Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Human STEAP4 (Six-Transmembrane Epithelial Antigen of Prostate 4) Regulates Inflammatory Cytokines and the Proliferation of Fibroblast-Like Synoviocyte in Patients with RA.

Tanaka,  Yoko, Matsumoto,  Isao, Umeda,  Naoto, Yamamoto,  Kayo, Tanaka,  Yuki, Inoue,  Asuka, Sumida,  Takayuki

Background:

We recently demonstrated that TNFa-induced- adipose related protein (TIARP) plays a crucial role in TNFa-dependent arthritis model such as glucose-352-phosphate isomerase (GPI) -induced arthritis. STEAP4 mRNA and protein expression was reported to be upregulated by TNFa in a dose-dependent manner by using human adipose tissue, however, the function of STEAP4 in other tissue is still unclear. The purpose of this study is to clarify the function of STEAP4 in fibroblast-like synoviocyte (FLS) from RA patients and the relationship between STEAP4 and RA.

Methods:

1) To unravel localization of STEAP4, the expression of EEA1 (known to be a endosome marker) or CD68 in FLS was examined by fluorescence immunohistochemistry (IF). 2) FLS obtained from RA synovium were treated with TNFa (2ng/ml), and the fluctuation of STEAP4 was evaluated by Western blot analysis (WB). 3) FLS obtained from RA was transfected by siRNA specific for STEAP4, and cultured for 24 h. IL-6 mRNA was quantified by real time PCR. 4) GFP-STEAP4 or GFP-empty plasmid DNA were transfected to FLS, then cultured for 24 h with TNFa. Secretion of IL-6, IL-8, MMP3, and GM-CSF was examined by ELISA. 5) Proliferation and apoptosis of GFP-STEAP4 transfectant were investigated by BrdU assay or flow cytometry. 6) The expression of STEAP4 in PBMC was measured before and after therapy with infliximab (N=40).

Results:

1) STEAP4 was co-localized with CD68 in the FLS obtained from RA patients. STEAP4, EEA1 and CD68 were clearly co-localized in cytoplasm (endosome and lysosome) of the synovium. 2) In vitro analysis, the expressions of STEAP4 protein in FLS was up regulated by TNFa stimulation confirmed by WB. 3) The expression of IL-6 mRNA was up regulated by STEAP4 siRNA (p<0.05). 4) The amount of IL-6, IL-8, GM-CSF secretion were down-regulated by overexpression of STEAP4 (p<0.05), although MMP3 were upregulated after TNFa stimulation. 5) Proliferation was decreased and apoptotic cells were increased in GFP-STEAP4 transfectant compared to GFP-empty transfectant. 6) The expression of STEAP4 was decreased after infliximab treatment especially in good responder (p<0.05).

Conclusion:

STEAP4 expression was observed in rheumatoid synovium, was clearly up regulated by TNFa stimulation, and controlled inflammatory cytokines and proliferation of FLS. In addition, the expression of STEAP4 in PBMC was upregulated by TNF antagonist in RA, suggest that it may play a potential role in the pathogenesis of TNF-a- induced arthritis.

To cite this abstract, please use the following information:
Tanaka, Yoko, Matsumoto, Isao, Umeda, Naoto, Yamamoto, Kayo, Tanaka, Yuki, Inoue, Asuka, et al; Human STEAP4 (Six-Transmembrane Epithelial Antigen of Prostate 4) Regulates Inflammatory Cytokines and the Proliferation of Fibroblast-Like Synoviocyte in Patients with RA. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :352
DOI: 10.1002/art.28121

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