TLR4-dependent induction of vascular adhesion molecule-1 in rheumatoid arthritis synovial fibroblasts: Roles of cytosolic phospholipase A(2)alpha/cyclooxygenase-2.
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)alpha 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)alpha in these responses. This notion was further confirmed by knockdown of cPLA(2)alpha expression by transfection with cPLA(2)alpha 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)alpha phosphorylation was attenuated by pretreatment with a MEK1/2 inhibitor (U0126), suggesting that LPS-stimulated cPLA(2)alpha 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)alpha phosphorylation and COX-2 expression/PGE(2) synthesis in RASFs.
Wu
Cheng-Ying
CY
Department of Physiology and Pharmacology, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan.
Chi
Pei-Ling
PL
Hsieh
Hsi-Lung
HL
Luo
Shue-Fen
SF
Yang
Chuen-Mao
CM
D006631:Amine Oxidase (Copper-Containing) / Q000235:genetics / Q000378:metabolism*; D001095:Arachidonic Acids / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000503:physiopathology; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000187:drug effects; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism* / Q000503:physiopathology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
D001095:Arachidonic Acids; D015815:Cell Adhesion Molecules; D052246:Cyclooxygenase 2 Inhibitors; D004791:Enzyme Inhibitors; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018078:Receptors, Prostaglandin E; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C081565:arachidonyltrifluoromethane; D015118:Eicosapentaenoic Acid; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; C076668:AOC3 protein, human; D006631:Amine Oxidase (Copper-Containing); D048049:Extracellular Signal-Regulated MAP Kinases; D054513:Group IV Phospholipases A2; D015232:Dinoprostone