Possible Involvement of Stress-Activated Protein Kinase Signaling Pathway and Fas Receptor Expression in Prevention of Ischemia/Reperfusion-Induced Cardiomyocyte Apoptosis by Carvedilol

Abstract

Carvedilol, a new vasodilating beta-adrenoceptor antagonist and a potent antioxidant, produces a high degree of cardioprotection in a variety of experimental models of ischemic cardiac injury. Recent clinical studies in patients with heart failure have demonstrated that carvedilol reduces morbidity and mortality and inhibits cardiac remodeling. The present study was designed to explore whether the protective effects of carvedilol on the ischemic myocardium include inhibition of apoptosis of cardiomyocytes and, if so, to determine its mechanism of action. Anesthetized rabbits were subjected to 30 minutes of coronary artery occlusion followed by 4 hours of reperfusion. Detection of apoptosis of cardiomyocytes was based on the presence of nucleosomal DNA fragments on agarose gels (DNA ladder) and in situ nick end labeling. Carvedilol (1 mg/kg IV), administered 5 minutes before reperfusion, reduced the number of apoptotic myocytes in the ischemic area from 14.7 +/- 0.4% to 3.4 +/- 1.8% (77% reduction, P<.001). Propranolol, administered at equipotent beta-blocking dosage, reduced the number of apoptotic myocytes to 8.9 +/- 2.1% (39% reduction, P<.05). DNA ladders were observed in the hearts of all six vehicle-treated rabbits but only one of six carvedilol-treated rabbits (P<.01). Immunocytochemical analysis of rabbit hearts demonstrated an upregulation of Fas protein in ischemic cardiomyocytes, and treatment with carvedilol reduced both the intensity of staining as well as the area stained. Myocardial ischemia/reperfusion led to a rapid activation of stress-activated protein kinase (SAPK) in the ischemic area but not in nonischemic regions. SAPK activity was increased from 2.1 +/- 0.3 mU/mg (basal) to 8.9 +/- 0.8 mU/mg after 30 minutes of ischemia followed by 20 minutes of reperfusion. Carvedilol inhibited the activation of SAPK by 53.4 +/- 6.5% (P<.05). Under the same conditions, propranolol (1 mg/kg) had no effect on SAPK activation. Taken together, these results suggest that carvedilol prevents myocardial ischemia/reperfusion-induced apoptosis in cardiomyocytes possibly by downregulation of the SAPK signaling pathway, by inhibition of Fas receptor expression, and by beta-adrenergic blockade. The former two actions represent novel and important mechanisms that may contribute to the cardioprotective effects of carvedilol.

Transcription factor AP-2α triggers apoptosis in cardiac myocytes

“…Apoptosis has been described in heart failure due to IDC and other cardiac diseases, 5 and beneficial effects of a long-term therapy with angiotensin-converting enzyme inhibitors as well as carvedilol, an antagonist at b-and a-adrenergic receptors, may involve the inhibition of cardiac apoptosis. [39][40][41] Up to now, the molecular pathways leading to the activation of the apoptotic signaling cascade, in particular, in the heart are not understood in detail. AP-2a has been shown to inhibit the activation of apoptosis mediated by the proto-oncogene c-myc, 42 and recently, AP-2a has been implicated in the antiapoptotic effects of the retinoblastoma gene product and in the induction of Bcl-2 in epithelial but not in NIH 3T3 mesenchymal cells.…”

The Novel β-Blocker, Carvedilol, Provides Neuroprotection in Transient Focal Stroke

“…The current study supports an antiapoptotic role for carvedilol in focal ischemia as evidenced by fewer TUNEL positive cells in the treated groups compared with controls ( Fig 3). There is also evidence that carvedilol prevents apoptosis in congestive heart failure (Yue et al, 1998). It should be noted that a TUNEL-positive reaction can occur in cells undergoing necrosis (Rink et al, 1995).…”

“…Carvedilol's antiapoptotic effects may be related to its antioxidant properties. However, Yue et al (1998Yue et al ( , 1999 have shown that carvedilol may inhibit ischemia-induced myocardial apoptosis by downregulating the stress-activated protein kinase (SAPK) pathway and the expression of the Fas receptor.…”

Inhibition of p38 Mitogen-Activated Protein Kinase Decreases Cardiomyocyte Apoptosis and Improves Cardiac Function After Myocardial Ischemia and Reperfusion

“…The hearts were "freeze-clamped" by using precooled aluminum tongs and pulverized under LN 2 . 20 The powder was resuspended in ice-cold lysis buffer, and the protein content in the detergent-soluble supernatant fraction was measured as described previously. 7 SAPK, p38 MAPK, and MAPKAP K2 kinases were immunoprecipitated with antibodies specific for JNK1 and JNK2 (Santa Cruz), p38 MAPK (SmithKline Beecham), or MAPKAP K2 (Dr J. Landry, University of Quebec, Montreal) and assayed by using glutathione-S-transferase-c-Jun , glutathione-S-transferase-activating transcription factor-2, or heat shock protein 27 as the substrate, respectively, as described in our previous studies.…”