Thrombin induced by the extrinsic pathway and PAR-1 regulated inflammation at the site of fracture repair

The Roles of Fibrinolytic Factors in Bone Destruction Caused by Inflammation

Chronic inflammatory diseases, such as rheumatoid arthritis, spondyloarthritis, systemic lupus erythematosus, Crohn's disease, periodontitis, and carcinoma metastasis frequently result in bone destruction. Pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and IL-17 are known to influence bone loss by promoting the differentiation and activation of osteoclasts. Fibrinolytic factors, such as plasminogen (Plg), plasmin, urokinase-type plasminogen activator (uPA), its receptor (uPAR), tissue-type plasminogen activator (tPA), α2-antiplasmin (α2AP), and plasminogen activator inhibitor-1 (PAI-1) are expressed in osteoclasts and osteoblasts and are considered essential in maintaining bone homeostasis by regulating the functions of both osteoclasts and osteoblasts. Additionally, fibrinolytic factors are associated with the regulation of inflammation and the immune system. This review explores the roles of fibrinolytic factors in bone destruction caused by inflammation.

Bioinformatics analysis identifies coagulation factor II receptor as a potential biomarker in stomach adenocarcinoma

Coagulation factor 2 thrombin receptor (F2R), a member of the G protein-coupled receptor family, plays an important role in regulating blood clotting through protein hydrolytic cleavage mediated receptor activation. However, the underlying biological mechanisms by which F2R affects the development of gastric adenocarcinoma are not fully understood. This study aimed to systematically analyze the role of F2R in gastric adenocarcinoma. Stomach adenocarcinoma (STAD)-related gene microarray data and corresponding clinicopathological information were downloaded from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Differential expression genes (DEGs) associated with F2R were analyzed using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) networks. F2R mRNA expression data were utilized to estimate stromal cell and immune cell scores in gastric cancer tissue samples, including stromal score, immune score, and ESTIMATE score, derived from single-sample enrichment studies. Analysis of TCGA and GEO databases revealed significantly higher F2R expression in STAD tissues compared to normal tissues. Patients with high F2R expression had shorter survival times than those with low F2R expression. F2R expression was significantly correlated with tumor (T) stage, node (N) stage, histological grade and pathological stage. Enrichment analysis of F2R-related genes showed that GO terms were mainly related to circulation-mediated human immune response, immunoglobulin, cell recognition and phagocytosis. KEGG analysis indicated associations to extracellular matrix (ECM) receptor interactions, neuroactive ligand-receptor interactions, the phosphoinositide-3-kinase-protein kinase B/Akt (PI3K-AKT) signaling pathway, the Wnt signaling pathway and the transforming growth factor-beta (TGF-β) signaling pathway. GSEA revealed connections to DNA replication, the Janus kinase/signal transducers and activators of transcription (JAK-STAT) signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway and oxidative phosphorylation. Drug sensitivity analysis demonstrated positive correlations between F2R and several drugs, including BEZ235, CGP-60474, Dasatinib, HG-6-64-1, Aazopanib, Rapamycin, Sunitinib and TGX221, while negative correlation with CP724714, FH535, GSK1904529A, JNK-9L, LY317615, pyrimidine, rTRAIL and Vinorelbine. Knocking down F2R in GC cell lines resulted in slowed proliferation, migration, and invasion. All statistical analyses were performed using R software (version 4.2.1) and GraphPad Prism 9.0. p < 0.05 was considered statistically significant. In conclusion, this study underscores the significance of F2R as a potential biomarker in gastric adenocarcinoma, shedding light on its molecular mechanisms in tumorigenesis. F2R holds promise for aiding in the diagnosis, prognosis, and targeted therapy of STAD.

Network analysis, in vivo, and in vitro experiments identified the mechanisms by which Piper longum L. [Piperaceae] alleviates cartilage destruction, joint inflammation, and arthritic pain

Osteoarthritis (OA) is characterized by irreversible joint destruction, pain, and dysfunction. Piper longum L. [Piperaceae] (PL) is an East Asian herbal medicine with reported anti-inflammatory, analgesic, antioxidant, anti-stress, and anti-osteoporotic effects. This study aimed to evaluate the efficacy of PL in inhibiting pain and progressive joint destruction in OA based on its anti-inflammatory activity, and to explore its potential mechanisms using in vivo and in vitro models of OA. We predicted the potential hub targets and signaling pathways of PL through network analysis and molecular docking. Network analysis results showed that the possible hub targets of PL against OA were F2R, F3, MMP1, MMP2, MMP9, and PTGS2. The molecular docking results predicted strong binding affinities for the core compounds in PL: piperlongumine, piperlonguminine, and piperine. In vitro experiments showed that PL inhibited the expression of LPS-induced pro-inflammatory factors, such as F2R, F3, IL-1β, IL-6, IL-17A, MMP-1, MMP-2, MMP-3, MMP-9, MMP-13, NOS2, PTGS2, PGE2, and TNF-β. These mechanisms and effects were dose-dependent in vivo models. Furthermore, PL inhibited cartilage degradation in an OA-induced rat model. Thus, this study demonstrated that multiple components of PL may inhibit the multilayered pathology of OA by acting on multiple targets and pathways. These findings highlight the potential of PL as a disease-modifying OA drug candidate, which warrants further investigation.

Osteogenesis in human periodontal ligament stem cell sheets is enhanced by the protease-activated receptor 1 (PAR1) in vivo

Human periodontal ligament stem cells (PDLSCs) have been studied as a promising strategy in regenerative approaches. The protease-activated receptor 1 (PAR₁) plays a key role in osteogenesis and has been shown to induce osteogenesis and increase bone formation in PDLSCs. However, little is known about its effects when activated in PDLSCs as a cell sheet construct and how it would impact bone formation as a graft in vivo. Here, PDLSCs were obtained from 3 patients. Groups were divided into control, osteogenic medium and osteogenic medium + PAR₁ activation by TFLLR-NH2 peptide. Cell phenotype was determined by flow cytometry and immunofluorescence. Calcium deposition was quantified by Alizarin Red Staining. Cell sheet microstructure was analyzed through light, scanning electron microscopy and histology and transplanted to Balb/c nude mice. Immunohistochemistry for bone sialoprotein (BSP), integrin β1 and collagen type 1 and histological stains (H&E, Van Giesson, Masson’s Trichrome and Von Kossa) were performed on the ex-vivo mineralized tissue after 60 days of implantation in vivo. Ectopic bone formation was evaluated through micro-CT. PAR₁ activation increased calcium deposition in vitro as well as BSP, collagen type 1 and integrin β1 protein expression and higher ectopic bone formation (micro-CT) in vivo.

The probable role and therapeutic potential of the PI3K/AKT signaling pathway in SARS-CoV-2 induced coagulopathy

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is associated with a high mortality rate. The majority of deaths in this disease are caused by ARDS (acute respiratory distress syndrome) followed by cytokine storm and coagulation complications. Although alterations in the level of the number of coagulation factors have been detected in samples from COVID-19 patients, the direct molecular mechanism which has been involved in this pathologic process has not been explored yet. The PI3K/AKT signaling pathway is an intracellular pathway which plays a central role in cell survival. Also, in recent years the association between this pathway and coagulopathies has been well clarified. Therefore, based on the evidence on over-activity of the PI3K/AKT signaling pathway in SARS-CoV-2 infection, in the current review, the probable role of this cellular pathway as a therapeutic target for the prevention of coagulation complications in patients with COVID-19 is discussed.

Role of tissue factor in delayed bone repair induced by diabetic state in mice

Background

Tissue factor (TF) is the primary activator of the extrinsic coagulation protease cascade. Although TF plays roles in various pathological states, such as thrombosis, inflammatory diseases, cancer, and atherosclerosis, its involvement in bone metabolism remains unknown.

Materials and methods

The present study examined the roles of TF in delayed bone repair induced by a diabetic state in mice using wild-type (WT) and low TF-expressing (LTF) male mice. A diabetic state was induced by intraperitoneal injections of streptozotocin (STZ).

Results

A prolonged diabetic state significantly reduced total and trabecular bone mineral densities (BMD) as well as cortical bone thickness in WT and LTF mice; these BMD parameters were similar between WT and LTF mice treated with or without STZ. The diabetic state induced in WT mice delayed the repair of the femur following injury. The diabetic state induced in LTF mice was associated with further delays in bone repair. In in vitro experiments, TF significantly decreased receptor activator of nuclear factor-κB ligand-induced osteoclast formation and osteoclastogenic gene expression in RAW264.7 cells. However, it did not affect the gene expression levels of runt-related transcription factor 2 and osterix as well as alkaline phosphatase activity in mouse primary osteoblasts.

Conclusion

Low TF state was associated with enhanced bone repair delay induced by diabetic state in mice. The TF-induced suppression of bone remodeling may be a contributing factor to the protective effects of TF against delayed bone repair in a diabetic state.

Protease-Activated Receptor-1 Antagonist Protects Against Lung Ischemia/Reperfusion Injury

Protease-activated receptor (PAR)-1 is a thrombin-activated receptor that plays an essential role in ischemia/reperfusion (IR)-induced acute inflammation. PAR-1 antagonists have been shown to alleviate injuries in various IR models. However, the effect of PAR-1 antagonists on IR-induced acute lung injury (ALI) has not yet been elucidated. This study aimed to investigate whether PAR-1 inhibition could attenuate lung IR injury. Lung IR was induced in an isolated perfused rat lung model. Male rats were treated with the specific PAR-1 antagonist SCH530348 (vorapaxar) or vehicle, followed by ischemia for 40 min and reperfusion for 60 min. To examine the role of PAR-1 and the mechanism of SCH530348 in lung IR injury, western blotting and immunohistochemical analysis of lung tissue were performed. In vitro, mouse lung epithelial cells (MLE-12) were treated with SCH530348 or vehicle and subjected to hypoxia-reoxygenation (HR). We found that SCH530348 decreased lung edema and neutrophil infiltration, attenuated thrombin production, reduced inflammatory factors, including cytokine-induced neutrophil chemoattractant-1, interleukin-6 and tumor necrosis factor-α, mitigated lung cell apoptosis, and downregulated the phosphoinositide 3-kinase (PI3K), nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways in IR-injured lungs. In addition, SCH530348 prevented HR-induced NF-κB activation and inflammatory chemokine production in MLE12 cells. Our results demonstrate that SCH530348 exerts protective effects by blocking PAR-1 expression and modulating the downstream PI3K, NF-κB and MAPK pathways. These findings indicate that the PAR-1 antagonist protects against IR-induced ALI and is a potential therapeutic candidate for lung protection following IR injury.

Exogenous parathyroid hormone attenuates ovariectomy-induced skeletal muscle weakness in vivo

Osteoporosis commonly affects the elderly and is associated with significant morbidity and mortality. Loss of bone mineral density induces muscle atrophy and increases fracture risk. However, muscle lipid content and droplet size are increased by aging and mobility impairments, inversely correlated with muscle function, and a cause of reduced motor function. Teriparatide, the synthetic form of human parathyroid hormone (PTH) 1-34, has been widely used to treat osteoporosis. Although PTH positively affects muscle differentiation in vitro, the precise function and mechanisms of muscle mass and power preservation are still poorly understood, especially in vivo. In this study, we investigated the effect of PTH on skeletal muscle atrophy and dysfunction using an ovariectomized murine model. Eight-week-old female C57BL/6J mice were ovariectomized or sham-operated. Within each surgical group, the mice were divided into PTH injection or control subgroups. Motor function was evaluated based on grip strength, treadmill running, and lactic acid concentration. PTH receptor was expressed in skeletal muscle cells and myoblasts. PTH inhibited ovariectomy-induced bone loss but not uterine atrophy or increased body weight; PTH not only abolished ovariectomy-induced reduction in grip strength and maximum running speed, but also significantly reduced the ovariectomy-induced increase in lactic acid concentration (compared with that observed in the vehicle control). PTH also abrogated the ovariectomy-induced reduction in the oxidative capacity of muscle fibers, their cross-sectional area, and intramyocellular lipid content, and induced cell proliferation, cell migration, and muscle differentiation, while reducing lipid secretion by C2C12 myoblasts via the Wnt/β-catenin pathway. PTH significantly ameliorated muscle weakness and attenuated exercise-induced lactate levels in ovariectomized mice. Our in vitro study demonstrated that PTH/Wnt signaling regulated the proliferation, migration, and differentiation of myoblasts and also reduced lipid secretion in myoblasts. Thus, PTH could regulate several aspects of muscle function and physiology, and may represent a novel therapeutic strategy for patients with osteoporosis.

Combined Anticancer Effect of Plasma-Activated Infusion and Salinomycin by Targeting Autophagy and Mitochondrial Morphology

Non-thermal atmospheric pressure plasma (NTAPP)-activated liquids have emerged as new promising anticancer agents because they preferentially injure malignant cells. Here, we report plasma-activated infusion (PAI) as a novel NTAPP-based anti-neoplastic agent. PAI was prepared by irradiating helium NTAP to form a clinically approved infusion fluid. PAI dose-dependently killed malignant melanoma and osteosarcoma cell lines while showing much lower cytotoxic effects on dermal and lung fibroblasts. We found that PAI and salinomycin (Sal), an emerging anticancer stem cell agent, mutually operated as adjuvants. The combined administration of PAI and Sal was much more effective than single-agent application in reducing the growth and lung metastasis of osteosarcoma allografts with minimal adverse effects. Mechanistically, PAI explicitly induced necroptosis and increased the phosphorylation of receptor-interacting protein 1/3 rapidly and transiently. PAI also suppressed the ambient autophagic flux by activating the mammalian target of the rapamycin pathway. PAI increased the phosphorylation of Raptor, Rictor, and p70-S6 kinase, along with decreased LC3-I/II expression. In contrast, Sal promoted autophagy. Moreover, Sal exacerbated the mitochondrial network collapse caused by PAI, resulting in aberrant clustering of fragmented mitochondrial in a tumor-specific manner. Our findings suggest that combined administration of PAI and Sal is a promising approach for treating these apoptosis-resistant cancers.

Network Pharmacology-Based Prediction of Catalpol and Mechanisms against Stroke

Aim

To apply the network pharmacology method to screen the target of catalpol prevention and treatment of stroke, and explore the pharmacological mechanism of Catalpol prevention and treatment of stroke.

Methods

PharmMapper, GeneCards, DAVID, and other databases were used to find key targets. We selected hub protein and catalpol which were screened for molecular docking verification. Based on the results of molecular docking, the ITC was used to determine the binding coefficient between the highest scoring protein and catalpol. The GEO database and ROC curve were used to evaluate the correlation between key targets.

Results

27 key targets were obtained by mapping the predicted catalpol-related targets to the disease. Hub genes (ALB, CASP3, MAPK1 (14), MMP9, ACE, KDR, etc.) were obtained in the key target PPI network. The results of KEGG enrichment analysis showed that its signal pathway was involved in angiogenic remodeling such as VEGF, neurotrophic factors, and inflammation. The results of molecular docking showed that ACE had the highest docking score. Therefore, the ITC was used for the titration of ACE and catalpol. The results showed that catalpol had a strong binding force with ACE.

Conclusion

Network pharmacology combined with molecular docking predicts key genes, proteins, and signaling pathways for catalpol in treating stroke. The strong binding force between catalpol and ACE was obtained by using ITC, and the results of molecular docking were verified to lay the foundation for further research on the effect of catalpol on ACE. ROC results showed that the AUC values of the key targets are all >0.5. This article uses network pharmacology to provide a reference for a more in-depth study of catalpol's mechanism and experimental design.

Mechanisms of Bone Remodeling Disorder in Hemophilia

Hemophilia is caused by a lack of antihemophilic factor(s), for example, factor VIII (FVIII; hemophilia A) and factor IX (FIX; hemophilia B). Low bone mass is widely reported in epidemiological studies of hemophilia, and patients with hemophilia are at an increased risk of fracture. The detailed etiology of bone homeostasis imbalance in hemophilia is unclear. Clinical and experimental studies show that FVIII and FIX are involved in bone remodeling. However, it is likely that antihemophilic factors affect bone biology through thrombin pathways rather than via their own intrinsic properties. In addition, among patients with hemophilia, there are pathophysiological processes in several systems that might contribute to bone loss. This review summarizes studies on the association between hemophilia and bone remodeling, and might shed light on the challenges facing the care and prevention of osteoporosis and fracture in patients with hemophilia.

Gemcitabine and Rapamycin Exhibit Additive Effect against Osteosarcoma by Targeting Autophagy and Apoptosis

The overall prognosis for sarcoma-based cancer patients has remained largely unchanged over the past 10 years. Because there is no effective anticancer drug for patients with chemoresistant osteosarcoma (OS), novel approaches are needed to improve the prognosis. Here, we investigated whether rapamycin (Rapa) could enhance the anti-tumor effects of gemcitabine (Gem) in OS. Gem dose-dependently killed the OS cells, but exhibited much lower cytotoxicity on osteoblasts. Treatment with a combination Gem and Rapa was much more effective than that of either single agent with respect to reducing cell viability, cell invasion, cell migration, and vascular endothelial growth factor production in vitro. Moreover, the combination of these agents suppressed tumor growth, angiogenesis, and lung metastasis in allograft and xenograft murine models of OS with minimal adverse effects. Overall, the combination therapy prolonged the overall survival of tumor-bearing mice. Mechanistically, Gem induced apoptosis and increased the levels of cleaved caspases, while Rapa induced autophagy and microtubule-associated protein light chain 3 (LC3)-I/LC3-II expression both in vitro and in vivo. Our findings suggest that chemotherapy using Gem combined with Rapa may be a novel and promising therapeutic approach for the treatment of OS.

Coagulation factor 2 thrombin receptor promotes malignancy in glioma under SOX2 regulation

Glioma is the most common human primary brain cancer with high mortality and unfavorable clinical outcome. Coagulation factor 2 thrombin receptor (F2R), is a key component in the thrombosis process and has been demonstrated upregulated in various cancers. However, the effect and molecular mechanisms of F2R in glioma remains unclear. In our study, we confirmed that the expression of F2R was upregulated in glioma and predicted poor prognosis. Gene Set Enrichment Analysis (GSEA) and function assays demonstrated that F2R overexpression promoted glioma cell proliferation, metastasis and epithelial-mesenchymal transition (EMT) in vitro and tumor growth in vivo. Then, we identified and validated F2R was the target gene of SRY-box 2 (SOX2) by dual luciferase reporter assay and chromatin immunoprecipitation assay. Besides, High expression of F2R in malignant glioma was associated with β-catenint signaling pathway activation. Our findings conclude that F2R promotes glioma cell proliferation and metastasis under SOX2 and actives WNT/β-catenin Signaling pathway, which provides novel insight to the therapeutic regimen in glioma.

Analyzing Genome-Wide Association Study Dataset Highlights Immune Pathways in Lip Bone Mineral Density

Osteoporosis is a common complex human disease. Until now, large-scale genome-wide association studies (GWAS) using single genetic variant have reported some novel osteoporosis susceptibility variants. However, these risk variants only explain a small proportion of osteoporosis genetic risk, and most genetic risk is largely unknown. Interestingly, the pathway analysis method has been used in investigation of osteoporosis mechanisms and reported some novel pathways. Until now, it remains unclear whether there are other risk pathways involved in BMD. Here, we selected a lip BMD GWAS with 301,019 SNPs in 5,858 Europeans, and conducted a gene-based analysis (SET SCREEN TEST) and a pathway-based analysis (WebGestalt). On the gene level, BMD susceptibility genes reported by previous GWAS were identified to be the top 10 significant signals. On the pathway level, we identified 27 significant KEGG pathways. Three immune pathways including T cell receptor signaling pathway (hsa04660), complement and coagulation cascades (hsa04610), and intestinal immune network for IgA production (hsa04672) are ranked the top three significant signals. Evidence from the PubMed and Google Scholar databases further supports our findings. In summary, our findings provide complementary information to these nine risk pathways.

Regenerative Effect of Platelet Concentrates in Oral and Craniofacial Regeneration

Platelet concentrates (PCs) are biological autologous products derived from the patient's whole blood and consist mainly of supraphysiologic concentration of platelets and growth factors (GFs). These GFs have anti-inflammatory and healing enhancing properties. Overall, PCs seem to enhance bone and soft tissue healing in alveolar ridge augmentation, periodontal surgery, socket preservation, implant surgery, endodontic regeneration, sinus augmentation, bisphosphonate related osteonecrosis of the jaw (BRONJ), osteoradionecrosis, closure of oroantral communication (OAC), and oral ulcers. On the other hand, no effect was reported for gingival recession and guided tissue regeneration (GTR) procedures. Also, PCs could reduce pain and inflammatory complications in temporomandibular disorders (TMDs), oral ulcers, and extraction sockets. However, these effects have been clinically inconsistent across the literature. Differences in study designs and types of PCs used with variable concentration of platelets, GFs, and leucocytes, as well as different application forms and techniques could explain these contradictory results. This study aims to review the clinical applications of PCs in oral and craniofacial tissue regeneration and the role of their molecular components in tissue healing.

Protease-Activated Receptor Type 1 Activation Enhances Osteogenic Activity in Human Periodontal Ligament Stem Cells

Protease-activated receptor 1 (PAR₁) has been associated to tissue repair and bone healing. The aim of the present study was to evaluate the effect of PAR₁ activation on the osteogenic activity of human periodontal ligament stem cells (PDLSCs). PDLSCs were cultured in the presence of PAR₁-selective agonist peptide (100 nM), thrombin (0.1 U/mL), or PAR₁ antagonist peptide (100 nM). Calcium deposits, calcium concentration (supernatant), alkaline phosphatase activity (ALP), cell proliferation, and gene (qPCR) and protein expression (ELISA assay) of osteogenic factors were assessed at 2, 7, and 14 days. PAR₁ activation led to increased calcium deposits (p < 0.05), calcium concentration (p < 0.05), ALP activity (p < 0.05), and cell proliferation (p < 0.05). Further, PAR₁ activation may increase gene and protein expression of Runx2 (p < 0.05) and OPG (p < 0.05). In conclusion, PAR₁ activation increases osteogenic activity of PDLSCs, providing a possible new strategy for periodontal regenerative therapies.

Protease-Activated Receptor 1 Deletion Causes Enhanced Osteoclastogenesis in Response to Inflammatory Signals through a Notch2-Dependent Mechanism

We found that protease-activated receptor 1 (PAR1) was transiently induced in cultured osteoclast precursor cells. Therefore, we examined the bone phenotype and response to resorptive stimuli of PAR1-deficient (knockout [KO]) mice. Bones and bone marrow-derived cells from PAR1 KO and wild-type (WT) mice were assessed using microcomputed tomography, histomorphometry, in vitro cultures, and RT-PCR. Osteoclastic responses to TNF-α (TNF) challenge in calvaria were analyzed with and without a specific neutralizing Ab to the Notch2-negative regulatory region (N2-NRR Ab). In vivo under homeostatic conditions, there were minimal differences in bone mass or bone cells between PAR1 KO and WT mice. However, PAR1 KO myeloid cells demonstrated enhanced osteoclastogenesis in response to receptor activator of NF-κB ligand (RANKL) or the combination of RANKL and TNF. Strikingly, in vivo osteoclastogenic responses of PAR1 KO mice to TNF were markedly enhanced. We found that N2-NRR Ab reduced TNF-induced osteoclastogenesis in PAR1 KO mice to WT levels without affecting WT responses. Similarly, in vitro N2-NRR Ab reduced RANKL-induced osteoclastogenesis in PAR1 KO cells to WT levels without altering WT responses. We conclude that PAR1 functions to limit Notch2 signaling in responses to RANKL and TNF and moderates osteoclastogenic response to these cytokines. This effect appears, at least in part, to be cell autonomous because enhanced osteoclastogenesis was seen in highly purified PAR1 KO osteoclast precursor cells. It is likely that this pathway is involved in regulating the response of bone to diseases associated with inflammatory signals.

Platelet-Derived TGF-β Induces Tissue Factor Expression via the Smad3 Pathway in Osteosarcoma Cells

Over the last three decades, the prognosis of osteosarcoma has remained unchanged; the prognosis for patients with lung metastasis is still poor, and the development of new treatments is urgently required. We previously showed that aggressive osteosarcoma cells express more tissue factor (TF) and demonstrate enhanced extrinsic pathway capacity. Furthermore, tumor growth can be suppressed with the anticoagulant low molecular weight heparin. However, the molecular mechanisms underlying TF regulation are still unclear. Here, we report that transforming growth factor-β (TGF-β) upregulates TF, which can occur via activated platelets. TF was found to be expressed on osteosarcoma cell surfaces, which mediated the production of Xa and thrombin. TF induction by TGF-β was observed in several osteosarcoma cells, and especially in MG 63 cells. Both TF expression by TGF-β and extrinsic pathway activity through TF were rapidly increased. This reaction was inhibited by a TGF-β type I receptor inhibitor and TGF-β neutralizing antibody. Although TGF-β was found to phosphorylate both Smad2 and Smad3, their roles were markedly disparate. Surprisingly, Smad2 knockdown resulted in no inhibitory effect, whereas Smad3 knockdown completely suppressed TGF-β-induced TF expression. Next, data suggested that platelets were the source of TGF-β. We confirmed that thrombin-activated platelets and osteosarcoma cells could release TGF-β, and that platelet-derived TGF-β could induce TF expression. These processes were also inhibited by a TGF-β type I receptor inhibitor and Smad3 knockdown. Moreover, CD42b, TF, TGF-β, Smad2/3, and p-Smad2/3 were also detected in a biopsy sample from an osteosarcoma patient. Collectively, these finding suggested that the interaction between osteosarcoma cells and platelets, via thrombin and TGF-β, results in a continuous cycle, and that anti-platelet or anti-TGF-β therapy could be a promising tool for disease treatment. © 2018 American Society for Bone and Mineral Research.

Effect of Thrombin-Induced MCP-1 and MMP-3 Production Via PAR1 Expression in Murine Intervertebral Discs

Structural changes in nucleus pulposus cells induce intervertebral disc (IVD) degeneration as a consequence of cytokine generation, biochemical products, and changes in the local environment. We have previously shown that inflammatory cytokines induce murine IVD (mIVD) angiogenesis and macrophage migration. Although the physiological roles of thrombin, a known proinflammatory factor, are documented, its relationship to IVD degeneration remains largely unexplored. Thrombin mediates cellular responses via the activation of protease-activated receptors such as PAR1 which has been studied in numerous cell types, but not extensively in IVD cells. This study was designed to investigate the endogenous expression of thrombin, tissue factor, and PAR1 in cultured coccygeal mIVDs. Thrombin exclusively induced MCP-1 via the MAPK-ERK and PI3K-AKT pathways. MCP-1 produced by mIVDs induced macrophage migration and thrombin treatment increased MMP-3 production to induce mIVD degeneration. These effects of thrombin on mIVDs were abrogated by a PAR1 inhibitor and suggest that thrombin may be a novel factor capable of stimulating cytokine activity implicated in the regulation several aspects of mIVDs. Mechanisms governing mIVDs, which are regulated by thrombin/PAR1 signaling, require elucidation if our understanding of IVD degenerative mechanisms is to advance.

Mast cells are critical for the limitation of thrombin-induced skin inflammation

Thrombin, a key player in coagulation, is widely held to induce and promote inflammation. As of now, the features, kinetics and control of thrombin's proinflammatory effects on the skin remain to be characterized in detail. We, therefore, injected thrombin into the ear skin of mice and observed strong, dose-dependent and transient ear swelling responses as well as mast cell (MC) degranulation. Unexpectedly, thrombin induced even stronger, not reduced, ear swelling in MC-deficient Kit^W-sh/W-sh mice. Prior local reconstitution of Kit^W-sh/W-sh mice with MCs inhibited this effect, indicating that MCs may contribute to the control of thrombin-induced skin inflammation. In line with previous studies, we found that MCs express the thrombin receptors PAR1, PAR3 and PAR4, thrombin induces direct and dose-dependent MC degranulation, and that degranulated MCs inactivate thrombin. Further findings suggested that MC-mediated protection from thrombin-induced inflammation is likely to rely on the effects of MC proteases. We show for the first time that MC-deficient mice and MC protease 4-deficient mice with normal numbers of MCs show markedly increased ear swelling in response to thrombin as compared to wild-type mice. Taken together, these results suggest that thrombin-induced skin inflammation is controlled, in part, by MC protease 4 released from activated MCs. For MC-driven diseases such as chronic spontaneous urticaria, which has been linked to increased thrombin generation, this might mean that MCs may contribute to the resolution of skin inflammatory responses.

TGF-β induced PAR-1 expression promotes tumor progression and osteoclast differentiation in giant cell tumor of bone

Although protease activated receptor-1 (PAR-1) has been confirmed as an oncogene in many cancers, the role of PAR-1 in giant cell tumor (GCT) of bone has been rarely reported. The mechanism of PAR-1 in tumor-induced osteoclastogenesis still remains unclear. In the present study, we detected that PAR-1 was significantly upregulated in GCT of bone compared to normal tissues, while TGF-β was also overexpressed in GCT tissues and could promote the expression of PAR-1 in a dose and time dependent manner. Using the luciferase reporter assay, we found that two downstreams of TGF-β, Smad3 and Smad4, could activate the promoter of PAR-1, which might explain the mechanism of TGF-β induced PAR-1 expression. Meanwhile, PAR-1 was also overexpressed in microvesicles from stromal cells of GCT (GCTSCs), and might be transported from GCTSCs to monocytes through microvesicles. In addition, knockout of PAR-1 by TALENs in GCTSCs inhibited tumor growth, angiogenesis and osteoclastogenesis in GCT in vitro. Using the chick CAM models, we further showed that inhibition of PAR-1 suppressed tumor growth and giant cell formation in vivo. Using microarray assay, we detected a number of genes involved in osteoclastogenesis as the possible downstreams of PAR-1, which may partly explain the mechanism of PAR-1 in GCT. In brief, for the first time, these results reveal an upstream regulatory role of TGF-β in PAR-1 expression, and PAR-1 expression promotes tumor growth, angiogenesis and osteoclast differentiation in GCT of bone. Hence, PAR-1 represents a novel potential therapeutic target for GCT of bone.