title: Nitric oxide-dependent suppression of thioredoxin-interacting protein expression enhances thioredoxin activity.
abstract: OBJECTIVE
  Cellular redox balance is regulated by enzymatic and nonenzymatic systems and freely diffusible nitric oxide (NO) promotes antioxidative mechanisms. We show the NO-dependent transcriptional regulation of the antioxidative thioredoxin system.
  
  
  RESULTS
  Incubation of rat pulmonary artery smooth muscle cells (RPaSMC) with the NO donor compound S-nitroso-glutathione (GSNO, 100 micromol/L) suppressed thioredoxin-interacting protein (Txnip), an inhibitor of thioredoxin function, by 71+/-18% and enhanced thioredoxin reductase 2.7+/-0.2 fold (n=6; both P<0.001 versus control). GSNO increased thioredoxin activity (1.9+/-0.5-fold after 4 hours; P<0.05 versus control). Promoter deletion analysis revealed that NO suppression of Txnip transcription is mediated by cis-regulatory elements between -1777 and -1127 bp upstream of the start codon. Hyperglycemia induced Txnip promoter activity (3.9+/-0.2-fold; P<0.001) and abolished NO effects (-37.4+/-1.0% at 5.6 mmol/L glucose versus 12.4+/-2.1% at 22.4 mmol/L glucose; P<0.05). Immunoprecipitation experiments demonstrated that GSNO stimulation and mutation of thioredoxin at Cys69, a site of nitrosylation, had no effect on the Txnip/thioredoxin interaction.
  
  
  CONCLUSIONS
  NO can regulate cellular redox state by changing expression of Txnip and thioredoxin reductase. This represents a novel antioxidative mechanism of NO independent of posttranslational protein S-nitrosylation of thioredoxin.
authors.affiliation: Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass, USA. christian.schulze@bmc.org
authors.forename: P Christian
authors.initials: PC
authors.lastname: Schulze
authors.forename: Heling
authors.initials: H
authors.lastname: Liu
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Choe
authors.forename: Jun
authors.initials: J
authors.lastname: Yoshioka
authors.forename: Anath
authors.initials: A
authors.lastname: Shalev
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Bloch
authors.forename: Richard T
authors.initials: RT
authors.lastname: Lee
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D006943:Hyperglycemia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000235:genetics / Q000378:metabolism*; D009574:Nitro Compounds / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011499:Protein Processing, Post-Translational; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D009574:Nitro Compounds; D012333:RNA, Messenger; C116027:S-nitroglutathione; C493796:TXNIP protein, rat; D009569:Nitric Oxide; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione