TRK-530 inhibits accumulation of superoxide anions derived from human polymorphonuclear leukocytes and bone resorption induced by activated osteoclasts

Structure-Dependent Effects of Bisphosphonates on Inflammatory Responses in Cultured Neonatal Mouse Calvaria

Bisphosphonates (BPs) are classified into two groups, according to their side chain structures, as nitrogen-containing BPs (NBPs) and non-nitrogen-containing BPs (non-NBPs). In this study, we examined the effects of NBPs and non-NBPs on inflammatory responses, by quantifying the inflammatory mediators, prostaglandin E₂ (PGE₂) and nitric oxide (NO), in cultured neonatal mouse calvaria. All examined NBPs (pamidronate, alendronate, incadronate, risedronate, zoledronate) stimulated lipopolysaccharide (LPS)-induced PGE₂ and NO production by upregulating COX-2 and iNOS mRNA expression, whereas non-NBPs (etidronate, clodronate, tiludronate) suppressed PGE₂ and NO production, by downregulating gene expression. Additionally, [4-(methylthio) phenylthio] methane bisphosphonate (MPMBP), a novel non-NBP with an antioxidant methylthio phenylthio group in its side chain, exhibited the most potent anti-inflammatory activity among non-NBPs. Furthermore, results of immunohistochemistry showed that the nuclear translocation of NF-κB/p65 and tyrosine nitration of cytoplasmic protein were stimulated by zoledronate, while MPMBP inhibited these phenomena, by acting as a superoxide anion (O₂⁻) scavenger. These findings indicate that MPMBP can act as an efficacious agent that causes fewer adverse effects in patients with inflammatory bone diseases, including periodontitis and rheumatoid arthritis.

[MPMBP, a novel bisphosphonate with an antioxidant side chain, stimulates bone formation through inhibition of NF-κB nuclear translocation]

Bisphosphonates (BPs) are chemically characterized by a P-C-P bond with two lateral side chains on the carbon atom, and have been widely used as anti-resorptive agents in various metabolic bone diseases. 4-[(methylthio) phenylthio] methanebisphosphonate (MPMBP) is a novel non-nitrogen-containing BP with an antioxidant side chain that possesses anti-inflammatory properties. Since inflammation is known to be a cause of the pathological bone resorption, we investigated the effects of MPMBP on bone metabolism both in vitro and in vivo. The results showed that: i) MPMBP dose-dependently increased alkaline-phosphatase activity in a culture of osteoblastic MC3T3-E1 cells, ii) MPMBP increased the synthesis of collagen (type-I) in an organ culture of mouse calvaria, iii) local injection of MPMBP to alveolar bone induced prominent increases in both the bone mass and thickness of alveolar bone at the local site of injection in rabbits, iv) MPMBP increased the mRNA expression of alkaline-phosphatase, type-I collagen, osteocalcin, and bone sialoprotein in MC3T3-E1 cells, v) MPMBP inhibited the translocation of NF-κB/p65 to the nuclei in osteoblasts of cultured mouse calvaria. Taken together, these findings suggest that MPMBP is a promising agent to prevent bone loss, or even accelerate new bone formation, through inducing an uncoupling between bone resorption and bone formation, which is preferable to maintain bone mass and quality.

The novel bisphosphonate disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate increases bone mass in post-ovariectomy rats

The novel bisphosphonate (BP) disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate (MPMBP) is a non-nitrogen-containing BP with an antioxidant side chain that possesses anti-inflammatory properties. We investigated the systemic effects of this compound on bone loss induced by ovariectomy (OVX) in adult rats. Micro-computed tomography revealed that MPMBP increased bone mass and density in both the metaphysis and diaphysis, and improved the structural properties important for mechanical strength of osteoporotic bone. Sequential bone labeling with tetracycline and calcein indicated that MPMBP decreased longitudinal growth of the primary spongiosa (PS), but stimulated cortical bone formation in the diaphysis. MPMBP increased type I collagen accumulation in the PS, and decreased the number and size of adipocytes in the bone marrow, suggesting inhibition of increased bone marrow adipogenesis induced by OVX. Furthermore, MPMBP reduced the number of bone resorbing cathepsin K-positive osteoclasts induced by OVX. These results suggest that MPMBP could improve bone loss induced by estrogen deficiency. Both stimulation of bone formation and inhibition of bone resorption might play a role in the increase in bone mass and bone density after MPMBP treatment.

Inhibitory Effect of a Novel Bisphosphonate, TRK-530, on Dental Calculus Formation in Rats

BACKGROUND

A newly developed bisphosphonate, TRK-530 (disodium dihydrogen[4-(methylthio)phenylthio]methanebisphosphonate), has recently been reported to show anti-inflammatory and anti-bone-resorbing activity. Since bisphosphonates have been shown to inhibit the formation of calcium-phosphate crystals in vitro, TRK-530 may inhibit the formation of dental calculus. Therefore, the present study was performed to examine whether this compound has such an effect.

METHODS

Three groups of Wistar rats fed a calculogenic diet (RC16) were treated with TRK-530 in drinking water at concentrations of 0 (control group), 0.75, and 1.5 mM. Another group received a daily subcutaneous injection of TRK-530 at a dose of 2.25 micromoles/rat, which was assumed to correspond to the maximum amount of this compound absorbed from the intestine when rats received 1.5 mM TRK-530 in drinking water. Rat dental calculus formation was evaluated. The crystalline nature of dental calculus was studied by x-ray diffraction analysis. Finally, the effects of TRK-530 on the precipitation of calcium-phosphate from solution were tested in vitro.

RESULTS

TRK-530 in drinking water inhibited dental calculus formation dose-dependently. However, subcutaneous injection of TRK-530 did not have any significant effect, suggesting that the anticalculus effect of TRK-530 in drinking water was topical, not systemic. The calculus that formed in both the control and experimental groups was primarily hydroxyapatite, a main constituent of human dental calculus. TRK-530 inhibited the precipitation of calcium-phosphate from solution in vitro.

CONCLUSIONS

TRK-530 inhibited the formation of dental calculus in a dose-dependent fashion via a local effect. Inhibition of the precipitation of calcium-phosphate from solution might be involved in the anticalculogenic mechanism of this drug.

A novel bisphosphonate inhibits inflammatory bone resorption in a rat osteolysis model with continuous infusion of polyethylene particles

This study examined the inhibitory effect of a new bisphosphonate (TRK-530) on wear debris-mediated bone resorption in a rat osteolysis model involving continuous infusion of high density polyethylene (HDPE) particles. TRK-530 (TRK) is a novel synthetic bisphosphonate that has been shown to decrease the level of tumor necrosis factor alpha (TNF-alpha) in the bone marrow of rats with adjuvant arthritis. Forty Wistar rats were randomized to two groups (n = 20 each). In each rat, a Kirshner (K) wire was inserted into the femur and HDPE particles were continuously infused into the knee joint. Thereafter, the animals were subcutaneously injected with saline (control group) or 1 mg/kg of TRK (TRK group) every second day, and were sacrificed at 4 or 8 weeks after surgery. Radiographs obtained at the time of sacrifice were evaluated for periprosthetic osteolysis. We also examined the thickness of the reactive membrane as well as the number of osteoclast-like cells around the K-wire. In addition, we examined the expression of genes for bone-resorbing cytokines in the reactive membrane. Radiographic peri-implant osteolysis was more frequent in the control group compared with the TRK group at each time of assessment (p < 0.01). The interfacial membrane was significantly thinner in the TRK group compared with the control group (p < 0.01) and the average number of osteoclast-like cells around the K-wire was significantly fewer in the TRK group (p < 0.01). In addition, the expression of interleukin 1-alpha messenger ribonucleic acid (IL-1alpha mRNA) and TNF-alpha mRNA was suppressed in the TRK group at each time of assessment. We conclude that the TRK can inhibit the formation of inflammatory peri-implant osteolysis induced by HDPE particles.