title: Oxidized lipids activate autophagy in a JNK-dependent manner by stimulating the endoplasmic reticulum stress response.
abstract: Excessive production of unsaturated aldehydes from oxidized lipoproteins and membrane lipids is a characteristic feature of cardiovascular disease. Our previous studies show that unsaturated lipid peroxidation-derived aldehydes such as 4-hydroxy-trans-2-nonenal (HNE) promote autophagy in rat aortic smooth muscle cells (RASMC). In this study, we examined the mechanism by which HNE induces autophagy. Exposure of RASMC to HNE led to the modification of several proteins, most of which were identified by mass spectrometry and confocal microscopy to be localized to the endoplasmic reticulum (ER). HNE stimulated the phosphorylation of PKR-like ER kinase and eukaryotic initiation factor 2α and increased heme oxygenase-1 (HO-1) abundance. HNE treatment also increased LC3-II formation and the phosphorylation of JNK and p38. Pharmacological inhibition of JNK, but not p38, prevented HNE-induced HO-1 expression and LC3-II formation. Inhibition of JNK increased cell death in HNE-treated cells. Pretreatment with the chemical chaperone phenylbutryic acid prevented LC3-II formation as well as JNK phosphorylation and HO-1 induction. Taken together, these data suggest that autophagic responses triggered by unsaturated aldehydes could be attributed, in part, to ER stress, which stimulates autophagy by a JNK-dependent mechanism and promotes cell survival during oxidative stress.
authors.affiliation: Diabetes and Obesity Center, Institute of Molecular Cardiology, University of Louisville, Louisville, KY, USA.
authors.forename: Petra
authors.initials: P
authors.lastname: Haberzettl
authors.forename: Bradford G
authors.initials: BG
authors.lastname: Hill
mesh_terms: D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001011:Aorta / Q000166:cytology; D001343:Autophagy; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D015227:Lipid Peroxidation; D020935:MAP Kinase Signaling System / Q000187:drug effects; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000447:Aldehydes; D000873:Anthracenes; C432165:pyrazolanthrone; D048055:Mitogen-Activated Protein Kinase 8; C027576:4-hydroxy-2-nonenal
keywords: 4-hydroxynonenal; ATF6, activating transcription factor 6; Autophagy; DMEM, Delbucco's Eagle Modified Medium; DMSO, dimethylsulfoxide; DNPH, 2,4-dinitrophenylhydrazine; DTT, dithiothreitol; ECL, enhanced chemiluminescence; ER, endoplasmic reticulum; FBS, fetal bovine serum; Grp, glucose regulated protein; HEPES, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; HNE, 4-hydroxy-trans-2-nonenal; HRP, horseradish peroxidase; IRE, inositol requiring enzyme; JNK; JNK, c-jun N-terminal kinase; LC3, microtubule-associated protein 1 light chain 3; NP-40, noniodet P40; Oxidative stress; PDI, protein disulfide isomerase; PERK, PKR-like ER kinase; PVDF, polyvinylidene fluoride; RASMC, rat aortic smooth muscle cells; SDS, sodium dodecyl sulfate; Smooth muscle cells; UPR, unfolded protein response; Unfolded protein response; eIF2α, elongation initiation factor 2 α
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