Aldosterone directly induces myocyte apoptosis through calcineurin-dependent pathways.
BACKGROUND
Aldosterone has recently attracted considerable attention for its involvement in the pathophysiology of heart failure, in which apoptotic cell loss plays a critical role. This study examined whether aldosterone directly induces myocyte apoptosis via its specific receptors.


RESULTS
Neonatal rat cardiac myocytes were exposed to aldosterone (10(-8) to 10(-5) mol/L). Nuclear staining with Hoechst 33258 showed that aldosterone induced myocyte apoptosis in a dose- and time-dependent fashion. Treatment of myocytes with 10(-5) mol/L aldosterone significantly increased the percentage of apoptosis (15.5+/-1.4%) compared with serum-deprived control (7.3+/-0.6%). Radio ligand binding assay revealed the existence of plasma membrane receptor with high affinity (K(d), 0.2 nmol/L) for aldosterone in cardiac myocytes but not in fibroblasts. Aldosterone rapidly (approximately 30 seconds) mobilized [Ca2+]i that was blocked by neomycin. Aldosterone induced dephosphorylation of the proapoptotic protein Bad, enhancement of mitochondrial permeability transition, decrease in mitochondrial membrane potential, and release of cytochrome c from the mitochondria into the cytosol with concomitant activation of caspase-3. These effects of aldosterone were inhibited by concurrent treatment with either an L-type Ca2+ channel antagonist, nifedipine, or inhibitors for the Ca2+-dependent phosphatase calcineurin, cyclosporin A and FK506.


CONCLUSIONS
The present study demonstrates for the first time that the specific plasma membrane receptor (coupled with phospholipase C) for aldosterone is present on cardiac myocytes and that aldosterone accelerates the mitochondrial apoptotic pathway through activation of calcineurin and dephosphorylation of Bad, suggesting that the proapoptotic action of aldosterone may directly contribute to the progression of heart failure.
Mano
Akiko
A
Department of Cardiovascular Medicine, Kyoto Prefectural University School of Medicine, Japan.
Tatsumi
Tetsuya
T
Shiraishi
Jun
J
Keira
Natsuya
N
Nomura
Tetsuya
T
Takeda
Mitsuo
M
Nishikawa
Susumu
S
Yamanaka
Satoshi
S
Matoba
Satoaki
S
Kobara
Miyuki
M
Tanaka
Hideo
H
Shirayama
Takeshi
T
Takamatsu
Tetsuo
T
Nozawa
Yoshihisa
Y
Matsubara
Hiroaki
H
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism; D008564:Membrane Potentials; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000032:analysis; D018161:Receptors, Mineralocorticoid / Q000032:analysis; D015398:Signal Transduction; D051025:bcl-Associated Death Protein
C494821:Bad protein, rat; D065095:Calcineurin Inhibitors; D002121:Calcium Channel Blockers; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011956:Receptors, Cell Surface; D018161:Receptors, Mineralocorticoid; D051025:bcl-Associated Death Protein; D000450:Aldosterone; D045304:Cytochromes c; D019703:Calcineurin; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D002118:Calcium