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Oxidation of ellipticine by human cytochromes P450 expressed in prokaryotic and eukaryotic systems
Vejvodová, Lucie ; Stiborová, Marie (advisor) ; Hýsková, Veronika (referee)
Ellipticine is an alkaloid with antitumor activity, whose mechanism of action is based on intercalation into DNA, inhibition of topoisomerase II and formation of covalent adducts with DNA, after its enzymatic activation by cytochromes P450 and/or peroxidases. Ellipticine is oxidized by cytochromes P450 to form up to five metabolites (7-hydroxy-, 9-hydroxy, 12- hydroxy-, 13-hydroxyellipticine and N2 -oxide ellipticine). 9-Hydroxy- and 7- hydroxyellipticine are considered to be detoxification metabolites, whereas 12-hydroxy-, 13- hydroxyellipticine and N2 -oxide of ellipticine are considered as activation metabolites, which are responsible for formation of covalent DNA adducts. The aim of this thesis was to examine the efficiency of human recombinant cytochromes P450 expressed in eukaryotic (SupersomesTM ) and two prokaryotic expression systems (Bactosomes) in oxidation of ellipticine. Cytochromes P450 expressed in prokaryotic systems differed in the amounts of "coexpressed" NADPH:CYP reductase. The resulting ellipticine metabolites were analyzed by HPLC. The results obtained in this thesis demonstrate that human cytochromes P450 2C9/2D6/2C19 expressed in prokaryotic or eukaryotic systems oxidize ellipticine to form up to four metabolites: 9-hydroxy-, 12-hydroxy-, 13-hydroxyellipticine and N2 -oxide...
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Metabolism carcinogens and drugs by the system of monooxygenases
Moserová, Michaela ; Stiborová, Marie (advisor) ; Entlicher, Gustav (referee) ; Čeřovská, Noemi (referee)
Ellipticine, an alkaloid isolated from Apocynaceae plants, exhibits significant antitumor and HIV activities. Ellipticine is a pro-drug, whose pharmacological and genotoxic effects depend on activation by cytochromes P450 (CYP) and peroxidases (Px) to a reactive species generating DNA adducts. To elucidate contribution of CYPs (and which of them) and Px to ellipticine activation, we used rat and mouse models, mice with deleted gene of NADPH:CYP reductase in the liver, thus absenting this enzyme in the liver (HRNTM ) and a control mouse line (WT), rats treated with ellipticine, and microsomal systems isolated from the liver of mouse lines and from the liver, kidney and lung of rats. The purified enzymes, CYP1A1 and 3A4, reconstituted with NADPH:CYP reductase were also used. The effect of cytochrome b5, a facultative component of the mixed function monooxygenase system, on ellipticine oxidation by CYP1A1 and 3A4 was also investigated. Carcinogenic benzo(a)pyrene (BaP), known to covalently bind to DNA after its activation with CYPs, was investigated for its potential to generate DNA adducts and to induce CYP and NADPH:CYP reductase enzymes in mouse livers. We investigated an influence of each of components of the mixed function oxidases (MFO) system on metabolism of BaP. CYP1A1 is widely accepted to be the...
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Modulation of activities and expression of enzymes metabolizing ellipticine by histone deacetylase inhibitor trichostatin A
Kopejtková, Barbora
Histone deacetylase inhibitor trichostatin A (TSA) increases cytotoxicity of antineoplastic agent ellipticine to human neuroblastoma cells. Its mechanism of action has not yet been explained. One of the possible mode of action is conformational change in chromatin, which leads to changes in DNA that is more accessible to covalent modification and intercalation. The aim of this work is to study another mode of action, which can explain this phenomenon. The question is, if TSA can increase cytotoxicity of ellipticine to human neuroblastoma cells by modulation of activities and expression of cytochromes P450 and peroxidases. These enzymes are responsible for cytotoxicity of ellipticine to human neuroblastoma cells. TSA has no effect on oxidation of ellipticine mediated by cytochromes P450 leading to metabolites responsible for formation of ellipticine-DNA adducts and detoxication metabolites. TSA increases formation of ellipticine dimer, which is a detoxication metabolite, forming during its oxidation by peroxidases. TSA has no effect on activities of CYP1A1, CYP1A2, CYP3A, which significantly participate in oxidation of ellipticine. TSA modulates expression of enzymes oxidizing ellipticin in human neuroblastoma cells. TSA in the presence of ellipticine increases expression of CYP1A1 a CYP3A4 in...
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Mechanisms of anticancer drug action in neuroblastomas
Groh, Tomáš
Cancer cells are able to adapt to different stress factors such as hypoxia, which is caused by insufficient tumor vascularization. An increased acetylation status of histones H3 and H4 in UKF-NB-3 and UKF-NB-4 neuroblastoma cell lines was found to be a mechanism of adaptation of these cells to hypoxia. An increase in acetylation of histones H3 and H4 is suggested to cause changes in the structure of chromatin that lead to activation of gene transcription. In addition, cultivation of tested neuroblastoma cells under hypoxic conditions changes expression of proteins of a transcription factor N-myc, which is essential for development of neuroblastomas. This transcription factor is also responsible for a metabolic adaptation of neuroblastoma cells, increases their aggressiveness and its expression leads to a worse prognosis of the disease. Inhibitors of histone deacetylases (HDAC) are suggested to be the promising agents exhibiting various anticancer effects. They can induce cell cycle arrest, differentiation or programmed cell death in sensitive tumors. In this study, the effect of one of inhibitors of HDACs, valproate, on expression of proteins of transcription factors N-myc and hypoxia inducible factor 1α (HIF-1α) was investigated. Valproate decreases protein levels of both transcription factors in...
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The study of properties of anticancer drugs ellipticine, etoposide and doxorubicin in the forms of nanocarriers
Lengálová, Alžběta
Currently available anticancer therapies are inadequate and spur demand for improved technologies. Among others, the utilization of nanocarriers for anticancer drug delivery has shown great potential in cancer treatment. Nanocarriers can improve the therapeutic efficiency of the drugs with minimization of the undesirable side effects. To evaluate potential application of this technology, two forms of nanocarriers have been studied: multi-walled carbon nanotubes (MWCNTs) and apoferritin. The aim of this study was to determine, whether given cytostatics (ellipticine, etoposide and doxorubicin) are bound to these nanotransporters and how are they released from them, especially depending on pH. Since the pH of the tumor cells is lower than the pH of healthy cells it would be preferred that the drugs would release from nanocarriers at the lower pH while at the physiological pH the release of the drug would be eliminated. The results found show that ellipticine is actually released from its MWCNT- and apoferrtin-encapsulated form at acidic pH (5.0), while at pH 7.4 its interaction with nanocarriers is stable. Ellipticine released from MWCNT is activated by microsomal enzymes to reactive metabolites (13- hydroxyellipticine and 12-hydroxyellipticine) forming DNA adducts. The results indicate that both...
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The mechanism of action of anticancer drug ellipticin in target tissues of its effect
Mrízová, Iveta
Ellipticine is an alkaloid isolated from Apocynaceae plants exhibiting significant antitumor and anti-HIV activities. Cytochromes P450 (CYP) and peroxidases are the enzymes participating in metabolism of ellipticine. This process provides activation and detoxication metabolites of ellipticine. The CYP enzymes, which participate in oxidation of ellipticine in different tissues (liver, lung and kidney) of rat, a model organism simulating the fate of ellipticine in humans have already been identified. In this work, the effects of ellipticine on contents and catalytic activities of CYPs and other components of the mixed-function oxidase (MFO) system in this animal system were studied. For detection of contents of CYPs and other components of the MFO system, spectroscopic and electrochemical methods were used. To determine catalytic activities of CYPs and NADPH:cytochrome P450 reductase, reactions with specific substrates of these enzymes were utilized. The results found in this study demonstrate that expression and catalytic activity of CYP1A is induced by ellipticine in all of the tested organs (liver, kidney and lung) of rats treated with the drug. Moreover in liver, the cytochrome b5 expression is also induced. In addition, in this organ, expression and catalytic activity of CYP3A was increased by...
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The effect of antitumor agents on the expression and activity of cytochrome P450 subfamily 2C
Uher, Tomáš ; Dračínská, Helena (advisor) ; Feglarová, Tereza (referee)
Targeted therapies, acting by blocking essential biochemical pathways required for tumor cell growth and survival, are being used lately in multiple cases of cancer treatment. Cabozantinib, a small molecule inhibitor of receptor tyrosine kinases, is an example of a targeted drug, regulating growth, angiogenesis and metastatic pro- gression of medullary thyroid cancer. Such drugs are also often complemented by cytotoxic agents, e.g. ellipticine; however, therapeutic usage of ellipticine itself is limited due to its poor solutibility and variety of adverse effects. In this bachelor thesis, effects of cabozantinib, ellipticine, or their combina- tion on gene and protein expression of cytochromes P450 2C6 and 2C11 have been studied in vivo. Aforementioned cytochromes have an important role in biotrans- formation of xenobiotics in rat liver. Their protein expression has been assessed by Western blot immunoassay technique, while the gene expression was evaluated by quantitative PCR method. Furthermore, the effects of studied substances and their combination on CYP2C6 and CYP2C11 specific activity have been determined by diclofenac 4'-hydroxylation and testosterone 16α-hydroxylation, respectively. Additionally, direct inhibitory effect of cabozantinib on recombinant CYP2C11 rat isoform has been studied in...
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Anticancer drugs in forms of nanoparticles and mechanisms potentiating their anticancer efficiency
Meskařová, Veronika ; Indra, Radek (advisor) ; Bělonožníková, Kateřina (referee)
Cancer has been one of the most common diseases of civilization for centuries. In the 18th century, some cancers were described and the first treatments were proposed. Currently, oncosurgery, chemotherapy, radiotherapy, immunotherapy and hormonal treatment are used to treat cancer. At the same time, efforts are being made to find new anticancer drugs that target tumor cells more selectively. Recently, nanomedicine has also started to be used. This bachelor thesis deals with minimizing the binding of the amount of cytostatic ellipticine to the surface of the nanotransporter apoferritin and achieving higher encapsulation efficiency. Two types of apoferritins at different weight ratios to ellipticine were studied. It has been found that by finding a suitable weight ratio of the two molecules, binding can be minimized, and encapsulation efficiency can be increased. When working with commercial apoferritin, there was a higher encapsulation and a lower binding of ellipticine to the surface at the weight ratio of 1:10. In contrast, when working with recombinant apoferritin, the encapsulation is higher and ellipticine binding are lower at the lower ratio of 1: 2,5. Key words: oncological diseases, anticancer drugs, nanomedicine, cytostatic, nanotransporter, ellipticine, apoferritin [IN CZECH]
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Effect of tyrosine kinase inhibitor cabozantinib and cytotoxic alkaloid ellipticine on expression and activity of cytochromes P450 1A1, 1A2 and 1B1
Měkotová, Barbora ; Dračínská, Helena (advisor) ; Jeřábek, Petr (referee)
In recent years, tyrosine kinase inhibitors have been more and more used for the targeted cancer therapy, due to their ability to disrupt intracellular signalling pathways associated with the development of tumours. Cabozantinib is the tyrosine kinase inhibitor which has been approved for the treatment of thyroid cancer and it is also effective against several other types of cancer. However, multiple drugs combination is often used in anticancer therapy, which may result in their cytochrome P450-mediated interactions. Although this may affect the therapeutic effect of the drugs and cause adverse effects on the organism, very little is known about the effect of cabozantinib on biotransformation enzymes. Therefore, the effect of cabozantinib not only alone but also in combination with the known cytostatic ellipticine on the expression and the activity of cytochromes P450 1A1, 1A2 and 1B1 in rat liver and kidney in vivo was studied in this work. The gene expression was determined by quantitative PCR, the amount of protein was studied by Western blotting and consecutive immunodetection. The enzyme activity was studied using specific marker reactions, 7-ethoxyresorufin O-deethylation for CYP1A1, 7-methoxyresorufin O-demethylation for CYP1A2 and 17β-estradiol 4-hydroxylation for CYP1B1. Our results...
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Effect of cytochromes P450 on metabolism of anticancer drugs bound into apoferritin nanoparticle
Wilhelm, Marek ; Indra, Radek (advisor) ; Ptáčková, Renata (referee)
Tumour-related diseases are the second most common cause of death in the Czech Republic, right after cardiovascular diseases. Nanomedicine - a novel scientific discipline - shows captivating potential in anticancer treatment with help of so called nanotranporters - nanoparticles capable of transporting other molecules. Encapsulation of a cytostatic drug into a nanoparticle improves its pharmacokinetical and pharmacodynamical properties which helps to reduce adverse side effects on non-tumour healthy tissue. In the scope of this diploma thesis apoferritin - apo-form of ferritin - was studied, since this nanotransporter shows promise for clinical use in anticancer treatment. Effect of hepatic microsomes from premedicated and control rats on biotransformation of doxorubicin cytostatic (Dox) in free and apoferritin nanoparticle-bound forms was investigated at pH 7,4. Over the course of biotransformation two types of metabolites - M1 and M2 - were observed. Regardless of the employed inductor all studied microsomes have exhibited similar metabolism of free doxorubicin and its apoferritin encapsulated form (ApoDox). Our results also imply that doxorubicin can be metabolically processed by rat hepatic microsomes in both free and ApoDox form with similar efficiency. We have also studied biotransformation...
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