Investigation of the acute and chronic anti-inflammatory properties of diphosphonates using a broad spectrum of immune and non-immune inflammatory reactions

Differences in osteoclast formation between proximal and distal tibial osteoporosis in rats with adjuvant arthritis: inhibitory effects of bisphosphonates on osteoclasts

Patients with rheumatoid arthritis commonly suffer both systemic and periarticular osteoporosis. Bisphosphonates (BPs) are inhibitors of bone resorption, and several derivatives have been developed for treatment of enhanced bone resorption. We aimed to characterize osteoclast formation in two different sites, the proximal tibial and distal tibial areas, in rats with adjuvant arthritis, and to investigate the impact of amino or non-amino types of bisphosphonate. Adjuvant arthritis was initiated in rats while administering daily injections of either etidronate, a non-amino BP, or alendronate, an amino BP, for 3 weeks. On the day following the last injection, bone mineral density (BMD) was measured in the proximal tibia to assess systemic osteoporosis and in the distal tibia for periarticular osteoporosis using dual-energy X-ray absorptiometry. Subsequently, bone marrow cells from either end of the tibia were collected and incubated for 7 days before staining and counting tartrate-resistant acid phosphatase positive cells. In the rats with adjuvant arthritis, BMD of either end of the tibia was lower than in normal rats. Although etidronate prevented bone mineral loss at both ends, distal loss was significantly less than proximal. In contrast, alendronate significantly inhibited mineral loss primarily in the proximal area. Large osteoclasts, defined as having five or more nuclei, formed preferentially in the proximal tibia, while small osteoclasts with fewer than four nuclei were found mainly distally. The suppressive effect of alendronate was greater on the large osteoclasts, while etidronate had a greater effect on the small osteoclasts. These results show that the size and multinuclearity of osteoclasts and the number of osteoclasts formed are different in the distal and proximal areas of the tibia, and that alendronate and etidronate may suppress different types of osteoclasts as discriminated by the number of nuclei.

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.

Inhibition of inflammatory actions of aminobisphosphonates by dichloromethylene bisphosphonate, a non-aminobisphosphonate

1. When injected intraperitoneally into mice in doses larger than those used clinically, all the amino derivatives of bisphosphonates (aminoBPs) tested induce a variety of inflammatory reactions such as induction of histidine decarboxylase (HDC, the histamine-forming enzyme), hypertrophy of the spleen, atrophy of the thymus, hypoglycaemia, ascites and accumulation of exudate in the thorax, and an increase in the number of macrophages and/or granulocytes in the peritoneal cavity of blood. On the other hand, dichloromethylene bisphosphonate (Cl2MBP) a typical non-aminoBP, has no such inflammatory actions. In the present study, we found that this agent can suppress the inflammatory actions of aminoBPs. 2. Cl2MBP, when injected into mice before or after injection of 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid (AHBuBP; a typical aminoBP), inhibited the induction of HDC activity by AHBuBP in a dose- and time-dependent manner. The increase in HDC activity induced by AHBuBP was largely suppressed by the injection of an equimolar dose of Cl2MBP. Cl2MBP also inhibited other AHBuBP-induced inflammatory reactions, as well as the inflammatory actions of two other aminoBPs. However, Cl2MBP did not inhibit the increase in HDC activity induced by lipopolysaccharide (LPS). 3. We have previously reported that AHBuBP augments the elevation of HDC activity and the production of interleukin-1beta (IL-1beta) that are induced by LPS. These actions of AHBuBP were also inhibited by Cl2MBP. 4. Based on these results and reported actions of bisphosphonates, the mechanisms underlying the contrasting effects of aminoBPs and Cl2MBP, a non-aminoBP are discussed. The results suggest that combined administration of Cl2MBP and an aminoBP in patients might be a useful way of suppressing the inflammatory side effects of aminoBPs.

Contrast between effects of aminobisphosphonates and non-aminobisphosphonates on collagen-induced arthritis in mice

1. Bisphosphonates (BPs) are inhibitors of bone resorption, and many derivatives have been developed for the treatment of enhanced bone resorption. Aminobisphosphonates (aminoBPs) are particularly potent in this respect. We have shown previously that aminoBPs, such as 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid (AHBuBP), induce histidine decarboxylase, the enzyme forming histamine, and increase macrophages, granulocytes and osteoclast numbers. Non-aminoBPs do not show this activity. 2. In the present study, an additional aminoBP, cycloheptyl-aminomethylene bisphosphonate (CHAMBP), was shown to have similar properties to AHBuBP suggesting that these actions are common among aminoBPs. 3. In experiments carried out to determine if aminoBPs affect immune responses, we found that CHAMBP and AHBuBP each exacerbated the arthritis induced in mice by the co-injection of type II collagen and an adjuvant, a model for rheumatoid arthritis. In contrast, dichloromethylene bisphosphonate (C12MBP), a typical non-aminoBP, did suppress the arthritis. 4. On the basis of these results, and those obtained previously, we propose that the exacerbating effects of CHAMBP and AHBuBP may be related to their ability to stimulate the synthesis of histamine and to increase macrophages and granulocytes. Conversely, we propose that the suppressive effect of C12MBP on arthritis is related to its cytotoxic action on macrophages or granulocytes.