title: Increased Expression of Glutaminase in Osteoblasts Promotes Macrophage Recruitment in Periapical Lesions.
abstract: BACKGROUND
  Recently, we have shown that tissue hypoxia stimulates the progression of periapical lesions by up-regulating glycolysis-dependent apoptosis of osteoblasts. Other facets of hypoxia-induced metabolic reprogramming in disease pathogenesis require further investigation. In this study, we examined the connection between hypoxia-augmented glutamine catabolism in osteoblasts and the development of periapical lesions.
  
  
  METHODS
  Primary human osteoblasts were cultured under hypoxia. The expression of glutaminase 1 (GLS1) was examined using Western blot analysis. The production of glutamate was measured by colorimetric assay. Knockdown of GLS1 was performed with small interfering RNA technology. C-C motif chemokine ligand 2 (CCL2) secretion and chemotaxis of J774 macrophages were examined by enzyme-linked immunosorbent assay and transwell migration assay, respectively. In a rat model of induced periapical lesions, the relations between disease progression and osteoblastic expression of GLS1 or macrophage recruitment were studied.
  
  
  RESULTS
  Hypoxia enhanced GLS1 expression and subsequent glutamate production in osteoblasts. Glutamate induced chemoattraction of macrophages by osteoblasts through up-regulation of CCL2 synthesis. Hypoxia promoted CCL2 secretion and macrophage recruitment through augmentation of glutaminolysis. Knockdown of GLS1 abolished hypoxia-induced effects. In rat periapical lesions, progressive bone resorption was significantly related to elevated GLS1 expression in osteoblasts and increased macrophage recruitment.
  
  
  CONCLUSIONS
  In addition to the rise in glycolytic activity, the progression of periapical lesions is also associated with enhanced glutamine catabolism in osteoblasts. GLS1 may be a potential therapeutic target in the management of periapical lesions.
authors.affiliation: Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Kuo-Liang
authors.initials: KL
authors.lastname: Hou
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Sze-Kwan
authors.initials: SK
authors.lastname: Lin
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Sang-Heng
authors.initials: SH
authors.lastname: Kok
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Han-Wei
authors.initials: HW
authors.lastname: Wang
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Eddie Hsiang-Hua
authors.initials: EH
authors.lastname: Lai
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan; College of Bio-Resources and Agriculture, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chi-Yuan
authors.initials: CY
authors.lastname: Hong
authors.affiliation: Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Hsiang
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Juo-Song
authors.initials: JS
authors.lastname: Wang
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Li-Deh
authors.initials: LD
authors.lastname: Lin
authors.affiliation: Department of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: jennyzc@ms3.hinet.net.
authors.forename: Jenny Zwei-Chieng
authors.initials: JZ
authors.lastname: Chang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D018450:Disease Progression; D005972:Glutaminase / Q000378:metabolism* / Q000502:physiology; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000502:physiology*; D010006:Osteoblasts / Q000201:enzymology* / Q000502:physiology; D010485:Periapical Periodontitis / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005973:Glutamine; C579480:GLS protein, human; D005972:Glutaminase
keywords: Bone resorption; C-C motif chemokine ligand 2; glutamate; glutaminolysis; hypoxia; inflammation