Load-Induced Cardiomyocyte Apoptosis in Cultured Multicellular Myocardial Preparations Is Unaltered in Presence of the β-Adrenoceptor Antagonist Nebivolol

Abstract

Overload-induced heart failure is associated with enhanced apoptosis of cardiomyocytes, and increased mechanical load is an inductor of this apoptosis. It is unknown whether nebivolol, a third generation β₁-adrenoceptor antagonist, possesses properties that can attenuate this apoptosis. Multicellular preparations from rabbit hearts were mounted in a culture system that allows for measurement of contractile parameters over several days. Culturing these muscles on a constant high preload induces apoptosis of the cardiomyocytes. Of each heart, 1 preloaded muscle preparation was treated with nebivolol (10^–6 mol/l), 1 preloaded without continuous exposure to nebivolol (positive control) and 1 unloaded (negative control). After 48 h of continuous loaded contractions, apoptosis was assessed by TUNEL-assay to confirm that nuclei of myocytes were affected, or by DNA-ladder intensity analysis for semiquantification. Maximal twitch force development was slightly, but significantly, lower in preparations contracting in presence of nebivolol (compared to solvent) while twitch-timing parameters were similar. After 48 h of continuous contractions, no additional differences were observed between the groups regarding contractile parameters. DNA-ladder analysis showed a similar rate of apoptosis in presence of nebivolol. Nebivolol does not increase, nor decrease, the rate of load-induced cardiomyocyte apoptosis.