1,721,049 research outputs found
Evidence for superoxide generation from the autoxidation of the favism-inducing aglycone divicine
No full textThe formation of the superoxide anion radical (O2-) during the autoxidation of divicine, an unstable aglycone involved in the hemolytic anemia occurring in favism, has been demonstrated by EPR with two different procedures. In the first case (chemical method) an O2--mediated reduction of a nitroxide by cysteine was shown to occur when divicine was allowed to cycle between the oxidized and the reduced form. In the second case (enzymatic method) the specific reaction between superoxide and superoxide dismutase was used as superoxide detector. It was shown that the enzyme attained a steady-state condition when mixed with divicine in the presence of air, as monitored by EPR evaluation of the oxidation state of the catalytic copper: this result is a direct, specific indicator of an O2- flux
Electron spin resonance characterization of the radicals produced by enzymatic or chemical cleavage of vicine
No full textVicine is a glucoside from broad beans (Vicia faba) that is hydrolyzed upon ingestion to the unstable aglycon divicine, the autoxidation of which has been implicated in the onset of hemolysis in favism,possibly via production of superoxide and hydrogen peroxide. The autoxidation of divicine proceeds through a series of reactions involving the formation of a radical species. In this study divicine radicals were produced either by incubation of vicine with beta-glucosidase or by boiling vicine in hydrochloric acid. On the basis of electron spin resonance spectra, it was shown that the two treatments produce different radicals. By spectral simulation the acid-produced radical was demonstrated to be a deaminodivicine. The autoxidation rates of the two radicals were determined from the disappearence of their electron spin resonance signals in the presence of air: at physiological pH the enzymatically produced divicine radical was much more stable to oxygen than the chemically produced radical. The two radicals may thus be expected to behave differently in a biological system. The repercussions of these findings could be considerable, given that most of the pharmacological and biochemical studies on vicine action have been done with the chemically produced compound, which is shown here to be an unphysiological intermediate
Modulation of the nitric oxide pathway by copper in glial cells RID A-4573-2009
No full textThe action of copper on the nitric oxide (NO) pathway was investigated in rat C6 glioma cells expressing both inducible and constitutive NO synthase (NOS) isoforms, The inducible NOS-II-mediated NO synthesis (i.e., nitrite production induced by LPS plus IFN gamma) was found to be increased upon copper uptake by cells, this effect being attributable to NOS-II mRNA transcriptional over-expression. On the other hand, the constitutive neuronal isoform (NOS-I) was inhibited after copper uptake, as revealed by the decrease of basal intracellular cGMP levels in C6 cells. Consistently, in vitro experiments showed that copper selectively blocked the catalytic activity of NOS-I, but not of NOS-II, The observed modulation of NOS isoforms by copper in C6 cells is in line with the previous hypothesis that selective inhibition of NOS-I leads to enhanced NO production through transcriptional activation of NOS-II. (C) 2000 Academic Press
Effect of ceruloplasmin on 6-hydroxydopamine oxidation
No full textThe effects of ceruloplasmin, a blu copper-containing serum glycoprotein, on the oxidation of the neurotoxin 6-hydroxydopamine in several chemical environments were studied. The spontaneous autoxidation of 6-hydroxydopamine proceeded by a free radical chain reaction involving O-2(-.) and produced the corresponding chromogen 6-hydroxydopaminequinone and hydrogen peroxide. The process was accelerated in the presence of horse plasma ceruloplasmin. Yields of hydrogen peroxide in the presence of ceruloplasmin were significantly less than those measured in its absence. This is the first evidence of oxidase activity of ceruloplasmin toward a natural substrate, the 6-hydroxydopamine
Copper induces type II nitric oxide synthase in vivo
No full textIntravenous administration of copper (up to a final concentration of ca. 35 μmol/l in the plasma) led to a progressive, dramatic fall of mean arterial pressure in rats. Copper-induced pressure changes were comparable to those elicited by 2 mg/kg LPS, and were greatly prevented by previous infusion of the inducible NOS (NOS-II) inhibitors aminoguanidine or l-N(6)-(L-imino-ethyl)lysine. RT-PCR analysis showed a significant transcriptional induction of NOS-II in a number of tissues, including aorta, liver, and lungs. Immunohistochemistry revealed that NOS-II was massively synthesized in these tissues upon copper or LPS treatment. The protein was active, as revealed by enzymatic assays on lung homogenates and by the large increase of nitrite/nitrate levels in the plasma. Copper-challenged rats displayed elevated plasma levels of TNFα. Extensive formation of nitrotyrosines, indicative of peroxynitrite production, was accompanied by marked morphological changes in examined tissues. Our results clearly show that copper can act as a proinflammatory agent through activation of the nitric oxide pathway, leading to the same pathological frame induced by bacterial lipopolysaccharide
INVOLVEMENT OF THE COPPER IN THE INHIBITION OF CU,ZN SUPEROXIDE-DISMUTASE ACTIVITY AT HIGH PH RID A-4573-2009
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