Early physiopathological mechanisms involved in different induced cardiomyopathies

Les stress physiopathologiques cardiaques sont associés dans la plupart des cas à une production d’espèces réactives oxygénées (ROS). Les ROS entrent dans plusieurs mécanismes physiologiques, cependant, des niveaux élevés de production de ROS produisent généralement des changements délétères dans la performance contractile et conduisent à un remodelage cardiaque défavorable. Il est maintenant établit qu’un stress oxydant important entraîne une altération de l'expression et/ou la fonction des protéines sarcomériques contribuant aux dysfonctions contractiles observées dans les diverses pathologies cardiaques. Ce travail de thèse a consisté à étudier l’impact du stress oxydant sur la fonction contractile cardiaque in-vivo, ex-vivo, et in-vitro dans diffèrent modèles de stress physiopathologiques cardiaques. Plus précisément, nous avons étudié le remodelage précoce de la machinerie contractile in-vitro, notamment les modifications post-traductionnelles des protéines sarcomériques dépendantes directement ou indirectement des ROS, mais aussi, la conséquence de ces modifications sur la fonction contractile cardiaque in-vivo et ex-vivo. Pour cela, nous avons généré deux modèles animaux de stress physiopathologiques cardiaques (exercice physique et chimiothérapie) ayants des mécanismes moléculaires différents tout en étant reliés par une perturbation commune : une production importante de ROS. Ainsi, ce travail de thèse s’est intéressé à la compréhension des mécanismes physiopathologiques à l’origine de : i) la dysfonction diastolique résultante d’un exerce physique épuisant, ii) la cardiomyopathie résultante de la prise d’anthracyclines. Dans ces études, nous avons étudié les modifications post-traductionnelles induites par les ROS des protéines sarcomériques (MyBP-C et TnI), ainsi que les conséquences sur la fonction cardiaque in-vivo, ex-vivo, et in-vitro. Ce travail de thèse a permis de montrer l’importance de la voie oxydative dans la régulation/dérégulation de la fonction cardiaque, aussi bien à l’échelle de l’organe qu’à l’échelle de la cellule. Il démontre notamment, que la voie oxydative peut interagir avec la voie adrénergique pour modifier les propriétés contractiles (étude #1). De plus, ce travail a permis de mettre en évidence que la voie oxydative induit des modifications précoces des propriétés contractiles qui sont hétérogènes à travers le ventricule gauche (étude #2).Cardiac pathophysiological stress is generally associated with reactive oxygen species (ROS) production. ROSs are involved in several physiological mechanisms, however, high levels of ROS production induce deleterious changes in contractile performance and lead to adverse cardiac remodeling. It is now established that significant oxidative stress results in impaired expression and/or function of sarcomeric proteins and contribute to contractile dysfunctions observed in various cardiac pathologies.This work aim to study the oxidative stress impact on cardiac contractile function in-vivo, ex-vivo, and in-vitro, in different models of cardiac pathophysiological stress. Specifically, we studied the in-vitro contractile machinery early remodeling, including post-translational modifications of sarcomeric proteins directly or indirectly related to ROS, and the consequences of these modifications on cardiac contractile function in-vivo and ex-vivo. For this purpose, we used two animal models of cardiac pathophysiological stress (intense physical exercise and chemotherapy) having different molecular mechanisms but connected by an important ROS production.Thus, this thesis work focused on the pathophysiological mechanisms involved in diastolic dysfunction induced by an exhausting physical exercise and the anthracyclines induced cardiomyopathy. In these studies, we investigated ROS-induced post-translational modifications of sarcomeric proteins (MyBP-C and TnI), as well as, the consequences on cardiac function in-vivo, ex-vivo, and in-vitro. This work has shown the oxidative pathway importance in the cardiac function regulation/deregulation. Especially, it demonstrates that the oxidative pathway can interfere with the adrenergic pathway to modify contractile properties (study #1). In addition, this work has shown that the oxidative pathway induces early heterogeneous changes across the left ventricle in contractile properties (study #2)

Screening for in-vivo regional contractile defaults to predict the delayed Doxorubicin Cardiotoxicity in Juvenile Rat

Anthracyclines are key chemotherapeutic agents used in various adult and pediatric cancers, however, their clinical use is limited due to possible congestive heart failure (HF) caused by acute and irreversible cardiotoxicity. Currently, there is no method to predict the future development of the HF in these patients. In order to identify early biomarkers to predict anthracycline cardiotoxicity in long-term survivors of childhood cancer, this longitudinal study aimed to analyze early and late in-vivo regional myocardial anthracycline-induced cardiotoxicity, related to in-vitro cardiac myocytes dysfunction, in a juvenile rat model. Methods: Young male Wistar rats (4 weeks-old) were treated with different cumulative doses of doxorubicin (7.5, 10 or 12.5 mg/kg) or NaCl (0.9%) once a week for 6 weeks by intravenous injection. Cardiac function was evaluated in-vivo by conventional (left ventricular ejection fraction, LVEF) and regional two-dimensional (2D) speckle tracking echocardiography over the 4 months after the last injection. The animals were assigned to preserved (pEF) or reduced EF (rEF) groups at the end of the protocol and were compared to controls. Results: We observed a preferential contractile dysfunction of the base of the heart, further altered in the posterior segment, even in pEF group. The first regional alterations appeared 1 month after chemotherapy. Functional investigation of cardiomyocytes isolated from the LV base 1 month after doxorubicin treatment showed that early in-vivo contractile alterations were associated with both decreased myofilament Ca2+ sensitivity and length-dependent activation. Changes in post-translational modifications (phosphorylation; S-glutathionylation) and protein degradation of the cardiac myosin binding protein-C may contribute to these alterations. Conclusion: Our data suggest that screening of the contractile defaults of the base of the heart by regional 2D strain echocardiography is useful to detect subclinical myocardial dysfunction prior to the development of delayed anthracycline-induced cardiomyopathy in pediatric onco-cardiology

Stress-induced protein S-glutathionylation and phosphorylation crosstalk in cardiac sarcomeric proteins - Impact on heart function

International audienc

New role of TRPM4 channel in the cardiac excitation-contraction coupling in response to physiological and pathological hypertrophy in mouse

International audienc

The TRPM4 channel is functionally important for the beneficial cardiac remodeling induced by endurance training

International audienc

New role of TRPM4 channel in the cardiac excitation-contraction coupling in response to physiological and pathological hypertrophy in mouse

International audienc

Fibroblast growth factor homologous factors tune arrhythmogenic late NaV1.5 current in calmodulin binding–deficient channels

The Ca2+-binding protein calmodulin has emerged as a pivotal player in tuning Na+ channel function, although its impact in vivo remains to be resolved. Here, we identify the role of calmodulin and the NaV1.5 interactome in regulating late Na+ current in cardiomyocytes. We created transgenic mice with cardiac-specific expression of human NaV1.5 channels with alanine substitutions for the IQ motif (IQ/AA). The mutations rendered the channels incapable of binding calmodulin to the C-terminus. The IQ/AA transgenic mice exhibited normal ventricular repolarization without arrhythmias and an absence of increased late Na+ current. In comparison, transgenic mice expressing a lidocaine-resistant (F1759A) human NaV1.5 demonstrated increased late Na+ current and prolonged repolarization in cardiomyocytes, with spontaneous arrhythmias. To determine regulatory factors that prevent late Na+ current for the IQ/AA mutant channel, we considered fibroblast growth factor homologous factors (FHFs), which are within the NaV1.5 proteomic subdomain shown by proximity labeling in transgenic mice expressing NaV1.5 conjugated to ascorbate peroxidase. We found that FGF13 diminished late current of the IQ/AA but not F1759A mutant cardiomyocytes, suggesting that endogenous FHFs may serve to prevent late Na+ current in mouse cardiomyocytes. Leveraging endogenous mechanisms may furnish an alternative avenue for developing novel pharmacology that selectively blunts late Na+ current