vitamin-k-semiquinone-radical and duroquinone

In the present study, we investigated the changes in blood-brain barrier (BBB) permeability following brain endothelial cell exposure to different xenobiotics able to promote free radical generation during their metabolism. Our in vitro BBB model consisted of confluent monolayers of immortalized rat brain capillary endothelial cells (RBE4) grown on collagen-coated filters in the presence of C6 glioma cells grown in the lower compartment. We have recently shown that a range of xenobiotics, including menadione, nitrofurazone, and methylviologen (paraquat) may undergo monoelectronic redox cycling in isolated brain capillaries, giving rise to reactive oxygen species. In this study, addition of 100 microM menadione to the culture medium for 30 min significantly increased the permeability of endothelial cell monolayers to radiolabeled sucrose. The effect on endothelial permeability induced by menadione was dose-dependent and reversible. These permeability changes preceded the onset of cell death, as assessed by the Trypan blue exclusion method. Pre-incubation with superoxide dismutase and catalase blocked changes in sucrose permeability to control levels in a dose-dependent manner, suggesting the involvement of reactive oxygen species in menadione-induced BBB opening.

Topics: Animals; Benzoquinones; Blood-Brain Barrier; Brain; Catalase; Cell Line; Cell Membrane Permeability; Cell Survival; Coculture Techniques; Endothelium, Vascular; Free Radicals; Nitrofurazone; Paraquat; Rats; Sucrose; Superoxide Dismutase; Superoxides; Trypan Blue; Tumor Cells, Cultured; Vitamin K

Quinones caused quenching of Chl a fluorescence in native and model systems. Menadione quenched twofold the fluorescence of Chl a and BChl a in pea chloroplasts, chromatophores of purple bacteria, and liposomes at concentrations of 50-80 microM. To obtain twofold quenching in Triton X-100 micelles and in ethanol, the addition of 1.3 mM and 11 mM menadione was required, respectively. A proportional decrease in the lifetime and yield of Chl a fluorescence in chloroplasts, observed as the menadione concentration increased, is indicative of the efficient excitation energy transfer from bulk Chl to menadione. The decrease in the lifetime and yield of fluorescence was close to proportional in liposomes, but not in detergent micelles. The insensitivity of the menadione quenching effect to DCMU in chloroplasts, and similarity of its action in chloroplasts and liposomes indicate that menadione in chloroplasts interacts with antenna Chl, i.e., nonphotochemical quenching of fluorescence occurs.

Topics: Bacterial Chromatophores; Bacteriochlorophylls; Benzoquinones; Chlorophyll; Chlorophyll A; Chloroplasts; Diuron; Fluorescence; Liposomes; Micelles; Pisum sativum; Quinones; Rhodobacter sphaeroides; Rhodospirillum rubrum; Spectrometry, Fluorescence; Ubiquinone; Vitamin K

In guinea pig and rat cardiac tissue, redox cycling benzoquinones (2,5-dimethyl-p-benzoquinone and duroquinone) and naphthoquinones (menadione and 2,3-dimethoxy-1,4-naphthoquinone) generated superoxide anion (O2-.) both through one- and two-electron reductions, the generation being significantly greater in guinea pig than in rat tissue. In electrically driven left atria isolated from guinea pig and rat, menadione and 2,5-dimethyl-p-benzoquinone but not duroquinone caused a concentration-dependent positive inotropic effect. Unlike guinea pig, 2,3-dimethoxy-1,4-naphthoquinone had no effect in rat tissue. Naphthoquinones and 2,5-dimethyl-p-benzoquinone were more active in guinea pig than in rat tissue, their effect being dependent on the release of catecholamines from adrenergic stores. A linear relationship (r = 0.90) between the amount of O2-. generated by benzo- and naphthoquinones in guinea pig and rat heart and the extent of catecholamine-dependent positive inotropic effect was evident. An amount of O2-. higher than 600 nmol/g of tissue per min was calculated to be necessary to determine the catecholamine-mediated increase in contractility. Lipid peroxidation was not involved in quinone-induced catecholamine release.

Topics: Animals; Atrial Function; Benzoquinones; Catecholamines; Cyclohexenes; Free Radicals; Guinea Pigs; Heart Atria; In Vitro Techniques; Lipid Peroxidation; Microsomes; Mitochondria, Heart; Myocardial Contraction; Naphthoquinones; Oxidation-Reduction; Rats; Superoxides; Vitamin K

The interaction of quinones (menadione and duroquinone) with DT-diaphorase and mitochondrial electron transport chain translocators at low (120 mosM) and high (400 mosM) values of the medium tonicity in the quinone concentration range of 6-90 microM was studied. It was shown that with a rise in menadione (K3) concentration the number of electron transport carriers interacting with it increase. At K3 concentration of 6 microM the latter is reduced by DT-diaphorase and fully oxidized via the Q-cycle. At K3 concentration of 15 microM the latter is also reduced by DT-diaphorase via the Q-cycle, but in this case the oxidation is incomplete (about 30% K3H2 is oxidized by the terminal part of the respiratory chain). At 90 microM K3 50% of quinone is reduced by DT-diaphorase and 50% by the respiratory chain NADH dehydrogenase complex enzymes; about 30% of K3H2 is oxidized via the Q-cycle, about 20%--by the terminal part of the respiratory chain and about 50%--by O2 without cytochrome oxidase. Unlike menadione, duroquinone (6-90 microM) is reduced only by DT-diaphorase and is oxidized in all cases by cytochrome oxidase. It was shown that the increase in the mitochondrial matrix volume in low tonicity media decreases the rate of the DT-diaphorase shunt operation.

Topics: Animals; Antifungal Agents; Antimycin A; Benzoquinones; Electron Transport; Methacrylates; Mitochondria, Liver; NAD(P)H Dehydrogenase (Quinone); Oxidation-Reduction; Oxygen; Rats; Rotenone; Thiazoles; Vitamin K

The effects of redox cycling, alkylating and mixed redox cycling/alkylating benzo- and naphthoquinones were examined in electrically driven guinea pig left atria. Cardiac microsomal and mitochondrial NAD(P)H-dependent metabolism of the quinones and consequent generation of superoxide anion (O2.-) were also measured. Mixed redox cycling/alkylating 2-methyl-1,4-naphthoquinone, redox cycling 2,3-dimethoxy-1,4-naphthoquinone and alkylating p-benzoquinone determined concentration-dependent positive inotropic responses, whereas redox cycling 2,3,5,6-tetramethyl-p-benzoquinone had no effect. The positive inotropic effect of 2,3-dimethoxy-1,4-naphthoquinone was completely catecholamine-mediated, that of 2-methyl-1,4-naphthoquinone was approximately 70% adrenergic and 30% direct. p-Benzoquinone acted directly on heart muscle. In time, quinones with alkylating properties caused increases in the resting force of atria, whereas redox cycling quinones did not produce toxic effects. Mitochondrial NADH-oxidoreductase accounted for 90 to 95% of the metabolism of all quinones, whereas the contribution of the microsomal pathway was negligible. Considerable amounts of O2.- were produced by mitochondrial biotransformation of 2-methyl-1,4-naphthoquinone and 2,3-dimethoxy-1,4-naphthoquinone but not of 2,3,5,6-tetramethyl-p-benzoquinone and p-benzoquinone, suggesting a kind of relation between O2.- generation and the release of catecholamines.

Topics: Alkylating Agents; Animals; Atrial Function, Left; Benzoquinones; Guinea Pigs; Heart; Heart Atria; Mice; Microsomes; Mitochondria, Heart; Myocardial Contraction; NADH, NADPH Oxidoreductases; Naphthoquinones; Oxidation-Reduction; Quinones; Substrate Cycling; Superoxides; Vitamin K

The effects of quinone-generated active oxygen species on rat hepatocyte protein kinase C were investigated. The specific activity of cytosolic protein kinase C was increased 2-3-fold in hepatocytes incubated with the redox-cycling quinones, menadione, duroquinone or 2,3-dimethoxy-1,4-naphthoquinone, without alterations in particulate protein kinase C specific activity or Ca2+- and lipid-independent kinase activities. Redox-cycling quinones did not stimulate translocation of protein kinase C; however, activated protein kinase C was redistributed from cytosol to the particulate fraction when quinone-treated hepatocytes were exposed to 12-O-tetradecanoylphorbol 13-acetate (TPA). Quinone treatment did not alter cytosolic phorbol 12,13-dibutyrate (PDBu) binding capacity, and the cytosol of both control and quinone-treated hepatocytes exhibited a Kd for PDBu binding of 2 nM. Quinone-mediated activation of cytosolic protein kinase C was reversed by incubation with 10 mM-beta-mercaptoethanol, dithiothreitol or GSH, at 4 degrees C for 24 h. Furthermore, protein kinase C specific activity in control cytosol incubated in air increased by over 100% within 3 h; this increase was reversed by thiol-reducing agents. Similarly, incubation of partially-purified rat brain protein kinase C in air, or with low concentrations of GSSG in the presence of GSH, resulted in a 2-2.5-fold increase in Ca2+- and lipid-dependent kinase activity. In contrast with the effects of the redox-cycling quinones, when hepatocytes were treated with the thiol agents N-ethylmaleimide (NEM), p-benzoquinone (pBQ) or p-chloromercuribenzoic acid (pCMB), the cytosolic Ca2+- and lipid-dependent kinase activity was significantly inhibited, but the particulate-associated protein kinase C activity was unaffected. The Ca2+- and lipid-independent kinase activity of both the cytosolic and particulate fractions was significantly stimulated by NEM, but was unaffected by pBQ and pCMB. These results show that hepatocyte cytosolic protein kinase C is activated to a high-Vmax form by quinone-generated active oxygen species, and this effect is due to a reduction-sensitive modification of the thiol/disulphide status of protein kinase C.

Topics: Animals; Benzoquinones; Cell Separation; Cytosol; Enzyme Activation; Liver; Oxidation-Reduction; Protein Kinase C; Quinones; Rats; Rats, Inbred Strains; Sulfhydryl Compounds; Vitamin K

Incorporation of 32P from [gamma-32P]ATP into endogenous proteins, added histone and the copolymers Glu 80 Tyr 20 by rat liver plasma membranes was markedly increased by several naphthoquinones, including menadione. This stimulation was most marked with Glu 80 Tyr 20, has an absolute requirement for either dithiothreitol or reduced glutathione, and was inhibited by superoxide dismutase, catalase, and desferrioxamine to varying degrees depending on the quinones used. Their effectiveness in stimulating the apparent tyrosine-specific protein phosphorylation correlated with the rates of DTT-dependent redox cycling measured by oxygen consumption. Increased protein phosphorylation was also seen with particulate fractions isolated from hepatocytes incubated with quinones. A free radical-mediated mechanism is suggested for the quinone stimulation of protein phosphorylation.

Topics: Adenosine Triphosphate; Animals; Benzoquinones; Cell Membrane; Deferoxamine; Free Radicals; Hydroquinones; Liver; Naphthoquinones; Oxidation-Reduction; Oxygen; Oxygen Consumption; Protein-Tyrosine Kinases; Quinones; Rats; Structure-Activity Relationship; Superoxide Dismutase; Vitamin K