Sjögren's Syndrome Antigen B Acts as an Endogenous Danger Molecule to Induce Interleukin-8 Gene Expression in Polymorphonuclear Neutrophils.
BACKGROUND
Sjögren's syndrome antigen B is expressed in the nucleus and surface membrane of human polymorphonuclear neutrophils and is released after cell death. However, its biological role is not clear. This study is aimed to investigate the effect of Sjögren's syndrome antigen B on human polymorphonuclear neutrophils.


METHODS
Human recombinant Sjögren's syndrome antigen B (rSSB) purified from E. coli was incubated with human polymorphonuclear neutrophils as well as retinoid acid-induced granulocytic differentiated HL-60 cells, HL-60 (RA). Interleukin (IL)-8 protein production and mRNA expressions were measured by enzyme-linked immunosorbent assay and quantitative-polymerase chain reaction, respectively. Uptake of fluorescein isothiocyanate (FITC)-rSSB was assessed by flow cytometry and fluorescence microscopy. Moreover, mitogen-activated protein kinase (MAPK) pathways and nuclear factor-kappaB activation were investigated.


RESULTS
Human rSSB stimulated IL-8 production from normal human neutrophils and HL-60 (RA) cells in a time- and dose-dependent manner. This IL-8-stimulated activity was blocked by chloroquine and NH4Cl, indicating that endosomal acidification is important for this effect. We found rSSB activated both MAPK pathway and nuclear factor-kappaB signaling to transcribe the IL-8 gene expression of cells. Furthermore, tumor necrosis factor-α exerted an additive effect and rSSB-anti-SSB immune complex exhibited a synergistic effect on rSSB-induced IL-8 production.


CONCLUSIONS
Sjögren's syndrome antigen B might act as an endogenous danger molecule to enhance IL-8 gene expression in human polymorphonuclear neutrophils.
Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan; Division of Immunology, Rheumatology and Allergy, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
Cheng-Han
CH
Wu
Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Immunology, Rheumatology and Allergy, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
Ko-Jen
KJ
Li
Division of Immunology, Rheumatology and Allergy, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan; Institute of Molecular Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.
Chia-Li
CL
Yu
Section of Allergy, Immunology and Rheumatology, Taipei Veterans General Hospital, Taipei, Taiwan.
Chang-Youh
CY
Tsai
Division of Immunology, Rheumatology and Allergy, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
Song-Chou
SC
Hsieh
D000643:Ammonium Chloride / Q000494:pharmacology; D001324:Autoantigens / Q000276:immunology* / Q000502:physiology; D002738:Chloroquine / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000502:physiology*; D020935:MAP Kinase Signaling System; D008856:Microscopy, Fluorescence; D009504:Neutrophils / Q000276:immunology / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins; D012261:Ribonucleoproteins / Q000276:immunology* / Q000502:physiology; D012859:Sjogren's Syndrome / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D000097585:SS-B Antigen
D000643:Ammonium Chloride; D001324:Autoantigens; D002738:Chloroquine; D016209:Interleukin-8; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D014409:Tumor Necrosis Factor-alpha; D000097585:SS-B Antigen