Drug disposition of incadronate, a new bisphosphonate, in rats with bone metastases

Zoledronic acid enhances lipopolysaccharide-stimulated proinflammatory reactions through controlled expression of SOCS1 in macrophages

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious side effect of nitrogen-containing bisphosphonate (NBP) use. Many studies have shown that BRONJ is limited to the jawbone and does not occur in the other bones. We hypothesized that BRONJ is related to local bacterial iections and involves the innate immune system. To examine the relationship between BRONJ and innate immunity, we examined the effects of NBPs on macrophages, one of the important cell types in innate immunity. The expression of toll-like receptor-4 (TLR4) in cells after pretreatment with zoledronic acid (ZOL) did not considerably differ from that in untreated control cells. However, cytokine levels and nitric oxide (NO) production increased after pretreatment with ZOL. Furthermore, ZOL induced NF-κB activation by enhancing IκB-α degradation. Lipopolysaccharide (LPS)-induced apoptosis also increased after pretreatment with ZOL. This effect was mediated by a reduction of suppressor of cytokine signaling-1 (SOCS1), which is a negative regulator of myeloid differentiation primary response gene 88 (MyD 88)-dependent signaling. These results suggest that ZOL induced excessive innate immune response and proinflammatory cytokine production and that these processes may be involved in the bone destruction observed in BRONJ.

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin regulation of bone remodeling in health and disease

Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor kappaB ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis.

Differential inhibition of invasion and proliferation by bisphosphonates: anti-metastatic potential of Zoledronic acid in prostate cancer

OBJECTIVES

To determine the mode of action of Zoledronic acid in the inhibition of metastasis in prostate cancer and the reduction of prostate cancer bone metastases.

METHODS

Benign and malignant primary prostatic epithelial cells (PEC) and the PC-3 prostate cancer cell line were studied in co-culture using human bone marrow stroma in the presence of escalating doses of EDTA, Clodronate, Pamidronate and Zoledronic acid. PEC binding and colony growth in bone marrow stroma was measured using standardised quantitative techniques. PEC cellular invasion through Matrigel and an endothelial monolayer was measured either in invasion chambers or by the measurement of endothelial monolayer permeability to fluorescent dextran. Co-culture supernatants were assayed for specific cytokine levels. Bone marrow cellular toxicity was assessed using a standard Mix assay.

RESULTS

Treatment of PEC with up to 100 microM bisphosphonate did not affect their ability to bind to bone marrow endothelium or stroma. Bone marrow endothelial permeability was reduced by 100 microM Zoledronic acid by 3.8% (p = 0.03856). Both Pamidronate (40% at 100 microM, p < or = 0.05) and Zoledronic acid inhibited PEC invasion, with Zoledronic acid being the most potent (40% at 10 microM, p < or = 0.05 rising to 91% at 100 microM, p < or = 0.001). Zoledronic acid inhibits malignant PEC proliferation in bone marrow stroma co-culture (26.5% at 10 microM rising to 66.5% at 40 microM). This was accompanied by changes within the cytokine milieu with a >800% rise in TIMP-2.

CONCLUSION

Zoledronic acid is a potent inhibitor of PEC invasion across bone marrow endothelium and colony formation with the bone marrow stroma, affecting the MMP: TIMP-2 balance to favour MMP inhibition.

Long-term effects of neridronate on human osteoblastic cell cultures

Bisphosphonates (BPs) are widely used in the treatment of a variety of bone-related diseases, particularly where the bone turnover is skewed in favor of osteolysis. The mechanisms by which BPs reduce bone resorption directly acting on osteoclasts are now largely clarified even at molecular level. Researches concerning the BP's effects on osteoblast have instead shown variable results. Many in vitro studies have reported positive effects on osteoblasts proliferation and mineralization for several BPs; however, the observed effects differ, depending on the variety of different model system that has been used.

OBJECTIVES

We have investigated if neridronate, an aminobisphosphonate suitable for pulsatory parenteral administration, could have an effect on human osteoblastic proliferation and differentiation in vitro.

METHODS

We have investigated whether prolonged addition of neridronate (from 10(-3) to 10(-11) M) to different human osteoblasts cultures, obtained from 14 different bone specimens, could affect the cells number, the endogenous cellular alkaline phosphatase (ALKP) activity, and the formation of mineralized nodules.

RESULTS

Our results show that neridronate does not negatively affect in vitro the viability, proliferation, and cellular activity of normal human osteoblasts even after a long period addition of the drug (20 days) at concentrations equal or lower than 10(-5) mol/l (therapeutic dose). In addition, neridronate seems to enhance the differentiation of cultured osteoblasts in mature bone-forming cells. A maximum increase of alkaline phosphatase activity (+50% after 10 days; P < 0.01) and mineralized nodules (+48% after 20 days; P < 0.05) was observed in cultures treated with neridronate 10(-8) M.

CONCLUSIONS

These results encourage the use of neridronate in long-term therapy of demineralizing metabolic bone disorders.

Zoledronic acid induces apoptosis and inhibits adhesion to mineralized matrix in prostate cancer cells via inhibition of protein prenylation

OBJECTIVE

To investigate effects of zoledronic acid on apoptosis and adhesion to mineralized matrix in prostate cancer cells, to quantify these actions, and to elucidate some of the underlying molecular mechanisms, in terms of dependence on caspase activation and involvement of protein prenylation.

MATERIALS AND METHODS

DU145 and PC-3 prostate cancer cell lines were used; cells were treated with zoledronic acid, with or without several other reagents, to investigate its mechanism of action. Apoptosis was detected using a cell-death detection enzyme-linked immunosorbent assay. Adhesion was measured by seeding cells onto mineralized dentine inserts for 24 h, and counting cells after washing.

RESULTS

Apoptosis depended on time and dose; there was significant apoptosis with higher concentrations of zoledronic acid (100 micromol/L) after 24 h of exposure, and in DU145 cells with concentrations as low as 1 micromol/L after 72 h of exposure. The apoptotic effect was diminished by co-treating with a broad-spectrum caspase inhibitor, Z-VAD-FMK. Zoledronic acid at 1 micromol/L also significantly inhibited cell adhesion to the mineralized matrix. The lipid isoprenoid analogue geranylgeraniol reduced the apoptotic and anti-adhesive effects of zoledronic acid to a greater degree than farnesol. There was also apoptosis and inhibition of adhesion with direct inhibitors of prenylation, e.g. manumycin A and GGTI-298. C3 exoenzyme, an inhibitor of RhoA, inhibited adhesion but did not cause apoptosis.

CONCLUSION

Zoledronic acid induces apoptosis in prostate cancer cells via a caspase-dependent mechanism, and at concentrations as low as 1 micromol/L it also inhibits adhesion of cells to mineralized matrix. These effects appear to be exerted via inhibiting G-protein prenylation and in particular geranylgeranylation.

The nitrogen-containing bisphosphonate, zoledronic acid, influences RANKL expression in human osteoblast-like cells by activating TNF-alpha converting enzyme (TACE)

Bisphosphonates are used to prevent osteoclast-mediated bone loss. Zoledronic acid inhibits osteoclast maturation indirectly by increasing OPG protein secretion and decreasing transmembrane RANKL expression in human osteoblasts. The decreased transmembrane RANKL expression seems to be related to the upregulation of the RANKL sheddase, TACE.

INTRODUCTION

Bisphosphonates (BPs) exhibit high affinity for hydroxyapatite mineral in bone and are used extensively to treat malignancy-associated bone disease and postmenopausal bone loss by inhibiting osteoclast (OC)-mediated bone resorption.

MATERIALS AND METHODS

We examined the effect of the most potent nitrogen-containing BP available, zoledronic acid (ZOL), on the expression of RANKL and osteoprotegerin (OPG), critical factors in the regulation of OC formation and activation, in primary osteoblast (OB)-like cells derived from human bone, using flow cytometry, ELISA, semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), in situ immunofluorescence staining, and Western blotting.

RESULTS

Our studies show that ZOL, while not significantly affecting RANKL or OPG gene expression, markedly increased OPG protein secretion and reduced transmembrane RANKL protein expression in OB-like cells. The reduction in transmembrane RANKL expression was preceded by a marked increase in the expression of the metalloprotease-disintegrin, TNF-alpha converting enzyme (TACE). In addition, the decreased transmembrane expression of RANKL could be partially reversed by a TACE inhibitor, TAPI-2.

CONCLUSIONS

Our studies indicate that ZOL, in addition to its direct effects on mature OCs, may inhibit the recruitment and differentiation of OCs by cleavage of transmembrane RANKL in OB-like cells by upregulating the sheddase, TACE.

New insights into the actions of bisphosphonate zoledronic acid in breast cancer cells by dual RhoA-dependent and -independent effects

Zoledronic acid (ZOL) is a nitrogen-containing bisphosphonate and its use in reducing osteoporosis and cancer-induced osteolysis is increasing. Recent findings indicated that ZOL has a direct effect on cancer cells. In this study, the effect of ZOL was examined on the aggressive MDA-MB-231 breast cancer cell line. ZOL induces an important inhibition of cell invasion at low concentrations (1 microM). This is not explained by modifications of proteases involved in cell invasiveness (matrix metalloproteinases and urokinase-type plasminogen activator), but by a disorganisation of actin cytoskeleton due to RhoA inhibition related to its defective prenylation as it was reversed by geranylgeraniol (GGOH) and mimicked by the Rho selective inhibitor C3 exoenzyme. In addition, ZOL inhibits the chemotactic effect induced by stromal cell-derived factor 1(SDF-1), a chemokine greatly involved in cancer metastasis to bone. This effect is related to both reduction of cell motility induced by RhoA inhibition and to a decreased expression of CXCR-4, the SDF-1 receptor. Finally, ZOL reduces Cox-2 expression and, consequently, the secretion of prostaglandins E2 (PGE2) in a RhoA-independent manner. This inhibition could contribute to bone protection in breast cancers because PGE2 stimulates osteoclast-mediated bone resorption. In summary, new insights in the mechanism of ZOL action on aggressive breast cancer cells are demonstrated and could explain its beneficial action in both the reduction of osteolysis and prevention of metastasis.

Osteogenesis imperfecta: perspectives and opportunities

The last 2 years have seen additions proposed to the very limited armamentarium of treatments for osteogenesis imperfecta. These include the use of bisphosphonates to decrease bone resorption, growth hormone to augment growth and collagen production, and bone marrow transplantation to create chimeras at the level of the collagen production unit in bone. Although there are optimistic proponents for each strategy, the lack of well-controlled studies and the absence of clearly defined objectives for therapy hinder clear assessment.