Des approches thérapeutiques visant à la stimulation de la régénération et/ou à l’inhibition des processus de dégénérescence neuromusculaire pourraient constituer des stratégies efficaces pour préserver le tonus musculaire des patients et augmenter ainsi leur espérance de vie. L’activation de la Calcineurine A (CnA), une phosphatase des sérines et thréonines, contrôle une large gamme de réseaux régulateurs dans le muscle squelettique, notamment en stimulant l’expression de gènes spécifiques des fibres musculaires lentes (de type I). La CnA est considérée comme un acteur clé de la réponse hypertrophique et du processus de régénération dans le muscle squelettique. L’activation de la CnA est ainsi considérée comme une stratégie potentielle pour stimuler la régénération musculaire dans les cas de myopathie. Nous avons identifié un aptamère peptidique qui active la CNA in vitro et in vivo. Dans un modèle murin d’atrophie musculaire induite par dénervation, l’aptamère a montré de significatives capacités thérapeutiques. L’effet curatif de l’aptamère a notamment été observable par une augmentation générale de la surface des muscles traités, mais aussi par un accroissement de la surface individuelle des fibres musculaires.Une augmentation du niveau de NFAT nucléaire dans ces fibres a été observée, en cohérence avec les capacités d’activation de la CnA par notre aptamère. Par ailleurs, une autre observation faite dans les muscles traités avec l’aptamère a été l’augmentation de noyaux centraux, caractéristiques de la présence de nouvelles fibres. Finalement, l’identification du site d’interaction entre la CnA et notre aptamère, permise par l’utilisation de plusieurs formes tronquées de la phosphatase, a offert un aperçu du mécanisme d’action de l’aptamère à l’échelle moléculaire. Dans l’ensemble, les études présentées ici ont offert la première démonstration qu’une activation directe de la CnA endogène a un impact significatif sur les processus cellulaires, résultant en la stimulation de la régénération musculaire et l’amélioration de l’état physiopathologique chez les modèles animaux utilisés. / Therapeutic approaches leading to the stimulation of regeneration, and/or inhibition of degeneration processes in neuromuscular disorders are believed to offer valid therapeutic strategies that would preserve muscle tone and contribute to the quality of life while lengthening patient life span. Activation of CalcineurinA (CnA), a threonine-serine phosphatase, controls gene regulatory programs in skeletal muscle by stimulating slow muscle fiber (type I) gene expression. This phosphatase has been also identified as a key mediator in the hypertrophic response and in skeletal muscle regeneration. Activation of CnA is, therefore, considered as a potentially interesting means of stimulating muscle regeneration in myopathies. We have identified a peptide aptamer that activates CnA in vitro, in cells and in vivo. In a mouse model for denervation-induced muscle atrophy, CnA-activating peptide aptamers show significant positive impact. This is reflected in larger overall muscle cross-sectional surface area due to an increased number of fibers and larger individual fiber surface area. Insight into the biological mechanism is afforded by observation of increased levels of nuclear NFAT transcription factor in these fibers, in agreement with peptide aptamer-mediated activation of CnA. Furthermore, a significant increase in central nuclei, characteristic of the presence of new fibers, is observed in muscles treated with the peptide aptamers specifically activating CnA. Identification of the specific binding site of the peptide aptamer on CnA was achieved using several truncations of the phosphatase, offering insight into the molecular mechanism of action. Together, these studies offer the first proof that direct activation of endogenous CnA has a measureable impact on cellular responses resulting in stimulation of muscle regeneration and enhancement of pathophysiological state in selected animal models. / Specifici approcci terapeutici diretti alla stimolazione della rigenerazione e/o dell’inibizione dei processi degenerativi in patologie neuromuscolari, sono considerati come strategie efficaci per preservare il tono muscolare e aumentare in questo modo la speranza di vita dei pazienti. L’attivazione della Calcineurin A (CnA), una treonina/serina fosfatasi, controlla una vasta gamma di vie di trasduzione nel muscolo scheletrico, stimolando in particolare l’espressione dei geni specifici delle fibre muscolari lente (tipo 1). La Cna rappresenta un elemento chiave nella risposta ipertrofica e nel processo di rigenerazione muscolare. Per questo motivo, l’attivazione della CnA é considerata come un’approccio terapeutico interessante per stimolare la rigenerazione muscolare nelle miopatie. Nel nostro laboratorio, abbiamo identificato un aptamero peptidico che attiva la CnA sia in vitro che in vivo. In un modello murino di atrofia muscolare indotta tramite denervazione, l’aptamero petidico risulta avere delle significative potenzialità terapeutiche. Tale effetto si riflette in un aumento della superficie totale delle sezioni trasversali dei muscoli trattati, dovuto all’aumento sia del numero delle fibre che alla loro superficie individuale. L’effetto dell’aptamero peptidico sull’attivazione della CnA , nelle fibre trattate in vivo é dimostrata dall’osservazione della localizzazione prevalentemente nucleare del fattore di trascrizione NFAT, principale substrato della CnA. Un notevole aumento di nuclei centrali, caratteristica principale del processo di rigenerazione muscolare, é inoltre osservato in queste fibre. L’identificazione del sito d’interazione dell’aptamero peptidico e la proteina tramite l’utilizzo di vari costrutti della CnA ha permesso di avanzare delle ipotesi sul meccanismo d’azione dell’aptamero a livello molecolare. In conclusione, gli studi esposti in questa tesi rappresentano la prima dimostrazione che la diretta attivazione della CnA endogena ha un notevole effetto sulla stimolazione della rigenerazione muscolare e porta al miglioramento dello stato fisio-patologico nei modelli murini utilizzati.

Acid-sensing ion channels (ASIC) are a class of ligand gated plasma membrane ion channels that are activated by low extracellular pH. During ischemia, ASIC1a are activated and contribute to the demise of neurons. Pharmacological block of ASIC1a provides neuroprotection at delayed time points. However, no endogenous receptors have been implicated in the modulation of ASIC1a activity. The hypothesis presented is that sigma receptor activation inhibits ASIC1a function and ASIC1a-induced [Ca²?]i elevations during acidosis and ischemia, which may be a mechanism by which sigma ligands provide neuroprotection following stroke. This hypothesis is based on the following observations: First, sigma receptors regulate multiple ion channels that become activated during ischemia. Second, ASIC1a remain functionally active hours beyond the ischemic insult and sigma receptors have been shown to be neuroprotective at delayed time points following stroke. Ratiometric Ca²+ fluorometry and whole-cell patch clamp experiments showed that sigma-1 receptor activation depresses elevations in [Ca²+]i and membrane currents mediated by ASIC1a channels in cortical neurons. Furthermore, most of the elevations in [Ca²+]i triggered by acidosis are the result of Ca²+ channels opening downstream of ASIC1a activation. Stimulation of sigma-1 receptors effectively suppressed these secondary Ca²+ fluxes both by inhibiting ASIC1a and the other channels directly. The signaling cascade linking sigma-1 receptors and ASIC1a was determined to involve a pertussis toxin-sensitive G protein and A-Kinase Anchoring Protein 150/calcineurin complex, which resulted in a decrease of acid-induced [Ca²+]i elevations and ASIC1a-mediated currents. Furthermore, immunohistochemical studies confirmed that sigma-1 receptors, ASIC1a and AKAP150 colocalize in the plasma membrane of cortical neuron cell bodies and in the dendritic processes of these cells. Additionally, concurrent exposure to acidosis and ischemia resulted in synergistic potentiation of [Ca²+]i dysregulation. Although ASIC1a activation does not induce long-lived priming of synaptic vesicles for release, channel activation does have a temporal effect on ischemia-mediated [Ca²+]i increases after ischemia onset. Moreover, presynaptic ASIC1a channels promote synaptic transmission during ischemia by overcoming block of neurotransmission and thus enhance postsynaptic [Ca²+]i elevations. Sigma-1 receptor activation decreased ischemia-mediated Ca²+ dysregulation at pH values of 7.4 - 6.0 and prevented the synergistic interaction between ischemia and acidosis.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23421号 / 医博第4766号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 小濱 和貴, 教授 妹尾 浩, 教授 川口 義弥 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Calmodulin is a prevalent calcium sensing protein found in all cells. Three genes exist for calmodulin and all three of these genes encode for the exact same protein sequence. Recently mutations in the amino acid sequence of calmodulin have been identified in living human patients. Thus far, patients harboring these mutations in the calmodulin sequence have only displayed an altered cardiac related phenotype. Calcineurin is involved in many key physiological processes and its activity is regulated by calcium and calmodulin. In order to assess whether or not calcineurin contributes to calmodulinopathy (a pathological state arising from dysfunctional calmodulin), a comprehensive search of relevant literature has been performed. Herein, the physiological roles of calcineurin and consequences of dysfunction have been reviewed for literature focused on the heart.

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Thesis (Ph.D. in Neuroscience) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 110-125). Online version available via ProQuest Digital Dissertations.

The introduction of calcineurin inhibitors (CNI) into immunosuppressive regimens significantly improved patients prognosis after heart transplantation. Some of the most significant complications have been recognized, such as the development of arterial hypertension and renal impairment due to calcineurin inhibitor toxicity. The aim of the study was to compare the effect of the dual blockade of the renin-angiotensin system (dual RAS combination) with standard antihypertensive medication on blood pressure control. The second aim was to evaluate whether effective antihypertensive combination therapy (dual RAS or a standard antihypertensive drugs combination) would reduce the progression of chronic kidney disease in patients with chronic immunosuppressive prophylaxis. Treatment of arterial hypertension involving the combination of angiotensin-converting enzyme inhibitor (ACEi) and angiotensin II receptor blocker (ARB) was similarly effective compared to the standard combination of antihypertensives. Blood pressure treatment targets were achieved in both studies. Administration of antihypertensive combination therapy including dual blockade of RAS alleviated the progression of chronic renal disease in the experimental and clinical part, where the nephroprotective effect of dual RAS blockade...

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