Serotonin (5-hydroxytryptamine [5-HT]) is a key enteric signaling molecule that is implicated in many gastrointestinal (GI) disorders, including inflammatory bowel disease (IBD). Enterochromaffin (EC) cells are a key subgroup of enteric endocrine cells and produce the majority of 5-HT via tryptophan hydroxylase 1 (Tph1) in the gut. Recently, we have identified a pivotal role of 5-HT in the pathogenesis of experimental colitis, whereby 5-HT plays as a pro-inflammatory molecule. Gut function as well as pathology rely on interactions with gut microbiota. The intestinal epithelial cells produce antimicrobial peptides (AMPs), maintaining the mucosal barrier by shaping gut microbiota composition. Among the AMPs, β-defensins are the most well investigated subtype in the colon. Aberrant β-defensin expression has been reported in association with various GI disease pathogenesis including IBD. As EC cells are dispersed throughout the intestinal epithelium, it seems possible that 5-HT can modify β-defensin production which can regulate gut inflammation by influencing gut microbial composition. Colitis was induced with dextran sulfate sodium (DSS) in Tph1+/+ and Tph1-/- (which have lower amounts of 5-HT in gut). Tph1-/- mice exhibited higher levels of β-defensin in the colon, compared with wild-type littermates post-DSS. In addition, increased expression of β-defensin in Tph1-/- mice was suppressed by 5-hydroxytryptophan (5-HTP; precursor of 5-HT) treatment. 5-HT treatment resulted in decreased human β-defensin (hBD) 1 and hBD-2 expression in HT-29 cells. Peroxisome proliferator-activated receptor gamma (PPAR-γ) is essential for maintaining β-defensin expression in the colon. GW-9662, PPAR-γ antagonist, reduced mouse β-defensin (mBD) 1 and mBD-3 (orthologue of hBD-2). Furthermore, disrupting 5-HT7 receptors, but not 5-HT3 or 5-HT4, led to enhanced expression of PPAR-γ via ERK1/2-dependent mechanism. These observations provide us with novel information on pivotal role of gut-derived 5-HT in innate immune response and highlight the potential benefits of targeting 5-HT signaling in various GI disorders such as IBD. / Thesis / Master of Science (MSc)

En 2004, les maladies cardiovasculaires (MCV) causaient environ 72 000 décès au Canada. Le National Cholesterol Education Program reconnaît maintenant la taille des particules de lipoprotéines de faible densité (LDL) comme un facteur de risque émergeant. La taille des particules LDL peut être influencée par l'alimentation et la génétique. Celle-ci a été déterminée par électrophorèse sur gels de polyacrylamide. L'utilisation des profils alimentaires permet d'évaluer l'impact global de l'alimentation sur un facteur de risque. Les profils "Prudent" et "Western" ont été déterminés par analyse factorielle et associés à la taille des particules LDL. Les peroxisome proliferator-activated receptors (PPARs) sont des gènes connus pour avoir un effet sur la taille des particules LDL. Des effets d'interactions gènes-diète ont été observés pour les trois polymorphismes (PPARα L162V, PPARγ P12A et PPAR[delta] -87T>C) à l'étude. Ces résultats illustrent l'importance de considérer différents facteurs lors de l'étude des facteurs de risque de MCV.

O carcinoma hepatocelular (HCC) é a sexta neoplasia mais comum e a terceira causa de mortalidade por câncer no mundo. Está relacionado, principalmente, à exposição a diversos fatores de risco, como a doença hepática gordurosa não alcoólica (NAFLD). O HCC apresenta mau prognóstico; neste sentido, é importante a adoção de medidas de controle, como a quimioprevenção. A quimioprevenção é o método mais apropriado para se evitar o câncer e consiste na prevenção, inibição ou reversão das etapas iniciais da carcinogênese, pela administração de um ou mais compostos químicos sintéticos ou naturais. Diversos compostos presentes nos alimentos podem apresentar atividade quimiopreventiva, dentre esses, a tributirina (TB), pró-fármaco do ácido butírico. Dessa forma, propôs-se avaliar o efeito quimiopreventivo da TB nas etapas de iniciação/promoção inicial, em ratos submetidos ao modelo de hepatocarcinogênese do hepatócito resistente (RH) associado à NAFLD. Ratos Wistar machos foram distribuídos em Grupo dos animais não tratados (NT), e dois outros grupos experimentais, o grupo RH + NAFLD + maltodextrina (grupo controle isocalórico, CI), e o grupo RH + NAFLD + tributirina (grupo TB). Os animais do grupo CI foram tratados diariamente, por gavagem, com emulsão hiperlipídica [1 mL/100 g de peso corpóreo (p. c)], e maltodextrina (300 mg/ 100 g p.c.), enquanto que os animais do Grupo TB foram tratados diariamente, por gavagem, com emulsão hiperlipídica [1 mL/100 g de p. c.], e TB (200 mg/ 100 g de p.c.), durante 13 semanas consecutivas quando foram eutanasiados. Após esse período, a análise por cromatografia a gás revelou que o grupo dos animais tratados com a tributirina apresentou uma concentração de AB 2.118 vezes superior (p < 0.05) às concentrações de AB constatadas no grupo controle. Em relação aos dados de morfometria de LPNs [lesões pré-neoplásicas persistentes (pLPN) ou em remodelação (rLPN)], a atividade quimiopreventiva da tributirina foi observada a partir da redução (p < 0,05) significativa do número de lesões pré-neoplásicas persistentes (pLPN) em comparação ao grupo controle. A área das pLPNs, contudo, foi maior (p < 0,05) no Grupo TB quando comparada à do grupo controle isocalórico. Não foram observadas diferenças estatisticamente significativas (p >= 0,05) no número e na área de rLPN, bem como na % da área do corte do fígado ocupada por LPNs entre os dois grupos experimentais. A quantificação da apoptose por H&E revelou maior (p < 0,05) índice apoptótico em pLPN e em rLPN nos animais tratados com TB, quando comparados aos animais do grupo 6 controle. Nesse sentido, observou-se que os animais tratados com a tributirina apresentaram maior (p < 0,05) ativação de Caspase 3 do que os ratos do grupo controle isocalórico. Em relação à avaliação da proliferação celular, o Grupo TB apresentou redução (p < 0,05) do índice de proliferação tanto em pLPNs como em rLPNs, quando comparado ao do grupo controle isocalórico. Não foi observada diferença estatisticamente significativa (p > 0,05) entre os surroundings dos dois grupos experimentais. A determinação do perfil lipídico sérico revelou que os animais tratados com a tributirina apresentaram menores (p < 0,05) concentrações séricas de LDL-colesterol e maiores (p < 0,05) concentrações séricas de HDL-colesterol, quando comparados às do grupo controle. Além disso, foram observadas menores (p < 0,05) concentrações hepáticas de colesterol no Grupo TB quando comparadas às do Grupo CI. Em relação a análise por PAS, embora, o presente estudo não tenha revelado diferença estatisticamente significativa (p >= 0,05) entre os dois grupos experimentais, o score entre os graus de marcação por PAS apresentou tendência (p = 0,07) a ser maior nos animais tratados com a tributirina quando comparados aos ratos do grupo controle. Em relação à expressão gênica de FGF-21, o Grupo TB apresentou maior (p < 0,05) expressão em comparação a seu grupo controle (Grupo CI). Além disso, esses dados são corroborados por meio da marcação imunoistoquímica de FGF-21, que revelou que os animais tratados com a tributirina apresentaram maior (p < 0,05) score desta marcação quando comparados aos ratos do grupo controle isocalórico. A análise de expressão em nível proteico de PPAR-&#945; revelou que o Grupo TB apresentou maior (p < 0,05) expressão em comparação ao Grupo CI. O presente estudo demonstrou que o tratamento com a tributirina apresentou um efeito quimiopreventivo quando administrada nas etapas de iniciação/promoção inicial em modelo de hepatocarcinogênese associado à NAFLD. Adicionalmente, sugere-se que a atividade como HDACi da TB poderia modular a expressão de genes supressores de tumor, bem como a daqueles relacionados ao metabolismo lipídico, atenuando os fatores de risco relacionados à NAFLD. / Hepatocellular carcinoma (HCC) is the sixth most common neoplasm and the third leading cause of cancer mortality in the world. It is mainly related to exposure to several risk factors, such as non-alcoholic fatty liver disease (NAFLD). HCC presents poor prognosis; In this sense, it is important to adopt control measures, such as chemoprevention. Chemoprevention is the most appropriate method to avoid cancer and consists in the prevention, inhibition or reversal of the early stages of carcinogenesis by the administration of one or more synthetic or natural chemical compounds. Several compounds present in foods may present chemopreventive activity, among them, tributyrin (TB), a prodrug of butyric acid. Thus, it was proposed to evaluate the chemopreventive effect of TB in the initiation / initial promotion stages in rats submitted to the hepatocyte-resistant hepatocyte model (HR) associated with NAFLD. Male Wistar rats were divided into two groups: RH + NAFLD + maltodextrin (isocaloric control group, CI), and RH + NAFLD + tributyrin group (TB group). The animals of the CI group were treated daily with gavage with hyperlipid emulsion [1 mL / 100 g body weight (wt.)], and maltodextrin (300 mg / 100 g body wt.), while the animals of the TB Group were treated daily by gavage with hyperlipid emulsion [1 mL / 100 g of body wt.], and TB (200 mg / 100 g body wt.) for 13 consecutive weeks when they were euthanized. After this period, the gas chromatographic analysis revealed that the group of animals treated with tributyrin had a concentration of AB 2184 times higher (p < 0.05) than the concentrations of AB found in the control group. Regarding the morphometry data of PNLs [persistent pre-neoplastic lesions (pPNL) or remodeling (rPNL)], the chemopreventive activity of tributyrin was observed from a significant (p < 0.05) reduction in the number of pPNL compared to the control group. The area of the pPNLs, however, was higher (p < 0.05) in the TB Group when compared to the isocaloric control group. There were no statistically significant differences (p >= 0.05) in the number and area of rPNL, as well as in the area of the cut of the liver occupied by LPNs between the two experimental groups. The quantification of apoptosis by H&E revealed a higher (p < 0.05) apoptotic index in pPNL and rPNL in the TB treated animals, when compared to the animals in the control group. In this sense, animals treated with tributyrin showed greater (p < 0.05) activation of Caspase 3 than the rats of the isocaloric control group. In relation to the evaluation of cell proliferation, the TB group presented a reduction (p < 0.05) in the proliferation index in both pPNLs and rPNLs, when compared to the isocaloric control group. No statistically significant difference (p> 0.05) was observed between the two experimental groups. The determination of serum lipid profile revealed that the animals treated with tributyrin showed lower (p < 0.05) serum LDL-cholesterol concentrations and higher (p < 0.05) serum HDL-cholesterol concentrations when compared to those in the group control. In addition, lower hepatic concentrations (p < 0.05) of cholesterol were observed in the TB Group when compared to those in the CI Group. Regarding the SBP analysis, although the present study did not reveal a statistically significant difference (p >= 0.05) between the two experimental groups, the score between the PAS presented a tendency (p = 0.07) to be greater in animals 8 treated with tributyrin compared to the rats in the control group. In relation to the gene expression of FGF-21, the TB Group presented higher (p <0.05) expression in comparison to its control group (CI Group). In addition, these data are corroborated by FGF-21 immunohistochemical labeling, which revealed that animals treated with tributyrin showed a higher (p <0.05) score for this marker when compared to the isocaloric control rats. Analysis of protein-level expression of PPAR-&#945; revealed that the TB Group had higher (p <0.05) expression compared to the CI Group. The present study demonstrated that treatment with tributyrin had a chemopreventive effect when administered in the initiation / initial promotion steps in a hepatocarcinogenesis model associated with NAFLD. In addition, it is suggested that the activity as HDACi of TB could modulate the expression of tumor suppressor genes, as well as those related to lipid metabolism, attenuating the risk factors related to NAFLD.

Die 12/15-Lipoxygenasen (12/15-LOXs) gehören zu einer heterogenen Klasse Lipid-peroxidierender Enzyme, deren biologische Rolle noch nicht vollständig geklärt ist. Eine Reihe experimenteller Daten deuten darauf hin, dass diese Enzym an Reifungs- und Differenzierungsprozessen beteiligt sind und auch für die Pathogenese verschiedener Erkrankungen (Asthma bronchiale, Entzündung, Atherosklerose) bedeutsam zu sein scheinen. Die Expression von 12/15-LOXs wird in vielen Säugetierzellen durch TH2-Zytokine reguliert und die Zytokin-induzierte Signaltransduktionskaskade verläuft über die Aktivierung van JAK-Kinasen und STAT6. Nach einer Stimulation von A549 Lungenkarzinomzellen mit Interleukin-4 (IL-4) kommt es erst nach 12 Stunden zu einer Hochregulation der 12/15-LOX mRNA Expression. Untersuchungen zum Induktionsmechanismus haben gezeigt, dass Genistein, ein Hemmstoff von Tyrosinkinasen, die Phosphorylierung von STAT6 und dessen Bindung an den Promoter des 12/15-LOX Gens verhinderte. Damit konnte die Induktion der katalytisch aktiven LOX geblockt werden. In Gegensatz dazu verhinderte Zykloheximid, ein spezifischer Hemmstoff der Proteinbiosynthese, die Expression der 12/15-LOX mRNA nicht, Dieses Ergebnis deutet darauf hin, dass die Neusynthese eines Transkriptionsfaktors im Rahmen der IL-4 induzierten Transduktionskaskade unwahrscheinlich ist. Weiterhin wurde beobachtet, dass IL-4 die zelluläre Histonacetyltransferase-Aktivität stark erhöhte und dass dieser Effekt überwiegend auf die enzymatische Aktivität des (CREB-bindenden Protein)-bindenden Proteins (CBP) zurückzuführen ist. Transfektion der Zellen mit E1A, einem viralen Protein, welches als Hemmstoff der Histonacetyltransferase-Aktivität von CBP/p300 bekannt ist, führte zu einer Unterdrückung der 12/15-LOX Expression. Andererseits stimuliert Natriumbutyrat, ein Hemmstoff der Histondeacetylase, die 12/15-LOX Synthese. Damit konnte gezeigt werden, dass die Acetylierung von Histonproteinen und von STAT6 ein essentieller Prozesse bei der IL-4 induzierten 12/15-LOX Expression in A549 Zellen ist. Weiterhin belegen diese Daten, dass sowohl die Phosphorylierung als auch die Acetylierung von STAT6 an der transkriptionellen Aktivierung des 12/15-LOX Gens beteiligt sind, obwohl beide Prozesse eine unterschiedliche Kinetik aufweisen. STAT6 Phosphorylierung erfolgt innerhalb der ersten Stunde nach IL-4 Stimulation, während die Acetylierungsreaktion zeitlich verzögert abläuft. Zusammenfassend kann die Signaltransduktionskaskade, die in A549 Zellen zur Expression der 12/15-LOX führt, wie folgt beschrieben werden: IL-4 induziert über die Aktivierung von JAK-Kinasen eine Phosphorylierung von STAT6, dessen Bindung an den 12/15-LOX Promotor jedoch zunächst durch nicht-acetylierte Histonproteine verhindert wird. Nach 9-11 Stunden werden Histone und der phosphorylierte STAT6 durch die Acetyltransferase-Aktivität von CBP/p300 acetyliert. Diese Reaktion führt zu einer Veränderung der Histonstruktur, wodurch die Bindung von modifizierten STAT6 und damit die Expression des 12/15-LOX Gens ermöglicht wird. Als wesentliche zellphysiologische Konsequenz der IL-4 induzierten 12/15-LOX Expression in A549 Zellen, wurde eine Apoptoseinduktion beobachtet. Das endogene 12/15-LOX Produkt 15-HETE bindet an den Kernrezeptor PPARg und induziert damit den programmierten Zelltod. Vorinkubation von A549 Zellen mit dem LOX-Hemmstoff NDGA oder der Einsatz von PPARg Dominant Negativ Vektor verhinderten die Apoptose. Mechanistische Untersuchungen zum Ablauf des durch IL-4 induzierten Zelltodes zeigten, dass der Prozess überwiegend dem extrinsischen Mechanismus folgt, bei dem Kaspasen-8 direkt zu einer Aktivierung der Effektorkaspase-3 führt. Der mitochondriale Mechanismus (Spaltung von Bid bzw. initiale Cytochrom C Freisetzung) scheint dabei nicht involviert zu sein. Die IL-4 induzierte Apoptose könnte von patho-physiologischer Bedeutung für den Verlauf von Lungenerkrankungen sein, bei denen Zellen mit hoher konstitutiver 12/15-LOX Expression, z.B. eosinophile Granulozyten, beteiligt sind. Hepoxiline sind bioaktive Mediatoren des 12/15-LOX Weges der Arachidonsäurekaskade, die durch Isomerisierung des primären Oxygenierungsproduktes 12S-HpETE gebildet werden. Zu Beginn unserer Untersuchungen war überwiegend unklar, welche Enzyme an der Isomerisierungsreaktion beteiligt sind. Bei der Suche nach geeigneten zellulären Modellen für die Untersuchung dieser Fragestellung fanden wir heraus, dass in den Ratteninsulinom-Zellen Rinm5F, die wegen ihres Mangels an Glutathionperoxidasen eine geringe Kapazität zur Reduktion von 12S-HpETE aufweisen, die Synthese von Hepoxilin A3 (HXA3) besonders hoch ist. Da wir vermuteten, dass 12/15-LOXs für die Isomerisierung von 12S-HpETE zu HXA3 verantwortlich sein könnten, verfolgten wir eine duale Forschungsstrategie um experimentelle Hinweise für unsere Arbeitshypothese zu finden. In den 12/15-LOX exprimierenden Rinm5F Zellen führte eine Immunopräzipitation mit 12/15-LOX spezifischen Antikörper zu einen vollständigen Verlust der 12/15-LOX- und der Hepoxilinsynthase-Aktivität eines Zelllysates. Beide Aktivitäten wurden fast vollständig im Immunopräzipitat wiedergefunden. 2. Transfektion von HeLa Zellen, die selbst keine 12/15-LOX exprimieren, mit 12/15-LOX und gleichzeitige Hemmung der zellulären Glutathionperoxidasen (Depletion von GSH mit Diethlmaleat) führte zu einer deutlichen zellulären Hepoxilinsynthese. Bei entsprechenden Kontrolltransfektanten wurde diese Aktivität nicht beobachtet. Weiterhin konnte festgestellt werden, dass rekombinante 12/15-LOXs (Expression in E. coli) in vitro eine intrinsische Hepoxinsynthase-Aktivität aufweisen, wenn 12S-HpETE als Substrat angeboten wird. Diese Daten belegen, dass 12/15-LOXs neben den bisher beschriebenen katalytischen Aktivitäten (Oxygenase, Hydroperoxidase, Leukotrienesynthase) auch Hepoxilinsynthase-Aktivität aufweisen. / 12/15-Lipoxygenases (human 15-LOX-1, rat 12/15-lipoxygenase) belong to family of lipid peroxidising enzymes. The enzyme has been implicated with roles in a variety of pathological conditions such as asthma, atherosclerosis, inflammation and in cellular differentiation. The enzyme expression in most human cell types is tightly regulated by Th2 cytokines, interleukin-4 (IL-4) and interleukin-13 (IL-13). Interleukin-4 (IL-4) induces expression of reticulocyte-type 15-lipoxygenase-1 (15-LOX-1) in various mammalian cells via the Janus kinase/signal transducer and activator of transcription 6 (STAT6) signaling system. 15-LOX-1 mRNA expression was first observed only 12h post IL-4 stimuation and required a minimum of 11h exposure to the cytokine. The mechanism of 15-LOX-1 induction in A549 lung epithelial cells and the observed delay was studied and it was found that genistein, a potent tyrosine kinase inhibitor, prevented phopsphorylation of STAT6, its binding to the 15-LOX-1 promoter, and the expression of catalytically active enzyme. In contrast, cycloheximide did not prevent 15-LOX-1 induction. Surprisingly, it was observed that IL-4 up-regulated the histone acetyltransferase activity of CREB-binding protein (CBP)/p300, which is responsible for acetylation of nuclear histones and STAT6. The acetylation of both proteins appears to be essential for the IL-4-induced signal transduction cascade, because inhibition of CBP/p300 by the viral wild-type E1A oncoprotein abrogated acetylation of both histones and STAT6 and strongly suppressed transcriptional activation of the 15-LOX-1 gene. Moreover, the inhibition by sodium butyrate of histone deacetylases, which apparently suppress 15-LOX-1 gene transcription, synergistically enhanced the IL-4-stimulated 15-LOX-1 expression. These data suggest that both phosphorylation and acetylation of STAT6 as well as acetylation of nuclear histones are involved in transcriptional activation of the 15-LOX-1 gene, although these reactions follow differential kinetics. STAT6 phosphorylation proceeds within the first hour of IL-4 stimulation. In contrast, CBP/p300-mediated acetylation requires 9-11 h, and similar kinetics were observed for the expression of the active enzyme. Thus, the results suggest that in the absence of IL-4, nuclear histones may be bound to regulatory elements of the 15-LOX-1 gene, preventing its transcription. IL-4 stimulation causes rapid phosphorylation of STAT6, but its binding to the promoter appears to be prevented by nonacetylated histones. After 9-11 h, when histones become acetylated, STAT6 binding sites may be demasked so that the phosphorylated and acetylated transcription factor can bind to activate gene transcription. The proinflammatory cytokine IL-4 is secreted in large amounts during allergic inflammatory response in asthma and plays a pivotal role in the airway inflammation. IL-4 has been shown to up-regulate 15-lipoxygenase and produce 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) in A549 cells via the Janus kinase/STAT6 pathway under coactivation of CREB binding protein/p300. IL-4 has also been shown to up-regulate peroxisome proliferator-activated receptor (PPARg ) nuclear receptors in macrophages and A549 cells. In this study it is observed that 15(S)-HETE binds to PPARg nuclear receptors and induces apoptosis in A549 cells. Moreover, pre-treatment of cells with nordihydroguaiaretic acid, a 15-lipoxygenase inhibitor, prevented PPARg activation and apoptosis. The latter was accomplished by the interaction of the 15(S)-HETE/PPARg complex with the adapter protein Fas-associating protein with death domain and caspase-8, as shown by transfection of Fas-associating protein with death domain dominant negative vector and cleavage of caspase 8 to active subunits p41/42 and p18. Whereas IL-4 and PPARg ligands failed to induce cleavage of Bid and release of cytochrome c from mitochondria, they caused translocation of the proapoptotic protein Bax from cytoplasm to mitochondria with a concomitant decrease in the Bcl-XL level. The cells were, thereofre, observed to follow the extrinsic pathway of apoptosis where caspase-8 directly activates the effector caspase-3, bypassing the mitochondria. The data also suggests that in IL-4-stimulated cells the 15(S)-HETE/PPARg complex down-regulates Bcl-XL, and the translocation of Bax to the mitochondria commits the cell to apoptosis. The IL-4-induced apoptosis may contribute to severe loss of alveolar structures and infiltration of eosinophils, mononuclear phagocytes, etc., into the lung tissue as observed in chronic asthma patients. The 12(S)-lipoxygenase (12-LOX) pathway of arachidonic acid (AA) metabolism after dioxygenation to 12(S)-hydroperoxy-eicosatetraenoic acid is bifurcated in a reduction route to formation of 12(S)-hydroxy-eicosatetraenoic acid (12-HpETE) and an isomerization route to formation of hepoxilins. Interestingly, rat insulinoma RINm5F cells, which are devoid of cytoplasmic glutathione peroxidase (cGPx)/phospholipid hydroperoxide glutathione peroxidase (PHGPx), were observed to produce solely hepoxilin A3 (HXA3). Since HXA3 synthesis was abolished in heat-denatured or cGPx- or PHGPx-transfected cells, suggesting that a HXA3 synthase activity regulated by cGPx/PHGPx is present. To confirm this assumption AA was incubated with HeLa cells overexpressing the rat 12/15-LOX. Neither HXA3 nor 12(S)-HETE were detected due to abundance of cGPx/PHGPx. But, pretreatment of transfected cells with diethyl maleate, an inhibitor of glutathione and PHGPx, restored HXA3 synthase and 12-LOX activities. Moreover, recombinant rat 12/15-LOX produced HXA3 when incubated with 12-HpETE. Further confirmation was obtained by immunoprecipitation with 12/15-LOX specific antibodies. Immunoprecipitation of Rinm5F lysates results in the depletion of hepoxilin synthase activity. The hepoxilin synthase activity was localised in the immunoprecipitated protein. Thus, cells containing rat 12/15-LOX also possess an intrinsic HXA3 synthase activity, which is activated by inhibition of cGPx/PHGPx. In normal cells HXA3 is down-regulated by cGPx/PHGPx, but, it is persistently activated in oxidatively stressed cells deficient in cGPx/PHGPx, such as Rinm5F. Furthermore, formation of corresponding epoxyhydroxy products was observed when 15-HpETE was used as substrate, indicating a broad range of specificity for the enzyme.

O consumo de ácidos graxos n-3 tem sido associado à proteção contra a obesidade, inflamação e resistência à insulina. Os n-3 são ligantes fracos dos receptores nucleares PPAR&gamma;, e pela ativação deste podem exercer suas ações metabólicas e anti-inflamatórias. No presente trabalho, foi investigado se o aumento da disponibilidade dos n-3 geneticamente ou por dieta, via ativação de PPAR&gamma;, protege camundongos do desenvolvimento da obesidade, intolerância a glicose e inflamação do tecido adiposo. Foi visto em um modelo com camundongos fat-1 (elevados níveis endógenos de n-3) que dentre as ações dos ácidos graxos n-3, a proteção contra o aumento de peso/adiposidade associada à obesidade, bem como a melhora da intolerância à glicose são dependentes de PPAR&gamma;. Além disso, por meio da utilização de camundongos com deleção de PPAR&gamma; em hepatócitos os dados desse trabalho mostram que os PPAR&gamma; são, ao menos em parte, essenciais ao aumento da oxidação de ácidos graxos induzida pelos n-3 devido à modulação da expressão gênica e protéica de enzimas mitocondriais e peroxissomais. / The intake of n-3 fatty acids have been associated to the protection against obesity, inflammation and insulin resistance. The n-3 fatty acids are ligands of the nuclear receptor PPAR&gamma;, and by the activation of this receptor can promote their metabolic and anti-inflammatory effects. Herein, we investigated whether increasing body n-3 fatty acids levels either genetically or by a n-3 enriched diet protects mice from diet-induced obesity, glucose intolerance and adipose tissue inflammation through PPAR&gamma; activation. Fat-1 mice were protected from diet-induced obesity, glucose intolerance and adipose tissue inflammation. To better investigate PPAR&gamma; involvement in n-3 beneficial actions, mice with genetic deletion of PPAR&gamma; specifically in hepatocytes. In spite of the absence of changes in body weight and glucose homeostasis PPAR&gamma; deletion in hepatocytes completely abolished the increase in liver fatty acid oxidation and hepatic gene expression of genes associated to mitochondrial and peroxisomal activity.

O consumo de ácidos graxos n-3 tem sido associado à proteção contra a obesidade, inflamação e resistência à insulina. Os n-3 são ligantes fracos dos receptores nucleares PPAR&gamma;, e pela ativação deste podem exercer suas ações metabólicas e anti-inflamatórias. No presente trabalho, foi investigado se o aumento da disponibilidade dos n-3 geneticamente ou por dieta, via ativação de PPAR&gamma;, protege camundongos do desenvolvimento da obesidade, intolerância a glicose e inflamação do tecido adiposo. Foi visto em um modelo com camundongos fat-1 (elevados níveis endógenos de n-3) que dentre as ações dos ácidos graxos n-3, a proteção contra o aumento de peso/adiposidade associada à obesidade, bem como a melhora da intolerância à glicose são dependentes de PPAR&gamma;. Além disso, por meio da utilização de camundongos com deleção de PPAR&gamma; em hepatócitos os dados desse trabalho mostram que os PPAR&gamma; são, ao menos em parte, essenciais ao aumento da oxidação de ácidos graxos induzida pelos n-3 devido à modulação da expressão gênica e protéica de enzimas mitocondriais e peroxissomais. / The intake of n-3 fatty acids have been associated to the protection against obesity, inflammation and insulin resistance. The n-3 fatty acids are ligands of the nuclear receptor PPAR&gamma;, and by the activation of this receptor can promote their metabolic and anti-inflammatory effects. Herein, we investigated whether increasing body n-3 fatty acids levels either genetically or by a n-3 enriched diet protects mice from diet-induced obesity, glucose intolerance and adipose tissue inflammation through PPAR&gamma; activation. Fat-1 mice were protected from diet-induced obesity, glucose intolerance and adipose tissue inflammation. To better investigate PPAR&gamma; involvement in n-3 beneficial actions, mice with genetic deletion of PPAR&gamma; specifically in hepatocytes. In spite of the absence of changes in body weight and glucose homeostasis PPAR&gamma; deletion in hepatocytes completely abolished the increase in liver fatty acid oxidation and hepatic gene expression of genes associated to mitochondrial and peroxisomal activity.

O carcinoma hepatocelular (HCC) é a sexta neoplasia mais comum e a terceira causa de mortalidade por câncer no mundo. Está relacionado, principalmente, à exposição a diversos fatores de risco, como a doença hepática gordurosa não alcoólica (NAFLD). O HCC apresenta mau prognóstico; neste sentido, é importante a adoção de medidas de controle, como a quimioprevenção. A quimioprevenção é o método mais apropriado para se evitar o câncer e consiste na prevenção, inibição ou reversão das etapas iniciais da carcinogênese, pela administração de um ou mais compostos químicos sintéticos ou naturais. Diversos compostos presentes nos alimentos podem apresentar atividade quimiopreventiva, dentre esses, a tributirina (TB), pró-fármaco do ácido butírico. Dessa forma, propôs-se avaliar o efeito quimiopreventivo da TB nas etapas de iniciação/promoção inicial, em ratos submetidos ao modelo de hepatocarcinogênese do hepatócito resistente (RH) associado à NAFLD. Ratos Wistar machos foram distribuídos em Grupo dos animais não tratados (NT), e dois outros grupos experimentais, o grupo RH + NAFLD + maltodextrina (grupo controle isocalórico, CI), e o grupo RH + NAFLD + tributirina (grupo TB). Os animais do grupo CI foram tratados diariamente, por gavagem, com emulsão hiperlipídica [1 mL/100 g de peso corpóreo (p. c)], e maltodextrina (300 mg/ 100 g p.c.), enquanto que os animais do Grupo TB foram tratados diariamente, por gavagem, com emulsão hiperlipídica [1 mL/100 g de p. c.], e TB (200 mg/ 100 g de p.c.), durante 13 semanas consecutivas quando foram eutanasiados. Após esse período, a análise por cromatografia a gás revelou que o grupo dos animais tratados com a tributirina apresentou uma concentração de AB 2.118 vezes superior (p < 0.05) às concentrações de AB constatadas no grupo controle. Em relação aos dados de morfometria de LPNs [lesões pré-neoplásicas persistentes (pLPN) ou em remodelação (rLPN)], a atividade quimiopreventiva da tributirina foi observada a partir da redução (p < 0,05) significativa do número de lesões pré-neoplásicas persistentes (pLPN) em comparação ao grupo controle. A área das pLPNs, contudo, foi maior (p < 0,05) no Grupo TB quando comparada à do grupo controle isocalórico. Não foram observadas diferenças estatisticamente significativas (p >= 0,05) no número e na área de rLPN, bem como na % da área do corte do fígado ocupada por LPNs entre os dois grupos experimentais. A quantificação da apoptose por H&E revelou maior (p < 0,05) índice apoptótico em pLPN e em rLPN nos animais tratados com TB, quando comparados aos animais do grupo 6 controle. Nesse sentido, observou-se que os animais tratados com a tributirina apresentaram maior (p < 0,05) ativação de Caspase 3 do que os ratos do grupo controle isocalórico. Em relação à avaliação da proliferação celular, o Grupo TB apresentou redução (p < 0,05) do índice de proliferação tanto em pLPNs como em rLPNs, quando comparado ao do grupo controle isocalórico. Não foi observada diferença estatisticamente significativa (p > 0,05) entre os surroundings dos dois grupos experimentais. A determinação do perfil lipídico sérico revelou que os animais tratados com a tributirina apresentaram menores (p < 0,05) concentrações séricas de LDL-colesterol e maiores (p < 0,05) concentrações séricas de HDL-colesterol, quando comparados às do grupo controle. Além disso, foram observadas menores (p < 0,05) concentrações hepáticas de colesterol no Grupo TB quando comparadas às do Grupo CI. Em relação a análise por PAS, embora, o presente estudo não tenha revelado diferença estatisticamente significativa (p >= 0,05) entre os dois grupos experimentais, o score entre os graus de marcação por PAS apresentou tendência (p = 0,07) a ser maior nos animais tratados com a tributirina quando comparados aos ratos do grupo controle. Em relação à expressão gênica de FGF-21, o Grupo TB apresentou maior (p < 0,05) expressão em comparação a seu grupo controle (Grupo CI). Além disso, esses dados são corroborados por meio da marcação imunoistoquímica de FGF-21, que revelou que os animais tratados com a tributirina apresentaram maior (p < 0,05) score desta marcação quando comparados aos ratos do grupo controle isocalórico. A análise de expressão em nível proteico de PPAR-&#945; revelou que o Grupo TB apresentou maior (p < 0,05) expressão em comparação ao Grupo CI. O presente estudo demonstrou que o tratamento com a tributirina apresentou um efeito quimiopreventivo quando administrada nas etapas de iniciação/promoção inicial em modelo de hepatocarcinogênese associado à NAFLD. Adicionalmente, sugere-se que a atividade como HDACi da TB poderia modular a expressão de genes supressores de tumor, bem como a daqueles relacionados ao metabolismo lipídico, atenuando os fatores de risco relacionados à NAFLD. / Hepatocellular carcinoma (HCC) is the sixth most common neoplasm and the third leading cause of cancer mortality in the world. It is mainly related to exposure to several risk factors, such as non-alcoholic fatty liver disease (NAFLD). HCC presents poor prognosis; In this sense, it is important to adopt control measures, such as chemoprevention. Chemoprevention is the most appropriate method to avoid cancer and consists in the prevention, inhibition or reversal of the early stages of carcinogenesis by the administration of one or more synthetic or natural chemical compounds. Several compounds present in foods may present chemopreventive activity, among them, tributyrin (TB), a prodrug of butyric acid. Thus, it was proposed to evaluate the chemopreventive effect of TB in the initiation / initial promotion stages in rats submitted to the hepatocyte-resistant hepatocyte model (HR) associated with NAFLD. Male Wistar rats were divided into two groups: RH + NAFLD + maltodextrin (isocaloric control group, CI), and RH + NAFLD + tributyrin group (TB group). The animals of the CI group were treated daily with gavage with hyperlipid emulsion [1 mL / 100 g body weight (wt.)], and maltodextrin (300 mg / 100 g body wt.), while the animals of the TB Group were treated daily by gavage with hyperlipid emulsion [1 mL / 100 g of body wt.], and TB (200 mg / 100 g body wt.) for 13 consecutive weeks when they were euthanized. After this period, the gas chromatographic analysis revealed that the group of animals treated with tributyrin had a concentration of AB 2184 times higher (p < 0.05) than the concentrations of AB found in the control group. Regarding the morphometry data of PNLs [persistent pre-neoplastic lesions (pPNL) or remodeling (rPNL)], the chemopreventive activity of tributyrin was observed from a significant (p < 0.05) reduction in the number of pPNL compared to the control group. The area of the pPNLs, however, was higher (p < 0.05) in the TB Group when compared to the isocaloric control group. There were no statistically significant differences (p >= 0.05) in the number and area of rPNL, as well as in the area of the cut of the liver occupied by LPNs between the two experimental groups. The quantification of apoptosis by H&E revealed a higher (p < 0.05) apoptotic index in pPNL and rPNL in the TB treated animals, when compared to the animals in the control group. In this sense, animals treated with tributyrin showed greater (p < 0.05) activation of Caspase 3 than the rats of the isocaloric control group. In relation to the evaluation of cell proliferation, the TB group presented a reduction (p < 0.05) in the proliferation index in both pPNLs and rPNLs, when compared to the isocaloric control group. No statistically significant difference (p> 0.05) was observed between the two experimental groups. The determination of serum lipid profile revealed that the animals treated with tributyrin showed lower (p < 0.05) serum LDL-cholesterol concentrations and higher (p < 0.05) serum HDL-cholesterol concentrations when compared to those in the group control. In addition, lower hepatic concentrations (p < 0.05) of cholesterol were observed in the TB Group when compared to those in the CI Group. Regarding the SBP analysis, although the present study did not reveal a statistically significant difference (p >= 0.05) between the two experimental groups, the score between the PAS presented a tendency (p = 0.07) to be greater in animals 8 treated with tributyrin compared to the rats in the control group. In relation to the gene expression of FGF-21, the TB Group presented higher (p <0.05) expression in comparison to its control group (CI Group). In addition, these data are corroborated by FGF-21 immunohistochemical labeling, which revealed that animals treated with tributyrin showed a higher (p <0.05) score for this marker when compared to the isocaloric control rats. Analysis of protein-level expression of PPAR-&#945; revealed that the TB Group had higher (p <0.05) expression compared to the CI Group. The present study demonstrated that treatment with tributyrin had a chemopreventive effect when administered in the initiation / initial promotion steps in a hepatocarcinogenesis model associated with NAFLD. In addition, it is suggested that the activity as HDACi of TB could modulate the expression of tumor suppressor genes, as well as those related to lipid metabolism, attenuating the risk factors related to NAFLD.

Le placenta humain est un organe indispensable au maintien de la grossesse et au développement foetal. Son unité structurale et fonctionnelle est la villosité choriale constituée principalement de trophoblastes qui se différencient selon la voie villeuse endocrine ou extravilleuse invasive. Ces deux populations trophoblastiques sécrètent de l'hormone chorionique gonadotrope humaine (hCG), hormone indispensable à la grossesse. C'est une glycoprotéine constituée de deux sous-unités: la sous-unité alpha commune avec la LH, FSH et la TSH et la sous-unité beta, spécifique à chaque hormone, codée par un cluster de gênes regroupés en type I (gêne beta 7) et type II (gênes beta 3, 5 et 8). L'hCG est sécrétée dans le compartiment maternel où elle joue un rôle endocrine essentiel au maintien de la grossesse en stimulant la production de progestérone par l'ovaire. L'hCG joue également un rôle localement en stimulant la différenciation de chaque type de trophoblaste. Elle présente, dans le sang maternel, un pic de sécrétion à 10-12 semaines d'aménorrhée (SA), période ou le statut oxydatif placentaire change. En effet, les bouchons trophoblastiques obstruant la lumière des artères spiralées utérines se délitent à cette période, permettant l'entrée progressive du sang maternel dans la chambre intervilleuse. La pression en oxygène augmente de 18 mm/Hg (8-9 SA, 1er trimestre précoce) à 60 mm/Hg (12-14 SA, 1er trimestre tardif). Dans mon travail de thèse, j'ai cherché à mettre en évidence in situ et in vitro l'impact de ce changement de statut oxydatif sur la différenciation des trophoblastes villeux du 1er trimestre, et plus particulièrement sur l'expression des hCG beta de type I et de type II. J'ai ainsi mis en évidence que les trophoblastes villeux mononucléés du 1er trimestre précoce sécrétaient plus d'hCG beta de type I et II, fusionnaient plus rapidement et exprimaient un panel de facteurs de transcription différents par rapport aux trophoblastes villeux du 1er trimestre tardif. Dans un deuxième temps, j'ai comparé in vitro l'expression et la régulation des deux types d'hCG beta entre les trophoblastes villeux et extravilleux. J'ai montré que: 1) les trophoblastes villeux expriment plus d'hCG beta de type I et II que les trophoblastes extravilleux, 2) dans les deux cas l'hCG beta de type II est majoritaire et 3) PPAR gamma régule de façon opposée ces deux types d'hCG entre les trophoblastes villeux et extravilleux. Enfin j'ai mis en évidence que l'expression de ces deux types d'hCG était dérégulée dans la pré-éclampsie et le RCIU. L'étude des mécanismes impliqués dans la régulation des gênes codants pour l'hCG représente un enjeu important pour la compréhension de la différenciation du trophoblaste humain, du développement précoce du placenta et des pathologies de la grossesse. / The human placenta is an essential organ to maintain pregnancy and for foetal growth. Its structural and functional unit is the chorionic villous, which is mainly composed of cytotrophoblasts that follow two differentiation pathways: the endocrine villous and the invasive extravillous trophoblasts. These two trophoblastic subtypes secrete the human chorionic gonadotropin hormone (hCG), an essential hormone for trophoblast differentiation, placental development and pregnancy. hCG is a glycoprotein composed of two subunits: the alpha subunit, which is common to LH, FSH and TSH, and the beta subunit that confers hormone specificity. A gene cluster encodes the beta subunit, type I (CGB7) and type II (CGB3, 5 and 8), that code for two different proteins. hCG is detected in the maternal blood from the first week of pregnancy, with a peak level at 10-12 weeks of gestation (WG). During the first trimester the oxygen concentration in the intervillous space changes from about 2% (prior to 10 WG) to approximately 6-8% (after 12 WG) due to development of blood flow to the placenta. During my PhD work, I studied in situ and in vitro the impact of these different environments during the first trimester on villous cytotrophoblast differentiation, and more specifically on the type I and type II beta hCG gene expression. I showed that type I and type II beta hCG are more expressed in early first trimester cytotrophoblasts and that these cells exibit more fusion features and express a different panel of transcription factors compare to cells from late first trimester. In the second part of my work, I compared the expression and the regulation in vitro of the two types of beta hCG between villous and extravillous cytotrophoblasts. I demonstrated: 1) villous trophoblast express more type I and type II beta hCG compared to the extravillous trophoblast, 2) in both case type II hCG beta is the major form of beta hCG and 3) PPAR gamma differentially regulates type I and type II beta hCG expression in villous and extravillous trophoblasts. Lastly I showed that the expression of type I and type II beta hCG is deregulated in pre-eclampsia and FGR. The study of the mechanisms involved in hCG regulation represents an important issue for the understanding of human trophoblast differenciation and pregnancy pathophysiology.

Depuis plusieurs années, un nombre conséquent d’études décrivent une augmentation de l’incidence de pathologies liées à la fonction de reproduction masculine. Ces anomalies ont été regroupées sous le terme de « syndrome de dysgénésie testiculaire ». Ce syndrome aurait pour origine les effets délétères de polluants environnementaux sur le développement du testicule en période fœtale. Parmi ces polluants environnementaux, les phtalates et le bisphénol A (BPA) sont les plastifiants les plus produits et les plus répandus dans les objets de consommation courante. De nombreuses études leur sont consacrées et ont permis de les classer au rang de perturbateurs endocriniens en mettant notamment en cause leurs effets reprotoxiques. Mon travail de thèse est une étude des effets de ces deux perturbateurs endocriniens sur le développement du testicule fœtal.Nous avons réalisé une première étude concernant les effets du BPA sur le développement du testicule fœtal. Grâce au modèle de culture organotypique, nous avons développé notre étude dans trois espèces : le rat, la souris et l’Homme. Nous démontrons que le BPA diminue la sécrétion de testostérone dans le testicule fœtal humain à partir d’une concentration de 10-8M, alors que chez le rat et la souris, la sécrétion de testostérone n’est affectée qu’à partir de 10-5M de BPA. Nous avons également démontré une diminution de l’expression du gène de l’Insl-3, dans ces mêmes conditions. Ceci nous a permis de mettre en évidence une différence de sensibilité entre les espèces. Pour tenter de comprendre les mécanismes par lesquels le BPA exerce son effet toxique, nous avons comparé ses effets à ceux du DES, autre perturbateur endocrinien œstrogénomimétique. Contrairement au BPA, le DES diminue la sécrétion de testostérone fœtale chez les rongeurs, et non chez l’Homme. Ce résultat suggère l’implication de deux voies de signalisation différentes pour ces deux xéno-œstrogènes. Cette hypothèse est d’ailleurs renforcée par l’étude que nous avons SourceMécanismes d’action des perturbateurs endocriniens bisphénol A et phtalates sur le développement du testicule fœtal / par Thierry N’Tumba-Byn ; sous la direction de Virginie Rouiller-Fabre, Université Paris Sud, 2013 [Thèse de Biologie de la Reproduction et du Développement]réalisée sur des souris invalidées pour le récepteur des œstrogènes ERα, dans lesquelles l’effet anti-androgénique du BPA persiste, contrairement à celui du DES.Parallèlement, nous avons recherché les mécanismes d’action des phtalates et de leur métabolite actif le plus répandu, le MEHP (mono-2-éthyl-hexyl phtalate). Dans la continuité de plusieurs travaux réalisés dans notre laboratoire sur les effets du MEHP, nous avons tenté de comprendre les mécanismes par lesquels le MEHP induit un effet pro-apoptotique dans les cellules germinales mâles. Nous avons mis en évidence une augmentation de l’expression du gène Stra8 dans les cellules germinales traitées au MEHP. Ce résultat nous suggère que le MEHP pourrait induire une différenciation erronée des cellules germinales mâles. De plus, nous avons recherché les récepteurs et la voie de signalisation activée par le MEHP. Nous observons que les agonistes des récepteurs PPARα et de PPARγ entrainent dans les cellules germinales les mêmes phénotypes que le MEHP, à savoir une augmentation du taux d’apoptose et de l’expression du gène Stra8. / For several years, an increase in the incidence of pathologies connected to the male reproductive functions has been described in numerous studies. These anomalies are classified under the term “testicular dysgenesis syndrome”. This syndrome might find its origins in the deleterious effects of environmental pollutants on the testis development in fetal period. Among theses environmental pollutants, phthalates and bisphenol A (BPA) are the most produced plasticizers found in products of common use. Many studies were performed in order to determine their effects, and allowed to classify them as endocrine disruptors because of their reprotoxic effects. My thesis work is a study of the effects of these two endocrine disruptors on the fetal testis development.Our first study focuses on the effects of BPA on the fetal testis development. Using the organotypic culture model, we developed our study in three species: rat, mouse and human. We demonstrated that BPA decreases the testosterone secretion in the human fetal testis from a 10-8M concentration, while in rat and mouse the testosterone secretion is only affected by 10-5M BPA. We also demonstrated a decreased Insl-3 gene expression, in the same conditions. These results allowed us to evidence a difference of sensibility between species. To understand the mechanisms involved in the BPA toxic effect, we compared it with the effect of DES, another endocrine disruptor with estrogenic activity. Unlike BPA, DES decreases the fetal testosterone secretion in rodents and not in human. This result suggests the involvement of two different signalisation pathways for these two xenoestrogens. This hypothesis is reinforced by the study that we performed in mice invalidated for the estrogen receptor ERα. In those mice, the anti-androgenic effect of BPA is maintained, unlike DES effect.In parallel, we investigated the mechanisms of action of phtalates and particularly of their most prevalent active metabolite, the MEHP (mono-2-ethyl-hexyl phthalate). Following previous studies performed in our laboratory concerning the effects of MEHP, we intended to understand the mechanisms by which MEHP induces the apoptosis in male germ cells. We evidenced an increase in Stra8 gene expression in MEHP treated germ cells. This result suggests that MEHP might induce a wrong differentiation in male germ cells. Furthermore, we investigated the receptors and the signalisation pathway activated by MEHP. We observe that PPARα and PPARγ receptors agonists induce the same phenotypes as MEHP, namely an increase in the apoptosis and in Stra8 gene expression in germ cells.

<p>A central aim in drug development is to ensure that the new drug is efficacious and safe in the intended patient population.</p><p>Mathematical models describing the pharmacokinetic-pharmacodynamic (PK-PD) properties of a drug are valuable to increase the knowledge about drug effects and disease and can be used to inform decisions. The aim of this thesis was to develop mechanism-based PK-PD-disease models for important safety and efficacy biomarkers used in anti-diabetic drug development. </p><p>Population PK, PK-PD and disease models were developed, based on data from clinical studies in subjects with varying degrees of renal function, non-diabetic subjects with insulin resistance and patients with type 2 diabetes mellitus (T2DM), receiving a peroxisome proliferator-activated receptor (PPAR) α/γ agonist, tesaglitazar.</p><p>The PK model showed that a decreased renal elimination of the metabolite in renally impaired subjects leads to increased levels of metabolite undergoing interconversion and subsequent accumulation of tesaglitazar. Tesaglitazar negatively affects the glomerular filtration rate (GFR), and since renal function affects tesaglitazar exposure, a PK-PD model was developed to simultaneously describe this interrelationship. The model and data showed that all patients had decreases in GFR, which were reversible when discontinuing treatment. </p><p>The PK-PD model described the interplay between fasting plasma glucose (FPG), glycosylated haemoglobin (HbA1c) and haemoglobin in T2DM patients. It provided a mechanistically plausible description of the release and aging of red blood cells (RBC), and the glucose dependent glycosylation of RBC to HbA1c. The PK-PD model for FPG and fasting insulin, incorporating components for β-cell mass, insulin sensitivity and impact of disease and drug treatment, realistically described the complex glucose homeostasis in the heterogeneous patient population. </p><p>The mechanism-based PK, PK-PD and disease models increase the understanding about T2DM and important biomarkers, and can be used to improve decision making in the development of future anti-diabetic drugs. </p>