title: Regulation of TNFalpha and IL1beta in rheumatoid arthritis synovial fibroblasts by leukotriene B4.
abstract: Arachidonic acid metabolites, such as leukotriene B4 (LTB4), are known to play an important role in pathogenesis of rheumatoid arthritis (RA). Apart from leukocytes, RA synovial fibroblasts (RASF) produce a broad array of inflammatory mediators to recruit, retain and activate immune cells and resident mesenchymal cells in the joints to promote ongoing inflammation and tissue destruction. To determine how LTB4 may contribute to this process, RASF was cultured from synovial tissues collected from RA patients undergoing total knee replacement. The level of LTB4 in culture medium was determined using ELISA, and expression of LTB4 receptors (BLT1 and BLT2) by RT-PCR. In the presence of exogenous LTB4, mRNA and protein levels of tumor necrosis factor-alpha (TNFalpha) and interleukin 1beta (IL1beta) were determined by real-time PCR and ELISA. Furthermore, we examined the effects of leukotrienes synthesis inhibitors, MK886 and bestatin, on mRNA and protein levels of TNFalpha and IL1beta in RASF. We found that LTB4 was present at a low concentration in the culture medium of RASF, and the major LTB4 receptor expressed in RASF was BLT2. LTB4 synthesis was activated by treatment with LIT (LPS, ionomycin and thapsogargin), and suppressed by MK886 and bestatin. Exogenous LTB4 remarkably increased the expression of TNFalpha and IL1beta at both the mRNA level and the protein level. In contrast, MK886 and bestatin significantly inhibited their expression. These data suggested that LTB4 contributed to RA by regulating the expression of TNFalpha and IL1beta in RASF. BLT2 was probably the major receptor mediating such effects.
authors.affiliation: Arthritis Institute, Peking University, Beijing, China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Xu
authors.forename: Houshan
authors.initials: H
authors.lastname: Lu
authors.forename: Jianhao
authors.initials: J
authors.lastname: Lin
authors.forename: Zhankun
authors.initials: Z
authors.lastname: Chen
authors.forename: Dongfang
authors.initials: D
authors.lastname: Jiang
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism*; D005347:Fibroblasts / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007962:Leukocytes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D007975:Leukotriene B4 / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics / Q000276:immunology; D018102:Receptors, Leukotriene B4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D018836:Inflammation Mediators; D053583:Interleukin-1beta; C513240:LTB4R protein, human; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018102:Receptors, Leukotriene B4; D014409:Tumor Necrosis Factor-alpha; D007975:Leukotriene B4