title: Glutaminase 1 plays a key role in the cell growth of fibroblast-like synoviocytes in rheumatoid arthritis.
abstract: The recent findings of cancer-specific metabolic changes, including increased glucose and glutamine consumption, have provided new therapeutic targets for consideration. Fibroblast-like synoviocytes (FLS) from rheumatoid arthritis (RA) patients exhibit several tumor cell-like characteristics; however, the role of glucose and glutamine metabolism in the aberrant proliferation of these cells is unclear. Here, we evaluated the role of these metabolic pathways in RA-FLS proliferation and in autoimmune arthritis in SKG mice.
  
  
  
  The expression of glycolysis- or glutaminolysis-related enzymes was evaluated by real-time polymerase chain reaction (PCR) and Western blotting, and the intracellular metabolites were evaluated by metabolomic analyses. The effects of glucose or glutamine on RA-FLS cell growth were investigated using glucose- or glutamine-free medium. Glutaminase (GLS)1 small interfering RNA (siRNA) and the GLS1 inhibitor compound 968 were used to inhibit GLS1 in RA-FLS, and compound 968 was used to study the effect of GLS1 inhibition in zymosan A-injected SKG mice.
  
  
  
  GLS1 expression was increased in RA-FLS, and metabolomic analyses revealed that glutamine metabolism was increased in RA-FLS. RA-FLS proliferation was reduced under glutamine-deprived, but not glucose-deprived, conditions. Cell growth of RA-FLS was inhibited by GLS1 siRNA transfection or GLS1 inhibitor treatment. Treating RA-FLS with either interleukin-17 or platelet-derived growth factor resulted in increased GLS1 levels. Compound 968 ameliorated the autoimmune arthritis and decreased the number of Ki-67-positive synovial cells in SKG mice.
  
  
  
  Our results suggested that glutamine metabolism is involved in the pathogenesis of RA and that GLS1 plays an important role in regulating RA-FLS proliferation, and may be a novel therapeutic target for RA.
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Soshi
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan. jsaegusa@med.kobe-u.ac.jp.|Department of Clinical Laboratory, Kobe University Hospital, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan. jsaegusa@med.kobe-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Saegusa
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Sendo
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Takaichi
authors.initials: T
authors.lastname: Okano
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Akashi
authors.affiliation: Division of Evidence-Based Laboratory Medicine, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Irino
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-Cho, Chuo-Ku, Kobe, 650-0017, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Morinobu
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000201:enzymology / Q000473:pathology*; D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000473:pathology*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000502:physiology; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology*; D055785:Gene Knockdown Techniques; D005972:Glutaminase / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D060888:Real-Time Polymerase Chain Reaction; D000070918:Synoviocytes / Q000201:enzymology / Q000473:pathology*
chemical_list: D005973:Glutamine; C574238:GLS1 protein, mouse; D005972:Glutaminase
keywords: Fibroblasts; Glutamine; Glutaminolysis; Metabolomics; Rheumatoid arthritis