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PRECLINICAL STUDY

Activation of Apoptotic Caspase Cascade During the Transition to Pressure Overload-Induced Heart Failure

Narain Moorjani, MRCS^_*,_*, Manzoor Ahmad, PhD, Pedro Catarino, FRCS^_*, Robin Brittin, MSc, Danyah Trabzuni, BSc, Futwan Al-Mohanna, PhD, Navneet Narula, MD, Jagat Narula, MD, PhD and Stephen Westaby, MS, PhD, FETCS^_*

^_* Department of Cardiothoracic Surgery, Oxford Heart Centre, John Radcliffe Hospital, Oxford, England
Department of Biological and Medical Research, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
University of California, Irvine School of Medicine, Orange, California

Manuscript received February 27, 2006; revised manuscript received May 16, 2006, accepted May 26, 2006.

^_* Reprint requests and correspondence: Dr. Narain Moorjani, c/o Mr. Stephen Westaby's Office, Department of Cardiothoracic Surgery, Oxford Heart Centre, John Radcliffe Hospital, Oxford OX3 9DY, England (Email: narain.moorjani{at}doctors.org.uk).

Presented at the British Cardiac Society, Glasgow, Scotland, April 2003.

OBJECTIVES: A pressure overload model was developed to simulate aortic stenosis and assess caspase activity during the transition to heart failure.

BACKGROUND: Cardiomyocyte apoptosis is implicated in the pathogenesis of heart failure, and caspase activation is central to this pathophysiological process.

METHODS: A total of 10 sheep were banded with variable aortic constriction devices, progressively inflated to increase left ventricular (LV) afterload. Serial LV endomyocardial biopsy samples were obtained to measure caspase activity and presence of apoptosis.

RESULTS: Over the first 3 to 4 weeks, hypertrophy developed in the sheep (LV mass index 90.8 ± 4.9 g/m² vs. 44.0 ± 3.0 g/m², p < 0.01), followed by gradual dilatation of the left ventricle (diastolic LV internal diameter 4.23 ± 0.08 cm vs. 3.39 ± 0.07 cm, p < 0.01). Ventricular function remained stable until 7 to 8 weeks after banding, when there was significant deterioration (fractional shortening 18.3 ± 2.4% vs. 46.9 ± 2.6%, p < 0.01), associated with clinical heart failure. Serial LV endomyocardial biopsy samples were obtained at each echocardiographically defined stage (LV hypertrophy, LV dilation, and LV failure). Activity of caspases-3, -8, and -9 (measured by specific fluorogenic peptide substrates and immunohistochemistry) increased progressively, particularly with the onset of myocardial dysfunction (caspase-3 7.92 ± 1.19 vs. 1.00 ± 0.15, caspase-8 1.94 ± 0.21 vs. 1.00 ± 0.04, caspase-9 5.87 ± 0.97 vs. 1.00 ± 0.18 relative fluorescent units, p < 0.05). No evidence of deoxyribonucleic acid (DNA) fragmentation, however, was identified by immunohistochemical assays.

CONCLUSIONS: Activation of cardiomyocyte caspase enzymes occurs during the transition to heart failure, without completion of apoptotic DNA fragmentation. Increased activity of caspase-8 and -9 suggests both mitochondrial and death-receptor mediated pathways are involved in this pathological process. Further knowledge of these pathways may stimulate development of apoptosis-based strategies for slowing progression of heart failure in aortic stenosis patients.

Abbreviations and Acronyms   DNA = deoxyribonucleic acid   FS = fractional shortening   ISOL = in situ oligoligation   IVSd/s = interventricular septal thickness in diastole/systole   LV = left ventricle/ventricular   LVIDd/s = left ventricular internal diameter in diastole/systole   LVMI = left ventricular mass index   PWTd/s = posterior wall thickness in diastole/systole   TUNEL = terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling