title: The lipid peroxidation product 4-hydroxy-trans-2-nonenal causes protein synthesis in cardiac myocytes via activated mTORC1-p70S6K-RPS6 signaling.
abstract: Reactive oxygen species (ROS) are elevated in the heart in response to hemodynamic and metabolic stress and promote hypertrophic signaling. ROS also mediate the formation of lipid peroxidation-derived aldehydes that may promote myocardial hypertrophy. One lipid peroxidation by-product, 4-hydroxy-trans-2-nonenal (HNE), is a reactive aldehyde that covalently modifies proteins thereby altering their function. HNE adducts directly inhibit the activity of LKB1, a serine/threonine kinase involved in regulating cellular growth in part through its interaction with the AMP-activated protein kinase (AMPK), but whether this drives myocardial growth is unclear. We tested the hypothesis that HNE promotes myocardial protein synthesis and if this effect is associated with impaired LKB1-AMPK signaling. In adult rat ventricular cardiomyocytes, exposure to HNE (10 μM for 1h) caused HNE-LKB1 adduct formation and inhibited LKB1 activity. HNE inhibited the downstream kinase AMPK, increased hypertrophic mTOR-p70S6K-RPS6 signaling, and stimulated protein synthesis by 27.1 ± 3.5%. HNE also stimulated Erk1/2 signaling, which contributed to RPS6 activation but was not required for HNE-stimulated protein synthesis. HNE-stimulated RPS6 phosphorylation was completely blocked using the mTOR inhibitor rapamycin. To evaluate if LKB1 inhibition by itself could promote the hypertrophic signaling changes observed with HNE, LKB1 was depleted in adult rat ventricular myocytes using siRNA. LKB1 knockdown did not replicate the effect of HNE on hypertrophic signaling or affect HNE-stimulated RPS6 phosphorylation. Thus, in adult cardiac myocytes HNE stimulates protein synthesis by activation of mTORC1-p70S6K-RPS6 signaling most likely mediated by direct inhibition of AMPK. Because HNE in the myocardium is commonly increased by stimuli that cause pathologic hypertrophy, these findings suggest that therapies that prevent activation of mTORC1-p70S6K-RPS6 signaling may be of therapeutic value.
authors.affiliation: Myocardial Biology Unit, Cardiovascular Medicine, and Diabetes and Metabolism Research Unit, Section of Endocrinology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Calamaras
authors.affiliation: Brigham and Women׳s Hospital, Boston, MA 02115, USA.
authors.forename: Charlie
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Endocrinology, Second Affiliated Hospital Chongqing Medical University, Chongqing, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Lan
authors.affiliation: Diabetes and Metabolism Research Unit, Section of Endocrinology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ido
authors.affiliation: Myocardial Biology Unit, Cardiovascular Medicine, and Diabetes and Metabolism Research Unit, Section of Endocrinology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Siwik
authors.affiliation: Myocardial Biology Unit, Cardiovascular Medicine, and Diabetes and Metabolism Research Unit, Section of Endocrinology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA. Electronic address: Wilson.colucci@bmc.org.
authors.forename: Wilson S
authors.initials: WS
authors.lastname: Colucci
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D017379:Hypertrophy, Left Ventricular / Q000473:pathology; D015227:Lipid Peroxidation / Q000502:physiology*; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D000447:Aldehydes; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D038601:Ribosomal Protein S6; C448579:ribosomal protein S6, mouse; C013166:2-nonenal; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C491654:Stk11 protein, mouse; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D055372:AMP-Activated Protein Kinases; C027576:4-hydroxy-2-nonenal; D020123:Sirolimus
keywords: 4-HNE; Cardiac myocytes; Erk1/2; Free radicals; Protein synthesis; mTORC1