Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China.
PLoS One. 2013 May 29;8(5):e64757. doi: 10.1371/journal.pone.0064757. Print 2013.
Left ventricular hypertrophy is a maladaptive response to pressure overload and an important risk factor for heart failure. Intermedin (IMD), a multi-functional peptide, plays important roles in cardiovascular protection. In this study, we revealed an autophagy-dependent mechanism involved in IMD's protection against cardiac remodeling and cardiomyocyte death in heart hypertrophy. We observed that transverse aortic contraction (TAC) induction, Ang II or ISO exposure induced remarkable increase in the expression of endogenous IMD and its receptor components, CRLR, RAMP1 and RAMP3, in mouse hearts and H9c2 cell cultures, respectively. Furthermore, the heart size, heart weight/body weight ratios, cardiomyocyte size and apoptosis, interstitial collagen, hypertrophic markers including ANP and BNP expression were also significantly increased, which were effectively suppressed by IMD supplementation. In addition, IMD induced capillary angiogenesis and improved functions in hypertrophic hearts. We further observed that IMD induced strong autophagy in hypertrophic hearts and cultured cells, which was paralleling with the decrease in cardiomyocyte size and apoptosis. Furthermore, an autophagy inhibitor, 3-MA, was used to block the IMD-augmented autophagy level, and then the protection of IMD on cardiomyocyte hypertrophy and apoptosis was almost abrogated. We also observed that IMD supplementation stirred intracellular cAMP production, and augmented the ERK1/2 phosphorylation induced by Ang II/ISO exposure in H9c2 cells. In addition, we inhibited PI3K, PKA and MAPK/ERK1/2 signaling pathways by using wortamannin, H89 and PD98059, respectively, in H9c2 cells co-incubating with both IMD and Ang II or ISO, and observed that these inhibitors effectively reduced IMD-augmented autophagy level, but only H89 and PD98059 pre-incubation abrogated the anti-apoptotic action of IMD. These results indicate that the endogenous IMD and its receptor complexes are induced in hypertrophic cardiomyocytes and proposed to play an important role in the pathogenesis of cardiac hypertrophy, and the autophagy stirred by IMD supplementation is involved in its protection against cardiomyocyte hypertrophy and apoptosis through the activation of both cAMP/PKA and MAPK/ERK1/2 pathways.
左心室肥厚是压力超负荷的一种适应性反应，也是心力衰竭的重要危险因素。中介素（IMD）是一种多功能肽，在心血管保护中发挥重要作用。在这项研究中，我们揭示了 IMD 保护心脏重构和心肌细胞死亡的自噬依赖性机制。我们观察到，横主动脉收缩（TAC）诱导、Ang II 或 ISO 暴露分别在小鼠心脏和 H9c2 细胞培养物中显著增加内源性 IMD 及其受体成分 CRLR、RAMP1 和 RAMP3 的表达。此外，心脏大小、心脏重量/体重比、心肌细胞大小和凋亡、间质胶原、肥厚标志物包括 ANP 和 BNP 的表达也显著增加，而 IMD 的补充则有效地抑制了这些变化。此外，IMD 诱导了肥厚心脏中的毛细血管血管生成并改善了其功能。我们进一步观察到，IMD 在肥厚心脏和培养细胞中诱导强烈的自噬，这与心肌细胞大小和凋亡的减少平行。此外，自噬抑制剂 3-MA 用于阻断 IMD 增强的自噬水平，随后 IMD 对心肌细胞肥大和凋亡的保护作用几乎被消除。我们还观察到，IMD 补充刺激细胞内 cAMP 的产生，并增强 Ang II/ISO 暴露在 H9c2 细胞中诱导的 ERK1/2 磷酸化。此外，我们分别使用wortamannin、H89 和 PD98059 抑制 PI3K、PKA 和 MAPK/ERK1/2 信号通路，在 H9c2 细胞与 IMD 和 Ang II 或 ISO 共孵育时观察到，这些抑制剂有效降低了 IMD 增强的自噬水平，但只有 H89 和 PD98059 的预孵育消除了 IMD 的抗凋亡作用。这些结果表明，内源性 IMD 及其受体复合物在肥厚心肌细胞中被诱导，并被提出在心脏肥厚的发病机制中发挥重要作用，而 IMD 补充诱导的自噬通过激活 cAMP/PKA 和 MAPK/ERK1/2 途径参与其对心肌细胞肥大和凋亡的保护作用。
