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Open Access Research article

Inhibitory effects of ZSTK474, a novel phosphoinositide 3-kinase inhibitor, on osteoclasts and collagen-induced arthritis in mice

Shoko Toyama1, Naoto Tamura1*, Kazuhiko Haruta2, Takeo Karakida3, Shigeyuki Mori2, Tetsuo Watanabe2, Takao Yamori4 and Yoshinari Takasaki1

Author Affiliations

1 Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan

2 Central Research Laboratory, Zenyaku Kogyo Co., Ltd, 2-33-7 Oizumimachi, Nerima-ku, Tokyo, 178-0062, Japan

3 Department of Biochemistry, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama, Kanagawa, 230-8501, Japan

4 Division of Molecular Pharmacology, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 3-10-6 Ariake, Koto-ku, Tokyo, 135-8550, Japan

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Arthritis Research & Therapy 2010, 12:R92  doi:10.1186/ar3019

Published: 18 May 2010

Abstract

Introduction

Targeting joint destruction induced by osteoclasts (OCs) is critical for management of patients with rheumatoid arthritis (RA). Since phosphoinositide 3-kinase (PI3-K) plays a critical role in osteoclastogenesis and bone resorption, we examined the effects of ZSTK474, a novel phosphoinositide 3-kinase (PI3-K)-specific inhibitor, on murine OCs in vitro and in vivo.

Methods

The inhibitory effect of ZSTK474 on OC formation was determined and compared with other PI3-K inhibitors by counting tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells after culturing murine bone marrow monocytic OC precursors, and RAW264.7 cells. Activation of Akt and expression of nuclear factor of activated T cells (NFAT) c1 in cultured RAW264.7 cells were examined. The suppressing effect of ZSTK474 on bone resorption was assessed by the pit formation assay. The in vivo effects of ZSTK474 were studied in collagen-induced arthritis (CIA) in the mouse. Oral daily administration of ZSTK474 was started either when more than half or when all mice developed arthritis. Effects of ZSTK474 were evaluated using the arthritis score and histological score of the hind paws.

Results

ZSTK474 inhibited the differentiation of bone marrow OC precursors and RAW264.7 cells in a dose-dependent manner. The inhibitory effect of ZSTK474 was much stronger than that of LY294002, the most commonly used PI3-K inhibitor. In addition, ZSTK474 suppressed the bone resorbing activity of mature OCs. Moreover, oral daily administration of ZSTK474, even when begun after the development of arthritis, ameliorated CIA in mice without apparent toxicity. Histological examination of the hind paw demonstrated noticeable reduction of inflammation and of cartilage destruction in ZSTK474-treated mice. ZSTK474 also significantly decreased OC formation adjacent to the tarsal bone of the hind paw.

Conclusions

These findings suggest that inhibition of PI3-K with ZSTK474 may potentially suppress synovial inflammation and bone destruction in patients with RA.