Decreased creatine kinase is linked to diastolic dysfunction in rats with right heart failure induced by pulmonary artery hypertension

Abstract

Our objective was to investigate the role of creatine kinase in the contractile dysfunction of right ventricular failure caused by pulmonary artery hypertension. Pulmonary artery hypertension and right ventricular failure were induced in rats by monocrotaline and compared to saline-injected control animals. In vivo right ventricular diastolic pressure–volume relationships were measured in anesthetized animals; diastolic force–length relationships in single enzymatically dissociated myocytes and myocardial creatine kinase levels by Western blot. We observed diastolic dysfunction in right ventricular failure indicated by significantly steeper diastolic pressure–volume relationships in vivo and diastolic force–length relationships in single myocytes. There was a significant reduction in creatine kinase protein expression in failing right ventricle. Dysfunction also manifested as a shorter diastolic sarcomere length in failing myocytes. This was associated with a Ca2 +-independent mechanism that was sensitive to cross-bridge cycling inhibition. In saponin-skinned failing myocytes, addition of exogenous creatine kinase significantly lengthened sarcomeres, while in intact healthy myocytes, inhibition of creatine kinase significantly shortened sarcomeres. Creatine kinase inhibition also changed the relatively flat contraction amplitude–stimulation frequency relationship of healthy myocytes into a steeply negative, failing phenotype. Decreased creatine kinase expression leads to diastolic dysfunction. We propose that this is via local reduction in ATP:ADP ratio and thus to Ca2 +-independent force production and diastolic sarcomere shortening. Creatine kinase inhibition also mimics a definitive characteristic of heart failure, the inability to respond to increased demand. Novel therapies for pulmonary artery hypertension are needed. Our data suggest that cardiac energetics would be a potential ventricular therapeutic target.

Diastolic dysfunction in pulmonary artery hypertension: Creatine kinase and the potential therapeutic benefit of beta‐blockers

“…We interpreted this as a decreased ability of MCT myocytes to respond to an increase in demand, which is a definition of heart failure. We concluded that decreased CK expression leads to diastolic dysfunction, via local reduction in ATP:ADP ratio and thus to Ca 2+ ‐independent force production and diastolic sarcomere shortening …”

“…The end diastolic pressure–volume relationship (EDPVR) was measured using a Millar catheter inserted into the RV of anesthetized animals. The EDPVR was significantly steeper in monocrotaline‐injected rats (MCT; [FAIL in Fowler et al …”

“…Experiments were conducted with local ethical approval and in accordance with UK Home Office and European Parliament Directive 2010/63/EU guidelines on the use of animals in research. Methodological details can be found in Fowler et al PAH and RV failure were induced in rats by a single IP injection (60 mg/kg) of monocrotaline. When PAH was established, metoprolol in sucrose solution (10 mg/kg per day, MCT+BB) or sucrose solution (MCT) was administered by voluntary syringe feeding.…”

“…The human equivalent dose of 10 mg/kg per day was 1.62 mg/kg per day, within the typical clinical dose range for a 75 kg patient (0.17‐2.67 mg/kg per day). Animals were killed when showing external signs of heart failure (weight loss, lethargy, laboured breathing, piloerection) (see Fowler et al). Data from the three experimental groups were compared by one‐way ANOVA.…”

“…Ventricular weights are given in Table and show RV hypertrophy in both PAH groups. EDPVRs were measured in anaethetised rats by Millar catheter in the RV during vena cava occlusion (Figure A, see Fowler et al . for details of methodology).…”