The Haber‐weiss Cycle

Koppenol, Willem H.; Butler, J. A. V.; Leeuwen, Johan W. van

doi:10.1111/j.1751-1097.1978.tb06989.x

Cited by 186 publications

(61 citation statements)

References 11 publications

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“…Recent evidence suggests that oxidative damage is a critical factor in disease progression since antioxidants may reduce the onset or severity of cardiovascular disease (3) and inflammatory bowel diseases (4). The mechanisms of cellular oxidation processes have been subjected to intense scrutiny, but despite these efforts the physiological source(s) of transition metals required for metal ion-dependent oxidation reactions is not known (4,5). A clue to the resolution of this enigma may be found in the observation by Cathcart et al (6,7) that activated human monocytes, or monocytic cells such as the U937 cell line, oxidize LDL in vitro even in iron and copper ion-free media.…”

Section: Introductionmentioning

confidence: 99%

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

Ehrenwald¹,

Fox²

1996

J. Clin. Invest.

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Oxidation of lipids and lipoproteins by macrophages is an important event during atherogenesis. Activation of monocytic cells by zymosan and other agonists results in the release of multiple oxidant species and consequent oxidation of LDL. We now show evidence that ceruloplasmin, a copper-containing acute phase reactant, is secreted by zymosan-activated U937 monocytic cells, and that the protein has an important role in LDL oxidation by these cells. In one approach, ceruloplasmin has been shown to exhibit oxidant activity under the appropriate conditions. Exogenous addition of purified human ceruloplasmin stimulates U937 cell oxidation of LDL to nearly the same extent as activation by zymosan. In contrast to previous cell-free experiments (Ehrenwald, E., G. IntroductionActivated monocytes and macrophages are recognized for their remarkable diversity of secreted products, including multiple reactive oxygen and nitrogen intermediates, involved in the injury or killing of invasive organisms such as bacteria, parasites, and tumor cells (1). The same oxidation reactions may also cause secondary oxidative damage to host macromolecules and tissues during chronic inflammatory processes. For example, there is now abundant evidence that particles resembling oxidatively modified LDL are present in atherosclerotic lesions (2). Recent evidence suggests that oxidative damage is a critical factor in disease progression since antioxidants may reduce the onset or severity of cardiovascular disease (3) and inflammatory bowel diseases (4). The mechanisms of cellular oxidation processes have been subjected to intense scrutiny, but despite these efforts the physiological source(s) of transition metals required for metal ion-dependent oxidation reactions is not known (4, 5). A clue to the resolution of this enigma may be found in the observation by Cathcart et al. (6,7) that activated human monocytes, or monocytic cells such as the U937 cell line, oxidize LDL in vitro even in iron and copper ion-free media. This finding distinguishes these cells from endothelial cells and smooth muscle cells that require exogenous copper or iron salts in the medium to achieve optimal oxidation rates (8, 9). One explanation is that monocytic cells may provide their own transition metal ions to maintain high oxidation rates and the inhibition of monocytic cell lipid oxidation by divalent cation chelators is consistent with this idea (10). Alternatively, macrophage-derived hypochlorous acid or nitric oxide may be precursors of highly reactive hydroxyl radicals by metal ion-independent mechanisms (11).We have recently shown that physiological concentrations of purified human ceruloplasmin (200-400 g/ml in healthy adults) increase the oxidation of LDL in vitro by up to 50-fold when measured as thiobarbituric acid-reactive substances (TBARS) 1 (12). Ceruloplasmin is a monomeric, 132-kD acute

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Section: Introductionmentioning

confidence: 99%

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

Ehrenwald¹,

Fox²

1996

J. Clin. Invest.

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“…The Fact that in the presence of ethanol the G-value decreases to about 4.4 indicates that no OH 'radicals are formed as intermediate products upon reduction of H202, which is in contrast to the Haber-Weiss cycle [17]. If O H ' radicals were formed they would be scavenged by the ethanol and transformed into MV'.…”

Section: Reduction Of' Methyl Viologen and Cytochrome C3 By Alcohol Rmentioning

confidence: 96%

A Pulse‐Radiolysis Study of Cytochrome c₃

Leeuwen

Dijk

Grande

et al. 1982

European Journal of Biochemistry

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1. Pulse-radiolysis experiments were performed in the presence of methyl viologen and cytochrome c3. After the pulse, methyl viologen radicals are formed and the kinetics of these radicals with cytochrome c3 are studied. The reaction between cytochrome c3 and methyl viologen radicals (MV') is diffusion controlled. The ionic strength dependence and the pH-dependence of this reaction were studied. From the ionic strength dependence (at pH 7.8) we found that the net charge of the fully oxidized cytochrome c3 molecule was Z = + 4.7 f 0.7.2. After the pulse an equilibrium is reached for the reaction of MV' with cytochrome c'3. From this equilibrium an apparent midpoint potential can be obtained. The apparent midpoint potential of this multihaem molecule was found to depend on the degree of reduction, E. With the help of the Nernst equation an empirical equation is obtained to describe this dependence of the midpoint potential: EO = -0.250-0.088~ (in V).3. An estimation is made of the energy of interaction between the haems due to electrostatic interactions (At; < 32 mV) and due to ionic strength effects (-12 mV < Ae < 26 mV). The results suggest that the redox properties of the individual haems in the cytochrome c3 molecule are dependent on the degree of reduction of the other haems in the molecule. 4. The reaction of cytochrome c3 with MV' or with ethanol radicals (EtOH') has been compared with the reactions of horse-heart cytochrome c and of metmyoglobin with the same radicals. The reaction of MV' or EtOH' with horse-heart cytochrome c is found to be diffusion controlled; the reactions with metmyoglobin on the other hand are most probably controlled by an activation energy.Cytochrome c3 from the sulphate-reducing bacterium Desulfovibrio vulgaris strain Hildenborough, NCIB 8303, is a well characterized protein [I -31 which contains four closely packed haem c groups. Its relative molecular mass is 13000 and it is easily soluble in water. The physiological role of cytochrome c3 is to act as an electron carrier between hydrogenase and ferredoxin. In the sulphate-reducing mode cytochrome c3 accepts electrons from hydrogenase and in the pyruvate-oxidating mode it donates electrons to hydrogenase [2,4]. One needs to know the midpoint potentials of the four haems in order to be able to describe these electron-transfer processes. It is generally accepted that the midpoint potentials of the four haems are located between -350mV and -250 mV [2,5-81. It is still not known whether the redox properties of the cytochrome c3 molecule should be described by the sum of four sites each of which has a fixed midpoint potential or by four redox sites whose midpoint potentials are not fixed but can vary depending on the interactions between the sites and the degree of reduction of the protein.EPR measurements of cytochrome c3 from D. vulgaris at 10 K have been analysed in terms of four fixed midpoint potentials: -284 mV, -310 mV, -319 mV, and -324 mV [5]. These values are microscopic midpoint potentials, i.e. they are characteristic valu...

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“…George showed already in 1947 that the second reaction is too slow in comparison to the disproportionation of superoxide 4 . Nevertheless, a number of groups, unaware of George's work (see also [5][6][7] , set out in the early seventies to determine the rate constant of Reaction 2, and all concluded, like George, that the rate constant was of the order of 1 M , or smaller [8][9][10][11][12][13][14] . The recent suggestion 15 that Reaction 2 is significant and that the dioxygen is produced in the 1 ∆ g singlet state must be rejected as erroneous on kinetic and thermodynamic grounds.…”

Section: The Chemistry Of Peroxynitrite a Biological Toxin Introductionmentioning

confidence: 99%

The chemistry of peroxynitrite, a biological toxin<a name=TOP1></a>

Koppenol¹

1998

Quím. Nova

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Recebido em 22/8/97Oxyradicals play a role in several diseases. While for several decades the hydroxyl radical -produced via the Fenton reaction -has been considered the species that initiates oxyradical damage, new findings suggest that much of this damage can be ascribed to peroxynitrite, O=NOO -, formed from the reaction of the superoxide anion with nitrogen monoxide near activated macrophages. The rate constant for the reaction of this reaction has been investigated by flash photolysis and was found to be significantly higher than previously described in the literature, 1.9 x 10 10 M -1 s -1 . Studies of the isomerization to nitrate resulted in the discovery of a complex between peroxynitrite and its protonated form with a stability constant of 1 x 10 4 M -1 . Some of the harmful reaction of peroxynitrous acid have been ascribed to the hydroxyl radical as a product of homolysis of the O-O bond during the conversion to nitrate. Kinetics of the isomerization reaction as a function of pressure show that the activation volume is only +1.5+1.0 ml mol -1 , which is inconsistent with homolysis. Instead, an intermediate, possibly a distorted trans-isomer of O=NOOH could be responsible for the harmful reactions of peroxynitrite.

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The Haber‐weiss Cycle

Cited by 186 publications

References 11 publications

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

A Pulse‐Radiolysis Study of Cytochrome c₃

The chemistry of peroxynitrite, a biological toxin<a name=TOP1></a>

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The Haber‐weiss Cycle

Cited by 186 publications

References 11 publications

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells.

A Pulse‐Radiolysis Study of Cytochrome c3

The chemistry of peroxynitrite, a biological toxin<a name=TOP1></a>

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Product

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A Pulse‐Radiolysis Study of Cytochrome c₃