title: Reverse signaling initiated from GITRL induces NF-kappaB activation through ERK in the inflammatory activation of macrophages.
abstract: Glucocorticoid-induced TNF receptor family related protein ligand (GITRL) is known to interact with its cognate receptor GITR. In order to investigate the potential role of GITRL in the pro-inflammatory activation of macrophages and the signaling pathway induced by GITRL, we stimulated the macrophage cell line, THP-1, and primary macrophages with an anti-GITRL monoclonal antibody or a GITR:Fc fusion protein and analyzed the cellular responses. The stimulation of GITRL induced the expression of pro-inflammatory cytokines and matrix metalloproteinase (MMP)-9 and up-regulated ICAM-1 expression levels, which was responsible for enhanced cellular aggregation and adhesion to extracellular matrix proteins. The activation of these pro-inflammatory mediators required the activation of ERK1/2 mitogen-activated protein kinase (MAPK) and negatively regulated by p38 MAPK and JNK. Immunofluorescence analysis detected nuclear translocation of the NF-kappaB p50 subunit and this was blocked by ERK inhibitor, indicating that GITRL stimulation induced ERK1/2 phosphorylation and subsequent activation of NF-kappaB. Furthermore, the expression of GITRL and GITR was detected in macrophages in inflammatory disease specimens such as atherosclerotic plaques and synovial tissues of rheumatoid arthritis. These observations raise the possibility that the GITRL-mediated inflammatory activation of macrophages is involved in the pathogenesis of inflammatory diseases.
authors.affiliation: Department of Genetic Engineering, School of Life Sciences and Biotechology, Kyungpook National University, Taegu 702-701, Republic of Korea.
authors.forename: Eun Mi
authors.initials: EM
authors.lastname: Bae
authors.forename: Won-Jung
authors.initials: WJ
authors.lastname: Kim
authors.forename: Kyoungho
authors.initials: K
authors.lastname: Suk
authors.forename: Young-Mo
authors.initials: YM
authors.lastname: Kang
authors.forename: Jeong-Euy
authors.initials: JE
authors.lastname: Park
authors.forename: Won Young
authors.initials: WY
authors.lastname: Kim
authors.forename: Eun Mi
authors.initials: EM
authors.lastname: Choi
authors.forename: Beom Kyu
authors.initials: BK
authors.lastname: Choi
authors.forename: Byoung S
authors.initials: BS
authors.lastname: Kwon
authors.forename: Won-Ha
authors.initials: WH
authors.lastname: Lee
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002448:Cell Adhesion; D002449:Cell Aggregation; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D053450:Glucocorticoid-Induced TNFR-Related Protein / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000201:enzymology*; D018836:Inflammation Mediators / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000166:cytology / Q000201:enzymology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction; D048069:Tumor Necrosis Factors / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics
chemical_list: D018925:Chemokines; D053450:Glucocorticoid-Induced TNFR-Related Protein; D018836:Inflammation Mediators; D016328:NF-kappa B; C478967:TNFSF18 protein, human; D048069:Tumor Necrosis Factors; D018799:Intercellular Adhesion Molecule-1; D048049:Extracellular Signal-Regulated MAP Kinases; D020780:Matrix Metalloproteinase 9