Cardiac dysfunction in mice lacking cytochrome-c oxidase subunit VIaH

Area of Science:

• Biochemistry
• Cardiology
• Molecular Biology

Background:

• Cytochrome-c oxidase subunit VIaH (COXVIaH) is known to modulate Cytochrome-c oxidase (COX) activity.
• Its precise role in cardiac energy production and mechanical function requires further elucidation.

Purpose of the Study:

• To investigate the function of COXVIaH in regulating oxidative energy production and cardiac mechanical performance.
• To determine the impact of COXVIaH deficiency on myocardial function and energy metabolism.

Main Methods:

• Generation of gene-targeted mice lacking COXVIaH.
• Assessment of total COX activity and myocardial ATP levels in wild-type and mutant hearts.
• Evaluation of myocardial performance using isolated working heart preparations.
• Measurement of left ventricular end-diastolic volume via magnetic resonance imaging.

Main Results:

• Mutant mice exhibited decreased total COX activity in the heart, attributed to altered COX holoenzyme assembly.
• Despite reduced COX activity, myocardial ATP levels remained comparable between wild-type and mutant mice.
• Hearts from mutant mice demonstrated impaired stroke work generation at increased filling pressures.
• Magnetic resonance imaging indicated diastolic dysfunction, specifically impaired ventricular filling, in mutant mice.

Conclusions:

• Genetic deficiency of COXVIaH significantly impacts myocardial diastolic performance.
• COXVIaH plays a critical role in cardiac mechanical function, independent of cellular ATP levels.
• Altered COX holoenzyme assembly due to COXVIaH absence contributes to cardiac dysfunction.