Dose and time-dependent apoptotic effects by angiotensin II infusion on left ventricular cardiomyocytes.
OBJECTIVE
To gain insight into the regulation of cardiac apoptosis we studied the dose-response and time-course effects of angiotensin II (Ang II) infusion on ventricular cardiomyocyte apoptosis and on the expression of Bax and Bcl-2 genes and proteins.


METHODS
In the dose-response study, Ang II was infused subcutaneously at doses of 100, 200, 400, 800 and 1200 ng/kg per min for 14 days. In the time-course study, rats infused with Ang II at doses of 200 and 400 ng/kg per min were followed for 7 and 14 days. The cardiomyocyte apoptotic density was assessed by DNA end labelling (terminal deoxynucleotide nick-end labelling; TUNEL). Gene and protein expression of Bcl-2 and Bax were evaluated by reverse transcriptase-polymerase chain reaction and by Western blots.


RESULTS
Systolic blood pressure and left ventricular mass were increased in a dose-dependent manner in Ang II-infused rats. A statistically significant increase in the rate of cardiac apoptosis and pro-apoptotic changes of Bcl-2 and Bax gene and protein expression was observed when high doses of Ang II (800-1200 ng/kg per min) were infused. A positive correlation of apoptotic density with Bax and a negative correlation with Bcl-2 and Bcl-2/Bax ratio were found. Cardiac apoptosis was greatly influenced by the timing of Ang II infusion. Losartan-treated Ang II-infused rats exhibited normalized systolic blood pressure, left ventricular weight, apoptosis, and Bax and Bcl-2 levels.


CONCLUSIONS
Our results are consistent with the pathophysiological role of Ang II in induction of cardiac apoptosis, and explain the cardioprotective effect of Ang II receptor antagonists.
Fabris
Bruno
B
Dipartimento di Medicina Clinica e Neurologia, University of Trieste, Trieste, Italy. b.fabris@fmc.units.it
Candido
Riccardo
R
Bortoletto
Monica
M
Zentilin
Lorena
L
Sandri
Marco
M
Fior
Francesco
F
Toffoli
Barbara
B
Stebel
Marco
M
Bardelli
Moreno
M
Belgrado
Dario
D
Giacca
Mauro
M
Carretta
Renzo
R
D000804:Angiotensin II / Q000008:administration & dosage*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D015870:Gene Expression / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020287:In Situ Nick-End Labeling; D015918:Infusion Pumps, Implantable; D007279:Injections, Subcutaneous; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
C494828:Bax protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D014662:Vasoconstrictor Agents; D051028:bcl-2-Associated X Protein; D000804:Angiotensin II