Selective endothelin receptor blockade reverses mitochondrial dysfunction in canine heart failure

Mitochondrial enzymatic activity reductions in both myocardial and skeletal muscle tissues have been reported in a canine model of pacing-induced congestive heart failure (CHF). Endothelin-1 (ET-1), a vasoconstrictor peptide with diverse biological properties, has been implicated in CHF pathogenesis, and ET-1 receptor blockade has been shown to attenuate CHF progression. We hypothesized that the beneficial effect of ET-1 receptor blockade may be mediated in part by improved mitochondrial function.

Myocardium and skeletal muscle tissues were evaluated for respiratory complex I-V and citrate synthase activity levels in paced animals treated with and without LU 135252, a specific type A ET-1 receptor (ET(A)) antagonist.

Specific activity levels of complex V and III, which were 65% to 85% lower in both cardiac and skeletal muscle in paced compared to unpaced animals, were significantly increased in ET(A) antagonist-treated animals (50%-300% compared to untreated paced animals). Levels of other mitochondrial respiratory complex activities including complex I, II, and IV as well as citrate synthase were not significantly changed.

These findings suggest that endothelin activation may be involved in the myocardial dysfunction and mitochondrial enzyme deficiencies observed in pacing-induced CHF. Improvement of mitochondrial function may be a novel mechanism mediating the beneficial effect of ET(A) receptor blockade in CHF.