SAT0020 A Role for P38 Mitogen-Activated Protein Kinase (MAPK) in Gliostatin Production in Rheumatoid Fibroblast-Like Synoviocytes

Background Fibroblast-like synoviocytes (FLSs) play a key role in joint destruction in rheumatoid arthritis (RA). Gliostatin (GLS) has thymidine phosphorylase activity and is produced in the synovial tissue of RA patients. We have previously reported its angiogenic and arthritogenic activities. Objectives This study aimed to investigate whether p38 MAPK signalling played a role in GLS gene expression in RA. We also studied the effect of cycloheximide on GLS production in RA FLSs. Since GLS production by cultured FLSs was enhanced by TNFα and IL-1β, we postulated that the NF-κB-p38 MAPK cascade could modulate the expression of GLS genes. Methods FLSs were cultured from synovial specimens obtained from 10 RA patients during total knee arthroplasty. The effects of TNFα and various enzyme inhibitors on GLS expression in these cells were measured using real-time PCR for mRNA expression and ELISAs for protein expression. Results TNFα significantly induced GLS mRNA expression and protein synthesis in RA FLSs. The p38 MAPK inhibitors SB203580 and SB202190 both significantly suppressed the enhanced production of GLS induced by TNFα. However mitogen- activated protein kinase kinase (MEK) 1/2 inhibitor, PD98059, c-Jun N-terminal kinase (JNK) inhibitor, SP600125, and NF-κB inhibitor, SN50, did not suppress GLS production. Pre-treatment with cycloheximide, to inhibit protein synthesis, reduced the expression of GLS mRNA in a dose-dependent manner in TNFα-treated FLSs. Conclusions Our results showed that RA FLSs expressed GLS after treatment with TNFα and this was blocked by p38MAPK inhibitors. The induction of GLS mRNA required de novo protein synthesis. References Waguri Y, et al. Gliostatin/platelet-derived endothelial cell growth factor as a clinical marker of rheumatoid arthritis and its regulation in fibroblast like synoviocytes. Br J Rheumatol 1997; 36: 315-321. Ikuta K, et al. The Sp1 transcription factor is essential for the expression of gliostatin/thymidine phosphorylase in rheumatoid fibroblast-like synoviocytes. Arthritis Res Ther. 2012; 14:R87 Acknowledgements This research was supported by a Grant-in-Aid for Scientific Research (C) (26462309) from the Japan Society for the Promotion of Science. Disclosure of Interest K. Ikuta: None declared, Y. Waguri-Nagaya Grant/research support from: Biomet Japan, Inc, Chugai Pharmaceutical Co., Ltd., Astellas Pharma Inc., Merck Sharp & Dohme Co., AbbVie Japan Co., Ltd., Ono Pharmaceutical Co., Ltd., N. Tatematsu: None declared, Y. Kawaguchi: None declared, T. Terazawa: None declared, M. Kobayashi: None declared, M. Aoyama: None declared, K. Asai: None declared, T. Otsuka: None declared