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Introduction Physical activity is an important factor for the prevention of heart disease and also an important component of rehabilitation for patients with established cardiovascular disease (Perez-Terzic 2012). Even so, [...], Exercise enhances cardiac sarcoplasmic reticulum [Ca.sup.2+]-ATPase 2a (SERCA2a) function through unknown mechanisms. The present study tested the hypothesis that the positive effects of exercise on SERCA2a expression and function in the left ventricle is dependent on adenosine-monophosphate-activated protein kinase (AMPK) [[alpha].sub.2] function. [AMPK[alpha].sub.2] kinase-dead (KD) transgenic mice, which overexpress inactivated [AMPK[alpha].sub.2] subunit, and wild-type C57Bl/6 (WT) mice were randomized into sedentary groups or groups with access to running wheels. After 5 months, exercised KD mice exhibited shortened deceleration time compared with sedentary KD mice. In left ventricular tissue, the ratio of phosphorylated [AMPK[alpha].sup.Thr72]:total AMPK[alpha] was 65% lower (P < 0.05) in KD mice compared with WT mice. The left ventricle of KD mice had 37% lower levels of SERCA2a compared with WT mice. Although exercise increased SERCA2a protein levels in WT mice by 53%, this response of exercise was abolished in exercised KD mice. Exercise training reduced total phospholamban protein content by 23% in both the WT and KD mice but remained 20% higher overall in KD mice. Collectively, these data suggest that AMPK[alpha] influences SERCA2a and phospholamban protein content in the sedentary and exercised heart, and that exercise-induced changes in SERCA2a protein are dependent on AMPK[alpha] function. Key words: AMPK, SERCA, exercise training, phospholamban, [Ca.sup.2+] handling, left ventricle, diastolic function. L&apos;exercice physique permet d&apos;ameliorer le fonctionnement de la pompe [Ca.sup.2+]-ATPase 2a du reticulum sarcoplasmique (SERCA2a) par l&apos;intermediaire de modes d&apos;action inconnus. La presente etude tentait de verifier l&apos;hypothese selon laquelle les effets positifs de l&apos;exercice physique sur l&apos;expression de la SERCA2a et la fonction ventriculaire gauche dependent du fonctionnement de la proteine kinase [[alpha].sub.2] activee par l&apos;AMP ([AMPK[alpha].sub.2]). Nous avons reparti aleatoirement des souris transgeniques KD (pour<>), qui surexpriment la sous-unite [AMPK[alpha].sub.2] inactivee, ainsi que des souris C57Bl/6 de type sauvage (WT) dans des groupes sedentaires ou avec acces a des roues porteuses. Apres 5 mois, les souris entrainees presentaient une diminution du temps de deceleration par rapport aux souris KD sedentaires. Dans le tissu ventriculaire gauche, le ratio entre les taux d&apos;[AMPK[alpha].sup.Thr172] phosphorylee et d&apos;AMPK[alpha] totale etait 65 % plus bas chez les souris KD que chez les souris WT (P < 0,05). Le ventricule gauche des souris KD presentait des taux de SERCA2a 37 % plus bas que les souris WT. Meme si l&apos;exercice physique entrainait une augmentation des taux de SERCA2a en proteines de 53 % chez les souris WT, cette reaction etait abolie chez les souris KD entrainees. L&apos;exercice physique entrainait une diminution des taux de phospholamban en proteines total de 23 % chez les souris WT comme chez les souris KD, mais ils demeuraient 20 % plus eleves pour l&apos;ensemble des souris KD. Collectivement, ces resultats laissent entendre que l&apos;AMPK[alpha] influencerait les taux de SERCA2 et de phospholamban en proteines dans les creurs sedentaires ou entraines, et que les variations engendrees par l&apos;exercice physique quant aux taux de SERCA2a en proteines dependent du fonctionnement de l&apos;AMPK[alpha]. [Traduit par la Redaction] Mots-cles: AMPK, SERCA, entrainement physique, phospholamban, gestion du [Ca.sup.2+], ventricule gauche, fonction diastolique.

Myocardial ischemia-reperfusion (I/R) injury increases the generation of oxidized phosphatidylcholines (OxPCs), which results in cell death. However, the mechanism by which OxPCs mediate cell death and cardiac dysfunction is largely unknown. The aim of this study was to determine the mechanisms by which OxPC triggers cardiomyocyte cell death during reperfusion injury. Adult rat ventricular cardiomyocytes were treated with increasing concentrations of various purified fragmented OxPCs. Cardiomyocyte viability, bioenergetic response, and calcium transients were determined in the presence of OxPCs. Five different fragmented OxPCs resulted in a decrease in cell viability, with 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-(9'-oxo-nonanoyl)- sn-glycero-3-phosphocholine (PONPC) having the most potent cardiotoxic effect in both a concentration and time dependent manner (P < 0.05). POVPC and PONPC also caused a significant decrease in Ca2+ transients and net contraction in isolated cardiomyocytes compared to vehicle treated control cells (P < 0.05). PONPC depressed maximal respiration rate (P < 0.01; 54%) and spare respiratory capacity (P < 0.01; 54.5%). Notably, neither caspase 3 activation or TUNEL staining was observed in cells treated with either POVPC or PONPC. Further, cardiac myocytes treated with OxPCs were indistinguishable from vehicle-treated control cells with respect to nuclear high-mobility group box protein 1 (HMGBP1) activity. However, glutathione peroxidase 4 activity was markedly suppressed in cardiomyocytes treated with POVPC and PONPC coincident with increased ferroptosis. Importantly, cell death induced by OxPCs could be suppressed by E06 Ab, directed against OxPCs or by ferrostatin-1, which bound the sn-2 aldehyde of POVPC during I/R. The findings of the present study demonstrate that oxidation of phosphatidylcholines during I/R generate bioactive phospholipid intermediates that disrupt mitochondrial bioenergetics and calcium transients and provoke wide spread cell death through ferroptosis. Neutralization of OxPC with E06 or with ferrostatin-1 prevents cell death during reperfusion. Our study demonstrates a novel signaling pathway that operationally links generation of OxPC during cardiac I/R to ferroptosis. Interventions designed to target OxPCs may prove beneficial in mitigating ferroptosis during I/R injury in individuals with ischemic heart disease. [ABSTRACT FROM AUTHOR]

Introduction: We have recently identified two oxidized phosphatidylcholines: POVPC and PONPC to be produced during ischemia/reperfusion and to have cardiotoxic effect in cardiomyocytes. However, it is still unknown whether they have an effect on Ca2+ handling in cardiomyocytes leading to contractile dysfunction and ultimately cell death during ischemia/reperfusion injury. Hypothesis: Oxidized phosphatidylcholines: POVPC and PONPC will have a negative impact on Ca2+ handling in cardiomyocytes, leading to contractile dysfunction and cell death during ischemia/reperfusion injury. Methods: Single isolated cardiomyocytes were loaded with Fura-2 Am for 20 min at 37°C prior to the treatment. Then cells were perfused at 1ml/min with either Hepes buffer on its own or Hepes buffer that contained POVPC, PONPC or PSPC (control phospholipid) at the final concentration of 0.1μM. Cardiomyocytes were treated for one hour and the data was collected for 30 sec each 5 minutes. Platinum electrodes were used to pulse myocytes at 0.5 Hz with a duration of 200ms during the experiments. Cell length was determined by calibrating the signal with a stage micrometer and recording the results with Felix GX software. The calcium signal was collected on a PTI Ratiomaster spectrofluorometer and quantified ratiometrically as the 340/380 ratio with Felix GX software. Results: Treatment of cardiomyocytes with 0.1 μM POVPC or PONPC lead to a significant decrease in Ca2+ transients compared to control and PSPC. Moreover, there was a change in net contraction between 30 and 60 min of treatment with POVPC and PONPC compared to control and PSPC. Conclusion: This data suggests that OxPCs affect Ca2+ handling leading to contractile dysfunction. This is important giving the fact that OxPCs are largely produced during ischemia/reperfusion injury and have cardiotoxic effect, possibly by leading to contractile dysfunction. [ABSTRACT FROM AUTHOR]