Neonatal Rat Ventriculomyocytes are Stimulated to Undergo Apoptosis through a β1-Selective Adrenergic Pathway

Abstract

Apoptosis is found in failing human hearts. Catecholamines are upregulated in heart failure and appear to cause cardiomyocyte apoptosis. Recent randomised c l i c a l studies show mortaliity benefit h m plselective-blockade in patients with heart failure. However it remains uncerhm ' if cardiomyocyte apoptosis is a pselective process. Method: Neonatal rat ventriculomyocytes (NRVM) were plated to subconfluence. Experiments were carried out in serum-five medium with ascorbic acid. Cells were incubated with wpdine(ISO.O.Ol-lpM), with or without CGP20712A (plblocker) and 1C1118,551 (p2blocker); with or without IBMX(phosphodiesterase inhibitor). Apoptosis was quantified by an anti-DNNanti-histone ELISA k i t (ROCHE) and confirmed with time-lapse. videomicroscopy, H33342 stain for nuclear morphology and DNA electrophoresis. Adenylyl cyclase (AC) assay using a recovery method with a-AW and 'H-CAMP was performed on human atrial-and neonatal rat ventricular-membrane preparations incubated with IS0 with or without CGP, ICI and pertussis toxin (PTX). Results. IS0 increased apoptosis in a dose-dependent manner up to 1 . 6~ control (pd.05). Degree of apoptosis with ISoeCGP was equivalent to control @=0.09). ISOtICl however augmented apoptosis up to 2% control(p4.01). Apoptosis was augmented in all groups by IBMX. In NRVM membrane preps AC activity with lSOcCGP was augmented 2 . 5~ H3Kn PTX was added (pd.05). This augmentation was not seen in the human atrialmembrane preps. Conclusion: In NRVM IS0 upregulates apoptosis via a plselective pathway appears to be CAMP-related. p2AR appear to be protective via a PTX-sensitive inhibition of AC activity. However p2 protection may not be present in human 2 MONOCYTE APOPTOSIS IN ATHEROGENESIS