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TLR4‐dependent induction of vascular adhesion molecule‐1 in rheumatoid arthritis synovial fibroblasts: Roles of cytosolic phospholipase A 2 α/cyclooxygenase‐2
Author(s) -
Wu ChengYing,
Chi PeiLing,
Hsieh HsiLung,
Luo ShueFen,
Yang ChuenMao
Publication year - 2010
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.22059
Subject(s) - small interfering rna , tlr4 , transfection , arachidonic acid , phospholipase a , mapk/erk pathway , phospholipase a2 , microbiology and biotechnology , chemistry , pharmacology , biology , signal transduction , cell culture , biochemistry , genetics , enzyme
Lipopolysaccharide (LPS)/Toll‐like receptor 4 (TLR4)‐mediated signaling pathways have caught the attention of strategies designed for rheumatoid arthritis (RA). In this study, we identified that cPLA 2 α acted as a modulator of LPS‐induced VCAM‐1 expression and THP‐1 (human acute monocytic leukemia cell line) adherence. Treatment of RA synovial fibroblasts (RASFs) with LPS, a TLR4 agonist, promoted the VCAM‐1 expression and THP‐1 adherence which were decreased by pretreatment with a selective cytosolic phospholipase A 2 (cPLA 2 ) inhibitor (AACOCF 3 ), implying the involvement of cPLA 2 α in these responses. This notion was further confirmed by knockdown of cPLA 2 α expression by transfection with cPLA 2 α small interfering RNA (siRNA) leading to a decrease in VCAM‐1 expression and THP‐1 adherence induced by LPS. Subsequently, the LPS‐stimulated cPLA 2 α phosphorylation was attenuated by pretreatment with a MEK1/2 inhibitor (U0126), suggesting that LPS‐stimulated cPLA 2 α phosphorylation and activity are mediated through an ERK‐dependent mechanism. Moreover, COX‐2‐derived PGE 2 production appeared to involve in LPS‐induced VCAM‐1 expression which was attenuated by pretreatment with selective COX‐2 inhibitors (NS‐398 and celecoxib), transfection with COX‐2 siRNA, or PGE 2 receptor antagonists. In addition, pretreatment with ecosapentaenoic acid (EPA), a substrate competitor of arachidonic acid (AA), also blocked LPS‐induced VCAM‐1 mRNA and protein expression, and THP‐1 adherence. Collectively, these results suggest that LPS‐induced VCAM‐1 expression and adhesion of THP‐1 cells are mediated through the TLR4/ERK/cPLA 2 α phosphorylation and COX‐2 expression/PGE 2 synthesis in RASFs. J. Cell. Physiol. 223: 480–491, 2010. © 2010 Wiley‐Liss, Inc.