scholarly journals Cycle Network Model of Prostaglandin H Synthase-1

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.

scholarly journals Cycle network model of Prostaglandin H Synthase-1

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.

Factors affecting in vitro and in vivo antioxidant effects. Experimental conditions and nature of oxidants determine antioxidant efficacy

2021 ◽  
pp. 1-9
Author(s):  
Etsuo Niki
Keyword(s):  
Biological Molecules ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Beneficial Effects ◽  
Multiple Oxidants ◽  
Antioxidant Effects

Reactive oxygen and nitrogen species have been implicated in the onset and progression of various diseases and the role of antioxidants in the maintenance of health and prevention of diseases has received much attention. The action and effect of antioxidants have been studied extensively under different reaction conditions in multiple media. The antioxidant effects are determined by many factors. This review aims to discuss several important issues that should be considered for determination of experimental conditions and interpretation of experimental results in order to understand the beneficial effects and limit of antioxidants against detrimental oxidation of biological molecules. Emphasis was laid on cell culture experiments and effects of diversity of multiple oxidants on antioxidant efficacy.

Anionic and cationic exchange mechanisms in the skin of anurans, with special reference to Leptodactylidae in vivo

1971 ◽  
Vol 262 (842) ◽  
pp. 163-174 ◽  
Keyword(s):  
Transport Mechanism ◽  
Selective Inhibition ◽  
The Other ◽  
Sodium Absorption ◽  
Experimental Conditions ◽  
Net Flux ◽  
Cationic Exchange

In several species of anurans, the in vivo skin has been shown to absorb Na + and Cl - independently from dilute external solutions. That the mechanism for sodium absorption is different from that of chloride absroption is born out by the following: (1) Either of these ions is absorbed without an accompanying ion when this latter is impermeant. (2) From NaCl solutions there can be an unequal absorption of sodium and chloride. (3) A selective inhibition of the absorption of one of the ions can be produced experimentally, while the net flux of the other remains unchanged. In all these situations, the absorbed ion has to be exchanged against an endogenous ion of the same charge. In Calyptocephalella gayi , H + and HCO - 3 are exchanged against sodium and chloride respectively. A comparison of the relationships between H + excretion and Na + absorption in vivo skins and shortcircuited in vitro skins shows that in the latter no H + excretion occurs, only the Na + transport being maintained under these experimental conditions. From this, one must conclude that the active Na + transport is the motive factor of the transport mechanism. H + excretion by the in vivo skin plays the role of physiologically short-circuiting the Na + transport.

scholarly journals Inositol 1,4-bisphosphate is an allosteric activator of muscle-type 6-phosphofructo-1-kinase

1989 ◽  
Vol 259 (2) ◽  
pp. 463-470 ◽  
Author(s):  
G W Mayr
Keyword(s):  
Inositol Phosphates ◽  
Head Group ◽  
Muscle Type ◽  
Allosteric Effectors ◽  
Fructose 1,6 Bisphosphate ◽  
Regulatory Properties ◽  
Allosteric Activator

The allosteric effects of various inositol biphosphate (InsP2) isomers and other inositol phosphates, of glycerophosphoinositol phosphates (GroPInsPx) and of phosphoinositides (PtdInsPx) on muscle-type 6-phosphofructo-1-kinase (PFK) were investigated. The binding of these substances to PFK was indirectly estimated by their ability to stabilize the tetrameric enzyme. At near-physiological concentrations of other allosteric effectors, muscle PFK was activated AMP-dependently by Ins(1,4)P2 (Ka = 43 microM), Ins(2,4)P2 (Ka = 70 microM) and GroPIns4P (Ka = 20 microM). These compounds activated PFK by a mechanism similar to that established for activating hexose bisphosphates. Indirect binding experiments indicated minimal Kd,app. values of about 5 microM for the binding of Ins(1,4)P2 in the presence of 0.1 mM-AMP at pH 7.4. This apparent affinity was comparable with that of fructose 1,6-bisphosphate and glucose 1,6-bisphosphate at identical conditions. The enzyme was also found to interact specifically with PtdIns4P (Kd,app. = 37 microM), the inositol phospholipid carrying Ins(1,4)P2 as its head group. The regulatory behaviour of muscle-type PFK in vitro and the concentrations of Ins(1,4)P2 in vivo (between 4 and greater than 50 nmol/g wet wt. of tissue) are consistent with the hypothesis that there is a functional interaction in vivo. Furthermore, a role of PtdIns4P in membrane compartmentation of PFK is suggested. Comparative experiments with liver PFK indicate that these regulatory properties may be relatively specific for the muscle isoform. Unlike muscle PFK, the liver isoform was slightly activated by sub-micromolar concentrations of Ins(1,4,5)P3.

Cytochrome P-450 and Peroxidase Oxidize Detoxication Products of Carcinogenic Aristolochic Acids (Aristolactams) to Reactive Metabolites Binding to DNA in vitro

1995 ◽  
Vol 60 (12) ◽  
pp. 2189-2199 ◽  
Author(s):  
Marie Stiborová ◽  
Eva Frei ◽  
Heinz H. Schmeiser ◽  
Manfred Wiessler
Keyword(s):  
Dna Adducts ◽  
Microsomal Cytochrome ◽  
Aristolochic Acids ◽  
Nuclease P1 ◽  
Order Of Magnitude ◽  
Prostaglandin H ◽  
Cytochrome P 450

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.

scholarly journals Corepression of the P1 Addiction Operon by Phd and Doc

1998 ◽  
Vol 180 (23) ◽  
pp. 6342-6351 ◽  
Author(s):  
Roy Magnuson ◽  
Michael B. Yarmolinsky
Keyword(s):  
Fusion Protein ◽  
Binding Sites ◽  
Wild Type ◽  
Dna Complexes ◽  
Present Evidence ◽  
Cooperative Interactions ◽  
Regulatory Properties

ABSTRACT The P1 plasmid addiction operon encodes Doc, a toxin that kills plasmid-free segregants, and Phd, an unstable antidote that neutralizes the toxin. Additionally, these products repress transcription of the operon. The antidote binds to two adjacent sites in the promoter. Here we present evidence concerning the regulatory role of the toxin, which we studied with the aid of a mutation,docH66Y. The DocH66Y protein retained the regulatory properties of the wild-type protein, but not its toxicity. In vivo, DocH66Y enhanced repression by Phd but failed to affect repression in the absence of Phd, suggesting that DocH66Y contacts Phd. In vitro, a MalE-DocH66Y fusion protein was found to bind Phd. Binding of toxin to antidote may be the physical basis for the neutralization of toxin. DocH66Y failed to bind DNA in vitro yet enhanced the affinity, cooperativity, and specificity with which Phd bound the operator. Although DocH66Y enhanced the binding of Phd to two adjacent Phd-binding sites, DocH66Y had relatively little effect on the binding of Phd to a single Phd-binding site, indicating that DocH66Y mediates cooperative interactions between adjacent Phd-binding sites. Several electrophoretically distinct protein-DNA complexes were observed with different amounts of DocH66Y relative to Phd. Maximal repression and specificity of DNA binding were observed with subsaturating amounts of DocH66Y relative to Phd. Analogous antidote-toxin pairs appear to have similar autoregulatory circuits. Autoregulation, by dampening fluctuations in the levels of toxin and antidote, may prevent the inappropriate activation of the toxin.

scholarly journals Inflammation and cancer: role of phagocyte-generated oxidants in carcinogenesis

Blood ◽  
1990 ◽  
Vol 76 (4) ◽  
pp. 655-663 ◽  
Author(s):  
SA Weitzman ◽  
LI Gordon
Keyword(s):  
Cancer Chemoprevention ◽  
Beta Carotene ◽  
Antioxidant Defenses ◽  
Inflammatory Drugs ◽  
Intervention Trials ◽  
Endogenous Antioxidant ◽  
Complete Carcinogens

Abstract We have reviewed some of the data that link the reactive oxygen species produced by inflammatory phagocytes to cancer development. While it is clear that these substances induce phenotypic changes characteristic of those produced by known carcinogens, the precise mechanisms by which these effects are produced require much further study. In vitro, it would appear that phagocyte-generated oxidants could be complete carcinogens, ie, could cause both tumor initiation and promotion. In vivo, however, these substances appear usually to function as tumor promoters or cocarcinogens perhaps because of high levels of endogenous antioxidant defenses. This suggests that there may be even more reason to be optimistic about the potential for positive results in cancer chemoprevention trials in humans, and provides further rationale for the continuing interest in the use of antioxidants and anti- inflammatory drugs in current and future trials. For example, the Chemoprevention Branch of the National Cancer Institute is currently sponsoring seven extramural human efficacy intervention trials testing whether the antioxidant beta carotene can prevent cancer.

Interaction of Measles Virus Vectors with Auger Electron Emitting Radioisotopes.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 5525-5525
Author(s):  
David Dingli ◽  
Kah-Whye Peng ◽  
Mary E. Harvey ◽  
Sompong Vongpunsawad ◽  
Elizabeth R. Bergert ◽  
...  
Keyword(s):  
Measles Virus ◽  
Auger Electron ◽  
Viral Vectors ◽  
Soluble Form ◽  
Sodium Iodide Symporter ◽  
Experimental Conditions ◽  
Oncolytic Activity

Abstract Background: Viral vectors based on the Edmonston strain of measles virus (MV-Edm) selectively destroy all tumor cell lines tested in vitro. The oncolytic activity of the virus is enhanced by expression of the thyroidal sodium iodide symporter (MV-NIS) that allows selective 131I uptake by infected tumor cells and eliminates myeloma tumor xenografts that are resistant to the parent virus. MV-NIS is being considered for therapy of patients with relapsed or refractory multiple myeloma. Advanced myeloma is associated with significant immunosuppression with the potential risk of uncontrolled virus proliferation. The number of agents with activity against MV is limited. Low energy (Auger) electrons have a short path length and selectively damage cells in which the isotope decays. Thus, we hypothesized that the Auger electron emitting isotope 125I, selectively taken up by cells expressing NIS, can be used to control viral proliferation. Methods: A replication competent MV that expressed both a soluble form of carcinoembryonic antigen (CEA) and NIS (MV-NICE) was rescued and characterized. Cells were infected with MV-NICE or control vectors and exposed to 125I with appropriate controls. CEA expression and viral titers were determined at different time points. The role of free radical generation on virus replication was explored. In vivo control of MV-NICE replication with 125I was attempted. Results: MV-NICE replication in vitro is inhibited by the selective uptake of 125I by cells expressing NIS. Extracellular decay of the isotope has no effect on virus proliferation. Auger electron damage is in part mediated by free radicals and abrogated by glutathione. In myeloma xenografts, control of MV-NICE with 125I was not possible under the conditions of the experiment. Conclusion: MV-NICE does not replicate faster in the presence of radiation under our experimental conditions. Auger electron emitting isotopes effectively stop propagation of MV vectors expressing NIS in vitro. Additional work is necessary to translate these observations in vivo.

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

1985 ◽  
Vol 6 (9) ◽  
pp. 1379-1387 ◽  
Author(s):  
Y. Yamazoe ◽  
D.W. Miller ◽  
C.C. Weis ◽  
K.L. Dooley ◽  
T.V. Zenser ◽  
...  
Keyword(s):  
Dna Adducts ◽  
Prostaglandin H Synthase ◽  
Ring Oxidation ◽  
Prostaglandin H

scholarly journals Inflammation and cancer: role of phagocyte-generated oxidants in carcinogenesis

Blood ◽  
1990 ◽  
Vol 76 (4) ◽  
pp. 655-663 ◽  
Author(s):  
SA Weitzman ◽  
LI Gordon
Keyword(s):  
Cancer Chemoprevention ◽  
Beta Carotene ◽  
Antioxidant Defenses ◽  
Inflammatory Drugs ◽  
Intervention Trials ◽  
Endogenous Antioxidant ◽  
Complete Carcinogens

We have reviewed some of the data that link the reactive oxygen species produced by inflammatory phagocytes to cancer development. While it is clear that these substances induce phenotypic changes characteristic of those produced by known carcinogens, the precise mechanisms by which these effects are produced require much further study. In vitro, it would appear that phagocyte-generated oxidants could be complete carcinogens, ie, could cause both tumor initiation and promotion. In vivo, however, these substances appear usually to function as tumor promoters or cocarcinogens perhaps because of high levels of endogenous antioxidant defenses. This suggests that there may be even more reason to be optimistic about the potential for positive results in cancer chemoprevention trials in humans, and provides further rationale for the continuing interest in the use of antioxidants and anti- inflammatory drugs in current and future trials. For example, the Chemoprevention Branch of the National Cancer Institute is currently sponsoring seven extramural human efficacy intervention trials testing whether the antioxidant beta carotene can prevent cancer.

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