Free radical research communications最新文献

A new series of metal ligands containing the 1,3-dimethyl-6-amino-5- nitrosouracil moiety has been synthesized and they have been studied as potential inhibitors of iron-dependent lipid peroxidation. For this purpose, these new derivatives have been tested in the Fenton induced deoxyribose degradation assay, which allows a quantitative measurement of their inhibitory effect towards hydroxyl radical generation. When iron(II) is complexed by these ligands, a strong inhibition of deoxyribose degradation is observed, especially in the case of tris-[2-(1,3-dimethyl-5-nitrosouracil-6-yl)aminoethyl] amine (5). This inhibitory effect is clearly related to a specific complexation of iron(II) and is not due to the direct scavenging of hydroxyl radical by the ligand. Inhibition of the iron mediated Fenton reaction presumably results from inactivation of the reactivity of the metal center towards hydrogen peroxide. These derivatives, as well as long alkyl chain substituted nitrosouracils were evaluated in the protection of biological membranes against lipid peroxidation (induced by iron(II)/dihydroxyfumaric acid and determined with the 2-thiobarbituric acid test). Ligand 5 inhibited lipid peroxidation at a rate similar to Desferal (desferrioxamine B) and slightly higher than bathophenanthroline sulphonate (BPS), which are respectively good iron(III) and iron(II) chelators. When covalently bound with a long alkyl chain, the increase of lipophilic character of the ligand allows its location near the mitochondrial membrane, where lipid peroxidation occurs. Lower concentrations (IC50 = 4 microM) are then necessary to inhibit lipid peroxidation. This IC50 concentration should be compared to those obtained for Trolox (IC50 = 3 microM) or the 21-aminosteroid U74500A (IC50 = 1 microM) described previously.

In the presence of ascorbate, bleomycin (BLM) is converted to a redox-inactive form that is incapable of inducing DNA strand scission. We have employed EPR spin trapping with 5,5-dimethylpyrroline-1-oxide (DMPO) to examine free radical production during this process. The introduction of ascorbate to an Fe(III)BLM-DMPO system results in the formation of three EPR observable free radicals. One of these radicals is the resonance-stabilized ascorbate free radical (aH = 1.8 G) that is not spin trapped by DMPO; the other two are the result of DMPO spin trapping. These radicals appear to be two carbon-centered radicals, DMPO/.CR1, (aN1 = 15.75 G, aH1 = 22.30 G, aN/aH = 0.706) and DMPO/.CR2 (aN2 = 15.20 G, aH2 = 19.20 G, aN/aH = 0.79). Although it is not possible to identify the exact structures of the carbon-centered radicals that are spin trapped, the hyperfine splittings, as well as the aN/aH values, are characteristic of the presence of electron-withdrawing groups, such as the oxygen atom when attached to the carbon atom. In fact, these parameters are characteristic of DMPO spin trapping results obtained when sugars are subjected to oxidative insult from HO.. Thus, these BLM-ascorbate produced radicals may well be derived from the sugar moiety of BLM.

Effects of the combination of vitamin E, selenium, and beta-carotene on oxidative damage to rat heart, kidney, lung, and spleen were studied by measurement of the production of oxidized heme proteins (OHP) during spontaneous and prooxidant-induced oxidation. Male SD rats were fed with a vitamin E and selenium deficient diet or a diet supplemented with vitamin E, selenium, and beta-carotene. Homogenates of heart, kidney, lung, and spleen were incubated at 37 degrees C with and without the presence of bromotrichloromethane (CBrCl3). The diet supplemented with antioxidants showed a strong protective effect against oxidative damage to heme proteins during the early stages of both spontaneous and CBrCl3-induced oxidation in contrast to the antioxidant deficient diet. Synergism of multiple antioxygenic nutrients against oxidative damage to various animal tissues is discussed.

Twenty-four healthy students undertook one hour of box-stepping exercise. Prior to exercise eight had received no medication (Group A), eight received 400 mg of vitamin C daily for three weeks before and one week after exercise (Group C) and eight received 400 mg of vitamin E for the same period (Group E). Groups C and E had significantly higher levels of vitamin C (p < 0.01) and vitamin E (p < 0.01) respectively than group A at the commencement of exercise. Plasma total antioxidant capacity rose significantly during exercise in all group (A - p < 0.05; C - p < 0.001; E - p < 0.001). This rise was accounted for by increases in plasma uric acid in all groups. In addition there were significant increases in vitamin C in group C (p < 0.001) and vitamin E in group E (p < 0.05). There were no significant changes in plasma malondialdehyde following exercise in any group. It is concluded that plasma antioxidant capacity rises in response to one hour of eccentric exercise and that the contribution of individual antioxidants to this change can be influenced by vitamin supplementation. The possible mechanisms of the antioxidant changes during exercise and their implications are discussed.

Oxygen free radicals have been considered as a cause of ischemia-reperfusion injury in several organs, but this injury in a stomach, containing acid, may progress to severe damage. Thus, we examined the effect of ischemia-reperfusion and milk-intake on rabbit gastric mucosa. The gastric mucosal blood flow was increased after milk-intake, and gastric rupture was detected. Superoxide dismutase activity measured by an improved nitroblue tetrazolium reduction method and thiobarbituric acid reactive substances in serum is increased during ischemia-reperfusion and milk-intake. By using alpha-phenyl N-tert-butyl nitrone (PBN) as a spin trap and electron paramagnetic resonance (EPR), we detected lipidic radicals from tissue samples in chloroform-methanol solvent only during reperfusion and milk-intake period; no signal was detected before. The EPR signal of spin adducts obtained in the sample after ischemia-reperfusion and milk-intake would be a mixture of peroxyl and alkoxyl radicals from the analysis of coupling constants.

In vivo EPR measurements were carried out with whole mice to evaluate the influence of inspired oxygen and ischemia-reperfusion injury on spin-clearance of the nitroxide radicals which were administered intravenously or intramuscularly. Nitroxide radicals in head, abdomen, or muscle domains were composed of sharp triplet lines. The peak heights decreased gradually with time. The reduction of nitroxide radicals depended both on the inspired oxygen concentration and on the domains. Femoral ischemia-reperfusion injury also affected spin-clearance of the nitroxide radical in the thigh. The results were discussed with regard to the generation of active oxygen species.

Kampo medicines, aqueous extracts of a mixture of natural crude drugs, have numerous ingredients. Recent pharmacologic studies on Kampo medicines have clarified their many and varied biological activities. In this study, based on recent research that has been directed toward the excellent antioxidant properties of Kampo medicines, we investigated antioxidant activities of three Kampo medicines (TJ-10, TJ-35, TJ-43), which are clinically used for gastritis or peptic ulcer, by the electron paramagnetic resonance (EPR) spin trapping method. These Kampo medicines, especially TJ-35 scavenged superoxide generated from the hypoxanthine-xanthine oxidase system, and slightly inhibited the superoxide generation from polymorphonuclear leukocytes stimulated by phorbol myristate acetate or opsonized zymosan. Three Kampo medicines, especially TJ-35 also inhibited the generation of hydroxyl radicals by the Fenton reaction. These results suggest that these antioxidant properties may be partly responsible for anti-ulcer actions of these three Kampo medicines, especially TJ-35.

Electron paramagnetic resonance spectroscopy (EPR) coupled to the spin trapping technique was used to detect carbon-centered radicals in rat liver mitochondria and submitochondrial particles exposed to t-butyl-hydroperoxide (TBH), using the spin trapping agent 3,5-dibromo-4-nitroso-benzenesulfonic acid (DBNBS). The signal recorded was unambiguously assigned to the methyl radical adduct. DBNBS was added to isolated rat liver mitochondria energized with succinate, and the methyl radical adduct was observed. The addition of NADH, NADPH, inhibitors of the respiratory chain, and of monoaminoxidase (MAO) inhibitors did not cause any relevant modification in the yield of radical adduct formation. Boiling and the addition of a non-ionic detergent inhibited the formation of the radical adduct, while experiments carried out under hypoxic conditions generated a significant increase in methyl radical formation. Further experiments were carried out on sub-mitochondrial particles (SMP) giving rise to, basically, the same results. From the above results, we are proposing that haem prosthetic groups are the likely source of TBH bioactivation in mitochondria.

Two force fields (MM2 and Genmol) have been applied to the modeling of five membered ring aminoxyl radicals. For the six molecules which were investigated the geometry of the conformation with the lowest strain energy was in very good agreement with the X-ray geometry. However owing to the high flexibility of five membered rings other conformations were shown to have a strain energy close to the energy minimum.

Nitric Oxide (NO) is synthesized in the intestinal tract and may serve as a physiological regulator of intestinal ion transport and/or a pathophysiologic mediator of secretory diarrhea associated with inflammatory mucosal diseases. Indirect approaches, employing inhibitors of nitric oxide synthase or compounds capable of donating NO in solution, have been used to demonstrate the effects on gastrointestinal muscle and the mucosa. To determine directly whether nitric oxide itself is capable of stimulating electrolyte secretion we mounted muscle-stripped rat distal colon in Ussing chambers and monitored short-circuit current (Isc), as an indicator of effects on mucosal ion transport. Comparisons were made to sodium nitroprusside (SNP). NO and SNP stimulated concentration-dependent (0.1 microM to 100 microM) increases in Isc, with NO being more potent than SNP. The EC50 for NO was approximately 8 microM compared to a value < 20 microM for SNP. The response to NO was immediate. In contrast, SNP required a mean lag-time of 41 +/- 4 seconds, and a significantly longer time was required for SNP to reach its maximum effect. The response to both of these agonists was blocked by bumetanide, indicating that they were stimulating a chloride ion secretory response. The cyclooxygenase inhibitor piroxicam, the neurotoxin tetrodotoxin and the inhibitor of guanylate cyclase, methylene blue, all inhibited the response to both agonists. These studies demonstrate that NO itself can stimulate chloride secretion by the rat colonic mucosa through a prostaglandin-dependent, and partially neural mechanism that may involve guanylate cyclase.