title: Inhibition of autophagic flux by ROS promotes apoptosis during DTT-induced ER/oxidative stress in HeLa cells.
abstract: As targets for cancer therapy, endoplasmic reticulum (ER) stress and autophagy are closely linked. However, the signaling pathways responsible for induction of autophagy in response to ER stress and its cellular consequences appear to vary with cell type and stimulus. In the present study, we showed that dithiothreitol (DTT) induced ER stress in HeLa cells in a time- and dose-dependent fashion. With increased ER stress, reactive oxygen species (ROS) production increased and autophagy flux, assessed by intracellular accumulation of LC3B-II and p62, was inhibited. N-acetyl-L-cysteine (NAC), a classic antioxidant, exacerbated cell death induced by 3.2 mM of DTT, but attenuated that induced by 6.4 mM DTT. Low cytotoxic doses of DTT transiently activated c-JNU N-terminal kinase (JNK) and p38, whereas high dose of DTT persistently activated JNK and p38 and simultaneously reduced extracellular signal-regulated kinase (ERK) activity. Combined treatment with DTT and U0126, an inhibitor of ERK upstream activators mitogen-activated protein kinase (MAPK) kinase 1 and 2 (MEK1/2), blocked autophagy flux in HeLa cells. This effect was similar to that caused by a combination of DTT and chloroquine (CQ). These data suggested that insufficient autophagy was accompanied by increased ROS production during DTT-induced ER stress. ROS appeared to regulate MAPK signaling, switching from a pro-survival to a pro-apoptotic signal as ER stress increased. ERK inhibition by ROS during severe ER stress blocked autophagic flux. Impaired autophagic flux, in turn, aggravated ER stress, ultimately leading to cell death. Taken together, our data provide the first reported evidence that ROS may control cell fate through regulating the MAPK pathways and autophagic flux during DTT-induced ER/oxidative stress.
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Xi-Yan
authors.initials: XY
authors.lastname: Xiang
authors.affiliation: Centre of Nephrology and Urology, Shenzhen University Health Science Centre, Shenzhen 130021, P.R. China.
authors.forename: Xiao-Chun
authors.initials: XC
authors.lastname: Yang
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Jin
authors.initials: J
authors.lastname: Su
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Jing-Song
authors.initials: JS
authors.lastname: Kang
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Xue
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Yu-Tong
authors.initials: YT
authors.lastname: Dong
authors.affiliation: Department of Pathophysiology, Basic College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Lian-Kun
authors.initials: LK
authors.lastname: Sun
mesh_terms: D001343:Autophagy / Q000187:drug effects*; D004229:Dithiothreitol / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
chemical_list: D017382:Reactive Oxygen Species; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D004229:Dithiothreitol