DNA adducts formed by ring-oxidation of the carcinogen 2-naphthylamine with prostaglandin H synthase in vitro and in the dog urothelium in vivo

We report the analysis of DNA adducts formed from aristolactams I and II, which are the final metabolites derived from carcinogenic aristolochic acids in vivo, after their oxidation by microsomal cytochrome P-450 and horseradish peroxidase in vitro. DNA adducts were detected and quantified using the nuclease P1-enhanced variation of the 32P-postlabeling assay. Quantitative analysis revelead that the extent of modification of DNA by aristolactams activated by peroxidase was more than one order of magnitude higher than for activation by microsomal cytochrome P-450. Peroxidase catalyzes the formation of active oxygen in the presence of NADH, H2O2 and aristolactams. Aristolactams are also oxidized by mammalian peroxidase prostaglandin H synthase. The possible role of aristolactams in carcinogenesis induced by aristolochic acid is discussed.

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Cycle Network Model of Prostaglandin H Synthase-1

Pharmaceuticals ◽

10.3390/ph13100265 ◽

2020 ◽

Vol 13 (10) ◽

pp. 265

Author(s):

Alexey Goltsov ◽

Maciej Swat ◽

Kirill Peskov ◽

Yuri Kosinsky

Keyword(s):

Enzyme Activation ◽

Prostaglandin H Synthase ◽

Experimental Conditions ◽

Peroxidase Enzyme ◽

Inflammatory Drugs ◽

Prostaglandin H ◽

Regulatory Properties

The kinetic model of Prostaglandin H Synthase-1 (PGHS-1) was developed to investigate its complex network kinetics and non-steroidal anti-inflammatory drugs (NSAIDs) efficacy in different in vitro and in vivo conditions. To correctly describe the complex mechanism of PGHS-1 catalysis, we developed a microscopic approach to modelling of intricate network dynamics of 35 intraenzyme reactions among 24 intermediate states of the enzyme. The developed model quantitatively describes interconnection between cyclooxygenase and peroxidase enzyme activities; substrate (arachidonic acid, AA) and reducing cosubstrate competitive consumption; enzyme self-inactivation; autocatalytic role of AA; enzyme activation threshold; and synthesis of intermediate prostaglandin G2 (PGG2) and final prostaglandin H2 (PGH2) products under wide experimental conditions. In the paper, we provide a detailed description of the enzyme catalytic cycle, model calibration based on a series of in vitro kinetic data, and model validation using experimental data on the regulatory properties of PGHS-1. The validated model of PGHS-1 with a unified set of kinetic parameters is applicable for in silico screening and prediction of the inhibition effects of NSAIDs and their combination on the balance of pro-thrombotic (thromboxane) and anti-thrombotic (prostacyclin) prostaglandin biosynthesis in platelets and endothelial cells expressing PGHS-1.

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In vitro and in vivo localization of prostaglandin H synthase in fetal sheep neurons

Neuroscience Letters ◽

10.1016/s0304-3940(98)00040-8 ◽

1998 ◽

Vol 242 (1) ◽

pp. 29-32 ◽

Cited By ~ 10

Author(s):

Clara R Thore ◽

Tracy C Beasley ◽

David W Busija

Keyword(s):

Prostaglandin H Synthase ◽

Fetal Sheep ◽

Prostaglandin H

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To the Mechanism of 2-Nitroanisole Carcinogenicity: in vitro Metabolism of 2-Nitroanisole Mediated by Peroxidasesand Xanthine Oxidase

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19980857 ◽

1998 ◽

Vol 63 (6) ◽

pp. 857-869 ◽

Cited By ~ 8

Author(s):

Marie Stiborová ◽

Heinz H. Schmeiser ◽

Eva Frei

Keyword(s):

Horseradish Peroxidase ◽

Xanthine Oxidase ◽

Dna Adducts ◽

Active Oxygen Species ◽

Radical Mechanism ◽

Maximal Velocity ◽

Prostaglandin H Synthase ◽

Nuclease P1 ◽

Prostaglandin H

The in vitro enzymatic metabolism of carcinogenic 2-nitroanisole was investigated using peroxidases (horseradish peroxidase and prostaglandin H synthase) and xanthine oxidase catalyzing oxidative and reductive reactions, respectively. The oxidation of 2-nitroanisole catalyzed by horseradish peroxidase exhibits the Michaelis-Menten kinetics. The Michaelis constant (Km) and the maximal velocity (Vmax) values for this substrate were determined at pH 5.0, 7.0, 7.6 and 8.0. At optimal pH (7.6), the Km and Vmax values are 0.219 μmol/l and 34.45 pmol/min per nmol peroxidase, respectively. The oxidation of 2-nitroanisole is inhibited by radical trapping agents (NADH, ascorbate, glutathione and nitrosobenzene). This indicates that the peroxidase-mediated oxidation of 2-nitroanisole proceeds via a radical mechanism. Active oxygen species are formed during the horseradish peroxidase-catalyzed reactions in the presence of NADH, hydrogen peroxide and 2-nitroanisole. 2-Nitroanisole is also oxidized by mammalian prostaglandin H synthase. Using the nuclease P1-enhanced variation of the 32P-postlabelling assay, the formation of DNA adducts was detected in DNA treated with 2-nitroanisole and xanthine oxidase. No DNA binding was detected after oxidation of 2-nitroanisole with horseradish peroxidase and prostaglandin H synthase. The results presented (the formation of DNA adducts after 2-nitroanisole activation by xanthine oxidase and that of radicals and/or superoxide radicals during the reactions with peroxidases) strongly suggest the participation of 2-nitroanisole both in the initiation and in the promotion phases of carcinogenesis.

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Cycle network model of Prostaglandin H Synthase-1

10.1101/2020.08.12.246124 ◽

2020 ◽

Author(s):

Alexey Goltsov ◽

Maciej Swat ◽

Kirill Peskov ◽

Yuri Kosinsky

Keyword(s):

Enzyme Activation ◽

Prostaglandin H Synthase ◽

Experimental Conditions ◽

Peroxidase Enzyme ◽

Inflammatory Drugs ◽

Prostaglandin H ◽

Regulatory Properties

AbstractThe kinetic model of Prostaglandin H Synthase-1 (PGHS-1) was developed to investigate its complex network kinetics and non-steroidal anti-inflammatory drugs (NSAIDs) efficacy in different in vitro and in vivo conditions. To correctly describe the complex mechanism of PGHS-1 catalysis, we developed a microscopic approach to modelling of intricate network dynamics of 35 intraenzyme reactions among 24 intermediate states of the enzyme. The developed model quantitatively describes interconnection between cyclooxygenase and peroxidase enzyme activities; substrate (arachidonic acid, AA) and reducing cosubstrate competitive consumption; enzyme self-inactivation; autocatalytic role of AA; enzyme activation threshold, and synthesis of intermediate PGG2 and final PGH2 products under wide experimental conditions. In the paper we provided the detailed description of the enzyme catalytic cycle, model calibration based on a series of in vitro kinetic data and model validation using experimental data on the regulatory properties of PGHS-1.The validated model of PGHS-1 with a unified set of kinetic parameters is applicable for in silico screening and prediction of the inhibition effects of NSAIDs and their combination on the balance of pro-thrombotic (thromboxane) and anti-thrombotic (prostacyclin) prostaglandin biosynthesis in platelets and endothelial cells expressing PGHS-1.

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