Les Entérovirus, et notamment les coxsackievirus B (CV-B), sont une cause commune de myocardite. Cette maladie peut évoluer vers une myocardite chronique jusqu’au stade de cardiomyopathie dilatée (CMD). Le mécanisme moléculaire permettant le passage de l’infection aigue à l’infection persistante dans le tissu cardiaque humain reste méconnu. Pour étudier les activités de réplication des CV-B persistant, un réplicon a été généré à partir d’une souche cardiotrope. Il a permis de caractériser les activités de réplication de CV-B persistant dans des cellules cardiaques humaines. Une analyse par séquençage à moyen débit a permis de mettre en évidence la sélection de variants tronqués dans le cœur pouvant expliquer la progression de la myocardite virale vers la CMD. De plus, l’existence de populations majoritaires tronquées de 19 à 50 nucléotides associées à des formes virales minoritaires complètes a été mise en évidence chez 8 patients atteints de CMD. La proportion de populations tronquées s’est révélée négativement corrélée au ratio ARN+/ARN- et à la charge virale (R2=0,748; P=0,016; R2= 0,36, P=0,038, respectivement). Des études immuno-histologiques et par hybridation in situ des tissus cardiaques ont montrées que le clivage de la dystrophine était uniquement retrouvé dans les cardiomyocytes infectés par les CV-B. La transfection d’ARN de synthèse complets et tronqués dans des cultures de cardiomyocytes humains primaires a mis en évidence une trans-complémentation entre les 2 formes virales induisant de faibles activités de réplication. Nos résultats démontre l’existence d’un nouveau mécanisme moléculaire de coopération entre des populations persistantes d’entérovirus B tronquées et complètes qui contribue à la physiopathologie de la CMD. / Enteroviruses, especially group B coxsackieviruses (CV-B) are considered to be a common cause of acute human myocarditis, a disease that is a precursor of chronic myocarditis cases as well as dilated cardiomyopathy (DCM). The molecular mechanisms related to the switch from the acute to the CV-B chronic persistent infection in human cardiac tissues are still unknown. To study the replication activities of CV-B a replicon from a cardiotropic prototype strain was generated and was used to study persistent CV-B replication activities into human cardiac cells. Using NGS analyses, our results evidenced that the molecular selection of TD viral forms in heart could explain pathophysiological progression from acute viral myocarditis to DCM. Moreover, we demonstrated in 8 end-stage DCM patients the existence of CV-B major populations characterized by 5’NTR deletions ranging from 19 to 50 nucleotides that were associated with minor full-length viral forms. The amounts of persistent deleted populations appeared to be negatively correlated to RNA(+)/RNA(-) minus ratio and viral load values (R2=0.748; P=0.016; R2= 0.36, P=0.038, respectively). In situ hybridization and immunohistological assays in cardiac tissues demonstrated that the dystrophin disruption was only present in EV-B infected cardiomyocytes. Transfection of deleted and full-length RNA-populations in cultured primary human cardiomyocytes evidenced a trans-acting genomic complementation system between the two viral forms resulting in low viral replication activities. Our findings suggest a new molecular mechanism through which persistent low replicative EV-B deleted and full-length collaborative populations contribute to the pathogenesis of idiopathic DCM cases.

Dilated Cardiomyopathy (DCM) with conduction disease and Atrial Fibrillation (AF) are the two cardiac-specific diseases associated with lamin A/C gene (LMNA) mutations. Protein Kinase C Alpha, (PKCα) functions as a nodal integrator of cardiac contractility by “sensing” intracellular calcium and signal transduction. PKCα has been implicated in heart failure and cardiac hypertrophy. Moreover, abnormal PKCα function results in irregular atrial potassium channel activity associated with chronic AF PKCα is a lamin A/C binding partner. Thus, the deregulation of PKCα signaling can contribute to the development of DCM and AF. Our hypothesis is that the AF (Thr528Met), DCM-associated (Arg541Cys) and (Arg541Gly) and DCM/AF-associated (Tyr481Stop) LMNA variants will disrupt the cellular distribution of PKCα therefore resulting in impaired PKCα function. The first objective was to phenotypically characterise Arg541Cys LMNA variant in murine skeletal myoblasts cell line (C2C12) in comparison to cellular phenotypes induced by LMNA variants associated with AF, DCM and DCM with AF. Arg541Cys lamin A and C variants formed circular and sickle-shaped lamin A/C in the nucleus of C2C12 cells. The second objective was to determine the effect of these lamin variants on cellular distribution of PKCα in C2C12 cells. PKCα mislocalized into the nucleus of C2C12 cells transfected with AF and DCM-associated variants (Thr528Met and Arg541Cys). Colocalization analysis showed significant increase in PKCα in the nucleus of AF (Thr528Met) and DCM (Arg541Cys) variants when lamin A and C, were co-transfected compared to wild-type, DCM (Arg541Gly) and DCM/AF (Tyr481Stop) variants. Densitometry analysis showed statistically significant increase in phosphorylated PKCα, the active form of PKCα, in nuclear and cytoplasmic extracts of C2C12 cells expressing Arg541Cys variant. Densitometry analysis also showed statistically significant increase in non-phosphorylated PKCα in the nuclear extract of Thr528Met variant expressing cells. The third objective was to determine the effect of AF and DCM-associated variants on the activity of PKCα. PKCα activity is quantified by measuring the phosphorylation of a known phosphorylated PKCα substrate. Alpha-6-tubulin phospho (Ser165) is phosphorylated by PKCα. Hence, this was used to quantify PKCα activity. No statistical significance was observed in the level of phosphorylated alpha-6-tubulin at (Ser165) in the C2C12 cells that were transfected with lamin A and C variants compared to wild type. Furthermore, PKCα phosphorylation state is cyclic in nature and this could have had an impact on the phosphorylation state of the chosen substrate in this study. The functional consequence of nuclear translocation of PKCα with respect to laminopathies is unknown. Abnormal activation of the Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2) which are branches of the mitogen-activated protein kinase (MAPK) signalling cascade in hearts of mice, and humans prior to the onset of cardiomyopathy. These findings have been associated to cardiac disease-causing lamin A/C alteration to signal transduction pathways implicated in heart function and cardiomyopathy. Human LMNA cardiomyopathy, could lead to abnormal activation of MAPK signalling pathways via abnormal PKCα activation in cardiomyocytes.

No description available.

Objective: Unusual clinical course Background: "Bath salts" is the street name for a group of recently identified and increasingly abused stimulant synthetic cathinones that are associated with multiple systemic effects. We present a case of a patient who developed reversible dilated cardiomyopathy secondary to their use. Case Report: A 27 year old male with no past medical history was brought to emergency department with agitation. He had been inhaling and intravenously injecting "bath salts", containing a mephedrone/Methylenedioxypyrovalerone (MDPV) combination. On presentation, he was tachycardic, hypotensive and febrile. His initial labs showed an elevated white count, creatinine and creatinine phosphokinase levels. His erythrocyte sedimentation rate; C-reactive protein; urinalysis; urine drug screen; Human Immunodeficiency Virus, hepatitis, coxsackie, and influenza serology were normal. EKG showed sinus tachycardia. An echocardiogram was done which showed dilated cardiomyopathy with an ejection fraction (EF) of 15-20% and global hypokinesia. A left heart catheterization was done and was negative for coronary artery disease. At a 20 week follow up, he had stopped abusing bath salts and was asymptomatic. A repeat echocardiogram showed an EF of 52%. Cocnlusions: Bath salts (MDPV, mephedrone) are synthetic cathinones with amphetamine/cocaine like properties with potential cardiotoxic effects. Cardiovascular manifestations reported include tachycardia, hypertension, myocardial infarction, arrhythmias and cardiac arrest. "Bath salts" can also cause severe reversible dilated cardiomyopathy. Prior to diagnosis, other causes of cardiomyopathy including ischemic, infectious, familial, immunological, metabolic and cytotoxic may need to be ruled out; as was done in our patient.

Objective: Unusual clinical course Background: "Bath salts" is the street name for a group of recently identified and increasingly abused stimulant synthetic cathinones that are associated with multiple systemic effects. We present a case of a patient who developed reversible dilated cardiomyopathy secondary to their use. Case Report: A 27 year old male with no past medical history was brought to emergency department with agitation. He had been inhaling and intravenously injecting "bath salts", containing a mephedrone/Methylenedioxypyrovalerone (MDPV) combination. On presentation, he was tachycardic, hypotensive and febrile. His initial labs showed an elevated white count, creatinine and creatinine phosphokinase levels. His erythrocyte sedimentation rate; C-reactive protein; urinalysis; urine drug screen; Human Immunodeficiency Virus, hepatitis, coxsackie, and influenza serology were normal. EKG showed sinus tachycardia. An echocardiogram was done which showed dilated cardiomyopathy with an ejection fraction (EF) of 15-20% and global hypokinesia. A left heart catheterization was done and was negative for coronary artery disease. At a 20 week follow up, he had stopped abusing bath salts and was asymptomatic. A repeat echocardiogram showed an EF of 52%. Cocnlusions: Bath salts (MDPV, mephedrone) are synthetic cathinones with amphetamine/cocaine like properties with potential cardiotoxic effects. Cardiovascular manifestations reported include tachycardia, hypertension, myocardial infarction, arrhythmias and cardiac arrest. "Bath salts" can also cause severe reversible dilated cardiomyopathy. Prior to diagnosis, other causes of cardiomyopathy including ischemic, infectious, familial, immunological, metabolic and cytotoxic may need to be ruled out; as was done in our patient.

Myeloid differentiation protein-88 (MyD88) is a crucial adaptor protein in the innate immune response. A protective role for MyD88 in normal cardiac function has been proposed in a surgical hypertrophic model. To assess the in vivo role of MyD88 in cardiac remodeling, we generated transgenic mice with cardiac-restricted expression of a dominant negative mutant of MyD88 (dnMyD88). Surprisingly, dnMyD88 transgenic mice displayed characteristic features of heart failure; including heart weight increase, cardiomyocytes enlargement, interstitial fibrosis, and re-expression of "fetal" genes. Echocardiographic examination of dnMyD88 hearts revealed dilated chamber volume and reduced cardiac contractility. DnMyD88 mice died from heart failure before they were 7 months old, as shown by Kaplan-Meier analysis. Additionally, the heart failure phenotype of dnMyD88 mice was associated with abnormal activation of the Akt/GSK-3β signaling pathway. These data provide the first evidence that normal MyD88 signaling is crucial for maintaining the physiological function of the adult heart.

We identified a unique family with autosomal dominant heart disease variably expressed as restrictive cardiomyopathy (RCM), hypertrophic cardiomyopathy (HCM), and dilated cardiomyopathy (DCM), and sought to identify the molecular defect that triggered divergent remodeling pathways. Polymorphic DNA markers for nine sarcomeric genes for DCM and/ or HCM were tested for segregation with disease. Linkage to eight genes was excluded, but a cardiac troponin T (TNNT2) marker cosegregated with the disease phenotype. Sequencing of TNNT2 identified a heterozygous missense mutation resulting in an I79N substitution, inherited by all nine affected family members but by none of the six unaffected relatives. Mutation carriers were diagnosed with RCM (n = 2), non-obstructive HCM (n = 3), DCM (n = 2), mixed cardiomyopathy (n = 1), and mild concentric left ventricular hypertrophy (n = 1). Endomyocardial biopsy in the proband revealed non-specific fibrosis, myocyte hypertrophy, and no myofibrillar disarray. Restrictive Doppler filling patterns, atrial enlargement, and pulmonary hypertension were observed among family members regardless of cardiomyopathy subtype. Mutation of a sarcomeric protein gene can cause RCM, HCM, and DCM within the same family, underscoring the necessity of comprehensive morphological and physiological cardiac assessment in familial cardiomyopathy screening.

No description available.

No description available.

Both hypertrophied and failing hearts are characterised by pathological left ventricular (LV) remodelling, impaired myocardial energy status and alteration in substrate metabolism. Cardiac magnetic resonance imaging (CMR) and magnetic resonance spectroscopy (MRS) are powerful tools in the characterisation of these disease conditions. More recent techniques have allowed assessment of myocardial steatosis using ¹H-MRS and tissue oxygenation using blood oxygen level dependent (BOLD) CMR. In hypertrophy and heart failure, studies on steatosis and the relationship with other parameters such as myocardial function and fibrosis, especially in humans are limited. I therefore investigated the presence of steatosis in severe aortic stenosis (AS) and dilated cardiomyopathy (DCM), and further assessed its relation to contractile function. This study found that myocardial triglyceride (TG) content is increased in both symptomatic and asymptomatic AS patients (lipid/water ratio 0.89±0.42% in symptomatic AS; 0.75±0.36% in asymptomatic AS vs. controls 0.45±0.17%, both p<0.05) and DCM patients (lipid/ratio 0.64±0.44% vs. controls 0.40±0.13%, p=0.03). Circumferential strain was lower in both AS (-16.4±2.5% in symptomatic AS; -18.9±2.9% in asymptomatic AS vs. controls 20.7±2.0%, both p<0.05) and DCM patients (-12.3±3.4% vs. controls -20.9±1.7%, p<0.001). In AS, myocardial contractility is related to the degree of steatosis, and were both reversible following aortic valve replacement (AVR), lipid/water ratio 0.92±0.41% vs. pre AVR 0.45±0.17%, p=0.04 and circumferential strain -17.2±2.0% vs. pre AVR -19.5±3.2%, p=0.04. A novel finding of this study was significant correlation of MRS-measured TG content with histological staining of TG of the myocardium, taken from endomyocardial biopsy during AVR. In DCM, myocardial TG was independently associated with LV dilatation and correlated significantly with hepatic TG, which suggests that both cardiac and hepatic steatosis might be a common feature in the failing heart. Additionally, although the hypertrophied heart is characterised by impaired perfusion, it is unknown if this is severe enough to translate into tissue deoxygenation and ischaemia. I assessed this by using adenosine vasodilator stress test and BOLD-CMR in patients with severe AS. It was found that AS patients had reduced perfusion (myocardial perfusion reserve index-MPRI 1.0±0.3 vs. controls 1.7±0.3, p<0.001), and blunted tissue oxygenation (blood-oxygen level dependent-BOLD signal intensity-SI change 4.8±9.6% vs. controls 18.2±11.6%, p=0.001) during stress. Importantly, there was a substantial improvement in perfusion and oxygenation towards normal after AVR, MPRI 1.5±0.4, p=0.005 vs. pre AVR and BOLD SI change 16.4±7.0%, p=0.014 vs. pre AVR. Overall, the work in this thesis supports the powerful role of CMR in assessing LV function and elucidating metabolic mechanisms in the hypertrophied and failing heart.