No abstract

The mechanisms of TSH-induced growth stimulation of thyrocytes in vivo have yet to be elucidated. We examined the antiapoptotic effect of TSH toward Fas antigen-mediated apoptosis of thyrocytes. Fas antigen was expressed on approximately 40% of unstimulated thyrocytes, and the expression was significantly inhibited by the addition of TSH in a dose-dependent manner. Treatment of thyrocytes with 8-bromo-cAMP mimicked the effect of TSH, suggesting that the inhibitory effect of TSH on Fas antigen expression was mediated by activating protein kinase A. In contrast, treatment of thyrocytes with either interleukin-1 beta (IL-1 beta) or interferon- gamma (IFN gamma) markedly increased Fas antigen expression on thyrocytes, and these effects were inhibited in the presence of TSH. The expression of the protooncogene product Bcl-2 did not change after the addition of TSH, 8-bromo-cAMP, IL-1 beta, IFN gamma, or a combination of TSH and IL-1 beta or IFN gamma. When thyrocytes stimulated with either IL-1 beta or IFN gamma were treated with anti-Fas IgM mAb, the cells were committed to apoptosis, whereas this apoptotic process was significantly inhibited by the addition of TSH. These results indicate that the Fas antigen is functionally expressed on the surface of thyrocytes, and TSH inhibits Fas antigen-mediated apoptosis of thyrocytes through the inhibitory effect of Fas antigen expression, resulting in the promotion of growth of the thyroid gland.

Objective. To investigate the mitogenic and anti-apoptotic effects of transforming growth factor Pl (TGFPI) on rheumatoid synodal cells in vitro.Methods. Synovial cells were cultured with or wjthout TGFPl. After incdbatiod, the proliferative response of synoyial cells and the expression of Fas antigen and bcl-2 on synovial 'cells were examined. Finally, Fas hntigen-mediated apoptosis of synovial cells was investigated by the addition of anti-Fas antibody.Results. TGF/31 enhanced the proliferation of synovial cells in a dose-dependent madner. In addition, Fas antigen expression on synovial cells was inhibited by the addition of TCFPl with up-regulation of bcl-2 expression. The addition of anti-Fas antibody induced synovial. cell apoptosis. However, stimulation of synovial cells with TGFPl became markedly resistant to Fas antigen-mediated apoptosis. The results were not affected by the addition of a neutralizing antibody to platelet-derived growth factor type AA (PDGF-AA), which suggests that the effect of TCFPl on synovial cells was promoted via PDGF-AA-independent mechanisms. Supported in part by a grant-in-aid for Scientific Research (05670426) from ihe Ministry of Education, Science, Sport and Culture, Japan.Atsushi Kawakami. MD, Katsumi Eguchi, MD, Ndoki Matsuoka, MD, Masahiko Tsuboi. MD, Yojiro Kawabe, MD, Shigenobu Nagataki, MD: Nagasaki University School of Medicine, Nagasaki, Japan; Takahiko Aoyagi, MD: Ureshino National Hospital, Saga, Japan.Addrcss reprint requests to Katsumi Eguchi, MD, ,First Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852, Japan.Submitted for publication September 2Y. 1995; accepted in revised form March 11, 1996. Conclusion. Our results suggest that TGFpl promotes synovial cell proliferation through its mitogenic effect on synovial cells and interference with the apoptotic process mediated by the Fas antigen, resulting in the perpetuation of the synovial hyperplasia in patients with rheumatoid arthritis.

SUMMARYThis study was undertaken to investigate the immunomodulatory effect of clarithromycin against synovial fibroblast-like cells (synoviocytes). Synovial tissue obtained from rheumatoid arthritis (RA) or osteoarthritis (OA) patients was enzymatically digested to separate synoviocytes. The synoviocytes were cultured with or without cytokines in the presence of various concentrations of clarithromycin. The expression of costimulatory molecules was examined on the surface of the synoviocytes, using specific MoAbs and flow cytometry. The production of cytokines by synoviocytes was also measured using an immunoenzymatic assay. Finally, autologous T cells were stimulated by interferon-gamma (IFN-)-treated synoviocytes in response to purified protein derivative (PPD). In some experiments, MoAbs specific for costimulatory molecules or clarithromycin were added and 3 H-thymidine incorporation was counted. Intercellular adhesion molecule-1 (ICAM-1), LFA-3 and vascular cell adhesion molecule-1 (VCAM-1) were detected on the surface of both RA and OA synoviocytes. However, ICAM-2, B7-1 and B7-2 were not detected, and cytokines failed to induce these molecules. Both spontaneous and upregulated expression of ICAM-1, LFA-3 and VCAM-1 by IFN-, IL-1 or 12-o-tetradecanoyl phorbol 13-acetate (TPA) were markedly suppressed by clarithromycin in a dose-dependent manner at concentrations between 0 . 1 and 10 g/ml. The production of IL-1, IL-6, IL-8, granulocyte colonystimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) but not IL-1 and tumour necrosis factor-alpha (TNF-) by synoviocytes was detected. Clarithromycin significantly suppressed the production of these cytokines, but did not enhance IL-10 production. Finally, autologous T cells were stimulated by IFN--treated synoviocytes in response to PPD. As clarithromycin suppressed HLA-DR and costimulatory molecule expression was enhanced by IFN-, autologous T cell proliferation was markedly inhibited by clarithromycin. Clarithromycin has a considerable immunosuppressive effect on synoviocytes by inhibiting costimulatory molecule expression, cytokine production and antigen-specific T cell proliferation induced by synoviocytes.

We investigated the cellular and humoral interactions between peripheral blood mononuclear cells (PBMCs) and human osteoblasts, leading to apoptosis of osteoblasts. Human osteoblastic cell line MG63 and human primary osteoblast-like cells obtained from biopsy specimens were used in this study. PBMCs were isolated from healthy donors and cultured with or without stimulation by recombinant interleukin-2 followed by 12-o-tetradecanoylphorbol 13-acetate with ionomycin.