Abstract 9575: Myocyte-Specific Catalase Overexpression Prevents Age-Related Left Ventricular Diastolic Dysfunction: Association with Reduction of Oxidation of SERCA at Cysteine 674

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Background: Age-related myocardial diastolic dysfunction is associated with impaired calcium handling and reduced sarcoplasmic reticulum calcium ATPase (SERCA) activity. Oxidative sulfonylation of SERCA at cysteine 674 inhibits SERCA activity. We tested the hypothesis that a) aging is associated with sulfonylation of SRECA at cysteine 674, and b) cardiac myocyte-specific over-expression of catalase would decrease SERCA sulfonylation, restore SERCA activity, improve myocyte function and correct diastolic dysfunction. Methods and Results: Young (Y, 5-month) and senescent (S, 21-month) wild-type (WT) or CAT mice were compared (n=8-13). In S-WT there was markedly impaired diastolic function as reflected by a) decreased peak early-to-late diastolic transmitral velocity ratio (E/A, 1.36±0.06 vs. 1.96±0.10 in Y-WT or 1.89±0.06 in Y-CAT, P<0.01), b) decreased early myocardial tissue velocity (E m , mm/s, 20.1±0.6 vs. 26.6±0.1 in Y-WT or 24.9±0.7 in Y-CAT, P<0.01), and c) leftward/upward shift in the end-diastolic pressure volume relationship by Langendorff perfusion. Diastolic dysfunction in S-WT was associated with decreased SERCA activity (nmol/mg protein/min, 3.37±0.45 vs. 5.50±0.55 in Y-WT, P<0.01) and increased oxidation of SERCA at cysteine 674 (Scores, 2.4±0.3 vs. 1.1±0.2 in Y-WT or 1.1±0.1 in Y-CAT, P<0.02). Likewise, in isolated myocytes from S-WT there was slowed relaxation (+dL/dt, μ m/s, 1.35±0.07 vs. 2.68±0.17 in Y-WT, P<0.01) and prolongation of Ca 2+ reuptake (Tau, ms, 46.7±0.15 vs. 35.7±0.16 in Y-WT, P<0.01). In senescent mice with CAT overexpression (S-CAT) there was complete normalization of LV diastolic function (E/A, 1.97±0.12; E m , 24.9±1.4), SERCA activity (6.10±0.36 nmol/mg/min), SERCA oxidation (Score, 1.23±0.08), myocyte relaxation (+dL/dt, 2.34±0.14 μ m/s) and myocyte calcium handling (Tau, 38.3±0.08 ms). Conclusion: Age-related impairment of SERCA activity is associated with sulfonylation of cysteine 674. Myocyte-specific overexpression of CAT, which prevents aging-induced LV diastolic dysfunction and myocyte calcium dysregulation, prevents SERCA sulfonylation at cysteine 674 and restores SERCA activity, suggesting that SERCA sulfonylation plays a central role in the age-related myocyte dysfunction.