Protection of gastric mucosa from ethanol induced injury by recombinant epidermal growth factor in rats

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Protection of gastric mucosa in rats

We have studied the protective effects of truncal vagotomy, atropine, and PGE₂ against gastric mucosal injury produced by necrotizing agents (0.2 N NaOH, 0.6 N HCl, absolute ethanol), acetylsalicylic acid (ASA) and HCl, or serotonin (5HT). Vagotomy, atropine, and PGE₂ prevent the effects of different noxious agents. Vagotomy is protective only against 5HT and against ASA+0.15 N or 0.35 N HCl, whereas atropine and PGE₂ are also protective against the necrotizing agents. The effectiveness of vagotomy against ASA+0.35 N HCl does not depend on the inhibition of acid secretion and supports the hypothesis that removal of the vagal drive counteracts the effect of H⁺ back-diffusion.     

Time as a factor in the expression of ethanol injury to the gastric mucosa

A technique of quantitative histology was used to assess the influence of time after injury on the histological expression of gastric mucosal damage. Rats, pretreated with either natural prostaglandin E2 or saline, were subjected to intragastric administration of either 50% or 100% ethanol. Fifteen minutes later the ethanol was removed from the stomach. Rats were sacrificed at either 30 min or 24 h after ethanol instillation. In rats pretreated with saline and subjected to 100% ethanol with or without prostaglandin pretreatment, the extent of deep mucosal damage was markedly underestimated by early evaluation. Only 5.4% of the volume of the gastric mucosa showed evidence of damage at 30 min after ethanol, compared with 57.3% of the volume of the mucosa, at 24 h after 100% ethanol exposure. Assessment of gastric mucosa 24 h after ethanol injury showed that PGE2 reduces the extent of surface area damaged and the volume of the mucosal damage. When 50% ethanol was used as the injurious agent, no difference was noted in the volume of the mucosa damaged when the stomach was assessed at either 30 min or 24 h after injury. These results indicate that full histological expression of injury is not present 30 min after 100% ethanol instillation, at least in part because of fixation of the gastric mucosa by 100% ethanol. Fifty per cent ethanol, which does not cause mucosal fixation, may be better as a test agent.     

聚普瑞锌诱导HSP70保护大鼠胃黏膜损伤

目的探讨聚普瑞锌诱导热休克蛋白70(heat shock protein 70,HSP70)减轻大鼠胃黏膜损伤的作用机制。方法无水乙醇灌胃致大鼠胃黏膜损伤后分别应用聚普瑞锌100 mg/kg、200 mg/kg灌胃及赋形剂灌胃,同时以空白组作对照,检测胃黏膜HSP70蛋白表达。同时检测各实验组大鼠胃黏膜IGF-1含量和SOD活性。结果聚普瑞锌100 mg/kg治疗组治疗3 d时HSP70表达的相对灰度值为278.3%±10.8%;聚普瑞锌200 mg/kg治疗组治疗3 d时HSP70表达的相对灰度值为471.1%±24.7%,与空白组和赋形剂组相比,差异均有统计学意义(P0.01)。各实验组大鼠胃黏膜IGF-1含量和SOD活性差异无统计学意义(P0.05)。结论聚普瑞锌能够诱导损伤后大鼠胃黏膜产生大量HSP70,发挥保护胃黏膜的作用。     

Protection by trimipramine against gastric mucosal barrier dysfunction induced by ethanol + HC1 in rats.

The effects of trimipramine (5 mg . kg-1 . h-1 intravenously) on the changes in gastric mucosal function evoked by 20% ethanol + HCl has been stuided in rats. The magnitude of the changes in potential difference, ionic fluxes (H+, Na+, and K+), and mucosal lesion score induced by ethanol + HCl were significantly less in animals treated with trimipramine than in control animals. It is concluded that trimipramine decreases the gastric mucosal damage produced the ethanol + HCl in rats. This activity may be responsible, at least in part, for the beneficial effect of trimipramine treatment in peptic ulcer disease.     

缺血后处理对再灌注大鼠胃黏膜细胞的保护作用

目的探讨缺血后处理对再灌注大鼠胃黏膜的保护作用及其抗氧化机制。方法制备胃缺血后处理模型;实验分为5组（n=6）：假手术组（S）、单纯缺血-再灌注组（I—R）、缺血预处理组（IPC）、缺血后处理组（I-post）、缺血后处理＋缺血预处理组（I-post＋IPC）。记录各组胃黏膜损伤指数并检测胃黏膜丙二醛（MDA）含量、超氧化物歧化酶（SOD）的活性变化;末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）检测胃黏膜细胞的凋亡。结果 与S组相比,I—R组胃黏膜损伤指数和黏膜细胞凋亡率显著升高,胃黏膜MDA含量屁著增加,SOD活性明屁降低;在IPC组、I-post组和I-post＋IPC组,胃黏膜损伤指数与细胞凋亡率较I—R组显著降低,胃黏膜MDA含量也显著降低,而SOD活性明显升高;I-post＋IPC组对再灌注的胃黏膜损伤无叠加保护作用,分别与IPC组和I-post组相比,各项指标的差异无统计学意义。结论缺血后处理可显著减轻胃黏膜再灌注损伤,其效应与缺血预处理相似,其机制之一可能与其再灌注后氧自由基的生成减少,抑制胃黏膜细胞膜脂质过氧化、使冉灌注的胃黏膜细胞凋亡减轻有关。     

Peroxiredoxin I protects gastric mucosa from oxidative injury induced by H. pylori infection

Background and Aim: Helicobacter pylori (H. pylori) infection enhances the production of reactive oxygen species and peroxynitrite, thereby resulting in oxidative tissue damage. In this study, we examined the role of peroxiredoxin I (Prx I), a stress‐induced antioxidant enzyme, in protecting gastric mucosa from H. pylori‐induced gastric mucosal injury. Methods: Wild type (Prx I^+/+) and Prx I‐deficient type (Prx I^–/–) mice were maintained for 2 to 12 months with or without infection of H. pylori, Sydney strain‐1. Gastric mucosal expression of Prx I was assessed by immunoblot analysis and immunohistochemistry. The degree of gastritis was evaluated by the updated Sydney system and by mucosal levels of inflammatory cytokines (MIP‐2, IL‐1β, and TNF‐α). Oxidative DNA injury and apoptosis were analyzed by mucosal level of 8‐hydroxy‐2′‐deoxyguanosine, and the number of apoptotic cells stained with a single‐stranded DNA antibody, respectively. Results: H. pylori infection upregulated gastric mucosal Prx I expression in the Prx I^+/+ but not the Prx I^–/– mice. H. pylori infection also induced more severe gastritis and a more prominent increase in MIP level, more marked oxidative DNA injury, and apoptosis in the Prx I^–/– than the Prx I^+/+ mice. In the absence of H. pylori infection, no changes were demonstrated in gastric mucosa in either the Prx I^+/+ or the Prx I^?/? mice. Conclusion: These data suggest that H. pylori infection upregulates gastric mucosal Prx I expression, and further, that Prx I plays an important role in gastric mucosal protection against oxidative injury induced by H. pylori infection.     

Effects of dopamine on gastric mucosal lesions induced by ethanol in rats

Acidified ethanol (60% ethanol in 150 mM HCl, per os) induced elongated bands of hemorrhagic lesions along the long axis of the stomach within 1 hr in rats. Pretreatment with dopamine hydrochloride (DA: 1-10 mg/kg, subcutaneously) dose-dependently reduced the severity of these lesions. In parallel study, DA had no effect on acid secretion but inhibited gastric motor activity in a dose-related manner. The inhibitory effects of DA on both acidified ethanol-induced lesions and gastric motor activity were significantly reversed by pretreatment with yohimbine, an inhibitor of alpha 2-adrenoceptors (5 mg/kg, subcutaneously), but not by prazosin, haloperidol, or indomethacin. Similar to DA, both norepinephrine (NE: 1 mg/kg, subcutaneously) and epinephrine (EPI: 1 mg/kg, subcutaneously) showed inhibition of the motor activity and gastroprotection against acidified ethanol, but these effects were also significantly attenuated by yohimbine. A highly significant relationship was found between the inhibitory effects of DA, NE, and EPI on the motor activity and the mucosal lesions (r = 0.8577, P less than 0.05). In addition, administration of gentian violet (0.5% w/v, per os) stained the mucosa deep blue as elongated wide bands in the corpus region, and such localized staining was significantly prevented by DA, suggesting a flattening of the mucosal foldings in the presence of DA. These results suggest that DA (and other catecholamines) protects the rat gastric mucosa against injury caused by acidified ethanol, probably through inhibition of gastric motor activity mediated with stimulation of alpha 2-adrenoceptors.     

Prostaglandin protection of rat colonic mucosa from damage induced by ethanol

The effects of pretreatment with 16,16-dimethyl prostaglandin E₂ (dmPGE₂) on ethanol-induced colonic damage were studied in the rat. Colonic damage was assessed macroscopically, histologically, and using cytoplasmic (lactate dehydrogenase) and lysosomal (acid phosphatase) enzyme markers of cell disruption. Intrarectal administration of 30% ethanol produced grossly visible regions of hyperemia and hemorrhage. Histologically, the ethanol injury was characterized by complete destruction of the surface epithelium and necrosis extending throughout most of the mucosal layer. When incubatedin vitro after challenge with ethanolin vivo, the colons released significantly more acid phosphatase and lactate dehydrogenase than did controls. Intrarectal pretreatment with dmPGE₂ caused a dose-dependent reduction in ethanol-induced damage, as measured by all three parameters. A significant (P<0.05) reduction of macroscopically visible damage was observed with 0.2 g/kg dmPGE₂, while at higher doses (20 g/kg) the histological signs of damage, including that to the colonic epithelium, were reduced or completely prevented. This dose of dmPGE₂ also reduced (P<0.01) the release of the enzymemarkers to control levels. The possibility that this protection was mediated by increased colonic fluid secretion was studied. Pretreatment with dmPGE₂ had no effect on net colonic fluid secretion (measured using the nonabsorbable marker [³H]inulin) or on the absorption of ethanol by the colon. This study demonstrates that intrarectal administration of dmPGE₂ can protect the colonic mucosa from damage induced by direct application of a potent topical irritant. With the highest dose of dmPGE₂ tested (20 g/kg), protection of the colonic epithelium from ethanol injury was observed.     

促愈颗粒对胃溃疡实验大鼠胃黏膜表皮生长因子及其受体表达的影响

[目的]研究促愈颗粒对乙酸烧灼型胃溃疡(GU)大鼠胃黏膜表皮生长因子(EGF)及其受体(EGFR)表达的影响。[方法]将大鼠随机分为4组:正常对照组,模型组,促愈颗粒组和雷尼替丁组。乙酸制备慢性GU大鼠模型后,于给药14 d和28 d后分2次处死大鼠,观察胃黏膜组织形态,免疫组织化学技术检测大鼠胃黏膜EGF及EGFR水平。[结果]与模型组比较,促愈颗粒组和雷尼替丁组囊状扩张腺体数量均显著减少(P<0.01,<0.05),EGF及EGFR水平均显著增高(P<0.01,<0.05),且促愈颗粒组作用均优于雷尼替丁组(均P<0.05)。[结论]促愈颗粒可能通过增加胃黏膜EGF和EGFR的水平,进而提高GU再生黏膜结构和功能成熟度,从而促进溃疡愈合,提高溃疡愈合质量,并防止溃疡复发。     

Role of Superoxide and hydroxyl radicals in rat gastric mucosal injury induced by ethanol

It has been reported that oxygen-derived free radicals play an important role in the pathogenesis of mucosal injury in the small intestine as well as in the stomach. The aims of this study were to test whether ethanol-induced damage in the rat stomach was prevented by the administration of (1) Superoxide dismutase (SOD; a scavenger of Superoxide radicals), (2) allopurionol (ALP; an inhibitor of xanthine oxidase), (3) dimethyl sulfoxide (DMSO; a scavenger of hydroxyl radicals). SOD significantly decreased the ulcer index from 100±8.5% (control) to 39.6±8.2% (P<0.001). Ethanol-induced damage was reduced by the administration of ALP by 37.4% (P<0.01). DMSO also diminished the ulcer index from 100±8.5% (control) to 31.6±5.8% (P<0.01). Histochemical studies supported these results. A scanning EM study, however, revealed that surface epithelial cells were not protected by SOD against ethanol-induced damage. These results demonstrated that SOD, ALP and DMSO had the ability to protect gastric mucosa against ethanol-induced injury. Accordingly, oxygen-derived free radicals may be involved in the pathogenesis of ethanol-induced gastric mucosal damage. Surface epithelial cells, however, were not protected even by SOD against ethanol-induced injury. This paper was presented in 87th Annual Meeting of American Gastroenterological Association (1986).     

Role of superoxide and hydroxyl radicals in rat gastric mucosal injury induced by ethanol

It has been reported that oxygen-derived free radicals play an important role in the pathogenesis of mucosal injury in the small intestine as well as in the stomach. The aims of this study were to test whether ethanol-induced damage in the rat stomach was prevented by the administration of (1) superoxide dismutase (SOD; a scavenger of superoxide radicals), (2) allopurionol (ALP; an inhibitor of xanthine oxidase), (3) dimethyl sulfoxide (DMSO; a scavenger of hydroxyl radicals). SOD significantly decreased the ulcer index from 100 +/- 8.5% (control) to 39.6 +/- 8.2% (P less than 0.001). Ethanol-induced damage was reduced by the administration of ALP by 37.4% (P less than 0.01). DMSO also diminished the ulcer index from 100 +/- 8.5% (control) to 31.6 +/- 5.8% (P less than 0.01). Histochemical studies supported these results. A scanning EM study, however, revealed that surface epithelial cells were not protected by SOD against ethanol-induced damage. These results demonstrated that SOD, ALP and DMSO had the ability to protect gastric mucosa against ethanol-induced injury. Accordingly, oxygen-derived free radicals may be involved in the pathogenesis of ethanol-induced gastric mucosal damage. Surface epithelial cells, however, were not protected even by SOD against ethanol-induced injury.     

Non-mitogenic acidic fibroblast growth factor reduces intestinal dysfunction induced by ischemia and reperfusion injury in rats

BACKGROUND: Acidic fibroblast growth factor (aFGF) has potentially therapeutic uses in some diseases, but the mitogenic activity of aFGF has been found to contribute to several human pathologies, so the extensive applications of wild-type aFGF have been limited. The purpose of the present study was to explore the effects and mechanisms of wild-type (aFGF) and non-mitogenic aFGF on gut ischemia-reperfusion injury in rats. METHODS: Rat intestinal ischemia-reperfusion injury (I/R) was produced by clamping the superior mesenteric artery (SMA) for 45 min followed by reperfusion. One hundred and fourteen rats were randomly divided into four groups: sham operation (group C, n = 6), intestinal I/R + 0.1 mL saline (group S, n = 36), intestinal I/R + 4 microg/0.1 mL wild-type aFGF (group W, n = 36) and intestinal I/R + 4 microg/0.1 mL modified aFGF (i.e. non-mitogenic aFGF; group M, n = 36). According to different periods after reperfusion, groups S, W and M were further divided into 0.5-, 1-, 2-, 6-, 12- and 24-h subgroups. The contents of D-lactate and nitrite/nitrate were determined, the changes of intestinal histology were analyzed, the protein expressions of caspase-3, extracellular signal-regulated kinase (ERK)1/2, and p38 were detected by western blot, and apoptotic cells were examined by the terminal deoxynucleotidyl transferase (TdT)-mediated dUDP-biotin nick end labeling (TUNEL) assay at 0.5, 1, 2, 6, 12 and 24 h after I/R, respectively. RESULTS: Compared with rats in group S, intestinal histological damage, apoptotic index, d-lactate content and nitrite/nitrate level all decreased significantly in group W and group M rats. However, there was no difference between rats treated with wild-type aFGF and those with non-mitogenic aFGF. The protein expression of caspase-3, ERK1/2, and p38 in saline-treated rats was higher than those in aFGF-treated rats. CONCLUSIONS: Both types of aFGF had protective effects on gut I/R and there was no significant difference between the two aFGF. The protective effects of aFGF may come from the non-mitogenic activity rather than the mitogenic activity of aFGF in tissue repair, indicating a potentially clinical use for the non-mitogenic effects of aFGF in preventing visceral organ injury triggered by I/R injury in the future.     

Roles of hepatocyte growth factor and its receptor in gastric mucosa

Hepatocyte growth factor (HGF) stimulates the growth of hepatocytes and other epithelial cells. A gene for the HGF receptor,c-met, is detected in the intestinal tract and the liver, as well as in gastric carcinoma cells. However, the role of HGF in the regeneration of the normal gastric mucosa is not known. The purpose of the present study was to elucidate the effects of HGF on the morphogenesis of cultured gastric mucosal cells and to evaluate the role of HGF andc-met in the healing process in rat gastric mucosa. The cultured gastric mucosal cells developed a branching morphology in a collagen matrix supplemented with HGF or fetal calf serum. They did not form this morphology on a plastic dish or in the collagen without HGF or the serum. In anin vivo study, total RNA was extracted from rat gastric mucosa 6, 24, 48, and 96 hr after the exposure to a solution of 0.6 M HCl. HGF messenger RNA was not detected, butc-met was expressed in the mucosa. The increased expression ofc-met was followed by healing of the mucosal injury. These results indicate that HGF plays important roles in the morphogenesis of gastric mucosal cells and that the HGF receptor gene participates in the healing process of gastric mucosa.     

Characterization of the epidermal growth factor receptor in the gastric mucosa

The effects of epidermal growth factor (EGF), a potent mitogen involved in mucosal protection, are mediated by specific cellular receptors. Here, we present the characteristics and binding properties of EGF receptors in the gastric mucosa. The studies were conducted using cell membranes isolated by subcellular fractionation of rat stomach mucosal scrapings. Specific binding of [125I]-EGF to the membrane preparations was assessed at room temperature for various periods of time and at different pHs. The results showed that the binding was proportional to the incubation time up to 1 h and was not affected by a pH change between 4.0 and 7.0. Scatchard analysis of the binding data infer the presence of 2 binding sites, one of high affinity (Kd = 1.34 nM, Bmax = 34 fmol/mg protein) and the other of low affinity (Kd = 484 nM, Bmax = 2.29 pmol/mg protein). Cross-linking experiments using disuccinimidyl suberate to link the [125I]-EGF to gastric membranes followed by polyacrylamide gel electrophoresis and autoradiography revealed that the major receptor for EGF was a protein of 170 kilodaltons. When the solubilized membranes were subjected to wheat germ agglutinin affinity chromatography, the purified material was found to act as substrate for EGF-stimulated phosphorylation. The major component which was labeled by the [gamma-32P]-ATP was also found to be a 170-kilodalton protein. The data are the first to provide evidence that the gastric mucosa possesses a functional EGF receptor and describe its binding characteristics.     

Artemisia asiatica extracts protect against ethanol-induced injury in gastric mucosa of rats

Background and Aim:  Based on our previous studies that Artemisia asiatica extracts exert either antioxidative or cytoprotective actions against non-steroidal anti-inflammatory drugs or Helicobacter pylori -induced gastric mucosal injury, or imposes qualified ulcer healing in an acetic acid-induced gastric ulcer model, we investigated the protective effects of Artemisia asiatica extracts against ethanol-induced gastric mucosal injury.
Methods:  Sprague–Dawley rats received 4 g/kg body weight (BW) of absolute ethanol intragastrically, which produced visible hemorrhagic gastric lesions 60 min later.
Results:  In this animal setting, the pretreatment of Artemisia extracts (30 or 100 mg/kg BW), 1 h before ethanol administration, significantly attenuated the source of gastric injury, which was assessed with gross and microscopic analysis ( P  < 0.01). Protection from alcohol-induced damage with Artemisia pretreatment was associated with significantly decreased lipid peroxidation, protecting gastric mucosa from glutathione depletion, as well as the inhibition of the cytochrome 2E1 ethanol-metabolizing enzyme. It attenuated the expressions of ethanol-induced pro-inflammatory cytokines, including interleukin (IL)-1β and interferon-γ, a weak activation of IL-10, the inhibition of the alcohol-induced overexpression of intercellular adhesion molecule-1, and the considerable induction of heat shock protein-72 expression in gastric mucosal homogenates .
Conclusion:  The data suggest that the ethanol extracts of Artemisia asiatica exerted significant protection from alcohol-induced gastric mucosal injury through bioregulation, which is essential for cytoprotection and anti-inflammation.     

Role of leukotrienes in acute gastric lesions induced by ethanol,taurocholate, aspirin,platelet-activating factor and stress in rats

This study was designed to determine the role of leukotriene C₄ (LTC₄) in the formation of acute gastric lesions induced by 100% ethanol, acidified taurocholate (TC), acidified aspirin (ASA), platelet-activating factor (PAF), and water-immersion and restraint stress. Exogenous LTC₄ alone administered in gradually increasing doses (5–20g/kg/hr) caused only mild hemorrhagic lesions in the gastric mucosa but when combined with 100% ethanol, acidified TC, acidified ASA, or stress, it increased significantly the mean lesion area and lesion number as compared to those produced by these ulcerogens alone. FPL 55712, a LTC₄ antagonist, given orally (2.5–10 mg/kg) reduced dose-dependently the extent of gastric lesions in all experimental models used and completely prevented the deleterious effects of exogenous LTC₄ on gastric mucosa. PAF augmented the mucosal lesions induced by 100% ethanol, and this was also reduced by the pretreatment with FPL 55712. FPL 55712-induced gastroprotection against various ulcerogens was reversed, in part, by indomethacin, indicating that it could be attributed not only to the LTC₄ antagonism but also to increased biosynthesis of PGs. This study provides evidence that LTC₄ is involved in the formation of acute gastric damage and the antagonism of LTC₄ may protect the mucosa against various ulcerogens.