TNF activates calcium-nuclear factor of activated T cells (NFAT)c1 signaling pathways in human macrophages

Combining TNF-α silencing with Wnt3a overexpression: a promising gene therapy for particle-induced periprosthetic osteolysis

Wear particle-induced periprosthetic osteolysis is a prevalent issue that frequently leads to the failure of joint replacements, necessitating the development of effective therapeutic strategies. In this study, we established a mouse model of prosthetic loosening and evaluated the therapeutic effects of targeting tumor necrosis factor-alpha (TNF-α) and wingless-type MMTV integration site family, member 3A (Wnt3a) on osteolysis. TNF-α knockdown reduced inflammation and osteoclast-related gene expression, while Wnt3a overexpression increased osteoblast-related gene expression. Notably, the combination of these interventions showed superior efficacy in inhibiting osteolysis compared to monotherapy. Biomechanical imaging and histological staining revealed that combined therapy enhanced bone density and minimized the gaps between the peri-prosthetic bone and the prosthesis, reducing fibrous connective tissue proliferation. Adeno-associated virus-mediated gene therapy was found to be safe, with no adverse effects observed in liver, brain, spleen, and kidney tissues. Our findings suggest that combining TNF-α silencing with Wnt3a overexpression may be a promising approach for treating particle-induced peri-implant osteolysis and warrants further clinical investigation.

CRISPR/Cas9-induced knockout of tumor necrosis factor-alpha-type I augments viral infection in zebrafish

Tumor necrosis factor-alpha (TNF-α) is a pleiotropic cytokine with critical roles in inflammation, cell survival, and defense. As a member of the TNF superfamily, it exerts its effects by binding to transmembrane receptors and triggering various downstream signaling pathways. Although TNF-α's involvement in antiviral responses in mammals is well-established, its role in teleost remains poorly understood. This study investigated the contribution of TNF-α1 to antiviral immunity in zebrafish using a tnf-α1(-/-) knockout (KO) line. We challenged both wild-type and tnf-α1(-/-) zebrafish with viral hemorrhagic septicemia virus (VHSV) at both embryonic and adult stages. Mortality was observed at 4 days post-infection (dpi) in tnf-α1-deficient adult fish challenged with 5 × 106 TCID50 (VHSV) and at 5 dpi in adult wild fish challenged with the same concentration. In addition, tnf-α1(-/-) KO adult fish reached the maximum mortality of 100 % at 20 dpi, whereas wild adult fish reached 54 % mortality at the same time point. This increased susceptibility to early mortality was associated with a higher viral burden and altered expression of key immune genes, including the pro-inflammatory cytokines il-6 and il-1β, the anti-inflammatory cytokine il-10, and interferon-related genes such as irf1 and ifn-γ. Our findings demonstrate the crucial role of TNF-α1 in antiviral defense mechanisms in zebrafish and provide valuable insights into the functional conservation of TNF-α signaling across vertebrate species. This knowledge may contribute to the development of strategies to combat viral diseases in fish.

Mesenchymal Stem Cells-Involved Strategies for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the joints and bone destruction. Because of systemic administration and poor targeting, traditional anti-rheumatic drugs have unsatisfactory treatment efficacy and strong side effects, including myelosuppression, liver or kidney function damage, and malignant tumors. Consequently, mesenchymal stem cells (MSCs)-involved therapy is proposed for RA therapy as a benefit of their immunosuppressive and tissue-repairing effects. This review summarizes the progress of MSCs-involved RA therapy through suppressing inflammation and promoting tissue regeneration and predicts their potential clinical application.

Parkinson's disease-derived α-synuclein assemblies combined with chronic-type inflammatory cues promote a neurotoxic microglial phenotype

Parkinson's disease (PD) is a common age-related neurodegenerative disorder characterized by the aggregation of α-Synuclein (αSYN) building up intraneuronal inclusions termed Lewy pathology. Mounting evidence suggests that neuron-released αSYN aggregates could be central to microglial activation, which in turn mounts and orchestrates neuroinflammatory processes potentially harmful to neurons. Therefore, understanding the mechanisms that drive microglial cell activation, polarization and function in PD might have important therapeutic implications. Here, using primary microglia, we investigated the inflammatory potential of pure αSYN fibrils derived from PD patients. We further explored and characterized microglial cell responses to a chronic-type inflammatory stimulation combining PD patient-derived αSYN fibrils (FPD), Tumor necrosis factor-α (TNFα) and prostaglandin E2 (PGE2) (TPFPD). We showed that FPD hold stronger inflammatory potency than pure αSYN fibrils generated de novo. When combined with TNFα and PGE2, FPD polarizes microglia toward a particular functional phenotype departing from FPD-treated cells and featuring lower inflammatory cytokine and higher glutamate release. Whereas metabolomic studies showed that TPFPD-exposed microglia were closely related to classically activated M1 proinflammatory cells, notably with similar tricarboxylic acid cycle disruption, transcriptomic analysis revealed that TPFPD-activated microglia assume a unique molecular signature highlighting upregulation of genes involved in glutathione and iron metabolisms. In particular, TPFPD-specific upregulation of Slc7a11 (which encodes the cystine-glutamate antiporter xCT) was consistent with the increased glutamate response and cytotoxic activity of these cells toward midbrain dopaminergic neurons in vitro. Together, these data further extend the structure-pathological relationship of αSYN fibrillar polymorphs to their innate immune properties and demonstrate that PD-derived αSYN fibrils, TNFα and PGE2 act in concert to drive microglial cell activation toward a specific and highly neurotoxic chronic-type inflammatory phenotype characterized by robust glutamate release and iron retention.

Innate immune memory in inflammatory arthritis

The concept of immunological memory was demonstrated in antiquity when protection against re-exposure to pathogens was observed during the plague of Athens. Immunological memory has been linked with the adaptive features of T and B cells; however, in the past decade, evidence has demonstrated that innate immune cells can exhibit memory, a phenomenon called 'innate immune memory' or 'trained immunity'. Innate immune memory is currently being defined and is transforming our understanding of chronic inflammation and autoimmunity. In this Review, we provide an up-to-date overview of the memory-like features of innate immune cells in inflammatory arthritis and the crosstalk between chronic inflammatory milieu and cell reprogramming. Aberrant pro-inflammatory signalling, including cytokines, regulates the metabolic and epigenetic reprogramming of haematopoietic progenitors, leading to exacerbated inflammatory responses and osteoclast differentiation, in turn leading to bone destruction. Moreover, imprinted memory on mature cells including terminally differentiated osteoclasts alters responsiveness to therapies and modifies disease outcomes, commonly manifested by persistent inflammatory flares and relapse following medication withdrawal.

NFAT signaling dysregulation in cancer: Emerging roles in cancer stem cells

The nuclear factor of activated T cells (NFAT) was first identified as a transcriptional regulator of activated T cells. The NFAT family is involved in the development of tumors. Furthermore, recent evidence reveals that NFAT proteins regulate the development of inflammatory and immune responses. New discoveries have also been made about the mechanisms by which NFAT regulates cancer progression through cancer stem cells (CSC). Here, we discuss the role of the NFAT family in the immune system and various cancer types.

Periodontal Fibroblasts-Macrophage Crosstalk in External Inflammatory Root Resorption

INTRODUCTION

This study aimed to understand the influence of periodontal fibroblasts (PDLFs) on clastic differentiation of macrophages (Mφ) in different resorptive environments.

METHODS

PDLF-Mφ direct coculture (juxtacrine) was seeded on dentin, cementum, and polystyrene with/without lipopolysaccharide, macrophage colony-stimulating factor, and receptor activator of nuclear factor kappa beta ligand for 7 and 14 days and stained for tartrate-resistant acid phosphatase (TRAP) activity. PDLF-Mφ cocultured on polystyrene were immunostained for CD80, CD206, NFATc1, STAT6, and periostin, and cell culture supernatants were assessed for cytokines on days 2 and 7. Mφ grown in conditioned media of PDLFs (paracrine) and Mφ monoculture were used as controls. Data was analyzed using Student t test and one-way analysis of variance with the Tukey multiple comparisons test (P < .05).

RESULTS

PDLF-Mφ coculture showed a higher number of TRAP-positive multinucleated cells than Mφ monoculture on dentin and polystyrene. No TRAP-positive multinucleated cells were observed in paracrine and cementum. The expression of CD80 and CD206 in PDLF-Mφ was similar at day 2, whereas CD206 was greater than CD80 at day 7. The expression of STAT6 was greater than NFATc1 at both days 2 and 7 (P < .05). Periostin expression in the presence of the lipopolysaccharide, macrophage colony-stimulating factor, and receptor activator of nuclear factor kappa beta ligand combination was down-regulated in PDLF monoculture, whereas it was up-regulated in PDLF-Mφ coculture. The cytokine profile of PDLF-Mφ on day 2 was predominated by interleukin (IL)-1β, tumor necrosis factor alpha, and MMP9 and MMP2 on day 7. IL-6 and IL-8 showed steady expression at both days 2 and 7.

CONCLUSIONS

The study highlights the juxtacrine effect of PDLFs on the clastic differentiation of Mφ with a difference in clastic activity between dentin and cementum. The study also emphasizes the temporal effect of tumor necrosis factor alpha, MMP2, MMP9, and IL-1β on intercellular crosstalk in resorptive environments.

Mechanistic insight of interleukin-9 induced osteoclastogenesis

Interleukin (IL)-9 is an emerging player in the pathogenesis of various chronic inflammatory diseases including bone disorders like rheumatoid arthritis (RA) and psoriatic arthritis. Recently, IL-9 was shown to enhance the osteoclast formation and their function in RA. However, the mechanisms by which IL-9 influences osteoclastogenesis are not known. Therefore, in this study we aimed to unravel the direct and indirect ways by which IL-9 can influence osteoclast formation. We used mouse bone marrow precursor cells for checking the effect of IL-9 on osteoclast differentiation and its function. Next, IL-9 induced signalling pathway were checked in the process of osteoclastogenesis. T cells play an important role in enhancing osteoclastogenesis in inflammatory conditions. We used splenic T cells to understand the impact of IL-9 on the functions of T effector (Teff) and regulatory T (Treg) cells. Furthermore, the effect of IL-9 mediated modulation of the T cell response on osteoclasts was checked using a coculture model of T cells with osteoclast precursors. We showed that IL-9 enhanced osteoclast formation and its function. We found that IL-9 activates STAT3, P38 MAPK, ERK1/2, NFκB and we hypothesize that it mediates the effect on osteoclastogenesis by accelerating mitochondrial biogenesis. Additionally, IL-9 was observed to facilitate the functions of pro-osteoclastogenic IL-17 producing T cells, but inhibits the function of anti-osteoclastogenic Treg cells. Our observations suggest that IL-9 can influence osteoclastogenesis directly by modulating the signalling cascade in the precursor cells; indirectly by enhancing IL-17 producing T cells and by reducing the functions of Treg cells.

MicroRNAs-mediated regulation pathways in rheumatic diseases

Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are two common rheumatic disorders marked by persistent inflammatory joint disease. Patients with RA have osteodestructive symptoms, but those with AS have osteoproliferative manifestations. Ligaments, joints, tendons, bones, and muscles are all affected by rheumatic disorders. In recent years, many epigenetic factors contributing to the pathogenesis of rheumatoid disorders have been studied. MicroRNAs (miRNAs) are small, non-coding RNA molecules implicated as potential therapeutic targets or biomarkers in rheumatic diseases. MiRNAs play a critical role in the modulation of bone homeostasis and joint remodeling by controlling fibroblast-like synoviocytes (FLSs), chondrocytes, and osteocytes. Several miRNAs have been shown to be dysregulated in rheumatic diseases, including miR-10a, 16, 17, 18a, 19, 20a, 21, 27a, 29a, 34a, 103a, 125b, 132, 137, 143, 145, 146a, 155, 192, 203, 221, 222, 301a, 346, and 548a.The major molecular pathways governed by miRNAs in these cells are Wnt, bone-morphogenic protein (BMP), nuclear factor (NF)-κB, receptor activator of NF-κB (RANK)-RANK ligand (RANKL), and macrophage colony-stimulating factor (M-CSF) receptor pathway. This review aimed to provide an overview of the most important signaling pathways controlled by miRNAs in rheumatic diseases.

A Review of Plant Selenium-Enriched Proteins/Peptides: Extraction, Detection, Bioavailability, and Effects of Processing

As an essential trace element in the human body, selenium (Se) has various physiological activities, such as antioxidant and anticancer activity. Selenium-enriched proteins/peptides (SePs/SePPs) are the primary forms of Se in plants and animals, and they are the vital carriers of its physiological activities. On the basis of current research, this review systematically describes the extraction methods (aqueous, alkaline, enzymatic, auxiliary, etc.) and detection methods (HPLC-MS/MS, GC-ICP-MS, etc.) for SePs/SePPs in plants. Their bioavailability and bioactivity, and the effect of processing are also included. Our review provides a comprehensive understanding and theoretical guidance for the utilization of selenium-enriched proteins/peptides.

RANKL-responsive epigenetic mechanism reprograms macrophages into bone-resorbing osteoclasts

Monocyte/macrophage lineage cells are highly plastic and can differentiate into various cells under different environmental stimuli. Bone-resorbing osteoclasts are derived from the monocyte/macrophage lineage in response to receptor activator of NF-κB ligand (RANKL). However, the epigenetic signature contributing to the fate commitment of monocyte/macrophage lineage differentiation into human osteoclasts is largely unknown. In this study, we identified RANKL-responsive human osteoclast-specific superenhancers (SEs) and SE-associated enhancer RNAs (SE-eRNAs) by integrating data obtained from ChIP-seq, ATAC-seq, nuclear RNA-seq and PRO-seq analyses. RANKL induced the formation of 200 SEs, which are large clusters of enhancers, while suppressing 148 SEs in macrophages. RANKL-responsive SEs were strongly correlated with genes in the osteoclastogenic program and were selectively increased in human osteoclasts but marginally presented in osteoblasts, CD4+ T cells, and CD34+ cells. In addition to the major transcription factors identified in osteoclasts, we found that BATF binding motifs were highly enriched in RANKL-responsive SEs. The depletion of BATF1/3 inhibited RANKL-induced osteoclast differentiation. Furthermore, we found increased chromatin accessibility in SE regions, where RNA polymerase II was significantly recruited to induce the extragenic transcription of SE-eRNAs, in human osteoclasts. Knocking down SE-eRNAs in the vicinity of the NFATc1 gene diminished the expression of NFATc1, a major regulator of osteoclasts, and osteoclast differentiation. Inhibiting BET proteins suppressed the formation of some RANKL-responsive SEs and NFATc1-associated SEs, and the expression of SE-eRNA:NFATc1. Moreover, SE-eRNA:NFATc1 was highly expressed in the synovial macrophages of rheumatoid arthritis patients exhibiting high-osteoclastogenic potential. Our genome-wide analysis revealed RANKL-inducible SEs and SE-eRNAs as osteoclast-specific signatures, which may contribute to the development of osteoclast-specific therapeutic interventions.

TNFα Enhances Calcium Influx by Interacting with AMPA Receptors in the Spinal Dorsal Horn Neurons

Tumor necrosis factor alpha (TNFα) is a proinflammatory cytokine and has been implicated in pain regulation. Neuronal activity in the spinal dorsal horn contributes to nociceptive transmission. However, it is not fully understood how TNFα affects the activity of spinal dorsal horn neurons. In the present study, we used calcium imaging to characterize the mechanism by which TNFα regulates calcium influx in the cultured spinal dorsal horn neurons. We observed that TNFα incubation caused an increase in fluorescent intensity of Fura-2, a specific intracellular calcium indicator, in the cultured spinal dorsal horn neurons, and such effect was significantly inhibited by co-incubation with R7050, a selective TNFα receptor antagonist, which suggests that TNFα can enhance calcium influx and increase neuronal activity via activating TNFα receptors in the spinal dorsal horn. Using double immunofluorescence staining, we showed that TNFα receptors were co-expressed with a-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor subunit GluA1 in the spinal dorsal horn neurons. We further observed that treatment with 1-naphthyl acetyl spermine (NASPM), a specific calcium-permeable AMPA receptor blocker, completely blocked the effect of TNFα incubation on calcium influx in the cultured neurons. Moreover, lipopolysaccharide (LPS)-induced calcium influx was inhibited by co-incubation with R7050. Together, our results suggest that TNFα in the spinal dorsal horn can increase calcium-indicated neuronal activity through the interaction between its receptor and calcium-permeable AMPA receptors.

Dendritic cell-specific transmembrane protein is required for synovitis and bone resorption in inflammatory arthritis

Objective

Dendritic Cell-Specific Transmembrane Protein (DC-STAMP) is essential for the formation of fully functional multinucleated osteoclasts. DC-STAMP deficient mice, under physiological conditions, exhibit osteopetrosis and develop systemic autoimmunity with age. However, the function of DC-STAMP in inflammation is currently unknown. We examined whether genetic ablation of DC-STAMP attenuates synovitis and bone erosion in TNF transgenic (Tg) and K/BxN serum-induced murine rheumatoid arthritis.

Methods

We evaluated arthritis onset in Tg(hTNF) mice lacking DC-STAMP and 50:50 chimeric mice by visual examination, measurement of ankle width, micro-CT-scan analysis and quantitation of the area occupied by osteoclasts in bone sections. To further investigate the cellular and molecular events modulated by DC-STAMP, we measured serum cytokines, determined changes in cytokine mRNA expression by monocytes activated with IL4 or LPS/IFNγ and enumerated immune cells in inflamed mouse joints.

Results

Synovitis, bone loss and matrix destruction are markedly reduced in Dcstamp-/-;Tg(hTNF) mice. These mice had significantly lower CCL2 and murine TNF serum levels and exhibited impaired monocyte joint migration compared to Tg(hTNF) mice. The reduced arthritic severity in Dcstamp deficient mice was associated with compromised monocyte chemotaxis, cytokine production, and M2 polarization.

Conclusion

These results reveal that DC-STAMP modulates both bone resorption and inflammation and may serve as an activity biomarker and therapeutic target in inflammatory arthritis and metabolic bone disease.

Boswellic acid protects against Bisphenol-A and gamma radiation induced hepatic steatosis and cardiac remodelling in rats: role of hepatic PPAR-α/P38 and cardiac Calcineurin-A/NFATc1/P38 pathways

Bisphenol-A (BPA) and gamma-radiation are two risky environmental pollutants that human beings are exposed to in everyday life and consequently they threaten human health via inducing oxidative stress, inflammation, and eventually tissue damage. This study aims at appraising the protective effect of Boswellic Acid (BA) (250 mg/kg/day, orally) administration on BPA (150 mg/kg/day, i.p) and γ-irradiation (IR) (3 Gy/week for 4 weeks up to cumulative dose of 12 Gy/experimental course) for 4 weeks-induced damage to liver and heart tissues of rats. The present results indicated a significant improvement against damage induced by BPA and IR revealed in biochemical investigations (hepatic PPAR-α/P38 and cardiac ET-1/Calcineurin-A/NFATc1/P38) and histopathological examination of liver and heart. It could be concluded that BA possesses a protective effect against these two deleterious environmental pollutants which attracted major global concerns due to their serious toxicological impact on human health.

The role of NFATc1/c-myc/PKM2/IL-10 axis in activating cervical cancer tumor-associated M2 macrophage polarization to promote cervical cancer progression

Nuclear factor of activated T cells 1 (NFATc1) is mainly expressed in tumor microenvironment, especially in macrophages. However, whether NFATc1 is involved in the polarization of tumor associated macrophages (TAMs) and tumor progression in cervical cancer (CC) remains unclear. Immunofluorescence staining was used to detect the expression of CD68 and NFATc1 in CC tissues or adjacent normal tissues of patients. RT-qPCR, flow cytometry, ELISA, and inhibitors treatment were used to observe the effect of NFATc1 on TAMs polarization. Clonal formation, scratch, and transwell assays were used to examine the effects of NFATc1-transfected macrophages or NFATc1-transfected TAM on tumor proliferation, migration, and invasion. Further, a xenograft model was established to confirm the roles of NFATc1⁺ TAM in CC tumorigenesis. NFATc1⁺CD68⁺/CD68⁺ TAMs ratio was significantly increased in CC tissues compared with the normal tissue, and NFATc1⁺ TAM showed an M2-like TAM subtype. NFATc1 induced macrophages to secrete IL-10, which further induced M2 polarization of macrophages. Mechanically, the c-myc-PKM2 pathway mediated the expression of IL-10 in NFATc1-induced macrophages. Functionally, NFATc1 induced M2 macrophages promoted the proliferation, migration, and invasion of CC cells, and the knockout of NFATc1 in TAMs significantly inhibited the tumor-promoting function of TAMs. Further, the tumorigenesis test in nude mice confirmed that NFATc1⁺ TAM promoted the tumorigenicity of CC cells in vivo. In conclusion, NFATc1 mediated IL-10 secretion by regulating the c-myc/PKM2 pathway, thereby induce M2 polarization of TAMs and promote the progression of CC.

The dominant-negative mitochondrial calcium uniporter subunit MCUb drives macrophage polarization during skeletal muscle regeneration

[Figure: see text].

Characterization and Function of Tumor Necrosis Factor and Interleukin-6-Induced Osteoclasts in Rheumatoid Arthritis

Objective

We have previously reported that stimulation of mouse bone marrow–derived macrophages with tumor necrosis factor (TNF) and interleukin‐6 (IL‐6) induces differentiation of osteoclast‐like cells. We undertook this study to clarify the characterization and function of human TNF and IL‐6–induced osteoclasts using peripheral blood collected from patients with rheumatoid arthritis (RA) and healthy donors.

Methods

Peripheral blood monocytes were cultured with a combination of TNF and IL‐6, TNF alone, IL‐6 alone, or with RANKL, and their bone resorption ability was evaluated. Expression levels of NFATc1, proinflammatory cytokines, and matrix metalloproteinase 3 were analyzed. The effects of NFAT inhibitor and JAK inhibitor were examined. Furthermore, the relationship between the number of TNF and IL‐6–induced osteoclasts or RANKL‐induced osteoclasts differentiated from peripheral blood mononuclear cells (PBMCs) in patients with RA and the modified total Sharp score (mTSS) or whole‐body bone mineral density (BMD) was examined.

Results

Peripheral blood monocytes stimulated with a TNF and IL‐6–induced osteoclasts were shown to demonstrate the ability to absorb bone matrix. Cell differentiation was not inhibited by the addition of osteoprotegerin. Stimulation with a combination of TNF and IL‐6 promoted NFATc1 expression, whereas the NFAT and JAK inhibitors prevented TNF and IL‐6–induced osteoclast formation. Expression levels of IL1β, TNF, IL12p40, and MMP3 were significantly increased in TNF and IL‐6–induced osteoclasts, but not in RANKL‐induced osteoclasts. The number of TNF and IL‐6–induced osteoclasts differentiated from PBMCs in patients with RA positively correlated with the mTSS, whereas RANKL‐induced osteoclast numbers negatively correlated with the whole‐body BMD of the same patients.

Conclusion

Our results demonstrate that TNF and IL‐6–induced osteoclasts may contribute to the pathology of inflammatory arthritis associated with joint destruction, such as RA.

Inositol 1,4,5-trisphosphate 3-kinase B promotes Ca2+ mobilization and the inflammatory activity of dendritic cells

Innate immune responses to Gram-negative bacteria depend on the recognition of lipopolysaccharide (LPS) by a receptor complex that includes CD14 and TLR4. In dendritic cells (DCs), CD14 enhances the activation not only of TLR4 but also that of the NFAT family of transcription factors, which suppresses cell survival and promotes the production of inflammatory mediators. NFAT activation requires Ca²⁺ mobilization. In DCs, Ca²⁺ mobilization in response to LPS depends on phospholipase C γ2 (PLCγ2), which produces inositol 1,4,5-trisphosphate (IP₃). Here, we showed that the IP₃ receptor 3 (IP₃R3) and ITPKB, a kinase that converts IP₃ to inositol 1,3,4,5-tetrakisphosphate (IP₄), were both necessary for Ca²⁺ mobilization and NFAT activation in mouse and human DCs. A pool of IP₃R3 was located on the plasma membrane of DCs, where it colocalized with CD14 and ITPKB. Upon LPS binding to CD14, ITPKB was required for Ca²⁺ mobilization through plasma membrane-localized IP₃R3 and for NFAT nuclear translocation. Pharmacological inhibition of ITPKB in mice reduced both LPS-induced tissue swelling and the severity of inflammatory arthritis to a similar extent as that induced by the inhibition of NFAT using nanoparticles that delivered an NFAT-inhibiting peptide specifically to phagocytic cells. Our results suggest that ITPKB may represent a promising target for anti-inflammatory therapies that aim to inhibit specific DC functions.

Navigating the diverse immune landscapes of psoriatic arthritis

The goal of remission in psoriatic arthritis (PsA) has remained elusive despite the influx of a range of new therapies over the last 20 years. In contrast, therapeutic responses to agents that inhibit IL-23 or IL-17 have demonstrated impressive efficacy in psoriasis. In part, the divergent responses in these two disorders are likely related to the heterogeneity of tissue involvement in PsA and the interplay of multiple different cell populations and molecular pathways. In this narrative review, we will examine the plasticity of the immune response in PsA from the perspective of the Th17 cell and monocyte and discuss recent findings regarding the importance of CD8+ T resident cells in disease pathogenesis. We will then examine the effects of cytokines on epithelial cell and stromal populations and finally discuss new data regarding immune cell and tissue resident cell cross-talk in entheses and bone. Lastly, the potential therapeutic targets that have emerged from these investigations will be discussed.

A data-driven computational model enables integrative and mechanistic characterization of dynamic macrophage polarization

Macrophages are highly plastic immune cells that dynamically integrate microenvironmental signals to shape their own functional phenotypes, a process known as polarization. Here we develop a large-scale mechanistic computational model that for the first time enables a systems-level characterization, from quantitative, temporal, dose-dependent, and single-cell perspectives, of macrophage polarization driven by a complex multi-pathway signaling network. The model was extensively calibrated and validated against literature and focused on in-house experimental data. Using the model, we generated dynamic phenotype maps in response to numerous combinations of polarizing signals; we also probed into an in silico population of model-based macrophages to examine the impact of polarization continuum at the single-cell level. Additionally, we analyzed the model under an in vitro condition of peripheral arterial disease to evaluate strategies that can potentially induce therapeutic macrophage repolarization. Our model is a key step toward the future development of a network-centric, comprehensive "virtual macrophage" simulation platform.

Role of Synovial Exosomes in Osteoclast Differentiation in Inflammatory Arthritis

This study aimed to investigate the characteristics of exosomes isolated from synovial fluid and their role in osteoclast differentiation in different types of inflammatory arthritis. Exosomes isolated from synovial fluid of rheumatoid arthritis (RA), ankylosing spondylitis (AS), gout, and osteoarthritis (OA) patients were co-incubated with CD14+ mononuclear cells from healthy donors without macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-B ligand (RANKL). Osteoclast differentiation was evaluated via tartrate-resistant acid phosphatase (TRAP) staining and activity and F-actin ring formation. RANKL expression on synovial exosomes was assessed using flow cytometry and an enzyme-linked immunosorbent assay (ELISA). Synovial exosomes were the lowest in OA patients; these induced osteoclastogenesis in the absence of M-CSF and RANKL. Osteoclastogenesis was significantly higher with more exosomes in RA (p = 0.030) than in OA patients, but not in AS or gout patients. On treating macrophages with a specified number of synovial exosomes from RA/AS patients, exosomes induced greater osteoclastogenesis in RA than in AS patients. Synovial exosomal RANKL levels were significantly higher in RA (p = 0.035) than in AS patients. Synovial exosome numbers vary with the type of inflammatory arthritis. Synovial exosomes from RA patients may bear the disease-specific “synovial signature of osteoclastogenesis.”

Exosomal lncRNAs NONMMUT000375.2 and NONMMUT071578.2 derived from titanium particle treated RAW264.7 cells regulate osteogenic differentiation of MC3T3-E1 cells

Periprosthetic osteolysis and the subsequent aseptic loosening can lead to the failure of joint replacement. Wear particles are well known to be the initiative cause inducing osteolysis through enhancing osteoclast-mediated bone resorption and reducing osteogenic differentiation. The purpose of this study was to investigate the effects of osteoclast-secreted exosomal long noncoding RNAs (lncRNAs) on osteogenesis in the process of particle-induced osteolysis. RAW264.7 cells were treated by titanium particles (TI). The inflammatory cytokines were increased, and expression of Receptor Activator of Nuclear Factor-κB and Nuclear factor of activated T cells c1 were also increased, indicating osteoclast differentiation occurred. The purified exosomes from RAW264.7 cells induced with TI inhibited osteogenic differentiation of MC3T3-E1 cells. RNA sequencing generated lncRNAs expression profiles (458 up-regulated and 1641 down-regulated) of the exosomes derived from RAW264.7 cells treated with TI. Based on the results of gene ontology/Kyoto Encyclopedia of Genes and Genomes analysis and quantitative real time polymerase chain reaction validation, we confirmed two candidate lncRNAs, NONMMUT000375.2 and NONMMUT071578.2. The regulation network presented that some vital genes involved in osteoclast differentiation, such as Bcl2, Wnt11, TGF-β, and Pdk1, were under the regulation of NONMMUT000375.2 and NONMMUT071578.2. Taken together, exosomes derived from TI treated RAW264.7 cells inhibit the osteogenic activity of MC3T3-E1 cells. Exosomal lncRNAs, NONMMUT000375.2 and NONMMUT071578.2 may potentially play their roles in promoting osteoclast differentiation and suppressing osteogenesis, which aggravates the osteoclastogenesis/osteogenesis imbalance.

FK506 induces lung lymphatic endothelial cell senescence and downregulates LYVE-1 expression, with associated decreased hyaluronan uptake

BACKGROUND

Therapeutic lymphangiogenesis in an orthotopic lung transplant model has been shown to improve acute allograft rejection that is mediated at least in part through hyaluronan drainage. Lymphatic vessel endothelial hyaluronan receptor (LYVE-1) expressed on the surface of lymphatic endothelial cells plays important roles in hyaluronan uptake. The impact of current immunosuppressive therapies on lung lymphatic endothelial cells is largely unknown. We tested the hypothesis that FK506, the most commonly used immunosuppressant after lung transplantation, induces lung lymphatic endothelial cell dysfunction.

METHODS

Lung lymphatic endothelial cells were cultured in vitro and treated with FK506. Telomerase activity was measured using the TRAP assay. Protein expression of LYVE-1 and senescence markers p21 and β-galactosidase was assessed with western blotting. Matrigel tubulation assay were used to investigate the effects of FK506 on TNF-α-induced lymphangiogenesis. Dual luciferase reporter assay was used to confirm NFAT-dependent transcriptional regulation of LYVE-1. Flow cytometry was used to examine the effects of FK506 on LYVE-1 in precision-cut-lung-slices ex vivo and on hyaluronan uptake in vitro.

RESULTS

In vitro, FK506 downregulated telomerase reverse transcriptase expression, resulting in decreased telomerase activity and subsequent induction of p21 expression and cell senescence. Treatment with FK506 decreased LYVE-1 mRNA and protein levels and resulted in decreased LEC HA uptake. Similar result showing reduction of LYVE-1 expression when treated with FK506 was observed ex vivo. We identified a putative NFAT binding site on the LYVE-1 promoter and cloned this region of the promoter in a luciferase-based reporter construct. We showed that this NFAT binding site regulates LYVE-1 transcription, and mutation of this binding site blunted FK506-dependent downregulation of LYVE-1 promoter-dependent transcription. Finally, FK506-treated lymphatic endothelial cells show a blunted response to TNF-α-mediated lymphangiogenesis.

CONCLUSION

FK506 alters lymphatic endothelial cell molecular characteristics and causes lymphatic endothelial cell dysfunction in vitro and ex vivo. These effects of FK506 on lymphatic endothelial cell may impair the ability of the transplanted lung to drain hyaluronan macromolecules in vivo. The implications of our findings on the long-term health of lung allografts merit more investigation.

JAK-Inhibitors for the Treatment of Rheumatoid Arthritis: A Focus on the Present and an Outlook on the Future

Janus kinase inhibitors (JAKi) belong to a new class of oral targeted disease-modifying drugs which have recently revolutionized the therapeutic panorama of rheumatoid arthritis (RA) and other immune-mediated diseases, placing alongside or even replacing conventional and biological drugs. JAKi are characterized by a novel mechanism of action, consisting of the intracellular interruption of the JAK-STAT pathway crucially involved in the immune response. The aim of this narrative review is to globally report the most relevant pharmacological features and clinical outcomes of the developed and incoming JAKi for RA, based on the available preclinical and clinical evidence. A total of 219 papers, including narrative and systematic reviews, randomized controlled trials (RCTs), observational studies, case reports, guidelines, and drug factsheets, were selected. The efficacy and safety profile of both the first generation JAKi (baricitinib and tofacitinib) and the second generation JAKi (upadacitinib, filgotinib, peficitinib, decernotinib and itacitinib) were compared and discussed. Results from RCTs and real-life data are encouraging and outline a rapid onset of the pharmacologic effects, which are maintained during the time. Their efficacy and safety profile are comparable or superior to those of biologic agents and JAKi proved to be efficacious when given as monotherapy. Finally, the manufacturing of JAKi is relatively easier and cheaper than that of biologics, thus increasing the number of compounds being formulated and tested for clinical use.

Regulatory network mediated by RBP-J/NFATc1-miR182 controls inflammatory bone resorption

Bone resorption is a severe consequence of inflammatory diseases associated with osteolysis, such as rheumatoid arthritis (RA), often leading to disability in patients. In physiological conditions, the differentiation of bone-resorbing osteoclasts is delicately regulated by the balance between osteoclastogenic and anti-osteoclastogenic mechanisms. Inflammation has complex impact on osteoclastogenesis and bone destruction, and the underlying mechanisms of which, especially feedback inhibition, are underexplored. Here, we identify a novel regulatory network mediated by RBP-J/NFATc1-miR182 in TNF-induced osteoclastogenesis and inflammatory bone resorption. This network includes negative regulator RBP-J and positive regulators, NFATc1 and miR182, of osteoclast differentiation. In this network, miR182 is a direct target of both RBP-J and NFATc1. RBP-J represses, while NFATc1 activates miR182 expression through binding to specific open chromatin regions in the miR182 promoter. Inhibition of miR182 by RBP-J servers as a critical mechanism that limits TNF-induced osteoclast differentiation and inflammatory bone resorption. Inflammation, such as that which occurs in RA, shifts the expression levels of the components in this network mediated by RBP-J/NFATc1-miR182-FoxO3/PKR (previously identified miR182 targets) towards more osteoclastogenic, rather than healthy conditions. Treatment with TNF inhibitors in RA patients reverses the expression changes of the network components and osteoclastogenic potential. Thus, this network controls the balance between activating and repressive signals that determine the extent of osteoclastogenesis. These findings collectively highlight the biological significance and translational implication of this newly identified intrinsic regulatory network in inflammatory osteoclastogenesis and osteolysis.

Intrinsic Restriction of TNF-Mediated Inflammatory Osteoclastogenesis and Bone Resorption

TNF (Tumor necrosis factor) is a pleiotropic cytokine that plays an important role in immunity and inflammatory bone destruction. Homeostatic osteoclastogenesis is effectively induced by RANKL (Receptor activator of nuclear factor kappa-B ligand). In contrast, TNF often acts on cell types other than osteoclasts, or synergically with RANKL to indirectly promote osteoclastogenesis and bone resorption. TNF and RANKL are members of the TNF superfamily. However, the direct osteoclastogenic capacity of TNF is much weaker than that of RANKL. Recent studies have uncovered key intrinsic mechanisms by which TNF acts on osteoclast precursors to restrain osteoclastogenesis, including the mechanisms mediated by RBP-J signaling, RBP-J and ITAM (Immunoreceptor tyrosine-based activation motif) crosstalk, RBP-J mediated regulatory network, NF-κB p100, IRF8, and Def6. Some of these mechanisms, such as RBP-J and its mediated regulatory network, uniquely and predominantly limit osteoclastogenesis mediated by TNF but not by RANKL. As a consequence, targeting RBP-J activities suppresses inflammatory bone destruction but does not significantly impact normal bone remodeling or inflammation. Hence, discovery of these intrinsic inhibitory mechanisms addresses why TNF has a weak osteoclastogenic potential, explains a significant difference between RANKL and TNF signaling, and provides potentially new or complementary therapeutic strategies to selectively treat inflammatory bone resorption, without undesirable effects on normal bone remodeling or immune response in disease settings.

Does TNF Promote or Restrain Osteoclastogenesis and Inflammatory Bone Resorption?

Chronic inflammation is one of the most evident and common pathological conditions leading to deregulated osteoclastogenesis and bone remodeling. Tumor necrosis factor (TNF) as a pleiotropic cytokine plays a key role, not only in inflammation, but also in bone erosion in diseases associated with bone loss. TNF can stimulate the proliferation of osteoclast precursors and, in most conditions, act together with other cytokines and growth factors such as receptor activator of nuclear factor (NF)-[kappa]B ligand (RANKL), interleukin-6, and transforming growth factor beta to synergistically promote osteoclast formation and bone resorption in vivo. A longstanding enigma in the field is why TNF alone is not able to induce osteoclast differentiation as effectively as the same superfamily member RANKL, a physiological master osteoclastogenic cytokine. Recent studies have highlighted several lines of evidence showing the intrinsic mechanisms through RBP-J, NF-[kappa]B p100/TNF receptor-associated factor 3, or interferon regulatory factor-8 that restrain TNF-induced osteoclast differentiation and bone resorption. These feedback inhibitory mechanisms driven by TNF shed light into the current paradigm of osteoclastogenesis and would provide novel therapeutic implications on controlling inflammatory bone resorption.

SRC-3/AIB-1 may Enhance Hepatic NFATC1 Transcription and Mediate Inflammation in a Tissue-Specific Manner in Morbid Obesity

BACKGROUND

Obesity is a global epidemic which is associated with several cardiometabolic comorbidities and is characterized by chronic, low grade systemic inflammation. Numerous biomarkers have been implicated in the pathophysiology of the disease, including transcription factors and coregulators. Steroid Receptor Coactivator (SRC)-family represent the master regulators of metabolic pathways and their dysregulation is strongly associated with numerous metabolic disorders.

METHODS

50 morbidly obese patients participated in the present study. Biopsies were collected from visceral adipose tissue, subcutaneous adipose tissue, skeletal muscle, extra-myocellular adipose tissue and liver. We evaluated the differential protein expression of NFATc1, SRC-2/TIF-2, SRC-3/AIB-1 and inflammatory biomarkers CD68 and CD3 by immunohistochemistry. The current study was designed to determine any correlations between the transcription factor NFATc1 and the SRC coregulators, as well as any associations with the inflammatory biomarkers.

RESULTS

We identified SRC-3 as a hepatic NFATc1 coactivator and we demonstrated its possible role in energy homeostasis and lipid metabolism. Moreover, we revealed a complex and extensive intraand inter-tissue network among the three main investigated proteins and the inflammatory biomarkers, suggesting their potential participation in the obesity-induced inflammatory cascade.

CONCLUSION

Steroid receptor coactivators are critical regulators of human metabolism with pleiotropic and tissue-specific actions. We believe that our study will contribute to the better understanding of the complex multi-tissue interactions that are disrupted in obesity and can therefore lead to numerous cardiometabolic diseases. Further on, our present findings suggest that SRC-3/AIB-1 could constitute possible future drug targets.

Role of the Ca2+-Calcineurin-Nuclear Factor of Activated T cell Pathway in Mitofusin-2-Mediated Immune Function of Jurkat Cells

Background:

Mitofusin-2 (MFN2), a well-known mitochondrial fusion protein, has been shown to participate in innate immunity, but its role in mediating adaptive immunity remains poorly characterized. In this study, we explored the potential role of MFN2 in mediating the immune function of T lymphocytes.

Methods:

We manipulated MFN2 gene expression in Jurkat cells via lentiviral transduction of MFN2 small interfering RNA (siRNA) or full-length MFN2. After transduction, the immune response and its underlying mechanism were determined in Jurkat cells. One-way analysis of variance and Student's t-test were performed to determine the statistical significance between the groups.

Results:

Overexpression of MFN2 enhanced the immune response of T lymphocytes by upregulating Ca²⁺ (359.280 ± 10.130 vs. 266.940 ± 10.170, P = 0.000), calcineurin (0.513 ± 0.014 vs. 0.403 ± 0.020 nmol/L, P = 0.024), and nuclear factor of activated T cells (NFATs) activation (1.040 ± 0.086 vs. 0.700 ± 0.115, P = 0.005), whereas depletion of MFN2 impaired the immune function of T lymphocytes by downregulating Ca²⁺ (141.140 ± 14.670 vs. 267.060 ± 9.230, P = 0.000), calcineurin (0.054 ± 0.030 nmol/L vs. 0.404 ± 0.063 nmol/L, P = 0.000), and NFAT activation (0.500 ± 0.025 vs. 0.720 ± 0.061, P = 0.012). Furthermore, upregulated calcineurin partially reversed the negative effects of MFN2 siRNA on T cell-mediated immunity evidenced by elevations in T cell proliferation (1.120 ± 0.048 vs. 0.580 ± 0.078, P = 0.040), interleukin-2 (IL-2) production (473.300 ± 24.100 vs. 175.330 ± 12.900 pg/ml, P = 0.000), and the interferon-γ/IL-4 ratio (3.080 ± 0.156 vs. 0.953 ± 0.093, P = 0.000). Meanwhile, calcineurin activity inhibitor depleted the positive effects of overexpressed MFN2 on T cells function.

Conclusions:

Our findings suggest that MFN2 may regulate T cell immune functions primarily through the Ca²⁺-calcineurin-NFAT pathway. MFN2 may represent a potential therapeutic target for T cell immune dysfunction-related diseases.

High-performance gene expression and knockout tools using sleeping beauty transposon system

Background

Similar to retro-/lenti- virus system, DNA transposons are useful tools for stable expression of exogenous genes in mammalian cells. Sleeping Beauty (SB) transposon has adopted for integrating genes into host genomes in recent studies. However, SB-derived vector system for proteins purifying/tracking and gene knockout are still not available.

Results

In this study, we generated a series of vectors (termed as pSB vectors) containing Sleeping Beauty IRDR-L/R that can be transposed by SB transposase. Gateway cassette was combined to the pSB vectors to facilitate the cloning. Vectors with various tags, Flag, Myc, HA, V5 and SFB, were generated for multiple options. Moreover, we incorporated the CRISPR-Cas9 cassette into the pSB plasmids for gene knockout. Indeed, using one of these vectors (pSB-SFB-GFP), we performed Tandem Affinity Purification and identified that NFATc1 is a novel binding partner of FBW7. We also knocked out RCC2 and BRD7 using pSB-CRISPR vector respectively, and revealed the novel roles of these two proteins in mitosis.

Conclusion

Our study demonstrated that the pSB series vectors are convenient and powerful tools for gene overexpression and knockout in mammalian cells, providing a new alternative approach for molecular cell biology research.

Bone erosions in rheumatoid arthritis: recent developments in pathogenesis and therapeutic implications

Bone erosions develop early in the course of rheumatoid arthritis (RA) and deteriorate progressively, causing joint damage and resulting in impaired functional capacity of patients. During the last years, considerable number of studies has increased our understanding of the pathogenetic mechanisms mediating the development of bone erosions in RA. Increased production of RANKL and other cytokines, dysregulation of innate immune mechanisms, autoantibodies specific to RA and alterations of microRNA expression stimulate differentiation and function of osteoclasts, which are responsible for the development of bone erosions. Besides, increased levels of cytokines, overproduction of antagonists of the canonical Wnt signaling pathway and deficient production of bone morphogenetic proteins result in impaired osteoblast differentiation and function, undermining the capacity of bone erosions to repair. Disease-modifying antirheumatic drugs, synthetic or biological, currently used in the treatment of RA, can halt the progression of bone erosions and may even lead to partial repair, although complete repair is unattainable. Targeting pathogenetic mechanisms participating in the erosive process may add to the therapeutic effect of DMARDs and help in the prevention or repair of bone erosions. However, more studies are still needed to confirm whether such therapeutic strategies are effective.

Gene Modification of Transforming Growth Factor β (TGF-β) and Interleukin 10 (IL-10) in Suppressing Mt Sonicate Induced Osteoclast Formation and Bone Absorption

Background

Osteoarticular tuberculosis is an osteolytic lesion caused by Mycobacterium tuberculosis (MTB). Inflammatory factors such as TNF-α play a critical role in anti-tuberculosis immunity by regulating osteoblast and osteoclast functions. Both TGF-β and IL-10 have immune suppression effects to downregulate secretion and release of inflammatory factors, such as TNF-α, that play roles in regulating osteoblast and osteoclast functions. This study thus investigated the effects of osteoclast with modified TGF-β and IL-10 gene expression on MTB-induced osteoclast formation and bone absorption.

Material/Methods

Bone marrow mononuclear cells were induced to differentiate into osteoblasts and osteoclasts in vitro to generate a co-culture system. MTB powder lysed by ultrasound (Mt sonicate) were added in gradients to observe osteoblast formation and osteoclast absorption. Cell apoptosis was measured by flow cytometry, while ELISA was used assess TNF-α, TGF-β, and IL-10. Viral vectors carrying TGF-β or IL-10 gene were used to transfect osteoclasts, followed by ELISA assay. Bone absorption and osteoblast apoptosis were compared among groups.

Results

Mt sonicate significantly facilitated osteoclast formation and bone formation. It upregulated contents of TNF-α, TGF-β, and IL-10, induced osteoblast apoptosis, enhanced RANKL expression in osteoblasts, and decreased OPG expression. Overexpression of TGF-β and/or IL-10 significantly decreased its upregulation effect on TNF-α by Mt sonicate, and hindered Mt sonicate-induced osteoblast apoptosis, osteoclast formation, and bone absorption.

Conclusions

Overexpression of TGF-β and IL-10 significantly inhibits TMB-induced TNF-α synthesis and release, suppresses osteoblast apoptosis, and hinders osteoclast formation and bone absorption.

Inflammation in bone physiology and pathology

PURPOSE OF REVIEW

Bone is constantly being remodeled throughout adult life through constant anabolic and catabolic actions that maintain tissue homeostasis. A number of hormones, cytokines growth factors, and the proximity of various cells to bone surfaces influence this process. Inflammatory changes at the bone microenvironment result in alterations leading to both excessive bone loss and bone formation. Detailed understanding of the physiological and pathological mechanisms that dictate these changes will allow us to harness inflammatory signals in bone regeneration.

RECENT FINDINGS

Recent reports have suggested that inflammatory signals are able to stimulate transcription factors that regulate osteoblast differentiation from their precursors.

SUMMARY

In this review, we summarized current understanding of the roles of inflammation in bone resorption and bone formation, which give rise to different disorders and discuss the huge potential of harnessing these inflammatory signals to achieve bone regeneration.

Common signalling pathways in macrophage and osteoclast multinucleation

Macrophage cell fusion and multinucleation are fundamental processes in the formation of multinucleated giant cells (MGCs) in chronic inflammatory disease and osteoclasts in the regulation of bone mass. However, this basic cell phenomenon is poorly understood despite its pathophysiological relevance. Granulomas containing multinucleated giant cells are seen in a wide variety of complex inflammatory disorders, as well as in infectious diseases. Dysregulation of osteoclastic bone resorption underlies the pathogenesis of osteoporosis and malignant osteolytic bone disease. Recent reports have shown that the formation of multinucleated giant cells and osteoclast fusion display a common molecular signature, suggesting shared genetic determinants. In this Review, we describe the background of cell-cell fusion and the similar origin of macrophages and osteoclasts. We specifically focus on the common pathways involved in osteoclast and MGC fusion. We also highlight potential approaches that could help to unravel the core mechanisms underlying bone and granulomatous disorders in humans.

Altered Bone Remodeling in Psoriatic Disease: New Insights and Future Directions

Psoriatic arthritis (PsA) is an inflammatory rheumatic disorder that occurs in patients with psoriasis and predominantly affects musculoskeletal structures, skin, and nails. The etiology of PsA is not well understood but evidence supports an interplay of genetic, immunologic, and environmental factors which promote pathological bone remodeling and joint damage in PsA. Localized and systemic bone loss due to increased activity of osteoclasts is well established in PsA based on animal models and translational studies. In contrast, the mechanisms responsible for pathological bone remodeling in PsA remain enigmatic although new candidate molecules and pathways have been identified. Recent reports have revealed novel findings related to bone erosion and pathologic bone formation in PsA. Many associated risk factors and contributing molecular mechanisms have also been identified. In this review, we discuss new developments in the field, point out unresolved questions regarding the pathogenetic origins of the wide array of bone phenotypes in PsA, and discuss new directions for investigation.

Bone Loss in Rheumatoid Arthritis: Basic Mechanisms and Clinical Implications

Patients with rheumatoid arthritis (RA) have historically developed progressive damage of articular bone and cartilage, which correlates with disability over time. In addition, these patients are prone to periarticular and systemic bone loss, carrying additional morbidity. In contrast to what is seen in many other rheumatic diseases, the impact of inflammation on bone in RA is uniquely destructive. Loss of articular bone (erosions) and periarticular bone (demineralization) is a result of excessive bone resorption and markedly limited bone formation. There has been tremendous progress in preventing net bone loss in RA with the advent of disease-modifying agents, including biologic agents and small molecules, that both limit inflammation and may have a direct impact on the prevention of cytokine- and antibody-driven osteoclastogenesis. However, repair of existing bone erosions, although feasible, is observed infrequently. Lack of repair is a consequence of suppression of osteoblast function and bone formation by some of the same mechanisms that promote osteoclastogenesis and bone resorption. As new agents are introduced to control inflammation in RA, and novel mechanisms to target synovitis are identified, it may be possible in the future to fully repair damaged bone.

Local administration of nuclear factor of activated T cells (NFAT) c1 inhibitor to suppress early resorption and inflammation induced by bone morphogenetic protein-2

Nuclear factor of activated T cells (NFAT)-c1 is known as a key regulator in osteoclast differentiation and immune response. This study is a follow-up to our previous study showing the antiresorptive activity of VIVIT, a peptide type NFATc1 inhibitor, using absorbable collagen sponge (ACS). This study aimed to investigate the effective concentration range of local VIVIT that suppresses early excessive osteoclast activation and inflammation induced by high-dose recombinant human bone morphogenetic protein (rhBMP)-2 and concomitantly enhances bone healing in a rat critical-sized calvaria defect model. High-dose rhBMP-2 (40 μg/defect) alone significantly increased in vivo osteoclast activation and expression of the inflammatory cytokines interleukin-1β and transforming necrosis factor-α on the scaffold at 7 days after surgery. However, rhBMP-2 had no direct effect on osteoclast activation in vitro. Osteoclast activation by rhBMP-2 was significantly suppressed by combined treatment with VIVIT at concentrations of 75 and 150 μM, but not at 15 μM, whereas suppression of inflammation occurred at all doses of VIVIT. Microcomputed tomography at 4 and 8 weeks after implantation revealed that the combination of rhBMP-2 and VIVIT at 75 μM VIVIT led to a greater bone fraction at the initial defect area, compared with rhBMP-2 alone. These findings revealed that local administration of VIVIT at certain concentrations has multiple positive effects that weaken early excessive osteoimmunological responses and enhance bone healing after rhBMP-2 administration. VIVIT has the potential to expand the therapeutic area of high-dose rhBMP-2 therapy to inflammatory bone loss. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1299-1310, 2018.

TNF-α induces expression of the circadian clock gene Bmal1 via dual calcium-dependent pathways in rheumatoid synovial cells

Tumor necrosis factor (TNF)-α is responsible for expressions of several clock genes and affects joint symptoms of rheumatoid arthritis (RA) with diurnal fluctuation. We tried to determine the mechanism involved in over-expression of Bmal1, induced by TNF-α, in primary cultured rheumatoid synovial cells. Cells were incubated with intra-cellular Ca2+ chelator BAPTA-AM, calcineurin inhibitor FK506 and p300/CBP (CREB binding protein) inhibitor C646, respectively, or transfected with p300 and CBP small interfering RNA (siRNA) before stimulation with TNF-α. Oscillation phase and amplitude of Bmal1, transcriptional activator Rorα, transcriptional repressor Rev-erbα, and histone acetyltransferases (p300 and Cbp) were evaluated by quantitative real-time PCR. As results, TNF-α did not influence the oscillation phase of Rev-erbα, while enhanced those of Rorα, resulting in over-expression of Bmal1. When Ca2+ influx was inhibited by BAPTA-AM, TNF-α-mediated up-regulation of Rorα was cancelled, however, that of Bmal1 was still apparent. When we further explored another pathway between TNF-α and Bmal1, TNF-α suppressed the expression of Rev-erbα in the absence of Ca2+ influx, as well as those of p300 and Cbp genes. Finally, actions of TNF-α, in increasing Bmal1/Rorα and decreasing Rev-erbα, were cancelled by C646 treatment or silencing of both p300 and Cbp. In conclusion, we determined a novel role of TNF-α in inducing Bmal1 via dual calcium dependent pathways; Rorα was up-regulated in the presence of Ca2+ influx and Rev-erbα was down-regulated in the absence of that. Results proposed that inhibition of p300/CBP could be new therapeutic targets for RA.

Ca2+-Dependent Regulation of NFATc1 via KCa3.1 in Inflammatory Osteoclastogenesis

In inflammatory arthritis, the dysregulation of osteoclast activity by proinflammatory cytokines, including TNF, interferes with bone remodeling during inflammation through Ca²⁺-dependent mechanisms causing pathological bone loss. Ca²⁺-dependent CREB/c-fos activation via Ca²⁺-calmodulin kinase IV (CaMKIV) induces transcriptional regulation of osteoclast-specific genes via NFATc1, which facilitate bone resorption. In leukocytes, Ca²⁺ regulation of NFAT-dependent gene expression oftentimes involves the activity of the Ca²⁺-activated K⁺ channel KCa3.1. In this study, we evaluate KCa3.1 as a modulator of Ca²⁺-induced NFAT-dependent osteoclast differentiation in inflammatory bone loss. Microarray analysis of receptor activator of NF-κB ligand (RANKL)-activated murine bone marrow macrophage (BMM) cultures revealed unique upregulation of KCa3.1 during osteoclastogenesis. The expression of KCa3.1 in vivo was confirmed by immunofluorescence staining on multinucleated cells at the bone surface of inflamed mouse joints. Experiments on in vitro BMM cultures revealed that KCa3.1^-/- and TRAM-34 treatment significantly reduced the expression of osteoclast-specific genes (p < 0.05) alongside decreased osteoclast formation (p < 0.0001) in inflammatory (RANKL+TNF) and noninflammatory (RANKL) conditions. In particular, live cell Ca²⁺ imaging and Western blot analysis showed that TRAM-34 pretreatment decreased transient RANKL-induced Ca²⁺ amplitudes in BMMs by ∼50% (p < 0.0001) and prevented phosphorylation of CaMKIV. KCa3.1^-/- reduced RANKL+/-TNF-stimulated phosphorylation of CREB and expression of c-fos in BMMs (p < 0.01), culminating in decreased NFATc1 protein expression and transcriptional activity (p < 0.01). These data indicate that KCa3.1 regulates Ca²⁺-dependent NFATc1 expression via CaMKIV/CREB during inflammatory osteoclastogenesis in the presence of TNF, corroborating its role as a target candidate for the treatment of bone erosion in inflammatory arthritis.

Virion encapsidated HIV-1 Vpr induces NFAT to prime non-activated T cells for productive infection

The majority of T cells encountered by HIV-1 are non-activated and do not readily allow productive infection. HIV-1 Vpr is highly abundant in progeny virions, and induces signalling and HIV-1 LTR transcription. We hence hypothesized that Vpr might be a determinant of non-activated T-cell infection. Virion-delivered Vpr activated nuclear factor of activated T cells (NFAT) through Ca²⁺ influx and interference with the NFAT export kinase GSK3β. This leads to NFAT translocation and accumulation within the nucleus and was required for productive infection of unstimulated primary CD4⁺ T cells. A mutagenesis approach revealed correlation of Vpr-mediated NFAT activation with its ability to enhance LTR transcription and mediate cell cycle arrest. Upon NFAT inhibition, Vpr did not augment resting T-cell infection, and showed reduced G2/M arrest and LTR transactivation. Altogether, Vpr renders unstimulated T cells more permissive for productive HIV-1 infection and stimulates activation of productively infected as well as virus-exposed T cells. Therefore, it could be involved in the establishment and reactivation of HIV-1 from viral reservoirs and might have an impact on the levels of immune activation, which are determinants of HIV-1 pathogenesis.

Age-dependent alterations in osteoblast and osteoclast activity in human cancellous bone

It is assumed that the activity of osteoblasts and osteoclasts is decreased in bone tissue of aged individuals. However, detailed investigation of the molecular signature of human bone from young compared to aged individuals confirming this assumption is lacking. In this study, quantitative expression analysis of genes related to osteogenesis and osteoclastogenesis of human cancellous bone derived from the distal radius of young and aged individuals was performed. Furthermore, we additionally performed immunohistochemical stainings. The young group included 24 individuals with an average age of 23.2 years, which was compared to cancellous bone derived from 11 body donators with an average age of 81.0 years. In cancellous bone of young individuals, the osteogenesis-related genes RUNX-2, OSTERIX, OSTEOPONTIN and OSTEOCALCIN were significantly up-regulated compared to aged individuals. In addition, RANKL and NFATc1, both markers for osteoclastogenesis, were significantly induced in cancellous bone of young individuals, as well as the WNT gene family member WNT5a and the matrix metalloproteinases MMP-9. However, quantitative RT-PCR analysis of BMP-2, ALP, FGF-2, CYCLIN-D1, MMP-13, RANK, OSTEOPROTEGERIN and TGFb1 revealed no significant difference. Furthermore, Tartrate-resistant acid phosphatase (TRAP) staining was performed which indicated an increased osteoclast activity in cancellous bone of young individuals. In addition, pentachrome stainings revealed significantly less mineralized bone matrix, more osteoid and an increased bone density in young individuals. In summary, markers related to osteogenesis as well as osteoclastogenesis were significantly decreased in the aged individuals. Thus, the present data extends the knowledge about reduced bone regeneration and healing capacity observed in aged individuals.

Maternal Pregravid Obesity Remodels the DNA Methylation Landscape of Cord Blood Monocytes Disrupting Their Inflammatory Program

Prepregnancy maternal obesity is associated with adverse outcomes for the offspring, including increased incidence of neonatal bacterial sepsis and necrotizing enterocolitis. We recently reported that umbilical cord blood (UCB) monocytes from babies born to obese mothers generate a reduced IL-6/TNF-α response to TLR 1/2 and 4 ligands compared to those collected from lean mothers. These observations suggest altered development of the offspring's immune system, which in turn results in dysregulated function. We therefore investigated transcriptional and epigenetic differences within UCB monocytes stratified by prepregnancy maternal body mass index. We show that UCB monocytes from babies born to obese mothers generate a dampened response to LPS stimulation compared with those born to lean mothers, at the level of secreted immune mediators and transcription. Because gene expression profiles of resting UCB monocytes from both groups were comparable, we next investigated the role of epigenetic differences. Indeed, we detected stark differences in methylation levels within promoters and regulatory regions of genes involved in TLR signaling in resting UCB monocytes. Interestingly, the DNA methylation status of resting cells was highly predictive of transcriptional changes post-LPS stimulation, suggesting that cytosine methylation is one of the dominant mechanisms driving functional inadequacy in UCB monocytes obtained from babies born to obese mothers. These data highlight a potentially critical role of maternal pregravid obesity-associated epigenetic changes in influencing the function of an offspring's monocytes at birth. These findings further our understanding of mechanisms that explain the increased risk of infection in neonates born to mothers with high prepregnancy body mass index.

Genome-wide methylation analysis reveals differentially methylated loci that are associated with an age-dependent increase in bovine fibroblast response to LPS

BACKGROUND

Differences in DNA methylation are known to contribute to the development of immune-related disorders in humans but relatively little is known about how methylation regulates immune function in cattle. Utilizing whole-transcriptome analyses of bovine dermal fibroblasts, we have previously identified an age and breed-dependent up-regulation of genes within the toll-like receptor 4 (TLR4) pathway that correlates with enhanced fibroblast production of IL-8 in response to lipopolysaccharide (LPS). Age-dependent differences in IL-8 production are abolished by treatment with 5-aza-2-deoxycytidine and Trichostatin A (AZA-TSA), suggesting epigenetic regulation of the innate response to LPS. In the current study, we performed reduced representation bisulfite sequencing (RRBS) on fibroblast cultures isolated from the same animals at 5- and 16-months of age to identify genes that exhibit variable methylation with age. To validate the role of methylation in gene expression, six innate response genes that were hyper-methylated in young animals were assessed by RT-qPCR in fibroblasts from animals at different ages and from different breeds.

RESULTS

We identified 14,094 differentially methylated CpGs (DMCs) that differed between fibroblast cultures at 5- versus 16-months of age. Of the 5065 DMCs that fell within gene regions, 1117 were located within promoters, 1057 were within gene exons and 2891 were within gene introns and 67% were more methylated in young cultures. Transcription factor enrichment of the promoter regions hyper-methylated in young cultures revealed significant regulation by the key pro-inflammatory regulator, NF-κB. Additionally, five out of six chosen genes (PIK3R1, FES, NFATC1, TNFSF13 and RORA) that were more methylated in young cultures showed a significant reduction in expression post-LPS treatment in comparison with older cultures. Two of these genes, FES and NFATC1, were similarly down-regulated in Angus cultures that also exhibit a low LPS response phenotype.

CONCLUSIONS

Our study has identified immune-related loci regulated by DNA methylation in cattle that may contribute to differential cellular response to LPS, two of which exhibit an identical expression profile in both low-responding age and breed phenotypes. Methylation biomarkers of differential immunity may prove useful in developing selection strategies for replacement cows that are less susceptible to severe infections, such as coliform mastitis.

ADAMTS5 Deficiency in Calcified Aortic Valves Is Associated With Elevated Pro-Osteogenic Activity in Valvular Interstitial Cells

OBJECTIVE

Extracellular matrix proteinases are implicated in the pathogenesis of calcific aortic valve disease. The ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5) enzyme is secreted, matrix-associated metalloendopeptidase, capable of degrading extracellular matrix proteins, particularly matrilin 2. We sought to determine the role of the ADAMTS5/matrilin 2 axis in mediating the phenotype transition of valvular interstitial cells (VICs) associated with calcific aortic valve disease.

APPROACH AND RESULTS

Levels of ADAMTS5, matrilin 2, and α-SMA (α-smooth muscle actin) were evaluated in calcified and normal human aortic valve tissues and VICs. Calcified aortic valves have reduced levels of ADAMTS5 and higher levels of matrilin 2 and α-SMA. Treatment of normal VICs with soluble matrilin 2 caused an increase in α-SMA level through Toll-like receptors 2 and 4, which was accompanied by upregulation of runt-related transcription factor 2 and alkaline phosphatase. In addition, ADAMTS5 knockdown in normal VICs enhanced the effect of matrilin 2. Matrilin 2 activated nuclear factor (NF) κB and NF of activated T cells complex 1 and induced the interaction of these 2 NFs. Inhibition of either NF-κB or NF of activated T cells complex 1 suppressed matrilin 2's effect on VIC phenotype change. Knockdown of α-SMA reduced and overexpression of α-SMA enhanced the expression of pro-osteogenic factors and calcium deposit formation in human VICs.

CONCLUSIONS

Matrilin 2 induces myofibroblastic transition and elevates pro-osteogenic activity in human VICs via activation of NF-κB and NF of activated T cells complex 1. Myofibroblastic transition in human VICs is an important mechanism of elevating the pro-osteogenic activity. Matrilin 2 accumulation associated with relative ADAMTS5 deficiency may contribute to the mechanism underlying calcific aortic valve disease progression.