Interferon-γ contributes to HLA-B27-associated unfolded protein response in spondyloarthropathies.
ABSTRACT 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.
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)
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).
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.
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ABSTRACT: Ankylosing spondylitis (AS) is an autoimmune disease and is associated with abnormall B cell function. However, the roles of different B cell subsets are less clear. This study aimed to examine the frequency of different subsets of B cells in AS patients following standard therapies. Eighteen newly diagnosed AS patients and 10 healthy controls (HC) were recruited in this study. The expression of CD27, CD38, CD86, CD95 and IgD on CD19(+) B cells were examined by flow cytometry. The disease activity was scored according to the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). Serum levels of C-reactive protein (CRP), rheumatoid factor (RF), IgG, IgA and IgM, and the erythrocyte sedimentation rate (ESR) were measured. The frequency of CD27(+) B cells was decreased in AS patients compared with HC (p=0.018), while CD86(+) and CD27(-)CD95(+) B cell subsets increased in AS patients (p<0.001). Meanwhile, the frequencies of CD38(+) and CD95(+) B cell positively correlated with BASDAI (r=0.6505, p=0.0035; r=0.6854, p=0.0017, respectively), while CD38(-)CD86(+) B cell negatively correlated with BASDAI (r=-0.7329, p<0.001). We also found that CD27(-) and CD95(+) B cell negatively correlated with RF levels (r=-0.5141, p=0.0290; r=-0.4944, p=0.0370, respectively), while CD27(+) B cell positively correlated with IgG levels (p=0.0148, r=0.5640). Moreover, CD86(+) and CD27(-)CD95(+) B cell subsets increased following treatment with Meloxicam and Etanercept for one month (p<0.001; p<0.001). These findings suggest that CD27(-)CD95(+)CD19(+) and CD86(+)CD19(+) B cells may be reasonable cellular targets for the therapeutic intervention of AS.Life sciences 09/2013; · 2.56 Impact Factor
- Annals of the rheumatic diseases 10/2013; · 8.11 Impact Factor
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ABSTRACT: Understanding how HLA-B27 contributes to the pathogenesis of spondyloarthritis continues to be an important goal. Current efforts are aimed largely on three areas of investigation; peptide presentation to CD8T cells, abnormal forms of the HLA-B27 heavy chain and their recognition by leukocyte immunoglobulin-like receptors on immune effector cells, and HLA-B27 heavy chain misfolding and intrinsic biological effects on affected cells. In this chapter we review our current understanding of the causes and consequences of HLA-B27 misfolding, which can be defined biochemically as a propensity to oligomerize and form complexes in the endoplasmic reticulum (ER) with the chaperone BiP (HSPA5/GRP78). HLA-B27 misfolding is linked to an unusual combination of polymorphisms that identify this allele, and cause the heavy chain to fold and load peptides inefficiently. Misfolding can result in ER-associated degradation (ERAD) of heavy chains, which is mediated in part by the E3 ubiquitin ligase HRD1 (SYVN1), and the ubiquitin conjugating enzyme UBE2JL. Upregulation of HLA-B27 and accumulation of misfolded heavy chains can activate ER stress signaling pathways that orchestrate the unfolded protein response. In transgenic rats where HLA-B27 is overexpressed, UPR activation is prominent. However, it is specific for heavy chain misfolding, since overexpression of HLA-B7, an allele that does not misfold, fails to generate ER stress. UPR activation has been linked to cytokine dysregulation, promoting lL-23, IFNβ, and lL-1α production, and may activate the IL-23/IL-17 axis in these rats. IL-1α and IFNβ are pro- and anti-osteoclastogenic cytokines, respectively, that modulate osteoclast development in HLA-B27-expressing transgenic rat monocytes. Translational studies of patient derived cells expressing HLA-B27 at physiologic levels have provided evidence that ER stress and UPR activation can occur in peripheral blood, but this has not been reported to date in isolated macrophages. Inflamed gastrointestinal tissue reveals evidence for HLA-B27 misfolding, ERAD, and autophagy, without acute UPR activation. A more complete picture of conditions that impact HLA-B27 folding and misfolding, the full spectrum and time course of consequences of ER stress, and critical cell types involved is needed to understand the role of HLA-B27 misfolding in spondyloarthritis pathogenesis.Molecular Immunology 08/2013; · 2.65 Impact Factor