Kiichi Matsuyama

Neutrophils, Lipid Peroxidation, and Nitric Oxide in Gastric Reperfusion Injury in Rats

Nitric oxide (NO) modulation of ischemia-reperfusion injury was investigated by measuring lipid peroxide and neutrophil accumulation in rat stomachs treated with NG-nitro-L-arginine (L-NNA), a specific NO synthase inhibitor. Ischemia-reperfusion injury was induced in the rat stomach. Treatment with L-NNA for 3 days at a dose of 3 mg/kg/day significantly enhanced this injury. This enhancement was reversed by the simultaneous administration of L-arginine at a dose of 30 mg/kg/day. Both thiobarbituric acid (TBA)-reactive substances, an index of lipid peroxidation, and myeloperoxidase (MPO) activity, an index of tissue-associated neutrophil accumulation, were increased in the gastric mucosa after ischemia-reperfusion. L-NNA treatment enhanced these increases in TBA-reactive substances and MPO activity. The increase in the area of gastric erosions correlated closely with accumulation of TBA-reactive substances as well as the increase in MPO activity. Enhancement of ischemia-reperfusion injury by L-NNA treatment was inhibited by injection with anti-neutrophil antibody, anti-platelet activating factor (PAF) antagonist, and anti-leukotriene B4 (LTB4) receptor antagonist. In addition, the increase in TBA-reactive substances and MPO activity was decreased by these antibodies or antagonists. Enhancement of reperfusion-induced gastric mucosal injury associated with inhibition of NO synthesis may involve neutrophil infiltration and lipid peroxide accumulation in the gastric mucosa, mediated by PAF and LTB4.

Role of neutrophil-mediated inflammation in aspirin-induced gastric mucosal injury.

The objectives of this study were to determine the roles of neutrophil-endothelial cell interactions and oxygen-derived free radicals in the pathogenesis of aspirin-induced gastric mucosal injury in rats. Oral administration of acidified aspirin (200 mg/kg) resulted in linear hemorrhagic erosions and an increase in myeloperoxidase activity, an index of neutrophil infiltration, in the gastric mucosa. Aspirin-induced gastric damage and the increase in myeloperoxidase activity were significantly inhibited by the injection of anti-CD11a, anti-CD11b, anti-intercellular adhesion molecule-1 monoclonal antibodies, and the combination of superoxide dismutase and catalase, which are scavengers of active oxygen species. These results suggest that neutrophil-endothelial adhesive interactions, which occur via CD11a/CD18-and CD11b/CD18-dependent interactions with intercellular adhesion molecule-1, and oxygen-derived free radicals produced by neutrophils are implicated in the production of aspirin-induced gastric mucosal injury.

The inducible nitric oxide synthase inhibitor ONO-1714 blunts dextran sulfate sodium colitis in mice

In mice with acute dextran sulfate sodium colitis, we examined the effect of inducible nitric oxide synthase inhibition by (1S,5S,6R,7R)-7chloro-3-amino-5methyl-2-azabicyclo[4.1.0]heptane hydrochloride (ONO-1714) on colonic biochemistry, injury, and inflammation. Colonic luminal nitrate and nitrite were measured by the Griess reaction; inducible nitric oxide synthase messenger RNA expression by reverse transcription-polymerase chain reaction; and nitrotyrosine by immunohistochemistry. Mice with colitis showed increases in nitrate and nitrite, inducible nitric oxide synthase messenger RNA, and numbers of cells staining for nitrotyrosine. Colonic inflammation was severe. ONO-1714 inhibited increases in nitrate and nitrite and numbers of nitrotyrosine-positive cells; injury and inflammation also were reduced. Dextran sulfate sodium-induced increases in thiobarbituric acid-reactive substances, a lipid peroxidation marker, were blunted by ONO-1714, which also inhibited increases in mucosal inflammatory cytokines. Nitric oxide produced by inducible nitric oxide synthase may contribute to colonic inflammation by nitrosation, oxidative damage, and enhanced inflammatory cytokines.

Effects of Polaprezinc on Lipid Peroxidation, Neutrophil Accumulation, and TNF-α Expression in Rats with Aspirin-Induced Gastric Mucosal Injury

We examined the roles of lipid peroxidation, neutrophil accumulation, and inflammatory cytokines in the protective effect of polaprezinc against aspirin-induced gastric mucosal injury in rats. The intragastric administration of acidified aspirin induced hyperemia and hemorrhagic erosions in rat stomachs. The increase in the total gastric erosive area after aspirin administration was significantly inhibited in a dose-dependent manner by treatment with polaprezinc. The increases in thiobarbituric acid-reactive substances and tissue-associated myeloperoxidase activity 3 hr after aspirin administration were significantly inhibited by pretreatment with polaprezinc. The gastric concentration of TNF-α increased after aspirin administration, and the increase was also inhibited in a dose-dependent manner by treatment with polaprezinc. The peak expression of TNF-α mRNA 1 hr after aspirin administration was inhibited by 30 mg/kg of polaprezinc. Based on these data, the beneficial effects of polaprezinc on aspirin-induced gastric mucosal injury may be attributed to its antioxidative and antiinflammatory properties.

Pioglitazone, a specific PPAR‐γ ligand, inhibits aspirin‐induced gastric mucosal injury in rats

Neutrophils activation and tumour necrosis factor‐α (TNF‐α) induction play a critical role in aspirin‐induced gastric mucosal injury. Peroxisome proliferator‐activated receptor‐γ (PPAR‐γ), a member of the nuclear hormone receptor superfamily, has recently been implicated as a regulator of inflammatory responses. The aim of the present study was to determine whether pioglitazone, a specific PPAR‐γ ligand, can ameliorate aspirin‐induced gastric mucosal injury in rats, and whether the agent can inhibit the increase in neutrophil accumulation associated with TNF‐α expression.

Effects of free radical scavengers on indomethacin-induced aggravation of gastric ulcer in rats

Effects of treatment with free radical scavengers in the healing process of acetic acid-induced gastric ulcer on the ulcer aggravation induced by indomethacin were investigated. Gastric ulcers were produced on the anterior wall of the stomach of male Sprague-Dawley rats by submucosal injection of 20% acetic acid. To investigate the role of oxygen radicals, rats with gastric ulcer were treated with scavengers for six weeks and then treated with indomethacin (1 mg/kg/day). While superoxide dismutase (10,000 units/kg/day) did not affect the ulcer area after indomethacin treatment, allopurinol (50 mg/kg/day) slightly inhibited the increase in ulcer area. Dimethyl sulfoxide (1% solution,ad libitum) produced a significant decrease in size of the ulcer after indomethacin treatment. Increased lipid peroxides in the gastric mucosa after indomethacin treatment decreased significantly in the rats of the dimethyl sulfoxide and allopurinol groups. These results indicate that lipid peroxidation mediated by oxygen radicals plays an important role in the mechanism of ulcer aggravation induced by indomethacin.

A new gastric ulcer model in rats produced by ferrous iron and ascorbic acid injection.

We developed a new gastric ulcer model in which the ulcers are induced by the local injection of a ferrous iron and ascorbic acid (Fe/ASA) solution into the gastric wall. These ulcers resemble human gastric ulcers that penetrate the muscularis mucosa. The involvement of oxygen radical-mediated lipid peroxidation as the cause of these ulcers was investigated. With ferrous iron or ascorbic acid alone, gastric ulcers did not form, whereas penetrating ulcers were produced by the simultaneous injection of the Fe/ASA solution in a dose-dependent manner. Lipid peroxides significantly accumulated in the gastric mucosa from 1 to 24 h after the injection of the Fe/ASA solution. This increase in lipid peroxides preceded grossly evident gastric ulcer. Treatment with superoxide dismutase (SOD, recombinant human CuZnSOD) significantly reduced the size of the ulcers and inhibited the accumulation in lipid peroxides in the gastric mucosa, while treatment with apo-SOD or heat-inactivated SOD did not. These results suggest that lipid peroxidation mediated by oxygen radicals plays a crucial role in the pathogenesis of the gastric ulceration induced by the Fe/ASA solution.

α-Phenyl-N-tert-Butylnitrone Provides Protection from Dextran Sulfate Sodium-Induced Colitis in Mice

Nuclear factor-κB (NF-κB)-dependent up-regulation of inflammatory cytokines and inducible nitric oxide (iNOS) occurs in inflammatory bowel disease. We investigated the effect of α-phenylN-tert-butylnitrone (PBN), a spin-trapping agent that inhibits NF-κB activity, on dextran sulfate sodium (DSS)-induced colonic mucosal injury and inflammation in mice. Acute colitis was induced with DSS in female BALB/c mice receiving 0, 0.3, 3, and 30 mg/kg i.p. PBN daily. Colonic mucosal inflammation was evaluated biochemically and histologically. Nitric oxide was evaluated as luminal nitrite/nitrite concentration by the Griess reaction and as immunoreactive nitrotyrosine in mucosal cells. Mucosal tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were determined by immunoassay. Colonic mRNA expression for iNOS, TNF-α, and IFN-γ was measured by reverse transcription-polymerase chain reaction, and NF-κB activation was evaluated by electrophoretic mobility shift assay. After DSS administration, mice showed increased ...

Effect of rebamipide, a novel anti-ulcer agent, on acute gastric mucosal injury induced by ischemia-reperfusion in rats

The protective effect of a novel anti-ulcer agent rebamipide on the acute gastric mucosal injury induced by ischemia-reperfusion was studied in rats. Ischemia/reperfusion injury was produced on the rat stomach by applying a small clamp to the celiac artery for 30 min and by removal of the clamp for 60 min. The decrease in the gastric mucosal blood flow was not influenced by the treatment with rebamipide. The increase in the total area of erosions on the stomach after ischemia-reperfusion and the increase in lipid peroxides in the gastric mucosa were significantly inhibited by the oral administration of rebamipide at doses of 30 and 100 mg/kg. These results suggest that the protective effect of rebamipide against the ischemia/reperfusion-induced aggravation of gastric mucosal injury may be the result of its inhibitory effect on lipid peroxidation.

EFFECT OF A NOVEL HISTAMINE H2- RECEPTOR ANTAGONIST, IT-066 ON ACUTE GASTRIC INJURY INDUCED BY ISCHEMIA REPERFUSION IN RATS AND ITS ANTIOXIDATIVE PROPERTIES

The effect of a novel histamine H2 receptor antagonist IT-066 (3-amino-4-[4-[4-(1-piperidinomethyl)-2-pyridyloxy]-cis-2-++ +butenylamino]- 3-cyclobutene-1,2-dione hydrochloride), on acute gastric mucosal injury induced by ischemia-reperfusion was investigated from the standpoint of oxygen radical-mediated lipid peroxidation in rats. Ischemia-reperfusion injury was produced in the rat stomach by applying a small vascular clamp to the celiac artery for 30 min and subsequent removal of the clamp for 60 min. The decrease in gastric mucosal blood flow was not influenced by treatment with IT-066. The antiulcer activity of IT-066 was demonstrated in this injury after intragastric ingestion as well as after intravenous injection. IT-066 significantly inhibited this injury in the presence of exogenous HCl. The mucosal protection by IT-066 was not reversed by pretreatment with indomethacin or nitric oxide synthase inhibitor. The increase in lipid peroxides in the gastric mucosa after ischemia-reperfusion was significantly inhibited by the intragastric treatment with IT-066 at doses of 1.0 and 3.0 mg/kg. The total area of erosions closely paralleled the accumulation of lipid peroxide with a significant correlation. A spin trapping method using 5,5-dimethyl-1-pyrroline-N-oxide showed that IT-066 scavenged superoxide radical and hydroxyl radical generated by the hypoxanthine-xanthine oxidase system and the hydrogen peroxide-ferrous iron system, respectively. IT-066 also significantly inhibited the in vitro increase of lipid peroxide in the gastric mucosal homogenates induced by a free radical initiator. These results suggest that the protective effect of IT-066 against ischemia/reperfusion-induced gastric mucosal injury may result in part from its antioxidative properties.