Duodenal ulcer. Discovery of a new mechanism and development of angiogenic therapy that accelerates healing

Dual roles of peptic ulcer in the carcinogenesis or extension of early gastric cancer

BACKGROUND

Early gastric cancer (EGC) often coexists with peptic ulcer. In this study we investigated the roles of peptic ulcer in the carcinogenesis and extension of gastric cancer.

METHODS

The clinicopathological characteristics of EGC and peptic ulcer and their relationship, as well as that of the background intestinal metaplasia, were compared among the following three groups: patients with peptic ulcer only inside the EGC (Contained group, 53 patients); patients with peptic ulcer only outside the EGC (Separate group, 26 patients); and patients of EGC with no peptic ulcer (Absent group, 43 patients).

RESULTS

In the Separate group, a male preponderance was observed (P = .006), and all EGCs developed in the middle or lower third of the stomach (P = .06). Most of the EGCs were an intestinal type of cancer with severe background intestinal metaplasia. Topographically, 88% of the peptic ulcers in the Separate group developed proximal to the EGC. On the other hand, in the Contained group, most EGCs developed in the middle third of the stomach with an intestinal/diffuse type ratio of 1:1. Peptic ulcers inside the EGC were significantly more shallow than those that developed outside the EGC (P = 0.008). Although the incidences of submucosal cancer were nearly the same among the three groups, the maximum cancer diameter tended to be increased in the Contained group compared to that in the Absent group, and the incidence of lymph node involvement tended to be higher in the Contained group (8%) as compared with the other two groups (4%-5%).

CONCLUSIONS

These results suggest that peptic ulcer outside the EGC contributes to the development of the intestinal type of EGC, with the background of more severe intestinal metaplasia during the peptic ulcer healing processes, whereas peptic ulcer inside the EGC develops secondary to EGC and favors cancer extension and metastasis. Peptic ulcer associated with EGC can be considered to exert different biological roles in the carcinogenesis or extension of ECG according to the location of the peptic ulcer.

Effects of growth factors and trefoil peptides on migration and replication in primary oxyntic cultures

Restitution, the lateral migration of cells over an intact basement membrane, maintains mucosal integrity. We studied the regulation of migration and proliferation of enzyme-dispersed canine oxyntic mucosa cells in primary culture. Confluent monolayers were wounded and cultured in serum-free medium, and cells migrating into the wound were counted. [3H]thymidine incorporation into DNA was studied using subconfluent cultures. Considerable migration occurred in untreated monolayers; however, epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, basic fibroblast growth factor (bFGF), insulin-like growth factor I (IGF-I), two trefoil peptides, and interleukin (IL)-1beta further enhanced migration. The specific EGF receptor (EGFR) monoclonal antibody, MAb-528, inhibited both basal and TGF-alpha- or IL-1beta-stimulated migration, but not the response to trefoil peptide, bFGF, or IGF-I. Exogenous TGF-beta inhibited cell proliferation but did not alter migration. Immunoneutralization with anti-TGF-beta blocked the response to exogenous TGF-beta and produced a small enhancement of basal thymidine incorporation but did not attenuate basal or TGF-alpha-stimulated migration. In conclusion, endogenous EGFR ligands regulate proliferation and migration. TGF-beta inhibits mitogenesis; it did not upregulate migration in these cultures. Although bFGF, IGF-I, and IL-1beta enhance gastric epithelial migration, only IL-1beta acted in a TGF-alpha-dependent fashion.

The clinical manipulation of angiogenesis: pathology, side-effects, surprises, and opportunities with novel human therapies

The first phase of angiogenesis research has provided knowledge of the basic pathobiology of angiogenesis and its manipulation in models, mouse, and man. The first line of therapeutic substances has been devised and is now in clinical trials. New lessons are being learned from clinical observations. Unexpected side-effects are being noted, particularly affecting the nervous system. Other side-effects may be anticipated from a sound knowledge of clinical pathology and recognition of the commonality of angiogenesis to multiple disease mechanisms, but these may be tolerable or avoidable. Angiogenesis researchers await further feedback and ideas from the clinic to stimulate the next phase of basic and applied research.

Effects of pantoprazole, a novel H+/K+-ATPase inhibitor, on duodenal ulcerogenic and healing responses in rats: a comparative study with omeprazole and lansoprazole

BACKGROUND

Pantoprazole, 2-[(2-pyridylmethyl) sulphinyl] benzimidazole, is a new substituted benzimidazole that inhibits the parietal cell H+/K+-ATPase.

METHODS

In the present study, the anti-secretory and anti-ulcer activities of pantoprazole were compared with those of omeprazole and lansoprazole in rats.

RESULTS

Pantoprazole (0.3-3 mg/kg, p.o.) as well as omeprazole (1-10 mg/kg, p.o.) and lansoprazole (1-10 mg/kg, p.o.) dose-dependently decreased both basal acid secretion in pylorus-ligated rats and the stimulated acid secretion induced by mepirizole in acute fistula rats, and the effects of pantoprazole were more potent than those of omeprazole and lansoprazole, the ED50 values for the stimulated acid secretion being 0.8, 2.0 and 1.2 mg/kg, respectively. Neither of these drugs had any effect on duodenal HCO3- secretion. These pump inhibitors prevented the development of duodenal lesions in response to mepirizole in a dose-related manner, the ED50 values for pantoprazole, omeprazole and lansoprazole being 0.4, 2.0 and 1.3 mg/kg, respectively. Likewise, pantoprazole showed the healing promoting action on chronic duodenal ulcers induced by acetic acid, and this effect was also more potent when compared to omeprazole or lansoprazole.

CONCLUSIONS

We conclude that pantoprazole exhibited both anti-ulcer and healing promoting effects on duodenal ulcers in rats, and the effects may be attributable to its potent anti-secretory action. Other pump inhibitors such as omeprazole and lansoprazole were almost equally effective as pantoprazole, yet this drug was most potent on the basis of ED50 values.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

The possible role of vascular endothelial growth factor (VEGF) in gastric ulcer healing: effect of sofalcone on VEGF release in vitro

Angiogenesis plays an important role in gastric ulcer repair. Several growth factors are involved in angiogenesis and, of these, vascular endothelial growth factor (VEGF) has received considerable attention because it is the only factor that acts specifically on endothelial cells and, unlike other angiogenic growth factors, has the hydrophobic signal peptide required for extracellular transport according to classical secretory pathways. We have lately demonstrated the role of VEGF in gastric ulcer repair. Previous reports confirmed that sofalcone has remarkable effects on gastric ulcer healing, which may be mediated by its stimulatory effect on prostaglandin (PG) release in gastric cells. Our data indicate that PGs stimulate VEGF expression in gastric fibroblasts. In this report we hypothesize that the clinical effect of sofalcone is mediated by VEGF expression and we demonstrate that sofalcone stimulates VEGF release by gastric fibroblasts in primary culture.

Effects of cigarette smoking on gastric ulcer formation and healing: possible mechanisms of action

Epidemiologic studies have shown that cigarette smoking is closely related to peptic ulcer disease. The mechanisms by which cigarette smoking adversely affects gastric mucosa have been suggested and elucidated. This article reviews some of the mechanisms involved in cigarette smoking-related gastric ulceration and healing. Experimental findings suggest that cigarette smoking increases xanthine oxidase activity, leukotrienes, and nitric oxide production and also neutrophil infiltration in the gastric mucosa. On the other hand, it reduces blood flow, prostaglandin production, epithelial cell proliferation, and formation of blood vessels in the tissue. These actions are important for ulcer formation and healing. The evidence thus far available strengthens the hypothesis that cigarette smoke is indeed harmful to gastric mucosa through defined mechanisms.

Cigarette smoking delays ulcer healing: role of constitutive nitric oxide synthase in rat stomach

Epidemiological studies have shown that cigarette smoking is associated with peptic ulceration. This study aims to investigate the mechanisms by which cigarette smoking delays ulcer healing in rats. Gastric ulcers were induced by applying acetic acid to the luminal surfaces in rats. Twenty-four hours later, rats were exposed to different concentrations of cigarette smoke (0, 2, or 4%) for a 1-h period once daily for 3 or 6 days. Cigarette smoke exposure delayed ulcer healing and decreased gastric blood flow and angiogenesis at the ulcer margin. These changes were accompanied by a significant reduction of constitutive nitric oxide synthase (cNOS) activity but not PGE2 production and vascular endothelial growth factor levels. Administration of L-arginine (10 mg/kg iv) completely reversed the adverse actions on ulcer healing, gastric blood flow, and angiogenesis in the mucosa at the ulcer margin but partially restored angiogenesis in granulation tissues. In conclusion, cigarette smoke exposure delays ulcer healing through depression of gastric blood flow and angiogenesis at the ulcer margin. Reduction of cNOS expression and activity is suggested to be involved in these ulcerogenic processes.

Angiogenesis: possibilities for therapeutic interventions

Vascular proliferation normally occurs only during embryonic development, the female reproductive cycle and wound healing. Various pathological conditions such as diabetic retinopathy are characterized by persistent, uncontrolled angiogenesis. At the other hand, impaired development of new blood vessels has been found to be related with myocardial infarction. A series of anti-angiogenic drugs are currently included in experimental cancer treatment, whereas the failure of ulcers to heal may be limited by increased angiogenesis upon administration of growth factors. In the present review control mechanisms of the vasculature are summarized and therapeutic approaches discussed.

Angiogenesis and hypertension

BACKGROUND

The formation of new blood vessels is an important process in embryonic development and in physiological repair processes. Abnormalities in blood vessel growth have been associated with various pathologies.

HYPERTENSION AND IMPAIRED VASCULAR GROWTH

The basic observation underlying the hypothesis that essential hypertension is based on an impaired capacity for vascular growth is the nature of the structural alterations of microvascular beds in essential hypertension. Recent advances in understanding the molecular and cellular mechanisms of vascular growth suggest that the remodeling of individual vessels and vascular networks in hypertension may be a pathological variant of the formation of mature networks.

PATHOGENESIS OF IMPAIRED VASCULAR GROWTH

Genetic and fetal influences appear to have significant effects in determining impaired vascular development as an early cause of essential hypertension.

Expression of basic fibroblast growth factor in intact and ulcerated human gastric mucosa

BACKGROUND

Basic fibroblast growth factor (bFGF) promotes angiogenesis and healing of gastric ulcers in rats, and bFGF expression is up regulated in such ulcers. However, little is known about expression of bFGF in human gastric mucosa.

AIMS

To investigate bFGF expression in intact human gastric mucosa and gastric ulcers and to determine whether low bFGF content or altered binding by mucosa is associated with ulceration.

SUBJECTS

Endoscopy outpatients, gastrectomy patients, and organ donors.

METHODS

bFGF was isolated by heparin affinity chromatography and characterised by western blotting and endothelial cell bioassay. bFGF was measured by immunoassay and its distribution defined by immunohistochemistry and in situ hybridisation. Binding of bFGF by heparan sulphate proteoglycans was investigated by sodium chloride and heparin extraction.

RESULTS

Bioactive bFGF (19 kDa) was detected in normal mucosa but bFGF mRNA was not found. bFGF expression was up regulated in granulation tissue endothelial cells, mononuclear cells, and epithelial cells at the ulcer rim. Gastric ulcer patients had constitutively low bFGF concentrations in intact antral mucosa which were not explained by changes in binding to heparan sulphate proteoglycans.

CONCLUSIONS

bFGF expression is up regulated in human gastric ulcers. Low intact mucosal bFGF content is associated with gastric ulceration.

Induction of proliferation in isolated guinea pig gastric epithelium during restitution after superficial injury

Immediate repair of the gastrointestinal epithelium after superficial injury is called restitution. It is based on the migration of the surviving mucoid neck cells over the area of injury. The involvement of growth factors in the process has been recently documented. They are known to enhance the process (ie, EGF, FGF, TGF-beta) and to activate the basolateral Na+-H+-antiport (EGF). They may exert their effect by activating intracellular tyrosine kinases or by inducing chemotaxis. Yet, their precise mechanism of action in the process is unknown. The aim of the present study was to investigate the effect of modulation of the signal transduction pathway on the occurrence of proliferative mucoid neck and foveolar cells in guinea pig gastric epithelium. Therefore guinea pig gastric epithelium was mounted in Ussing chambers in vitro and perfused 4 hr after superficial injury with 1.25 M NaCl. The potential difference over the epithelium and tissue resistance were recorded simultaneously. The tissue was exposed either to cycloheximide, genistein, or to 4-phorbol myristate 13-acetate (PMA) during the 4-hr recovery, and the expression of proliferative cells was assessed by staining the tissue for proliferative cells (Ki-67). The mean proliferative index of tissues subjected to NaCl injury was significantly higher than that of uninjured control tissues after 4 hr of restitution. Inhibition of the signaling pathway with genistein decreased the proliferative index significantly, while its stimulation with phorbol myristate increased it. Both electrophysiologic and morphologic restitution were sensitive to genistein, but not to PMA or cycloheximide. Superficial epithelial injury results in a significantly increased occurrence of proliferative cells in isolated guinea pig gastric epithelium. This endogenous activation of the tissue is sensitive to inhibition by tyrosine kinases and to stimulation by protein kinases. Electrophysiologic and morphologic recovery are also affected by the modulation of the signaling pathway. This suggests that it is involved in the immediate repair process.

Mechanisms of ulcer healing and effects of nonsteroidal anti-inflammatory drugs

Ulceration of the gastroduodenal mucosa occurs frequently in humans, particularly in patients with a history of peptic ulcer disease. In order for healing to occur, mucosal damage stimulates secretion of growth factors in the adjacent mucosa and ulcer bed. Peptic ulcer healing is accomplished by the filling of the mucosal defect with cells that migrate from the ulcer margin and by connective tissue, including microvessels originating from granulation tissue. Peptic ulcer healing is accelerated both in humans and experimental models by gastric acid inhibition, which enhances cell migration and maturation of the granulation tissue. In experimental models, peptic ulcer healing can also be accelerated by oral administration of basic fibroblast growth factor, which increases angiogenesis in the ulcer bed, or by nitric oxide-releasing compounds, which improve gastric blood flow. Clinical and experimental data indicate that traditional nonsteroidal anti-inflammatory drugs (NSAIDs) delay the healing of peptic ulcers by interfering with the action of growth factors, decreasing epithelial cell proliferation in the ulcer margin, decreasing angiogenesis in the ulcer bed, and slowing maturation of the granulation tissue. In order to reduce the gastroduodenal side-effects of NSAIDs, selective cyclo-oxygenase (COX)-2 inhibitors have been developed, which inhibit the inducible COX-2 isoform in inflammatory tissue but have only limited effect on the constitutive COX-1 isoform in the stomach. It has been reported that the selective COX-2 inhibitor L-745,337 has a reduced liability for gastrointestinal ulceration. In our chronic experimental gastric ulcer model in rats, however, delay of gastric ulcer healing with L-745,337 was comparable to that with ordinary NSAIDs. It has also been reported that nitric oxide-releasing NSAIDs have a low relative risk of gastrointestinal ulceration but, again, in our chronic gastric ulcer model, nitric oxide did not reverse NSAID-induced deleterious effects on ulcer healing. In contrast, the proton pump inhibitor omeprazole has been shown to reverse NSAID-induced deleterious effects on gastric ulcer healing in our model. Comparable results have also been reported in humans. Histologic analysis has shown that omeprazole reverses the effects of NSAIDs on cell proliferation, angiogenesis, and maturation of the granulation tissue. In conclusion, only highly effective gastric acid inhibition reliably reverses NSAID-induced delay of gastric ulcer healing.

Changes in mucosal levels of transforming growth factor-alpha from the oxyntic region and ulcer site during duodenal ulcer healing with ranitidine or sucralfate

Changes in the levels of transforming growth factor-alpha (TGF-alpha) in gastric mucosa during ulcer healing were studied in 24 patients with endoscopically confirmed duodenal ulcers, treated either with ranitidine (300 mg daily, at night) or with sucralfate (2 g twice daily). Endoscopic biopsies were taken from the gastric fundus and from the ulcer margin at baseline and after 7-10 days of treatment. TGF-alpha levels were determined by radioimmunoassay in paired samples from 22 patients (fundal) and 18 patients (duodenal). There were no significant changes in TGF-alpha levels in the fundus of the whole group or of either treatment group. At the ulcer site, however, there was a significant increase in TGF-alpha levels in the whole group (from 16.4 to 33 pg/mg protein (medians); P < 0.005), and an increasing trend was seen in both treatment groups but was statistically significantly only in the group treated with sucralfate (P < 0.03).

Effects of inhibition of prostaglandin endoperoxide synthase-2 in chronic gastro-intestinal ulcer models in rats

1. In the stomach, prostaglandins protect the gastric mucosa against injuries. One rate-limiting step in prostaglandin synthesis is mediated by prostaglandin endoperoxide synthase (PGHS), the target enzyme of non-steroidal anti-inflammatory drugs (NSAIDs). Two isoforms of PGHS exist: a constitutive (PGHS-1) and an inducible (PGHS-2) enzyme. PGHS-1 is the major source of gastric prostaglandins under physiological conditions. Inhibition of prostaglandin synthesis by traditional NSAIDs such as indomethacin and diclofenac which non-selectively inhibit both PGHS-1 and PGHS-2, causes gastric and intestinal ulceration and delays gastric ulcer healing in chronic models. It has been shown that selective PGHS-2 inhibitors such as L-745,337 (5-methanesulphonamide-6-(2,4-difluorothio-phenyl)-1-inda none) are not ulcerogenic and do not inhibit gastro-intestinal prostaglandin synthesis. However, minimal information is available on the long-term effects of PGHS-2 inhibitors on the healing of previously established gastric injuries. We assessed the cellular localization and expression of PGHS-1 and PGHS-2 during gastric ulcer healing and assessed the effects of L-745,337 on previously established cryoulcers in the rat gastric stomach. 2. PGHS-1 and PGHS-2 were located and quantified by immunohistochemistry during experimental gastric ulcer healing. PGHS-2 immunoreactivity was only negligible in the normal gastric wall, but after gastric ulcerations, it was strongly detected in monocytes, macrophages, fibroblasts and endothelial cells below and between the regenerative glands. PGHS-1 immunoreactivity detected in normal gastric mucosa, disappeared after gastric ulceration in the mucosa adjacent to the ulcer crater. However, it reappeared in the regenerative glands from day 5 onwards. Thus, PGHS-1 and PGHS-2 were located at different sites and their maximal expression followed a different time-sequence. 3. We assessed the effects of L-745,337, indomethacin and diclofenac on gastric ulcer healing and histological healing parameters in rats. L-745,337, indomethacin and diclofenac dose-dependently decreased the healing of gastric ulcers. L-745,337, indomethacin and diclofenac decreased epithelial cell proliferation in the ulcer margin and microvessel density in the ulcer bed on day 8 and increased the thickness of the granulation tissue below the ulcer crater and the gap between both edges of the muscularis mucosae on day 15. Indomethacin and diclofenac, but not L-745,337, decreased synthesis of 6-keto-PGF1alpha and PGE2 in tissue fragments from the stomach and terminal ileum and decreased platelet thromboxane B2 synthesis in clotting whole blood. 4. Dose-response curves for the inhibition of chronic gastric ulcer healing by L-745,337 (administered twice daily intragastrically) showed an ID50 value of 1.7 mg (4.3 micromol) kg(-1). Dose-response curves for the inhibition of PGE2 synthesis in inflammatory exudates in the acute carrageenin sponge rat model, showed ID50 values of 1.1 mg (3.1 micromol) kg(-1) and 1.3 (3.3 micromol) mg kg(-1) for indomethacin and L-745,337, respectively. Thus, inhibition of chronic gastric ulcer healing by L-745,337 occurs within a potentially therapeutic dose-range. 5. In summary, PGHS-2 is markedly accumulated after gastric ulceration in monocytes, macrophages, fibroblasts and endothelial cells in regions of maximal repair activity. Selective inhibition of PGHS-2 by L-745,337 delayed gastric ulcer healing though interference with epithelial cell proliferation, angiogenesis and maturation of granulation tissue in a potentially therapeutic dose range. PGHS-2-derived prostaglandins seem to have an important role in gastric ulcer healing.

Effect of sofalcone on the expression of hepatocyte growth factor (HGF) and a brief review of HGF in the stomach

Previous studies of hepatocyte growth factor (HGF) in the stomach are briefly reviewed. Exogenous HGF has a strong effect on proliferation and migration of gastric epithelial cells. These effects of HGF are mediated by the specific receptor c-MET. Our previous immunohistochemical study revealed that the main source of endogenous HGF in human gastric ulcer is gastric fibroblasts. These findings suggest that HGF may play an important role in the repair of gastric ulcers through a paracrine mechanism. Therefore, regulation of HGF expression by gastric fibroblasts may be important. We have demonstrated that prostaglandins (PGs) E1 and E2 strongly stimulate HGF expression by gastric fibroblasts, indicating that the clinical efficacy of PGs is mediated by HGF, PGE1 actually facilitates restitution in an in vitro gastric mucosal model consisting of gastric epithelial cells and fibroblasts, which was completely inhibited by anti-HGF antibody. In this study we investigated the effect of an anti-ulcer drug, sofalcone, on PGE2 release and HGF expression by human gastric fibroblasts in primary culture. Sofalcone induced PGE2 release by human gastric fibroblasts in a dose-dependent manner. It also stimulated HGF expression by gastric fibroblasts, indicating that PGs induced by sofalcone increased HGF expression. These findings suggest that clinical efficacy of PGs and sofalcone might be mediated, at least in part, by HGF.

Alteration of basic fibroblast growth factor concentration and immunoreactivity in healing of ethanol-induced gastric mucosal damage: effect of sofalcone

To clarify the interaction of endothelial cells, myofibroblasts, and basic fibroblast growth factor (bFGF) in healing of gastric mucosal damage, histochemical and biochemical observations were undertaken. In addition, the effect of sofalcone on ulcer healing and especially on angiogenesis was studied. Male Wistar rats were used. Ethanol (50%) was administered through an orogastric tube. Thirty minutes after ethanol administration, an aqueous solution of sofalcone (100 mg/100 g b.w.) or the same amount of physiologic saline was administered in the same way. At 1, 3, and 12 h after sofalcone treatment, the localization of endothelial cells and myofibroblasts was studied. The bFGF concentration was decreased at 3 and 12 h in rats treated with ethanol alone, but addition of sofalcone did not alter the content of bFGF 3.5 and 12.5 h after sofalcone administration. Sofalcone had a strong influence on healing of ethanol-induced gastric mucosal damage, possibly through an indomethacin-sensitive, prostanoid-related increase in bFGF concentration.

Basic fibroblast growth factor increases constitutive nitric oxide synthase during healing of rat gastric ulcers

The purpose of this study was to clarify the effect of basic fibroblast growth factor (bFGF) on nitric oxide (NO) synthesis during healing of rat gastric ulcers. After experimental gastric ulcers were induced by acetic acid, rats were treated with vehicle, recombinant human bFGF (CS23, 10 micrograms/kg) and NG-nitro-L-arginine methyl ester (L-NAME, 1 mg/kg), an NO synthase (NOS) inhibitor, through an orogastric tube twice daily for 3 days or 1 week. CS23 significantly reduced ulcer size, and L-NAME significantly delayed healing compared with the vehicle group and significantly inhibited the efficacy of CS23. Although constitutive NOS (cNOS) activity significantly decreased and inducible NOS (iNOS) activity significantly increased in the vehicle group, CS23 significantly inhibited these changes. cNOS immunoreactivity on the vessels and neurons disappeared in the vehicle group, and newly formed vessels as well as neurons were observed with positive endothelial and neuronal NOS immunoreactivity in the CS23-treated group. External administration of bFGF accelerated ulcer healing, with recovery of NO synthesis in both endothelial cells and neurons. These observations suggested that increased NO synthesis with angiogenesis and reinnervation has a beneficial effect on gastric ulcer healing.

Effect of combined administration of lansoprazole and sofalcone on microvascular and connective tissue regeneration after ethanol-induced gastric mucosal damage

We undertook the present study to clarify the alteration of localization of basic fibroblast growth factor (bFGF), endothelial cells, and myofibroblasts in the healing of ethanol-induced gastric mucosal damage by the combined administration of lansoprazole and sofalcone. Wistar strain male rats were used. Ethanol 50% was given through orogastric intubation. Thirty minutes later, an aqueous solution of lansoprazole, sofalcone, a combination of lansoprazole and sofalcone, or physiologic saline was given orally. The stomach was removed and the localization of bFGF, myofibroblast, and endothelial cells was examined using monoclonal antibodies. Some rats were pretreated with indomethacin to rule out the effect of endogenous prostaglandin. The combined administration of lansoprazole and sofalcone brought about increased concentrations and immunoreactive areas of bFGF and a greater number of endothelial cells, compared with the ethanol-alone treatment. The number of myofibroblasts increased more significantly in the group treated with a combination of agents than in that treated with ethanol alone, ethanol plus sofalcone, or ethanol plus lansoprazole. Indomethacin pretreatment partly abolished the effects of single and combined administration of these agents. In conclusion, the mixed administration of lansoprazole and sofalcone accelerated the microvascular and connective tissue regeneration during the healing of ethanol-induced gastric mucosal damage.

Recombinant human transforming growth factor beta 3 accelerates gastric ulcer healing in rats

BACKGROUND

Gastric ulcer healing is mediated by various endogenous growth factors. In this experimental study effect of locally and systemically applied recombinant human transforming growth factor beta 3 (rhTGF-beta 3) on gastric ulcer healing was investigated in the rat.

METHODS AND RESULTS

Gastric ulcers were induced with a cryoprobe, and ulcer healing was evaluated 7 days after local infiltration (0.5 micrograms, 1.0 microgram, 2.5 micrograms, and 50 micrograms) or systemic (intravenous) application of TGF-beta 3 (500 micrograms/kg body weight). Compared with controls, a dose-dependent stimulation of ulcer healing (as evidenced by a reduction in ulcer size) was observed 7 days after local infiltration of TGF-beta 3 (1.0 microgram, 2.5 micrograms, and 50 micrograms). Corresponding increases in the levels of proliferating cell nuclear antigen (PCNA) and intracellular TGF-beta 3 expression and a downregulation of the TGF-beta type-II receptor expression were also observed in the granulation tissue of the ulcer margins. Systemic application of TGF-beta 3 produced effects similar to those observed after local treatment with 50 micrograms of the compound.

CONCLUSION

Local and systemic TGF-beta 3 treatment accelerates gastric ulcer healing in rats.

Acute erosions of the gastric mucosa in burned rats: effect of sucralfate

The effect of intragastric sucralfate on development of gastric erosions in burns was studied in 20 rats anaesthetised with midazolam/fentanyl/fluanisone. Gastric blood flow was measured by radioactive microspheres immediately before, and 20, 40, and 120 minutes after the rats had been burned. Significantly fewer erosions were found in the 10 rats treated with sucralfate (less than 2% of the gastric mucosal surface was affected) compared with the controls (16% of the mucosa affected). There was no difference in the rate of gastric blood flow in any part of the stomach between the rats treated with sucralfate and the controls. We conclude that sucralfate is effective in preventing gastric erosions in burned rats, but that other mechanisms of action than increase gastric blood flow are responsible for its protective effect.

Nitric oxide mediates angiogenesis induced in vivo by platelet-activating factor and tumor necrosis factor-alpha

We evaluated the role of an endogenous production of nitric oxide (NO) in the in vitro migration of endothelial cells and in the in vivo angiogenic response elicited by platelet-activating factor (PAF), tumor necrosis factor-alpha (TNF), and basic fibroblast growth factor (bFGF). The NO synthase inhibitor, N omega-nitro-L-arginine-methyl ester (L-NAME), but not its enantiomer D-NAME, prevented chemotaxis of endothelial cells induced in vitro by PAF and by TNF. The motogenic activity of TNF was also inhibited by WEB 2170, a specific PAF-receptor antagonist. In contrast, chemotaxis induced by bFGF was not prevented by L-NAME or by WEB 2170. Angiogenesis was studied in vivo in a murine model in which Matrigel was used as a vehicle for the delivery of mediators. In this model, the angiogenesis induced by PAF and TNF was inhibited by WEB 2170 and L-NAME but not by D-NAME. In contrast, angiogenesis induced by bFGF was not affected by L-NAME or by WEB 2170. TNF, but not bFGF, induced PAF synthesis within Matrigel. These results suggest that NO mediates the angiogenesis induced by PAF as well as that induced by TNF, which is dependent on the production of PAF. In contrast, the angiogenic effect of bFGF appears to be both PAF and NO independent.

Influence of intravenously administered ciprofloxacin on aerobic intestinal microflora and fecal drug levels when administered simultaneously with sucralfate

Ciprofloxacin, when given intravenously (i.v.), is secreted in significant amounts via the mucosa into the intestinal lumen. Sucralfate inhibits the antimicrobial activity of ciprofloxacin. The effect of combined therapy on the intestinal flora was investigated in 16 healthy volunteers. They were randomly assigned to two groups. Group A received 2 g of sucralfate orally three times a day for 7 days and 400 mg of ciprofloxacin i.v. twice a day (b.i.d.) starting 3 days after the sucralfate administration began. Group B was given only 400 mg of ciprofloxacin i.v. b.i.d. for 4 days. A total of 9 stool samples were collected from each subject beginning the week before ciprofloxacin was administered and on days -1, 1, 2, 3, 4, 7, 9, and 10 or 11 after commencement of the infusion period. The aerobic fecal flora was determined by standard microbiological methods. Measurements of fecal ciprofloxacin levels were based on high-performance liquid chromatography. Counts of bacteria of the family Enterobacteriaceae decreased in all subjects and were below 10(2) CFU/g in eight of eight subjects (group A) and six of eight subjects (group B) on day 4, but they returned to normal in all but one subject (group A) 10 days after the last infusion. The decreases in levels of bacteria of the family Enterobacteriaceae were not significantly different in groups A and B (Kaplan-Meier test). Staphylococci and nonfermenters responded variably, enterococci and lactobacilli remained unchanged, and candida levels increased transiently in four subjects (two in each group). Maximum fecal drug levels ranged from 251 to 811 microg/g. No significant difference could be found between the two groups. The i.v. application of ciprofloxacin eliminates intestinal bacteria of the family Enterobacteriaceae in a rapid and selective manner. This effect is not affected by simultaneous oral application of sucralfate.

Suramin enhances ethanol-induced injury to gastric mucosa in rats

Suramin is currently used in clinical practice as antineoplastic agent because of its complex interaction with the biological activity of various growth factors involved in tumor progression. The influence exerted by suramin on gastric injury induced in rats by intraluminal injection of absolute ethanol was investigated in the present study. The morphometric analysis of gastric histological sections revealed that suramin, 18 mg/kg, administered intraperitoneally for 14 days every other day, caused a marked enhancement of ethanol-induced mucosal damage. This effect was more pronounced 1-8 hr following ethanol administration, and it was still significant after 48 hr. In suramin-treated animals the evaluation of Alcian blue recovery from gastric-bound mucus showed that the levels of adherent mucus were significantly lower than those detected in untreated rats. In addition, pretreatment with suramin did not modify basal acid secretion, but caused potentiation of acid output stimulated by pylorus ligation or electrical vagal stimulation. Overall, the present results indicate that suramin exerts a negative influence on both gastric protective and repairing mechanisms. Due to the peculiar pharmacodynamic profile of suramin, it is suggested that interference with endogenous growth factors, endowed with physiological protective activity on gastric mucosa, might account for the damage-enhancing action of this drug.

Immunohistochemical studies on EGF family growth factors in normal and ulcerated human gastric mucosa

Expression of members of the epidermal growth factor family, including epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), amphiregulin (AR), and Cripto, as well as their putative receptor, epidermal growth factor receptor (EGFR), was studied immunohistochemically in human gastric mucosa to evaluate their possible roles in cell proliferation of normal and regenerative gastric mucosa. We also examined the correlation betwen cell proliferation and EGFR by double immunohistochemical staining for proliferating cell nuclear antigen (PCNA) and EGFR. In normal gastric mucosa, TGF-alpha, Cripto, and AR immunoreactivities were observed in the surface epithelial and parietal cells of gastric fundic glands, respectively. EGF immunoreactivity was not observed in any of normal mucosa examined. EGFR immunoreactivity was detected on foveolar cells in proliferative zones and in parietal cells. Double immunostaining revealed that EGFR immunoreactivity was distributed much more widely than PCNA immunoreactivity. PCNA positive epithelial cells adjacent to gastric ulcer margin expressed relatively intense EGFR but did not express any of the growth factors examined. On the other hand, relatively intense immunoreactivity of both TGF-alpha and Cripto was detected in PCNA-negative regenerative epithelium located distant from gastric ulcer margin. Relative immunoreactivity of AR in regenerative gastric epithelium associated with ulcer was not different from that in normal gastric mucosa. TGF-alpha, AR, and Cripto are considered to play important roles in normal gastric mucosal proliferation, and TGF-alpha and Cripto may be involved in ulcer healing, possibly via a paracrine mechanism.

Prevention of gastric ulcer relapse induced by indomethacin in rats by a mutein of basic fibroblast growth factor

We found indomethacin aggravates healed gastric ulcers (ulcer relapse) in rats. In the present study, we examined the effects of human basic fibroblast growth factor (bFGF) mutein CS23 (TGP-580) and histamine H2-receptor antagonists (H2-RAs) on ulcer relapse in this model. In male SD rats, gastric ulcers were induced in the antrum by injection of acetic acid. Indomethacin (1 mg/kg/day) given s.c. for 2 weeks starting 4 weeks after the operation aggravated the healed ulcer; the areas with and without indomethacin were 4.8 +/- 1.4 and 0.4 +/- 0.3 mm2, respectively. Drugs were given orally once daily for 4 weeks starting 2 days after the operation or for the 2-week indomethacin administration period. Treatment with ranitidine (100 mg/kg), cimetidine (100 mg/kg) and TGP-580 (0.1 mg/kg) for 4 weeks accelerated the healing. The aggravation by indomethacin was significantly inhibited by pretreatment with TGP-580 and mildly inhibited by cimetidine but not ranitidine. When the drugs were co-administered with indomethacin for 2 weeks, the aggravation was significantly prevented by ranitidine and mildly inhibited by cimetidine and TGP-580. Both TGP-580 and H2-RAs can prevent the ulcer relapse induced by indomethacin but via different modes of action: TGP-580 inhibits relapse mainly by acting on the process of healing, while H2-RAs act mainly on the process of aggravation.

Increased expression of transforming growth factor-beta1 during gastric ulcer healing in rats

This study was done to investigate the expression and localization of transforming growth factor-beta1 (TGF-beta1) in the gastric ulcerated tissues produced by acetic-acid during the healing process, by northern blot analysis and immunohistochemical technique. Ulcerated TGF-beta1 mRNA levels were significantly increased from days 3 to 18, in a similar manner to extracellular matrix proteins, and returned to control levels at the scarred phase. Immunoreactive TGF-beta1 was localized in epithelial cells beneath proliferative zone in intact tissues. In ulcerated tissues, TGF-beta1 was localized in macrophages in the ulcer bed and in fibroblasts or myofibroblasts in the granulation tissues. Treatment with prostaglandin E1 (PGE1) further stimulated ulcerated TGF-beta1 expression, being associated with the acceleration of gastric ulcer healing, while treatment with indomethacin reduced TGF-beta1 expression, being accompanied by the delayed ulcer healing. The combination of PGE1 and indomethacin reversed the indomethacin-induced decrease in ulcerated TGF-beta1. Thus, TGF-beta1 may be implicated in the acceleration of gastric ulcer healing.

Pharmaceutical applications of cyclodextrins. III. Toxicological issues and safety evaluation

The objective of this review is to summarize recent findings on the safety profiles of three natural cyclodextrins (alpha-, beta- and gamma-CDs) and several chemically modified CDs. To demonstrate the potential of CDs in pharmaceutical formulations, their stability against non-enzymatic and enzymatic degradations in various body fluids and tissue homogenates and their pharmacokinetics via parenteral, oral, transmucosal, and dermal routes of administration are outlined. Furthermore, the bioadaptabilities of CDs, including in vitro cellular interactions and in vivo safety profiles, via a variety of administration routes are addressed. Finally, the therapeutic potentials of CDs are discussed on the basis of their ability to interact with various endogenous and exogenous lipophiles or, especially for sulfated CDs, their effects on cellular processes mediated by heparin binding growth factors.

Serum basic fibroblast growth factor in pediatric Crohn's disease. Implications for wound healing

Basic fibroblast growth factor is a heparin-binding protein known to stimulate angiogenesis and promote wound healing in tissues. Since Crohn's disease is characterized in part by submucosal vascular proliferation, we sought to determine whether serum basic fibroblast growth factor is elevated in children with Crohn's disease and whether serum levels reflect disease activity. Sera were obtained from 64 children with Crohn's disease, 44 children with ulcerative colitis, 20 children with functional abdominal pain, and 29 from children with documented inflammatory disease evaluated in our gastroenterology program. Disease activity indices and clinical data were gathered prospectively for the inflammatory bowel disease patients. Serum basic fibroblast growth factor levels were measured by enzyme-linked immunosorbent assay. Although the mean basic fibroblast growth factor level did not significantly differ between children with Crohn's disease and other conditions, there was a strong (r = 0.53, P < 0.001) correlation between basic fibroblast growth factor level and disease activity. The relationship of basic fibroblast growth factor with disease activity persisted even after adjusting for other covariates (including age, sex, hematocrit, albumin, and sedimentation rate) in a multivariate linear regression model. There was also a statistically significant, although less strong correlation (r = 0.33, P = 0.03) between basic fibroblast growth factor level and disease activity in ulcerative colitis. While basic fibroblast growth factor is not a specific marker for Crohn's disease, serum levels reflect disease activity. Therefore, basic fibroblast growth factor release may be important in mediating the angiogenesis and wound healing seen in Crohn's disease.

Keratinocyte growth factor is an endogenous stimulant of rabbit gastric epithelial cell proliferation and migration in primary culture

Mesenchymal-epithelial interactions are important in the gastric mucosal repair. However, specific factors responsible for such interactions have not been established. In the present study, keratinocyte growth factor (KGF) significantly stimulated proliferation of gastric epithelial cells dose dependently and synergistically with hepatocyte growth factor (HGF), epidermal growth factor (EGF) and insulin. Restitution of gastric epithelial monolayers was also assessed, using a round wound restitution model. Keratinocyte growth factor facilitated the restitution of gastric epithelial cells significantly but did not have any effects on gastric fibroblasts. Keratinocyte growth factor receptor mRNA was expressed by gastric epithelial cells, indicating that these effects were elicited by the specific receptor mediated pathway. Northern blot analysis revealed the expression of KGF mRNA in gastric fibroblasts but not in gastric epithelial cells, indicating the production of KGF. These results suggest that KGF might be involved in gastric mucosal repair, through mesenchymal-epithelial interaction.

Experimental corneal neovascularisation using sucralfate and basic fibroblast growth factor

PURPOSE

To develop a non-inflammatory model of both acute and chronic angiogenesis in the rabbit cornea using a known directly angiogenic cytokine.

METHODS

Pellets made of the slow-release polymer Hydron (polyhydroxyethylmethacrylate) and containing sucralfate and/or basic fibroblast growth factor (basic-FGF) were implanted into rabbit corneas. The neovascular response to the implantation of pellets containing basic-FGF alone, sucralfate alone or a titration of basic-FGF in the presence of a constant amount of sucralfate was measured. The role of inflammation in the neovascular response was also investigated.

RESULTS

The addition of sucralfate to the pellets led to the sustained release of basic-FGF resulting in a predictable and aggressive neovascular response with a low dose of basic-FGF that by itself was unable to elicit neovascularisation. At a dose of 500 ng per pellet, approximately one-third of the surface area of the cornea was vascularised within eight days of implantation. Minimal or no vascularisation occurred with the same dose of basic-FGF without sucralfate. While this dose of basic-FGF induced corneal oedema, only minimal inflammation was observed and the response was unaffected by ionising radiation. A less aggressive though still robust neovascular response with no or only minimal oedema was observed when the dose was lowered to 50 ng of basic-FGF per pellet. Some induced vessels persisted for more than three months.

CONCLUSION

This is an inexpensive in vivo model of angiogenesis with the advantages of the neovascularisation being aggressive, predictable, persistent, unassociated with an obvious inflammatory response and induced by the sustained release of an agent known to have a direct stimulatory action on endothelial cells.

Effects of growth factors and gut hormones on proliferation of primary cultured gastric mucous cells of guinea pig

Almost completely homogenous gastric mucous epithelial cells of guinea pigs were grown to confluence in the presence of 10% fetal calf serum (FCS). FCS, epidermal growth factor (EGF), and insulin significantly increased 5-bromo-2'-deoxyuridine (BrdU) uptake by the cells and EGF together with insulin increased the cells' [3H] thymidine uptake. Basic fibroblast growth factor (bFGF) enhanced EGF-induced DNA synthesis by the cells, but vasoactive intestinal peptide (VIP), secretin, prostaglandin E2 (PGE2), and dibutyryl cyclic AMP (dbcAMP) neither induced DNA synthesis nor enhanced the effect of EGF on DNA synthesis by the cells. Gastrin, cholecystokinin-octapeptide (CCK8), and carbamylcholine chloride (CCh) also did not enhance the effect of EGF on DNA synthesis. 125I-EGF, 125I-bFGF, and 125I-gastrin binding to the gastric mucous cells revealed the presence of high-affinity receptors for EGF and bFGF, but not for gastrin. Northern blot analysis showed the expression of EGF receptor mRNA, but not gastrin receptor mRNA. These results suggest that EGF, insulin, and bFGF may cooperatively regulate gastric mucous cell growth, but that gastrin and other gastrointestinal hormones do not have a direct stimulatory effect on mucous cell growth in the guinea pig.

Effect of long-term sucralfate ingestion on antral and fundic epithelial proliferation in the rat

Sucralfate accelerates the healing of chronic gastric ulcers, but its mechanism is not well understood. We studied the effect of long-term administration of sucralfate on gastric epithelial proliferation in the rat by means of tritiated thymidine autoradiography. Rats were treated perorally with 500 mg/kg sucralfate once a day. After 28 days, rats were injected with tritiated thymidine 1 microCi/g body weight and sacrificed 1 hr later. Autoradiographs from antral and fundic mucosae were prepared and a number of proliferative measurements were made. Long-term sucralfate administration produced an increase in tritiated thymidine labeling of epithelial cells and expansion of the proliferative zone in antral mucosa. These results indicate that long-term sucralfate ingestion stimulates gastric antral epithelial proliferation in the rat. In light of the fact that chronic gastric ulcers are usually located in the antral region in humans, this enhanced epithelial proliferation may contribute to the beneficial effect of sucralfate in accelerating the healing of gastric ulcers.

Effects of leminoprazole, omeprazole and sucralfate on indomethacin-induced delayed healing of kissing gastric ulcers in rats

We have examined whether or not repeated treatment with indomethacin delays the healing of kissing gastric ulcers induced in rats. The effects of leminoprazole, omeprazole and sucralfate on any delay in ulcer healing caused by indomethacin were also determined in relation to myeloperoxidase activity. Kissing gastric ulcers were induced by luminal application of an acetic acid solution. Indomethacin significantly delayed ulcer healing in a dose-dependent manner. Leminoprazole and omeprazole decreased the size and depth of ulcers, the healing of which was delayed by indomethacin, while sucralfate only decreased the ulcer depth. Histological studies showed that indomethacin inhibited tissue contraction and regeneration of the ulcerated mucosa. Leminoprazole and omeprazole prevented the inhibition of these parameters. The myeloperoxidase (MPO) activity of the ulcer portion in animals treated with indomethacin was markedly higher than in the control group. Both leminoprazole and omeprazole, but not sucralfate, significantly reduced MPO activity in contrast to the control value (in the presence of indomethacin). There was a significant relationship between the ulcerated area and myeloperoxidase activity. These results suggested that: (i) leminoprazole and omeprazole prevent the indomethacin-induced delay in ulcer healing by promoting tissue contraction and regeneration of the ulcerated mucosa; (ii) sucralfate prevents the indomethacin-induced delay in ulcer healing via the promotion of the formation of granulation tissue; and (iii) MPO activity will be useful to biochemically ensure the healing state of ulcers.

Basic fibroblast growth factor and PDGF in GI diseases

This chapter is focused on the relatively recent investigations demonstrating a pharmacological and pathophysiological role for bFGF and PDGF in ulcerative and inflammatory lesions in the upper and lower GI tract. Our initial animal model experiment revealed a potent healing of chronic cysteamine-induced duodenal ulcer in rats treated by intragastric administration of bFGF-w, the acid-resistant bFGF-CS23 or PDGF-BB without decreasing gastric acid secretion or concentration. Subsequently we and others have demonstrated that these peptides accelerate the healing of chronic gastric ulcers, chronic erosive gastritis and ulcerative colitis. Contrary to the potent ulcer healing properties of bFGF and PDGF, these growth factors exert no or modest acute gastroprotection. Nevertheless, new biochemical, molecular biological and immunohistochemical studies indicate that both bFGF and PDGF play a pathophysiological role in the natural history of ulcer healing.

Restitution at the cellular level: regulation of the migrating phenotype

Intestinal epithelial cells migrating across a mucosal defect are generally described as dedifferentiated, a term that suggests a loss of regulatory biology. Since cell biology may be more readily studied in established cell lines than in vivo, a model is developed using the human Caco-2 intestinal epithelial cell migrating across matrix proteins. This resembles in vivo models of mucosal healing in its sheet migration and loss of the brush border enzymes, which are conventional markers for intestinal epithelial differentiation. Immunohistochemical studies of migrating Caco-2 cells suggest, however, that the rearrangements of cytoskeletal, cell-cell and cell-matrix proteins during migration are not random but seem adapted to the migratory state. Indeed, Caco-2 migration may be substantially regulated by a variety of physiologic and pharmacologic stimuli and differentiation, measured by the specific activity of the intestinal epithelial brush border enzymes alkaline phosphatase and dipeptidyl dipeptidase, may be independently pharmacologically programmed during the stimulation or inhibition of cell motility.

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.