Galectin 3 induces a distinctive pattern of cytokine and chemokine production in rheumatoid synovial fibroblasts via selective signaling pathways.
OBJECTIVE
High expression of galectin 3 at sites of joint destruction in rheumatoid arthritis (RA) suggests that galectin 3 plays a role in RA pathogenesis. Previous studies have demonstrated the effects of galectins on immune cells, such as lymphocytes and macrophages. This study was undertaken to investigate the hypothesis that galectin 3 induces proinflammatory effects in RA by modulating the pattern of cytokine and chemokine production in synovial fibroblasts.


METHODS
Matched samples of RA synovial and skin fibroblasts were pretreated with galectin 3 or tumor necrosis factor alpha (TNFalpha), and the levels of a panel of cytokines, chemokines, and matrix metalloproteinases (MMPs) were determined using enzyme-linked immunosorbent assays and multiplex assays. Specific inhibitors were used to dissect signaling pathways, which were confirmed by Western blotting and NF-kappaB activation assay.


RESULTS
Galectin 3 induced secretion of interleukin-6 (IL-6), granulocyte-macrophage colony-stimulating factor, CXCL8, and MMP-3 in both synovial and skin fibroblasts. By contrast, galectin 3-induced secretion of TNFalpha, CCL2, CCL3, and CCL5 was significantly greater in synovial fibroblasts than in skin fibroblasts. TNFalpha blockade ruled out autocrine TNFalpha-stimulated induction of chemokines. The MAPKs p38, JNK, and ERK were necessary for IL-6 production, but phosphatidylinositol 3-kinase (PI 3-kinase) was required for selective CCL5 induction. NF-kappaB activation was required for production of both IL-6 and CCL5.


CONCLUSIONS
Our findings indicate that galectin 3 promotes proinflammatory cytokine secretion by tissue fibroblasts. However, galectin 3 induces the production of mononuclear cell-recruiting chemokines uniquely from synovial fibroblasts, but not matched skin fibroblasts, via a PI 3-kinase signaling pathway. These data provide further evidence of the role of synovial fibroblasts in regulating the pattern and persistence of the inflammatory infiltrate in RA and suggest a new and important functional consequence of the observed high expression of galectin 3 in the rheumatoid synovium.
Filer
Andrew
A
University of Birmingham, Division of Immunity and Infection, Birmingham, UK. a.filer@bham.ac.uk
Bik
Magdalena
M
Parsonage
Greg N
GN
Fitton
John
J
Trebilcock
Emily
E
Howlett
Katherine
K
Cook
Michelle
M
Raza
Karim
K
Simmons
David L
DL
Thomas
Andrew M C
AM
Salmon
Mike
M
Scheel-Toellner
Dagmar
D
Lord
Janet M
JM
Rabinovich
Gabriel A
GA
Buckley
Christopher D
CD
D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D054405:Chemokine CCL3 / Q000378:metabolism; D018946:Chemokine CCL5 / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D037502:Galectin 3 / Q000502:physiology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin / Q000166:cytology / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D018932:Chemokine CCL2; D054405:Chemokine CCL3; D018946:Chemokine CCL5; D018925:Chemokines; D016207:Cytokines; D037502:Galectin 3; D015850:Interleukin-6; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019869:Phosphatidylinositol 3-Kinases; D019278:Matrix Metalloproteinase 3