title: Potential role and mechanism of IFN-gamma inducible protein-10 on receptor activator of nuclear factor kappa-B ligand (RANKL) expression in rheumatoid arthritis.
abstract: BACKGROUND
  IFN-gamma inducible protein-10 (CXCL10), a member of the CXC chemokine family, and its receptor CXCR3 contribute to the recruitment of T cells from the blood stream into the inflamed joints and have a crucial role in perpetuating inflammation in rheumatoid arthritis (RA) synovial joints. Recently we showed the role of CXCL10 on receptor activator of nuclear factor kappa-B ligand (RANKL) expression in an animal model of RA and suggested the contribution to osteoclastogenesis. We tested the effects of CXCL10 on the expression of RANKL in RA synoviocytes and T cells, and we investigated which subunit of CXCR3 contributes to RANKL expression by CXCL10.
  
  
  METHODS
  Synoviocytes derived from RA patients were kept in culture for 24 hours in the presence or absence of TNF-α. CXCL10 expression was measured by reverse transcriptase polymerase chain reaction (RT-PCR) of cultured synoviocytes. Expression of RANKL was measured by RT-PCR and western blot in cultured synoviocytes with or without CXCL10 and also measured in Jurkat/Hut 78 T cells and CD4+ T cells in the presence of CXCL10 or dexamethasone. CXCL10 induced RANKL expression in Jurkat T cells was tested upon the pertussis toxin (PTX), an inhibitor of Gi subunit of G protein coupled receptor (GPCR). The synthetic siRNA for Gαi(2) was used to knock down gene expression of respective proteins.
  
  
  RESULTS
  CXCL10 expression in RA synoviocytes was increased by TNF-α. CXCL10 slightly increased RANKL expression in RA synoviocytes, but markedly increased RANKL expression in Jurkat/Hut 78 T cell or CD4+ T cell. CXCL10 augmented the expression of RANKL by 62.6%, and PTX inhibited both basal level of RANKL (from 37.4 ± 16.0 to 18.9 ± 13.0%) and CXCL10-induced RANKL expression in Jurkat T cells (from 100% to 48.6 ± 27.3%). Knock down of Gα(i2) by siRNA transfection, which suppressed the basal level of RANKL (from 61.8 ± 17.9% to 31.1 ± 15.9%) and CXCL10-induced RANKL expression (from 100% to 53.1 ± 27.1%) in Jurkat T cells, is consistent with PTX, which inhibited RANKL expression.
  
  
  CONCLUSIONS
  CXCL10 increased RANKL expression in CD4+ T cells and it was mediated by Gα(i) subunits of CXCR3. These results indicate that CXCL10 may have a potential role in osteoclastogenesis of RA synovial tissue and subsequent joint erosion.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul, 110-744, Republic of Korea.
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Miran
authors.initials: M
authors.lastname: Seo
authors.forename: Yong-Sung
authors.initials: YS
authors.lastname: Juhnn
authors.forename: Jeong Yeon
authors.initials: JY
authors.lastname: Kim
authors.forename: Yoo Jin
authors.initials: YJ
authors.lastname: Hong
authors.forename: Yun Jong
authors.initials: YJ
authors.lastname: Lee
authors.forename: Eun Bong
authors.initials: EB
authors.lastname: Lee
authors.forename: Yeong Wook
authors.initials: YW
authors.lastname: Song
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D010010:Osteoclasts / Q000276:immunology; D053245:RANK Ligand / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: C114753:CXCL10 protein, human; D054357:Chemokine CXCL10; D053245:RANK Ligand; D034741:RNA, Small Interfering; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D014409:Tumor Necrosis Factor-alpha; D051960:GTP-Binding Protein alpha Subunit, Gi2