Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Annexin-1 Regulates Inflammation and Glucocorticoid Sensitivity of Human RA Synovial Fibroblasts
Morand1, Eric F., Li2, Zhanguo, Ngo1, Devi, Song1, Wuqi, Jia1, Yuan, Yang1, Yuan
Annexin-1 (Anxa1) is a mediator of the anti-inflammatory actions of glucocorticoids (GC). Anxa1 is expressed in RA synovium, and Anxa1-/- mice exhibit increased experimental arthritis. The mechanism of action of Anxa1 is not well understood. We explored inflammatory signal transduction events modulated by Anxa1 in rheumatiud arthritis (RA) synovial like fibroblasts (FLS) and normal human lung fibroblasts (NHLF).
Anxa1 siRNA, GC-induced leucine zipper (GILZ)- and mitogen-activated protein kinase (MAPK) phosphotase-1 (MKP-1)-luc plasmid were transfected using lipofectamine and Amaxa. Promoter activities were examined by luciferase assay. Transfected fibroblasts were treated with TNF and/or dexamethasone (DEX) or TNF and/or MAPK or NF-kB inhibitors. IL-6 was measured by ELISA and real-time PCR. MAPK activities were detected by Western Blot and ELISA kits. Proliferation was measured by H3-thymidine incorporation.
Anxa1 mRNA and protein were successfully knocked down in RA FLS using Anxa1 siRNA. Anxa1 silencing in RA FLS significantly increased TNF-induced proliferation and impaired inhibitory effect of DEX on TNF-induced IL-6 production. ERK and serine-536 NF-kB p65 phosphorylation were increased by Anxa1 silencing. Inhibition of ERK, JNK or NF-kB pathways significantly reduced TNF-induced proliferation of RA FLS. GC induction of FLS expression of the anti-inflammatory genes G ILZ and MKP-1 was significantly impaired in the absence of Anxa1, which paralleled the impaired inhibitory effect of DEX on TNF induced IL-6. Similarly, silencing of Anxa1 in NHL fibroblasts significantly increased responsiveness to TNF, including increased IL-6, proliferation, and ERK activity, impaired inhibitory effects of DEX on TNF-induced IL-6 release, and impaired DEX-induced GILZ and MKP-1 mRNA. Cotransfection studies in NHL fibroblasts showed that Anxa1 silencing significantly reduced DEX-induced GILZ- and MKP-1 promoter activity in comparison to control siRNA transfected cells.
These data demonstrate that endogenous Anxa1 is a critical endogenous inhibitory regulator of cytokine expression, proliferation and MAPK activation, and mediates GC sensitivity via activation of GILZ and MKP-1.
To cite this abstract, please use the following information:
Morand, Eric F., Li, Zhanguo, Ngo, Devi, Song, Wuqi, Jia, Yuan, Yang, Yuan; Annexin-1 Regulates Inflammation and Glucocorticoid Sensitivity of Human RA Synovial Fibroblasts [abstract]. Arthritis Rheum 2009;60 Suppl 10 :40