Interleukin-1 mediated signal transduction associated with synovial cell activation

Effect of hypoxia and interleukin-1beta on expression of tenascin-C in temporomandibular joint

OBJECTIVE

The expression of tenascin-C in the synovial membrane of the internal derangement (ID) of the temporomandibular joint (TMJ) has been reported. Hypoxia of the synovial membrane in TMJ is considered to be a cause for the pathophysiology of ID. In this study, we clarify the contribution of hypoxia and interleukin-1beta in the expression of tenascin-C in ID of TMJ.

MATERIALS AND METHODS

Synovial fibroblasts and disk cells obtained from ID of TMJs were cultured and treated with interleukin-1beta under normoxia and hypoxia. A Western blot analysis and reverse transcription-polymerase chain reaction analysis were used to identify tenascin-C in cultured synovial fibroblasts and disk cells. In addition, the immunohistochemical staining of tenascin-C was carried out for the specimens of ID of TMJs and normal.

RESULTS

The combination of hypoxia and interleukin-1beta caused a significant increase in tenascin-C protein and mRNA of synovial fibroblasts. In contrast, the combination caused no increase in tenascin-C in disk cells. However, the immunohistochemical staining demonstrated tenascin-C to be significantly detected in both the synovial tissue and disks in ID of TMJ.

CONCLUSIONS

These results indicate that hypoxic conditions with inflammation modulate the tenascin-C expression in synovial fibroblasts, but not in disk cells.

The effect of IL-1beta on the expression of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in human chondrocytes

Interleukin-1 (IL-1) plays key roles in altering cartilage matrix turnover. This turnover is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). In the present study, we examined the effect of IL-1beta on cell proliferation, alkaline phosphatase (ALPase) activity, and the expression of MMPs, and TIMPs in chondrocytes derived from normal human femoral cartilage. The cells were cultured in Dulbecco's modified Eagle's medium containing 15% fetal bovine serum and 0, 1, 10, or 100 U/ml of IL-1beta for up to 28 days. The level of expression of MMPs and TIMPs was estimated by determining mRNA levels using real-time PCR and by determining protein levels using an enzyme-linked immunosorbent assay. Cell proliferation decreased in the presence of IL-1beta after day 21 of culture. ALPase activity decreased significantly in the presence of IL-1beta after day 10 of culture. The expression of MMP-1, -2, and -3 increased markedly in the presence of IL-1beta after day 21 of culture. MMP-13 expression increased markedly in the presence of IL-1beta on day 1 of culture, but decreased markedly after day 7. The expression of TIMP-1 increased significantly after day 14 of culture. The expression of TIMP-2 decreased significantly on day 1, but increased significantly from day 3 to day 14 of culture. These results suggest that IL-1beta may stimulate cartilage matrix turnover by increasing mainly MMP-13 production by the cells.

Effect of IL-1alpha on the expression of cartilage matrix proteins in human chondrosarcoma cell line OUMS-27

We examined the effect of the inflammatory mediator interleukin-1alpha (IL-1alpha) on cell proliferation, alkaline phosphatase (ALPase) activity, and the expressions of cartilage matrix proteins, bone morphogenetic protein-2 (BMP-2), and BMP-2 receptors in human chondrosarcoma cell line OUMS-27 (chondrocytes). The cells were cultured with Dulbecco's modified Eagle's medium containing 15% fetal bovine serum with 0, 1, 10, or 100 units/ml of IL-1alpha for up to 14 days. The expressions of cartilage matrix proteins, BMP-2, and BMP-2 receptors were estimated by determining mRNA levels using semiquantitative or real-time PCR and/or by determining protein levels using Enzyme-linked immunosorbent assay. Cell proliferation was decreased after 5 days in culture with IL-1alpha. The ALPase activity was decreased significantly in the presence of IL-1alpha until day 10 of culture. The expression of type II collagen was significantly decreased after 7 days in culture with IL-1alpha. The expressions of aggrecan and link protein were significantly decreased through day 14 of culture with IL-1alpha. The expression of BMP-2 was increased at days 3, 7, and 14 of culture with IL-1alpha, while the expression of type II receptor for BMP-2 was significantly decreased in the samples. These results suggest that IL-1alpha suppresses the expression of cartilage matrix proteins through a suppression of the autocrine action of BMP-2, brought about by the decrease in BMP-2 receptor expression in chondrocytes.

Interleukin-1beta stimulates interleukin-8 production and gene expression in synovial cells from human temporomandibular joint

PURPOSE

The aims of the present study were to isolate and characterize cultured synovial cells from human temporomandibular joint (TMJ) specimens and to investigate the effect of interleukin (IL)-1beta on IL-8 production and gene expression in those cells.

MATERIALS AND METHODS

Synovial cells (HTS cells) were isolated from TMJ synovial tissues using an outgrowth method and then primary cultured. The cells were examined for cell-specific markers of fibroblast, macrophage, and dendritic cells using immunocytochemistry. HTS cells were then treated with IL-1beta, and amounts of IL-8 were measured by enzyme-linked immunosorbent assay. IL-8 production and expression were also investigated using immunocytochemistry and a reverse transcription-polymerase chain reaction method.

RESULTS

HTS cells were positive for the fibroblast-specific markers, such as vimentin and propyl 4-hydroxylase. The macrophage or dendritic cell markers and HLA class II antigen were negative. Furthermore, IL-1beta enhanced IL-8 production in HTS cells in a time- and dose-dependent manner and stimulated IL-8 gene expression.

CONCLUSIONS

HTS cells may provide important advantages for studies of the cellular and molecular mechanisms in the TMJ. In addition, we found that IL-1beta stimulated IL-8 production through an increase in IL-8 gene expression in HTS cells, which may be associated with the increase of infiltrating inflammatory cells seen in the synovial membrane of TMJ disorders.

Interleukin-1 beta induces interleukin-6 mRNA expression and protein production in synovial cells from human temporomandibular joint

BACKGROUND

Interleukin (IL)-1 beta and IL-6 were found to be elevated in fluid from the temporomandibular joint (TMJ), although the source of these cytokines was not elucidated. There is little known about the function and response of synovial cells in the TMJ. The purpose of this study was to prepare cultured human synovial cells (HTS cells) from the TMJ and to investigate IL-6 production in HTS cells incubated with IL-1 beta.

METHODS

HTS cells were isolated from temporomandibular joint synovial tissue using an outgrowth method and then cultured in Ham's F12 medium containing 10% fetal bovine serum. The HTS cells were treated with or without IL-1 beta for 3, 6, 9 and 24 h. IL-6 and soluble IL-6 receptor (sIL-6R) levels in cultured supernatant were measured by ELISA. IL-6 mRNA expression was investigated using immunocytochemistry and RT-PCR.

RESULTS

HTS cells were morphologically heterogeneous. IL-1 beta increased IL-6 production in HTS cells. In those treated with IL-1 beta, several cells were strongly stained in the cytoplasm around the nucleus, while several cells were weakly stained in this area. IL-1 beta also stimulated IL-6 mRNA expression. In contrast, sIL-6R could not be detected in cells treated with or without IL-1 beta.

CONCLUSIONS

IL-1 beta increased IL-6 production in synovial cells resulting from an increase in IL-6 mRNA expression. Enhanced production of IL-6, which is associated with bone resorption and inflammatory response, seems to be related to the progression of TMJ disorders.

Age-dependent stimulation of Leydig cell steroidogenesis by interleukin-1 isoforms

Different isoforms of testicular interleukin-1 (IL-1) were analysed to determine whether there were differences in the ability to modulate rat Leydig cell steroidogenesis in vitro. Rat 17K IL-1alpha and IL-1beta, 32K IL-1alpha precursor (32proIL-1alpha) and a 24K splice variant (24proIL-1alpha) stimulated testosterone production by Leydig cells from 40- but not 80-day-old rats. The potency of the isoforms was IL-1alpha>IL-1beta>32proIL-1alpha>24proIL-1alpha, IL-1alpha being 50-fold more potent than IL-1beta. IL-1 receptor antagonist reversed the effects and IL-1 receptor type I mRNA was expressed by the responding Leydig cells, indicating a receptor mediated action. Inhibition of PKA and Ca(2+) channels abolished IL-1-induced steroidogenesis, while inhibition of PKC had no significant effect. Except for 24proIL-1alpha which was stimulatory, all IL-1 isoforms suppressed hCG-driven testosterone production. This inhibitory effect was abolished by androstendione, suggesting that P450c17 was suppressed by IL-1. Our results indicate that IL-1 plays a paracrine role in the regulation of Leydig cell steroidogenesis.