Mano Akiko, Tatsumi Tetsuya, Shiraishi Jun, Keira Natsuya, Nomura Tetsuya, Takeda Mitsuo, Nishikawa Susumu, Yamanaka Satoshi, Matoba Satoaki, Kobara Miyuki, Tanaka Hideo, Shirayama Takeshi, Takamatsu Tetsuo, Nozawa Yoshihisa, Matsubara Hiroaki
Department of Cardiovascular Medicine, Kyoto Prefectural University School of Medicine, Japan.
Circulation. 2004 Jul 20;110(3):317-23. doi: 10.1161/01.CIR.0000135599.33787.CA. Epub 2004 Jul 12.
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.
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.
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.
醛固酮最近因其参与心力衰竭的病理生理学过程而备受关注，其中凋亡性细胞丢失起关键作用。本研究检测醛固酮是否通过其特异性受体直接诱导心肌细胞凋亡。
将新生大鼠心肌细胞暴露于醛固酮（10⁻⁸至10⁻⁵mol/L）。用Hoechst 33258进行核染色显示，醛固酮以剂量和时间依赖性方式诱导心肌细胞凋亡。与血清剥夺对照组（7.3±0.6%）相比，用10⁻⁵mol/L醛固酮处理心肌细胞显著增加了凋亡百分比（15.5±1.4%）。放射性配体结合分析显示心肌细胞中存在对醛固酮具有高亲和力（解离常数K(d)为0.2 nmol/L）的质膜受体，而成纤维细胞中不存在。醛固酮迅速（约30秒）动员细胞内钙离子浓度[Ca²⁺]i，这一过程被新霉素阻断。醛固酮诱导促凋亡蛋白Bad去磷酸化，增强线粒体通透性转换，降低线粒体膜电位，并使细胞色素c从线粒体释放到细胞质中，同时激活半胱天冬酶-3。醛固酮的这些作用可被L型钙通道拮抗剂硝苯地平或钙依赖性磷酸酶钙调神经磷酸酶抑制剂环孢素A和FK506同时处理所抑制。
本研究首次证明心肌细胞上存在醛固酮的特异性质膜受体（与磷脂酶C偶联），且醛固酮通过激活钙调神经磷酸酶和Bad去磷酸化加速线粒体凋亡途径，提示醛固酮的促凋亡作用可能直接促进心力衰竭的进展。
