A P-glicoproteína (P-gp) é uma transportadora transmembrana de múltiplos fármacos, produto do gene MDR1 (ABCB1). A P-gp contribui para a função de barreira de vários tecidos e órgãos, funcionando como uma bomba de efluxo para muitos substratos. Diminuição na expressão desta proteína é associada à sensibilidade a fármacos. Cães da linhagem dos Collies possuem uma alta incidência de uma mutação no gene MDR1, denominada nt230(del4). Animais homozigotos para a mutação apresentam a supressão total de uma P-gp funcional e um animal heterozigoto apresenta uma maior sensibilidade para substratos da P-gp, devido a uma diminuição na expressão da mesma. Alguns fármacos opioides, como a morfina e a metadona, foram identificados como substratos da P-gp. O tramadol é um dos analgésicos opioides mais utilizados em cães. No presente trabalho, a mutação MDR1 nt230(del4) foi analisada em vinte cães Collie, utilizando reação em cadeia de polimerase (PCR). A identificação foi realizada por eletroforese em gel de poliacrilamida de alta resolução, sendo o resultado confirmado por análise de sequênciamento de DNA. Como resultado, seis cães apresentaram normalidade nos dois alelos e 14 apresentaram heterozigose para a mutação. Estes animais foram submetidos à segunda fase do experimento, quando se administrou uma dose única de 100 mg de tramadol oral de liberação prolongada (SR), objetivando investigar o tramadol como sendo substrato da P-gp. Outro objetivo foi avaliar a farmacocinética deste tipo de formulação, pois ainda não foi estabelecida para cães. A análise farmacocinética do tramadol foi realizada utilizando cromatografia líquida de alta eficiência (CLAE) com detecção por espectrometria de massas para a determinação e quantificação de tramadol no soro canino. O analito e o padrão interno foram extraídos do soro por método líquido-líquido. A separação cromatográfica foi obtida a partir de uma coluna analítica C18, mantida a 30°C, sob condições isocráticas de uma fase móvel constituída por uma mistura de acetonitrila e ácido fórmico a 0,1% (80:20). A concentração de tramadol no soro foi maior do que o limite de quantificação (LOQ), em 17 cães. Os cães foram divididos em dois grupos, cães normais (MDR1 +/+) e heterozigotos (MDR1 +/-). Os cálculos farmacocinéticos para o tramadol oral SR obtiveram valores médios de concentração máxima no soro (Cmax) de 63,12 ng/mL ± 33,35 para o grupo normal e 58,00 ng/mL ± 27,29 para o grupo heterozigoto. Tmax (tempo de concentração plasmática maxima) foi de 4 h para ambos os grupos e t ½ (meia-vida) foram 2,85 h ± 1,61 e 2,81 ± 1,46 h para os cães normais e heterozigotos, respectivamente. A área sob a curva (AUC) média para o tramadol oral SR para o grupo normal e heterozigoto foram 350,20 ± 216,61 e 312,15 ± 155,43 ng.h/mL, respectivamente. A biodisponibilidade foi de 22% e 23% para os cães normais e heterozigotos, respectivamente. Não houve diferença estatística entre os grupos em todos os parâmetros farmacocinéticos. Os resultados sugerem que o tramadol não é um substrato da Pgp. A quantidade de dados farmacocinéticos do tramadol oral na formulação de liberação prolongada (SR) em cães é escassa, sendo necessários mais estudos farmacocinéticos e farmacodinâmicos para o tramadol oral de liberação prolongada em cães para estabelecer adequada dose e frequência de administração em cães. / The P-glycoprotein (P-gp) is a transmembrane multidrug transporter, product of the MDR1 (ABCB1) gene. P-gp contributes to the barrier function of several tissues and organs, acting as an efflux pump for many substrates. Decreased expression of this protein is associated with sensitivity to drugs. Collie dogs have a high incidence of a mutation in MDR1 gene, denominated MDR1 nt230 (del4). In homozygosis, this mutation results in the total absence of a functional P-gp and a heterozygote animal presents a greater sensibility to P-gp substrates, probably due to a decrease in the expression thereof. Some opioid drugs such as morphine and methadone were identified as P-gp substrates. Tramadol is one of the most commonly opioid used in dogs. In the present work MDR1nt230 (del4) mutation was analyzed in 20 healthy Collie dogs using allele-specific polymerase chain reaction (PCR) method. Thereby, 6 homozygous intact and 14 heterozygous mutated MDR1 genotypes can be differentiated by high resolution polyacrylamide gel electrophoresis, confirmed by DNA sequence analysis. These animals underwent the second phase of the experiment, when a single oral administration of 100 mg of sustained release (SR) tramadol was administrated to investigate the tramadol as P-gp substrate. In addition, another aim was evaluate the pharmacokinetics of sustained release formulation, which has not been established for dogs. Pharmacokinetic analysis of tramadol was evaluated using high performance liquid chromatography (HPLC) with tandem mass spectrometry for determination and quantification of tramadol in canine serum. The analyte and internal standard (IS) were extracted from serum using liquid-liquid method. Chromatographic separation was achieved on a C18 analytical column, kept at 30°C, under isocratic conditions of a mobile phase consisted by a mixture of acetonitrile and water contained 0,1% formic acid (80:20). Serum tramadol concentration was greater than the limit of quantification (LOQ) in 17 dogs. The dogs were divided into two groups, normal dogs (MDR1 +/+) and heterozygous (MDR1 +/-) according to the MDR1 genotype. The median values of maximum serum concentration (Cmax) were 63.13 ng/mL ± 33.35 for the normal group and 58.01 ng/mL ± 27.29 for the heterozygous group. Tmax (time to maximum serum concentration) was 4 h for both groups and t ½ (half-life) were 2,85h ± 1,61 e 2,81h ± 1,46 for normal and heterozygous dogs, respectively. The mean area-under-the-curve (AUC) values for the sustained release tramadol compounds for the normal and heterozygous group were 350,20 ±216,61 and 312,15 ± 155,43 ng.h/mL, respectively. The bioavailability was 22% and 23% for normal and heterozygous dogs respectively. There was no statistic difference between groups in all pharmacokinetics parameters. The findings suggest that tramadol is not a P-gp substrate. The amount of pharmacokinetics data of SR formulation of tramadol in dogs is sparse. Therefore, more studies of oral SR tramadol in dogs are needed to establish appropriate dose and frequency of administration in dogs.

O estudo da expressão gênica é de grande aplicabilidade nas áreas de pesquisa científica e clínica. Por ser um método pouco invasivo e permitir coletas seriadas, a utilização de amostras sanguíneas facilita a análise da transcrição gênica. O maior desafio para a precisão nos ensaios moleculares é manter uma amostra com qualidade desde a coleta, armazenamento e transporte até o momento de sua análise. Este estudo utilizou um sistema de conservação de RNA sanguíneo que manteve amostras de qualidade após a coleta, transporte e armazenamento, permitindo extração de RNA e identificação da expressão do gene MDR1 em cavalos da raça Crioulo. Foram coletadas amostras sanguíneas de 27 cavalos a campo em tubos PAXgene® Blood RNA, que após o transporte e armazenamento a -20°C por 90 dias foram processadas em laboratório. A extração do RNA sanguíneo foi realizada com o kit Nucleo Spin® RNA II, a conversão em cDNA foi com o kit High-Capacity cDNA Reverse Transcription, utilizando a fluorimetria para as avaliações. A identificação da expressão do gene MDR1 em sangue conservado utilizou primer específico para cDNA e PCR em tempo real. Houve extração de RNA em todas as amostras coletadas, sendo que as leituras das concentrações de RNA das amostras com DNA contaminante não tiveram diferença estatística das amostras sem DNA contaminante. Ocorreu amplificação do gene MDR1 a partir do RNA das amostras, independente de contaminação de DNA. A coleta de sangue venoso dos cavalos a campo com os tubos PAXgene foi realizada sem complicações. A amplificação do mRNA com primer específico para transcrito do gene MDR1, de amostras submetidas aos métodos de coleta, armazenamento e processamento executados neste trabalho, confirma que o mRNA extraído, com a metodologia descrita, é viável, sendo sua expressão identificada em leucócitos sanguíneos de equinos da raça Crioulo. / Efficient nucleic acid extraction methods are paramount for gene expression studies and applications in the scientific and clinical research. Whole blood samples provide material for gene transcription analysis allowing serial trials with a not much invasive procedure. Still, a major challenge for molecular assays accuracy and reliability is to maintain RNA stability during sample collection and storage. A whole blood collection system for RNA preservation was used during collection, transport and storage of samples intended for RNA extraction and identification of the MDR1 gene in Crioulo horses. The blood samples were obtained from 27 horses in the field using the PAXgene® Blood RNA tubes. After 2h transport at room temperature, the samples were stored at -20oC for 90 days before processing. RNA extraction was performed with the Nucleo Spin® RNA II kit and cDNA conversion carried out with the High-Capacity cDNA Reverse Transcription kit. RNA concentration was determined by fluorometry. MDR1 gene expression was assessed using real time polymerase chain reaction (PCR) with a specific primer for cDNA. RNA was successfully extracted from all samples. Total RNA yield from DNA contaminated samples was not statistically different from those without DNA contamination. MDR1 gene amplification occurred regardless of DNA contamination. There were no complications during horse handling and blood sampling direct into PAXgene tubes in the field. Successful amplification of MDR1 gene transcript with a specific primer showed that blood samples collected, stored and processed under the described methodology provided viable mRNA for down-stream applications of molecular analyses. This study allowed the identification of the gene MDR1 in blood leucocytes of Crioulo horses.

Multidrug resistance phosphoglycoprotein (MDR1/P-gp) and breast cancer resistance protein (BCRP) were first isolated in chemoresistant cancer cells and have since been found in a variety of normal tissue, including the placenta. The potential function of MDR1/P-gp and BCRP in the human placenta is to protect the fetus from maternally circulating endogenous steroids and hormones, therapeutic drugs and toxins. The objective of this study was to examine the role of maternal steroids in the regulation of MDR1/P-gp and BCRP in the human placenta. Trophoblast cells were isolated from term placenta tissues and immunohistochemistry, western blot analysis and transport studies were used to determine the effect of maternal steroids on MDR1/P-gp and BCRP regulation. Maternal steroids, present at high concentrations in maternal serum, did not have an effect on BCRP in human syncytiotrophoblast. Estrogen and progesterone did not alter MDR1/P-gp levels in human syncytiotrophoblast, but cortisol significantly decreased MDR1/P-gp levels.

Multidrug resistance (MDR) in breast cancer treatment is the major cause leading to the failure of chemotherapy. P-glycoprotein (P-gp), the product of the human MDR1 gene, plays a key role in resistance to chemotherapy and confers cross-resistance to many structurally unrelated anticancer drugs. We have previously reported that integrin αvβ6 plays a critical role in breast cancer invasion and metastasis. However, whether and how αvβ6 is associated with P-gp and regulated by potential genetic mechanisms in breast cancer remains unclear. In the present study, we further investigated the reversal effect and underlying mechanisms of MDR in breast cancer. Two small interfering RNA constructs (pSUPER-β6shRNAs) targeting two different regions of the β6 gene have been designed to inhibit αvβ6 expression by transfecting them into adriamycin-resistant MCF-7/ADR cell lines. Suppression of αvβ6 dramatically downregulated the levels of MDR1 gene mRNA and P-gp. In particular, β6shRNA-mediated silencing of αvβ6 gene increased significantly the cellular accumulation of Rhodamine 123 and markedly decreased drug efflux ability, suggesting that β6shRNAs indeed inhibit P-gp mediated drug efflux and effectively overcome drug resistance. In addition, inhibition of integrin αvβ6 suppressed the expression of ERK1/2. Interestingly, our data demonstrate that suppression of integrin αvβ6 caused significant downregulation of Bcl-2, Bcl-xL and upregulation of caspase 3, Bad, accompanied by increasing activity of cytochrome C. A possible connection between αvβ6 and P-gp in drug resistance biology is suggested. Taken together, β6shRNA could efficiently inhibit αvβ6 and MDR1 expression in vitro and these findings may offer specifically useful means to reverse MDR in breast cancer therapy.

No description available.

P-Glykoprotein als Produkt des MDR1-Gens stellt einen gut untersuchten Mediator der Multidrugresistenz (MDR) in humanen Malignomen dar. Die Überexpression dieses ABC-Transporters steht in Korrelation zu einer erniedrigten Tumorremission und einer kürzeren Überlebensrate der Patienten. Bisherige Versuche, das Protein über niedermolekulare Substanzen (MDR-Modulatoren) zu inhibieren, vermochten in allen bisherigen klinischen Studien nicht zu überzeugen, so daß diese bis heute keinen Eingang in Standardtherapieschemata gefunden haben. Ziel dieser Arbeit war es, mittels RNA-Interferenz Strategien die Expression von MDR1 zu hemmen und eine Reversion der zellulären Chemoresistenz sowohl im Zellkultur- als auch im Tiermodell zu erreichen. Für die in vitro Untersuchungen an drei humanen multidrug-resistenten Karzinomzellinien wurden verschiedene siRNA (short interfering) Duplexe und shRNA (short hairpin)-exprimierende Vektoren gegen die MDR1 mRNA entwickelt. Die Behandlung der Zellen mit siRNAs führte zu einer bis zu 91 %igen Inhibition der MDR1 mRNA-Expression und zu einer Sensitivierung der Zellen gegenüber dem Anthrazyklin um 89 %. Diese Effekte konnte über einen Zeitraum von drei bis fünf Tagen aufrechterhalten werden. Die stabile Expression von anti-MDR1 shRNAs führte in zwei der untersuchten Zellmodelle zu einer dauerhaften und kompletten Überwindung des MDR1-abhängigen Resistenzphänotyps. Im Mausmodell konnte durch intratumorale Applikation des anti-MDR1 shRNA-kodierenden Vektors mittels low-volume Jet-Injektion eine komplette Reversion der MDR1-Überexpression sowie eine Wiederherstellung der Chemosensitivität gegenüber Doxorubicin in dem resistenten Tumormodell erreicht werden. Die Effizienz der kombinierten Gen- und Chemotherapie wird durch die Verminderung des in vivo Tumorwachstums auf das Volumen des von der sensiblen Zellinien-abgeleiteten Tumors reflektiert. / Multidrug resistance (MDR) is the major cause of failure of effective chemotherapeutic treatment of disseminated neoplasms. The "classical" MDR phenotype of human malignancies is mediated by drug extrusion by the adenosine triphosphate binding cassette (ABC)-transporter P-glycoprotein (MDR1/P-gp). For stable reversal of "classical" MDR in three human cancer cell lines by RNA interference (RNAi) technology, two small interfering RNA (siRNA) constructs and four H1-RNA gene promoter-driven expression vectors encoding anti-MDR1/P-gp short hairpin RNA (shRNA) molecules were constructed. In all cellular systems, siRNAs could specifically inhibit MDR1 expression up to 91% at the mRNA and protein levels. Resistance against daunorubicin was decreased to a maximum of 89%. The introduction of anti-MDR1/P-gp shRNA expression vectors leads in two of the three human cancer cell lines to a complete reversion of the MDR phenotype. The reversal of MDR was accompanied by a complete suppression of MDR1/P-gp expression on mRNA and protein level, and by a considerable increased intracellular anthracyline accumulation in the anti-MDR1/P-gp shRNA-treated cells. In a mouse xenograft model a complete in vivo restoration of MDR1 overexpression and chemosensitivity to doxorubicin could be obtained by intratumorally jet-injected anti-MDR1 shRNA in a multidrug resistant human cancer tumor model.

No description available.

MUDr. Olga Matoušková - the dissertation theses The influence of individual genetic predisposition to the pharmacokinetics and pharmacodynamics of chosen opioids ABSTRACT Introduction: The aim of this thesis is to study the influence of polymorphism of CYP2D6 and MDR1 on the pharmacokinetics and pharmacodynamics of tramadol in healthy volunteers using measurement. A secondary objective is to evaluate these polymorphisms in relation to the analgesic efficacy and side effects of piritramide for acute postoperative pain. Materials and methods: In two prospective work studying the influence of genetic predisposition on the pharmacokinetic and pharmacodynamic parameters of tramadol, we included a total of 90 healthy volunteers. Clinical studies on opioid analgesia and influence of genetic predisposition to the pharmaco-therapeutic effects and side effects in patients with acute postoperative pain, we included a total of 161 patients with acute postoperative pain. Polymorphism genotyping CYP2D6 and MDR1 gene we performed PCR - RFLP analysis, to determine concentrations of tramadol and metabolite, we used gas and liquid chromatography and pharmacodynamic effects of opioids was evaluated by pupilometric measurement and visual analogue scale. Results and conclusion: Variability of the opioid effect is influenced by...

Frequency of occurrence of selected single nucleotide polymorphisms of CYP2C8 and MDR1 in the Czech population and their influence on the effect of amiodarone Introduction: Variability in drug response is sometimes conditioned by genetic differences in the metabolism and the transport of drugs. Interindividual differences are often caused by polymorphisms affecting biotransformation activity of enzymes and expression of transporters. In the thesis we paid attention to the cytochrome P450 CYP2C8 and MDR1. First, we described the frequency of occurrence of selected variant alleles CYP2C8 * 2, CYP2C8 * 3 (2 substitution in exon 3 and 8, CYP2C8 and CYP2C8 * 3G416A * 3A1196G), CYP2C8 * 4, CYP2C8 P404A in the healthy Czech population and MDR1 variant alleles in these exons: 26 C3435T, 21 G2677A/T, 12 C1236T a 17 T-76A. Subsequently, we studied the influence of these polymorphisms on effects of amiodarone in the selected group of patients. Methods: We determined genotypes MDR1 a CYP2C8 by PCR-RFLP by using restriction enzymes and specific primers. We determined the frequency of MDR1 genotypes in 189 healthy volunteers and CYP2C8 in 161 healthy subjects. Further we included into the study 63 patients treated with amiodarone for longer than two months. Their treatment was assessed from medical records and...

Les membranes cellulaires jouent un rôle important dans l’absorption des médicaments et la distribution de ceux-ci dans le corps humain. Elles contiennent différents transporteurs membranaires qui sont responsables des profils pharmacocinétiques, d’innocuité et d’efficacité des xénobiotiques. Lors du développement d’un médicament, il s’avère donc indispensable, de prédire l’interaction des nouveaux composés avec les transporteurs présents dans l’organisme. Le but du projet de recherche est de créer un nouvel outil pour étudier le comportement de la glycoprotéine-P (P-gp), un transporteur membranaire responsable du rejet de nombreux composés, sur différents médicaments. Pour cela, un modèle non cellulaire est développé en utilisant des protéoliposomes : des liposomes dans lesquels des transporteurs sont incorporés. La méthodologie consiste tout d’abord à produire, extraire et purifier la protéine d’intérêt à partir de deux systèmes d’expression : MDCK-MDR1 (cellules de chien transfectées avec le gène humain MDR1) et Pichia pastoris (levures) fin de déterminer les avantages et les limites de ces deux types cellulaires. Différentes méthodes de reconstitution dans des protéoliposomes ont ensuite été testées avec la P-gp obtenue. Puis, l’activité ATPasique de la P-gp reconstituée a été évaluée en présence de différents substrats. Les protocoles de culture cellulaire, d’extraction et de purification des deux systèmes d’expression ont été implémentés avec succès au sein du laboratoire. Les résultats montrent que les rendements obtenus sont supérieurs avec les levures qu’avec les cellules de mammifère. En outre, Pichia pastoris offre les avantages d’être facile et rapide à cultiver et peu couteux. Les premiers résultats d’activité ATPasique obtenus avec la P-gp reconstituée en protéoliposomes étaient prometteurs mais n’ont pas été reproduits en raison de la dégradation de la protéine membranaire. Les prochaines études du projet porteront sur un autre transporteur membranaire de la famille ABC, BCRP, une protéine de plus petite taille qui devrait montrer une plus grande stabilité pour mener à bien les tests. / Cellular membranes play an important role in the absorption and distribution of drugs in the human body. They contain different membrane transporters, which are responsible for the pharmacokinetic properties of drugs, as well as the safety and efficiency of their diffusion. When developing a new drug, it is thus of utmost importance to study the way that it will interact with the transporters present within the body. The aim of this study was to evaluate a new tool for measuring permeability in order to understand the function and mecanisms of P-glycoprotein (P-gp). P-gp is a transporter that is responsible for the rejection of many different compounds found in various drugs. This study thus seeks to use proteoliposomes to develop non-cellular models of membrane permeability including efflux and uptake transporters. This novel model of permeability will be utilized to study the underlying mechanisms of membrane permeability to xenobiotics. The human P-gp was produced, extracted and purified using two different expression systems: MDCK-MDR1 cells (Madin-Darby canine kidney cells transfected with the human MDR1 gene) and Pichia pastoris. Both expression systems were studied in order to compare the strengths and weaknesses of each system. We then tested different methods of reconstituting the P-gp into protéoliposomes. Finally, we measured the level of ATPase activity using different substrates. The protocols of cell culture, extraction and purification of both expression systems were accomplished in a laboratory during this study. These results demonstrated that expressing P-gp using yeast was more effective than that of mammalian cells. Furthermore, working with Pichia pastoris offers multiple advantages: expressing P-gp was easier, faster and cheaper than working with mammalian cells. The first measurements of ATPase activity using reconstituted P-gp proteoliposomes were promising, however they proved difficult to reproduce due to the possible degradation of the membrane protein.Further studies in this project will look to evaluate another ABC membrane transporter, BCRP. This smaller protein should prove to be more stable than P-gp, facilitating experimentation.