Overexpression of transcription factor Ets-1 in rheumatoid arthritis synovial membrane: regulation of expression and activation by interleukin-1 and tumor necrosis factor alpha.
OBJECTIVE
To investigate the expression of the transcription factor Ets-1 in synovial tissue and cultured synovial fibroblasts from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and to study the regulation of Ets-1 expression and activation in synovial fibroblasts by proinflammatory cytokines.


METHODS
In situ expression of Ets-1 in synovial tissue from RA and OA patients was examined by double immunohistochemistry. The effects of interleukin-1 (IL-1) or tumor necrosis factor alpha (TNFalpha) on Ets-1 expression and activation (DNA binding) in cultured synovial fibroblasts were analyzed by Western blotting and DNA gel shift assay, respectively. In addition, the intracellular location of Ets-1 in synovial fibroblasts was determined by immunofluorescence.


RESULTS
Pronounced expression of Ets-1 was detected in synovial tissues from all RA patients evaluated, particularly in the synovial lining layer and the sublining areas. Ets-1 was expressed by both fibroblasts and macrophages as well as by endothelial cells, while only a few T cells stained positive for Ets-1. In synovial specimens from OA patients, Ets-1 expression was much less frequently observed and was largely restricted to vascular cells. Ets-1 was expressed to a similar degree in cultured synovial fibroblasts from RA and OA patients, as demonstrated by reverse transcriptase-polymerase chain reaction and Western blotting. Both IL-1 and TNFalpha induced pronounced up-regulation of Ets-1 in synovial fibroblasts. Moreover, binding of Ets-1 to its specific DNA binding site was induced by both cytokines, although with different time courses. Immunofluorescence staining revealed a dominant nuclear localization of Ets-1 in IL-1- or TNFalpha-stimulated synovial fibroblasts.


CONCLUSIONS
The overexpression of Ets-1 observed in RA synovial tissue appears to be caused by TNFalpha and IL-1, suggesting that Ets-1 may be an important factor in the cytokine-mediated inflammatory and destructive cascade characteristic of RA.
University of Vienna, Austria.
K
K
Redlich
H P
HP
Kiener
G
G
Schett
M
M
Tohidast-Akrad
E
E
Selzer
I
I
Radda
G H
GH
Stummvoll
C W
CW
Steiner
M
M
Gröger
P
P
Bitzan
P
P
Zenz
J S
JS
Smolen
G
G
Steiner
D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D010003:Osteoarthritis / Q000378:metabolism; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000502:physiology; D050783:Proto-Oncogene Proteins c-ets; D013583:Synovial Membrane / Q000378:metabolism*; D014157:Transcription Factors / Q000032:analysis / Q000096:biosynthesis* / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
C494041:ETS1 protein, human; D007375:Interleukin-1; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha