Abstract 3156: Protein Kinase G Corrects High Cardiomyocyte Resting Tension in Diastolic Heart Failure
Cardiomyocytes isolated from LV myocardium of diastolic heart failure (DHF) patients have high in-vitro resting tension (RT), which is corrected by administration of protein kinase A (PKA) and which contributes to in-vivo left ventricular (LV) diastolic stiffness. Treatment with nitric oxide donors or sildenafil, both of which raise myocardial protein kinase G (PKG) activity, improves in-vivo diastolic LV stiffness in humans and in experimental rodent models. In-vitro effect of PKG administration on RT of cardiomyocytes of DHF patients was therefore investigated. Cardiomyocytes were isolated from endomyocardial biopsies of DHF patients (n = 7), of aortic stenosis (AS) patients (n = 20) and of controls (CON) (n = 8). All patients were free of coronary artery disease and had no inflammatory infiltration in their biopsy. Cardiomyocytes were treated with Triton X-100, attached to a force transducer and stretched to a sarcomere length of 2.2 microm to measure RT before and after administration of PKG and PKA. Expression and phosphorylation of myosin binding protein C, troponin I (TnI), troponin T, desmin, myosin light chain 2, stiff N2B titin isoform and compliant N2BA titin isoform were analysed using gel electrophoresis with SYPRO Ruby and Pro-Q Diamond Phosphoprotein Stain. Baseline RT was higher in DHF than in AS or in CON and fell after administration of both PKG and PKA (Table⇓). PKA had no effects on RT in AS or in CON. DHF had lower baseline phosphorylation of troponin I compared to AS (p < 0.05) and of the stiff N2B titin isoform compared to both AS (p < 0.05) and CON (p < 0.01).
Conclusion: In vitro administration of PKG or PKA lowers the high RT of cardiomyocytes of DHF patients probably through correction of a phosphorylation deficit of troponin I or of the stiff N2B titin isoform. These observations support the clinical use of nitric oxide donors or of sildenafil for the treatment of high diastolic LV stiffness in DHF.