Edgar S.L. Liu

Effect of polysaccharides from Angelica sinensis on gastric ulcer healing.

Our previous study showed that a crude extract from Angelica sinensis (ASCE), which mainly consisted of polysaccharides, significantly promoted migration and proliferation of normal gastric epithelial cells. These results strongly suggest that ASCE has a direct wound healing effect on gastric mucosa. However, there is no report concerning the effect of ASCE on gastric ulcer healing in animal models. In this study, we found that ASCE promoted ulcer healing. The area of the ulcer was reduced. This was accompanied with a significant increase in mucus synthesis when compared with the control. Angiogenesis was inhibited by the treatment of ASCE. Cell proliferation, ODC and EGFR protein expression was not affected in this process. Thus, the mechanism of how ASCE accelerates ulcer healing in addition to its effect on mucus synthesis remains to be investigated.

A mechanistic study of proliferation induced by Angelica sinensis in a normal gastric epithelial cell line.

It has been reported that an extract from Angelica sinensis mainly consisting of polysaccharides (95%) prevented ethanol- or indomethacin-induced gastric mucosal damage (Cho CH et al. Planta Med 2000;66:348-51). However, it is not known whether Angelica sinensis has a direct stimulatory effect on the healing of gastric mucosal lesions. To study the hypothesis that Angelica sinensis has a direct mucosal healing effect in rats and in isolated gastric epithelial cells, we assessed the wound repair in both animals and normal cell culture (RGM-1), as well as [3H]thymidine incorporation, ornithine decarboxylase (ODC) activity, and ODC protein and c-Myc protein expression after different treatments in RGM-1 cells. We found that Angelica sinensis crude extract (ASCE) dose-dependently enhanced gastric ulcer healing in rats and promoted wound repair in RGM-1 cells. It also significantly stimulated [3H]thymidine incorporation and ODC activity in RGM-1 cells in a concentration-dependent manner. ODC and c-Myc protein expression was also increased as a result of this process. DL-alpha-difluoromethyl-ornithine repressed the [3H]thymidine incorporation and ODC activity induced by ASCE. Pretreatment with c-Myc antisense oligodeoxynucleotides blocked the stimulatory action of ASCE on [3H]thymidine incorporation and ODC protein expression. These data suggest that ASCE has a direct mucosal healing effect on gastric epithelial cells, while ODC and c-Myc are closely associated with this effect.

Relationship between Ethanol-Induced Gastritis and Gastric Ulcer Formation in Rats

Background/Aims: Patients with peptic ulcer diseases have a high prevalence of coexisting chronic gastritis. The mechanism of how gastritis leads to gastric ulcer formation is yet to be determined. The purpose of this study was to clarify the relationship between gastritis and gastric ulcer in rats. Methods: Ethanol (80% v/v, p.o.) was given repeatedly in rats to induce subchronic gastritis. Gastric ulcer was then induced by 60% acetic acid. Results: Findings showed that subchronic gastritis potentiated gastric ulcer formation. It also produced more apoptotic cells, together with an overexpression of tumor necrosis factor-α (TNFα) in the gastric mucosa. Inhibition of the production/release of TNFα by pentoxifylline prevented the increase in apoptosis and the enhancement of susceptibility to ulcerative damage by subchronic gastritis. However, such subchronic gastritis did not further affect the rate of ulcer healing in these animals. Conclusion: The induction of gastritis resulted in an activation of TNFα expression followed by apoptosis in the gastric mucosa. This could lead to an increase in the severity of ulcerative damage in the stomach.

Cigarette smoke extracts delay wound healing in the stomach: Involvement of polyamine synthesis

The association between cigarette smoking and peptic ulcer diseases has been well established. Ornithine decarboxylase (ODC) is crucial for the gastroprotective and mucosal growth promoting effects in gastric ulcer healing. The aim of this study is to elucidate the possible mechanism of how Inhibition of ODC activity is involved in the delay of ulcer healing, if any, by cigarette smoke extracts (CSE). CSE were fractionated into chloroform extract (CE) and ethanol extract (EE). In in vivo study, rats with acetic acid-induced ulcers were given CE or EE intragastrically (2.5 or 5 mg/kg) once daily for 3 days. Ulcer sizes were significantly larger after CE or EE administration, followed by an increase in myeloperoxidase activity and a reduction in cell proliferation. However, both CSE stimulated the number of microvessels following the increase of basic fibroblast growth factor. In In vitro studies, the effect of CE or EE (10, 40, or 100 μg/ml) on cell migration and cell proliferation were measured using an In vitro wound model and [3H]-thymidlne incorporation assay, respectively. Both CSE delayed cell migration and decreased cell proliferation, which were accompanied with a reduction in ODC activity. Exogenous spermidine (5 or 10 μM) could reverse the inhibitory action on cell proliferation and ODC activity induced by CSE. In conclusion, both CSE significantly delayed ulcer healing as a result of reduction in cell proliferation and cell migration. All these effects are, in part, related to the reduction of polyamine synthesis.

Protective role of cyclooxygenase inhibitors in the adverse action of passive cigarette smoking on the initiation of experimental colitis in rats

Clinical and experimental findings had indicated that cigarette smoke exposure, and cyclooxygenase-2, are strongly associated with inflammatory bowel disease. The present study aimed to evaluate the role of cyclooxygenase-2 in the pathogenesis of experimental inflammatory bowel disease as well as in the adverse action of cigarette-smoke exposure. Rats were pretreated with different cyclooxygenase-2 inhibitors (indomethacin, nimesulide, or SC-236 (4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide)) along with cigarette-smoke exposure before 2,4,6-trinitrobenzenesulfonic acid-enema. Results indicated that pretreatment with cyclooxygenase-2 inhibitors not only protected against 2,4,6-trinitrobenzenesulfonic acid-induced inflammatory bowel disease, but also attenuated the potentiating effect of cigarette-smoke exposure on colonic damage. Furthermore, the colonic cyclooxygenase-2 protein and mRNA expression was markedly induced by 2,4,6-trinitrobenzenesulfonic acid-enema, and it was potentiated further by cigarette-smoke exposure, while the cyclooxygenase-1 expression was not changed. The present study suggests that the highly induced cyclooxygenase-2 expression not only plays a pathogenic role in 2,4,6-trinitrobenzenesulfonic acid-induced inflammatory bowel disease, but also contributes to the adverse action of cigarette-smoke exposure on this disorder.

Pathogenesis of nicotine treatment and its withdrawal on stress-induced gastric ulceration in rats

Previous studies showed that cigarette smoking was closely associated with gastric ulceration. People usually smoke under stress conditions, and together, these could induce more gastric damage. In the present study, we aimed to study the effects of nicotine administration and its withdrawal on stress-induced gastric ulceration in rats. Male Sprague-Dawley rats were given nicotine (25 or 50 microg/ml) for 10 days and then withdrawn for 2, 4 or 6 days. They were subjected to cold-restraint stress for 2 h after nicotine treatment or after nicotine withdrawal, and then killed. The results indicated that both nicotine treatment and its withdrawal potentiated stress-induced gastric damage. The mucosal glutathione (GSH) and mucus levels were reduced by stress and decreased further by nicotine. The prostaglandin E(2) concentration remained unchanged. To conclude, the adverse effect of nicotine on stress ulceration was prostaglandin E(2)-independent but mediated by the depression of glutathione and mucus levels in the gastric mucosa.

Nicotine suppresses gastric wound repair via the inhibition of polyamine and K+ channel expression

Nicotine is one of the most representative components in cigarette smoke leading to gastric ulceration. Both ornithine decarboxylase and potassium ion (K(+)) channels are essential for cell growth and wound repair. The aim of the present study is to elucidate the causative relationship of these two factors during wound healing and the influence of nicotine on this healing process in rat gastric mucosal epithelial cells (RGM-1). Nicotine markedly inhibited cell migration and proliferation in RGM-1 cells. The latter effect was significantly antagonized by a nicotinic receptor blocker, mecamylamine. Nicotine also suppressed ornithine decarboxylase activity significantly. Our data showed that inhibition of cell proliferation and ornithine decarboxylase activity by nicotine was accompanied with a reduction in K(+) channel protein expression, all of which were significantly alleviated by spermidine pretreatment. These results suggested that there was a cause/effect link between ornithine decarboxylase and K(+) channel on wound repair. Nicotine in cigarette smoke inhibited this healing process and delayed wound repair in gastric epithelial cells.

Morphine as a drug for stress ulcer prevention and healing in the stomach

Morphine pretreatment protects against stress-induced gastric ulceration, however, the exact mechanism is still undefined. Interestingly, the effect of morphine on ulcer healing has not been investigated. In this report, we would like to study these effects in a defined stress ulcer model and to delineate a new implication for morphine to promote stress ulcer healing in rats. Our study showed that cold-restraint stress for 3 h induced hemorrhagic lesions and increased myeloperoxidase activity in the gastric mucosa. Stress also reduced the dimension of layer of periodic acid-Schiff reagent-stained cells in the gastric mucosa by about 50%. Morphine pretreatment (2 or 8 mg/kg, given intraperitoneally) at the time of stress dose-dependently reversed stress-induced gastric ulceration, increase of myeloperoxidase activity and reduction of thickness of mucus-stained cells in the gastric mucosa. Morphine treatment after stress (given at the end of a 3-h stress and also at 3 h thereafter) increased ulcer healing by reducing the ulcer size measured 24 h later. Such action was blocked by naloxone (8 mg/kg) given intraperitoneally 15 min before morphine treatment. Morphine also increased the number of cell proliferation and dimension of layer of cells stained for mucus but not the number of microvessels in the gastric mucosa. Moreover, the number of apoptotic cells was less evidenced in the morphine-treated rats. This study reports for the first time that morphine not only prevents stress ulceration but also promotes healing of stress ulcer through a defined mechanism.

A 3.0-kDa low molecular weight heparin promotes gastric ulcer healing in rats.

Previous studies have shown that intragastric administration of unfractionated heparin enhances gastric ulcer healing in rats. As the large molecule of heparin may be partially degraded in the upper gastrointestinal tract, it is likely that fragments of heparin, derived from the unfractionated parent compound, are involved in the anti‐ulcer action in the stomach. Therefore, it is possible that low molecular weight heparin may have a similar ulcer healing effect.

Differential Effects of Cigarette Smoke Extracts on Cell Proliferation in Gastric and Colon Cells

Substantial evidence show a higher incidence of gastric cancer in smokers than nonsmokers and that cigarette smoking is highly associated with colon cancer. The present study was designed to examine the effect of cigarette smoke extracts on gastric and colon cancer cell proliferation, which is important for tumor growth. Two different cell lines were used. One was gastric cancer cell line AGS, and the other was colon cancer cell line HT-29. It was found that cigarette smoke extracts stimulated cell proliferation and c-myc expression in AGS cells. Furthermore, this proliferative action was partially blocked by the c-myc antisense. However, the extracts significantly inhibited HT-29 cell proliferation and suppressed c-myc expression. In conclusion, cigarette smoke extracts stimulated AGS cell proliferation, while inhibiting HT-29 proliferation, which were partially mediated by a c-myc-related pathway. The former action may play a contributory role in the carcinogenic action of cigarette smoking in the stomach.