Overexpression of human truncated peroxisome proliferator-activated receptor alpha induces apoptosis in HL-1 cardiomyocytes.
OBJECTIVE
Our goal was to analyse whether truncated peroxisome proliferator-activated receptor alpha (PPARalpha) overexpression induces apoptosis of cardiomyocytes.


RESULTS
We constructed a recombinant vector of human truncated PPARalpha and a mammalian expression vector to transfect PPARalpha into a line of murine cardiomyocytes designated HL-1. Four hallmarks of apoptosis were measured in these transfected cells: depolarization of mitochondrial membrane, activation of caspase-3, phosphatidylserine (PS) externalization, and DNA fragmentation. Co-transfection with human cyclic adenosine monophosphate response element-binding protein (CREB) and human CREB binding protein (CBP) and analysis of apoptosis regulatory proteins, Bcl-2 and Bax, were also performed in truncated PPARalpha-transfected cells to determine the potential mechanisms by which truncated PPARalpha may influence apoptosis. Progressive depolarization of mitochondrial membrane, activation of caspase-3, PS externalization, DNA fragmentation, and cell death were observed in HL-1 cells upon increasing levels of transfected truncated PPARalpha. The expression of the antiapoptotic protein Bcl-2 decreased in transfected HL-1 cardiomyocytes, whereas no changes in the proapoptotic protein Bax were observed in these cells. Overexpression of CREB plus CBP abolished the inhibitory effect of truncated PPARalpha on Bcl-2 protein.


CONCLUSIONS
These results demonstrate that human truncated PPARalpha overexpression induces apoptosis in HL-1 cardiomyocytes. In addition, our findings suggest that truncated PPARalpha may induce cardiomyocyte apoptosis through the inhibition of the antiapoptotic protein, Bcl-2. It is proposed that competition with CREB for coactivators like CBP could be involved in this inhibitory effect.
Beaumont
Javier
J
Division of Cardiovascular Sciences, Centre for Applied Medical Research, University of Navarra, CIMA, Avda. Pío XII 55, 31008 Pamplona, Spain.
Arias
Teresa
T
Ravassa
Susana
S
Díez
Javier
J
D000818:Animals; D017209:Apoptosis; D050882:CREB-Binding Protein / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D047493:PPAR alpha / Q000235:genetics / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein / Q000378:metabolism
C494826:BAX protein, human; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D047493:PPAR alpha; D010718:Phosphatidylserines; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3