Inhibitory effects of TRK-530 on rat adjuvant arthritis

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.

AK106-001616, a Potent and Selective Inhibitor of Cytosolic Phospholipase A2: In Vivo Efficacy for Inflammation, Neuropathic Pain, and Pulmonary Fibrosis

3-[3-Amino-4-(indan-2-yloxy)-5-(1-methyl-1H-indazol-5-yl)-phenyl]-propionic acid (AK106-001616) is a novel, potent, and selective inhibitor of the cytosolic phospholipase A₂ (cPLA₂) enzyme. Unlike traditional nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors, AK106-001616 reduced prostaglandin E₂ (PGE₂) and leukotriene B₄ (LTB₄) production by stimulated cells. The suppression of PGE₂ and LTB₄ production was also confirmed using an air pouch model in rats administered a single oral dose of AK106-001616. AK106-001616 alleviated paw swelling in a rat adjuvant-induced arthritis (AIA) model. The maximum effect of the inhibitory effect of AK106-001616 was comparable with that of naproxen on paw swelling in a rat AIA model. Meanwhile, the inhibitory effect of AK106-001616 was more effective than that of naproxen in the mouse collagen antibody-induced arthritis model with leukotrienes contributing to the pathogenesis. AK106-001616 dose dependently reversed the decrease in paw withdrawal threshold not only in rat carrageenan-induced hyperalgesia, but also in a rat neuropathic pain model induced by sciatic nerve chronic constriction injury (CCI). However, naproxen and celecoxib did not reverse the decrease in the paw withdrawal threshold in the CCI model. Furthermore, AK106-001616 reduced the disease score of bleomycin-induced lung fibrosis in rats. In addition, AK106-001616 did not enhance aspirin-induced gastric damage in fasted rats, increase blood pressure, or increase the thromboxane A₂/ prostaglandin I₂ ratio that is thought to be an underlying mechanism of thrombotic cardiovascular events increased by selective cyclooxygenase-2 inhibitors. Taken together, these data demonstrate that oral AK106-001616 may provide valuable effects for wide indications without attendant gastrointestinal and cardiovascular risks.

[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.

Effects of the selective EP4 antagonist, CJ-023,423 on chronic inflammation and bone destruction in rat adjuvant-induced arthritis

Prostaglandin E2 (PGE2) produced by cyclooxygenase (COX) is a potent pro-inflammatory mediator. We have recently discovered CJ-023,423, a highly selective antagonist of EP4 receptors, one of the PGE2 receptors. This agent is suitable for exploring the effects of blocking EP4 receptors following oral administration in rats. In this study, CJ-023,423 was used in rats with adjuvant-induced arthritis (AIA) to investigate the role of the EP4 receptor in chronic inflammation and bone destruction. These effects were compared with those of rofecoxib, a selective COX-2 inhibitor. CJ-023,423 had significant inhibitory effects on paw swelling, inflammatory biomarkers, synovial inflammation and bone destruction in AIA rats. In particular, the inhibitory effect on paw swelling in AIA rats was comparable to that of rofecoxib. These results suggest that PGE2 acting via the EP4 receptor is involved in the development of chronic inflammation and bone destruction, particularly with respect to oedema in AIA rats. This is the first study to confirm the in-vivo effects of EP4 receptor blockade on inflammation and bone destruction in AIA rats with a small-molecule compound.

Minodronic acid influences receptor activator of nuclear factor kappaB ligand expression and suppresses bone resorption by osteoclasts in rats with collagen-induced arthritis

We investigated the inhibitory mechanism of bone resorption by minodronic acid in collagen-induced arthritis (CIA) in rats. Four groups of female Sprague-Dawley rats, aged 7 months, were studied: three groups of collagen-sensitized rats, including one placebo-administered group (CIA-P), and two minodronic acid-administered groups at 0.2 mg/kg/2 day (CIA-BIS) and 2.0 mg/kg/2 day (CIA-BIS10). These were studied with an additional untreated observation group (Cont group). Minodronic acid was administered orally a day after the initial sensitization. The femoral posteromedial condyle was analyzed histologically and immunohistologically 4 weeks after the initial sensitization. Western blotting was also performed to assess the receptor activator of nuclear factor kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) expression of the knee joints. In CIA-P rats, many tartrate-resistant acid phosphatase (TRAP)-positive cells were found at the pannus-lining layer and the epiphyseal medulla. The bone-lining cells in the epiphyseal medulla and the cells in the pannus strongly expressed RANK and RANKL. In the minodronic acid-administered group, the number of TRAP-positive cells and the severity of arthritis were reduced. The reduction in the CIA-BIS10 group was significant compared with the CIA-P group (P < 0.05). Dosage-dependent reduction of RANK and RANKL expression was confirmed by immunohistology and Western blotting. With or without minodronic acid administration, no apoptotic cells were found in any groups using the TdT-mediated dUTP-biotinnick end labeling (TUNEL) method. The expression of OPG was not clear in all groups. These results demonstrated that minodronic acid inhibited the differentiation and the activation of osteoclasts not by inducing apoptosis but by inhibiting the RANKL-RANK system, and thereby suppressing bone resorption.

Contribution of cell surface protein antigen PAc of Streptococcus mutans to bacteremia

Streptococcus mutans, a major cariogenic bacterium, is occasionally isolated from the blood of patients with bacteremia and infective endocarditis. Mutant strains of S. mutans MT8148, defective in the major surface proteins glucosyltransferase (GTF) B-, C-, and D-, and protein antigen c (PAc), were constructed by insertional inactivation of each respective gene with an antibiotic resistant cassette. Susceptibility to phagocytosis was determined by analyses of interactions of the bacteria with human polymorphonuclear leukocytes, and the PAc-defective mutant strain (PD) showed the lowest rate of phagocytosis. Further, when PD and MT8148 were separately injected into the jugular veins of Sprague-Dawley rats, PD was recovered in significantly larger numbers and for a longer duration, and caused more severe systemic inflammation than MT8148, indicating that S. mutans PAc is associated with its systemic virulence in blood. Next, 100 S. mutans clinical isolates from 100 Japanese children and adolescents were analyzed by Western blotting using antisera raised against recombinant PAc, generated based on the pac sequence of MT8148. Four of the 100 strains showed no positive band and each exhibited a significantly lower phagocytosis rate than that of 25 randomly selected clinical strains (P < 0.01). In addition, three of the 100 strains possessed a lower molecular weight PAc and a significantly lower rate of phagocytosis than the 25 reference strains (P < 0.05). These results suggest that S. mutans PAc may be associated with phagocytosis susceptibility to human polymorphonuclear leukocytes, with approximately 7% of S. mutans clinical isolates possible high-risk strains for the development of bacteremia.

Contribution of biofilm regulatory protein A of Streptococcus mutans, to systemic virulence

Streptococcus mutans is occasionally isolated from the blood of patients with bacteremia and infective endocarditis (IE), and the possibility that it could be pathogenic for those diseases has been discussed. The initial important step for the involvement of bacterial pathogens in the virulence of IE is thought to be survival in blood for an extended period. Recently, the brpA gene encoding biofilm regulatory protein A (BrpA) of S. mutans was cloned and sequenced, after which it was shown that inactivation of brpA in an isogenic mutant strain resulted in longer chain formation than in the parental strain. In the present study, a BrpA-defective isogenic mutant strain (MT8148BRD) was constructed from strain MT8148. In an analysis of its susceptibility to phagocytosis by human polymorphonuclear leukocytes (PMNs), the phagocytosis rate of MT8148BRD was shown to be significantly lower than that of MT8148 (P < 0.01). Next, strains with various chain lengths were produced by culturing MT8148 in media with various initial pH levels, which revealed that there was a statistically negative correlation between phagocytosis susceptibility and chain length (P < 0.01). Further, MT8148BRD was found to possess higher platelet aggregation properties than MT8148 (P < 0.05). In addition, injection of MT8148BRD into the jugular vein of specific pathogen-free Sprague-Dawley rats resulted in a longer duration of bacteremia, which prolonged systemic inflammation for a longer period than in those infected with MT8148. These results indicate that S. mutans BrpA is associated with virulence in blood, due to its correlation to phagocytosis susceptibility and platelet aggregation properties.

Contribution of glucan-binding protein C of Streptococcus mutans to bacteremia occurrence

Our previous analysis of major cell surface proteins of Streptococcus mutans isolated from the blood of a patient with bacteremia showed variations of glucan-binding protein C (GbpC) expression. In the present study, we analyzed the contribution of GbpC of S. mutans to bacteremia occurrence. A GbpC-defective mutant strain (C1) was significantly less susceptible to phagocytosis by human polymorphonuclear leukocytes than its parent strain (MT8148) (P < 0.001). When 21 rats were injected with C1 or streptomycin-resistant MT8148R into the jugular vein, strain C1 was recovered from blood in larger numbers and for a longer duration than MT8148R. Further, infection with C1 resulted in significant increases in serum sialic acid (SSA) concentrations, and splenomegaly, as well as body weight reduction. We also evaluated GbpC expression in 20 clinical oral isolates by immunoblotting with anti-GbpC serum, and found that expression intensity was positively correlated to phagocytosis rate (P < 0.05). These results suggest that S. mutans GbpC may be associated with systemic virulence, since a weak expression of GbpC causes the organisms to be refractory to phagocytosis, resulting in a longer survival of the bacterium in the bloodstream.

Targeting osteoclasts with zoledronic acid prevents bone destruction in collagen-induced arthritis

OBJECTIVE

To study the effect of zoledronic acid (ZA) on synovial inflammation, structural joint damage, and bone metabolism in rats during the effector phase of collagen-induced arthritis (CIA).

METHODS

CIA was induced in female dark agouti rats. At the clinical onset of CIA, rats were assigned to treatment with vehicle or single subcutaneous doses of ZA (1.0, 10, 50, or 100 microg/kg). Clinical signs in all 4 paws were scored on a daily basis. After 2 weeks, the joints in the hind paws were assessed using plain radiographs, microfocal computed tomography (micro-CT), histologic scoring, and histomorphometry, and the serum levels of type I collagen crosslinks were measured by enzyme-linked immunosorbent assay.

RESULTS

Although ZA mildly exacerbated synovitis, it effectively suppressed structural joint damage. At doses of >/=10 microg/kg, ZA significantly reduced radiographic bone erosions, Larsen scores, and juxtaarticular trabecular bone loss as quantified by micro-CT. ZA prevented increased type I collagen (bone) breakdown in CIA and diminished histologic scores of focal bone erosion by up to 80%. Increases in the percentage of eroded surface, osteoclast surface, and osteoclast numbers associated with CIA were prevented by ZA, even though synovitis scores were unchanged.

CONCLUSION

Single doses (>/=10 microg/kg) of ZA strikingly reduced focal bone erosions and juxtaarticular trabecular bone loss, although synovitis was mildly exacerbated. Targeting osteoclasts with ZA may therefore be an effective strategy for preventing structural joint damage in rheumatoid arthritis.

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.

Effect of minodronic acid (ONO-5920) on bone mineral density and arthritis in adult rats with collagen-induced arthritis

OBJECTIVE

To study the effect of minodronic acid (ONO-5920) on bone loss and arthritis in rats with collagen-induced arthritis (CIA) treated according to 2 different schedules.

METHODS

Four groups of female Sprague-Dawley rats (7 months old) were studied: rats without CIA treated with vehicle (controls), CIA rats treated with vehicle (CIA-V), CIA rats treated therapeutically with minodronic acid (CIA-T), and CIA rats treated prophylactically with minodronic acid (CIA-P). Minodronic acid was administered orally at 0.2 mg/kg 3 times a week, beginning 2 weeks after initial sensitization in the CIA-T rats and beginning the day after initial sensitization in the CIA-P rats. Bone mineral density (BMD) was measured by peripheral quantitative computed tomography in the proximal metaphysis and diaphysis of the tibia every 2 weeks until week 8, when the rats were killed. The BMD and bone microstructure of the excised femur were evaluated by dual x-ray absorptiometry and microfocal computed tomography, respectively. Histomorphometry of the proximal tibia was also performed.

RESULTS

In CIA-P rats, the incidence of arthritis and the severity of posterior limb swelling were reduced early after sensitization, and the decrease in BMD was prevented throughout the observation period. Bone and joint destruction evaluated by radiography of the foot was reduced in CIA-P rats. The eroded surface was reduced and the microstructure was maintained in CIA-P rats compared with CIA-V rats. The mineral apposition and bone formation rates were not reduced in the CIA-P rats. In CIA-T rats, however, the inflammation was not suppressed and the inhibitory effect on bone loss was smaller than that in CIA-P rats.

CONCLUSION

Minodronic acid suppressed the decrease in BMD and the deterioration of the bone microstructure caused by arthritis. Prophylactic administration of minodronic acid had a preventive effect on arthritis at the early stage, although not throughout the observation period.

Effect of bisphosphonates on cartilage turnover assessed with a newly developed assay for collagen type II degradation products

BACKGROUND

Animal studies of arthritis have suggested that bisphosphonates may have chondroprotective abilities.

OBJECTIVE

To evaluate the effect of bisphosphonate treatment on cartilage degradation.

METHODS

Type II collagen is almost exclusively localised in cartilage, where it is the major structural component of the tissue. Hence fragments derived from this protein should represent a specific index for cartilage degradation. The urinary concentration of collagen type II C-telopeptide degradation products (CTX-II) was measured by a new immunoassay (enzyme linked immunosorbent assay (ELISA)). The serum concentration of collagen type I C-telopeptide degradation products (CTX-I), a marker of bone degradation, was also measured by ELISA.

PARTICIPANTS

Two groups were studied. The alendronate group included 63 healthy postmenopausal women aged 45-54 randomly allocated to receive three years' treatment with 1 mg, 5 mg, 10 mg, or 20 mg alendronate daily or placebo. In the third year the women receiving 20 mg were switched to placebo. The ibandronate group included 119 women at least 10 years after the menopause aged <75 randomly allocated to receive 12 months' treatment with 0.25 mg, 0.5 mg, 1.0 mg, 2.5 mg, or 5 mg ibandronate daily or placebo followed by 12 months without treatment.

RESULTS

20 mg of alendronate and 2.5 and 5 mg of ibandronate treatment produced significant decreases in urinary CTX-II to about 50% of baseline. The level reached after three months of treatment remained practically constant during the following 12-36 treatment months. When treatment was withdrawn CTX-II values returned towards baseline. Serum CTX-I also decreased rapidly within three months, but to a level of about 30% of baseline.

CONCLUSIONS

The urinary excretion of CTX-II, a new marker of cartilage degradation, decreases significantly in response to bisphosphonate. This suggests that bisphosphonates may have chondroprotective effects in humans. By measurement of CTX-II it should be possible to monitor the effects of drugs that potentially inhibit cartilage destruction.

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.

Chemokines, nitric oxide and antiarthritic effects of 9-(2-phosphonomethoxyethyl)adenine (Adefovir)

Antiarthritic effects of two acyclic nucleoside phosphonates, 9-(2-phosphonomethoxyethyl)adenine (PMEA; Adefovir) and 9-(2-phosphonomethoxypropyl)adenine (PMPA), as well as their more bioavailable prodrugs, bis(pivaloyloxymethyl)ester of PMEA [bis(POM)-PMEA; Adefovir Dipivoxil] and bis(isopropyloxycarbonyloxymethyl)ester of PMPA [bis(POC)-PMPA], were investigated in a model of adjuvant-induced arthritis in Lewis rats. The drugs were injected subcutaneously at doses of 5-50 mg/kg. PMEA and its prodrug inhibited by > 80% arthritic paw swelling, splenomegaly and fibroadhesive perisplenitis. Both prophylactic and therapeutic dosing regimens were effective. Neither PMPA nor bis(POC)-PMPA suppressed development of arthritic lesions. Substantially reduced nitrite + nitrate levels were detected in serum and urine of PMEA-treated animals as compared to those of untreated diseased controls. Also, complete suppression of the disease-associated, greatly enhanced systemic levels of the chemokine, RANTES (regulated upon activation, normal T cell expressed and secreted), was observed in rats injected with PMEA. Additional in vitro studies showed that PMEA does not change, PMPA enhances, and both prodrugs inhibit the immune-activated NO production. Under the same conditions PMEA inhibits, while PMPA slightly stimulates, secretion of RANTES. Collectively, these data suggest that the in vivo-inhibited production of nitric oxide (NO) is a consequence rather than a mechanism of antiarthritic action of PMEA. Possible mechanisms for the anti-RANTES activity of PMEA remains to be firmly established.