The bcl-2 gene product prevents programmed cell death of ventricular myocytes.
BACKGROUND
To formally test whether the antiapoptotic protein bcl-2 would prevent programmed cell death in cardiac muscle cells provoked by p53, a known trigger of apoptosis in a variety of different cell types, we used replication defective adenovirus encoding either the bcl-2 and p53 genes to deliver bcl-2 and p53 to ventricular myocytes with high efficiency and uniformity.


RESULTS
Vital staining of ventricular myocytes revealed a significant (7-fold, P<.05) increase in myocyte cell death in the presence of p53 in contrast to uninfected cells or those infected with a control virus. In addition, in the presence of p53, nucleosomal DNA fragmentation observed by Hoescht 33258 staining and terminal transferase deoxynucleotide end labeling indicated a significant increase in apoptotic cardiac nuclei compared with control cells, confirming the hypothesis that p53 alone is sufficient to trigger apoptosis of ventricular myocytes. Moreover, a significant increase in transcription of the bax promoter was seen in the presence but not in the absence of p53 compared with control cells. Expression of the antiapoptotic gene bcl-2 in ventricular myocytes was sufficient to prevent ventricular myocyte death and apoptosis provoked by p53. Importantly, the antiapoptotic effects of bcl-2 were independent of altered p53 expression or localization of p53 to cardiac nuclei. However, p53 dependent transcription of bax was repressed 4-fold (P<.05) by bcl-2, suggesting a tentative link between p53-mediated apoptosis and the protective properties conferred by bcl-2 in ventricular myocytes.


CONCLUSIONS
To our knowledge, the data provide the first indication for the operation of bcl-2 in ventricular myocytes as an antiapoptotic factor.
Kirshenbaum
L A
LA
Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada. Lorrie@SBRC.umanitoba.ca
de Moissac
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D
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein