title: Beta-adrenergic receptor subtypes differentially affect apoptosis in adult rat ventricular myocytes.
abstract: BACKGROUND-Catecholamine-induced apoptosis is mediated by activation of the beta-adrenergic signaling pathway. We tested the hypothesis that beta(1)- and beta(2)-adrenergic receptor (AR) subtypes differentially affect apoptosis in adult rat ventricular myocytes in vitro. METHODS AND RESULTS-Myocytes were first exposed to norepinephrine (NE) alone (10 mcmol/L) or NE+atenolol (AT) (10 mcmol/L) for 12 hours. AT, a beta(1)-selective AR antagonist, abolished the NE-induced increase in nick end-labeling (TUNEL)-positive cells compared with control (NE, 33+/-3% versus control, 3+/-1%, P<0.0001; NE+AT, 4+/-2% versus control, 3+/-1%, P=0. 98). Annexin V staining, DNA laddering, and caspase activity determinations corroborated these results. Subsequent experiments under prazosin treatment established the apoptosis dose-response curves for the increasingly beta(2)-selective AR agonists isoproterenol (ISO) (beta(1) approximately beta(2)) and albuterol (ALB) (beta(2)>beta(1)). ISO and ALB induced significantly less apoptosis than NE (beta(1)>beta(2)) at equimolar concentrations as assessed by TUNEL staining [1 mcmol/L: NE (8+/-2%) approximately ISO (7+/-1%)>ALB (2+/-1%); 10 mcmol/L: NE (35+/-2%)>ISO (23+/-1%)>ALB (3+/-1%); 100 mcmol/L: NE (50+/-2%)>ISO (29+/-2%)>ALB (14+/-1%), P<0.0001 except for NE versus ISO at 1 mcmol/L with P=0.62]. ALB-induced apoptosis at 100 mcmol/L was abolished by AT (10 mcmol/L), indicating a beta(1)AR-mediated effect. Importantly, ICI 118551 (0.1 mcmol/L), a highly selective beta(2)AR antagonist, did not decrease the percentage of NE-, ISO-, and ALB-induced apoptosis. Reverse transcription-polymerase chain reaction studies revealed that AT completely reversed the beta-adrenergic signaling-induced changes in the Bcl-2-to-Bax ratio. CONCLUSIONS-These observations provide evidence that beta AR-mediated apoptotic death signaling is largely dissociated from beta(2)ARs and selectively mediated by beta(1)ARs in adult rat ventricular myocytes.
authors.affiliation: Department of Anesthesiology, Health Science Center at Brooklyn, State University of New York, USA.
authors.forename: M
authors.initials: M
authors.lastname: Zaugg
authors.forename: W
authors.initials: W
authors.lastname: Xu
authors.forename: E
authors.initials: E
authors.lastname: Lucchinetti
authors.forename: S A
authors.initials: SA
authors.lastname: Shafiq
authors.forename: N Z
authors.initials: NZ
authors.lastname: Jamali
authors.forename: M A
authors.initials: MA
authors.lastname: Siddiqui
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001262:Atenolol / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000166:cytology; D009638:Norepinephrine / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D020033:Protein Isoforms / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D016276:Ventricular Function; D051028:bcl-2-Associated X Protein
chemical_list: D000319:Adrenergic beta-Antagonists; C494828:Bax protein, rat; D011412:Propanolamines; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011943:Receptors, Adrenergic, beta; D051028:bcl-2-Associated X Protein; C026777:ICI 118551; D001262:Atenolol; D007545:Isoproterenol; D000420:Albuterol; D009638:Norepinephrine