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International audience; Aging is the major risk factor for the development of chronic diseases. After decades of research focused on extending lifespan, current efforts seek primarily to promote healthy aging. Recent advances suggest that biological processes linked to aging are more reliable than chronological age to account for an individual's functional status, i.e. frail or robust. It is becoming increasingly apparent that biological aging may be detectable as a progressive loss of resilience much earlier than the appearance of clinical signs of frailty. In this context, the INSPIRE program was built to identify the mechanisms of accelerated aging and the early biological signs predicting frailty and pathological aging. To address this issue, we designed a cohort of outbred SWISS mice (1576 male and female mice) in which we will continuously monitor spontaneous and voluntary physical activity from 6 to 24 months of age under either normal or high fat/high sucrose diet. At different age points (6, 12, 18, 24 months), multiorgan functional phenotyping will be carried out to identify early signs of organ dysfunction and generate a large biological fluids/feces/organs biobank (100,000 samples). A comprehensive correlation between functional and biological phenotypes will be assessed to determine: 1) the early signs of biological aging and their relationship with chronological age; 2) the role of dietary and exercise interventions on accelerating or decelerating the rate of biological aging; and 3) novel targets for the promotion of healthy aging. All the functional and omics data, as well as the biobank generated in the framework of the INSPIRE cohort will be available to the aging scientific community. The present article describes the scientific background and the strategies employed for the design of the INSPIRE Mouse cohort.

Heart failure (HF) is a leading cause of death in industrialized countries. Although the intrinsic mechanisms are complex, oxidative stress has been described as a key player in the progression of ventricular dysfunction during the pathology. Thus, the team has been interested in monoamine oxidase A (MAO-A), an enzyme located at the outer mitochondrial membrane, which is the main degradation pathway for catecholamines and serotonin. In recent years, MAO-A has been identified as a major source of oxidative stress in the heart. The aim of this thesis was to better characterize the mechanisms of action of MAO-A, oxidative stress and its downstream effectors in cardiac remodeling, which would constitute an important advance in the understanding of HF pathophysiology.In the first part, we were interested in chronic myocardial infarction (MI), which is the main leading cause of HF. We observed that MAO-A was activated during chronic ischemia in patients as well as in mice, and this activation was involved in post-MI deleterious remodeling. From a mechanistic point of view, we saw that MAO-A activation promoted mitochondrial accumulation of 4-hydroxynonenal (4-HNE), a highly reactive aldehyde, through intra-mitochondrial lipid peroxidation. This accumulation triggered 4-HNE binding on specific mitochondrial targets, favoring calcium overload within the organelle, alteration of the respiratory chain and energetic failure, further contributing to deleterious post-MI remodeling. This study therefore highlighted the key role of mitochondrial dysfunction in MAO-A-induced damage. In a second part, we sought to characterize the consequences of long-term MAO-A overactivation on mitochondrial quality control. Indeed, dysfunctional mitochondria are normally eliminated by the autophagy-lysosome pathway, but studies have shown that this pathway is progressively impaired during HF. Our results showed that MAO-A activation led to an alteration of lysosomal acidification and a lack of nuclear translocation of the transcription factor EB (TFEB), a “master regulator” of autophagy and lysosomal biogenesis. As a result, we observed a blockade of autophagic flux leading to cardiomyocyte necrosis. Interestingly, TFEB overexpression in MAO-A-overexpressing mice mitigated autophagosomes accumulation, mitochondrial fission, cardiomyocytes death and cardiac dysfunction, which spontaneously occur in this mouse model. Despite these very exciting results, this project highlighted a dramatic lack of lysosomotropic tools that could be used in research and/or as therapeutic tools. We thus collaborated with the company « Chromalys » in order to develop nanoparticles (NPs) able to (re)acidify lysosomes with an altered pH. After showing a lysosomal addressing of these NPs, we evaluated their functional consequences on cells treated with doxorubicin, a clinically used anthracycline which has been pointed to alter lysosomal pH in cardiac cells. We observed that NPs improved lysosomal acidification, autophagic flux and cell viability that were altered by doxorubicin, making these NPs very interesting tools in the study of lysosomal alteration and in the restoration of their function. This thesis dealt with several axes corresponding to different HF aspects and brought new advances on the understanding of the pathophysiological mechanisms of this complex disease. It has also allowed the identification of potentially interesting therapeutic tools that could open new tracks in HF treatment., L’insuffisance cardiaque (IC) est une cause majeure de mortalité dans les pays industrialisés. Bien que les mécanismes intrinsèques de l’IC soient complexes, il a été démontré que le stress oxydant était un déterminant essentiel dans la progression de la dysfonction ventriculaire au cours de la pathologie. En ce sens, l’équipe s’est intéressée à la monoamine oxydase A (MAO-A), une enzyme située au niveau de la membrane externe mitochondriale, qui constitue la principale voie de dégradation des catécholamines et de la sérotonine. Au cours des dernières années, la MAO-A a été identifiée comme une source importante de stress oxydant dans le cœur. Le but de cette thèse a été de mieux caractériser les mécanismes d’action de la MAO-A, du stress oxydant et de ses effecteurs dans l’altération cardiaque, ce qui pourrait constituer une avancée importante dans la compréhension des mécanismes physiopathologiques de l’IC. Dans une première partie, nous nous sommes intéressés à l’infarctus du myocarde (IDM) chronique qui constitue la cause principale d’IC. Nous avons observé que la MAO-A était activée au cours de l’ischémie chronique chez des patients ainsi que chez des souris, et que cette activation participait au remodelage délétère post-IDM. D’un point de vue mécanistique, nous avons montré que l’activation de la MAO-A favorisait l’accumulation mitochondriale de 4-hydroxynonénal (4-HNE), un aldéhyde très réactif, via une peroxydation lipidique intra-mitochondriale. Cette accumulation a conduit à la fixation du 4-HNE sur certaines cibles mitochondriales, favorisant une surcharge calcique dans l’organite, une altération de la chaîne respiratoire et un déficit énergétique, qui participent au remodelage délétère post-IDM. Cette étude a donc permis de mettre en évidence le rôle clé de la dysfonction mitochondriale dans les dommages induits par la MAO-A. Dans une deuxième partie, nous avons cherché à caractériser les conséquences de la suractivation de la MAO-A sur le contrôle qualité mitochondrial à long terme. Les mitochondries dysfonctionnelles sont normalement éliminées par la voie autophagie-lysosome, mais des études ont montré que cette voie était progressivement altérée dans l’IC. Nos travaux ont montré que l’activation chronique de la MAO-A entrainait une altération de l’acidification lysosomale et un défaut de translocation nucléaire du facteur de transcription EB (TFEB), un « master régulateur » de l'autophagie et de la biogenèse des lysosomes.