The effects of disodium ethane-1-hydroxy-1, 1-diphosphonate on adjuvant induced arthritis in rats

Bisphosphonates in inflammatory rheumatic diseases

The main well recognized action of bisphosphonates (BPs) is their antiresorptive capacity, making them first-line drugs in the treatment of osteoporosis and other metabolic bone diseases. In this review we have compiled other possible actions of BPs, particularly in the areas of immunomodulation, anti-inflammatory capacity and in the prevention of structural joint damage in inflammatory rheumatic diseases. The immunomodulatory capacity of BPs has been focused on the mechanisms involved in the acute-phase response associated with the administration of nitrogen containing BPs (N-BPs), with the stimulus of pro-inflammatory cytokines, through the mevalonate pathway, activation of T-cells and the decrease in the cytotoxic T-lymphocyte antigen-4 (CTLA-4). In relation to their anti-inflammatory capacity, special attention has been given to their effect on preventing structural damage in inflammatory joint diseases and on the differential immune response in bone lesions of the most common and representative inflammatory rheumatic diseases, i.e. rheumatoid arthritis and spondyloarthropathies. The present data indicate that more studies are needed to improve the knowledge on the effect of BPs on inflammatory-mediated diseases and particularly on the prevention and/or treatment of the structural damage in these disorders, since these agents could be a potential useful concomitant therapy.

Bisphosphonates: Future perspective for neurological disorders

Neurodegenerative disorders and osteoporosis share some common underlying pathological features including calcium overload, accumulation of toxic chemicals, inflammation and impaired protein prenylation by isoprenoids (farnesyl pyrophosphate and geranylgeranyl pyrophosphate) appear later stage of life. Substantial number of pre-clinical and clinical reports as well as in vitro data univocally acknowledged the negative impact of altered post-translational modification (prenylation) of proteins like small GTPases (Rffhes, Rho, Rac etc.) and cholesterol levels in both serum and brain on CNS integrity. Bisphosphonates (BPs), referred to as gold standard for osteoporosis treatment, have well established role in attenuation of bone resorption and osteoclast apoptosis by inhibition of farnesyl pyrophosphate synthase enzyme (FPPS) in mevalonate pathway. BPs mainly nitrogen containing BPs (NBPs) have potential to offer new therapeutic targets for neurological disorders and received increasing attention in recent years. A year back clinical and pre-clinical studies revealed that NBPs have the potential to alleviate the symptoms of neurological disorders like brain calcification, Alzheimer's disease and Huntington's disease by targeting mevalonate pathway. Though these drugs have well developed role in inhibition of isoprenoids synthesis, these were demonstrated to inhibit acetyl cholinesterase enzyme and cholesterol synthesis in brain that are considered as the critical factors for impairment of cognitive functions which is the hallmark of several neurological disorders. Still the current understanding of BPs' effect in CNS is limited due to lack of studies focusing the molecular and cellular mechanism. The present review aims to reveal the updated discussion on the mechanism contributing BPs' effect in CNS disorders.

The potential of liposomal drug delivery for the treatment of inflammatory arthritis

OBJECTIVE

To review the use of liposomes as a delivery agent in inflammatory arthritis.

METHODS

The literature on liposomes and liposomal drug delivery for the treatment of inflammatory arthritis was reviewed. A PubMed search of articles in the English-language journals from 1965 to 2007 was performed. The index words used were as follows: "rheumatoid arthritis," "liposomes," and "targeted delivery." Papers identified were reviewed, abstracted, and summarized.

RESULTS

Liposomes have the capacity to be used as delivery and targeting agents for the administration of antirheumatic drugs at lower doses with reduced toxicity. In other areas of medicine, the pace of progress has been rapid. In the case of infectious diseases and cancer, liposomal drug delivery has progressed and developed into commercially viable therapeutic options for the treatment of fungal infections (amphotericin B), or metastatic breast cancer and Kaposi sarcoma (doxorubicin, daunorubicin), respectively. In arthritis, the efficacy of prednisolone-loaded long-circulating liposomes is currently being evaluated in a phase II clinical trial. Liposome's application to arthritis is still in its infancy but appears promising as new patents are filed. With improvements in liposomal formulation and targeted synovial delivery, liposomes offer increased therapeutic activity and improvement in the risk-benefit ratio.

CONCLUSION

Recent research into synovial targets and improved liposomal formulations continues to improve our capacity to use liposomes for targeted delivery. With time, this approach has the potential to improve drug delivery and reduce systemic complications.

Amino-bisphosphonates in heterotopic ossification: first experience in five consecutive cases

STUDY DESIGN

Retrospective, observational study in five consecutive cases.

OBJECTIVES

The management of heterotopic ossification (HO), a frequent complication after spinal cord injury (SCI) and after orthopaedic surgery, is a therapeutic challenge with high recurrence rates of over 50%. Conflicting data were reported for Etidronate. The use of the more potent new generation of amino-bisphosphonates has been put forward in different inflammatory, dysmorphogenic bone disease. In order to try and halt the underlying dysfunctional bone metabolism we have studied the action of pamidronate in five consecutive high-risk patients with established HO of different etiology undergoing surgical removal.

SETTING

University Hospital of Basel, Switzerland, Division of Endocrinology, Diabetology and Clinical Nutrition and the Department of Orthopedic Surgery.

METHODS

In all five patients, ranging from 47 to 68 years of age, we used continuous pamidronate infusions perioperatively at a dosage of 120 mg in the first 12 h and subsequent reduction to 75-60-30-15 mg/12 h over a period of 10-14 days.

RESULTS

None of these patients showed clinical, radiographical and laboratory signs of HO recurrence or new forming HO in the follow-up 5-54 month after surgery. Potential side effects of high-dose bisphosphonate therapy such as osteoporosis and osteomalacia were not reported in any case.

CONCLUSION

We postulate that pamidronate might have pronounced beneficial effects in high-risk patients with established HO undergoing excision surgery. Since the therapeutic window of amino-bisphosphonates has not yet been defined and the minimal necessary doses for preventing new HO are unknown, further studies are encouraged to confirm our findings and to identify the necessary dosage and duration of treatment and to pinpoint, which patients will benefit most from this treatment.

Single infusion of neridronate (6-amino-1-hydroxyhexylidene-1,1-bisphosphonate) in patients with active rheumatoid arthritis: effects on disease activity and bone resorption markers

AIMS

The aim of this study was to assess the effects of a single infusion of the bisphosphonate neridronate (N) on parameters of inflammation and bone resorption in rheumatoid arthritis (RA).

METHODS

Forty-five patients with active RA were randomly allocated on a double blind basis to receive a single intravenous infusion of either N 25 mg (15 patients), N 50 mg (15 patients), or placebo (15 patients). At baseline and after 7 and 21 days, we assessed the following: erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and Ritchie's articular index as indices of disease activity; and urinary free deoxypyridinoline (DPyr), N-telopeptide of type I collagen (NTx) and hydroxyproline (OHP) as indices of bone resorption.

RESULTS

At day 7, N 25 mg significantly decreased ESR compared to N 50 mg (p=0.002), and CRP compared to placebo (p=0.036). With regard to bone resorption markers, at day 7, both N 25 mg and 50 mg compared to placebo significantly decreased NTx (p<0.0005 and p=0.003, respectively) and OHP (p=0.001 and p=0.004, respectively). At day 21, N 50 mg significantly decreased OHP compared to placebo (p=0.017). DPyr levels remained unchanged in the three groups.

CONCLUSIONS

N 25 mg and 50 mg exerted different effects on RA activity parameters, since only the lower dose significantly decreased ESR and CRP. Both doses of N inhibited bone resorption, with a transient, significant reduction in urinary NTx and OHP, but without any effect on DPyr.

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.

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.

Bisphosphonates induce apoptosis in mouse macrophage-like cells in vitro by a nitric oxide-independent mechanism

Bisphosphonates (BPs) are an important class of antiresorptive drugs used in the treatment of bone diseases, including osteoporosis. Although their mechanism of action has not been identified at the molecular level, there is substantial evidence that BPs can have a direct effect on osteoclasts by mechanisms that may lead to osteoclast cell death by apoptosis. BPs can also inhibit proliferation and cause cell death in macrophages in vitro. We have now shown that the toxic effect of BPs on macrophages is also due to the induction of apoptotic, rather than necrotic, cell death. Morphological and biochemical features that are definitive of apoptosis (chromatin condensation, nuclear fragmentation, and endonuclease-mediated internucleosomal cleavage of DNA) could be identified in mouse macrophage-like J774 and RAW264 cells, following treatment with 100 microM pamidronate, alendronate, and ibandronate for 24 h or more. Clodronate was much less potent, even at 2000 microM, while 2000 microM etidronate did not cause apoptosis. Apoptosis was not due to increased synthesis of nitric oxide and could not be prevented by inhibitors of nitric oxide synthases. Since macrophages, like osteoclasts, are particularly susceptible to BPs, these observations support the recent suggestion that the mechanism by which BPs inhibit bone resorption may involve osteoclast apoptosis. Furthermore, the macrophage-like cell lines used in this study may be a convenient model with which to identify the molecular mechanisms by which BPs promote apoptosis in osteoclasts. Induction of macrophage apoptosis by BPs in vivo may also account, at least in part, for the anti-inflammatory properties of BPs as well as the ability of BPs to cause an acute phase response.

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.

Effect of clodronate on established adjuvant arthritis

The rat adjuvant arthritis model was used to study the effect of disodium clodronate on inflammation and destruction of tarsal bones and joints. Male Lewis rats were given an intradermal injection of mycobacteria. Fourteen days after immunization, rats with similar scores were assigned to the different experimental groups. They were treated subcutaneously either with saline (controls) or with clodronate at doses of 12.5 and 25 mg/kg/day five times a week for 2 weeks. Clinical signs of arthritis including the severity of paw swelling were assessed weekly. At the time of sacrifice, histological features of the non-decalcified tarsus with ankle, intertarsal and tarsometatarsal joints were assessed for inflammatory soft-tissue, articular and bone changes. The total histological score of the hindpaw indicated that 58% of the control rats developed moderate arthritis and 42%, severe arthritis. The treatment with clodronate (25 mg/kg) decreased clinical signs of arthritis and the activity of the collagen-degrading lysosomal enzyme, beta-N-acetylglucosaminidase, in inflamed hindpaw tissue. Histological evaluation indicated moderate arthritis in 83%, but no severe arthritis. The lower dose of clodronate also decreased the severity of the disease; the decrease was, however, statistically insignificant. The results show that clodronate given therapeutically to adjuvant arthritic rats suppresses the intensity of the inflammation and prevents secondary articular and bone lesions in the tibiotarsal region.

Intravenous disodium etidronate therapy in spinal cord injury patients with heterotopic ossification

The goal of the present study was to use intravenous etidronate in the acute phase of heterotopic ossification (HO) in an attempt to achieve a high initial drug concentration at the site of the active ectopic ossification. The study included 27 consecutive patients with an acute onset of HO after spinal cord injury (SCI). The three-phase bone scan was used to confirm clinical diagnosis of HO. Disodium etidronate (Didronel) 300 mg was administered intravenously daily for 3 to 5 days. In 20 patients there was a rapid (1-2 days) decrease of soft tissue swelling (p < 0.01) with no side effects associated with the intravenous administration. In seven patients there was minimal or no improvement of edema after intravenous etidronate. In these patients deep vein thrombosis was found in the affected limbs. The effect of high dose etidronate on HO was determined in the group of 13 patients with positive clinical and scintigraphic finding of an acute HO, but negative radiographic studies. After intravenous administration of etidronate for 3 days (300 mg/day) the drug was continued orally with 20 mg/kg/day for 6 months. A placebo was not used in this study. In eight patients there was no radiographic evidence of HO after therapy while two patients had minimal ossifications. In three patients therapy was interrupted and all developed HO in 1-2 months.

Application of computer-based histomorphometry to the quantitative analysis of methylprednisolone-treated adjuvant arthritis in rats

Analyses of paw edema and histomorphometry were performed on tibio-talar joints to determine arthritic pathological responses in untreated 28-day adjuvant-induced polyarthritis (AIP) rats, and to determine the drug effect on inhibiting these responses in AIP rats treated with methylprednisolone. Histomorphometric measurements were performed on regions including articular joint space, synovial tissue, articular and epiphyseal cartilage, epiphyseal and metaphyseal bone marrow, and endosteal and periosteal cortical bone surfaces. Analysis of paw edema indicated that paw volume was significantly increased in untreated AIP rats. This increase in paw volume was partially prevented in AIP rats treated with 0.3 mg methylprednisolone/kg per day, and completely prevented in AIP rats treated with the two higher dose levels (1 and 3 mg/kg per day). Histomorphometric analysis of untreated AIP tibio-talar joints showed decreased articular joint space whereas synovial tissue area increased and a minor, but significant, articular cartilage erosion area occurred. Epiphyseal growth cartilage area was decreased. Trabecular bone area in distal tibial epiphyseal and metaphyseal regions was markedly decreased whereas bone marrow area increased involving a large number of macrophages and osteoclasts. Eroded endocortical bone area was increased while cortical bone area decreased. Marked osteophyte proliferation occurred on the periosteal surface. These arthritic pathological changes were inhibited by the treatment of methylprednisolone in a dose-dependent fashion. The animals treated with the highest dose of methylprednisolone complete prevented the development of the AIP-induced pathological changes. These data confirmed qualitative histological evaluation of arthritic changes but did not correlate with the anti-edema effects of methylprednisolone (100% inhibition at 1.0 and 3.0 mg/kg, p.o.). It is suggested that quantitative histomorphometry be used to determine more precisely the AIP rat model and the effects of drugs on different histopathological features in this experimental model of arthritis in preference to paw edema which gives a more limited picture of the arthritic response.

Quantification of fluid changes in rat leg joints with adjuvant arthritis by a one-dimensional magnetic resonance imaging experiment

A simple and reliable method for quantifying the fluid content and characterizing the tissue T2 relaxation properties of animal extremities has been devised. This one-dimensional magnetic resonance imaging experiment, applied to the adjuvant arthritis model in rats, provides a useful, noninvasive monitor of the course of the disease in vivo. Tissue is characterized through the analysis of the biexponential T2 decay of the NMR-active hydrogen in the rat leg joint tissue. Long and short T2 components are identified, both of which are sensitive to the arthritic process. The long component is suggested to come from edema and increases by a factor of ca. 9 during the course of the disease, whereas the short T2 component may represent cellular influx into the joint and increases by a factor of ca. 3. These changes correlate with the severity of the disease and can be used to monitor therapeutic response. The main advantage of the technique over the more traditional two-dimensional imaging approach is that only one spatial variable has to be resolved, resulting in shorter imaging time.

Bisphosphonates in collagen arthritis

Bisphosphonates suppress bone destruction in various diseases. We studied the effects of 3-amino-hydroxypropylidene-1,1-bisphosphonate (APD), and dimethyl-APD in the collagen model of chronic arthritis in rats. The incidence and severity of arthritis was not lower in rats treated with APD or dimethyl-APD compared with controls. The cellular and humoral immune responses to collagen were also similar in the treated and untreated animals. In all animal groups the same bone destruction was found radiographically 42 days after immunization. This study demonstrates that bisphosphonates do not suppress the course of collagen arthritis in rats.

Bisphosphonates: a new class of drugs in diseases of bone and calcium metabolism

The geminal bisphosphonates are characterized by a PCP bond and are therefore analogs of pyrophosphate. They bind strongly to hydroxyapatite crystals and in vitro inhibit both crystal formation and dissolution. In vivo they inhibit soft tissue calcification and when given in large amounts also normal calcification. This effect is due to the inhibition of calcium phosphate crystal growth. Furthermore, the bisphosphonates are very potent inhibitors of bone resorption. The mechanism(s) of action is not yet known but is likely to be at a cellular level. The extent of the biological activity of each compound depends on the specific chemical structure, so that each individual bisphosphonate must be considered as a separate compound. The only common characteristic is the PCP group, which gives the compound its high affinity to bone. The individual effects, however, are determined by the side groups on the carbon atom. This opens interesting possibilities for the development of new compounds. No bisphosphonate analyzed so far can be degraded in vivo; all are either deposited in the skeleton, where they remain for years until the bone is destroyed, or are excreted in the urine. The high affinity for bone explains the specificity of the compounds for bone and the fact that they have relatively few nonosseous effects. Bisphosphonates are used in man to inhibit ectopic calcification, including dental tartar and ectopic ossification. Furthermore, they are used to inhibit bone resorption, especially in diseases such as Paget's disease and tumoral osteolysis. Finally, when linked to 99nTc, bisphosphonates are employed as bone scanning agents.

The cross-linking and structure modification of the collagen matrix in the design of cardiovascular prosthesis

Glutaraldehyde cross-linking of native or reconstituted collagen fibrils and tissues rich in collagen significantly reduces biodegradation. Other aldehydes are less efficient than glutaraldehyde in generating chemically, biologically, and thermally stable cross-links. Implants of collagenous materials cross-linked with glutaraldehyde are subject long-term to calcification, biodegradation, and low-grade immune reactions. We have attempted to overcome these problems by enhancing cross-linking through (a) bridging of activated carboxyl groups with diamines and (b) using glutaraldehyde to cross-link the epsilon-NH2 groups in collagen and the unreacted amines introduced by aliphatic dismines. This cross-linking reduces tissue degradation and nearly eliminates humoral antibody induction. Covalent binding of diphosphonates, specifically 3-amino-1-hydroxypopane-1, 1-diphosphonic acid (3-APD), and to a lesser extent chondroitin sulfate to collagen or to the cross-ling-enhanced collagen network reduces its potential for calcification. Platelet aggregation also is reduced by glutaraldehyde cross-linking and nearly eliminated by the covalent binding of chondroitin sulfate to collagen. The cytotoxicity of residual glutaraldehyde can be minimized by chemical neutralization and thorough rough rinsing.

A clinical and biochemical assessment of etidronate disodium in patients with active rheumatoid arthritis

Diphosphonates reduce the rate of bone turnover. They have additional pharmacological properties improving adjuvant arthritis in rats and lowering ESR in this condition. We have evaluated etidronate disodium, a diphosphonate commonly prescribed in the United Kingdom for Paget's disease in patients with rheumatoid arthritis. Apart from an early improvement in articular index, perhaps reflecting anti-inflammatory activity, no significant change occurred in clinical variables or in laboratory indices of 'secondline' action at a dose of 5 mg/kg/day.

Chemically modified collagen: a natural biomaterial for tissue replacement

Glutaraldehyde crosslinking of native or reconstituted collagen fibrils and tissues rich in collagen significantly reduces biodegradation. Other aldehydes are less efficient than glutaraldehyde in generating chemically, biologically, and thermally stable crosslinks. Tissues crosslinked with glutaraldehyde retain many of the viscoelastic properties of the native collagen fibrillar network which render them suitable for bioprostheses. Implants of collagenous materials crosslinked with glutaraldehyde are subject long-term to calcification, biodegradation, and low-grade immune reactions. We have attempted to overcome these problems by enhancing crosslinking through bridging of activated carboxyl groups with diamines and using glutaraldehyde to crosslink the epsilon-NH2 groups in collagen and the unreacted amines introduced by aliphatic diamines. This crosslinking reduces tissue degradation and nearly eliminates humoral antibody induction. Covalent binding of diphosphonates, specifically 3-amino-1-hydroxypropane-1, 1-diphosphonic acid (3-APD), and chondroitin sulfate to collagen or to the crosslink-enhanced collagen network reduces its potential for calcification. Platelet aggregation is also reduced by glutaraldehyde crosslinking and nearly eliminated by the covalent binding of chondroitin sulfate to collagen. The cytotoxicity of residual glutaraldehyde--leaching through the interstices of the collagen fibrils or the tissue matrix--and of reactive aldehydes associated with the bound polymeric glutaraldehyde can be minimized by neutralization and thorough rinsing after crosslinking and storage in a nontoxic bacteriostatic solution.

Effect of bisphosphonates on proliferation and viability of mouse bone marrow-derived macrophages

Bisphosphonates (BP) are powerful inhibitors of bone resorption. Their mechanism of action, although still unclear, is now believed to be at the cellular level. In this study we investigated the effects of these compounds on proliferation, induced either by L-cell conditioned medium (CSF-1) or 4-phorbol 12-myristate 13-acetate (PMA) of bone marrow cells (BMC) and on CSF-1-induced proliferation and viability of bone marrow derived macrophages (BMDM phi). BMC proliferation, measured by [3H]-TdR incorporation or by clonal assay in soft agar, was significantly inhibited by 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP) and 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP) at 2.5 x 10(-7) M and by dichloromethylenebisphosphonate (Cl2MBP) at 2.5 x 10(-6) M. This inhibitory effect was also confirmed on the proliferation, measured by [3H]-TdR incorporation, of BMDM phi. In the absence of CSF-1, the viability of this latter cell population, estimated by DNA content per well and lactate dehydrogenase (LDH) released into the medium, was affected in the following order of concentrations: Cl2MBP, 1.0 x 10(-4) M; AHBuBP, 5.0 x 10(-5) M; and AHPrBP, 2.5 x 10(-5) M. Since osteoclasts and macrophages might share a common early progenitor cell, probably under the control of CSF-1, the effect exerted by BP on the proliferation of the macrophage precursors may also be extended to the osteoclast precursors.

Studies on the chronic phase of adjuvant arthritis: effect of SR 41319, a new diphosphonate

We studied the course of adjuvant arthritis in rats by measuring clinical, biochemical, and histological parameters on day 36 after induction (representing the secondary reaction) and on day 171, which is at the stage of permanent deformity. The effect of SR 41319, a new diphosphonate, was evaluated on days 36 and 171, after three weeks of treatment (days 14-35 inclusive). In the absence of treatment all the measured parameters were markedly abnormal on day 36, indicating the presence of lesions that were still evolving. On day 171 clinical parameters and the lesion histological index remained the same, whereas the biochemical parameters and disease activity histological index had returned to normal, indicating that the lesions at this stage although severe were not inflammatory and consequently not progressing. SR 41319 treatment reduced the severity and progression of the disease both on day 36 and on day 171. We conclude that SR 41319 may be a potentially useful drug for the treatment of rheumatoid arthritis.

Effects of 1-hydroxyethylidene-1,1 bisphosphonate and (chloro-4 phenyl) thiomethylene bisphosphonic acid (SR 41319) on the mononuclear cell factor-mediated release of neutral proteinases by articular chondrocytes and synovial cells

Articular chondrocytes and synovial cells were stimulated to produce collagenase, neutral casein and proteoglycan-degrading proteinases by conditioned medium from human peripheral blood mononuclear cells. Collagenase, neutral casein and proteoglycan-degrading proteinase secretion was inhibited by SR 41319, a new bisphosphonate, in a concentration-dependent manner. Complete inhibition was achieved at about 0.3 mM. EHDP exhibited the same general profile but was about 10-fold less active and never completely inhibited the enzyme secretion. When added before MCF, SR 41319 had a protective effect against subsequent activation of the cells by MCF. SR 41319 also inhibited the increase of enzyme secretion by cells previously stimulated with MCF. The results suggest that the ability of SR 41319 to inhibit the MCF-mediated secretion of neutral enzymes involved in cartilage destruction could be valuable in the management of connective tissue damage in rheumatoid arthritis.

Penetration and effect of topically applied dimethylsulfoxide or indomethacin on adjuvant arthritis in the rat

The present study, using 14C-DMSO, established the systemic and local load and distribution of topically applied DMSO in adjuvant arthritic rats. Under equivalent conditions, the antiinflammatory effects (systemic and local) of topical DMSO treatments were compared with a topical treatment of a control vehicle or of indomethacin, a known effective antiinflammatory agent. No significant systemic or local antiinflammatory effect of topical DMSO was seen in the adjuvant arthritic rats. Indomethacin, applied topically, had a significant systemic antiinflammatory effect; however, no significant local antiinflammatory effect of indomethacin was observed.

Diphosphonates: history and mechanisms of action

The history of diphosphonates began with studies of inorganic pyrophosphate. This compound was found to occur in many biological fluids and inhibited the precipitation of calcium phosphates. It also slowed the transformation of amorphous calcium phosphate to its crystalline form, and inhibited crystal aggregation and dissolution. These observations suggested that it might be a compound of physiological or pathophysiological significance, perhaps in hypophosphatasia and in renal lithiasis. Diphosphonates are compounds where the P-O-P bond of pyrophosphate is replaced by a P-C-P bond. Many diphosphonates have been synthesized and tested and some relationship of their structure to the spectrum of biological effects has been observed. These analogues have similar properties to pyrophosphate, but unlike pyrophosphate they are resistant to enzymic degradation. Their experimental properties have led to their clinical development as bone scanning agents and in the treatment of disorders of ectopic mineralization and increased bone resorption.

Comparative antiinflammatory and bone protective effects of two diphosphonates in adjuvant arthritis

The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) and disodium dichloromethane diphosphonate (Cl2MDP) were evaluated in the rat adjuvant model of arthritis to directly compare their ability to inhibit arthritic processes. The results of the experiment indicated that both diphosphonates inhibited osseous changes, pedal inflammation, and the change in body weight gain patterns which are characteristic of this model. The latter effects suggest that diphosphonates may have antinflammatory activity that is not related to their previously known actions on bone. Cl2MDP appeared to be more effective than EHDP in this particular model when all aspects were considered. The relationship of these results to the potential safety of these compounds in clinical situations is discussed.

The inhibitory effect of new diphosphonic acids on aortic and kidney calcification in vivo

Three new diphosphonic acids, i.e. compounds containing a P-C-P bond, have been investigated for their ability to inhibit the vitamin D-induced calcification of aortas and kidneys in rats. The compounds were applied orally in various doses. All of the compounds, which had previously been shown to effectively inhibit the in vitro crystallization of apatite, markedly decreased the amount of calcium deposited in aortas and kidneys. One of the new compounds was substantially more effective than ethane-1-hydroxy-1,1-diphosphonic acid (EHDP), which was used as a reference compound. Diphosphonic acids might be used therapeutically in man against soft tissue calcification.

The effects of various diphosphonates on a rat model of cardiac calciphylaxis

Seven diphosphonate analogs were treated for their effects on myocardial and cardiovascular degeneration and calcification in an experimental model of cardiac calciphylaxis. A single oral dose of dihydrotachysterol (DHT) administered to rats induced myocardial and vascular degeneration, focal myocarditis and vasculitis, and myocardial and vascular mineralization. The results demonstrated a considerable variation among the various diphosphonates in their ability to block the pathological changes observed in this model. Ethane-1-hydroxy-1,1-diphosphonate (EHDP) was the most effective diphosphonate in reducing myocardial and vascular degeneration and calcification, whereas diphosphonates such as ethane-1-amino-1,1-diphosphonate (EADP) and hydroxymethylene diphosphonate (HMDP) had little or no effect compared to saline controls. For those diphosphonates which were effective, e.g., EHDP, the tissue-protective effects were observed whether the rats were treated with drug prior to the administration of DHT, or whether drug treatment commenced after DHT administration. The results are discussed in terms of the known biological properties of the diphosphonate drugs.

Disodium etidronate in the prevention of heterotopic ossification following spinal cord injury (preliminary report)

Heterotopic ossification is a frequent complication following spinal cord injury with 16 per cent to 53 per cent of patients developing varying degrees of pathologic ossification. The diphosphonates are known to block the transformation of amorphous calcium phosphate into crystalline hydroxyapatite. Therefore, one of the diphosphonates, disodium etidronate (generic name of disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) was selected fro clinical trials to study the effectiveness of EHDP in preventing heterotopic ossification following spinal cord injury. In a double-blind, clinical study of 149 spinal cord injury patients, disodium etidronate has proven its effectiveness in the prevention of heterotopic ossification. The extent of heterotopic ossification development as measured by the total heterotopic ossification X-ray grade was significantly less in EHDP-treated patients compared to placebo-treated patients (P less than 0-05). For maximal effectiveness, EHDP treatment must be started before the onset of the pathological process initiating the development of heterotopicossification. Further studies are necessary to determine the optimal time to institute EHDP treatment, length of treatment, and minimal effective dose. EHDP is the first hterapeutic agent known to alter the formation of heterotopic ossification after spinal injury and may prove useful in other conditions where heterotopic ossification prevention is clinically indicated.

Experimental renal osteodystrophy. The response to 25-hydroxycholecalciferol and dicholomethylene diphosphate therapy

Bone mineral and matrix maturation in chronically uremic, nonacidotic rats were investigated after 25-hydroxcholecalciferol (25OHD) and/or dichloromethylene diphosphonate (C12MDP) therapy utilizing bromoform-toluene density gradient fractionation and X-ray diffraction analyses. The bromoform-toluene density gradient analyses demonstrated that the progressive accumulation of less dense, more immature bone characteristic of progressive uremia was reversed by 25OHD and/or C12MDP therapy for a 2-wk period, and that after 4 wk of therapy the maturational profile of bones from chronically uremic animals treated with 250HD and/or C12MDP was comparable to that from nonuremic littermates. X-ray diffraction analysis revealed that by the 4th wk of therapy with 25OHD and C12MDP both the degree of crystallinity and the crystal size/perfection parameters in the uremic bones were comparable to those of nonuremic, pair-fed control littermates. Treatment for 4 wk with 25OHD resulted in enlarged and/or more perfect apatite crystallites, while C12MDP alone slightly inhibited crystal growth and/or perfection after 2 wk of treatment. Soft tissue calcification was diminished in uremic animals treated for 4 wk with C12MDP or a combined C2MDP/25OHD regimen, the latter being much more effective in this regard. The accumulated data in this study support the premise that the attendant accelerated bone resorption, soft tissue calcification, and abnormal mineralization and maturation of the skeletal tissue, well documented to characterize experimental ranal insufficiency, may be alleviated with therapeutic dosages of 25OHD and/or C12MDP.

The surface chemistry of bone mineral and related calcium phosphates

A review of the surface chemistry of bone mineral, hydroxyapatite and amorphous calcium phosphate is presented. Small-angle x-ray scattering and low-temperature nitrogen adsorption measurements show the magnitude of bone mineral surface to range from 100-200 m-2/g; the synthetic hydroxyapatite surface can vary from 25-200 m-2/g, while synthetic amorphous calcium phosphate ranges in surface from 20-60 m-2/g, according to the respective preparation conditions. The magnitude of heats of adsorption of certain small molecules (CO, Ar, N2, H2O, CH3OH) on bone mineral and hydroxyapatite show that these are polarizing surfaces that form strong bonds with polar or polarizable molecules; water is hydrogen-bonded to these surfaces with energies ranging from 23 kcal/mole for low coverage to 11 kcal/mole after two full monolayers; concomitantly, methanol ranges from 24 kcal/mole to 9 kcal/mole after the adsorption of one and a half monolayers. Stearic acid will close-pack perpendicularly on bone apatite surfaces when adsorbed from cyclohexane solution in a way reminiscent of the adsorption of this long, straight-chain molecule on water surface. It is believed that these molecules are hydrogen-bonded to electronegative ions on the apatite surface. Synthetic hydroxyapatite has long been used in chromatographic adsorption columns because of the specific bonding capacity the surfaces have for certain proteins and polynucleotides. The metabolic interrelationship of bone mineral and the body fluids is in great part dependent upon the nature and magnitude of mineral surface. From the surface studies described herein it was suggested that a chemical linkage could exist in bone between the mineral surface and certain free polar groups of collagen.