title: Intermedin suppresses pressure overload cardiac hypertrophy through activation of autophagy.
abstract: 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.
authors.affiliation: Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China.
authors.forename: Huali
authors.initials: H
authors.lastname: Chen
authors.forename: Xue
authors.initials: X
authors.lastname: Wang
authors.forename: Mingming
authors.initials: M
authors.lastname: Tong
authors.forename: Dan
authors.initials: D
authors.lastname: Wu
authors.forename: Sisi
authors.initials: S
authors.lastname: Wu
authors.forename: Jiaxiang
authors.initials: J
authors.lastname: Chen
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Wang
authors.forename: Xulei
authors.initials: X
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Kang
authors.forename: Hong
authors.initials: H
authors.lastname: Tang
authors.forename: Chaoshu
authors.initials: C
authors.lastname: Tang
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001343:Autophagy; D002460:Cell Line; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004452:Echocardiography; D005355:Fibrosis; D006352:Heart Ventricles / Q000378:metabolism / Q000473:pathology; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D058261:Receptor Activity-Modifying Proteins / Q000235:genetics / Q000378:metabolism; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000209:etiology; D020257:Ventricular Remodeling / Q000235:genetics
chemical_list: D009479:Neuropeptides; D058261:Receptor Activity-Modifying Proteins; C514552:intermedin protein, mouse; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases