Alendronate stimulates collagenase 3 expression in osteoblasts by posttranscriptional mechanisms

5'-Methylthioadenosine strongly suppresses RANKL-induced osteoclast differentiation and function via inhibition of RANK-NFATc1 signalling pathways

Excessive osteoclast-mediated bone resorption is a critical cause of osteoporosis affecting many aging people worldwide. 5'-Methylthioadenosine (MTA) is a natural sulfur-containing nucleoside normally produced in prokaryotes, plants, yeast, and higher eukaryotes via polyamine metabolism. MTA affects various physiological responses particularly the inflammatory pathway in both normal and cancerous cells and modulates the activation of nuclear factor-κB involved in the osteoclastogenesis signalling process. While several studies have reported that natural products possess anti-osteoclastogenesis phenolics and flavonoids, the effect of nucleoside derivatives on osteoclastogenesis remains limited. Therefore, this study aimed to explore the molecular mechanisms by which MTA affects pre-osteoclastic RAW 264.7 cells as a potential alleviation compound for inflammation-mediated bone loss. Osteoclasts were established by incubating RAW264.7 macrophage cells with receptor activator of nuclear factor kappa B ligand (RANKL) and macrophage colony-stimulating factor, the vital cytokines for activation of osteoclast differentiation. Cell viability was measured using MTT assays at 24, 48, and 72 h. The suppressive effect of MTA on RANKL-induced osteoclast differentiation and function was assessed using tartrate-resistant acid phosphatase (TRAP) analysis, qRT-PCR, and pit formation, Western blot, and immunofluorescence assays. MTA showed dose-dependent anti-osteoclastogenic activity by inhibiting TRAP-positive cell and pit formation and reducing essential digestive enzymes, including TRAP, cathepsin K, and matrix metallopeptidase 9. MTA was observed to suppress the osteoclast transduction pathway through (RANKL)-induced nuclear factor kappa-light-chain-enhancer of activated B cells (NFƘB); it attenuated NFƘB-P65 expression and down-regulated cFos proto-oncogene and nuclear factor of activated T cell c1 (NFATc1), the main regulators of osteoclasts. Moreover, the suppression of RANK (the initial receptor triggering several osteoclastogenic transduction pathways) was observed. Thus, this study highlights the potential of MTA as an effective therapeutic compound for restoring bone metabolic disease by inhibiting the RANK-NFATc1 signal pathway.

Dietary ω-3 Fatty Acid Supplementation Improves Murine Sickle Cell Bone Disease and Reprograms Adipogenesis

Sickle cell disease (SCD) is a genetic disorder of hemoglobin, leading to chronic hemolytic anemia and multiple organ damage. Among chronic organ complications, sickle cell bone disease (SBD) has a very high prevalence, resulting in long-term disability, chronic pain and fractures. Here, we evaluated the effects of ω-3 (fish oil-based, FD)-enriched diet vs. ω-6 (soybean oil-based, SD)- supplementation on murine SBD. We exposed SCD mice to recurrent hypoxia/reoxygenation (rec H/R), a consolidated model for SBD. In rec H/R SS mice, FD improves osteoblastogenesis/osteogenic activity by downregulating osteoclast activity via miR205 down-modulation and reduces both systemic and local inflammation. We also evaluated adipogenesis in both AA and SS mice fed with either SD or FD and exposed to rec H/R. FD reduced and reprogramed adipogenesis from white to brown adipocyte tissue (BAT) in bone compartments. This was supported by increased expression of uncoupling protein 1(UCP1), a BAT marker, and up-regulation of miR455, which promotes browning of white adipose tissue. Our findings provide new insights on the mechanism of action of ω-3 fatty acid supplementation on the pathogenesis of SBD and strengthen the rationale for ω-3 fatty acid dietary supplementation in SCD as a complementary therapeutic intervention.

Alteration of macrophage viability, differentiation, and function by bisphosphonates

BACKGROUND

A serious adverse effect of long-term bisphosphonate (BP) administration is bisphosphonate-related osteonecrosis of the jaw (BRONJ). Among different proposed pathogenesis, suppression of immune cells is gaining interest. Because monocytes/macrophages could get access to BP since residing in the blood and bone microenvironment, the aim of this study was to analyze the behaviors of macrophages after BP treatments in vitro.

METHODS

THP-1 cell, an established human monocytic cell model, was used in this study. The effects of BPs, alendronate (ALN) and zoledronic acid (ZA), on macrophage viability, differentiation, and function were investigated. MTT, morphological analysis, flow cytometry, quantitative PCR, and gelatin zymography assay were performed.

RESULTS

BPs impaired macrophage viability at almost all concentration tested (1-100 μM). Cell morphology was altered in the presence of 100 μM BPs. Furthermore, differentiating macrophage viability was also affected by both ALN and ZA at 100 and 10-100 μM, respectively. At high concentration (100 μM), ZA caused a reduction in cell differentiation. On the contrary, ALN and ZA increased matrix metalloproteinase mRNA expressions and activities at low doses (1-10 μM).

CONCLUSION

BPs directly acted on macrophage by reducing macrophage survival, inducing morphological alterations, impairing differentiation from monocytes to macrophages, and affecting macrophage function at both mRNA and activity levels.

Dynamic expression of matrix metalloproteinases 2, 9 and 13 in ovariectomy-induced osteoporosis rats

The aim of the present study was to examine the dynamic expression of matrix metalloproteinase (MMP)-2, MMP-9 and MMP-13 in an ovariectomy (OVX)-induced osteoporosis rat model. A total of 80 Sprague-Dawley female rats (age, 3 months) were randomly divided into the OVX and sham groups, with 40 rats in each group. Rats in the sham group received sham surgery, while the remaining rats were ovariectomized. After 12, 16, 20 and 24 weeks, 10 rats from each group were randomly sacrificed, respectively. It was observed that the bone mineral density (BMD) and the trabecular bone area in the OVX group were significantly lower as compared with those in the sham group (P<0.01). The expression levels of MMP-2 and MMP-9 were negatively correlated with the BMD, while MMP-13 was positively correlated with the BMD. The expression levels of MMP-2 and MMP-9 increased more abruptly and were significant higher in the OVX group in comparison with those in the sham group between 12 and 24 weeks after surgery (P<0.01). More specifically, the MMP-9 mRNA expression level in the OVX group increased abruptly between 12 and 24 weeks after surgery. By contrast, in the sham group, the MMP-9 mRNA level was undetectable between 12 and 16 weeks, and increased steadily between 16 and 24 weeks. Furthermore, the mRNA and protein expression levels of MMP-13 initially increased and then decreased in the OVX group (P<0.01 vs. the sham group), whereas they continuously increased in the sham group between 12 and 24 weeks after surgery. In conclusion, MMP-2, MMP-9 and MMP-13 regulated the development of osteoporosis, and MMP-9 may be used as an important marker in the early diagnosis of osteoporosis.

Matrix Metalloproteinases in Bone Resorption, Remodeling, and Repair

Matrix metalloproteinases (MMPs) are the major protease family responsible for the cleavage of the matrisome (global composition of the extracellular matrix (ECM) proteome) and proteins unrelated to the ECM, generating bioactive molecules. These proteins drive ECM remodeling, in association with tissue-specific and cell-anchored inhibitors (TIMPs and RECK, respectively). In the bone, the ECM mediates cell adhesion, mechanotransduction, nucleation of mineralization, and the immobilization of growth factors to protect them from damage or degradation. Since the first description of an MMP in bone tissue, many other MMPs have been identified, as well as their inhibitors. Numerous functions have been assigned to these proteins, including osteoblast/osteocyte differentiation, bone formation, solubilization of the osteoid during bone resorption, osteoclast recruitment and migration, and as a coupling factor in bone remodeling under physiological conditions. In turn, a number of pathologies, associated with imbalanced bone remodeling, arise mainly from MMP overexpression and abnormalities of the ECM, leading to bone osteolysis or bone formation. In this review, we will discuss the functions of MMPs and their inhibitors in bone cells, during bone remodeling, pathological bone resorption (osteoporosis and bone metastasis), bone repair/regeneration, and emergent roles in bone bioengineering.

Zoledronate upregulates MMP-9 and -13 in rat vascular smooth muscle cells by inducing oxidative stress

Background

Bisphosphonates, including zoledronate, target osteoclasts and are widely used in the treatment of osteoporosis and other bone resorption diseases, despite side effects that include damaging the stomach epithelium. Beneficial and adverse effects on other organ systems, including the cardiovascular system, have also been described and could impact on the use of bisphosphonates as therapeutic agents. Vascular smooth muscle cells (VSMCs) are major constituents of the normal vascular wall and have a key role in intimal thickening and atherosclerosis, in part by secreting MMPs that remodel the extracellular matrix and cleave cell surface proteins or secreted mediators. In this study, we investigated the effects of zoledronate on MMP expression.

Methods

Rat VSMCs were stimulated by PDGF (50 ng/mL) plus TNF-α (10 ng/mL) or left unstimulated for a further 24 hours in serum-free medium. In other series of experiments, cells were pre-treated either with SC-514 (50 μM) or with apocynin (20 nM) for 2 hours, then zoledronate (100 μM) was added into 2% fetal calf serum containing medium for 24 hours.

Results and discussion

Using isolated rat VSMCs in culture, zoledronate (100 μM) increased MMP-9 and -13 mRNA expressions but inhibited MMP-2 expression. MMP-9 and MMP-13 up-regulation was shown to depend on the NF-κB pathway; and this was activated by zoledronate. Furthermore, zoledronate elevated the levels of reactive oxygen species detected by either dichlorofluorescein in isolated VSMCs or lucigenin enhanced chemiluminescence in rat aortic rings in vitro. Apocynin, an inhibitor of NADPH oxidase, reversed NF-κB activation and MMP-9 and MMP-13 up-regulation by zoledronate.

Conclusion

We conclude that zoledronate increases MMP-9 and MMP-13 expressions in rat VSMCs dependent upon stimulation of the NF-κB pathway by reactive oxygen species. Effects on MMP expression may contribute to the pharmacologic profile of bisphosphonates.

The effect of bisphosphonates on gene expression: GAPDH as a housekeeping or a new target gene?

BACKGROUND

RT-PCR has been widely used for the analysis of gene expression in many systems, including tumor samples. GAPDH (Glyceraldehyde-3-phosphate dehydrogenase) has been frequently considered as a constitutive housekeeping gene and used to normalize changes in specific gene expression. However, GAPDH has been shown to be up-regulated in many cancers and down-regulated by chemotherapic drugs. Bisphosphonates, potent inhibitors of bone resorption, have recently shown a direct and indirect antitumor effect in vitro and in animal models. They exert their effects mainly by inhibiting the mevalonate pathway but also by modulating the expression of many genes not only in osteoclasts but also in cancer cells.

METHODS

We evaluated GAPDH gene expression by real time RT PCR in breast (MCF-7 and T47D) and prostate (PC3 and DU-145) cancer cell lines treated with amino and non-amino bisphosphonates.

RESULTS

Our results showed that amino-bisphosphonates significantly decrease in a dose-dependent manner the expression of GAPDH gene.

CONCLUSION

Therefore, GAPDH is inaccurate to normalize mRNA levels in studies investigating the effect of bisphosphonates on gene expression and it should be avoided. On the other hand, this gene could be considered a potential target to observe the effects of bisphosphonates on cancer cells.

Neridronate and human osteoblasts in normal, osteoporotic and osteoarthritic subjects

The objective of this study was to evaluate the metabolic in vitro effect of the bisphosphonate neridronate on normal and pathological human osteoblasts. Primary human osteoblast cultures were obtained from cancellous bone of osteoarthritic (OA) and osteoporotic (OP) patients and a corresponding healthy control group. Osteocalcin production was evaluated by cultured cells in neridronate 10(-4) M and 10(-6) M, both under basal conditions and after vitamin D3 stimulation. In the absence of neridronate, vitamin D3 increased osteocalcin production in all cell cultures; under the same conditions, and in the absence of vitamin D3, OA osteoblasts showed a significantly higher osteocalcin production whereas OP osteoblasts showed a significantly lower osteocalcin production compared to the normal osteoblasts, respectively. In all cellular populations neridronate at a higher concentration (10(-4) M) induced a reduction in osteocalcin synthesis, but in normal and osteoarthritic osteoblasts did not reduce the stimulatory effect of vitamin D3, whereas it inhibited the vitamin D3-induced increase of osteocalcin synthesis in the osteoporotic cells. In normal and osteoporotic osteoblasts stimulation with the lower neridronate concentration (10(-6) M) significantly increased osteocalcin production, which was further enhanced by vitamin D3 as an additional effect of the combined treatment. In OA osteoblasts, neridronate 10(-6) M did not induce an increase in osteocalcin synthesis and the additional effect of combined treatment with vitamin D3 was not observed. Neridronate can modify the metabolic activity of human osteoblasts by enhancing or decreasing their biosynthetic activity, both in normal and in pathological conditions, depending on compound concentration and on different cell types. These results confirm the validity of using neridronate at doses usually administered in treating osteoporosis, and they suggest using it to treat other diseases which show an altered osteoblast metabolism, such as osteoarthritis.

Zoledronic acid up-regulates bone sialoprotein expression in osteoblastic cells through Rho GTPase inhibition

Clinical practice reveals that osteoporotic women treated with BPs (bisphosphonates) show an increased bone mass density and a reduced risk of fractures. However, the mechanisms leading to these beneficial effects of BPs are still poorly understood. We hypothesized that ZOL (zoledronic acid), a potent third-generation BP, may induce the expression of proteins associated with the bone-forming potential of osteoblastic cells such as BSP (bone sialo-protein). Expression of BSP gene is up-regulated by hormones that promote bone formation and has been associated with de novo bone mineralization. Using real-time reverse transcriptase-PCR and Western-blot analysis, we demonstrated that ZOL increased BSP expression in Saos-2 osteoblast-like cells. Nuclear run-on and mRNA decay assays showed no effect at the transcriptional level but a stabilization of BSP transcripts in ZOL-treated cells. ZOL effect on BSP expression occurred through an interference with the mevalonate pathway since it was reversed by either mevalonate pathway intermediates or a Rho GTPase activator. We showed that ZOL impaired membrane localization of RhoA in Saos-2 cells indicating reduced prenylation of this protein. By the use of small interfering RNAs directed to RhoA and Rac1, we identified both Rho GTPases as negative regulators of BSP expression in Saos-2 cells. Our study demonstrates that ZOL induces BSP expression in osteoblast-like cells through inactivation of Rho GTPases and provides a potential mechanism to explain the favourable effects of ZOL treatment on bone mass and integrity.

Immediately Loaded Bar-Connected Implants with an Anodized Surface Inserted in the Anterior Mandible in a Patient Treated with Diphosphonates for Osteoporosis: A Case Report with a 12-Month Follow-Up

BACKGROUND

It has been suggested that tooth loss is greater in the osteoporotic patient population. Only a few cases have been reported in the literature about the use of dental implants in patients with osteoporosis. Diphosphonates are stable analogs of pyrophosphate, a physiologic regulator of calcification and bone resorption. Multiple implant failures have been reported in a patient undergoing treatment with diphosphonates. Recently, several clinical and experimental reports have shown that immediate loading of dental implants is possible in selected situations.

PURPOSE

The aim of this case report was to present the clinical outcome of immediate loading of implants in a patient undergoing diphosphonate treatment for osteoporosis.

MATERIALS AND METHODS

In a 65-year-old patient undergoing diphosphonate treatment for osteoporosis, four implants were inserted in the anterior mandible. The implants were connected with a bar supporting an overdenture and were then loaded the same day.

RESULTS

No problems occurred in the postoperative period. At 1-year follow-up, all four of the implants appeared to be clinically osseointegrated, and no mobility was present. Minimal bone resorption was present around all implants.

CONCLUSIONS

Our case report points to the fact that, contrary to what has been reported in the literature, it is possible to successfully insert and load immediately after surgery dental implants in a patient undergoing diphosphonate treatment for osteoporosis.

Regulation of MMP-9 (gelatinase B) in activated human monocyte/macrophages by two different types of bisphosphonates

Metalloproteinases (MMP), particularly MMP-9 produced by the intratumor monocyte/macrophages, play an important role in tumor invasion and metastases. Recent clinical trials in patients with primary breast cancer suggest that bisphosphonates (BP), above all clodronate, may reduce bone metastases. The aim of the present study was to evaluate whether the effects of BPs on cancer dissemination include inhibition of MMP-9 production in human monocyte/macrophages. The effects of clodronate and pamidronate on the MMP-9 expression in and secretion from stimulated human monocyte/macrophages were measured using quantitative reverse transcriptase - polymerase chain reaction (RT-PCR) and enzyme-linked immunoadsorbent assay (ELISA), respectively. The MMP-9 mRNA levels remained relatively stable in the presence of clodronate. In contrast, pamidronate at 30 microM-300 microM increased the mRNA levels 5- to 10-fold. MMP-9 secretion was dose-dependently down-regulated by clodronate whereas pamidronate at 30 microM induced a 50% increase on MMP-9 secretion (p < 0.05), followed by a down-regulation at higher concentrations. The results suggest that MMP-9 is differentially regulated at mRNA and enzyme protein level by BPs, which affect ATP-dependent intracellular enzymes (clodronate) or post-translational modification of GTPases (pamidronate). These findings may have implications for the therapeutic use of these compounds.

Translational repression of human matrix metalloproteinases-13 by an alternatively spliced form of T-cell-restricted intracellular antigen-related protein (TIAR)

Human matrix metalloproteinases-13 (HMMP13) shows a wide substrate specificity, and its expression is limited to pathological situations such as chronic inflammation and cancer. The coding sequence for HMMP13 is 86% identical to rat matrix metalloproteinases-13 (RMMP13); however, the regulation of HMMP13 and RMMP13 protein synthesis in renal mesangial cells is strikingly different. In human cells there is a discordance between HMMP13 mRNA levels and protein expression. Following IL-1 beta or TGF-beta(1) stimulation, HMMP13 mRNA levels increase significantly, whereas the protein expression is absent. This discordance is because of a species-dependent translational repression. In addition to the 3'-untranslated region of the matrix metalloproteinases-13 (MMP13) gene, the differential expression of an alternatively spliced transcript of the RNA-binding protein TIAR in human cell cultures is also critical for this post-transcriptional regulation. Transient expression of the 17-amino acid insert of the alternatively spliced form of TIAR reverses the HMMP13 mRNA silencing observed in human and primate species. In addition, co-transfection of the alternatively spliced form of TIAR and HMMP13 into Rat2 cells suppresses HMMP13 protein expression. Thus, we report for the first time that a species-dependent TIAR isoform plays a major role in the post-transcriptional silencing for HMMP13.

Alendronate interacts with the inhibitory effect of 1,25(OH)2D3 on parathyroid hormone-related protein expression in human osteoblastic cells

The bisphosphonate alendronate is a potent inhibitor of bone resorption by its direct action on osteoclasts. In addition, there is some data suggesting that alendronate could also inhibit bone resorption indirectly by interacting with osteoblasts. Parathyroid hormone-related protein (PTHrP) produced by osteoblasts and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] are regulators of bone remodeling, which have interrelated actions in these cells. In this study, we assessed whether alendronate can affect PTHrP expression in the presence or absence of 1,25(OH)2D3 in human primary osteoblastic (hOB) cells from trabecular bone. Cell total RNA was isolated, and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) was carried out using human PTHrP-specific primers. PTHrP in the hOB cell-conditioned medium was analyzed by a specific immunoradiometric assay. We found that PTHrP mRNA and secreted PTHrP were maximally inhibited by 10(-8) - 10(-6) M of 1,25(OH)2D3 treatment within 8-72 h in hOB cells. Alendronate (10(-14) - 10(-8) M) modified neither PTHrP mRNA nor PTHrP secretion, although it consistently abrogated the decrease in PTHrP production induced by 1,25(OH)2D3 in these cells. On the other hand, alendronate within the same dose range did not affect either the vitamin D receptor (VDR) mRNA or osteocalcin secretion, with or without 1,25(OH)2D3, in hOB cells. The inhibitory effect of alendronate on the 1,25(OH)2D3-induced decrease in PTHrP in these cells was mimicked by the calcium ionophore A23187 (5 x 10-6 M), while it was eliminated by 5 x 10(-5) M of nifedipine. Furthermore, although alendronate alone failed to affect [Ca2+]i in these cells, it stimulated [Ca2+]i after pretreatment of hOB cells with 10(-8) M of 1,25(OH)2D3, an effect that was abolished by 5 x 10(-5) M of nifedipine. These results show that alendronate disrupts the modulatory effect of 1,25(OH)2D3 on PTHrP production in hOB cells. Our findings indicate that an increase in calcium influx appears to be involved in the mechanism mediating this effect of alendronate.

[Pharmacological and clinical properties of alendronate sodium hydrate]

Alendronate (alendronate sodium hydrate; Bonalon Tablet, 5 mg) is a nitrogen-containing bisphosphonate, which combines with the bone surface and reduces osteoclast-mediated bone resorption. It is a third-generation bisphosphonate compound, specifically distributed on the surface of bone resorption and taken into osteoclasts. Under the closed circumstances which is formed with osteoclast and the bone surface, alendronate becomes detached from the bone surface and taken into osteoclast since acid released from osteoclast leads to pH decrease (acidified). The uptaken alendronate blocks the pathway of mevalonic acid synthesis, which is cholesteric synthesis, inhibits the prenylation of GTP binding protein, and decreases the osteoclast's function by influencing the cytoskeleton. This restraint of alendronate in bone resorption against osteoclasts is reversible, showing no cytotoxicity at more than hundredfold concentration level at which action occurs. Alendronate is an agent for the treatment of osteoporosis that has established safety with regards to bone quality since it neither inhibits bone calcification nor influences fracture healing in chronic administration. The most serious morbidity in osteoporosis is developing fractures. The efficacy of alendronate on restraining fracture, as well as on increase in BMD, is evidenced in Japan. Recently, in addition to senile or postmenopausal osteoporosis, drug-induced osteoporosis, such as steroid-induced osteoporosis, has attracted attention. In this regard, alendronate has been found to be an effective agent for the treatment of osteoporosis overseas, being approved in over 90 countries and used by more than 4.5 million patients. This review will give an outline of alendronate, the preparation to have introduced a concept of Evidence Based Medicine earlier, from pharmacodynamic action to clinical efficacy.

Bisphosphonates pamidronate and zoledronic acid stimulate osteoprotegerin production by primary human osteoblasts

Bisphosphonates are potent antiresorptive drugs commonly employed in the treatment of metabolic bone diseases. Despite their frequent use, the mechanisms of bisphosphonates on bone cells have largely remained unclear. Receptor activator of nuclear factor-kappaB ligand (RANKL) is essential for osteoclast formation and activation, whereas osteoprotegerin (OPG) neutralizes RANKL. Various osteotropic drugs have been demonstrated to modulate osteoblastic production of RANKL and OPG. In this study, we assessed the effects of the bisphosphonates pamidronate (PAM) and zoledronic acid (ZOL) on OPG mRNA steady-state levels (by semiquantitative RT-PCR) and protein production (by ELISA) in primary human osteoblasts (hOB). PAM increased OPG mRNA levels and protein secretion by hOB by up to 2- to 3-fold in a dose-dependent fashion with a maximum effect at 10(-6) M (P < 0.001) after 72 h. Similarly, ZOL enhanced OPG gene expression and protein secretion by hOB in a dose-dependent fashion with a maximum effect at 10(-8) M after 72 h, consistent with the higher biological potency of ZOL. Time course experiments indicated a stimulatory effect of PAM and ZOL on osteoblastic OPG protein secretion by 6-fold, respectively (P < 0.001). Pretreatment with PAM and ZOL prevented the inhibitory effects of the glucocorticoid dexamethasone on OPG mRNA and protein production. Analysis of cellular markers of osteoblastic differentiation revealed that PAM and ZOL induced type I collagen secretion and alkaline phosphatase activity by 2- and 4-fold, respectively (P < 0.0001 by ANOVA). In conclusion, our data suggest that bisphosphonates modulate OPG production by normal human osteoblasts, which may contribute to the inhibition of osteoclastic bone resorption. Since, OPG production increases with osteoblastic cell maturation, enhancement of OPG by bisphosphonates could be related to their stimulatory effects on osteoblastic differentiation.