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Role of active oxygens and lipid peroxidation in the pathogenesis of acute duodenal ulcer
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Antoxidant Compounds ~TIOXIDANT ACTIVITY OF PHOSPHATIDYL-L-ASCORBIC ACID ~I:ihiko Nagao and Junji Terao National Food Research Institute, Ministry of Agriculture. Forestry and Fisheries, Tsukuba, Ibaraki, 305 Japan L-Ascorbic acid is one of the water-soluble a n t i o x i dants in c e l l u l a r defense system against active oxygens. I f L-ascorbic acid is introduced as a polar head group of phospholipid in l i p i d bilayer of membranes, i t may exert an excellent antioxidant a c t i v i ty against l i p i d peroxidation i n i t i a t e d by aqueous radicals. Phosphatidyl-L-ascorbic acid was newly synthesized and its antioxidant a c t i v i t y was examined. Phospholipase D(EC 3.1.4.4) of Streptomyces species could catalyze transphosphatidylation to Lascorbic acid from phosphatidylcholine(PC)in a biphasic reaction system and the product was identified as 1,2-diacyl- sn-glycero- 3-phospho-6'-L-ascorbic acid(PA-AsA). The conversion of PC to PA-AsA could be attained at more than 80%. The antioxidant a c t i v i t y of dimyristoyl phosphatidyl-L-ascorbic acid was investigated in a homogeneoussolution and a liposomal suspension. In an apolar solvent, one molecule of PA-AsA could trap one peroxy radical. When PA-AsA was included in multilamellar liposomes of egg yolk phosphatidylcholine, i t could retard the autoxidation of phosphatidylcholine i n i t i a t e d by water-soluble azo compound. On the other hand, L-ascorbic acid scarcely retard the autoxidation and 6-O-palmitoyl-L-ascorbic acid was less effective than PA-AsA. We conclude that L-ascorbic acid moiety of PA-AsA is located on the membrane surface so that the attack of radical from aqueous phase can be suppressed effectively.
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FORMATION OF TROLOX C AND VITAMIN E RADICALS BY PEROXIDASES. M.Nakamura, Biophysics Division, Research Institute of Applied Electricity, Hokkaido University, Sapporo 060, Japan. To verify the direct formation of Trolox C and vitamin E radicals by peroxidases, the oxidation mechanism was examined by using the stopped flow and ESR techniques. During the oxidation of Trolox C, the results revealed that peroxidase Compound II was the catalytic intermediate. The formation of phenoxyl radicals of Trolox C was followed by ESR and the time course of the signal was similar to that of the optical absorbance change at 440 nm, assigned as the peak of Trolox C radical. The signal exhibited a hyperfine structure characteristic of phenoxyl radicals and the spectrum changed from that of theTrolox C radical to that of the ascorbate radical, when the reaction was carried out in the presence of both ascorbate and Trolox C. The Trolox C-mediated oxidation of ascorbate was observed spectrophotometrically. To elucidate the oxidation mechanism o f vitamin E, the reaction of Trolox C with peroxidases was first performed in 50% methanol solution. The decrease of Trolox C radical concentration can be explained by decreasing in the reaction rate of Compound II with Trolox C. Although a significant decrease of the catalytic activity was observed owing to changing the solvent, the increase of solubility of vitamin E enabled to measure the reaction of peroxidases with the vitamin. The oxidation mechanism of vitamin E with peroxidase was similar to that of Trolox C. The vitamin E phenoxyl radicals resulting from the peroxidase reaction were directly detected by the method of continuous-flow ESR spectroscopy.
ROLE OF ACTIVE OXYGENS AND LIPID PEROXIDATION IN THE PATHOGENESIS OF ACUTE DUODENAL ULCER Yuji Naitol),Toshikazu Yoshikawa,Akihiko Kishi, Takashi Tomii,Hiroshi Ichikawa,Mitunori Yasuda, Tomoyuki Yoneta, Motoharu Kondo 2) l)Dep, of Digestive Diseases, Hikone Central Hospital, Hikone, Shiga 522, Japan 2)First Dep. of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602, Japan
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In order to clarify the role of active oxygens and lipid peroxidation in the pathogenesis of acute duodenal ulcer, the effects of active oxygen scavengers and a novel synthesized antioxidant, zinc-carnosine chelate compound(Z-103), on duodenal mucosal injuries induced by cysteamine or mepirizole were investigated in rats. Male Sprague-Dawley rats were used and not fed 18 h but allowed free access to water before experiment. Twenty four h after administration with these agents, duodenal ulcerative lesion was observed, and the total area of the ulcers and thiobarbituric acid-reactive substances(TBARS) in the duodenal mucosa were measured. The treatment with SOD + catalase or dimethylsulfoxide significantly inhibited the increase in total area of ulcers and that in TBARS in these two models. The treatment with Z-103 more efficiently inhibited the aggravation of these duodenal ulcers, and also significantly inhibited the increase in TBARS. These results suggest that active oxygens and lipid peroxidation may play an important role in the pathogenesis of acute duodenal ulcer.
ANTIOXIDANT AND RADICAL SCAVENGING ABILITIES OF EBSELEN AND RELATION TO VITAMIN E. Vasanthy Narayanaswamil,Christian Sch6neich2, Klaus DieterAsmus2 and Helmut Sies1. llnstitut fiir Physiologische Chemic I, Universit/it Diisseldorf, D-4000 Diisseldorf, F.R.G. and 2Hahn Meitner Institut, Bereich Strahlenchemie, D-1000 Berlin, F.R.G. The antioxidant activity of ebselen was studied in rat fiver microsomes and mitochondria during iron/ascorbate -induced lipid peroxidation and examined in relation to the ,g-tocopherol status of the membranes. In state 4 mitochondria, a biphasic pattern of loss of ,<-tocopherol was observed, which was significantly diminished by 1/gM ebselen. Ebselen doubled the lag phase before onset of lipid peroxidation at 0.4 ktM in mitochondria and at 0.13/~M in microsomes (1,2). In vitamin E deficient microsomes the lag doubling concentration was 20/~1. Pulse radiolysis studies showed that ebselen was an efficient scavenger of dichloroethane radical cations or trichloromethylperoxyl radicals~ the rate constant for reaction with the latter being 2.9 x 108M-ls -1, comparable to those of *¢-tocopherol and ascorbate (3). 1. Biochem. Pharmacol.1990, (in press). 2 Free Radical Res. Commun., 1990, (in press). 3. Arch. Biochem. Biophys., 1990, (in press)
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Antoxidant Compounds ~TIOXIDANT ACTIVITY OF PHOSPHATIDYL-L-ASCORBIC ACID ~I:ihiko Nagao and Junji Terao National Food Research Institute, Ministry of Agriculture. Forestry and Fisheries, Tsukuba, Ibaraki, 305 Japan L-Ascorbic acid is one of the water-soluble a n t i o x i dants in c e l l u l a r defense system against active oxygens. I f L-ascorbic acid is introduced as a polar head group of phospholipid in l i p i d bilayer of membranes, i t may exert an excellent antioxidant a c t i v i ty against l i p i d peroxidation i n i t i a t e d by aqueous radicals. Phosphatidyl-L-ascorbic acid was newly synthesized and its antioxidant a c t i v i t y was examined. Phospholipase D(EC 3.1.4.4) of Streptomyces species could catalyze transphosphatidylation to Lascorbic acid from phosphatidylcholine(PC)in a biphasic reaction system and the product was identified as 1,2-diacyl- sn-glycero- 3-phospho-6'-L-ascorbic acid(PA-AsA). The conversion of PC to PA-AsA could be attained at more than 80%. The antioxidant a c t i v i t y of dimyristoyl phosphatidyl-L-ascorbic acid was investigated in a homogeneoussolution and a liposomal suspension. In an apolar solvent, one molecule of PA-AsA could trap one peroxy radical. When PA-AsA was included in multilamellar liposomes of egg yolk phosphatidylcholine, i t could retard the autoxidation of phosphatidylcholine i n i t i a t e d by water-soluble azo compound. On the other hand, L-ascorbic acid scarcely retard the autoxidation and 6-O-palmitoyl-L-ascorbic acid was less effective than PA-AsA. We conclude that L-ascorbic acid moiety of PA-AsA is located on the membrane surface so that the attack of radical from aqueous phase can be suppressed effectively.
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FORMATION OF TROLOX C AND VITAMIN E RADICALS BY PEROXIDASES. M.Nakamura, Biophysics Division, Research Institute of Applied Electricity, Hokkaido University, Sapporo 060, Japan. To verify the direct formation of Trolox C and vitamin E radicals by peroxidases, the oxidation mechanism was examined by using the stopped flow and ESR techniques. During the oxidation of Trolox C, the results revealed that peroxidase Compound II was the catalytic intermediate. The formation of phenoxyl radicals of Trolox C was followed by ESR and the time course of the signal was similar to that of the optical absorbance change at 440 nm, assigned as the peak of Trolox C radical. The signal exhibited a hyperfine structure characteristic of phenoxyl radicals and the spectrum changed from that of theTrolox C radical to that of the ascorbate radical, when the reaction was carried out in the presence of both ascorbate and Trolox C. The Trolox C-mediated oxidation of ascorbate was observed spectrophotometrically. To elucidate the oxidation mechanism o f vitamin E, the reaction of Trolox C with peroxidases was first performed in 50% methanol solution. The decrease of Trolox C radical concentration can be explained by decreasing in the reaction rate of Compound II with Trolox C. Although a significant decrease of the catalytic activity was observed owing to changing the solvent, the increase of solubility of vitamin E enabled to measure the reaction of peroxidases with the vitamin. The oxidation mechanism of vitamin E with peroxidase was similar to that of Trolox C. The vitamin E phenoxyl radicals resulting from the peroxidase reaction were directly detected by the method of continuous-flow ESR spectroscopy.
ROLE OF ACTIVE OXYGENS AND LIPID PEROXIDATION IN THE PATHOGENESIS OF ACUTE DUODENAL ULCER Yuji Naitol),Toshikazu Yoshikawa,Akihiko Kishi, Takashi Tomii,Hiroshi Ichikawa,Mitunori Yasuda, Tomoyuki Yoneta, Motoharu Kondo 2) l)Dep, of Digestive Diseases, Hikone Central Hospital, Hikone, Shiga 522, Japan 2)First Dep. of Medicine, Kyoto Prefectural University of Medicine, Kyoto 602, Japan
2.38
In order to clarify the role of active oxygens and lipid peroxidation in the pathogenesis of acute duodenal ulcer, the effects of active oxygen scavengers and a novel synthesized antioxidant, zinc-carnosine chelate compound(Z-103), on duodenal mucosal injuries induced by cysteamine or mepirizole were investigated in rats. Male Sprague-Dawley rats were used and not fed 18 h but allowed free access to water before experiment. Twenty four h after administration with these agents, duodenal ulcerative lesion was observed, and the total area of the ulcers and thiobarbituric acid-reactive substances(TBARS) in the duodenal mucosa were measured. The treatment with SOD + catalase or dimethylsulfoxide significantly inhibited the increase in total area of ulcers and that in TBARS in these two models. The treatment with Z-103 more efficiently inhibited the aggravation of these duodenal ulcers, and also significantly inhibited the increase in TBARS. These results suggest that active oxygens and lipid peroxidation may play an important role in the pathogenesis of acute duodenal ulcer.
ANTIOXIDANT AND RADICAL SCAVENGING ABILITIES OF EBSELEN AND RELATION TO VITAMIN E. Vasanthy Narayanaswamil,Christian Sch6neich2, Klaus DieterAsmus2 and Helmut Sies1. llnstitut fiir Physiologische Chemic I, Universit/it Diisseldorf, D-4000 Diisseldorf, F.R.G. and 2Hahn Meitner Institut, Bereich Strahlenchemie, D-1000 Berlin, F.R.G. The antioxidant activity of ebselen was studied in rat fiver microsomes and mitochondria during iron/ascorbate -induced lipid peroxidation and examined in relation to the ,g-tocopherol status of the membranes. In state 4 mitochondria, a biphasic pattern of loss of ,<-tocopherol was observed, which was significantly diminished by 1/gM ebselen. Ebselen doubled the lag phase before onset of lipid peroxidation at 0.4 ktM in mitochondria and at 0.13/~M in microsomes (1,2). In vitamin E deficient microsomes the lag doubling concentration was 20/~1. Pulse radiolysis studies showed that ebselen was an efficient scavenger of dichloroethane radical cations or trichloromethylperoxyl radicals~ the rate constant for reaction with the latter being 2.9 x 108M-ls -1, comparable to those of *¢-tocopherol and ascorbate (3). 1. Biochem. Pharmacol.1990, (in press). 2 Free Radical Res. Commun., 1990, (in press). 3. Arch. Biochem. Biophys., 1990, (in press)
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