title: Redox activation of DUSP4 by N-acetylcysteine protects endothelial cells from Cd²⁺-induced apoptosis.
abstract: Redox imbalance is a primary cause of endothelial dysfunction (ED). Under oxidant stress, many critical proteins regulating endothelial function undergo oxidative modifications that lead to ED. Cellular levels of glutathione (GSH), the primary reducing source in cells, can significantly regulate cell function via reversible protein thiol modification. N-acetylcysteine (NAC), a precursor for GSH biosynthesis, is beneficial for many vascular diseases; however, the detailed mechanism of these benefits is still not clear. From HPLC analysis, NAC significantly increases both cellular GSH and tetrahydrobiopterin levels. Immunoblotting of endothelial NO synthase (eNOS) and DUSP4, a dual-specificity phosphatase with a cysteine as its active residue, revealed that both enzymes are upregulated by NAC. EPR spin trapping further demonstrated that NAC enhances NO generation from cells. Long-term exposure to Cd(2+) contributes to DUSP4 degradation and the uncontrolled activation of p38 and ERK1/2, leading to apoptosis. Treatment with NAC prevents DUSP4 degradation and protects cells against Cd(2+)-induced apoptosis. Moreover, the increased DUSP4 expression can redox-regulate the p38 and ERK1/2 pathways from hyperactivation, providing a survival mechanism against the toxicity of Cd(2+). DUSP4 gene knockdown further supports the hypothesis that DUSP4 is an antioxidant gene, critical in the modulation of eNOS expression, and thus protects against Cd(2+)-induced stress. Depletion of intracellular GSH by buthionine sulfoximine makes cells more susceptible to Cd(2+)-induced apoptosis. Pretreatment with NAC prevents p38 overactivation and thus protects the endothelium from this oxidative stress. Therefore, the identification of DUSP4 activation by NAC provides a novel target for future drug design.
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: Alma
authors: A
authors: Barajas-Espinosa
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: Ariel
authors: A
authors: Basye
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: Erin
authors: E
authors: Jesse
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: Haixu
authors: H
authors: Yan
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: David
authors: D
authors: Quan
authors: Department of Emergency Medicine, College of Medicine, The Ohio State University, Columbus OH, 43210 USA.
authors: Chun-An
authors: CA
authors: Chen
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002104:Cadmium / Q000633:toxicity; D002417:Cattle; D048708:Cell Growth Processes; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D019610:Cytoprotection / Q000187:drug effects; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D005978:Glutathione / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D054639:Mitogen-Activated Protein Kinase Phosphatases / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D015854:Up-Regulation
chemical_list: D034741:RNA, Small Interfering; D002104:Cadmium; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D054639:Mitogen-Activated Protein Kinase Phosphatases; D054637:Dual-Specificity Phosphatases; C094132:Dusp4 protein, rat; D005978:Glutathione; D000111:Acetylcysteine
keywords: DUSP4; Endothelial dysfunction; Free radicals; MAP kinases; N-acetylcysteine; Nitric oxide synthase; Phosphatase; Reactive oxygen species; Redox signaling