Norio Kawabe

Inhibitory Effects of TRK-530 on Rat Adjuvant Arthritis

TRK-530 is a novel bisphosphonate derivative. We examined the anti-inflammatory effects of TRK-530 on adjuvant arthritis (AA) rats. When TRK-530 at a dose of 2.5 mg/kg was administered for 2 weeks to AA rats, it inhibited destructive changes in arthritic joints such as paw edema, bone loss and joint degeneration. TRK-530 also inhibited splenomegaly and suppressed the increase in serum sialic acid which is measured as a systemic parameter of inflammation. To clarify the inhibitory mechanism of TRK-530, interleukin-1 (IL-1)-like activities of resident peritoneal macrophages in AA rats given TRK-530 were compared with those of control rats. We found that TRK-530 inhibited IL-1-like activity induced by bacterial lipopolysaccharide 6 weeks after administration when the IL-1-like activities of control rats were still at high levels. These findings suggest that TRK-530 exerts anti-inflammatory activities in AA rats.

Inhibitory Effect of TRK-530 on Inflammatory Cytokines in Bone Marrow of Rats with Adjuvant Arthritis

TRK-530 is a novel synthetic bisphosphonate compound which exhibits inhibitory activity in the rat adjuvant arthritis (AA) model. We found that, during AA development, the concentrations of cytokine-induced neutrophil chemoattractant-1 (CINC-1) and tumor necrosis factor α (TNF-α) in the bone marrow increased, and that administration of TRK-530 decreased the concentrations of these cytokines. The suppression of these concentration increases paralleled the inhibition of paw edema. Paw edema inhibition by TRK-530 in rat AA may be the result of decreasing CINC-1 and TNF-α concentrations.

TRK-530 Inhibits Accumulation of Superoxide Anions Derived from Human Polymorphonuclear Leukocytes and Bone Resorption Induced by Activated Osteoclasts

TRK-530, a newly synthesized bisphosphonate, was assessed for its effects on the accumulation of superoxide anions derived from human formyl-methionyl-leucyl-phenylalanine-stimulated polymorphonuclear leukocytes (PMN), and for its effects on bone resorption using a pit formation assay. TRK-530 concentration-dependently inhibited superoxide accumulation derived from PMN and osteoclast pit formation stimulated by 1,25-dihydroxyvitamin D3. Incadronate and risedronate had a strong inhibitory effect on pit formation, but no antioxidative activity. These data suggest that the anti-bone resorption activities of TRK-530 are possibly unrelated to its antioxidant properties. However, it is difficult to conclude at present which mechanisms play the most important role in the anti-bone resorption activities of TRK-530.