β1-Adrenoceptor antibodies induce apoptosis in adult isolated cardiomyocytes

beta(1)-Adrenoceptor autoantibodies are present in about 30% of patients suffering from dilated cardiomyopathy. The apoptotic effects mediated by beta(1)-adrenoceptor antibodies remain to be studied. Monoclonal antibodies were raised against a synthetic peptide corresponding to the second extracellular loop of the human beta(1)-adrenoceptor in balb/C mouse, and were characterized by enzyme immumoassay. Purified immunoglobulin G from nonimmunized animals (controls) did not influence the rate of apoptosis. beta(1)-Adrenoceptor antibodies caused a dose-related increase in apoptotic cells: annexin test (dilution 1:2: 21 +/- 1.1% apoptotic cells vs. 4 +/- 0.4% apoptotic cells in controls; p < 0.01); TdT-mediated dUTP nick end labeling (TUNEL) test (dilution 1:2: 26 +/- 2% apoptotic cells vs. 10 2% apoptotic cells in controls; p < 0.01). The effect of the pl-adrenoceptor antibodies was blocked by the antigenic peptide and by the antagonist metoprolol (10 mumol/l). The apoptotic effect induced by isoproterenol was attenuated by the beta(1)-adrenoceptor antibody. After pre-incubation of cardiomyocytes with the protein kinase A inhibitor Rp-Adenosine-3',5'-cyclic monophosphothioate triethylamine (RpcAMPS), beta(1)-adrenoceptor antibody was not capable of inducing an increase of the rate of apoptosis. beta(1)-Adrenoceptor antibodies induced apoptosis in adult rat cardiomyocytes via the protein kinase A cascade. (C) 2003 Elsevier Science B.V. All rights reserved.