Endothelin receptor b (Ednrb) and its ligand Endothelin 3 (Edn3) have been implicated in melanoma. Several studies have shown an upregulation of EDNRB and EDN3 at both the protein and mRNA levels, as melanoma becomes more aggressive. This study investigated the putative role played by Edn3 over-expression in melanoma progression and angiogenesis in vivo. We crossed Tg(Grm1)Epv transgenic mice that aberrantly express metabotropic glutamate receptor1 under the Dopachrome tautomerase promoter, leading to spontaneous melanocytic lesions in the ears and tails that do not metastasize, with transgenics that overexpress Edn3 under the Keratin 5 promoter (K5-Edn3) or overexpress Ednrb in melanocytes (Tg(Ednrb)1Lk). In both the Tg(Grm1)Epv/K5-Edn3 and Tg(Grm1)Epv/Tg(Ednrb)1Lk mice, tumors appeared earlier and grew significantly larger and faster when compared to Tg(Grm1)Epv mice. Approximately eighty-one percent of Tg(Grm1)Epv/ K5-Edn3 mice and 76% of Tg(Grm1)Epv/Tg(Ednrb)1Lk mice had pigmented lesions in distant organs such as the lung and brain. Real-Time PCR analysis showed higher expression levels of genes involved in cell-cell and cell-matrix interactions and angiogenesis in lesions of Tg(Grm1)Epv/K5-Edn3 when compared to controls. Considering the rapid tumor growth rate of in the Tg(Grm1)Epv/K5-Edn3 mice, differences in the angiogenic response compared to control mice were investigated. Immunofluorescence analysis with the endothelial cell marker CD31 showed that there were more endothelial cells per tumor area in the Tg(Grm1)Epv/K5-Edn3 mice than the controls. Proteome analysis showed that the Dct-Grm1/K5-Edn3 mice had significant increases in other angiogenic related genes such as Angiogenin, CXCL 16 and Endoglin, when compared to controls, while real time PCR analysis of tail tumors also showed higher expression levels of angiogenic related genes such as Hif-1α. The results of this study showed that the EDNRB/EDN3 axis is sufficient to alter the kinetics of melanocytic tumors’ progression, lead them to a fully malignant state, and increase the tumor angiogenic response.

Para avaliar os efeitos de angiotensina II (Ang II) ou endotelina-3 (ET-3), ratos Wistar foram organizados nos grupos: controle, tratados com Ang II ou ET-3 por 42 dias, tratados com losartan, atrasentan ou BQ788 ou co-tratados com Ang II e losartan ou ET-3 e atrasentan ou BQ 788. Foram avaliados: pressão arterial, concentrações plasmáticas e intrarrenais das Angs e ETs, morfologia e função renal. A Ang II induziu hipertensão arterial, aumentou as concentrações plasmáticas das ETs e das Angs e a expressão de RNAm para renina; induziu injuria glomerular e remodelamento das arteríolas renais. O tratamento com losartan reverteu a maioria dos efeitos da Ang II. A ET-3 induziu hipertensão arterial, injúria glomerular, alteração da função renal e aumento de RNAm intrarrenal para os componentes do SRA. O bloqueio do receptor ETA atenuou os efeitos de ET-3 na hipertensão, enquanto o bloqueio de ETB foi melhor nos parâmetros renais. Nossos resultados sugerem uma interação entre os sistemas SRA e endotelinas, induzindo mudanças na estrutura e função renal. / To evaluate the chronic effects of angiotensin II (Ang II) and /or losartan or endothelin-3 (ET-3) and /or atrasentan or BQ788, Wistar rats were organized as: control, treated with Ang II, or ET-3 for 42 days, losartan-treated, co-treated with Ang II and losartan. Treated with ET-3, treated with BQ788 or atrasentan, co-treated with ET-3 and antagonists. Were evaluated: blood pressure, plasma and intrarenal concentrations of Angs and ETs, protein expression, renal morphology and function. Ang II induced hypertension, increased plasma levels of ETs and Angs; increased mRNA for renin; induced glomerular injury and renal arterioles remodeling. Treatment with losartan restored most of the changes induced by Ang II. ET-3 induced hypertension, glomerular injury, renal dysfunction and increased intrarenal mRNA for SRA components. The ETA receptor blockage reverted the ET-3 effects on hypertension, while ETB blockage reverted renal parameters. Our results suggest a crosstalk of renin-angiotensin and endothelin systems, inducing renal structural and functional changes.

<p><em>Panax ginseng</em> is a traditional herb that has been used for over 2000 years to promote health and longevity. Active components of ginseng include ginsenosides, polysaccharides, flavonoids, polyacetylenes, peptides, vitamins, phenols and enzymes, of which the ginsenosides are considered to be the major bioactive constituents. Although widely used, the exact mechanisms of ginseng and its compounds remain unclear. In this thesis we use melanophores from <em>Xenopus laevis</em> to investigate the effects of <em>Panax ginseng</em> extract G115 and its constituents on organelle transport and signalling. Due to coordinated bidirectional movement of their pigmented granules (melanosomes), in response to defined chemical signals, melanophores are capable of fast colour changes and provide a great model for the study of intracellular transport. The movement is regulated by alterations in cyclic adenosine 3’:5’-monophosphate (cAMP) concentration, where a high or low level induce anterograde (dispersion) or retrograde (aggregation) transport respectively, resulting in a dark or light cell. Here we demonstrate that <em>Panax ginseng</em> and its constituents ginsenoside Rc and Rd and flavonoid quercetin induce a concentration-dependent anterograde transport of melanosomes. The effect of ginseng is shown to be independent of cAMP changes and protein kinase A activation. Upon incubation of melanophores with a combination of Rc or Rd and quercetin, a synergistic increase in anterograde movement was seen, indicating cooperation between the ginsenoside and flavonoid parts of ginseng. Protein kinase C (PKC) inhibitor Myristoylated EGF-R Fragment 651-658 decreased the anterograde movement stimulated by ginseng and ginsenoside Rc and Rd. Moreover, ginseng, but not ginsenosides or quercetin, stimulated an activation of 44/42-mitogen activated protein kinase (MAPK), previously shown to be involved in both aggregation and dispersion of melanosomes. PKC-inhibition did not affect the MAPK-activation, suggesting a role for PKC in the ginseng- and ginsenoside-induced dispersion but not as an upstream activator of MAPK.</p> / <p><em>Panax ginseng </em>är ett av de vanligaste naturläkemedlen i världen och används traditionellt för att öka kroppens uthållighet, motståndskraft och styrka. Ginseng är ett komplext ämne bestående av ett antal olika substanser, inklusive ginsenosider, flavonoider, vitaminer och enzymer, av vilka de steroidlika ginsenosiderna anses vara de mest aktiva beståndsdelarna. Flavonoider (som finns i till exempel frukt och grönsaker) och ginseng har genom forskning visat sig motverka bland annat hjärt-och kärlsjukdomar, diabetes, cancer och demens. Trots den omfattande användningen är dock mekanismen för hur ginseng verkar fortfarande oklar. I den här studien har vi använt pigmentinnehållande celler, melanoforer, från afrikansk klogroda för att undersöka effekterna av <em>Panax ginseng</em> på pigment-transport och dess maskineri. Melanoforer har förmågan att snabbt ändra färg genom samordnad förflyttning av pigmentkorn fram och tillbaka i cellen, och utgör en utmärkt modell för studier av intracellulär transport. Förflyttningen regleras av förändringar i halten av cykliskt adenosin-monofosfat (cAMP) i cellen, där en hög eller låg koncentration medför spridning av pigment över hela cellen (dispergering) eller en ansamling i mitten (aggregering), vilket resulterar i mörka respektive ljusa celler. Här visar vi att <em>Panax ginseng</em>, ginsenosiderna Rc och Rd samt flavonoiden quercetin stimulerar en dispergering av pigmentkornen. När melanoforerna inkuberades med en kombination av ginsenosid Rc eller Rd och quercetin, kunde en synergistisk ökning av dispergeringen ses, vilket tyder på en samverkan mellan ginsenosid- och flavonoid-delarna av ginseng. Ett protein som tidigare visats vara viktigt för pigmenttransporten är mitogen-aktiverat protein kinas (MAPK), och här visar vi att också melanoforer stimulerade med ginseng, men dock inte med ginsenosider eller quercetin, innehåller aktiverat MAPK. Genom att blockera enzymet protein kinas C (PKC) (känd aktivator av dispergering), minskade den ginseng- och ginsenosid-inducerade dispergeringen, medan aktiveringen av MAPK inte påverkades alls. Detta pekar på en roll för PKC i pigment-transporten men inte som en aktivator av MAPK.</p>

Panax ginseng is a traditional herb that has been used for over 2000 years to promote health and longevity. Active components of ginseng include ginsenosides, polysaccharides, flavonoids, polyacetylenes, peptides, vitamins, phenols and enzymes, of which the ginsenosides are considered to be the major bioactive constituents. Although widely used, the exact mechanisms of ginseng and its compounds remain unclear. In this thesis we use melanophores from Xenopus laevis to investigate the effects of Panax ginseng extract G115 and its constituents on organelle transport and signalling. Due to coordinated bidirectional movement of their pigmented granules (melanosomes), in response to defined chemical signals, melanophores are capable of fast colour changes and provide a great model for the study of intracellular transport. The movement is regulated by alterations in cyclic adenosine 3’:5’-monophosphate (cAMP) concentration, where a high or low level induce anterograde (dispersion) or retrograde (aggregation) transport respectively, resulting in a dark or light cell. Here we demonstrate that Panax ginseng and its constituents ginsenoside Rc and Rd and flavonoid quercetin induce a concentration-dependent anterograde transport of melanosomes. The effect of ginseng is shown to be independent of cAMP changes and protein kinase A activation. Upon incubation of melanophores with a combination of Rc or Rd and quercetin, a synergistic increase in anterograde movement was seen, indicating cooperation between the ginsenoside and flavonoid parts of ginseng. Protein kinase C (PKC) inhibitor Myristoylated EGF-R Fragment 651-658 decreased the anterograde movement stimulated by ginseng and ginsenoside Rc and Rd. Moreover, ginseng, but not ginsenosides or quercetin, stimulated an activation of 44/42-mitogen activated protein kinase (MAPK), previously shown to be involved in both aggregation and dispersion of melanosomes. PKC-inhibition did not affect the MAPK-activation, suggesting a role for PKC in the ginseng- and ginsenoside-induced dispersion but not as an upstream activator of MAPK. / Panax ginseng är ett av de vanligaste naturläkemedlen i världen och används traditionellt för att öka kroppens uthållighet, motståndskraft och styrka. Ginseng är ett komplext ämne bestående av ett antal olika substanser, inklusive ginsenosider, flavonoider, vitaminer och enzymer, av vilka de steroidlika ginsenosiderna anses vara de mest aktiva beståndsdelarna. Flavonoider (som finns i till exempel frukt och grönsaker) och ginseng har genom forskning visat sig motverka bland annat hjärt-och kärlsjukdomar, diabetes, cancer och demens. Trots den omfattande användningen är dock mekanismen för hur ginseng verkar fortfarande oklar. I den här studien har vi använt pigmentinnehållande celler, melanoforer, från afrikansk klogroda för att undersöka effekterna av Panax ginseng på pigment-transport och dess maskineri. Melanoforer har förmågan att snabbt ändra färg genom samordnad förflyttning av pigmentkorn fram och tillbaka i cellen, och utgör en utmärkt modell för studier av intracellulär transport. Förflyttningen regleras av förändringar i halten av cykliskt adenosin-monofosfat (cAMP) i cellen, där en hög eller låg koncentration medför spridning av pigment över hela cellen (dispergering) eller en ansamling i mitten (aggregering), vilket resulterar i mörka respektive ljusa celler. Här visar vi att Panax ginseng, ginsenosiderna Rc och Rd samt flavonoiden quercetin stimulerar en dispergering av pigmentkornen. När melanoforerna inkuberades med en kombination av ginsenosid Rc eller Rd och quercetin, kunde en synergistisk ökning av dispergeringen ses, vilket tyder på en samverkan mellan ginsenosid- och flavonoid-delarna av ginseng. Ett protein som tidigare visats vara viktigt för pigmenttransporten är mitogen-aktiverat protein kinas (MAPK), och här visar vi att också melanoforer stimulerade med ginseng, men dock inte med ginsenosider eller quercetin, innehåller aktiverat MAPK. Genom att blockera enzymet protein kinas C (PKC) (känd aktivator av dispergering), minskade den ginseng- och ginsenosid-inducerade dispergeringen, medan aktiveringen av MAPK inte påverkades alls. Detta pekar på en roll för PKC i pigment-transporten men inte som en aktivator av MAPK.

Para avaliar os efeitos de angiotensina II (Ang II) ou endotelina-3 (ET-3), ratos Wistar foram organizados nos grupos: controle, tratados com Ang II ou ET-3 por 42 dias, tratados com losartan, atrasentan ou BQ788 ou co-tratados com Ang II e losartan ou ET-3 e atrasentan ou BQ 788. Foram avaliados: pressão arterial, concentrações plasmáticas e intrarrenais das Angs e ETs, morfologia e função renal. A Ang II induziu hipertensão arterial, aumentou as concentrações plasmáticas das ETs e das Angs e a expressão de RNAm para renina; induziu injuria glomerular e remodelamento das arteríolas renais. O tratamento com losartan reverteu a maioria dos efeitos da Ang II. A ET-3 induziu hipertensão arterial, injúria glomerular, alteração da função renal e aumento de RNAm intrarrenal para os componentes do SRA. O bloqueio do receptor ETA atenuou os efeitos de ET-3 na hipertensão, enquanto o bloqueio de ETB foi melhor nos parâmetros renais. Nossos resultados sugerem uma interação entre os sistemas SRA e endotelinas, induzindo mudanças na estrutura e função renal. / To evaluate the chronic effects of angiotensin II (Ang II) and /or losartan or endothelin-3 (ET-3) and /or atrasentan or BQ788, Wistar rats were organized as: control, treated with Ang II, or ET-3 for 42 days, losartan-treated, co-treated with Ang II and losartan. Treated with ET-3, treated with BQ788 or atrasentan, co-treated with ET-3 and antagonists. Were evaluated: blood pressure, plasma and intrarenal concentrations of Angs and ETs, protein expression, renal morphology and function. Ang II induced hypertension, increased plasma levels of ETs and Angs; increased mRNA for renin; induced glomerular injury and renal arterioles remodeling. Treatment with losartan restored most of the changes induced by Ang II. ET-3 induced hypertension, glomerular injury, renal dysfunction and increased intrarenal mRNA for SRA components. The ETA receptor blockage reverted the ET-3 effects on hypertension, while ETB blockage reverted renal parameters. Our results suggest a crosstalk of renin-angiotensin and endothelin systems, inducing renal structural and functional changes.

Melanoma is one of the most aggressive types of cancer. It originates from the transformation of melanocytes present in the epidermal/dermal junction of the human skin. It is commonly accepted that melanomagenesis is influenced by the interaction of environmental factors, genetic factors, as well as tumor-host interactions. DNA photoproducts induced by UV radiation are, in normal cells, repaired by the nucleotide excision repair (NER) pathway. The prominent role of NER in cancer resistance is well exemplified by patients with Xeroderma Pigmentosum (XP). This disease results from mutations in the components of the NER pathway, such as XPA and XPC proteins. In humans, NER pathway disruption leads to the development of skin cancers, including melanoma. Similar to humans afflicted with XP, Xpa and Xpc deficient mice show high sensibility to UV light, leading to skin cancer development, except melanoma. The Endothelin 3 (Edn3) signaling pathway is essential for proliferation, survival and migration of melanocyte precursor cells. Excessive production of Edn3 leads to the accumulation of large numbers of melanocytes in the mouse skin, where they are not normally found. In humans, Edn3 signaling pathway has also been implicated in melanoma progression and its metastatic potential. The goal of this study was the development of the first UV-induced melanoma mouse model dependent on the over-expression of Edn3 in the skin. The UV-induced melanoma mouse model reported here is distinguishable from all previous published models by two features: melanocytes are not transformed a priori and melanomagenesis arises only upon neonatal UV exposure. In this model, melanomagenesis depends on the presence of Edn3 in the skin. Disruption of the NER pathway due to the lack of Xpa or Xpc proteins was not essential for melanomagenesis; however, it enhanced melanoma penetrance and decreased melanoma latency after one single neonatal erythemal UV dose. Exposure to a second dose of UV at six weeks of age did not change time of appearance or penetrance of melanomas in this mouse model. Thus, a combination of neonatal UV exposure with excessive Edn3 in the tumor microenvironment is sufficient for melanomagenesis in mice; furthermore, NER deficiency exacerbates this process.

by Chi Fung Yeung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 83-120). / Abstracts in English and Chinese. / abstract --- p.1 / table of contents --- p.3 / acknowledgments --- p.8 / declaration --- p.9 / list of figures and tables --- p.10 / list of abbreviations --- p.13 / Chapter chapter 1- --- general introduction --- p.15 / Chapter 1.1 --- VASOACTIVE PEPTIDES --- p.18 / Chapter 1.1.1 --- HISTORICAL BACKGROUND --- p.18 / Chapter 1.1.1.1 --- Adrenomedullin --- p.20 / Chapter 1.1.1.2 --- Calcitonin gene-related peptide --- p.21 / Chapter 1.1.1.3 --- Endothelin-3 --- p.22 / Chapter 1.1.2 --- "SYNTHESIS AND RELEASE OF ADRENOMEDULLIN, CALCITONIN GENE RELATED PEPTIDE AND ENDOTHELINS" / Chapter 1.1.2.1 --- SYNTHESIS AND RELEASE OF Adrenomeduulin --- p.24 / Chapter 1.1.2.2 --- SYNTHESIS AND RELEASE OF calcitonin gene related peptide --- p.25 / Chapter 1.1.2.3 --- SYNTHESIS AND RELEASE OF ENDOTHELINS --- p.25 / Chapter 1.1.3 --- "ADRENOMEDULLIN, CALCITONIN GENE RELATED PEPTIDE AND ENDOTHELINS IN THE CNS" --- p.26 / Chapter 1.1.4 --- "RECEPTORS OF ADRENOMEDULLIN, CALCITONIN GENE RELATED PEPTIDE AND ENDOTHELINS AND SIGNAL TRANSDUCTION" --- p.27 / Chapter 1.1.5 --- "BIOLOGICAL ACTIONS OF ADRENOMEDULLIN, CALCITONIN GENE RELATED PEPTIDE AND ENDOTHELINS" / Chapter 1.1.5.1 --- BIOLOGICAL ACTIONS OF ADRENOMEDULLIN --- p.30 / Chapter 1.1.5.1.1 --- haemodynamic effects of adrenomedullin --- p.30 / Chapter 1.1.5.1.2 --- Renal effects of Adrenomedullin --- p.31 / Chapter 1.1.5.1.3 --- Endocrine effects of Adrenomedullin --- p.31 / Chapter 1.1.5.1.4 --- Central effects of Adrenomedullin --- p.32 / Chapter 1.1.5.2 --- CALCITONIN GENE RELATED PEPTIDE / Chapter 1.1.5.2.1 --- haemodynamic effects of calcitonin gene related peptide --- p.33 / Chapter 1.1.5.2.2 --- Renal effects of calcitonin gene related peptide --- p.34 / Chapter 1.1.5.2.3 --- Endocrine effects of calcitonin gene related peptide --- p.34 / Chapter 1.1.5.2.4 --- Central effects of calcitonin gene related peptide --- p.35 / Chapter 1.1.5.3 --- ENDOTHELINS / Chapter 1.1.5.3.1 --- haemodyamic effects of endothelins --- p.36 / Chapter 1.1.5.3.2 --- Renal effects of Endothelins --- p.36 / Chapter 1.1.5.3.3 --- endocrine effects of endothelins --- p.37 / Chapter 1.1.5.3.4 --- Central effects of Endothelins --- p.37 / Chapter 1.1.6. --- PROLIFERATIVE OR ANTI-PROLIFERATIVE EFFECTS --- p.38 / Chapter 1.1.7 --- CLINICAL RELEVANCE OF VASOACTIVE PEPTIDES / Chapter 1.1.7.1 --- Clinical relevance of Adrenomedullin --- p.39 / Chapter 1.1.7.2 --- Clinical relevance of calcitonin gene related peptide --- p.40 / Chapter 1.1.7.3 --- Clinical relevance of Endothelins --- p.41 / Chapter 1.2 --- ASTROCYTES / Chapter 1.2.1 --- Historical background and astrocyte morphology --- p.42 / Chapter 1.2.2 --- Physiological roles of astrocytes --- p.44 / Chapter 1.2.3 --- Pathology of astrocytes --- p.45 / Chapter 1.3 --- NEUROPEPTIDE RECEPTORS AND ASTROCYTES / Chapter 1.3.1 --- Neuropeptide receptors on astrocytes --- p.47 / Chapter 1.3.2 --- Consequences of receptor activation --- p.49 / Chapter 1.4 --- AIMS OF THE THESIS --- p.50 / Chapter CHAPTER 2 --- "GENERAL MATERIALS AND METHODS, AND DATA ANALYSIS" / Chapter 2.1 --- MATERIALS / Chapter 2.1.1 --- ANIMALS --- p.54 / Chapter 2.1.2 --- PEPTIDE HORMONES --- p.54 / Chapter 2.1.3 --- ISOTOPES AND RADIOIMMUNOASSAY KITS --- p.54 / Chapter 2.1.4 --- CULTURE MATERIALS AND CHEMICALS --- p.55 / Chapter 2.1.5 --- PREPARATION OF MATERIALS / Chapter 2.1.5.1 --- Preparation of primary cultures of astrocytes --- p.55 / Chapter 2.1.5.2 --- Preparation of medium and binding buffer --- p.56 / Chapter 2.1.5.3 --- Preparation of 125I-labelled vasoactive peptides --- p.56 / Chapter 2.1.6 --- MEASUREMENT OF CELLULAR CYCLIC AMP --- p.57 / Chapter 2.1.7 --- DETERMINATION OF PROTEIN CONTENT OF CULTURED ASTROCYTES --- p.60 / Chapter 2.2 --- METHODS --- p.61 / Chapter 2.2.1 --- LIGAND BINDING: MEASUREMENT OF 125I-AM AND 125I-CGRP BINDING / Chapter 2.2.1.1 --- Binding kinetics --- p.61 / Chapter 2.2.1.2 --- Determination of specific binding of 125I-AM and 125I-CGRP --- p.61 / Chapter 2.2.1.3 --- Competition binding studies --- p.62 / Chapter 2.2.2 --- "BIOCHEMICAL INTERACTIONS BETWEEN ET3, AM, CGRP AND PKC-ANALOG" / Chapter 2.2.2.1 --- Determination of the production of cAMP in response to AM and CGRP --- p.62 / Chapter 2.2.2.2 --- Determination of the effect of PMA on AM and CGRP-dependent CAMP production --- p.63 / Chapter 2.2.2.3 --- Determination of the effect of the phorbol esters on AM and CGRP-dependent cAMP production --- p.63 / Chapter 2.2.2.4 --- Elucidation of antagonistic effect of staurosporine and Ro31-8220 --- p.64 / Chapter 2.2.2.5 --- Determination of the effects of ET-3 on AM and CGRP- dependent CAMP accumulation --- p.64 / Chapter 2.2.2.6 --- Determination of the effects of PKC inhIBition on ET-3 suppression of AM- and CGRP-induced CAMP responses --- p.64 / Chapter 2.2.2.7 --- Elucidation of antagonistic effect of cycloheximide --- p.65 / Chapter 2.3 --- STATISTIC ANALYSIS --- p.65 / Chapter CHAPTER 3 --- RESULTS / Chapter 3.1 --- BINDING KINETICS OF 125I-AM AND 125I-CGRP --- p.68 / Chapter 3.2 --- SPECIFIC BINDING OF 125I-AM AND 125I-CGRP --- p.68 / Chapter 3.3 --- COMPETITION BINDING --- p.68 / Chapter 3.4 --- DOSE RESPONSE OF ADRENOMEDULLIN AND CGRP- STIMULATED CAMP PRODUCTION --- p.69 / Chapter 3.5 --- EFFECTS OF PHORBOL ESTERS ON AM AND CGRP DEPENDENT CAMP ACCUMULATION --- p.69 / Chapter 3.6 --- EFFECT OF PMA ON AM AND CGRP-DEPENDENT CAMP ACCUMULATION --- p.70 / Chapter 3.7 --- EFFECT OF ET-3 ON AM AND CGRP-DEPENDENT CAMP ACCUMULATION --- p.70 / Chapter 3.8 --- "THE EFFECTS OF STAUROSPORINE, RO 31-8220" --- p.71 / Chapter 3.9 --- EFFECT OF CYCLOHEXIMIDE ON THE SUPPRESSIVE ACTION OF ET3 --- p.72 / Chapter CHAPTER 4 --- DISCUSSION --- p.73 / Chapter CHAPTER 5 --- GENERAL CONCLUSION --- p.80 / REFERENCES --- p.83 / APPENDIX-PUBLISHED PAPER

Le système endothéline (ET) est activé en condition d’hypertension pulmonaire (HTP). L’efficacité des antagonistes des récepteurs à l’ET a clairement été démontrée et a menée à l’approbation clinique de tels antagonistes dans le traitement de l’hypertension artérielle pulmonaire (HTAP). Toutefois, il existe présentement un important débat opposant l’utilisation d’un antagoniste sélectif des récepteur ETA à l’utilisation d’un antagoniste double ETA/ETB dans le traitement de cette pathologie. Bien que nous sachions que le système ET est activé et contribue à l’HTAP, les modifications locales de ce système induites par la pathologie, particulièrement au niveau des artères de résistance pulmonaires, demeurent inconnues. De plus, l’impact de ces modifications sur la réponse pharmacologique aux divers antagonistes des récepteurs à l’ET (sélectifs versus double) est d’une importance capitale. Ainsi, le but de la première étude de cette thèse était d’évaluer les modifications potentielles de la pharmacologie du système ET au niveau des artères de résistance pulmonaires induites par l’HTAP. Dans cette étude, nous avons démontré qu’en condition contrôle l’antagoniste sélectif ETA et l’antagoniste double n’ont eu aucun effet sur la réponse vasoconstrictrice à l’ET-1. Toutefois, en condition d’HTAP, les antagonistes sélectif et double ont tous deux été en mesure de réduire la vasoconstriction pulmonaire induite par l’ET-1. Une diminution importante de l’expression génique du récepteur ETB pourrait être à l’origine de cette modification du profil pharmacologique des antagonistes. Une meilleure compréhension des rôles joués par les récepteurs ETA et ETB au niveau des artères de résistance pulmonaires pourrait permettre l’optimisation des traitements de l’HTAP. Ainsi, le but de la deuxième étude était d’évaluer les effets d’un traitement antisens ex vivo dirigé contre l’ARNm des récepteurs ETA et ETB dans la vasoconstriction des artères de résistance pulmonaires induite par l’ET-1. Dans cette étude, nous avons démontré dans un premier temps que les récepteurs ETA et ETB pouvaient former des dimères au niveau des artères de résistance pulmonaires. De plus, nous avons observé qu’une réduction de l’expression protéique du R-ETA entraînait une potentialisation de la vasoconstriction ETB dépendante suggérant ainsi qu’en condition contrôle, le récepteur ETA aurait un effet inhibiteur sur la vasoconstriction pulmonaire induite par la stimulation du récepteur ETB. Les effets délétères de l’ET-1 sur la circulation pulmonaire sont bien connus, toutefois seules quelques études ont porté leur attention sur l’implication de l’ET-3 dans l’HTAP. Ainsi, le but de la troisième étude était d’évaluer l’implication potentielle de l’ET-3 dans l’HTAP. Dans cette étude, nous avons démontré qu’il était nécessaire en condition contrôle de bloquer simultanément les récepteurs ETA et ETB afin de réduire la réponse vasoconstrictrice pulmonaire à l’ET-3. En condition d’HTAP, nous avons observé une augmentation non-significative des concentrations plasmatiques d’ET-3 ainsi qu’une modification du profil pharmacologique des antagonistes des récepteurs à l’ET. En effet, l’utilisation de l’antagoniste sélectif ETA ou de l’antagoniste double était dans les deux cas en mesure de réduire la vasoconstriction pulmonaire à l’ET-3. Les résultats de ces trois études suggèrent qu’il est préférable d’utiliser un antagoniste double dans le traitement de l’HTAP. En effet, (1) en condition d’HTAP, l’utilisation d’un antagoniste double est aussi efficace que l’utilisation d’un antagoniste sélectif ETA; (2) les récepteurs ETA et ETB peuvent former des dimères au niveau des artères de résistance pulmonaires et (3) le récepteur ETB joue un rôle prédominant dans la vasoconstriction pulmonaire, il semble donc essentiel de bloquer simultanément les récepteurs ETA et ETB afin d’inhiber la réponse vasoconstrictrice induite par l’ET. Mots-clés: endothéline-1, endothéline-3, artère de résistance pulmonaire, récepteur vasculaire, antagoniste des récepteurs à l’ET, dimérisation, phosphorothioate, hypertension artérielle pulmonaire / The endothelin (ET) system is activated in pulmonary arterial hypertension (PAH); indeed, increased plasma levels of ET-1 were detected in patients with various forms of PAH and in various experimental models. The therapeutic value of pharmacological blockade of ET receptors has been demonstrated in various animal models and led to the current approval and continued development of these drugs for the therapy of human PAH. Whether the net effect of either selective ETA receptor blockade or combined ETA/ETB receptor blockade provides greater therapeutic benefit remains a subject of debate. Although the ET system contributes to PAH, we currently incompletely comprehend which local modifications of this system occur as a consequence of PAH, particularly in small resistance arteries, and how this could affect the pharmacological response to ET receptor antagonists. The purpose of the first study was therefore to evaluate potential modifications of the pharmacology of the ET system in rat pulmonary resistance arteries from monocrotaline-induced PAH. Our results reveal striking changes in pulmonary vasculature sensitivity to ET receptor antagonism in PAH that may be related to a reduction in ETB receptor expression. A better understanding of the exact role played by both ETA and ETB receptors on pulmonary resistance arteries might contribute to optimization of PAH treatments. Therefore the aim of the second study was to clarify the role played by both ETA and ETB receptors in ET-1 induced pulmonary vasoconstriction using an antisense (AS) oligonucleotide ex vivo treatment. In this study we have demonstrated that ETA and ETB receptors can form heterodimers in pulmonary resistance arteries. Furthermore, suppression of ETA receptors potentiated the response to ET-1 suggesting that in control condition the ETA receptor has an inhibitory action on the ET-1 induced pulmonary vasoconstriction induced by the stimulation of the ETB receptor. Although the deleterious effects of ET-1 on the pulmonary circulation are well established, only a few studies have focused on ET-3 in PAH. Therefore, the purpose of the last study was to evaluate the potential implication of ET-3 in MCT-induced PAH and evaluate the roles of ETA and ETB receptors on ET-3-induced pulmonary vascular reactivity. In control condition, the use of a combination of both ETA and ETB receptor antagonists is necessary to reduce the ET-3 induced pulmonary vasoconstriction. In PAH, we found an increased ET-3 plasma levels and a modification of the pharmacological profile of ET receptor antagonists. Indeed, the use of either the ETA receptor antagonist or the dual antagonist was able to reduce the ET-3 response. The results from these three studies suggest that it is preferable to use a dual antagonist in the treatment of PAH. Indeed, (1) in PAH the use of a dual antagonist is as effective as the use of a selective ETA receptor antagonist (2) ETA and ETB receptors can form heterodimers in pulmonary resistance arteries and (3) ETB receptor plays an important role in the ET-1 induced pulmonary vasoconstriction, suggesting that it is necessary to block both receptors to reduce the ET-1 induced pulmonary vasoconstriction. Keywords: endothelin-1, endothelin-3, pulmonary resistance artery, receptor, endothelin receptor antagonist, dimerisation, phosphorothioate pulmonary arterial hypertension

Le système endothéline (ET) est activé en condition d’hypertension pulmonaire (HTP). L’efficacité des antagonistes des récepteurs à l’ET a clairement été démontrée et a menée à l’approbation clinique de tels antagonistes dans le traitement de l’hypertension artérielle pulmonaire (HTAP). Toutefois, il existe présentement un important débat opposant l’utilisation d’un antagoniste sélectif des récepteur ETA à l’utilisation d’un antagoniste double ETA/ETB dans le traitement de cette pathologie. Bien que nous sachions que le système ET est activé et contribue à l’HTAP, les modifications locales de ce système induites par la pathologie, particulièrement au niveau des artères de résistance pulmonaires, demeurent inconnues. De plus, l’impact de ces modifications sur la réponse pharmacologique aux divers antagonistes des récepteurs à l’ET (sélectifs versus double) est d’une importance capitale. Ainsi, le but de la première étude de cette thèse était d’évaluer les modifications potentielles de la pharmacologie du système ET au niveau des artères de résistance pulmonaires induites par l’HTAP. Dans cette étude, nous avons démontré qu’en condition contrôle l’antagoniste sélectif ETA et l’antagoniste double n’ont eu aucun effet sur la réponse vasoconstrictrice à l’ET-1. Toutefois, en condition d’HTAP, les antagonistes sélectif et double ont tous deux été en mesure de réduire la vasoconstriction pulmonaire induite par l’ET-1. Une diminution importante de l’expression génique du récepteur ETB pourrait être à l’origine de cette modification du profil pharmacologique des antagonistes. Une meilleure compréhension des rôles joués par les récepteurs ETA et ETB au niveau des artères de résistance pulmonaires pourrait permettre l’optimisation des traitements de l’HTAP. Ainsi, le but de la deuxième étude était d’évaluer les effets d’un traitement antisens ex vivo dirigé contre l’ARNm des récepteurs ETA et ETB dans la vasoconstriction des artères de résistance pulmonaires induite par l’ET-1. Dans cette étude, nous avons démontré dans un premier temps que les récepteurs ETA et ETB pouvaient former des dimères au niveau des artères de résistance pulmonaires. De plus, nous avons observé qu’une réduction de l’expression protéique du R-ETA entraînait une potentialisation de la vasoconstriction ETB dépendante suggérant ainsi qu’en condition contrôle, le récepteur ETA aurait un effet inhibiteur sur la vasoconstriction pulmonaire induite par la stimulation du récepteur ETB. Les effets délétères de l’ET-1 sur la circulation pulmonaire sont bien connus, toutefois seules quelques études ont porté leur attention sur l’implication de l’ET-3 dans l’HTAP. Ainsi, le but de la troisième étude était d’évaluer l’implication potentielle de l’ET-3 dans l’HTAP. Dans cette étude, nous avons démontré qu’il était nécessaire en condition contrôle de bloquer simultanément les récepteurs ETA et ETB afin de réduire la réponse vasoconstrictrice pulmonaire à l’ET-3. En condition d’HTAP, nous avons observé une augmentation non-significative des concentrations plasmatiques d’ET-3 ainsi qu’une modification du profil pharmacologique des antagonistes des récepteurs à l’ET. En effet, l’utilisation de l’antagoniste sélectif ETA ou de l’antagoniste double était dans les deux cas en mesure de réduire la vasoconstriction pulmonaire à l’ET-3. Les résultats de ces trois études suggèrent qu’il est préférable d’utiliser un antagoniste double dans le traitement de l’HTAP. En effet, (1) en condition d’HTAP, l’utilisation d’un antagoniste double est aussi efficace que l’utilisation d’un antagoniste sélectif ETA; (2) les récepteurs ETA et ETB peuvent former des dimères au niveau des artères de résistance pulmonaires et (3) le récepteur ETB joue un rôle prédominant dans la vasoconstriction pulmonaire, il semble donc essentiel de bloquer simultanément les récepteurs ETA et ETB afin d’inhiber la réponse vasoconstrictrice induite par l’ET. Mots-clés: endothéline-1, endothéline-3, artère de résistance pulmonaire, récepteur vasculaire, antagoniste des récepteurs à l’ET, dimérisation, phosphorothioate, hypertension artérielle pulmonaire / The endothelin (ET) system is activated in pulmonary arterial hypertension (PAH); indeed, increased plasma levels of ET-1 were detected in patients with various forms of PAH and in various experimental models. The therapeutic value of pharmacological blockade of ET receptors has been demonstrated in various animal models and led to the current approval and continued development of these drugs for the therapy of human PAH. Whether the net effect of either selective ETA receptor blockade or combined ETA/ETB receptor blockade provides greater therapeutic benefit remains a subject of debate. Although the ET system contributes to PAH, we currently incompletely comprehend which local modifications of this system occur as a consequence of PAH, particularly in small resistance arteries, and how this could affect the pharmacological response to ET receptor antagonists. The purpose of the first study was therefore to evaluate potential modifications of the pharmacology of the ET system in rat pulmonary resistance arteries from monocrotaline-induced PAH. Our results reveal striking changes in pulmonary vasculature sensitivity to ET receptor antagonism in PAH that may be related to a reduction in ETB receptor expression. A better understanding of the exact role played by both ETA and ETB receptors on pulmonary resistance arteries might contribute to optimization of PAH treatments. Therefore the aim of the second study was to clarify the role played by both ETA and ETB receptors in ET-1 induced pulmonary vasoconstriction using an antisense (AS) oligonucleotide ex vivo treatment. In this study we have demonstrated that ETA and ETB receptors can form heterodimers in pulmonary resistance arteries. Furthermore, suppression of ETA receptors potentiated the response to ET-1 suggesting that in control condition the ETA receptor has an inhibitory action on the ET-1 induced pulmonary vasoconstriction induced by the stimulation of the ETB receptor. Although the deleterious effects of ET-1 on the pulmonary circulation are well established, only a few studies have focused on ET-3 in PAH. Therefore, the purpose of the last study was to evaluate the potential implication of ET-3 in MCT-induced PAH and evaluate the roles of ETA and ETB receptors on ET-3-induced pulmonary vascular reactivity. In control condition, the use of a combination of both ETA and ETB receptor antagonists is necessary to reduce the ET-3 induced pulmonary vasoconstriction. In PAH, we found an increased ET-3 plasma levels and a modification of the pharmacological profile of ET receptor antagonists. Indeed, the use of either the ETA receptor antagonist or the dual antagonist was able to reduce the ET-3 response. The results from these three studies suggest that it is preferable to use a dual antagonist in the treatment of PAH. Indeed, (1) in PAH the use of a dual antagonist is as effective as the use of a selective ETA receptor antagonist (2) ETA and ETB receptors can form heterodimers in pulmonary resistance arteries and (3) ETB receptor plays an important role in the ET-1 induced pulmonary vasoconstriction, suggesting that it is necessary to block both receptors to reduce the ET-1 induced pulmonary vasoconstriction. Keywords: endothelin-1, endothelin-3, pulmonary resistance artery, receptor, endothelin receptor antagonist, dimerisation, phosphorothioate pulmonary arterial hypertension