Transcriptional induction of cyclooxygenase-2 in osteoblasts is involved in interleukin-6-induced osteoclast formation

Brassinin alleviates cancer cachexia by suppressing diverse inflammatory mechanisms in mice

Cancer cachexia is a multifactorial condition that contributes to the death of about 20% of cancer patients. It has the potential to cause weight loss, reduction in muscle mass, and loss of fat tissue, significantly lowering the quality of life. Currently, there are no approved drugs for cancer cachexia. Here, we have explored the possible impact of brassinin (BSN) on cancer cachexia under in vitro and in vivo settings. After differentiation, C2C12 and 3T3-L1 cells were incubated with colorectal carcinoma cells conditioned media or BSN. For preclinical studies, mice were injected with HT-29 cells followed by intraperitoneal administration of BSN, and muscle and adipose tissues were evaluated by Western blotting and hematoxylin and eosin staining. BSN effectively suppressed muscle atrophy by down-regulating the levels of Muscle RING-finger protein-1 and Atrogin-1, while also increasing the expression of myosin heavy chain in cachexia-induced-C2C12 myotubes. The induction of adipogenesis by BSN prevented adipocyte atrophy in cachexia-induced 3T3-L1 adipocytes. We also noted that BSN disrupted the interaction between COX-2 and signaling transducer and activator of transcription 3 (STAT3) promoter, leading to down-regulation of STAT3 activation. Moreover, it was found that BSN inhibited weight loss in mice and demonstrated anti-cachexic effects. Overall, our observations indicate that BSN can attenuate cancer cachexia through diverse mechanisms.

Control of articular degeneration by extracellular vesicles from stem/stromal cells as a potential strategy for the treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative joint condition that contributes to years lived with disability. Current therapeutic approaches are limited as there are no disease-modifying interventions able to delay or inhibit the progression of disease. In recent years there has been an increasing interest in the immunomodulatory and regenerative properties of mesenchymal stem/stromal cells (MSCs) to develop new OA therapies. Extracellular vesicles (EVs) mediate many of the biological effects of these cells and may represent an alternative avoiding the limitations of cell-based therapy. There is also a growing interest in EV modifications to enhance their efficacy and applications. Recent preclinical studies have provided strong evidence supporting the potential of MSC EVs for the development of OA treatments. Thus, MSC EVs may regulate chondrocyte functions to avoid cartilage destruction, inhibit abnormal subchondral bone metabolism and synovial tissue alterations, and control pain behavior. EV actions may be mediated by the transfer of their cargo to target cells, with an important role for proteins and non-coding RNAs modulating signaling pathways relevant for OA progression. Nevertheless, additional investigations are needed concerning EV optimization, and standardization of preparation procedures. More research is also required for a better knowledge of possible effects on different OA phenotypes, pharmacokinetics, mechanism of action, long-term effects and safety profile. Furthermore, MSC EVs have a high potential as vehicles for drug delivery or as adjuvant therapy to potentiate or complement the effects of other approaches.

Extraction, Purification, Structural Characteristics, Biological Activity and Application of Polysaccharides from Portulaca oleracea L. (Purslane): A Review

Portulaca oleracea L. (purslane) is a widely distributed plant with a long history of cultivation and consumption. Notably, polysaccharides obtained from purslane exhibit surprising and satisfactory biological activities, which explain the various benefits of purslane on human health, including anti-inflammatory, antidiabetic, antitumor, antifatigue, antiviral and immunomodulatory effects. This article systematically reviews the extraction and purification methods, chemical structure, chemical modification, biological activity and other aspects of polysaccharides from purslane collected in the Chinese Pharmacopoeia, Flora of China, Web of Science, PubMed, Baidu Scholar, Google Scholar and CNKI databases in the last 14 years, using the keywords "Portulaca oleracea L. polysaccharides" and "purslane polysaccharides". The application of purslane polysaccharides in different fields is also summarized, and its application prospects are also discussed. This paper provides an updated and deeper understanding of purslane polysaccharides, which will provide useful guidance for the further optimization of polysaccharide structures and the development of purslane polysaccharides as a novel functional material, as well as a theoretical basis for its further research and application in human health and manufacturing development.

Ca2+-independent phospholipase A2β-derived PGE2 contributes to osteogenesis

Bone modeling can be modulated by lipid signals such as arachidonic acid (AA) and its cyclooxygenase 2 (COX2) metabolite, prostaglandin E₂ (PGE₂), which are recognized mediators of optimal bone formation. Hydrolysis of AA from membrane glycerophospholipids is catalyzed by phospholipases A₂ (PLA₂s). We reported that mice deficient in the Ca²⁺- independent PLA₂beta (iPLA₂β), encoded by Pla2g6, exhibit a low bone phenotype, but the cause for this remains to be identified. Here, we examined the mechanistic and molecular roles of iPLA₂β in bone formation using bone marrow stromal cells and calvarial osteoblasts from WT and iPLA₂β-deficient mice, and the MC3T3-E1 osteoblast precursor cell line. Our data reveal that transcription of osteogenic factors (Bmp2, Alpl, and Runx2) and osteogenesis are decreased with iPLA₂β-deficiency. These outcomes are corroborated and recapitulated in WT cells treated with a selective inhibitor of iPLA₂ β (10 μM S-BEL), and rescued in iPLA₂β-deficient cells by additions of 10 μM PGE₂. Further, under osteogenic conditions we find that PGE₂ production is through iPLA₂β activity and that this leads to induction of Runx2 and iPLA₂β transcription. These findings reveal a strong link between osteogenesis and iPLA₂β-derived lipids and raise the intriguing possibility that iPLA₂β-derived PGE₂ participates in osteogenesis and in the regulation of Runx2 and also iPLA₂β.

Cytokine Profile From the Ligamentum Flavum in Patients with Ossification of the Posterior Longitudinal Ligament in the Cervical Spine

STUDY DESIGN

Histological, immunohistochemical, and suspension array analyses of cytokine expression in human cervical ossification of the posterior longitudinal ligament (OPLL).

OBJECTIVES

The aim of this study was to determine whether changes in the cytokine profile reflect the maturation of chondrocytes and osteoblasts are associated with OPLL development.

SUMMARY OF BACKGROUND DATA

OPLL progresses gradually over a prolonged period and may lead to serious spinal cord complications. However, treatment methods only include conservative therapy for neurological symptoms or surgical decompression, whereas preventive therapy for OPLL remains nonexistent.

METHODS

Ligamentous samples were harvested from 24 patients with OPLL who underwent spinal surgery, and five control samples from cervical spondylotic myelo/radiculopathy patients without OPLL. Tissue sections were used for immunohistochemical studies and primary cells were cultured from the ligamentous samples for cytokine profiling. Using a suspension array system, concentrations of 27 inflammatory cytokines or growth factors were measured to generate the cytokine profiles.

RESULTS

Suspension array and immunoblot analysis revealed significant increments in the levels of interleukin (IL)-6, IL-1α, basic fibroblast growth factor, and RANTES in patients with OPLL. Immunohistochemical analysis further revealed that these factors were present in mesenchymal cells within the degenerative portion of the ligamentous matrix.

CONCLUSION

Our findings suggest that specific changes in the cytokine profile during ossification promote osteoblast differentiation, thereby providing new insights into OPLL pathogenesis. Moreover, this work supports the development of a new therapeutic method for preventing OPLL progression by regulating the cytokine profiles.Level of Evidence: 3.

Role of interleukin-6 in bone destruction and bone repair in rheumatoid arthritis

Rheumatoid arthritis (RA) is a common inflammatory form of arthritis leading to the progressive bone and joint destruction. Many factors are closely involved in the pathology of RA, in particular bone-related cells and inflammatory cytokines such as TNF-α and interleukin-6 (IL-6). Because RA patients with progressive bone destruction experience accelerated deterioration of their quality of life, inhibition of disease progression and joint destruction has become an important clinical goal. Recent studies have also found that drug intervention targeting proinflammatory cytokines such as IL-6 results in bone repair in addition to suppression of bone and joint destruction, and these results suggest the potential for new therapeutic goals. Regarding the relationship between IL-6 and bone destruction, essential roles of osteoclasts have been reported over many years; however, more recent studies have explored the relationship of IL-6 with osteoblasts and osteocytes. In this review, we highlight the perspectives of basic and clinical research, adding new findings on the relationships between IL-6 and bone-related cells associated with inflammation, and the possibility of bone repair by blocking IL-6.

Anti-inflammatory activity of novel thiosemicarbazone compounds indole-based as COX inhibitors

BACKGROUND

In this article, a series of 20 new thiosemicarbazone derivatives containing indole were synthesized and evaluated for their anti-inflammatory potential.

METHODS

The compounds were obtained through a synthetic route of only two steps, with yields that varied between 33.6 and 90.4%, and characterized by spectroscopic and spectrometric techniques.

RESULTS

An initial screening through the lymphoproliferation assay revealed that compounds LT76, LT81, and LT87 were able to inhibit lymphocyte proliferation, with CC₅₀ of 0.56 ± 0.036, 0.9 ± 0.01 and 0.5 ± 0.07 µM, respectively, better results than indomethacin (CC₅₀ > 12 µM). In addition, these compounds were able to suppress the in-vitro production of TNF-α and NO, in addition to stimulating the production of IL-4. Reinforcing in-vitro assays, the compounds were able to inhibit COX-2 similar to Celecoxib showing greater selectivity for this isoform (LT81 SI: 23.06 versus Celecoxib SI: 11.88). Animal studies showed that compounds LT76 (64.8% inhibition after 6 h), LT81 (89% inhibition after 6 h) and LT87 (100% inhibition after 4 h) were able to suppress edema in mice after inoculation carrageenan with greater potency than indomethacin, and immunohistochemistry revealed that the groups treated with LT76, LT81 and LT87 reduced the expression of COX-2, similar or better results when compared to indomethacin. Complementarily, in-silico studies have shown that these compounds have a good pharmacokinetic profile, for respecting the parameters of Lipinski and Veber, showing their good bioavailability.

CONCLUSIONS

These results demonstrate the potency of thiosemicarbazone derivatives containing indole and confirm their importance as scaffolds of molecules with notorious anti-inflammatory activity.

Role and Regulation of Mechanotransductive HIF-1α Stabilisation in Periodontal Ligament Fibroblasts

Orthodontic tooth movement (OTM) creates compressive and tensile strain in the periodontal ligament, causing circulation disorders. Hypoxia-inducible factor 1α (HIF-1α) has been shown to be primarily stabilised by compression, but not hypoxia in periodontal ligament fibroblasts (PDLF) during mechanical strain, which are key regulators of OTM. This study aimed to elucidate the role of heparan sulfate integrin interaction and downstream kinase phosphorylation for HIF-1α stabilisation under compressive and tensile strain and to which extent downstream synthesis of VEGF and prostaglandins is HIF-1α-dependent in a model of simulated OTM in PDLF. PDLF were subjected to compressive or tensile strain for 48 h. In various setups HIF-1α was experimentally stabilised (DMOG) or destabilised (YC-1) and mechanotransduction was inhibited by surfen and genistein. We found that HIF-1α was not stabilised by tensile, but rather by compressive strain. HIF-1α stabilisation had an inductive effect on prostaglandin and VEGF synthesis. As expected, HIF-1α destabilisation reduced VEGF expression, whereas prostaglandin synthesis was increased. Inhibition of integrin mechanotransduction via surfen or genistein prevented stabilisation of HIF-1α. A decrease in VEGF expression was observed, but not in prostaglandin synthesis. Stabilisation of HIF-1α via integrin mechanotransduction and downstream phosphorylation of kinases seems to be essential for the induction of VEGF, but not prostaglandin synthesis by PDLF during compressive (but not tensile) orthodontic strain.

Obesity, Inflammation, and Advanced Prostate Cancer

Obesity is associated with high-grade and advanced prostate cancer. While this association may be multi-factorial, studies suggest that obesity-induced inflammation may play a role in the progression of advanced prostate cancer. The microenvironment associated with obesity increases growth factors and pro-inflammatory cytokines which have been implicated mechanistically to promote invasion, metastasis, and androgen-independent growth. This review summarizes recent findings related to obesity-induced inflammation which may be the link to advanced prostate cancer. In addition, this review while introduce novel targets to mitigate prostate cancer metastasis to the bone. Specific emphasis will be placed on the role of the pro-inflammatory cytokines interleukin (IL)-6, tumor necrosis factor (TNF)α, and IL-1β.

Low-Intensity Pulsed Ultrasound Stimulates Osteogenic Differentiation of Periosteal Cells In Vitro

Adequate bone volume is required for osseointegrated implants to restore lost teeth and oral function. Several studies have demonstrated potential advantage of stem cells in regenerative medicine using osteoblasts. The periosteum is composed of osteoblasts, fibroblasts, and osteoprogenitor cells. It may be an alternative source for bone tissue engineering because of easy isolation and rapid proliferation in vivo and in vitro. Low-intensity pulsed ultrasound (LIPUS) has proved successful in recoveries from nonunions, delayed unions, and fracture of the bone in both animal experiments and clinical treatments. The study was to investigate the influence of LIPUS on the osteogenic differentiation in murine periosteum-derived cells (PDCs) and the underlying mechanism of LIPUS. PDCs were treated daily with LIPUS for 20 min up to 21 days with 3 MHz frequency, 30 mW/cm² intensity, and pulse repetition frequency of 1 kHz. The effects of LIPUS on cell proliferation and viability were investigated. Osteogenic differentiation was analyzed by alkaline phosphatase (ALP)-positive cell staining, ALP activity assay, mineralized nodule formation, real-time reverse transcription-polymerase chain reaction, as well as western blotting. The results indicated that ultrasound stimulation did not significantly affect the proliferation of PDCs. But LIPUS significantly increased ALP activity on day 7 and markedly promoted formation of mineralized nodules on day 21. mRNA expression of ALP and osteocalcin was significantly upregulated by stimulation with LIPUS. LIPUS enhanced gene expression of both bone morphogenetic protein-2 (BMP-2) and osterix only in the presence of osteogenic medium. LIPUS stimulation did not affect Smad 1 and Smad 5 protein expression, but significantly upregulated protein levels of BMP-2 and phosphor-Smad 1/5/9 in PDCs. Thus, LIPUS stimulation increased early osteogenic differentiation in a normal medium and further enhanced expression of BMP-2 and subsequent osterix expression through the canonical Smad-signaling pathway in an osteogenic medium, leading to mineral apposition. Therefore, LIPUS might have potential to promote osteogenesis in PDCs. Impact statement There are few studies on periosteum-derived cells (PDCs) because conventional methods of their isolation are relatively difficult to procure abundant cells for cell culture and the total cell numbers are limited. In this study, a modified isolation technique of murine calvarial PDCs using gelatin is described. PDCs were initiated to emerge as early as day 3 and showed increased proliferation, which can be used for further studies. Low-intensity pulsed ultrasound stimulation increased early osteogenic differentiation in a normal medium and further enhanced expression of bone morphogenic protein-2 and subsequent osterix expression through the canonical Smad-signaling pathway in an osteogenic medium, leading to mineral apposition.

Etoricoxib decreases subchondral bone mass and attenuates biomechanical properties at the early stage of osteoarthritis in a mouse model

Etoricoxib, a selective Cyclooxygenase-2 (COX-2) inhibitor, is commonly used in osteoarthritis (OA) for pain relief, however, little is known about the effects on subchondral bone. In the current study, OA was induced via destabilization of the medial meniscus (DMM) in C57BL/6 mice. Two days after surgery, mice were treated with different concentrations of Etoricoxib. Four weeks after treatment, micro computed tomography (Micro-CT) analysis, histological analysis, atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM) were performed to evaluate OA progression. We demonstrated that Etoricoxib inhibited osteophyte formation in the subchondral bone. However, it also reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th), and more microfractures and pores were observed in the subchondral bone. Moreover, Etoricoxib reduced the elastic modulus of subchondral bone. Exposure to Etoricoxib further increased the empty/total osteocyte ratio of the subchondral bone. Etoricoxib did not show significant improvement in articular cartilage destruction and synovial inflammation in early OA. Together, our observations suggested that although Etoricoxib can relieve OA-induced pain and inhibit osteophyte formation in the subchondral bone, it can also change the microstructures and biomechanical properties of subchondral bone, promote subchondral bone loss, and reduce subchondral bone quality in early OA mice.

Prostaglandins and Bone

Prostaglandins (PGs) are highly bioactive fatty acids. PGs, especially prostaglandin E₂ (PGE₂), are abundantly produced by cells of both the bone-forming (osteoblast) lineage and the bone-resorbing (osteoclast) lineage. The inducible cyclooxygenase, COX-2, is largely responsible for most PGE₂ production in bone, and once released, PGE₂ is rapidly degraded in vivo. COX-2 is induced by multiple agonists - hormones, growth factors, and proinflammatory factors - and the resulting PGE₂ may mediate, amplify, or, as we have recently shown for parathyroid hormone (PTH), inhibit responses to these agonists. In vitro, PGE₂ can directly stimulate osteoblast differentiation and, indirectly via stimulation of RANKL in osteoblastic cells, stimulate the differentiation of osteoclasts. The net balance of these two effects of PGE₂ in vivo on bone formation and bone resorption has been hard to predict and, as expected for such a widespread local factor, hard to study. Some of the complexity of PGE₂ actions on bone can be explained by the fact that there are four receptors for PGE₂ (EP1-4). Some of the major actions of PGE₂ in vitro occur via EP2 and EP4, both of which can stimulate cAMP signaling, but there are other distinct signaling pathways, important in other tissues, which have not yet been fully elucidated in bone cells. Giving PGE₂ or agonists of EP2 and EP4 to accelerate bone repair has been examined with positive results. Further studies to clarify the pathways of PGE₂ action in bone may allow us to identify new and more effective ways to deliver the therapeutic benefits of PGE₂ in skeletal disorders.

Protective Effects of Polysaccharide Extracted from Portulacae oleracea L. on Colitis Induced by Dextran Sulfate Sodium

Polysaccharide from Ma-chi-xian (Portulacae oleracea L., POLP) was prepared and the therapeutic effect on dextran sodium sulfate-induced colitis mice was investigated in this study. The results of clinical activity score and H&E staining confirmed the therapeutic effect of POLP. POLP could diminished the symptoms of colitis and improve colon histopathological structure of the colitis mice. The expression levels of four cytokines were determined. The concentrations of PGE₂ and IL-6 were downregulated by POLP treatment. The COX-2 protein expression levels and the STAT3 phosphorylation levels were detected. The results showed that these two protein levels were all increased in colitis and decreased after POLP treatment, indicating that these two proteins were closely related with the protective effect of POLP. Because the synthesis of PGE₂ is catalyzed by COX-2 and phosphorylation of STAT3 can induce the expression of COX-2, it was concluded that STAT3 was a key protein related to the POLP exerting its activity in colitis.

Effects of telmisartan and losartan treatments on bone turnover markers in patients with newly diagnosed stage I hypertension

INTRODUCTION

Telmisartan is an angiotensin-II receptor type-1 blocker and a partial agonist for peroxisome proliferator-activated receptor-γ. The aim of this study was to determine the potential effects of telmisartan on bone metabolism and turnover markers.

METHODS

Forty-two patients with newly diagnosed stage I hypertension who were prescribed telmisartan 80 mg/day or losartan 100 mg/day were included. Serum levels of calcium, phosphorus, 25-hydroxy vitamin D, bone-specific alkaline phosphatase, osteocalcin, interleukin 6 and 24-hour urinary N-terminal telopeptide were measured at the beginning and after 12 weeks of treatment.

RESULTS

When treatment arms were evaluated together, significantly increased 25-hydroxy vitamin D levels (p=0.01), and decreased parathormone (PTH) (p<0.001), bone-specific alkaline phosphatase (p=0.01), osteocalcin (p=0.045), urinary N-terminal telopeptide (p<0.001) and interleukin 6 levels (p=0.006) were observed. After eliminating the 25-hydroxy vitamin D effect, significant changes were not observed at any of the parameters. None of the levels of parameters were different between groups.

CONCLUSIONS

Neither telmisartan, despite its partial peroxisome proliferator-activated receptor-γ agonistic effect, nor losartan treatment had significant effects on bone turnover markers in newly diagnosed stage I hypertensive patients.

ONO-1301 Enhances in vitro Osteoblast Differentiation and in vivo Bone Formation Induced by Bone Morphogenetic Protein

STUDY DESIGN

In vitro and in vivo assessment of osteogenic effect by prostacyclin agonist (ONO-1301).

OBJECTIVE

The aim of this study was to investigate the effects of ONO-1301 on in vitro osteoblastic differentiation and in vivo bone formation induced by bone morphogenetic protein (BMP).

SUMMARY OF BACKGROUND DATA

Among prostaglandins (PGs), PGE2 is the most abundant in bone tissue and its effects on bone formation have been well studied. PGI2 (prostacyclin) is the second most abundant PG in bone tissue and plays important roles in hemodynamics. However, the effects of PGI2 on osteoblast differentiation and bone regeneration have not been elucidated.

METHODS

The effects of PGI2 agonist (ONO-1301), with and without recombinant human (rh) BMP-2, on osteoblastic differentiation and cell proliferation were investigated in vitro using alkaline phosphatase (ALP) and WST-1 assays. Murine primary osteoblasts and cell lines (ST2, MC3T3-E1, C2C12, and CH310T1/2) were used for the study. The effects of ONO-1301 on rhBMP-2 induced bone formation were investigated in a mouse model of muscle pouch transplantation (ectopic model) and in a rat model of spinal fusion (orthotopic model).

RESULTS

ONO-1301 significantly increased ALP activity in the primary osteoblasts and ST2 cells. In addition, cotreatment with ONO-1301 and rhBMP-2 significantly increased ALP activity in the primary osteoblasts, as well as in ST2 and MC3T3-E1 cells. Cell proliferation was not affected by both ONO-1301 and ONO-1301 as well as rhBMP-2. In the ectopic model, ONO-1301 significantly increased the volume of ectopic bone whose formation was induced by BMP. In addition, in the orthotopic model, ONO-1301 significantly increased bone volume and fusion rate.

CONCLUSION

This study has demonstrated that the PG IP agonist ONO-1301 improves in vitro BMP-2 induced osteoblast differentiation and in vivo ectopic and orthotopic bone formation. The results suggest that ONO-1301 has a potential clinical application as an enhancer of BMP-induced bone formation.

LEVEL OF EVIDENCE

N/A.

Extracellular Vesicles from Adipose-Derived Mesenchymal Stem Cells Downregulate Senescence Features in Osteoarthritic Osteoblasts

Osteoarthritis (OA) affects all articular tissues leading to pain and disability. The dysregulation of bone metabolism may contribute to the progression of this condition. Adipose-derived mesenchymal stem cells (ASC) are attractive candidates in the search of novel strategies for OA treatment and exert anti-inflammatory and cytoprotective effects on cartilage. Chronic inflammation in OA is a relevant factor in the development of cellular senescence and joint degradation. In this study, we extend our previous observations of ASC paracrine effects to study the influence of conditioned medium and extracellular vesicles from ASC on senescence induced by inflammatory stress in OA osteoblasts. Our results in cells stimulated with interleukin- (IL-) 1β indicate that conditioned medium, microvesicles, and exosomes from ASC downregulate senescence-associated β-galactosidase activity and the accumulation of γH2AX foci. In addition, they reduced the production of inflammatory mediators, with the highest effect on IL-6 and prostaglandin E₂. The control of mitochondrial membrane alterations and oxidative stress may provide a mechanism for the protective effects of ASC in OA osteoblasts. We have also shown that microvesicles and exosomes mediate the paracrine effects of ASC. Our study suggests that correction of abnormal osteoblast metabolism by ASC products may contribute to their protective effects.

STAT3 and NF-κB are common targets for kaempferol-mediated attenuation of COX-2 expression in IL-6-induced macrophages and carrageenan-induced mouse paw edema

Cycloxygenase-2 (COX-2) is the inducible isoform of cycloxygenase enzyme family that catalyzes synthesis of inflammatory mediators, prostanoids and prostaglandins, and therefore, can be targeted by anti-inflammatory drugs. Here, we showed a plant polyphenol, kaempferol, attenuated IL-6-induced COX-2 expression in human monocytic THP-1 cells suggesting its beneficial role in chronic inflammation. Kaempferol deactivated and prevented nuclear localization of two major transcription factors STAT3 and NF-κB, mutually responsible for COX-2 induction in response to IL-6. Moreover, STAT3 and NF-κB were simultaneously deactivated by kaempferol in acute inflammation, as shown by carrageenan-induced mouse paw edema model. The concomitant reduction in COX-2 expression in paw tissues suggested kaempferol’s role in mitigation of inflammation by targeting STAT3 and NF-κB.

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IL-6-induced COX-2 expression was attenuated by kaempferol in macrophages.

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The attenuation is attributed to simultaneous deactivation of STAT3 and NF-κB.

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The nuclear translocation of both transcription factors are prevented by kaempferol treatment.

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Kaempferol targets STAT3 and NF-κB and inhibits COX-2 expression to reduce carrageenan-induced mouse paw edema.

Signaling Pathways Regulating IL-1α-induced COX-2 Expression

Interleukin-1α(IL-1α) stimulates the production of prostaglandin E2 (PGE2) in odontogenic keratocyst fibroblasts. However, the signaling pathways remain obscure. In this study, we investigated IL-1αsignaling pathways that regulate cyclooxygenase-2 (COX-2) expression in odontogenic keratocyst fibroblasts. IL-1αincreased the expression of COX-2 mRNA and protein, and PGE2 secretion in the fibroblasts. IL-1αincreased the phosphorylation of extracellular signal-regulated protein kinase-1/2 (ERK1/2), p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK). PD-98059, SB-203580, SP-600125, and PDTC—which are inhibitors of ERK1/2, p38, JNK, and nuclear factor-κB (NF-κB), respectively—attenuated the IL-1α-induced COX-2 mRNA expression and activated protein kinase C PGE2 secretion. IL-1α(PKC), and PKC inhibitor staurosporine inhibited IL-1α-induced phosphorylation of ERK1/2, p38, and JNK, and decreased IL-1α-induced COX-2 mRNA expression. Thus, in odontogenic keratocyst fibroblasts, IL-1αmay stimulate COX-2 expression both through the PKC-dependent activation of ERK1/2, p38, and JNK signaling pathways, and through the NF-κB cascade.

Immunohistochemical localization of key arachidonic acid metabolism enzymes during fracture healing in mice

This study investigated the localization of critical enzymes involved in arachidonic acid metabolism during the initial and regenerative phases of mouse femur fracture healing. Previous studies found that loss of cyclooxygenase-2 activity impairs fracture healing while loss of 5-lipoxygenase activity accelerates healing. These diametric results show that arachidonic acid metabolism has an essential function during fracture healing. To better understand the function of arachidonic acid metabolism during fracture healing, expression of cyclooxygenase-1 (COX-1), cyclooxygenase -2 (COX-2), 5-lipoxygenase (5-LO), and leukotriene A4 hydrolase (LTA4H) was localized by immunohistochemistry in time-staged fracture callus specimens. All four enzymes were detected in leukocytes present in the bone marrow and attending inflammatory response that accompanied the fracture. In the tissues surrounding the fracture site, the proportion of leukocytes expressing COX-1, COX-2, or LTA4H decreased while those expressing 5-LO remained high at 4 and 7 days after fracture. This may indicate an inflammation resolution function for 5-LO during fracture healing. Only COX-1 was consistently detected in fracture callus osteoblasts during the later stages of healing (day 14 after fracture). In contrast, callus chondrocytes expressed all four enzymes, though 5-LO appeared to be preferentially expressed in newly differentiated chondrocytes. Most interestingly, osteoclasts consistently and strongly expressed COX-2. In addition to bone surfaces and the growth plate, COX-2 expressing osteoclasts were localized at the chondro-osseous junction of the fracture callus. These observations suggest that arachidonic acid mediated signaling from callus chondrocytes or from callus osteoclasts at the chondro-osseous junction regulate fracture healing.

β-Amyloid context intensifies vascular smooth muscle cells induced inflammatory response and de-differentiation

Several studies have shown that the accumulation of β-amyloid peptides in the brain parenchyma or vessel wall generates an inflammatory environment. Some even suggest that there is a cause-and-effect relationship between inflammation and the development of Alzheimer's disease and/or cerebral amyloid angiopathy (CAA). Here, we studied the ability of wild-type Aβ1-40 -peptide (the main amyloid peptide that accumulates in the vessel wall in sporadic forms of CAA) to modulate the phenotypic transition of vascular smooth muscle cells (VSMCs) toward an inflammatory/de-differentiated state. We found that Aβ1-40 -peptide alone neither induces an inflammatory response, nor decreases the expression of contractile markers; however, the inflammatory response of VSMCs exposed to Aβ1-40 -peptide prior to the addition of the pro-inflammatory cytokine IL-1β is greatly intensified compared with IL-1β-treated VSMCs previously un-exposed to Aβ1-40 -peptide. Similar conclusions could be drawn when tracking the decline of contractile markers. Furthermore, we found that the mechanism of this potentiation highly depends on an Aβ1-40 preactivation of the PI3 Kinase and possibly NFκB pathway; indeed, blocking the activation of these pathways during Aβ1-40 -peptide treatment completely suppressed the observed potentiation. Finally, strengthening the possible in vivo relevance of our findings, we evidenced that endothelial cells exposed to Aβ1-40 -peptide generate an inflammatory context and have similar effects than the ones described with IL-1β. These results reinforce the idea that intraparietal amyloid deposits triggering adhesion molecules in endothelial cells, contribute to the transition of VSMCs to an inflammatory/de-differentiated phenotype. Therefore, we suggest that acute inflammatory episodes may increase vascular alterations and contribute to the ontogenesis of CAA.

Current insights on the regenerative potential of the periosteum: molecular, cellular, and endogenous engineering approaches

While century old clinical reports document the periosteum's remarkable regenerative capacity, only in the past decade have scientists undertaken mechanistic investigations of its regenerative potential. At a Workshop at the 2012 Annual Meeting of Orthopaedic Research Society, we reviewed the molecular, cellular, and tissue scale approaches to elucidate the mechanisms underlying the periosteum's regenerative potential as well as translational therapies engineering solutions inspired by its remarkable regenerative capacity. The entire population of osteoblasts within periosteum, and at endosteal and trabecular bone surfaces within the bone marrow, derives from the embryonic perichondrium. Periosteal cells contribute more to cartilage and bone formation within the callus during fracture healing than do cells of the bone marrow or endosteum, which do not migrate out of the marrow compartment. Furthermore, a current healing paradigm regards the activation, expansion, and differentiation of periosteal stem/progenitor cells as an essential step in building a template for subsequent neovascularization, bone formation, and remodeling. The periosteum comprises a complex, composite structure, providing a niche for pluripotent cells and a repository for molecular factors that modulate cell behavior. The periosteum's advanced, "smart" material properties change depending on the mechanical, chemical, and biological state of the tissue. Understanding periosteum development, progenitor cell-driven initiation of periosteum's endogenous tissue building capacity, and the complex structure-function relationships of periosteum as an advanced material are important for harnessing and engineering ersatz materials to mimic the periosteum's remarkable regenerative capacity.

The effect of enamel matrix derivative (Emdogain®) on gene expression profiles of human primary alveolar bone cells

Emdogain® is frequently used in regenerative periodontal treatment. Understanding its effect on gene expression of bone cells would enable new products and pathways promoting bone formation to be established. The aim of the study was to analyse the effect of Emdogain® on expression profiles of human-derived bone cells with the help of the micro-array, and subsequent validation. Bone was harvested from non-smoking patients during dental implant surgery. After outgrowth, cells were cultured until subconfluence, treated for 24 h with either Emdogain® (100 µg/ml) or control medium, and subsequently RNA was isolated and micro-array was performed. The most important genes demonstrated by micro-array data were confirmed by qPCR and ELISA tests. Emdogain tipped the balance between genes expressed for bone formation and bone resorption towards a more anabolic effect, by interaction of the PGE2 pathway and inhibition of IL-7 production. In addition the results of the present study indicate that Emdogain possibly has an effect on gene expression for extracellular matrix formation of human bone cells, in particular on bone matrix formation and on proliferation and differentiation. With the micro-array and the subsequent validation, the genes possibly involved in Emdogain action on bone cells were identified. These results can contribute to establishing new products and pathways promoting bone formation.

Detection of pain-related molecules in the subchondral bone of osteoarthritic knees

Knee pain is predominant among osteoarthritis (OA) patients, but the mechanism is poorly understood. We investigated subchondral bone as a source of OA knee pain using immunohistochemistry. Fifteen medial-type OA knees with minimum involvement of the lateral compartment determined by X-ray as well as magnetic resonance imaging that received total knee arthroplasty (TKA) were involved. Each pair of the medial femoral condyle (MFC) and lateral femoral condyle (LFC) was compared obtained at the time of TKA. Osteocartilaginous MFC and LFC specimens were histologically examined and stained with antibodies against cyclooxygenase 1 (Cox-1), cyclooxygenase 2 (Cox-2), substance P, tumor necrosis factor-alpha (TNF-alpha), and neuron-specific class III beta-tubulin (TUJ1), a pan-neuronal marker. Formation of cystic lesions was more frequently seen in the MFC. The lesions were composed of vascular endothelial cells, osteoclasts, and mononuclear cells and were present in similar proportions between the MFC and the LFC. Four out of 15 MFC specimens were positive for Cox-1, 15 for Cox-2, and 13 for TNF-alpha. No LFC specimens were positive for any antibodies. Substance P-positive and TUJ1-positive fibers were found in the subchondral area of the MFC, but not in the LFC. Pathological changes in the subchondral bone can be a source of knee pain, which was detectable by the positive immunoreactivity of substance P, Cox-2, TNF-alpha, and TUJ1, in the subchondral bone of affected compartments. The relatively immediate reduction in pain obtained by TKA might account for the involvement of the subchondral bone in knee pain because most of the affected subchondral plate is excised in TKA (debridement effect of TKA).

Parecoxib and indomethacin delay early fracture healing: a study in rats

Nonsteroidal antiinflammatory drugs (NSAIDs) are used to reduce inflammatory response and pain. These drugs have been reported to impair bone metabolism. Parecoxib, a specific COX-2 inhibitor, exerts an inhibitory effect on the mineralization of fracture callus after a tibial fracture in rats. Decreased bone mineral density (BMD) at a fracture site may indicate impairment of early healing, casting doubt on the safety of using COX-2 inhibitors during the early treatment of diaphyseal fractures. Forty-two female Wistar rats were randomly allocated to three groups. They were given parecoxib, indomethacin, or saline intraperitoneally for 7 days after being subjected to a closed tibial fracture stabilized with an intramedullary nail. Two and 3 weeks after surgery, the bone density at the fracture site was measured using dual energy xray absorptiometry (DEXA). Three weeks after the operation the rats were euthanized and the healing fractures were mechanically tested in three-point cantilever bending. Parecoxib decreased BMD at the fracture site for 3 weeks after fracture, indomethacin for 2 weeks. Both parecoxib and indomethacin reduced the ultimate bending moment and the bending stiffness of the healing fractures after 3 weeks. These results suggest COX inhibitors should be avoided in the early phase after fractures.

The relationship between clustering health-promoting components of lifestyle and bone status among middle-aged women in a general population

OBJECTIVE

The association between clustering health-promoting components of lifestyle and bone status was examined among middle-aged women.

METHODS

A cross-sectional study was conducted in Tadami Town, Fukushima Prefecture, Japan, in 2007. A total of 305 middle-aged women (mean age 55.2 years) participated. The Health-Promoting Lifestyle Profile II was used to assess health-promoting components of lifestyle. Participants' bone status was examined using quantitative ultrasonic calcaneal measurement.

RESULTS

A total of 139 participants (45.6%) were defined as having low bone stiffness. In the low bone stiffness group, the mean age was significantly higher, and prevalence of interpersonal relationships score over 3.0 was lower than that in the normal bone stiffness group. There were significant trends in the prevalence of low bone stiffness, each health-promoting component of lifestyle, and presence of hypertension and diabetes mellitus, based on the number of frequently selected health-promoting components of lifestyle. The number of frequently selected health-promoting components of lifestyle correlated negatively with the prevalence of low bone stiffness in both crude and adjusted results.

CONCLUSION

This research is particularly important as we suggest health-promotion strategies for the prevention of osteoporosis. A synthetic approach, which includes health responsibility, spiritual growth, interpersonal relations, and stress management, and physical activity and nutrition, may be effective and complement traditional strategies.

The effect of endothelin-1 on the production of interleukin-6 in cultured human detrusor smooth muscle cells, and the effect of interleukin-6 on the contractile response of bladder smooth muscle strips from rats

OBJECTIVE

To determine the effect of endothelin-1 (ET-1) on the production of interleukin-6 (IL-6) in cultured human detrusor smooth muscle cells (HDSMCs) and the effect of IL-6 on the contractile response of bladder smooth muscle strips from rats.

MATERIALS AND METHODS

The expression of IL-6 mRNA and production of IL-6 protein in cultured HDSMCs treated with the different concentrations of ET-1 were assayed by reverse transcriptase-polymerase chain reaction and specific enzyme-linked immunosorbent assay, respectively. The strips from Sprague-Dawley rats were either untreated or treated with 1 ng/mL of IL-6 for 60 min. Using increasing cumulative concentrations of acetylcholine (ACh), bethanechol (BCh), or sodium nitroprusside, we assessed the concentration-contraction or the relaxation responses. In cystitis-induced strips, change of contractions induced by noradrenaline (NA) with or without treatment of IL-6 were assessed. The IL-6-treated strips were incubated for 30 min in the presence or absence indomethacin or SQ29548, and then the effects on ACh- or BCh-induced contractions were measured.

RESULTS

The expression of IL-6 mRNA and the production of IL-6 protein on the cultured HDSMCs pretreated by ET-1 were significantly higher than in the control (P<0.05). The ACh- and BCh-induced contractions were increased in the IL-6 pretreated strips from both dome and trigone, regardless of the presence of urothelium (P<0.05). The presence of cystitis augmented the NA-induced contractions (P<0.05). The contractions induced by ACh and BCh were inhibited by indomethacin and SQ29548.

CONCLUSIONS

ET-1 induces expression of IL-6 mRNA and production of IL-6 protein on HDSMCs. IL-6 enhances detrusor smooth muscle contractility via the muscarinic or adrenergic receptor pathway.

Pathophysiology of cyclooxygenase inhibition in animal models

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandins (PGs), which play a significant role in health and disease in the gastrointestinal tract (GI) and in the renal, skeletal, and ocular systems. COX-1 is constitutively expressed and found in most normal tissues, whereas COX-2 can be expressed at low levels in normal tissues and is highly induced by pro-inflammatory mediators. Inhibitors of COX activity include: (1) conventional nonselective, nonsteroidal anti-inflammatory drugs (ns-NSAIDs) and (2) COX-2 selective nonsteroidal anti-inflammatory drugs (COX-2 s-NSAIDs). Inhibition of COX-1 often elicits GI toxicity in animals and humans. Therefore, COX-2 s-NSAIDs were developed to provide a selective COX-2 agent, while minimizing the attendant COX-1-mediated GI toxicities. Rats and dogs overpredict COX inhibition for renal effects such as renal handling of electrolytes in humans. COX inhibitors are shown to have both beneficial and detrimental effects, such as on healing of ligament or tendon tears, on the skeletal system in animal models. Certain ophthalmic conditions such as glaucoma and keratitis are associated with increased COX-2 expression, suggesting a potential role in their pathophysiology.

Staphylococcus aureus induces expression of receptor activator of NF-kappaB ligand and prostaglandin E2 in infected murine osteoblasts

Osteomyelitis is an inflammatory disease of the bone that is characterized by the presence of necrotic bone tissue and increased osteoclast activity. Staphylococcus aureus is responsible for approximately 80% of all cases of human osteomyelitis. While the disease is especially difficult to treat, the pathogenesis of S. aureus-induced osteomyelitis is poorly understood. Elucidating the molecular mechanisms by which S. aureus induces osteomyelitis could lead to a better understanding of the disease and its progression and development of new treatments. Osteoblasts can produce several soluble factors that serve to modulate the activity or formation of osteoclasts. Receptor activator of NF-kappaB ligand (RANK-L) and prostaglandin E(2) (PGE(2)) are two such molecules which can promote osteoclastogenesis and stimulate bone resorption. In addition, previous studies in our laboratory have shown that osteoblasts produce inflammatory cytokines, such as interleukin 6, following infection with S. aureus, which could induce COX-2 and in turn PGE(2), further modulating osteoclast recruitment and differentiation. Therefore, we hypothesized that following infection with S. aureus, osteoblasts will express increased levels of RANK-L and PGE(2). The results presented in this study provide evidence for the first time that RANK-L mRNA and protein and PGE(2) expression are upregulated in S. aureus-infected primary osteoblasts. In addition, through the use of the specific COX-2 inhibitor NS 398, we show that when PGE(2) production is inhibited, RANK-L production is decreased. These data suggest a mechanism whereby osteoblasts regulate the production of RANK-L during infection.

Age-related changes in bone morphology are accelerated in group VIA phospholipase A2 (iPLA2beta)-null mice

Phospholipases A(2) (PLA(2)) hydrolyze the sn-2 fatty acid substituent, such as arachidonic acid, from phospholipids, and arachidonate metabolites are recognized mediators of bone modeling. We have previously generated knockout (KO) mice lacking the group VIA PLA(2) (iPLA(2)beta), which participates in a variety of signaling events; iPLA(2)beta mRNA is expressed in bones of wild-type (WT) but not KO mice. Cortical bone size, trabecular bone volume, bone mineralizing surfaces, and bone strength are similar in WT and KO mice at 3 months and decline with age in both groups, but the decreases are more pronounced in KO mice. The lower bone mass phenotype observed in KO mice is not associated with an increase in osteoclast abundance/activity or a decrease in osteoblast density, but is accompanied by an increase in bone marrow fat. Relative to WT mice, undifferentiated bone marrow stromal cells (BMSCs) from KO mice express higher levels of PPAR-gamma and lower levels of Runx2 mRNA, and this correlates with increased adipogenesis and decreased osteogenesis in BMSCs from these mice. In summary, our studies indicate that age-related losses in bone mass and strength are accelerated in iPLA(2)beta-null mice. Because adipocytes and osteoblasts share a common mesenchymal stem cell origin, our findings suggest that absence of iPLA(2)beta causes abnormalities in osteoblast function and BMSC differentiation and identify a previously unrecognized role of iPLA(2)beta in bone formation.

Feedback Control of the Arachidonate Cascade in Osteoblastic Cells by 15-deoxy-Delta-Prostaglandin J(2)

15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) and an anti-diabetic thiazolidinedione, troglitazone (TRO) are peroxisome proliferator-activated receptor (PPAR)-γ ligands, which regulate immuno-inflammatory reactions as well as adipocyte differentiation. We previously reported that 15d-PGJ₂ can suppress interleukin (IL)-1β-induced prostaglandin E₂ (PGE₂) synthesis in synoviocytes of rheumatoid arthritis (RA). IL-1 also stimulates PGE₂ synthesis in osteoblasts by regulation of cyclooxygenase (COX)-2 and regulates osteoclastic bone resorption in various diseases such as RA and osteoporosis. In this study, we investigated the feedback mechanism of the arachidonate cascade in mouse osteoblastic cells, MC3T3-E1 cells, which differentiate into mature osteoblasts. Treatment with 15d-PGJ₂ led to a significant increase in IL-1α-induced COX-2 expression and PGE₂ production in a dose dependent manner. The effect of 15d-PGJ₂ was stronger than that of TRO. However, it did not affect the expression of COX-1. In addition, cell viability of MC3T3-E1 cells was not changed in the condition we established. This means that 15d-PGJ₂ exerts a positive feedback regulation of the arachidonate cascade of PGE₂ in osteoblastic cells. These results may provide important information about the pathogenesis and treatment of bone resorption in a variety of diseases such as RA and osteoporosis.

Micro-CT imaging analysis for the effect of celecoxib, a cyclooxygenase-2 inhibitor, on inflammatory bone destruction in adjuvant arthritis rats

Cyclooxygenase (COX)-2 is known to play an important role in the differentiation and maturation of osteoclasts. However, the role of COX-1 in bone metabolism has not been well explored. In this study, the bone-conserving effects of COX-2-specific (celecoxib), COX-nonselective (loxoprofen), and COX-1-specific agents (SC-58560) were compared using an adjuvant-induced arthritis (AIA) rat model. Arthritis was induced by injecting 50 microl liquid paraffin containing 1 mg Mycobacterium butyricum into the left footpad of Lewis rats. Drugs were given orally twice daily for 10 days beginning 15 days after adjuvant injection. Celecoxib was administered at the rate of 3 mg/kg per day, loxoprofen at 3 mg/kg per day, and SC-58560 at 10 mg/kg per day. The therapeutic effects on 3-D architectural bone changes in the arthritic condition, e.g., the bone volume/total tissue volume ratio and the amount of trabecular bone pattern factor, were determined by analyzing the hindpaw calcaneus of AIA rats using microcomputed tomography (micro-CT). In addition, dual-energy X-ray absorptiometry 2-D bone analysis was performed to compare with micro-CT analysis. AIA rats are prone to substantial bone erosion, which allows for significant changes in the 3-D architectural index. This inflammatory bone destruction was suppressed potently by celecoxib, only moderately by loxoprofen, and not at all by SC-58560. These data suggest that COX-2 plays an important role in the inflammatory bone destruction that occurs with rheumatoid arthritis. The results also suggest that COX-2 is more effective than COX-1 at suppressing the destruction of bone associated with arthritis.

Activation of PKA and phosphorylation of sodium-dependent vitamin C transporter 2 by prostaglandin E2 promote osteoblast-like differentiation in MC3T3-E1 cells

Sodium-dependent vitamin C transporter (SVCT) 2-mediated L-ascorbic acid (AA) uptake is required in osteoblast-like differentiation of MC3T3-E1 cells, and prostaglandin E2 (PGE2) is among the most important local factors in bone formation, but the detailed mechanism by which PGE2 induces osteoblast differentiation remains obscure. We revealed that PGE2 induced AA uptake and osteoblast-like differential markers including alkaline phosphatase, collagen, osteocalcin expression, and mineralization in MC3T3-E1 cells. Inhibition of AA uptake by SVCT2 short isoform functioning as a dominant-negative mutant not only robustly attenuated PGE2-induced markers expression and mineralization, but also decreased their basal levels. However, upregulation of AA uptake resulted from PGE2-induced plasma membrane translocation of cytoplasm SVCT2, and this effect was abolished by pretreatment with EP4 receptor antagonist, AH-23848B or cAMP-dependent protein kinase A (PKA) inhibitor, H-89. Moreover, we showed SVCT2 physically interacted with PKA in immunoprecipitates, and PKA phosphorylated SVCT2 in vitro and in intact cells at Ser402 and Ser639 sites; however, mutation of Ser402 or/and Ser639 in SVCT2 severely diminished SVCT2 translocation in response to PGE2. Together, these results suggest that PGE2-induced SVCT2 plasma membrane translocation through EP4 receptor and subsequent phosphorylation of SVCT2 at Ser402 and Ser639 sites by PKA results in an increase of AA uptake and consequent promotion of osteoblast-like differentiation in MC3T3-E1 cells.

Regulation of COX-2 mediates acid-induced bone calcium efflux in vitro

Chronic metabolic acidosis induces net Ca efflux from bone; this osteoclastic bone resorption is mediated by increased osteoblastic prostaglandin synthesis. Cyclooxygenase, the rate-limiting enzyme in prostaglandin synthesis, is present in both constitutive (COX-1) and inducible (COX-2) forms. We report here that acidosis increases both osteoblastic RNA and protein levels for COX-2 and that genetic deficiency or pharmacologic inhibition of COX-2 significantly reduces acid-induced Ca efflux from bone.

INTRODUCTION

Incubation of neonatal mouse calvariae in medium simulating physiologic metabolic acidosis induces an increase in osteoblastic prostaglandin E2 (PGE2) release and net calcium (Ca) efflux from bone. Increased PGE2 is necessary for acid-induced bone resorption, because inhibition of cyclooxygenase activity with indomethacin significantly decreases not only PGE2 production but also Ca release. Cyclooxygenase is present in both constitutive (COX-1) and inducible (COX-2) forms. Because COX-2 activity has been implicated in several forms of pathological bone resorption, we tested the hypothesis that COX-2 is critical for acid-induced, cell-mediated bone Ca efflux.

MATERIALS AND METHODS

To determine the effect of metabolic acidosis on COX-2 RNA and protein, primary cells isolated from neonatal CD-1 mouse calvariae were cultured in neutral (Ntl) or physiologically acidic medium (Met). RNA levels for COX-2 and COX-1 were measured by quantitative real-time PCR. Levels of COX-2 and COX-1 protein were measured by immunoblot analysis. To determine the effect of acidosis on bone Ca efflux in genetically deficient COX-2 mice, mice heterozygous for the COX-2 knockout (strain B6;129S7-Ptgs2(tm1Jed)/J) were used as breeders, and neonatal calvariae were cultured in Ntl or Met. To determine the effects of the specific COX-2 inhibitor, NS398, on acid-induced bone resorption, CD-1 calvariae were incubated in Ntl or Met with or without NS398 (1 microM). Medium PGE2 was assayed by ELISA.

RESULTS

Incubation of mouse calvarial cells in Met significantly increased COX-2 RNA and protein levels without a change in COX-1. Increased COX-2 protein levels in response to Met were also observed in cultured calvariae. Acid-induced, cell-mediated Ca efflux from B6;129S7-Ptgs2(tm1Jed)/J calvariae was dependent on genotype. From 0 to 24 h, when physicochemical Ca efflux predominates, Met significantly increased net Ca efflux in all genotypes. After 24 h, when cell-mediated Ca efflux predominates, Met induced greater Ca efflux from (+/+) than from (+/-), and there was no increase from (-/-). In calvariae from CD-1 mice, NS398 significantly inhibited both the acid-induced increase in PGE2 and Ca release.

CONCLUSIONS

The specific acid-induced increase in COX-2 RNA and protein levels and the dependency of the increased Ca efflux on COX-2 activity, as determined by both genetic deficiency and pharmacologic inhibition, show that COX-2 is critical for acid-induced, cell-mediated bone resorption.

Inhibitory effects of Ficus erecta leaves on osteoporotic factors in vitro

Osteoporosis is recognized as a major concern among menopausal women and the elderly. When estrogen is reduced in the body, local factors such as IL-1beta, IL-6 and PGE2, which are known to be related to bone resorption, are increased and promote osteoclastogenesis, which is responsible for bone resorption and results in the clinical disorder osteoporosis. In this study, we investigated the anti-osteoporotic activity of Ficus erecta. MG-63 cells were stimulated with IL-1beta (10 ng/mL) to induce osteoporotic factors (IL-6, COX-2 and PGE2) and RAW 264.7 cells were stimulated with RANKL (100 ng/mL) to induce their differentiation into osteoclasts. We found F. erecta fractions decreased the mRNA expression of IL-6 and COX-2, and protein levels of COX-2 and PGE2 production. Among sequential solvent fractions, hexane and EtOAc fractions decreased differentiation into osteoclasts of RAW 264.7 cells. These results suggest that F. erecta may have significant effects on osteoporotic factors and may be provided as a possible anti-osteoporotic therapeutic plant.

Effects of arachidonic acid, docosahexaenoic acid, prostaglandin E(2) and parathyroid hormone on osteoprotegerin and RANKL secretion by MC3T3-E1 osteoblast-like cells

Bone is continuously remodeled through resorption by osteoclasts and the subsequent synthesis of the bone matrix by osteoblasts. Cell-to-cell contact between osteoblasts and osteoclast precursors is required for osteoclast formation. RANKL (receptor activator of nuclear factor-kappaB ligand) expressed on osteoblastic cell membranes stimulates osteoclastogenesis, while osteoprotegerin (OPG) secreted by osteoblasts inhibits osteoclastogenesis. Although polyunsaturated fatty acids (PUFAs) have been implicated in bone homeostasis, the effects thereof on OPG and RANKL secretion have not been investigated. MC3T3-E1 osteoblasts were exposed to the n-6 PUFA arachidonic acid (AA) and the n-3 PUFA docosahexaenoic acid (DHA); furthermore, the bone-active hormone parathyroid hormone (PTH) and the effects thereof were tested on OPG and RANKL secretion. Prostaglandin E(2) (PGE(2)), a product of AA metabolism that was previously implicated in bone homeostasis, was included in the study. AA (5.0-20 microg/ml) inhibited OPG secretion by 25-30%, which was attenuated by pretreatment with the cyclooxygenase blocker indomethacin, suggesting that the inhibitory effect of AA on OPG could possibly be PGE(2)-mediated. MC3T3-E1 cells secreted very low basal levels of RANKL, but AA stimulated RANKL secretion, thereby decreasing the OPG/RANKL ratio. DHA suppressed OPG secretion to a smaller extent than AA. This could, however, be due to endogenous PGE(2) production. No RANKL could be detected after exposing the MC3T3-E1 cells to DHA. PTH did not affect OPG secretion, but stimulated RANKL secretion. This study demonstrates that AA and PTH reduce the OPG/RANKL ratio and may increase osteoclastogenesis. DHA, however, had no significant effect on OPG or RANKL in this model.

Lipopolysaccharide stimulates the production of prostaglandin E2 and the receptor Ep4 in osteoblasts

Previous studies have indicated that one of the causes of alveolar bone destruction with periodontitis is lipopolysaccharide (LPS) from the cell wall of gram-negative bacteria in plaque, and that prostaglandin E(2) (PGE(2)) is one of the bone resorption factors that stimulate osteoclast formation through an intercellular interaction between osteoblasts and osteoclast precursors. The present study was undertaken to determine the effect of LPS on cell growth, alkaline phosphatase (ALPase) activity, the production of PGE(2), and the expression of receptors by PGE(2), cyclooxygenase (COX)-1, and COX-2, using human osteosarcoma cell line Saos-2 as osteoblasts. The cells were cultured with 0, 1, or 10 microg mL(-1) of LPS for up to 14 days. The production of PGE(2) and the gene expression of COX-1, COX-2, and PGE(2) receptors, including Ep1, Ep2, Ep3, and Ep4, were determined using enzyme-linked immunosorbent assay (ELISA) and real-time reverse transcription-polymerase chain reaction (real-time RT-PCR), respectively. With the addition of LPS, cell growth and ALPase activity decreased by day 5 of the culture, while PGE(2) production increased in a dose-dependent manner throughout the entire 14-day culture period. LPS-reduced ALP activity and LPS-induced PGE(2) production returned to the control level by the addition simultaneously with indomethacin. The expression of COX-1, Ep1, Ep2, and Ep3 receptors decreased on day 14 of the culture, whereas the expression of COX-2 and Ep4 receptors increased significantly with the addition of LPS. These results suggest that LPS promotes PGE(2) production by increasing the expression of COX-2, and that LPS promotes the production of Ep4 receptors in osteoblasts. These results also indicate that LPS-induced PGE(2) may combine with osteoblast Ep4 receptors in autocrine or paracrine modes, and may promote the formation of osteoclasts.

Oncogenic RAS mutations in myeloma cells selectively induce cox-2 expression, which participates in enhanced adhesion to fibronectin and chemoresistance

Oncogenic RAS expression occurs in up to 40% of multiple myeloma (MM) cases and correlates with aggressive disease. Since activated RAS induces cyclooxygenase-2 (cox-2) expression in other tumor models, we tested a role for cox-2 in mutant RAS-containing MM cells. We used the ANBL-6 isogenic MM cell lines in which the IL-6-dependent parental line becomes cytokine independent following transfection with mutated N-RAS or K-RAS. Both mutated N-RAS- and K-RAS-expressing ANBL-6 cells demonstrated a selective up-regulation of cox-2 expression and enhanced secretion of PGE2, a product of cox-2. Furthermore, in 3 primary marrow specimens, which contained MM cells expressing mutated RAS, 15% to 40% of tumor cells were positive for cox-2 expression by immunohistochemistry. We used cox-2 inhibitors, NS398 and celecoxib, and neutralizing anti-PGE2 antibody to test whether cox-2/PGE2 was involved in the aggressive phenotype of MM ANBL-6 cells containing mutated RAS. Although these interventions had no effect on IL-6-independent growth or adhesion to marrow stromal cells, they significantly inhibited the enhanced binding of mutant RAS-containing MM cells to fibronectin and the enhanced resistance to melphalan. These results indicate a selective induction of cox-2 in MM cells containing RAS mutations, which results in heightened binding to extracellular matrix protein and chemotherapeutic drug resistance.

Short-term supplementation of COX-2 inhibitor suppresses bone turnover in gonad-intact middle-aged male rats

There is an increasing body of evidence supporting the idea that nonsteroidal antiinflammatory drugs can effectively suppress ovariectomy-induced bone loss in adult rats. The present study investigated the effects of supplementation of selective cyclooxygenase-2 inhibitor [5,5-dimethyl-3-(3 flurophenyl)-4-(4 methylsulphonal) phenyl-2 (6H) furanone, DFU] to diets on bone metabolism, bone mineral density (BMD), and histomorphometry in middle-aged male rats. Forty 16-month-old male rats (n = 8/group) were fed diets containing 0 (control), 5, 10, 15, or 20 mg/kg DFU body weight/day for 4 weeks. Supplementation of DFU resulted in higher plasma levels of pyridinoline, insulin-like growth factor I, and parathyroid hormone, but lower bone-specific alkaline phosphatase activity, prostaglandin E(2,) and 1,25-(OH)(2) vitamin D(3). Compared to the control, DFU supplementation at 20 mg/kg did not affect total scanned area, BMD, and bone mineral content as determined by DEXA. Histomorphometric data showed that rats fed DFU at 20 mg/kg had lower values of mineralizing surface, eroded surface, mineral apposition rate, and bone formation rate, but no difference in trabecular thickness, number, and separation compared to the control. The present data demonstrate that the short-term supplementation of selective COX-2 inhibitor to gonad-intact middle-aged male rats resulted in suppression of bone formation and increased bone resorption, and thereby suppressed bone turnover rate, without significant loss of bone. Such action was through modulating local factors and systemic hormones.

Up-regulation of astrocyte cyclooxygenase-2, CCAAT/enhancer-binding protein-homology protein, glucose-related protein 78, eukaryotic initiation factor 2 alpha, and c-Jun N-terminal kinase by a neurovirulent murine retrovirus

In susceptible strains of mice, infection with the mutant retrovirus MoMuLV-ts1 causes a neurodegeneration and immunodeficiency syndrome that resembles human human immunodeficiency virus-acquired immunodeficiency syndrome (HIV-AIDS). In this study the authors show increased expression of cyclooxygenase-2 (COX-2) in the brainstem tissues of ts1-infected mice. Up-regulated central nervous system (CNS) levels of this enzyme are associated with HIV-associated dementia and other inflammatory and neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease. In brainstem sections, the authors find that astrocytes surrounding spongiform lesions contain increased amounts of immunoreactive COX-2. COX-2 is also up-regulated in cultured ts1-infected cells from the C1 astrocytic cell line, and activation of c-Jun N-terminal kinase, or JNK, pathway. Markers of endoplasmic reticulum (ER) stress, specifically the CCAAT/enhancer-binding protein (CHOP), the glucose-related protein 78 (GRP78), and phosphorylated eukaryotic initiation factor 2 alpha (eIF2 alpha), were also up-regulated in ts1-infected C1 astrocytes. Up-regulation of COX-2 and the above ER signaling factors was reversed by treatment of the infected cells with curcumin which specifically inhibits the JNK/c-Jun pathway. These findings indicate that the JNK/c-Jun pathway is most likely responsible for COX-2 expression induced by ts1 in astrocytes, and that ts1 infection in astrocytes may lead to up-regulation of both inflammatory and ER stress pathways in the central nervous system. Because COX-2 inhibitors are now widely used to treat inflammatory conditions in animals and humans, this finding suggests that these drugs may be useful for therapeutic intervention in neurodegenerative syndromes as well.

Transcriptional induction of cyclooxygenase-2 in osteoclast precursors is involved in RANKL-induced osteoclastogenesis

Regulation of osteoclast differentiation is key to understanding the pathogenesis and to developing treatments for bone diseases such as osteoporosis. To gain insight into the mechanism of the receptor activator of nuclear factor (NF)–κB ligand (RANKL)–specific induction of the osteoclast differentiation program, we took a suppression-subtractive hybridization screening approach to identify genes specifically induced via the RANKL-Rac1 signaling pathway. Among identified targets, we show that RANKL selectively induces cyclooxygenase (COX) 2 expression via Rac1 that results in turn in production of prostaglandin E2 (PGE2) in RAW 264.7 cells. By using transient transfection assays, we found that the –233/–206 region of the COX-2 promoter gene was critical for RANKL-induced promoter activity. This RANKL-responsive region contained an NF-κB site that, when mutated, completely abolished the induction of NF-κB DNA-binding activity by RANKL. Blockade of COX-2 by celecoxib inhibits differentiation of bone marrow-derived monocyte/macrophage precursor cells (BMMs) into tartrate-resistant acid phosphatase-positive (TRAP+) osteoclastic cells. This inhibition can be rescued by the addition of exogenous PGE2, suggesting that COX-2–dependent PGE2 induction by RANKL in osteoclast precursors is required for osteoclast differentiation.

Do cyclooxygenase-2 knockout mice have primary hyperparathyroidism?

The absence of cyclooxygenase-2 (COX-2) activity in vitro reduces differentiation of both bone-forming and bone-resorbing cells. To examine the balance of COX-2 effects on bone in vivo, we studied COX-2 knockout (KO) and wild-type (WT) mice. After weaning, KO mice died 4 times faster than WT mice, consistent with reports of progressive renal failure in KO mice. Among KO mice killed at 4 months of age, some had renal failure with marked secondary hyperparathyroidism, but others appeared healthy. On the assumption that renal failure was not inevitable in COX-2 KO mice and that phenotypic differences might increase with age, we studied KO mice surviving to 10 months of age with serum creatinine levels similar to those of WT mice. In 10-month-old male KO mice, serum calcium and PTH, but not phosphorus, levels were increased compared with those in WT mice. 1,25-Dihydroxyvitamin D(3) levels were markedly elevated in KO mice. Skeletal analysis showed small nonsignificant decreases in cortical bone density by BMD and either an increase (distal femur, by microcomputed tomography) or no difference (distal femur, by static histomorphometry) in trabecular bone density in KO mice. There was a trend toward increased percent osteoblastic and osteoclastic surfaces, and on dynamic histomorphometry, the rates of trabecular bone formation and mineral apposition were increased in KO mice relative to WT mice. Similar trends were observed for most parameters in 10-month-old female COX-2 KO mice. However, rates of trabecular bone formation and mineral apposition were increased in 10-month-old WT females compared with males and did not increase further in female KO mice. These data suggest that COX-2 KO mice with intact renal function have primary hyperparathyroidism, and that effects of increased PTH and 1,25-dihydroxyvitamin D(3) to increase bone turnover may compensate for the absence of COX-2.

Cross-talk between the interleukin-6 and prostaglandin E(2) signaling systems results in enhancement of osteoclastogenesis through effects on the osteoprotegerin/receptor activator of nuclear factor-{kappa}B (RANK) ligand/RANK system

The osteoprotegerin (OPG)/receptor activator of nuclear factor-kappaB ligand (RANKL)/receptor activator of nuclear factor-kappaB (RANK) system is the dominant and final mediator of osteoclastogenesis. Abnormalities of this system have been implicated in the pathogenesis of many skeletal diseases. Cyclooxygenase (COX)-2 and prostaglandin (PG)E(2), a major eicosanoid product of the COX-2-catalyzed pathway, play key roles in normal bone tissue remodeling. PGE(2) exerts its actions by binding and activating the E series of prostaglandin (EP) receptor. Activation of EP(2) and EP(4) receptors is associated with PGE(2)-induced osteoclast differentiation. IL-6, a major proinflammatory cytokine, has also been reported to induce osteoclast differentiation. Although interactions between the COX-2/PGE(2) and IL-6 systems have been described in bone cells, the mechanisms underlying these cooperative signaling pathways and the possible involvement of the OPG/RANKL/RANK system have not been fully elucidated. We demonstrate that COX-2, PGE(2), and IL-6 stimulate osteoblast growth and osteoclast differentiation. Effects on osteoclast differentiation, particularly with IL-6, were most marked when osteoclast precursor cells were grown in coculture with osteoblasts, indicating a possible role of the RANK/RANKL/OPG system. COX-2 and PGE(2) stimulated osteoclastogenesis through inhibition of OPG secretion, stimulation of RANKL production by osteoblasts, and up-regulation of RANK expression in osteoclasts. PGE(2) stimulated IL-6 secretion by bone cells, whereas COX-2 inhibitors decreased this same parameter. IL-6, in turn, increased PGE(2) secretion, COX-2, and EP receptor subtype expression in bone cells. Finally, IL-6 was the mediator of PGE(2)-induced suppression of OPG production by osteoblasts. These findings provide evidence for cross-talk between the PGE(2) and IL-6 signaling enhance osteoclast differentiation via effects on the OPG/RANKL/RANK system in bone cells.

Mechanism of acid-induced bone resorption

PURPOSE OF REVIEW

This review presents our current understanding of the way metabolic acidosis induces calcium efflux from bone, and in the process, buffers additional systemic hydrogen ions associated with acidosis.

RECENT FINDINGS

Acid-induced changes in bone mineral are consistent with a role for bone as a proton buffer. In response to metabolic acidosis in an in-vitro bone organ culture system, we observed a fall in mineral sodium, potassium, carbonate and phosphate, which each buffer protons and in vivo should increase systemic pH towards the physiologic normal. Initially, metabolic acidosis stimulates physicochemical mineral dissolution and subsequently cell-mediated bone resorption. Acidosis suppresses the activity of bone-resorbing cells, osteoblasts, decreasing gene expression of specific matrix proteins and alkaline phosphatase activity. There is concomitant acid stimulation of prostaglandin production by osteoblasts, which acting in a paracrine manner increases synthesis of the osteoblastic receptor activator of nuclear factor kappa B ligand (RANKL). The acid induction of RANKL then stimulates osteoclastic activity and recruitment of new osteoclasts to promote bone resorption and buffering of the proton load. Both the regulation of RANKL and acid-induced calcium efflux from bone are mediated by prostaglandins.

SUMMARY

Metabolic acidosis, which occurs during renal failure, renal insufficiency or renal tubular acidosis, results in decreased systemic pH and is associated with an increase in urine calcium excretion. The apparent protective function of bone to help maintain systemic pH, which has a clear survival advantage for mammals, will come partly at the expense of its mineral stores.

A prostanoid receptor EP4 agonist enhances ectopic bone formation induced by recombinant human bone morphogenetic protein-2

The anabolic effects of prostaglandin E(2) on bone are effected through the activation of EP4, a G protein-coupled receptor. In the present study, we examined the effects of a prostanoid receptor-selective agonist (ONO-4819) in an experimental system of ectopic bone formation using recombinant human bone morphogenetic protein-2 (rhBMP-2). Collagen pellets containing rhBMP-2 were implanted onto the back muscles of mice and then treated with ONO-4819 administered every 8 h by subcutaneous injection. The ossicles elicited ectopically by rhBMP-2 in mice treated with 30 microg/kg ONO-4819 were significantly larger in size and had a higher bone mineral density and bone mineral content when compared to the controls. We also noted that the anabolic effect of ONO-4819 was seen only in the early phase of the rhBMP-2-induced bone-forming process. These experimental results indicate that the EP4 receptor agonist enhances the rhBMP-2-induced bone formation through a selective effect on early stage mesenchymal cells, which in turn may result in increased responsiveness of the host animals to rhBMP-2.