title: Leptin induces IL-8 expression via leptin receptor, IRS-1, PI3K, Akt cascade and promotion of NF-kappaB/p300 binding in human synovial fibroblasts.
abstract: Leptin, the adipocyte-secreted hormone that centrally regulates weight control, is known to function as an immunomodulatory regulator. We investigated the signaling pathway involved in IL-8 production caused by leptin in both rheumatoid arthritis synovial fibroblasts (RASF) and osteoarthritis synovial fibroblasts (OASF). RASF and OASF expressed the long (OBRl) and short (OBRs) isoforms of the leptin receptor. Leptin caused concentration- and time-dependent increases in IL-8 production. Leptin-mediated IL-8 production was attenuated by OBRl receptor antisense oligonucleotide, JAK2 inhibitor or STAT3 small interference RNA (siRNA). Transfection with insulin receptor substrate (IRS)-1 siRNA or dominant-negative mutant of p85 and Akt or pretreatment with phosphatidylinositol 3-kinase inhibitor (Ly294002 and wortmannin), Akt inhibitor, NF-kappaB inhibitor (PDTC) and NF-kappaB inhibitor peptide also inhibited the potentiating action of leptin. Stimulation of RASF with leptin activated IkappaB kinase alpha/beta (IKK alpha/beta), p65 phosphorylation at Ser(276), p65 translocation from the cytosol to the nucleus, and kappaB-luciferase activity. Moreover, pretreatment with p300 inhibitor (curcumin) also blocked IL-8 expression. The binding of p65 to the NF-kappaB elements, as well as the recruitment of p300 and the enhancement of histone H3 acetylation on the IL-8 promoter was enhanced by leptin, which was inhibited by wortmannin, Akt inhibitor or IRS-1 siRNA. These results suggest that leptin increased IL-8 production in synovial fibroblast via the OBRl/JAK2/STAT3 pathway, as well as the activation of IRS1/PI3K/Akt/NF-kappaB-dependent pathway and the subsequent recruitment of p300.
authors.affiliation: Department of Orthopaedics, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Kwok-Man
authors.initials: KM
authors.lastname: Tong
authors.forename: Dong-Chen
authors.initials: DC
authors.lastname: Shieh
authors.forename: Chao-Ping
authors.initials: CP
authors.lastname: Chen
authors.forename: Chung-Yuh
authors.initials: CY
authors.lastname: Tzeng
authors.forename: Shun-Ping
authors.initials: SP
authors.lastname: Wang
authors.forename: Kui-Chou
authors.initials: KC
authors.lastname: Huang
authors.forename: Yung-Cheng
authors.initials: YC
authors.lastname: Chiu
authors.forename: Yi-Chin
authors.initials: YC
authors.lastname: Fong
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Tang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000276:immunology*; D001665:Binding Sites; D002478:Cells, Cultured; D005347:Fibroblasts / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D053614:Janus Kinase 2 / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D010003:Osteoarthritis / Q000201:enzymology / Q000276:immunology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D054411:Receptors, Leptin / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology*; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D006657:Histones; D055504:Insulin Receptor Substrate Proteins; D016209:Interleukin-8; D053614:Janus Kinase 2; D020738:Leptin; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C526292:IRS1 protein, human