La scoliose idiopathique de l’adolescent (SIA) est définie comme une courbure de la colonne vertébrale supérieure à 10 degrés, qui est de cause inconnue et qui affecte de façon prépondérante les adolescents. Des études précédentes sur des modèles murins ont démontré une inactivation partielle du gène Pitx1. Cette inactivation partielle provoque une déformation spinale sévère lors du développement des souris Pitx1+/-, ce qui est grandement similaire au phénotype de la SIA. En se basant sur ces observations, nous postulons que la perte de fonction de Pitx1 pourrait avoir un rôle dans la SIA et pourrait être régulée par des mécanismes moléculaires spécifiques. En effet, des études faites sur l’expression de Pitx1 révèlent une perte de son expression dans les ostéoblastes dérivés de patients SIA au niveau de l’ARNm. Nous émettons l’hypothèse que la perte de Pitx1 dans la SIA pourrait être déclenchée par des facteurs hypoxiques puisqu’il est connu que Pitx1 est réprimé par l’hypoxie et que HIF-2 alpha est surexprimés dans les ostéoblastes des patients SIA même dans des conditions normoxiques. De plus, nous avons découvert une mutation dans le domaine ODD des HIF-1 alpha chez certains patients SIA (3,1%). Une fonction connue de ce domaine est de stabiliser et d’augmenter l’activité transcriptionnelle de HIF-1 alpha dans des conditions normoxiques. Nous avons confirmé, par la technique EMSA, l’existence d’un élément de réponse fonctionnel à l’hypoxie au niveau du promoteur de Pitx1. Cependant, des co-transfections avec des vecteurs d’expression pour HIF-1 alpha et HIF-2 alpha, en présence de leur sous-unité beta ARNT, ont conduit à une activation du promoteur de Pitx1 dans la lignée cellulaire MG-63 ainsi que dans les ostéoblastes des sujets contrôles. Il est intéressant de constater qu’aucune activité du promoteur de Pitx1 dans les ostéoblastes SIA n’a été observée, même après la co-expression de HIF-2 alpha et ARNT, confirmant le fait que l’expression de Pitx1 est abrogée dans la SIA. Dans l’ensemble, nos résultats démontrent un rôle important de Pitx1 dans la SIA et une possible régulation par des facteurs hypoxiques. / Adolescent Idiopathic Scoliosis is a lateral curvature of the spine greater than 10 degrees, with an unknown cause, affecting primarily adolescents. Previous mouse model studies showed that partial inactivation of Pitx1 gene resulted in the development of severe spinal deformities in Pitx1 +/- mice, which is strikingly similar to the AIS phenotype. Based on this observation, we postulated that loss of Pitx1 function might have a role in AIS and could be regulated through specific molecular mechanisms. Indeed, expression studies revealed a loss of Pitx1 expression in osteoblasts derived from AIS patients, at the mRNA level. We hypothesized that the loss of Pitx1 in AIS could be triggered by hypoxic factors, since Pitx1 is known to be repressed by hypoxia and that HIF-2 alpha was up regulated in AIS osteoblasts even under normoxic conditions. Also, we found a mutation in the ODD domain of HIF-1 alpha in some AIS patients (3.1%), which is known to stabilize and enhance HIF-1 alpha transcriptional activity in normoxic conditions. We confirmed through EMSA the existence of a functional hypoxia response element on Pitx1 promoter. However, co-transfection assays with HIF-1 alpha and HIF-2 alpha expression vectors in the presence of their beta subunit ARNT led to the activation of Pitx1 promoter in human osteoblast cell line MG-63 cells and osteoblasts from control subjects. Interestingly, no Pitx1 promoter activity was observed in AIS osteoblasts, even after the co expression of HIF2 alpha and ARNT, consolidating the fact that Pitx1 expression is abrogated in AIS. Taken together, our findings show an important role for Pitx1 in AIS and hypoxic factors could be one of its regulators.

Les tumeurs solides sont souvent confrontées à un environnement déficient en oxygène, dit hypoxique. Hypoxia-Inducible Factor 1 (HIF1) est le facteur de transcription clé de l’adaptation cellulaire à l’hypoxie, régulant de nombreux gènes impliqués dans l’angiogenèse, le métabolisme cellulaire ou la régulation du pH. Ma thèse s’articule en trois axes autour de HIF1 et de la reprogrammation métabolique hypoxique. J’ai d’abord étudié Factor-Inhibiting HIF1 (FIH), l’un des deux senseurs d’oxygène régulant HIF1. Nous avons montré que FIH est essentiel dans le développement tumoral en inhibant à la fois l’activité transcriptionnelle de HIF1 et la voie p53-p21. J’ai ensuite étudié le « shift » du métabolisme cellulaire vers la glycolyse induit par HIF1, générant une addiction pour le glucose. Nos travaux ont montré que paradoxalement, les cellules hypoxiques synthétisent du glycogène via HIF1 constituant ainsi une réserve de glucose intracellulaire. Le glycogène confère alors une résistance accrue des cellules tumorales suite à une carence en glucose. Enfin, j’ai pu montrer que l’AMPK, « gardien de la balance énergétique », n’est pas nécessaire au maintien d’un niveau viable d’ATP suite à l’inhibition de la glycolyse, via le blocage de l’export de lactate, mais exerce, un effet protecteur en absence de glucose. Cependant, l’inhibition conjointe du transporteur de lactate, MCT4, et de l’AMPK réduit fortement le développement tumoral dans un modèle de xénogreffes chez la souris, suggérant un rôle crucial de ces deux acteurs dans ce contexte. L’ensemble de ces travaux a permis d’identifier plusieurs cibles potentielles impliquées dans la plasticité métabolique en hypoxie. / Cells of solid tumors are often exposed to an environment deficient in oxygen, i.e. hypoxic. The Hypoxia-Inducible Factor-1 (HIF-1) is the major transcription factor involved in cellular adaptation to hypoxia. HIF-1 regulates a wide array of genes involved in angiogenesis, cellular metabolism or pH regulation. My thesis is organized into three axes around HIF-1 and metabolic reprogramming in hypoxia. I first studied Factor-Inhibiting HIF-1 (FIH), one of two oxygen sensors regulating HIF-1. We showed that FIH is essential for tumor development through inhibition of the HIF-1 transcriptional activity as well as through the suppression of the p53-p21 axis. I then studied the HIF-1-induced « shift » in cellular metabolism toward glycolysis, which generates a type of “glucose addiction”. We showed that paradoxically, tumor cells store glycogen in hypoxia through a HIF-1 dependant mechanism. Glycogen served as a reservoir of intracellular glucose, which allows hypoxic cells to survive periods of glucose starvation. Finally, I studied AMPK «the guardian of energy », and showed that surprisingly, this kinase is not necessary in maintaining a viable level of ATP when glycolysis is inhibited (by blockade of lactate export). However, as expected, AMPK protected cells during glucose starvation. Moreover, combined inhibition of the lactate transporter MCT4 and of AMPK reduced dramatically tumor development in a xenograft model, suggesting a crucial role for these two actors in the context of growth of tumor cells in a hostile environment. Taken together these results identified several potential drug targets involved in the metabolic plasticity of hypoxic cells.

No description available.

L'hypoxie intermittente (HI), induite par les apnées du sommeil, conduit à des altérations de la sensibilité à l'insuline et de l'homéostasie glucidique mais les mécanismes impliqués restent mal connus. L'objectif de ce travail était d'étudier les effets et les mécanismes sous jacents d'une exposition chronique à l'HI sur l'homéostasie glucidique. L'HI induit une résistance à l'insuline à la fois systémique et tissulaire, ainsi qu'une amélioration de la tolérance au glucose associée à une activation de l'AMPK musculaire. L'HI cause également des altérations du foie et du tissu adipeux associées à un changement du pattern d'expression des gènes dans ces tissus et à un risque accru de développement de pathologies vasculaires comme l'athérosclérose. Enfin, la délétion de PHD1, une des protéines régulatrices de HIF-1, entraîne une résistance à l'insuline associée une stéatose hépatique, faisant de HIF-1 une cible potentielle impliquée dans les altérations metaboliques induites par l'HI. / Intermittent hypoxia (IH), induced by sleep apnea, leads to alterations in insulin sensitivity and glucose homeostasis but the mechanisms involved remains poorly understood. The objective of this work was to study the effects and the underlying mechanisms of chronic exposure to IH on glucose homeostasis. IH induces both systemic and tissue-specific insulin resistance , as well as improved glucose tolerance associated with an activation of muscle AMPK. IH also causes a change in the pattern of gene expression in liver and adipose tissue and an increased risk of vascular pathologies such as atherosclerosis development. Finally, the deletion of PHD1, a regulatory protein of HIF-1, leads to insulin resistance associated with hepatic steatosis, making HIF-1 a possible target involved in the metabolic changes induced by IH.

Le syndrome d’apnées obstructives du sommeil est un problème de santé publique affectant plus de 5 % de la population, se caractérisant par des obstructions répétées des voies aériennes durant la nuit. L’hypoxie intermittente (HI) qui en résulte, induit des complications cardiovasculaires (hypertension, athérosclérose, insuffisance cardiaque). Le but de cette thèse est d’explorer le remodelage cardiovasculaire induit par l’HI et de comprendre le rôle de HIF-1 et de l’endothéline (ET-1) dans ces modifications. Pour cela nous avons exposé à 14 jours d’HI des souris HIF1α+/- ou traitées avec un antagoniste des récepteurs à l’ET-1. Chez les souris contrôles, nous avons observé un épaississement de la paroi aortique, une inflammation systémique et locale dans l’aorte ainsi qu’une hypertrophie du ventricule droit qui sont absents chez les souris HIF1α+/- ou traitées au bosentan. La délétion de HIF1a prévient également l’augmentation de contractilité observée dans le ventricule gauche après HI. En conclusion HIF-1 et ET-1 semblent fortement impliqués dans le remodelage vasculaire et myocardique induit par l’HI. / Obstructive sleep apnea is a public health problem affecting more than 5% of the population, characterized by repeated airway obstructions during sleep. The resulting intermittent hypoxia (IH) induces cardiovascular complications (hypertension, atherosclerosis, heart failure). The aim of this thesis is to characterize the cardiovascular remodeling induced IH and understand the role of HIF-1 and endothelin (ET-1) in these alterations. For this, we exposed to IH for 14 days HIF1α+/- mice or mice treated with an ET-1 receptor antagonist. Control mice developed thickening of the aortic wall, systemic and local inflammation in the aorta and right ventricular hypertrophy that were absent in HIF1α+/- or bosentan-treated mice. HIF1a deletion also prevents the increase in left ventricular contractility observed after HI. In conclusion, HIF-1 and ET-1 appear to be strongly involved in the vascular and myocardial remodeling induced by HI.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-09T12:38:26Z No. of bitstreams: 2 Dissertação - Maisa Ribeiro - 2015.pdf: 1621645 bytes, checksum: 2b3a1e65f1e53b4a1264cf3febb2c630 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-09T12:41:15Z (GMT) No. of bitstreams: 2 Dissertação - Maisa Ribeiro - 2015.pdf: 1621645 bytes, checksum: 2b3a1e65f1e53b4a1264cf3febb2c630 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-10-09T12:41:15Z (GMT). No. of bitstreams: 2 Dissertação - Maisa Ribeiro - 2015.pdf: 1621645 bytes, checksum: 2b3a1e65f1e53b4a1264cf3febb2c630 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-02-19 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In the lesions carcinomatous, low oxygen tension plays a crucial step in the self-renewal, metastatic potential, and therapy resistance of cancers. To adapt to the hypoxic microenvironment, neoplastic cells activate hypoxia-induced factor-1 alpha (HIF-1 alpha), which may mediates invasion and metastasis. In addition, the human THY-1 (CD90) cell surface protein mediates cell adhesion expressed in stem cells, and seens to drive tumor development in some malignant tumors. The present study investigates HIF-1 alpha (n=98) and CD90 (n=97) expression in oral squamous cell carcinoma (OSCC) and metastatic lymph nodes (n=24), the intratumoral region and the invasive front, by immunohistochemistry. Furthermore, clinicopathological data revised from the medical records. In superficial OSCCs, most tumor cells overexpressed HIF-1 alpha, whereas was restricted in the intratumoral region in invasive conventional SCCs. Interestingly, metastatic lymph nodes (91.7%, p=0.001), and intratumoral regions of its corresponding primary tumors (83.3%, p<0.001) were invaded by HIF-1 alpha-positive neoplastic cells. Overall survival was poor in patients with nodal involvement. CD90 was expressed mostly in microvessels and granulocyte cells similar to mast cells. These cells expressed CD90 mostly in the peritumoral region of invasive SCC (p<0.001). Microvessels CD90 positive were higher in the intratumoral region (p=0.032). Interesting, mast cell and microvessels positively correlated in OSCC (p=0.006; r²=0.077). In conclusion, hypoxic environment may facilitate regional metastasis and serve as a potential diagnostic and prognostic marker in OSCC primary tumors. Microvessels CD90 positive seems to promote tumor growth except in BSCC. Mast cell may occur via CD90 for tumor progression. / Nas lesões carcinomatosas a baixa tensão de oxigênio desempenha um passo crucial para a auto-renovação, potencial metastático, e resistência à terapia no câncer. Para se adaptar ao ambiente hipóxico, células neoplásicas ativam o fator induzido por hipóxia-1 alfa (HIF-1 alfa), que pode facilitar a invasão e metástase. Além disso, o THY-1 (CD90) humano, uma proteína de superfície celular expressa em células estaminais, medeia a adesão celular, e parece promover o desenvolvimento em alguns tumores malignos. O presente estudo analisou a expressão das proteínas HIF-1 alfa (n = 98) e CD90 (n = 97) no carcinoma espinocelular de boca (CEC de boca) e linfonodos metastáticos (n=24), na região intratumoral e no fronte de invasão, por meio de imunoistoquímica. Além disso os dados clinicopatológicos foram revisados a partir dos prontuários médicos e a sobrevida foi analisada. No CEC microinvasivo, a maioria das células tumorais apresentaram superexpressão do HIF-1 alfa, enquanto que no CEC invasivo a superexpressão foi restrita na região intratumoral. Verificou-se que em linfonodos metastáticos (91,7%, p = 0,001), e regiões intratumorais dos seus tumores primários correspondentes (83,3%, p <0,001) houve forte expressão do HIF-1 alfa em células neoplásicas. A sobrevida global foi pior em pacientes com metástase regional. A proteína CD90 foi expressa principalmente em microvasos e células de granulócitos semelhantes aos mastócitos. Estas células expressaram CD90 principalmente na região fronte de invasão do CEC invasivo (p<0,001). A média de microvasos CD90 positivo foi maior na região intratumoral (p=0,032). Interessantemente, mastócitos e microvasos foram positivamente correlacionados no CEC de boca (p=0,006; r²=0,077). Em conclusão, o ambiente hipóxico pode facilitar metástases regionais e funcionar como um potencial marcador de diagnóstico e prognóstico em tumores primários do CEC de boca. Os microvasos CD90 positivo parecem promover o crescimento do tumor, exceto no carcinoma escamoso basalóide (CEB). Os mastócitos ativados via CD90 podem contribuir com a progressão do tumor.

Alterações no mecanismo de transporte de oxigênio (O2) frequentes em inflamações, infecções, tumores, transplantes e isquemia, levam a hipóxia tecidual. Espécies reativas do O2 são produzidas e citocinas inflamatórias são liberadas engatilhando uma série de eventos, os quais são amplificados após a restituição do fluxo sanguíneo resultando em inflamação sistêmica. No presente estudo, caracterizamos a regulação da Resposta Inflamatória Aguda (AIR) após indução de isquemia e reperfusão intestinal (I/Ri) e a participação do HIF-1&alpha; neste fenótipo. Camundongos selecionados para alta (AIRmax) e baixa (AIRmin) AIR foram submetidos a I/Ri e avaliados em diferentes períodos de reperfusão (0, 1, 4 e 24h). Nossos resultados demonstraram maior sensibilidade da linhagem AIRmax frente a I/Ri, confirmada por: 1) maior mobilização de neutrófilos para circulação periférica; 2) maior adesão celular e aumento da migração granulocítica no intestino e pulmão; 3) aumento da expressão de genes de citocinas e daqueles expressos em hipóxia (Tnfa, Il1, Il6 e Hif1a); 4) Translocação Bacteriana (TB); 5) maior expressão pulmonar da proteína HIF-1&alpha; e de proteínas envolvidas em processos inflamatórios tais como S100A9, Anexina 1, Profilina 1, Tropomiosina. Por outro lado, a linhagem AIRmin foi considerada pouco responsiva aos efeitos da I/Ri. Diante do exposto, nós concluímos que a sensibilidade dos camundongos AIRmax à injuria após indução de IRi está associada ao agravamento da inflamação sistemica, a qual foi determinada pela indução de HIF-1&alpha; atrelada à expressão de proteínas pró- inflamatórias e TB, indicando o compartilhamento ou a co- segregação entre os genes envolvidos na AIR e na hipóxia. / Changes in oxygen transport mechanism (O2) frequent in inflammation, infection, tumors, transplantation and ischemia, lead to tissue hypoxia. Reactive species of O2 are produced and inflammatory cytokines are released triggering a series of events, which are amplified after blood flow refund resulting in systemic inflammation. In the present study, we characterized the regulation of Acute Inflammatory Response (AIR) after intestinal ischemia and reperfusion (I/Ri) induction and the involvement of HIF-1&alpha; in this phenotype. Mice selected for high (AIRmax) and low (AIRmin) AIR were subjected to I/Ri and evaluated in different periods of reperfusion (0, 1, 4 and 24h). Our results show sensitivity of AIRmax front line I/Ri, confirmed by: 1) higher neutrophils mobilization to peripheral circulation; 2) increase in cell adhesion and granulocyte migration in lung and intestine; 3) higher expression of cytokine genes and those expressed in hypoxia (TNFa, IL-1, IL-6 and HIF1a); 4) Bacterial Translocation (BT), 5) increase in HIF-1&alpha; pulmonary protein expression and those involved in inflammatory processes such as S100A9, Annexin 1, profilin 1 Tropomyosin. On the other hand, the AIRmin line was considered unresponsive to effects of I/Ri. We concluded that the I/Ri sensitivity of the AIRmax mice were associated with worsening of systemic inflammation, which was determined by HIF-1&alpha; induction linked to the expression of pro- inflammatory proteins and TB, indicating the share and/or co-segregation of the genes involved in AIR.

Objetivos: Determinar a expressão imunohistoquímica do fator indutor de hipóxia 1-alfa (HIF-1-alfa) e suas variáveis associadas em pacientes com câncer de mama localmente avançado. Pacientes e método: Vinte e sete mulheres foram biopsiadas para diagnóstico histopatológico do carcinoma mamário e submetidas a tratamento quimioterápico pré-cirúrgico. Analisou-se a associação do HIF-1-alfa com idade, tamanho tumoral, grau histológico, estadio clínico, status hormonal e axilar, resposta clínica e patológica após tratamento quimioterápico, expressão do receptor de estrogênio, progesterona e cerbB2. Resultados: A expressão de HIF-1-alfa foi presente em 66,7% das pacientes. O único fator associado à sua presença foi o status axilar positivo (p=0,02), tendo permanecido durante a análise univariada. As demais variáveis não apresentaram associação estatisticamente significante. Conclusão: Existe uma associação estatisticamente significante entre o acometimento linfonodal e a presença de HIF-1-alfa em pacientes com câncer de mama localmente avançado. / Objectives: To assess the expression of HIF-1 and its associated variables with locally advanced breast cancer (LABC) patients. Methods: Twenty-seven women were submitted to incisional biopsy for histopathological diagnosis of breast carcinoma and undertaken to neoadjuvant chemotherapy (NACT). It was studied the association of HIF-1 with age, tumoral size, histological grade, clinical stage, hormonal and axillary status, clinical and pathological response after NACT, expression of estrogen and progesterone receptors, as well as the presence of cerbB2 antigen. Results: HIF-1-alpha expression was found in 66.7% of patients. Only axillary status was the associated factor with its presence (p=0.02), and remained after univariate analysis. The others did not present any significant statistically difference. Conclusion: There is a significant statistically association between axillary status and HIF-1-alpha expression in LABC patients.

Abstract Adequate oxygen supply is necessary for aerobic cell survival. Cellular oxygen deprivation, also known as hypoxia, leads to various responses that aim to increase cellular oxygen delivery and reduce oxygen consumption. Oxygen homeostasis is mainly regulated by the hypoxia-inducible factor (HIF), which regulates the expression of over 300 genes in response to hypoxia. The stability of HIF is regulated by the HIF prolyl 4-hydroxylases (HIF-P4Hs), enzymes that catalyze the hydroxylation of proline residues in HIFα subunits and target them towards proteasomal degradation. HIF-P4Hs require oxygen as a cosubstrate for the reaction, allowing for hypoxic HIF stabilization and target gene induction at low oxygen concentrations. In this study we investigated the role of HIF-P4H-2 in the regulation of red blood cell production, erythropoiesis. We showed that Tibetans living at high altitude have genetically adapted to their hypoxic environment via mutations in the gene encoding for HIF-P4H-2. The Tibetan HIF-P4H-2 D4E,C127S variant showed enhanced hydroxylation of HIFα at low oxygen concentrations, resulting in reduced HIFα protein stabilization under hypoxia. In other studies we used a genetically modified HIF-P4H-2 hypomorphic mouse line which expresses a reduced amount of wild-type Hif-p4h-2 mRNA in tissues. We showed that these mice develop mild age-dependent erythrocytosis due to splenic extramedullary erythropoiesis, which is independent of serum erythropoietin concentration. In addition, these mice were protected against inflammation-induced anemia, a condition commonly seen in patients with inflammatory diseases. The HIF-P4H-2 hypomorphic mice also had altered basal metabolism in their skeletal muscles, which, together with an increase in mean capillary area, reduced their infarct size after skeletal muscle ischemia-reperfusion injury. These studies suggest that pharmacological HIF-P4H-2 inhibition may provide a novel treatment for EPO-resistant anemias and peripheral artery disease. / Tiivistelmä Riittävä hapensaanti on välttämätöntä aerobisten solujen selviytymiselle. Solun alentunut hapen määrä, toiselta nimeltään hypoksia, johtaa useisiin vasteisiin joiden tarkoituksena on turvata solun hapensaanti ja vähentää hapenkulutusta. Happitasapainoa säätelee hypoksiassa indusoituva tekijä (HIF), joka aktivoi yli 300 geenin luentaa hypoksisissa oloissa. HIF&#945;:n määrää soluissa säätelevät HIF prolyyli-4-hydroksylaasientsyymit (HIF-P4H:t), jotka hydroksyloivat proliini-aminohappotähteitä HIF&#945;-alayksiköissä ja ohjaavat ne proteasomaaliseen hajotukseen. HIF-P4H:t tarvitsevat reaktiossa happea mahdollistaen HIF:n stabilisaation ja kohdegeenien lisääntyneen luennan matalassa hapen osapaineessa. Tässä tutkimuksessa selvitimme HIF-P4H-2-entsyymin roolia punasolujen muodostuksen eli erytropoieesin säätelyssä. Osoitimme, että korkealla vuoristossa asuvat tiibetiläiset ovat geneettisesti sopeutuneet hypoksiseen elinympäristöönsä johtuen HIF-P4H-2-entsyymiä tuottavan geenin mutaatiosta. Tiibetiläisiltä löytynyt HIF-P4H-2D4E,C127S variantti hydroksyloi tehokkaammin HIF&#945;-alayksiköitä matalassa hapen osapaineessa johtaen vähäisempään HIF&#945;-alayksiköiden stabiloitumiseen hypoksiassa. Muissa tutkimuksissamme käytimme geneettisesti muunneltua HIF-P4H-2-hiirikantaa, joka tuottaa alentunutta määrää villityypin Hif-p4h-2 lähetti-RNA:ta kudoksissaan. Näille hiirille kehittyi ikäriippuvaisesti lievä punasoluylimäärä eli erytrosytoosi johtuen pernan kiihtyneestä punasolutuotannosta riippumatta seerumin erytropoietiinikonsentraatiosta. Lisäksi nämä hiiret olivat suojassa tulehduksen aiheuttamalta anemialta, joka on yleinen ilmiö tulehduksellisista sairauksista kärsivillä potilailla. HIF-P4H-2-muuntogeenisten hiirten lihasten energia-aineenvaihdunta oli muuttunut siten, että se yhdessä suurentuneen keskimääräisen kapillaaripinta-alan kanssa pienensi vaurioituneen kudoksen pinta-alaa alaraajaiskemia-altistuksen jälkeen. Nämä tutkimukset osoittavat, että lääkkeellinen HIF-P4H-2-entsyymin estäminen on mahdollinen uusi hoitomuoto erytropoietiinille resistenteissä anemioissa sekä alaraajojen valtimoahtaumataudissa.

Les gliomes malins de l’enfant (GME), de pronostic sombre, se distinguent des gliomes malins de l’adulte (GMA) sur le plan biologique mais aussi clinique, avec des taux de réponse au témozolomide (chimiothérapie alkylante de référence chez l’adulte) moindres. L’efficacité du temozolomide est réduite par l’action de l’enzyme de réparation de l’ADN, l’O6-methylguanine-DNA-methyltransferase (MGMT), dont l’expression est fréquemment inhibée par méthylation du promoteur de son gène dans les GMA. En première partie, la mise au point d’une nouvelle technique de PCR spécifique de méthylation a montré une fréquence plus faible dans les GME (15%) vs les GMA (45%, p<0,001). En deuxième partie, l’hypoxie intra-tumorale et la dérégulation en amont de l’axe mTOR-HIF-1α, connus pour être impliqués dans la chimio-résistance, ont été étudiés dans les GME et ciblés par l’association rapamycin-irinotecan dans une étude in vitro, pour laquelle des lignées dérivées de GME ont été développées. / Pediatric malignant glioma (PMGs), are associated with a very dismal prognosis. They are distinct from their adult counterparts (AMGs), biologically but also clinically, with a lower response to temozolomide (the current reference alkylating chemotherapy) compared to AMGs. Temozolomide efficacy is reduced by the activity of the DNA repair enzyme, O6-methylguanine-DNA-methyltransferase (MGMT), whose expression is frequently silenced by promoter methylation. First, the development of a new methylation-specific PCR showed a lower frequency of MGMT methylation in PMGs (15%) vs AMGs (45%, p<0,001). Secondly, intra-tumor hypoxia and the upstream deregulation of mTOR-HIF-1α axis, well-known to be involved in chemo-resistance and the up-regulation of MGMT expression, were studied in a PMG cohort. The targeting of this axis was then studied in vitro using a therapy combining rapamycin and irinotecan. For this, pediatric patient-derived malignant glioma cell lines were developed.