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Study of metabolism air pollutants and mutagens 3-nitrobenzanthrone and 2-nitrobenzanthrone
Čechová, Tereza ; Stiborová, Marie (advisor) ; Martínek, Václav (referee)
Nitroaromatic compounds are mutagenic and carcinogenic substances present in environment. Most of nitroaromatic compounds are potent mutagens in bacterial and mammalian systems. They are also carcinogens causing development of tumors, primarily in the liver, lung and mammary glands. 3-Nitrobenzanthrone (3-NBA, 3-nitro-7H-benz [de] anthracene-7-one) is one of the polycyclic aromatic nitro compounds possesing high toxic effects. 3-NBA is an environmental pollutant present in diesel exhaust and was also detected in soil and in rain water. 2-Nitrobenzanthrone (2-NBA, 2-nitro-7H-benz [de] anthracene-7-one) is an isomer 3-NBA, which also occurs as a pollutant in air. Although the 2-NBA is a weakly toxic substance, its high abundance in air could exhibit a high health risk to humans. This thesis investigates the metabolism of 3-NBA and its isomeric derivate, isomer 2 NBA, under anaerobic and aerobic conditions. To study the metabolism of these compounds, microsomal systems isolated from the liver of rats pretreated with Sudanem I, -naphthoflavone, phenobarbital, ethanol and pregnenolon 16-carbonitrile (PCN), the inducers of cytochromes P450 1A, 2B, 2E1 and 3A, were used. We also used mouse models, a control mouse line (wild type WT) and mice with deleted gene of NADPH:CYP reductase in the liver, thus absenting...
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Development and analysis of a database of reactions catalyzed by cytochrome P450 enzymes for machine learning applications
Komorníková, Natália ; Pluskal, Tomáš (advisor) ; Berka, Karel (referee)
Cytochrome P450 enzymes are hemoproteins showing extraordinary di- versity in the reactions they catalyze. We developed a database containing all the needed data to provide a comprehensive data source on reactions cat- alyzed by cytochrome P450 enzymes. This data mainly includes information about the substrates, products of characterized reactions, and the sequence of these enzymes. The database was developed by collecting data from reliable protein and reaction databases like UniProt and RHEA. The work presents an in-depth analysis of the created database of reactions catalyzed by cy- tochrome P450 enzymes. This database can be utilized for future machine learning approaches to predict the function of uncharacterized cytochrome P450s.
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Effect of pH and other factors on the metabolic conversion of tyrosine kinase inhibitors.
Čillíková, Olívia ; Indra, Radek (advisor) ; Čermáková, Michaela (referee)
Targeted anti-tumor therapy is a modern and effective approach to cancer treatment. This type of therapy includes several groups of anticancer drugs. The second most commonly used group of targeted chemotherapeutic substances are tyrosinkinase inhibitors. These are small- molecular agents that target specific signalling pathways of the tumor cell, thereby inhibiting it's growth, proliferation and angiogenesis. Representatives of this drug group include vandetanib and sunitinib. Vandetanib is primarily used for the treatment of medullary thyroid cancer and sunitinib has been approved for the treatment of gastrointestinal stromal tumor and advanced renal cell carcinoma. The diploma thesis focuses on the effect of pH and temperature on the in vitro metabolism of vandetanib and sunitinib using first-phase biotrasnformation enzymes. Differently premedicated and control rat liver microsomes were used in the experiments. Human and rat recombinant cytochromes P450 were used for comparison. The primary purpose of the experiments was to find the experimental pH and temperature optimum of the in vitro metabolism of vandetanib and sunitinib. These experiments also investigated the effect of pH and temperature on the drugs themselves and their stability. The effect of pH and temperature on the metabolism of the...
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Effect of selected perfumes on aromatase activity
Drejslarová, Iva ; Hodek, Petr (advisor) ; Smrček, Stanislav (referee)
Cytochromes P450 are enzymes involved in many physiological processes in the body, besides the metabolism of xenobiotics also in the biosynthesis and catabolism of endogenous substances such as hormones and steroids. Cytochromes P450 that are responsible for the transformation of endogenous compounds can be affected by xenobiotics, which interfere with the secretion, metabolism, transport or elimination of endogenous hormones by various mechanisms. These substances are also referred to as endocrine disruptors and include, for example, pesticides, insecticides, certain pharmaceuticals, or compounds contained in cosmetic products. One of their mechanisms of action is to interfere with steroid hormone biosynthesis through interactions with steroidogenic enzymes. One such enzyme is cytochrome P450 19, aromatase, which catalyses the conversion of testosterone to ß-estradiol in the final step of steroid hormone biosynthesis. Modulation of the activity of this enzyme by endocrine disruptors results in an imbalance of estrogen levels in the body, which can lead to impaired reproduction, osteoporosis, atherosclerosis, dementia, and the development of certain types of cancer. In this context, the effect of commercially available perfumes on the conversion of testosterone to ß-estradiol, which is catalyzed by...
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Modulation of cytochrome P450 activity by the anticancer drug lenvatinib
Ivančík, Martin ; Dračínská, Helena (advisor) ; Mrízová, Iveta (referee)
Lenvatinib, commercially marketed as Lenvima®, is an oral drug approved for the treatment of thyroid cancer, hepatocellular carcinoma and renal cell carcinoma that acts as a tyrosine kinase inhibitor. In vitro and in vivo studies have shown that lenvatinib is in the human body metabolised in liver and kidney by the cytochrome P450 enzyme system and aldehyde oxidase. Therefore, the aim of this bachelor thesis was to determine the effect of lenvatinib on the activity of individual isoforms of human cytochrome P450. Among the isoforms studied, those that ensure the metabolism of majority of foreign substances in the human body were selected. Measurements were performed in vitro using recombinant CYPs expressed in SupersomesTM and using marker reactions that are provided by individual cytochrome P450 isoforms. The activity of the enzyme in the reaction mixtures containing lenvatinib was compared with the activity of the enzyme in the reaction mixtures where only the solvent DMSO was added instead of lenvatinib. The concentration of lenvatinib corresponded to the concentration of the given substrate or was 10 times higher. Based on these measurements, the percentage activity of cytochrome P450 isoforms 1A1, 1A2, 1B1, 2B6, 2C8, 2C9, 2E1 and 3A4 in the presence of lenvatinib was calculated. A decrease in...
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Metabolism of the mitotic inhibitor BTB-1 by first phase biotransformation enzymes
Vančurová, Kateřina ; Indra, Radek (advisor) ; Martináková, Lenka (referee)
Cancer is still one of the most common deaths in the world and therefore new drugs are needed to be developed to stop or slow down this disease. Recently, there has been a huge expansion in drug development. Cytostatics that are still widely used include a group of mitotic inhibitors aimed at inhibiting mitosis. A representative of a mitotic inhibitor is the small newly discovered molecule BTB-1. This molecule mediates reversible inhibition of the molecular motor Kif18A, which plays an important role in cell division. In the first part of this presented bachelor thesis, a suitable method for the determination of BTB-1 using high performance liquid chromatography was developed and subsequently its sensitivity was verified. Furthermore, a suitable extracting reagent was found. In the second part of the bachelor thesis, the metabolism of BTB-1 was studied by the microsomal system of non-premedicated rats and rats premedicated with various cytochrome P450 inducers. Subsequently, the time dependence of BTB-1 conversion was studied by the microsomal system of premedicated rats. The effect of different concentrations of BTB-1 on its metabolism was also studied using the microsomal system of premedicated rats. Furthermore, the metabolism of this new molecule was studied using cytosolar systems isolated...
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Activity of cytochromes P450 1A1, 1A2 and 3A4 expressed in eukaryotic and prokaryotic systems
Indra, Radek ; Stiborová, Marie (advisor) ; Mizerovská, Jana (referee)
Cytochromes P450 (CYP) are a superfamily of heme proteins distributed widely throughout nature, involved in metabolism of a broad variety of substrates and catalyzing a variety of interesting chemical reactions. They play a central role in metabolism of chemotherapeutic agents. Several prodrug antitumor agents have been found as CYP substrates. Ellipticine, an alkaloid found in Apocynaceae plants, is an example of such type of pro-drug. Here, we investigate the efficiencies of human recombinant CYPs expressed in eukaryotic and prokaryotic expression systems, namely in SupersomesTM , microsomes isolated from insect cells transfected with baculovirus construct containing cDNA of human CYP1A1, 1A2 and 3A4 with NADPH:CYP reductase or in Bactosomes, the membrane fraction of E. coli transfected with cDNA of the same human CYP enzymes and NADPH:CYP reductase to oxidize their marker substrates and ellipticine. Cytochrome b5, an aditional component of the mixed function oxidase system, which metabolize xenobiotics was also expressed in some of the systems. The results found in this work demonstrate that human CYP1A1, 1A2 or 3A4 expressed in both eukaryotic and procaryotic systems oxidize their marker substrates (EROD for CYP1A1/2, MROD for CYP1A2 and testosterone 6β-hydroxylation for CYP3A4). They also oxidize...
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Isolation and characterization of microsomal fraction of fungus Pleurotus ostreatus and its role in the degradation of 17α-ethinylestradiol
Valášková, Petra ; Černá, Věra (advisor) ; Hodek, Petr (referee)
A synthetic hormone 17α-ethinylestradiol (EE2) which is a component of hormonal contraception pills has been identified as a main component of the endocrine-disrupting compounds (EDc). EDc are substances that mimic natural hormones in their action. Recently their amount especially in the groundwater and the surface water has been increased, which results in a negative impact on the hormonal system especially of aquatic organisms. Since it is not easy to replace these substances from the environment by conventional techniques other possibilities of their biodegradation are examined. White rot fungi, which are able to degrade lignin in nature, have promising biodegradation abilities towards many pollutants. These fungi contain a wide range of non-specific extracellular and intracellular enzymes that play an important role in the degradation. This bachelor thesis was targeted on the study of a white rot fungus, Pleurotus ostreatus, and especially on the degradation potential of its intracellular enzymes in the biodegradation of EE2. Initially, the ability of fungi Pleurotus ostreatus to degrade EE2 in vivo was tested. During the 48 hour incubation there was replaced 95,5 % of EE2. However, the role of cytochromes P450 (CYPs) in a metabolism of EE2 was not confirmed in this experiment by reason that an...
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Chicken antibodies as a tool of cytochrome P450 immunodetection
Mácová, Iva ; Hodek, Petr (advisor) ; Koblas, Tomáš (referee)
Cytochrome P450 is an important enzyme which catalyzes a large amount of reactions of endogenous and exogenous metabolism. There are compounds which increase expression of this enzyme and it leads up to the carcinogen activation and cancer formation. It includes much propagated chemopreventive compounds which are consumed abundantly in dietary supplements. It is therefore important to have the methods for determination of cytochrome P450 induction. One of these methods is the cytochrome P450 immunodetection by Western blotting. The detection of proteins on the membrane is done by the specific antibodies mostly gained from mammals. In this bachelor thesis there is the evidence that the antibodies from hen egg serve as well as the mammalian antibodies. The cytochromes P450 1A1 and 1A2 was detected by these egg antibodies after rat exposure to the model chemopreventive compounds β-naphthoflavone.
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Study on potentiaion of pharmacological efficiencies of ellipticine
Vranová, Iveta ; Stiborová, Marie (advisor) ; Mrázová, Barbora (referee)
Cytotoxic chemotherapy offers tool for clinical treatment of neoplasia. One of the drugs suitable for chemotherapy is ellipticine. Ellipticine is an alkaloid, which has significant antineoplastic properties. It acts as a DNA intercalator, inhibitor of topoisomerase II and forms also covalent DNA adducts mediated by cytochrome P450 and/or peroxidases. Oxidation of ellipticine by CYP (CYP3A4, CYP1A1/2, CYP2C9, CYP1B1) provides several metabolites (7-hydroxyellipticine, 9-hydroxyellipticine, 12-hydroxyellipticine, 13- hydroxyellipticine, and ellipticine N2 -oxide). Metabolites 12-hydroxyellipticine and 13- hydroxyellipticine, formed by CYP3A4, are responsible for formation of two major DNA adducts. Two carbenium ions, ellipticine-13-ylium and ellipticine-12-ylium were proposed as a reactive species binding to DNA. The main metabolites generated by peroxidases are the ellipticine dimer and ellipticine N2 -oxide, which provide the same carbenium ions and same DNA adducts. Modern chemotherapy uses targeting for higher selectivity for malignant cells and lower cytotoxicity for normal cells. Ellipticine-conjugates and his derivates (N-(2-hydroxypropyl)methakrylamid-ellipticine conjugates, vasoactive intestinal peptide-ellipticine conjugates and human serum albumin-ellipticine conjugates) and epidermal...
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