Intermedin Suppresses Pressure Overload Cardiac Hypertrophy through Activation of Autophagy

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