Experimental rat model for acute tubular injury induced by high water hardness and high water fluoride: efficacy of primary preventive intervention by distilled water administration.

BACKGROUND: High water hardness associated with high water fluoride and the geographical distribution of Chronic Kidney Disease of unknown etiology (CKDu) in Sri Lanka are well correlated. We undertook this study to observe the effects of high water hardness with high fluoride on kidney and liver in rats and efficacy of distilled water in reducing the effects. METHODS: Test water sample with high water hardness and high fluoride was collected from Mihinthale region and normal water samples were collected from Kandy region. Twenty-four rats were randomly divided into 8 groups and water samples were introduced as follows as daily water supply. Four groups received normal water for 60 (N1) and 90 (N2) days and test water for 60 (T1) and 90 (T2) days. Other four groups received normal (N3) and test (T3) water for 60 days and followed by distilled water for additional 60 days and normal (N4) and test (T4) water for 90 days followed by distilled water for another 90 days. The rats were sacrificed following treatment. Serum samples were subjected to biochemical tests; serum creatinine, urea, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and elemental analysis. Histopathological examinations were carried out using kidney and liver samples. RESULTS: Test water treated groups were associated with acute tubular injury with loss of brush border and test water followed with distilled water treated groups maintained a better morphology with minimal loss of brush border. Serum creatinine levels in T1 and T2 groups and urea level in T2 group were significantly (p < 0.05) increased compared to control groups. After administration of distilled water, both parameters were significantly reduced in T4 group (p < 0.05) compared to T2. Serum AST activity was increased in T4 group (p < 0.05) compared to control group with no histopathological changes in liver tissues. The serum sodium levels were found to be much higher compared to the other electrolytes in test groups. CONCLUSION: Hard water with high fluoride content resulted in acute tubular injury with a significant increase in serum levels of creatinine, urea and AST activity. These alterations were minimized by administering distilled water.

The role of IL-3 in bone.

In the recent past, there has been a burgeoning interest in targeting cytokines such as IL-3 for specific disease conditions of bone such as rheumatoid arthritis and multiple myeloma. Unlike other cytokines, IL-3 is a cytokine with a multilineage potential and broad spectrum of target cells and it plays a vital role in hematopoiesis. Due to its common receptor subunit, the action of IL-3 shows functional redundancy with other cytokines such as the granulocyte-macrophage colony-stimulating factor and IL-5. IL-3 has been successfully used in ameliorating radiation-induced bone marrow aplasia and similar conditions. However, the role of IL-3 in bone cells has not been fully unraveled yet; therefore, the aim of this overview is to present the effects of IL-3 in bone with a special emphasis on osteoclasts and osteoblasts in a concise manner.

Effect of fluoride on major organs with the different time of exposure in rats.

BACKGROUND: High fluoride levels in drinking water in relation to the prevalence of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka were investigated using rats as an experimental model. METHOD: The effects of fluoride after oral administration of Sodium fluoride (NaF) at levels of 0, 0.5, 5 and 20 ppm F- were evaluated in adult male Wistar rats. Thirty-six rats were randomly divided into 4 groups (n = 9), namely, control, test I, II, and III. Control group was given daily 1 ml/rat of distilled water and test groups I, II, and III were treated 1 ml/rat of NaF doses of 0.5, 5, and 20 ppm, respectively, by using a stomach tube. Three rats from the control group and each experimental group were sacrificed after 15, 30, and 60 days following treatment. Serological and histopathological investigations were carried out using blood, kidney, and liver. RESULTS: No significant differences were observed in body weight gain and relative organ weights of the liver and kidney in fluoride-treated groups compared to control group. After 60 days of fluoride administration, group I showed a mild portal inflammation with lytic necrosis while multiple areas of focal necrosis and various degrees of portal inflammation were observed in groups II and III. This was further confirmed by increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) activities. As compared with control and other treated groups, group III showed a significantly higher serum AST activity (p < 0.05) and ALT activity (p < 0.05) after 60 days and ALP activity with a significant difference (p < 0.05) after 15, 30, and 60 days. The renal histological analysis showed normal histological features in all groups with the elevated serum creatinine levels in group III compared to those in the groups I and II (p < 0.05) after 60 days. Significantly elevated serum fluoride levels were observed in group II of 30 and 60 days and group III after 15, 30, and 60 days with respective to control groups (p < 0.05). CONCLUSION: Taken together, these findings indicate that there can be some alterations in liver enzyme activities at early stages of fluoride intoxication followed by renal damage.

Osteoclast function and bone-resorbing activity: An overview.

Bone resorption is an important cellular function in skeletal development and remodeling of the adult skeleton. Most of the pathological bone disease conditions like osteoporosis reflect increased osteoclast activity; hence, increased bone resorption. Researchers have unraveled most of the intracellular mechanisms responsible for osteoclast bone-resorbing activity in last few decades. Therefore, understanding the fundamentals of osteoclast-induced bone resorption and the cytokines and other substances that modulate the osteoclast activity unequivocally provide insights into the development of drugs to ameliorate pathological bone diseases with enhanced bone resorption. The aim of this review is to examine the literature on osteoclast function and bone-resorbing activity.

NF-κB RELA-deficient bone marrow macrophages fail to support bone formation and to maintain the hematopoietic niche after lethal irradiation and stem cell transplantation.

Bone remodeling and hematopoiesis are interrelated and bone marrow (BM) macrophages are considered to be important for both bone remodeling and maintenance of the hematopoietic niche. We found that NF-κB Rela-deficient chimeric mice, generated by transplanting Rela (-/-) fetal liver cells into lethally irradiated hosts, developed severe osteopenia, reduced lymphopoiesis and enhanced mobilization of hematopoietic stem and progenitor cells when BM cells were completely substituted by Rela-deficient cells. Rela (-/-) hematopoietic stem cells from fetal liver had normal hematopoietic ability, but those harvested from the BM of osteopenic Rela (-/-) chimeric mice had reduced repopulation ability, indicating impairment of the microenvironment for the hematopoietic niche. Osteopenia in Rela (-/-) chimeric mice was due to reduced bone formation, even though osteoblasts differentiated from host cells. This finding indicates impaired functional coupling between osteoblasts and hematopoietic stem cell-derived cells. Rela-deficient BM macrophages exhibited an aberrant inflammatory phenotype, and transplantation with wild-type F4/80(+) BM macrophages recovered bone formation and ameliorated lymphopoiesis in Rela (-/-) chimeric mice. Therefore, RELA in F4/80(+) macrophages is important both for bone homeostasis and for maintaining the hematopoietic niche after lethal irradiation and hematopoietic stem cell transplantation.

Defective microtubule-dependent podosome organization in osteoclasts leads to increased bone density in Pyk2(-/-) mice.

The protein tyrosine kinase Pyk2 is highly expressed in osteoclasts, where it is primarily localized in podosomes. Deletion of Pyk2 in mice leads to mild osteopetrosis due to impairment in osteoclast function. Pyk2-null osteoclasts were unable to transform podosome clusters into a podosome belt at the cell periphery; instead of a sealing zone only small actin rings were formed, resulting in impaired bone resorption. Furthermore, in Pyk2-null osteoclasts, Rho activity was enhanced while microtubule acetylation and stability were significantly reduced. Rescue experiments by ectopic expression of wild-type or a variety of Pyk2 mutants in osteoclasts from Pyk2(-/-) mice have shown that the FAT domain of Pyk2 is essential for podosome belt and sealing zone formation as well as for bone resorption. These experiments underscore an important role of Pyk2 in microtubule-dependent podosome organization, bone resorption, and other osteoclast functions.

The tumor necrosis factor type 2 receptor plays a protective role in tumor necrosis factor-α-induced bone resorption lacunae on mouse calvariae.

Tumor necrosis factor (TNF)-α exerts its biological function via TNF type 1 and type 2 receptors (TNFR1 and TNFR2). We have previously reported that bone resorption induced by lipopolysaccharide (LPS) in TNFR2-deficient mice is accelerated compared to that in wild-type (WT) mice. Although these results suggested that TNFR2 might have a protective role in bone resorption, we could not exclude the possibility that TNFR2 has no role in bone resorption. To clarify the role of TNFR2, we developed a TNF-α-induced bone resorption model using cholesterol-bearing pullulan nanogel as a TNF-α carrier to minimize the influence of inflammatory cytokines other than TNF-α. Injections of human TNF-α (hTNF), an agonist of mouse TNFR1, stimulated bone resorption lacunae on the calvariae in WT mice, but mouse TNF-α (mTNF), an agonist of both mouse TNFR1 and TNFR2, could not. To eliminate the possibility that the TNFR1 agonistic effects of hTNF were stronger than those of mTNF, we used the same model in TNFR2-deficient mice. Injection of mTNF resulted in clear bone resorption lacunae to the same extent observed after using hTNF in the TNFR2-deficient mice. Histomorphometric analysis of osteoclast number supported the observed changes in bone resorption lacunae. These data suggest that TNFR2 has a protective role in TNF-α-induced bone resorption.

Three-dimensional characterization of osteoclast bone-resorbing activity in the resorption lacunae.

Confocal laser microscopy is a well-recognized research tool in the fields of biological and material science which enables high-resolution images of samples with minimum requirements for specimen preparation. Here we introduce an innovative technique for the 3-D description and measurement of resorption pits using Super Depth Surface Profile Measurement Microscope based on the principle of confocal microscope. We show one example of culturing for 48 h with an established NF-kappaB inhibitor named NBD-peptide after plating mature osteoclasts on dentine slices with osteoblasts. The activity of osteoclasts is measured by determining the volume of resorbed portion of dentine by osteoclasts in vitro. The 3-D surface profile could be obtained by detecting the position at which the reflected laser intensity from the target becomes the maximum on z-axis. The volume and depth of resorption lacunae by stimulated osteoclasts is significantly increased compared to the un-stimulated group without changing of resorption area. The increase in volume and depth are dose-dependently inhibited by the NBD-peptide. Comparing to the classical method by measuring 2-D area of pits, analysis based on this technique could provide reliable quantitative assessment reflecting the osteoclast activity.

Positive and negative regulators of osteoclast apoptosis.

Survival and apoptosis are of major importance in the osteoclast life cycle. As osteoclasts have short lifespan, any alteration that prolongs their viability may cause enhanced osteoclast activity. Hence, the regulation of OC apoptosis has been recognized as a critical factor in bone remodeling. An imbalance in bone remodeling due to increased osteoclast activity leads to most adult bone diseases such as osteoporosis, rheumatoid arthritis and multiple myeloma. Therefore, manipulating osteoclast death would be a viable therapeutic approach in ameliorating bone diseases, with accelerated resorption. Over the last few decades we have witnessed the unraveling of many of the intracellular mechanisms responsible for osteoclast apoptosis. Thus, an understanding of the underlying mechanisms by which osteoclasts undergo programmed cell death and the regulators that modulate that activity will undoubtedly provide an insight into the development of pharmacological agents to treat such pathological bone diseases.

Efficacy of articaine vs lignocaine in maxillary and mandibular infiltration and block anesthesia in the dental treatments of adults: A systematic review and meta-analysis.

The aim of the present systematic review and meta-analysis was to address the following Population, Intervention, Comparison, and Outcome question: Is the efficacy of articaine better than lignocaine in adults requiring dental treatment? Four percent articaine was compared with 2% lignocaine for maxillary and mandibular infiltrations and block anesthesia, and with the principal outcome measures of anesthetic success. Using RevMan software, the weighted anesthesia success rates and 95% confidence intervals (CIs) were estimated and compared using a random-effects model. For combined studies, articaine was more likely to achieve successful anesthesia than lignocaine (N = 18, odds ratio [OR]: 1.92, 95% CI: 1.45-2.56, P < 0.00001, I2  = 32%). Maxillary and mandibular infiltration studies showed obvious superiority of articaine to lignocaine (N = 8, OR: 2.50, 95% CI: 1.51-4.15, P = 0.0004, I2  = 41%). Maxillary infiltration subgroup analysis showed no significant difference between articaine and lignocaine (N = 5, OR: 1.69, 95% CI: 0.88-3.23, P = 0.11, I2  = 19%). For combined mandibular anesthesia studies, articaine was superior to lignocaine (N = 14, OR: 1.99, 95% CI: 1.45-2.72, P < 0.0001, I2  = 32%), with further subgroup analysis showing significant differences in both mandibular block anesthesia (N = 11, OR: 1.55, 95% CI: 1.19-2.03, P = 0.001), I2  = 0%) and mandibular infiltration (N = 3, OR: 3.87, 95% CI: 2.62-5.72, P < 0.00001, I2  = 0%), indicating that articaine is more effective than lignocaine in providing anesthetic success in routine dental procedures.

Nanogel-crosslinked nanoparticles increase the inhibitory effects of W9 synthetic peptide on bone loss in a murine bone resorption model.

We investigated the biological activity of W9, a bone resorption inhibitor peptide, using NanoClik nanoparticles as an injectable carrier, where acryloyl group-modified cholesterol-bearing pullulan (CHPOA) nanogels were crosslinked by pentaerythritol tetra (mercaptoethyl) polyoxyethylene. Thirty 5-week-old male C57BL/6J mice were fed a low calcium diet and received once-daily subcutaneous injections of the carrier alone, W9 24 mg/kg/day alone, W9 24 mg/kg/day incorporated in cholesterol bearing pullulan (CHP) nanogels, or W9 (8 and 24 mg/kg/day) incorporated in NanoClik nanoparticles for 4 days (n=5). Mice that received a normal calcium diet with NanoClik nanoparticle injections without W9 were used as a control group. Radiological analyses showed that administration of W9 24 mg/kg/day significantly prevented low calcium-induced reduction of bone mineral density in the long bones and lumbar vertebrae, but only when the NanoClik nanoparticles were used as a carrier. Histomorphometric analyses of the proximal tibiae revealed that W9 24 mg/kg/day incorporated in NanoClik nanoparticles prevented the increase in bone resorption indices induced by a low calcium diet, which was confirmed by measurement of serum bone resorption markers. These data suggest that NanoClik nanoparticles could be a useful carrier for peptide therapeutics, and also demonstrate that daily subcutaneous injections of the W9 peptide with the nanoparticles were able to inhibit bone loss in vivo. An osteoclastogenesis inhibition assay performed in vitro confirmed a slower release profile of W9 from NanoClik nanoparticles compared with conventional CHP nanogels.

Disruption of NF-κB1 prevents bone loss caused by mechanical unloading.

Mechanical unloading, such as in a microgravity environment in space or during bed rest (for patients who require prolonged bed rest), leads to a decrease in bone mass because of the suppression of bone formation and the stimulation of bone resorption. To address the challenges presented by a prolonged stay in space and the forthcoming era of a super-aged society, it will be important to prevent the bone loss caused by prolonged mechanical unloading. Nuclear factor κB (NF-κB) transcription factors are activated by mechanical loading and inflammatory cytokines. Our objective was to elucidate the role of NF-κB pathways in bone loss that are caused by mechanical unloading. Eight-week-old wild-type (WT) and NF-κB1-deficient mice were randomly assigned to a control or mechanically unloaded with tail suspension group. After 2 weeks, a radiographic analysis indicated a decrease in bone mass in the tibias and femurs of the unloaded WT mice but not in the NF-κB1-deficient mice. An NF-κB1 deficiency suppressed the unloading-induced reduction in bone formation by maintaining the proportion and/or potential of osteoprogenitors or immature osteoblasts, and by suppression of bone resorption through the inhibition of intracellular signaling through the receptor activator of NF-κB ligand (RANKL) in osteoclast precursors. Thus, NF-κB1 is involved in two aspects of rapid reduction in bone mass that are induced by disuse osteoporosis in space or bed rest.

Osteoclast formation and differentiation: an overview.

Osteoclasts are multinucleated cells of hematopoietic origin which are unique in their ability to resorb bone. Osteoclasts are generated from myeloid progenitors through a progression that involves the fusion of mononuclear precursor cells. The identification of RANK-RANKL signaling as the main signal regulating osteoclast differentiation was a major breakthrough in the bone biology field. In addition remarkable discoveries have been made to broaden the knowledge of the molecular mechanisms of osteoclast formation and differentiation. Despite the vital requirement of osteoclasts in bone modeling and remodeling, bone-related conditions like osteoporosis, Paget's disease and rheumatoid arthritis where accelerated bone resorption takes place pose a major socioeconomic burden to the society. Hence, a better understanding of the pathways leading to osteoclast differentiation is vital in successfully managing such diseases. This is an attempt to give a birds-eye-view of the players in osteoclast formation and differentiation in a brief and concise manner.

Peptide-based delivery to bone.

Peptides are attractive as novel therapeutic reagents, since they are flexible in adopting and mimicking the local structural features of proteins. Versatile capabilities to perform organic synthetic manipulations are another unique feature of peptides compared to protein-based medicines, such as antibodies. On the other hand, a disadvantage of using a peptide for a therapeutic purpose is its low stability and/or high level of aggregation. During the past two decades, numerous peptides were developed for the treatment of bone diseases, and some peptides have already been used for local applications to repair bone defects in the clinic. However, very few peptides have the ability to form bone themselves. We herein summarize the effects of the therapeutic peptides on bone loss and/or local bone defects, including the results from basic studies. We also herein describe some possible methods for overcoming the obstacles associated with using therapeutic peptide candidates.

A structural modulator of tumor necrosis factor type 1 receptor promotes bone formation under lipopolysaccharide-induced inflammation in a murine tooth extraction model.

Recently an increase in the serum levels of a bone formation marker after anti-tumor necrosis factor (TNF)-α therapy in rheumatoid arthritis patients has been reported. However, there remains no direct evidence that TNF-α antagonist could accelerate bone formation under inflammatory condition. Cavity-induced allosteric modification (CIAM) compound, F002, is a newly developed-TNF-α antagonist, which was designed by using the structure of TNF type 1 receptor, thus preventing TNF-α-induced signaling. In this study, we examined whether the CIAM compound can promote bone formation under inflammatory condition induced by lipopolysaccharide (LPS). Thirty-six 10-week-old male mice (C57BL/6J) were used. Half of the mice received 10 mg/kg LPS, while the other half received PBS. Thereafter, incisor extraction was performed at 4 days after either LPS or PBS injection. Intraperitoneal injections of 2 mg/kg/day, 4 mg/kg/day CIAM, or vehicle (10% DMSO) were performed once a day from day 0 to day 7 after incisor tooth extraction. The mice were sacrificed at 21 days after the extraction. The regenerated bone mineral density (BMD) in the tooth socket, and the mineral apposition rate and the bone formation rate, direct evidences of bone formation, were significantly decreased in the LPS-injected group compared to the PBS-injected group. CIAM compound dose-dependently prevented the decrease of BMD under the LPS-injected condition, and promoted both the mineral apposition rate and the bone formation rate significantly compared to the LPS-injected group. We did not observe any significant differences among the PBS-injected groups. Taken together, TNF-α antagonist CIAM compound, was found to accelerate bone formation under LPS-induced inflammatory condition.

Increased bone mass in adult prostacyclin-deficient mice.

Prostaglandins (PGs) are key regulatory factors that affect bone metabolism. Prostaglandin E(2) (PGE(2)) regulates bone resorption and bone formation. Prostacyclin (PGI(2)) is one of the major products derived from arachidonic acid by the action of cyclooxygenase and PGI(2) synthase (PGIS). Unlike PGE(2), there are few reports about the role of PGI(2) in bone regulation. Therefore, we investigated the potential effect of PGI(2) on bone metabolism. We used PGIS knockout (PGIS(-/-)), PGIS heterozygous (PGIS(+)(/-)), and wild-type mice to investigate the role of PGI(2). Notably, PGIS(-/-) mice gradually displayed an increase in trabecular bone mass in adolescence. Adult PGIS(-/-) mice showed an increase in trabecular bone volume/tissue volume. Histomorphometric analysis showed that PGIS(-/-) mice displayed increases in both bone formation and bone resorption parameters. Levels of serum osteocalcin and C-telopeptides were increased in adult PGIS(-/-) mice. Furthermore, the increased bone mass patterns were rescued in PGIS(-)/(tg) mice. In conclusion, adult PGIS(-/-) mice displayed an overall increase in the levels of both bone formation and bone resorption parameters, which suggests that PGI(2) deficiency accelerates high bone turnover activity with a greater increase in bone mass in aging. These results indicated that PGI(2) may contribute to the maintenance of normal bone mass and micro-architecture in mice in age-dependent manner. Our findings demonstrate for the first time that PGI(2) is involved in bone metabolism in vivo.

The pivotal role of the alternative NF-kappaB pathway in maintenance of basal bone homeostasis and osteoclastogenesis.

The alternative NF-kappaB pathway consists predominantly of NF-kappaB-inducing kinase (NIK), IkappaB kinase alpha (IKKalpha), p100/p52, and RelB. The hallmark of the alternative NF-kappaB signaling is the processing of p100 into p52 through NIK, thus allowing the binding of p52 and RelB. The physiologic relevance of alternative NF-kappaB activation in bone biology, however, is not well understood. To elucidate the role of the alternative pathway in bone homeostasis, we first analyzed alymphoplasic (aly/aly) mice, which have a defective NIK and are unable to process p100, resulting in the absence of p52. We observed increased bone mineral density (BMD) and bone volume, indicating an osteopetrotic phenotype. These mice also have a significant defect in RANKL-induced osteoclastogenesis in vitro and in vivo. NF-kappaB DNA-binding assays revealed reduced activity of RelA, RelB, and p50 and no binding activity of p52 in aly/aly osteoclast nuclear extracts after RANKL stimulation. To determine the role of p100 itself without the influence of a concomitant lack of p52, we used p100(-/-) mice, which specifically lack the p100 inhibitor but still express p52. p100(-/-) mice have an osteopenic phenotype owing to the increased osteoclast and decreased osteoblast numbers that was rescued by the deletion of one allele of the relB gene. Deletion of both allele of relB resulted in a significantly increased bone mass owing to decreased osteoclast activity and increased osteoblast numbers compared with wild-type (WT) controls, revealing a hitherto unknown role for RelB in bone formation. Our data suggest a pivotal role of the alternative NF-kappaB pathway, especially of the inhibitory role of p100, in both basal and stimulated osteoclastogenesis and the importance of RelB in both bone formation and resorption.

Processing of the NF-kappa B2 precursor p100 to p52 is critical for RANKL-induced osteoclast differentiation.

Gene targeting of the p50 and p52 subunits of NF-kappaB has shown that NF-kappaB plays a critical role in osteoclast differentiation. However, the molecular mechanism by which NF-kappaB regulates osteoclast differentiation is still unclear. To address this issue, we analyzed alymphoplasia (aly/aly) mice in which the processing of p100 to p52 does not occur owing to an inactive form of NF-kappaB-inducing kinase (NIK). Aly/aly mice showed a mild osteopetrosis with significantly reduced osteoclast numbers. RANKL-induced osteoclastogenesis from bone marrow cells of aly/aly mice also was suppressed. RANKL still induced the degradation of I kappaB alpha and activated classical NF-kappaB, whereas processing of p100 to p52 was abolished by the aly/aly mutation. Moreover, RANKL-induced expression of NFATc1 was impaired in aly/aly bone marrow. Overexpression of constitutively active IKK alpha or p52 restored osteoclastogenesis in aly/aly cells. Finally, transfection of either wild-type p100, p100 Delta GRR that cannot be processed to p52, or p52 into NF-kappaB 2-deficient cells followed by RANKL treatment revealed a strong correlation between the number of osteoclasts induced by RANKL and the ratio of p52 to p100 expression. Our data provide a new finding for a previously unappreciated role for NF-kappaB in osteoclast differentiation.

Suppression of NF-kappaB increases bone formation and ameliorates osteopenia in ovariectomized mice.

Bone degenerative diseases, including osteoporosis, impair the fine balance between osteoclast bone resorption and osteoblast bone formation. Single-agent therapy for anabolic and anticatabolic effects is attractive as a drug target to ameliorate such conditions. Inhibition of nuclear factor (NF)-κB reduces the osteoclast bone resorption. The role of NF-κB inhibitors on osteoblasts and bone formation, however, is minimal and not well investigated. Using an established NF-κB inhibitor named S1627, we demonstrated that inhibition of NF-κB increases osteoblast differentiation and bone formation in vitro by up-regulating the mRNAs of osteoblast-specific genes like type I collagen, alkaline phosphatase, and osteopontin. In addition, S1627 was able to increase bone formation and repair bone defect in a murine calvarial defect model. To determine the effect of NF-κB on a model of osteoporosis, we injected two doses of inhibitor (25 and 50 mg/kg·d) twice a day in sham-operated or ovariectomized 12-wk-old mice and killed them after 4 wk. The anabolic effect of S1627 on trabecular bone was determined by micro focal computed tomography and histomorphometry. Bone mineral density of inhibitor-treated ovariectomized animals was significantly increased compared with sham-operated mice. Osteoblast-related indices like osteoblast surface, mineral apposition rate, and bone formation rate were increased in S1627-treated animals in a dose-dependent manner. NF-κB inhibition by S1627 increased the trabecular bone volume in ovariectomized mice. Furthermore, S1627 could inhibit the osteoclast number, and osteoclast surface to bone surface. In vitro osteoclastogenesis and bone resorbing activity were dose-dependently reduced by NF-κB inhibitor S1627. Taken collectively, our results suggest that NF-κB inhibitors are effective in treating bone-related diseases due to their dual anabolic and antiresorptive activities.

Inhibition of the classical NF-kappaB pathway prevents osteoclast bone-resorbing activity.

The classical NF-kappaB pathway plays an important role in osteoclast formation and differentiation; however, the role of NF-kappaB in osteoclast bone-resorbing activity is not well understood. To elucidate whether NF-kappaB is important for osteoclast bone-resorbing activity, we used a selective peptide inhibitor of the classical NF-kappaB pathway named the NBD peptide. Osteoclasts were generated using bone marrow macrophages in the presence of M-CSF and RANKL. The NBD peptide dose-dependently blocked the bone-resorbing activity of osteoclasts by reducing area, volume (p < 0.001) and depths (p < 0.05) of pits. The reduced resorption by the peptide was due to reduced osteoclast bone-resorbing activity, but not reduced differentiation as the number of osteoclasts was similar in all groups. The peptide inhibited bone resorption by reducing TRAP activity, disrupting actin rings and preventing osteoclast migration. Gene expressions of a panel of bone resorption markers were significantly reduced. The NBD peptide dose-dependently reduced the RANKL-induced c-Src kinase activity, which is important for actin ring formation and osteoclast bone resorption. Therefore, these data suggest that the classical NF-kappaB pathway plays a pivotal role in osteoclast bone-resorbing activity.