β-Adrenergic receptor blockade modulates Bcl-XS expression and reduces apoptosis in failing myocardium

Academic Article

Abstract

  • The mechanisms by which β-adrenergic receptor (β-AR) blockade modulates apoptosis in heart failure (HF) are unclear. We examined the impact of β-AR blockade with metoprolol on myocardial remodeling, apoptosis, pro-apoptotic (Fas, Fas ligand, Bax, and Bcl-X ) and anti-apoptotic (Bcl-X and Bcl-2) gene expression, and Bcl-X and Bcl-X protein in post-infarction HF in rats. In untreated rats, there was significant (P < 0.001) LV dilatation and systolic dysfunction compared to sham. Myocardial apoptosis was significantly increased (P < 0.005). Fas, Bax, and Bcl-2 mRNA expression was unchanged. However, Fas ligand mRNA and Bcl-X mRNA and protein, all undetectable in sham, were markedly elevated (P < 0.001), whereas Bcl-X mRNA and protein was unchanged. Immunohistochemistry confirmed increased Bcl-X staining in failing myocardium, with unchanged Bcl-X . Metoprolol treatment resulted in: (1) improved LV remodeling (P < 0.025), (2) reduced myocardial apoptosis (P < 0.005), and (3) selective reduction in myocardial Bcl-X expression (P < 0.001) without change in Fas, Fas ligand, Bax, Bcl-2, or Bcl-X . Studies in isolated rat myocytes revealed that prolonged isoproterenol (ISO) stimulation significantly increased Bcl-X protein, reducing the Bcl-X /X ratio and myocyte survival (P < 0.005). ISO-induced Bcl-X expression was significantly attenuated (P < 0.001) by both metoprolol and CGP20712A, a β -AR selective antagonist, but not by ICI118,551, a β -AR selective antagonist. We conclude that adrenergic activation, such as occurs in HF, increases pro-apoptotic Bcl-X expression via the β -AR. β-AR blockade in HF reduces myocardial apoptosis; attenuation of Bcl-X expression may be one mechanism underlying this effect. © 2003 Elsevier Science Ltd. All rights reserved. S L L S S L S L S L S L S S 1 2 S 1 S
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Prabhu SD; Wang G; Luo J; Gu Y; Ping P; Chandrasekar B
  • Start Page

  • 483
  • End Page

  • 493
  • Volume

  • 35
  • Issue

  • 5