title: Lipid-induced NOX2 activation inhibits autophagic flux by impairing lysosomal enzyme activity.
abstract: Autophagy is a catabolic process involved in maintaining energy and organelle homeostasis. The relationship between obesity and the regulation of autophagy is cell type specific. Despite adverse consequences of obesity on cardiac structure and function, the contribution of altered cardiac autophagy in response to fatty acid overload is incompletely understood. Here, we report the suppression of autophagosome clearance and the activation of NADPH oxidase (Nox)2 in both high fat-fed murine hearts and palmitate-treated H9C2 cardiomyocytes (CMs). Defective autophagosome clearance is secondary to superoxide-dependent impairment of lysosomal acidification and enzyme activity in palmitate-treated CMs. Inhibition of Nox2 prevented superoxide overproduction, restored lysosome acidification and enzyme activity, and reduced autophagosome accumulation in palmitate-treated CMs. Palmitate-induced Nox2 activation was dependent on the activation of classical protein kinase Cs (PKCs), specifically PKCβII. These findings reveal a novel mechanism linking lipotoxicity with a PKCβ-Nox2-mediated impairment in pH-dependent lysosomal enzyme activity that diminishes autophagic turnover in CMs.
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112; Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112; Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242.
authors.forename: Bharat
authors.initials: B
authors.lastname: Jaishy
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112; Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242.
authors.forename: Quanjiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University, Baltimore, MD 21224.
authors.forename: Heaseung S
authors.initials: HS
authors.lastname: Chung
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112; Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242.
authors.forename: Christian
authors.initials: C
authors.lastname: Riehle
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112; Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242.
authors.forename: Jamie
authors.initials: J
authors.lastname: Soto
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112.
authors.forename: Stephen
authors.initials: S
authors.lastname: Jenkins
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112.
authors.forename: Patrick
authors.initials: P
authors.lastname: Abel
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29403.
authors.forename: L Ashley
authors.initials: LA
authors.lastname: Cowart
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University, Baltimore, MD 21224; Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21224; Bayview Proteomics Center, Johns Hopkins University, Baltimore, MD 21224.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Van Eyk
authors.affiliation: Division of Endocrinology, Metabolism, and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112; Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112; Fraternal Order of Eagles Diabetes Research Center and Division of Endocrinology and Metabolism, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242. Electronic address: DRCadmin@uiowa.edu.
authors.forename: E Dale
authors.initials: ED
authors.lastname: Abel
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D002460:Cell Line; D004041:Dietary Fats / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000201:enzymology*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D019308:Palmitic Acid / Q000494:pharmacology*; D064546:Protein Kinase C beta / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013481:Superoxides / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D008562:Membrane Glycoproteins; D013481:Superoxides; D019308:Palmitic Acid; C488842:Cybb protein, mouse; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C579055:Prkcb protein, mouse; C579056:Prkcb protein, rat; D064546:Protein Kinase C beta
keywords: NADPH oxidase 2; autophagy; cardiomyocytes; fatty acids; lysosomes; protein kinase Cβ