title: Histone deacetylase inhibitor suberoylanilide hydroxamic acid attenuates Toll-like receptor 4 signaling in lipopolysaccharide-stimulated mouse macrophages.
abstract: OBJECTIVE
  We have previously demonstrated that pretreatment and posttreatment of animals with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, can improve survival in a mouse model of lipopolysaccharide (LPS)-induced severe shock. This study was designed to assess whether SAHA affects LPS/Toll-like receptor 4 signaling through acetylation of heat shock protein 90 (HSP90) and degradation of its client protein interleukin-1 receptor-associated kinase 1 (IRAK1).
  
  
  METHODS
  RAW264.7 cells were exposed to LPS (1 μg/mL) for 2 h, followed by treatment with SAHA (10 μM) or geldanamycin (3 μM), an inhibitor of HSP90. Sham (no SAHA, no LPS) macrophages served as a control. The cells were harvested at different time points, and time zero served as the reference point.
  
  
  RESULTS
  LPS dramatically increased protein expression of myeloid differentiation factor 88 and IRAK1, and stimulated nuclear translocation of nuclear factor κB, leading to an increases of gene expression and protein production of tumor necrosis factor α and interleukin-6. Treatment with SAHA significantly attenuated these LPS-stimulated alterations. LPS or SAHA did not change the levels of HSP90 protein, but immunoprecipitation studies demonstrated that SAHA treatment enhanced acetylation of HSP90, and increased the dissociation of IRAK1, compared to the LPS control.
  
  
  CONCLUSIONS
  SAHA suppresses LPS/Toll-like receptor 4 signaling in LPS-stimulated macrophages through multiple potential mechanisms. It inhibits the function of HSP90 through hyperacetylation of the chaperone protein, which results in dissociation and degradation of the client protein IRAK1 and, at least in part, leads to a decrease in nuclear translocation of nuclear factor κB and attenuation of key proinflammatory cytokine expression.
authors.affiliation: Department of Surgery, Division of Trauma, Emergency Surgery and Surgical Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Chong
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Li
authors.forename: Baoling
authors.initials: B
authors.lastname: Liu
authors.forename: Ting
authors.initials: T
authors.lastname: Zhao
authors.forename: Eugene Y
authors.initials: EY
authors.lastname: Fukudome
authors.forename: Zhengcai
authors.initials: Z
authors.lastname: Liu
authors.forename: William M
authors.initials: WM
authors.lastname: Smith
authors.forename: George C
authors.initials: GC
authors.lastname: Velmahos
authors.forename: Marc A
authors.initials: MA
authors.lastname: deMoya
authors.forename: Hasan B
authors.initials: HB
authors.lastname: Alam
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D002478:Cells, Cultured; D018841:HSP90 Heat-Shock Proteins / Q000032:analysis; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006877:Hydroxamic Acids / Q000494:pharmacology*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000032:analysis; D015850:Interleukin-6 / Q000032:analysis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000032:analysis; D016328:NF-kappa B / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051197:Toll-Like Receptor 4 / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000235:genetics; D000077337:Vorinostat
chemical_list: D018841:HSP90 Heat-Shock Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D015850:Interleukin-6; D008070:Lipopolysaccharides; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D000077337:Vorinostat; D053592:Interleukin-1 Receptor-Associated Kinases; C507769:Irak1 protein, mouse