Aminoalkylbisphosphonates, potent inhibitors of bone resorption, induce a prolonged stimulation of histamine synthesis and increase macrophages, granulocytes, and osteoclasts in vivo

The effectiveness of autologous platelet concentrates in prevention and treatment of medication-related osteonecrosis of the jaws: A systematic review

The systematic review aims to answer the PICOS question: "Are the autologous platelet concentrates (APCs) an effective strategy in prevention and/or treatment of patients at risk of/affected by medication-related osteonecrosis of the jaws (MRONJ)?". A literature search was conducted via PubMed, MEDLINE, EMBASE, and CINAHL (January 2006 - September 2023). 30 articles were included, evaluating preventive (n = 8*) and treatment strategies (n = 23*). The risk of bias and quality of studies were assessed utilising ROB-2, ROBIN-1 and GRADE criteria. Meta-analysis was undertaken for eligible studies. The application of APCs demonstrated a statistically significant effectiveness in prevention of MRONJ in 86.13% (p < 0.001) but failed to achieve the same level of certainty in treatment of established MRONJ in 83.4% (p = 0.08). High levels of bias were identified; thus, the results should be interpreted with caution. More high quality prospective randomised controlled trials are needed to further evaluate the effectiveness of APCs in management of MRONJ.

Nitrogen-containing bisphosphonates and lipopolysaccharide mutually augment inflammation via adenosine triphosphate (ATP)-mediated and interleukin 1β (IL-1β)-mediated production of neutrophil extracellular traps (NETs)

Among the bisphosphonates (BPs), nitrogen-containing BPs (N-BPs) have much stronger anti-bone-resorptive actions than non-N-BPs. However, N-BPs have various side effects such as acute influenza-like reactions after their initial administration and osteonecrosis of the jawbones after repeated administration. The mechanisms underlying such effects remain unclear. To overcome these problems, it is important to profile the inflammatory nature of N-BPs. Here, we analyzed the inflammatory reactions induced in mouse ear pinnae by the N-BPs alendronate (Ale) and zoledronate (Zol). We found the following: (i) Ale and Zol each induced two phases of inflammation (early weak and late strong ear swelling); (ii) both phases were augmented by lipopolysaccharides (LPSs; cell-surface constituent of gram-negative bacteria, including oral bacteria), but prevented by inhibitors of the phosphate transporters of solute carrier 20/34 (SLC20/SLC34); (iii) macrophages and neutrophils were involved in both phases of Ale+LPS-induced ear-swelling; (iv) Ale increased or tended to increase various cytokines, and LPS augmented these effects, especially that on interleukin 1β (IL-1β); (v) adenosine triphosphate (ATP) was involved in both phases, and Ale alone or Ale+LPS increased ATP in ear pinnae; (vi) the augmented late-phase swelling induced by Ale+LPS depended on both IL-1 and neutrophil extracellular traps (NETs; neutrophil-derived net-like complexes); (vii) neutrophils, together with macrophages and dendritic cells, also functioned as IL-1β-producing cells, and upon stimulation with IL-1β, neutrophils produced NETs; (viii) stimulation of the purinergic 2X7 (P2X7) receptors by ATP induced IL-1β in ear pinnae; (ix) NET formation by Ale+LPS was confirmed in gingiva, too. These results suggest that (i) N-BPs induce both early-phase and late-phase inflammation via ATP-production and P2X7 receptor stimulation; (ii) N-BPs and LPS induce mutually augmenting responses both early and late phases via ATP-mediated IL-1β production by neutrophils, macrophages, and/or dendritic cells; and (iii) NET production by IL-1β-stimulated neutrophils may mediate the late phase, leading to prolonged inflammation. These results are discussed in relation to the side effects seen in patients treated with N-BPs. © 2021 American Society for Bone and Mineral Research (ASBMR).

Effect of nitrogen-containing bisphosphonates on osteoclasts and osteoclastogenesis: an ultrastructural study

We have previously indicated that a single injection of alendronate, one of the nitrogen-containing bisphosphonates (NBPs), affects murine hematopoietic processes, such as the shift of erythropoiesis from bone marrow (BM) to spleen, disappearance of BM-resident macrophages, the increase of granulopoiesis in BM and an increase in the number of osteoclasts. NBPs induce apoptosis and the formation of giant osteoclasts in vitro and/or in patients undergoing long-term NBP treatment. Therefore, the time-kinetic effect of NBPs on osteoclasts needs to be clarified. In this study, we examined the effect of alendronate on mouse osteoclasts and osteoclastogenesis. One day after the treatment, osteoclasts lost the clear zone and ruffled borders, and the cell size decreased. After 2 days, the cytoplasm of osteoclasts became electron dense and the nuclei became pyknotic. Some of the cells had fragmented nuclei. After 4 days, osteoclasts had euchromatic nuclei attached to the bone surface. Osteoclasts had no clear zones or ruffled borders. After 7 days, osteoclasts formed giant osteoclasts via the fusion of multinuclear and mononuclear osteoclasts. These results indicate that NBPs affect osteoclasts and osteoclastogenesis via two different mechanisms.

The Case of Medication-Related Osteonecrosis of the Jaw Addressed from a Pathogenic Point of View. Innovative Therapeutic Strategies: Focus on the Most Recent Discoveries on Oral Mesenchymal Stem Cell-Derived Exosomes

Bisphosphonates-related osteonecrosis of the jaw (BRONJ) was firstly reported by Marx in 2003. Since 2014, the term medication-related osteonecrosis of the jaw (MRONJ) is recommended by the American Association of Oral and Maxillofacial Surgeons (AAOMS). Development of MRONJ has been associated to the assumption of bisphosphonates but many MRONJ-promoting factors have been identified. A strong involvement of immunity components has been suggested. Therapeutic intervention includes surgical and non-surgical treatments, as well as regenerative medicine procedures for the replacement of the lost tissues. The literature confirms that the combination of mesenchymal stem cells (MSCs), biomaterials and local biomolecules can support the regeneration/repair of different structures. In this review, we report the major open topics in the pathogenesis of MRONJ. Then, we introduce the oral tissues recognized as sources of MSCs, summing up in functional terms what is known about the exosomes release in physiological and pathological conditions.

Extensive protein expression changes induced by pamidronate in RAW 264.7 cells as determined by IP-HPLC

Background

Bisphosphonate therapy has become a popular treatment for osteoporosis, Paget’s disease, multiple myeloma, osteogenesis imperfecta, myocardial infarction, and cancer despite its serious side effects. Bisphosphonate-induced molecular signaling changes in cells are still not clearly elucidated.

Methods

As bisphosphonates are primarily engulfed by macrophages, we treated RAW 264.7 cells (a murine macrophage cell line) with pamidronate and investigated global protein expressional changes in cells by immunoprecipitation high performance liquid chromatography (IP-HPLC) using 218 antisera.

Results

Pamidronate upregulated proliferation-activating proteins associated with p53/Rb/E2F and Wnt/β-catenin pathways, but downregulated the downstream of RAS signaling, pAKT1/2/3, ERK-1, and p-ERK-1, and subsequently suppressed cMyc/MAX/MAD network. However, in situ proliferation index of pamidronate-treated RAW264.7 cells was slightly increased by 3.2% vs. non-treated controls. Pamidronate-treated cells showed increase in the expressions of histone- and DNA methylation-related proteins but decrease of protein translation-related proteins. NFkB signaling was also suppressed as indicated by the down-regulations of p38 and p-p38 and the up-regulation of mTOR, while the protein expressions related to cellular protection, HSP-70, NRF2, JNK-1, and LC3 were upregulated. Consequently, pamidronate downregulated the protein expressions related to immediate inflammation,cellular differentiation, survival, angiogenesis, and osteoclastogenesis, but upregulated PARP-1 and FAS-mediated apoptosis proteins. These observations suggest pamidronate affects global protein expressions in RAW 264.7 cells by stimulating cellular proliferation, protection, and apoptosis but suppressing immediate inflammation, differentiation, osteoclastogenesis, and angiogenesis. Accordingly, pamidronate appears to affect macrophages in several ways eliciting not only its therapeutic effects but also atypical epigenetic modification, protein translation, RAS and NFkB signalings. Therefore, our observations suggest pamidronate-induced protein expressions are dynamic, and the affected proteins should be monitored by IP-HPLC to achieve the therapeutic goals during treatment.

[Basic Studies on the Mechanism, Prevention, and Treatment of Osteonecrosis of the Jaw Induced by Bisphosphonates]

Since the first report in 2003, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been increasing, without effective clinical strategies. Osteoporosis is common in elderly women, and bisphosphonates (BPs) are typical and widely used anti-osteoporotic or anti-bone-resorptive drugs. BRONJ is now a serious concern in dentistry. As BPs are pyrophosphate analogues and bind strongly to bone hydroxyapatite, and the P-C-P structure of BPs is non-hydrolysable, they accumulate in bones upon repeated administration. During bone-resorption, BPs are taken into osteoclasts and exhibit cytotoxicity, producing a long-lasting anti-bone-resorptive effect. BPs are divided into nitrogen-containing BPs (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). N-BPs have far stronger anti-bone-resorptive effects than non-N-BPs, and BRONJ is caused by N-BPs. Our murine experiments have revealed the following. N-BPs, but not non-N-BPs, exhibit direct and potent inflammatory/necrotic effects on soft-tissues. These effects are augmented by lipopolysaccharide (the inflammatory component of bacterial cell-walls) and the accumulation of N-BPs in jawbones is augmented by inflammation. N-BPs are taken into soft-tissue cells via phosphate-transporters, while the non-N-BPs etidronate and clodronate inhibit this transportation. Etidronate, but not clodronate, has the effect of expelling N-BPs that have accumulated in bones. Moreover, etidronate and clodronate each have an analgesic effect, while clodronate has an anti-inflammatory effect via inhibition of phosphate-transporters. These findings suggest that BRONJ may be induced by phosphate-transporter-mediated and infection-promoted mechanisms, and that etidronate and clodronate may be useful for preventing and treating BRONJ. Our clinical trials support etidronate being useful for treating BRONJ, although additional clinical trials of etidronate and clodronate are needed.

Augmentation of Lipopolysaccharide-Induced Production of IL-1α and IL-1β in Mice Given Intravenous Zoledronate (a Nitrogen-Containing Bisphosphonate) and Its Prevention by Clodronate (a Non-nitrogen-containing Bisphosphonate)

Bisphosphonates (BPs) bind strongly to bone and exhibit long-acting anti-bone-resorptive effects. Among BPs, nitrogen-containing BPs (N-BPs) have far stronger anti-bone-resorptive effects than non-N-BPs. However, N-BPs induce acute inflammatory reactions (fever, arthralgia and myalgia, etc.) after their first injection. The mechanisms underlying these side effects remain unclear. Zoledronate (one of the most potent N-BPs) is given intravenously to patients, and the side-effect incidence is reportedly the highest among N-BPs. Our murine experiments have clarified that (a) intraperitoneally injected N-BPs induce various inflammatory reactions, including a production of interleukin-1 (IL-1) (a typical inflammatory cytokine), and these inflammatory reactions are weak in IL-1-deficient mice, (b) subcutaneously injected N-BPs induce inflammation/necrosis at the injection site, (c) lipopolysaccharide (LPS; a cell-wall component of Gram-negative bacteria) and N-BPs mutually augment their inflammatory/necrotic effects, (d) the non-N-BP clodronate can reduce N-BPs' inflammatory/necrotic effects. However, there are few animal studies on the side effects of intravenously injected N-BPs. Here, we found in mice that (i) intravenous zoledronate exhibited weaker inflammatory effects than intraperitoneal zoledronate, (ii) in mice given intravenous zoledronate, LPS-induced production of IL-1α and IL-1β was augmented in various tissues, including bone, resulting in them increasing in serum, and (iii) clodronate (given together with zoledronate) prevented such augmentation and enhanced, slightly but significantly, zoledronate's anti-bone-resorptive effect. These results suggest that infection may be a factor promoting the acute inflammatory side effects of N-BPs via augmented production of IL-1 in various tissues (including bone), and that clodronate may be useful to reduce or prevent such side effects.

Underlying Mechanisms and Therapeutic Strategies for Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ)

Bisphosphonates (BPs), with a non-hydrolysable P-C-P structure, are cytotoxic analogues of pyrophosphate, bind strongly to bone, are taken into osteoclasts during bone-resorption and exhibit long-acting anti-bone-resorptive effects. Among the BPs, nitrogen-containing BPs (N-BPs) have far stronger anti-bone-resorptive effects than non-N-BPs. In addition to their pyrogenic and digestive-organ-injuring side effects, BP-related osteonecrosis of jaws (BRONJ), mostly caused by N-BPs, has been a serious concern since 2003. The mechanism underlying BRONJ has proved difficult to unravel, and there are no solid strategies for treating and/or preventing BRONJ. Our mouse experiments have yielded the following results. (a) N-BPs, but not non-N-BPs, exhibit direct inflammatory and/or necrotic effects on soft tissues. (b) These effects are augmented by lipopolysaccharide, a bacterial-cell-wall component. (c) N-BPs are transported into cells via phosphate transporters. (d) The non-N-BPs etidronate (Eti) and clodronate (Clo) competitively inhibit this transportation (potencies, Clo>Eti) and reduce and/or prevent the N-BP-induced inflammation and/or necrosis. (e) Eti, but not Clo, can expel N-BPs that have accumulated within bones. (f) Eti and Clo each have an analgesic effect (potencies, Clo>Eti) via inhibition of phosphate transporters involved in pain transmission. From these findings, we propose that phosphate-transporter-mediated and inflammation/infection-promoted mechanisms underlie BRONJ. To treat and/or prevent BRONJ, we propose (i) Eti as a substitution drug for N-BPs and (ii) Clo as a combination drug with N-BPs while retaining their anti-bone-resorptive effects. Our clinical trials support this role for Eti (we cannot perform such trials using Clo because Clo is not clinically approved in Japan).

A Strategy against the Osteonecrosis of the Jaw Associated with Nitrogen-Containing Bisphosphonates (N-BPs): Attempts to Replace N-BPs with the Non-N-BP Etidronate

Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) can occur when enhanced bone-resorptive diseases are treated with nitrogen-containing BPs (N-BPs). Having previously found, in mice, that the non-N-BP etidronate can (i) reduce the inflammatory/necrotic effects of N-BPs by inhibiting their intracellular entry and (ii) antagonize the binding of N-BPs to bone hydroxyapatite, we hypothesized that etidronate-replacement therapy (Eti-RT) might be useful for patients with, or at risk of, BRONJ. In the present study we examined this hypothesis. In each of 25 patients receiving N-BP treatment, the N-BP was discontinued when BRONJ was suspected and/or diagnosed. After consultation with the physician-in-charge and with the patient's informed consent, Eti-RT was instituted in one group according to its standard oral prescription. We retrospectively compared this Eti-RT group (11 patients) with a non-Eti-RT group (14 patients). The Eti-RT group (6 oral N-BP patients and 5 intravenous N-BP patients) and the non-Eti-RT group (5 oral N-BP patients and 9 intravenous N-BP patients) were all stage 2-3 BRONJ. Both in oral and intravenous N-BP patients (particularly in the former patients), Eti-RT promoted or tended to promote the separation and removal of sequestra and thereby promoted the recovery of soft-tissues, allowing them to cover the exposed jawbone. These results suggest that Eti-RT may be an effective choice for BRONJ caused by either oral or intravenous N-BPs and for BRONJ prevention, while retaining a level of anti-bone-resorption. Eti-RT may also be effective at preventing BRONJ in N-BP-treated patients at risk of BRONJ. However, prospective trials are still required.

Inhibition of phosphate transporters ameliorates the inflammatory and necrotic side effects of the nitrogen-containing bisphosphonate zoledronate in mice

Bisphosphonates (BPs) are pyrophosphate analogs. They are widely used against enhanced bone-resorption in various diseases. Nitrogen-containing BPs (N-BPs) exhibit strong anti-bone-resorptive effects but have inflammatory and necrotic side effects. The non-nitrogen-containing BPs (non-N-BPs) etidronate and clodronate lack such side effects, but their anti-bone-resorptive effects are weak. In mice, etidronate and clodronate reduce the inflammatory/necrotic effects of N-BPs, even those of zoledronate, the N-BP with the strongest anti-bone-resorptive effect yet reported and the highest risk of inflammation/necrosis. Here, to explore the mechanisms underlying this protection, we used a mouse model in which a single reagent or a mixture of two reagents was injected subcutaneously into ear-pinnas. These reagents included zoledronate, four non-N-BPs, pyrophosphate, and inhibitors of various organic-anion-transporters. Pyrophosphate and two of the four non-N-BPs (not etidronate or clodronate) had inflammatory/necrotic effects. These effects were reduced by etidronate and clodronate, but not by phosphonoformate, an inhibitor of two of the three known phosphate-transporter families. Phosphonoformate reduced the inflammatory/necrotic effects of zoledronate, but not those of pyrophosphate or of non-N-BPs. Conversely, pyrophosphate, at non-inflammatory/necrotic concentrations, reduced the inflammatory/necrotic effects of non-N-BPs, but not those of zoledronate. The efficacies of the protective effects against the inflammatory/necrotic effects of zoledronate were clodronate > etidronate > phosphonoformate. These findings suggest that (i) the N-BP zoledronate may enter soft-tissue cells via phosphonoformate-inhibitable phosphate-transporters, (ii) other phosphate-transporters may carry pyrophosphate and inflammatory/necrotic non-N-BPs into such cells, and (iii) etidronate and clodronate inhibit all these transporters, and they ameliorate the side effects of zoledronate by inhibiting phosphonoformate-inhibitable phosphate-transporters.

Analgesic effects of the non-nitrogen-containing bisphosphonates etidronate and clodronate, independent of anti-resorptive effects on bone

Nitrogen-containing bisphosphonates (NBPs) have greater anti-bone-resorptive effects than non-nitrogen-containing bisphosphonates (non-NBPs). Hence, NBPs are the current first-choice drug for osteoporosis. However, NBPs carry a risk of osteonecrosis of jaws. Some animal and human studies suggest that non-NBPs may have anti-bone-resorptive effect-independent analgesic effects, but there has been no detailed comparison between NBPs and non-NBPs. Here, we compared the analgesic effects of several non-NBPs and NBPs, using (a) writhing responses induced in mice by intraperitoneal injection of 1% acetic acid, (b) acetic acid-induced neuronal expression of c-Fos, (c) acetic acid-induced elevation of blood corticosterone, and (d) hindpaw-licking/biting responses induced by intraplantar injection of capsaicin. Among the NBPs and non-NBPs tested, only etidronate and clodronate displayed clear analgesic effects, with various routes of administration (including the oral one) being effective. However, they were ineffective when intraperitoneally injected simultaneously with acetic acid. Intracerebroventricular administration of etidronate or clodronate, but not of minodronate (an NBP), was also effective. The effective doses of etidronate and clodronate were much lower in writhing-high-responder strains of mice. Etidronate and clodronate reduced acetic acid-induced c-Fos expression in the brain and spinal cord, and also the acetic acid-induced corticosterone increase in the blood. Etidronate and clodronate each displayed an analgesic effect in the capsaicin test. Etidronate and clodronate displayed their analgesic effects at doses lower than those inducing anti-bone-resorptive effects. These results suggest that etidronate and clodronate exert potent, anti-bone-resorptive effect-independent analgesic effects, possibly via an interaction with neurons, and that they warrant reappraisal as safe drugs for osteoporosis.

Influence of bisphosphonate treatment on medullary macrophages and osteoclasts: an experimental study

Nitrogen-containing bisphosphonates are widely used for treating diverse bone pathologies. They are anticatabolic drugs that act on osteoclasts inhibiting bone resorption. It remains unknown whether the mechanism of action is by decreasing osteoclast number, impairing osteoclast function, or whether they continue to effectively inhibit bone resorption despite the increase in osteoclast number. There is increasing evidence that bisphosphonates also act on bone marrow cells like macrophages and monocytes. The present work sought to evaluate the dynamics of preosteoclast fusion and possible changes in medullary macrophage number in bisphosphonate-treated animals. Healthy female Wistar rats received olpadronate, alendronate, or vehicle during 5 weeks, and 5-bromo-2-deoxyuridine (BrdU) on day 7, 28, or 34 of the experiment. Histomorphometric studies were performed to study femurs and evaluate: number of nuclei per osteoclast (N.Nu/Oc); number of BrdU-positive nuclei (N.Nu BrdU+/Oc); percentage of BrdU-positive nuclei per osteoclast (%Nu.BrdU+/Oc); medullary macrophage number (mac/mm²) and correlation between N.Nu/Oc and mac/mm². Results showed bisphosphonate-treated animals exhibited increased N.Nu/Oc, caused by an increase in preosteoclast fusion rate and evidenced by higher N.Nu BrdU+/Oc, and significantly decreased mac/mm². Considering the common origin of osteoclasts and macrophages, the increased demand for precursors of the osteoclast lineage may occur at the expense of macrophage lineage precursors.

Nickel allergy-promoting effects of microbial or inflammatory substances at the sensitization step in mice

Microbial components stimulate innate immunity via Toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), and/or IL-1. We recently reported that in mice, Escherichia coli lipopolysaccharide (LPS, TLR4-ligand) promotes allergic responses to nickel (Ni) at both the sensitization and elicitation steps. Here, we examined in mice the effects of administering other microbial or inflammatory materials at the Ni-sensitization step. A mixture of 1mM NiCl(2) and a test solution was injected into BALB/c mice intraperitoneally (0.1 ml/10 g body weight), and 10 days later 5mM NiCl(2) was challenged intradermally into the ear pinnas of the mice (20 μl/ear). The following preparations or substances exhibited adjuvant activities: Prevotella intermedia LPS, Saccharomyces cerevisiae mannan, a synthetic muramyl dipeptide (NOD2-stimulating cell-wall component of bacteria), Pam(3)Cys-SKKKK (TLR2-stimulating synthetic peptide), poly I:C (TLR3-stimulating double-stranded RNA), concanavalin A (a typical T-cell mitogen and T-cell-mediated hepatitis-inducer), heat-killed Propionibacterium acnes (Gram-positive bacterium that causes pimples and induces macrophage-mediated experimental hepatitis), and nitrogen-containing bisphosphonates (chemicals stimulating IL-1 production). Unexpectedly, P. intermedia LPS, which displayed the most potent adjuvant activity among the tested preparations, was effective in TLR4-dysfunctional mutant mice, but not in TLR2-deficient mice, whereas the reverse was true for S. cerevisiae mannan. These results suggest that (i) for the establishment of Ni-allergy in mice, stimulation of innate immunity (including TLRs, NLRs, IL-1 production, and/or other factors) may be important at the sensitization step, and (ii) P. intermedia may produce a substance(s) that potently promotes Ni-allergy via stimulation of TLR2.

Inhibition of necrotic actions of nitrogen-containing bisphosphonates (NBPs) and their elimination from bone by etidronate (a non-NBP): a proposal for possible utilization of etidronate as a substitution drug for NBPs

PURPOSE

Nitrogen-containing bisphosphonates (NBPs) have powerful anti-bone-resorptive effects (ABREs). However, recent clinical applications have disclosed an unexpected side effect, osteonecrosis of the jaw. We previously found in mice that etidronate (a non-NBP), when coadministered with alendronate (an NBP), inhibited the latter's inflammatory effects. However, etidronate also reduced the ABRE of alendronate. The present study examined in mice the modulating effects of etidronate on the inflammatory and necrotic actions of zoledronate (the NBP with the strongest anti-bone-resorptive activity and the highest incidence of osteonecrosis of the jaw) and on ABREs of various NBPs including zoledronate.

MATERIALS AND METHODS

NBPs were subcutaneously injected into ear pinnas of mice and ensuing inflammation and necrosis at the site of the injection were evaluated. ABREs of NBPs were evaluated by analyzing sclerotic bands induced in mouse tibias.

RESULTS

Coinjection of etidronate reduced inflammatory and necrotic reactions induced by zoledronate, and also reduced the amount of zoledronate retained within the ear tissue. When both agents were intraperitoneally injected, etidronate reduced the ABRE of zoledronate and those of other NBPs. Notably, etidronate reduced the ABRE of zoledronate even when this non-NBP was injected 16 hours after the injection of zoledronate. Bone scintigram indicated that etidronate reduced the amount of zoledronate that had already bound to bone.

CONCLUSIONS

These results suggest that etidronate may 1) inhibit the entry of NBPs into cells related to inflammation and/or necrosis, 2) inhibit the binding of NBPs to bone hydroxyapatite, 3) at least partly eliminate (or substitute for) NBPs that have already accumulated within bones, and thus 4) if used as a substitution drug for NBPs, be effective at treating or preventing NBP-associated osteonecrosis of the jaw.

Bisphosphonate-associated osteonecrosis of the jaw: a key role of inflammation?

Osteonecrosis of the jaw (ONJ) can be associated with nitrogen-containing bisphosphonates (NBPs) therapy. Various mechanisms of NBP-associated ONJ have been proposed and there is currently no consensus of the underlying pathogenesis. The detailed medical and dental histories of 30 ONJ patients treated with NBPs for malignant diseases (24) or osteoporosis (6) were analyzed. The necrotic bone was resected and analyzed histologically after demineralization. In 10 patients the perinecrotic bone was also resected and processed without demineralization. Alveolar bone samples from 5 healthy patients were used as controls. In 14 ONJ patients, serial technetium-99m-methylene diphosphonate scintigraphic scans were also available and confronted to the other data. Strong radionuclide uptake was detected in some patients several months before clinical diagnosis of ONJ. The medullary spaces of the necrotic bone were filled with bacterial aggregates. In the perinecrotic bone, the bacteria-free bone marrow characteristically showed an inflammatory reaction. The number of medullary inflammatory cells taken as an index of inflammation allowed us to discriminate two inflammation grades in the ONJ samples. Low-grade inflammation, characterized by marrow fibrosis and low inflammatory cells infiltration, increased numbers of TRAP(+) mono- and multineacleated cells was seen in patients with bone exposure<2 cm(2). High-grade inflammation, associated with larger lesions, showed amounts of tartrate-resistant acid phosphatase(+)/calcitonin receptor(-) mono- and multinucleated cells, osteocyte apoptosis, hypervascularization and high inflammatory cell infiltration. The clinical extent of ONJ was statistically linked to the numbers of inflammatory cell. Taken together these data suggest that bone necrosis precedes clinical onset and is an inflammation-associated process. We hypothesize that from an initial focus, bone damage spreads centrifugally, both deeper into the jaw and towards the mucosa before the oral bone exposure and the clinical diagnosis of ONJ.

Bisphosphonate-related osteonecrosis of the jaw around dental implants in the maxilla: report of a case

OBJECTIVE

We describe a patient who developed bisphosphonate (BP)-related osteonecrosis of the jaw (ONJ) around implants in the upper molar area.

PATIENTS AND METHODS

The patient was a 54-year-old woman with ulceration of the gum, bone exposure, and severe spontaneous pain around implants in the upper left molar area. She had received BPs intravenously for 2 years to treat bone metastases of breast cancer. She was diagnosed with BP-related ONJ. Sequestrum including implants was resected, and hyperbaric oxygen therapy was performed. Undecalcified ground sections were prepared from the resected bone around the implants and stained with toluidine blue. For the bone around the lesion, decalcified sections were prepared, and examined by histological and immunohistological analysis.

RESULTS

The surgical wound became completely covered with mucosal epithelia, and postoperative pain disappeared. No recurrence of ONJ was noted during a 6-month postoperative follow-up period. However, the patient died from metastatic disease. Although histopathological examination of the resected jaw bone revealed sequestrum, osseointegration of the implant was maintained. In the area around the lesion, there was no progression of bone necrosis, and reactive bone formation, fibrosis, and invasion of lymphoid cells into the marrow cavity were observed.

CONCLUSION

There is no effective treatment for ONJ caused by BPs, and conservative therapy based on clinicians' experience is recommended. However, if chemotherapy is planned, or if bone necrosis around implants is thought to harbor infection, the option of jaw resection should be considered.

Necrotic actions of nitrogen-containing bisphosphonates and their inhibition by clodronate, a non-nitrogen-containing bisphosphonate in mice: potential for utilization of clodronate as a combination drug with a nitrogen-containing bisphosphonate

Nitrogen-containing bisphosphonates (NBPs) exhibit powerful anti-bone-resorptive effects (ABREs) via inhibition of farnesyl pyrophosphate synthase during cholesterol biosynthesis. Clinical applications have disclosed an unexpected side effect, namely osteonecrosis of jaw bones, and although thousands of cases have been documented in the last few years the mechanism remains unclear. Since NBPs accumulate in bone-hydroxyapatite, more jaw bone osteonecrosis cases may come to light if NBPs continue to be used as they are being used now. We have previously reported that in mice, systemic (intraperitoneal) injection of clodronate (a non-NBP) prevents the inflammatory effects of NBPs. Here, we examined in mice the local necrotic actions of various NBPs and the anti-necrotic effects of clodronate. A single subcutaneous injection of an NBP into the ear pinna induced necrosis at the injection site (relative potencies of necrotic actions of NBPs: zoledronate >> pamidronate > or = alendronate > risedronate), while non-NBPs lacked this effect. Clodronate, when injected together with an NBP, reduced or prevented the necrosis induced by that NBP, but not its ABRE. Clodronate reduced the amount of each NBP retained within tissues. These results, together with those of previous studies, suggest that (i) clodronate inhibits the inflammatory and necrotic actions of NBPs by inhibiting their incorporation into cells related to inflammation and/or necrosis, (ii) clodronate could be useful as a combination drug with NBPs for preventing their necrotic actions while retaining their ABREs and (iii) clodronate could also be useful as a substitution drug for NBPs in patients at risk of osteonecrosis of jaw bones.

Alendronate augments interleukin-1beta release from macrophages infected with periodontal pathogenic bacteria through activation of caspase-1

Nitrogen-containing bisphosphonates (NBPs) are anti-bone-resorptive drugs with inflammatory side effects that include osteomyelitis and osteonecrosis of the jaw. Oral bacteria have been considered to be a trigger for these NBP-associated jaw bone diseases. The present study examined the effects of alendronate (a typical NBP) and clodronate (a non-NBP) on the production of proinflammatory cytokines by macrophages infected with Porphyromonas gingivalis and Tannerella forsythia, which are important pathogens of periodontal diseases. Pretreatment with alendronate augmented IL-1beta, but not TNFalpha, production by macrophages infected with P. gingivalis or T. forsythia. This augmentation of IL-1beta production was inhibited by clodronate. Furthermore, caspase-1, a promoter of IL-1beta production, was activated by treatment with alendronate, and caspase-1 inhibitor reduced the production of IL-1beta induced by alendronate and P. gingivalis. These results suggest that NBPs augment periodontal pathogenic bacteria-induced IL-1beta release via caspase-1 activation, and this phenomenon may contribute to the development of NBP-associated inflammatory side effects including jaw osteomyelitis. Co-treatment with clodronate may prevent and/or reduce these inflammatory effects induced by NBPs.

Bone resorption inhibitor alendronate normalizes the reduced bone thickness of TRPV5(-/-) mice

TRPV5 is a Ca(2+)-selective channel involved in transcellular Ca(2+) absorption expressed in kidney and in the ruffled border of osteoclasts. Studies in hypercalciuric TRPV5 knockout (TRPV5(-/-)) mice, which display significantly increased vitamin D levels, showed that TRPV5 ablation increases number and size of osteoclasts but impairs osteoclast-mediated bone resorption. The latter is not in line with the observed decreased bone thickness in TRPV5(-/-) mice. Bisphosphonates also inhibit osteoclast-mediated bone resorption. The aim of this study was to evaluate the effect of alendronate on the expression of the Ca(2+) transporters in bone, kidney, and duodenum and, importantly, the bone phenotype in TRPV5(-/-) mice. Wildtype (TRPV5(+/+)) and TRPV5(-/-) mice were treated during 10 wk with 2 mg/kg alendronate or vehicle weekly and housed in metabolic cages at the end of treatment. Urine and blood samples were taken for biochemical analysis, and duodenum, kidney, and femur were sampled. Expression of Ca(2+) transporters and osteoclast ruffled border transporters in bone and cultured osteoclasts was determined by QPCR analysis. Femurs were scanned using muCT, and resorption pit assays were performed in bone marrow cultures isolated from TRPV5(+/+) and TRPV5(-/-) mice. Alendronate treatment enhanced bone thickness in TRPV5(+/+) mice but also normalized the disturbed bone morphometry parameters in TRPV5(-/-) mice. Bone TRPV5 expression was specifically enhanced by alendronate, whereas the expression of Ca(2+) transporters in kidney and intestine was not altered. The expression of the osteoclast ruffled border membrane proteins chloride channel 7 (CLC-7) and the vacuolar H(+)-ATPase did not differ between both genotypes, but alendronate significantly enhanced the expression and PTH levels in TRPV5(-/-) mice. The expression of TRPV5, CLC-7, and H(+)-ATPase in osteoclast cultures was not affected by alendronate. The number of resorption pits was reduced in TRPV5(-/-) bone marrow cultures, but the response to vitamin D was similar to that in TRPV5(+/+) cultures. The alendronate-induced upregulation of TRPV5 in bone together with the decreased resorptive capacity of TRPV5(-/-) osteoclasts in vitro suggests that TRPV5 has an important role in osteoclast function. However, our data indicate that significant bone resorption still occurs in TRPV5(-/-) mice, because alendronate treatment normalized bone thickness in these mice. Thus, TRPV5(-/-) mice are able to rescue the resulting defect in osteoclast-mediated bone resorption, possibly mediated by the long-term hypervitaminosis D or other (non)hormonal compensatory mechanisms.

Alendronate prevents bone loss and improves tendon-to-bone repair strength in a canine model

Previously we showed a loss of bone and a concomitant decrease in mechanical properties in the first 21 days after flexor tendon insertion site injury and repair in a canine model. The goal of this short-term study was to suppress bone loss after insertion site repair using alendronate in an attempt to prevent the reduction in biomechanical properties. Flexor tendons of the second and fifth digits of the right forelimbs of canines were injured and repaired. Dogs received a daily oral dose of alendronate (2 mg/kg). One digit in each dog also received a local dose of alendronate in the bone tunnel at the time of surgery. The repair was evaluated for bone mineral density (BMD) and biomechanical properties and compared to data from a previous study in which no alendronate was used. Alendronate was effective in protecting the distal phalanx from resorption during tendon-to-bone healing (BMD was 94 and 104% of control for systemic alendronate and for systemic plus local alendronate, respectively). Alendronate treatment prevented much of the decrease in ultimate load that occurs in the first 21 days. Without treatment, ultimate load was 42% of control. With systemic alendronate treatment and systemic plus local alendronate treatment, ultimate load was 78 and 69% of control, respectively. Failure mode was significantly different when comparing alendronate treatment to repair alone. A lower incidence of suture pull through was found in alendronate treated dogs, suggesting less tendon degeneration. Ultimate load can be improved in association with preventing the bone loss that normally occurs during the early period following tendon-to-bone repair. These initial short-term data demonstrate the potential for a clinical treatment that could enhance tendon-to-bone healing.

Histidine decarboxylase-stimulating and inflammatory effects of alendronate in mice: Involvement of mevalonate pathway, TNFα, macrophages, and T-cells

Nitrogen-containing bisphosphonates (NBPs) are powerful anti-bone-resorptive drugs, but they frequently induce various inflammatory side effects. Recent clinical applications have disclosed an unexpected new side effect, jaw-bone necrosis and exposure. In vitro studies suggest that the inflammatory effects of NBPs are due to Vgamma2Vdelta2 T-cells, stimulated directly and/or indirectly [the latter via isopentenylpyrophosphate (IPP) in the mevalonate pathway]. Rats and mice, however, lack Vgamma2Vdelta2 T-cells, yet NBPs still induce necrotic and inflammatory reactions. In mice, NBPs induce IL-1-dependent inflammatory reactions, such as inductions of histidine decarboxylase (HDC, the histamine-forming enzyme) in the liver, lung, spleen, and bone marrow, an increase in granulocytic cells in the peritoneal cavity, pleural exudation, and splenomegaly. Here, we examined the involvement of IPP, TNF, macrophages, and T-cells in the inflammatory actions of alendronate (a typical NBP) in mice. Various statins (mevalonate-synthesis inhibitors) suppressed the alendronate-induced HDC inductions, while mevalonate itself augmented such inductions. IPP injection also induced HDC. Like IL-1-deficient mice, TNF-deficient mice were resistant to alendronate-stimulated HDC induction. Alendronate-stimulated HDC inductions were significantly weaker in macrophage-depleted mice and in nude mice than in control mice. Similar, though generally less clear-cut, results were obtained when other alendronate-induced inflammatory reactions were examined. These results suggest that (i) inhibition of the mevalonate pathway causes and/or modifies at least some inflammatory actions of alendronate in mice, (ii) in addition to IL-1, TNF is also involved in the inflammatory actions of alendronate, and (iii) alendronate may act on a variety of cells, including macrophages and T-cells.

Extra-skeletal effects of bisphosphonates

Bisphosphonates are pharmacological agents which are currently used both in osteoporosis than in other pathological conditions characterised by an increased bone resorption, such as Paget's disease of bone, malign hypocalcaemia during myeloma, osteolytic bone metastasis and fibrous dysplasia of bone. The most important biological effect of bisphosphonates is the reduction of bone remodelling through the inhibition of osteoclastic activity, but there are many clinical and experimental evidences of extra-skeletal biological effects of bisphosphonates. It has been shown that bisphosphonates exert their effects not only on bone tissue cells, but also on those of the immune system with an "immuno-modulating" effect, influencing the production of pro- and anti-inflammatory cytokines and changing the molecular expression involved in the immune processes and anti-inflammatory response. Although the available data are conflicting, there are several reports concerning the beneficial effects of bisphosphonates in controlling the progression of chronic joint inflammatory diseases, suggesting a wider use for these therapeutic agents in clinical practice.

Comparative appraisal of clodronate, aspirin and dexamethasone as agents reducing alendronate-induced inflammation in a murine model

Among the bisphosphonates, the nitrogen-containing bisphosphonates have much stronger anti-bone-resorptive activities than bisphosphonates containing no nitrogen, but nitrogen-containing bisphosphonates mostly have inflammatory side effects. Our previous murine-model experiments with a single intraperitoneal bisphosphonate injection demonstrated that (i) nitrogen-containing bisphosphonates induce various inflammatory reactions via an IL-1-dependent mechanism, (ii) alendronate (an nitrogen-containing bisphosphonate) produces a clear sclerotic line in the tibia that is easily detectable by radiography a few weeks later (tentatively called the bisphosphonate line, a useful marker for the anti-bone-resorptive activities of bisphosphonates), and (iii) clodronate (a non-nitrogen-containing bisphosphonate) reduces the inflammatory reactions induced by alendronate but does not reduce the bisphosphonate line formation induced by alendronate. We compared the effects of clodronate, aspirin and dexamethasone on the inflammatory reactions induced by alendronate (40 micromol/kg) (induction of the histamine-forming enzyme, accumulation of pleural exudate and splenomegaly) and on the bisphosphonate line formation induced by alendronate (0.1 micromol/kg). The effects of aspirin (833 micromol/kg) were weak. However, like clodronate, dexamethasone (10 micromol/kg, injected 5 min. after alendronate), strongly inhibited the alendronate-induced inflammatory reactions but did not reduce the alendronate-induced bisphosphonate line formation. Alendronate produced normal bisphosphonate lines in IL-1-deficient mice, too. These results suggest that clodronate and/or dexamethasone may be suitable for preventing or reducing the inflammatory side effects of nitrogen-containing bisphosphonates while preserving their powerful anti-bone-resorptive activities (although in practice the known side effects of dexamethasone may limit its use), and that the anti-bone resorptive activities of nitrogen-containing bisphosphonates are not influenced by IL-1.

Effect of Topical Administration of Monosodium Olpadronate on Experimental Periodontitis in Rats

BACKGROUND

Periodontitis is characterized by gingival inflammation, periodontal pocket formation, and bacterial plaque that lead to alveolar bone destruction. Research studies have recently begun to evaluate the effect of antiresorptive agents using experimental models of periodontitis. Bisphosphonates are the most frequently tested antiresorptive agents; their main effect is inhibition of bone resorption. The aim of this study was to perform a histomorphometric evaluation of the preventive effect of monosodium olpadronate (OPD), an aminobisphosphonate, on experimental periodontitis (EP).

METHODS

Twenty male Wistar rats were used in this experiment. The animals were assigned to one of two groups: group I: EP; and group II: EP plus topical administration of OPD (EP + OPD). The contralateral side in both groups served as untreated controls (CI and CII), respectively. Mesio-distally oriented sections of each lower first molar were obtained for histomorphometric evaluation.

RESULTS

The treated group (EP + OPD) exhibited marked inhibition of bone loss; interradicular bone volume was significantly greater than that observed in the EP group. The height of the periodontal ligament in the interradicular alveolar bone, which served as an indirect measure of bone loss, was found to be significantly increased in the EP group as compared to the EP + OPD group. Osteoclasts in the OPD treated group were detached from the bone surface, were round in shape, and exhibited a loss of polarity and lack of ruffled borders.

CONCLUSIONS

The dose used herein was found to inhibit bone loss and to cause marked morphologic changes in osteoclasts. The drug effectively prevented bone loss caused by periodontitis.

Mutual augmentation of the induction of the histamine-forming enzyme, histidine decarboxylase, between alendronate and immuno-stimulants (IL-1, TNF, and LPS), and its prevention by clodronate

Nitrogen-containing bisphosphonates (N-BPs), powerful anti-bone-resorptive drugs, have inflammatory side effects, while histamine is not only an inflammatory mediator, but also an immuno-modifier. In murine models, a single intraperitoneal injection of an N-BP induces various inflammatory reactions, including the induction of the histamine-forming enzyme histidine decarboxylase (HDC) in tissues important in immune responses (such as liver, lungs, spleen, and bone marrow). Lipopolysaccharide (LPS) and the proinflammatory cytokines IL-1 and TNF are also capable of inducing HDC. We reported previously that in mice, (i) the inflammatory actions of N-BPs depend on IL-1, (ii) N-BP pretreatment augments both LPS-stimulated IL-1 production and HDC induction, and (iii) the co-administration of clodronate (a non-N-BP) with an N-BP inhibits the latter's inflammatory actions (including HDC induction). Here, we add the new findings that (a) pretreatment with alendronate (a typical N-BP) augments both IL-1- and TNF-induced HDC elevations, (b) LPS pretreatment augments the alendronate-induced HDC elevation, (c) co-administration of clodronate with alendronate abolishes these augmentations, (d) alendronate does not induce HDC in IL-1-deficient mice even if they are pretreated with LPS, and (e) alendronate increases IL-1beta in all tissues tested, but not in the serum. These results suggest that (1) there are mutual augmentations between alendronate and immuno-stimulants (IL-1, TNF, and LPS) in HDC induction, (2) tissue IL-1beta is important in alendronate-stimulated HDC induction, and (3) combination use of clodronate may have the potential to reduce the inflammatory effects of alendronate (we previously found that clodronate, conveniently, does not inhibit the anti-bone-resorptive activity of alendronate).

Inhibition of inflammatory and bone-resorption-inhibitory effects of alendronate by etidronate

Among the bisphosphonates (BPs), the aminobisphosphonates (aminoBPs) have much stronger bone-resorption-inhibitory activities (BRIAs) than nonaminobisphosphonates (nonaminoBPs). However, aminoBPs have inflammatory effects. We previously reported that in mice: (i) all aminoBPs tested (10-40 micromol/kg) induced various inflammatory reactions (including induction of histidine decarboxylase), whereas clodronate (a non-aminoBP) (10-160 micromol/kg) inhibited these reactions; and (ii) a clear sclerotic line (tentatively called the BP line) was detectable in the tibia by radiography a few weeks after a single injection of either alendronate (a typical aminoBP) (1.6 micromol/kg) or clodronate (160 micromol/kg), and this BP-line formation (a marker for the BRIAs of BPs) was not reduced in mice given both alendronate and clodronate. In this study, using this murine model, we compared clodronate, etidronate (another typical non-aminoBP), alendronate, etidronate + alendronate, and clodronate + alendronate in terms of their inflammatory effects and/or BP-line formation. For BP-line formation, 480 micromol/kg etidronate was needed (single injection). At 160 micromol/kg, etidronate inhibited the histidine decarboxylase induction, but not the other inflammatory reactions induced by alendronate. However, etidronate (unlike clodronate) also inhibited alendronate-induced BP-line formation (even at 40 micromol/kg). Etidronate (160 micromol/kg) also inhibited the physicochemical changes in the tibia induced by six, weekly injections of alendronate. Therefore, depending on the dose, etidronate can inhibit alendronate's inflammatory actions and its BRIA. These results, together with those reported previously, suggest that a strategy utilizing clodronate (but not etidronate) plus an aminoBP might prevent or reduce the inflammatory side effects induced by aminoBPs while preserving their powerful BRIAs. We discuss the mechanisms underlying the antagonism between aminoBPs and non-aminoBPs.

Histamine participates in the early phase of trabecular bone loss in ovariectomized rats

We have previously reported that cimetidine, a reference H2 receptor antagonist, attenuates the initial osteoclastic burst and subsequent trabecular bone loss induced by ovariectomy (ovx) in rats. This study was designed to determine whether these effects are specific to H2 antagonism. To this end, we compared the effects of two H2 receptor antagonists, cimetidine and famotidine. In addition, we analyzed the response of histamine-producing cells to these inhibitors. Seventy-two 90-day-old female Sprague-Dawley rats were ovariectomized or sham-operated, and received single daily intramuscular injections of cimetidine (125 mg/kg), famotidine (10 mg/kg), or vehicle. The animals were killed 14 days after surgery and their femurs were processed for histomorphometry. Trabecular bone volume was reduced by 30% in ovx rats and by 15% in cimetidine- and famotidine-treated rats. Architectural parameters were reduced by about 20% in ovx rats. Cimetidine and famotidine attenuated these consequences of ovx by about 50%. Trabecular connectivity was deteriorated by ovx, while cimetidine and famotidine attenuated this effect. Resorption parameters were increased by ovx, while cimetidine and famotidine prevented this increase. Kinetic bone formation parameters were increased by ovx, while cimetidine and famotidine had no influence. Neither cimetidine nor famotidine had any observable effect in sham-treated rats. Mast cell numbers increased by 250% in ovx rats and by only 40% in H2 antagonists-treated ovx rats. A resident histamine-positive, non-mast cell, population found in bone marrow was increased by 25% by ovx. Interestingly, cimetidine and famotidine reduced this population in both sham-operated and ovx rats, famotidine being more potent than cimetidine. These results show that H(2) receptor blockade partially prevents the consequences of castration on cancellous bone resorption in female rats, and strongly suggest that histamine participates in the mediator network regulating estrogen deficiency induced bone resorption. A large population of histamine-producing cells, which differ morphologically from mast cells and belong to an immature marrow population, may be a source of histamine in this model. The H(2) blockers targeted this population, and this effect appeared to explain the anti-resorptive action of the two drugs.

The antineoplastic role of bisphosphonates: from basic research to clinical evidence

Bisphosphonates are now well established as successful agents for the prevention and treatment of postmenopausal osteoporosis, corticosteroid-induced bone loss and Paget's disease. Bisphosphonates have also recently become important in the management of cancer-induced bone disease, and they now have a widely recognized role for patients with multiple myeloma and bone metastases secondary to breast cancer and prostate cancer. Recent studies suggest that, besides the strong antiosteoclastic activity, the efficacy of such compounds in the oncological setting could also be due also to direct antitumor effect, exerted at different levels. Here, after a brief analysis of the chemical structure, we will review the antineoplastic and biological properties of bisphosphonates. We will start from well estabilished mechanisms of action and go on to discuss the latest evidence and hypotheses. In particular, we will review the antiresorptive properties in malignant osteolysis and the recent evidence of a direct antitumor effect. Furthermore, this review will analyze the influence of bisphosphonates on cancer growth factor release, their effect on cancer cell adhesion, invasion and viability, the proapoptotic potential on cancer cells, the antiangiogenic effect, and, finally, the immunomodulating properties of bisphosphonates on the gammadelta T cell population.

The histamine H2-receptor antagonist, cimetidine, inhibits the articular osteopenia in rats with adjuvant-induced arthritis by suppressing the osteoclast differentiation induced by histamine

The effects of cimetidine on rat adjuvant arthritis (AA) and rat osteoclast differentiation were studied. For the in vivo experiments, AA was induced by injections of Mycobacterium tuberculosis H37RA either subcutaneously into the base of the tail or into the right hind paw. The osteoclast differentiation was assessed by estimating the number of tartrate-resistant acid phosphatase-positive multinuclear cells in the bone marrow culture. Cimetidine, at the dose of 25 mg/kg body weight, reduced the paw swelling by 70% (P<0.01). Cimetidine, at 10 microM concentration, inhibited 1,25-dihydroxyvitamin D(3) (1,25[OH](2)D(3)) and histamine mediated osteoclast differentiations by 40% (P<0.01) and 60% (P<0.001), respectively. Dimaprit, at 0.3 microM, stimulated the cell differentiation by 100% (P<0.01). Mepyramine reduced osteoclast differentiation, but the reduction was not statistically significant. Measurements of bone mineral density of the femur indicated that 5 mg/kg of cimetidine treated animals had 30% (P<0.01) higher mineral density in comparison with that of the AA control group that received no cimetidine. These results suggest that histamine is a potent inducer of osteoclast differentiation, at least in part, through the histamine H(2)-receptor, and cimetidine has a preventive effect on articular destruction and accompanying inflammation in arthritic rats. These observations may provide critical insights into the pathogenesis of the bone pathology seen in patients with RA.

Generation and activity of equine osteoclasts in vitro: effects of the bisphosphonate pamidronate (APD)

Equine osteoclast-like cells (OCLs) were generated from the bone marrow (BM) of two ponies and one horse in the presence of RANKL, the receptor activator of NF kappa B ligand and macrophage colony-stimulating factor (M-CSF). The phenotype of these cells was confirmed by demonstration of characteristics typical of osteoclasts (OCs) including: the expression of tartrate-resistant acid phosphatase (TRAP), the vitronectin receptor (VNR) and the calcitonin receptor (CTR), the demonstration of responsiveness to calcitonin (CT) and the ability to form resorption lacunae on ivory slices and calcium phosphate films. The bisphosphonate pamidronate (APD) dose-dependently inhibited resorption of calcium phosphate films by equine OCLs with an IC(50) of 5.8 x 10(-7) M in one horse. APD also dose-dependently inhibited the number of OCLs present in BM cultures after 7 days. However, this effect is most likely attributable to increased OCL death rather than decreased OCL formation. Paradoxically, ADP appeared to cause an early, transient, increase in OCL formation in BM cultures, however, this effect was reversed after 7 days. These preliminary in vitro data support the potential use of APD in clinical conditions characterised by increased bone turnover such as osteomyelitis, osteitis, septic osteoarthritis, navicular disease, cystic bone lesions and immobilisation-induced osteoporosis and provide useful information for future pharmacokinetic studies and clinical trials in vivo.

Short-term prevention of osteoclastic resorption and osteopenia in ovariectomized rats treated with the H(2) receptor antagonist cimetidine

Ovariectomy rapidly induces strong osteoclast differentiation, leading to a marked loss of cancellous bone in the rat appendicular skeleton. As we found that histamine inhibition prevented periosteal bone resorption in rats, we tested the hypothesis that cimetidine, an H(2) receptor antagonist, prevents the osteoclastic burst and subsequent trabecular bone loss in this setting. Forty female Sprague-Dawley rats were ovariectomized (ovx) or sham-operated. Rats from each group received daily intramuscular injections of cimetidine (125 mg/kg per day) or vehicle. The animals were killed 14 days after surgery, and their femora were processed for morphometry. Cimetidine had no effect on serum estradiol levels in the control and ovx rats. BV/TV was reduced by 36% in the ovx rats, and by 10% in the cimetidine treated rats (p < 0.01). Tb.N and Tb.Wi were significantly reduced by 30% in the ovx rats and by 15% ovx-treated ones. OcS/BS did not change in the treated ovx rats, but increased 3.7-fold in the untreated ovx ones (p < 0.001). The N.Oc/TBPm increased markedly in the ovx rats (2.6-fold, p < 0.0001 vs. controls), but only slightly in the cimetidine-treated animals (+18%, p < 0.05 vs. controls), with a significant difference between the cimetidine-treated and -untreated ovx animals (p < 0.001). Cimetidine had no effect on these parameters in sham-operated animals. These results show that histamine inhibition by an H(2) receptor antagonist partially prevents the consequences of castration on cancellous bone, possibly by an action on osteoclast differentiation. Interestingly, cimetidine had no effect on basal resorption along trabecular bone. Histamine inhibition by H(2) blockers warrants further investigation in this model of osteopenia.

Analgesic effect of bisphosphonates in mice

Bisphosphonates are analogues of inorganic pyrophosphate and are inhibitors of bone resorption. Many derivatives have been developed for the treatment of enhanced bone resorption; several reports reveal that treatment with bisphosphonates is able to reduce the pain associated with different painful diseases. This study tested the antinociceptive action of four bisphosphonates, clodronate, alendronate, pamidronate and etidronate, in comparison with that of morphine and acetylsalicylic acid using two algesimetric tests in mice, tail-flick and writhing tests. In the tail-flick test, after intravenous (i.v.) injection, a dose-dependent antinociception was present after pamidronate, clodronate and acetylsalicylic acid whereas etidronate and alendronate produced an analgesic effect only with the highest dose tested. We also studied the central effect of clodronate and pamidronate and, after intracerebroventricular injection, both bisphosphonates showed a dose-dependent antinociceptive effect. In the writhing test clodronate and pamidronate showed a statistically significant antinociceptive action after i.v. and intramuscular administration. To verify if clodronate and pamidronate could modulate the peripheral opioid receptors we evaluated the gastrointestinal transit time in mice, but we did not find any effect on the gastrointestinal motility. These data indicate that clodronate and pamidronate present a central and peripheral antinociceptive effect; however, the main mechanism cannot be determined from the present data. We discuss the possible pharmacological hypothesis to interpret the present results. The findings suggest a pharmacological role of the bisphosphonates in the modulation of antinociception even in acute conditions not related to accelerated osteolytic and inflammatory response, with a possible clinical application to control pain.

Pamidronate prevents bone loss associated with carrageenan arthritis by reducing resorptive activity but not recruitment of osteoclasts

Carrageenan arthritis is associated with high-turnover bone loss. We sought to determine whether the bisphosphonate pamidronate can modify this effect of inflammatory arthritis. Sixty mature, New Zealand White rabbits were randomly assigned to five groups: normal; normal with a therapeutic dose of pamidronate (300 microg/kg/day, administered subcutaneously); arthritis (induced in the right tibiofemoral joint with 10 intraarticular carrageenan injections); arthritis with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous); and arthritis with a low dose of pamidronate (7.5 microg/kg/day, subcutaneous). All animals received the fluorochrome calcein green (0.5 g/l/day) in drinking water ad libitum from days 21 to 49. Undecalcified, transverse sections of the distal femur were photographed or imaged to determine bone volume; new bone volume; resting, eroded, osteoid, and osteoblast perimeters; and osteoclast number. Results were evaluated with analysis of variance and pairwise Bonferroni's tests. In trabecular bone adjacent to the joint affected by carrageenan arthritis, resting perimeter was substantially reduced compared with normal joints, and primary indices of osteoblast and osteoclast activity were abnormally high (p < 0.001). Daily treatment with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous) during the induction of arthritis significantly decreased new bone volume, osteoid perimeter, and osteoblast perimeter compared with the untreated arthritis group (p < 0.001). Osteoclast number and eroded perimeter remained abnormally high despite treatment with pamidronate. The concomitant increase of bone volume and these osteoclast indices show that pamidronate prevents bone loss in this model of experimental inflammatory arthritis by inhibiting the resorptive activity, but not the formation or recruitment, of osteoclasts. These findings are relevant to the use of bisphosphonates in the treatment of rheumatoid arthritis.

Concentration of bisphosphonate (incadronate) in callus area and its effects on fracture healing in rats

The aim of the present study was to investigate effects of incadronate on early stages of fracture healing and to detect its concentration in callus area (Ca.Ar). Rats were injected three times per week with either two doses of incadronate (10 microg/kg and 100 microg/kg) or vehicle for 2 weeks. Femora were then fractured and fixed and animals were divided into pretreatment (P-10 and P-100) and continuous treatment (C-10 and C-100) groups. Incadronate treatment was stopped in P-10 and P-100 groups but continued in C-10 and C-100 groups. Animals were killed at 2 weeks and 4 weeks after fracture. Results showed significantly large callus, compared with the control, only in C-100 group at 4 weeks but not at 2 weeks. Both linear labeled surface (LS) and eroded surface (ES) decreased significantly in C-10 and C-100 groups at 2 weeks and 4 weeks. Osteoclast number (N.Oc) decreased significantly in C-10 and C-100 groups at 2 weeks but increased slightly at 4 weeks. However, there was no significant difference in the above parameters in P-10 and P-100 groups at 4 weeks. Apoptotic osteoclasts were observed only in the C-100 group at 4 weeks. A time-course decrease in incadronate concentration was detected in P-10 and P-100 groups whereas an increase was observed in C-10 and C-100 groups. These findings suggest that larger callus under incadronate treatment may result from the inhibition of bone resorption, histological characteristics of callus may be correlated with incadronate concentration, and metabolism of incadronate in bone may be related to the rate of bone turnover.

Elevation of histidine decarboxylase activity in the mandible of mice by Prevotella intermedia lipopolysaccharide and its augmentation by an aminobisphosphonate

Lipopolysaccharide (LPS) produced by Gram-negative bacteria is an important cause of inflammation. Aminobisphosphonates are potent inhibitors of bone resorption but have inflammatory side-effects. Here, the effects of LPS from Prevotella intermedia (a prevalent Gram-negative bacterium both in periodontitis and endodontal infections) and alendronate (an aminobisphosphonate) on the activity of the histamine-forming enzyme, histidine decarboxylase (HDC), were examined in mouse mandible. Intravenous injection of P. intermedia LPS increased HDC activity in the mandible, maximal activity being induced within 3-6 h of the injection. The elevation of HDC activity was dependent on the dose of LPS, 10 microg/kg (0.25 microg/mouse) producing a significant elevation in enzyme activity. Intraperitoneal injection of alendronate (40 micromol/kg) also produced an increase in HDC activity. Moreover, the elevation of HDC activity induced by P. intermedia LPS was markedly augmented in mice given alendronate 3 days before the LPS injection. These results (i) suggest that P. intermedia LPS may stimulate the synthesis of histamine in the mandible and that the newly formed histamine may make at least some contribution to the development of inflammation (apical periodontitis and/or osteomyelitis); (ii) should encourage the clinical testing of antihistaminergic agents against inflammation; and (iii) confirm that care needs to be taken when administering aminobisphosphonates to patients.

Involvement of interleukin-1 in the inflammatory actions of aminobisphosphonates in mice

Aminobisphosphonates (aminoBPs) are potent inhibitors of bone resorption. However, they cause undesirable inflammatory reactions, including fever, in humans. Intraperitoneal injection of aminoBPs into mice also induces inflammatory reactions, including a prolonged elevation of the activity of the histamine-forming enzyme, histidine decarboxylase (HDC). Because interleukin-1 (IL-1) is a typical pyrogen and a strong inducer of HDC, we examined whether aminoBPs induce inflammatory reactions in mice deficient in genes for both IL-1alpha and IL-1beta (IL-1-KO mice). In control mice, aminoBPs induced an elevation of HDC activity and other inflammatory reactions (enlargement of the spleen, atrophy of the thymus, exudate in the thorax and increase in granulocytic cells in the peritoneal cavity). These responses were all weak or undetectable in IL-1-KO mice. We have previously shown that lipopolysaccharides (LPSs) from Escherichia coli and Prevotella intermedia (a prevalent gram-negative bacterium both in periodontitis and endodontal infections) are capable of inducing HDC activity in various tissues in mice. In control mice treated with an aminoBP, the LPS-induced elevations of serum IL-1 (alpha and beta) and tissue HDC activity were both markedly augmented. However, such an augmentation of HDC activity was small or undetectable in IL-1-KO mice. These results, taken together with our previous findings (i) suggest that IL-1 is involved in the aminoBP-induced inflammatory reactions and (ii) lead us to think that under some conditions, inflammatory reactions induced by gram-negative bacteria might be augmented in patients treated with an aminoBP. In this study, we also obtained a result suggesting that IL-1-deficiency might be compensated by a second, unidentified, mechanism serving to induce HDC in response to LPS when IL-1 is lacking.

A time kinetic study of the effect of aminobisphosphonate on murine haemopoiesis

We previously showed that aminobisphosphonates (aminoBPs), potent inhibitors of bone resorption, increased the number of osteoclasts and granulocytes, and enhanced the cell size of osteoclasts in vivo, indicating that aminoBPs have a profound effect on murine haemopoiesis. The possible effect of an aminoBP (4-amino-1-hydroxybutylidene-1,1-bisphosphonate; AHBuBP) on murine haemopoiesis in vivo was examined in more detail. Macroscopically, AHBuBP induced the whitened bone marrow (BM) and splenomegaly. Flow cytometric analysis indicated that in BM, AHBuBP reduced the number of mature monocyte-macrophage lineage cells and erythroid cells 1 and 2 d after treatment, respectively, whereas it enhanced granulopoiesis on day 4. In the spleen, both erythropoiesis and granulopoiesis were significantly increased. BM haemopoietic progenitors of granulocyte lineage and of monocyte-macrophage lineage (CFU-G, CFU-M and CFU-GM) were well maintained by the injection of AHBuBP, and even a small increment in these progenitors was observed 2-4 d after treatment. Immunohistochemical examination of BM demonstrated that residential macrophages of erythroblastic islands disappeared. Increased numbers of osteoclasts, as well as enlarged cell size, was confirmed up to 7 d after the treatment, implicating that the inhibition of bone resorption was not due to the reduced generation of osteoclasts by AHBuBP. These results suggest (1) that AHBuBP treatment in vivo rapidly deleted mature residential macrophages from BM, (2) that mature macrophages once deleted did not reappear even when CFU-M and CFU-GM increased in number and the number of Mac-1+/Gr-1- cells recovered to normal, (3) that BM erythropoiesis was significantly decreased due to the lack of erythroblastic islands, and (4) that compensatory erythropoiesis was evoked in the spleen to induce splenomegaly.

Pro-inflammatory effects of the aminobisphosphonate ibandronate in vitro and in vivo

OBJECTIVES

To investigate the effects of the aminobisphosphonate, ibandronate, on the course of joint inflammation in rat antigen-induced arthritis (AIA) and the release of pro-inflammatory cytokines in partially purified human peripheral blood mononuclear cells (PBMC).

METHODS

Rats with AIA received a single intra-articular injection of ibandronate (1 mg) 7 days post-arthritis induction and knee swelling was measured for 7 days thereafter. The effects of ibandronate (300 microg/ml) on PBMC cytokine production and activation marker expression were determined using polymerase chain reaction (PCR)/ELISA and FACS analysis, respectively.

RESULTS

Joint swelling, associated with AIA, was sustained in ibandronate-treated rats compared with saline-treated control rats. Ibandronate stimulated the production of interferon gamma (IFN-gamma) in adherent PBMC, and increased the surface expression of FcgammaRI and HLA DP, DQ, DR on the adherent monocyte population. Activation by lipopolysaccharide (LPS) of PBMC previously incubated with ibandronate led to enhanced levels of tumour necrosis factor alpha (TNF-alpha) secretion, and this could be partially inhibited by neutralizing antibodies to IFN-gamma.

CONCLUSIONS

The enhanced production of TNF-alpha by ibandronate-treated PBMC in vitro involves stimulation of adherent monocytes by IFN-gamma prior to LPS-induced activation. Similar cellular interactions may be involved in the pro-inflammatory effects of ibandronate in vivo.

An ultrastructural study of the effects of bisphosphonate administration on osteoclastic bone resorption during relapse of experimentally moved rat molars

This study was designed to clarify the effects of systemic administration of bisphosphonate, pamidronate, on the bone resorbing activity of osteoclasts during relapse of rat molars, after experimental movement. An elastic band was inserted between the upper first and second molars of 7-week-old rats and removed 21 days later. At 1 day before elastic band removal, bisphosphonate was administered via a tail vein. After elastic band removal, the rats were further maintained for 0, 5, or 10 days. The relapse of the first molars was studied by means of light and scanning-electron and transmission-electron microscopy. When an elastic band was removed, the mean interdental distance between the first and second molars in all rats was approximately 435 micrometer. In the control rats, it had decreased to 108 micrometer by day 5 and 57 micrometer by day 10. In these control rats, numerous osteoclasts appeared along the alveolar bone surface in the compressed side of the periodontal ligament of first molars. Administration of bisphosphonate significantly inhibited the prominent decrease in interdental distance. In these rats, it averaged 313 micrometer at day 5 and 115 micrometer at day 10. In bisphosphonate-treated rats, osteoclasts aggregated mainly in vascular canals of alveolar bone but were occasionally observed along the alveolar bone surfaces facing the periodontal ligament. Administration of bisphosphonate also induced structural changes, such as disappearance of ruffled borders and cytoplasmic polarity, in osteoclasts. A degenerated osteoclast was also observed in a bisphosphonate-treated rat. However, bisphosphonate induced no structural changes in osteoblasts, osteocytes, or periodontal ligament fibroblasts. These results suggest that a single systemic administration of bisphosphonate decreases the extent of initial relapse in experimentally moved rat molars via a mechanism involving impairment of the structure and resorptive functions of osteoclasts.

Contrasting effects of alendronate and clodronate on RAW 264 macrophages: the role of a bisphosphonate metabolite

Clodronate (dichloromethylidene-bisphosphonate), a halogen-containing bisphosphonate, can inhibit the release of cytokines from RAW 264 macrophages and has anti-inflammatory properties in rheumatoid arthritis, whilst amino-containing bisphosphonates such as alendronate (4-amino-1-hydroxybutylidene-bisphosphonate), have pro-inflammatory properties and can cause an acute phase response. The basis for these pharmacological properties is unclear. Recently, it was demonstrated that clodronate is metabolised by certain cell lines in vitro to an analogue of ATP, whereas amino-bisphosphonates are not. We therefore investigated whether clodronate can also be metabolised by RAW 264 macrophages and whether intracellular accumulation of the metabolite (AppCCl2p) could account for the anti-inflammatory properties of clodronate. The effect of alendronate and AppCCl2p on the release of cytokines (IL-1beta, IL-6, and TNFalpha) from RAW 264 cells was compared, and the effect of the bisphosphonates and AppCCl2p on the DNA binding activities of transcription factors, NF-kappaB and AP-1, was investigated. Pretreatment of RAW 264 macrophages with alendronate augmented the LPS-stimulated release of IL-1beta and increased the binding of NF-kappaB to DNA in an electrophoretic mobility shift assay. Without LPS-induction, alendronate did not affect cytokine release or NF-kappaB binding. Clodronate was metabolised by RAW 264 cells to AppCCl2p. Like clodronate, AppCCl2p inhibited the LPS-induced release of cytokines and NO from RAW 264 macrophages. Both clodronate and its metabolite also inhibited the LPS-stimulated binding of NF-kappaB to DNA. In conclusion, these results suggest that the metabolite of clodronate may be responsible for the anti-inflammatory properties of clodronate, and that the contrasting effects of different bisphosphonates on the release of cytokines could be mediated partly through changes in the DNA binding activity of NF-kappaB.

Morphometric evidence that YM175, a bisphosphonate, reduces trabecular bone resorption in ovariectomized dogs with dietary calcium restriction

We examined mechanisms by which incadronate disodium (YM175) prevented bone resorption in ovariectomized dogs with dietary calcium restriction using the morphometrical method. YM175 (0.01-1.0 mg/kg) was given to ovariectomized dogs for 18 months. Because lumbar bone mineral density remained constant at month 17, we assumed that the trabecular bone resorption rate was equal to the bone formation rate and that wall thickness equaled resorption cavity depth. YM175 decreased both the bone resorption rate per number of osteoclasts and resorption cavity depth of cancellous pockets which were increased in ovariectomized dogs. These results suggest that YM175 reduces bone loss by decreasing the resorbing activity of osteoclasts.