IL-6 inhibits the proliferation of fibroblastic synovial cells from rheumatoid arthritis patients in the presence of soluble IL-6 receptor

Abstract

IL-6 and tumor necrosis factor (TNF)-alpha have been proven to play an important role in the development of rheumatoid arthritis (RA). It is well known that TNF-alpha induces IL-6 production from synovial cells as well as their proliferation. The effect of IL-6 on synovial cells, however, is not clear. An in vitrostudy was performed to determine the effect of IL-6 on the proliferation of synovial cells. Fibroblastic synovial cells isolated from the synovial tissues of eight RA patients were employed after the third to sixth passages. IL-6 in the presence of soluble IL-6 receptor (sIL-6R) inhibited the proliferation of synovial cells in a dose-dependent manner in seven cases without increasing the number of necrotic or apoptotic cells, while TNF-alpha increased synovial cell proliferation in all cases. The inhibitory effect of IL-6 was observed only in the presence of sIL-6R although small amounts of IL-6R were detected in these cells by RT-PCR analysis. However, anti-IL-6R or anti-gp130 mAb treatment increased spontaneous growth of synovial cells in all eight cases, suggesting that endogenous IL-6 and a small amount of IL-6R expressed in synovial cells suppressed their growth without exogenous IL-6 or sIL-6R. In addition, the IL-6-sIL-6R complex reduced the TNF-alpha-induced proliferation of synovial cells while TNF-alpha induced their IL-6 production. These data suggest that IL-6 may act as a negative feedback factor for TNF-alpha-induced synovial cell growth.

Cross-Talk Between IL-1 and IL-6 Signaling Pathways in Rheumatoid Arthritis Synovial Fibroblasts

“…1A, lane 2); binding activity was not detected using the IRF oligonucleotide that binds Stat5 and Stat6 (data not shown). This result is consistent with previous reports suggesting that SFs express only the gp130 signaling subunit of the IL-6R, but not the IL-6-binding ␣ subunit (27,28). As previously described in other cells types (40), addition of extracellular soluble IL-6R␣ subunit (sIL-6R␣) together with IL-6 resulted in initiation of signal transduction, as determined by activation of STAT DNA-binding activity (Fig.…”

“…SOCS3 and IRF-1 genes are directly transcriptionally activated by STATs, and thus these results demonstrate that IL-6 activation of the Jak-STAT pathway in RA SFs is coupled to transcriptional responses. Addition of IL-6 and sIL-6R␣ suppressed synoviocyte proliferation, reproducing recently reported results (27) (Fig. 2B).…”

“…Our studies focused upon IL-6, a pleiotropic cytokine that has pro-and anti-inflammatory effects on different cell types, but overall likely plays a suppressive role vis a vis SFs (27,28,31). These studies could not be extended to the anti-inflammatory cytokine IL-10, as activation of Jak-STAT signaling by IL-10 in SFs was not detected (D. Deon, unpublished results).…”

“…We hypothesized that one mechanism by which inflammatory cytokines perpetuate synovitis in the presence of anti-inflammatory factors in the synovium is through inhibition or modulation of signaling by anti-inflammatory or pleiotropic cytokines. This hypothesis was tested by analyzing the effects of IL-1 and TNF on IL-6 signaling in RA SFs, cells in which IL-6 has effects consistent with an anti-inflammatory role, such as inhibition of proliferation and induction of TIMP-1 production (27,28). Our results show that Janus kinase (Jak)-STAT signaling by IL-6 in RA synoviocytes is inhibited by IL-1 and TNF-␣.…”

Interleukin-6/Soluble Interleukin-6 Receptor Signaling Attenuates Proliferation and Invasion, and Induces Morphological Changes of a Newly Established Pleomorphic Malignant Fibrous Histiocytoma Cell Line

“…Five g of total RNA was reverse-transcribed with 200 U of SuperScript III reverse transcriptase (Invitrogen) and 0.5 nmol of oligo (dT) [12][13][14][15][16][17][18] primer, then PCR was performed in 50 l of reaction solution containing cDNA derived from 100 ng of total RNA, 1.25 U of TaqDNA polymerase (Sigma), 10 nmol of each dNTP (Sigma), and 0.5 nmol of sense and anti-sense primer pairs shown below with a DNA thermal cycler. PCR cycles were operated on a regimen of 30 seconds of denaturation of 94°C; 30 seconds of primer annealing at the temperature as below; and 60 seconds extension/synthesis at 72°C for 30 cycles for IL-6, IL-6R, sIL-6R and 25 cycles for gp130.…”