Stattic inhibits RANKL-mediated osteoclastogenesis by suppressing activation of STAT3 and NF-κB pathways

Intratumoral injection of mRNA encoding survivin in combination with STAT3 inhibitor stattic enhances antitumor effects

Intratumoral delivery of mRNA encoding immunostimulatory molecules can initiate a robust, global antitumor response with little side effects by enhancing local antigen presentation in the tumor and the tumor draining lymph node. Neoantigen-based mRNA nanovaccine can inhibit melanoma growth in mice by intratumoral injection. Myeloid-derived suppressor cells (MDSCs) suppress antitumor immune responses by secreting immunosuppressive agents, such as reactive oxygen species (ROS). Suppression of STAT3 activity by stattic may reduce MDSC-mediated immunosuppression in the TME and promote the antitumor immune responses. In this study, in vitro transcribed mRNA encoding tumor antigen survivin was prepared and injected intratumorally in BALB/c mice bearing subcutaneous colon cancer tumors. In vivo studies demonstrated that intratumoral survivin mRNA therapy could induce antitumor T cell response and inhibit tumor growth of colon cancer. Depletion of CD8+ T cells could significantly inhibit survivin mRNA-induced antitumor effects. RT-qPCR and ELISA analysis indicated that survivin mRNA treatment led to increased expression of receptor activator nuclear factor-κB ligand (RANKL). In vitro experiment showed that MDSCs could be induced from mouse bone marrow cells by RANKL and RANKL-induced MDSCs could produce high level of ROS. STAT3 inhibitor stattic suppressed activation of STAT3 and NF-κB signals, thereby inhibiting expansion of RANKL-induced MDSCs. Combination therapy of survivin mRNA and stattic could significantly enhance antitumor T cell response, improve long-term survival and reduce immunosuppressive tumor microenvironment compared to each monotherapy. In addition, combined therapy resulted in a significantly reduced level of tumor cell proliferation and an obviously increased level of tumor cell apoptosis in CT26 colon cancer-bearing mice, which could be conducive to inhibit the tumor growth and lead to immune responses to released tumor-associated antigens. These studies explored intratumoral mRNA therapy and mRNA-based combined therapy to treat colon cancer and provide a new idea for cancer therapy.

Regulation of bone homeostasis: signaling pathways and therapeutic targets

As a highly dynamic tissue, bone is continuously rebuilt throughout life. Both bone formation by osteoblasts and bone resorption by osteoclasts constitute bone reconstruction homeostasis. The equilibrium of bone homeostasis is governed by many complicated signaling pathways that weave together to form an intricate network. These pathways coordinate the meticulous processes of bone formation and resorption, ensuring the structural integrity and dynamic vitality of the skeletal system. Dysregulation of the bone homeostatic regulatory signaling network contributes to the development and progression of many skeletal diseases. Significantly, imbalanced bone homeostasis further disrupts the signaling network and triggers a cascade reaction that exacerbates disease progression and engenders a deleterious cycle. Here, we summarize the influence of signaling pathways on bone homeostasis, elucidating the interplay and crosstalk among them. Additionally, we review the mechanisms underpinning bone homeostatic imbalances across diverse disease landscapes, highlighting current and prospective therapeutic targets and clinical drugs. We hope that this review will contribute to a holistic understanding of the signaling pathways and molecular mechanisms sustaining bone homeostasis, which are promising to contribute to further research on bone homeostasis and shed light on the development of targeted drugs.

PSTPIP2 protects against alcoholic liver injury and invokes STAT3-mediated suppression of apoptosis

Alcoholic liver injury (ALI) stands as a prevalent affliction within the spectrum of complex liver diseases. Prolonged and excessive alcohol consumption can pave the way for liver fibrosis, cirrhosis, and even hepatocellular carcinoma. Recent findings have unveiled the protective role of proline serine-threonine phosphatase interacting protein 2 (PSTPIP2) in combating liver ailments. However, the role of PSTPIP2 in ALI remains mostly unknown. This study aimed to determine the expression profile of PSTPIP2 in ALI and to uncover the mechanism through which PSTPIP2 affects the survival and apoptosis of hepatocytes in ALI, using both ethyl alcohol (EtOH)-fed mice and an EtOH-induced AML-12 cell model. We observed a consistent decrease in PSTPIP2 expression both in vivo and in vitro. Functionally, we assessed the impact of PSTPIP2 overexpression on ALI by administering adeno-associated virus 9 (AAV9)-PSTPIP2 into mice. The results demonstrated that augmenting PSTPIP2 expression significantly shielded against liver parenchymal distortion and curbed caspase-dependent hepatocyte apoptosis in EtOH-induced ALI mice. Furthermore, enforcing PSTPIP2 expression reduced hepatocyte apoptosis in a stable PSTPIP2-overexpressing AML-12 cell line established through lentivirus-PSTPIP2 transfection in vitro. Mechanistically, this study also identified signal transducer and activator of transcription 3 (STAT3) as a direct signaling pathway regulated by PSTPIP2 in ALI. In conclusion, our findings provide compelling evidence that PSTPIP2 has a regulatory role in hepatocyte apoptosis via the STAT3 pathway in ALI, suggesting PSTPIP2 as a promising therapeutic target for ALI.

Targeting STAT3 potentiates CDK4/6 inhibitors therapy in head and neck squamous cell carcinoma

Anti-CDK4/6 therapy has been employed for the treatment for head and neck squamous cell carcinoma (HNSCC) with CDK4/6 hyperactivation, but the response rate is relatively low. In this study, we first showed that CDK4 and CDK6 was over-expressed and conferred poor prognosis in HNSCC. Moreover, in RB-positive HNSCC, STAT3 signaling was activated induced by CDK4/6 inhibition and STAT3 promotes RB deficiency by upregulation of MYC. Thirdly, the combination of Stattic and CDK4/6 inhibitor results in striking anti-tumor effect in vitro and in Cal27 derived animal models. Additionally, phospho-STAT3 level negatively correlates with RB expression and predicts poor prognosis in patients with HNSCC. Taken together, our findings suggest an unrecognized function of STAT3 confers to CDK4/6 inhibitors resistance and presenting a promising combination strategy for patients with HNSCC.

A Multifunctional Therapeutic Strategy Using P7C3 as A Countermeasure Against Bone Loss and Fragility in An Ovariectomized Rat Model of Postmenopausal Osteoporosis

By 2060, an estimated one in four Americans will be elderly. Consequently, the prevalence of osteoporosis and fragility fractures will also increase. Presently, no available intervention definitively prevents or manages osteoporosis. This study explores whether Pool 7 Compound 3 (P7C3) reduces progressive bone loss and fragility following the onset of ovariectomy (OVX)-induced osteoporosis. Results confirm OVX-induced weakened, osteoporotic bone together with a significant gain in adipogenic body weight. Treatment with P7C3 significantly reduced osteoclastic activity, bone marrow adiposity, whole-body weight gain, and preserved bone area, architecture, and mechanical strength. Analyses reveal significantly upregulated platelet derived growth factor-BB and leukemia inhibitory factor, with downregulation of interleukin-1 R6, and receptor activator of nuclear factor kappa-B (RANK). Together, proteomic data suggest the targeting of several key regulators of inflammation, bone, and adipose turnover, via transforming growth factor-beta/SMAD, and Wingless-related integration site/be-catenin signaling pathways. To the best of the knowledge, this is first evidence of an intervention that drives against bone loss via RANK. Metatranscriptomic analyses of the gut microbiota show P7C3 increased Porphyromonadaceae bacterium, Candidatus Melainabacteria, and Ruminococcaceae bacterium abundance, potentially contributing to the favorable inflammatory, and adipo-osteogenic metabolic regulation observed. The results reveal an undiscovered, and multifunctional therapeutic strategy to prevent the pathological progression of OVX-induced bone loss.

Interplay between mesenchymal stem cells and macrophages: Promoting bone tissue repair

The repair of bone tissue damage is a complex process that is well-orchestrated in time and space, a focus and difficulty in orthopedic treatment. In recent years, the success of mesenchymal stem cells (MSCs)-mediated bone repair in clinical trials of large-area bone defects and bone necrosis has made it a candidate in bone tissue repair engineering and regenerative medicine. MSCs are closely related to macrophages. On one hand, MSCs regulate the immune regulatory function by influencing macrophages proliferation, infiltration, and phenotype polarization, while also affecting the osteoclasts differentiation of macrophages. On the other hand, macrophages activate MSCs and mediate the multilineage differentiation of MSCs by regulating the immune microenvironment. The cross-talk between MSCs and macrophages plays a crucial role in regulating the immune system and in promoting tissue regeneration. Making full use of the relationship between MSCs and macrophages will enhance the efficacy of MSCs therapy in bone tissue repair, and will also provide a reference for further application of MSCs in other diseases.

RANK/RANKL axis promotes migration, invasion, and metastasis of osteosarcoma via activating NF-κB pathway

Osteosarcoma (OS) is one of the most prevalent primary bone tumors with a high degree of metastasis and poor prognosis. Epithelial-to-mesenchymal transition (EMT) is a cellular mechanism that contributes to the invasion and metastasis of cancer cells, and OS cells have been reported to exhibit EMT-like characteristics. Our previous studies have shown that the interaction between tumor necrosis factor superfamily member 11 (TNFRSF11A; also known as RANK) and its ligand TNFSF11 (also known as RANKL) promotes the EMT process in breast cancer cells. However, whether the interaction between RANK and RANKL enhances aggressive behavior by inducing EMT in OS cells has not yet been elucidated. In this study, we showed that the interaction between RANK and RANKL increased the migration, invasion, and metastasis of OS cells by promoting EMT. Importantly, we clarified that the RANK/RANKL axis induces EMT by activating the nuclear factor-kappa B (NF-κB) pathway. Furthermore, the NF-κB inhibitor dimethyl fumarate (DMF) suppressed migration, invasion, and EMT in OS cells. Our results suggest that the RANK/RANKL axis may serve as a potential tumor marker and promising therapeutic target for OS metastasis. Furthermore, DMF may have clinical applications in the treatment of lung metastasis in patients with OS.

CD274 (PD-L1) negatively regulates M1 macrophage polarization in ALI/ARDS

Background

Acute lung injury (ALI)/severe acute respiratory distress syndrome (ARDS) is a serious clinical syndrome characterized by a high mortality rate. The pathophysiological mechanisms underlying ALI/ARDS remain incompletely understood. Considering the crucial role of immune infiltration and macrophage polarization in the pathogenesis of ALI/ARDS, this study aims to identify key genes associated with both ALI/ARDS and M1 macrophage polarization, employing a combination of bioinformatics and experimental approaches. The findings could potentially reveal novel biomarkers for the diagnosis and management of ALI/ARDS.

Methods

Gene expression profiles relevant to ALI were retrieved from the GEO database to identify co-upregulated differentially expressed genes (DEGs). GO and KEGG analyses facilitated functional annotation and pathway elucidation. PPI networks were constructed to identify hub genes, and differences in immune cell infiltration were subsequently examined. The expression of hub genes in M1 versus M2 macrophages was evaluated using macrophage polarization datasets. The diagnostic utility of CD274 (PD-L1) for ARDS was assessed by receiver operating characteristic (ROC) analysis in a validation dataset. Experimental confirmation was conducted using two LPS-induced M1 macrophage models and an ALI mouse model. The role of CD274 (PD-L1) in M1 macrophage polarization and associated proinflammatory cytokine production was further investigated by siRNA-mediated silencing.

Results

A total of 99 co-upregulated DEGs were identified in two ALI-linked datasets. Enrichment analysis revealed that these DEGs were mainly involved in immune-inflammatory pathways. The following top 10 hub genes were identified from the PPI network: IL-6, IL-1β, CXCL10, CD274, CCL2, TLR2, CXCL1, CCL3, IFIT1, and IFIT3. Immune infiltration analysis revealed a significantly increased abundance of M1 and M2 macrophages in lung tissue from the ALI group compared to the control group. Subsequent analysis confirmed that CD274 (PD-L1), a key immunological checkpoint molecule, was highly expressed within M1 macrophages. ROC analysis validated CD274 (PD-L1) as a promising biomarker for the diagnosis of ARDS. Both in vitro and in vivo experiments supported the bioinformatics analysis and confirmed that the JAK-STAT3 pathway promotes CD274 (PD-L1) expression on M1 macrophages. Importantly, knockdown of CD274 (PD-L1) expression potentiated M1 macrophage polarization and enhanced proinflammatory cytokines production.

Conclusion

This study demonstrates a significant correlation between CD274 (PD-L1) and M1 macrophages in ALI/ARDS. CD274 (PD-L1) functions as a negative regulator of M1 polarization and the secretion of proinflammatory cytokines in macrophages. These findings suggest potential new targets for the diagnosis and treatment of ALI/ARDS.

Janus Kinase Inhibitor Brepocitinib Rescues Myelin Phagocytosis Under Inflammatory Conditions: In Vitro Evidence from Microglia and Macrophage Cell Lines

Central nervous system (CNS) injuries induce cell death and consequently the release of myelin and other cellular debris. Microglia as well as hematogenous macrophages actively collaborate to phagocyte them and undergo their degradation. However, myelin accumulation persists in the lesion site long after the injury with detrimental effects on axonal regeneration. This might be due to the presence of inhibitors of phagocytosis in the injury site. As we recently published that some proinflammatory stimuli, like interferon-γ (IFNγ) and lipopolysaccharide (LPS), inhibit myelin phagocytosis in macrophages, we have now studied the signaling pathways involved. A phagocytosis assay in Raw264.7 macrophages and N13 microglia cell lines with labeled myelin was developed with the pHrodo reagent that emits fluorescence in acidic cellular compartments (e.g.lysosomes). Pharmacological inhibition of Janus kinases (Jak) with Brepocitinib restored myelin phagocytosis and rescued the expression of genes related to phagocytosis, like triggering receptor expressed on myeloid cells 2 (TREM2), induced by IFNγ or LPS. In addition, while pharmacological inhibition of the signal transducer and activator of transcription 3 (STAT3) rescued myelin phagocytosis and the expression of phagocytosis related genes in the presence of LPS, it did not have any effect on IFNγ-treated cells. Our results show that Jak pathways participate in the inhibition of myelin phagocytosis by IFNγ and LPS. They also indicate that the resolution of inflammation is important for the clearance of cellular debris by macrophages and subsequent regenerative processes.

Updates on ankylosing spondylitis: pathogenesis and therapeutic agents

Ankylosing spondylitis (AS) is an autoinflammatory disease that manifests with the unique feature of enthesitis. Gut microbiota, HLA-B*27, and biomechanical stress mutually influence and interact resulting in setting off a flame of inflammation. In the HLA-B*27 positive group, dysbiosis in the gut environment disrupts the barrier to exogenous bacteria or viruses. Additionally, biomechanical stress induces inflammation through enthesial resident or gut-origin immune cells. On this basis, innate and adaptive immunity can propagate inflammation and lead to chronic disease. Finally, bone homeostasis is regulated by cytokines, by which the inflamed region is substituted into new bone. Agents that block cytokines are constantly being developed to provide diverse therapeutic options for preventing the progression of inflammation. In addition, some antibodies have been shown to distinguish disease selectively, which support the involvement of autoimmune immunity in AS. In this review, we critically analyze the complexity and uniqueness of the pathogenesis with updates on the findings of immunity and provide new information about biologics and biomarkers.

Pharmacological inhibition of protein S-palmitoylation suppresses osteoclastogenesis and ameliorates ovariectomy-induced bone loss

Background

Excessive osteoclast formation disrupts bone homeostasis, thereby significantly contributing to pathological bone loss associated with a variety of diseases. Protein S-palmitoylation is a reversible post-translational lipid modification catalyzed by ZDHHC family of palmitoyl acyltransferases, which plays an important role in various physiological and pathological processes. However, the role of palmitoylation in osteoclastogenesis has never been explored. Consequently, it is unclear whether this process can be targeted to treat osteolytic bone diseases that are mainly caused by excessive osteoclast formation.

Materials and methods

In this study, we employed acyl-biotin exchange (ABE) assay to reveal protein S-palmitoylation in differentiating osteoclasts (OCs). We utilized 2-bromopalmitic acid (2-BP), a pharmacological inhibitor of protein S-palmitoylation, to inhibit protein palmitoylation in mouse bone marrow-derived macrophages (BMMs), and tested its effect on receptor activator of nuclear factor κβ ligand (RANKL)-induced osteoclast differentiation and activity by TRAP staining, phalloidin staining, qPCR analyses, and pit formation assays. We also evaluated the protective effect of 2-BP against estrogen deficiency-induced bone loss and bone resorption in ovariectomized (OVX) mice using μCT, H&E staining, TRAP staining, and ELISA assay. Furthermore, we performed western blot analyses to explore the molecular mechanism underlying the inhibitory effect of 2-BP on osteoclastogenesis.

Results

We found that many proteins were palmitoylated in differentiating OCs and that pharmacological inhibition of palmitoylation impeded RANKL-induced osteoclastogenesis, osteoclast-specific gene expression, F-actin ring formation and osteoclastic bone resorption in vitro, and to a lesser extent, osteoblast formation from MC3T3-E1 cells. Furthermore, we demonstrated that administration of 2-BP protected mice from ovariectomy-induced osteoporosis and bone resorption in vivo. Mechanistically, we showed that 2-BP treatment inhibited osteoclastogenesis partly by downregulating the expression of c-Fos and NFATc1 without overtly affecting RANKL-induced activation of osteoclastogenic AKT, MAPK, and NF-κB pathways.

Conclusion

Pharmacological inhibition of palmitoylation potently suppresses RANKL-mediated osteoclast differentiation in vitro and protects mice against OVX-induced osteoporosis in vivo. Mechanistically, palmitoylation regulates osteoclast differentiation partly by promoting the expression of c-Fos and NFATc1. Thus, palmitoylation plays a key role in promoting osteoclast differentiation and activity, and could serve as a potential therapeutic target for the treatment of osteoporosis and other osteoclast-related diseases.

The translational potential of this article

The translation potential of this article is that we first revealed palmitoylation as a key mechanism regulating osteoclast differentiation, and therefore provided a potential therapeutic target for treating osteolytic bone diseases.

Regulation and therapy, the role of JAK2/STAT3 signaling pathway in OA: a systematic review

Osteoarthritis (OA) is a multifactorial chronic disease primarily characterized by the degeneration of articular cartilage. Currently, there is a lack of effective treatments for OA other than surgery. The exploration of the mechanisms of occurrence is important in exploring other new and effective treatments for OA. The current evidence shows that the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a vital role in cytogenesis and is involved in OA progression. The terms "JAK2", "STAT3", and "Osteoarthritis"were used in a comprehensive literature search in PubMed to further investigate the relationship between the JAK2/STAT3 signaling pathway and OA. This review focuses on the role and mechanism of JAK2/STAT3 signaling in cartilage degradation, subchondral bone dysfunction, and synovial inflammation. In addition, this review summarizes recent evidence of therapeutic approaches to treat OA by targeting the JAK2/STAT3 pathway to accelerate the translation of evidence into the progression of strategies for OA treatment. Video abstract.

RANKL Promotes Chemotherapy Resistance in Breast Cancer Cells Through STAT3 Mediated Autophagy Induction

BACKGROUND

This study was to investigate the functional role and mechanism of receptor activator of nuclear factor-kappa B ligand (RANKL) associated autophagy and chemoresistance in breast cancer.

MATERIALS AND METHODS

Cell Counting Kit-8 (CCK-8) assay was used to detect the cell viability. Real-time polymerase chain reaction (PCR) was used for determining the relative mRNA levels of key genes and protein expression was assessed by Western blotting. Immunofluorescence was performed to evaluate the changes in the autophagy flux. Short hairpin (shRNA) was used to knockdown the expression of the target genes in breast cancer cells. Based on The Cancer Genome Atlas (TCGA) database, we explored the expression of receptor activator of nuclear factor-kappa B (RANK), autophagy and signal transducer and activator of transcription 3 (STAT3) signaling associated genes and analyzed their correlation with the prognosis of breast cancer patients.

RESULTS

The findings showed that receptor activator of nuclear factor-kappa B ligand (RANKL), the ligand of RANK, could effectively enhance the chemoresistance potential of breast cancer cells. Our results showed that RANKL induced autophagy and enhanced the expression of autophagy associated genes in breast cancer cells. The knockdown of RANK suppressed RANKL mediated autophagy induction in these cells. Furthermore, the inhibition of autophagy suppressed RANKL mediated chemoresistance in breast cancer cells. We found STAT3 signaling pathway was involved in RANKL-induced autophagy. Analysis of the expression of RANK, and autophagy and STAT3 signaling associated genes in breast cancer tissues showed that the expression of autophagy and STAT3 signaling associated genes was correlated with the prognosis of breast cancer patients.

CONCLUSION

The present study suggests that the RANKL/RANK axis may potentially mediate chemoresistance in breast cancer cells by inducing autophagy through the STAT3 signaling pathway.

Synthesis and evaluation of naphthalene derivatives as potent STAT3 inhibitors and agents against triple-negative breast cancer growth and metastasis

PURPOSE

Triple-negative breast cancer (TNBC) represents the worst prognostic subtype of breast cancer and lacks targeted therapeutic drugs. Signal transducer and activator of transcription 3 (STAT3) is overexpressed and constitutively activated in TNBCs and associated with poor patient outcomes. However, no agents targeting STAT3 have been successfully developed and marketed. Selective Estrogen Receptor Modulators (SERMs) have been reported as potential inhibitors of the IL-6/STAT3 signaling pathway. Naphthalene compounds have good pharmacological activity and significant anti-cancer activity. In this study, we synthesized a new series of naphthalene derivatives with the general structure of SERM and evaluated their effects on TNBC and STAT3 signals.

METHODS

A new series of compounds based on the scaffold of SERMs and an amino group were designed and screened based on the structure-activity relationship by MTT assay. The binding activity of SMY002 to STAT3 was predicted and validated by docking and SPR. The STAT3 signaling target and anti-cancer effects of SMY002 were evaluated with three TNBC cell lines and the mice transplanted tumor model.

RESULTS

Among the compounds, SMY002 displayed the most potent activity, which could directly interact with STAT3 SH2-domain, and strongly inhibit the phosphorylation, dimerization, nuclear distribution, transcriptional activity, and target genes expression of STAT3. Furthermore, SMY002 markedly suppressed migration, invasion, survival, growth, and metastasis of TNBC cells in vitro and in vivo via down-regulating the expression of Cyclin D1 and MMP9.

CONCLUSIONS

SMY002 can significantly inhibit the growth and metastasis of TNBC cells by targeting the STAT3 signal.

Advances in the role of STAT3 in macrophage polarization

The physiological processes of cell growth, proliferation, differentiation, and apoptosis are closely related to STAT3, and it has been demonstrated that aberrant STAT3 expression has an impact on the onset and progression of a number of inflammatory immunological disorders, fibrotic diseases, and malignancies. In order to produce the necessary biological effects, macrophages (M0) can be polarized into pro-inflammatory (M1) and anti-inflammatory (M2) types in response to various microenvironmental stimuli. STAT3 signaling is involved in macrophage polarization, and the research of the effect of STAT3 on macrophage polarization has gained attention in recent years. In order to provide references for the treatment and investigation of disorders related to macrophage polarization, this review compiles the pertinent signaling pathways associated with STAT3 and macrophage polarization from many fundamental studies.

MiR-124-3p Reduces Bone Mineral Density in Postmenopausal Osteoporosis Rats Through Regulating Signal Transducer and Activator of Transcription 3 Pathway

We aimed to study the effect of miR-124-3p on postmenopausal osteoporosis (POP) rats through regulating the signal transducer and activator of transcription 3 (STAT3) pathway. Rats were randomly divided into normal group, model group and miR-124-3p antagomir group. Enzyme-linked immunosorbent assay (ELISA) was performed to determine the levels of receptor activator of nuclear factor-κB (RANK) and osteoprotegerin (OPG). BMD of femur was significantly lower in model group and miR-124-3p antagomir group than that in normal group at 12 weeks after modeling, while it was significantly higher in miR-124-3p antagomir group than that in model group. Positive expression of BMP2 was obviously higher in miR-124-3p antagomir group than that in model group. Protein expression of p-STAT3 was evidently lower in miR-124-3p antagomir group than that in model group. Besides, POP rats have significantly increased level of miR-124-3p compared with that in normal group. In model group and miR-124-3p antagomir group, the content of OPG was remarkably lower, and the content of RANK was remarkably higher than those in normal group. In miR-124-3p antagomir group, the content of OPG was remarkably higher, and RANK was remarkably lower than those in model group. MiR-124-3p reduces BMD in POP rats through up-regulating the STAT3 pathway.

Advance in bone destruction participated by JAK/STAT in rheumatoid arthritis and therapeutic effect of JAK/STAT inhibitors

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic joint inflammation and bone erosion. The bones in the human body are constantly undergoing bone remodeling throughout their lives, which is the process of bone resorption by osteoclasts to damaged bone tissue and new bone formation by osteoblasts. Osteoblasts (OBs) are the main functional cells in bone formation, responsible for the synthesis, secretion and mineralization of the bone matrix. On the contrary, osteoclasts (OCs) mediate bone breakdown during natural bone turnover, but excessive breakdown occurs in RA. Under the condition of RA inflammation, many molecules, such as IL-1β, IL-6, TNF-α, IL-17 and hypoxia-inducible factor-1α (HIF-1α) are produced that could mediate bone loss. Studies have shown that cytokines mainly promote the formation of OCs and play a role in bone resorption by stimulating OBs to express receptor activator of NF-κB ligand (RANKL). JAK/STAT plays a crucial role in the process of bone destruction. And JAK/STAT pathway mediates the RANKL/receptor activator of NF-κB (RANK)/osteoprotegerin (OPG) axis. Tofacitinib, Baricitinib, Peficitinib and Filgotinib are now being used in patients with moderate to severe RA, as well as in patients with RA who have an inadequate response to methotrexate therapy and bone destruction. Currently, Tofacitiniband Baritinib areapprovedfor thetreatmentof moderate-to-severely active RA. JAK inhibitors have been reported to have better efficacy and lower adverse effects compared with methotrexate and adalimumab. In addition, two JAK inhibitors are currently in development: the JAK1 selective Upadacitinib, and the JAK3 selective inhibitor Decernotinib. In addition to the above JAK inhibitors, some small molecular compounds inhibit bone destruction by inhibiting the Phosphorylation of STAT3. In this paper, the research progress of bone destruction participated by JAK/ STAT in rheumatoid arthritis and therapeutic effect of JAK/STAT inhibitors were reviewed.

Ganoderic acid A improves osteoarthritis by regulating RANKL/OPG ratio

Ganoderma mushrooms have been used to treat rheumatoid arthritis (RA) in East Asia. Whether Ganoderic acid A (GAA), the natural product extracted from Ganoderma, could be utilized to alleviate osteoarthritis (OA) is investigated in this study. Destabilization of the medial meniscus (DMM) model was constructed to reveal the in vivo effect of GAA. We found that GAA could significantly alleviate the pathology of DMM, as confirmed by the diminished maximum histologic scores. On the other hand, GAA could down-regulate the relative expression of osteoprotegerin (OPG) and up-regulate the relative expression of nuclear factor-kappa B ligand (RANKL) in DMM cartilage and human articular chondrocytes (HC-A) cells with diminished matrix metallopeptidase 13 (MMP-13) secretion in the synovial fluid. It was further demonstrated that the serum concentration of OPG was correlated with the severity of osteoarthritis. All these data reveal that GAA could improve OA by regulating the RANKL/OPG ratio to inhibit the secretion of MMP-13.

SAPHO Syndrome Complicated by Ankylosing Spondylitis Successfully Treated With Tofacitinib: A Case Report

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, a type of chronic inflammatory disease, is rare and difficult to treat. Osteoarthropathy with skin involvement is the primary clinical manifestation of SAPHO syndrome. The unknown pathogenesis of SAPHO syndrome is speculated to be related to individual genetic differences, immune levels, microorganisms, and environmental factors. Tofacitinib, a novel small-molecule Janus kinase (JAK) inhibitor, has been used to treat rheumatoid arthritis. However, it also has great potential for the treatment of other immune diseases, including SAPHO syndrome. A 36-year-old man with chest and back pain for more than two months was admitted to our hospital. After admission, the patient developed a pustular rash and enteritis. SAPHO syndrome was diagnosed based on the above clinical manifestations, computed tomography (CT), and bone scintigraphy findings. Notably, the patient also had ankylosing spondylitis. Tofacitinib significantly improved the patient’s skin symptoms while preventing worsening of chest and back pain when adalimumab was discontinued. We report the first case of ankylosing spondylitis with SAPHO syndrome. In addition, it is also the first successful treatment thereof with tofacitinib. We hope to provide valuable information regarding the pathogenesis and treatment of SAPHO syndrome in this case.

Stat3 Signaling Pathway: A Future Therapeutic Target for Bone-Related Diseases

Signal transducer and activator of transcription 3 (Stat3) is activated by phosphorylation and translocated to the nucleus to participate in the transcriptional regulation of DNA. Increasing evidences point that aberrant activation or deletion of the Stat3 plays a critical role in a broad range of pathological processes including immune escape, tumorigenesis, and inflammation. In the bone microenvironment, Stat3 acts as a common downstream response protein for multiple cytokines and is engaged in the modulation of cellular proliferation and intercellular interactions. Stat3 has direct impacts on disease progression by regulating mesenchymal stem cells differentiation, osteoclast activation, macrophage polarization, angiogenesis, and cartilage degradation. Here, we describe the theoretical basis and key roles of Stat3 in different bone-related diseases in combination with in vitro experiments and animal models. Then, we summarize and categorize the drugs that target Stat3, providing potential therapeutic strategies for their use in bone-related diseases. In conclusion, Stat3 could be a future target for bone-related diseases.

N,N-Dimethylformamide inhibits high glucose-induced osteoporosis via attenuating MAPK and NF-κB signalling

Aims

The role of N,N-dimethylformamide (DMF) in diabetes-induced osteoporosis (DM-OS) progression remains unclear. Here, we aimed to explore the effect of DMF on DM-OS development.

Methods

Diabetic models of mice, RAW 264.7 cells, and bone marrow macrophages (BMMs) were established by streptozotocin stimulation, high glucose treatment, and receptor activator of nuclear factor-κB ligand (RANKL) treatment, respectively. The effects of DMF on DM-OS development in these models were examined by micro-CT analysis, haematoxylin and eosin (H&E) staining, osteoclast differentiation of RAW 264.7 cells and BMMs, H&E and tartrate-resistant acid phosphatase (TRAP) staining, enzyme-linked immunosorbent assay (ELISA) of TRAP5b and c-terminal telopeptides of type 1 (CTX1) analyses, reactive oxygen species (ROS) analysis, quantitative reverse transcription polymerase chain reaction (qRT-PCR), Cell Counting Kit-8 (CCK-8) assay, and Western blot.

Results

The established diabetic mice were more sensitive to ovariectomy (OVX)-induced osteoporosis, and DMF treatment inhibited the sensitivity. OVX-treated diabetic mice exhibited higher TRAP5b and c-terminal telopeptides of type 1 (CTX1) levels, and DMF treatment inhibited the enhancement. DMF reduced RAW 264.7 cell viability. Glucose treatment enhanced the levels of TRAP5b, cathepsin K, Atp6v0d2, and H⁺-ATPase, ROS, while DMF reversed this phenotype. The glucose-increased protein levels were inhibited by DMF in cells treated with RANKL. The expression levels of antioxidant enzymes Gclc, Gclm, Ho-1, and Nqo1 were upregulated by DMF. DMF attenuated high glucose-caused osteoclast differentiation by targeting mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signalling in BMMs.

Conclusion

DMF inhibits high glucose-induced osteoporosis by targeting MAPK and NF-κB signalling.

Cite this article: Bone Joint Res 2022;11(4):200–209.

Nitazoxanide, an Antiprotozoal Drug, Reduces Bone Loss in Ovariectomized Mice by Inhibition of RANKL-Induced Osteoclastogenesis

Nitazoxanide (NTZ) is an FDA-approved anti-parasitic drug with broad-spectrum anti-infective, anti-inflammatory, and antineoplastic potential. However, its regulatory effects on osteoclastogenesis and the underlying mechanisms remain unclear. The present study found that NTZ potently inhibited osteoclast formation at the early stage of receptor activator of NF-κB ligand-induced osteoclastogenesis in a concentration-dependent manner at a non-growth inhibitory concentration. NTZ suppressed actin ring formation and decreased osteoclast marker gene expression, including TRAP, MMP9, and cathepsin K. NTZ significantly impaired the bone resorption activity of osteoclasts. In vivo, ovariectomized mice were treated with 50, 100 and 200 mg/kg/d NTZ for 3 months. NTZ (100 mg/kg/d) administration markedly reduced ovariectomy-induced bone loss by suppressing osteoclast activity. Mechanistically, osteoclastogenesis blockade elicited by NTZ resulted from inhibition of STAT3 phosphorylation, and reduction of the Ca2+ fluorescence intensity and NFATc1 expression. NTZ weakened the binding between STAT3 and the NFATc1 promoter region. Furthermore, enforced NFATc1 expression partly rescued the impaired osteoclast differentiation in NTZ-treated RAW264.7 cells. In summary, NTZ could inhibit osteoclastogenesis and bone loss through modulation of the receptor activator of NF-κB ligand-induced STAT3-NFATc1 signaling pathway, which might be a potential alternative treatment regimen against bone destruction-related diseases including osteoporosis.

The Th17/Treg cell balance: crosstalk among the immune system, bone and microbes in periodontitis

Periodontopathic bacteria constantly stimulate the host, which causes an immune response, leading to host-induced periodontal tissue damage. The complex interaction and imbalance between Th17 and Treg cells may be critical in the pathogenesis of periodontitis. Furthermore, the RANKL/RANK/OPG system plays a significant role in periodontitis bone metabolism, and its relationship with the Th17/Treg cell imbalance may be a bridge between periodontal bone metabolism and the immune system. This article reviews the literature related to the Th17/Treg cell imbalance mediated by pathogenic periodontal microbes, and its mechanism involving RANKL/RANK/OPG in periodontitis bone metabolism, in an effort to provide new ideas for the study of the immunopathological mechanism of periodontitis.

Stattic sensitizes osteosarcoma cells to epidermal growth factor receptor inhibitors via blocking the interleukin 6-induced STAT3 pathway

Osteosarcoma (OS), the most common malignant bone tumor with high metastatic potential, frequently affects children and adolescents. Epidermal growth factor receptor (EGFR)-targeted tyrosine kinase inhibitors exhibit encouraging anti-tumor activity for patients with solid tumors, whereas their effects on OS remain controversial. In the present study, we aimed to elucidate the anti-tumor activity of gefitinib for OS, as well as to explore the underlying mechanisms. Gefitinib inhibits cell viability, tumor growth, cell migration, and invasion and promotes cell apoptosis and G1 cycle arrest in OS at a relatively high concentration via suppressing the PI3K/Akt and ERK pathways. However, gefitinib treatment results in the feedback activation of signal transducer and activator of transcription 3 (STAT3) induced by interleukin 6 (IL-6) secretion. Combined treatment with gefitinib and stattic, an inhibitor for STAT3 phosphorylation, engenders more evident inhibitory effects on cell proliferation, migration, and invasion and promotive effects on cell apoptosis and G1 phase arrest in OS, compared with the single exposure to gefitinib or stattic. Western blot analysis demonstrates that stattic treatment in gefitinib-treated OS abrogates the IL-6-induced STAT3 activation and subsequently further restrains the activities of EGFR, Akt, and ERK pathways in tumor cells. This study confirms that the EGFR inhibitor of gefitinib has moderate anti-tumor effects on OS through IL-6 secretion-mediated STAT3 activation. Additional administration of stattic in EGFR-targeted therapies may contribute to improve the efficacy for OS.

Glycolysis Rate-Limiting Enzymes: Novel Potential Regulators of Rheumatoid Arthritis Pathogenesis

Rheumatoid arthritis (RA) is a classic autoimmune disease characterized by uncontrolled synovial proliferation, pannus formation, cartilage injury, and bone destruction. The specific pathogenesis of RA, a chronic inflammatory disease, remains unclear. However, both key glycolysis rate-limiting enzymes, hexokinase-II (HK-II), phosphofructokinase-1 (PFK-1), and pyruvate kinase M2 (PKM2), as well as indirect rate-limiting enzymes, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), are thought to participate in the pathogenesis of RA. In here, we review the latest literature on the pathogenesis of RA, introduce the pathophysiological characteristics of HK-II, PFK-1/PFKFB3, and PKM2 and their expression characteristics in this autoimmune disease, and systematically assess the association between the glycolytic rate-limiting enzymes and RA from a molecular level. Moreover, we highlight HK-II, PFK-1/PFKFB3, and PKM2 as potential targets for the clinical treatment of RA. There is great potential to develop new anti-rheumatic therapies through safe inhibition or overexpression of glycolysis rate-limiting enzymes.

TRPV4-induced Müller cell gliosis and TNF-α elevation-mediated retinal ganglion cell apoptosis in glaucomatous rats via JAK2/STAT3/NF-κB pathway

Background

Glaucoma, the leading cause of irreversible blindness worldwide, is a type of retinal disease characterized by the selective death of retinal ganglion cells (RGCs). However, the pathogenesis of glaucoma has not been fully elucidated. Transient receptor potential vanilloid 4 (TRPV4) is a pressure-sensitive and calcium-permeable cation channel. TRPV4 is widely distributed in the retina and its sustained activation leads to RGC death; indicating that TRPV4 may be a possible target for glaucoma treatment. Here, we investigated the effects of TRPV4 on RGC apoptosis in a rat model of chronic ocular hypertension (COH), then examined the mechanism underlying these effects.

Methods

The COH model was established by injection of micro-magnetic beads into the anterior chamber of adult male rats. The expression levels of TRPV4, glial fibrillary acidic protein, and inflammatory factors were assessed by immunohistochemistry and immunoblotting. RGC apoptosis and visual dysfunction were evaluated by TUNEL assay and photopic negative response. Functional expression of TRPV4 was examined by electrophysiology and calcium imaging. Real-time polymerase chain reaction and immunoblotting were employed to investigate the molecular mechanism underlying the effects of TRPV4 on tumor necrosis factor-α (TNF-α) release.

Results

We found that TRPV4 played an essential role in glaucoma, such that high levels of TRPV4 expression were associated with elevated intraocular pressure. Furthermore, TRPV4 activation was involved in glaucoma-induced RGC apoptosis and RGC-related reductions in visual function. Mechanistic investigation demonstrated that TRPV4 activation led to enhanced Müller cell gliosis and TNF-α release via the JAK2/STAT3/NF-kB pathway, while TRPV4 inhibition could reverse these effects. Finally, TRPV4 activation could lead to elevated expression of TNF receptor 1 in RGCs, while inhibition of TNF-α could reduce TRPV4-mediated RGC apoptosis.

Conclusions

TRPV4 activation induces Müller cell gliosis and TNF-α elevation via the JAK2/STAT3/NF-κB pathway, which may exacerbate RGC apoptosis in glaucoma; these results suggest that TRPV4 can serve as a therapeutic target in glaucoma treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02315-8.

Exploring the Effect of Jiawei Buguzhi Pills on TGF-β-Smad Pathway in Postmenopausal Osteoporosis Based on Integrated Pharmacological Strategy

Objective

To explore the effect of Jiawei Buguzhi Pills (JWBGZP) on the TGF-β-Smad pathway in postmenopausal osteoporosis (PMO) based on integrated pharmacological strategy.

Method

The ETCM database was used to collect JWBGZP. GeneCards and OMIM databases were utilized to obtain PMO-related genes. Cytoscape was used for network construction and analysis, and DAVID was used for GO and KEGG enrichment analysis of key targets. Animal experiments and cell experiments were conducted to further explore the mechanism. The bone mass density was detected by dual-energy X-ray bone densitometer. The TGF-β1 and Smad4 mRNA in bone tissue were detected by RT-qPCR. The TGF-β1 and Smad4 protein in bone tissue were detected by the western blot. The TGF-β1 and Smad4 protein in osteoblasts were determined by immunohistochemistry.

Result

A total of 721 JWBGZP potential targets and 385 PMO-related genes were obtained. The enrichment analysis showed that JWBGZP may regulate the TGF-beta signaling pathway, oxidation-reduction process, aging, response to hypoxia, response to ethanol, negative regulation of cell proliferation, PI3K-Akt, HIF-1, and other signaling pathways. The animal experiments showed that compared with the model group, the femoral bone mineral density and lumbar bone mineral density of the JWBGZP group increased (P < 0.05); the expression levels of TGF-β1 and Smad mRNA and proteins in the JWBGZP group were significantly higher (P < 0.05). The cell experiment results showed a large number of osteoblast stained blue-purple and orange-red calcified nodules. The expression levels of TGF-β1 and Smad proteins in the JWBGZP group were significantly higher than those in the blank control group and the sham operation group, and the protein expression levels in the model group were the lowest (P < 0.05).

Conclusion

JWBGZP may be involved in PI3K-Akt, HIF-1, estrogen, prolactin, and other signaling pathways and regulate MAPK1, AKT1, PIK3CA, JAK2, and other gene targets, regulate bone metabolism, and thereby treat PMO.

Cytokine Networks in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic systemic inflammation causing progressive joint damage that can lead to lifelong disability. The pathogenesis of RA involves a complex network of various cytokines and cells that trigger synovial cell proliferation and cause damage to both cartilage and bone. Involvement of the cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 is central to the pathogenesis of RA, but recent research has revealed that other cytokines such as IL-7, IL-17, IL-21, IL-23, granulocyte macrophage colony-stimulating factor (GM-CSF), IL-1β, IL-18, IL-33, and IL-2 also play a role. Clarification of RA pathology has led to the development of therapeutic agents such as biological disease-modifying anti-rheumatic drugs (DMARDs) and Janus kinase (JAK) inhibitors, and further details of the immunological background to RA are emerging. This review covers existing knowledge regarding the roles of cytokines, related immune cells and the immune system in RA, manipulation of which may offer the potential for even safer and more effective treatments in the future.

STAT3 phosphorylation inhibition for treating inflammation and new bone formation in ankylosing spondylitis

OBJECTIVE

AS is a rheumatic disease characterized by chronic inflammation and bony ankylosis. This study was to evaluate whether a signal transducer and activator of transcription 3 phosphorylation inhibitor (stat3-p Inh) could treat both chronic inflammation and bone formation in AS.

METHODS

Primary AS osteoprogenitor cells and spinal entheseal cells were examined for osteogenic differentiation. SF mononuclear cells (SFMCs) and lamina propria mononuclear cells (LPMCs) were obtained from AS patients. Inflammatory cytokine-producing cells were analysed using flow cytometry and ELISA. Female SKG mice were treated with stat3-p Inh, IL-17A blocker or vehicle. Inflammation and new bone formation were evaluated using immunohistochemistry, PET and micro-CT.

RESULTS

In the SKG mouse model, stat3-p Inh significantly suppressed arthritis, enthesitis, spondylitis and ileitis. In experiments culturing SFMCs and LPMCs, the frequencies of IFN-γ-, IL-17A- and TNF-α-producing cells were significantly decreased after stat3-p Inh treatment. When comparing current treatments for AS, stat3-p Inh showed a comparable suppression effect on osteogenesis to Janus kinase inhibitor or IL-17A blocker in AS-osteoprogenitor cells. Stat3-p Inh suppressed differentiation and mineralization of AS-osteoprogenitor cells and entheseal cells toward osteoblasts. Micro-CT analysis of hind paws revealed less new bone formation in stat3-p Inh-treated mice than vehicle-treated mice (P = 0.005). Hind paw and spinal new bone formation were similar between stat3-p Inh- and anti-IL-17A-treated SKG mice (P = 0.874 and P = 0.117, respectively).

CONCLUSION

Stat-3p inhibition is a promising treatment for both inflammation and new bone formation in AS.

Trilobolide-6-O-isobutyrate suppresses hepatocellular carcinoma tumorigenesis through inhibition of IL-6/STAT3 signaling pathway

Currently available therapies for hepatocellular carcinoma (HCC), with a high morbidity and high mortality, are only marginally effective and with sharp adverse side effects, which makes it compulsory to explore novel and more effective anticancer molecules. Chinese medicinal herbs exhibited prominent anticancer effects and were applied to supplement clinical cancer treatment. Here, we reported a compound, trilobolide-6-O-isobutyrate (TBB), isolated from the flowers of Wedelia trilobata with a markedly cytotoxic effect on HCC cells. We found that TBB time- and dose-dependently inhibited HCC cells' growth and colony formation in vitro. Moreover, TBB induced cell cycle arrest at the G2/M phase, mitochondrial caspase-dependent apoptosis, and suppressed migration and invasion, as well as the glycolysis of HCC cells. Mechanistically, our data indicated that TBB inhibited the STAT3 pathway activation by directly interacting with the TYR 640/657 sites of the STAT3 protein and decreasing the level of p-STAT3. TBB also regulated the expression of PCNA, Ki67, Cyclin B1, Cyclin E, Bax, Bcl2, MMP2/9, and PGK1 through the inhibition of the IL-6/STAT3 signaling pathway. Lastly, we confirmed that TBB effectively eliminated tumor growth without causing overt toxicity to healthy tissues in the xenograft tumor model. The exploration of anticancer activity and the underlying mechanism of TBB suggested its usage as a promising chemotherapeutic agent for HCC.

TPCA-1 negatively regulates inflammation mediated by NF-κB pathway in mouse chronic periodontitis model

The dysregulation of immune system plays a crucial function in periodontitis development. Pro-inflammatory cytokines are thought to be critical for the generation and development of periodontitis. The enhanced activity of osteoclasts contributes to periodontitis pathogenesis. Nuclear factor-κB (NF-κB) signaling pathway directly enhances osteoclast differentiation and maturation. 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1) is a IκB kinases (IKK) inhibitor. This research aimed to investigate whether TPCA-1 had influence on the pathogenesis of chronic periodontitis. Mouse chronic periodontitis was induced by an in vivo ligature-induced periodontitis model. TPCA-1 was intravenously injected into mice after chronic periodontitis induction. Bone marrow-derived macrophages were cultured in macrophage colony-stimulating factor (M-CSF)-conditioned media with receptor activator of nuclear factor-kappa B ligand (RANKL) induce in vitro osteoclast differentiation. Western blot was used to analyze protein levels and mRNA levels were analyzed through qRT-PCR. TPCA-1 promoted osteoclastogenesis and osteoclast-related gene expression in vitro. The production of pro-inflammatory cytokines in osteoclasts induced by lipopolysaccharides was inhibited by TPCA-1 in vitro. In vitro TPCA-1 treatment inhibited Aggregatibacter actinomycetemcomitans (A.a)-induced expression of pro-inflammatory cytokines and NF-κB signal activation in osteoclasts. The induction of chronic periodontitis was inhibited by the absence of IKKb in mice. This research demonstrates that the treatment of TPCA-1 negatively regulates inflammation response and inhibits the osteoclastogenesis through the inactivation of NF-κB pathway in mouse chronic periodontitis model.

Napabucasin Induces Mouse Bone Loss by Impairing Bone Formation via STAT3

The novel small molecule Napabucasin (also known as BBI608) was shown to inhibit gene transcription driven by Signal Transducer and Activator of Transcription 3 (STAT3), which is considered a promising anticancer target. Many preclinical studies have been conducted in cancer patients examining the selective targeting of cancer stem cells by Napabucasin, but few studies have examined side effects of Napabucasin in the skeleton system. In the present study, we found treating bone marrow mesenchymal stem cells (BMSCs) with Napabucasin in vitro impaired their osteogenic differentiation. In terms of mechanisms, Napabucasin disrupted differentiation of BMSCs by inhibiting the transcription of osteogenic gene osteocalcin (Ocn) through STAT3. Moreover, through micro-CT analysis we found 4 weeks of Napabucasin injections induced mouse bone loss. Histological analysis revealed that Napabucasin-induced bone loss in mice was the result of impaired osteogenesis. In conclusion, this study provided evidence for the effect of Napabucasin on mouse bone homeostasis and revealed its underlying mechanisms in vivo and in vitro.

Isobavachalcone prevents osteoporosis by suppressing activation of ERK and NF-κB pathways and M1 polarization of macrophages

Estrogen receptors alpha (ERα), a member of the nuclear receptor protein family, was found to play an important role in maintaining bone mass. Its downstream signaling proteins such as ERK and NF-κB were reported to be involved in development of osteoporosis, which meant that targeting ERα might be an effective strategy for searching for new drugs to prevent bone loss. In this study, we demonstrate that isobavachalcone (ISO), as one of bioactive compounds isolated from Psoralea corylifoliaLinn, has high affinity with ERα. The effects of ISO are investigated on receptor activator of NF-κB ligand (RANKL)-induced osteocalstogenesis. It is reported that ISO inhibits the RANKL-mediated increase of osteoclast-related genes MMP9, cathepsink and TRAR in RAW264.7 cells. Moreover, in vitro experiment shows that ISO exhibits an inhibitory effect on ERK and NF-κB signaling pathway, and suppresses RANKL-induced expression of osteoclast-related transcription factors NFATc1 and c-Fos. However, the impact of ISO in these molecules is eliminated by the application of ERα antagonist AZD9496.We further verified pharmacological effects of ISO in ovariectomized osteoporotic mice, and ISO significantly prevented bone loss and decreased M1 polarization of macrophages from marrow and spleen. Collectively, our data suggest that ISO prevents osteoporosis via suppressing activation of ERK and NF-κB signaling pathways as well as M1 polarization of macrophages.

Iguratimod inhibits osteoclastogenesis by modulating the RANKL and TNF-α signaling pathways

BACKGROUND

Iguratimod, a small molecular drug, has been proven to have effective bone protection for treatment of patients with bone loss-related diseases, such as rheumatoid arthritis (RA). However, the exact bone protective mechanism of iguratimod remains to be determined. The purpose of this study was to better explore the underlying mechanism of bone protection of iguratimod.

METHODS

Bone marrow monocytes from C57/BL6 mice were stimulated with either RANKL or TNF-α plus M-CSF. The effects of iguratimod on morphology and function of osteoclasts were confirmed by TRAP staining and bone resorption assay, respectively. The expression of osteoclast related genes was detected by RT-PCR and the activation of signal pathway was detected by Western blotting. We used rodent models of osteoporosis (ovariectomy) and of arthritis (modified TNF-α-induced osteoclastogenesis) to evaluate the osteoprotective effect of iguratimod in vivo.

RESULTS

Iguratimod potently inhibited osteoclast formation in a dose-dependent manner at the early stage of RANKL-induced osteoclastogenesis, whereas iguratimod had no effect on M-CSF-induced proliferation and RANK expression in bone marrow monocytes. Bone resorption was significantly reduced by both early and late addition of iguratimod. Administration of iguratimod prevented bone loss in ovariectomized mice. The blockage of osteoclastogenesis elicited by iguratimod results from abrogation of the p38、ERK and NF-κB pathways induced by RANKL. Importantly, Iguratimod also dampened TNF-α-induced osteoclastogenesis in vitro and attenuated osteoclasts generation in vivo through disrupting NF-κB late nuclear translocation without interfering with IκBα degradation.

CONCLUSIONS

Iguratimod not only suppresses osteoclastogenesis by interfering with RANKL and TNF-α signals, but also inhibits the bone resorption of mature osteoclasts. These results provided promising evidence for the therapeutic application of iguratimod as a unique treatment option against RA and especially in prevention of bone loss.

JAK/STAT pathway and molecular mechanism in bone remodeling

JAK/STAT signaling pathway is involved in many diseases, including autoimmune diseases, which are characterized by a close interconnection between immune and bone system. JAK/STAT pathway is involved in bone homeostasis and plays an important role in proliferation and differentiation of some cell types, including osteoblasts and osteoclasts. Different molecules, such as cytokines, hormones, and growth factors are responsible for the activation of the JAK/STAT pathway, which leads, at the nuclear level, to start DNA transcription of target genes. Bone cells and remodeling process are often influenced by many cytokines, which act as strong stimulators of bone formation and resorption. Our aim, through careful research in literature, has been to provide an overview of the role of the JAK/STAT pathway in bone remodeling and on bone cells, with a focus on cytokines involved in bone turnover through this signal cascade. The JAK/STAT pathway, through the signal cascade activation mediated by the interaction with many cytokines, acts on bone cells and appears to be involved in bone remodeling process. However, many other studies are needed to completely understand the molecular mechanism underlying these bone process.

Osteoimmunology in rheumatoid and psoriatic arthritis: potential effects of tofacitinib on bone involvement

Chronic inflammation, such as that present in rheumatoid arthritis (RA) and psoriatic arthritis (PsA), leads to aberrations in bone remodeling, which is mediated by several signaling pathways, including the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. In this light, pro-inflammatory cytokines are now clearly implicated in these processes as they can perturb normal bone remodeling through their action on osteoclasts and osteoblasts at both intra- and extra-articular skeletal sites. As a selective inhibitor of JAK1 and JAK3, tofacitinib has the potential to play a role in the management of rheumatic diseases such as RA and PsA. Preclinical studies have demonstrated that tofacitinib can inhibit disturbed osteoclastogenesis in RA, which suggests that targeting the JAK-STAT pathway may help limit bone erosion. Evidence from clinical trials with tofacitinib in RA and PsA is encouraging, as tofacitinib treatment has been shown to decrease articular bone erosion. In this review, the authors summarize current knowledge on the relationship between the immune system and the skeleton before examining the involvement of JAK-STAT signaling in bone homeostasis as well as the available preclinical and clinical evidence on the benefits of tofacitinib on prevention of bone involvement in RA and PsA.Key Points• Chronic inflammation in rheumatoid arthritis (RA) and psoriatic arthritis (PsA) leads to disturbances in bone remodeling• Bone remodeling is mediated by several signaling pathways, including the JAK-STAT pathway• Tofacitinib, a selective inhibitor of JAK1 and JAK3, is active in RA and PsA and may help limit systemic bone loss through inhibiting disturbed osteoclastogenesis• Clinical trials show that tofacitinib reduces articular bone erosion.

Direct Targeting Options for STAT3 and STAT5 in Cancer

Signal transducer and activator of transcription (STAT)3 and STAT5 are important transcription factors that are able to mediate or even drive cancer progression through hyperactivation or gain-of-function mutations. Mutated STAT3 is mainly associated with large granular lymphocytic T-cell leukemia, whereas mutated STAT5B is associated with T-cell prolymphocytic leukemia, T-cell acute lymphoblastic leukemia and γδ T-cell-derived lymphomas. Hyperactive STAT3 and STAT5 are also implicated in various hematopoietic and solid malignancies, such as chronic and acute myeloid leukemia, melanoma or prostate cancer. Classical understanding of STAT functions is linked to their phosphorylated parallel dimer conformation, in which they induce gene transcription. However, the functions of STAT proteins are not limited to their phosphorylated dimerization form. In this review, we discuss the functions and the roles of unphosphorylated STAT3/5 in the context of chromatin remodeling, as well as the impact of STAT5 oligomerization on differential gene expression in hematopoietic neoplasms. The central involvement of STAT3/5 in cancer has made these molecules attractive targets for small-molecule drug development, but currently there are no direct STAT3/5 inhibitors of clinical grade available. We summarize the development of inhibitors against the SH2 domains of STAT3/5 and discuss their applicability as cancer therapeutics.

Hypoxia induces rapid, STAT3 and ROS dependent, mitochondrial translocation of RelA(p65) and IκBα

The nuclear factor-κB (NF-κB) family of transcription factors can directly or indirectly regulate many important areas of biology, including immunity, inflammation and cell survival. One intriguing aspect of NF-κB crosstalk with other cell signalling pathways is its regulation of mitochondrial biology, including biogenesis, metabolism and apoptosis. In addition to regulating the expression of mitochondrial genes encoded in the nucleus, NF-κB signalling components are also found within mitochondria themselves and associated with mitochondrial DNA. However, complete biochemical analysis of mitochondrial and sub-mitochondrial localisation of all NF-κB subunits has not been undertaken. Here, we show that only the RelA NF-κB subunit and its inhibitor IκBα reside within mitochondria, whilst p50 is found in the endoplasmic reticulum (ER). Fractionation of mitochondria revealed that only RelA was found in the mitoplast, the location of the mtDNA. We demonstrate that hypoxia leads to a very rapid but transient accumulation of RelA and IκBα in mitochondria. This effect required reactive oxygen species (ROS) but was not dependent on the hypoxia sensing transcription factor subunit HIF1α or intracellular Ca2+ release. We also observed rapid mitochondrial localisation of transcription factor STAT3 following hypoxia. Inhibition of STAT3 blocked RelA and IκBα mitochondrial localisation revealing a previously unknown aspect of crosstalk between these key cellular regulators.

CXCR2 expression on granulocyte and macrophage progenitors under tumor conditions contributes to mo-MDSC generation via SAP18/ERK/STAT3

Myeloid-derived suppressor cells (MDSCs) comprise a critical component of the tumor environment and CXCR2 reportedly plays a key role in the pathophysiology of various inflammatory diseases. Here, CXCR2 expression on granulocyte and macrophage progenitor cells (GMPs) was found to participate in myeloid cell differentiation within the tumor environment. In CXCR2-deficient tumor-bearing mice, GMPs exhibited fewer macrophage and dendritic cell progenitor cells than wild-type tumor-bearing mice, thereby decreasing monocytic MDSCs (mo-MDSCs) expansion. CXCR2 deficiency increased SAP18 expression in tumor-bearing mice, which reduced STAT3 phosphorylation through restraining ERK1/2 activation. Our findings reveal a critical role for CXCR2 in regulating hematopoietic progenitor cell differentiation under tumor conditions, and SAP18 is a key negative regulator in this process. Thus, inhibiting CXCR2 expression may alter the tumor microenvironment and attenuate tumor progression.

TRPV1 mediates astrocyte activation and interleukin-1β release induced by hypoxic ischemia (HI)

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is a serious birth complication with high incidence in both advanced and developing countries. Children surviving from HIE often have severe long-term sequela including cerebral palsy, epilepsy, and cognitive disabilities. The severity of HIE in infants is tightly associated with increased IL-1β expression and astrocyte activation which was regulated by transient receptor potential vanilloid 1 (TRPV1), a non-selective cation channel in the TRP family.

METHODS

Neonatal hypoxic ischemia (HI) and oxygen-glucose deprivation (OGD) were used to simulate HIE in vivo and in vitro. Primarily cultured astrocytes were used for investigating the expression of glial fibrillary acidic protein (GFAP), IL-1β, Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), and activation of the nucleotide-binding, oligomerization domain (NOD)-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome by using Western blot, q-PCR, and immunofluorescence. Brain atrophy, infarct size, and neurobehavioral disorders were evaluated by Nissl staining, 2,3,5-triphenyltetrazolium chloride monohydrate (TTC) staining and neurobehavioral tests (geotaxis reflex, cliff aversion reaction, and grip test) individually.

RESULTS

Astrocytes were overactivated after neonatal HI and OGD challenge. The number of activated astrocytes, the expression level of IL-1β, brain atrophy, and shrinking infarct size were all downregulated in TRPV1 KO mice. TRPV1 deficiency in astrocytes attenuated the expression of GFAP and IL-1β by reducing phosphorylation of JAK2 and STAT3. Meanwhile, IL-1β release was significantly reduced in TRPV1 deficiency astrocytes by inhibiting activation of NLRP3 inflammasome. Additionally, neonatal HI-induced neurobehavioral disorders were significantly improved in the TRPV1 KO mice.

CONCLUSIONS

TRPV1 promotes activation of astrocytes and release of astrocyte-derived IL-1β mainly via JAK2-STAT3 signaling and activation of the NLRP3 inflammasome. Our findings provide mechanistic insights into TRPV1-mediated brain damage and neurobehavioral disorders caused by neonatal HI and potentially identify astrocytic TRPV1 as a novel therapeutic target for treating HIE in the subacute stages (24 h).

Human Dental Pulp Stem Cells Grown in Neurogenic Media Differentiate Into Endothelial Cells and Promote Neovasculogenesis in the Mouse Brain

Dental pulp stem cells (DPSCs) have the capacity to give rise to cells with neuronal-like phenotypes, suggesting their use in brain cell therapies. In the present work, we wanted to address the phenotypic fate of adult genetically unmodified human DPSCs cultured in Neurocult^TM (Stem Cell Technologies), a cell culture medium without serum which can be alternatively supplemented for the expansion and/or differentiation of adult neural stem cells (NSCs). Our results show that non-genetically modified human adult DPSCs cultured with Neurocult NS-A proliferation supplement generated neurosphere-like dentospheres expressing the NSC markers Nestin and glial fibrillary acidic protein (GFAP), but also the vascular endothelial cell marker CD31. Remarkably, 1 month after intracranial graft into athymic nude mice, human CD31+/CD146+ and Nestin+ DPSC-derived cells were found tightly associated with both the endothelial and pericyte layers of brain vasculature, forming full blood vessels of human origin which showed an increased laminin staining. These results are the first demonstration that DPSC-derived cells contributed to the generation of neovasculature within brain tissue, and that Neurocult and other related serum-free cell culture media may constitute a fast and efficient way to obtain endothelial cells from human DPSCs.

Silencing of Annexin A1 suppressed the apoptosis and inflammatory response of preeclampsia rat trophoblasts

Preeclampsia (PE) is a disorder that is characterized by pregnancy-induced hypertension. It has been reported that Annexin A1 (ANXA1) is highly expressed in the plasma of women diagnosed with PE. Therefore, the present study aimed to examine the effect of ANXA1 on PE rats. The PE animal model was constructed in rats using Nω-nitro-L-arginine methyl ester (L-NAME), and the blood pressure and urine protein levels of rats were detected. The pathological features of placental tissue, and the levels of inflammatory factors and ANXA1 were respectively measured by hematoxylin-eosin staining, enzyme-linked immunosorbent assay and immunohistochemical assay. The activity of trophoblasts obtained from PE placental tissue was measured using immunofluorescence staining, while cell apoptosis was assessed using flow cytometry. The levels of associated factors were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The results identified that systolic blood pressure, diastolic blood pressure, mean arterial pressure and urine protein levels were enhanced, and that the contents of ANXA1, tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6 and IL-8 were increased in the L-NAME group. Transfection with small interfering RNA (siRNA)-ANXA1 markedly decreased the apoptosis and inflammatory response of trophoblasts. In addition, siRNA-ANXA1 upregulated the levels of B-cell lymphoma-2 (Bcl-2) and pro-caspase-3, and downregulated the levels of Bcl-2-associated X protein, cleaved-caspase-3, TNF-α, IL-1β, IL-6 and IL-8. Furthermore, siRNA-ANXA1 repressed the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3); however, siRNA-ANXA1 did not alter the levels of JAK2 and STAT3. Therefore, silencing of ANXA1 suppressed the apoptosis and inflammatory response of PE rat trophoblasts, and downregulated JAK2/STAK3 pathway.