Effect of prostaglandin on indomethacin-induced increased intestinal permeability in man

NSAID enteropathy: could probiotics prevent it?

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used drugs in the world; nevertheless, about 50-70% of patients on long-term NSAIDs develop small intestine injury, namely NSAID enteropathy, sometimes with serious outcomes. No medications with proven efficacy are yet available to prevent NSAID enteropathy. A series of therapeutic strategies targeting the different mechanisms involved in small bowel injury have been investigated, but without definitive results. Intestinal bacteria and their degradation products are essential for the development of NSAID-induced small bowel lesions, because "germ-free" animals were found to be resistant to indomethacin injuries. Therefore, it has been suggested that modulating the intestinal flora, for example by using probiotics, could protect against NSAID enteropathy. In this work, we reviewed the main therapeutic strategies for NSAID enteropathy, in particular analyzing the available studies relating to the eventual protective role of probiotics. We found that results are not all concordant; nevertheless, the more recent studies provide better understanding about pathogenetic mechanisms involved in small intestinal injury and the role of probiotics, and show encouraging results. Larger and well-designed studies should be performed to evaluate the actual role of probiotics in NSAID enteropathy, the eventual differences among probiotic strains, dose-responses, and optimal duration of therapy.

Mechanisms, prevention and clinical implications of nonsteroidal anti-inflammatory drug-enteropathy

This article reviews the latest developments in understanding the pathogenesis, detection and treatment of small intestinal damage and bleeding caused by nonsteroidal anti-inflammatory drugs (NSAIDs). With improvements in the detection of NSAID-induced damage in the small intestine, it is now clear that this injury and the associated bleeding occurs more frequently than that occurring in the stomach and duodenum, and can also be regarded as more dangerous. However, there are no proven-effective therapies for NSAID-enteropathy, and detection remains a challenge, particularly because of the poor correlation between tissue injury and symptoms. Moreover, recent studies suggest that commonly used drugs for protecting the upper gastrointestinal tract (i.e., proton pump inhibitors) can significantly worsen NSAID-induced damage in the small intestine. The pathogenesis of NSAID-enteropathy is complex, but studies in animal models are shedding light on the key factors that contribute to ulceration and bleeding, and are providing clues to the development of effective therapies and prevention strategies. Novel NSAIDs that do not cause small intestinal damage in animal models offer hope for a solution to this serious adverse effect of one of the most widely used classes of drugs.

Exacerbation of indomethacin-induced small intestinal injuries in Reg I-knockout mice

Nonsteroidal anti-inflammatory drug (NSAID)-induced small intestinal injuries are serious clinical events and a successful therapeutic strategy is difficult. Regenerating gene (Reg) I protein functions as a regulator of cell proliferation and maintains intercellular integrity in the small intestine. The aim of this study was to evaluate the role of Reg I in NSAID-induced small intestinal injuries. First, to examine the effect of Reg I deficiency on such injuries, indomethacin, a widely used NSAID, was injected subcutaneously into 10-wk-old male Reg I-knockout (Reg I(-/-)) and wild-type (Reg I(+/+)) mice twice with an interval of 24 h, after which the mice were euthanized. Small intestinal injuries were assessed by gross findings, histopathology, and contents of IL-1beta and MPO in the experimental tissues. Next, we investigated the therapeutic potential of Reg I in indomethacin-induced small intestinal injuries. Recombinant Reg I protein (rReg I) was administered to 10-wk-old male ICR mice, then indomethacin was administered 6 h using the same protocol as noted above, after which small intestinal injuries were assessed after euthanasia. Our results showed that Reg I(-/-) mice had a greater number of severe small intestinal lesions after indomethacin administration. Histological examinations of the small intestines from those mice revealed deep ulcers with prominent inflammatory cell infiltration, whereas the mucosal content of proinflammatory agents was also significantly increased. In addition, rReg I administration inhibited indomethacin-induced small intestinal injuries in ICR mice. In conclusion, Reg I may be useful as a therapeutic agent in NSAID-induced small intestinal injuries.

Assessment and prevention of gastrointestinal toxicity of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for analgesic, anti-inflammatory and, in the case of aspirin, for anti-thrombotic actions. The serious gastrointestinal side-effects associated with these drugs are of concern and pose a significant obstacle to their use. This review discusses the pathogenic mechanisms by which the conventional acidic NSAIDs induce gastrointestinal toxicity, with particular emphasis on non-prostaglandin effects. Methods of assessment of NSAID-induced enteropathy are reviewed, with particular emphasis on the use of functional measurement of NSAID-induced changes in the gastrointestinal tract. The advances in our knowledge of the pathogenesis of these effects have resulted in the development of a range of novel NSAIDs. Where functional assessment of the effects of NSAIDs has been employed, it appears to be more useful as an indicator of early-stage changes rather than a predictor of the effects of long-term NSAID exposure. Successful pharmaceutical strategies now offer considerable promise for reducing the severity of NSAID damage to the gastrointestinal tract. The utility of intestinal permeability measurements for selection and assessment of these strategies is discussed.

Intestinal permeability in the pathogenesis of NSAID-induced enteropathy

BACKGROUND

The pathogenesis of nonsteroidal antiinflammatory drug (NSAID)-induced small bowel disease suggests that increased intestinal permeability is the central mechanism that translates biochemical damage to tissue damage. The purpose of this review is to summarize studies on the effect of NSAIDs to increase intestinal permeability in humans and methods for limiting this effect.

METHODS

A Medline search was made for papers that described measurements of increased intestinal permeability in humans.

RESULTS

Virtually all studies agree that all conventional NSAIDs increase intestinal permeability in the human within 24 h of ingestion and that this is equally evident when they are taken long term. Various methods have been tried to limit the damage. The most promising agents are coadministration of synthetic prostaglandins, micronutrients, pre-NSAIDs, and COX-2 selective agents. However, their efficacy in preventing the development of NSAID enteropathy in the long term has not been studied in detail, and, in the case of COX-2 selective agents, small bowel damage is comparable to that which is seen with conventional NSAIDs.

CONCLUSIONS

NSAID enteropathy is associated with significant morbidity and occasionally mortality. There are no proven effective ways of preventing this damage. Because increased intestinal permeability appears to be a central mechanism in the pathogenesis of NSAID enteropathy, it becomes a potential therapeutic target for prevention. At present there are a number of ways to limit the increased permeability, but additional studies are required to assess if this approach reduces the prevalence and severity of NSAID enteropathy.

Nonsteroidal antiinflammatory drugs and the small intestine

PURPOSE OF REVIEW

The small intestine may be a more common site for nonsteroidal antiinflammatory drug toxicity than the gastroduodenal mucosa. Two-thirds of regular nonsteroidal antiinflammatory drug users develop subclinical small bowel enteropathy. This review highlights this emerging issue in patients requiring antiinflammatory drugs.

RECENT FINDINGS

Nonsteroidal antiinflammatory drug enteropathy is a stepwise process involving direct mucosal toxicity, mitochondrial damage, breakdown of intercellular integrity, enterohepatic recirculation and neutrophil activation by luminal contents including bacteria. Unlike upper gastrointestinal toxicity, cyclooxygenase-mediated mechanisms are probably less important. Newer imaging modalities such as capsule endoscopy studies demonstrate nonsteroidal antiinflammatory drug-induced small bowel erosions, but the clinical implications are unclear.

SUMMARY

Nonsteroidal antiinflammatory drug toxicity to the small intestine is common. Useful research tools have been developed to indirectly measure intestinal inflammation and permeability, but these are not generally available to the clinician, although enteroscopy and capsule endoscopy can be illuminating. Anaemia or hypoalbuminaemia are useful indications of nonsteroidal antiinflammatory drug enteropathy. Cessation of the drug would be the preferred option, alternatively there are experimental data to support the use of sulphasalazine and metronidazole. Animal models are unravelling new mechanisms for mucosal toxicity beyond the cyclooxygenase model, including mucosal oxidative injury and nitric oxide mediated pathways.

Role of bile in pathogenesis of indomethacin-induced enteropathy

Ingestion of non-steroidal anti-inflammatory drugs (NSAIDs) causes an enteropathy. The pathogenesis involves biochemical initiation of intestinal mucosal damage due to NSAID-induced inhibition of cyclooxygenase and the topical effects of these drugs. These effects lead to increased intestinal permeability and inflammation. Luminal bile acids play a controversial role in the damage produced by these drugs. The aim of this study was to determine the role of bile in producing the enteropathy caused by indomethacin, an NSAID commonly used in toxicity studies. Sprague-Dawley rats were subjected to bile duct ligation. Twenty-four hours later, they were dosed with indomethacin. Intestinal permeability ((51)Cr-EDTA) and inflammation (faecal calprotectin) were measured in the animals at various time periods after the dose. Intestinal permeability was significantly higher in rats 1-6 h after dosing with indomethacin, but not at 24-29 h or day 4, when compared with corresponding values for control animals. Excretion of faecal calprotectin was elevated in the indomethacin-treated rats. The drug-treated animals showed no evidence of ulceration when they were sacrificed 29 h or a week after the dose of indomethacin. Bile acids per se did not affect intestinal permeability or faecal excretion of calprotectin, when given along with indomethacin or its vehicle. We conclude that macroscopic small bowel damage does not occur with indomethacin if bile is excluded, despite the induction of permeability and inflammation. This study highlights the importance of luminal factors, such as bile, in producing indomethacin-induced ulceration in the rat small intestine.

NSAIDs, coxibs, and the intestine

Nonsteroidal anti-inflammatory drugs (NSAIDs) are capable of damaging the whole gastrointestinal tract. Small and large intestinal injuries manifest as acute changes in permeability with endoscopic erosions, chronic erosions and ulcers, diaphragms in the small bowel, and an increase in small and large bowel complications including perforation and diverticular bleeding. It is quite likely, though not proven, that such lesions contribute to anemia in patients taking them. A growing body of data shows that selective inhibitors of the cyclooxygenase-2 enzyme have much reduced toxicity in this respect. In addition, NSAID use has also been associated with development or relapse of ulcerative colitis. Whether the same is true of Crohn's disease, particularly of the small bowel, is less clear. An important point is that there are data that suggest that paracetamol may also not be devoid of toxicity. This makes use of selective cyclooxygenase-2 inhibitors attractive. There have been a number of reports of their use in inflammatory bowel disease. However, many of these have principally involved Crohn's disease and there have not been enough to be clear whether they affect the influence of relapse of ulcerative colitis.

Systematic review: the lower gastrointestinal adverse effects of non-steroidal anti-inflammatory drugs

BACKGROUND

Lower gastrointestinal effects of non-steroidal anti-inflammatory drugs (NSAIDs) are much more poorly characterized than upper gastrointestinal effects.

AIM

To determine if NSAIDs increase lower gastrointestinal adverse effects and if the risk with non-selective NSAIDs is greater than with cyclooxygenase-2-selective inhibitors (coxibs).

METHODS

Computerized databases were searched to identify studies of NSAID use reporting on lower gastrointestinal integrity (e.g. permeability), visualization (e.g. erosions, ulcers) and clinical events.

RESULTS

Designs in 47 studies were randomized (18), case-control (14), cohort (eight) and before-after (seven). Non-selective-NSAIDs had significantly more adverse effects vs. no NSAIDs in 20 of 22 lower gastrointestinal integrity studies, five of seven visualization studies, seven of 11 bleeding studies (OR: 1.9-18.4 in case-control studies), two of two perforation studies (OR: 2.5-8.1) and five of seven diverticular disease studies (OR: 1.5-11.2). Coxibs had significantly less effect vs. non-selective-NSAIDs in three of four integrity studies, one endoscopic study (RR mucosal breaks: 0.3), and two randomized studies (RR lower gastrointestinal clinical events: 0.5; haematochezia: 0.4).

CONCLUSIONS

An increase in lower gastrointestinal injury and clinical events with non-selective-NSAIDs appears relatively consistent across the heterogeneous collection of trials. Coxibs are associated with lower rates of lower gastrointestinal injury than non-selective-NSAIDs. More high-quality trials are warranted to more precisely estimate the effects of non-selective-NSAIDs and coxibs on the lower gastrointestinal tract.

Indomethacin disrupts the protective effect of phosphatidylcholine against bile salt-induced ileal mucosa injury

BACKGROUND

Indomethacin (Indo) exerts local toxic effects on small intestinal mucosa, possibly in association with hydrophobic bile salts. We investigated the potential toxic effects of Indo on ileal mucosa and the role of phosphatidylcholine (PC).

MATERIALS AND METHODS

Transmucosal resistance and Na-fluorescein permeability of ileal mucosa segments from female Wistar rats were determined in Ussing chambers during a 30-min incubation with model systems containing: control-buffer, taurodeoxycholate (TDC), Indo, TDC-Indo, TDC-PC, or TDC-PC-Indo. Decrease of resistance and increase of permeability were considered as parameters for mucosal injury. After incubation in Ussing chambers, the histopathology was examined to quantify the extent of mucosal injury. Also, in CaCo-2 cells, LDH-release was determined as a measure of cytotoxicity, after incubation with various model systems.

RESULTS

Decrease of resistance and increase of permeability were highest in systems containing TDC-Indo (P < 0.01). Phosphatidylcholine protected against the cytotoxic effects of TDC in absence of Indo only. Extent of mucosal injury by histological examination was also highest in systems containing TDC-Indo (P = 0.006). Again, PC exhibited protective effects in absence of Indo only. The LDH-release by CaCo2-cells was strongest in TDC-Indo systems (P < 0.001).

CONCLUSIONS

Indomethacin disrupts protective effects of PC against bile salt-induced ileal mucosa injury. This finding is relevant for small intestinal injury induced by non-steroidal anti-inflammatory drugs.

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Paradox of simultaneous intestinal ischaemia and hyperaemia in inflammatory bowel disease

This review has focused on evidence regarding intestinal perfusion of inflammatory bowel disease (IBD). Basic investigation has defined an altered microvascular anatomy in the affected IBD bowel, which corresponds with diminished mucosal perfusion in the setting of chronic, long-standing inflammation. Diminished perfusion is linked to impaired wound healing, and may contribute to the continued refractory mucosal damage, which characterizes IBD. Alterations in vascular anatomy and physiology in IBD suggests additional possible mechanisms by which micro-vessels may contribute to the initiation and perpetuation of IBD. This begs the following questions: will angiogenesis within the gut lead to sustained inflammation, does the growing vasculature generate factors that transform the surrounding tissue and does angiogenesis generate vascular anastomosis within the gut, with shunting of blood away from the mucosal surface, impairment of metabolism and potentiation of gut damage? Further studies are required to define the mechanisms that underlie the vascular dysfunction and its role in pathophysiology of IBD.

Nonsteroidal antiinflammatory drugs and the small intestine

PURPOSE OF REVIEW

The small intestine is a more common site for nonsteroidal antiinflammatory drug (NSAID) toxicity than the well-recognized effects on the stomach and duodenum. Although NSAID strictures and perforation are rare, two thirds of regular NSAID users may be prone to small bowel enteropathy. This review highlights this emerging issue in patients requiring antiinflammatory drugs.

RECENT FINDINGS

NSAID enteropathy is a stepwise process involving direct mucosal toxicity, mitochondrial damage, breakdown of intercellular integrity, enterohepatic recirculation, and neutrophil activation by luminal contents, including bacteria. Unlike upper gastrointestinal toxicity, cyclooxygenase-mediated mechanisms are probably less important. Newer imaging modalities such as capsule endoscopy studies suggest that small bowel erosions may be common in nonselective NSAID users. Sulfasalazine and metronidazole may prove to be useful, therapeutic options for patients who cannot cease their NSAIDs.

SUMMARY

NSAID toxicity to the small intestine is common. Useful research tools have been developed to measure intestinal inflammation and permeability indirectly, but these are not generally available to the clinician, although enteroscopy and capsule endoscopy may be helpful. Anemia or hypoalbuminemia are useful clues to NSAID enteropathy. Cessation of the drug is ideal; otherwise, there is experimental data to support the use of sulfasalazine and metronidazole. Animal models are unraveling new mechanisms for mucosal toxicity beyond the cyclooxygenase model.

Determining small bowel integrity following drug treatment

Intestinal integrity is maintained by a delicate balance between mucosal defence and luminal aggressors that cause damage if exposed to the mucosa. The intestinal barrier function appears to be the gatekeeper for controlling this balance. It is becoming increasingly clear that if the intestinal barrier is disrupted the consequences are low grade intestinal inflammation which carry with it the risk of significant blood and protein loss both of which may cause clinical management problems. We review the strength and weaknesses of methods for assessing small bowel function that are useful for assessing drug-induced intestinal toxicity. There are a number of imaging methods for assessing intestinal integrity but these do not provide functional information. Intestinal permeability measurements have been optimized for specificity and there are now ways of measuring intestinal permeability regionally, but marker analyses continue to be cumbersome. Recent developments of faecal inflammatory markers make it a matter of routine to assess this in any routine chemical pathology laboratory. Bleeding, protein loss and other complications of inflammation can also be measured with good specificity, but again the methods are cumbersome. Using a combination of functional and imaging techniques it is now possible to characterize and define with precision, the small bowel side-effects of drugs, the best example being the small bowel side-effects of nonsteroidal anti-inflammatory drugs (NSAIDs).

Gastrointestinal mucosal injury following repeated daily oral administration of conventional formulations of indometacin and other non-steroidal anti-inflammatory drugs to pigs: a model for human gastrointestinal disease

Non-steroidal anti-inflammatory drugs (NSAIDs) vary in their propensity to cause damage in different regions of the gastrointestinal (GI) tract in laboratory animals and humans. This may depend on the type of drug formulation as well as the intrinsic pharmacological properties of the drugs. The purpose of this study was to determine the effects of NSAIDs, with cyclooxygenase 1 and 2 inhibitory activity but with different potency as inhibitors of prostaglandin production, when given orally as tablet/capsule formulations of NSAIDs for 10 days to pigs, a species that has close resemblance in structure and function of the tract to that in humans. Three capsule or tablet formulations of NSAIDs were given orally to pigs for 10 days. GI bleeding was measured by determination of radioactive iron in the faeces from (59)Fe-pre-labelled red blood cells. The blood loss was compared with the pathological changes in the GI mucosa observed at autopsy, mucosal myeloperoxidase (MPO) activity as an index of leucocyte infiltration, and plasma and mucosal concentrations of the drugs at termination assayed by high-performance liquid chromatography. Mucosal damage and bleeding varied according to the type of NSAID. Gastroduodenal ulcers and lesions occurred with the cyclooxygenase inhibitors indometacin (indomethacin) (Indocid capsules 10 or 5 mg kg(-1) day(-1) b.i.d.), aspirin (USP tablets 150 mg kg(-1) day(-1) b.i.d) and naproxen (Apotex tablets 50 or 75 mg kg(-1) day(-1) b.i.d.), and there was an increase in the cumulative (i.e. 10-day) blood loss at higher doses of indometacin and naproxen, and with aspirin. There was no statistically significant increase in gastric or intestinal mucosal MPO activity in the non-damaged mucosa with these drugs and this was confirmed by histological observations in non-lesioned areas of the mucosa. Indometacin produced focal ulcers in the caecum but this was not observed with the other drugs. All the NSAIDs produced significant blood loss coincident with gastric ulceration but no increase in gastric or intestinal MPO activity. Plasma concentrations of the non-aspirin NSAIDs were within the range encountered therapeutically in humans. The mucosal concentrations of indometacin in the gastric and intestinal mucosa correlated with mucosal injury. These findings show that: (i) NSAIDs vary in their propensity to produce mucosal injury in different regions of the GI tract according to their pharmacological properties and formulation; (ii) mucosal injury from some NSAIDs may not directly relate to blood loss at low doses of NSAIDs and this may depend on inhibition of platelet aggregation; and (iii) the occurrence of caecal ulcers uniquely observed with indometacin treatment may be relevant to the development of intestinal pathology (e.g. diaphragm-like structures) seen occasionally in humans. These results suggest that the pig model employed in the present studies may be useful for investigations of GI damage from NSAID tablets/capsules, especially in regions that are generally inaccessible to routine endoscopic investigations in humans (e.g. the proximal regions of the large intestine).

In vivo influence of nicotine on human basal and NSAID-induced gut barrier function

BACKGROUND

Smoking reduces the non-steroidal anti-inflammatory drug (NSAID)-induced small intestinal permeability increase in healthy people. It also affects inflammatory bowel disease that is associated with a disturbed gut barrier function. To assess the role of nicotine on barrier function, its influence on basal and NSAID-induced intestinal permeability was studied in healthy volunteers.

METHODS

Thirty-one healthy non-smoker subjects performed permeability tests with 51Cr-EDTA and sugar markers (sucrose, lactulose, mannitol, sucralose) before and during 2 weeks of nicotine patch application, and with and without indomethacin intake, respectively. Since smoking has been described as affecting motility, transit measurements were also done with the sodium[13C]-octanoate and lactose-[13C]-ureide breath tests before and during nicotine exposure. Correlations between permeability markers were checked and the influence of gastrointestinal transit was assessed.

RESULTS

Nicotine did not affect barrier function in vivo, nor gastric emptying, small-bowel transit time or orocaecal transit. 51Cr-EDTA and lactulose correlated in basal 0-6 h permeability testing (r = 0.529, P < 0.0001), as did 6-24 h excretion of 51Cr-EDTA and sucralose (r = 0.474, P < 0.001); 97% and 90% of the subjects had a permeability increase after indomethacin intake for 0-6 h and 6-24 h excretion of Cr-EDTA, respectively. This population proportion is 63% for lactulose/mannitol and 83% for sucralose.

CONCLUSIONS

Short-term exposure to nicotine does not alter normal basal or NSAID-induced gut barrier function or transit. 51Cr-EDTA and the respective sugar markers correlate well in in vivo permeability testing in healthy humans. The radioactive test detects more NSAID-induced permeability increase than does the lactulose/mannitol ratio permeability test.

Eicosanoids and the small intestine

Prostaglandins play an important role in modulation of various physiologic processes in the small intestine. In this review, the involvement of prostaglandins in various small-intestinal functions including small-intestinal secretion, mucosal protection, epithelial and endothelial barrier function, and motility are discussed.

Effect of glutamine on the intestinal permeability changes induced by indomethacin in humans

BACKGROUND

Long-term non-steroidal anti-inflammatory drug (NSAID) intake may induce increased intestinal permeability, eventually resulting in enteropathy. Because increased permeability might be related to cell damage resulting from energy depletion, it was hypothesized that glutamine--the major energy source of the intestinal mucosal cell--might prevent permeability changes.

METHODS

The 6-h urinary excretion of 51Cr-EDTA after an oral load of 51Cr-EDTA was used in this study as a measure for intestinal permeability. Healthy volunteers underwent a series of permeability tests: (i) basal test; (ii) test following NSAID (indomethacin); (iii) test following NSAID in combination with glutamine and/or misoprostol.

RESULTS

The NSAID induced increased permeability in all volunteers. Pre-treatment with glutamine (3x7 g daily, 1 week before NSAID-dosing) did not prevent the NSAID-induced increase in permeability. Multiple doses of glutamine close in time to NSAID-dosing resulted in significantly lower permeability compared to the NSAID without glutamine. Co-administration of misoprostol with the multiple-dose scheme of glutamine resulted in a further reduction in the NSAID-induced increase in permeability.

CONCLUSIONS

Glutamine decreases the permeability changes caused by NSAID-dosing when it is administered close in time, and misoprostol has a synergistic effect.

Influence of anti-rheumatic drugs on gut permeability and on the gut associated lymphoid tissue

There is great interest in the association between intestinal inflammation and the various arthropathies. However, most studies assessing intestinal function in these diseases are confounded by the fact that non-steroidal anti-inflammatory drugs (NSAIDs) have profound effects on the small intestine. Hence NSAIDs cause quite distinct and severe biochemical damage during drug absorption (uncoupling of mitochondrial oxidative phosphorylation proving to be most important) which results in increased intestinal permeability. All commonly used NSAIDs, apart from aspirin and nabumetone, are associated with increased intestinal permeability in man. Whilst reversible in the short term, it may take months to improve following prolonged NSAID use. Increased intestinal permeability appears to be the central mechanism of converting the biochemical damage to an inflammatory tissue reaction (NSAID enteropathy). The inflammatory enteropathy is not, however, unique to NSAIDs but similar changes are found with other permeability breakers. In intestinal infections and in diseases associated with reduced mucosal defence, suggesting that the small intestinal inflammation represents a common final pathway for a number of intestinal injuries. Spondylarthropathies are associated with a high prevalence of terminal ileitis, but as most patients have been receiving NSAIDs it has been difficult to dissociate the effects of NSAIDs on intestinal function from that of the ileitis itself. Nevertheless, two studies suggest that increased intestinal permeability in spondylarthropathies occur independently of NSAID ingestion. Whilst these findings may have implications for the development of arthritis, the permeability changes in spondylarthropathy do not differ quantitatively or qualitatively from that of NSAIDs or other permeability breakers. NSAID enteropathy can be differentiated from spondylarthropathic enteropathy by differences in location of disease and lack of predilection of certain HLA types. However, as the two may coexist both enteroscopy and ileocolonoscopy may be necessary for this distinction.

Intestinal permeability: an overview

The noninvasive assessment of intestinal permeability in humans has a 20-year history. Because the tests are increasingly used in clinical practice and research and because there is much controversy, we reviewed the literature and outlined the potential and possible shortcomings of these procedures. Data was obtained from personal files and from a systemic search through MEDLINE and EMBASE. The principle of the differential urinary excretion of orally administered test markers is explained with reference to the desired physicochemical properties of the markers and how the principle can be exploited to allow assessment of various other gastrointestinal functions. The use of intestinal permeability tests for diagnostic screen for small bowel disease and assessment of responses to treatment, the pathogenesis of disease, normal intestinal physiology, and the effect of drugs and toxins on the intestine is described and reviewed. The controversy surrounding the anatomic location of the permeation pathways that the markers use is highlighted. Noninvasive tests of intestinal permeability have fulfilled early promises of usefulness in clinical practice and research. There is now a need for integrated research into the basic mechanisms of regulatory control of the intestinal barrier function.

Assessment of patients who have experienced anaphylaxis: a 3-year survey

DESIGN

A quality-control retrospective review of medical records was conducted for cases of anaphylaxis encountered at Mayo Clinic Rochester during a 3 1/2-year period.

PATIENTS

For inclusion in the study, all patients had to manifest general symptoms of mediator release such as generalized pruritus, urticaria, angioedema, and flushing. Of the 179 patients with anaphylaxis (mean age, 36 years), 66% were female, 49% had atopy, and 37% had a previous history of immediate reactions to allergens. Of these study patients, 11 were receiving medications capable of exacerbating anaphylaxis (beta-blockers in 7 of them).

RESULTS

Consultation with an allergist was obtained in 142 cases, and a probable diagnosis was made after review of the medical records. Causes of anaphylaxis included foods in 59 patients, idiopathic in 34, Hymenoptera in 25, medications in 23, and exercise in 12; false-positive diagnoses were recorded in 18. Allergy prick tests were done in 104 patients, 71 of whom had positive results; allergen-specific IgE tests were done in 44 patients, 23 of whom had positive results. In 19 patients, only allergen-specific IgE testing was done, and results were positive in 12. Normal test results included C1 esterase inhibitor in 33 patients, metabisulfite challenge in 15, and dye or preservative challenge in 10. Food skin tests were graded on a relative value scale and revealed 15 highly allergic, 24 moderately allergic, and 39 weakly allergic food groups.

CONCLUSION

A standard protocol should be used for assessment of patients with anaphylaxis, and fresh food extracts should be used for prick skin testing. A national incidence study of anaphylaxis is needed. The public and school personnel should be educated about food anaphylaxis, and emergency treatment for anaphylaxis should be readily available for patients.

Intestinal epithelial function: the case for immunophysiological regulation. Implications for disease (2)

Substantial amounts of data have been reported showing a role for immunomodulation of epithelial function (particularly ion secretion and permeability) using animal models of anaphylactic reactions. In part one of this review we outlined the main immune cell types and mediators/cytokines that are currently known to influence epithelial physiology either directly, or indirectly via an intermediate cell type. Here we will expand on the significance of these studies and show how antigenic activation of the mucosal immune system can evoke changes in epithelial function that may be beneficial to the host by mediating loss/inactivation of the antigen. However, a continued and inappropriate immune stimulation can lead to pathophysiological reactions and disease. Thus, we will present data on immune regulation of epithelial function with direct applicability to understanding the mechanism underlying human intestinal inflammatory and secretory disease. Finally, we highlight key strategic points in the cascade of immune events that can control epithelial function and thus may be of relevance in the formulation of new therapeutic approaches to intestinal inflammation.

Effects of metronidazole and misoprostol on indomethacin-induced changes in intestinal permeability

In previous open studies, misoprostol and metronidazole reduced nonsteroidal anti-inflammatory drug-induced intestinal permeability changes and inflammation respectively. We assessed the effects of indomethacin treatment (50 mg three times a day) for one week with either coadministered metronidazole (400 mg twice a day, group 1, N = 9) or misoprostol (200 micrograms four times a day, group 2, N = 7) on intestinal permeability to [51Cr]EDTA and mannitol in healthy volunteers, using double-blind, placebo-controlled, randomized techniques. Given alone, neither metronidazole nor misoprostol affected [51Cr]EDTA permeation, whereas indomethacin alone increased it from 1.20 (0.40) [mean percent urinary recovery (SD) groups 1 and 2] to 2.43 (0.72), P < 0.002. Coadministered metronidazole (group 1) prevented this increase [1.10 (0.39) before, 1.55 (0.54) after, P > 0.05], whereas misoprostol (group 2) did not [1.31 (0.51) before, 3.26 (1.10) after, P = 0.005]. No drug regimen altered mannitol permeation. Indomethacin and misoprostol did not affect urinary recovery of intravenously administered probes. The results with metronidazole, if related to its antibacterial effects, support evidence from animal models that bacteria contribute to NSAID-induced intestinal damage. The previously reported reduction of indomethacin-induced increased permeability by misoprostol during a one-day study is not seen when the drugs are used in standard clinical doses for one week.

The effect of polyacrylic acid polymers on small-intestinal function and permeability changes caused by indomethacin

Non-steroidal anti-inflammatory drug (NSAID)-induced increased small-intestinal permeability appears to be a prerequisite for the development of NSAID enteropathy, which is a cause of much morbidity in patients with rheumatoid arthritis. We assessed, with a combined absorption-permeability test, the effects of Carbopol (a polyacrylic acid polymer capable of increasing mucus strength and viscosity) on intestinal function and whether it protected against indomethacin-induced increased intestinal permeability. Using a test solution of 3-0-methyl-D-glucose, D-xylose, L-rhamnose, and 51Cr-labelled ethylenediaminetetraacetic acid with 5-h urine collections for marker analyses, we tested 16 subjects, as base line, after 20 ml Carbopol 4 times daily for 4 days, after indomethacin alone (75 + 75 mg), and after coadministration of Carbopol and indomethacin. Carbopol had no significant effect on the permeation or absorption of the test substances. Indomethacin increased intestinal permeability significantly, and this was unaffected when Carbopol was coadministered with indomethacin, showing that Carbopol does not limit the immediate damage of NSAIDs on the small intestine.