fluxes of the radiolabel (represented by calculation of apparent permeability coefficients) were linear over 2 h. Fluxes of the marker increased significantly after treatment with histamine followed by omeprazole, but were unaltered in paired preparations exposed to the same drugs given in reverse order. Enhancements in paracellular permeability were mirrored in separate experiments using a detergent (Triton X-100), a bile salt (deoxycholate) and an agent that disrupts the cytoskeleton (cytochalasin D) to interfere with tight junctional integrity. The results suggest that exposure of acid-secreting gastric mucosa to omeprazole widens the interepithelial spacing in a manner that may facilitate enhanced macromolecular transport. Increases in antibiotic delivery from the blood to the gastric lumen via such a mechanism may account for the greater eradication rates observed with PPI-based triple therapy in H. pylori-associated gastritis.