title: The role of nitric oxide in the epigenetic regulation of THP-1 induced by lipopolysaccharide.
abstract: OBJECTIVE
  Changes in the gene expression are one of the molecular events involved in the Systemic of Inflammatory Response Syndrome during sepsis. The preconditioning with low doses of lipopolysaccharide (LPS) reduces the expression of pro-inflammatory genes leading to less tissue damage and better outcome. This hyporesponsive state called tolerance is associated to alterations in chromatin structure and nitric oxide (NO) production. In the current study, we demonstrated that tolerance induced by LPS was found to be NO-dependent and related to epigenetic changes.
  
  
  METHODS
  THP-1 cells were cultivated in RPMI medium (Control), submitted to tolerance (500ng/mL of LPS 24h before challenge with 1000ng/mL of LPS during 24h Tolerant group) and challenge (1000ng/mL of LPS during 24h Directly challenged group). The analyses performed were: cytokines production, histone acetyl transferases/histone deacetylases (HAT/HDAC) activity, nitrosylation of HDAC-2 and -3, expression of acetylated histones H3 and H4. HDAC and Nitric Oxide Synthases (NOS) activities were inhibited with 30mM trichostatin (TSA) and 100μM LNAME, respectively.
  
  
  RESULTS
  Administration of low doses of LPS repressed the production of IL-6 and IL-10, however this effect was abolished with the inhibition of NOS activity and by TSA in the case of IL-10. Tolerance modulates the activity of HAT and, consequently, the acetylation of histones H3 and H4. Inhibition of NO decreases acetylation of Histones. The HDACs 2 and 3 were nitrosylated after the tolerance induction.
  
  
  CONCLUSIONS
  The tolerance to LPS regulates the cytokine production by modulating chromatin structure and this event is NO dependent.
authors.affiliation: Universidade de São Paulo Medical School, Department of Emergency Medicine, Avenida Doutor Arnaldo, 455, Room 3189, São Paulo, SP CEP 01246903, Brazil. Electronic address: estercsrios@yahoo.com.br.
authors.forename: Ester Correia Sarmento
authors.initials: EC
authors.lastname: Rios
authors.affiliation: Universidade de São Paulo Medical School, Department of Emergency Medicine, Avenida Doutor Arnaldo, 455, Room 3189, São Paulo, SP CEP 01246903, Brazil.
authors.forename: Thais Martins
authors.initials: TM
authors.lastname: de Lima
authors.affiliation: Instituto do Coração, Avenida Doutor Enéas de Carvalho Aguiar, 44-Cerqueira Cesar, São Paulo, SP, Brazil.
authors.forename: Ana Iochabel Soares
authors.initials: AI
authors.lastname: Moretti
authors.affiliation: Universidade de São Paulo Medical School, Department of Emergency Medicine, Avenida Doutor Arnaldo, 455, Room 3189, São Paulo, SP CEP 01246903, Brazil.
authors.forename: Francisco Garcia
authors.initials: FG
authors.lastname: Soriano
mesh_terms: D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007108:Immune Tolerance / Q000502:physiology; D016753:Interleukin-10 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D009000:Monocytes / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D018746:Systemic Inflammatory Response Syndrome / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; D016207:Cytokines; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D015850:Interleukin-6; D008070:Lipopolysaccharides; D016753:Interleukin-10; D009569:Nitric Oxide; C012589:trichostatin A; D019001:Nitric Oxide Synthase; D051548:Histone Acetyltransferases; D006655:Histone Deacetylases
keywords: Endotoxemia; Endotoxin; Gene transcription; Tolerance