Chronic inflammation in biomaterial-induced periprosthetic osteolysis: NF-κB as a therapeutic target

STAT3/IL-6 dependent induction of inflammatory response in osteoblast and osteoclast formation in nanoscale wear particle-induced aseptic prosthesis loosening

BACKGROUND

Aseptic loosening is the main reason for surgical revision after arthroplasty. Although a series of mechanisms have been explored, a specific therapeutic target is still desired. In the present study, we explored the role of the signal transducer and activator of the transcription (STAT)/interleukin-6 (IL-6) pathway in the induction of the inflammatory response in osteoblast and osteoclast formation during aseptic prosthesis loosening.

METHODS

The expression of activated STAT3 was examined in osteoblasts treated with TiAl6V4 nanoparticles (TiPs) from materials used in prosthetics and specimens from particle-induced osteolysis (PIO) animal models. Inflammatory responses associated with the IL-6 family in osteoblasts were identified by Quantitative Real-time PCR. A mimicking coculture system was used to directly determine the number of activated osteoclasts in vitro, and immunohistochemical staining with tartrate-resistant acid phosphatase (TRAP) was used in vivo. CP690,550, an inhibitor of STAT3, was administered to examine the effect of STAT3 on the inflammatory response and osteoclast formation.

RESULTS

STAT3 was activated in both nanoparticle-treated osteoblasts and PIO model animals. On the one hand, the activation of STAT3 mediated nanoparticle-induced IL-6-dependent inflammatory responses in osteoblasts. On the other hand, the activation of STAT3 induced receptor activator of nuclear factor kappa B ligand (RANKL) production and stimulated osteoclast formation. The application of the STAT3 inhibitor CP690,550 reduced the production of the IL-6 family and the formation of osteoclasts both in vitro and in vivo.

CONCLUSION

STAT3 mediated inflammation-related signalling and osteoclast activation in nanoscale wear particle-induced aseptic loosening. Inhibition of STAT3 by tofacitinib may be a potential treatment for aseptic loosening.

Evaluating the bio-application of biomacromolecule of lignin-carbohydrate complexes (LCC) from wheat straw in bone metabolism via ROS scavenging

Lignin-carbohydrate complexes (LCC) arebiomacromolecules that can be obtained from different biomass. Even some works have shown the LCC can efficiently scavenge the intracellular and endogenous reactive oxygen species (ROS), while little work has been carried out to investigate the potential application of LCC for ROS-related treatment in biological filed, especially for the treatment of periprosthetic osteolysis in vivo. In this work, Lignin-rich (LCC-A) and carbohydrate-rich (LCC-B) fractions in wheat straw are isolated and used as the ROS scavenger to promote osteoblast differentiation and inhibit osteoclast differentiation. The chemical composition and structures are characterized by high performance anion exchange chromatography (HPAEC) and nuclear magnetic resonance (NMR) technologies (quantitative ¹³C NMR and 2D-HSQC NMR), respectively. The results showed LCC-A possesses higher in vitro ROS-scavenging ability than LCC-B (89.8% vs 57.8%) and to inhibit osteoclast differentiation, whereas LCC-B more significantly activates cellular antioxidant activities via the KEAP1-NRF2-ARE pathway (218.5% vs 438.0% in the level of HO-1), thus promoting osteoblast differentiation in an inflammatory environment. Moreover, the therapeutic administration of LCC-A and LCC-B for Ti-particle-induced osteolytic murine calvariae showed both of them positively regulate and restore the bone metabolism, while preventing calvaria impairment. Hence, LCC from wheat straw exhibits efficient bone protective effects, suggesting it may be used as the promising ROS scavenger for clinical treatment of periprosthetic osteolysis.

Anti-inflammatory and antinociceptive effects of Curcuma kwangsiensis and its bioactive terpenoids in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

"Curcumae Radix", the dried rhizomes of Curcuma kwangsiensis documented in Chinese pharmacopoeia, has been traditionally used for the treatment of inflammatory and pain diseases, such as jaundice and red urine, cleaning the heart-fire and depression, arthralgia, and dysmenorrhea. However, according to literature surveys, anti-inflammatory and antinociceptive studies of C. kwangsiensis have been seldom reported so far.

AIM OF THE STUDY

The current study focuses on the anti-inflammatory and antinociceptive effects of C. kwangsiensis and discovering the bioactive compounds for its traditional usages both in vivo and in vitro, which could provide scientific justification about its traditional use.

MATERIAL AND METHODS

The anti-inflammatory and antinociceptive assays of various layers (ME, EA, AQS) from C. kwangsiensis were achieved by carrageenan-induced paw edema and acetic acid-induced writhing animal models, respectively. The most bioactive part, EA layer was further phytochemically investigated by multiple step chromatography techniques. The structures of these isolates were unambiguously elucidated by means of extensive spectroscopic and chemical methods, and comparison with corresponding data of the reported literature. Four major sesquiterpenoids (4, 6, 14, and 15) were achieved for their anti-inflammatory and antinociceptive assays by the two aforementioned animal models in vivo. All the isolated compounds were evaluated for their anti-inflammatory effects via detecting inflammatory mediator releases (COX-2, IL-1β, and TNF-α) in RAW 264.7 macrophage cells induced by LPS.

RESULTS

The ME and EA layers significantly alleviated the paw edema caused by carrageenan and decreased the number of writhes induced by acetic acid at the dose of 200 and/or 100 mg/kg in comparison to the control group (p < 0.01/0.05), and the EA layer exhibited better activity than that of ME layer. Subsequent phytochemical investigation on EA layer of C. kwangsiensis exhibited that three new terpenoid compounds (1-3), identified as (12Z,14R)-7β-hydroxylabda-8(17),12-diene-14,15,16-triol (1), (12Z,14S)- 7β-hydroxlabda-8(17),12-diene-14,15,16-triol (2), and (4S)-hydroxy-(8)-methoxy-(5S)-(H)-guaia1(10),7(11)-dien-12,8-olide (3), together with twenty-two known analogs were isolated. Furthermore, four major sesquiterpenoids (4, 6, 14, and 15) significantly relieved the paw edema and number of writhes at 100 and/or 50 mg/kg (p < 0.05/0.01). Likewise, the majority of sesqui- and diterpenoids isolated could remarkably inhibited the secretion of inflammatory mediators (COX-2, IL-1β, and TNF-α) in LPS-stimulated RAW 264.7 macrophages cells at the concentration of 20 μg/mL, comparable to DXM used as the positive control. All the results suggested that EA layer from C. kwangsiensis possessed the anti-inflammatory and antinociceptive activities, and these sesqui- and diterpenoids could be the effective constituents responsible for relieving inflammation.

CONCLUSION

The present studies undoubtedly determined the anti-inflammatory and antinociceptive material basis of C. kwangsiensis, including the EA layer and its precise components, which presented equivalent or better anti-inflammatory effects than that of positive control (ASP/DXM) in vivo and in vitro. These results not only would account for scientific knowledge for traditional use of C. kwangsiensis, but also provide credible theoretical foundation for the further development of anti-inflammatory and antinociceptive agents.

Puerarin inhibits titanium particle-induced osteolysis and RANKL-induced osteoclastogenesis via suppression of the NF-κB signaling pathway

Osteolysis around the prosthesis and subsequent aseptic loosening are the main causes of prosthesis failure. Inflammation due to wear particles and osteoclast activation are the key factors in osteolysis and are also potential targets for the treatment of osteolysis. However, it is not clear whether puerarin can inhibit chronic inflammation and alleviate osteolysis. In this study, we investigated the effect of puerarin on Ti particle-induced inflammatory osteolysis in vivo in rat femoral models and in vitro in receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast activation models. Our in vivo results showed that puerarin significantly inhibited Ti particle-induced osteolysis and the expression of matrix metallopeptidase 9 (MMP-9), nuclear factor of activated T cells 1 (NFATc1), tumour necrosis factor (TNF)-α and interleukin (IL)-6. In vitro, puerarin prevented RANKL-induced osteoclast differentiation, bone resorption and F-actin ring formation in a concentration-dependent manner. Furthermore, puerarin decreased the phosphorylation of p65 and prevented p65 moving from the cytoplasm to the nucleus. Puerarin also reduced the expression of osteoclast-specific factors and inhibited the inflammatory response. In conclusion, our study proves that puerarin can block the NF-κB signalling pathway to inhibit osteoclast activation and inflammatory processes, which provides a new direction for the treatment of osteolysis-related diseases.

TET2 promotes IL-1β expression in J774.1 cell through TLR4/MAPK signaling pathway with demethylation of TAB2 promoter

Interleukin (IL)-1β produced by macrophages plays an important role in inflammation development. However, the underlying mechanism in epigenetic regulation of IL-1β production is not fully addressed. Though DNA methylcytosine dioxygenase ten-eleven translocation 2 (TET2) is known to be involved in the regulation of inflammatory factors by oxidizing 5-methylcytosine (5mC), the underlying molecular mechanism is largely unknown. In this study, we found that the expression of both IL-1β and TET2 is upregulated by lipopolysaccharide (LPS)-stimulated mononuclear macrophage. We then knocked down TET2 in mouse macrophagelike cell line (J774.1) and found that LPS-induced IL-1β is also downregulated. In addition, LPS-stimulated phosphorylation of the mitogen-activated protein kinase (MAPK) signaling pathway and intracellular effectors of the toll-like receptor 4 (TLR4) signaling pathway were also suppressed in TET2-knockdown cells. The methylation status in the promoter regions of myeloid differentiation primary response gene (MyD)88 and TAK1 binding protein 2 (TAB2) were estimated by bisulfite polymerase chain reaction. Compared with that of the control, the 5mC level on the TAB2 promoter is downregulated in the LPS-stimulated cells which can be reversed by TET2-knockdown. These findings altogether suggest that LPS-upregulated TET2 enhances IL-1β expression through demethylating the promoter region of TAB2, the key member of the TLR4/MAPK signaling pathway, a previously unreported molecular mechanism in TET2-regulated expression of inflammatory factors.

A multifaceted biomimetic interface to improve the longevity of orthopedic implants

The rise of additive manufacturing has provided a paradigm shift in the fabrication of precise, patient-specific implants that replicate the physical properties of native bone. However, eliciting an optimal biological response from such materials for rapid bone integration remains a challenge. Here we propose for the first time a one-step ion-assisted plasma polymerization process to create bio-functional 3D printed titanium (Ti) implants that offer rapid bone integration. Using selective laser melting, porous Ti implants with enhanced bone-mimicking mechanical properties were fabricated. The implants were functionalized uniformly with a highly reactive, radical-rich polymeric coating generated using a unique combination of plasma polymerization and plasma immersion ion implantation. We demonstrated the performance of such activated Ti implants with a focus on the coating's homogeneity, stability, and biological functionality. It was shown that the optimized coating was highly robust and possessed superb physico-chemical stability in a corrosive physiological solution. The plasma activated coating was cytocompatible and non-immunogenic; and through its high reactivity, it allowed for easy, one-step covalent immobilization of functional biomolecules in the absence of solvents or chemicals. The activated Ti implants bio-functionalized with bone morphogenetic protein 2 (BMP-2) showed a reduced protein desorption and a more sustained osteoblast response both in vitro and in vivo compared to implants modified through conventional physisorption of BMP-2. The versatile new approach presented here will enable the development of bio-functionalized additively manufactured implants that are patient-specific and offer improved integration with host tissue. STATEMENT OF SIGNIFICANCE: Additive manufacturing has revolutionized the fabrication of patient-specific orthopedic implants. Although such 3D printed implants can show desirable mechanical and mass transport properties, they often require surface bio-functionalities to enable control over the biological response. Surface covalent immobilization of bioactive molecules is a viable approach to achieve this. Here we report the development of additively manufactured titanium implants that precisely replicate the physical properties of native bone and are bio-functionalized in a simple, reagent-free step. Our results show that covalent attachment of bone-related growth factors through ion-assisted plasma polymerized interlayers circumvents their desorption in physiological solution and significantly improves the bone induction by the implants both in vitro and in vivo.

Titanium particles induce apoptosis by promoting autophagy in macrophages via the PI3K/Akt signaling pathway

Chronic inflammation and infection in the tissue surrounding implants after total joint replacement is closely associated with the innate immune response to surgical implants. Wear particles are known to increase apoptosis and impair the innate immunity in macrophages, which can cause immunosuppression around the implants. Excessive autophagy can induce apoptosis. However, the link between autophagy and apoptosis in macrophages during chronic inflammation and infection remains unknown. In this study, we investigated the autophagy and apoptosis induced by titanium particles in RAW264.7 macrophages, and in the interface membrane of patients with late-onset periprosthetic joint infection (PJI). We found that titanium particles stimulated autophagy and apoptosis in macrophages. Inhibition of autophagy significantly reduced titanium particle-induced apoptosis in macrophages, which may be related to the PI3K/Akt signaling pathway. The secretion of inflammatory factors, such as IL-1β, IL-6, and TNF-α, decreased after inhibition of autophagy in titanium particle-stimulated macrophages, which may be caused by immune dysfunction due to titanium particle-induced autophagy and apoptosis in macrophages. Furthermore, our in vivo mouse calvarial model also showed that autophagy inhibitors lowered the rate of cell apoptosis. Our findings indicate that wear particle-induced apoptosis may be caused by enhanced autophagy in macrophages, which could potentially impair the local innate immunity in periprosthetic tissues and could be a risk factor for PJI. Based on these results, autophagy modulators may act as a new therapeutic option for PJI.

The Effects of Biomaterial Implant Wear Debris on Osteoblasts

Aseptic loosening subsequent to periprosthetic osteolysis is the leading cause for the revision of arthroplasty failure. The biological response of macrophages to wear debris has been well established, however, the equilibrium of bone remodeling is not only dictated by osteoclastic bone resorption but also by osteoblast-mediated bone formation. Increasing evidence shows that wear debris significantly impair osteoblastic physiology and subsequent bone formation. In the present review, we update the current state of knowledge regarding the effect of biomaterial implant wear debris on osteoblasts. The interaction of osteoblasts with osteoclasts and macrophages under wear debris challenge, and potential treatment options targeting osteoblasts are also presented.

An In Vivo Study in Rat Femurs of Bioactive Silicate Coatings on Titanium Dental Implants

Silica-based ceramics have been proposed for coating purposes to enhance dental and orthopedic titanium (Ti) implant bioactivity. The aim of this study was to investigate the influence of sphene-based bioceramic (CaO.TiO₂.SiO₂) coatings on implant osseointegration in vivo. Sphene coatings were obtained from preceramic polymers and nano-sized active precursors and deposited by an automatic airbrush. Twenty customized Ti implants, ten sphene-coated and ten uncoated rough implants were implanted into the proximal femurs of ten Sprague-Dawley rats. Overall, cortical and cancellous bone-to-implant contact (BIC) were determined using micro-computed tomography (micro-CT) at 14 and 28 days. Moreover, peri-implant bone healing was histologically and histomorphometrically evaluated. The white blood cell count in the synovial fluid of the knee joints, if present, was also assessed. No difference in the BIC values was observed between the sphene-coated and uncoated implants, overall and in the two bone compartments (p > 0.05). Delamination of the coating occurred in three cases. Consistently with micro-CT data, the histological evaluation revealed no differences between the two groups. In addition, no synovial fluid could be collected on the test side, thus confirming sphene biocompatibility. In conclusion, sphene coating was found to be a suitable material for biomedical applications. Further studies are needed to improve coating adhesion to the implants.

The USP14-NLRC5 pathway inhibits titanium particle-induced osteolysis in mice by suppressing NF-κB and PI3K/AKT activities

Total hip arthroplasty (THA) is a widely-used surgical intervention for treating patients with end-stage degenerative and inflammatory osteoarthropathy. However, wear particles from the artificial titanium joint can induce osteolysis, limiting the long-term survivorship of THA. Monocyte/macrophage lineage cells are the key players in the response to wear particles, and the proinflammatory NF-κB and phosphoinositide 3-kinase (PI3K)-AKT Ser/Thr kinase (AKT)-signaling pathways have been shown to be the most important contributors to wear particle-induced osteolysis. In contrast, ubiquitin-specific protease 14 (USP14) specifically removes the polyubiquitin chains from the nucleotide-binding and oligomerization domain (NOD)-like receptor family Caspase recruitment domain (CARD)-containing 5 (NLRC5) and thereby enhances the NLRC5-mediated inhibition of NF-κB signaling. In this study, we aimed to clarify the role of the USP14-NLRC5 pathway in wear particle-induced osteolysis in vitro and in vivo We found that NLRC5 or USP14 overexpression inhibits titanium particle-induced proinflammatory tumor necrosis factor α (TNFα) production and NF-κB pathway activation, and it also decreases M1 macrophage polarization and PI3K/AKT pathway activation. Of note, NLRC5 and USP14 overexpression attenuated titanium particle-induced cranial osteolysis in mice. In conclusion, the findings of our study indicate that the USP14-NLRC5 pathway inhibits titanium particle-induced osteolysis by suppressing the NF-κB and PI3K/AKT pathways both in vitro and in vivo.

Biological Reactions to Metal Particles and Ions in the Synovial Layer of Mice

Metal particles and ions released from implants not only have a fundamental effect on the longevity of total joint replacements, but can also be disseminated to remote organs. Periprosthetic tissues harvested during revision surgeries mainly reflect end-stage failure but may not adequately reveal initial biological reactions and systemic side effects. Therefore, primary reactions caused by metal particles and ions were investigated in an established murine model. Left knee joints in three groups, each consisting of ten female BALB/c mice, received injections of metal ions (MI), metal particles (MP) and phosphate-buffered saline (PBS) (control). Seven days after the injection, immunohistochemical analyses of the synovial layer were performed with respect to some biological markers including Tumor necrosis factor -α (TNF-α), Interleukin-6 (IL-6), Interleukin-1β (IL-1β), Cluster of Differentiation 45 (CD45), Cluster of Differentiation 68 (CD68) and Cluster of Differentiation 3(CD3). The MP group showed significantly enhanced proinflammatory cytokine expression (TNF-α, IL-6 and IL-1β) compared with the other groups (p < 0.05). Interestingly, CD3, as a marker for T lymphocytes, did not increase in any of the groups. The MI group showed a significantly increased expression of CD45 compared with the control group (p < 0.05). Therefore, during the primary process, metal particles have stronger pro-inflammatory potential than metal ions, and T lymphocytes did not seem to be activated in our murine model. Systemic reactions caused by metal particles and ions were found by observing the untreated right knees.

Positive role of calcium phosphate ceramics regulated inflammation in the osteogenic differentiation of mesenchymal stem cells

Recently, researches have confirmed the crucial role of inflammatory response in Ca-P ceramic-induced osteogenesis, however, the underlying mechanism has not yet been fully understood. In this study, BCP and β-TCP ceramics were used as material models to investigate the effect of physicochemical properties on inflammatory response in vitro. The results showed that BCP and β-TCP could support macrophages attachment, proliferation, and spreading favorably, as well as promote gene expressions of inflammatory related cytokines (IL-1, IL-6, MCP-1, and TNF-α) and growth factors (TGF-β, FGF, PDGF, VEGF, IGF, and EGF). BCP showed a facilitating function on the gene expressions earlier than β-TCP. Further coculture experiments performed in vitro demonstrated that the CMs containing various increased cytokines for macrophages pre-culture could significantly promote MSCs osteogenic differentiation, which was confirmed by the gene expressions of osteogenic specific markers and the intracellular OCN product accumulation under the stimulation of BCP and β-TCP ceramics. Further evidence was found from the formation of mineralized nodules in BCM and TCM. In addition, this study showed a concise relationship between Ca-P ceramic induced inflammation and its osteoinductivity that the increased cytokines and growth factors from macrophages could promote MSCs osteogenic differentiation.

Anti-inflammatory potential of Trifolium pratense L. leaf extract in LPS-stimulated RAW264.7 cells and in a rat model of carrageenan-induced inflammation

This study evaluated the anti-inflammatory potential of a 40% prethanol extract of Trifolium pratense leaves (40% PeTP) using in vitro (RAW264.7 cells) and in vivo (carrageenan-induced inflammation model) experiments. Pretreatment with 40% PeTP significantly inhibited the LPS-induced expression of nitric oxide (NO), prostaglandin E₂ (PGE₂), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and inflammatory cytokines, including tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in RAW264.7 cells, without inducing cytotoxicity. The inhibitory effects of 40% PeTP are mediated through suppression of the nuclear translocation of nuclear factor (NF)-κB and the phosphorylation of mitogen-activated protein kinases (MAPKs). Oral administration of 40% PeTP at 50, 100, and 200 mg/kg of body weight suppressed carrageenan-induced oedema in a dose-dependent manner. Collectively, our results suggested that 40% PeTP exerts potential anti-inflammatory effects by suppressing the activation of the NF-κB and MAPK pathways in vitro, and by reducing carrageenan-induced paw oedema in vivo.

Hydrogen sulfide protects against particle-induced inflammatory response and osteolysis via SIRT1 pathway in prosthesis loosening

Wear debris-induced osteolysis and ensuing aseptic loosening is the main cause of implant failure and revision surgery. Wear debris-induced inflammatory response plays key roles in peri-implant osteolysis. Recently, substantial of evidence suggests that hydrogen sulfide (H₂ S), the third gasotransmitter, is a critical player regulating inflammation. However, the role and therapeutic potential of H₂ S in wear debris-induced inflammation and osteolysis remains to be defined. In the present study, we investigated the effect of H₂ S on wear debris-induced pro-inflammatory cytokines expression and osteolysis in vitro and in vivo. With a slow-releasing H₂ S donor GYY4137, our study demonstrated that H₂ S attenuated wear debris-induced osteolysis and osteoclastogenesis in murine calvaria resorption models. The expression of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) that stimulated by wear particles were significantly reduced by GYY4137. Further, the level of sirtuin 1 (SIRT1), which possesses anti-inflammation property, was examined in vivo and in macrophages. And we found that wear debris decreased the expression of SIRT1. Cotreated macrophages with GYY4137 in part reversed the decline of SIRT1. More importantly, with the SIRT1 recombinant lentivirus and small interfering RNAs (siRNA) against SIRT1, our data indicated that SIRT1 mediated the inhibitory effects of GYY4137 on wear debris-induced inflammation. Collectively, these results suggested that exogenous H₂ S production (via H₂ S donors) may represent a potential approach for the treatment of wear particle-induced osteolysis.

Modulation of the Inflammatory Response and Bone Healing

The optimal treatment for complex fractures and large bone defects is an important unsolved issue in orthopedics and related specialties. Approximately 5-10% of fractures fail to heal and develop non-unions. Bone healing can be characterized by three partially overlapping phases: the inflammatory phase, the repair phase, and the remodeling phase. Eventual healing is highly dependent on the initial inflammatory phase, which is affected by both the local and systemic responses to the injurious stimulus. Furthermore, immune cells and mesenchymal stromal cells (MSCs) participate in critical inter-cellular communication or crosstalk to modulate bone healing. Deficiencies in this inter-cellular exchange, inhibition of the natural processes of acute inflammation, and its resolution, or chronic inflammation due to a persistent adverse stimulus can lead to impaired fracture healing. Thus, an initial and optimal transient stage of acute inflammation is one of the key factors for successful, robust bone healing. Recent studies demonstrated the therapeutic potential of immunomodulation for bone healing by the preconditioning of MSCs to empower their immunosuppressive properties. Preconditioned MSCs (also known as "primed/ licensed/ activated" MSCs) are cultured first with pro-inflammatory cytokines (e.g., TNFα and IL17A) or exposed to hypoxic conditions to mimic the inflammatory environment prior to their intended application. Another approach of immunomodulation for bone healing is the resolution of inflammation with anti-inflammatory cytokines such as IL4, IL10, and IL13. In this review, we summarize the principles of inflammation and bone healing and provide an update on cellular interactions and immunomodulation for optimal bone healing.

Vinpocetine inhibits RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss

Osteoporosis is a result of impaired bone formation and/or excessive bone resorption. Osteoclasts are the only cells in the body that have a bone resorption function. Inhibiting osteoclast activity and differentiation is a way to treat osteoporosis. The current pharmacological treatment for osteoporosis has many shortcomings, and more effective treatments are needed. Vinpocetine (Vinp), a derivative of the alkaloid vincamine, has been used to treat cerebrovascular disorders and cognitive impairment for a long time. Vinp inhibits mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB)-dependent inflammatory responses and oxidative damage in which osteoclasts are often involved. However, the effects of Vinp on the regulation of osteoclast activity remain unknown. In this study, we found that Vinp significantly inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast and F-actin formation and decreased osteoclastic bone resorption in vitro. Vinp also suppressed the expression of osteoclast-specific genes, including NFATc1, c-Fos, tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), and cathepsin K (CTSK) at both the mRNA and protein levels. Vinp reduced activation of NF-κB, MAPK, and AKT signaling during osteoclastogenesis and prevented the production of reactive oxygen species with increased nuclear factor erythroid 2-related factor 2, heme oxygenase 1, and NAD(P)H:quinone acceptor oxidoreductase 1 expression. Animal experiments consistently demonstrated that Vinp treatment significantly attenuated ovariectomy-induced bone loss with a decrease in the osteoclast number and decreases in serum levels of RANKL, TRAP, interleukin-1β, and tumor necrosis factor-alpha, as well as increased serum levels of osteoprotegerin. Taken together, our findings reveal that Vinp may be a potential pharmacological choice for preventing and treating osteoporosis.

Effects of occlusal forces on the peri-implant-bone interface stability

The occlusal forces and their influence on the initiation of peri-implant bone loss or their relationship with peri-implantitis have created discussion during the past 30 years given the discrepancies observed in clinical, animal, and finite element analysis studies. Beyond these contradictions, in the case of an osseointegrated implant, the occlusal forces can influence the implant-bone interface and the cells responsible for the bone remodeling in different ways that may result in the maintenance or loss of the osseointegration. This comprehensive review focuses on the information available about the forces transmitted through the implant-crown system to the implant-bone interface and the mechano-transduction phenomena responsible for the bone cells' behavior and their interactions. Knowledge of the basic molecular biology of the peri-implant bone would help clinicians to understand the complex phenomenon of occlusal forces and their effects on the implant-bone interface, and would allow better control of the negative effects of mechanical stresses, leading to therapy with fewer risks and complications.

Tuning the surface immunomodulatory functions of polyetheretherketone for enhanced osseointegration

The adverse macrophage-mediated immune response elicited by the surface of polyetheretherketone (PEEK) is responsible for the formation of fibrous encapsulation and resulting inferior osseointegration of PEEK implants in the dental and orthopedic fields. Therefore, endowing the PEEK surface with immunomodulatory ability is an appealing strategy to enhance implant-bone integration. Herein, a reliable and cost-effective method to construct adherent films with tunable nanoporous structures on PEEK is described. The functionalized surface not only suppresses the acute inflammatory response of macrophages, but also provides a favorable milieu for osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Whole genome expression analysis reveals that the suppression effect arises from synergistic inhibition of focal adhesion, Toll-like receptor, and NOD-like receptor signaling pathways, as well as the attenuating loop through the JAK-STAT and TNF signaling pathways in macrophages. Further in vivo studies confirm that the functionalized surface induces less fibrous capsule formation and an improved bone regeneration. The nanoporous films fabricated on PEEK harmonize the early macrophage-mediated inflammatory response and subsequent hBMSCs-centered osteogenic functions consequently yielding superior osseointegration.

Genetic or pharmacologic blockade of enhancer of zeste homolog 2 inhibits the progression of peritoneal fibrosis

Dysregulation of histone methyltransferase enhancer of zeste homolog 2 (EZH2) has been implicated in the pathogenesis of many cancers. However, the role of EZH2 in peritoneal fibrosis remains unknown. We investigated EZH2 expression in peritoneal dialysis (PD) patients and assessed its role in peritoneal fibrosis in cultured human peritoneal mesothelial cells (HPMCs) and murine models of peritoneal fibrosis induced by chlorhexidine gluconate (CG) or high glucose peritoneal dialysis fluid (PDF) by using 3-deazaneplanocin A (3-DZNeP), and EZH2 conditional knockout mice. An abundance of EZH2 was detected in the peritoneum of patients with PD associated peritonitis and the dialysis effluent of long-term PD patients, which was positively correlated with expression of TGF-β1, vascular endothelial growth factor, and IL-6. EZH2 was found highly expressed in the peritoneum of mice following injury by CG or PDF. In both mouse models, treatment with 3-DZNeP attenuated peritoneal fibrosis and inhibited activation of several profibrotic signaling pathways, including TGF-β1/Smad3, Notch1, epidermal growth factor receptor and Src. EZH2 inhibition also inhibited STAT3 and nuclear factor-κB phosphorylation, and reduced lymphocyte and macrophage infiltration and angiogenesis in the injured peritoneum. 3-DZNeP effectively improved high glucose PDF-associated peritoneal dysfunction by decreasing the dialysate-to-plasma ratio of blood urea nitrogen and increasing the ratio of dialysate glucose at 2 h after PDF injection to initial dialysate glucose. Moreover, delayed administration of 3-DZNeP inhibited peritoneal fibrosis progression, reversed established peritoneal fibrosis and reduced expression of tissue inhibitor of metalloproteinase 2, and matrix metalloproteinase-2 and -9. Finally, EZH2-KO mice exhibited less peritoneal fibrosis than EZH2-WT mice. In HPMCs, treatment with EZH2 siRNA or 3-DZNeP suppressed TGF-β1-induced upregulation of α-SMA and Collagen I and preserved E-cadherin. These results indicate that EZH2 is a key epigenetic regulator that promotes peritoneal fibrosis. Targeting EZH2 may have the potential to prevent and treat peritoneal fibrosis. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The emerging role of IMD 0354 on bone homeostasis by suppressing osteoclastogenesis and bone resorption, but without affecting bone formation

Osteoporosis is caused by an imbalance between bone formation and bone resorption. Receptor activator of nuclear factor-κB ligand (RANKL) promotes the activity and differentiation of osteoclasts via activating the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. IMD 0354 is a selective molecular inhibitor of inhibitor of NF-κB kinase subunit beta (IKKβ) and effective for treatment of acute and subacute inflammatory diseases through the suppression of NF-κB activation. However, the effect of IMD 0354 on bone homeostasis is unknown. In this study, we demonstrated that IMD 0354 significantly attenuated ovariectomy-induced bone loss and inhibited osteoclastogenesis in mice, whereas bone formation was not affected. Additionally, IMD 0354 dramatically inhibited osteoclast differentiation and function induced by RANKL and macrophage colony-stimulating factor in bone marrow monocytes as verified by tartrate-resistant acid phosphatase (TRAP) staining as well as bone resorption assay in vitro. Subsequently, we found that activation of NF-κB signaling and the ERK/c-Fos axis were blunted during osteoclast formation induced by RANKL. Transcription factors nuclear factor of activated T cells c1 (NFATc1) and c-Fos were suppressed with the decreased expression of osteoclast-related genes by IMD 0354. Our findings suggest that IMD 0354 could be a potential preventive and therapeutic drug for osteoporosis.

Anti-inflammatory Effect of Pomelo Peel and Its Bioactive Coumarins

Citrus grandis (L.) Osbeck is a popular fruit cultivated around the world, and its peels are sometimes used for the treatment of cough, abdominal pain, and indigestion in China. However, the peel is discarded after fruit consumption in most cases, and its chemical constituents and biological activities have not been validated before. The present study focused on evaluation of the chemical and pharmacological profile of coumarins from peels of C. grandis against inflammation. The extracts and phytochemicals from peels of C. grandis were prepared, and anti-inflammatory activities were carried out in vivo and in vitro, including inhibiting xylene-induced ear edema and carrageenan-induced paw edema in mice and the production of inflammatory cytokines (interleukin 1β, prostaglandin 2, and tumor-necrosis factor α) in lipopolysaccharide (LPS)-induced RAW 264.7 cells. Results indicated that methanolic extract, ethyl acetate fraction, and four major coumarins (compounds 7, 8, 13, and 16) inhibited swelling induced by xylene and carrageenan, separately, in vivo. Furthermore, 18 coumarins inhibited inflammatory factor secretion in macrophages primed by LPS, in which compounds 4, 6, 7, 10, 17 showed the most pronounced change, which were comparable to dexamethasone. In summary, peel of C. grandis showed an anti-inflammatory effect and coumarin compounds were responsible for regulating inflammatory mediators and cytokines, which might provide a novel nutritional strategy for inflammatory diseases.

Role of Brd4 in the production of inflammatory cytokines in mouse macrophages treated with titanium particles

Brd4 protein is an important epigenetic regulator involved in the process of inflammatory cytokine production in many diseases. However, whether and how Brd4 participates in the process of wear-particle-induced inflammation remain unclear. This study aimed to investigate the potential role of Brd4 in titanium (Ti) particle-induced inflammatory cytokine production in mouse macrophage RAW264.7 cells. Our experiment detected Brd4 expressed in both normal synovium and periprosthetic osteolysis interface membrane, but the expression increased in the interface membrane as compared with that in normal synovium. Treatment with Ti particles significantly increased TNF-α, IL-6, and IL-1β production in RAW264.7 cells, which was inhibited by JQ1 or Brd4-siRNA. Ti particles enhanced the expression of Brd4, which was abrogated by JQ1. Ti particles enhanced NF-κB p65 and IKK phosphorylation and attenuated IκBα protein expression, which were abrogated by JQ1. Co-immunoprecipitation analysis indicated that Ti particles promoted the binding of Brd4 to acetylated NF-κB p65 (lysine-310), which was also abrogated in JQ1-treated RAW264.7 cells. In conclusion, Brd4 expression increases in interface membrane and Brd4 participates in the production of pro-inflammatory cytokines induced by Ti particles via promoting the activation of NF-κB signaling and binding to acetylated NF-κB p65 (lysine-310) in mouse macrophages.

Treating Titanium Particle-Induced Inflammation with Genetically Modified NF-κB Sensing IL-4 Secreting or Preconditioned Mesenchymal Stem Cells in Vitro

Titanium and titanium-based alloys are widely used in orthopaedic implants. Total joint replacement is very successful; however, the foreign body response and chronic inflammation caused by implant-derived biomaterial debris still remain as unsolved issues. Aseptic loosening accompanied by wear debris-induced osteolysis (bone loss) is one of the most frequent causes for late failure and revision surgery. Mesenchymal stem cells (MSCs) and IL-4 may be possible treatment strategies because of their immunomodulatory properties. We investigated the efficacy of novel MSC-based treatments on immunomodulation and osteogenic differentiation in an innovative cell coculture model of titanium particle-induced inflammation in the periprosthetic tissues. MSCs and macrophages were collected from the bone marrow of Balb/c mice. Both MSCs and macrophages (representing endogenous cells at the periprosthetic tissue) were seeded on the bottom wells of the 24-well transwell plates. We generated genetically modified NF-κB sensing IL-4 secreting MSCs (inflammatory responsive MSCs) and MSCs preconditioned by lipopolysaccharide and TNF-α to further enhance their immunomodulatory function. These modified MSCs (representing exogenous therapeutic cells implanted to the periprosthetic tissue) were seeded on the upper chambers of the transwell plates. These cocultures were then exposed to titanium particles for 7 days. NF-κB sensing IL-4 secreting MSCs showed strong immunomodulation (significantly reduced TNF-α and induced Arg1 expression) and promoted early osteogenesis (significantly induced Runx2, ALP, and β-catenin as well as reduced Smurf2 expression) at day 7. IL-4 secreting MSCs also decreased TNF-α protein secretion as early as day 3 and increased IL-1ra protein secretion at day 7, suggesting efficacious immunomodulation of particle-induced inflammation. Preconditioned MSCs did not show significant immunomodulation in this short-term experiment, but ALP and β-catenin expression were significantly induced at day 7. Our results suggest that genetically modified IL-4 secreting MSCs and preconditioned MSCs have the potential to optimize bone regeneration in inflammatory conditions including periprosthetic osteolysis.

Interleukin-27 prevents LPS-induced inflammatory osteolysis by inhibiting osteoclast formation and function

Osteolysis is a serious complication of several chronic inflammatory diseases and is closely associated with a local chronic inflammatory reaction with a variety of causes. Inflammatory factors and osteoclastogenesis can enhance bone erosion. Interleukin-27 (IL-27) is speculated to play an important role in the physiological immune response. However, there are few studies on its effects on osteoclastogenesis. In this study, IL-27 was shown to inhibit receptor activator nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis. The gene expression levels of osteoclast (OC)-specific genes, such as nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) and C-FOS, which are essential for OC differentiation and bone resorption, were significantly reduced. Further investigating the underlying mechanism, we found that IL-27 significantly reduced RANKL-induced osteoclastogenesis by inhibiting the phosphorylation of IκB and phosphorylation of nuclear factor κB (NF-κB) p65. Furthermore, IL-27 was shown to inhibit lipopolysaccharide (LPS)-induced osteolysis in vivo. Collectively, these results indicate that IL-27 may be a potential candidate for the treatment of osteolytic diseases.

Antiresorptive Agents are More Effective in Preventing Titanium Particle-Induced Calvarial Osteolysis in Ovariectomized Mice Than Anabolic Agents in Short-Term Administration

Aseptic loosening due to wear particle‐induced osteolysis is the main cause of arthroplasty failure and the influence of postmenopausal osteoporosis and anti‐osteoporosis treatment on Titanium (Ti) particle‐induced osteolysis remains unclear. 66 C57BL/6J female mice were used in this study. Ovariectomy (OVX) was performed to induce osteopenia mice and confirmed by micro‐CT. The Ti particle‐induced mouse calvaria osteolysis model was established subsequently and both OVX and Sham‐OVX mice were divided into four groups, respectively: Ti (‐) group, Ti group, Ti + zoledronic acid (ZOL) group (50ug/kg, local administration, single dose) and Ti + teriparatide (TPTD) group (40ug/kg/d, subcutaneous injection*14d). Mice calvarias were collected for micro‐CT and histomorphometric analysis 2 weeks after particle induction. 8 weeks after bilateral OVX, significantly reduced BMD and microstructure parameters in both proximal tibia and calvaria were observed in OVX mice when comparing with Sham‐OVX mice. OVX mice in Ti group had not only markly decreased BMD and BV/TV, but also significantly increased total porosity, eroded surface area and osteoclast numbers when comparing with Sham‐OVX mice. Shown by Two‐way ANOVA analysis, the interaction terms between OVX and Ti implantation on micro‐CT and histomorphometry parameters didn’t reach significant difference. As illustrated by micro‐CT and histological analysis, ZOL treatment markedly inhibited Ti particle‐induced osteolysis in OVX mice and Sham‐OVX mice, and there were significant differences when comparing to both Ti and Ti+TPTD group. The combination of osteoporosis and Ti particle implantation result in aggravated bone resorption, accompanied with increased osteoclasts and excessive inflammation response. ZOL was more effective in preventing Ti particle‐induced osteolysis in both OVX mice and Sham‐OVX mice than TPTD in short‐term administration. ZOL exert the protective effects on Ti particle‐induced bone loss via the suppression of osteoclasts.

The summary of the most important cell-biomaterial interactions that need to be considered during in vitro biocompatibility testing of bone scaffolds for tissue engineering applications

Tissue engineered products (TEPs), which mean biomaterials containing either cells or growth factors or both cells and growth factors, may be used as an alternative to the autografts taken directly from the bone of the patients. Nevertheless, the use of TEPs needs much more understanding of biointeractions between biomaterials and eukaryotic cells. Despite the possibility of the use of in vitro cellular models for initial evaluation of the host response to the implanted biomaterial, it is observed that most researchers use cell cultures only for the evaluation of cytotoxicity and cell proliferation on the biomaterial surface, and then they proceed to animal models and in vivo testing of bone implants without fully utilizing the scientific potential of in vitro models. In this review, the most important biointeractions between eukaryotic cells and biomaterials were discussed, indicating molecular mechanisms of cell adhesion, proliferation, and biomaterial-induced activation of immune cells. The article also describes types of cellular models which are commonly used for biomaterial testing and highlights the possibilities and drawbacks of in vitro tests for biocompatibility evaluation of novel scaffolds. Finally, the review summarizes recent findings concerning the use of adult mesenchymal stem cells for TEP generation and compares the potential of bone marrow- and adipose tissue-derived stem cells in regenerative medicine applications.

Analysis of Trauma Intensity during Surgical Bone Procedures Using NF-κB Expression Levels as a Stress Sensor: An Experimental Study in a Wistar Rat Model

Aim and objectives: It is well known that the transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and functions as a pivotal mediator of inflammatory responses. In the present study, we evaluated the trauma generated (inflammatory reaction) after osteotomy bone surgical procedures and placement of implants in the femoral cortical bone of Wistar rats. Surgical stress was evaluated measuring the release and activation of the NF-κB factor. Materials and Methods: Rats were divided into four groups (n = 10) and submitted to different surgical treatments: Control Group (G1 group), only bone perforation was performed without irrigation; Implant Group (G2 group), a titanium implant was inserted after bone perforation without irrigation; Irrigated Group (G3 group) perforations were performed with intense irrigation; and Vitaminic Compound Group (G4 group) surgical perforation was performed without irrigation and a vitaminic compound containing the principal ions present in the natural bone structure was used to fill the bone defect. All animals were euthanized six hours after the surgical procedure and NF-κB levels were determined through immunohistochemical stain followed by direct counting of labeled and unlabeled osteocytes. Results: Among different treated groups, the overall mean of the NF-κB positive cell count in all positions were higher for G1 group (33.4 ± 2.45 cells). NF-κB values were lower in the G2 group (28.9 ± 2.70 cells), whereas in the G3 group (24.3 ± 2.72 cells) as well as in G4 group still lesser NF-κB positive cells were counted (26.5 ± 2.60 cells). Conclusions: The results here presented suggest that maneuvers performed during osteotomy procedures can significantly affect inflammation levels. The NF-κB activation during the surgical procedures can be minimized and/or controlled thought the adequate irrigation or application of adequate substances.

Hesperetin suppresses RANKL-induced osteoclastogenesis and ameliorates lipopolysaccharide-induced bone loss

Destructive bone diseases caused by osteolysis are increasing in incidence. They are characterized by an excessive imbalance of osteoclast formation and activation. During osteolysis, the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways are triggered by receptor activator of NF-κB ligand (RANKL), inflammatory factors, and oxidative stress. Previous studies have indicated that the common flavanone glycoside compound hesperetin exhibits anti-inflammatory and antioxidant activity by inhibition of NF-κB and MAPK signaling pathways. However, the direct relationship between hesperetin and osteolysis remain unclear. In the present study, we investigated the effects of hesperetin on lipopolysaccharide (LPS)-induced osteoporosis and elucidated the related mechanisms. Hesperetin effectively suppressed RANKL-induced osteoclastogenesis, osteoclastic bone resorption, and F-actin ring formation in a dose-dependent manner. It also significantly suppressed the expression of osteoclast-specific markers including tartrate-resistant acid phosphatase, matrix metalloproteinase-9, cathepsin K, c-Fos, and nuclear factor of activated T-cells cytoplasmic 1. Furthermore, it inhibited osteoclastogenesis by inhibiting activation of NF-κB and MAPK signaling, scavenging reactive oxygen species, and activating the nuclear factor E2 p45-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling pathway. Consistent with in vitro results, hesperetin effectively ameliorated LPS-induced bone loss, reduced osteoclast numbers, and decreased the RANKL/OPG ratio in vivo. As such, our results suggest that hesperetin may be a great candidate for developing a novel drug for destructive bone diseases such as periodontal disease, tumor bone metastasis, rheumatoid arthritis, and osteoporosis.

Toll-like Receptor 2-Dependent NF-κB/AP-1 Activation by Damage-Associated Molecular Patterns Adsorbed on Polymeric Surfaces

The foreign body reaction is a chronic inflammatory response to an implanted biomaterial that ultimately leads to fibrous encapsulation of the implant. It is widely accepted that the host response to implanted biomaterials is largely dependent on the species and conformations of proteins adsorbed onto the material surface due to the adsorbate's role in mediating cellular interactions with the implanted material. While the cellular response to adsorbed serum-derived proteins has been studied extensively, the presence of endogenous, matrix- and cell-derived mediators of inflammation within the adsorbed protein layer and their impact on cell-material interactions is not well-understood. Damage associated molecular patterns (DAMPs) are endogenous ligands released by stressed or damaged tissues to stimulate sterile inflammatory responses via Toll-like receptors (TLRs) and other pattern recognition receptors. The present study investigated the potential role of tissue-derived, pro-inflammatory stimuli in macrophage responses to biomaterials using cell lysate as a complex source of cell-derived DAMPs and poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS) films as model biomaterials. We show that lysate-adsorbed PMMA and PDMS surfaces strongly induced NF-κB/AP-1 transcription factor activity and pro-inflammatory cytokine secretion in the RAW-Blue macrophage cell line compared to serum-adsorbed surfaces. Lysate-dependent NF-κB/AP-1 activation and cytokine expression were strongly attenuated by TLR2 neutralizing antibodies, while TLR4 inhibition resulted in a modest reduction. These data suggest that DAMPs, in their adsorbed conformations on material surfaces, may play a significant role in macrophage activation through TLR signaling, and that TLR pathways, particularly TLR2, merit further investigation as potential therapeutic targets to modulate host responses to implanted biomaterials.

Zishenwan Decreases Kidney Damage in Recurrent Urinary Tract Infection through the Inhibition of Toll-Like Receptor 4 Signal

Objectives

To investigate the mechanism of the protective effect of Zishenwan on pyelonephritis rats.

Methods

In the rat model of pyelonephritis, protective effects of Zishenwan, the content of secretory immunoglobulin A (SIg A), and interleukins were detected by ELISA. The expressions of TLR4-NFκB pathway were detected by Western blot in renal and urinary tract mucosa. The protective effect and influence on TLR4-NFκB pathway of Zishenwan were studied.

Results

Zishenwan protected rats from pyelonephritis which related to the increase of SIgA, the regulation of interleukins, and the inhibition of TLR4-NFκB pathway. Serum containing Zishenwan can significantly decrease LPS-induced expression of TLR4, MyD88, and NFκB in vitro. And the inhibition of TLR4 signal by Zishenwan related to the degradation of TRAF3 and TRAF6.

Conclusions

Zishenwan protected rats from urinary tract infection by clearance of bacteria and decrease of tissue damage. 20S proteasomes mediated the degradation of TRAF3 which is important to the decrease of tissue damage from Zishenwan.

(2R,3R)Dihydromyricetin inhibits osteoclastogenesis and bone loss through scavenging LPS-induced oxidative stress and NF-κB and MAPKs pathways activating

Osteolysis is a serious complication of several chronic inflammatory diseases and is closely associated with a local chronic inflammatory reaction with a variety of causes. However, similarities exist in the mechanisms of their pathological processes. Inflammatory factors and oxidative stress-induced nuclear factor κB (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways play a center role in bone erosion. Dihydromyricetin (DMY) is a natural compound with anti-inflammatory and antioxidative effect, which are commonly used in chronic pharyngitis and alcohol use disorders. In the current study, we identified that DMY attenuated lipopolysaccharide (LPS)-induced oxidative stress through inhibiting the production of reactive oxygen species (ROS) and nitric oxide (NO), downregulated COX-2 and iNOS, and promoted the activity of the antioxidative system by activating superoxide dismutase (SOD) and Nrf2/HO-1 pathway. To further investigate the underlying mechanism, we found that DMY inhibits osteoclast (OC) differentiation and bone resorption activity through blocking the RANKL-induced activation of the NF-κB and MAPKs signaling pathways and then downregulated c-Fos and NFATc1, which is essential for OC differentiation. Furthermore, DMY inhibited LPS-induced osteolysis in vivo. Collectively, these results indicate that DMY might be a promising prophylactic antiosteoclastic/resorptive agent in preventing or treating bone lysis diseases.

Monoterpenes modulating cytokines - A review

Inflammatory response can be driven by cytokine production and is a pivotal target in the management of inflammatory diseases. Monoterpenes have shown that promising profile as agents which reduce the inflammatory process and also modulate the key chemical mediators of inflammation, such as pro and anti-inflammatory cytokines. The main interest focused on monoterpenes were to develop the analgesic and anti-inflammatory drugs. In this review, we summarized current knowledge on monoterpenes that produce anti-inflammatory effects by modulating the release of cytokines, as well as suggesting that which monoterpenoid molecules may be most effective in the treatment of inflammatory disease. Several different inflammatory markers were evaluated as a target of monoterpenes. The proinflammatory and anti-inflammatory cytokines were found TNF-α, IL-1β, IL-2, IL-5, IL-4, IL-6, IL-8, IL-10, IL-12 IL-13, IL-17A, IFNγ, TGF-β1 and IFN-γ. Our review found evidence that NF-κB and MAPK signaling are important pathways for the anti-inflammatory action of monoterpenes. We found 24 monoterpenes that modulate the production of cytokines, which appears to be the major pharmacological mechanism these compounds possess in relation to the attenuation of inflammatory response. Despite the compelling evidence supporting the anti-inflammatory effect of monoterpenes, further studies are necessary to fully explore their potential as anti-inflammatory compounds.

Tatarinan N inhibits osteoclast differentiation through attenuating NF-κB, MAPKs and Ca2+-dependent signaling

Osteoclasts are multinucleated cells that originate from hemopoietic stem cells. Targeting over activated osteoclasts is thought to be an effective therapeutic approach to osteoporosis. In a previous study, we reported that Tatarinan O, a lignin-like compound, suppressed RANKL-induced osteoclastogenesis. In this study, we further examined the effects on osteoclast formation of three lignin-like compounds including Tatarinan N (TN), Tatarinan U (TU) and Tatarinan V (TV), all containing a common structure of asarone. We found that only TN suppressed RANKL-induced osteoclast differentiation, bone resorption pit formation and F-acting ring formation. TU and TV did not influence RANKL-induced osteoclastogenesis. We also found that TN dose-dependently inhibited the expression of osteoclastogenesis-associated genes, including TRAP, cathepsin K and MMP-9. Furthermore, we found that TN down-regulated the key transcription factor NFATc1 and c-Fos by preventing the activation of NF-κB and phosphorylation of MAPKs including ERK1/2 and p38 but not JNK. TN attenuated calcineurin expression via suppression of the Btk-PLCγ2 cascade and reduction of intracellular Ca²⁺, modulating NFATc1 activation. Taking together, our results indicated that TN might have therapeutic potential for osteoporosis.

Endotoxin Contributes to Artificial Loosening of Prostheses Induced by Titanium Particles

Background

Aseptic loosening of orthopedic implants caused by wear particles is a major cause of joint replacement failure. However, the mechanism of aseptic loosening has not yet been defined. The present study explored whether endotoxin adherent on the titanium (Ti) particles contributes to aseptic loosening.

Material/Methods

Limulus amebocyte lysate detection was conducted to detect the levels of endotoxin adhered to the Ti particles. A mouse air pouches model was established and mice were divided into 4 groups and injected with phosphate-buffered saline (PBS) or Ti particles suspensions (0.1, 1, 10 mg/mL), following detection of the number of macrophages and the level of endotoxin. Scanning electron microscopy (SEM) was used to characterize the microstructures of Ti particles adhered with endotoxin.

Results

In vitro experiments showed that the level of endotoxin adhered to the Ti particles was significantly increased after adding LPS back to these “endotoxin-free” particles. In vivo experiments showed that Ti particles injection significantly increased the number of macrophages and the level of endotoxin.

Conclusions

In conclusion, these results suggest that adherent endotoxin may play an important role in aseptic loosening induced by Ti particles.

Interleukin-1β/nuclear factor-κB signaling promotes osteosarcoma cell growth through the microRNA-181b/phosphatase and tensin homolog axis

So far, microRNA has attracted plenty of interest due to its role in tumorigenesis. Reportedly, miR-181b may be involved in the tumorigenesis of osteosarcoma (OS). In the current study, we attempted to investigate the detailed function and mechanism of miR-181b in OS carcinogenesis. Herein, miR-181a, miR-181b, miR-181c, and miR-181d expressions in OS tissues were higher than that in nontumor tissue samples as examined real-time polymerase chain reaction. Via direct targeting, miR-181b negatively regulated the expression of phosphatase and tensin homolog (PTEN), a well-known tumor suppressor. Furthermore, a small interfering RNA strategy was used to find that interleukin (IL)-1B and nuclear factor-κB (NF-κB) regulate miR-181b and PTEN expression. Consequently, the repression of PTEN by miR-181b promotes OS cell proliferation. In summary, our data support a critical role for NF-κB-dependent upregulation of miR-181b, which further inhibited PTEN expression and promoted the cell proliferation of OS cell lines. The above findings represent a new pathway for the repression of PTEN and the promotion of cell proliferation upon IL-1β induction.

Immunobiology of periprosthetic inflammation and pain following ultra-high-molecular-weight-polyethylene wear debris in the lumbar spine

INTRODUCTION

Wear debris-induced osteolysis is a common cause of arthroplasty failure in several joints including the knee, hip and intervertebral disc. Debris from the prosthesis can trigger an inflammatory response that leads to aseptic loosening and prosthesis failure. In the spine, periprosthetic pain also occurs following accumulation of wear debris through neovascularization of the disc. The role of the immune system in the pathobiology of periprosthetic osteolysis of joint replacements is debatable. Areas covered: We discussed the stimulation of pro-inflammatory and pro-protective and pro-regenerative pathways due to debris from the prosthetics. The balance between the two pathways may determine the outcome results. Also, the role of cytokines and immune cells in periprosthetic inflammation in the etiology of osteolysis is critically reviewed. Expert commentary: Therapies targeting the inflammatory process associated with ultra-high-molecular-weight polyethylene wear debris could reduce implant failure. Additionally, therapies targeting neovascularization of discs following arthroplasty could mitigate periprosthetic pain.

NFκB sensing IL-4 secreting mesenchymal stem cells mitigate the proinflammatory response of macrophages exposed to polyethylene wear particles

Total joint replacement is a highly effective treatment for patients with end-stage arthritis. Proinflammatory macrophages (M1) mediate wear particle-associated inflammation and bone loss. Anti-inflammatory macrophages (M2) help resolve tissue damage and favor bone regeneration. Mesenchymal stem cell (MSC)-based therapy mitigates the M1 dominated inflammatory reaction and favorably modulates the bone remodeling process. In the current study, the immunomodulating ability of (1) unmodified MSCs, (2) MSCs preconditioned by NFκB stimulating ligands [lipopolysaccharide (LPS) plus TNFα], and (3) genetically modified MSCs that secrete IL-4 as a response to NFκB activation (NFκB-IL4) was compared in a macrophage/MSC co-culture system. Sterile or LPS-contaminated ultra-high molecular weight polyethylene particles were used to induce the proinflammatory responses in the macrophages. Contaminated particles induced M1 marker expression (TNFα, IL1β, and iNOS), while NFκB-IL4 MSCs modulated the macrophages from an M1 phenotype into a more favorable M2 phenotype (Arginase 1/Arg 1 and CD206 high). The IL4 secretion by NFκB-IL4 MSCs was significantly induced by the contaminated particles. The induction of Arg 1 and CD206 in macrophages via the preconditioned or naïve MSCs was negligible when compared with NFκB-IL4 MSC. Our findings indicated that NFκB-IL4 MSCs have the "on-demand" immunomodulatory ability to mitigate wear particle-associated inflammation with minimal adverse effects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2744-2752, 2018.

Tectorigenin inhibits RANKL-induced osteoclastogenesis via suppression of NF-κB signalling and decreases bone loss in ovariectomized C57BL/6

Metabolism of bone is regulated by the balance between osteoblast‐mediated bone formation and osteoclast‐mediated bone resorption. Activation of osteoclasts could lead to osteoporosis. Thus, inhibiting the activity of osteoclasts becomes an available strategy for the treatment of osteoporosis. Tectorigenin is an extract of Belamcanda chinensis In the present study, the anti‐osteoclastogenesis effects of tectorigenin were investigated in vitro and in vivo. The results showed preventive and therapeutic effects of tectorigenin at concentrations of 0, 10, 40, and 80 μmol/L in the maturation and activation of osteoclasts. A signalling study also indicated that tectorigenin treatment reduces activation of NF‐κB signalling in osteoclastogenesis. Animal experiment demonstrated that tectorigenin treatment (1‐10 mg/kg, abdominal injection every 3 days) significantly inhibits bone loss in ovariectomized C57BL/6. Our data suggest that tectorigenin is a potential pharmacological choice for osteoporosis.

Dicalcium Silicate Induced Proinflammatory Responses through TLR2-Mediated NF-κB and JNK Pathways in the Murine RAW 264.7 Macrophage Cell Line

Proinflammatory responses are important aspects of the immune response to biomaterials, which may cause peri-implantitis and implant shedding. The purpose of this study was to test the cytotoxicity and proinflammatory effects of dicalcium silicate particles on RAW 264.7 macrophages and to investigate the proinflammatory response mechanism induced by C₂S and tricalcium phosphate (TCP). C₂S and TCP particles were characterized using scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD). Cytotoxicity and apoptosis assays with C₂S and TCP in the murine RAW 264.7 cell line were tested using the cell counting kit-8 (CCK-8) assay and flow cytometry (FCM). The detection results showed that C₂S and TCP particles had no obvious toxicity in RAW 264.7 cells and did not cause obvious apoptosis, although they both caused an oxidative stress response by producing ROS when the concentrations were at 100 μg/mL. C₂S particles are likely to induce a proinflammatory response by inducing high TLR2, TNF-α mRNA, TNF-α proinflammatory cytokine, p-IκB, and p-JNK1 + JNK2 + JNK3 expression levels. When we added siRNA-TLR2-1, a significant reduction was observed. These findings support the theory that C₂S particles induce proinflammatory responses through the TLR2-mediated NF-κB and JNK pathways in the murine RAW 264.7 macrophage cell line.

In vivo analysis of the effects of CoCrMo and Ti particles on inflammatory responses and osteolysis

Metal wear particles play a major role in periprosthetic osteolysis and aseptic loosening in patients with total joint arthroplasty. The ability to induce osteolysis depends on the size, shape, dose, and type of the particles. However, much remains unknown regarding which type of metal particles are most reactive. We compared the inflammatory response and bone loss induced by two metal wear particles, cobalt-chromium-molybdenum (CoCrMo) and titanium (Ti), in a mouse calvaria model of osteolysis. We found that CoCrMo particles caused markedly greater bone resorption than Ti particles, according to three-dimensional images of the calvariae. CoCrMo particles activated more functional osteoclasts by significantly increasing the expression of the osteoclast-specific gene tartrate-specific acid phosphatase (Trap), calcitonin receptor (Ctr), and nuclear factor of activated T cells c1 (Nfatc1), and induced a greater increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG) than Ti particles. CoCrMo particles also induced a stronger local inflammatory response, markedly increasing the expression and secretion of tumor necrosis factor-α and interleukin-1β compared with Ti particles. Therefore, CoCrMo particles induced a more severe inflammatory response and greater osteolysis than Ti particles in vivo.

Orthopaedic implant materials drive M1 macrophage polarization in a spleen tyrosine kinase- and mitogen-activated protein kinase-dependent manner

Total joint replacements (TJR) are costly procedures required to relieve pain and restore function in patients suffering from end-stage arthritis. Despite great progress in the development and durability of TJRs, the generation of prosthesis-associated wear particles over time leads to an inflammatory cascade which culminates in periprosthetic osteolysis. Studies suggest that wear particles drive the polarization/differentiation of immature macrophages towards a pro-inflammatory M1 phenotype rather than an anti-inflammatory M2 phenotype associated with normal bone and wound healing. This, in turn, contributes to the initiation of peri-implant inflammation. As a result, modulating M1 macrophage cytokine production has been recognised as a viable therapeutic option. The aim of this study was to examine the impact of hydroxyapatite (HA) and poly(methyl methacrylate) (PMMA) particles on human macrophage polarization by comparing their effect on M1/M2-associated gene expression using real-time PCR. Furthermore, using immunoblotting to assess kinase activation, we sought to identify the intracellular signalling molecules activated by PMMA/HA particles and to determine whether pharmacological blockade of these molecules impacts on macrophage phenotype and cytokine production as measured by ELISA. We report that wear particles preferentially polarize macrophages towards an M1 phenotype, an effect that is dependent on activation of the membrane proximal kinase, Syk and members of the mitogen-activated protein kinase (MAPK) family of signalling molecules. Pre-treatment of macrophages with Syk inhibitors (R788/piceatannol) or MAPK inhibitors (SB203580 and PD98059), not only prevents M1 polarization, but also attenuates production of key pro-inflammatory mediators that have been specifically implicated in periprosthetic osteolysis and osteoclast differentiation.

STATEMENT OF SIGNIFICANCE

It is now well established that wear-debris particles from implanted materials drive deleterious inflammatory responses which can eventually lead to implant loosening. In this study, we provide further insight into the specific cellular pathways activated by wear particles in primary human immune cells. We demonstrate that PMMA bone cement and hydroxyapatite, a commonly used biomaterial, drive the polarization of macrophages towards an inflammatory phenotype and identify the specific signalling molecules that are activated in this process. Pre-treatment of macrophages with pharmacological inhibitors of these molecules in turn prevents macrophage polarization and dampens inflammatory cytokine production. Hence these signalling molecules represent potential therapeutic targets to treat or possibly prevent particulate induced osteolysis.

Lithium-containing biomaterials inhibit osteoclastogenesis of macrophagesin vitroand osteolysisin vivo

Li-containing bioceramics were promising biomaterials for inhibiting osteoclastogenesis of macrophages and osteolysisin vivo, potentially using for treating osteoporosis.

Paeoniflorin regulates osteoclastogenesis and osteoblastogenesis via manipulating NF-κB signaling pathway both in vitro and in vivo

The metabolic balance between synthesis and resorption of the bone is maintained by osteoblasts and osteoclasts, respectively. Identification of agents that stimulate bone formation and suppress excessive osteoclast formation, may aid in preventing and treating conditions like osteoporosis and periprosthetic loosening. Paeoniflorin is a natural product derived from Paeonia lactiflora Pall with anti-inflammatory, analgesic, and diuretic properties. However, the effect of paeoniflorin on osteoclastogenesis and osteoblastogenesis is unknown. Herein, we demonstrated that paeoniflorin has a dose-dependent suppressive action on RANKL-evoked osteoclast differentiation and bone resorption, achieved by inhibiting the NF-κB pathway and subunit p65 nuclear translocation. Simultaneously, paeoniflorin was also found to stimulate osteoblast differentiation and bone mineralization, in addition to rescuing TNFα-impaired osteoblastogenesis. At the molecular level, paeoniflorin was found to inhibit NF-κB transcriptional activity and stimulate osteoblastogenesis-related marker gene expression (ALP, osteocalcin, OPN and Runx2), a trend that was inhibited by p65 overexpression. In ovariectomized mice, paeoniflorin was found to improve osteoblast activity, inhibit osteoclast activity, and thus, reduce ovariectomy-induced osteoporosis. Our study demonstrated that paeoniflorin simultaneously suppressed osteoclastogenesis and facilitated osteoblastogenesis by manipulating the actions of NF-κB. Therefore, paeoniflorin may serve as an ideal therapeutic antidote for osteoporosis.

The cysteinyl leukotriene receptor 1 (CysLT1R) antagonist montelukast suppresses matrix metalloproteinase-13 expression induced by lipopolysaccharide

Bacterial products such as LPS are critical factors responsible for bone destruction. MMP-13, a member of the matrix metalloproteinase family, plays a critical role in the proteolytic degradation of extracellular matrix components, which includes collagen fibrils in the bone matrix. Montelukast is a selective cysteinyl leukotrienes receptor 1 (cysLT1R) antagonist used clinically for the treatment of asthma, as it reduces eosinophilic inflammation in airways. This study aims to explore the role of montelukast in regulating MMP-13 expression induced by LPS in osteoblasts. Our results indicate that LPS stimulated cysLT1R expression in mouse MC3T3-E1 osteoblasts in a dose- and time-dependent manner. Notably, LPS-induced up-regulation of MMP-13 was ameliorated by treatment with montelukast in a dose-dependent manner. Furthermore, treatment with montelukast stimulated the expression of SOCS3, an inhibitor of MMP-13. Silencing of SOCS3 abolished the inhibitory effects of montelukast on MMP-13 expression. Mechanistically, we found that montelukast suppressed LPS-induced nuclear translocation of NF-κB p65 as well as NF-κB transcriptional activity by inhibiting the phosphorylation and degradation of IκBα. These data suggest that montelukast can modulate inflammatory events in bone diseases.