Transforming Growth Factor Alpha and Epidermal Growth Factor in Protection and Healing of Gastric Mucosal Injury

Transforming growth factor alpha (TGF) and epidermal growth factor (EGF) present in the gastric mucosa are polypeptides with similar biologic activity. This study compares the activity of TGF and EGF in the protection against injury by 100% ethanol and stress and in healing of acute gastric ulcerations. TGF and EGF (12.5-100 μg/kg-h) infused subcutaneously 30 min before and during ethanol or stress decreased mucosal lesions dose-dependently. The ID₅₀ for ethanol- and stress-induced lesions after TGF were 40 and 70 μg/kg-h and after EGF 60 and 100 ug/kg-h. TGF and EGF infused subcutaneously into intact rats inhibited gastric acid secretion but did not affect the gastric blood flow or mucosal generation of prostaglandin E₂ (PGE₂). Both TGF and EGF also significantly enhanced the healing of stress-induced lesions and the restoration of DNA synthesis. Ethanol and stress reduced blood flow in the oxyntic mucosa by 68% and 51%, respectively, and this effect was partially reversed by EGF and TGF. Pretreatment with indomethacin (5 mg/kg intraperitoneally), which reduced mucosal generation of PGE₂ by 85%, decreased in part the protection by TGF and EGF against ethanol-induced damage and virtually abolished the protective action of these peptides against stress-induced injury. We conclude therefore that 1) TGF and EGF show similar and comparable gastroprotective activity against ethanol- and stress-induced damage; 2) the protection by TGF and EGF is accompanied by an increase in gastric blood flow which appears to be an essential factor in gastroprotection; 3) mucosal PG is necessary for manifestation of the protective activity of TGF and EGF against acute gastric damage; and 4) TGF and EGF enhance the healing of gastric lesions, possibly via stimulation of DNA synthesis and cell proliferation.     

Transforming growth factor alpha and epidermal growth factor in protection and healing of gastric mucosal injury.

Transforming growth factor alpha (TGF) and epidermal growth factor (EGF) present in the gastric mucosa are polypeptides with similar biologic activity. This study compares the activity of TGF and EGF in the protection against injury by 100% ethanol and stress and in healing of acute gastric ulcerations. TGF and EGF (12.5-100 micrograms/kg-h) infused subcutaneously 30 min before and during ethanol or stress decreased mucosal lesions dose-dependently. The ID50 for ethanol- and stress-induced lesions after TGF were 40 and 70 micrograms/kg-h and after EGF 60 and 100 micrograms/kg-h. TGF and EGF infused subcutaneously into intact rats inhibited gastric acid secretion but did not affect the gastric blood flow or mucosal generation of prostaglandin E2 (PGE2). Both TGF and EGF also significantly enhanced the healing of stress-induced lesions and the restoration of DNA synthesis. Ethanol and stress reduced blood flow in the oxyntic mucosa by 68% and 51%, respectively, and this effect was partially reversed by EGF and TGF. Pretreatment with indomethacin (5 mg/kg intraperitoneally), which reduced mucosal generation of PGE2 by 85%, decreased in part the protection by TGF and EGF against ethanol-induced damage and virtually abolished the protective action of these peptides against stress-induced injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Healing of duodenal ulcers is not impaired by indomethacin or rofecoxib,the selective COX-2 inhibitor,in rats

BACKGROUND/AIM: Studies have demonstrated an important role for endogenous PG and NO in the healing of chronic gastric ulcers. We investigated the effects of COX and NOS inhibitors on the healing of duodenal ulcers, in comparison with gastric ulcers, in rats. METHODS: Gastric and duodenal ulcers were induced by serosal application of acetic acid (0.1 ml of 100% acetic acid) for 60 and 20 s, respectively. Indomethacin (a nonselective COX inhibitor) or rofecoxib (a selective COX-2 inhibitor) was given p.o. once daily for 14 days from 3 days after ulcer induction, while N(G)-nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor) or aminoguanidine (a relatively selective iNOS inhibitor) was given s.c. twice daily during this period. RESULTS: Both gastric and duodenal ulcers induced by acetic acid healed spontaneously within 17 days to a minimal size. Daily administration of indomethacin or rofecoxib significantly delayed the healing of gastric but not duodenal ulcers. In contrast, the healing of both gastric and duodenal ulcers was delayed by repeated administration of either L-NAME or aminoguanidine. Ulceration markedly increased the PGE(2) content of the ulcerated mucosa in both the stomach and duodenum, and the increased PG biosynthetic response was inhibited by either indomethacin or rofecoxib in both tissues. The expression of both COX-2 and iNOS mRNAs was upregulated in the ulcerated mucosa of the stomach and duodenum. CONCLUSION: These results suggest that COX-2/PG is actively involved in the healing of gastric but not duodenal ulcers, although the mRNA for COX-2 is expressed in the duodenal mucosa after ulceration, as potently as in the gastric mucosa. In contrast, NO produced by both cNOS and iNOS plays a role in the healing of both gastric and duodenal ulcers.     

Epidermal growth factor (EGF) in the gastroprotective and ulcer healing actions of colloidal bismuth subcitrate (De-Nol) in rats.

Colloidal bismuth subcitrate (CBS; De-Nol) exhibits gastroprotective properties in experimental animals and enhances the healing of chronic gastroduodenal ulcers, but the mechanisms of these actions have not been entirely elucidated. The present study was designed to determine whether epidermal growth factor (EGF), which also has gastroprotective and ulcer healing properties, contributes to the action of De-Nol on the stomach in rats. It was found that De-Nol protects the gastric mucosa against ethanol damage and that this is accompanied by increased mucosal generation of prostaglandins (PG). Removal of the endogenous source of EGF (sialoadenectomy) did not significantly decrease the protective and PG stimulating effects of De-Nol. Pretreatment with exogenous EGF partially protected the stomach against ethanol injury, but did not influence the protective action of De-Nol in sialoadenectomised animals. De-Nol, like EGF given orally, enhanced the healing of chronic gastric and duodenal ulcers induced by serosal acetic acid. De-Nol was found to bind EGF in a pH-dependent manner and to accumulate it in ulcer area. Thus the peptide is available locally in high concentrations to accelerate the re-epithelialisation and tissue repair of the ulcerated mucosa. These ulcer healing effects of De-Nol were reduced by sialoadenectomy and restored in part by oral administration of EGF. We conclude that salivary glands in rats are not essential for the gastroprotection induced by De-Nol, but seem to play an important role in the ulcer healing action of this drug possibly via an EGF mediated mechanism.     

Epidermal growth factor-stimulated rabbit oesophageal mucosal growth: Role of polyamines

Abstract Factors operative in oesophageal mucosal growth are poorly characterized. Epidermal growth factor (EGF) has been shown to stimulate mucosal growth throughout the gastrointestinal tract. The present study was performed to test the hypothesis that polyamine biosynthesis is required for stimulation of epithelial growth by EGF in oesophageal mucosa. Using an in vitro explant model, oesophageal mucosal growth was quantified in the presence or absence of EGF and α-difluoromethylornithine (DFMO), a specific inhibitor of polyamine synthesis. Administration of 50 nmol/L EGF significantly increased the rate of epithelial growth in oesophageal explants. Treatment with DFMO for 3 and 7 days not only depleted the tissue polyamines putrescine, spermidine and spermine, but also significantly impaired mucosal growth. The inhibitory effect of DFMO on mucosal growth was partially but significantly prevented when exogenous putrescine was given. Additionally, stimulation of epithelial growth by EGF was also blocked by depletion of cellular polyamines in DFMO-treated oesophageal explants. These results indicate that EGF stimulates epithelial growth of oesophageal mucosa at least partly through a process involving polyamine biosynthesis.     

Effect of sialoadenectomy on gastric mucosal integrity and growth in the rat

The effect of removal of the submandibular-sublingual salivary gland (sialoadenectomy) has been examined in terms of the effects on the susceptibility of the gastric mucosa to the inflammatory and damaging actions of ethanol. In addition, the effects of sialoadenectomy on cell turnover in the gastric mucosa has been examined. Animals were examined at one to five weeks after removal of the submandibular-sublingual salivary gland complex. In response to 100% w/v ethanol, sialoadenectomized rat displayed greater hemorrhagic damage to the gastric mucosa than sham-operated control rats. The difference between sialoadenectomized and sham control rats was significant at two to five weeks after surgery. The rate of [³H]thymidine incorporation into gastric mucosa was significantly reduced in sialoadenectomized rats at one and two weeks. Mucosal DNA concentration was significantly reduced in sialoadenectomized rats at four and five weeks after surgery. Mucosal myeloperoxidase activity was greater in sialoadenectomized rats treated with ethanol compared to control animals, but this difference was only significant at two weeks after surgery. Sialoadenectomy was also associated with a reduction in duodenal and gastric mucosal levels of immunoreactive epidermal growth factor (EGF). Differences between sialoadenectomized and control rats were not significant until three to four weeks after surgery. These data indicate that sialoadenectomy was associated with an increase in the susceptibility of rat gastric mucosa to ethanol-mediated damage. Sialoadenectomy also resulted in a reduction in gastric mucosal growth and gastroduodenal mucosal levels of EGF. However, the influence of sialoadenectomy on the susceptibility of the rat gastric mucosa to ethanol-mediated damage occurred prior to any significant effect on mucosal DNA concentration or EGF levels.This work was supported by a grant from the Medical Research Council of Canada, Grant No. MT6426.     

Roles of nocturnal melatonin and the pineal gland in modulation of water-immersion restraint stress-induced gastric mucosal lesions in rats

The roles of melatonin and the pineal gland in the circadian variation of water-immersion restraint stress-induced gastric mucosal lesions in rats were investigated. Fasted rats were subjected to water-immersion restraint stress during both the diurnal and nocturnal phases of a light:dark cycle. Pinealectomized and sham-operated rats were also subjected to water-immersion restraint stress at night. The lesion area after 4 hr of stress during the dark phase was significantly lower than in light-phase controls. Pinealectomy increased the lesion area in the dark phase, compared to the sham operation, but this effect was counteracted by intracisternal melatonin preadministration at a dose of 100 ng/rat. Melatonin concentrations in control rats during the light phase were significantly increased 4 hr after water-immersion restraint stress. In contrast, melatonin concentrations 4 hr after water-immersion restraint stress in the dark phase were significantly depressed compared with the control levels at the corresponding time. Melatonin levels after stress exposure were markedly decreased in pinealectomized rats as compared with sham-operated rats. These results suggest that circadian rhythm has an important role in the formation of stress-induced gastric mucosal lesions in rats and that melatonin responses to water-immersion restraint stress differ between day and night. The pineal gland modulates the stress response and melatonin contributes to gastric protection via a mechanism involving the central nervous system.     

Role of prostaglandin deficiency in pathogenetic mechanism of gastric lesions induced by indomethacin in rats

The present study was undertaken in rats using 2-deoxy-D-glucose (2DG) as a stimulator of gastric motility and a low dose of indomethacin as a prostaglandin (PG) synthesis inhibitor to investigate the roles of gastric motility and PG deficiency in the pathogenesis of indomethacin-induced gastric lesions. Subcutaneously administered indomethacin at 5 mg/kg did not induce any visible damage in the mucosa within 4 hr, but at 25 mg/kg produced linear hemorrhagic lesions along the long axis of the stomach. 2DG (100 mg/kg/hr), given intravenously, produced linear nonhemorrhagic lesions along the mucosal folds and, in the presence of 5 mg/kg of indomethacin, caused severe hemorrhagic lesions in the same areas of the stomach. Gastric motility was markedly enhanced by both indomethacin (25 mg/kg) and 2DG, while acid output and mucosal blood flow were increased only by the latter. Mucosal PGE ₂ levels were significantly reduced by indomethacin (25 mg/kg) but not by 2DG. Indomethacin at 5 mg/kg alone had no or little effect on any parameter except PG levels, which were reduced to similar degrees as caused by 25 mg/kg of the agent. Time-course development of the lesions was closely associated with those changes in gastric motility after administration of indomethacin (25 mg/kg) and 2DG. These results suggest that the enhanced gastric motility is, by itself, sufficient to induce damage (nonhemorrhagic) in the mucosa and that a PG deficiency alone does not induce any damage but is required for further extension to hemorrhagic lesions of nonhemorrhagic ones that are initially induced by enhanced gastric motility.     

Role of epidermal growth factor in healing of chronic gastroduodenal ulcers in rats

The healing of acetic acid-induced gastric and duodenal ulcers was examined together with biochemical indices of growth in gastric and duodenal mucosa in rats with intact or removed salivary glands after treatment with epidermal growth factor (EGF) or somatostatin, or both. After the extirpation of salivary glands, the healing rate of gastric and duodenal ulcerations was delayed and gastric content of immunoreactive EGF was reduced. This was accompanied by a significant decrease in the contents of deoxyribonucleic acid and ribonucleic acid in the gastric and duodenal mucosa. Repeated administration of EGF either subcutaneously or orally accelerated the healing of gastroduodenal ulcers in rats with intact salivary glands and completely reversed the delay in ulcer healing in sialoadenectomized animals. These effects were also accompanied by a significant increase in the growth parameters of gastric and duodenal mucosa. Administration of somatostatin, which prevented the growth-promoting action of subcutaneous EGF, resulted in a significant decrease in the EGF-stimulated healing of gastric and duodenal ulcerations in both intact and sialoadenectomized rats. Our findings suggest that cell proliferation is an important factor in healing of gastric and duodenal ulcerations and that EGF plays an important role in ulcer healing due to its mitogenic action.     

Effects of Celecoxib on Acid-Challenged Gastric Mucosa of Rats: Comparison with Metamizol and Piroxicam

Selective COX-2 inhibitors have been shown to produce fewer gastrointestinal adverse reactions than classical NSAIDs. Nevertheless, these new agents may worsen and delay the healing of experimentally induced gastric ulcers in animals. In this study, we compared the effects of a selective COX-2 inhibitor (celecoxib), a preferential COX-1 inhibitor (piroxicam), and a nonnarcotic analgesic (metamizol) on normal gastric mucosa of rats and, on the other hand, in a setting of preexisting acute gastric lesions induced by 0.6 N hydrochloric acid. Under normal conditions, only piroxicam produced appreciable gastric lesions. However, after acid challenge the three assayed drugs induced significant macroscopic and microscopic damage. Myeloperoxidase activity as an index of neutrophil infiltration was elevated with celecoxib and piroxicam on normal gastric mucosa. On inflamed mucosa, celecoxib augmented enzymatic activity at the lower dose, which was parallelled by an increase in the interleukin 1beta level. Acid instillaton produced a significant rise in PGE2 content at 7 hr. Drug treatment after acid challenge decreased prostaglandin values in all cases, although to a lesser extent than after single drug dose administration. COX-2 mRNA expression was visible 1 hr after acid application, whereas COX-2 protein could only be detected at 7 hr. Piroxicam increased both expression levels. All NSAIDs enhanced transforming growth factor alpha and epidermal growth factor receptor immunoreactivity around the acid-induced lesions. It is concluded that selective COX-2 inhibitors, like conventional NSAIDs, impair the healing of gastric damage, and therefore special attention should be paid in patients with gastric pathologies.     

Role of leukotrienes in hydrochloric acid-induced gastric lesions in rats

This study was designed to clarify the role of leukotrienes (LTs) in 0.6 N hydrochloric acid (HCl) — induced gastric lesions. In rats given 1 ml of 0.6 N HCl intragastrically, severe hemorrhagic lesions were observed in the gastric corpus mucosa 15 min, and 1, 3, and 5 hr after HCl administration. In the control rats treated with physiological saline, LTs in gastric mucosa were not observed throughout the experiments. Peptide LT contents (sum of LTC₄ and LTD₄) after 1 or 3 hr were increased to 13.2±2.9 ng/g tissue and 6.3±1.9, respectively, although peptide-LTs were not observed 15 min and 5 hr after HCl administration. Premedication with AA-861, a lipoxygenase inhibitor, decreased dose-dependently peptide LT contents 1 hr after HCl administration. Furthermore, gastric lesions caused by 0.6 N HCl were significantly prevented by 300 mg/kg of AA-861 3 hr after HCl administration, although the dose of AA-861 did not significantly prevent gastric lesions 1 hr after HCl administration. Administration of YM-638, a peptide LT antagonist, showed similar protective effects to AA-861 except inhibition of increase in LT levels after HCl administration. These results suggest that peptide LTs contribute to persistence of gastric lesions, although they might not participate in the onset of 0.6 N HCl-induced gastric lesions.     

Omentum and basic fibroblast growth factor in healing of chronic gastric ulcerations in rats

Omentum was shown to exhibit angiogenic activity, but its role in healing of chronic gastric ulcers is unknown. This study was designed to compare the effects of omentum and basic fibroblast growth factor (bFGF), a potent angiogenic factor, on healing of chronic gastric ulcers in rats. Several series of rats with gastric ulcers were used: series A with intact omentum (control), series B with omentum resected, and series C with omentum placed on the serosal side of the ulcer. Series A–C were divided into four groups treated with vehicle (I); indomethacin (II), an inhibitor of prostaglandin formation, difluoromethylornithine (DFMO) (III); an inhibitor of polyamine biosynthesis or bFGF (IV). Seven days after ulcer induction, the animals were anesthetized, the gastric blood flow (GBF) was determined by laser Doppler flowmetry (LDF), and the ulcer area was measured by planimetry. Biopsy samples of the ulcer margin were taken for determination of the number of capillaries and myofibroblasts in the granulation tissue. Attachment of omentum significantly accelerated ulcer healing, whereas omentectomy delayed this process. LDF revealed the decrease in the GBF at the ulcer margin to 45% and at the ulcer bed to 18% of the value recorded in the intact adjacent mucosa. Attachment of the omentum significantly increased the blood flow at the ulcer margin and increased the number of capillaries and myofibroblasts in the granulation tissue. Indomethacin (1 mg/kg/day) that inhibited mucosal PGE₂ by about 85% delayed significantly ulcer healing without affecting the blood flow in the ulcer area. DFMO (200 mg/kg intraperitoneally) suppressed ODC activity in the mucosa but did not influence the ulcer healing. bFGF given subcutaneously accelerated dose-dependently ulcer healing and stimulated angiogenesis to a similar extent as the attached omentum. We conclude that omentum enhances the ulcer healing in similar way as bFGF and that this effect is accompanied by the increased angiogenesis and blood flow in the ulcer area.     

Role of submandibular saliva and epidermal growth factor in gastric cytoprotection

The role of submandibular epidermal growth factor in protection of the gastric mucosa was investigated in rats. Removal of the submandibular glands and thereby submandibular epidermal growth factor (EGF) caused rats to develop gastric lesions (ulcerations and ulcers) after administration of the duodenal ulcerogen cysteamine. The median output of EGF in gastric juice was reduced from 45.6 pmol/12 h (total range 17.5-65.0) in unoperated controls to less than 0.06 pmol/12 h (total range less than 0.06-1.82) in rats given cysteamine after extirpation of the submandibular glands. The contents of EGF in the submandibular glands was unchanged during cysteamine treatment. Furthermore, the effects of intragastric instillation of exogenous EGF, infusion of saliva without EGF, and infusion of saliva with a high concentration of EGF on the development of cysteamine-induced gastric lesions were investigated in rats without submandibular glands. Exogenous EGF and saliva with a high but still physiological concentration of EGF significantly reduced the median area in the stomach displaying ulcers and ulcerations, whereas saliva without EGF had no effect. Although EGF is a known inhibitor of gastric acid secretion, the dose used in the present study had no effect on gastric acid secretion in chronic gastric fistula rats; removal of the submandibular glands also did not have any such effect. We conclude that exocrine secretion of submandibular EGF has a cytoprotective function in the stomach, an effect that may be physiological.     

Ornithine decarboxylase activity during gastric ulcer healing in dogs

Ornithine decarboxylase (ODC) activity has been associated with mucosal growth and injury, yet, little information is available on ODC activity during gastric ulcer healing. We measured ODC activity in the ulcer base submucosa and the surrounding mucosa at 1 cm and 2 cm and assessed ulcer surface healing and a histologic score in experimentally induced ulcers (Quinton ulcer-maker) at 0 and 5 hr and at one, two, three, four, and seven days. A total of 26 dogs were studied, eight of which received 2% difluoromethylornithine (DFMO, a specific inhibitor of ODC) in drinking water. Ulcer healing was assessed by digitizing initial (plug size), and final ulcer surface area and was expressed as percent ulcer surface reduction. A histologic score was assessed by two independent pathologists unaware of the treatment. ODC induction was observed in the submucosa of the ulcer base but not in the surrounding mucosa. The baseline submucosal ODC activity was measured at 0.2±0.1 pmol (¹⁴CO₂)/mg protein/hr, and at one day the ODC activity increased to 4.0±0.7, at three days to 15.2±5.5, and at seven days to 2.6±1.0 (P<0.001). DFMO treatment delayed GU healing significantly up to three days, but no difference was noted at seven days. The assessed histologic parameters did not correlate with ODC activity, and DFMO treatment did not alter the histologic score. These data suggest that polyamine biosynthesis occurs in the ulcer base submucosa during the first seven days of experimentally placed gastric ulcers. Suppression of ODC activity with DFMO delays ulcer surface reduction during the first three days, but the significance of ODC induction and polyamine biosynthesis during early ulcer healing remains in question.     

Role of epidermal growth factor, prostaglandin, and sulfhydryls in stress-induced gastric lesions

Epidermal growth factor promotes the growth of and protects gastric mucosa against various ulcerogens, including stress, but little is known about its role in the pathogenesis of stress ulcerations. In this study, Wistar rats with intact and resected salivary glands were exposed to water-immersion and restraint stress. During 2-14 hours of water-immersion restraint stress, the formation of gastric ulcerations increased progressively and the duration of stress was accompanied by a decrease in DNA synthesis in the gastric mucosa. Following sialoadenectomy, a significant increase in the number of stress ulcerations and further reduction in DNA synthesis were observed. Exogenous epidermal growth factor and dimethyl prostaglandin E2 significantly reduced the ulcerations in the stressed rats with intact salivary glands, but this reduction was significantly less pronounced after sialoadenectomy. Water-immersion restraint stress also resulted in about 50% reduction in mucosal prostaglandin E2 generation, and the pretreatment with indomethacin, which suppressed prostaglandin E2 by about 90%, almost doubled the number of stress ulcerations and abolished the gastro-protective effect of exogenous epidermal growth factor (but not dimethyl prostaglandin E2) against the stress lesions. An inhibition of ornithine decarboxylase activity by difluoromethyl ornithine also augmented stress-induced ulcerogenesis and abolished the protective action of epidermal growth factor while the administration of spermine almost completely prevented stress ulcerations in rats both without and with pretreatment with difluoromethylornithine. Water-immersion restraint stress also significantly reduced mucosal content of glutathione. Cysteamine increased tissue glutathione and reduced stress ulcerations but N-ethylmaleimide, an sulfhydryl blocker, decreased mucosal content of glutathione without affecting the stress ulcerations. This study indicates that the stress ulcers are accompanied by the reduction in mucosal synthesis of DNA, prostaglandin, and glutathione and that the presence of salivary glands attenuates the stress ulcerogenesis probably by releasing epidermal growth factor which acts, in part, by enhancing ornithine decarboxylase activity, mucosal growth, and prostaglandin and glutathione formation.     

Healing of chronic gastroduodenal ulcerations by antacids

Antacids show gastroprotective action against various irritants in experimental animals and enhance the healing of chronic gastroduodenal ulcers in humans but the mechanisms of these effects are unknown. The present study was designed to determine whether prostaglandin (PG) and epidermal growth factor (EGF), which also have protective and antiulcer properties, contribute to the action of antacids on rat's stomach. It was found that Maalox 70 and its active component, Al(OH)₃, enhance significantly the healing of chronic gastric and duodenal ulcers observed during 7 and 14 days after their induction. Pretreatment with indomethacin caused a significant prolongation of ulcer healing, and this was accompanied by a significant reduction in PG and EGF formation, suggesting that both factors may be involved in ulcer healing. Maalox and Al(OH)₃ failed to prevent the suppression of PG by indomethacin but were equally effective in ulcer healing in rats without and with indomethacin administration, suggesting that endogenous PG may not play any important role in the healing process by these drugs. Removal of salivary glands, the major source of EGF, also prolonged ulcer healing but, again, Maalox was as effective in ulcer healing as in rats with intact salivary glands. Our findings that Maalox at pH above 3.0 binds significant amounts of EGF, enhances the binding of EGF to the ulcer area, and stimulates mucosal growth, suggest that EGF may be involved in ulcer healing; however, because antacids are also effective after sialoadenectomy, EGF does not seem to be the major factor in ulcer healing by these drugs.     

Capsaicin-sensitive sensory neurons in healing gastric lesions induced by HCl in rats

The role of capsaicin-sensitive sensory neurons in the healing of HCl-induced gastric lesions was investigated in rats. Rats fasted for 18 hr were given 0.6 N HCl orally for induction of gastric lesions, and they were fed normally from 1 hr later. On various days after HCl treatment, area of lesions, acid secretion, mucosal H⁺ permeability, and blood flow responses were measured. Functional ablation of capsaicin-sensitive sensory neurons was performed two weeks before the experiment by subcutaneous injections of high-dose capsaicin. Sensory deafferentation did not affect the development of gastric damage in response to HCl but significantly delayed the healing of these lesions. The mucosa damaged by HCl secreted less acid but showed significant rise in H⁺ permeability, resulting in acid back-diffusion accompanied by an increase of mucosal blood flow. Sensory deafferentation had no effect on acid secretion and mucosal permeability changes in the damaged stomach but completely blocked the hyperemic response caused by acid back-diffusion. Capsaicin-sensitive sensory neurons may contribute to healing of gastric lesions, probably by mediating the mucosal hyperemic responses associated with acid back-diffusion and by facilitating acid disposal in the mucosa.     

Participation of Xanthine-Xanthine Oxidase System and Neutrophils in Development of Acute Gastric Mucosal Lesions in Rats with a Single Treatment of Compound 48/80, a Mast Cell Degranulator

The participation of xanthine-xanthine oxidaseand neutrophils in the development of acute gastricmucosal lesions was examined in rats injected once withcompound 48/80, a mast cell degranulator. Gastric mucosal lesions appeared 0.5 hr after compound48/80 injection and developed at 3 hr. The formation ofgastric mucosal lesions at 0.5 hr after compound 48/80injection was prevented by pretreatment with anti-neutrophil antiserum and NPC 14686, anantiinflammatory agent, but not with allopurinol, axanthine oxidase inhibitor. The development of gastricmucosal lesions at 3 hr after compound 48/80 injection was prevented by pretreatment withanti-neutrophil antiserum, NPC 14686, or allopurinol.Increases in the activities of gastric mucosal xanthineoxidase and myeloperoxidase, an index of neutrophilinfiltration, and the content of lipid peroxide occurred 0.5hr after compound 48/80 injection, and these increaseswere enhanced at 3 hr. The increases in gastric mucosalmyeloperoxidase activity and lipid peroxide content at 0.5 hr after compound 48/80injection were attenuated by pretreatment withanti-neutrophil antiserum and NPC 14686, while only theincrease in gastric mucosal xanthine oxidase activity atthe same time point was arrested by allopurinolpretreatment. The increases in gastric mucosal xanthineoxidase and myeloperoxidase activities and lipidperoxide content at 3 hr after compound 48/80 treatment were attenuated by pretreatment withanti-neutrophil antiserum, NPC 14686, or allopurinol.When compound 48/80-injected rats were treated withallopurinol at 0.5 hr after compound 48/80 injection,the progression of gastric mucosal lesions at 3 hr after theinjection was almost completely prevented withinhibition of the increases in gastric mucosal xanthineoxidase and myeloperoxidase activities and lipidperoxide content. These results indicate that in ratswith a single compound 48/80 treatment neutrophilsinfiltrated into the gastric mucosa participated in thedevelopment of acute gastric mucosal lesions and that the xanthine-xanthine oxidase system in thegastric mucosa participated in the progression ratherthan the formation of the gastric mucosallesions.     

Impairment of Gastric Ulcer Healing by Alendronate,a Nitrogen-Containing Bisphosphonate,in Rats

Bisphosphonates such as alendronate have been developed as antiresorptive agents capable of treating diseases related to bone remodeling. In the present study, we examined the effect of alendronate on the healing of acetic acid-induced gastric ulcers in rats and investigated the mechanism involved in this action both in vivo and in vitro using the rat gastric epithelial cell line (RGM1). Acetic acid-induced gastric ulcers healed spontaneously, with up-regulation of COX-2/prostaglandin E₂ production as well as expression of vascular endothelium-derived growth factor (VEGF) and basic fibroblast growth factor (bFGF) in ulcerated mucosa. The healing of ulcers was impaired by indomethacin (2 mg/kg, s.c.) or alendronate (60 mg/kg, p.o.) given once daily for 7 days, starting 3 days after acid application. Indomethacin, but not alendronate, inhibited mucosal prostaglandin E₂ production. Alendronate as well as indomethacin decreased the protein expression of both VEGF and bFGF in ulcerated mucosa, resulting in a reduction of angiogenesis in the ulcer base. Supplementation of recombinant bFGF significantly reverted the delay in ulcer healing caused by alendronate. On the other hand, the size of cell-free areas in RGM1 cells in vitro decreased with time after wound induction, and this process was promoted by epidermal growth factor (EGF; 10 ng/ml). Co-incubation with alendronate (1 mM) did not affect the spontaneous healing but significantly suppressed the accelerated wound healing caused by EGF. These results suggest that alendronate impairs the healing of gastric ulcers in rats, and this effect may be related to down-regulation of VEGF and bFGF, the important growth factors for vascularization/granulation, as well as suppression of the stimulatory action of EGF on epithelial proliferation/migration.