title: Depletion of cytosolic or mitochondrial thioredoxin increases CYP2E1-induced oxidative stress via an ASK-1-JNK1 pathway in HepG2 cells.
abstract: Thioredoxin is an important reducing molecule in biological systems. Increasing CYP2E1 activity induces oxidative stress and cell toxicity. However, whether thioredoxin protects cells against CYP2E1-induced oxidative stress and toxicity is unknown. SiRNA were used to knockdown either cytosolic (TRX-1) or mitochondrial thioredoxin (TRX-2) in HepG2 cells expressing CYP2E1 (E47 cells) or without expressing CYP2E1 (C34 cells). Cell viability decreased 40-60% in E47 but not C34 cells with 80-90% knockdown of either TRX-1 or TRX-2. Depletion of either thioredoxin also potentiated the toxicity produced either by a glutathione synthesis inhibitor or by TNFα in E47 cells. Generation of reactive oxygen species and 4-HNE protein adducts increased in E47 but not C34 cells with either thioredoxin knockdown. GSH was decreased and adding GSH completely blocked E47 cell death induced by either thioredoxin knockdown. Lowering TRX-1 or TRX-2 in E47 cells caused an early activation of ASK-1, followed by phosphorylation of JNK1 after 48 h of siRNA treatment. A JNK inhibitor caused a partial recovery of E47 cell viability after thioredoxin knockdown. In conclusion, knockdown of TRX-1 or TRX-2 sensitizes cells to CYP2E1-induced oxidant stress partially via ASK-1 and JNK1 signaling pathways. Both TRX-1 and TRX-2 are important for defense against CYP2E1-induced oxidative stress.
authors.affiliation: Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Yang
authors.forename: Defeng
authors.initials: D
authors.lastname: Wu
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Wang
authors.forename: Arthur I
authors.initials: AI
authors.lastname: Cederbaum
mesh_terms: D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005981:Glutathione Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D056945:Hep G2 Cells / Q000378:metabolism; D006801:Humans; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D048055:Mitogen-Activated Protein Kinase 8 / Q000037:antagonists & inhibitors / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013879:Thioredoxins / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C491203:TXN protein, human; D014409:Tumor Necrosis Factor-alpha; D013879:Thioredoxins; D019392:Cytochrome P-450 CYP2E1; D048055:Mitogen-Activated Protein Kinase 8; D048848:MAP Kinase Kinase Kinase 5; C482858:MAP3K5 protein, human; D005981:Glutathione Synthase