Lymphotoxin α stimulates proliferation and pro-inflammatory cytokine secretion of rheumatoid arthritis synovial fibroblasts.
OBJECTIVE
TNFα plays a crucial role in rheumatoid arthritis (RA) by stimulating fibroblast-like synoviocytes (FLS). Lymphotoxin α (LTα) is a pro-inflammatory cytokine with significant homology to TNFα. We compared the effects of both cytokines on cultured RA FLS.


METHODS
Receptor expression on RA FLS was analyzed by FACS. Cells were stimulated with LTα or TNFα and proliferation was measured by [3H]thymidine incorporation and secretion of inflammatory cytokines and metalloproteinase 3 by ELISA. Activation of MAP kinases and Akt was analyzed by Western blotting. Nuclear translocation of NFκB was visualized by immunofluorescence.


RESULTS
60-80% and 30-50% of the RA FLS tested expressed TNF receptors I and II, respectively, and 70-75% expressed HVEM. LTα induced RA FLS proliferation at the same level of TNFα, which was blocked by etanercept. Both LTα and TNFα induced activation of MAP kinases ERK1/2 and p38 as well as Akt. 95-98% of FLS showed nuclear translocation of NFκB after stimulation with either cytokines. LTα and TNFα were potent to induce secretion of IL-6, IL-8 and metalloproteinase 3 in FLS.


CONCLUSIONS
LTα is as effective as TNFα in stimulating RA FLS. Blocking both cytokines might allow a better control of inflammation and synovial proliferation in RA.
Institut de Génétique Moléculaire de Montpellier, 1919 route de Mende, CNRS UMR5535, Montpellier, France. flavia.calmon-hamaty@igmm.cnrs.fr
Flavia
F
Calmon-Hamaty
Bernard
B
Combe
Michael
M
Hahne
Jacques
J
Morel
D001172:Arthritis, Rheumatoid / Q000473:pathology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D000068800:Etanercept; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D018836:Inflammation Mediators / Q000378:metabolism*; D008233:Lymphotoxin-alpha / Q000494:pharmacology*; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor; D053240:Receptors, Tumor Necrosis Factor, Member 14 / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D013582:Synovial Fluid / Q000166:cytology* / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016207:Cytokines; D007074:Immunoglobulin G; D018836:Inflammation Mediators; D008233:Lymphotoxin-alpha; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D018124:Receptors, Tumor Necrosis Factor; D053240:Receptors, Tumor Necrosis Factor, Member 14; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; C506028:TNFRSF14 protein, human; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3; D000068800:Etanercept