Abstract 17754: Antioxidants Lower Diastolic Stiffness of Failing Human Cardiomyocytes
High cardiomyocyte (CM) stiffness is an important contributor to left ventricular (LV) diastolic dysfunction in heart failure (HF). The high stiffness of HF-CM is lowered in-vitro by administration of Protein Kinase A (PKA) or PKG. Both enhance phosphorylation of the giant cytoskeletal protein titin, which determines CM stiffness through transcriptional and posttranslational modifications. Antioxidants break disulfide bridges within the titin molecule thereby increasing titin's overall contour length and distensibility. The present study therefore investigated if in-vitro administration of the antioxidant dithiothreitol (DTT) could lower the high stiffness of HF-CM and if this action was additive to PKA- or PKG-induced effects. HF-CM (n=59) were isolated from transvascular endomyocardial LV biopsies procured in 16 HF patients (pts). Control CM (Con-CM) (n=30) were derived from LV myocardium of 5 donor hearts. All HF pts were free of significant coronary artery disease and referred for biopsy because of suspicion of infiltrative or inflammatory myocardial disease, which was subsequently ruled out by histological examination of the biopsy. Hemodynamic evaluation revealed a LV ejection fraction = 41±4 %, a LV end-diastolic volume index = 98±10 ml/m2 and a LV end-diastolic pressure = 27±2 mmHg. Isolated CM were attached between a force transducer and a piezoelectric motor. Resting tension (RT) at a sarcomere length of 2.2 μm was used to assess CM stiffness. RT of HF-CM (6.2±0.9 kN/m2) was higher than of Con-CM (2.5±0.2 kN/m2; p=0.001). After PKA or PKG, RT fell in HF-CM to respectively 4.4±0.6 kN/m2 (p<0.001) and 4.2±0.7 kN/m2 (p<0.001). After PKG, RT remained unaffected by subsequent PKA administration. Administration of the antioxidant DTT reduced RT in HF-CM to 4.0±0.4 kN/m2 (p<0.001). DTT and PKA failed to alter RT of HF-CM following prior administration of respectively PKA and DTT.
Conclusions: 1) In-vitro antioxidant treatment with DTT lowers RT in HF-CM. Redox sensitivity of RT in HF-CM is relevant to the pronounced diastolic LV dysfunction in HF patients. 2) The effects on RT in HF-CM of DTT, PKA or PKG are of similar magnitude and non-additive probably because of all three interventions sharing a similar site of action within the N2Bus domain of titin.
- © 2010 by American Heart Association, Inc.