Bacterial chemotactic oligopeptides and the intestinal mucosal barrier

Probiotics and the Gut Immune System: Indirect Regulation

The gastrointestinal tract (GIT) represents the largest interface between the human organism and the external environment. In the lumen and upper part of the mucus layer, this organ hosts an enormous number of microorganisms whose composition affects the functions of the epithelial barrier and the gut immune system. Consequentially, the microorganisms in the GIT influence the health status of the organism. Probiotics are living microorganisms which, in specific conditions, confer a health benefit to the host. Among others, probiotics have immunomodulatory properties that usually act directly by (a) increasing the activity of macrophages or natural killer cells, (b) modulating the secretion of immunoglobulins or cytokines, or indirectly by (c) enhancing the gut epithelial barrier, (d) altering the mucus secretion, and (e) competitive exclusion of other (pathogenic) bacteria. This review focuses on specific bacteria strains with indirect immunomodulatory properties. Particularly, we describe here the mechanisms through which specific probiotics enhance the gut epithelial barrier and modulate mucus production. Moreover, we describe the antimicrobial properties of specific bacteria strains. Recent data suggest that multiple pathologies are associated with an unbalanced gut microflora (dysbiosis). Although the cause-effect relationship between pathology and gut microflora is not yet well established, consumption of specific probiotics may represent a powerful tool to re-establish gut homeostasis and promote gut health.

Chemical modification of drug molecules as strategy to reduce interactions with mucus

Many drug molecules possess inadequate physical-chemical characteristics that prevent to surpass the viscous mucus layer present in the surface of mucosal tissues. Due to mucus protective role and its fast turnover, these drug molecules end up being removed from the body before being absorbed and, thus, before exerting any physiologic affect. Envisaging a better pharmacokinetics profile, chemical modifications, to render drug a more mucopenetrating character, have been introduced to drug molecules backbone towards more effective therapies. Mucus penetration increases when drug molecules are provided with net-neutral charge, when they are conjugated with mucolytic agents and through modifications that makes them resistant to enzymes present in mucus, with the overall increase of their hydrophilicity and the decrease of their molecular weight. All of these characteristics act as a whole and influence each other so they must be well thought when drug molecules are being designed for mucosal delivery.

Chemical and molecular factors in irritable bowel syndrome: current knowledge, challenges, and unanswered questions

Several chemical and molecular factors in the intestine are reported to be altered and to have a potentially significant role in irritable bowel syndrome (IBS), particularly in IBS with diarrhea. These include bile acids; short-chain fatty acids; mucosal barrier proteins; mast cell products such as histamine, proteases, and tryptase; enteroendocrine cell products; and mucosal mRNAs, proteins, and microRNAs. This article reviews the current knowledge and unanswered questions in the pathobiology of the chemical and molecular factors in IBS. Evidence continues to point to significant roles in pathogenesis of these chemical and molecular mechanisms, which may therefore constitute potential targets for future research and therapy. However, it is still necessary to address the interaction between these factors in the gut and to appraise how they may influence hypervigilance in the central nervous system in patients with IBS.

Maturation of gastric electrical activity, gastric emptying and intestinal permeability in preterm newborns during the first month of life

INTRODUCTION

Immaturity of motility, intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal diseases in preterms. We determined the gastric electrical activity and emptying, and intestinal permeability, in preterm newborns to verify if a maturation pattern exists in preterm newborns during the first month of life.

PATIENTS AND METHODS

Eighteen preterm newborns (median 34 wks, range 2 wks) completed the study. They underwent the recording of gastric electrical activity by means of cutaneous electrogastrography, the ultrasound examination of gastric emptying, and the lactulose-to-mannitol ratio from permeability-absorption test on days 3, 7, 15, and 30 after birth.

RESULTS

Gastric electrical activity and emptying showed only slight changes between day 3 and day 7. On the contrary, an evident maturation in permeability, expressed as L/Mratio, was evident over time (Friedman Repeated Measures Analysis, p = 0.004).

CONCLUSION

In preterm healthy newborns of 34 weeks gestational age, electrical and motor activity are completely developed at birth whilst the intestinal epithelial barrier clearly improves during the first week of life.

Recombinant human lactoferrin ingestion attenuates indomethacin-induced enteropathy in vivo in healthy volunteers

OBJECTIVE

To determine whether recombinant human lactoferrin ingestion inhibits nonsteroidal antiinflammatory drugs (NSAID)-induced gastroenteropathy in vivo in healthy volunteers as a model for disorders associated with a rise in permeability of the stomach and the small intestine.

DESIGN

A randomized crossover dietary intervention.

SUBJECTS AND INTERVENTIONS

In all, 15 healthy volunteers (age 23+/-1.4 y) were tested. A sucrose and a lactulose/rhamnose (L/R) permeability test was performed to assess gastroduodenal and small intestine permeability as indicator of NSAID-induced gastroenteropathy. All subjects consumed standardized meals for 2 days. On the second day at time=-24 h each subject ingested a drink containing 5 g recombinant human lactoferrin or placebo during breakfast. At t=-9 h, subjects ingested the same drink with 75 mg of the NSAID indomethacin and after an overnight fast at t=-1 h subjects consumed the drink and 50 mg indomethacin. After 1 h, at t=0, a permeability test was performed.

RESULTS

Small intestine permeability after indomethacin and placebo was significantly higher (L/R ratio=0.036; 0.014-0.092, P<0.05) compared to the permeability observed after ingestion of indomethacin and lactoferrin (0.028; 0.015-0.056), whereas gastroduodenal permeability did not differ between the two interventions (P=0.3).

CONCLUSION

Oral recombinant human lactoferrin supplementation during a short-term indomethacin challenge reduced the NSAID-mediated increase in small intestinal permeability and hence may provide a nutritional tool in the treatment of hyperpermeability-associated disorders.

SPONSORSHIP

Grant and human recombinant lactoferrin donated from Agennix Inc., Houston, TX.

Soymetide, an immunostimulating peptide derived from soybean beta-conglycinin, is an fMLP agonist

A tridecapeptide (MITLAIPVNKPGR) that stimulates phagocytosis of human neutrophils was isolated from a trypsin digest of soybean proteins. This peptide is derived from the soybean beta-conglycinin alpha' subunit and was named soymetide-13. The N-terminal methionine residue of soymetide-13 is essential for its activity, and removal of C-terminal residues revealed that soymetide-4 (MITL) is the minimal structure required for phagocytosis stimulation. Although they are not formylated at their N-termini, soymetides have a weak affinity for the N-formyl-methionyl-leucyl-phenylalanine (fMLP) receptor and their phagocytosis-stimulating activity is inhibited by the fMLP antagonist Boc-MLP. Interestingly, soymetide-4 promotes tumor necrosis factor alpha production at a higher level than soymetide-13 following oral administration in mice.

Intestinal permeation and gastrointestinal disease

The gastrointestinal tract constitutes one of the largest sites of exposure to the outside environment. The function of the gastrointestinal tract in monitoring and sealing the host interior from intruders is called the gut barrier. A variety of specific and nonspecific mechanisms are in operation to establish the host barrier; these include luminal mechanisms and digestive enzymes, the epithelial cells together with tight junctions in between them, and the gut immune system. Disruptions in the gut barrier follow injury from various causes including nonsteroidal anti-inflammatory drugs and oxidant stress, and involve mechanisms such as adenosine triphosphate depletion and damage to epithelial cell cytoskeletons that regulate tight junctions. Ample evidence links gut barrier dysfunction to multiorgan system failure in sepsis and immune dysregulation. Additionally, contribution of gut barrier dysfunction to gastrointestinal disease is an evolving concept and is the focus of this review. An overview of the evidence for the role of gut barrier dysfunction in disorders such as Crohn's disease, celiac disease, food allergy, acute pancreatitis, non-alcoholic fatty liver disease, and alcoholic liver disease is provided, together with critical insight into the implications of this evidence as a primary disease mechanism.

Intestinal permeability and carrier-mediated monosaccharide absorption in preterm neonates during the early postnatal period

Immaturity of intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal complications in preterm neonates during the early postnatal period. We determined the intestinal permeability and carrier-mediated absorption of monosaccharides in preterm neonates during the first 2 wk after birth. Fifty-nine preterm neonates born between 25 and 32 wk gestation were included within 24 h of birth. Neonates received exclusively parenteral nutrition during the first 7 d after birth; enteral feeding was initiated at d 8. An intestinal permeability-absorption test was performed at 1, 4, 7, and 14 d after birth. The lactulose-to-rhamnose ratio was determined as a marker of intestinal permeability. Urinary excretion percentages of D-xylose and 3-O-methyl-D-glucose were determined as markers of passive and active carrier-mediated monosaccharide absorption, respectively. Intestinal permeability transiently increased between d 1 and 7 in all neonates (p < 0.05). Carrier-mediated monosaccharide absorption increased between d 1 and 14 in neonates of 28-30 wk (p < 0.05) to the level observed in the neonates of 30-32 wk gestation. In neonates <28 wk, intestinal permeability at d 7 was higher (p < 0.05) and carrier-mediated monosaccharide absorption at d 14 was lower (p < 0.01) as compared with neonates >or=28 wk. The barrier function of the intestinal epithelium transiently decreases during the first week after birth in preterm neonates who are not enterally fed. Diminished barrier function and low monosaccharide absorptive capacity, particularly in neonates <28 wk, may predispose these patients to the development of intestinal complications during the early postnatal period.

Peroral administration of enzymes: strategies to improve the galenic of dosage forms for trypsin and bromelain

In this study, we investigated the presystemic metabolism of trypsin and bromelain and the influence of these proteolytic enzymes on the mucus layer covering the gastrointestinal (GI) epithelia. In vitro studies demonstrated that 77.3% +/- 4.0% (mean +/- SD, n = 3) of trypsin is autodegraded within 2 hr, whereas autodegradation of bromelain was negligible. In contrast to the metabolization of bromelain by all pancreatic serine proteases, trypsin is only degraded to some extent by elastase. Both therapeutically used enzymes remained stable after incubation with an excised porcine mucosa, demonstrating that proteolysis caused by brush border membrane-bound enzymes is negligible. Trypsin and bromelain were highly mucolytic active, thereby reducing the diffusion barrier based on the mucus gel layer. Strategies to improve the galenic of dosage forms for trypsin and bromelain include the use of bioadhesive polymers such as hydroxyethylcellulose or slightly modified chitosan-EDTA, providing strongly improved stability of these enzymes toward proteolytic degradation in vitro. The given information represents a good starting point to improve the galenic of dosage forms for orally administered proteolytic enzymes.

Mucosal barrier injury: biology, pathology, clinical counterparts and consequences of intensive treatment for haematological malignancy: an overview

Mucositis is an inevitable side-effect of the conditioning regimens used for haematopoietic stem cell transplantation. The condition is better referred to as mucosal barrier injury (MBI) since it is primarily the result of toxicity and is a complex and dynamic pathobiological process manifested not only in the mouth but also throughout the entire digestive tract. A model has been proposed for oral MBI and consists of four phases, namely inflammatory, epithelial, ulcerative and healing phases. A variety of factors are involved in causing and modulating MBI including the nature of the conditioning regimen, the elaboration of pro-inflammatory and other cytokines, translocation of the resident microflora and their products, for example, endotoxins across the mucosal barrier, exposure to antimicrobial agents and whether or not the haematopoietic stem cell graft is from a donor. Neutropenic typhlitis is the most severe gastrointestinal manifestation of MBI, but it also influences the occurrence of other major transplant-related complications including acute GVHD, veno-occlusive disease and systemic infections. The pathobiology, clinical counterparts and the means of measuring MBI are discussed together with potential approaches for prevention, amelioration and, perhaps, even cure. Bone Marrow Transplantation (2000) 25, 1269-1278.

Probiotics inhibit enteropathogenic E. coli adherence in vitro by inducing intestinal mucin gene expression

Probiotic agents, live microorganisms with beneficial effects for the host, may offer an alternative to conventional antimicrobials in the treatment and prevention of enteric infections. The probiotic agents Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG quantitatively inhibited the adherence of an attaching and effacing pathogenic Escherichia coli to HT-29 intestinal epithelial cells but did not inhibit adherence to nonintestinal HEp-2 cells. HT-29 cells were grown under conditions that induced high levels of either MUC2 or MUC3 mRNA, but HEp-2 cells expressed only minimal levels of MUC2 and no MUC3 mRNA. Media enriched for MUC2 and MUC3 mucin were added exogenously to binding assays and were shown to be capable of inhibiting enteropathogen adherence to HEp-2 cells. Incubation of L. plantarum 299v with HT-29 cells increased MUC2 and MUC3 mRNA expression levels. From these in vitro studies, we propose the hypothesis that the ability of probiotic agents to inhibit adherence of attaching and effacing organisms to intestinal epithelial cells is mediated through their ability to increase expression of MUC2 and MUC3 intestinal mucins.

Colonic sulfide in pathogenesis and treatment of ulcerative colitis

A role for colonic sulfide in the pathogenesis and treatment of ulcerative colitis (UC) has emerged based on biochemical, microbiological, nutritional, toxicological, epidemiological, and therapeutic evidence. Metabolism of isolated colonic epithelial cells has indicated that the bacterial short-chain fatty acid n-butyrate maintains the epithelial barrier and that sulfides can inhibit oxidation of n-butyrate analogous to that observed in active UC. Sulfur for fermentation in the colon is essential for n-butyrate formation and sulfidogenesis aids disposal of colonic hydrogen produced by bacteria. The numbers of sulfate-reducing bacteria and sulfidogenesis is greater in UC than control cases. Sulfide is mainly detoxified by methylation in colonic epithelial cells and circulating red blood cells. The enzyme activity of sulfide methylation is higher in red blood cells of UC patients than control cases. Patients with UC ingest more protein and thereby sulfur amino acids than control subjects. Removing foods rich in sulfur amino acids (milk, eggs, cheese) has proven therapeutic benefits in UC. 5-Amino salicylic acid reduces fermentative production of hydrogen sulfide by colonic bacteria, and aminoglycosides, which inhibit sulfate-reducing bacteria, are of therapeutic benefit in active UC. Methyl-donating agents are a category of drugs of potential therapeutic use in UC. A correlation between sulfide production and mucosal immune responses in UC needs to be undertaken. Control of sulfidogenesis and sulfide detoxification may be important in the disease process of UC, although whether their roles is in an initiating or promoting capacity has yet to be determined.

Gastrointestinal permeability following aspirin intake and prolonged running

We sought to evaluate the effects of exercise and aspirin on gastroduodenal and intestinal permeability. Seven volunteers (age = 29 +/- 3 yr, VO2max = 56.8 +/- 4.1 ml.kg-1.min-1) rested or performed treadmill exercise (60 min at approximately 68% VO2max), with or without aspirin ingestion. Placebo (glucose) or aspirin (1.3 g) was taken the night before and prior to rest or exercise (total 2.6 g). A permeability test solution (approximately 1300 mOsm.kg-1), containing 10 g lactulose (L), 5 g mannitol (M), and 10 g sucrose (S), was ingested prior to rest or exercise. Urinary excretion rates (6.h-1), expressed as a percentage of ingested dose, were used to quantify intestinal (L/M ratio) or gastroduodenal (S) permeability. Ingestion of aspirin before running increased (P < 0.05) intestinal permeability compared to placebo+running and placebo+rest, but not compared to aspirin+rest; mean (+/-SE) values for the L/M ratio were 0.248 +/- 0.046, 0.029 +/- 0.012, 0.012 +/- 0.004, and 0.104 +/- 0.057, respectively. Gastroduodenal permeability following aspirin+running (3.25 +/- 1.21%) was also elevated (P < 0.05) compared to placebo+running (0.43 +/- 0.15%) and placebo+rest (0.24 +/- 0.11%), but not compared to aspirin+rest (0.66 +/- 0.27%). Neither running nor aspirin ingestion was associated with gastrointestinal (GI) complaints. Thus, GI permeability while running can be markedly elevated by aspirin ingestion.

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 absorptive capacity, intestinal permeability and jejunal histology in HIV and their relation to diarrhoea

Intestinal function is poorly defined in patients with HIV infection. Absorptive capacity and intestinal permeability were assessed using 3-O-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose in 88 HIV infected patients and the findings were correlated with the degree of immunosuppression (CD4 counts), diarrhoea, wasting, intestinal pathogen status, and histomorphometric analysis of jejunal biopsy samples. Malabsorption of 3-O-methyl-D-glucose and D-xylose was prevalent in all groups of patients with AIDS but not in asymptomatic, well patients with HIV. Malabsorption correlated significantly (r = 0.34-0.56, p < 0.005) with the degree of immune suppression and with body mass index. Increased intestinal permeability was found in all subgroups of patients. The changes in absorption-permeability were of comparable severity to those found in patients with untreated coeliac disease. Jejunal histology, however, showed only mild changes in the villus height/crypt depth ratio as compared with subtotal villus atrophy in coeliac disease. Malabsorption and increased intestinal permeability are common in AIDS patients. Malabsorption, which has nutritional implications, relates more to immune suppression than jejunal morphological changes.

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.

Salicylates for ulcerative colitis--their mode of action

Delivery of 5-aminosalicylic acid to the colon by sulphasalazine, other azo-bonded compounds and controlled-release preparations is introduced in the context of metabolism by epithelial cells and therapeutic efficacy in ulcerative colitis. Potential modes of action are then reviewed, including actions on luminal bacteria, epithelial cell surface receptors, cellular events (such as nitric oxide release or butyrate oxidation), electrolyte transport and epithelial permeability. Evidence for an influence of salicylates on circulating and lamina propria inflammatory cells is presented, as well as actions on adhesion molecules, chemotactic peptides and inflammatory mediators, such as eicosanoids, platelet-activating factor, cytokines or reactive oxygen metabolites. The precise mechanism will remain uncertain as long as the aetiology of ulcerative colitis is unknown, but a pluripotential mode of action of salicylates is an advantage when influencing the network of events that constitute chronic inflammation.

Salicylates for inflammatory bowel disease

Targeted delivery of 5-aminosalicylic acid to the small intestine and colon by controlled-release or azo-bonded compounds potentially offers treatment for ileal Crohn's disease as well as ulcerative colitis. The pharmacokinetics of sulphasalazine and aminosalicylate derivatives have been discussed and potential modes of action reviewed. These include actions on epithelial cell-surface receptors, cellular events and barrier function. Evidence for an influence of salicylates on circulating and tissue inflammatory cells is presented, as well as actions on adhesion molecules, chemotactic peptides, eicosanoids, cytokines and reactive oxygen metabolites. The precise mechanism remains unknown, but a pluripotential mode of action is an advantage when influencing the network of events that constitutes chronic inflammation. Controlled clinical trials of salicylates in ulcerative colitis and Crohn's disease have been reviewed. Their main role remains as maintenance therapy for ulcerative colitis, but relatively high doses of controlled-release preparations benefit patients with ileal Crohn's disease, following resection, or those who have recently relapsed. Finally, issues of clinical relevance have been addressed, including the choice of salicylate and safety, indications for initiating therapy, dose and duration of treatment, role in managing refractory colitis and future developments.

Inactivation of chemotactic peptides by aminopeptidase Ey from hen's (Gallus gallus domesticus) egg yolk

Aminopeptidase Ey, purified from hen's (Gallus gallus domesticus) egg yolk, was studied for its specificity against N-blocked peptides. Only N-formylmethionyl peptides were hydrolyzed by the enzyme in the tested peptides. N-Formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) lost its chemotactic activity toward human neutrophil after incubation with aminopeptidase Ey.

Cardiopulmonary bypass impairs small intestinal transport and increases gut permeability

Gastrointestinal damage occurs in 0.6% to 2% of patients after cardiopulmonary bypass (CPB), and carries a mortality of 12% to 67%. The incidence of subclinical gastrointestinal damage may be much greater. We examined the effects of nonpulsatile, hypothermic CPB on intestinal absorption and permeability in 41 patients. Bowel mucosal saccharide transport and permeation were evaluated using 100 mL of an oral solution containing 3-O-methyl-D-glucose (0.2 g), D-xylose (0.5 g), L-rhamnose (1.0 g), and lactulose (5.0 g) to assess active carrier-mediated, passive carrier-mediated, transcellular, and paracellular transport, respectively, with a 5-hour urine analysis. Patients were studied before, immediately after, and 5 days after CPB. Immediately after CPB there was a decrease in urinary excretion of 3-O-methyl-D-glucose (from 34% +/- 2.2% to 5.2% +/- 0.7%; p < 0.0001), D-xylose (from 25.4% +/- 1.4% to 4.1% +/- 0.8%; p < 0.0001), and L-rhamnose (from 8.3% +/- 0.6% to 2.6% +/- 0.4%; p < 0.0001). The permeation of 3-O-methyl-D-glucose and D-xylose returned to normal levels 5 days after CPB, but that of L-rhamnose remained significantly below pre-CPB values at 6.6% +/- 0.5% (p = 0.004). However, the permeation of lactulose increased after CPB (from 0.35% +/- 0.04% to 0.59% +/- 0.1%; p = 0.018), and the lactulose/L-rhamnose gut permeability ratio increased markedly (from 0.045 +/- 0.04 to 0.36 +/- 0.08; normal = 0.06 to 0.08; p = 0.004). Patients who had a CPB time of 100 minutes or more had a greater increase in gut permeability (p = 0.049).(ABSTRACT TRUNCATED AT 250 WORDS)

Helicobacter pylori secretes a chemotactic factor for monocytes and neutrophils

Helicobacter pylori is associated with an inflammatory reaction in the stomach and duodenum, yet the mechanism of this inflammatory infiltrate is unknown. The ability of Helicobacter pylori to secrete a factor that attracts leucocytes is investigated. Helicobacter pylori conditioned supernatant attracted neutrophils and monocytes with 50-100% of the activity of control chemotactic factor, 10(-8) M formyl-methionine-leucine-phenylalanine. Strains derived from individuals with ulcer or non-ulcer associated H pylori infections displayed similar chemotactic activity. Preliminary characterisation shows that the factor has a molecular weight of less than 3000, is heat stable, is acid resistant, and can be diluted at least 10-fold. Checkerboard analysis confirmed that the activity was chemotactic rather than chemokinetic. This chemotactic activity could play a role in the pathogenesis of Helicobacter pylori gastritis.

Isolation and purification of N-formylmethionine aminopeptidase from rat intestine

The intestinal mucosal epithelium is exposed to products of intestinal bacteria including potent inflammatory N-formylmethionyl oligopeptides. An N-formylmethionine aminopeptidase has been purified 2300-fold from rat intestine and was shown to degrade natural fMet oligopeptides from Escherichia coli culture supernatants with loss of bioactivity (release of specific granule constituents from human polymorphonuclear leucocytes) and immuno-reactivity (assessed using a polyclonal anti-fMet-Leu-Phe antiserum). The enzyme which was specific for N-terminal acyl-methionine residues had a native Mr of 340,000 and comprised four sub-units of Mr 82,000. The presence of this enzyme in intestinal mucosa could prevent absorption of intact bioactive fMet peptides produced by commensal bacteria in the gut lumen.

Intestinal permeability in patients with Crohn's disease and their first degree relatives

It has been reported that intestinal permeability to polyethylene glycol 400 is increased in patients with Crohn's disease and their apparently unaffected first degree relatives. Because of the implications that these findings have for the aetiology of Crohn's disease these studies were repeated. Patients with Crohn's disease (n = 28) and 32 first degree relatives from 11 families underwent a polyethylene glycol 400 (PEG400) intestinal permeability test and a hyperosmotic (1500 mosmol/l) absorption/permeability test using 3-0-methyl-D-glucose, D-xylose, L-rhamnose, lactulose, and 51chromium labelled ethylenediamine-tetraacetate. The five hour urine excretion of polyethylene glycol 400 did not differ significantly between controls (n = 25) and first degree relatives, 25.5 (3.3)% v 24.6% (4)% (mean(SD)) p greater than 0.1, respectively. Patients with small bowel involvement excreted significantly less (p less than 0.01) polyethylene glycol 400 (16.3 (4.6)% than controls while those with Crohn's colitis did not (26.4 (3.9)% p greater than 0.1). The permeation of the monosaccharides in patients with Crohn's disease and their first degree relatives did not differ from normal subjects. The permeation of lactulose and 51chromium ethylenediaminetetraacetate was not significantly altered in first degree relatives but was significantly increased in the patients, as was the lactulose/L-rhamnose urine excretion ratio which is a specific measure of small intestinal permeability. These studies show normal absorption and permeability in first degree relatives of patients with Crohn's disease. A genetically determined abnormality of intestinal permeability is not likely to be an important aetiological factor in Crohn's disease.

Hepatobiliary excretion of bacterial formyl-methionyl peptides in rat. Structure activity studies

The bacterial chemotactic peptide formyl-met-leu-phe and its radioiodinated analog formyl-met-leu-[125I]tyr are rapidly excreted by the liver into bile following portal or systemic venous infusions in rats or after absorption from the gut lumen. To determine the molecular structural requirements for hepatobiliary excretion of formyl-methionyl peptides, structure-activity studies using portal venous infusions of 24 structural analogs of formyl-met-leu-tyr were performed in rats with biliary cannulae. Hepatic extraction of peptides was studied in vivo using external gamma counting after portal infusion. Efficient hepatobiliary excretion was not restricted to bioactive formyl peptides, but showed a broad specificity for different amino-acylated (formyl, acetyl, propionyl, carbobenzoxy) di- and tripeptides and no requirement for methionine in position one or for a free carboxy terminus. However, nonacylated peptides and an acyl-amino acid showed little excretion. Hepatic extraction of peptide was also related to N-acylation. Hepatic extraction and excretion of N-acyl peptides were also related to hydrophobicity. Thus, the presence of an N-acyl group is the key determinant of biliary excretion of inflammatory bacterial f-met peptides in the rat.

Neutrophil activation by Helicobacter pylori

Helicobacter pylori infection of the stomach is accompanied by a persistent polymorphonuclear leukocyte (PMNL) infiltrate of the mucosa. The aim of this work was to study the activation of human PMNL by substances produced by H pylori. Filtered H pylori conditioned media stimulated a significant PMNL oxidative burst (p less than 0.002). This was equal to 26% of the maximal response stimulated by the PMNL chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 mumol/l). The response to FMLP was prolonged by the combined presence of complement inactivated human anti-H pylori plasma and conditioned medium (p less than 0.002). High pressure liquid chromatography of an extract of conditioned medium showed a fraction that stimulated PMNL, eluted, and antigenically cross reacted with FMLP. Washed H pylori cells, and those opsonised with complement inactivated human anti-H pylori plasma, did not induce a significant oxidative burst. Opsonized H pylori, however, prolonged the oxidative burst induced by FMLP (p less than 0.02). In conclusion, H pylori synthesizes and secretes a substance, probably FMLP, that may account for the PMNL accumulation that accompanies H pylori infections. Immune complexes composed of H pylori antigen and specific antibody potentiate the PMNL oxidative burst. This combination of H pylori derived products, and host PMNL and antibodies, may be involved in the mucosal damage observed in H pylori associated gastritis.

Abnormal permeability precedes the development of a gluten sensitive enteropathy in Irish setter dogs

Intestinal permeability to 51Cr-EDTA was examined during the development of gluten sensitive enteropathy in dogs bred from affected Irish setters and reared on a normal wheat containing diet. Comparisons were made with litter mates reared on a gluten free diet and with a control group of age matched, clinically healthy Irish setters reared on the normal diet. Studies at 4, 6, 8, and 12 months of age were correlated with morphometric and biochemical examinations of peroral jejunal biopsy specimens. Permeability was increased at all ages in the group fed gluten free diet compared with control dogs, although there were no differences in villus height, intraepithelial lymphocyte density, and alkaline phosphatase activity. At four months, permeability in the normal diet group was greater than in controls, although comparable with that in the gluten free diet group. Permeability in the normal diet group increased further in conjunction with the development of partial villus atrophy and reduced alkaline phosphatase activity, and by 12 months permeability was significantly greater than in their gluten free diet litter mates and the control dogs. The findings suggest that an underlying permeability abnormality may be involved in the pathogenesis of gluten sensitive enteropathy in Irish setter dogs.

Dietary manipulation of methotrexate-induced enterocolitis

Administration of chemotherapy is limited by host toxicity, which is often manifested by severe enterocolitis. This study evaluated the effects of a liquid, elemental, chemically defined diet (ED) supplemented with 2% glutamine (Glu-ED) compared with a polypeptide diet (PPD) on the morbidity and mortality after methotrexate (MTX) administration. Fischer 344 rats (n = 80) were fed either a regular rat chow diet (RD), a 2% glycine supplemented elemental diet (Gly-ED), a 2% glutamine-supplemented elemental diet (GLU-ED), and a glycine-supplemented polypeptide diet(Gly-PPD) for 7 days prior to administration of MTX (20 mg/kg, ip). After 72 hours, eight rats per group were killed; portal vein and vena cava blood, mesenteric lymph nodes (MLN), liver, small intestine, and cecum were sampled for bacterial culture. Remaining animals were followed to calculate survival. One hundred percent of the Gly-PPD and 25% of the Glu-ED animals survived compared with 0% of the Gly-ED animals. Our data showed that ED resulted in an increased quantity of intestinal Gram-negative bacteria and diminished intestinal mucosal height and mucosal DNA/protein content. The polypeptide diet prevented intestinal mucosal atrophy, avoided MTX-induced enterocolitis and significantly improved animal survival compared with an elemental diet with or without glutamine supplementation.

Enzymes degrading bacterial chemotactic F-met peptides in human ileal and colonic mucosa

Bacterial chemotactic F-met peptides have been identified in culture supernatants of intestinal bacteria and in human faecal dialysates. These potent inflammatory agents could play a role in intestinal inflammatory disorders should they cross the epithelial barrier of the gut. We have identified mucosal peptidases which degrade F-met-leu-phe (FMLP) in ileal and colonic mucosal biopsies obtained at colonoscopy. A carboxypeptidase, inhibited by D-L-benzyl succinate (BzS), accounted for more than 60% of total FMLP-ase activity, other uncharacterized peptidases contributing the rest of the activity against the intact peptide. An F-met deformylase, inactive against di- and tri-peptides, cleaves released F-met completing the degradation. Total FMLP-ase, carboxypeptidase and F-met deformylase activities were measured in serial mucosal biopsies from 15 control patients undergoing colonoscopy for occult bleeding with negative findings and from 15 patients with ulcerative colitis (UC) and 10 with Crohn's disease (CD). Highest activities were found in terminal ileum and lowest in the rectum. Total FMLP-ase and carboxypeptidase activities were similar in controls and UC patients but were substantially reduced in CD, especially in the terminal ileum (controls 493 +/- 146 and 116 +/- 73 nmol/100 micrograms protein per h, respectively and CD 231 +/- 96 and 41 +/- 36 nmol/100 micrograms protein per h, respectively (P = 0.0018 and 0.015). F-met deformylase activities were similar in all groups. There was no correlation between enzyme activity and severity of inflammation. FMLP degrading peptidases probably contribute to the mucosal barrier of the gut in regions of high bacterial colonization, limiting intestinal absorption and inflammatory responses to these potent bacterial products in the intestinal lumen.

Radio-immunoassay for formyl methionyl leucyl phenylalanine. II. Demonstration of an enterohepatic circulation of immunoreactive bacterial chemotactic peptides in man

Bacterial chemotactic peptides (F-met-oligopeptides) are secreted by several species of commensal enteric bacteria and can be assayed by bioassay techniques in human colonic luminal fluid. We have previously demonstrated intestinal absorption and enterohepatic circulation of radiolabelled F-met peptides introduced into rat colon, and an eightfold increase in absorption and biliary excretion in rats with experimental colitis. This paper describes the application of a radio-immunoassay to measurements of formyl oligopeptides in human faecal dialysates, colonic and systemic venous blood and bile. All samples were fractionated by reverse-phase high performance liquid chromatography (HPLC) prior to assay. Immunoreactivity was found in faecal dialysates (5-700 nmol/L F-met-leu-phe equivalents) and bile samples (3-150 nmol/L) from normal subjects. After HPLC fractionation, up to five distinct peaks of immunoreactivity were identified. One of these co-chromatographed with authentic F-met-leu-phe; the others probably represented either closely related peptides or peptides of different chain lengths originating from the same F-met-leu-phe precursor protein. Colonic venous blood from two patients with ulcerative colitis contained immunoreactive peptide (10-30 nmol/L) and substantial immunoreactivity was found in ileostomy fluid and bile from two patients with primary sclerosing cholangitis. These results suggest the presence of an enterohepatic circulation of bacterial F-met oligopeptides in man and provide a basis for studies of the role of such pro-inflammatory peptides in patients with inflammatory bowel disease and associated hepatobiliary disorders.