Protective role of intracellular superoxide dismutase against extracellular oxidants in cultured rat gastric cells.

We examined the role of intracellular superoxide dismutase (SOD) as an antioxidant by studying the effect of diethyldithiocarbamate (DDC) on extracellular H2O2-induced damage in cultured rat gastric mucosal cells. 51Cr-labeled monolayers from rat stomachs were exposed to glucose oxidase-generated H2O2 or reagent H2O2, which both caused a dose-dependent increase in 51Cr release. DDC dose-dependently enhanced 51Cr release by hydrogen peroxide, corresponding with inhibition of endogenous SOD activity. This inhibition was not associated either with modulation of other antioxidant defenses, or with potentiation of injury by nonoxidant toxic agents. Enhanced hydrogen peroxide damage by DDC was significantly prevented by chelating cellular iron with deferoxamine or phenanthroline. Inhibition of cellular xanthine oxidase (possible source of superoxide production) by oxypurinol neither prevented lysis by hydrogen peroxide nor diminished DDC-induced sensitization to H2O2. We conclude that (a) extracellular H2O2 induces dose dependent damage to cultured gastric mucosal cells; (b) intracellular SOD plays an important role in preventing H2O2 damage; (c) generation of superoxide seems to occur intracellularly after exposure to H2O2, but independent of cellular xanthine oxidase; and (d) cellular iron mediates the damage by catalyzing the production of more reactive species from superoxide and H2O2, the process which causes ultimate cell injury.

Hepatocyte growth factor as a key to modulate anti-ulcer action of prostaglandins in stomach.

Although the clinical efficacy of prostaglandins (PGs), especially on gastric mucosal injuries induced by nonsteroidal antiinflammatory drugs, is widely appreciated, their mechanism of action, apart from acid suppression, is quite unclear. In this study, we have established a primary culture system of human gastric fibroblasts and clearly demonstrated that PGs strongly induce the expression of hepatocyte growth factor (HGF) in the fibroblasts, which is mediated by PGE specific receptor, EP2 or EP4. Since HGF facilitates repair and protection of gastric epithelial cells in a paracrine manner, it is assumed that some of the beneficial effects of PGs may be mediated by HGF. To confirm this assumption, we established a simplified in vitro culture gastric mucosal model which consists of gastric epithelial cells and gastric fibroblasts. Using the model, we performed a round wound restitution assay. PGE1 remarkably accelerated restitution which was completely inhibited by anti-HGF antibody, indicating that the action was mediated by HGF. To confirm these in vitro data, we further demonstrated that HGF mRNA expression is downregulated at the edges of nonsteroidal antiinflammatory drug-induced gastric ulcers where PGs should be depleted. In summary, we proposed that gastric fibroblasts are newly recognized targets of PGs, and HGF produced by human gastric fibroblasts may be a key factor for anti-ulcer action of PGs in the stomach.

Hepatocyte growth factor is the most potent endogenous stimulant of rabbit gastric epithelial cell proliferation and migration in primary culture.

Various growth factors are suggested to be involved in gastric mucosal repair. Our previous studies have shown that exogenous hepatocyte growth factor (HGF) has a proliferative effect on gastric epithelial cells. In the present study, comparison of the maximum proliferative effects and the optimum concentrations of several growth factors revealed that HGF was the most potent mitogen for gastric epithelial cells, as is the case for hepatocytes. Restitution of gastric epithelial cell monolayers was assessed using a round wound restitution model. HGF was the most effective agent for facilitating gastric epithelial restitution among those tested. A binding assay revealed specific binding of HGF to its receptor on gastric epithelial cells. Northern blot analysis confirmed the expression of specific HGF receptor mRNA (c-met) by gastric epithelial cells but not by gastric fibroblasts. To investigate endogenous HGF production, we determined the effect of gastric fibroblast-conditioned medium on epithelial proliferation and restitution. The conditioned medium produced similar effects to HGF and its activity was neutralized by an anti-HGF antibody. In addition, expression of HGF mRNA was detected in gastric fibroblasts but not in gastric epithelial cells. Our immunohistochemical study confirmed these in vitro data by means of demonstrating the existence and localization of HGF at human native gastric mucosa. HGF was localized at fibroblasts under the epithelial cell layer around gastric ulcers. These results suggest that HGF may be a potent endogenous promotor of gastric epithelial cell proliferation and migration, and may contribute to gastric mucosal repair through a paracrine mechanism.

Nitric oxide enhances cytotoxicity of cultured rabbit gastric mucosal cells induced by hydrogen peroxide.

While NO has been reported to act as a protective factor to gastric mucosa, it has been shown to be cytotoxic to various cells. NO also has been demonstrated to stimulate prostaglandin (PG) release and mucous glycoprotein secretion which could result in the activation of gastric defensive mechanisms. We examined the effect of NO on cytotoxicity induced by hydrogen peroxide, and mucous glycoprotein secretion and PGE2 release from cultured rabbit gastric mucosal cells. NO enhanced cytotoxicity induced by hydrogen peroxide. Defensive prostaglandin E2 release and mucous glycoprotein secretion were not altered by NO. Under certain circumstances, NO might behave as an aggressive factor in gastric mucosal injury.

Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)

Minimal change oesophagitis: a disease with characteristic differences to erosive oesophagitis.

BACKGROUND: The majority of gastro-oesophageal reflux disease (GERD) seems to be non-erosive reflux disease. Nonerosive reflux disease includes minimal change oesophagitis (whitish or reddish, oedematous change and erosion that is not regarded as mucosal break) and no endoscopic abnormalities. AIM: To investigate the accurate proportion of those with minimal change oesophagitis and to clarify its characteristics. In addition, we evaluated the effect of famotidine (40 mg/day) in those with minimal change. METHODS: Prospective endoscopic assessment was performed for consecutive 606 out-patients. Of the 582 patients suitable for analysis, 347 were non-treated. The latter were divided into those with erosive GERD or minimal change, and their endoscopic findings and characteristics were compared. RESULTS: Among 347 non-treated patients, 88 (25%) had erosive GERD and 249 (72%) had minimal change. Compared with patients who have erosive GERD and those with minimal change, the latter were less likely to have hiatal hernia or bile reflux, but more likely to have gastric atrophy. Symptomatic patients (n = 55) with minimal change oesophagitis were more likely to have hiatal hernia than those who were asymptomatic (n= 194). Most patients preferred taking famotidine on-demand, during a 4-week follow-up period. CONCLUSIONS: Most non-erosive reflux disease can be classified as minimal change oesophagitis, and that have different characteristics from erosive GERD. On-demand famotidine may be a suitable alternative treatment for patients with minimal change disease.

Promoters of epithelialization induce expression of vascular endothelial growth factor in human gastric epithelial cells in primary culture.

Both epithelialization and angiogenesis are indispensable processes in gastric ulcer healing. Coordination between these processes has not been well studied. In the present study, we have established a new primary culture system of human gastric epithelial cells and investigated the effect of epithelialization stimulants on a specific angiogenic factor, vascular endothelial growth characterized as epithelial cells. Both epithelialization stimulants, hepatocyte growth factor (HGF) and epidermal growth factor (EGF), significantly stimulated vascular EGF expression in gastric epithelial cells. HGF and EGF receptors were expressed by the cells, suggesting that regulation may be mediated through specific receptors.

Two different promoters direct expression of two distinct forms of mRNAs of human platelet-activating factor receptor.

The human platelet-activating factor (PAF) receptor gene exists as a single copy on chromosome 1. We identified two 5'-noncoding exons, each of which has distinct transcriptional initiation sites. These exons are alternatively spliced to a common splice acceptor site on a third exon that contains the total open reading frame to yield two different species of functional mRNA (Transcript 1 and 2). Transcript 1 has consensus sequences for transcription factor NF-kappa B and Sp-1, and the Initiator (Inr) sequence homologous to the murine terminal deoxynucleotidyltransferase gene. Transcript 2 also contains consensus sequences for transcription factor AP-1, AP-2, and Sp-1. Transcripts 1 and 2 were both detected in heart, lung, spleen, and kidney, whereas only Transcript 1 was found in peripheral leukocytes, a differentiated human eosinophilic cell line (EoL-1 cells), and brain. Existence of distinct promoters was thus suggested to play a role in the regulatory control of PAF receptor gene expression in different human tissues and cells.

Percutaneous ethanol injection therapy for hepatocellular-carcinoma (review).

Recently, ultrasound-guided percutaneous ethanol injection therapy (PEIT) has been widely performed in the treatment of hepatocellular carcinoma. Histopathologic examinations after the therapy have revealed that PEIT can destroy the tumor completely in most cases. Findings in imaging modalities and serum tumor marker levels have also shown a remarkable anticancer effect of this procedure. In addition, PEIT has achieved considerably high long-term survival rates. PEIT is a generally safe procedure and serious complications are rare. PEIT seems to be a valuable therapy and could even be an alternative to surgery in the treatment of hepatocellular carcinoma. This paper reviews the pertinent literature on this new therapy.

The effects of aspirin on antioxidant defences of cultured rat gastric mucosal cells.

BACKGROUND: Helicobacter pylori-associated inflammation leads to exposure of the gastric epithelium to reactive oxygen species (ROS) generated in the gastric mucosa. In some pathological conditions, such as those induced by nonsteroidal anti-inflammatory drugs, the gastric mucosa may become more susceptible to ROS. AIM: To examine the effects of aspirin on antioxidant defenses as well as on oxidant injury in cultured rat gastric mucosal cells. METHODS: Primary monolayer cultures of rat gastric fundic mucosa were exposed to an ROS-generating system, hypoxanthine/xanthine oxidase (XOD). Cytotoxicity was quantified by measuring 51Cr release from prelabelled cells. The effects of aspirin on antioxidants and on cellular injury brought about by the ROS-generating system were determined. RESULTS: XOD, in the presence of hypoxanthine, caused a dose-dependent increase in specific 51Cr release, which corresponded to the ability of XOD to produce ROS (as assessed by the production of uric acid from hypoxanthine). Incubation of cells with aspirin (1-100 microM) produced a dose-dependent increase in XOD-induced 51Cr release. Aspirin did not affect cellular glutathione content or activity of glutathione peroxidase, glutathione reductase or endogenous catalase. By contrast, aspirin caused a dose-dependent reduction in mucus synthesis. as assessed by incorporation of [3H]-glucosamine hydrochloride into the cells. CONCLUSIONS: Aspirin at therapeutically relevant concentrations rendered cultured gastric cells more susceptible to subsequent exposure to ROS. Aspirin affected neither the glutathione redox cycle nor catalase activity. Thus, the enhancement of ROS-induced injury by aspirin may be accomplished through diminished gastric mucus synthesis, since mucus is a potent scavenger of ROS. These findings provide insight into how gastric inflammation and injury (such as that induced by H. pylori infection) in human gastric mucosa is modulated by the administration of nonsteroidal anti-inflammatory drugs.

The effect of NSAIDs and a COX-2 specific inhibitor on Helicobacter pylori-induced PGE2 and HGF in human gastric fibroblasts.

BACKGROUND: There is compelling evidence for the pivotal role of Helicobacter pylori in the pathogenesis of gastrointestinal ulcer disease. However, despite the bacterium's toxicity, the majority of H. pylori infections are not accompanied by gastric ulcers. This implies the existence of a host mechanism offsetting H. pylori toxicity. AIMS: To evaluate gastric fibroblasts' expression of hepatocyte growth factor (HGF), which is known to facilitate gastric ulcer healing, in the presence of H. pylori; to compare the effect on H. pylori-induced HGF expression of a COX-2 selective inhibitor with that of nonselective nonsteroidal anti-inflammatory drugs METHODS: Human gastric fibroblasts were cultured from human gastric mucosa obtained at surgery. Prostaglandin E2 (PGE2) and HGF were measured by EIA. The expression of COX-2 mRNA was assessed by the TaqMan quantitative RT-PCR system. RESULTS: H. pylori increased PGE2 release in gastric fibroblasts. H. pylori induced expression of COX-2 mRNA, which indicates that PG induction by H. pylori is through COX-2. Sulindac sulphide, etodolac and NS 398 all inhibited H. pylori-induced PGE2 release to the same extent. These agents also inhibited H. pylori-induced HGF release. CONCLUSION: Gastric fibroblasts produce PG and HGF in response to the presence of H. pylori, which may be considered part of the human body's defensive reaction to H. pylori toxicity. This defensive mechanism is inhibited not only by COX-2 nonselective NSAIDs but also by a COX-2 selective inhibitor. These findings indicate the importance of COX-2 in chronic H. pylori infection.

Plasma transforming growth factor-beta1 level and efficacy of alpha-tocopherol in patients with non-alcoholic steatohepatitis: a pilot study.

BACKGROUND: Non-alcoholic steatohepatitis is a distinct entity, characterized by fatty change, lobular inflammation and fibrosis of the liver. Some cases of non-alcoholic steatohepatitis progress to cirrhosis, but it is not easy to distinguish this disease from non-alcoholic fatty liver by non-invasive examinations. No proven therapy for non-alcoholic steatohepatitis exists. Transforming growth factor-beta1 is implicated in the development of liver fibrosis, and is inhibited by alpha-tocopherol (vitamin E) in the liver. Therefore, in this study, the significance of the measurement of the level of plasma transforming growth factor-beta1 and the effect of alpha-tocopherol on the clinical course of non-alcoholic steatohepatitis were investigated. METHODS: Twelve patients with non-alcoholic steatohepatitis and 10 patients with non-alcoholic fatty liver, with a diagnosis confirmed by liver biopsy, were studied. None of the patients had a history of alcohol abuse, habitual medicine or malignant or inflammatory diseases. All patients were negative for hepatitis B, C and G virus. Patients were given dietary instruction for 6 months, and then alpha-tocopherol (300 mg/day) was given for 1 year. Blood chemistries, measurement of plasma transforming growth factor-beta1 level and liver biopsies were undertaken before and after the 1-year alpha-tocopherol treatment. RESULTS: The serum alanine transaminase level decreased in non-alcoholic fatty liver patients, but not in non-alcoholic steatohepatitis patients, after 6 months of dietary therapy. Although the serum alanine transaminase level in non-alcoholic steatohepatitis patients was reduced during the 1-year alpha-tocopherol treatment, alpha-tocopherol had no effect on the serum alanine transaminase level in non-alcoholic fatty liver patients. The histological findings, such as steatosis, inflammation and fibrosis, of the non-alcoholic steatohepatitis patients were improved after alpha-tocopherol treatment. The plasma transforming growth factor-beta1 level in non-alcoholic steatohepatitis patients was significantly elevated compared with that in non-alcoholic fatty liver patients and healthy controls, and decreased, accompanied by an improvement in serum alanine transaminase level, with alpha-tocopherol treatment. CONCLUSIONS: Our data suggest that the measurement of the level of plasma transforming growth factor-beta1 represents a possible method of distinguishing between non-alcoholic steatohepatitis and non-alcoholic fatty liver. Long-term alpha-tocopherol treatment may be safe and effective for non-alcoholic steatohepatitis. A randomized, controlled, double-blind trial is needed to confirm the full potential of alpha-tocopherol in the management of non-alcoholic steatohepatitis.

Effect of PPARgamma ligands on the viability of gastric epithelial cells.

BACKGROUND: [corrected] Peroxisome proliferator-activated receptors (PPAR) are a family of three nuclear receptors (PPARalpha, PPARdelta, and PPARgamma). Although recent evidence suggests a role for PPARgamma in the regulation of colonic epithelial cell growth, the role for PPARgamma in the stomach has not been established. AIM: To examine the expression of PPARgamma and the effects of PPARgamma ligands on the viability of gastric epithelial cells. METHODS: MKN45 cells and primary cultured rat gastric epithelial cells were used. Troglitazone (TGZ) and 15-deoxy-Delta12, 14-prostaglandin J2 (15d-PGJ2) were used as PPARgamma ligands. Expression of PPARgamma was examined by RT-PCR and Western blot analysis. Cell viability was measured by WST-1 assay and TUNEL assay was performed to detect apoptosis. RESULTS: MKN45 cells expressed all subtypes of PPAR. PPARgamma ligands decreased cell viability and induced cell death in a dose-dependent manner, whereas ligands for PPARalpha and PPARdelta had no significant effect. TUNEL assay showed that this cell death is apoptosis. Primary cultured rat gastric epithelial cells also expressed PPARgamma and activation of PPARgamma decreased cell viability. CONCLUSION: These results suggest that PPARgamma plays an important role in the regulation of cell growth and cell death in gastric epithelial cells.

Up-regulation of TFF expression by PPARgamma ligands in gastric epithelial cells.

BACKGROUND: Although trefoil factor family peptides (TFF peptides) are assumed to play important roles in gastric mucosal protection, the regulatory mechanism of gastric TFF expression has not been fully understood yet. Recent reports showed gastric expression of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor known to be involved in the regulation of cell growth and differentiation in other cell types, such as adipocytes. AIM: To determine whether PPARgamma affects the expression of TFF in gastric epithelial cells. METHODS: MKN45 gastric cells were used as a model of gastric epithelial cells. DNA synthesis of the cells was determined by the measurement of BrdU incorporation. The effects of PPARgamma ligands, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) and troglitazone (TGZ) on TFF expression were assessed by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: MKN45 cells expressed a significant amount of PPARgamma. Both 15d-PGJ2 and TGZ suppressed DNA synthesis of the cells in a dose-dependent manner. In the control condition, MKN45 cells most abundantly expressed TFF1 and the relative expression level of TFF1, TFF2, and TFF3 mRNA was 1700:32:1. TFF1 and TFF2 mRNA levels were significantly up-regulated by the incubation of the cells with 15d-PGJ2 (10 micro m) or TGZ (30 micro m), whereas TFF3 mRNA level was not affected. CONCLUSION: The results of the present study suggest a possible role of PPARgamma in the regulation of TFF expression in gastric epithelial cells.

Polaprezinc protects gastric mucosal cells from noxious agents through antioxidant properties in vitro.

BACKGROUND: Polaprezinc has been shown to exert an anti-oxidant property in a tube experiment, protect gastric mucosa from experimental ulcerations in vivo, and accelerate the healing of gastric ulcer in humans. AIM: To examine a possible protective effect of polaprezinc on oxidant-mediated injury in primary monolayer cultures of rat gastric fundic mucosa. METHODS: Cytotoxicity was quantified by measuring 51Cr release. Whether or not polaprezinc exerts an antioxidant property was investigated by determining the effect of this agent on hydrogen peroxide (H2O2)-induced injury. The effects of polaprezinc on superoxide (O2-. ) generation as well as on ethanol (EtOH)-induced injury were also examined. Generation of O2-. was assessed by the reduction in cytochrome c. RESULTS: H2O2 caused a time- and dose-dependent increase in 51Cr release. The dose-response curve of 51Cr release by H2O2 shifted to the right in the presence of polaprezinc. Polaprezinc, at submillimolar concentrations, prevented H2O2-induced 51Cr release. EtOH also caused a dose-dependent increase in 51Cr release, which was prevented by the addition of polaprezinc. The incubation of cells with EtOH caused an increase in cytochrome c reduction, as the concentrations of EtOH increased. Polaprezinc inhibited EtOH-induced cytochrome c reduction. Protection by polaprezinc was microscopically associated with the prevention of monolayer disruption. CONCLUSIONS: Polaprezinc is antioxidative and directly protects gastric mucosal cells from noxious agents through its antioxidant properties in vitro. This finding may provide the theoretical basis for the usage of an antiulcer drug with antioxidant properties for the treatment of gastric inflammation, such as that induced by ethanol.

Indometacin up-regulates TFF2 expression in gastric epithelial cells.

BACKGROUND: Trefoil factor family peptides are expressed in gastrointestinal epithelial cells and play a critical role in maintaining mucosal integrity. Although non-steroidal anti-inflammatory drugs (NSAIDs) are important causative agents of gastric mucosal lesions, few data are available about the effect of NSAIDs on trefoil family peptides in gastric mucosa. AIM: To examine whether indometacin, a widely used NSAID, affects trefoil factor family expression in gastric epithelial cells. METHODS: MKN45, a cell line derived from human gastric cancer, was used. TFF1, TFF2, and TFF3 mRNA expression was assessed by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). TFF2 gene transcription was also examined by luciferase reporter gene assay. RESULTS: Relative expression level of TFF1, TFF2, TFF3 mRNA was 616: 12: 1 in unstimulated MKN45 cells. Although indometacin (1-250 micro mol/L) had no significant effect on the expression of TFF1 and TFF3 mRNA, it up-regulated TFF2 mRNA expression in a dose- and time-dependent manner. Luciferase reporter gene assay confirmed the up-regulation of TFF2 gene transcription by indometacin. Indometacin-induced up-regulation of TFF2 expression was not antagonized by externally applied prostaglandin E2. CONCLUSION: These results suggest that indometacin up-regulates gastric epithelial cell TFF2 expression through a COX-independent mechanism. Since TFF peptides play an important role in gastric mucosal protection, indometacin-induced TFF2 may reduce the degree of gastric mucosal damage induced by indometacin.

Ultrasound-guided percutaneous injection of ethanolamine oleate for hypersplenism. An experimental study in dogs.

In order to evaluate a possible therapy for hypersplenism, an experiment with animals was done. In nine dogs, 0.6 ml/kg body weight of 5% ethanolamine oleate was injected percutaneously into the spleen under ultrasound guidance. The injection was repeated three times at intervals of 1 week. Three dogs each were killed at 1, 4, and 8 weeks after the final injection. All dogs tolerated the procedure well and lived until they were killed. The platelet count and leukocyte count increased after the injections, and remained higher than the pretreatment level until death. This effect probably is due to depressed splenic function. The autopsy showed 40% of the spleen to be infarcted with complete destruction of the normal structure. No serious complications occurred. In addition, injection of ethanolamine oleate in six fully heparinized dogs showed that there was little risk of hemorrhage. Ultrasound-guided percutaneous injection of ethanolamine oleate might be a simple and effective therapy for hypersplenism.

Cell culture model for antiulcerogenic agents.

To elucidate the mechanisms of antiulcerogenic agents, we established the cell culture model derived from rat gastric epithelium. The cultured cells were identified as mucus-producing cells by using histological analysis. This culture model is useful for investigating the untiulcer effect of various agents and to reveal the mechanisms of the drug action. In particular, the ulcer-healing model using the cultured monolayer is promising and convenient for the study of several growth factors such as HGF as well as antiulcerogenic agents. The effect of polaporezinc in the cultured model is introduced.

Role of calcitonin gene-related peptide and capsaicin-sensitive afferents in central thyrotropin-releasing hormone-induced hepatic hyperemia.

The involvement of capsaicin-sensitive afferent neurons and calcitonin gene-related peptide (CGRP) in the central thyrotropin-releasing hormone (TRH)-induced hepatic hyperemia was investigated in urethane anesthetized rats. Both systemic capsaicin pretreatment and intravenous administration of CGRP receptor antagonist, human CGRP-(8-37), completely abolished the stimulatory effect of hepatic blood flow induced by intracisternal injection of TRH analog (RX-77368; p-Glu-His-(3,3'-dimethyl)-Pro-NH2, 100 ng), assessed by the hydrogen gas clearance method. These data demonstrate the involvement of capsaicin-sensitive afferent neurons and CGRP in the central TRH-induced stimulation of hepatic blood flow.

Antioxidant defenses of cultured colonic epithelial cells against reactive oxygen metabolites.

Reactive oxygen metabolites produce colonic epithelial cellular injury. The present study evaluated the protective role of cellular superoxide dismutase, catalase, and glutathione (GSH) redox cycle in cultured rabbit colonic cells. Cultured rabbit colonic epithelial cells were exposed to reactive oxygen metabolites generated by hypoxanthine (1 mM) and xanthine oxidase (1 mU/ml) for up to 5 h. Cytotoxicity was quantified by measuring 51Cr release from prelabeled cells. Pretreatment with diethyldithiocarbamate (inhibitor of superoxide dismutase) reduced activity of cellular superoxide dismutase and increased 51Cr release caused by hypoxanthine/xanthine oxidase from colonic cells. Pretreatment with diethyl maleate (covalently binds GSH as catalyzed by GSH transferase), or buthionine sulfoximine (inhibitor of gamma-glutamylcysteine synthetase) decreased cellular GSH and enhanced reactive oxygen metabolites induced injury. Pretreatment with bis(chloroethyl)-nitrosourea (inhibitor of GSH reductase) inhibited activity of GSH reductase and increased 51Cr release from colonic cells. Preincubation with aminotriazole (inhibitor of catalase) reduced cellular catalase, but did not affect cellular injury. Therefore, we concluded that both cellular superoxide dismutase and the GSH redox cycle appeared to play a role in detoxifying reactive oxygen metabolites and that cellular catalase may be less important in rabbit colonic epithelial cells.