Doxazosin modifies Bcl-2 and Bax protein expression in the left ventricle of spontaneously hypertensive rats.
BACKGROUND
Increased apoptosis has recently been reported in the heart of spontaneously hypertensive rats (SHRs).


OBJECTIVE
To investigate the molecular basis of apoptosis in the left ventricle of SHRs in terms of the expression of Bcl-2 protein (which protects from apoptosis) and Bax protein (which acts as an apoptotic promoter). In addition, we analysed the involvement of alpha -adrenergic receptors in the left ventricular apoptosis of SHRs.


METHODS
The study was performed in untreated SHRs (n=16) and SHRs that were orally treated with doxazosin (10 mg/kg body weight per day, for 15 days), a selective alpha1-receptor blocker (n=16). A group of Wistar-Kyoto (WKY) rats (n=16) was used as the control.


RESULTS
The left ventricles of untreated SHRs showed a significant increase in Bcl-2 protein expression and a reduced presence of Bax protein. The ratio of Bcl-2:Bax in SHRs was higher than in WKY rats, suggesting an anti-apoptotic state. Paradoxically, both the number of apoptotic cardiac cells and the cleavage of an 85-kDa fragment of the poly (ADP-ribose) polymerase (PARP), a marker of caspase-3 activity, were higher in the left ventricle of SHRs than in WKY rats, suggesting an apoptotic situation. Bax promotes cell apoptosis when it is bound to Bcl-2. We then determined the abundance of Bax-Bcl-2 complexes in the left ventricle of the two groups of animals. Bax-Bcl-2 complexes were more abundant in SHRs than WKY rats. In a second set of experiments, we analysed the role of alpha1-adrenergic blockade by doxazosin in the above-described mechanisms. Doxazosin treatment reduced the formation of Bax-Bcl-2 complexes in the left ventricle of SHRs, and this was accompanied by a decrease in the levels of 85kDa PARP and a reduction in apoptotic left ventricular cells.


CONCLUSIONS
The present work suggests that the presence of Bax-Bcl-2 complexes in the left ventricle could be a more reliable marker of the apoptotic state than the determination of the absolute expression of Bcl-2 and Bax proteins. Moreover, the inhibition of alpha1 -adrenergic receptors by doxazosin decreased the abundance of BaxBcl-2 complexes and promoted a reduction of apoptosis in the left ventricle of SHRs.
Rodríguez-Feo
J A
JA
Hypertension and Cardiovascular Research Laboratory, Fundación Jiménez Diaz, Madrid, Spain.
Fortes
J
J
Aceituno
E
E
Farré
J
J
Ayala
R
R
Castilla
C
C
Rico
L
L
González-Fernández
F
F
García-Durán
M
M
Casado
S
S
López-Farré
A
A
D000818:Animals; D017209:Apoptosis; D001794:Blood Pressure; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D017292:Doxazosin / Q000494:pharmacology*; D006352:Heart Ventricles; D006973:Hypertension / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D017379:Hypertrophy, Left Ventricular / Q000473:pathology; D008297:Male; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012016:Reference Values; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D017292:Doxazosin