Tumor necrosis factor receptor-associated factor 6 (TRAF6) stimulates extracellular signal-regulated kinase (ERK) activity in CD40 signaling along a ras-independent pathway

Transcriptional and post-translational mechanisms of ECM remodeling in rotator cuff tendons under hyperlipidemic conditions

Rotator cuff injuries present significant clinical challenges, often resulting in chronic pain and functional impairment. In this study, we examined the effects of hyperlipidemia (HYP), a systemic metabolic condition, on tendon health. Histological analysis of infraspinatus tendons from hyperlipidemic swine revealed well-organized extracellular matrix (ECM) structures, comparable to those in non-hyperlipidemic (NONHYP) animals, suggesting ECM reorganization. Upstream SIGNOR3.0 analysis demonstrated that tumor necrosis factor receptor-associated factor 6 (TRAF6) activates transcription factor Yin Yang 1 (YY1) via kinase signaling, underscoring its role in tendon ECM remodeling. Hence, we futher examined the role of YY1, which is a critical regulator of collagen synthesis identified through network analysis. Although TRAF6 levels remained unchanged in HYP conditions, increased YY1 expression correlated with elevated COL1 gene expression. Additionally, twist-related protein 1 (TWIST1) emerged as another key molecule, existing in both homo- and heterodimer forms in NON-HYP conditions, but only as a heterodimer in HYP. YY1 enhanced COL1 transcription in the hyperlipidemic environment, while TWIST1 heterodimer formation facilitated collagen crosslinking. Notably, increased YY1 expression inhibited MMP3, resulting in the inactivity of MMP1, MMP8, and MMP9, thereby preserving collagen levels. These findings highlight the complex molecular interactions involving transcriptional regulation by YY1 and post-translational regulation by the TWIST1 heterodimer, essential for the deposition of mature collagen fibrils and driving tendon remodeling in hyperlipidemic conditions. This study offers valuable insights for the change of tendon health condition in hyperlipidemia disease or tendon pathology.

Exosome-delivered miR-410-3p reverses epithelial-mesenchymal transition, migration and invasion of trophoblasts in spontaneous abortion

Current studies have indicated that insufficient trophoblast epithelial-mesenchymal transition (EMT), migration and invasion are crucial for spontaneous abortion (SA) occurrence and development. Exosomal miRNAs play significant roles in embryonic development and cellular communication. Hereon, we explored the roles of serum exosomes derived from SA patients on trophoblast EMT, migration and invasion. Exosomes were isolated from normal control (NC) patients with abortion for unplanned pregnancy and SA patients, then characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blotting. Exosomal miRNA profiles were identified by miRNA sequencing. The effects of serum exosomes on trophoblast migration and invasion were detected by scratch wound healing and transwell assays, and other potential mechanisms were revealed by quantitative real-time PCR (RT-PCR), western blotting and dual-luciferase reporter assay. Finally, animal experiments were used to explore the effects of exosomal miR-410-3p on embryo absorption in mice. The serum exosomes from SA patients inhibited trophoblast EMT and reduced their migration and invasion ability in vitro. The miRNA sequencing showed that miR-410-3p was upregulated in SA serum exosomes. The functional experiments showed that SA serum exosomes restrained trophoblast EMT, migration and invasion by releasing miR-410-3p. Mechanistically, SA serum exosomal miR-410-3p inhibited trophoblast cell EMT, migration and invasion by targeting TNF receptor-associated factor 6 (TRAF6) at the post-transcriptional level. Besides, SA serum exosomal miR-410-3p inhibited the p38 MAPK signalling pathway by targeting TRAF6 in trophoblasts. Moreover, milk exosomes loaded with miR-410-3p mimic reached the maternal-fetal interface and aggravated embryo absorption in female mice. Clinically, miR-410-3p and TRAF6 expression were abnormal and negatively correlated in the placental villi of SA patients. Our findings indicated that exosome-derived miR-410-3p plays an important role between SA serum and trophoblasts in intercellular communication, suggesting a novel mechanism by which serum exosomal miRNA regulates trophoblasts in SA patients.

A TLR4/TRAF6-dependent signaling pathway mediates NCoR coactivator complex formation for inflammatory gene activation

The nuclear receptor corepressor (NCoR) forms a complex with histone deacetylase 3 (HDAC3) that mediates repressive functions of unliganded nuclear receptors and other transcriptional repressors by deacetylation of histone substrates. Recent studies provide evidence that NCoR/HDAC3 complexes can also exert coactivator functions in brown adipocytes by deacetylating and activating PPARγ coactivator 1α (PGC1α) and that signaling via receptor activator of nuclear factor kappa-B (RANK) promotes the formation of a stable NCoR/HDAC3/PGC1β complex that coactivates nuclear factor kappa-B (NFκB)- and activator protein 1 (AP-1)-dependent genes required for osteoclast differentiation. Here, we demonstrate that activation of Toll-like receptor (TLR) 4, but not TLR3, the interleukin 4 (IL4) receptor nor the Type I interferon receptor, also promotes assembly of an NCoR/HDAC3/PGC1β coactivator complex. Receptor-specific utilization of TNF receptor-associated factor 6 (TRAF6) and downstream activation of extracellular signal-regulated kinase 1 (ERK1) and TANK-binding kinase 1 (TBK1) accounts for the common ability of RANK and TLR4 to drive assembly of an NCoR/HDAC3/PGC1β complex in macrophages. ERK1, the p65 component of NFκB, and the p300 histone acetyltransferase (HAT) are also components of the induced complex and are associated with local histone acetylation and transcriptional activation of TLR4-dependent enhancers and promoters. These observations identify a TLR4/TRAF6-dependent signaling pathway that converts NCoR from a corepressor of nuclear receptors to a coactivator of NFκB and AP-1 that may be relevant to functions of NCoR in other developmental and homeostatic processes.

Extracellular Vesicles-mediated recombinant IL-10 protects against ascending infection-associated preterm birth by reducing fetal inflammatory response

Background

Fetal inflammatory response mediated by the influx of immune cells and activation of pro-inflammatory transcription factor NF-κB in feto-maternal uterine tissues is the major determinant of infection-associated preterm birth (PTB, live births < 37 weeks of gestation).

Objective

To reduce the incidence of PTB by minimizing inflammation, extracellular vesicles (EVs) were electroporetically engineered to contain anti-inflammatory cytokine interleukin (IL)-10 (eIL-10), and their efficacy was tested in an ascending model of infection (vaginal administration of E. coli) induced PTB in mouse models.

Study design

EVs (size: 30-170 nm) derived from HEK293T cells were electroporated with recombinant IL-10 at 500 volts and 125 Ω, and 6 pulses to generate eIL-10. eIL-10 structural characters (electron microscopy, nanoparticle tracking analysis, ExoView [size and cargo content] and functional properties (co-treatment of macrophage cells with LPS and eIL-10) were assessed. To test efficacy, CD1 mice were vaginally inoculated with E. coli (1010CFU) and subsequently treated with either PBS, eIL-10 (500ng) or Gentamicin (10mg/kg) or a combination of eIL-10+gentamicin. Fetal inflammatory response in maternal and fetal tissues after the infection or treatment were conducted by suspension Cytometer Time of Flight (CyTOF) using a transgenic mouse model that express red fluorescent TdTomato (mT+) in fetal cells.

Results

Engineered EVs were structurally and functionally stable and showed reduced proinflammatory cytokine production from LPS challenged macrophage cells in vitro. Maternal administration of eIL-10 (10 µg/kg body weight) crossed feto-maternal barriers to delay E. coli-induced PTB to deliver live pups at term. Delay in PTB was associated with reduced feto-maternal uterine inflammation (immune cell infiltration and histologic chorioamnionitis, NF-κB activation, and proinflammatory cytokine production).

Conclusions

eIL-10 administration was safe, stable, specific, delayed PTB by over 72 hrs and delivered live pups. The delivery of drugs using EVs overcomes the limitations of in-utero fetal interventions. Protecting IL-10 in EVs eliminates the need for the amniotic administration of recombinant IL-10 for its efficacy.

CD4+ T cell calibration of antigen-presenting cells optimizes antiviral CD8+ T cell immunity

Antiviral CD8+ T cell immunity depends on the integration of various contextual cues, but how antigen-presenting cells (APCs) consolidate these signals for decoding by T cells remains unclear. Here, we describe gradual interferon-α/interferon-β (IFNα/β)-induced transcriptional adaptations that endow APCs with the capacity to rapidly activate the transcriptional regulators p65, IRF1 and FOS after CD4+ T cell-mediated CD40 stimulation. While these responses operate through broadly used signaling components, they induce a unique set of co-stimulatory molecules and soluble mediators that cannot be elicited by IFNα/β or CD40 alone. These responses are critical for the acquisition of antiviral CD8+ T cell effector function, and their activity in APCs from individuals infected with severe acute respiratory syndrome coronavirus 2 correlates with milder disease. These observations uncover a sequential integration process whereby APCs rely on CD4+ T cells to select the innate circuits that guide antiviral CD8+ T cell responses.

p53 ubiquitination co-mediated by HUWE1 and TRAF6 contributes to WSSV infection in crustacean

p53, the guardian of the genome, is a short-lived protein that is tightly controlled at low levels by constant ubiquitination and proteasomal degradation in higher organisms. p53 stabilization and activation are early crucial events to cope with external stimuli in cells. However, the role of p53 ubiquitination and its relevant molecular mechanisms have not been addressed in invertebrates. In this study, our findings revealed that both HUWE1 (HECT, UBA, and WWE domain-containing E3 ubiquitin-protein ligase 1) and TRAF6 (tumor necrosis factor receptor-associated factor 6) could serve as E3 ubiquitin ligases for p53 in mud crabs (Scylla paramamosain). Moreover, the expression of HUWE1 and TRAF6 was significantly downregulated during white spot syndrome virus (WSSV) infection, and therefore the ubiquitination of p53 was interrupted, leading to the activation of apoptosis and reactive oxygen species (ROS) signals through p53 accumulation, which eventually suppressed viral invasion in the mud crabs. To the best of our knowledge, this is the first study to reveal the p53 ubiquitination simultaneously induced by two E3 ligases in arthropods, which provides a novel molecular mechanism of invertebrates for resistance to viral infection.

IMPORTANCE p53, which is a well-known tumor suppressor that has been widely studied in higher animals, has been reported to be tightly controlled at low levels by ubiquitin-dependent proteasomal degradation. However, recent p53 ubiquitination-relevant research mainly involved an individual E3 ubiquitin ligase, but not whether there exist other mechanisms that need to be explored. The results of this study show that HUWE1 and TRAF6 could serve as p53 E3 ubiquitin ligases and synchronously mediate p53 ubiquitination in mud crabs (Scylla paramamosain), which confirmed the diversity of the p53 ubiquitination regulatory pathway. In addition, the effects of p53 ubiquitination are mainly focused on tumorigenesis, but a few are focused on the host immune defense in invertebrates. Our findings reveal that p53 ubiquitination could affect ROS and apoptosis signals to cope with WSSV infection in mud crabs, which is the first clarification of the immunologic functions and mechanisms of p53 ubiquitination in invertebrates.

Anti-inflammatory, but not osteoprotective, effect of the TRAF6/CD40 inhibitor 6877002 in rodent models of local and systemic osteolysis

NFκB plays a key role in inflammation and skeletal disorders. Previously, we reported that pharmacological inhibition of NFκB at the level of TRAF6 suppressed RANKL, CD40L and IL1β-induced osteoclastogenesis and attenuated cancer-induced bone disease. TNFα is also known to regulate TRAF6/NFκB signalling, however the anti-inflammatory and osteoprotective effects associated with inhibition of the TNFα/TRAF6/NFκB axis have not been investigated. Here, we show that in vitro and ex vivo exposure to the verified small-molecule inhibitor of TRAF6, 6877002 prevented TNFα-induced NFκB activation, osteoclastogenesis and calvarial osteolysis, but it had no effects on TNFα-induced apoptosis or growth inhibition in osteoblasts. Additionally, 6877002 disrupted T-cells support for osteoclast formation and synoviocyte motility, without affecting the viability of osteoblasts in the presence of T-cells derived factors. Using the collagen-induced arthritis model, we show that oral and intraperitoneal administration of 6877002 in mice reduced joint inflammation and arthritis score. Unexpectedly, no difference in trabecular and cortical bone parameters were detected between vehicle and 6877002 treated mice, indicating lack of osteoprotection by 6877002 in the arthritis model described. Using two independent rodent models of osteolysis, we confirmed that 6877002 had no effect on trabecular and cortical bone loss in both osteoporotic rats or RANKL- treated mice. In contrast, the classic anti-osteolytic alendronate offered complete osteoprotection in RANKL- treated mice. In conclusion, TRAF6 inhibitors may be of value in the management of the inflammatory component of bone disorders, but may not offer protection against local or systemic bone loss, unless combined with anti-resorptive therapy such as bisphosphonates.

β-Boswellic Acid Inhibits RANKL-Induced Osteoclast Differentiation and Function by Attenuating NF-κB and Btk-PLCγ2 Signaling Pathways

Osteoporosis is a systemic metabolic bone disorder that is caused by an imbalance in the functions of osteoclasts and osteoblasts and is characterized by excessive bone resorption by osteoclasts. Targeting osteoclast differentiation and bone resorption is considered a good fundamental solution for overcoming bone diseases. β-boswellic acid (βBA) is a natural compound found in Boswellia serrata, which is an active ingredient with anti-inflammatory, anti-rheumatic, and anti-cancer effects. Here, we explored the anti-resorptive effect of βBA on osteoclastogenesis. βBA significantly inhibited the formation of tartrate-resistant acid phosphatase-positive osteoclasts induced by receptor activator of nuclear factor-B ligand (RANKL) and suppressed bone resorption without any cytotoxicity. Interestingly, βBA significantly inhibited the phosphorylation of IκB, Btk, and PLCγ2 and the degradation of IκB. Additionally, βBA strongly inhibited the mRNA and protein expression of c-Fos and NFATc1 induced by RANKL and subsequently attenuated the expression of osteoclast marker genes, such as OC-STAMP, DC-STAMP, β3-integrin, MMP9, ATP6v0d2, and CtsK. These results suggest that βBA is a potential therapeutic candidate for the treatment of excessive osteoclast-induced bone diseases such as osteoporosis.

Identification of a new TRAF6 inhibitor for the treatment of hepatocellular carcinoma

Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) is an E3 ubiquitin ligase that plays a crucial role in signal transduction. Previous studies have demonstrated that TRAF6 is overexpressed in hepatocellular carcinoma (HCC) and that TRAF6 knockdown dramatically attenuates tumor cell growth. Thus, TRAF6 may represent a potential therapeutic target for the treatment of HCC. Herein, we identified bis (4-hydroxy-3,5-dimethylphenyl) sulfone (TMBPS) as a novel inhibitor that can directly bind to and downregulate the level of TRAF6. In vitro experimental results showed that TMBPS arrests the cell cycle in the G2/M phase by inactivating the protein kinase B (AKT) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways and induces apoptosis by activating the p38/mitogen-activated protein kinase (MAPK) signaling pathway. In addition, TMBPS exhibited significant tumor growth inhibition in mouse xenograft models. In summary, our findings offer a proof-of-concept for the use of TMBPS as a novel chemotherapy drug for the prevention or treatment of HCC.

Carica papaya leaf extract inhibits prostatitis-associated prostatic hyperplasia via the TRAF6/TAK1/MEK/NF-κB pathway

Prostatitis, defined as a pathological inflammatory change in the prostate tissue, is one of the most prevalent urological conditions in men. However, optimal management of prostatitis remains unclear, and treatment outcomes are unsatisfactory owing to adverse effects. Carica papaya leaf extract (PAL) is known for its antioxidant, immunomodulatory, and anticancer properties; however, evidence of its anti-inflammatory effect in prostatic tissues remains elusive. In this study, the therapeutic effects and underlying molecular mechanisms of PAL in mice with experimental autoimmune prostatitis (EAP) and a prostatic cell line (RWPE-1 cells) exposed to inflammatory conditioned medium were investigated. PAL suppressed pathological alterations in EAP and markedly reduced prostate weight in EAP mice. Histological analysis revealed that PAL alleviates prostatic hyperplasia. Furthermore, PAL significantly reduced cyclooxygenase-2 mRNA and protein expression; production of inflammatory cytokines, including interleukin-6, tumor necrosis factor-α, and transforming growth factor-β; and TRAF6/TAK1/MEK/ERK and NF-κB pathway-related protein expression. TRAF6/TAK1/MEK/ERK and NF-κB pathway-related proteins were upregulated in inflammatory conditioned medium-stimulated RWPE-1 cells, but PAL reduced the expression of these markers. Particularly, PAL treatment suppressed the nuclear translocation of NF-κB p65 and phosphorylation of p65 in RWPE-1 cells exposed to the inflammatory conditioned medium. Collectively, the results demonstrate the anti-proliferative and anti-inflammatory effects of PAL in the experimental prostatitis model, which highlights the potential of PAL as a new therapeutic agent in the treatment of prostatic disease.

PKM2 Aggravates Cerebral Ischemia Reperfusion-Induced Neuroinflammation via TLR4/MyD88/TRAF6 Signaling Pathway

OBJECTIVES

Cerebral ischemia-reperfusion (I/R) injury is the leading cause of ischemic stroke. Pyruvate Kinase isozymes M2 (PKM2), as a critical glycolytic enzyme during glycolysis, is involved in neuronal apoptosis in rats with hypoxic-ischemic encephalopathy. This study focused on functional investigation and potential molecular mechanism toward PKM2 in cerebral I/R injury.

METHODS

Cerebral I/R injury model was established by middle cerebral artery occlusion (MCAO) in vivo or oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro. qRT-PCR and Western blot were used to detect the expression of PKM2 in I/R injury models. The effects of PKM2 on I/R injury were determined via triphenyl tetrazolium chloride staining and evaluation of neurological deficits. Cell Counting Kit-8 was employed to detect cell viability, and ELISA was conducted to detect pro-inflammatory cytokines. The underlying mechanism involved in regulation of PKM2 on I/R injury was investigated via ELISA and Western blot.

RESULTS

PKM2 was upregulated after cerebral I/R injury. Knockdown of PKM2 alleviated MCAO-induced infarction and neurological dysfunction. Moreover, PKM2 knockdown also alleviated OGD/R-induced neuronal cell injury and inflammatory response. Mechanistically, PKM2 knockdown-induced neuroprotection was accompanied by inhibition of high-mobility group box 1 (HMGB1), reflected by inactivation of TLR4/MyD88 (myeloid differentiation factor 88)/TRAF6 (TNF receptor-associated factor 6) signaling pathway.

CONCLUSIONS

Knockdown of PKM2 attenuated cerebral I/R injury through HMGB1-mediated TLR4/MyD88/TRAF6 expression change, providing a potential target for cerebral I/R injury treatment.

Molecular basis and therapeutic implications of CD40/CD40L immune checkpoint

The CD40 receptor and its ligand CD40L is one of the most critical molecular pairs of the stimulatory immune checkpoints. Both CD40 and CD40L have a membrane form and a soluble form generated by proteolytic cleavage or alternative splicing. CD40 and CD40L are widely expressed in various types of cells, among which B cells and myeloid cells constitutively express high levels of CD40, and T cells and platelets express high levels of CD40L upon activation. CD40L self-assembles into functional trimers which induce CD40 trimerization and downstream signaling. The canonical CD40/CD40L signaling is mediated by recruitment of TRAFs and NF-κB activation, which is supplemented by signal pathways such as PI3K/AKT, MAPKs and JAK3/STATs. CD40/CD40L immune checkpoint leads to activation of both innate and adaptive immune cells via two-way signaling. CD40/CD40L interaction also participates in regulating thrombosis, tissue inflammation, hematopoiesis and tumor cell fate. Because of its essential role in immune activation, CD40/CD40L interaction has been regarded as an attractive immunotherapy target. In recent years, significant advance has been made in CD40/CD40L-targeted therapy. Various types of agents, including agonistic/antagonistic monoclonal antibodies, cellular vaccines, adenoviral vectors and protein antagonist, have been developed and evaluated in early-stage clinical trials for treating malignancies, autoimmune diseases and allograft rejection. In general, these agents have demonstrated favorable safety and some of them show promising clinical efficacy. The mechanisms of benefits include immune cell activation and tumor cell lysis/apoptosis in malignancies, or immune cell inactivation in autoimmune diseases and allograft rejection. This review provides a comprehensive overview of the structure, processing, cellular expression pattern, signaling and effector function of CD40/CD40L checkpoint molecules. In addition, we summarize the progress, targeted diseases and outcomes of current ongoing and completed clinical trials of CD40/CD40L-targeted therapy.

The relationship between TRAF6 and tumors

Tumor necrosis factor receptor (TNFR)-related factors (TRAFs) are important linker molecules in the tumor necrosis factor superfamily (TNFSF) and the Toll-like/interleukin-1 receptor (TLR/ILR) superfamily. There are seven members: TRAF1-TRAF7, among those members, tumor necrosis factor receptor-associated factor 6 (TRAF6) is upregulated in various tumors, which has been related to tumorigenesis and development. With the in-depth study of the relationship between TRAF6 and different types of tumors, TRAF6 has oncogenic characteristics involved in tumorigenesis, tumor development, invasion, and metastasis through various signaling pathways, therefore, targeting TRAF6 has provided a novel strategy for tumor treatment. This review summarizes and analyzes the role of TRAF6 in tumorigenesis and tumor development in combination with the current research on TRAF6 and tumors.

Sarsasapogenin Suppresses RANKL-Induced Osteoclastogenesis in vitro and Prevents Lipopolysaccharide-Induced Bone Loss in vivo

INTRODUCTION

Osteoclasts are giant polynuclear cells; their main function is bone resorption. An increased number of osteoclasts and enhanced bone resorption exert significant effects on osteoclast-related bone-lytic diseases, including osteoporosis. Given the limitations of current therapies for osteolytic diseases, it is urgently required to develop safer and more effective alternatives. Sarsasapogenin, a major sapogenin from Anemarrhena asphodeloides Bunge, possesses potent antitumor effects and inhibits NF-κB and MAPK signaling. However, the manner in which it affects osteoclasts is unclear.

METHODS

We investigated the effects of anti-osteoclastogenic and anti-resorptive of sarsasapogenin on bone marrow-derived osteoclasts.

RESULTS

Sarsasapogenin inhibited multiple RANKL-induced signaling cascades, thereby inhibiting the induction of key osteoclast transcription factor NFATc1. The in vivo and in vitro results were consistent: sarsasapogenin treatment protected against bone loss in a mouse osteolysis model induced by lipopolysaccharide.

CONCLUSION

Our research confirms that sarsasapogenin can be used as a new treatment for osteoclast-related osteolytic diseases.

LPS stimulation during HCV infection induces MMP/TIMP1 imbalance in macrophages

Introduction. During chronic hepatitis C virus (HCV) infections, HCV antigens establish cross-tolerance of endotoxins, but additional lipopolysaccharide (LPS) stimulation effects in this condition are poorly understood.Aim. This study aims to investigate the effects of the upregulated LPS on MMP and TIMP expression during chronic hepatitis C infection.Methodology. In the present study, we analysed the effect of HCV antigens and LPS stimulation on peripheral blood mononuclear cells (PBMCs) both in vivo and in vitro. Macrophages from HCV patients were isolated and their association with endotoxin tolerance was examined. MMP/TIMP1 expression and the related signalling pathways in macrophages were analysed. The macrophage and Huh7.5 cell co-culture model was used to analyse the effects of the cross-tolerance on collagen I deposition.Results. LPS levels were found to be significantly higher in HCV patients, particularly in those with HCV-induced liver fibrosis. In addition, although LPS serum level was occasionally upregulated in the patients, it did not induce intense immune response in PBMCs due to endotoxin cross-tolerance, and this was measured according to the changes in IL-6 and TNF-α levels. However, TIMP1 expression increased significantly during stimulation, exhibiting a tolerance/resistance phenotype, which was associated with TGF-β/Erk activation in macrophages. However, MMP levels did not increase due to endotoxin tolerance, which ultimately led to MMP/TIMP imbalance and influenced the deposition of collagen I.Conclusion. Increased LPS stimulation of macrophage during HCV antigen-induced endotoxin cross-tolerance contributes to MMP/TIMP1 imbalance and collagen I deposition.

The regulatory protein GADD34 inhibits TRAIL-induced apoptosis via TRAF6/ERK-dependent stabilization of myeloid cell leukemia 1 in liver cancer cells

GADD34 (growth arrest and DNA damage-inducible gene 34) plays a critical role in responses to DNA damage and endoplasmic reticulum stress. GADD34 has opposing effects on different stimuli-induced cell apoptosis events, but the reason for this is unclear. Here, using immunoblotting analyses and various molecular genetic approaches in HepG2 and SMMC-7721 cells, we demonstrate that GADD34 protects hepatocellular carcinoma (HCC) cells from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by stabilizing a BCL-2 family member, myeloid cell leukemia 1 (MCL-1). We found that GADD34 knockdown decreased MCL-1 levels and that GADD34 overexpression up-regulated MCL-1 expression in HCC cells. GADD34 did not affect MCL-1 transcription but enhanced MCL-1 protein stability. The proteasome inhibitor MG132 abrogated GADD34 depletion-induced MCL-1 down-regulation, suggesting that GADD34 inhibits the proteasomal degradation of MCL-1. Furthermore, GADD34 overexpression promoted extracellular signal-regulated kinase (ERK) phosphorylation through a signaling axis that consists of the E3 ubiquitin ligase tumor necrosis factor receptor-associated factor 6 (TRAF6) and transforming growth factor-β-activated kinase 1 (MAP3K7)-binding protein 1 (TAB1), which mediated the up-regulation of MCL-1 by GADD34. Of note, TRAIL up-regulated both GADD34 and MCL-1 levels, and knockdown of GADD34 and TRAF6 suppressed the induction of MCL-1 by TRAIL. Correspondingly, GADD34 knockdown potentiated TRAIL-induced apoptosis, and MCL-1 overexpression rescued TRAIL-treated and GADD34-depleted HCC cells from cell death. Taken together, these findings suggest that GADD34 inhibits TRAIL-induced HCC cell apoptosis through TRAF6- and ERK-mediated stabilization of MCL-1.

Extracellular vesicles in bone: "dogrobbers" in the "eternal battle field"

Throughout human life, bone is constantly in a delicate dynamic equilibrium of synthesis and resorption, hosting finely-tuned bone mineral metabolic processes for bone homeostasis by collaboration or symphony among several cell types including osteoclasts (OCs), osteoblasts (OBs), osteocytes (OYs), vascular endothelial cells (ECs) and their precursors. Beyond these connections, a substantial level of communication seems to occur between bone and other tissues, and together, they form an organic unit linked to human health and disease. However, the current hypothesis, which includes growth factors, hormones and specific protein secretion, incompletely explains the close connections among bone cells or between bone and other tissues. Extracellular vesicles (EVs) are widely-distributed membrane structures consisting of lipid bilayers, membrane proteins and intravesicular cargo (including proteins and nucleic acids), ranging from 30 nm to 1000 nm in diameter, and their characters have been highly conserved throughout evolution. EVs have targeting abilities and the potential to transmit multidimensional, abundant and complicated information, as powerful and substantial "dogrobbers" mediating intercellular communications. As research has progressed, EVs have gradually become thought of as "dogrobbers" in bone tissue-the "eternal battle field" -in a delicate dynamic balance of destruction and reconstruction. In the current review, we give a brief description of the major constituent cells in bone tissues and explore the progress of current research on bone-derived EVs. In addition, this review also discusses in depth not only potential directions for future research to breakthrough in this area but also problems existing in current research that need to be solved for a better understanding of bone tissues.

Garcinol suppresses RANKL-induced osteoclastogenesis and its underlying mechanism

Osteoclasts (OCs) are multinuclear giant cells responsible for bone resorption, and an excessive bone resorption by OCs plays an important role in osteoporosis. Commonly used drugs for the treatment of osteoporosis have severe side effects. As such, identification of alternative treatments is essential. Garcinol, a polyisoprenylated benzophenone extracted from the fruit of Garcinia indica, has shown a strong antitumor effect through the nuclear factor-κB (NF-κB) and mitogen-associated protein kinases (MAPK) signaling pathways. However, the role of garcinol in the osteoclastogenesis is still unclear. Here, we demonstrated that garcinol can inhibit the receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis, osteoclastogenesis-related gene expression, the f-actin ring, and resorption pit formation. In addition, garcinol abrogated RANKL-induced osteoclastogenesis by attenuating the degradation of the MAPK, NF-κB, and PI3K-AKT signaling pathway as well as downstream factors c-jun, c-fos, and NFATC1. In vivo, suppression of osteoclastogenesis by garcinol was evidenced by marked inhibition of lipopolysaccharide-induced bone resorption. In conclusion, our data demonstrated that garcinol inhibited the RANKL-induced osteoclastogenesis by suppressing the MAPK, NF-κB, and PI3K-AKT signaling pathways and thus has potential as a novel therapeutic option for osteolytic bone diseases.

Asiaticoside, a component of Centella asiatica attenuates RANKL-induced osteoclastogenesis via NFATc1 and NF-κB signaling pathways

Identification of natural compounds that inhibit osteoclastogenesis will facilitate the development of antiresorptive treatment of osteolytic bone diseases. Asiaticoside is a triterpenoid derivative isolated from Centella asiatica, which exhibits varying biological effects like angiogenesis, anti-inflammation, wound healing, and osteogenic differentiation. However, its role in osteoclastogenesis remains unknown. Here, we show that Asiaticoside can suppress RANKL-induced osteoclast formation and bone resorption in a dose-dependent manner. Asiaticoside attenuated the expression of osteoclast marker genes including Ctsk, Atp6v0d2, Nfatc1, Acp5, and Dc-stamp. Furthermore, Asiaticoside inhibited RANKL-mediated NF-κB and NFATc1 activities, and RANKL-induced calcium oscillation. Collectively, this study demonstrates that Asiaticoside inhibited osteoclast formation and function through attenuating RANKL-induced key signaling pathways, which may indicate that Asiaticoside is a potential antiresorptive agent against osteoclast-related osteolytic bone diseases.

The emerging role of Hippo signaling pathway in regulating osteoclast formation

A delicate balance between osteoblastic bone formation and osteoclastic bone resorption is crucial for bone homeostasis. This process is regulated by the Hippo signaling pathway including key regulatory molecules RASSF2, NF2, MST1/2, SAV1, LATS1/2, MOB1, YAP, and TAZ. It is well established that the Hippo signaling pathway plays an important part in regulating osteoblast differentiation, but its role in osteoclast formation and activation remains poorly understood. In this review, we discuss the emerging role of Hippo-signaling pathway in osteoclast formation and bone homeostasis. It is revealed that specific molecules of the Hippo-signaling pathway take part in a stage specific regulation in pre-osteoclast proliferation, osteoclast differentiation and osteoclast apoptosis and survival. Upon activation, MST and LAST, transcriptional co-activators YAP and TAZ bind to the members of the TEA domain (TEAD) family transcription factors, and influence osteoclast differentiation via regulating the expression of downstream target genes such as connective tissue growth factor (CTGF/CCN2) and cysteine-rich protein 61 (CYR61/CCN1). In addition, through interacting or cross talking with RANKL-mediated signaling cascades including NF-κB, MAPKs, AP1, and NFATc1, Hippo-signaling molecules such as YAP/TAZ/TEAD complex, RASSF2, MST2, and Ajuba could also potentially modulate osteoclast differentiation and function. Elucidating the roles of the Hippo-signaling pathway in osteoclast development and specific molecules involved is important for understanding the mechanism of bone homeostasis and diseases.

Kaempferol alleviates LPS-induced neuroinflammation and BBB dysfunction in mice via inhibiting HMGB1 release and down-regulating TLR4/MyD88 pathway

Kaempferol is a natural flavonoid with many biological activities including anti-oxidation and anti-inflammation. Nevertheless, its anti-neuroinflammation role and the relevant mechanism remain unclear. The present study was to investigate effects of kaempferol against LPS-induced neuroinflammation and blood-brain barrier dysfunction as well as the mechanism in mice. BALB/c mice were treated with LPS 5mg/kg to induce inflammation after pre-treatment with kaempferol 25, 50, or 100mg/kg for 7days. The results showed that kaempferol reduced the production of various pro-inflammatory factors and inflammatory proteins including IL-1β, IL-6, TNF-α, MCP-1, COX-2 and iNOS in brain tissues. In addition, kaempferol also protected BBB integrity and increased BBB related proteins including occludin-1, claudin-1 and CX43 in brain of LPS-induced mice. Furthermore, kaempferol significantly reduced HMGB1 level and suppressed TLR4/MyD88 inflammatory pathway in both transcription level and translation level. These results collectively suggested that kaempferol might be a promising neuroprotective agent for alleviating inflammatory responses and BBB dysfunction by inhibiting HMGB1 release and down-regulating TLR4/MyD88 inflammatory pathway.

Microgravity influences maintenance of the human muscle stem/progenitor cell pool

Microgravity induces skeletal muscle atrophy; however, the underlying mechanism is not clarified. In particular, the influence of microgravity on human skeletal muscle stem/progenitor cells (SMPCs) is not well understood. In this study, we used induced pluripotent stem cell-derived human SMPCs to investigate the effect of microgravity on maintenance of the stem/progenitor cell pool. Human SMPCs were induced by free-floating spherical aggregation culture, and derivatized-SMPC spheres were maintained in a microgravity condition (10^-3 G) for 2 weeks using a clinostat rotation system. Microgravity culture deformed the SMPC spheres, with no signs of apoptosis. The most obvious change from microgravity culture was a significant decrease in the expression level of Pax7 in the SMPC spheres, with reduced numbers of myotubes in adhesion culture. Pax7 expression also decreased in the presence of the proteasome inhibitor MG132, indicating that the proteasomal degradation of Pax7 protein is not critical for its reduced expression in microgravity culture. Moreover, microgravity culture decreased the expression level of tumor necrosis factor receptor-associated factor 6 (TRAF6) and phosphorylation of its downstream molecule extracellular-related kinase (ERK) in SMPC spheres. Therefore, microgravity negatively regulates Pax7 expression in human SMPCs possibly through inhibition of the TRAF6/ERK pathway to consequently dysregulate SMPC pool maintenance. Overall, these results suggest that skeletal muscle atrophy is caused by microgravity-induced exhaustion of the stem cell pool.

Neutrophil elastase enhances IL-12p40 production by lipopolysaccharide-stimulated macrophages via transactivation of the PAR-2/EGFR/TLR4 signaling pathway

Proteinase-activated receptor 2 (PAR-2) and toll-like receptor 4 (TLR4) are involved in innate immune responses and signaling cross-talk between these receptor molecules has the potential to augment an ongoing inflammatory response. The aim of this study was to evaluate the possible cooperative influence of PAR-2 and TLR4 on IL-12p40 production by macrophages after stimulation with lipopolysaccharide (LPS). During culture, GM-CSF upregulated PAR-2 expression by macrophages in a time-dependent manner. Stimulation with LPS enhanced IL-12p40 production by macrophages in a concentration-dependent manner. While human neutrophil elastase (HNE) did not induce IL-12p40 production, pretreatment of macrophages with HNE synergistically increased the IL-12p40 protein level after LPS exposure. Silencing of TLR4 with small interfering RNA blunted the synergistic enhancement of IL-12p40 by HNE combined with LPS. Silencing of β-arrestin 2, p22phox, or ERK1/2 also inhibited an increase of IL-12p40. Interestingly, transfection of macrophages with small interfering RNA duplexes for DUOX-2, EGFR, TLR4, or TRAF6 significantly blunted the increase of IL-12p40 in response to treatment with HNE plus LPS. U73122 and Rottlerin also inhibited the increased production of IL-12p40. In conclusion, HNE is involved in transactivation of TLR4 through activation of DUOX-2/EGFR and synergistically enhances IL-12p40 production by macrophages stimulated with LPS.

Signaling Pathways in Osteoclast Differentiation

Osteoclasts are multinucleated cells of hematopoietic origin that are responsible for the degradation of old bone matrix. Osteoclast differentiation and activity are controlled by two essential cytokines, macrophage colony-stimulating factor (M-CSF) and the receptor activator of nuclear factor-κB ligand (RANKL). M-CSF and RANKL bind to their respective receptors c-Fms and RANK to stimulate osteoclast differentiation through regulation of delicate signaling systems. Here, we summarize the critical or essential signaling pathways for osteoclast differentiation including M-CSF-c-Fms signaling, RANKL-RANK signaling, and costimulatory signaling for RANK.

Triterpenoids and Polysaccharide Fractions of Ganoderma tsugae Exert Different Effects on Antiallergic Activities

This study was to investigate antiallergic effects of triterpenoids (Gt-TRE) and polysaccharide (Gt-PS) extracts from Ganoderma tsugae, using mast cell line RBL-2H3, T cell line EL4, primary T cells, and transfected RAW264.7 macrophage cells. The results showed that histamine secreted from activated RBL-2H3 mast cells was significantly suppressed by Gt-TRE but not Gt-PS. Interleukin- (IL-) 4 secreted from activated EL4 cells was significantly suppressed by Gt-TRE but not Gt-PS. Further primary CD4⁺ T cells cultures also confirmed that Gt-TRE (5 ~ 50 µg/mL) significantly suppressed Th2 cytokines IL-4 and IL-5 secretions but had no effect on Th1 cytokines IL-2 and interferon (IFN)-γ. Gt-PS did not affect IL-4 and IL-5 secretions until higher doses (400, 500 µg/mL) and significantly suppressed IFNγ secretions but enhanced IL-2 at these high doses. The reporter gene assay indicated that Gt-TRE inhibited but Gt-PS enhanced the transcriptional activity of NF-κB in activated transfected RAW264.7 cells and transfected EL4 cells. IL-4 secreted by this transfected EL-4 cells was also significantly decreased by Gt-TRE but not by Gt-PS, suggesting that these two fractions may exert different effects on NF-κB related cytokines expression. These data suggested that triterpenoids fraction of Ganoderma tsugae might be the main constituents to alleviate allergic asthma.

Regulation of NF-κB by TNF family cytokines

The NF-κB family of inducible transcription factors is activated in response to a variety of stimuli. Amongst the best-characterized inducers of NF-κB are members of the TNF family of cytokines. Research on NF-κB and TNF have been tightly intertwined for more than 25 years. Perhaps the most compelling examples of the interconnectedness of NF-κB and the TNF have come from analysis of knock-out mice that are unable to activate NF-κB. Such mice die embryonically, however, deletion of TNF or TNFR1 can rescue the lethality thereby illustrating the important role of NF-κB as the key regulator of transcriptional responses to TNF. The physiological connections between NF-κB and TNF cytokines are numerous and best explored in articles focusing on a single TNF family member. Instead, in this review, we explore general mechanisms of TNF cytokine signaling, with a focus on the upstream signaling events leading to activation of the so-called canonical and noncanonical NF-κB pathways by TNFR1 and CD40, respectively.

Antimicrobial activity and cytotoxicity of triterpenes isolated from leaves of Maytenus undata (Celastraceae)

Background

Plants of the genus Maytenus belong to the family Celastraceae and are widely used in folk medicine as anti-tumour, anti-asthmatic, analgesic, anti-inflammatory, antimicrobial and anti-ulcer agents, and as a treatment for stomach problems. The aim of this study was to isolate and identify active compounds with antifungal activity from Maytenus undata after a preliminary study highlighted promising activity in crude extracts.

Methods

Sequential extracts of M. undata leaves prepared using hexane, dichloromethane (DCM), acetone and methanol (MeOH) were tested for activity against Cryptococcus neoformans, a fungal organism implicated in opportunistic infections. Bioassay-guided fractionation of the hexane extract using C. neoformans as test organism was carried out to isolate antifungal compounds. The cytotoxicity of compounds isolated in sufficient quantities was evaluated using a tetrazolium-based colorimetric cellular assay (MTT) and a haemagglutination assay (HA).

Results

The hexane extract was most active with an MIC of 20 μg/ml against C. neoformans. The triterpene compounds friedelin (1), epifriedelanol (2), taraxerol (3), 3-oxo-11α-methoxyolean-12-ene-30-oic acid (4), 3-oxo-11α-hydroxyolean-12-ene-30-oic acid (5) and 3,11-dihydroxyolean-12-ene-30-oic acid (6) were isolated. Compound 6 was isolated for the first time from a plant species. The antimicrobial activity of compounds 1, 3, 5 and 6 was determined against a range of bacteria and fungi implicated in opportunistic and nosocomial infections. Compounds 5 and 6 were the most active against all the tested microorganisms with MIC values ranging between 24 and 63 μg/ml, except against Staphylococcus aureus which was relatively resistant. Compounds 1 and 3 had a low toxicity with an LC₅₀ > 200 μg/ml towards Vero cells in the MTT assay. Compounds 5 and 6 were toxic with LC₅₀ values of 6.03±0.02 and 2.98±0.01 μg/ml, respectively. Compounds 1 and 3 similarly were not toxic to the red blood cells (RBCs) but compounds 5 and 6 were toxic, showing HA titer values of 1.33 and 0.67 respectively.

Conclusions

Compounds 5 and 6 were the most active but were also relatively cytotoxic to monkey kidney cells and red blood cells, while the other isolated compounds were less active and less cytotoxic.

Neuroprotective effect of early and short-time applying sophoridine in pMCAO rat brain: down-regulated TRAF6 and up-regulated p-ERK1/2 expression, ameliorated brain infaction and edema

BACKGROUND

Matrine has been proven to protect ischemic injury in brain and sophoridine (SOP) is an isomeride of matrine. It is unknown whether SOP has this protective effect on ischemic injury in brain. We therefore investigated the potential neuroprotective role of SOP and the underlying mechanism.

METHODS

Male, Sprague-Dawley rats were randomly assigned into five groups: Vehicle (pMCAO+saline), High dose (pMCAO+SOP 10 mg/kg), Middle dose (pMCAO+SOP 5 mg/kg), Low dose (pMCAO+SOP 2.5 mg/kg) and Sham operated group. Permanent middle cerebral artery occlusion (pMCAO) model was used and SOP was administered intraperitoneally immediately after cerebral ischemia and once daily in the following days. Neurological deficit was evaluated using a modified six point scale; brain water content and infarct volume were measured. The expression of TRAF6 and ERK1/2 were measured by immunohistochemistry, Western blotting.

RESULTS

Compared with Vehicle group, the cerebral edema was alleviated in High dose group (P<0.05), and the infarct volume was decreased in Low dose group (P<0.05). Consistent with these results, immunohistochemistry and Western blot analysis indicated that TRAF6 expression was significantly decreased in SOP administrated groups at 24 h, and the expression of phosphorylated ERK1/2 increased in Low dose at 72 h.

CONCLUSIONS

SOP protected the brain from damage caused by pMCAO, and this effect may be through down-regulation of TRAF6 expression and up-regulation of ERK1/2 phosphorylation expression.

HIV-1 Nef induces proinflammatory state in macrophages through its acidic cluster domain: involvement of TNF alpha receptor associated factor 2

Background

HIV-1 Nef is a virulence factor that plays multiple roles during HIV replication. Recently, it has been described that Nef intersects the CD40 signalling in macrophages, leading to modification in the pattern of secreted factors that appear able to recruit, activate and render T lymphocytes susceptible to HIV infection. The engagement of CD40 by CD40L induces the activation of different signalling cascades that require the recruitment of specific tumor necrosis factor receptor-associated factors (i.e. TRAFs). We hypothesized that TRAFs might be involved in the rapid activation of NF-κB, MAPKs and IRF-3 that were previously described in Nef-treated macrophages to induce the synthesis and secretion of proinflammatory cytokines, chemokines and IFNβ to activate STAT1, -2 and -3.

Methodology/Principal Findings

Searching for possible TRAF binding sites on Nef, we found a TRAF2 consensus binding site in the AQEEEE sequence encompassing the conserved four-glutamate acidic cluster. Here we show that all the signalling effects we observed in Nef treated macrophages depend on the integrity of the acidic cluster. In addition, Nef was able to interact in vitro with TRAF2, but not TRAF6, and this interaction involved the acidic cluster. Finally silencing experiments in THP-1 monocytic cells indicate that both TRAF2 and, surprisingly, TRAF6 are required for the Nef-induced tyrosine phosphorylation of STAT1 and STAT2.

Conclusions

Results reported here revealed TRAF2 as a new possible cellular interactor of Nef and highlighted that in monocytes/macrophages this viral protein is able to manipulate both the TRAF/NF-κB and TRAF/IRF-3 signalling axes, thereby inducing the synthesis of proinflammatory cytokines and chemokines as well as IFNβ.

Inhibitory Effects of Ethyl Acetate Extract of Andrographis paniculata on NF-κB Trans-Activation Activity and LPS-Induced Acute Inflammation in Mice

This study was to investigate anti-inflammatory effect of Andrographis paniculata (Burm. f.) Nees (Acanthaceae) (AP). The effects of ethyl acetate (EtOAc) extract from AP on the level of inflammatory mediators were examined first using nuclear factor kappa B (NF-κB) driven luciferase assay. The results showed that AP significantly inhibited NF-κB luciferase activity and tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), macrophage inflammatory protein-2 (MIP-2) and nitric oxide (NO) secretions from lipopolysaccharide (LPS)/interferon-γ stimulated Raw264.7 cells. To further evaluate the anti-inflammatory effects of AP in vivo, BALB/c mice were tube-fed with 0.78 (AP1), 1.56 (AP2), 3.12 (AP3) and 6.25 (AP4) mg kg⁻¹ body weight (BW)/day in soybean oil, while the control and PDTC (pyrrolidine dithiocarbamate, an anti-inflammatory agent) groups were tube-fed with soybean oil only. After 1 week of tube-feeding, the PDTC group was injected with 50 mg kg⁻¹ BW PDTC and 1 h later, all of the mice were injected with 15 mg kg⁻¹ BW LPS. The results showed that the AP1, AP2, AP3 and PDTC groups, but not AP4, had significantly higher survival rate than the control group. Thus, the control, AP1, AP2, AP3 and PDTC groups were repeated for in vivo parameters. The results showed that the AP and PDTC groups had significantly lower TNF-α, IL-12p40, MIP-2 or NO in serum or peritoneal macrophages and infiltration of inflammatory cells into the lung of mice. The AP1 group also had significantly lower MIP-2 mRNA expression in brain. This study suggests that AP can inhibit the production of inflammatory mediators and alleviate acute hazards at its optimal dosages.

Crystallographic and mutational analysis of the CD40-CD154 complex and its implications for receptor activation

CD40 is a tumor necrosis factor receptor (TNFR) family protein that plays an important role in B cell development. CD154/CD40L is the physiological ligand of CD40. We have determined the crystal structure of the CD40-CD154 complex at 3.5 Å resolution. The binding site of CD40 is located in a crevice formed between two CD154 subunits. Charge complementarity plays a critical role in the CD40-CD154 interaction. Some of the missense mutations found in hereditary hyper-IgM syndrome can be mapped to the CD40-CD154 interface. The CD40 interaction area of one of the CD154 subunits is twice as large as that of the other subunit forming the binding crevice. This is because cysteine-rich domain 3 (CRD3) of CD40 has a disulfide bridge in an unusual position that alters the direction of the ladder-like structure of CD40. The Ser(132) loop of CD154 is not involved in CD40 binding but its substitution significantly reduces p38- and ERK-dependent signaling by CD40, whereas JNK-dependent signaling is not affected. These findings suggest that ligand-induced di- or trimerization is necessary but not sufficient for complete activation of CD40.

The death domain kinase RIP1 links the immunoregulatory CD40 receptor to apoptotic signaling in carcinomas

RIP1 is a component of a TRAF2 complex, required for caspase-8 activation and tumor cell killing in response to ligand binding of CD40.

CD40, a tumor necrosis factor (TNF) receptor family member, is widely recognized for its prominent role in the antitumor immune response. The immunostimulatory effects of CD40 ligation on malignant cells can be switched to apoptosis upon disruption of survival signals transduced by the binding of the adaptor protein TRAF6 to CD40. Apoptosis induction requires a TRAF2-interacting CD40 motif but is initiated within a cytosolic death-inducing signaling complex after mobilization of receptor-bound TRAF2 to the cytoplasm. We demonstrate that receptor-interacting protein 1 (RIP1) is an integral component of this complex and is required for CD40 ligand-induced caspase-8 activation and tumor cell killing. Degradation of the RIP1 K63 ubiquitin ligases cIAP1/2 amplifies the CD40-mediated cytotoxic effect, whereas inhibition of CYLD, a RIP1 K63 deubiquitinating enzyme, reduces it. This two-step mechanism of apoptosis induction expands our appreciation of commonalities in apoptosis regulatory pathways across the TNF receptor superfamily and provides a telling example of how TNF family receptors usurp alternative programs to fulfill distinct cellular functions.

Inhibitory effects of Angelica sinensis ethyl acetate extract and major compounds on NF-kappaB trans-activation activity and LPS-induced inflammation

AIM OF THE STUDY

Previous study showed that the ethyl acetate (EtOAc) fraction from Angelica sinensis (Oliv.) Diels (Apiaceae) (AS) inhibited nitric oxide (NO) and prostaglandin E(2) secretions in vitro. This study was to evaluate anti-inflammatory activity of AS EtOAc extract and its major compounds in vivo and in vitro.

MATERIALS AND METHODS

NF-kappaB luciferase activity and pro-inflammatory cytokine secretions from lipopolysaccharide (LPS) plus interferon (IFN)-gamma-stimulated RAW 264.7 cells pre-treated with EtOAc extract or compounds were analyzed. For further in vivo study, BALB/c mice were tube-fed with 1.56 (AS1 group), 6.25 (AS2 group) mg/kg body weight/day in 100 microl soybean oil, while the control and PDTC (pyrrolidine dithiocarbamate, an anti-inflammatory agent) groups were tube-fed with 100 microl soybean oil/day only. After 1 week of tube-feeding, the PDTC group was injected with 50 mg/kg BW PDTC and 1 h later, all of the mice were injected with 15 mg/kg BW LPS. The pro-inflammatory cytokine levels and lifespan of LPS-challenged mice were determined.

RESULTS

The results showed that AS EtOAc extract significantly inhibited NF-kappaB luciferase activity and TNF-alpha, IL-6, macrophage inflammatory protein-2 (MIP-2) and NO secretions from LPS/IFN-gamma-stimulated RAW 264.7 cells. The AS1 and PDTC groups, but not AS2, had significantly higher survival rate than the control group. This was characterized by the inhibition of the serum TNF-alpha and IL-12p40 levels after LPS injection (p<0.05). The major compounds of AS, ferulic acid and Z-ligustilide, also significantly decreased NF-kappaB luciferase activity, which may contribute to the anti-inflammatory activity of AS.

CONCLUSIONS

Low dose of AS EtOAc extract that inhibits the production of inflammatory mediators alleviates acute inflammatory hazards and protect mice from endotoxic shock.

Anti-inflammatory activity of new compounds from Andrographis paniculata by NF-kappaB transactivation inhibition

Previous studies showed that the ethyl acetate (EtOAc) fraction of Andrographis paniculata (AP) possessed anti-inflammatory activity. This study further isolated these active compounds from bioactivity-guided chromatographic fractionation and identified eight pure compounds. Reporter gene assay indicated that 5-hydroxy-7,8-dimethoxyflavone (1), 5-hydroxy-7,8-dimethoxyflavanone (2), a mix of beta-sitosterol (3a) and stigmasterol (3b), ergosterol peroxide (4), 14-deoxy-14,15-dehydroandrographolide (5), and a new compound, 19-O-acetyl-14-deoxy-11,12-didehydroandrographolide (6a), significantly inhibited the transcriptional activity of NF-kappaB in LPS/IFN-gamma stimulated RAW 264.7 macrophages (P < 0.05). The two most abundant compounds, 14-deoxy-11,12-didehydroandrographolide (7) and andrographolide (8), had less inhibitory activity but exerted greater inhibitory activity by hydrogenation, oxidation, or acetylation to become four derived compounds, 9, 10, 11, and 12. All of the compounds significantly decreased TNF-alpha, IL-6, macrophage inflammatory protein-2 (MIP-2), and nitric oxide (NO) secretions from LPS/IFN-gamma stimulated RAW 264.7 cells. Compounds 5, 11, and 12 exerted the strongest inhibitory effect on NF-kappaB-dependent transactivation in the RAW 264.7 cell, with IC(50) values of 2, 2.2, and 2.4 microg/mL, respectively, providing encouraging results for bioactive compound development.

Cytosol as battleground: ubiquitin as a weapon for both host and pathogen

Ubiquitin was first described as a tag allowing cells to degrade and recycle their own proteins. Recent research has shown ubiquitin to be central for immune system recognition of invading bacteria. This review describes a set of complex host-pathogen interactions that are dependent on ubiquitination. From the host perspective, ubiquitin-dependent activation of inflammation and degradation of bacterial effectors is protective. Several pathogens become ubiquitinated in the host cell cytosol, and recent research suggests that this could trigger a form of autophagy, increasingly recognized as an important mechanism for the control of infection by a variety of human pathogens. Meanwhile, bacteria have developed mechanisms to evade or exploit the fundamental processes activated by ubiquitination, producing both ubiquitin ligases and deubiquitinases that modulate host responses.

Ethyl acetate extracts of alfalfa (Medicago sativa L.) sprouts inhibit lipopolysaccharide-induced inflammation in vitro and in vivo

This study aimed to investigate if food components that exert anti-inflammatory effects may be used for inflammatory disorders by examining alfalfa sprout ethyl acetate extract (ASEA). The cytokine profile and life span of BALB/c mice with acute inflammation after intra-peritoneal (ip) injection of 15 mg/kg BW lipopolysaccharide (LPS) were determined. The results showed that the life span of LPS-induced inflammatory mice were negatively correlated with serum levels of TNF-α, IL-6, and IL-1β at 9 hr after LPS-injection, which indicated that suppressing these cytokines in the late phase of inflammation may be beneficial for survival. The in vitro experiment then showed that ASEA significantly reduced IL-6 and IL-1β production and the NF-κB trans-activation activity of mitogen-stimulated RAW264.7 cells. To further evaluate the anti-inflammatory effects of ASEA in vivo, BALB/c mice were tube-fed with 25 mg ASEA/kg BW/day in 50 μl sunflower oil, while the control and PDTC (pyrrolidine dithiocarbamate, an anti-inflammatory agent) groups were tube-fed with 50 μl sunflower oil/day only. After one week of tube-feeding, the PDTC group was injected with 50 mg/kg BW PDTC and one hour later, all of the mice were injected with 15 mg/kg BW LPS. The results showed that the ASEA and PDTC groups had significantly lower serum TNF-α, IL-6, and IL-1β levels at 9 hr after LPS challenge, and significantly higher survival rates than the control group. This study suggests that ASEA supplementation can suppress the production of pro-inflammatory cytokines and alleviate acute inflammatory hazards.

Nucling interacts with nuclear factor-kappaB, regulating its cellular distribution

Nucling is an Apaf1-binding proapoptotic protein involved in apoptosome-mediated apoptosis. Luciferase assays have revealed that the activation of nuclear factor-kappaB induced by tumor necrosis factor-alpha, interleukin-1beta and lipopolysaccharide is downregulated by the overexpression of Nucling in HEK293 cells. Moreover, the expression of endogenous cyclooxygenase 2, tumor necrosis factor-alpha and galectin-3, the end-point molecules in the pathway for the activation of nuclear factor-kappaB, as well as nuclear factor-kappaB (p65) itself, is upregulated in Nucling gene-deficient mouse embryonic fibroblasts, suggesting that nuclear factor-kappaB is a target of Nucling. Subsequent study has revealed that Nucling physically interacts with nuclear factor-kappaB (p65 and p50) and that the binding domain of Nucling is its amino-terminal region (amino acids 1-466) containing ankyrin repeats. Overexpression of Nucling prevents the translocation of nuclear factor-kappaB into the nucleus. In addition, the cytoplasmic retention of endogenous nuclear factor-kappaB in resting cells is not observed in Nucling gene-deficient mouse embryonic fibroblasts. These results reveal a novel function of Nucling as a suppressor of nuclear factor-kappaB, mediated by its cytoplasmic retention through physical interaction.

The production of nitric oxide and prostaglandin E2 in peritoneal macrophages is inhibited by Andrographis paniculata, Angelica sinensis and Morus alba ethyl acetate fractions

AIM OF THE STUDY

Traditional Chinese medicine herbs (TCMHs) are used in medicines as well as in daily dietary supplements in Asia. In this study, we employed pNF-kappaB-Luc or pIFN-gamma-Luc and BALB/c mice peritoneal macrophages or splenocytes to investigate both the immune and inflammatory effects of six selected plant species.

MATERIALS AND METHODS

Specifically, we used ethyl acetate fractions of Astragalus membranaceus (Fisch.) Bunge var. mongholicus (Bunge) Hsiao (Fabaceae) (AM), Andrographis paniculata (Burm. f.) Nees (Acanthaceae) (AP), Angelica sinensis (Oliv.) Diels (Apiaceae) (AS), Eucommia ulmodes Oliv. (Eucommiaceae) leaves (EU leaves), Isatis indigotica Fort. (Brassicaceae) (II) and Morus alba L. (Moraceae) (MA).

RESULTS

We found that ethyl acetate fractions of AP, AS and MA significantly decreased NF-kappaB luciferase activity and also the secretion of NO and PGE(2) in LPS/IFN-gamma stimulated mouse peritoneal macrophages (p<0.05). In contrast, they did not affect IFN-gamma luciferase activity or IFN-gamma production in concanavalin A (Con A)-activated mouse splenocytes. Our results indicated that the anti-inflammatory properties of these plant extracts might be resulted from the inhibition of pro-inflammatory mediators (e.g., NO and PGE(2)), at least in part via suppression of a signaling pathway such as NF-kappaB.

CONCLUSIONS

Collectively, we have found that three potent bioactive TCMH species exerted significant NF-kappaB inhibitory activity and acted in a cell type dependent fashion.

TRAF proteins in CD40 signaling

The tumor necrosis factor receptor (TNFR) superfamily molecule CD40 is expressed by a wide variety of cell types following activation signals, and constitutively on B lymphocytes, macrophages, and dendritic cells. CD40 signals to cells stimulate kinase activation, gene expression, production of a antibody and a variety of cytokines, expression or upregulation of surface molecules, and protection or promotion of apoptosis. Initial steps in CD40-mediated signal cascades involve the interactions of CD40 with various members of the TNFR-associated factor (TRAF) family of cytoplasmic proteins. This review summarizes current understanding of the nature of these interactions, and how they induce and regulate CD40 functions.

Inflammatory responses involving tumor necrosis factor receptor-associated factor 6 contribute to in-stent lesion formation in a stent implantation model of rabbit carotid artery

OBJECTIVE

Inflammatory responses are considered to represent a unique property after stent implantation, and we previously demonstrated that inflammatory signaling involving tumor necrosis factor receptor-associated factor 6 (TRAF6) contributes to neointimal formation in a balloon injury model of rabbit carotid artery. The purpose of this study was to examine the role of TRAF6 in in-stent lesion formation after stent implantation in the rabbit carotid artery.

METHODS

Rabbit carotid arteries were injured with a 2F Fogarty catheter, and 28 days later, the same arteries were implanted with a 3-mm-diameter Palmaz-Schatz stent. A dominant negative (DN) form of TRAF6 (pME-FLAG-T6deltaRZ5) was then transferred using a plasmid-based electroporation method. Its effects were evaluated compared with the findings in arteries treated with control plasmid (pME-FLAG).

RESULTS

Immunostaining with anti-FLAG tag antibody showed that an expression plasmid vector containing the DN-TRAF6 sequence was successfully transferred to the arterial intima and media. Morphometric analyses revealed that the increase of intimal area in in-stent lesions was significantly inhibited by DN-TRAF6 14 days after stent implantation (DN-TRAF6 group, 3.01 +/- 0.25 x 10(5) microm2 vs control group, 4.25 +/- 0.23 x 10(5) microm2, P < .01), and the cell density was increased compared with that in the control group. In the DN-TRAF6 plasmid-treated vessels, cell replication was prevented in both the intima and media, and fewer leukocytes adhered to the luminal surface. Moreover, DN-TRAF6 suppressed macrophage infiltration, activation of proteases, and proteoglycan accumulation in the in-stent intima.

CONCLUSIONS

These findings suggest that TRAF6 plays an important role in cell replication, inflammatory cell infiltration, protease activity, and extracellular matrix accumulation that contributes to in-stent lesion development.

AsialoGM1 and TLR5 cooperate in flagellin-induced nucleotide signaling to activate Erk1/2

Bacterial flagellin can interact with both Toll-like receptor 5 (TLR5) and the cell surface glycolipid, asialoGM1, to activate an innate immune response. The induction of mucin by flagellin in human lung epithelial cells (NCIH292) is dependent on asialoGM1 ligation, ATP receptor signaling, Ca2+ mobilization, and Erk1/2 activation. Conversely, the activation of NF-kappaB by flagellin is dependent on signaling through TLR5. These results prompted us to ask whether the flagellin-induced TLR5 signaling pathway was intersecting with or mutually independent of the nucleotide receptor pathway activated downstream of asialoGM1. Herein, we demonstrate that the release of ATP induced by flagellin is dependent on a Toll signaling cascade. Although Toll was able to activate NF-kappaB in the absence of extracellular ATP, Toll required ATP to activate Erk1/2. These results suggest interdependence between the asialoGM1 and TLR5 pathways and reveal a previously unsuspected role for autocrine extracellular ATP signaling in TLR signaling.

The TRAF6, but not the TRAF2/3, binding domain of CD40 is required for cytokine production in human lung fibroblasts

Fibroblasts are key effector cells in inciting inflammation, wound healing, and scarring. CD40, a member of the TNF receptor superfamily, mediates intercellular communication between fibroblasts and cells that express CD154 (CD40L), including T lymphocytes and platelets. To better understand the mechanisms by which CD40 regulates fibroblast function in inflammation and scarring, we examined the ability of CD40 cytoplasmic tail regions (CD40ct) containing the TRAF6 or the TRAF2/3 binding domains to regulate cytokine and chemokine expression by primary human lung fibroblasts. The full-length human CD40ct, the first 35 amino acids of the CD40ct encompassing the TRAF6 binding site (1-35), and amino acids 35-53 containing the TRAF2/TRAF3 binding domain were expressed in human lung fibroblasts as fusion proteins with the extracellular domain of human CD8alpha by retroviral transduction. The TRAF6, but not the TRAF2/3, binding domain was found to regulate IL-8 and IL-6 production, and induce activation of NF-kappaB and Jun kinase in lung fibroblasts, demonstrating for the first time that CD40ct domains can function independently to regulate pro-inflammatory responses of primary human fibroblasts. Thus, targeting TRAF6 function through pharmacological intervention may represent a viable strategy for modulating localized inflammation.

Jun N-terminal kinase is essential for CD40-mediated IgE class switching in B cells

BACKGROUND

CD40 ligation activates nuclear factor kappaB (NF-kappaB) and the mitogen-activated protein kinases p38 and C-Jun N-terminal kinase (JNK) and causes immunoglobulin class-switch recombination (CSR) in B cells. Both NF-kappaB and p38 are important for CD40-mediated CSR. The role of JNK activation in CD40-mediated isotype switching is unknown.

OBJECTIVE

We sought to determine the role of JNK activation in CD40-mediated isotype switching.

METHODS

Splenic B cells from BALB/c mice were stimulated with anti-CD40 mAb and IL-4 or with soluble CD40 ligand in the presence or absence of SP600125, an anthrapyrazolone inhibitor of JNK. The following events were examined: IgE production by means of ELISA; S(mu)-S(epsilon) deletional switch recombination by means of digestion circularization PCR; Cepsilon germline, mature epsilon, and activation-induced deaminase (AID) transcription by means of RT-PCR; and proliferation by tritiated thymidine incorporation and surface expression of CD23, CD54, and CD86 by means of FACS analysis.

RESULTS

SP600125 at 10 microM drastically inhibited JNK phosphorylation but had little effect on CD40-mediated p38 phosphorylation and expression of the NF-kappaB dependent genes c-Myc and bcl-xL. SP600125 inhibited IgE synthesis by approximately 88% but had no effect on B-cell proliferation and survival in response to anti-CD40 + IL-4 or on upregulation of CD23, CD54, and CD86 in response to CD40 ligation. Analysis of molecular events involved in IgE class switching revealed that SP600125 had no effect on the expression of C(epsilon) germline and AID transcripts. In contrast, SP600125 severely reduced S(mu)-S(epsilon) switch recombination and expression of mature epsilon transcripts.

CONCLUSION

These results demonstrate that JNK activation is essential for CD40-mediated CSR to IgE and suggest that JNK is important for AID activity in B cells.

TNF receptor-associated factor 6 is an essential mediator of CD40-activated proinflammatory pathways in monocytes and macrophages

The interaction between CD40 and its ligand, CD154, has been shown to play a role in the onset and maintenance of inflammatory disease. Contributing to this process is the ability of CD40 to signal monocyte and macrophage inflammatory cytokine production. We have shown that this event is dependent on Src family tyrosine kinase activity and the subsequent activation of ERK1/2. To address the role of TNFR-associated factor (TRAF) family members in facilitating this signaling pathway, we transfected a CD40-deficient macrophage cell line with wild-type human CD40, or with CD40 containing disrupted TRAF binding sites. Ligation of either wild-type CD40, or a CD40 mutant unable to bind TRAF2/3/5, resulted in the stimulation of inflammatory cytokine production. However, ligation of a CD40 mutant lacking a functional TRAF6 binding site did not initiate inflammatory cytokine production, and this mutant was found to be defective in CD40-mediated activation of ERK1/2, as well as IkappaB kinase (IKK) and NF-kappaB. Likewise, introduction of a dominant-negative TRAF6 into a wild-type (CD40(+)) macrophage cell line resulted in abrogation of CD40-mediated induction of inflammatory cytokine synthesis. Finally, treatment of monocytes with a cell-permeable peptide corresponding to the TRAF6-binding motif of CD40 inhibited CD40 activation of ERK1/2, IKK, and inflammatory cytokine production. These data demonstrate that TRAF6 acts as a critical adapter of both the Src/ERK1/2 and IKK/NF-kappaB proinflammatory signaling pathways in monocytes and macrophages.

MIP-1alpha induces differential MAP kinase activation and IkappaB gene expression in human B lymphocytes

The chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) stimulates migration of B cells and affects B cell immunoglobulin production. However, the molecular mechanisms by which MIP-1alpha modulates these biologic effects have not been completely defined. Previously, we demonstrated that treatment of B cells with MIP-1alpha induced the transcription factor, nuclear factor (NF)-kappaB, to bind to DNA, concomitant with the degradation of IkappaBalpha, a cytoplasmic inhibitor of NF-kappaB activation. Here, we report that MIP-1alpha treatment of tonsil B cells induced IkappaB gene expression that was dependent on MIP-1alpha-mediated activation of a pathway(s) involving NF-kappaB and phosphatidylinositol-3 kinase (PI3K). The NF-kappaB pathway is understood to be controlled in an autoregulatory fashion, so expression of IkappaB is thought to provide a means by which B cells modulate this pathway after stimulation with MIP-1alpha. Although the idea of NF-kappaB autoregulation is not novel, this is the first report to suggest the regulation of B cell gene expression by MIP-1alpha. In addition, we observed the activation of Jun N-terminal kinase (JNK) and p38 mitogenic-activated protein kinase (MAPK), but not extracellular signal-related kinase (ERK) in response to MIP-1alpha. Although p38 and NF-kappaB activity were both necessary for B cell migration, IkappaB gene expression was not affected by p38 inhibition, suggesting that p38 is involved in a separate MIP-1alpha-mediated signal transduction pathway.