Thesis (M. Phil.)--University of Hong Kong, 2006. / Also available online.

Bakgrund: År 1993 identifierades adrenomedullin (ADM) som är en 52 aminosyror långmultifunktionell peptid som utsöndras och syntetiseras från flera olika organ i kroppen. Exakt hur ADM verkar och utsöndras är ännu inte helt klarlagt. Friska personer har normalt en låg ADM,koncentration men vid olika sjukdomar stiger den. ADM påverkar bl.a. hormonet insulin på olika sätt och vid sjukdomen diabetes mellitus typ 2 (DM2) är insulinkänslighet och insulinfrisättning påverkade. Globalt sätt ökar DM2 delvis p.g.a. att befolkningen blir allt mer stillasittande vilket resulterar i att allt fler blir feta. I förlängningen drabbas många av metabola syndromet (MetS) som är en samling av olika komponenter däribland bukfetma och nedsatt glukostolerans. Adipocyterna i buken, och på andra ställen, lagrar och utsöndrar triglycerider under perioder av fasta för energiförsörjning av andra celler. Insulin deltar i fettmetabolismen och hämmar fettnedbrytningen i adipocyterna. Syfte: Syftet var att ta reda på om det är någon skillnad i frisättningen av ADM hos DM2-patienter och friska samt hur ADM frisätts. Vidare undersöks om ADM bildning skiljer sig mellan feta och magra personer. Metod: Arbetet är utfört som en litteraturstudie där databasen PubMed använts för att söka vetenskapliga artiklar. Sex studier inkluderades i arbetet. Resultat: Resultaten från studierna visar att koncentrationen av ADM ökar vid sjukdomstillstånd som DM2. Vid diabetskomplikationer blir koncentrationer ännu högre. Feta kvinnor syntetiserar mer ADM i omental-fettväv jämfört med magra. Slutsats: Koncentrationen av ADM ökar med ökande svårighetsgrad av diabeteskomplikationer som nefropati. ADM bildas i större uträckning i omental-vävnad hos feta kvinnor jämfört med magra.

In der vorliegenden Arbeit wurde erstmals mit Hilfe von drei unterschiedlichen experimentellen Modellen der Einfluß von Adrenomedullin (ADM) auf die myokardiale Kontraktilität des Rattenherzens untersucht. Die Methodik umfaßte die Verwendung des isolierten Herzen nach Langendorff, des isolierten Papillarmuskelpräparats und der konfokalen Laserscan Mikroskopie bei adulten Kardiomyozyten. In keinem der Ansätze konnte ein direkter Effekt von ADM auf die Kontraktilität nachgewiesen werden. An isolierten adulten Kardiomyozyten hatte ADM weder Einfluß auf die systolische Zellverkürzung noch auf den gleichzeitig registrierten zytosolischen Kalziumgehalt. Auch an isolierten Papillarmuskeln verursachte ADM keine Änderung der maximalen Kraftentwicklung oder Kraftanstiegsgeschwindigkeit. Endothelin-1 wurde sowohl am Papillarmuskelpräparat als auch an isolierten, adulten Kardiomyozyten als Positiv-Kontrolle verwendet und verursachte in beiden Versuchsaufbauten einen deutlichen Anstieg der kontraktilen Parameter. Als dritte Methode wurde das isoliert perfundierte Herz nach Langendorff verwendet. Unter Gabe von ADM zeigte sich ein Abfall des koronaren Perfusionsdrucks, entsprechend den bereits bekannten vasodilatierenden Eigenschaften des Peptids. Dieser Effekt war zwar begleitet von einer Abnahme der kontraktilen Parameter der Herzen, allerdings ist am isoliert und flußkonstant perfundierten Herz eine Abnahme des koronaren Perfusionsdrucks aufgrund des Gregg-Phänomes mit einer Abnahme der Kontraktilität vergesellschaftet. Aus den Ergebnissen dieser Arbeit kann daher der Schluß gezogen werden, das Adrenomedullin keinen Einfluß auf die Kontraktilität des Rattenherz hat. / The objective of this study was to investigate the influence of Adrenomedullin (ADM) on myocardial contractility of the rat heart in three different experimental models. First in the isolated rat heart preparation (Langendorf), second on the isolated papillary muscle preparation and third with confocal laserscan microscopy of isolated adult cardiomyocytes. None of these experimental models could show a direct effect of ADM on the contractility of the rat heart. In isolated adult cardiomyocytes, ADM had no influence on systolic cell shorting or on the simultaneously registered cytosolic calcium concentration. In isolated papillary muscle preparation ADM administration did not change maximal contractile force or time constants of contraction. Endothelin-1 was used as a positive control in both experimental setups and induced a marked increase in contraction parameters. In the isolated rat heart preparation (Langendorff), ADM induced a decrease of the coronary perfusion pressure, reflecting the already well described vasodilatatory properties of this peptide. This decrease was paralleled by a reduction of the contractile parameters of the heart, but in isolated rat heart preparations with constant coronary flow, a reduction of coronary perfusion pressure is always paralleled by a decrease of contractility due to the Gregg-Phenomenon. In conclusion the results of this study show that Adrenomedullin has no influence on myocardial contractility in the rat heart.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Anatomy / Master / Master of Philosophy

La croissance tumorale et le processus de métastatisation dépendent de la néoformation de vaisseaux sanguins ou néoangiogenèse. Parmi les molécules intervenant dans ce processus, l'adrenomédul1ine (AM) est un peptide, dont l'expression est corrélée à l'agressivité de certaines tumeurs, et qui représente un maillon «clé» dans les interactions entre les cellules tumorales et les cellules du microenvironnement. Les résultats spectaculaires qu'offre le traitement des xénogreffes de cellules issues de glioblastomes (GBM) humains par les anticorps dirigés contre l'AM ou son récepteur sont très encourageants, puisque la tumeur traitée régresse en quelques semaines, la vascularisation tumorale s'en trouve touchée de manière spécifique. C'est dans ce contexte, que nous avons choisi de poursuivre notre travail sur les mécanismes d'action de l'AM dans la néoangiogenèse. Grâce à des études in vitro et in vivo, nous avons pu montrer que l'AM est impliquée dans plusieurs étapes de la néoangiogenèse tumorale : migration des cellules endothéliales, stabilisation des contacts endothéliaux et endothélio-péricytaires, recrutement des cellules mésenchymateuses. Nos résultats démontrent que nous sommes en présence d'une molécule d'AM qui agit sur diverses cibles moléculaires et cellulaires, régulant la stabilité du complexe d”adhésion intercellulaire VE-cadhérine/-caténine, nécessaire à la protection des interactions homotypiques et hétérotypiques de l°endothélium nouvellement formé. Ainsi, l'étude des mécanismes d'action de l'AM réalisée pennettra d'établir ue stratégie thérapeutique autour de l'AM. / Tumoral growth and process of metastatization depend on the formation of new blood vessels or angiogenesis. Among the molecules implicated in this process, adrenomedullin (AM) is a peptide, which expression is correlated with the aggressiveness of tumors, and which represents a "key" link in the interactions between tumoral cells and the microenvironment cells. The spectacular results offered by the treatment of human glioblastoma (GBM) xenograft by antibodies directed against the AM or its receptor are very encouraging, as the treated tumor declines in some weeks, and the tumoral vascularization is also touched in a specific way. In this context, we chose to pursue our work on the mechanisms of action of AM in angiogenesis. In vitro and in vivo studies showed that AM is involved in several stages of tumoral angiogenesis : migration of endothelial cells, stabilization of endothelial contacts, stabilization of the pericyte coverage, recruitment of multipotent cells. Our results demonstrate that we are in presence of a molecule of AM which acts on diverse molecular and cellular targets, regulating the stability of the VE-cadherin/β-catenin complex, required for the protection of the homotypics and heterotypics interactions of the newly formed endothelium. The study of the mechanisms of action of AM realized will allow us to establish a therapeutic strategy around AM.

Le cancer du sein est la première cause de mortalité chez la femme par cancer. Différents travaux ont montré l’implication des fibroblastes associés au cancer (CAFs) dans la résistance thérapeutique, ainsi que leur rôle dans le développement de cancer du sein. L’adrénomédulline (AM) joue un rôle crucial dans la croissance des tumeurs. Dans notre étude, nous nous sommes interrogés sur l’apport de l’AM sécrétée par la composante majeure du stroma tumoral les CAFs, dans le développement du cancer du sein. Dans cette étude nous avons montré que les CAFs isolés à partir des tumeurs issues du cancer du sein, présentent une augmentation de l’expression du système d’AM (AM et ses récepteurs) par rapport aux fibroblastes non activés (NHDFs). Nos études dans le modèle d’angiogenèse in vivo montrent que les CAFs sont plus compétents à mettre en place une vascularisation stable et fonctionnelle par rapport aux NHDFs. Cependant, le traitement des souris avec des anticorps anti récepteurs de l’AM (αAMRs) bloque la vascularisation. De plus, les xénogreffes issues du mélange MCF-7/CAFs génèrent des tumeurs plus importantes par rapport aux tumeurs issues de MCF-7 seules ou combinées aux NHDFs. Les souris traitées par voie i.p. avec des αAMRs ou l’antagoniste AM22-52, montrent une inhibition de la croissance tumorale des xénogreffes. Les études immunohistochimiques montrent une vascularisation bien établie chez le groupe MCF-7/CAFs, qui est altérée suite au blocage du système de l’AM.Notre étude montre le rôle important de l’AM sécrétée par les CAFs dans le processus de la tumorigenèse du cancer du sein. / Breast cancer is the leading cause of death among women with cancer. Various studies have shown the involvement of cancer associated fibroblasts (CAFs) in this therapeutic resistance and their role in the development of the tumor. Adrenomedullin (AM) plays a critical role in tumor growth. In our study, we asked about the contribution of AM secreted by the major component of the tumor stroma CAFs in breast cancer development. In this study, we demonstrate that CAFs isolated from tumors derived from breast cancer, showed an increase in the expression of AM (AM and its receptors) compared to non-activated fibroblasts (NHDFs). Our studies in vivo angiogenesis model shows that CAFs are more competent to set-up a stable and functional vasculature compared to NHDFs. However, treatment of mice with antibodies anti AM receptor (αAMRs) blocks vascularization, indicating the role of AM secreted by CAFs in the establishment of neovascularization. Additionally, xenografts from MCF-7 mixture / CAFs generate larger tumors compared to tumors from MCF-7 alone or combined with NHDFs. Mice treated, mice treated by intra-peritoneal (i.p.) injection with αAMRs or antagonist AM22-52, show inhibition of tumor growth of xenografts. Immunohistochemical studies show an established vasculature in the MCF-7 / CAFs group, which is impaired due to the blocking of the AM system.Our study shows the important role of the AM secreted by CAFs in the process of breast cancertumorigenesis. It provides an evidence of the effectiveness of a therapy anti-AM, which will target as one of the most predominant components of breast cancer tumor microenvironment.

Le mésothéliome pleural malin (MPM) est un cancer rare et de mauvais pronostic. Le diagnostic de MPM restant difficile à ce jour, nous avons tout d'abord évalué l'intérêt de l'analyse du transcriptome, à partir des cellules présentes dans le liquide pleural, à des fins diagnostiques. Si cette approche parait faisable, ses contraintes techniques la rendent incompatibles avec une utilisation en routine. Notre deuxième axe de travail s'est inscrit dans le domaine du traitement local du MPM, avec l'évaluation de l'administration intrapleurale (IP) de deux molécules de chimiothérapie : le pemetrexed et le lipoplatine. Les résultats sur modèle animal montrent que les profils pharmacocinétiques de ces deux molécules sont significativement différents entre une administration intraveineuse et une administration IP. Dans l'optique d'identifier de nouvelles cibles thérapeutiques, nous avons évalué la voie de l'adrénomédulline (AM) dans le MPM. L'AM et ses récepteurs sont conjointement exprimés dans les biopsies pleurales de MPM. In vitro, l'AM augmente les capacités de prolifération, de migration et d'invasion des cellules de MPM, par l'intermédiaire de la voie des MAPK. L'inhibition de l'AM ou de ses récepteurs apparait comme une stratégie thérapeutique prometteuse dans le MPM, de part ses effets directs sur les cellules néoplasiques, mais aussi ses effets indirects, via une inhibition de l'angiogénèse et de la lymphangiogénèse tumorale (in vivo). Enfin, nous avons évalué de nouveaux critères de jugement pour les essais cliniques de phase II. Nous avons montré que le taux de survie sans progression à 9 semaines est le critère le plus performant pour prédire la survie globale. / Malignant pleural mesothelioma (MPM) is a rare cancer with poor prognosis. As MPM diagnosis remains difficult today, we first assessed the potential value of transcriptome analysis, from cells in pleural fluid, with diagnostic purpose. If this approach looks feasible, its technical constraints make it incompatible with routine practice. The second axis of our work concerned MPM local treatment, with the assessment of intrapleural (IP) administration of two chemotherapy drugs: pemetrexed and lipoplatin. Results obtained in an animal model show that the pharmacokinetic profiles of these two drugs are significantly different between intravenous and IP administration. With the goal of identifying new therapeutic targets, we explored the adrenomedullin (AM) pathway in MPM. AM and its receptors are jointly expressed in pleural biopsies from MPM. Moreover we demonstrated in vitro that AM increases the proliferation, migration and invasion abilities of MPM cells, through the MAPK signaling pathway. Inhibition of AM or its receptors appears as a promising therapeutic strategy, because of its direct effects on malignant cells, but also its indirect effects, via tumor angiogenesis and lymphangiogenesis inhibition (in vivo). Finally, we assessed new endpoints for phase II clinical studies. We showed that the progression-free survival rate at 9 weeks is the most performant criterion to predict overall survival.

Introdução: Adrenomedulina, peptídeo recentemente identificado, atua como mediador em diversos estados fisiológicos e patológicos, sendo expresso em inúmeros tecidos. Níveis elevados de adrenomedulina foram observados em quadros inflamatórios e sépticos, além de atividade inibitória da adrenomedulina sobre a liberação de insulina, o que poderia contribuir para a gênese e manutenção dos quadros hipeglicêmicos, situação comum em pacientes pediátricos internados em unidades de terapia intensiva, tendo sido comprovado que o controle glicêmico melhora o prognóstico nesses pacientes. O objetivo do estudo foi relacionar as concentrações de adrenomedulina com alterações de hormônios do eixo hipófise-adrenal e o controle glicêmico de crianças submetidas à cirurgia cardíaca com circulação extracorpórea (CEC) representando modelo de síndrome da resposta inflamatória sistêmica. Material e métodos: Foram incluídas 20 crianças com idade entre 11-84 meses submetidas à cirurgia cardíaca com CEC. Foram avaliadas concentrações sangüíneas de glicose, insulina, peptídeo-C, cortisol, ACTH, interleucina-6 e adrenomedulina nos tempos pré-CEC, pós-CEC, 1ºPO, 2ºPO e 3ºPO. Os resultados foram expressos em medianas e inter-quartis. Todas crianças receberam antibioticoterapia profilática (Cefuroxima 150mg/kg) e metilprednisolona (30mg/kg) na indução anestésica. Resultados: Adrenomedulina aumentou de 1,13 ng/mL (0.83 1.81) pré- CEC a 3,28 ng/mL (1.82 4.25) no 1ºPO (p=0,0005). A insulina e o peptídeo-C apresentaram queda do tempo pré-CEC ao 1ºPO: 10,9 U/mL (10.5 13.6) a 2,88 U/mL (1.68 3.46) (p= 0,0001) e 1,44 (0.93 2.08) a 0.89 ng/mL (0.58 2.06) (p=0,076), respectivamente. Houve aumento da glicemia de 86,5 mg/dL (67 88) pré-CEC a 169 mg/dL (153 201) no 1ºPO (p=0,0001). Não houve alterações significativas das concentrações de cortisol e ACTH. Após a CEC todas as concentrações de interleucina-6 encontravam-se elevadas retornando aos valores normais no 3ºPO. Houve correlação negativa entre as concentrações de peptídeo-C e de adrenomedulina no 1ºPO (R= - 0,70 - p< 0,0009). Conclusão: os resultados deste estudo indicam que a adrenomedulina possa ter contribuído para a gênese e manutenção da hiperglicemia em pacientes pediátricos com SRIS, agindo por intermédio da redução das concentrações de insulina e do peptídeo-C / Background: Adrenomedullin (AM), a recently identified vasoactive peptide, is expressed in a large number of tissues and was found to be increased in some pathophysiologic conditions such as sepsis and Systemic Inflammatory Response Syndrome (SIRS). It has been shown that AM inhibits insulin secretion by means of a direct action on pancreatic -cells thus contributing to the genesis and sustaining of hypeglicemia, a common condition in critically ill pediatric patients. Therefore, the strict control of glucose concentrations has proved beneficial and associated to decrement of morbimortality rates in adults and children. The aim of the present study was to monitor serum adrenomedullin concentration in parallel with interleukin-6, plasma glucose, insulin and C-peptide, as well as ACTH and cortisol in pediatric patients submitted to cardiac surgery and cardiopulmonary bypass (CPB) representing a SIRS model. Methods: Twenty children aged 11-84 months who underwent cardiac surgery requiring cardiopulmonary bypass were prospective studied. Blood glucose, insulin, C-peptide, adrenocorticotropic hormone, cortisol, interleukin- 6 and AM were measured immediately before cardiopulmonary bypass (BCPB), immediately after CPB, on the first (POD1), second (POD2) and third days (POD3) after surgery. Data were expressed by median values and inter quartile range. All children received profilatic antibiotic (cefuroxime 150mg/kg) and methylprednisolone (30mg/kg) during induction of anesthesia. Results: Adrenomedullin increased from 1.13 ng/mL (0.83 1.81) BCPB to 3.28 ng/mL (1.82 4.25) in POD1 (p=0.0005). Insulin dropped from 10.9 U/mL (10.5 13.6) BCPB to 2.88 U/mL (1.68 3.46) in POD1 (p=0.0000). C-peptide decreased from 1.44 (0.93 2.08) BCPB to 0.89 ng/mL (0.58 2.06) in POD1 (p=0.076). Glucose increased from 86.5 mg/dL (67 88) BCPB to 169 mg/dL (153 201) in POD1 (p=0.0000). No significant changes were observed in ACTH and cortisol levels. After CPB, IL-6 concentrations of all patients were significantly increased and returned to basal values in POD3 (p=0.0009). There was a negative correlation between C-peptide an adrenomedullin in POD1 (R= - 0.70 - p< 0.0009). Conclusion: Our results indicate that adrenomedullin might be partly responsible for the genesis and sustaining of hyperglycemia in pediatric SIRS patients, by means of the decrement of insulin and C- peptide levels

Introdução: Adrenomedulina, peptídeo recentemente identificado, atua como mediador em diversos estados fisiológicos e patológicos, sendo expresso em inúmeros tecidos. Níveis elevados de adrenomedulina foram observados em quadros inflamatórios e sépticos, além de atividade inibitória da adrenomedulina sobre a liberação de insulina, o que poderia contribuir para a gênese e manutenção dos quadros hipeglicêmicos, situação comum em pacientes pediátricos internados em unidades de terapia intensiva, tendo sido comprovado que o controle glicêmico melhora o prognóstico nesses pacientes. O objetivo do estudo foi relacionar as concentrações de adrenomedulina com alterações de hormônios do eixo hipófise-adrenal e o controle glicêmico de crianças submetidas à cirurgia cardíaca com circulação extracorpórea (CEC) representando modelo de síndrome da resposta inflamatória sistêmica. Material e métodos: Foram incluídas 20 crianças com idade entre 11-84 meses submetidas à cirurgia cardíaca com CEC. Foram avaliadas concentrações sangüíneas de glicose, insulina, peptídeo-C, cortisol, ACTH, interleucina-6 e adrenomedulina nos tempos pré-CEC, pós-CEC, 1ºPO, 2ºPO e 3ºPO. Os resultados foram expressos em medianas e inter-quartis. Todas crianças receberam antibioticoterapia profilática (Cefuroxima 150mg/kg) e metilprednisolona (30mg/kg) na indução anestésica. Resultados: Adrenomedulina aumentou de 1,13 ng/mL (0.83 1.81) pré- CEC a 3,28 ng/mL (1.82 4.25) no 1ºPO (p=0,0005). A insulina e o peptídeo-C apresentaram queda do tempo pré-CEC ao 1ºPO: 10,9 U/mL (10.5 13.6) a 2,88 U/mL (1.68 3.46) (p= 0,0001) e 1,44 (0.93 2.08) a 0.89 ng/mL (0.58 2.06) (p=0,076), respectivamente. Houve aumento da glicemia de 86,5 mg/dL (67 88) pré-CEC a 169 mg/dL (153 201) no 1ºPO (p=0,0001). Não houve alterações significativas das concentrações de cortisol e ACTH. Após a CEC todas as concentrações de interleucina-6 encontravam-se elevadas retornando aos valores normais no 3ºPO. Houve correlação negativa entre as concentrações de peptídeo-C e de adrenomedulina no 1ºPO (R= - 0,70 - p< 0,0009). Conclusão: os resultados deste estudo indicam que a adrenomedulina possa ter contribuído para a gênese e manutenção da hiperglicemia em pacientes pediátricos com SRIS, agindo por intermédio da redução das concentrações de insulina e do peptídeo-C / Background: Adrenomedullin (AM), a recently identified vasoactive peptide, is expressed in a large number of tissues and was found to be increased in some pathophysiologic conditions such as sepsis and Systemic Inflammatory Response Syndrome (SIRS). It has been shown that AM inhibits insulin secretion by means of a direct action on pancreatic -cells thus contributing to the genesis and sustaining of hypeglicemia, a common condition in critically ill pediatric patients. Therefore, the strict control of glucose concentrations has proved beneficial and associated to decrement of morbimortality rates in adults and children. The aim of the present study was to monitor serum adrenomedullin concentration in parallel with interleukin-6, plasma glucose, insulin and C-peptide, as well as ACTH and cortisol in pediatric patients submitted to cardiac surgery and cardiopulmonary bypass (CPB) representing a SIRS model. Methods: Twenty children aged 11-84 months who underwent cardiac surgery requiring cardiopulmonary bypass were prospective studied. Blood glucose, insulin, C-peptide, adrenocorticotropic hormone, cortisol, interleukin- 6 and AM were measured immediately before cardiopulmonary bypass (BCPB), immediately after CPB, on the first (POD1), second (POD2) and third days (POD3) after surgery. Data were expressed by median values and inter quartile range. All children received profilatic antibiotic (cefuroxime 150mg/kg) and methylprednisolone (30mg/kg) during induction of anesthesia. Results: Adrenomedullin increased from 1.13 ng/mL (0.83 1.81) BCPB to 3.28 ng/mL (1.82 4.25) in POD1 (p=0.0005). Insulin dropped from 10.9 U/mL (10.5 13.6) BCPB to 2.88 U/mL (1.68 3.46) in POD1 (p=0.0000). C-peptide decreased from 1.44 (0.93 2.08) BCPB to 0.89 ng/mL (0.58 2.06) in POD1 (p=0.076). Glucose increased from 86.5 mg/dL (67 88) BCPB to 169 mg/dL (153 201) in POD1 (p=0.0000). No significant changes were observed in ACTH and cortisol levels. After CPB, IL-6 concentrations of all patients were significantly increased and returned to basal values in POD3 (p=0.0009). There was a negative correlation between C-peptide an adrenomedullin in POD1 (R= - 0.70 - p< 0.0009). Conclusion: Our results indicate that adrenomedullin might be partly responsible for the genesis and sustaining of hyperglycemia in pediatric SIRS patients, by means of the decrement of insulin and C- peptide levels