title: Fecal HMGB1 is a novel marker of intestinal mucosal inflammation in pediatric inflammatory bowel disease.
abstract: OBJECTIVE
  High-mobility group box 1 (HMGB1) is a nuclear protein with functions in the regulation of transcription. In inflammatory conditions, HMGB1 is actively secreted from immune cells in the extracellular matrix, where it behaves as a proinflammatory cytokine. The aim of the present study was to investigate the role of HMGB1 in pediatric inflammatory bowel disease (IBD).
  
  
  METHODS
  We analyzed the stools of 19 children with Crohn's disease (CD), 21 with ulcerative colitis (UC), and 13 controls. The gene/protein expression levels of HMGB1 were assessed in bioptic specimens of all children using real-time PCR and western blot assay. Finally, intracellular localization of the protein was analyzed by western blot, after separation of nuclear and cytoplasmic extracts, and by immunohistochemistry.
  
  
  RESULTS
  HMGB1 protein levels were significantly increased (P<0.001) in the stools of patients, but were undetectable in the controls; fecal HMGB1 correlated well with fecal calprotectin levels (r: 0.77 in CD, r: 0.70 in UC; P<0.01); and mRNA and protein expression were unchanged in inflamed bioptic tissues compared with controls. However, by separately analyzing the nuclear and cytoplasmic fraction, we detected the cytoplasmic HMGB1 expression to be significantly enhanced (P<0.01) in the inflamed tissues of the patients. In addition, HMGB1 was significantly detected in 16 patients with inactive disease, whose endoscopic scores showed persisting inflammation, suggesting that it may be a sensitive marker of mucosal inflammation, although the disease is clinically inactive.
  
  
  CONCLUSIONS
  It was shown for the first time in our study that HMGB1 is secreted by human inflamed intestinal tissues and abundantly found in the stools of IBD patients. Hence, it can be considered as a novel marker for intestinal inflammation. We can also suggest that the presence of HMGB1 in large amounts in the fecal stream of IBD patients is mainly due to active secretion of the protein stored in the nucleus rather than a "de novo" synthesis.
authors.affiliation: Department of Radiobiology and Human Health, ENEA, Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Vitali
authors.forename: Laura
authors.initials: L
authors.lastname: Stronati
authors.forename: Anna
authors.initials: A
authors.lastname: Negroni
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Nardo
authors.forename: Maria
authors.initials: M
authors.lastname: Pierdomenico
authors.forename: Emanuela
authors.initials: E
authors.lastname: del Giudice
authors.forename: Paolo
authors.initials: P
authors.lastname: Rossi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Cucchiara
mesh_terms: D021581:Active Transport, Cell Nucleus; D000293:Adolescent; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D001706:Biopsy; D018938:Caco-2 Cells / Q000276:immunology / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003093:Colitis, Ulcerative / Q000378:metabolism* / Q000473:pathology; D003424:Crohn Disease / Q000378:metabolism* / Q000473:pathology; D005243:Feces / Q000737:chemistry*; D005260:Female; D024243:HMGB1 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007223:Infant; D016898:Interferon-alpha / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology; D016209:Interleukin-8 / Q000235:genetics; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; D024243:HMGB1 Protein; D016898:Interferon-alpha; D016209:Interleukin-8; D012333:RNA, Messenger; D007371:Interferon-gamma