title: Interferon-γ contributes to HLA-B27-associated unfolded protein response in spondyloarthropathies.
abstract: OBJECTIVE
  HLA-B27 positivity strongly influences the susceptibility to and phenotype of spondyloarthropathies (SpA). This study was designed to screen factors that activate the promoter of HLA-B27 in U937 cells, and to assess whether these promoter-activating factors induce the unfolded protein response (UPR) in HLA-B27-expressing cells.
  
  
  METHODS
  Cytometric Bead Array, flow cytometry, and real-time polymerase chain reaction were used to detect the expression of cytokines and UPR-associated proteins in peripheral blood and synovial fluid of patients with SpA. The HLA-B27 promotor transfectant was incubated separately with cytokines and Toll-like receptor ligands. After interferon-γ (IFN-γ) stimulation, expressions of GRP78, CHOP, and XBP-1 were tested in HLA-B27-expressing U937 cells and peripheral blood mononuclear cell (PBMC) of patients with ankylosing spondylitis (AS). (Clinical trial registration no. ChiCTR-OCC-11001565)
  
  
  RESULTS
  Expressions of GRP78, CHOP, and XBP-1 in monocytes/macrophages of SpA peripheral blood and synovial fluid were higher than those in healthy controls and patients with osteoarthritis (OA) (p < 0.05). Tumor necrosis factor-α (TNF-α) and IFN-α, IFN-ß, and IFN-γ were found to have activated the HLA-B27 promoter in the U937 cell line (p < 0.05). Following stimulation with IFN-γ, the expressions of GRP78, CHOP and XBP-1 in HLA-B27-transfected U937 cells and PBMC of HLA-B27-positive AS patients were more intense than those in A2-U937 cells, HLA-B27-negative AS patients, or healthy controls (p < 0.05).
  
  
  CONCLUSIONS
  Expressions of GRP78, CHOP, and XBP-1 were higher in monocytes/macrophages of patients with SpA than those in both OA patients and healthy controls, suggesting that UPR may participate in the pathogenesis of SpA. TNF-α and IFN-α, IFN-ß, and IFN-γ significantly activated HLA-B27 promoter in the U937 cell line, and IFN-γ, the strongest activating factor, may induce the UPR in HLA-B27-expressing cells.
authors.affiliation: Department of Clinical Immunology, State Key Discipline of Cell Biology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Feng
authors.forename: Jin
authors.initials: J
authors.lastname: Ding
authors.forename: Chun Mei
authors.initials: CM
authors.lastname: Fan
authors.forename: Ping
authors.initials: P
authors.lastname: Zhu
mesh_terms: D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000378:metabolism / Q000473:pathology; D016918:Arthritis, Reactive / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005260:Female; D015796:HLA-B27 Antigen / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D000071701:Regulatory Factor X Transcription Factors; D025242:Spondylarthropathies / Q000378:metabolism* / Q000473:pathology; D013167:Spondylitis, Ankylosing / Q000378:metabolism / Q000473:pathology; D051742:Transcription Factor CHOP / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D020298:U937 Cells; D056811:Unfolded Protein Response / Q000187:drug effects*; D000071717:X-Box Binding Protein 1
chemical_list: D016207:Cytokines; C497249:DDIT3 protein, human; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D015796:HLA-B27 Antigen; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; D051742:Transcription Factor CHOP; D007371:Interferon-gamma