Histone deacetylase inhibitor, FR901228, prevents the development of adjuvant arthritis in rats

T Nakamura MD^a, A Kukita PhD^a, T Shobuike PhD^a, T Kakimoto^a, T Kukita PhD^b, O Kohashi MD PhD^a

^aDepertment of Pathology and Biodefense, Saga University, Saga, Saga, Japan, ^bSection of Oral Cellular and Molecular Biology, Divition of Oral Biological Science, Kyushu University, Fukuoka, Fukuoka, Japan

Aim FR235222, histone deacetylase (HDAC) inhibitor, is known to suppress adjuvant　arthritis(AA). The present study is intended to elucidate whether another HDAC inhibitor, FR901228, known as a new class of anticancer drug, can also suppress AA or not. Methods To induce AA, LEW rats were intradermally injected at the base of the tail with 0.5mg/0.1 ml of CFA. FR901228 was dissolved in 10% HCO60 in saline and injected intravenously twice a week. The rats were observed clinically three times a week for evaluating the arthritis and at the end of the experiments, all the rats were sacrificed for radiographic and histological examinations. In vitro, RAW-D (mouse macrophage cell line) and mouse bone marrow cells were cultured in the presence of sRANKL, osteoclast differentiation factor with or without various doses of FR901228. The 3 days-cultured cells were stained by TRAP staining for the marker of osteoclast. By RT-PCR, the various mRNAs of the cultured cells were extracted for analyzing osteoclast-specific mRNA. By luciferase assay, NF-κB were measured using NF-κB-dependent reporter gene in RAW-D cell in the presence of sRANKL with or without FR901228. Results When 0.1, 0.2 mg/kg of FR901228 was injected simultaneously with CFA, CFA induced less severe arthritis, whereas 0.5 mg/kg of FR901228 completely suppressed AA, in terms of the body weight loss, the hind paw swelling, clinical score of arthritis and bone destruction. When 0.25, 0.5, 1.0 mg/kg of FR901228 was injected after onset day of AA, even higher doses of 1.0 mg/kg of FR901228 could not suppress AA. It is thus suggested that HDAC inhibitor, FR901228 could exert its prophylactic but not therapeutic activity on AA. On the other hand, sRANKL could effectively induce osteoclast formation in RAW-D cell and mouse bone marrow cell culture. When added to this culture, 0.1-1.0ng/ml of FR901228 apparently reduced the number of osteoclasts dose-dependently but also reduced the osteoclast-specific mRNA expression of calcitonin receptor and cathepsin K. In addition, luciferase reporter assay showed that FR901228 inhibited sRANKL-stimulated transactivation of NF-κB-dependent reporter genes, suggesting FR901228 exerts its inhibitory effects by modulating osteoclast-specific signals. Conclusions HDAC inhibitor, FR901228, effectively inhibited the sRANKL-induced osteoclast differentiation in vitro. It is therefore expected that FR901288 may exert its inhibiting effects on the joint inflammation of AA by inhibiting the bone destruction. The present study demonstrated that 0.5 mg/kg of FR901228 completely prevented the development of AA in dose response manner but not suppressed the ongoing or developing AA by therapeutical means. Since AA is believed to be a Th1-mediated autoimmune disease and be suppressed by Th2, it is suggested that the prophylactic but not therapeutic activity of FR901228 on AA may modify the balance of Th1/Th2 by still uncertain mechanisms of FR901228 in preventing an induction of the autoimmune AA.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in poster session 893 (Molecular pathology).