Inhibitory effects of ZSTK474, a novel phosphoinositide 3-kinase inhibitor, on osteoclasts and collagen-induced arthritis in mice.
BACKGROUND
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.
Toyama
Shoko
S
Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
Tamura
Naoto
N
Haruta
Kazuhiko
K
Karakida
Takeo
T
Mori
Shigeyuki
S
Watanabe
Tetsuo
T
Yamori
Takao
T
Takasaki
Yoshinari
Y
D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D001862:Bone Resorption / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D050778:NFATC Transcription Factors / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D014227:Triazines / Q000494:pharmacology* / Q000627:therapeutic use; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D000081082:Phosphoinositide-3 Kinase Inhibitors; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D014227:Triazines; D014409:Tumor Necrosis Factor-alpha; C510150:ZSTK474; D051057:Proto-Oncogene Proteins c-akt