Foi definido que elementos regulatórios da expressão atrial-específica do promotor da SMyHC3 estão contidos em um elemento complexo de resposta a receptores nucleares (ECRRN). Ensaios de transativação celular indicam que alguns receptores nucleares se ligam nesta região. A partir destes ensaios verificamos a ativação do promotor por um receptor nuclear, o COUP-TFII. Ele regula muitos processos biológicos, como angiogênese e o próprio desenvolvimento atrial. Através da deleção do ECRRN observamos que o promotor não era ativado por COUP-TFII, indicando a sua ligação nessa região. Verificamos ainda que somente o domínio de ligação ao ligante do COUP-TFII é capaz de ativar o promotor, sugerindo a necessidade de uma interação com outros RNs para ativar o promotor. Uma análise proteômica indica que a maioria dos interactores de COUP-TFII está relacionada com complexos reguladores da transcrição e com a via de sinalização do receptor de andrógenos (AR). Ensaios de transativação celular mostram que juntos, COUP-TFII e AR, são capazes de aumentar a ativação do promotor. / It was determined that regulatory elements of the atrial-specific expression of the promoter SMyHC3 are contained in a complex nuclear receptor response element (CNRRE). Cellular transactivation assays indicated certain nuclear receptors (NR) can bind in this region. From these trials, was observed the promoter activation by a nuclear receptor, COUP-TFII. It regulates many biological processes such as angiogenesis and atrial development. Deletion of CNRRE resulted in no activation of the promoter by COUP-TFII, indicating their connection in this region. We also verified that only the ligand binding domain of COUP-TFII is able to activate the promoter, suggesting interaction with other NRs to activate it. A proteomic analysis revealed that most of COUP-TFII partners relates to complexes of transcription regulators and the androgen receptor (AR) signaling pathway. Cell transactivation assays showed that together, COUP - TFII and AR, are able to increase promoter activation.

Charles University, Faculty of Pharmacy in Hradec Králové, Department of Biological and Medical Sciences University of Vienna, Faculty of Life Sciences, Department of Pharmacognosy Candidate: Lenka Kovářová Supervisor: Pharmdr. Miroslav Kovařík, Ph.D. Consultant: Dr. Angela Ladurner Title of the diploma thesis: Characterization of a synthetic leoligin derivative, with agonistic FXR and enhancing macrophage cholesterol efflux activity Atherosclerosis is a pathologic multifactorial process triggering the development of cardiovascular diseases, which are the leading causes of death in the western world. The initial phase of atherosclerosis is characterized by the accumulation of lipid particles, mainly low-density lipoproteins (LDL) and macrophage-derived foam cells in large arteries, leading to the gradual thickening of the vessel wall. These progressive alterations elicit plaque formation, followed by rupture, thrombosis and finally can lead to a cardiovascular event. Reverse cholesterol transport is an important preventive mechanism, which ensures removal of excessive atherogenic lipoproteins from macrophages. This efflux is facilitated by ATP binding cassette transporters, mainly ABCA1 and ABCG1 and in part by scavenger receptor B1 (SR-B1). Several nuclear receptors, including PPARγ, LXRα and LXRβ...

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A &#946;-ionona (BI) é um isoprenóide que apresenta atividade quimiopreventiva durante a fase de promoção da hepatocarcinogênese. O presente trabalho teve como objetivo avaliar a expressão de genes modulados pela BI envolvidos na quimioprevenção durante a fase de promoção da hepatocarcinogênese induzida pelo modelo do \"Hepatócito Resistente\" (RH). Ratos Wistar machos foram submetidos ao modelo do RH e tratados durante 4 semanas consecutivas com BI (16 mg/100 g de p.c.) ou óleo de milho (OM) (0,25 ml/100 g de p.c.; grupo controle). O perfil da expressão de 1.176 genes foi analisado por macroarray no fígado dos grupos BI, OM e de ratos considerados normais (grupo N). A expressão gênica foi considerada aumentada, quando a razão de expressão foi &#8805; 1,5 ou diminuída, quando &#8804; 0,5. Aplicou-se análise hierárquica de clustering e classificação ontológica dos genes diferencialmente expressos. A expressão gênica foi validada por RT-PCR do tipo \"duplex\", utilizando-se tecido hepático microdissecado de: lesões pré-neoplásicas persistentes (pLPN) ou em remodelação (rLPN) e de regiões ao redor das LPN (surrounding). Um total de 133 e 32 genes foi considerado diferencialmente expresso entre os grupos OM (em relação ao N) e BI (em relação ao OM), respectivamente. Trinta e sete por cento dos genes diferencialmente expressos no grupo BI vs OM referiam-se a receptores celulares. Destes, 4 genes codificantes para receptores nucleares foram identificados como possíveis alvos da BI na quimioprevenção da hepatocarcinogênese: RXR&#945; (receptor X de retinóide &#945;), RAR&#946; (receptor de ácido retinóico &#946;), COUP-TFI (chicken ovalbumin upstream promoter-transcription factor I) e Nur77 (nuclear receptor 77). Em comparação ao grupo OM, a expressão de RXR&#945; e RAR&#946; foi maior (p<0,05) especificamente em pLPN e rLPN do grupo &#946;I, respectivamente. Em comparação ao grupo N, Nur77 apresentou maior (p<0,05) expressão no surrounding e nas rLPN do grupo OM. Por outro lado, a expressão de Nur77 em rLPN foi menor (p<0,05) no grupo BI do que no OM. Comparada ao grupo N, a expressão de COUP-TFI foi maior (p<0,05) no grupo OM, tanto no surrounding das LPN como nas pLPN e rLPN. Em comparação ao grupo OM, a expressão de COUP-TFI foi menor (p<0,05) no grupo BI, especificamente nas pLPN e nas rLPN. Os resultados sugerem que os receptores nucleares RXR&#945;, RAR&#946;, Nur77 e COUP-TFI representam alvos moleculares da BI relevantes para a quimioprevenção da hepatocarcinogênese em ratos. / &#946;-ionone (BI) is an isoprenoid which has chemopreventive activity during the promotion phase of hepatocarcinogenesis. This study aimed to evaluate the expression of genes modulated by BI involved in chemoprevention during the promotion phase of hepatocarcinogenesis induced model of \"Resistant Hepatocyte (RH). Male Wistar rats were submitted to the RH model and treated for 4 consecutive weeks with BI (16 mg/100 g bw) or corn oil (CO) (0.25 ml/100 g bw, control group). The expression profile of 1,176 genes was analyzed by macroarray in the liver of groups BI, CO and normal rats (group N). Gene expression was considered increased when the expression ratio was 1.5 or decreased when 0.5. Hierarchical clustering analysis and ontological classification of differentially expressed genes were applied. Gene expression was validated by RT-PCR \"duplex\", using microdissected hepatic tissue from: persistent pre-neoplastic lesions (pPNL) or remodeling pre-neoplastic lesions (rPNL) and regions around the PNL (surrounding). A total of 133 genes and 32 were considered differentially expressed between the two groups (CO to N) and BI (relative to CO), respectively. 37% of differentially expressed genes in group BI vs CO were related to cell receptors. Of these, four genes encoding for nuclear receptors have been identified as possible targets of BI in the chemoprevention of hepatocarcinogenesis: RXR (retinoid X receptor &#945;), RAR&#946; (retinoic acid receptor &#946;), COUP-TFI (chicken ovalbumin upstream promoter-transcription factor I) and Nur77 (nuclear receptor 77). Compared to CO group, the expression of RXR&#945; and RAR&#946; was higher (p <0.05) specifically in pPNL and rPNL of BI group, respectively. Compared to the group N, Nur77 showed higher (p <0.05) expression in the surrounding and rPNL of CO group. The expression of Nur77 in rPNL was lower (p <0.05) in BI than the CO group. Compared to N group, the expression of COUP-TFI was higher (p <0.05) in CO group (surrounding, pPNL and rPNL). Compared to CO group, the expression of COUP-TFI was lower (p <0.05) in BI group, specifically in the pPNL and rPNL. The results suggest that the nuclear receptors RXR&#945;, RAR&#946;, Nur77 and COUP-TFI represent relevant molecular targets of BI in the chemoprevention of hepatocarcinogenesis in rats.

Os cânceres de próstata e de mama estão entre as neoplasias mais comuns diagnosticadas na população ocidental. No Brasil, estes dois tipos de neoplasia são as principais causas de morte cuja incidência continua crescendo anualmente, sendo mais comum na população acima de 40 anos. As terapias utilizadas para os tratamentos de ambas as neoplasias estão baseadas principalmente nos receptores de hormônio (andrógeno e estrógeno). Embora muitos fármacos tenham sido desenvolvidos para os tratamentos destas patologias ao longo do tempo, eles perdem eficácia em caso de neoplasias resistentes, que apresentam mutações nas macromoléculas alvo. Assim, novas substâncias bioativas estão sendo investigadas a partir dos alvos biológicos consolidados e também para novos alvos. Neste trabalho, ensaios in vitro foram utilizados para avaliar as atividades farmacológicas e citotóxica de novas substâncias bioativas desenvolvidas no Grupo de Química Medicinal (NEQUIMED), a partir de duas linhagens celulares hormônio-dependentes para o estudo do câncer de próstata (LNCaP) e de mama (MCF-7). A partir das triagens realizadas, duas substâncias foram as mais potentes (Neq0502 e Neq0504) que levaram a morte das linhagens LNCaP e MCF-7 com IC50 na ordem de 20 a 30 &micro;mol/L, respectivamente. No ensaio de ciclo celular, Neq0502 apresentou um perfil semelhante a enzalutamida (fármaco usado como referência), sem perturbações substanciais no ciclo. No entanto, Neq0504 teve um perfil bem distinto do raloxifeno (fármaco usado como referência) para a perturbação do ciclo celular. Finalmente, o índice de seletividade estabelecido a partir dos ensaios com as células de fibroblasto (Balb/C 3T3 clone A31) demonstrou que Neq0502 foi uma substância com a maior seletividade e baixa citotoxicidade em relação à célula não tumoral dentre toda a série estudada. A partir destes dados as novas substâncias poderão ser otimizadas usando Neq0502 como matriz em estudos futuros. / Prostate and breast cancers are among the most common cancers diagnosed in the western population. In Brazil, these two types of cancer are the leading causes of death whose incidence continues to increase annually and is more common in older population than 40 years. The therapies used for the treatment of both cancers are mainly based on the hormone receptors (androgen and estrogen). Although many drugs have been developed for the treatment of these pathologies over time, lose efficacy in case of resistant cancers which have mutations on the target macromolecules. Thus, new bioactive substances are being investigated based on stable biological targets and for new targets. In this study, in vitro assays were used to evaluate the pharmacological and cytotoxic activities of new bioactive substances developed in Medicinal Chemistry Group (NEQUIMED) from two hormone-dependent cell lines for the study of prostate (LNCaP) and breast (MCF-7) cancer. From trials screenings carried out, two compounds were found the most potent (Neq0502 and Neq0504) leading to death of LNCaP and MCF-7 lines with IC50 in the range of 20 to 30 &micro;mol/L, respectively. In the cell cycle assay, Neq0502 made a similar profile to enzalutamide (drug used as a reference), without substantial disruption in the cycle. On the other hand, Neq0504 had a very different profile from raloxifene (a drug used as a reference) to the perturbation of the cell cycle. Finally, the selectivity index established from tests with fibroblast cells (Balb/C 3T3 clone A31) demonstrated that Neq0502 was a substance with high selectivity and low cytotoxicity in order to non-tumor cell from all the substances on the screening. From these data, new substances can be optimized using Neq0502 as a template in future studies.

Li, Sui Mui. / On t.p. "beta" appears as the Greek letter. / Thesis submitted in: December 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 182-189). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (Chinese) --- p.iii / Acknowledgements --- p.v / Table of contents --- p.vi / List of figures --- p.xii / List of appendices --- p.xix / Abbreviations --- p.xx / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter Chapter 2 --- Role of PPARP in adipocyte differentiation - an in vitro study --- p.20 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Materials and Methods --- p.23 / Chapter 2.2.1 --- Preparation ofPPARβ (+/+) and PPARβ (-/-) MEFs --- p.23 / Chapter 2.2.1.1 --- Materials --- p.23 / Chapter 2.2.1.2 --- Methods --- p.23 / Chapter 2.2.1.2.1 --- Isolation of MEFs --- p.23 / Chapter 2.2.1.2.2 --- Passage ofMEF culture --- p.25 / Chapter 2.2.2 --- Genotyping of PPARβ (+/+) and PPARβ (-/-) MEFs --- p.25 / Chapter 2.2.2.1 --- Materials --- p.26 / Chapter 2.2.2.2 --- Methods --- p.26 / Chapter 2.2.2.2.1 --- Primer design --- p.26 / Chapter 2.2.2.2.2 --- Genomic DNA extraction --- p.27 / Chapter 2.2.2.2.3 --- PCR reaction --- p.29 / Chapter 2.2.3 --- Western blotting of PPARβ(+/+) and PPARβ (-/-) MEFs --- p.30 / Chapter 2.2.3.1 --- Materials --- p.30 / Chapter 2.2.3.2 --- Methods --- p.31 / Chapter 2.2.3.2.1 --- Preparation of nuclear extracts --- p.31 / Chapter 2.2.3.2.2 --- Western blot --- p.32 / Chapter 2.2.4 --- Induction of adipocyte differentiation of PPARβ (+/+) and PPARβ(-/-) MEFs --- p.33 / Chapter 2.2.4.1 --- Materials --- p.34 / Chapter 2.2.4.2 --- Methods --- p.34 / Chapter 2.2.4.2.1 --- Seeding ofMEFs --- p.34 / Chapter 2.2.4.2.2 --- Adipocyte differentiation --- p.35 / Chapter 2.2.5 --- Oil Red O staining of differentiated PPARβ(+/+) and PPARβ(-/-) MEFs --- p.36 / Chapter 2.2.5.1 --- Materials --- p.36 / Chapter 2.2.5.2 --- Method --- p.37 / Chapter 2.2.5.2.1 --- Oil Red O staining --- p.37 / Chapter 2.2.6 --- Determination of triglyceride-protein assay of differentiated PPARβ (+/+) and PPARβ (-/-) MEFs --- p.37 / Chapter 2.2.6.1 --- Materials --- p.39 / Chapter 2.2.6.2 --- Methods --- p.39 / Chapter 2.2.6.2.1 --- Lysis of differentiated MEFs --- p.39 / Chapter 2.2.6.2.2 --- Measurement of triglyceride concentration in cell lysate --- p.40 / Chapter 2.2.6.2.3 --- Measurement of protein concentration in cell lysate --- p.41 / Chapter 2.2.7 --- Preparation of PPARβ(+/+) and PPARβ (-/-) MEF RNA for RT-PCR and Northern blot analysis --- p.42 / Chapter 2.2.7.1 --- Materials --- p.42 / Chapter 2.2.7.2 --- Method --- p.42 / Chapter 2.2.7.2.1 --- RNA isolation --- p.42 / Chapter 2.2.8 --- RT-PCR analysis of differentiated PPARβ(+/+) and PPARβ (-/-) MEFs --- p.44 / Chapter 2.2.8.1 --- Materials --- p.45 / Chapter 2.2.8.2 --- Methods --- p.45 / Chapter 2.2.8.2.1 --- Primer design --- p.45 / Chapter 2.2.8.2.2 --- RT-PCR --- p.46 / Chapter 2.2.9 --- Northern blot analysis of differentiated PPARβ(+/+) and PPARβ (-/-) MEFs --- p.47 / Chapter 2.2.9.1 --- Materials --- p.48 / Chapter 2.2.9.2 --- Methods --- p.49 / Chapter 2.2.9.2.1 --- Preparation of cDNA probes for Northern blotting --- p.49 / Chapter 2.2.9.2.1.1 --- RNA extraction --- p.49 / Chapter 2.2.9.2.1.2 --- Primer design --- p.49 / Chapter 2.2.9.2.1.3 --- RT-PCR of extracted mRNA --- p.50 / Chapter 2.2.9.2.1.4 --- Subcloning of amplified cDNA products --- p.50 / Chapter 2.2.9.2.1.5 --- Screening of recombinant clones by phenol-chloroform extraction --- p.51 / Chapter 2.2.9.2.1.6 --- Confirmation of the recombinant clones by restriction enzyme site mapping --- p.52 / Chapter 2.2.9.2.1.7 --- Confirmation of the recombinant clones by PCR method --- p.52 / Chapter 2.2.9.2.1.8 --- Mini-preparation of plasmid DNA from the selected recombinant clones --- p.54 / Chapter 2.2.9.2.1.9 --- Preparation of cDNA probes --- p.54 / Chapter 2.2.9.2.1.10 --- Formaldehyde agarose gel electrophoresis of RNA --- p.55 / Chapter 2.2.9.2.1.11 --- Hybridization and color development --- p.56 / Chapter 2.3 --- Results --- p.58 / Chapter 2.3.1 --- Confirmation of PPARβ(+/+) and PPARβ (-/-) MEFs genotypes --- p.58 / Chapter 2.3.2 --- PPARβ (-/-) MEFs differentiated similarly to PPARβ(+/+) MEFs as measured by Oil Red O staining --- p.61 / Chapter 2.3.3 --- PPARβ (-/-) MEFs differentiated similarly to PPARβ(+/+) MEFs as reflected by their intracellular triglyceride contents --- p.64 / Chapter 2.3.4 --- PPARβ(-/-) MEFs expressed the adipocyte differentiation marker genes similarly to PPARβ (+/+) MEFs --- p.66 / Chapter 2.4 --- Discussion --- p.77 / Chapter Chapter 3 --- Role of PPARβ in adipocyte differentiation and lipid homeostasis - an in vivo study --- p.82 / Chapter 3.1 --- Introduction --- p.83 / Chapter 3.2 --- Materials and Methods --- p.85 / Chapter 3.2.1 --- Animal and high fat diet treatment --- p.85 / Chapter 3.2.1.1 --- Materials --- p.85 / Chapter 3.2.1.2 --- Method --- p.86 / Chapter 3.2.1.2.1 --- Animal treatment --- p.86 / Chapter 3.2.2 --- Tail-genotyping of PPARβ (+/+) and PPARβ (-/-) mice --- p.87 / Chapter 3.2.2.1 --- Materials --- p.87 / Chapter 3.2.2.2 --- Methods --- p.88 / Chapter 3.2.2.2.1 --- DNA extraction from tail --- p.88 / Chapter 3.2.2.2.2 --- PCR tail-genotyping --- p.89 / Chapter 3.2.3 --- "Measurement of serum triglyceride, cholesterol and glucose levels by enzymatic and spectrophometric methods" --- p.89 / Chapter 3.2.3.1 --- Materials --- p.90 / Chapter 3.2.3.2 --- Methods --- p.91 / Chapter 3.2.3.2.1 --- Serum preparation --- p.91 / Chapter 3.2.3.2.2 --- Measurement of serum triglycerides --- p.91 / Chapter 3.2.3.2.3 --- Measurement of serum cholesterol --- p.92 / Chapter 3.2.3.2.3 --- Measurement of serum glucose --- p.93 / Chapter 3.2.4 --- Measurement of serum insulin and leptin levels by ELISA --- p.94 / Chapter 3.2.4.1 --- Materials --- p.95 / Chapter 3.2.4.2 --- Methods --- p.95 / Chapter 3.2.4.2.1 --- Measurement of serum insulin --- p.95 / Chapter 3.2.4.2.2 --- Measurement of serum leptin --- p.97 / Chapter 3.2.5 --- "Histological studies of liver, interscapular BF and gonadal WF pads" --- p.99 / Chapter 3.2.5.1 --- Materials --- p.100 / Chapter 3.2.5.2 --- Methods --- p.100 / Chapter 3.2.5.2.1 --- "Fixation, dehydration, embedding in paraffin and sectioning" --- p.100 / Chapter 3.2.5.2.2 --- H&E staining --- p.101 / Chapter 3.2.6 --- Analyses of fecal lipid contents --- p.102 / Chapter 3.2.6.1 --- Materials --- p.102 / Chapter 3.2.6.2 --- Method --- p.103 / Chapter 3.2.6.2.1 --- Extraction of lipid contents from stools --- p.103 / Chapter 3.2.7 --- Statistical analysis --- p.104 / Chapter 3.3 --- Results --- p.105 / Chapter 3.3.1 --- Confirmation of genotypes by PCR --- p.105 / Chapter 3.3.2 --- PPARβ (-/-) mice were more resistant to high fat diet-induced obesity --- p.105 / Chapter 3.3.3 --- PPARβ (-/-) mice consumed similarly as to PPARβ (+/+) counterparts… --- p.122 / Chapter 3.3.4 --- Effect of high fat diet on organ weights --- p.128 / Chapter 3.3.4.1 --- PPARβ (-/-) mice were more resistant to high fat diet-induced liver hepatomegaly --- p.134 / Chapter 3.3.4.2 --- PPARβ (-/-) mice were resistant to high fat diet-induced increased white fat depots --- p.134 / Chapter 3.3.4.3 --- PPARβ (-/-) mice were resistant to high fat diet-induced increased brown fat mass --- p.137 / Chapter 3.3.5 --- Effect of high fat diet on organ histology --- p.142 / Chapter 3.3.5.1 --- PPARβ(-/-) mice were more resistant to high fat diet-induced liver steatosis --- p.143 / Chapter 3.3.5.2 --- No defect in white adipocyte expansion in PPARβ(-/-) mice upon high fat diet feeding --- p.153 / Chapter 3.3.5.3 --- No defect in brown adipocyte expansion in PPARβ (-/-) mice upon high fat diet feeding --- p.159 / Chapter 3.3.6 --- "Effect on high fat diet on serum cholesterol, triglyceride, glucose, insulin and leptin levels" --- p.164 / Chapter 3.3.6.1 --- "PPARβ (-/-) mice had a lower serum cholesterol level, but a similar triglyceride level as compared to PPARβ (+/+) mice upon high fat diet feeding" --- p.165 / Chapter 3.3.6.2 --- PPARβ (-/-) mice were resistant to high fat diet-induced insulin resistance --- p.167 / Chapter 3.3.6.3 --- PPARβ (-/-) mice had a similar serum leptin level as PPARβ (+/+) mice --- p.170 / Chapter 3.3.7 --- No decision made in fecal lipid content of PPARβ (+/+) and PPARβ (-/-) mice --- p.173 / Chapter 3.4 --- Discussion --- p.176 / References --- p.182 / Appendices --- p.190

L’homéostasie glucidique est, durant un jeûne normal, maintenue grâce à un réseau de régulation complexe contrôlé principalement par le glucagon, produit par le pancréas. S’opposant aux effets de l’insuline, celui-ci orchestre notamment l'utilisation, le stockage et la synthèse du glucose par le foie, principal organe de production du glucose au cours du jeûne. Cette dernière s’effectue d’abord suite à la dégradation du glycogène ou glycogénolyse puis par la synthèse de novo de glucose ou néoglucogenèse. La néoglucogenèse hépatique est contrôlée par la modulation de l’activité et/ou de l’expression de différentes enzymes-clefs selon des mécanismes allostériques ou transcriptionnels.De multiples facteurs de transcription sont impliqués dans la régulation, au niveau transcriptionnel, de la néoglucogenèse hépatique. Le récepteur nucléaire des acides biliaires FXR est exprimé dans le foie et dans plusieurs organes impliqués dans le maintien de l’homéostasie glucidique. FXR participe à la régulation de nombreuses fonctions hépatiques essentielles, en contrôlant notamment les métabolismes des acides biliaires et lipidique. Le rôle exact de FXR sur la néoglucogenèse reste toujours débattu. L’objectif de cette thèse a donc été d’étudier le rôle de FXR dans le contrôle de la néoglucogenèse hépatique dans des conditions expérimentales reflétant certains aspects du jeûne. Nous avons démontré que FXR, en présence de glucagon, régulait positivement la néoglucogenèse selon deux mécanismes.Le premier mécanisme implique la phosphorylation de FXR par la PKA, une kinase activée par le glucagon. Cette modification post-traductionnelle de FXR permet une induction synergique de l’expression des enzymes-clefs de la néoglucogenèse par FXR et le facteur de transcription CREB. L’identification de ce mécanisme constitue la majeure partie des travaux présentés dans cette thèse. Ceux-ci ont été intégrés à des travaux menés précédemment dans le laboratoire qui nous ont permis d’identifier un mécanisme additionnel de régulation de la gluconéogenèse. L’interaction directe de FXR avec le facteur de transcription FOXA2, lui-même activé par le glucagon, inhibe la capacité de FXR à induire l’expression de SHP, un récepteur nucléaire inhibiteur de la néoglucogenèse.Ce travail a donc permis d’identifier pour la première fois que la néoglucogenèse hépatique est régulée positivement par FXR dans le cadre de la voie de signalisation du glucagon. Pour cela, FXR intègre le signal « glucagon » par deux mécanismes distincts: via une modification post-traductionnelle, sa phosphorylation par la PKA sur les sérines S325 et S357 et via une interaction protéine-protéine avec FOXA2. / Glucose homeostasis is maintained during normal fasting through a complex regulatory network controlled mainly by glucagon, a pancreatic hormone. Opposing the effects of insulin, it orchestrates the glucose use, storage and synthesis by the liver, the main organ that produces glucose during fasting. The latter is carried out first by the degradation of glycogen or glycogenolysis and then by de novo glucose synthesis or gluconeogenesis. Hepatic gluconeogenesis is controlled by modulation of various key enzymes activity and/or expression according to allosteric or transcriptional mechanisms.Multiple transcription factors are involved in the transcriptional regulation of hepatic gluconeogenesis. The nuclear bile acid receptor FXR is expressed in the liver and in several organs involved in glucose homeostasis. FXR regulates many essential liver functions, including controlling bile acid and lipid metabolism. The exact role of FXR on gluconeogenesis is still debated. The objective of this work was therefore to study the role of FXR in the control of hepatic gluconeogenesis under experimental conditions reflecting certain aspects of fasting. We demonstrated that FXR, in the presence of glucagon, positively regulated gluconeogenesis according to two mechanisms.The first mechanism involves phosphorylation of FXR by PKA, a glucagon-activated kinase. This FXR post-translational modification allows synergistic induction of key gluconeogenic enzymes expression by FXR and the CREB transcription factor. This mechanism identification constitutes the major part of the work presented in this thesis. These were integrated with work previously conducted in the laboratory that allowed us to identify an additional mechanism for regulating gluconeogenesis. The FXR direct interaction with the transcription factor FOXA2, itself activated by glucagon, inhibits the ability of FXR to induce the expression of SHP, a gluconeogenesis inhibitory nuclear receptor.This work has therefore identified for the first time that hepatic gluconeogenesis is positively regulated by FXR in the glucagon signalling pathway. For this, FXR integrates the "glucagon" signal by two distinct mechanisms: via post-translational modification, its phosphorylation by PKA on S325 and S357 serines and via protein-protein interaction with FOXA2.

Fish are particularly vulnerable to the exposure of anthropogenic pollutants, with a vast array of endocrine disrupting chemicals (EDCs) introduced into the aquatic environment via sewage discharge, waste disposal and land runoff. Brominated flame retardants (BFRs) are halogenated flame retardants that are used to effectively inhibit the flammability of various materials including plastic products, electrical appliances, construction materials and textiles. BFRs are ubiquitous environmental contaminants and are known to disrupt thyroid hormone (TH) homeostasis in several vertebrate species, including fish. Given the vital role of THs in a wide range of developmental processes and physiological functions, assessing and identifying thyroid disrupting chemicals is crucial for safe guarding the long-term health of humans and wildlife. In fish the molecular mechanisms underlying TH disruption by BFRs and the effects on TH-sensitive tissues during early life stages remains unclear. This has been limited by the lack of fundamental knowledge on the TH system of fish and the difficulties associated with examining transcriptional changes in discrete embryonic-larval tissues. Here I have established the expression profiles of a suite of genes in the hypothalamic-pituitary-thyroid (HPT) axis of zebrafish (Danio rerio) during embryonic-larval stages and their regulation by the biologically active TH (3, 5, 3′- tri-iodothyronine; T3). Using molecular tools (whole mount is situ hybridisation and RT-PCR), I demonstrate that a number of genes display spatial and temporal expression profiles during embryo/larval development, and their regulation by T3 was tissue- and developmental stage-specific. I subsequently demonstrated that TBBPA and BDE-47, two important BFR compounds, disrupted TH homeostasis at multiple levels of the HPT axis of zebrafish embryo-larvae after short sub-acute exposures. These compounds altered the expression of genes associated with TH conjugation and clearance, thyroid follicle development and TH transport. In addition, we suggest that TH target genes in the brain, liver, pronephric ducts and craniofacial tissues of zebrafish embryo-larvae may be particularly vulnerable to TBBPA and BDE-47 exposure. It has been proposed that environmental pollutants can disrupt TH signalling in wildlife by disrupting the activity of thyroid receptors (TRs), ligand-binding transcription factors, which mediate the genomic actions of THs. The ability of BFRs to disrupt fish TRs has not yet been examined. Here I developed an in vitro reporter gene transcriptional assay for zebrafish thyroid hormone receptors (zfTRα and zfTRβ) in human embryonic kidney cells and investigated their interactions with several BFR compounds. The assays were optimised and validated using the natural TR agonist T3 in cells transiently transfected with two reporter vector constructs, pGL4.24-PAL and pGL4.24-DR4. None of the six brominated flame retardants tested, namely, tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), 2,2′,4,4′-tetra-bromodiphenyl ether (BDE-47), 2,2′,4,4′,6-penta-bromodiphenyl ether (BDE-100), 2,2′,3,4,4′,5′,6-hepta-bromodiphenyl ether (BDE-183) and deca-bromodiphenyl ether (BDE-209) had an agonistic effect on zfTRα and zfTRβ activity. These results are consistent with our previous finding which suggests that altered TH homeostasis may be a result of increased metabolism and excretion of THs and/or changes in the production of TH by the thyroid follicles. In conclusion, this investigative work aids the understanding of fundamental TH processes in fish, such as gene expression and regulation, and increases our understanding of the mechanisms and potential targets of BFRs in fish.

Os receptores ativadores da proliferação de peroxissomos (PPARs) são fatores de transcrição dependentes da ligação de ligantes e possuem um papel chave no controle do metabolismo dos lipídios e da glicose. Existem três isotipos desse receptor: PPAR&alpha;, PPAR&beta; e PPAR&gamma;. O PPAR&gamma; é alvo molecular para os compostos TZDs, os quais são fármacos usados clinicamente no controle da diabetes do tipo 2, aumentando a sensibilidade à insulina. Enquanto que os fibratos são os fármacos que atuam no PPAR&alpha; e são utilizados para diminuir os níveis de triglicerídeos. A maioria dos pacientes que sofrem com a diabetes do tipo 2 apresentam desordens no metabolismo de lipídios. Mesmo com a existência de fármacos capazes de controlar estas desordens metabólicas, a busca de um agonista dual para os PPAR&alpha; e PPAR&gamma; é um grande desafio no controle da síndrome metabólica, uma vez que este composto pode combinar os dois efeitos terapêuticos em uma única molécula. O GL479 é um agonista dual que foi sintetizado com dois grupos farmacóforos, ligando-se tanto ao PPAR&alpha; quanto ao PPAR&gamma;. Dentro desse contexto, este estudo apresenta as bases estruturais de interação do agonista dual GL479 aos PPARs por meio da determinação estrutural dos complexos PPAR&alpha;-LBD:GL479 e PPAR&gamma;-LBD:GL479. A análise detalhada desses complexos revelou diferentes modos de interação do ligante em cada receptor, porém em ambos os casos o GL479 interage com a Tyr da H12. Na estrutura do PPAR&alpha;-LBD, o ligante adquiriu a característica de um agonista total e no caso do PPAR&gamma;-LBD, o GL479 adotou características de um agonista parcial dependente da interação com a H12. Além das analises do agonista dual, 16 compostos foram identificados por docking como ligantes do PPAR&gamma;. Três desses ligantes (8, 10 e 15) foram caracterizados por ThermoFluor e fluorescência de polarização com valores de IC50 menor que 10 &micro;M. Adicionalmente, um dos compostos identificados no docking (16) foi cocristalizado com PPAR&gamma;-LBD. A conformação adotada pelo ligante não permitiu que ele interagisse diretamente com a H12, sugerindo que este composto possa atuar como um agonista parcial independente da H12. Todas estas descobertas podem ser exploradas no desenho de novos moduladores dos PPARs com menores efeitos adversos ou até mesmo na busca de agonistas duais PPAR&alpha; &frasl;&gamma;, que combine os efeitos terapêuticos no tratamento da diabetes do tipo 2 e da dislipidemia. / Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors that control various functions in human organism and they play key roles in the control of glucose and lipid metabolism. There are three different PPAR isotypes: PPAR&alpha;, PPAR&beta; e PPAR&gamma;. PPAR&gamma; is a molecular target of TZD agonists, which are clinically used drugs in the control of type 2 diabetes by increasing insulin sensitivity. Whereas fibrates are drugs that act on PPAR&alpha; and are used to lower serum triglyceride levels. The most patients who have type 2 diabetes also display lipid metabolism disorders. Even with the existence of drugs that can control these metabolic disorders, the search of dual agonist for PPAR&alpha; and PPAR &gamma; is a major challenge in the control of metabolic syndrome, because this compound could combine both therapeutic effects in a single molecule. GL479 is a dual agonist that was synthesized based on a combination of two key pharmacophores, with the ability to bind in the both PPARs, &alpha;, and &gamma;. Thus, this study reveals the structural basis for this dual agonist GL479 by structural determination of the complexes PPAR&alpha;-LBD:GL479 and PPAR&gamma;-LBD:GL479. The detailed analysis of these complexes showed different ligand binding modes for each receptor, however, in the both cases the GL479 interacted with the Tyr of H12. In the PPAR&alpha;-LBD structure the ligand acquired the features of full agonist and in the case of PPAR&gamma;-LBD, GL479 adopted features of a partial agonist dependent of H12 interaction. In addition to the dual agonist analysis, sixteen compounds were identified as PPAR&gamma; ligand by docking. Three of these ligands were characterized by ThermoFluor and fluorescence polarization, which resulted in IC50 values smaller than 10 &micro;M. Additionally, one of the compounds, identified by docking, was co-crystallized with PPAR&gamma;. The ligand conformation adopted would not allow it a direct interaction with the H12. These contacts were mediated by one water molecule, suggesting this compound might also act as a partial agonist, independent of H12 interaction. All these findings may be explored for the design of PPARs novel modulators with lower side effects, as well, in the exploration of dual agonists PPAR&alpha; &frasl; &gamma; that combines the therapeutic effects in the treatment of type 2 diabetes and dyslipidemia.

Nuclear receptors (NRs) are ligand-activated transcription factors that regulate the expression of genes involved in all physiological activities. Disruption in NR function (e.g. mutations) can lead to a variety of diseases; making these receptors important targets for drug discovery. The ability to bind a broad range of 'drug-like' molecules also make these receptors attractive candidates for protein engineering, such that they can be engineered to bind novel small molecule ligands, for several applications. One application is the creation of potential molecular switches, tools that can be used for controlling gene expression. Gaining knowledge of specific molecular interactions that occur between a receptor and its ligand is of interest, as they contribute towards the activation or repression of target genes. The focus of this work has been to investigate the structural and functional relationships between the human vitamin D receptor (hVDR) and its ligands. To date, mutational assessments of the hVDR have focused on alanine scanning and residues typically lining the ligand binding pocket (LBP)that are involved in direct interactions with the ligand. A comprehensive analysis of the tolerance of these residues in the binding and activation of the receptor by its ligands has not been performed. Furthermore, residues not in contact with the ligand or that do not line the LBP may also play an important role in determining the activation profiles observed for NRs, and therefore need to be explored further. In order to engineer and use the hVDR in chemical complementation, a genetic selection system in which the survival of yeast is linked to the activation of a NR by an agonist, the hVDR gene was isolated from cDNA. To gain insight into how chemical and physical changes within the ligand binding domain (LBD) affect receptor-ligand interactions, libraries of hVDR variants exploring the role and tolerance of hVDR residues were created. To develop a comprehensive mutational analysis while also engineering the hVDR to bind a novel small molecule ligand, a rational and a random mutagenic approach were used to create the libraries. A variant, hVDRC410Y, that displayed enhanced activity with lithocholic acid (LCA), a known hVDR ligand, and novel activation with cholecalciferol (chole), a precursor of the hVDR's natural ligand known not to activate the wild-type hVDR, was discovered. The presence of a tyrosine at the C410 position resulting in novel activation profiles with both LCA and chole, and the fact that this residue does not line the hVDR's LBP led to interest in determining whether a physical or chemical property of the residue was responsible for the observed activity. When residue C410 was further assessed for its tolerance to varying amino acids, the results indicated that bulkiness at this end of the pocket is important for activation with these ligands. Both LCA and chole have reduced molecular volumes compared to the natural ligand, 1alpha, 25(OH)2D3. As a result, increased bulkiness at the C410 position may contribute additional molecular interactions between the receptor and ligands. Results obtained throughout this work suggest that the end of the hVDR's LBP consisting of two ligand anchoring residues, H305 and H397, and residue C410 tolerates structural variations, as numerous variants with mutations at these positions displayed enhanced activity. The receptor contains two tyrosines, Y143 and Y147, which were targeted for mutagenesis in one of the rationally designed libraries, located at the exact opposite end of the pocket. In an effort to gain further insight into the role of these residues at the other end of the LBP, mutagenesis assessing the tolerance of tyrosines 143 and 147 was performed. Overall, most changes at these positions proved to be detrimental to the function of the receptor supporting the hypothesis that this end of the LBP is less tolerant of structural changes, compared to the opposite end consisting of residues H305, H397 and C410. Overall, a better understanding of the structural and functional relationships between the human vitamin D receptor (hVDR) and its ligands was achieved. The effects of residue C410 on specificity and activation with the different ligands studied were unforeseen, as this residue does not line the receptor's ligand binding pocket (LBP). However, they serve as an example of the significant impact distant residues can have on receptor activation and also emphasize the important role physical properties of residues, such as volume, can play for specific ends of the LBP compared to chemical properties.