Increase of MZB1 in B cells in systemic lupus erythematosus: proteomic analysis of biopsied lymph nodes

• Main Authors: Aya Miyagawa-Hayashino, Hajime Yoshifuji, Koji Kitagori, Shinji Ito, Takuma Oku, Yoshitaka Hirayama, Adeeb Salah, Toshiki Nakajima, Kaori Kiso, Norishige Yamada, Hironori Haga, Tatsuaki Tsuruyama
• Format: Article
• Language: English
• Published: BMC 2018-01-01
• Series: Arthritis Research & Therapy
• Subjects: Formalin-fixed paraffin-embedded; Lupus-prone mice; Proteomic analysis; Systemic lupus erythematosus; SLE lymphadenopathy; TUNEL
• Online Access: http://link.springer.com/article/10.1186/s13075-018-1511-5

Abstract Background Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease in which dysregulation of B cells has been recognized. Here, we searched for potential biomarkers of SLE using liquid chromatography-tandem mass spectrometry (LC-MS). Methods Lymph nodes from SLE patients and controls were analyzed by LC-MS. To validate the identified molecules, immunoblotting and immunohistochemistry were performed and B cells from SLE patients were analyzed by quantitative RT-PCR. B-cell subsets from NZB/W F1 mice, which exhibit autoimmune disease resembling human SLE, were analyzed by flow cytometry. Endoplasmic reticulum (ER) stress was induced by tunicamycin and the serum concentration of anti-dsDNA antibodies was determined by ELISA. TUNEL methods and immunoblotting were used to assess the effect of tunicamycin. Results MZB1, which comprises part of a B-cell-specific ER chaperone complex and is a key player in antibody secretion, was one of the differentially expressed proteins identified by LC-MS and confirmed by immunoblotting. Immunohistochemically, larger numbers of MZB1+ cells were located mainly in interfollicular areas and scattered in germinal centers in specimens from SLE patients compared with those from controls. MZB1 colocalized with CD138+ plasma cells and IRTA1+ marginal zone B cells. MZB1 mRNA was increased by 2.1-fold in B cells of SLE patients with active disease (SLE Disease Activity Index 2000 ≥ 6) compared with controls. In aged NZB/W F1 mice, splenic marginal zone B cells and plasma cells showed elevated MZB1 levels. Tunicamycin induced apoptosis of MZB1+ cells in target organs, resulting in decreased serum anti-dsDNA antibody levels. Additionally, MZB1+ cells were increased in synovial tissue specimens from patients with rheumatoid arthritis. Conclusions MZB1 may be a potential therapeutic target in excessive antibody-secreting cells in SLE.