Inhibition of bone resorption by bisphosphonates: Interactions between bisphosphonates,osteoclasts, and bone

Summary Bisphosphonates are nonbiodegradable pyrophosphate analogues that are being used increasingly to inhibit bone resorption in disorders characterized by excessive bone loss. We have previously found that dichloromethylene bisphosphonate (Cl₂MBP) inhibits bone resorption through injury to the cells that resorb Cl₂MBP-contaminated surfaces. 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP) is a more potent inhibitor of bone resorptionin vivo, and we have attempted to identify a step in the resorptive pathway that accounts for this increased potency. We found that when osteoclasts, isolated from neonatal rat long bones, were incubated on bone slices in the presence of bisphosphonates, AHPrBP was less, rather than more potent as a resorption-inhibitor than Cl₂MBP. The greater sensitivity of resorption to AHPrBPin vivo could neither be attributed to an effect of AHPrBP on the ability of osteoblastic cells to stimulate resorption in response to calcium-regulating hormonesin vitro nor to an effect on osteoclast generation: osteoclast formation was unaffected by concentrations of AHPrBP 10-fold higher than those of Cl₂MBP which inhibit bone resorption in the bone slice assay. We also found no evidence for impaired osteoclast generationin vivo in AHPrBP-treated rats. These results suggest that the comparisons of potencyin vitro do not include all the factors responsible for determining bisphosphonate potencyin vivo. Because bisphosphonates owe the specificity of their actions to their ability to bind to bone surfaces, we performed experiments using bone slices that had been immersed in bisphosphonates before use. Bone resorption was virtually abolished on bone slices preincubated in 10⁻³ M AHPrBP. Inhibition was associated with degenerative changes in osteoclasts and a more rapid decrease in the number remaining on the bone surface than occurred with Cl₂MBP. The effect was specific for osteoclasts, could be prevented if bone resorption was suppressed by calcitonin, and was not seen in osteoclasts incubated in AHPrBP on plastic coverslips. These observations suggest that AHPrBP inhibits bone resorption through injury to osteoclasts when they solubilize bisphosphonate-contaminated bone. We found that the concentration of AHPrBP used in the preincubation phase could be reduced by an order of magnitude if the volume of the AHPrBP solution was correspondingly increased. This implies that the concentration of bisphosphonate is less relevant to potency comparisons than the density of bisphosphonate on the bone surface. The latter will be strongly influencedin vivo not only by affinity for bone but by the pharmacokinetic and other properties of the compound.     

Effect of diacylglycerols on osteoclastic bone resorption

We studied the effect of various synthetic diacylglycerols (DAGs) on bone resorption by rat and chick osteoclasts. l-stearoyl-2-arachidonoyl-sn-glycerol (DAG IV), at a concentration of 100 ΜM, caused a significant reduction in resorption pit number in both species at 6 and 24 hours without any toxic effect. Over a 6-hour incubation period, a significant inhibition was seen at 10 and 100 ΜM in both species. 1,2-dioctanoyl-sn-glycerol (DAG I) and 1, 2-dihexanoyl-sn-glycerol (DAG III) caused a marked inhibition of resorption by rat osteoclasts at 6 hours, but there was recovery of bone-resorptive ability over a 24-hour incubation period. DAGs with the -rac conformation failed to have any effect on bone resorption. In time-lapse video studies, osteoclast motility was not influenced by any of the DAGs at any of the concentrations used. Our results indicate that DAGs with the -sn conformation inhibit bone resorption, and DAGs with the -rac conformation do not. The finding that DAGs, the physiological activators of protein kinase C (PKC), inhibit bone resorption provides further evidence for an important role of the PKC pathway in the regulation of osteoclast activity.     

Genistein对破骨细胞分化和骨吸收功能的影响及其机制探讨

目的 探讨三羟异黄酮类药Genistein对破骨细胞性骨吸收的作用及其机制。方法 1，25(OH)2D3诱导小鼠骨髓细胞形成破骨样细胞，分别加入0moL／L、10^-9moL／L、10～moL／L、10^-7moL／L、10～moL／L、10^-5moL／LGenistein，于培养3，5和8d分别计数抗酒石酸酸性磷酸酶阳性细胞个数；于培养12d利用图像分析系统对骨吸收陷窝的面积进行测量分析。另从小鼠颅盖骨分离培养获得原代成骨细胞，分别加入0，10^-8，10^-7，10^-6和10^-5moL／LGenistein并以10^-9moL／L^-7 β雌二醇为对照，采用RT-PCR的方法检测Genistein对骨保护因子(osteoprotegerin，OPG)及破骨细胞分化因子(receptor activator of NF-κB ligand，RANKL)mRNA表达的影响。结果 利用1，25(OH)2D3成功诱导出破骨样细胞；随Genistein浓度增加，抗酒石酸酸性磷酸酶阳性细胞(单核、双核和多核)个数和骨吸收陷窝面积呈剂量依赖性减少。同时，应用Genistein后原代成骨细胞中OPG和RANKL的mRAN表达都有增强，但其最终效应表现为剂量依赖性和时间依赖性地增大OPG／RANKL的浓度比。结论 Genistein通过抑制破骨前体细胞分化来抑制其体外骨吸收功能，其分子机制与OPG／RANKL mRNA表达比值的升高有关。     

淫羊藿苷对小鼠骨髓源性破骨细胞诱导生成及骨吸收功能的影响

目的探讨淫羊藿苷对破骨细胞诱导产生及骨吸收功能的影响。方法用终浓度分别为25ng·mL^-1、30ng·mL^-1、10^-8mol·L^-1的M—CSF、RANKL、1，25（OH）2VitD3体外诱导培养小鼠骨髓源性破骨细胞，在此过程中加入终浓度分别为0、10^-7mol·L^-1、10^-6mol·L^-1、10^-5mol·L^-1的淫羊藿苷。倒置相差显微镜下观察活体细胞、HE染色、TRAP染色及降钙素受体染色鉴定破骨细胞，计数骨片上骨吸收陷窝数及面积，玻片上TRAP阳性多核细胞数。结果加药组随淫羊藿苷浓度的增加，骨片上形成的骨吸收陷窝数及面积，玻片上的TRAP阳性多核细胞数呈量的依赖性的减少，与非加药组比较，10^-5mol·L^-1、10^-5mol·L^-1浓度的淫羊藿苷组，差异有显著性（P〈0．05）。结论淫羊藿苷具有抑制破骨细胞诱导产生及骨吸收功能的作用，并随浓度增加抑制作用增强。     

The effects of bisphosphonates on the resorption cycle of isolated osteoclasts

Binding sites for wheat germ agglutinin (WGA)-lectin have been shown to become revealed in the demineralized resorption lacunae that osteoclasts excavate on bone substrate. Peroxidase-conjugated WGA-lectin, which binds to bone matrix glycoconjugates and proteoglycans, was used in pit formation assays to assess the activity of isolated osteoclasts cultured on either 3-amino-1,1-hydroxy-propylidene-bisphosphonate (APD)-or dichloromethylene bisphosphonate (Cl₂MBP)-covered bone slices. Immunofluorescence and histochemical techniques were also used to study the effects of bone-bound bisphosphonates on isolated rat osteoclasts. Neither APD nor Cl₂MBP interfered with the special organization of actin or vinculin in osteoclasts when the cells were initializing their resorption cycle. After 24 hours of culture, the number of resorbing osteoclasts increased strongly on control slices, but remained low on either APD- or Cl₂MBP-treated slices. At this time, the actin and vinculin rings in osteoclasts also started to exhibit abnormal, more diffuse staining. Both bisphosphonates studied resulted in signs of cytotoxicity: the number of osteoclasts decreased on APD- or Cl₂MBP-covered bone during the course of the study and those remaining attached exhibited severe cytoplasmic retractions. The total areas of resorption remained at significantly lower levels in both experimental groups studied, and this was due to decreases in both the number and sizes of individual resorption pits. The size of the most extensive lacunae detected on the Cl₂MBP slices did not exceed 5x10³ m², whereas on the control slices, resorption pits bigger than 15x10^{3 2} were frequently discovered.     

Mechanisms of bone resorption in calcium-deficient rats

Summary A study of surface remodeling activity and osteocyte lacunar area was made in young and adult rats maintained on a low-calcium diet, to explore cellular mechanisms of bone resorption. The diet produced active remodeling of the endosteal part of the femoral cortex, with a decrease in the amount of bone present. Surface resorption, with numerous osteoclasts, was evident, but there was no evidence of osteocytic osteolysis in bone which, by tetracycline labeling, could be identified as existing at the commencement of the experimental period. Osteocyte lacunae in bone formed during the period of calcium deprivation were somewhat larger than lacunae in control animals, apparently because of interference with the formation or maturation of the perilacunar tissue.     

Urinary gamma-glutamyltransferase (GGT) as a potential marker of bone resorption

We recently identified γ-glutamyltransferase (GGT) as a novel bone-resorbing factor. The present study was undertaken to determine whether GGT is a marker of bone resorption in two genetic models of hyper- and hypo-function of osteoclasts, as well as in postmenopausal women with accelerated bone resorption, using type I collagen N-telopeptide (NTX) and deoxypyridinoline (DPD) as established biochemical markers. Urinary excretion of GGT, corrected for creatinine, was found to be increased in osteoprotegerin (OPG)-deficient osteoporotic mice as well as in patients with postmenopausal osteoporosis (67–83 years of age); in both cases the urinary level decreased after treatment of patients or mice with alendronate, a selective inhibitor of bone resorption, concomitantly with a reduction in DPD and NTX. Conversely, in osteopetrotic op/op mice, urinary GGT increased in parallel with DPD after induction of osteoclasts with M-CSF injection. Constant infusion of parathyroid hormone (PTH) also increased urinary GGT along with DPD. In a survey of 551 postmenopausal women (50–89 years of age) at their regular health checkup, urinary GGT excretion exhibited a high correlation with DPD (ρ = 0.49, p < 0.0001). The calculated sensitivity and specificity for diagnosing elevated bone resorption, as determined by a DPD value higher than 7.6 nM/mM Cr, were 61% and 92%, respectively, when a cut-off value of 40 IU/g Cr was assigned for urinary GGT. Since GGT activity can be measured inexpensively in large numbers in a very short time, the measurement of urinary level may provide a convenient and useful method for mass screening to identify those with increased bone turnover and hence at increased risk for bone fracture.     

Hydrochlorothiazide inhibits osteoclastic bone resorption In vitro

Long-term thiazide diuretic use is associated with higher bone mineral density and reduced hip fracture rates, which are attributed to increased serum calcium levels and decreased parathyroid activity that lead to decreased bone resorption. The present study shows that 1–100 M hydro-chlorothiazide (HCTZ) dose dependently inhibits bone resorption by isolated rat osteoclasts in the bone slice assay with an IC₅₀ of 20 M. At these concentrations, HCTZ did not affect osteoclast survival on bone slices and had no effect on the proliferation of UMR-106 rat osteoblasts, indicating that the compound is not cytotoxic. However, such concentrations of HCTZ are unlikely to be achieved in man where therapeutic doses are usually 12.5–100 mg/day. That the in vitro effect of HCTZ on bone resorption may be due to inhibition of osteoclast carbonic anhydrase is discussed.     

Differential response in alveolar bone osteoclasts residing at two different bone sites

Summary Using a histochemical method for demonstrating acid phosphatase activity, we have studied osteoclasts residing at two different bone sites in rat incisor alveolar bone, one at the endosteum and the other at the tooth socket, and compared the response of these osteoclasts to systemic changes. After 12 days of calcium (0%) or phosphorus (0.2%) deprivation, the number of osteoclasts/cross section at the endosteum increased 463% (P<0.001) and 103% (P<0.002), respectively. After 10 days of calcium or phosphorus replenishment, the number of osteoclasts at this bone site decreased to levels not significantly different from those in the control. In contrast, the number of osteoclasts at the incisor socket remained insignificantly changed throughout the experimental period. A similar osteoclast differential response was also observed in the alveolar bone surrounding the first molar tooth. After 12 days of calcium deprivation, the number of osteoclasts/mm bone surface increased 371% (P<0.001) at the endosteum but remained insignificantly changed at the first molar socket. These results suggest that an osteoclast differential response exists in alveolar bone and that the response may be of significance inasmuch as the major function of alveolar bone is to support the teeth. The work described here supports the concept of local as well as systemic regulation of bone metabolism to simultaneously perform the dual functions of mineral homeostasis and mechanical support.     

Promethazine inhibits osteoclastic bone resorption In vitro

Summary Several studies have shown that promethazine can reduce age-related osteopenia in mice. Furthermore, prolonged treatment with promethazine (50 mg/day) increases bone mineral content in the lumbar spine in post-menopausal women with osteopenia. However, the mechanism of action of promethazine has not been elucidated. The present study shows that promethazine HCl (0.01 – 10 M) dose-dependently inhibits bone resorption by isolated rat osteoclasts in the bone slice assay with an IC₅₀ of 1 M. Since these concentrations are likely to be achieved in vivo, it is suggested that the beneficial effect of promethazine on osteopenia is at least partly due to a direct inhibitory effect on osteoclast activity.     

Lack of effect of ipriflavone on osteoclast motility and bone resorption inIn vitro andEx vivo studies

Summary Usingin vitro andex vivo experimental procedures specifically designed to visualize pharmacological effects on parameters of bone resorption, studies were performed to elucidate whether ipriflavone's reported effect in osteoporosis is due to an effect on the motility and resorptive activity of osteoclasts, as has been shown to be the case with salmon calcitonin. Concentrations of ipriflavone used were higher by a factor of>100 than peak blood levels measured in patients given standard therapeutic doses. Despite this, neither quantitative nor qualitative changes were observed in the motility of isolated rat osteoclasts or in their resorptive activity when incubated with bone slices. The conclusion is that ipriflavone does not possess antiosteoclastic and antiresorptive activity of the type documented for salmon calcitonin in the models employed and that further investigation of its mode of action is therefore necessary.     

Flurbiprofen-induced stimulation of periosteal bone formation and inhibition of bone resorption in older rats

The skeletal effects of flurbiprofen (Fb), a nonsteroidal antiinflammatory drug, was studied by histomorphometry in 9-month-old retired female breeder, Sprague-Dawley rats. Flurbiprofen was given subcutaneously at 0, 0.2, 0.1, 0.5, 2.5, or 5 mg/kg/d for 21 days. Flurbiprofen had no effect on longitudinal growth, but stimulated radial growth (+200%) over controls. In the tibial shaft, Fb stimulated the mineral apposition rate (+25%), mineral bone formation rate (+100%), and periosteal labeling length (+64%) at the 2.5 and 5.0 mg Fb/kg dose levels, and had no effect on marrow cavity size compared to controls. However, these changes were insufficient to increase cortical bone mass. In the proximal tibial metaphysis, Fb suppressed osteoclasts/mm² of metaphyseal tissue (-47%), osteoclasts/mm of bone surface (-46%), and the osteoclast/osteoblast ratio (-50%), increased the calcified cartilage core population (+100%), and had no effect on osteoblast numbers at all dose levels. There was an insignificant increase in metaphyseal cancellous bone mass. The current study leads to the conclusion that flurbiprofen-stimulated periosteal bone growth was due to direct stimulation of osteoblast recruitment and activity independent of longitudinal bone growth. Further, it confirms early findings in young rats that flurbiprofen induced depressed bone resorption without lowering bone formation. However, because of insufficient treatment time, the older rat did not accumulate bone as the young rats did.     

Optimal bone resorption by isolated rat osteoclasts requires chloride bicarbonate exchange

Summary We have examined the effect of DIDS (4,4′-diisothiocyanatostilbene sulfonic acid) a potent, specific and irreversible inhibitor of chloride/ bicarbonate exchange on bone resorption by disaggregated rat osteoclasts, using anin vitro bone slice assay. DIDS inhibited bone resorption in concentration dependent fashion, without affecting osteoclast viability or survival on bone slices. The role of anion exchange in the resorptive process is discussed.     

淫羊藿抑制颌骨骨吸收的体外实验研究

从乳兔长骨分离出培养破骨细胞，并与人下颌骨骨磨片体外共同培养，分别加入不同浓度(0，0．15，1．5和15mg／ml)的淫羊藿注射液，倒置相差显微镜观察破骨细胞形成的骨吸收陷窝，并对陷窝数目和面积进行图像分析，探讨淫羊藿对破骨细胞性颌骨骨吸收的影响。结果显示，与对照组相比，淫羊藿3个实验组(0．15，1．5和15mg／ml)均能有效抑制破骨细胞在下颌骨片上形成的吸收陷窝的数量和面积，并且抑制作用呈剂量依赖性递增。     

黔岭藿对体外培养的破骨细胞作用的研究

从新生兔四肢长骨中分离的破骨细胞与牛骨片在体外培养后，加入不同浓度黔岭霍注射液再培养，并设立对照，用倒置相差显微镜观察黔岭霍对破骨细胞形成骨吸收陷窝的影响。结果显示黔岭著３个浓度组（０．１５ｍｇ／ｍｌ、１．５ｍｇ／ｍｌ、１５ｍｇ／ｍｌ）与对照组比较均能抑制破骨细胞在骨片上形成吸收陷窝的数量，增加药物浓度抑制作用亦趋增强（Ｐ＜０．０５）。     

鸡破骨细胞分离培养方法的建立

为了寻找一种获得大量、纯化、有活力的破骨细胞的方法，我们对已经建立的兔破骨细胞体外分离培养方法的基础上加以改进。利用冲洗的方法，从２８天的鸡的长骨中得到细胞团１破骨细胞后，又对鸡的长骨相继进行胶原酶和胰蛋白酶的消化，得到细胞团２和细胞团３破骨细胞。将这些分离的细胞与盖玻片或骨磨片共同培养，通过相差显微镜观察到：这些分离的多核巨细胞能够运动，并能在骨磨片上形成吸收陷窝。另外，这些细胞对酸性磷酸酶染色呈阳性反应，而酸性磷酸酶是鉴别破骨细胞的标志。表明此分离培养鸡破骨细胞的实验技术是成功的。通过此方法获得的鸡破骨细胞比用以往方法获得的兔破骨细胞量多，且活力强。本方法的建立，为进一步研究骨吸收机理奠定了基础。     

新伐他汀体外对破骨细胞性骨吸收及大鼠骨代谢的影响

目的探讨新伐他汀体外对破骨细胞骨吸收功能的作用及其大鼠骨代谢的影响.方法采用体外成熟破骨细胞和大鼠颅盖骨培养体系,检测新伐他汀作用7 d后破骨细胞骨吸收陷窝和培养上清钙的变化;检测大鼠颅盖骨培养上清碱磷酶和钙含量,组织学观察颅盖骨形态学变化.结果新伐他汀体外可明显抑制破骨细胞骨吸收陷窝的形成及培养上清钙的释放,新伐他汀体外可增强大鼠颅盖骨培养上清碱磷酶的活性,组织学观察到新伐他汀使大鼠颅盖骨矿化增强.结论新伐他汀体外不仅可促进大鼠颅盖骨的成骨活性,并且可明显抑制破骨细胞骨吸收功能,对骨质疏松有重要的防治作用.     

Avian osteoblast conditioned media stimulate bone resorption by targeting multinucleating osteoclast precursors

Summary Osteoblasts are thought to secrete factors that regulate the rate of osteoclastic bone resorption. We studied the effect of osteoblast conditioned medium on bone degradation by multinucleated osteoclast-like cells generated in vitro from mononuclear precursors and found that the medium stimulates bone degradation primarily through interactions with osteoclast precursors. The conditioned medium also stimulates expression of the osteoclast-specific antigen 121F. The increased bone degradation, but not increased 121F expression, is due to the conditioned medium maintaining activity of the osteoclast precursors. Although the osteoclast precursors exhibit the DNA fragmentation characteristic of apoptosis, the osteoblast conditioned medium does not prevent such fragmentation. Chicken macrophage growth factor neither mimics nor augments the ability of the conditioned medium to stimulate bone degradation. Studies of osteoclast generation or function should carefully consider whether the effects are dependent on the viability of the resorbing cells.A preliminary account of these results was presented at the 12th Annual Meeting of the American Society for Bone and Mineral Research, August 28–31, 1990     

Docetaxel inhibits bone resorption through suppression of osteoclast formation and function in different manners

Osteoclasts are formed from the monocyte-macrophage lineage in response to receptor activator of nuclear factor κB ligand (RANKL) expressed by osteoblasts. Bone is the most common site of breast cancer metastasis, and osteoclasts play roles in the metastasis. The taxane-derived compounds paclitaxel and docetaxel are used for the treatment of malignant diseases, including breast cancer. Here we explored the effects of docetaxel on osteoclastic bone resorption in mouse culture systems. Osteoclasts were formed within 6 days in cocultures of osteoblasts and bone marrow cells treated with 1,25-dihydroxyvitamin D₃ plus prostaglandin E₂. Docetaxel at 10⁻⁸ M inhibited osteoclast formation in the coculture when added for the entire culture period or for the first 3 days. Docetaxel, even at 10⁻⁶ M added for the final 3 days, failed to inhibit osteoclast formation. Osteoprotegerin, a decoy receptor of RANKL, completely inhibited osteoclast formation when added for the final 3 days. Docetaxel at 10⁻⁸ M inhibited the proliferation of osteoblasts and bone marrow cells. RANKL mRNA expression induced by 1,25-dihydroxyvitamin D₃ plus prostaglandin E₂ in osteoblasts was not affected by docetaxel even at 10⁻⁶ M. Docetaxel at 10⁻⁶ M, but not at 10⁻⁸ M, inhibited pit-forming activity of osteoclasts cultured on dentine. Actin ring formation and l-glutamate secretion by osteoclasts were also inhibited by docetaxel at 10⁻⁶ M. Thus, docetaxel inhibits bone resorption in two different manners: inhibition of osteoclast formation at 10⁻⁸ M and of osteoclast function at 10⁻⁶ M. These results suggest that taxanes have beneficial effects in the treatment of bone metastatic cancers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cytochalasin D reduces osteoclastic bone resorption by inhibiting development of ruffled border-clear zone complex

Summary The osteoclastic cytoskeleton has been demonstrated to be composed of microfilaments. Osteoclastic multinucleated cells were suspended on dentine slices and cultured for 24 hours in the presence or absence of cytochalasin D (CD), a specific and potent inhibitor of actin filament elongation to determine the role of this cytoskeleton. Cultured cells and co-cultured dentine slices were examined ultrastructurally. Unlike those in control cultures without CD, osteoclasts in CD-treated cultures became spherical in shape and lacked microvilli on their basolateral cell surfaces. Most importantly, CD treatment induced a complete disappearance of the ruffled border-clear zone complexes in osteoclasts, which resulted in loss of osteoclast-cytoplasmic polarity. Morphometric analysis of backscattered electron micrographs of co-cultured dentine slices revealed that CD treatment strongly inhibited the formation of resorption lacunae in a dose-dependent manner. These results suggest that the cytoarchitecture, as well as the bone-resorbing function, of the osteoclast is highly regulated by the F-actin-containing microfilamentous cytoskeleton in the ruffled border-clear zone complex.