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.

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.

Polysaccharide nanogel delivery of a TNF-alpha and RANKL antagonist peptide allows systemic prevention of bone loss.

We report here a nanogel-mediated peptide drug delivery system. Low stability is a major drawback towards clinical application of peptide drugs. The W9-peptide, a TNF-alpha and RANKL antagonist, was used as a model for testing the feasibility of cholesterol-bearing pullulan (CHP)-nanogel as the drug delivery system. We found CHP-nanogel could form complex with the W9-peptide and prevents its aggregation in vitro. Murine bone resorption model using low dietary calcium was used to investigate the in vivo effect. Two-time-injection of 24 mg/kg W9-peptide per day with or without CHP-nanogel was given for 7 days. Thereafter, radiological, and histological assessments were performed. The injections of the W9-peptide (24 mg/kg) with CHP-nanogel prevented the reduction in bone mineral density whereas the same dose without CHP-nanogel could not show any inhibitory effect. Histomorphometric analysis of tibiae showed significant decrease of osteoclast number and surface in CHP-W9 complex treated group and the levels of urinary deoxypyridinoline reflected these decrease of bone resorption parameters. Taken together these data shows that CHP-nanogel worked as a suitable carrier for the W9-peptide and it prevented aggregation and increased the stability of the W9-peptide. This study reveals the feasibility of CHP-nanogel-mediated peptide delivery in preventing bone resorption in vivo.

LPS-induced inhibition of osteogenesis is TNF-alpha dependent in a murine tooth extraction model.

TNF-alpha is a major etiologic factor of inflammatory bone diseases such as periodontitis and rheumatoid arthritis. In addition, patients with metabolic diseases such as chronic heart disease and diabetes have significantly increased plasma levels of TNF-alpha. Several lines of evidence show inhibition of osteoblastogenesis by TNF-alpha in vitro. Therefore, bone formation and osteogenesis in these patients might be inhibited because of TNF-alpha. However, little is known about the inhibitory role of TNF-alpha in bone formation/osteogenesis in vivo. The purpose of this study was to investigate the role of TNF-alpha in osteogenesis using a murine tooth extraction model. Lipopolysaccharide (LPS) was injected subcutaneously into the calvariae of either wildtype (WT) or TNF-alpha-deficient (KO) mice. The left incisor was extracted 4 days after LPS injection. The measuring area was established as the tooth socket under the mesial root of the first molar. A significant increase in serum TNF-alpha levels after LPS injection was observed in WT mice. The BMD of the tooth socket was significantly decreased by LPS injection 21 days after extraction in WT but not in KO mice. Histomorphometric analysis showed a significant decrease in the mineral apposition rate after LPS injection, which appeared at an early stage in WT but not in KO mice. Injection of a peptide that blocked the TNF-alpha signaling pathway by preventing transmission of the NF-kappaB signal recovered the inhibition of osteogenesis observed after LPS injection. In conclusion, TNF-alpha might play a major role in LPS-induced inhibition of osteogenesis under inflammatory conditions.

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.

Cytotoxic drugs, radiotherapy and oral candidiasis.

The increased incidence of oral candidiasis in patients with malignancies stems partly from the systemic disease itself and, partly from the therapeutic measures such as cytotoxic and other immunosuppressive drugs and radiotherapy they receive during management of such malignancies. In this review we discuss the clinical and laboratory findings on the relationship between cytotoxics, radiotherapy and oral candidiasis, possible mechanisms of pathogenicity following such therapy, as well as precautions that could be taken to minimize such recalcitrant yeast infections.