title: The relationship between deiodinase activity and inflammatory responses under the stimulation of uremic toxins.
abstract: BACKGROUND
  It is unclear to what extent uremic toxins participate in inflammatory responses and the activities of deiodinases, as well as the effects of deiodinases on inflammatory cytokines.
  
  
  METHODS
  Hepatocellular carcinoma cell lines (HepG2) were transfected with small interfering ribonucleic acid (siRNA) specific for deiodinase type 1 (DIO1) and cultured with or without uremic toxins. The mRNA expression of DIO1, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α was detected by quantitative real-time PCR. The presence of selenoprotein M (SelM) and DIO1 was assessed by western blotting. Sonicate deiodinase activities in HepG2 cells were measured by a dithiothreitol-stimulated assay. The NF-κB, AP-1 and CREB-1 inflammatory signal pathways were confirmed by EMSA.
  
  
  RESULTS
  After culturing for 24 h, the mRNA expression of DIO1 was significantly decreased by the specific siRNA (reduced by 76%, P = 0.0002). Uremic toxins significantly increased the mRNA expression (P < 0.01) of IL-1β, IL-6 and TNF-α and inhibited DIO1 mRNA expression (P < 0.01) compared with controls. Suppression of DIO1 by siRNA significantly decreased the mRNA expression of IL-1β and IL-6 (P < 0.05) but not TNF-α (P = 0.093). Uremic toxins and specific siRNA synchronously reduced the protein expression of SelM and DIO1.
  
  
  CONCLUSIONS
  Uremic toxins activate the expression of inflammatory cytokines. The major findings of this study indicate that the uremic toxins, more than inflammatory cytokines, play direct inhibitory roles in DIO1 enzyme activity, which then provides a negative feedback to the growing accumulation of inflammatory cytokines.
authors.affiliation: Nanchang University, Nanchang, China. gaosixu@163.com.
authors.forename: Gaosi
authors.initials: G
authors.lastname: Xu
authors.forename: Weiping
authors.initials: W
authors.lastname: Tu
authors.forename: Shulan
authors.initials: S
authors.lastname: Qin
mesh_terms: D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D018836:Inflammation Mediators / Q000378:metabolism*; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051140:Selenoproteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014118:Toxins, Biological / Q000494:pharmacology*; D014511:Uremia / Q000378:metabolism*
chemical_list: D018836:Inflammation Mediators; D034741:RNA, Small Interfering; C448999:SELM protein, human; D051140:Selenoproteins; D014118:Toxins, Biological; C109812:iodothyronine deiodinase type I; D007453:Iodide Peroxidase