Toll-like receptor 9 regulates tumor necrosis factor-alpha expression by different mechanisms. Implications for osteoclastogenesis

Mitochondrial DNA and Inflammation in Alzheimer's Disease

Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

APOBEC3-mediated mutagenesis in cancer: causes, clinical significance and therapeutic potential

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptides (APOBECs) are cytosine deaminases involved in innate and adaptive immunity. However, some APOBEC family members can also deaminate host genomes to generate oncogenic mutations. The resulting mutations, primarily signatures 2 and 13, occur in many tumor types and are among the most common mutational signatures in cancer. This review summarizes the current evidence implicating APOBEC3s as major mutators and outlines the exogenous and endogenous triggers of APOBEC3 expression and mutational activity. The review also discusses how APOBEC3-mediated mutagenesis impacts tumor evolution through both mutagenic and non-mutagenic pathways, including by inducing driver mutations and modulating the tumor immune microenvironment. Moving from molecular biology to clinical outcomes, the review concludes by summarizing the divergent prognostic significance of APOBEC3s across cancer types and their therapeutic potential in the current and future clinical landscapes.

Antibody-Pattern Recognition Receptor Agonist Conjugates: A Promising Therapeutic Strategy for Cancer

Antibody-drug conjugates (ADCs) are composed of monoclonal antibodies linked to cytotoxic payload drugs, each of which can be diversely designed in accordance with pharmacological and clinical requirements. The use of ADCs is effective for the treatment of different diseases, including cancers, and is gaining widespread attention. To date, 12 ADCs have been approved by the U.S. Food and Drug Administration for treating cancer and improving the quality of life of patients. To expand the application of ADCs and improve their treatment efficiency, various formats have recently been manufactured, including pattern recognition receptor (PRR) agonist-based ADCs. The antibody has a unique structure that enables the specific delivery of PRR agonists to the tumor area, and this improves the therapeutic efficacy while minimizing systemic toxicity. This review briefly discusses the current landscape and future perspectives of antibody-PRR agonist conjugates for cancer therapy.

A Squalene-Based Nanoemulsion for Therapeutic Delivery of Resiquimod

Agonists for toll-like receptors (TLRs) have shown promising activities against cancer. In the present study, a squalene-based nanoemulsion (NE) was loaded with resiquimod, a TLR7/8 agonist for therapeutic delivery. R848 NE was developed and characterized for long-term stability. In vitro and in vivo antitumor immunity of R848 NE were also evaluated in combination with SD-101, a CpG-containing TLR9 agonist. In vitro studies demonstrated strong long-term stability and immune responses to R848 NE. When combined with SD-101, strong antitumor activity was observed in MC38 murine colon carcinoma model with over 80% tumor growth inhibition. The combination treatment showed a 4-fold increase in systemic TNFa production and a 2.6-fold increase in Cd8a expression in tumor tissues, suggesting strong cell-mediated immune responses against the tumor. The treatment not only demonstrated a strong antitumor immunity by TLR7/8 and TLR9 activations but also induced PD-L1 upregulation in tumors, suggesting a potential therapeutic synergy with immune checkpoint inhibitors.

The Toll-like receptor ligand, CpG oligodeoxynucleotides, regulate proliferation and osteogenic differentiation of osteoblast

BACKGROUND

This study aimed to investigate the regulation of CpG oligodeoxynucleotides (ODNs) on proliferation and osteogenic differentiation of MC3T3 cells.

METHODS

The laser co-focusing and flow cytometry assay were employed to detect cell uptake of CpG ODN 2006. Twelve ODNs were sythesized, and their effects on proliferation and differentiation were detected by MTT and alkaline phosphatase (ALP) activity assay. Flow cytometry assay was used to examine the regulation of CpG ODN on cell cycle. Quantitative real-time PCR (qRT-PCR) and western blot were used to evaluate the regulation of CpG ODN on mRNA and protein expression of osteogenic differentiation genes.

RESULTS

The phosphorothioate CpG ODN 2006 could efficiently enter the MC3T3 cells in 1 h and locate in the cytoplasm. The MTT assay demonstrated CpG ODNs could promote MC3T3 cell proliferation and differentiation in the early stage, and gradually attenuated along with the increase of treating time, except for BW001 and FC001. qRT-PCR assay demonstrated that all the 12 CpG ODNs could promote the relative expression level of osteogenic differentiated genes, SP7 and OCN. In addition, western blot analysis suggested the CpG ODNs of BW001 and FC001 could increase the protein expression of P27Kip1 and Runx2 and decrease the protein expression of cyclin D1.

CONCLUSION

The selected CpGODNs may be a potential gene therapy for bone regeneration of periodontitis.

The APOBEC3 genes and their role in cancer: insights from human papillomavirus

The interaction between human papillomaviruses (HPV) and the apolipoprotein-B mRNA-editing catalytic polypeptide-like (APOBEC)3 (A3) genes has garnered increasing attention in recent years, with considerable efforts focused on understanding their apparent roles in both viral editing and in HPV-driven carcinogenesis. Here, we review these developments and highlight several outstanding questions in the field. We consider whether editing of the virus and mutagenesis of the host are linked or whether both are essentially separate events, coincidentally mediated by a common or distinct A3 enzymes. We discuss the viral mechanisms and cellular signalling pathways implicated in A3 induction in virally infected cells and examine which of the A3 enzymes might play the major role in HPV-associated carcinogenesis and in the development of therapeutic resistance. We consider the parallels between A3 induction in HPV-infected cells and what might be causing aberrant A3 activity in HPV-independent cancers such as those arising in the bladder, lung and breast. Finally, we discuss the implications of ongoing A3 activity in tumours under treatment and the therapeutic opportunities that this may present.

An oligodeoxynucleotide that induces differentiation of bone marrow mesenchymal stem cells to osteoblasts in vitro and reduces alveolar bone loss in rats with periodontitis

To investigate the effect of oligodeoxynucleotides (ODNs) on the differentiation of rat bone marrow mesenchymal stem cells (BMSCs) to osteoblasts, in order to find a candidate ODN with potential for the treatment of periodontitis, a series of ODNs were designed and selected to test their effect on the promotion of the differentiation of BMSCs to osteoblasts in vitro and on the repair of periodontal tissue in rats with periodontitis. It was found that MT01, one of the ODNs with the sequences of human mitochondrial DNA, stimulated the proliferation of BMSCs, the differentiation of BMSCs to osteoblasts and mRNA expression of bone-associated factors including Runx2, Osterix, OPG, RANKL and collagen I in vitro. In vivo study showed that MT01 prevented the loss of alveolar bone in the rats with periodontitis and induced the production of proteins of OPG and Osterix in the bone tissue. These results indicated that MT01 could induce differentiation of BMSCs to osteoblasts and inhibit the alveolar bone absorption in rats with periodontitis.

An oligodeoxynucleotide with promising modulation activity for the proliferation and activation of osteoblast

The paper explored the regulatory role of oligodeoxynucleotides (ODNs) with specific sequences in the proliferation and activation of osteoblast, using human osteoblast-like cell line MG 63 as the model. Through the administration of ODNs to MG 63 cells at a concentration of 1.0 μg/mL, ODN MT01 with positive effects on proliferation and activation of osteoblast was selected from 11 different ODNs by methyl thiazolyl tetrazolium (MTT) assay and alkaline phosphatase (ALP) activity measurement. To get a deeper insight into the molecular mechanism, effects of ODN MT01 treatment on the expression level of Sp7, runx-2, collagen-I, osteoprotegerin (OPG) and RANK ligand (RANKL) were determined using quantitative real time PCR and Western blotting. Remarkably, the mRNA and protein expression levels of Sp7, runx-2, collagen-I and OPG were improved after ODN MT01 treatment. Meanwhile, the protein expression level of RANKL was dramatically decreased. These results suggested that ODN MT01 had a significant impact in facilitating osteogenic proliferation and activation, and provided a direct evidence for the notion that single strand ODN could regulate the balance of bone formation and resorption, and thus was of great potential in the rebuilding of alveolar bone.

Hypothesis-driven candidate gene association studies: practical design and analytical considerations

Candidate gene association studies (CGAS) are a useful epidemiologic approach to drawing inferences about relations between genes and disease, especially when experimental data support the involvement of specific biochemical pathways. The value of CGAS is apparent when allele frequencies are low, effect sizes are small, or the study population is limited or unique. CGAS is also valuable for validating previous reports of genetic associations with disease in different populations. Despite the many advantages, the information generated from CGAS is sometimes compromised because of either inefficient study design or suboptimal analytical approaches. Here the authors discuss issues related to the study design and statistical analyses of CGAS that can help to optimize their usefulness and information content. These issues include judicious hypothesis-driven selection of biochemical pathways, genes, and single nucleotide polymorphisms, as well as appropriate quality control and analytical procedures for measuring main effects and for evaluating environmental exposure modifications and interactions. A study design algorithm using the example of DNA repair genes and cancer is presented for purposes of illustration.

Enhanced inhibitory effects of a novel CpG motif on osteoclast differentiation via TREM-2 down-regulation

Recognition of oligodeoxynucleotides containing CpG motifs (CpG-ODNs) by toll-like receptor 9 (TLR9) inhibits RANKL-induced osteoclastogenesis from precursors. This inhibitory effect suggests the possibility of using this strategy to block pathological bone loss. However, the enhancing effect of CpG-ODNs on OC formation from RANKL-primed pre-osteoclasts (pOCs) has hampered their clinical use. In this report, we developed a CpG-KSK13 oligonucleotide with an alternative CpG motif, and tested its effect on osteoclastogenesis in comparison with previously used murine CpG motif (CpG-1826) or human CpG motif (CpG-2006) oligonucleotides. Murine CpG-1826 inhibited RANKL-induced OC formation from BMMs but not from RANKL-primed pOCs, while CpG-KSK13 treatment strongly inhibited OC formation from both BMM and primed pOC cells. CpG-KSK13 also showed a potent inhibitory effect on human OC differentiation using peripheral blood mononuclear cells (PBMCs), which was in contrast to the species-specific response of murine CpG-1826 or human CpG-2006. Moreover, CpG-KSK13 effectively inhibited NFATc1 activity, but not NF-kappaB or AP-1 activity, and decreased TREM-2 promoter activity and subsequent surface expression of the TREM-2 protein induced by M-CSF and RANKL. These results demonstrate that the recognition of CpG-KSK13 via TLR9 inhibits osteoclastogenesis by down-regulating TREM-2 expression. Thus, our findings provide evidence for the potential use of CpG-KSK13 as an anti-osteoclastogenic agent for human and for pre-clinical animals.

Broad-spectrum drugs against viral agents

Development of antivirals has focused primarily on vaccines and on treatments for specific viral agents. Although effective, these approaches may be limited in situations where the etiologic agent is unknown or when the target virus has undergone mutation, recombination or reassortment. Augmentation of the innate immune response may be an effective alternative for disease amelioration. Nonspecific, broad-spectrum immune responses can be induced by double-stranded (ds)RNAs such as poly (ICLC), or oligonucleotides (ODNs) containing unmethylated deocycytidyl-deoxyguanosinyl (CpG) motifs. These may offer protection against various bacterial and viral pathogens regardless of their genetic makeup, zoonotic origin or drug resistance.

Rutin inhibits osteoclast formation by decreasing reactive oxygen species and TNF-alpha by inhibiting activation of NF-kappaB

Rutin, a glycoside of flavonol, inhibits osteoclast formation induced by receptor activator of NF-kappaB ligand (RANKL) in bone marrow-derived macrophages. It reduces reactive oxygen species produced by RANKL and its inhibitory effect results from reduced levels of TNF-alpha. Rutin also lowers NF-kappaB activation in response to RANKL.

Stimulation of osteoclastogenesis by enhanced levels of MIP-1alpha in BALB/c mice in vitro

OBJECTIVES

We compared osteoclast (OC) formation in bone marrow-derived macrophages (BMM) from C57BL/6 (B/6) and BALB/c (B/c) mice. After stimulation of receptor activator of nuclear factor-kappaB ligand (RANKL), enhanced OC formation and higher level of macrophage inflammatory protein-1alpha (MIP-1alpha) were observed in the BMM from B/c mice. In this study, we determined whether MIP-1alpha is responsible for stimulated OC formation in the BMM.

MATERIALS AND METHODS

OC formation was evaluated in BMM. Expression of MIP-1alpha during OC formation was analyzed at the mRNA and protein levels. Apoptosis of mature OCs was evaluated by observing the degradation of DNA. Activation of nuclear factor-kappaB (NF-kappaB) was measured by electrophoretic mobility shift assay.

RESULTS

After stimulation by RANKL expression of MIP-1alpha at the mRNA and protein levels was much higher in BMM from B/c mice than in BMM from B/6 mice. Transcripts of the MIP-1alpha receptors, CCR1 and CCR5, were present at similar levels in unstimulated BMM of the two strains. Blockade of MIP-1alpha inhibited OC formation, and exogenously added MIP-1alpha stimulated it in RANKL-stimulated BMM. MIP-1alpha affected not only the early precursors but also mature OCs. It prevented apoptosis of mature OCs by activating NF-kappaB, and the effect of RANKL on survival was dependent on its ability to induce MIP-1alpha.

CONCLUSIONS

MIP-1alpha, induced by RANKL during OC differentiation, increases OC formation by acting on OC progenitor cells, and prolongs survival of mature OC via signaling through NF-kappaB. The enhanced OC formation in BMM from B/c mice could be due to, at least in part, to their higher levels of MIP-1alpha.

Toll-like receptor 9 ligand blocks osteoclast differentiation through induction of phosphatase

CpG-ODN, in addition to stimulation of osteoclastogenic signals in early osteoclast precursors, also induces phosphatase, shifting the pattern of ERK phosphorylation from sustained to transient. This shift results in the degradation of c-fos, an essential molecule for osteoclast differentiation. Therefore, CpG-ODN blocks osteoclast differentiation.

INTRODUCTION

Activation of either Toll-like receptor 9 (TLR9) or RANK induces similar responses in osteoclast precursors. Paradoxically, activation of TLR9 results in inhibition of RANKL-induced osteoclastogenesis.

MATERIALS AND METHODS

We used bone marrow-derived osteoclast precursors. Analyses of signaling molecules phosphorylation were performed using Western blotting. Different levels of gene expression analyses were performed using RT-PCR, Northern, and run-on analyses (for RNA), and EMSA, Western, and pulse-chase experiments (for protein). Phosphatase activity was measured spectrophotometrically.

RESULTS

We found that RANKL and TLR9 ligand, oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG-ODN), induce sustained and transient extracellular signal-regulated kinase (ERK) phosphorylation, respectively. Furthermore, together they induce a transient phosphorylation of ERK. The duration of ERK phosphorylation is a key factor in determining induction of c-fos, a protein critical for osteoclastogenesis. Indeed, we found that CpG-ODN does not induce c-fos and inhibits its induction by RANKL by enhancing c-fos mRNA and protein degradation. Our observation that CpG-ODN, but not RANKL, induces the expression of the phosphatase PP2A suggests that CpG-ODN exerts its inhibitory activity by induction of ERK dephosphorylation. Moreover, together with the phosphatase inhibitor okadaic acid, CpG-ODN induces sustained ERK phosphorylation and c-fos expression.

CONCLUSIONS

Our findings suggest that the increased rate of c-fos degradation by the TLR9 ligand mediates the inhibition of RANKL-induced osteoclast differentiation. The TLR9 ligand, through induction of dephosphorylation, prevents the sustained ERK phosphorylation needed for maintaining high c-fos levels that are essential for osteoclast differentiation.

Role of CD40-Dependent Down-Regulation of CD154 in Impaired Induction of CD154 in CD4+ T Cells from HIV-1-Infected Patients

CD40-CD154 interaction is pivotal for cell-mediated immunity. There are contradictory reports on whether HIV-1 infection impairs CD154 induction. The interaction between CD40 and CD154 is important not only because it results in activation of APCs but also because it controls CD154 by diminishing expression of this molecule. Compared with healthy controls, CD4(+) T cells from HIV-1(+) patients had impaired induction of CD154 when T cell activation was mediated by CD40(+) APCs. In contrast, T cell activation in the absence of these cells resulted in normal CD154 expression. CD154 induction in HIV-1(+) patients and controls were similar upon blockade of CD40-CD154 binding. Defective regulation of CD154 appeared to occur downstream of the control of mRNA levels because up-regulation of CD154 mRNA was not impaired by HIV-1 infection. This work identifies CD40 as a mediator of impaired CD154 induction in HIV-1 infection and explains why this defect was not detected by studies where T cell activation was triggered independently of CD40(+) APCs. In addition, dysregulation of CD154 in HIV-1 infection likely contributes to immunodeficiency because diminished expression of CD154 induced by CD40 is of functional relevance, resulting in decreased dendritic cell maturation.

Interleukin (IL)-12 mediates the anti-osteoclastogenic activity of CpG-oligodeoxynucleotides

Bacterial DNA activates the innate immune system via interactions with Toll-like receptor 9 (TLR9). This receptor recognizes CpG-oligodeoxynucleotides (CpG-ODNs) mimicking the CpG dinucleotides in certain sequence contexts characterizing this DNA. Most studies have shown increased osteoclast differentiation by TLR ligands. We found that activation of TLRs (specifically TLR4 and TLR9) in early osteoclast precursors results in inhibition of receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast differentiation. Our objective is to identify the mechanism leading to this inhibitory effect of a TLR ligand. Since both RANKL-RANK and CpG-ODN-TLR9 interactions result in NF-kappaB activation, p38 and ERK phosphorylation, and TNF-alpha synthesis (all implicated in osteoclastogenesis), we hypothesized that CpG-ODN (but not RANKL) in addition induces the synthesis of an anti-osteoclastogenic factor. Control osteoclast precursors, and cells treated with RANKL, CpG-ODN, or their combination were studied using DNA arrays (GEArray Q Series Mouse NF-kappaB Signaling Pathway Gene Array, MM-016, SuperArray). We found a marked increase in the mRNA levels of the osteoclastogenesis inhibitor interleukin-12 (IL-12) in osteoclast precursors treated with CpG-ODN and CpG-ODN + RANKL. Northern and Western analyses, together with ELISA, confirmed the DNA array studies. In correlation with these findings, IL-12 inhibited RANKL-induced osteoclast differentiation and specific anti-IL-12-antibodies inhibited the anti-osteoclastogenic effect of CpG-ODN. In conclusion, activation of TLR9 by its ligand, CpG-ODN, results in synthesis and release of IL-12 opposing RANKL-induced osteoclast differentiation.

Differential contribution of osteoclast- and osteoblast-lineage cells to CpG-oligodeoxynucleotide (CpG-ODN) modulation of osteoclastogenesis

CpG-ODNs modulate osteoclast differentiation through Toll-like receptor 9 (TLR9). Using TLR9-deficient mice, we found that activation of TLR9 on both osteoclast precursors and osteoblasts mediate the osteoclastogenic effect of CpG-ODN. Osteoclastic TLR9 is more important for this activity.

INTRODUCTION

Bacterial infections cause pathological bone loss by accelerating differentiation and activation of the osteoclast. A variety of bacteria-derived molecules have been shown to enhance osteoclast differentiation through activation of Toll-like receptors (TLRs). We have shown that CpG-oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA and exerting their cellular activities through TLR9, modulate osteoclast differentiation in a complex manner: the ODNs inhibit the activity of the physiological osteoclast differentiation factor RANKL in early osteoclast precursors (OCPs) but markedly stimulate osteoclastogenesis in cells primed by RANKL.

MATERIALS AND METHODS

Osteoclast precursors and osteoblasts from TLR9-deficient (TLR9-/-) and wildtype (TLR9+/+) mice were used for in vitro analyses of osteoclast differentiation and modulation of signal transduction and gene expression.

RESULTS

As expected CpG-ODN did not exert any activity in cells derived from TLR9-/-mice; these cells, however, responded in a normal manner to other stimuli. Using bone marrow/osteoblasts co-cultures from all possible combinations of TLR9-/- and TLR9+/+ mice-derived cells, we showed that TLR9 in the two lineages is required for CpG-ODN induction of osteoclastogenesis.

CONCLUSIONS

CpG-ODN modulates osteoclastogenesis in a TLR9-dependent manner. Activation of TLR9 in bone marrow-derived osteoclasts precursors is more crucial to induction of osteoclastogenesis than activation of the osteoblastic TLR9.

Effect of oral administration of foreign plasmid DNA on immune function in mice

AIM: To investigate the effect of foreign plasmid DNA on immune function in mice through oral administration.

METHODS: After oral administration of foreign plasmid pcDNA3, thymus and spleen index, anti- sheep red blood cell (SRBC), number of antibody secreting cell (NASC) in spleen and phagocytic activity were detected. lymphocytic transformation rate (LTR) in spleen was determined using MTT methods. Serum IgA, IgG and IgM in immune suppression mice were also examined with immunoglobulin kit.

RESULTS: Thymus and spleen index, LTR, anti-SRBC and NASC in spleen significantly increased after administration of foreign plasmid pcDNA3 (3.53 ± 0.80 vs 5.10 ± 0.47 mg/g, P < 0.05; 5.69 ± 0.92 vs 7.49 ± 1.18 mg/g, P < 0.05; 1.047 ± 0.012 vs 1.154 ± 0.016, P < 0.05; 6.46 ± 0.12 vs 8.18 ± 0.29, P < 0.05; 0.403 ± 0.008 vs 0.471 ± 0.007, P < 0.05; respectively). Phagocytic activity also increased significantly (phagocytic index: 0.53 ± 0.017 vs 0.72 ± 0.029, P < 0.01); (phagocytic ratio: 32.30 ± 1.098 vs 60.53 ± 2.022, P < 0.01). The serum IgA, IgG and IgM of immune suppression mice resumed to normal level.

CONCLUSION: Foreign plasmid DNA can induce humoral and cell mediated immune in mice after administration via the gastrointestinal tract.