Open AccessHeme oxygenase 1 attenuates interleukin‐1β–induced cytosolic phospholipase A 2 expression via a decrease in NADPH oxidase/reactive oxygen species/activator protein 1 activation in rheumatoid arthritis synovial fibroblasts
Author(s) -
Chi PeiLing,
Chen YuWen,
Hsiao LiDer,
Chen YuhLien,
Yang ChuenMao
Publication year - 2012
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.34371
Subject(s) - apocynin , nadph oxidase , small interfering rna , heme oxygenase , reactive oxygen species , transfection , microbiology and biotechnology , chemistry , activator (genetics) , phospholipase a2 , biology , heme , biochemistry , receptor , enzyme , gene
Objective Reactive oxygen species (ROS) produced by cytokines induce the expression of inflammatory mediators in rheumatoid arthritis (RA). Heme oxygenase 1 (HO‐1) exerts an antiinflammatory effect. The aim of this study was to examine the mechanisms underlying interleukin‐1β (IL‐1β)–induced cytosolic phospholipase A 2 (cPLA 2 ) expression through ROS generation as modulated by HO‐1 in RA synovial fibroblasts (RASFs). Methods IL‐1β–induced ROS generation was determined by flow cytometry. The involvement of MAPKs and NADPH oxidase (NOX)/ROS in IL‐1β–induced cPLA 2 expression was investigated using pharmacologic inhibitors and transfection with small interfering RNAs (siRNAs) and was analyzed by Western blotting and promoter assay. Overexpression of HO‐1 was performed by transfection of RASFs with a recombinant adenovirus containing human HO‐1 plasmid. SCID mice with inflammation caused by IL‐1β were infected with adenovirus containing HO‐1. Histologic characterization of joint inflammation and local expression of cPLA 2 were evaluated after treatment. Results IL‐1β–induced cPLA 2 expression was mediated through NOX activation/ROS production, which was attenuated by N ‐acetylcysteine (NAC; a scavenger of ROS), the inhibitors of NOX (diphenyleneiodonium chloride and apocynin), MEK‐1/2 (U0126), and JNK‐1/2 (SP600125), transfection with the respective siRNAs, and the overexpression of HO‐1 in RASFs. IL‐1β–induced cPLA 2 expression was mediated through recruitment of activator protein 1 (AP‐1) to the cPLA 2 promoter region, which was attenuated by NAC and overexpression of HO‐1. Furthermore, HO‐1 overexpression inhibited IL‐1β–mediated cPLA 2 expression in SCID mice. Conclusion In RASFs, IL‐1β induced cPLA 2 expression via activation of p42/p44 MAPK and JNK‐1/2, leading to p47 phox phosphorylation, ROS production, and AP‐1 activation. The induction of HO‐1 exerted protective effects on the pathogenesis of RA.