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

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.

Genetically-achieved disturbances to the expression levels of TNFSF11 receptors modulate the effects of zoledronic acid on growing mouse skeletons

Zoledronic acid (ZOL), a nitrogen bisphosphonate (N-BP), is currently used to treat and control pediatric osteolytic diseases. Variations in the intensity of the effects and side effects of N-BPs have been reported with no clear explanations regarding their origins. We wonder if such variations could be associated with different levels of RANKL signaling activity in growing bone during and after the treatment with N-BPs. To answer this question, ZOL was injected into neonate C57BL/6J mice with different genetically-determined RANKL signaling activity levels (Opg^+/+\Rank^Tg-, Opg^+/+\Rank^Tg+, Opg^+/-\Rank^Tg-, Opg^+/-\Rank^Tg+, Opg^-/-\Rank^Tg- and Opg^-/-\Rank^Tg+ mice) following a protocol (4 injections from post-natal day 1 to 7 at the dose of 50 μg/kg) that mimics those used in onco-pediatric patients. At the end of pediatric growth (1 and half months) and at an adult age (10 months), the bone morphometric and mineral parameters were measured using μCT in the tibia and skull for the different mice. A histologic analysis of the dental and periodontal tissues was also performed. At the end of pediatric growth, a delay in long bone and skull bone growth, a blockage of tooth eruption, some molar root alterations and a neoplasia-like structure associated with incisor development were found. Interestingly, the magnitude of these side effects was reduced by Opg deficiency (Opg^-/-) but increased by Rank overexpression (Rank^Tg). Analysis of the skeletal phenotype at ten months confirmed respectively the beneficial and harmful effects of Opg deficiency and Rank overexpression. These results validated the hypothesis that the RANKL signaling activity level in the bone microenvironment is implicated in the modulation of the response to ZOL. Further studies will be necessary to understand the underlying molecular mechanisms, which will help decipher the variability in the effects of N-BPs reported in the human population. SIGNIFICANT STATEMENTS: The present study establishes that in mice the RANKL signaling activity level is a major modulator of the effects and side-effects of bisphosphonates on the individual skeleton during growth. However, the modulatory actions are dependent on the ways in which this level of activity is increased. A decrease in OPG expression is beneficial to the skeletal phenotype observed at the end of growth, while RANK overexpression deteriorates it. Far removed from pediatric treatment, in adults, the skeletal phenotypes initially observed at the end of growth for the different levels of RANKL signaling activity were maintained, although significant improvement was associated only with reductions in OPG expression.

Bisphosphonate use in the horse: what is good and what is not?

Background

Bisphosphonates (BPs) are a family of molecules characterized by two key properties: their ability to bind strongly to bone mineral and their inhibitory effects on mature osteoclasts and thus bone resorption. Chemically two groups of BPs are recognized, non-nitrogen-containing and nitrogen-containing BPs. Non-nitrogen-containing BPs incorporate into the energy pathways of the osteoclast, resulting in disrupted cellular energy metabolism leading to cytotoxic effects and osteoclast apoptosis. Nitrogen-containing BPs primarily inhibit cholesterol biosynthesis resulting in the disruption of intracellular signaling, and other cellular processes in the osteoclast.

Body

BPs also exert a wide range of physiologic activities beyond merely the inhibition of bone resorption. Indeed, the breadth of reported activities include inhibition of cancer cell metastases, proliferation and apoptosis in vitro. In addition, the inhibition of angiogenesis, matrix metalloproteinase activity, altered cytokine and growth factor expression, and reductions in pain have been reported. In humans, clinical BP use has transformed the treatment of both post-menopausal osteoporosis and metastatic breast and prostate cancer. However, BP use has also resulted in significant adverse events including acute-phase reactions, esophagitis, gastritis, and an association with very infrequent atypical femoral fractures (AFF) and osteonecrosis of the jaw (ONJ).

Conclusion

Despite the well-characterized health benefits of BP use in humans, little is known regarding the effects of BPs in the horse. In the equine setting, only non-nitrogen-containing BPs are FDA-approved primarily for the treatment of navicular syndrome. The focus here is to discuss the current understanding of the strengths and weaknesses of BPs in equine veterinary medicine and highlight the future utility of these potentially highly beneficial drugs.

Bisphosphonates and Cancer: A Relationship Beyond the Antiresorptive Effects

Bisphosphonates (BPs) are stable analogues of the Inorganic Pyrophosphate (PPi), an endogenous regulator of bone mineralization, which can resist the hydrolysis in the gastrointestinal tract. Their conformation allows targeting the bone as a result of their three-dimensional structure, which makes them primary agents against osteoclast-mediated bone loss. They are used in many bone pathological conditions, like bone metastasis, because of its ability to modulate bone metabolism into a less favorable place to cancer cell growth, through the inhibition of osteoclastogenesis and bone resorption. This review is focused on the mechanisms of action through which BPs affect the cellular activity and survival, mainly on their antitumoral effects. In conclusion, BPs are considered the primary therapy for skeletal disorders due to its high affinity for bone, but now they are also considered as potential antitumor agents due to its ability to induce tumor cell apoptosis, inhibition of cell adhesion, invasion and proliferation, modulation of the immune system to target and eliminate cancer cells as well as affect the angiogenic mechanisms. Like any other drug, they also have some adverse effects, but the most common, the acute phase reaction, can be minimized with the intake of calcium and vitamin D.

Zoledronate suppressed angiogenesis and osteogenesis by inhibiting osteoclasts formation and secretion of PDGF-BB

PURPOSE

Bisphosphonates related osteonecrosis of jaw (BRONJ) is a severe complication of systemic BPs administration, the mechanism of which is still unclarified. Recently, platelet-derived growth factor-BB (PDGF-BB) secreted by preosteoclasts was reported to promote angiogenesis and osteogenesis. This study aimed to clarify whether bisphosphonates suppressed preosteoclasts releasing PDGF-BB, and whether the suppression harmed coupling of angiogenesis and osteogenesis, which could contribute to BRONJ manifestation.

METHODS AND RESULTS

Zoledronate significantly inhibited osteoclast formation by tartrate-resistant acid phosphatase (TRAP) staining and PDGF-BB secretion tested by ELISA. In line with decreasing secretion of PDGF-BB by preosteoclasts exposed to zoledronate, conditioned medium (CM) from the cells significantly induced less migration of endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) compared to CM from unexposed preosteoclasts. Meanwhile, angiogenic function of EPCs and osteoblastic differentiation of MSCs also declined when culturing with CM from preosteoclasts treated by zoledronate (PZ-CM), evidenced by tube formation assay of EPCs and alkaline phosphatase activity of MSCs. Western blot assay showed that the expression of VEGF in EPCs and OCN, RUNX2 in MSCs declined when culturing with PZ-CM compared to CM from preostoeclasts without exposure of zoledronate.

CONCLUSION

Our study found that zoledronate was able to suppress preosteoclasts releasing PDGF-BB, resulting in suppression of angiogenesis and osteogenesis. Our study may partly contributed to the mechanism of BRONJ.

[Formation of bone in critical calvarias defects in rats under the influence of bisphosphonate alendronate Na complex]

The aim of the study was to investigate dynamic of tissue structures in critical defects of calvaria of rats after inoculation of bisphosphonate (BF) alendronate Na complex into bone defects. Animal model included 24 Wistar rats divided in 3 groups: spontaneous healing under blot clot (1), inoculation of carbonate hydroxide apatite β-tricalcium phosphate blocks (2) and BF alendronate Na complex (3) on 15, 30, 60 and 90 experiment day. New bone formation was observed in group 3 as opposed to groups 1 and 2.

Effect of alendronate on the mandible and long bones: an experimental study in vivo

BACKGROUND

Bisphosphonates are anticatabolic agents that inhibit bone resorption and are widely used to treat osteoporosis and bone metastases in adults. They are also used in young patients with diseases like osteogenesis imperfecta or juvenile osteoporosis. Bone modeling/remodeling is elevated in growing subjects, and inhibition of osteoclastic activity has been shown to interfere with growth. Thus, our objective was to evaluate the effect of alendronate (ALN) on growing animals.

METHODS

Healthy male Wistar rats, aged 1 mo, received ALN or vehicle for 8 wk. Serum levels (calcemia, phosphatemia, and total alkaline phosphatase) were determined. Morphometric (rat: femur and tibia weight and length and hemimandible growth) and histomorphometric parameters (thickness of tibial epiphyseal cartilage and each cartilage zone, interradicular bone volume in the first lower molar, trabeculae volume, percentage of bone and cartilage, and osteoclast number in mandibular condyles) were assessed.

RESULTS

ALN caused a significant decrease in femur and tibia length, tibial cartilage thickness, and longitudinal growth of hemimandibles. It increased interradicular bone volume and mandibular condyle trabeculae volume, increasing the percentage of cartilage and osteoclast number.

CONCLUSION

These findings indicate that administration of ALN to growing animals alters the endochondral ossification process, and thus alters growth.

The effect of dipeptidyl peptidase-IV inhibition on bone in a mouse model of type 2 diabetes

BACKGROUND

Individuals with type 2 diabetes (T2D) are at greater risk of bone fractures than those without diabetes. Certain oral diabetic medications may further increase the risk of fracture. Dipeptidyl peptidase-IV (DPP-IV) inhibitors are incretin-based therapies that are being increasingly used for the management of T2D. It has been hypothesized that these agents may reduce fracture risk in those with T2D. In this study, we used a mouse model of T2D to examine the effects of the DPP-IV inhibitor, MK-0626, on bone.

METHODS

Male wild type (WT) and diabetic muscle-lysine-arginine (MKR) mice were treated with MK-0626, pioglitazone, alendronate or vehicle. The effects of treatment with MK-0626 on bone microarchitecture and turnover were compared with treatment with pioglitazone, alendronate and vehicle. Osteoblast differentiation was determined by alkaline phosphatase staining of bone marrow cells from WT and MKR mice after treatment with pioglitazone, MK-0626 or phosphate buffered saline.

RESULTS

We found that MK-0626 had neutral effects on cortical and trabecular bone in diabetic mice. Pioglitazone had detrimental effects on the trabecular bone of WT but not of diabetic mice. Alendronate caused improvements in cortical and trabecular bone architecture in diabetic and WT mice. MK-0626 did not alter osteoblast differentiation, but pioglitazone impaired osteoblast differentiation in vitro.

CONCLUSIONS

Overall, the DPP-IV inhibitor, MK-0626, had no adverse effects on bone in an animal model of T2D or directly on osteoblasts in culture. These findings are reassuring as DPP-IV inhibitors are being widely used to treat patients with T2D who are already at an increased risk of fractures.

Diverse osteoclastogenesis of bone marrow from mandible versus long bone

BACKGROUND

Mandibles (MB) and maxillae possess unique metabolic and functional properties and demonstrate discrete responses to homeostatic, mechanical, hormonal, and developmental stimuli. Osteogenic potential of bone marrow stromal cells (BMSCs) differs between MB versus long bones (LB). Furthermore, MB- versus LB-derived osteoclasts (OCs) have disparate functional properties. This study explores the osteoclastogenic potential of rat MB versus LB marrow in vitro and in vivo under basal and stimulated conditions.

METHODS

Bone marrow from rat MB and LB was cultured in osteoblastic or osteoclastic differentiation media. Tartrate-resistant acid phosphatase (TRAP) staining, resorption pit assays, and real-time polymerase chain reaction were performed. Additionally, osmotic mini-pumps were implanted in animals, mandibles and tibiae were isolated, and multinucleated cells (MNCs) were measured.

RESULTS

MB versus LB marrow cultures that were differentiated with receptor activator of nuclear factor-κB ligand (RANKL) and macrophage colony-stimulating factor produced more TRAP(+) MNCs and greater resorptive area. To explore MB versus LB BMSC-supported osteoclastogenesis, confluent BMSCs were cultured with parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3 (1,25D3), or PTH+1,25D3. 1,25D3- or PTH+1,25D3-treated LB BMSCs expressed significantly higher RANKL and lower osteoprotegerin (OPG) mRNA and increased RANKL:OPG ratio. When whole marrow was cultured with PTH+1,25D3, more TRAP(+) MNCs were seen in LB versus MB cultures. Ultimately, rats were infused with PTH+1,25D3, and MB versus tibia MNCs were measured. Hormonal stimulation increased osteoclastogenesis in both MB and tibiae. However, higher TRAP(+) MNC numbers were observed in tibiae versus MB under basal and hormonal stimulation.

CONCLUSION

Collectively, these data illustrate differences of both osteoclastogenic potential and OC numbers of MB versus LB marrow.