L’hypertrophie du ventricule gauche (HVG) est un processus adaptif et compensatoire qui se développe conséquemment à l’hypertension artérielle pour s’opposer à l’élévation chronique de la pression artérielle. L’HVG est caractérisée par une hypertrophie des cardiomyocytes suite à l’augmentation de la synthèse d’ADN, une prolifération des fibroblastes, une augmentation du dépôt de collagène et une altération de la matrice extracellulaire (MEC). Ces changements génèrent des troubles de relaxation et mènent au dysfonctionnement diastolique, ce qui diminue la performance cardiaque. La suractivité du système nerveux sympathique (SNS) joue un rôle essentiel dans le développement de l’hypertension artérielle et de l’HVG à cause de la libération excessive des catécholamines et de leurs effets sur la sécrétion des cytokines pro-inflammatoires et sur les différentes voies de signalisation hypertrophiques et prolifératives. Le traitement antihypertenseur avec de la moxonidine, un composé sympatholytique d’action centrale, permet une régression de l’HVG suite à une réduction soutenue de la synthèse d'ADN et d’une stimulation transitoire de la fragmentation de l'ADN qui se produit au début du traitement. En raison de l’interaction entre l’HVG, les cytokines inflammatoires, le SNS et leurs effets sur les protéines de signalisation hypertrophiques, l’objectif de cette étude est de détecter dans un modèle animal d’hypertension artérielle et d’HVG, les différentes voies de signalisation associées à la régression de l’HVG et à la performance cardiaque. Des rats spontanément hypertendus (SHR, 12 semaines) ont reçu de la moxonidine à 0, 100 et 400 µg/kg/h, pour une période de 1 et 4 semaines, via des mini-pompes osmotiques implantées d’une façon sous-cutanée. Après 4 semaines de traitement, la performance cardiaque a été mesurée par écho-doppler. Les rats ont ensuite été euthanasiés, le sang a été recueilli pour mesurer les concentrations des cytokines plasmatiques et les cœurs ont été prélevés pour la détermination histologique du dépôt de collagène et de l'expression des protéines de signalisation dans le ventricule gauche. Le traitement de 4 semaines n’a eu aucun effet sur les paramètres systoliques mais a permis d’améliorer les paramètres diastoliques ainsi que la performance cardiaque globale. Par rapport au véhicule, la moxonidine (400 µg/kg/h) a permis d’augmenter transitoirement la concentration plasmatique de l’IL-1β après une semaine et de réduire la masse ventriculaire gauche. De même, on a observé une diminution du dépôt de collagène et des concentrations plasmatiques des cytokines IL-6 et TNF-α, ainsi qu’une diminution de la phosphorylation de p38 et d’Akt dans le ventricule gauche après 1 et 4 semaines de traitement, et cela avec une réduction de la pression artérielle et de la fréquence cardiaque. Fait intéressant, les effets anti-hypertrophiques, anti-fibrotiques et anti-inflammatoires de la moxonidine ont pu être observés avec la dose sous-hypotensive (100 µg/kg/h). Ces résultats suggèrent des effets cardiovasculaires bénéfiques de la moxonidine associés à une amélioration de la performance cardiaque, une régulation de l'inflammation en diminuant les niveaux plasmatiques des cytokines pro-inflammatoires ainsi qu’en inhibant la MAPK p38 et Akt, et nous permettent de suggérer que, outre l'inhibition du SNS, moxonidine peut agir sur des sites périphériques. / Left ventricular hypertrophy (LVH) is an adaptive and compensatory process that develops in hypertension to oppose the chronic elevation of blood pressure. LVH is characterized by hypertrophy of cardiomyocytes following the increase in DNA synthesis, proliferation of fibroblasts, increased collagen deposition and alteration of the extracellular matrix (ECM). These changes generate relaxation and diastolic dysfunction which reduced cardiac performance. The overactivity of the sympathetic nervous system plays an essential role in the development of hypertension and left ventricular hypertrophy pathogenesis due to the excessive release of catecholamines and norepinephrine spillover and their effects on the secretion of pro-inflammatory cytokines and hypertrophic signaling pathways. Antihypertensive treatment with moxonidine, a centrally acting sympatholytic imidazoline compound, results in prevention of left ventricular hypertrophy, resulting from a sustained reduction of DNA synthesis and transient stimulation of DNA fragmentation that occur early after treatment. Due to the interaction between LVH, inflammatory cytokines, the SNS and their effects on hypertrophic signaling proteins, the objective of this study is to detect in an animal model of hypertension and LVH, the different signaling pathways associated with regression of LVH and cardiac performance. Spontaneously hypertensive rats (SHR, 12 weeks old) received moxonidine at 0, 100 and 400 µg/kg/h, for 1 and 4 weeks, via subcutaneously implanted osmotic minipumps. After 4 weeks of treatment, cardiac performance was measured by echo-Doppler. Then the rats were euthanized, blood was collected for measurement of plasma cytokines and hearts for histologic determination of collagen deposition and for measurement of left ventricular expression of downstream signaling proteins. Treatment for 4 weeks had no effect on systolic parameters but improved diastolic parameters and global cardiac performance. Compared to vehicle, moxonidine (400 µg/kg/h) transiently increased plasma IL-1β after 1 week and reduced left ventricular mass. Similarly, there was a decrease in collagen deposition and plasma concentrations of IL-6 and TNF-α, and decreased phosphorylation of p38 and Akt in the left ventricle after 1 and 4 weeks treatment, in association with reduced blood pressure and heart rate. Interestingly, the anti-hypertrophic, anti-fibrotic, and anti-inflammatory effects of moxonidine were observed with a sub-hypotensive dose (100µg/kg/h). These results suggest the beneficial cardiovascular effects of moxonidine associated with improved cardiac performance, regulation of inflammation by decreasing pro-inflammatory plasma levels, inhibition of p38 MAPK and Akt, and allow us to suggest that besides inhibiting the SNS, moxonidine may act on peripheral sites.

La moxonidine, un médicament antihypertenseur sympatholytique de type imidazolinique, agit au niveau de la médulla du tronc cérébral pour diminuer la pression artérielle, suite à l’activation sélective du récepteur aux imidazolines I1 (récepteur I1, aussi nommé nischarine). Traitement avec de la moxonidine prévient le développement de l’hypertrophie du ventricule gauche chez des rats hypertendus (SHR), associé à une diminution de la synthèse et une élévation transitoire de la fragmentation d’ADN, des effets antiprolifératifs et apoptotiques. Ces effets se présentent probablement chez les fibroblastes, car l’apoptose des cardiomyocytes pourrait détériorer la fonction cardiaque. Ces effets apparaissent aussi avec des doses non hypotensives de moxonidine, suggérant l’existence d’effets cardiaques directes. Le récepteur I1 se trouvé aussi dans les tissus cardiaques; son activation ex vivo par la moxonidine stimule la libération de l’ANP, ce qui montre que les récepteurs I1 cardiaques sont fonctionnels malgré l’absence de stimulation centrale. Sur la base de ces informations, en plus du i) rôle des peptides natriurétiques comme inhibiteurs de l’apoptose cardiaque et ii) des études qui lient le récepteur I1 avec la maintenance de la matrix extracellulaire, on propose que, à part les effets sympatholytiques centrales, les récepteurs I1 cardiaques peuvent contrôler la croissance-mort cellulaire. L’activation du récepteur I1 peut retarder la progression des cardiopathies vers la défaillance cardiaque, en inhibant des signaux mal adaptatifs de prolifération et apoptose. Des études ont été effectuées pour : 1. Explorer les effets in vivo sur la structure et la fonction cardiaque suite au traitement avec moxonidine chez le SHR et le hamster cardiomyopathique. 2. Définir les voies de signalisation impliquées dans les changements secondaires au traitement avec moxonidine, spécifiquement sur les marqueurs inflammatoires et les voies de signalisation régulant la croissance et la survie cellulaire (MAPK et Akt). 3. Explorer les effets in vitro de la surexpression et l’activation du récepteur I1 sur la survie cellulaire dans des cellules HEK293. 4. Rechercher la localisation, régulation et implication dans la croissance-mort cellulaire du récepteur I1 in vitro (cardiomyocytes et fibroblastes), en réponse aux stimuli associés au remodelage cardiaque : norépinephrine, cytokines (IL-1β, TNF-α) et oxydants (H2O2). Nos études démontrent que la moxonidine, en doses hypotensives et non-hypotensives, améliore la structure et la performance cardiaque chez le SHR par des mécanismes impliquant l’inhibition des cytokines et des voies de signalisation p38 MAPK et Akt. Chez le hamster cardiomyopathique, la moxonidine améliore la fonction cardiaque, module la réponse inflammatoire/anti-inflammatoire et atténue la mort cellulaire et la fibrose cardiaque. Les cellules HEK293 surexprimant la nischarine survivent et prolifèrent plus en réponse à la moxonidine; cet effet est associé à l’inhibition des voies ERK, JNK et p38 MAPK. La surexpression de la nischarine protège aussi de la mort cellulaire induite par le TNF-α, l’IL-1β et le H2O2. En outre, le récepteur I1 s’exprime dans les cardiomyocytes et fibroblastes, son activation inhibe la mort des cardiomyocytes et la prolifération des fibroblastes induite par la norépinephrine, par des effets différentiels sur les MAPK et l’Akt. Dans des conditions inflammatoires, la moxonidine/récepteur aux imidazolines I1 protège les cardiomyocytes et facilite l’élimination des myofibroblastes par des effets contraires sur JNK, p38 MAPK et iNOS. Ces études démontrent le potentiel du récepteur I1/nischarine comme cible anti-hypertrophique et anti-fibrose à niveau cardiaque. L’identification des mécanismes cardioprotecteurs de la nischarine peut amener au développement des traitements basés sur la surexpression de la nischarine chez des patients avec hypertrophie ventriculaire. Finalement, même si l’effet antihypertenseur des agonistes du récepteur I1 centraux est salutaire, le développement de nouveaux agonistes cardiosélectifs du récepteur I1 pourrait donner des bénéfices additionnels chez des patients non hypertendus. / Moxonidine, an antihypertensive sympatholytic imidazoline compound, reduces blood pressure by selective activation of non-adrenergic imidazoline I1-receptors (also known as nischarin) in brainstem medulla. Moxonidine prevents left ventricular hypertrophy development in hypertensive rats, associated with reduced cardiac DNA synthesis and early transient increase in DNA fragmentation. It is likely that the anti-proliferative and apoptotic effects occur in fibroblasts, as cardiomyocyte apoptosis may deteriorate cardiac function. The effects also occurred to sub-hypotensive doses, suggesting a blood-pressure-independent mechanism and pointing to a local cardiac action. Imidazoline I1-receptors have been identified in cardiac tissues, and their ex vivo activation by moxonidine stimulates ANP release, demonstrating that cardiac imidazoline I1-receptors are functional without the contribution of the central nervous system. Based on the above studies and on i) the role of natriuretic peptides in inhibition of myocardial cell apoptosis and ii) studies linking imidazoline I1-receptors to the maintenance of the extracellular matrix and PC12 cell survival, we propose that apart from centrally-mediated sympatholytic function, imidazoline I1-receptors in the heart may control cell growth and death. Activation of imidazoline receptors may delay the progression of cardiac pathologies into heart failure by inhibition of maladaptive proliferative signalling and downstream apoptotic pathways. In order to test this hypothesis studies were performed to: 1. Explore the in vivo effects of moxonidine on cardiac structure and function in SHR and cardiomyopathic hamsters. 2. Define the pathways involved in the observed changes following moxonidine treatment, specifically, on inflammatory markers and pathways involved in LVH and cardiac cell survival/death (MAPK and Akt). 3. Explore in vitro the effect of imidazoline I1-receptor activation by moxonidine, on cell survival by over-expressing nischarin in HEK293 cells, to circumvent the lack of specific imidazoline I1-receptor agonists and antagonists. 4. Investigate in vitro, imidazoline I1-receptor localization (cardiomyocytes and fibroblasts), regulation and implication in cell growth/death in response to cardiac remodelling-associated stimuli: norepinephrine, cytokines (IL-1β, TNF-α), and oxidants (H2O2). The studies reveal that hypotensive and sub-hypotensive concentrations of moxonidine improve cardiac structure and performance in SHR by mechanisms that involve inhibition of cytokines, p38MAPK, and Akt signalling pathways. In cardiomyopathic hamsters moxonidine improves cardiac performance, in association with differential inflammatory/anti-inflammatory responses that culminate in attenuated cardiomyocyte death and fibrosis and altered collagen type expression. HEK293 cells, transfected with nischarin cDNA, show increased viability/proliferation in response to moxonidine. The overall survival response is associated with moxonidine’s inhibition of ERK, JNK, and p38MAPK. Nischarin also opposes the reduced cell viability in response to oxidative stimuli (TNF-α, IL-1β and H2O2), with differential responses to moxonidine. Furthermore, the imidazoline I1-receptor is expressed in cardiac fibroblasts and myocytes and its activation inhibits norepinephrine-induced cardiomyocyte death and fibroblast proliferation, through differential effects on MAPKs and Akt. Moxonidine/imidazoline I1-receptor protects cardiomyocytes and facilitates elimination of myofibroblasts in inflammatory conditions, through opposite effects on JNK, p38MAPK and iNOS activity. These studies emphasize the potential importance of imidazoline I1-receptor/nischarin as an anti-hypertrophic and anti-fibrotic target. Identification of the cardio-protective mechanisms of cardiac nischarin could result in specifically-tailored cell/gene-driven nischarin treatments, which could be important for patients with heart disease. Also, while the antihypertensive action of centrally acting compounds is appreciated, new cardiac-selective I1-receptor agonists may confer additional benefit.

A doença cardiovascular (DCV) é a principal causa de mortalidade nos pacientes com doença renal crônica (DRC) e a hipertrofia de ventrículo esquerdo (HVE), a alteração mais freqüente. A remodelação cardíaca (RC) patológica ocorre em resposta a agressões como sobrecarga de volume ou de pressão e é influenciada por ativação neurohormonal, fatores locais, inflamação, isquemia, necrose e apoptose celular. Os miócitos são as principais células envolvidas na RC. Avaliamos o papel da hiperfosfatemia e do paratormônio (PTH) em animais urêmicos. Trinta e dois ratos Wistar machos foram submetidos à paratireoidectomia (PTX) e nefrectomia (Nx), com reposição contínua de PTH em concentração fisiológica (PTHf= 0,022 ug/100g/h) ou elevada (PTHe=0,11 ug/100g/h). Os animais sham (N=16) foram operados e recebiam infusão de veículo. Apenas o conteúdo de fósforo nas dietas era diferente, ou seja: pobre=0,2% (pP) ou rica em fósforo=1,2% (rP). Dividimos os animais em 6 grupos: Sham: Sham-pP (G1), Sham-rP (G2); PTX+Nx: PTHf-pP (G3), PTHf-rP (G4), PTHe-pP (G5), PTHe-rP (G6). Semanalmente determinamos o peso e a pressão arterial caudal. Creatinina, fósforo, cálcio PTH e hematócrito foram analisados. Após 8 semanas os animais foram sacrificados. A hipertrofia e fibrose miocárdicas foram analisadas com o sistema digital Leica. O peso do coração corrigido por 100g peso corporal foi maior nos grupos G5 e G6 e apresentou uma correlação positiva com hipertrofia e fibrose miocárdica. A hipertrofia e fibrose foram menores no G3, quando comparado aos grupos Nx. A hipertrofia miocárdica foi maior no G6, evidenciando o papel do P neste processo. A fibrose mocárdica ocorreu principalmente em subendocárdio e foi mais intensa no G6. Analisamos a expressão do fator transformador de crescimento (TGF-beta) e angiotensina II que foram mais intensas nos grupos G5 e G6. As lesões das artérias coronarianas foram avaliadas de forma semi-quantitativa e os animais G5 e G6 mostraram calcificações de camada média. A expressão da alfa-actina se correlacionou negativamente com as lesões coronarianas. Nossos resultados demonstraram a importância do fósforo e PTH na fisiopatologia da DCV, sendo necessário um melhor controle destes elementos para prevenção de mortalidade nos pacientes com DRC. / Cardiovascular disease (CVD) is the leading cause of mortality in patients with chronic kidney disease (CKD), and left ventricular hypertrophy (LVH) is the most common alteration. Pathologic cardiac remodeling (CR) occurs in response to injuries such as volume or pressure overload, and it is influenced by neurohormonal activation, local factors, inflammation, ischemia, necrosis and cellular apoptosis. Myocytes are the principal cells involved in CR. We evaluated the role of hyperphosphatemia and parathyroid hormone (PTH) in uremic animals. Thirty-two male Wistar rats were submitted to parathyroidectomy (PTX) and nephrectomy (Nx), with PTH continuous replacement in physiologic concentration (PTHf=0.022ug/100g/h) or elevated (PTHe=0.11ug/100g/h). The sham animals (N=16) were operated and received vehicle infusion. Only the phosphorus content in diets was different, that is: poor = 0.2% (pP) or rich in phosphorus = 1.2% (rP). We divided the animals into 6 groups: Sham: Sham-pP (G1), Sham-rP (G2); PTX+Nx: PTHf-pP (G3), PTHf-rP (G4), PTHe-pP (G5), PTHe-rP (G6). We determined the weight and caudal blood pressure weekly. Creatinine, phosphorus, PTH calcium and hematocrit were analyzed. After 8 weeks, the animals were sacrificed. Myocardial hypertrophy and fibrosis were analyzed using Leica digital system. The weight of the heart corrected for 100g body weight was greater in groups G5 and G6 and presented a positive correlation with myocardial hypertrophy and fibrosis. Hypertrophy and fibrosis were lower in G3, when compared to Nx groups. Myocardial hypertrophy was higher in G6, determining the role of P in this process. Myocardial fibrosis occurred mainly in subendocardium and was more intense in G6. We analyzed the expression of transforming growth factor (TGF-alfa) and angiotensin II, which were more intense in groups G5 and G6. Coronary artery lesions were evaluated semiquantitatively and G5 and G6 animals showed middle layer calcifications. Expression of alfa-actin correlated negatively with coronary lesions. Our results demonstrated the importance of phosphorus and PTH in the pathophysiology of CVD; therefore, a better control of these elements is required in order to prevent mortality in patients with CKD.

<p>Anemia is common in patients with chronic kidney disease (CDK), contributes to reduced Quality of Life (QoL) and is associated with cardiovascular disease, morbidity and mortality. Epoetin raises hemoglobin (Hb) and increases QoL and physical exercise capacity. Because of concerns about safety and economics, current anemia treatment with epoetin aims to achieve subnormal Hb (110-120 g/l). Normalization of Hb may be of additional benefit regarding QoL and cardiovascular effects. The present study examines the effects of Hb normalization with epoetin on safety variables, QoL, graft function after kidney transplantation, dialysis adequacy, hemorheology, hemodynamics and cardiac autonomic function in CKD patients. </p><p>In a randomized, multicenter study comprising 416 pre-dialysis and dialysis patients no difference was observed between patients treated to a normal or a subnormal Hb level on mortality, thrombovascular events, serious adverse events, vascular access thrombosis and residual renal function. QoL was enhanced in a subgroup of hemodialysis patients. Pretransplant epoetin treatment directed toward normal Hb levels did not result in worse graft function during 6 postoperative months. Dialysis adequacy was reduced in a subgroup of hemodialysis patients after normalization of Hb. The blood flow properties of pre-dialysis patients were altered. The hemorheological investigation demonstrated that Hb normalization caused a parallel increase in hematocrit and blood viscosity without other hemorheological changes. While the total peripheral resistance index increased, the cardiac index (CI) decreased. In a separate study cardiac autonomic function, measured by heart rate variability, was decreased in pre-dialysis patients. It was improved, but not fully normalized, by Hb normalization. </p><p>On the basis of this study, Hb normalization with epoetin appears to be safe and increases QoL in hemodialysis patients though may result in lower dialysis adequacy and increased blood pressure. A reduction in CI and improved cardiac autonomic function indicate a positive effect on cardiovascular function.</p>

Anemia is common in patients with chronic kidney disease (CDK), contributes to reduced Quality of Life (QoL) and is associated with cardiovascular disease, morbidity and mortality. Epoetin raises hemoglobin (Hb) and increases QoL and physical exercise capacity. Because of concerns about safety and economics, current anemia treatment with epoetin aims to achieve subnormal Hb (110-120 g/l). Normalization of Hb may be of additional benefit regarding QoL and cardiovascular effects. The present study examines the effects of Hb normalization with epoetin on safety variables, QoL, graft function after kidney transplantation, dialysis adequacy, hemorheology, hemodynamics and cardiac autonomic function in CKD patients. In a randomized, multicenter study comprising 416 pre-dialysis and dialysis patients no difference was observed between patients treated to a normal or a subnormal Hb level on mortality, thrombovascular events, serious adverse events, vascular access thrombosis and residual renal function. QoL was enhanced in a subgroup of hemodialysis patients. Pretransplant epoetin treatment directed toward normal Hb levels did not result in worse graft function during 6 postoperative months. Dialysis adequacy was reduced in a subgroup of hemodialysis patients after normalization of Hb. The blood flow properties of pre-dialysis patients were altered. The hemorheological investigation demonstrated that Hb normalization caused a parallel increase in hematocrit and blood viscosity without other hemorheological changes. While the total peripheral resistance index increased, the cardiac index (CI) decreased. In a separate study cardiac autonomic function, measured by heart rate variability, was decreased in pre-dialysis patients. It was improved, but not fully normalized, by Hb normalization. On the basis of this study, Hb normalization with epoetin appears to be safe and increases QoL in hemodialysis patients though may result in lower dialysis adequacy and increased blood pressure. A reduction in CI and improved cardiac autonomic function indicate a positive effect on cardiovascular function.

L’hypertrophie du ventricule gauche (HVG) est un processus adaptif et compensatoire qui se développe conséquemment à l’hypertension artérielle pour s’opposer à l’élévation chronique de la pression artérielle. L’HVG est caractérisée par une hypertrophie des cardiomyocytes suite à l’augmentation de la synthèse d’ADN, une prolifération des fibroblastes, une augmentation du dépôt de collagène et une altération de la matrice extracellulaire (MEC). Ces changements génèrent des troubles de relaxation et mènent au dysfonctionnement diastolique, ce qui diminue la performance cardiaque. La suractivité du système nerveux sympathique (SNS) joue un rôle essentiel dans le développement de l’hypertension artérielle et de l’HVG à cause de la libération excessive des catécholamines et de leurs effets sur la sécrétion des cytokines pro-inflammatoires et sur les différentes voies de signalisation hypertrophiques et prolifératives. Le traitement antihypertenseur avec de la moxonidine, un composé sympatholytique d’action centrale, permet une régression de l’HVG suite à une réduction soutenue de la synthèse d'ADN et d’une stimulation transitoire de la fragmentation de l'ADN qui se produit au début du traitement. En raison de l’interaction entre l’HVG, les cytokines inflammatoires, le SNS et leurs effets sur les protéines de signalisation hypertrophiques, l’objectif de cette étude est de détecter dans un modèle animal d’hypertension artérielle et d’HVG, les différentes voies de signalisation associées à la régression de l’HVG et à la performance cardiaque. Des rats spontanément hypertendus (SHR, 12 semaines) ont reçu de la moxonidine à 0, 100 et 400 µg/kg/h, pour une période de 1 et 4 semaines, via des mini-pompes osmotiques implantées d’une façon sous-cutanée. Après 4 semaines de traitement, la performance cardiaque a été mesurée par écho-doppler. Les rats ont ensuite été euthanasiés, le sang a été recueilli pour mesurer les concentrations des cytokines plasmatiques et les cœurs ont été prélevés pour la détermination histologique du dépôt de collagène et de l'expression des protéines de signalisation dans le ventricule gauche. Le traitement de 4 semaines n’a eu aucun effet sur les paramètres systoliques mais a permis d’améliorer les paramètres diastoliques ainsi que la performance cardiaque globale. Par rapport au véhicule, la moxonidine (400 µg/kg/h) a permis d’augmenter transitoirement la concentration plasmatique de l’IL-1β après une semaine et de réduire la masse ventriculaire gauche. De même, on a observé une diminution du dépôt de collagène et des concentrations plasmatiques des cytokines IL-6 et TNF-α, ainsi qu’une diminution de la phosphorylation de p38 et d’Akt dans le ventricule gauche après 1 et 4 semaines de traitement, et cela avec une réduction de la pression artérielle et de la fréquence cardiaque. Fait intéressant, les effets anti-hypertrophiques, anti-fibrotiques et anti-inflammatoires de la moxonidine ont pu être observés avec la dose sous-hypotensive (100 µg/kg/h). Ces résultats suggèrent des effets cardiovasculaires bénéfiques de la moxonidine associés à une amélioration de la performance cardiaque, une régulation de l'inflammation en diminuant les niveaux plasmatiques des cytokines pro-inflammatoires ainsi qu’en inhibant la MAPK p38 et Akt, et nous permettent de suggérer que, outre l'inhibition du SNS, moxonidine peut agir sur des sites périphériques. / Left ventricular hypertrophy (LVH) is an adaptive and compensatory process that develops in hypertension to oppose the chronic elevation of blood pressure. LVH is characterized by hypertrophy of cardiomyocytes following the increase in DNA synthesis, proliferation of fibroblasts, increased collagen deposition and alteration of the extracellular matrix (ECM). These changes generate relaxation and diastolic dysfunction which reduced cardiac performance. The overactivity of the sympathetic nervous system plays an essential role in the development of hypertension and left ventricular hypertrophy pathogenesis due to the excessive release of catecholamines and norepinephrine spillover and their effects on the secretion of pro-inflammatory cytokines and hypertrophic signaling pathways. Antihypertensive treatment with moxonidine, a centrally acting sympatholytic imidazoline compound, results in prevention of left ventricular hypertrophy, resulting from a sustained reduction of DNA synthesis and transient stimulation of DNA fragmentation that occur early after treatment. Due to the interaction between LVH, inflammatory cytokines, the SNS and their effects on hypertrophic signaling proteins, the objective of this study is to detect in an animal model of hypertension and LVH, the different signaling pathways associated with regression of LVH and cardiac performance. Spontaneously hypertensive rats (SHR, 12 weeks old) received moxonidine at 0, 100 and 400 µg/kg/h, for 1 and 4 weeks, via subcutaneously implanted osmotic minipumps. After 4 weeks of treatment, cardiac performance was measured by echo-Doppler. Then the rats were euthanized, blood was collected for measurement of plasma cytokines and hearts for histologic determination of collagen deposition and for measurement of left ventricular expression of downstream signaling proteins. Treatment for 4 weeks had no effect on systolic parameters but improved diastolic parameters and global cardiac performance. Compared to vehicle, moxonidine (400 µg/kg/h) transiently increased plasma IL-1β after 1 week and reduced left ventricular mass. Similarly, there was a decrease in collagen deposition and plasma concentrations of IL-6 and TNF-α, and decreased phosphorylation of p38 and Akt in the left ventricle after 1 and 4 weeks treatment, in association with reduced blood pressure and heart rate. Interestingly, the anti-hypertrophic, anti-fibrotic, and anti-inflammatory effects of moxonidine were observed with a sub-hypotensive dose (100µg/kg/h). These results suggest the beneficial cardiovascular effects of moxonidine associated with improved cardiac performance, regulation of inflammation by decreasing pro-inflammatory plasma levels, inhibition of p38 MAPK and Akt, and allow us to suggest that besides inhibiting the SNS, moxonidine may act on peripheral sites.

Abstract Left ventricular hypertrophy (LVH), a common complication of elevated blood pressure (BP), is a risk factor for cardiovascular (CV) morbidity and mortality. Adiponectin has been shown to have cardioprotective effects and is inversely associated with LVH. BP can be measured at a clinical visit, as a momentary value. Ambulatory blood pressure (APB) measurement (ABPM) is a method of repeated BP measurements through a defined period, targeted to evaluate the circadian BP profile. High BP and ABPM have been shown to be associated with LVH and left ventricular diastolic dysfunction (LVDD). A high sodium intake has been associated with elevated BP and adverse CV outcome. The aim of this study was to investigate the associations between adiponectin and left ventricular mass index (LVMI), a measure of LVH, ABPM and the development of LVDD during long-term follow-up, ABPM and the change in LVMI during long-term follow-up, and the role of dietary sodium intake in the incidence of AF. Adiponectin has been shown to have vasoprotective, anti-inflammatory and cardioprotective effects. Hypoadiponectinemia has been associated with hypertension, coronary artery disease (CAD) and LVH. In this study, adiponectin levels were inversely associated with LVMI, even after adjustment with conventional risk factors of LVH, in a fairly large sample of middle-aged subjects. Elevated BP and pulse pressure (PP) have been associated with echocardiographic measures of LVDD. In this study, the association between APBM and the development of LVDD during a 20-year follow-up was evaluated. Ambulatory PP (APP) was shown to independently associate with the development of LVDD, even after adjustment with conventional risk factors of LVDD. APBM has been associated with LVH in cross-sectional assessments and has also been shown to have predictive value in future LVMI or LVH. In a few studies the predictive value of APP in future LVMI was observed. In the present study, an increase in APP was shown to predict the change in LVMI during long-term follow-up. In this study, the association between dietary sodium intake and the incidence of AF was evaluated. A high sodium intake predicted the occurrence of AF, which is a novel finding. In conclusion, this study offers novel findings about predictive factors in the entity of cardiac remodelling. / Tiivistelmä Vasemman kammion hypertrofia on yleinen kohonneen verenpaineen seuraus ja sen on todettu olevan sydän- ja verisuonitapahtumien riskitekijä. Adiponektiinin on osoitettu suojaavan vasemman kammion hypertrofialta. Ambulatorinen verenpaineen mittaus on menetelmä, jossa verenpaine mitataan määritellyllä ajanjaksolla toistuvasti, mikä antaa kuvan verenpaineesta vuorokauden eri jaksoissa. Kohonneella ambulatorisella verenpaineella on osoitettu olevan yhteys vasemman kammion hypertrofiaan sekä vasemman kammion diastoliseen vajaatoimintaan. Runsas natriumin saanti on yhteydessä kohonneeseen verenpaineeseen sekä sydän- ja verisuonisairauksiin. Tämän tutkimuksen tarkoituksena on selvittää yhteyksiä adiponektiinin ja vasemman kammion massaindeksin välillä, ambulatorisen verenpaineen ja vasemman kammion diastolisen vajaatoiminnan kehittymisen välillä, ambulatorisen verenpaineen ja vasemman kammion massaindeksin muutoksen välillä sekä natriumin saannin ja eteisvärinän ilmaantuvuuden välillä. Adiponektiinilla on todettu olevan suotuisia vaikutuksia verisuonistoon, tulehdusreaktion hillintään sekä sydänlihakseen. Matalan adiponektiinitason on osoitettu olevan yhteydessä verenpainetautiin, sepelvaltimotautiin sekä vasemman kammion hypertrofiaan. Tässä tutkimuksessa adiponektiinihormonilla osoitettiin olevan käänteinen yhteys vasemman kammion massaindeksiin, vaikka perinteiset riskitekijät otettiin huomioon. Kohonneella verenpaineella sekä pulssipaineella on osoitettu olevan yhteys vasemman kammion diastoliseen vajaatoimintaan. Tässä tutkimuksessa arvioitiin ambulatorisen verenpaineen merkitystä vasemman kammion diastolisen vajaatoiminnan kehittymisessä. Ambulatorinen pulssipaine osoittautui riskitekijäksi, vaikka perinteiset riskitekijät otettiin huomioon. Ambulatorisella verenpaineella ja pulssipaineella on osoitettu olevan yhteys vasemman kammion hypertrofiaan poikkileikkaustutkimuksissa ja seurantatutkimuksissa. Tässä tutkimuksessa ambulatorisen pulssipaineen nousun havaittiin ennustavan vasemman kammion massaindeksin kasvua pitkäaikaisseurannassa. Tässä tutkimuksessa korkean natriumin saannin todettiin olevan yhteydessä lisääntyneeseen eteisvärinän ilmaantuvuuteen. Tätä yhteyttä ei ole aiemmin todettu muissa tutkimuksissa. Tässä tutkimuksessa löydettiin uusia riskitekijöitä sydämen patologisiin ilmentymiin liittyen.

A doença cardiovascular (DCV) é a principal causa de mortalidade nos pacientes com doença renal crônica (DRC) e a hipertrofia de ventrículo esquerdo (HVE), a alteração mais freqüente. A remodelação cardíaca (RC) patológica ocorre em resposta a agressões como sobrecarga de volume ou de pressão e é influenciada por ativação neurohormonal, fatores locais, inflamação, isquemia, necrose e apoptose celular. Os miócitos são as principais células envolvidas na RC. Avaliamos o papel da hiperfosfatemia e do paratormônio (PTH) em animais urêmicos. Trinta e dois ratos Wistar machos foram submetidos à paratireoidectomia (PTX) e nefrectomia (Nx), com reposição contínua de PTH em concentração fisiológica (PTHf= 0,022 ug/100g/h) ou elevada (PTHe=0,11 ug/100g/h). Os animais sham (N=16) foram operados e recebiam infusão de veículo. Apenas o conteúdo de fósforo nas dietas era diferente, ou seja: pobre=0,2% (pP) ou rica em fósforo=1,2% (rP). Dividimos os animais em 6 grupos: Sham: Sham-pP (G1), Sham-rP (G2); PTX+Nx: PTHf-pP (G3), PTHf-rP (G4), PTHe-pP (G5), PTHe-rP (G6). Semanalmente determinamos o peso e a pressão arterial caudal. Creatinina, fósforo, cálcio PTH e hematócrito foram analisados. Após 8 semanas os animais foram sacrificados. A hipertrofia e fibrose miocárdicas foram analisadas com o sistema digital Leica. O peso do coração corrigido por 100g peso corporal foi maior nos grupos G5 e G6 e apresentou uma correlação positiva com hipertrofia e fibrose miocárdica. A hipertrofia e fibrose foram menores no G3, quando comparado aos grupos Nx. A hipertrofia miocárdica foi maior no G6, evidenciando o papel do P neste processo. A fibrose mocárdica ocorreu principalmente em subendocárdio e foi mais intensa no G6. Analisamos a expressão do fator transformador de crescimento (TGF-beta) e angiotensina II que foram mais intensas nos grupos G5 e G6. As lesões das artérias coronarianas foram avaliadas de forma semi-quantitativa e os animais G5 e G6 mostraram calcificações de camada média. A expressão da alfa-actina se correlacionou negativamente com as lesões coronarianas. Nossos resultados demonstraram a importância do fósforo e PTH na fisiopatologia da DCV, sendo necessário um melhor controle destes elementos para prevenção de mortalidade nos pacientes com DRC. / Cardiovascular disease (CVD) is the leading cause of mortality in patients with chronic kidney disease (CKD), and left ventricular hypertrophy (LVH) is the most common alteration. Pathologic cardiac remodeling (CR) occurs in response to injuries such as volume or pressure overload, and it is influenced by neurohormonal activation, local factors, inflammation, ischemia, necrosis and cellular apoptosis. Myocytes are the principal cells involved in CR. We evaluated the role of hyperphosphatemia and parathyroid hormone (PTH) in uremic animals. Thirty-two male Wistar rats were submitted to parathyroidectomy (PTX) and nephrectomy (Nx), with PTH continuous replacement in physiologic concentration (PTHf=0.022ug/100g/h) or elevated (PTHe=0.11ug/100g/h). The sham animals (N=16) were operated and received vehicle infusion. Only the phosphorus content in diets was different, that is: poor = 0.2% (pP) or rich in phosphorus = 1.2% (rP). We divided the animals into 6 groups: Sham: Sham-pP (G1), Sham-rP (G2); PTX+Nx: PTHf-pP (G3), PTHf-rP (G4), PTHe-pP (G5), PTHe-rP (G6). We determined the weight and caudal blood pressure weekly. Creatinine, phosphorus, PTH calcium and hematocrit were analyzed. After 8 weeks, the animals were sacrificed. Myocardial hypertrophy and fibrosis were analyzed using Leica digital system. The weight of the heart corrected for 100g body weight was greater in groups G5 and G6 and presented a positive correlation with myocardial hypertrophy and fibrosis. Hypertrophy and fibrosis were lower in G3, when compared to Nx groups. Myocardial hypertrophy was higher in G6, determining the role of P in this process. Myocardial fibrosis occurred mainly in subendocardium and was more intense in G6. We analyzed the expression of transforming growth factor (TGF-alfa) and angiotensin II, which were more intense in groups G5 and G6. Coronary artery lesions were evaluated semiquantitatively and G5 and G6 animals showed middle layer calcifications. Expression of alfa-actin correlated negatively with coronary lesions. Our results demonstrated the importance of phosphorus and PTH in the pathophysiology of CVD; therefore, a better control of these elements is required in order to prevent mortality in patients with CKD.

Submitted by Adriana Martinez (amartinez@unoeste.br) on 2018-02-07T17:06:20Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Francilene.pdf: 356698 bytes, checksum: 1dbb03ec82dfb5f6f0997237b2784d9a (MD5) / Made available in DSpace on 2018-02-07T17:06:20Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Francilene.pdf: 356698 bytes, checksum: 1dbb03ec82dfb5f6f0997237b2784d9a (MD5) Previous issue date: 2017-10-30 / Introduction: Systemic Arterial Hypertension (SAH) is a serious public health problem, especially for the elderly, and can lead to concentric hypertrophy an important risk factor for heart failure, which is considered a predictor of increased cardiovascular morbimortality. Studies have shown that High Intensity Interval Training (HIIT) may also be indicated for hypertensive patients. However, to the authors’ knowledge, no studies have evaluated HIIT in cardiac remodeling of animals with systemic arterial hypertension. Objective: to evaluate in spontaneously hypertensive rats (SHR) submitted to HIIT, pressure control, exercise tolerance and cardiac remodeling. Methods: 20 SHR rats were divided into two groups: sedentary (SHR-SED, n= 9) and HIIT training (SHR-HIIT, n= 11); and Wistar Kyoto rats composed the control group (WKY, n= 6), 12 months of age. The animals were familiarized with HIIT for a week with 10 minutes on the treadmill adapted for rodents. An incremental stress test was performed to exhaustion to adjust exercise intensity. The HIIT was performed five times a week for eight weeks. Before and after HIIT, blood pressure (BP) was measured by plethysmography and a maximal exercise capacity test was performed. Cardiac remodeling was assessed through echocardiography and after euthanasia, the isolated papillary muscle was evaluated. For comparison between groups, we used ANOVA followed by the Tukey test or Kruskal-Wallis and Dunn tests (p <0.05). Results: HIIT decreased the variation (Δ%) of SBP (SHR-SED=Δ% 12.5 vs. SHR-HIIT=Δ% -4.34; p = 0.005), increased the distance traveled, being 82.7% higher in the SHR-HIIT group (SHR-SED=183.0±88.08m; vs. SHR-HIIT=1126.0±187.1m; p<0.001) and reduced the resting tension of the papillary muscle (WKY=0.77 ± 0.216; SHR-SED=1.26 ± 0.20; SHR-HIIT=0.67 ± 0.23; p=0.0001). Conclusion: In SHR rats, HIIT decreased BP variation, improved functional capacity and ameliorated pathological cardiac remodeling. / Introdução: a Hipertensão Arterial Sistêmica (HAS), um grave problema de saúde pública, pode levar à hipertrofia concêntrica – um importante fator de risco para insuficiência cardíaca, que é considerada um preditor de maior morbimortalidade cardiovascular. Estudos evidenciam que o Treinamento Intervalado de Alta Intensidade (HIIT) pode ser indicado para hipertensos. Entretanto, para conhecimento, não há estudos que avaliaram o HIIT na remodelação cardíaca de animais com hipertensão arterial sistêmica. Objetivo: avaliar em ratos espontaneamente hipertensos (SHR) submetidos ao HIIT, o controle pressórico, a tolerância aos exercícios e o remodelamento cardíaco. Métodos: foram utilizados 20 ratos SHR divididos em dois grupos: sedentários (SHR-SED, n=9) e com treinamento HIIT (SHR-HIIT, n=11); e ratos Wistar Kyoto no grupo controle (WKY, n=6), com 12 meses. Os animais foram familiarizados antes do início do teste durante uma semana com 10 minutos, na velocidade de 6 metros por minutos na esteira adaptada para roedores. Realizou-se um teste de esforço incremental, iniciando-se com 10 minutos de aquecimento na velocidade de 6 metros por minutos, sem inclinação até que os ratos chegassem a exaustão, para graduar a intensidade do exercício. O HIIT foi executado cinco vezes por semana, durante oito semanas. Antes e após o HIIT, a pressão arterial (PA) foi aferida por pletismosgrafia e foi realizado um teste de capacidade máxima ao exercício. O remodelamento cardíaco foi avaliado pelo ecocardiograma e, após eutanásia, avaliou-se o músculo papilar isolado. Para comparação entre os grupos foi utilizado ANOVA seguido de Tukey ou Kruskal-Wallis e Dunn’s (p<0.05). Resultados: o HIIT diminuiu a PAS (SHR-SED=Δ%12.05 vs. SHR-HIIT=Δ%-4.34; p=0.005), aumentou a distância percorrida, sendo 82,7% maior no grupo SHR-HIIT (SHR-SED=183.0±88.08m vs. SHR-HIIT=1126.0±187.1m; p<0.0001) e reduziu a tensão de repouso do músculo papilar (WKY=0.77 ± 0.216; SHR-SED=1.26 ± 0.20; SHR-HITT=0.67 ± 0.23; p=0.0001). Conclusão: o HIIT em ratos SHR diminuiu a variação da PA, melhorou a capacidade funcional e amenizou o remodelamento cardíaco patológico.

L’hypertension artérielle chronique induit une hypertrophie ventriculaire gauche, à l’origine d’une dysfonction diastolique caractérisée par des troubles de la relaxation, de la compliance et du remplissage ventriculaires gauches, le tout aggravé par toute augmentation de la fréquence cardiaque. Le couplage contraction-relaxation physiologique implique, en cas de préservation dans ce contexte d’hypertrophie ventriculaire gauche, que cette dysfonction diastolique s’accompagne d’une dysfonction systolique. Ainsi, ce travail de thèse s’est attaché (1) à caractériser la fonction ventriculaire gauche et le couplage contraction-relaxation à l’aide de la mesure de la torsion et la détorsion, (2) à étudier les mécanismes cellulaires impliqués dans le couplage contraction-relaxation et (3) à explorer les effets d’une stratégie thérapeutique visant à réduire la fréquence cardiaque sur la torsion et la détorsion du ventricule gauche dans un modèle d’hypertension artérielle chronique et d’hypertrophie ventriculaire induites chez le porc chroniquement instrumenté par la perfusion continue d’angiotensine II pendant 28 jours. A J28, la torsion et la détorsion étaient diminuées et la détorsion également retardée au sein du cycle cardiaque, alors que la fraction d’éjection ventriculaire gauche était préservée. Le couplage contraction-relaxation était préservé, tant au niveau du ventricule gauche qu’à l’échelon cardiomyocytaire, suggérant que toute dysfonction diastolique devrait faire rechercher une dysfonction systolique. A J28, ces anomalies fonctionnelles s’accompagnaient d’une diminution de l’expression de la SERCA2a et de sa protéine régulatrice le phospholamban. Des anomalies du récepteur de la ryanodine de type 2 étaient aussi observées avec son hyperphosphorylation et la dissociation de sa protéine régulatrice calstabine 2, à l’origine de fuites calciques systoliques et diastoliques. Ce dernier pourrait ainsi jouer un rôle clé dans la préservation du couplage contraction-relaxation et représenter l’intégrateur entre les anomalies ventriculaire gauche systolique et diastolique observées. Enfin, la réduction pharmacologique de la fréquence cardiaque à J28 par l’ivabradine, un inhibiteur sélectif des canaux If, permettait d’améliorer, en partie par des effets fréquence-indépendants dont les mécanismes cellulaires restent à élucider, tant les anomalies ventriculaire gauche diastolique que systolique, avec une amélioration des temps de contraction et de relaxation isovolumiques, de la torsion et de la détorsion ainsi que du remplissage du ventricule gauche. En l’absence d’hypertrophie ventriculaire gauche, la réduction de la fréquence cardiaque à des valeurs inférieures à 60 batt/min s’accompagnait d’un effet délétère fréquence-dépendant, à l’origine d’une altération isolée de la fonction diastolique caractérisée par une diminution de la détorsion du ventricule gauche et une augmentation de la pression télédiastolique ventriculaire gauche. La caractérisation de la fonction ventriculaire gauche et l’étude du couplage contraction-relaxation par la mesure de la torsion et de la détorsion en cas de décompensation cardiaque restent à déterminer. / Chronic hypertension induces left ventricular (LV) hypertrophy, resulting in abnormalities in LV relaxation, passive stiffness and filling. The higher the heart rate, the more pronounced the LV diastolic dysfunction. Moreover, in the normal heart, there is a tight coupling between LV contraction and relaxation, implying that in case of preserved contraction-relaxation coupling during LV hypertrophy, there is no diastolic dysfunction without systolic dysfunction. Thus, the three main objectives of this thesis were to investigate 1) the LV function and contraction-relaxation coupling with LV twist and untwist, which represent LV myocardial deformation during systole and diastole, 2) the cellular mechanisms of the LV contraction-relaxation coupling and 3) the effects effects of heart rate reduction on LV twist and untwist in the context of chronic hypertension and LV hypertrophy. All experiments were conducted in a pig model of chronic hypertension and LV hypertrophy induced by four weeks of continuous angiotensin II infusion. Chronic angiotensin II infusion decreased LV twist and untwist but also delayed LV untwist in the cardiac cycle, whereas the LV ejection fraction was preserved. The contraction-relaxation coupling was preserved as illustrated by the strong relationship between LV twist and untwist. The contraction-relaxation coupling was also preserved at the level of cardiomyocytes. This implies that LV hypertrophy is associated with concomitant LV diastolic and systolic dysfunction despite preserved LV ejection fraction. Thus, LV diastolic dysfunction is always accompanied by LV systolic dysfunction, i.e., the discovery of LV diastolic dysfunction with preserved ejection fraction might imply the track of LV systolic dysfunction. At the cellular level, LV systolic and diastolic dysfunctions were associated to aberrant calcium handling with a remodelling of the type 2 ryanodine receptor calcium release channel (RyR2), i.e., PKA-hyperphosphorylation and depletion of calstabin 2 (FKBP12.6). RyR2 were leaky and hypersensitive to cytosolic calcium, during both the contraction and the relaxation phases. Since both LV systolic and diastolic dysfunctions were associated to leaky and hypersensitive RyR2 channels, it might suggest considering RyR2 as an integrator contributing to control contraction-relaxation coupling during chronic hypertension and LV hypertrophy. Finally, we investigated the effects of heart rate reduction induced by ivabradine, an If-channel blocker, which does not modify atrioventricular or LV conduction and is devoid of any intrinsic negative inotropic or lusitropic effects. In the context of chronic hypertension and LV hypertrophy, ivabradine improved both LV systolic and diastolic functions, as attested by the improvement in contraction and relaxation times, LV twist and untwist as well as LV filling. Heart-rate independent effects of ivabradine, i.e., pleiotropic effects, participate to its beneficial effect. However, the cellular mechanisms of these beneficial effects of ivabradine were not elucidated and require further investigations. In normal heart, when heart rate was reduced to a low level (approximately <60 beats/min) with ivabradine, LV twist was not affected but LV diastolic function was altered as suggested by decreased LV untwist parameters and increased LV end-diastolic pressure. Investigation of contraction-relaxation coupling during decompensation from stable LV hypertrophy remains a goal to achieve.