title: Expression of heat shock proteins in periapical granulomas.
abstract: BACKGROUND
  Cells from virtually all organisms respond to a variety of stresses by the rapid synthesis of a highly conserved set of polypeptides termed heat shock proteins (HSPs). HSPs protect cells under adverse conditions such as infection, inflammation, and disease. We hypothesize that endodontic infection might result in an imbalance in the expression of heat shock genes, accounting for different clinical outcomes in periapical lesions.
  
  
  METHODS
  We analyzed the expression of 44 HSPs genes using a pathway-specific real-time polymerase chain reaction array in 93 human periapical granulomas and 24 healthy periodontal ligament tissues collected postoperatively. Observed variations in the expression of HSP genes were also analyzed based on the classification of periapical granulomas as active or inactive. In addition, U937 cells were differentiated into macrophages, infected with different concentrations of purified Escherichia coli lipopolysaccharide (LPS), and used as templates for the HSP gene array. Protein expression was assessed by immunohistochemistry.
  
  
  RESULTS
  The expression of HSP genes was significantly increased in granulomas compared with healthy periodontal ligament (P < .00001). Among the 44 HSP genes, DNAJC3, HSPA4, HSPA6, and HSPB1 showed the highest expression levels in both granulomas and LPS-treated macrophages. DNAJC3, HSPA6, and HSPB1 were highly expressed in active lesions, whereas HSPA4 expression was higher in inactive lesions (P < .005). Higher concentrations of LPS led to increased HSP expression in macrophages (P < .0001). Immunocytochemistry confirmed the expression and colocalization of HSPB1 and HSPA6 proteins in the cytoplasm of LPS-infected macrophages.
  
  
  CONCLUSIONS
  The observed differential expression patterns of HSPs in periapical granulomas and LPS-infected macrophages suggest that HSP genes and proteins are involved in periapical lesion development and may account for different clinical outcomes. Understanding the role of the heat shock response might provide additional insights into the process of periapical lesion development.
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Goodman
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas.
authors.forename: Ariadne
authors.initials: A
authors.lastname: Letra
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas.
authors.forename: Samuel
authors.initials: S
authors.lastname: Dorn
authors.affiliation: Osteoimmunology Lab, Department of Biological Sciences, School of Dentistry of Bauru, University of São Paulo, São Paulo, Brazil.
authors.forename: Ana Claudia
authors.initials: AC
authors.lastname: Araujo-Pires
authors.affiliation: Osteoimmunology Lab, Department of Biological Sciences, School of Dentistry of Bauru, University of São Paulo, São Paulo, Brazil.
authors.forename: Andreia Espindola
authors.initials: AE
authors.lastname: Vieira
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas.
authors.forename: Letícia
authors.initials: L
authors.lastname: Chaves de Souza
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas.
authors.forename: Mamatha
authors.initials: M
authors.lastname: Yadlapati
authors.affiliation: Osteoimmunology Lab, Department of Biological Sciences, School of Dentistry of Bauru, University of São Paulo, São Paulo, Brazil.
authors.forename: Gustavo Pompermaier
authors.initials: GP
authors.lastname: Garlet
authors.affiliation: Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, Texas. Electronic address: Renato.M.Silva@uth.tmc.edu.
authors.forename: Renato Menezes
authors.initials: RM
authors.lastname: Silva
mesh_terms: D000293:Adolescent; D000328:Adult; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000502:physiology; D003593:Cytoplasm / Q000737:chemistry; D004926:Escherichia coli / Q000276:immunology; D050957:HSP110 Heat-Shock Proteins / Q000032:analysis; D055551:HSP27 Heat-Shock Proteins / Q000032:analysis; D050956:HSP40 Heat-Shock Proteins / Q000032:analysis; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis; D006360:Heat-Shock Proteins / Q000032:analysis*; D006801:Humans; D053583:Interleukin-1beta / Q000032:analysis; D015850:Interleukin-6 / Q000032:analysis; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000737:chemistry / Q000276:immunology; D008875:Middle Aged; D018832:Molecular Chaperones; D010484:Periapical Granuloma / Q000378:metabolism*; D010513:Periodontal Ligament / Q000737:chemistry; D053245:RANK Ligand / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D020298:U937 Cells; D055815:Young Adult
chemical_list: C494651:DNAJC3 protein, human; D050957:HSP110 Heat-Shock Proteins; D055551:HSP27 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C121993:HSPA4 protein, human; C544598:HSPA6 protein, human; C491129:HSPA7 protein, human; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; C508600:IL6 protein, human; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D018832:Molecular Chaperones; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D014409:Tumor Necrosis Factor-alpha
keywords: Apical periodontitis; gene expression; heat shock protein; macrophages; protein expression