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Relationship Between Cathepsin B and Thrombin in Rheumatoid Arthritis
TAKUYA MISHIRO, SHUNJI NAKANO, SHIGEYUKI TAKAHARA, MARI MIKI, YOICHI NAKAMURA, SUSUMU YASUOKA, TAKESHI NIKAWA, and NATSUO YASUI
ABSTRACT.
Methods. Thrombin and cathepsin B activities of samples from patients with RA and osteoarthritis (OA) were measured using fluorogenic synthetic substrates. The concentration of interleukin 8 (IL-8) in SF was measured by ELISA. The effect of thrombin on the proliferation of synovial fibroblast-like cells (SFC) was examined by measuring 3H-thymidine incorporation. The effect of thrombin on the release of IL-8 and cathepsin B from SFC was investigated. The expression of IL-8 mRNA in SFC after stimulation with thrombin was evaluated using real-time quantitative RT-PCR. The effect of recombinant IL-8 on the activation of cathepsin B was examined using the knee joints of rabbits. Results. In SF supernatants, cathepsin B and thrombin-like activity was significantly higher in RA than in OA, and there was a significant correlation between them. Cathepsin B activity was also significantly higher in SF cells and synovial tissue extracts from RA patients than in those from OA patients. There was a significant correlation between cathepsin B activity and the concentration of IL-8 in RA SF. Thrombin enhanced the proliferation of SFC in a dose-dependent manner. Thrombin significantly enhanced the release of IL-8 from SFC as well as the expression of IL-8 mRNA in SFC. IL-8 induced activation of cathepsin B in the knee joints of rabbits. However, thrombin did not directly increase cathepsin B activity in SFC. Conclusion. In RA, thrombin was found to be related to the enhanced growth of SFC and the release of IL-8 from these cells; thus thrombin is probably related to worsening of inflammation through the recruitment of leukocytes (neutrophils), which release cathepsin B into the SF. Thrombin can induce activation of cathepsin B in SFC via increased expression of IL-8. (J Rheumatol 2004;31:1265-73) Key Indexing Terms:
RHEUMATOID ARTHRITIS
From the Department of Orthopedics, School of Medicine, The University of Tokushima; Clinical Research Center, Kochi National Hospital, Kochi; Hakuai Kinen Hospital, Tokushima; and Department of Nutrition, School of Medicine, The University of Tokushima, Tokushima, Japan. Supported by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology. T. Mishiro, MD; S. Nakano, MD, PhD; S. Takahara, MD, Department of Orthopedics, School of Medicine, University of Tokushima; M. Miki, MD, PhD; Y. Nakamura, MD, PhD, Kochi National Hospital; S. Yasuoka, MD, PhD, Hakuai Kinen Hospital; T. Nikawa, MD, PhD, Department of Nutrition, School of Medicine, University of Tokushima; N. Yasui, MD, PhD, Department of Orthopedics, School of Medicine, University of Tokushima. Address reprint requests to Dr. S. Nakano, Department of Orthopedics, School of Medicine, The University of Tokushima, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan. E-mail: nakano@clin.med.tokushima-u.ac.jp Submitted February 5, 2003; revision accepted December 2, 2003. |