Conditional loss of TGF-beta signalling leads to increased susceptibility to gastrointestinal carcinogenesis in mice.

BACKGROUND: Downregulation of TGF-beta receptors is implicated in colon cancer development. Inactivation of either of the two transmembrane serine/threonine kinases, TGF-beta1 types I/II receptors, is now implicated in carcinogenesis, especially gastrointestinal carcinogenesis. METHODS: We generated transgenic mice, called pS2-dnRII or ITF-dnRII, of which the dominant negative mutant of the TGF-beta type II receptor was expressed under the control of tissue-specific promoters, the pS2 promoter for stomach and ITF for intestine. They were either infected with H.pylori (ATCC 43504 strain, CagA+ and VacA+) or administered with azoxymethane to determine the significance of loss of TGF-beta signalling in gastrointestinal carcinogenesis. RESULTS: Gastric adenocarcinoma developed in pS2-dnRII mice, whereas only chronic active gastritis was noted in wild-type littermates after 36 weeks of H.pylori infection. Mice lacking in TGF-beta signalling specifically in the stomach showed a significantly higher proliferation cell nuclear antigen-labelling index when infected with H.pylori than wild-type littermates (P < 0.01). Development of colonic aberrant crypt foci was provoked in mice by intraperitoneal injections of azoxymethane, and ITF-dnRII mice showed significantly higher incidences of ACF and colon cancers than wild-type littermates. CONCLUSIONS: Maintaining normal TGF-beta signalling in the gastrointestinal tract seems to be important either for preventing abnormal mucosal proliferation, or for suppressing or retarding carcinogenesis.

Oxidative stress is more important than acid in the pathogenesis of reflux oesophagitis in rats.

BACKGROUND: Although antisecretory medications such as histamine type II receptor antagonists or proton pump inhibitors have been used to treat reflux oesophagitis, a considerable number of patients do not achieve complete mucosal healing or suffer from either sustained symptoms or ensuing complications, suggesting other damaging factors or impaired mucosal resistance are also involved in the pathogenesis of reflux oesophagitis. AIMS: The present study was designed to evaluate oxidative stress as the major pathogenic factor of reflux oesophagitis and to determine the usefulness of antioxidants in the treatment of reflux oesophagitis. MATERIALS AND METHODS: Reflux oesophagitis was induced by insertion of a 3 mm calibre ring into the duodenum, 1 cm distal to the ligament of Treitz, in Sprague-Dawley rats. RESULTS: DA-9601, a novel antioxidant substance, significantly attenuated the gross and histopathological scores of reflux oesophagitis compared with those treated with ranitidine alone or reflux oesophagitis controls in a dose dependent manner. Only scattered erosions were observed in the antioxidant pretreated group but acid suppression by ranitidine was not effective in decreasing the severity of reflux oesophagitis. Significantly increased amounts of malondialdehyde (MDA), increased nuclear factor kappaB (NFkappaB) activation, and depletion of reduced glutathione (GSH) were observed in experimentally induced reflux oesophagitis. DA-9601 pretreatment attenuated the decrement in mucosal GSH levels and decreased MDA formation significantly. DA-9601 treatment caused significant reductions in activation of NFkappaB transcription factor, especially the p50 subunit, in accordance with the significantly higher levels of inhibitory protein of NFkappaB expression. CONCLUSION: Reflux oesophagitis caused considerable levels of oxidative stress in the oesophageal mucosa and antioxidant treatment should be considered as supplementary therapy in the prevention or treatment of reflux oesophagitis with acid suppression.

Involvement of oxidative stress in experimentally induced reflux esophagitis and Barrett's esophagus: clue for the chemoprevention of esophageal carcinoma by antioxidants.

Oxidative damage has long been related to mucosal damages of gastrointestinal tracts and their ensuing carcinogenesis. In spite of treatment with anti-secretory medications for reflux esophagitis, considerable portions of patient did not achieve the complete mucosal healings or suffered from sustaining symptoms or development of dread complication like Barrett's esophagus, suggesting other damaging factors or impaired mucosal resistance are also involved in their pathogenesis. The present study was designed either to evaluate the oxidative stress as the major pathogenic factor of reflux esophagitis or to find out the usefulness of antioxidant in the treatment of reflux esophagitis and the prevention of development of Barrett's esophagus. Acute or chronic reflux esophagitis was induced through either narrowing the third portion of duodenal lumen or performing myotomy of lower esophageal sphincter in rats, respectively. DA-9601, a new phytopharmaceutical possessing antioxidative properties, significantly attenuated the gross and histopathologic scores of acute reflux esophagitis in a dose-dependent manner compared to those treated with ranitidine alone. Only scattered erosions were observed in antioxidant pre-treated group, but acid suppression by ranitidine was not so effective in decreasing the severity of reflux esophagitis. Significantly increased amounts of malondialdehyde (MDA), increased NF-kappa B activations, and depletions of reduced glutathione (GSH) were observed in experimentally induced reflux esophagitis, but DA-9601 pre-treatment attenuated the decrement of mucosal GSH levels and decreased MDA formations significantly. DA-9601 treatment showed significant reductions in the activation of NF-kappa B transcription factor. DA-9601 significantly decreased the proliferating cell nuclear antigen-labeling index (PCNA-LI) of esophagus (P<0.05) in chronic reflux esophagitis model and prevented the development of Barrett's esophagus. In conclusion, reflux esophagitis provoked considerable levels of oxidative stress in the esophageal mucosa. Antioxidant treatment seems to be the first line therapeutics in the prevention or treatment of reflux esophagitis. Moreover, antioxidant possibly played the chemopreventive role through preventing the development of Barrett's esophagus.

Efficacy of use of colonoscopy in dextran sulfate sodium induced ulcerative colitis in rats: the evaluation of the effects of antioxidant by colonoscopy.

The goals in developing animal models of inflammatory bowel disease (IBD) are to determine the underlying mechanisms and the action of currently available drugs and to evaluate the value of new therapeutic approaches. Because of the difficulty in determining the severity of colitis in living animals, it has been necessary to kill the experimental animals at varying stages in the studies. If colonoscopic evaluation or endoscopic biopsy is feasible in these experimental animals, continuous observations could be possible, thus avoiding the need to kill them. The aims of the current study were to assess the efficacy of endoscopic examination as a monitoring tool for the severity of colitis in rats and to the efficacy of DA-9601, an extract from Artemisia asiatica which has both antioxidative and cytoprotective actions, on dextran sulfate sodium induced ulcerative colitis in rats endoscopically. Sprague-Dawley rats received 4% DSS in drinking water for 5 consecutive days. Either DA-9601 or sulfasalazine was administered twice a day for 8 days, starting 3 days before DSS administration. After the colonoscopic evaluations on days 2, 4, and 5 after DSS administration the rats were also killed for gross and histopathological evaluations. Simultaneous measurements of malondialdehyde (MDA) and myeloperoxidase (MPO) activities were performed. There was a statistically significant correlation between the scores evaluated by the gross examination and colonoscopic scores, between the colonoscopic scores and the levels of MDA or mucosal MPO activities, and between colonoscopic scores and histopathological activity index. DA-9601 showed excellent improvement in gross lesion scores, decreased MDA amounts and MPO activities compared to sulfasalazine. In conclusion, the introduction of appropriate colonoscopic examination in animal models of IBD could avoid the sacrifice of experimental animals for interim evaluation and provide the valuable information on the course and efficacy of treatment. The potential usefulness of antioxidants in treating IBD is very promising based on the colonoscopic intervention of IBD.

Effects of taurine on cerulein-induced acute pancreatitis in the rat.

Taurine, or 2-aminoethane sulfonic acid, is an intracellular amino acid and has been suggested to have a function in protecting biological systems from oxidative tissue damage. The aim of this study was to determine the effect of taurine against cerulein-induced acute pancreatitis in rats. Acute pancreatitis was induced by administering three subcutaneous injections of cerulein (40 microg/kg body weight) at 1-hour intervals, while taurine was administered intravenously at graded doses (30, 100, or 300 mg/kg, respectively) following the first cerulein injection. The severities of pancreatitis and lung injury were determined by measuring biochemical parameters, tissue myeloperoxidase (MPO), and histological changes. To clarify the mechanism of taurine, serum IL-1beta and TNF-alpha levels and tissue concentrations of malondialdehyde (MDA) were evaluated. In cerulein-induced acute edematous pancreatitis, treatment with taurine significantly decreased hyperamylasemia, tissue MPO, pancreatic edema, and the extent of pancreatic and pulmonary injury. Taurine decreased MDA concentration in the pancreas and lung, but not the serum cytokine concentration. We would conclude that taurine has beneficial effects in cerulein-induced acute pancreatitis and lung injuries by preventing the production of oxygen free radicals.

Oxidative damages are critical in pathogenesis of reflux esophagitis: implication of antioxidants in its treatment.

BACKGROUND: The facts that the severity of reflux esophagitis cannot be accurately predicted on the basis of acid exposure and acid suppression treatment is not enough for the complete healing, suggested that other damaging factors might be involved in pathogenesis of reflux esophagitis. AIMS: The present study was designed to evaluate the oxidative stress as the major pathogenic factor of reflux esophagitis and the importance of antioxidant in treatment of reflux esophagitis. MATERIALS AND METHODS: Reflux esophagitis was induced by the insertion of small caliber ring (3 mm in diameter) into the duodenum 1 cm distal to the ligament of Treitz in rats. RESULTS: DA-9601, a novel antioxidant substance, attenuated the gross esophagitis significantly compared to that treated with ranitidine, histamine-2 receptor antagonist (H2-RA), in a dose-dependent manner. Severe, hemorrhagic, and longitudinal ulcerations were developed in H2-RA pretreated group, whereas mildly scattered erosions were observed in antioxidant-pretreated group. Significantly increased amounts of malondialdehyde (MDA), increased NF-kappaB activation, and the mucosal depletion of reduced glutathione (GSH) were observed in the esophagus of reflux esophagitis. H2-RA treatment didn't affect the levels of GSH and MDA, whereas DA-9601 attenuated the decrement of the GSH levels and significantly decreased lipid peroxides in the esophagus. Antioxidants treatment showed significant reductions in the activation of NF-kappaB, inflammation-associated transcription factor, especially p50 component in accordance with significant higher levels of NF-kappaB repressor, IkappaBalpha expression. CONCLUSION: Oxygen-derived free radicals seem to be one of the important mediators in generation of reflux esophagitis, which suggests that the combination of antioxidant and anti-secretory medications will be ideal and more beneficial in the prevention and treatment of reflux esophagitis than currently prescribed antisecretory treatment alone.

One-month parenteral toxicity study of recombinant human basic fibroblast growth factor in dogs.

A 1-mo toxicity study followed by a 1-mo recovery period of recombinant human basic fibroblast growth factor (bFGF) was performed using Beagle dogs at doses of 30, 120 or 480 mg/kg/d to estimate the no observed adverse effect level (NOAEL). Subcutaneous thickening was seen and its incidence, as well as that of stiffness of the injection sites, increased with dose. There were neither dead animals nor significant changes of body weight during the experimental period. In addition, no significant bFGF-related changes were found in ophthalmologic and histopathological examination, urinalysis and hematological, biochemical and organ weight parameters. At necropsy, red-brownish spots and/or nodule formations were recognized in a dose-dependent manner. Splenomegaly was noted in the 480 mg/kg group, but these findings had a low incidence in all dose groups. The findings in the dosing period disappeared or were ameliorated during the recovery period. The above data suggests the NOAEL of bFGF in Beagle dogs is >480 mg/kg/d.

A rat model for radiation-induced proctitis.

Radiation proctitis is a frequent acute complication encountered with pelvic irradiation. This study was aimed at establishing the optimal radiation dose for radiation-induced proctitis in rats. Female Wistar rats were used. The rectal specimens were examined morphologically at 5th and 10th day following 10-30 Gy irradiation in single fraction. With increasing dose, mucosal damage became worse, and there was a prominent reaction after > or =15 Gy. We selected 17.5 Gy as an optimal dose for radiation proctitis and examined specimens at day 1-14 and at week 4, 6, 8, and 12 after 17.5 Gy. The rectal mucosa revealed characteristic histological changes with time. An edema in lamina propria started as early as 1-2 days after irradiation and progressed into acute inflammation. On day 7 and 8, regeneration was observed with or without ulcer. Four weeks later, all regeneration processes have been completed with end result of either fibrosis or normal appearing mucosa. This study showed that the radiation injury of the rectum in rat develops in dose-dependent manner as it has reported in previous studies and suggested that 17.5 Gy in single fraction is the optimum dose to evaluate the protective effect of various medications for radiation proctitis in face of the clinical situation.

Studies on protective effect of DA-9601, Artemisia asiatica extract, on acetaminophen- and CCl4-induced liver damage in rats.

The hepatoprotective effect of DA-9601, a quality-controlled extract of Artemisia asiatica, on liver damage induced by acetaminophen (APAP) and carbon tetrachloride (CCl4) was investigated by means of serum-biochemical, hepatic-biochemical, and histopathological examinations. Doses of DA-9601 (10, 30, or 100 mg/kg) were administered intragastrically to each rat on three consecutive days i.e. 48 h, 24 h and 2 h before a single administration of APAP (640 mg/kg, i.p.) or CCl4 (2 ml/kg, p.o.). Four h and 24 h after hepatotoxin treatment, the animals were sacrificed for evaluation of liver damage. Pretreatment of DA-9601 reduced the elevation of serum ALT, AST, LDH and histopathological changes such as centrilobular necrosis, vacuolar degeneration and inflammatory cell infiltration dose-dependently. DA-9601 also prevented APAP- and CCl4-induced hepatic glutathione (GSH) depletion and CCl4-induced increase of hepatic malondialdehyde (MDA), a parameter of lipid peroxidation, in a dose-dependent manner. These findings suggest that pretreatment with DA-9601 may reduce chemically induced liver injury by complex mechanisms which involve prevention of lipid peroxidation and preservation of hepatic GSH.