Scand J Rheumatol 2004;33:33
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Tropisetron inhibits serotonin-induced PGE2 release from macrophage-like synovial cells in serum-free tissue culture MF Seidel1, G Ulrich-Merzenich1, B Fiebich2, E Candelario-Jalil2, FW Koch3, H Vetter1 1
University Outpatient Clinic for Internal Diseases, Rheumatology, Bonn, 2University Clinic for Psychiatry and Psychosomatic Medicine, Freiburg, and 3St. Josef Hospital, Orthopaedics, Troisdorf, Germany
Tropisetron has shown potent analgesic and antiphlogistic effects in patients with rheumatic diseases such as osteoarthritis (1) or tendinopathies (2). These observations suggest that serotonin (5-HT) plays an important role in pain and inflammation. Objectives: The objective of our study was to determine if 5-HT stimulates the release of further inflammatory mediators such as prostaglandin E2 (PGE2) and if this effect can be blocked by tropisetron. To resolve these questions, we used a novel serum-free tissue culture technique for dissociated synovial tissue (3). This method permits in vitro experiments without perturbation by serum factors. Our cultures are characterized by 80% synoviocytes expressing the macrophage-specific marker CD68. Methods: Dissociated synovial tissue from osteoarthritis patients (n~5, mean age 67.2¡6.2 years) was cultured for 11 days in Iscove’s Modified Dulbecco’s Eagle Medium supplemented with insulin. Cultures were then stimulated with 1025, 1026, and 1027 M 5-HT and antagonized with 50 mg/mL tropisetron. Positive controls consisted of stimulation with 100 U/ml interleukin 1b (IL-1b). Negative controls included unstimulated cells or co-culture with tropisetron alone. After 48 h, PGE2 levels were determined using a conventional enzymeimmunoassay (EIA). PGE2 concentrations/mg protein were expressed as percent of controls and compared using the Mann-Whitney rank sum test. In addition, RT-PCR analyses for 5-HT1A, 5-HT1B, 5-HT2A, 5-HT3, and 5-HT4 receptor subtypes (4) were performed using synovial tissue (n~5). Results: The results (Figure 1) showed an increase of PGE2 in response to 1025 M 5-HT by 421.8¡84.9% (mean¡standard error, p~v0.0001), whereas 1026 and 1027 M did not show significant effects (126.9¡28.7%; p~0.37 and 96.8¡28.7%; p~0.87, respectively). Stimulation by IL-1b caused an increase of 1347.5¡481.4% (p~0.0094). Preincubation with tropisetron completely suppressed the serotonin-induced PGE2 release. RT-PCR showed an expression of the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT3 but not 5-HT4 receptor subtype. Conclusions: The increase of PGE2 shows that serotonin is a potent proinflammatory mediator. The findings indicate the presence of 5-HT3 Matthias Seidel, Medizinische Universita¨ts-Poliklinik, Wilhelmstraße 35 – 37, D-53111 Bonn, Germany. E-mail:
[email protected]
Figure 1. Serotonin-induced PGE2 release in cultured synovial macrophage-like cells. Dissociated osteoarthritis tissue (n~5) was cultured for 10 days in serum-free medium and then stimulated with 1025, 1026, and 1027 M 5-HT or 100 U/ml IL-1b as positive controls. PGE2 concentrations in the supernatants were determined by an EIA and expressed as percent of controls. 1025 5-HT and IL-1b showed a significant PGE2 release.
receptors and a tropisetron-induced suppression of this response. Additional analyses are necessary to further elucidate the underlying inflammatory mechanisms and inhibitory effect of tropisetron. References 1. Samborski W, Atarowska M, Stratz T, Zaba R, Mackiewicz S, Mu¨ller W, et al. Intra-articular tropisetron compared with ethylprednisolone acetate in knee involvement in osteoarthritis and rheumatiod arthritis. Preliminary report. Ann Rheum Dis 2003;62 Suppl 1:405. 2. Stratz T, Fa¨rber L, Mu¨ller W. Local treatment of tendinopathies: a comparison between tropisetron and depot corticosteroids combined with local anesthetics. Scand J Rheumatol 2002;31:366 – 70. 3. Seidel MF, Koch FW, Vetter H. Osteoarthritic synovial macrophages are highly enriched in a serum-free culture medium. Ann Rheum Dis 2002;61 Suppl 1:357. 4. Fiebich, et al, in preparation.
# 2004 Taylor & Francis on license from Scandinavian Rheumatology Research Foundation DOI: 10.1080/03009740410007005
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