Epidermal growth factor is digested to smaller, less active forms in acidic gastric juice

Effect of Helicobacter pylori eradication on subsequent development of cancer after endoscopic resection of early gastric cancer in Japan

This article describes the characteristics of H. pylori infection dynamics in early gastric cancer cases in Japan and the reduced likelihood of metachronous cancer development and growth inhibition by H. pylori eradication based on healing of background gastric mucosa. In the future, these clinical studies and experimental studies in Mongolian gerbils and mice should elucidate the role of H. pylori infection in the development of gastric carcinogenesis to clinical cancer on the genetic level so that gastric cancer prevention by H. pylori eradication is established.

Gastric retention and stability of lipidized Bowman-Birk protease inhibitor in mice

Bowman-Birk protease inhibitor (BBI) was modified with a reversible lipidizing agent. The palmitoylated product, Pal-BBI, and BBI were iodinated and orally administered to mice using a gavage needle. A prolonged retention of Pal-BBI was found in the stomach. Furthermore, a significant amount of Pal-BBI was detected as intact polypeptide in the stomach of mice fed with Pal-BBI, while only degradation products were detected with BBI. There was also a significant increase of radioactivity in the blood and liver in mice 1.5 h post-administration of Pal-BBI. These results indicate that lipidized polypeptide can have a longer retention and lower digestion in the stomach. They also suggest that the Pal-BBI may have a higher gastrointestinal absorption than the original polypeptide.

Distinct pathways of cell migration and antiapoptotic response to epithelial injury: structure-function analysis of human intestinal trefoil factor

The trefoil peptide intestinal trefoil factor (ITF) plays a critical role in the protection of colonic mucosa and is essential to restitution after epithelial damage. These functional properties are accomplished through coordinated promotion of cell migration and inhibition of apoptosis. ITF contains a unique three-looped trefoil motif formed by intrachain disulfide bonds among six conserved cysteine residues, which is thought to contribute to its marked protease resistance. ITF also has a seventh cysteine residue, which permits homodimer formation. A series of cysteine-to-serine substitutions and a C-terminally truncated ITF were made by PCR site-directed mutagenesis. Any alteration of the trefoil motif or truncation resulted in loss of protease resistance. However, neither an intact trefoil domain nor dimerization was required to promote cell migration. This pro-restitution activity correlated with the ability of the ITF mutants to activate mitogen-activated protein (MAP) kinase independent of phosphorylation of the epidermal growth factor (EGF) receptor. In contrast, only intact ITF retained both phosphatidylinositol 3-kinase and the EGF receptor-dependent antiapoptotic effect in HCT116 and IEC-6 cells. The inability to block apoptosis correlated with a loss of trefoil peptide-induced transactivation of the EGF receptor or Akt kinase in HT-29 cells. In addition to defining structural requirements for the functional properties of ITF, these findings demonstrate that distinct intracellular signaling pathways mediate the effects of ITF on cell migration and apoptosis.

Colostrum and milk-derived peptide growth factors for the treatment of gastrointestinal disorders

Colostrum is the specific first diet of mammalian neonates and is rich in immunoglobulins, antimicrobial peptides, and growth factors. In this article we review some of these constituents of human and bovine colostrum in comparison with those of mature milk. Recent studies suggest that colostral fractions, or individual peptides present in colostrum, might be useful for the treatment of a wide variety of gastrointestinal conditions, including inflammatory bowel disease, nonsteroidal antiinflammatory drug-induced gut injury, and chemotherapy-induced mucositis. We therefore discuss the therapeutic possibilities of using whole colostrum, or individual peptides present in colostrum, for the treatment of various gastrointestinal diseases and the relative merits of the 2 approaches.

Salivary and gastric epidermal growth factor in patients with Zollinger-Ellison syndrome: its protective potential

OBJECTIVE

Evidence is accumulating that epidermal growth factor (EGF) is a major molecule contributing to the maintenance of the integrity of the upper alimentary tract mucosa before and after injury by acid and pepsin. Patients with Zollinger-Ellison Syndrome (ZES) typically have hypersecretion of acid and pepsin; however, the concentration and rate of secretion of salivary and gastric EGF that could counteract these potentially aggressive factors are unknown. Accordingly, this study was conducted to determine whether EGF affords mucosal protection in ZES patients.

METHODS

The concentration and output of salivary (sEGF) and gastric epidermal growth factor (gEGF) were measured in eight patients with ZES and the results compared to those in 17 patients with nonulcer dyspepsia (NUD), serving as a control group. All patients had normal esophageal and gastric mucosa as determined by endoscopy. Total saliva was collected during 1-h parafilm- and 1-h pentagastrin/parafilm-stimulated conditions, as well as basal and pentagastrin-stimulated gastric juice. The concentration and output of EGF were determined by radioimmunoassay.

RESULTS

The concentration of EGF in saliva collected from ZES patients after parafilm chewing was significantly higher compared to that in NUD patients (4.61 +/- 0.59 vs 2.75 +/- 0.50 ng/ml, p < 0.05). The concentration of EGF in saliva collected after pentagastrin stimulation in ZES patients was also significantly higher than in NUD patients (4.37 +/- 0.73 vs 2.22 +/- 0.37 ng/ml, p < 0.05). Salivary EGF output during parafilm chewing in ZES and NUD were similar (68 +/- 6.4 vs 109 +/- 25.2 ng/h). Salivary EGF output after administration of pentagastrin in ZES and NUD was also similar (66 +/- 6.1 vs 132 +/- 45.4 ng/h). Basal EGF output in the gastric juice of patients with ZES was 3-fold higher than in patients with NUD (801 +/- 73 vs 271 +/- 32 ng/h, p < 0.01). Pentagastrin-stimulated EGF output was similar in both groups (705 +/- 92 vs 675 +/- 168 ng/h).

CONCLUSIONS

Patients with ZES have a significantly higher EGF concentration in saliva and EGF output in basal gastric juice. This elevated content of salivary and gastric EGF in ZES patients may play a protective role in preventing the development of reflux esophagitis and gastric ulcer under the impact of gastric acid and pepsin hypersecretion.

Diminished epidermal growth factor levels in infants with necrotizing enterocolitis

BACKGROUND/PURPOSE

Because epidermal growth factor (EGF) is trophic to the intestinal mucosa, and neonatal necrotizing enterocolitis (NEC) is associated with a disrupted intestinal mucosal barrier, the authors sought to determine whether diminished levels of EGF were present in infants with NEC.

METHODS

Saliva, serum, and urine specimens were obtained from infants with NEC during a 3-year period (February 1995 to May 1998). Control patients without NEC were chosen based on similar postnatal age and birthweight. EGF levels were determined by enzyme-linked immunosorbent assay (ELISA). Differences between groups were compared using Mann-Whitney Rank sum test with P less than .05 considered significant. Results are presented as mean values +/-SEM.

RESULTS

Twenty-five infants with NEC were compared with 19 control patients. Birth weight (1,616+/-238 g control v. 1,271+/-124 g NEC) and postnatal age (23+/-6 days control v. 22+/-3 days NEC) were similar. Infants with NEC had significantly lower levels of EGF in both saliva (590+/-80 pg/mL control v. 239+/-41 pg/mL NEC; P<.001) and serum (35+/-8 pg/mL control v. 5.6+/-1.9 pg/mL NEC; P<.001). Urinary EGF was also lower in the NEC group, but was not statistically significant.

CONCLUSIONS

Premature infants with NEC have significantly diminished levels of salivary and serum EGF. Reduced levels of this growth factor may distinguish infants at risk for NEC and play a pivotal role in the pathogenesis of the perturbed intestinal mucosal barrier that is central to this condition.

Synthesis, development and in vitro evaluation of drug delivery systems with protective effect against degradation by pepsin

A (poly)peptide drug delivery system providing a protective effect against degradation by pepsin has been generated. A simplified pepstatin analogue was thereby synthesised displaying a terminally located primary amino group allowing an easy covalent attachment to anionogenic mucoadhesive polymers by the formation of amide bonds. The IC50 of this novel inhibitor was determined to be 6.65+/-1.05x10(-6) M. Mediated by a carbodiimide it was covalently bound to polycarbophil and sodium carboxy-methyl cellulose (NaCMC). In contrast to polycarbophil-inhibitor conjugates, NaCMC-inhibitor conjugates displayed a high inhibitory effect towards pepsin. The protective effect of tablets containing a NaCMC-pepsin inhibitor conjugate (10%), NaCMC (56.7%), insulin (3.3%), and mannitol (30%) was evaluated in vitro. Tablets were therefore incubated for 2 h at 37 degrees C with simulated gastric fluid according to the Pharmacopoeia Europea. Following analysis demonstrated that 50.8+/-8.6% (mean +/- SD; n = 3) of insulin were degraded within the swollen carrier matrix, whereas insulin was completely metabolised in tablets without the NaCMC-pepsin inhibitor conjugate. This protective effect against degradation by pepsin might make such dosage forms useful tools for a targeted (poly)peptide delivery to the stomach.

Development and evaluation of a competitive time-resolved immunofluorometric assay for the estrogen-regulated protein pS2

We have developed a competitive assay to measure the estrogen-regulated protein pS2. A monoclonal pS2 antibody (mAb) and a biotinylated pS2 peptide are used, with time-resolved fluorometry as a detection technique. The assay has a detection limit of 16 ng/mL and is precise (within-run and day-to-day Cvs 3-12%). We used this assay to determine steroid hormone activity of six steroids in cell culture, both in terms of time course and dose response. pS2 concentrations in the tissue culture supernatant of the BT-474 breast carcinoma cell line were significantly higher when estradiol was the stimulating steroid. There was a significant time course and dose response observed for estradiol, but not for the other steroids. The availability of a sensitive, reliable, and convenient method for quantifying pS2 will allow for many research applications including the screening of natural and synthetic compounds for putative estrogenic activity.

Epidermal growth factor, epidermal growth factor receptors, intestinal growth, and adaptation

Epidermal growth factor (EGF) is an important constituent of several gastrointestinal secretions. Many studies in both animals and humans have shown EGF to have multiple effects upon gut epithelial cells. These include cytoprotection, stimulatory effects on cell proliferation and migration, induction of gene expression such as mucosal enzymes and trefoil proteins, and inhibitory effects on gastric acid secretion. The main conundrum associated with EGF action is the disparity between experimental studies on its luminal and systemic actions. Opinion is sharply divided as to whether or not EGF has any action when given luminally and on the site of the EGF receptors on gut epithelial cells. Most studies agree that the EGF receptors are located on the basolateral surface, in which case EGF should only be active if surface ulceration has occurred--unless there is translocation across the epithelium. There are several clinical situations in which EGF might be useful in cytoprotection and in stimulating repair and regeneration in the gut. These include necrotizing enterocolitis and mucositis, and it is to be hoped that the solid basis of experimental studies on EGF might stimulate work on this topic.

Epidermal growth factor and the short bowel syndrome

Because epidermal growth factor (EGF) has multiple effects on the intestinal epithelium and endogenous EGF plays an important role in maintaining normal intestinal structure and the response to injury, EGF should be important in the intestinal adaptive response to resection. The accumulated data in the literature support a role for endogenous EGF in the intestinal adaptive response. Endogenous EGF is increased in saliva and diminished in urine after intestinal resection. This suggests increased tissue utilization of endogenous EGF during adaptation. Intestinal EGF receptor activity is increased after resection. Intestinal adaptation is impaired in animals with defective EGF receptors. Thus EGF receptor activity also is important during adaptation. The results of experimental studies suggest that EGF administered at the time of resection enhances the intestinal adaptive response. Both structural and functional adaptation are augmented. The route, dose, and timing of EGF administration are important factors. EGF has additive effects with glutamine and growth hormone on adaptation. Several observations from these reports have relevance to the potential clinical application of EGF therapy: (1) EGF should be given soon after resection; (2) early transient administration may lead to a substantial effect on adaptation; (3) both systemic and enteral therapy may be effective; (4) luminal nutrients are important but not essential in mediating EGF-stimulated adaptation; and (5) combined therapy with other nutrients and growth factors may have merit. In conclusion, endogenous EGF plays an important role in intestinal adaptation. Furthermore, experimental results suggest the potential clinical usefulness of EGF to stimulate intestinal adaptation after massive intestinal resection. There is currently no evidence to support the use of EGF in patients with well-adapted short bowel syndrome.

Growth factors and gut function

Growth factors play a key role in maintaining gut integrity and in stimulating repair. By understanding their physiological function we can use this information to apply to the treatment of conditions in which mucosal homeostasis has broken down.

Diet, reflux and the development of squamous cell carcinoma of the oesophagus in Africa

BACKGROUND

Squamous cancer of the oesophagus has reached epidemic proportions in Africa in the past few decades. There are many known associations but as yet no well established theory of causation.

METHODS

Relevant literature was found by manual review of appropriate journals and literature, Medline searches and cross-referencing. Published theories of causation of endemic cancer of the oesophagus were assessed in the light of available evidence. A hypothesis based on that evidence was formulated.

RESULTS AND CONCLUSION

A predominantly maize-based diet is high in linoleic acid, a precursor for gastric prostaglandin synthesis. In combination with low intake of other fatty acids and riboflavin, high levels of prostaglandin E2 are produced in gastric mucosa, leading to reduced gastric acid secretion, relaxation of the pylorus and a reduction in lower oesophageal sphincter pressure. These events result in combined reflux of duodenal and gastric juices low in acidity into the oesophagus. Resulting dysplasia strongly predisposes to local squamous carcinogenesis. This is now a fertile area for research, which may open the way for preventive action.

Interleukin-1beta inhibits growth factor-stimulated restoration of wounded rat gastric epithelial cell monolayers

We examined the effect of interleukin-1beta (IL-1beta) on spontaneous and enhanced restoration (cell migration and proliferation) using an in vitro wound model comprising a confluent monolayer of rat gastric epithelial RGM1 cells. Repair of an artificial wound in a cell monolayer was found to be time- and concentration-dependent when the cells were incubated with epidermal growth factor (EGF) or transforming growth factor (TGF) -alpha alone for up to 24 hr. The growth factors also stimulated DNA synthesis significantly for 24 hr in a concentration-related manner. IL-1beta had no effect on wound restoration in the absence of the growth factors. However, it markedly inhibited the restoration enhanced by EGF and TGF-alpha, the inhibition being about 60% and 70%, respectively. In addition, IL-1beta significantly reduced the DNA synthesis stimulated by the growth factors. The EGF- and TGF-alpha-enhanced restoration was reduced by about 30% by mitomycin C, which potently inhibited the stimulated DNA synthesis. Mitomycin C had no effect on the spontaneous restoration. Even when treated with mitomycin C, the inhibitory effect of IL-1beta on the enhanced wound repair was still observed; however, the extent of the inhibition was decreased. These results indicate that IL-1beta inhibits the migration as well as the proliferation of gastric epithelial cells enhanced by EGF and TGF-alpha, resulting in a failure of wound healing.

Bovine milk inhibits proteolytic degradation of epidermal growth factor in human gastric and duodenal lumen

Degradation of epidermal growth factor (EGF) in human gastric and duodenal lumen was analyzed by incubating 125I-labeled or unlabeled human recombinant EGF with human gastric or duodenal luminal fluids in vitro. Degradation of EGF was assessed by measuring the generation of acid soluble radioactivity or by reversed-phase high-performance liquid chromatography (HPLC). Incubation with gastric luminal fluids resulted in a time- and dose-dependent degradation of labeled and unlabeled EGF at pH 2.5 but not at pH 7.5. Duodenal luminal fluids, on the other hand, degraded EGF at pH 7.5 but not at pH 2.5. The rate of degradation of unlabeled EGF in gastric luminal fluids was nearly 12-fold higher than the rate of degradation of labeled EGF, whereas only a slight difference in rates of degradation of labeled and unlabeled EGF was observed in duodenal luminal fluids. High-performance liquid chromatography analysis detected three major degradation products that eluted with retention time of 17.5 min, 20.0 min, and 22.5 min that was associated with a reduction of intact EGF (retention time 23.5 min). Defatted and decaseinated supernatant of bovine milk effectively inhibited the degradation of EGF in both gastric and duodenal luminal fluids. Dietary derived protease inhibitors, such as soya bean trypsin inhibitor, lima bean trypsin inhibitor, egg white protease inhibitor, and Bowman-Birk protease inhibitor prevented EGF degradation in duodenal luminal fluids but failed to inhibit EGF degradation in gastric luminal fluids. These results suggest that bovine milk may contain specific inhibitors that protect EGF from proteolytic degradation in human gastric lumen.

Epidermal growth factor attenuates Clostridium difficile toxin A- and B-induced damage of human colonic mucosa

Epidermal growth factor (EGF) exhibits a cytoprotective effect on gastrointestinal epithelia via a receptor-mediated mechanism. We investigated the effect of EGF on Clostridium difficile toxin A (TxA)- and toxin B (TxB)-induced damage of human colon. Ussing-chambered colonic mucosa was exposed serosally to EGF before and during luminal exposure to TxA and TxB. Resistance was calculated from potential difference and short-circuit current. Epithelial damage was assessed by light microscopy and alteration of F-actin by fluoresceinated phalloidin. Luminal exposure of colonic strips to TxA and TxB caused a time- and dose-dependent decrease in electrical resistance, necrosis and dehiscence of colonocytes, and disruption and condensation of enterocyte F-actin. These effects were inhibited by prior, but not simultaneous, serosal application of EGF (20 nM). Administration of the tyrosine kinase inhibitor genistein (10(-6) M) inhibited the protective effects of EGF. We conclude that EGF protects against TxA and TxB probably by stabilizing the cytoskeleton, the main target of these toxins.

Effect of growth factors on epithelial restitution of human colonic mucosa in vitro

BACKGROUND

Epithelial restitution enables resurfacing of epithelial discontinuities by enterocyte migration. This study investigated the effect of basic fibroblast growth factor (bFGF), insulin-like growth factor (IGF-1), and epidermal growth factor (EGF) on restitution of human colonic mucosa in vitro.

METHODS

After base-line incubation human colonic mucosal strips, mounted in Ussing chambers, were luminally exposed to 0.5 mM sodium deoxycholate (NaDOC) for 10 min. Thereafter tissues were incubated with buffer alone or luminal buffer containing various concentrations of bFGF, IGF-1, and EGF for 3 h. Resistance (R) was calculated from potential difference (PD) and short-circuit current (Isc). All tissues were processed for light microscopy. Extent of damage was measured by morphometry.

RESULTS

Luminal 0.5 mM NaDOC for 10 min caused R to drop by 43% (n = 4; P < 0.05). Compared with controls 50 ng/ml EGF induced an approximately 30% R increase until the end of the experiments (P < 0.05, n = 4, paired). Ten minutes after injury 50.2 +/- 4% of the mucosa was damaged (n = 6), and after 3 h damage was significantly reduced by EGF (17.2 +/- 3% versus 31.7 +/- 4%, 50 ng/ml EGF versus controls) (P < 0.05, n = 6 per group). Histology showed that EGF stimulated enterocyte migration over the basal lamina. Various doses of bFGF and IGF-1 did not impair restitution when compared with controls.

CONCLUSION

In contrast to bFGF and IGF-1, EGF was shown to promote epithelial restitution of human colonic mucosa in vitro.

Impact of Helicobacter pylori colonization on immunoreactive epidermal growth factor and transforming growth factor-alpha in gastric juice. Its potential pathogenetic implications

Epidermal growth factor (EGF), pivotal in mucosal protection, is partly degraded proteolytically at low pH in the gastric milieu; gastric acid secretion, on the other hand, remains influenced by H. pylori colonization. The aim of this study, therefore, was to evaluate the impact of low pH and H. pylori colonization status on immunoreactive EGF and the other member of EGF-family, immunoreactive transforming growth factor-alpha (TGF-alpha). Eighteen patients with nonulcer dyspepsia (NUD) colonized by H. pylori and 55 NUD patients without H. pylori colonization were investigated. Gastric juice samples were aspirated at the beginning of the endoscopy procedure and immediately placed on ice, and their pH was recorded. The measurement of immunoreactive EGF and TGF-alpha was performed using commercially available radioimmunoassays (RIAs) after adjustment of pH to neutral using an assay buffer. Statistical analysis was performed using sigma-Stat for Windows. The concentration of immunoreactive EGF in patients with NUD colonized by H. pylori was 80% lower (P < 0.02) than in those without H. pylori and in both groups immunoreactive EGF was significantly lower when the pH of gastric juice was below 4.0. The concentration of immunoreactive EGF in H. pylori(+) and H. pylori(-) patients was similar when the pH of aspirated gastric juice was above 4.0. However, with gastric juice pH < 4.0, the EGF concentration was 64% lower in H. pylori(+) patients than H. pylori(-) patients (P < 0.05). In general, the concentration of immunoreactive TGF-alpha in gastric juice was unaffected by H. pylori colonization or pH of gastric juice. It is concluded that: (1) significantly lower immunoreactive EGF concentrations in patients with pH below 4.0 indicate that immunoreactive EGF but not immunoreactive TGF-alpha is affected by an acidic gastric milieu; (2) the further reduction of gastric juice immunoreactive EGF at pH below 4.0 in patients colonized by H. pylori suggests that this microorganism may elaborate factors that accelerate its proteolytic degradation or inhibit its rate of synthesis and/or secretion; and (3) this diminished content of immunoreactive EGF at low pH, especially in patients colonized by H. pylori, may facilitate the development and/or progression of mucosal damage.

The epidermal growth factor receptor (EGF-R) is present on the basolateral, but not the apical, surface of enterocytes in the human gastrointestinal tract

BACKGROUND

While it is clear that luminal epidermal growth factor (EGF) stimulates repair of the damaged bowel, its significance in maintaining normal gut growth remains uncertain. If EGF is important in maintaining normal gut growth, the EGF receptor (EGF-R) should be present on the apical (luminal) surface in addition to the basolateral surface. AIMS/SUBJECTS/METHODS: This study examined the distribution of the EGF-R in the epithelium throughout the human gastro-intestinal tract using immunohistochemistry, electron microscopy, and western blotting of brush border preparations.

RESULTS

Immunostaining of the oesophagus showed circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R negative. In the normal stomach, small intestine, and colon, immunostaining localised the receptor to the basolateral surface with the apical membranes being consistently negative. EGF-R positivity within the small intestine appeared to be almost entirely restricted to the proliferative (crypt) region. Western blotting demonstrated a 170 kDa protein in whole tissue homogenates but not in the brush border vesicle preparations.

CONCLUSIONS

As the EGF-R is located only on the basolateral surfaces in the normal adult gastrointestinal tract, the major role of luminal EGF is probably to stimulate repair rather than to maintain normal gut growth.

The potential physiological significance of milk-borne hormonally active substances for the neonate

This article reviews the presence and potential physiological significance of hormones and hormonally active substances (including growth factors) in human milk. Human milk has been found to contain several nonpeptide hormones and many peptide hormones and growth factors. In contrast to human breast milk, infant formulae lack some hormonally active peptides. There is little data concerning the effects of these agents on human neonates. Studies in immature experimental animals showing effects of orogastically administered hormones are summarized. The problems of supplementation of infant formula are discussed. Since hormones are present in the milk as a "cocktail" of potentially agonistic and antagonistic substances, one question is whether supplementation with a single agent would disturb this balance.

Stability of epidermal growth factor in the gastrointestinal lumen of suckling and weaned pigs

The stability of epidermal growth factor (EGF) in the gastrointestinal humen of 3-day-old suckling and 45-day-old weaned pigs was examined by incubating iodine labeled recombinant human EGF (hEGF) in the gastrointestinal fluids at 37 degrees C and monitoring the generation of acid soluble radioactivity. Chromatographic analysis and receptor binding study were also undertaken. The results showed that hEGF was quite stable in the gastric fluids in both suckling and weaned pigs with less than 20% degradation after 20 min incubation. The degradation rate in the intestinal fluids varied with the region of the small intestine and the age of the animals. At the proximal and mid regions of the small intestine in suckling pigs the degradation rate of hEGF after 20 min incubation was 5 and 20% respectively, while the degradation rate at the distal region was up to 50%. In the small intestinal lumen in weaned pigs the degradation rate of hEGF was much greater than that in suckling pigs, and the degradation rates at the proximal, mid and distal regions were 33, 51 and 56% respectively. Addition of acid soluble or casein fractions of porcine colostrum markedly reduced the degradation of hEGF in the intestinal fluids. These results indicate that milk-borne EGF is stable in the gastric and proximal intestinal humen in suckling pigs, and may play a role in regulating postnatal development in the suckling young.

Epidermal growth factor (EGF)

Despite the wealth of information concerning EGF and its related peptides, its precise role in the control of gastrointestinal functions is still not fully resolved. However, there is no doubt that it can have some very potent effects on the gastrointestinal tract. These may be related to the control of growth and development and to the regular control of cell renewal. Nevertheless, in the adult, EGF may only be active in response to luminal damage and repair, and furthermore this may also only occur if the luminal EGF is protected from proteolytic degradation. Notwithstanding this, 'EGF'-like responses may be evoked in the gut by intestinal TGF-alpha. The possible therapeutic use of EGF and members of its family in ulcer therapy will be discussed in later Chapters of this volume, other potential uses are in the control of necrotising enteritis and in the alleviation of the mucositis associated with cancer treatment.

Why is epidermal growth factor present in the gut lumen?

The jury is still out on the role of luminal EGF in the normal gastrointestinal tract. Recent evidence, however, suggests that its major function is to act as a 'luminal surveillance' peptide, which is available to stimulate repair and that it is not of major importance in maintaining normal gut growth. Recombinant EGF administered via the gut lumen could still prove a valuable tool for the treatment of gastrointestinal ulceration. Perhaps the old term for EGF, 'epidermal healing factor' or EHF, was more appropriate after all!

Growth factors and ulcerative gastrointestinal disease

A huge variety of peptides and cytokines are involved in the maintenance of mucosal integrity and in the inflammatory response at sites of ulceration. Most studies have focused on the effects of an individual factor in this complex process. However, it is becoming increasingly apparent that, to fully understand their importance in vivo, we should consider their function as part of a highly integrated system. It is also becoming clear that a relatively small number of common pathways are brought into play by the host in response to a wide variety of intestinal insults.

Effects of the anti-gastric secretory drugs IT-066 and omeprazole mitogenic activities in the gastric juice of the rat

BACKGROUND

Salivary epidermal growth factor (EGF) retains its biologic function in gastric juice and may play a physiologic role. Little is know, however, about the existence of mitogens other than EGF and the constitutional alterations of these factors in gastric juice by anti-secretagogues.

METHODS

The mitogenic activity was evaluated by measuring [3H]-thymidine incorporation, and the EGF contribution was determined by using a specific anti-rat EGF antibody. An H2-receptor antagonist (IT-066) and a proton pump inhibitor (omeprazole) were used to determine whether these drugs alter the relative composition of active mitogens in gastric juice.

RESULTS

Normal gastric juice significantly increased DNA synthesis. This activity was suppressed by antibody (87-88%). Both drugs increased EGF concentrations and activity dose-dependently IT-066 specifically increased total amount and activity of EGF. Approximately 50% of this activity was reduced by boiling or antibody.

CONCLUSION

The major mitogenic activity of normal rat gastric juice depends on EGF, and antisecretory drugs enhance the mitogenic activity by preserving and including intraluminal mitogens than EGF.

Peptides and gastrointestinal mucosal integrity

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