H. Oyamada

ROLE OF OXYGEN-DERIVED FREE RADICALS IN GASTRIC MUCOSAL INJURY INDUCED BY ISCHEMIA OR ISCHEMIA-REPERFUSION IN RATS

Oxygen-derived free radicals have been implicated as possible mediators in the development of tissue injury induced by ischemia and reperfusion. Clamping of the celiac artery in rats reduced the gastric mucosal blood flow to 10% of that measured before the clamping. The area of gastric erosions and thiobarbituric acid (TBA) reactants in gastric mucosa were significantly increased 60 and 90 min after clamping. These changes were inhibited by treatment with SOD and catalase. Thirty and 60 min after reoxygenation. produced by removal of the clamps following 30 min of ischemia, gastric mucosal injury and the increase in TBA reactants were markedly aggravated compared with those induced by ischemia alone. SOD and catalase significantly inhibited these changes. The serum alpha-tocopherol/cholesterol ratio, an index of in vivo lipid peroxidation, was significantly decreased after long periods of ischemia (60 and 90 min), or after 30 and 60 min of reperfusion following 30 min of ischemia. These results indicated that active oxygen species and lipid peroxidation may play a role in the pathogenesis of gastric mucosal injury induced by both ischemia alone and ischemia-reperfusion. Although, allopurinol inhibited the formation of gastric mucosal injury and the increase in TBA reactants in gastric mucosa, the depletion of polymorphonuclear leukocytes (PMN) counts induced by an injection of anti-rat PMN antibody did not inhibit these changes. As compared with the hypoxanthine-xanthine oxidase system. PMN seem to play a relatively small part in the formation of gastric mucosal injury induced by ischemia-reperfusion.

Effect of Zinc-Carnosine Chelate Compound (Z-103), A Novel Antioxidant, on Acute Gastric Mucosal Injury Induced by Ischemia-Reperfusion in Rats

The protective effect of a novel synthetic zinc-carnosine chelate compound, zinc N-(3-aminopropionyl)-L-histidine (Z-103), on the gastric mucosal injury induced by ischemia-reperfusion was studied in rats. Ischemia and 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 30 min. The decrease in the gastric mucosal blood flow was not influenced by the treatment with Z-103. The increase in total area of the 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 Z-103. In addition, Z-103 inhibited lipid peroxidation of rat brain homogenate and liver microsome in vitro. These results suggest that the protective effect of Z-103 against the aggravation of gastric mucosal injury induced by ischemia-reperfusion may be due to its inhibitory effect on lipid peroxidation.

Role of Free Radicals and Lipid Peroxidation in Gastric Mucosal Injury Induced by Ischemia-Reperfusion in Rats

Ischemia and reperfusion is of the greatest importance in the pathology of various diseases. This study was designed to investigate the role of oxygen-derived free radicals and lipid peroxidation in gastric mucosal injury induced by ischemia-reperfusion in rats. Clamping of the celiac artery in rats reduced the gastric mucosal blood flow to 10% of that measured before the clamping. Gastric mucosal injury, such as spotty and linear hemorrhagic erosions, was seen in rats 60 min of the reperfusion following 30 min of ischemia. Thiobarbituric acid (TBA) reactants in the gastric mucosa were increased after the reperfusion. The increase in gastric mucosal lesions and TBA reactants were significantly inhibited by the treatment with SOD+ catalase and allopurinol. These results suggest that oxygen-derived free radicals and lipid peroxidation may play an important role in the pathogenesis of acute gastric mucosal lesions induced by ischemia-reperfusion.

AUGMENTATIVE EFFECTS OF TUMOR NECROSIS FACTOR-ALPHA (HUMAN, NATURAL TYPE) ON POLYMORPHONUCLEAR LEUKOCYTE-DERIVED SUPEROXIDE GENERATION INDUCED BY VARIOUS STIMULANTS

We investigated the effects of tumor necrosis factor-alpha (human, natural type: n-TNF) on polymorphonuclear leukocyte (PMN)-derived superoxide generation by the new method of Cypridina luciferin analog-dependent chemiluminescence, which had high sensitivity and specificity to superoxide. Preincubation of PMNs with n-TNF for 3 min increased PMN-derived superoxide generation induced by phorbol myristate acetate, A23187, opsonized zymosan and N-formyl-methionyl-leucyl-phenylalanine in a concentration dependent manner (0.5-50 Japan reference units/ml of n-TNF). In addition, the enhanced PMN-derived superoxide generation by n-TNF showed a positive correlation to the preincubation time of PMNs with n-TNF (3-15 min). However, a direct incubation of PMNs with n-TNF for 1 h did not induce superoxide from PMNs without the above stimulants. The augmentative effects of n-TNF on PMN-derived superoxide generation should be useful in the PMN-mediated host defense mechanism, such as bactericidal and antitumor activity. The local concentration of n-TNF and the n-TNF-PMN contact time are considered very important in obtaining these effects more efficiently in addition to the presence of PMN-stimulants including complements, chemotactic peptides and phorbol esters.

Scavenging Effects of Aspalathus Linealis (Rooibos Tea) on Active Oxygen Species

Rooibos tea ia a totally unique South African product of the plantAspalathus linealis which is only produced in the Cadarberg mountains around Clanwilliam. In South Africa it is mainly used as a substitute for the Oriental black tea by people who enjoy it either hot or cold, or by those who regard it as a healthy drink. Clinically, Rooibos tea is often prescribed for nervous tension, allergies, stomach and digestive problems. For evaluation of its antioxidant action, reactivity of Aspalathus linealis, ascorbic acid, and quercetin which is one of non-glycosidically linked flavonoids included in Asparathus linealis, to various reactive oxygen species were assessed by electron spin resonance (ESR) sipectrometry using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trapper1,2.

Protection by Seleno-Organic Compound, Ebselen, Against Acute Gastric Mucosal Injury Induced by Ischemia-Reperfusion in Rats

Several pathogenetic mechanisms have been suggested to account for acute gastric mucosal injury. Recently, Oxigen-derived free radicals and lipid peroxidation have been suggested to play a role in the pathogenesis of gastric mucosal injury1,2,3). Ischemia and reperfusion are of the greatest importance in the pathology of many diseases. There has been great interest in the possible role of oxygen radical species in ischemia-reperfusion in the gastric mucosa4). A synthetic seleno-organic compound, 2-phenyl-1, 2 benzoisoselenazol-3(2H)-one(Ebselen), shows a glutathione peroxidase(GSHPx)-like activity-5,6). This study was designed to examine the protective effects of the agent, Ebselen against the gastric mucosal injury induced by ischemia-reperfusion.

Pathogenesis of platelet-activating factor-induced gastric mucosal damage in rats.

Platelet-activating factor (PAF), given intravenously, induced erosions and hyperemia to the rats stomachs. Gastric mucosal blood flow was decreased and thiobarbituric acid (TBA) reactants (an index of lipid peroxidation) in the gastric mucosa were increased 10 min after PAF injection. Superoxide dismutase plus catalase reduced the gastric mucosal lesions and TBA reactants, but had no influence on gastric mucosal blood flow. A reduction in the number of circulating polymorphonuclear leukocytes (PMN) reduced the gastric mucosal damage and TBA reactants, and inhibited the decrease in gastric mucosal blood flow, as observed 30 and 60 min after PAF injection. PAF induced superoxide production by rat PMN and enhanced that stimulated by opsonized zymosan or phorbol myristate acetate. These results suggest that microcirculatory disturbance and oxygen-derived free radicals generated by PMN play important roles in gastric mucosal lesions induced by PAF.

Antioxidative Action of Zinc-Carnosine Compound Z-103

The objective of the present study was to examine the anti-free radical action of Z-103 in vitro. Z-103 is a novel synthetic compound of zinc and carnosine (β-alanyl-L-histidine) which has strong anti-ulcer action in many types of animal models.1Free radicals have come to considered to be playing a role in the pathogenesis of gastric mucosal injuries2,3. The antifree radical action of Z-103 were expected because zinc and carnosine have antioxidative properties4,5. To know its anti-free radical action in vitro will be significant to understand its mechanism of action as anti-ulcer drug.

Zinc-Carnosine Chelate Compound (Z-103) Attenuates Acute Gastric Mucosal Injury Induced by Ischemia-Reperfusion in Rats

A novel synthesized agent, zinc N-(3-aminopropionyl)-L-histidine (Z-103, Fig. 1), is a chelate compound that consists of zinc iron and L-carnosine. Carnosine was discovered in 1900 by Gulewitsch and Amiradzibi1 from meat extract, and is reportedly present in the range of 1–20 mM in the skeletal muscle and brain of many animals and humans2. Recently, several reports have described the antioxidative activity of carnosine, such as efficient singlet oxygen scavengers3, peroxy radical scavengers4, efficient chelating agent for copper and other transitional metals4, and Superoxide scavenging activity in the presence of copper or zinc5.

Role of oxygen radicals and polymorphonuclear leukocytes in gastric mucosal injury

In platelet activating factor (PAF) or compound 48/80 (C48/80)-induced gastric injury in rats, gastric mucosal blood flow was decreased and thiobarbituric acid (TBA) reactants in the gastric mucosa were increased. Gastric injury and the increase in TBA reactants in the gastric mucosa were inhibited in rats treated with superoxide dismutase (SOD) and/or catalase, and in polymorphonuclear leukocyte (PMN)-depleted rats. Oxygen radicals derived from PMN and lipid peroxidation may be involved in the pathogenesis of gastric injury in these models.