title: Proteasome inhibitors up-regulate haem oxygenase-1 gene expression: requirement of p38 MAPK (mitogen-activated protein kinase) activation but not of NF-kappaB (nuclear factor kappaB) inhibition.
abstract: Regulation of intracellular protein stability by the ubiquitin-dependent proteasome system plays a crucial role in cell function. HO-1 (haem oxygenase) is a stress response protein, which confers cytoprotection against oxidative injury and provides a vital function in maintaining tissue homoeostasis. In the present study, we found a novel action of proteasome inhibitors MG132 and MG262 on HO-1 induction, and characterized the underlying mechanisms. MG132 (> or =0.1 microM) treatment resulted in a marked time- and concentration-dependent induction of the steady-state level of HO-1 mRNA in RAW264.7 macrophages, followed by a corresponding increase in HO-1 protein. Actinomycin D and cycloheximide inhibited MG132-responsive HO-1 protein expression, indicating a requirement for transcription and de novo protein synthesis. The involvement of signal pathways in MG132-induced HO-1 gene expression was examined using chemical inhibitors. Antioxidant N -acetylcysteine and SB203580, an antioxidant and inhibitor of p38 MAPK (mitogen-activated protein kinase), abolished MG132-inducible HO-1 expression. Furthermore, MG132 activated the p38 MAPK pathway. The half-life of HO-1 protein was prolonged by MG132, indicating that the upregulation of HO-1 by proteasome inhibitor is partially attributable to the inhibition of protein degradation. MG132 can ablate IkappaBalpha degradation and NF-kappaB (nuclear factor kappaB) activation induced by lipopolysaccharide, similar to the effect of another NF-kappaB inhibitor pyrrolidine dithiocarbamate. We found HO-1 upregulation by MG132 and pyrrolidine dithiocarbamate is unrelated to their inhibition of NF-kappaB, since leptomycin B, another NF-kappaB inhibitor, did not elicit similar induction of HO-1. Taken together, we found a novel effect of proteasome inhibitor on induction of HO-1 expression. This action is ascribed to the activation of the p38 MAPK pathway, but is not dependent on NF-kappaB inhibition.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Wen-Tung
authors.initials: WT
authors.lastname: Wu
authors.forename: Kwan-Hwa
authors.initials: KH
authors.lastname: Chi
authors.forename: Feng-Ming
authors.initials: FM
authors.lastname: Ho
authors.forename: Wei-Chia
authors.initials: WC
authors.lastname: Tsao
authors.forename: Wan-Wan
authors.initials: WW
authors.lastname: Lin
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D051547:Heme Oxygenase-1; D051550:I-kappa B Kinase; D007976:Leupeptins / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008565:Membrane Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009573:Nitrites / Q000032:analysis; D011392:Proline / Q000031:analogs & derivatives* / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013859:Thiocarbamates / Q000494:pharmacology; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D009573:Nitrites; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013859:Thiocarbamates; D018808:Transcription Factor AP-1; C066229:prolinedithiocarbamate; D011392:Proline; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde