Non-conventional signal transduction by type 1 interferons: The NF-κB pathway

Cytokines and microRNAs in SARS-CoV-2: What do we know?

The coronavirus disease 2019 (COVID-19) pandemic constitutes a global health emergency. Currently, there are no completely effective therapeutic medications for the management of this outbreak. The cytokine storm is a hyperinflammatory medical condition due to excessive and uncontrolled release of pro-inflammatory cytokines in patients suffering from severe COVID-19, leading to the development of acute respiratory distress syndrome (ARDS) and multiple organ dysfunction syndrome (MODS) and even mortality. Understanding the pathophysiology of COVID-19 can be helpful for the treatment of patients. Evidence suggests that the levels of tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1 and IL-6 are dramatically different between mild and severe patients, so they may be important contributors to the cytokine storm. Several serum markers can be predictors for the cytokine storm. This review discusses the cytokines involved in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, focusing on interferons (IFNs) and ILs, and whether they can be used in COVID-19 treatment. Moreover, we highlight several microRNAs that are involved in these cytokines and their role in the cytokine storm caused by COVID-19.

Protein kinase Cδ is essential for the IgG response against T-cell-independent type 2 antigens and commensal bacteria

Antigens (Ags) with multivalent and repetitive structure elicit IgG production in a T-cell-independent manner. However, the mechanisms by which such T-cell-independent type-2 (TI-2) Ags induce IgG responses remain obscure. Here, we report that B-cell receptor (BCR) engagement with a TI-2 Ag but not with a T-cell-dependent (TD) Ag was able to induce the transcription of Aicda encoding activation-induced cytidine deaminase (AID) and efficient class switching to IgG3 upon costimulation with IL-1 or IFN-α in mouse B cells. TI-2 Ags strongly induced the phosphorylation of protein kinase C (PKC)δ and PKCδ mediated the Aicda transcription through the induction of BATF, the key transcriptional regulator of Aicda. In PKCδ-deficient mice, production of IgG was intact against TD Ag but abrogated against typical TI-2 Ags as well as commensal bacteria, and experimental disruption of the gut epithelial barrier resulted in fatal bacteremia. Thus, our results have revealed novel molecular requirements for class switching in the TI-2 response and highlighted its importance in homeostatic commensal-specific IgG production.

When the human body faces a potentially harmful microorganism, the immune system responds by finding and destroying the pathogen. This involves the coordination of several different parts of the immune system. B cells are a type of white blood cell that is responsible for producing antibodies: large proteins that bind to specific targets such as pathogens. B cells often need help from other immune cells known as T cells to complete antibody production.

However, T cells are not required for B cells to produce antibodies against some bacteria. For example, when certain pathogenic bacteria coated with a carbohydrate called a capsule – such as pneumococcus, which causes pneumonia, or salmonella – invade our body, B cells recognize a repetitive structure of the capsule using a B-cell antigen receptor. This recognition allows B cells to produce antibodies independently of T cells. It is unclear how B cells produce antibodies in this situation or what proteins are required for this activity.

To understand this process, Fukao et al. used genetically modified mice and their B cells to study how they produce antibodies independently of T cells. They found that a protein called PKCδ is critical for B cells to produce antibodies, especially of an executive type called IgG, in the T-cell-independent response. PKCδ became active when B cells were stimulated with the repetitive antigen present on the surface of bacteria like salmonella or pneumococcus. Mice that lack PKCδ were unable to produce IgG independently of T cells, leading to fatal infections when bacteria reached the tissues and blood.

Understanding the mechanism behind the T cell-independent B cell response could lead to more effective antibody production, potentially paving the way for new vaccines to prevent fatal diseases caused by pathogenic bacteria.

Longitudinal transcriptome analyses show robust T cell immunity during recovery from COVID-19

Understanding the processes of immune regulation in patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial for improving treatment. Here, we performed longitudinal whole-transcriptome RNA sequencing on peripheral blood mononuclear cell (PBMC) samples from 18 patients with coronavirus disease 2019 (COVID-19) during their treatment, convalescence, and rehabilitation. After analyzing the regulatory networks of differentially expressed messenger RNAs (mRNAs), microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) between the different clinical stages, we found that humoral immunity and type I interferon response were significantly downregulated, while robust T-cell activation and differentiation at the whole transcriptome level constituted the main events that occurred during recovery from COVID-19. The formation of this T cell immune response might be driven by the activation of activating protein-1 (AP-1) related signaling pathway and was weakly affected by other clinical features. These findings uncovered the dynamic pattern of immune responses and indicated the key role of T cell immunity in the creation of immune protection against this disease.

NF-κB and Its Role in Checkpoint Control

Nuclear factor-κB (NF-κB) has been described as one of the most important molecules linking inflammation to cancer. More recently, it has become clear that NF-κB is also involved in the regulation of immune checkpoint expression. Therapeutic approaches targeting immune checkpoint molecules, enabling the immune system to initiate immune responses against tumor cells, constitute a key breakthrough in cancer treatment. This review discusses recent evidence for an association of NF-κB and immune checkpoint expression and examines the therapeutic potential of inhibitors targeting either NF-κB directly or molecules involved in NF-κB regulation in combination with immune checkpoint blockade.

The Interactions Between Cancer Stem Cells and the Innate Interferon Signaling Pathway

Interferons (IFNs) form a family of cytokines with pleiotropic effects that modulate the immune response against multiple challenges like viral infections, autoimmune diseases, and cancer. While numerous anti-tumor activities have been described for IFNs, IFNs have also been associated with tumor growth and progression. The effect of IFNs on apoptosis, angiogenesis, tumor cell immunogenicity, and modulation of immune cells have been largely studied; however, less is known about their specific effects on cancer stem cells (CSCs). CSCs constitute a subpopulation of tumor cells endowed with stem-like properties including self-renewal, chemoresistance, tumorigenic capacity, and quiescence. This rare and unique subpopulation of cells is believed to be responsible for tumor maintenance, metastatic spread, and relapse. Thus, this review aims to summarize and discuss the current knowledge of the anti- and pro-CSCs effects of IFNs and also to highlight the need for further research on the interplay between IFNs and CSCs. Importantly, understanding this interplay will surely help to exploit the anti-tumor effects of IFNs, specifically those that target CSCs.

An NFκB Activity Calculator to Delineate Signaling Crosstalk: Type I and II Interferons Enhance NFκB via Distinct Mechanisms

Nuclear factor kappa B (NFκB) is a transcription factor that controls inflammation and cell survival. In clinical histology, elevated NFκB activity is a hallmark of poor prognosis in inflammatory disease and cancer, and may be the result of a combination of diverse micro-environmental constituents. While previous quantitative studies of NFκB focused on its signaling dynamics in single cells, we address here how multiple stimuli may combine to control tissue level NFκB activity. We present a novel, simplified model of NFκB (SiMoN) that functions as an NFκB activity calculator. We demonstrate its utility by exploring how type I and type II interferons modulate NFκB activity in macrophages. Whereas, type I IFNs potentiate NFκB activity by inhibiting translation of IκBα and by elevating viral RNA sensor (RIG-I) expression, type II IFN amplifies NFκB activity by increasing the degradation of free IκB through transcriptional induction of proteasomal cap components (PA28). Both cross-regulatory mechanisms amplify NFκB activation in response to weaker (viral) inducers, while responses to stronger (bacterial or cytokine) inducers remain largely unaffected. Our work demonstrates how the NFκB calculator can reveal distinct mechanisms of crosstalk on NFκB activity in interferon-containing microenvironments.

Map and model-moving from observation to prediction in toxicogenomics

BACKGROUND

Chemicals induce compound-specific changes in the transcriptome of an organism (toxicogenomic fingerprints). This provides potential insights about the cellular or physiological responses to chemical exposure and adverse effects, which is needed in assessment of chemical-related hazards or environmental health. In this regard, comparison or connection of different experiments becomes important when interpreting toxicogenomic experiments. Owing to lack of capturing response dynamics, comparability is often limited. In this study, we aim to overcome these constraints.

RESULTS

We developed an experimental design and bioinformatic analysis strategy to infer time- and concentration-resolved toxicogenomic fingerprints. We projected the fingerprints to a universal coordinate system (toxicogenomic universe) based on a self-organizing map of toxicogenomic data retrieved from public databases. Genes clustering together in regions of the map indicate functional relation due to co-expression under chemical exposure. To allow for quantitative description and extrapolation of the gene expression responses we developed a time- and concentration-dependent regression model. We applied the analysis strategy in a microarray case study exposing zebrafish embryos to 3 selected model compounds including 2 cyclooxygenase inhibitors. After identification of key responses in the transcriptome we could compare and characterize their association to developmental, toxicokinetic, and toxicodynamic processes using the parameter estimates for affected gene clusters. Furthermore, we discuss an association of toxicogenomic effects with measured internal concentrations.

CONCLUSIONS

The design and analysis pipeline described here could serve as a blueprint for creating comparable toxicogenomic fingerprints of chemicals. It integrates, aggregates, and models time- and concentration-resolved toxicogenomic data.

Oncolytic Viruses on Drugs: Achieving Higher Therapeutic Efficacy

Over the past 20 years there has been a dramatic expansion in the testing of oncolytic viruses (OVs) for the treatment of cancer. OVs are unique biotherapeutics that induce multimodal responses toward tumors, from direct cytopathic effects on cancer cells, to tumor associated blood vessel disruption, and ultimately potent stimulation of anti-tumor immune activation. These agents are highly targeted and can be efficacious as cancer treatments resulting in some patients experiencing complete tumor regression and even cures from OV monotherapy. However, most patients have limited responses with viral replication in tumors often found to be modest and transient. To augment OV replication, increase bystander killing of cancer cells, and/or stimulate stronger targeted anti-cancer immune responses, drug combination approaches have taken center stage for translation to the clinic. Here we comprehensively review drugs that have been combined with OVs to increase therapeutic efficacy, examining the proposed mechanisms of action, and we discuss trends in pharmaco-viral immunotherapeutic approaches currently being investigated.

Negative regulation of type I IFN signaling

Type I IFNs (α, β, and others) are a family of cytokines that are produced in physiological conditions as well as in response to the activation of pattern recognition receptors. They are critically important in controlling the host innate and adaptive immune response to viral and some bacterial infections, cancer, and other inflammatory stimuli. However, dysregulation of type I IFN production or response can contribute to immune pathologies termed "interferonopathies", pointing to the importance of balanced activating signals with tightly regulated mechanisms of tuning this signaling. Here, we summarize the recent advances of how type I IFN production and response are controlled at multiple levels of the type I IFN signaling cascade.

Recent advances in vesicular stomatitis virus-based oncolytic virotherapy: a 5-year update

Oncolytic virus (OV) therapy is an anti-cancer approach that uses viruses that preferentially infect, replicate in and kill cancer cells. Vesicular stomatitis virus (VSV, a rhabdovirus) is an OV that is currently being tested in the USA in several phase I clinical trials against different malignancies. Several factors make VSV a promising OV: lack of pre-existing human immunity against VSV, a small and easy to manipulate genome, cytoplasmic replication without risk of host cell transformation, independence of cell cycle and rapid growth to high titres in a broad range of cell lines facilitating large-scale virus production. While significant advances have been made in VSV-based OV therapy, room for improvement remains. Here we review recent studies (published in the last 5 years) that address 'old' and 'new' challenges of VSV-based OV therapy. These studies focused on improving VSV safety, oncoselectivity and oncotoxicity; breaking resistance of some cancers to VSV; preventing premature clearance of VSV; and stimulating tumour-specific immunity. Many of these approaches were based on combining VSV with other therapeutics. This review also discusses another rhabdovirus closely related to VSV, Maraba virus, which is currently being tested in Canada in phase I/II clinical trials.

JAK inhibitor has the amelioration effect in lupus-prone mice: the involvement of IFN signature gene downregulation

Background

We previously reported that JAK–STAT-pathway mediated regulation of IFN-regulatory factor genes could play an important role in SLE pathogenesis. Here, we evaluated the efficacy of the JAK inhibitor tofacitinib (TOFA) for controlling IFN signalling via the JAK–STAT pathway and as a therapeutic for SLE.

Results

We treated NZB/NZW F1 mice with TOFA and assessed alterations in their disease, pathological, and immunological conditions. Gene-expression results obtained from CD4⁺ T cells (SLE mice) and CD3⁺ T cells (human SLE patients) were measured by DNA microarray and qRT-PCR. TOFA treatment resulted in reduced levels of anti-dsDNA antibodies, decreased proteinuria, and amelioration of nephritis as compared with those observed in control animals. Moreover, we observed the rebalance in the populations of naïve CD4⁺ T cells and effector/memory cells in TOFA-treated mice; however, treatment with a combination of TOFA and dexamethasone (DEXA) elicited a stronger inhibitory effect toward the effector/memory cells than did TOFA or DEXA monotherapy. We also detected decreased expression of several IFN-signature genes Ifit3 and Isg15 in CD4⁺ from SLE-prone mice following TOFA and DEXA treatment, and IFIT3 in CD3⁺ T cells from human patients following immunosuppressant therapy including steroid, respectively.

Conclusion

Modulation of type I IFN signalling via JAK–STAT inhibition may exert a beneficial effect in SLE patients, and our results suggest that TOFA could be utilised for the development of new SLE-specific therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0225-9) contains supplementary material, which is available to authorized users.

Impaired Antiviral Stress Granule and IFN-β Enhanceosome Formation Enhances Susceptibility to Influenza Infection in Chronic Obstructive Pulmonary Disease Epithelium

Chronic obstructive pulmonary disease (COPD) is a serious lung disease that progressively worsens lung function. Those affected are highly susceptible to influenza virus infections that result in exacerbations with exaggerated symptoms with increased mortality. The mechanisms underpinning this increased susceptibility to infection in COPD are unclear. In this study, we show that primary bronchial epithelial cells (pBECs) from subjects with COPD have impaired induction of type I IFN (IFN-β) and lead to heightened viral replication after influenza viral infection. COPD pBECs have reduced protein levels of protein kinase (PK) R and decreased formation of PKR-mediated antiviral stress granules, which are critical in initiating type I IFN inductions. In addition, reduced protein expression of p300 resulted in decreased activation of IFN regulatory factor 3 and subsequent formation of IFN-β enhanceosome in COPD pBECs. The decreased p300 induction was the result of enhanced levels of microRNA (miR)-132. Ectopic expression of PKR or miR-132 antagomiR alone failed to restore IFN-β induction, whereas cotreatment increased antiviral stress granule formation, induction of p300, and IFN-β in COPD pBECs. This study reveals that decreased induction of both PKR and p300 proteins contribute to impaired induction of IFN-β in COPD pBECs upon influenza infection.

Humanin inhibits apoptosis in pituitary tumor cells through several signaling pathways including NF-κB activation

Humanin (HN) and Rattin (HNr), its homologous in the rat, are peptides with cytoprotective action in several cell types such as neurons, lymphocytes and testicular germ cells. Previously, we have shown that HNr is expressed in pituitary cells and that HN inhibited the apoptotic effect of TNF-α in both normal and tumor pituitary cells. The aim of the present study was to identify signaling pathways that mediate the antiapoptotic effect of HN in anterior pituitary cells from ovariectomized rats and in GH3 cells, a somatolactotrope cell line. We assessed the role of STAT3, JNK, Akt and MAPKs as well as proteins of the Bcl-2 family, previously implicated in the antiapoptotic effect of HN. We also evaluated the participation of NF-κB in the antiapoptotic action of HN. STAT3 inhibition reversed the inhibitory effect of HN on TNF-α-induced apoptosis in normal and pituitary tumor cells, indicating that STAT3 signaling pathway mediates the antiapoptotic effect of HN on pituitary cells. Inhibition of NF-κB pathway did not affect action of HN on normal anterior pituitary cells but blocked the cytoprotective effect of HN on TNF-α-induced apoptosis of GH3 cells, suggesting that the NF-κB pathway is involved in HN action in tumor pituitary cells. HN also induced NF-κB-p65 nuclear translocation in these cells. In pituitary tumor cells, JNK and MEK inhibitors also impaired HN cytoprotective action. In addition, HN increased Bcl-2 expression and decreased Bax mitochondrial translocation. Since HN expression in GH3 cells is higher than in normal pituitary cells, we may suggest that through multiple pathways HN could be involved in pituitary tumorigenesis.

Type I Interferons and Natural Killer Cell Regulation in Cancer

Type I interferons (IFNs) are known to mediate antitumor effects against several tumor types and have therefore been commonly used in clinical anticancer treatment. However, how IFN signaling exerts its beneficial effects is only partially understood. The clinically relevant activity of type I IFNs has been mainly attributed to their role in tumor immune surveillance. Different mechanisms have been postulated to explain how type I IFNs stimulate the immune system. On the one hand, they modulate innate immune cell subsets such as natural killer (NK) cells. On the other hand, type I IFNs also influence adaptive immune responses. Here, we review evidence for the impact of type I IFNs on immune surveillance against cancer and highlight the role of NK cells therein.

Synergistic production of TNFα and IFNα by human pDCs incubated with IFNλ3 and IL-3

In this study, we investigated whether IFNλ3 and IL-3 reciprocally influence their capacity to activate various functions of human plasmacytoid dendritic cells (pDCs). In fact, we preliminarily observed that IFNλ3 upregulates the expression of the IL-3Rα (CD123), while IL-3 augments the expression of IFNλR1 in pDCs. As a result, we found that combination of IFNλ3 and IL-3 induces a strong potentiation in the production of TNFα, IFNα, as well as in the expression of Interferon-Stimulated Gene (ISG) mRNAs by pDCs, as compared to either IFNλ3 or IL-3 alone. In such regard, we found that endogenous IFNα autocrinally promotes the expression of ISG mRNAs in IL-3-, but not in IFNλ3 plus IL-3-, treated pDCs. Moreover, we uncovered that the production of IFNα by IFNλ3 plus IL-3-treated pDCs is mostly dependent on endogenously produced TNFα. Altogether, our data demonstrate that IFNλ3 and IL-3 collaborate to promote, at maximal levels, discrete functional responses of human pDCs.

miR-744 enhances type I interferon signaling pathway by targeting PTP1B in primary human renal mesangial cells

Renal mesangial cells (RMCs) constitute a population of cells in glomerular mesangium. Inflammatory cytokines produced by RMCs play a vital role in renal inflammation. miRNAs are key regulators of inflammatory cytokine expression. The abnormal expression of renal miRNAs and the consequent changes in inflammatory signal transduction are closely associated with renal inflammation. However, our knowledge of the functions of renal miRNAs is still limited. In this study, we investigated the role of miR-744 in type I interferon (IFN) signaling pathway in primary human RMCs. We show that overexpression of miR-744 enhances IFN-induced CCL2, CCL5, CXCL10, and IL6 expression specifically in RMCs. We found that the activation of TYK2, STAT1 and STAT3 was significantly enhanced by miR-744. miR-744 also enhanced the activation of non-classical signal components, such as ERK and p38. We then identified PTP1B, a ubiquitously expressed phosphatase, as the target of miR-744 that is responsible for enhancing type I IFN response. Finally, miR-744 expression was induced by type I IFN in RMCs. Collectively, our data indicate that by targeting PTP1B, miR-744 plays a feed-forward role in regulating type I IFN signaling pathway. These findings give us new insights into the functions of renal miRNAs in regulating important signaling pathways.

CYP11A1 in skin: an alternative route to photoprotection by vitamin D compounds

Topical 1,25-dihydroxyvitamin D (1,25D) and other vitamin D compounds have been shown to protect skin from damage by ultraviolet radiation (UVR) in a process that requires the vitamin D receptor. Yet, while mice which do not express the vitamin D receptor are more susceptible to photocarcinogenesis, mice unable to 1α-hydroxylate 25-hydroxyvitamin D to form 1,25D do not show increased susceptibility to UVR-induced skin tumors. A possible explanation is that an alternative pathway, which does not involve 1α-hydroxylation, may produce photoprotective compounds from vitamin D. The cholesterol side chain cleavage enzyme CYP11A1 is expressed in skin and produces 20-hydroxyvitamin D3 (20OHD) as a major product of vitamin D3. We examined whether topical 20OHD would affect UVR-induced DNA damage, inflammatory edema or immune suppression produced in Skh:hr1 mice. Photoprotection by 20OHD at 23 or 46pmol/cm(2) against cyclobutane pyrimidine dimers (DNA lesions) after UVR in mice was highly effective, up to 98±0.8%, (p<0.001) and comparable to that of 1,25D. Sunburn edema measured as skinfold thickness 24h after UVR was also significantly reduced by 20OHD (p<0.001). In studies of contact hypersensitivity (CHS), which is suppressed by UVR, topical application of 20OHD to mice protected against UVR-induced immunosuppression (p<0.05), similar to the effect of 1,25D at similar doses (46±0.6% protection with 20OHD, 44±0.5% with 1,25D). Both UVR-induced DNA damage and immunosuppression contribute to increased susceptibility to UVR-induced skin tumors. This study indicates a potentially anti-photocarcinogenic role of the naturally occurring vitamin D metabolite, 20OHD, which does not depend on 1α-hydroxylation for generation. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Porphyromonas gingivalis-induced reactive oxygen species activate JAK2 and regulate production of inflammatory cytokines through c-Jun

Pathogen-induced reactive oxygen species (ROS) play a crucial role in host innate immune responses through regulating the quality and quantity of inflammatory mediators. However, the underlying molecular mechanisms of this effect have yet to be clarified. In this study, we examined the mechanism of action of ROS stimulated by Porphyromonas gingivalis in gingival epithelial cells. P. gingivalis induced the rapid production of ROS, which lead to the phosphorylation of JAK2 and increased levels of secreted proinflammatory cytokines interleukin-6 (IL-6) and IL-1β. Neutralization of ROS by N-acetyl-l-cysteine (NAC) abrogated the phosphorylation of JAK2 and suppressed the production of IL-6 and IL-1β. ROS-mediated phosphorylation of JAK2 induced the phosphoactivation of c-Jun amino-terminal protein kinase (JNK) and the downstream transcriptional regulator c-Jun. Inhibition of JAK2, either pharmacologically or by small interfering RNA (siRNA), reduced both the phosphorylation of these molecules and the production of proinflammatory cytokines in response to P. gingivalis. Furthermore, pharmacological inhibition or siRNA-mediated gene silencing of JNK or c-Jun mimicked the effect of JAK2 inhibition to suppress P. gingivalis-induced IL-6 and IL-1β levels. The results show that ROS-mediated activation of JAK2 is required for P. gingivalis-induced inflammatory cytokine production and that the JNK/c-Jun signaling axis is involved in the ROS-dependent regulation of IL-1β and IL-6 production.

Activation of vascular endothelial growth factor receptor-3 in macrophages restrains TLR4-NF-κB signaling and protects against endotoxin shock

Toll-like receptors (TLRs) are critical in mediating innate immune responses against infections. However, uncontrolled TLR-triggered inflammation is associated with endotoxin shock. To better understand the homeostatic mechanisms induced by TLR4 signaling, we screened a group of key cytokines, chemokines, growth factors, and their receptors for bacteria- or LPS-induced expression. The surface vascular endothelial growth factor receptor-3 (VEGFR-3) and its ligand VEGF-C were upregulated in macrophages. VEGFR-3 ligation by VEGF-C significantly attenuated proinflammatory cytokine production. Notably, ablation of the ligand-binding domain or tyrosine kinase activity of VEGFR-3 rendered mice more sensitive to septic shock. VEGFR-3 restrained TLR4-NF-κB activation by regulating the PI3-kinase-Akt signaling pathway and SOCS1 expression. Aside from targeting lymphatic vessels, we suggest a key role of VEGFR-3 on macrophages to prevent infections that is complicated with lymphoedema. Thus, VEGFR-3-VEGF-C signaling represents a "self-control" mechanism during antibacterial innate immunity.

Triggering ubiquitination of IFNAR1 protects tissues from inflammatory injury

Type 1 interferons (IFN) protect the host against viruses by engaging a cognate receptor (consisting of IFNAR1/IFNAR2 chains) and inducing downstream signaling and gene expression. However, inflammatory stimuli can trigger IFNAR1 ubiquitination and downregulation thereby attenuating IFN effects in vitro. The significance of this paradoxical regulation is unknown. Presented here results demonstrate that inability to stimulate IFNAR1 ubiquitination in the Ifnar1(SA) knock-in mice renders them highly susceptible to numerous inflammatory syndromes including acute and chronic pancreatitis, and autoimmune and toxic hepatitis. Ifnar1(SA) mice (or their bone marrow-receiving wild type animals) display persistent immune infiltration of inflamed tissues, extensive damage and gravely inadequate tissue regeneration. Pharmacologic stimulation of IFNAR1 ubiquitination is protective against from toxic hepatitis and fulminant generalized inflammation in wild type but not Ifnar1(SA) mice. These results suggest that endogenous mechanisms that trigger IFNAR1 ubiquitination for limiting the inflammation-induced tissue damage can be purposely mimicked for therapeutic benefits.

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor κB signaling in glioblastoma cancer stem cells regulates the Notch pathway

Malignant gliomas are locally aggressive, highly vascular tumors that have a dismal prognosis, and present therapies provide little improvement in the disease course and outcome. Many types of malignancies, including glioblastoma, originate from a population of cancer stem cells (CSCs) that are able to initiate and maintain tumors. Although CSCs only represent a small fraction of cells within a tumor, their high tumor-initiating capacity and therapeutic resistance drives tumorigenesis. Therefore, it is imperative to identify pathways associated with CSCs to devise strategies to selectively target them. In this study, we describe a novel relationship between glioblastoma CSCs and the Notch pathway, which involves the constitutive activation of STAT3 and NF-κB signaling. Glioma CSCs were isolated and maintained in vitro using an adherent culture system, and the biological properties were compared with the traditional cultures of CSCs grown as multicellular spheres under nonadherent culture conditions. Interestingly, both adherent and spheroid glioma CSCs show constitutive activation of the STAT3/NF-κB signaling pathway and up-regulation of STAT3- and NF-κB-dependent genes. Gene expression profiling also identified components of the Notch pathway as being deregulated in glioma CSCs, and the deregulated expression of these genes was sensitive to treatment with STAT3 and NF-κB inhibitors. This finding is particularly important because Notch signaling appears to play a key role in CSCs in a variety of cancers and controls cell fate determination, survival, proliferation, and the maintenance of stem cells. The constitutive activation of STAT3 and NF-κB signaling pathways that leads to the regulation of Notch pathway genes in glioma CSCs identifies novel therapeutic targets for the treatment of glioma.

Activation of the type I interferon pathway is enhanced in response to human neuronal differentiation

Despite the crucial role of innate immunity in preventing or controlling pathogen-induced damage in most, if not all, cell types, very little is known about the activity of this essential defense system in central nervous system neurons, especially in humans. In this report we use both an established neuronal cell line model and an embryonic stem cell-based system to examine human neuronal innate immunity and responses to neurotropic alphavirus infection in cultured cells. We demonstrate that neuronal differentiation is associated with increased expression of crucial type I interferon signaling pathway components, including interferon regulatory factor-9 and an interferon receptor heterodimer subunit, which results in enhanced interferon stimulation and subsequent heightened antiviral activity and cytoprotective responses against neurotropic alphaviruses such as western equine encephalitis virus. These results identify important differentiation-dependent changes in innate immune system function that control cell-autonomous neuronal responses. Furthermore, this work demonstrates the utility of human embryonic stem cell-derived cultures as a platform to study the interactions between innate immunity, virus infection, and pathogenesis in central nervous system neurons.

Evolving therapeutic paradigms for multiple myeloma: back to the future

Multiple myeloma (MM) is an ancient disease, but until the alkylating agent melphalan was found to have anti-myeloma properties in the 1950s there was virtually no effective therapy. By the late 1960s, extended dosing with melphalan and prednisone tripled survival from diagnosis and became the standard of care for newly diagnosed MM. "Maintenance therapy" to prolong survival through sustained disease control following induction chemotherapy was sought by 1970, but early strategies were ineffective and toxic. Subsequent applications of high-dose therapy (HDT)/autologous stem cell transplant (ASCT) changed the treatment paradigm for MM from extended dosing to an intensive strategy designed to eradicate the malignant cells in a single course of treatment. Although HDT-ASCT resulted in prolonged duration of remission and improved survival, the vast majority of patients still relapsed. Interferon (IFN) and glucocorticoid maintenance therapies demonstrated marginal improvements in outcomes but significant adverse effects. Novel agents introduced over the last decade have prolonged survival when given for maintenance following HDT-ASCT, but have also challenged the HDT-ASCT paradigm by achieving comparable remission rates when used alone as extended frontline therapy. This article reviews the evolution of therapeutic strategies for MM and discusses future questions facing MM investigators.

Activation of the noncanonical NF-κB pathway by HIV controls a dendritic cell immunoregulatory phenotype

HIV modulates plasmacytoid dendritic cell (pDC) activation via Toll-like receptor 7, inducing type I IFN and inflammatory cytokines. Simultaneously, pDCs up-regulate the expression of indoleamine 2,3 dioxygenase (IDO), which is essential for the induction of regulatory T cells (Tregs), which function to down-modulate immune activation. Here we demonstrate the crucial importance of the noncanonical NF-κB pathway in the establishment of this immunoregulatory phenotype in pDCs. In response to HIV, the noncanonical NF-κB pathway directly induces IDO and involves the recruitment of TNF receptor-associated factor-3 to the Toll-like receptor/MyD88 complex, NF-κB-inducing kinase-dependent IκB kinase-α activation, and p52/RelB nuclear translocation. We also show that pDC-induced Tregs can inhibit conventional DC (cDC) maturation partially through cytotoxic T-lymphocyte antigen (CTLA)-4 engagement. Furthermore, CTLA-4 induces IDO in cDCs in a NF-κB-inducing kinase-dependent way. These CTLA-4-conditioned cDCs can in turn induce Treg differentiation in an IDO-dependent manner. Thus, the noncanonical NF-κB pathway is integral in controlling immunoregulatory phenotypes of both pDCs and cDCs.

The interferons and their receptors--distribution and regulation

The interferons (IFNs) were originally described over 50 years ago, identified by their ability to confer viral resistance to cells. We now know that they are much more than just anti-viral cytokines collectively having roles in both innate and adaptive immune responses, in tumor surveillance and defense, and modulation of immune cell function. Three types of IFN have now been described, simply referred to as type I, II and III. Distinguishable by the unique receptors that they rely on for signal transduction, the three types of IFN have specific and varied roles in the maintenance of human health and defense against pathogens. In mounting an IFN-mediated immune response, the human body has developed the ability to regulate IFN-mediated signal transduction. Like all cytokines, the ability of a cell to respond to IFN is completely dependent on the presence of its cognate receptor on the surface of the target cell. Thus, one of the major mechanisms used by the human body to regulate the strength and duration of the IFN response is through regulation of receptor levels, thereby altering the cytokine-specific responsiveness of the target cell. This review will discuss the receptor system utilized by the type I IFNs and compare it with that of the type II and III IFNs, which also regulate immune responses through controlling receptor level on the cell surface.

Inhibition of type I interferon-mediated antiviral action in human glioma cells by the IKK inhibitors BMS-345541 and TPCA-1

The nuclear factor-kappa B (NFκB) signal transduction pathway plays an important role in immunity, inflammation, cell growth, and survival. Since dysregulation of this pathway results in high, constitutive NFκB activation in various cancers and immune disorders, the development of specific drugs to target this pathway has become a focus for treating these diseases. NFκB regulates various aspects of the cellular response to interferon (IFN). However, the role of the upstream regulator of the NFκB signaling pathway, the inhibitor of κB kinase (IKK) complex, on IFN function has not been examined. In the present study, we examined the effects of 2 IKK inhibitors, N-(1,8-Dimethylimidazo[1,2-a]quinoxalin-4-yl)-1,2-ethanediamine hydrochloride (BMS-345541) and 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1), on IFN action in several human glioma cell lines. IKK inhibitors inhibit glioma cell proliferation, as well as TNF-induced RelA (p65) nuclear translocation and NFκB-dependent IL8 gene expression. Importantly, BMS-345541 and TPCA-1 differentially inhibit IFN-induced gene expression, completely suppressing MX1 and GBP1 gene expression, while having only a minor effect on ISG15 expression. Furthermore, these IKK inhibitors displayed marked differences in blocking IFN-induced antiviral action against cytopathic effects and replication of vesicular stomatitis virus (VSV) and encephalomyocarditis virus (EMCV). Our results show that the IKK complex plays an important function in IFN-induced gene expression and antiviral activity. Since VSV and EMCV are oncolytic viruses used in cancer therapy, our results indicate the potential synergy in combining IKK inhibitors with oncolytic viruses.

Oxidative stress induced interleukin-32 mRNA expression in human bronchial epithelial cells

Background

Chronic obstructive pulmonary disease (COPD) is characterized by airflow obstruction and persistent inflammation in the airways and lung parenchyma. Oxidative stress contributes to the pathogenesis of COPD. Interleukin (IL)-32 expression has been reported to increase in the lung tissue of patients with COPD. Here, we show that IFNγ upregulated IL-32 expression and that oxidative stress augmented IFNγ-induced-IL-32 expression in airway epithelial cells. We further investigated transcriptional regulation responsible for IFNγ induced IL-32 expression in human airway epithelial cells.

Methods

Human bronchial epithelial (HBE) cells were stimulated with H₂O₂ and IFNγ, and IL-32 expression was evaluated. The cell viability was confirmed by MTT assay. The intracellular signaling pathways regulating IL-32 expression were investigated by examining the regulatory effects of MAPK inhibitors and JAK inhibitor after treatment with H₂O₂ and IFNγ, and by using a ChIP assay to identify transcription factors (i.e. c-Jun, CREB) binding to the IL-32 promoter. Promoter activity assays were conducted after mutations were introduced into binding sites of c-Jun and CREB in the IL-32 promoter. IL-32 expression was also examined in HBE cells in which the expression of either c-Jun or CREB was knocked out by siRNA of indicated transcription factors.

Results

There were no significant differences of cell viability among groups. After stimulation with H₂O₂ or IFNγ for 48 hours, IL-32 expression in HBE cells was increased by IFNγ and synergistically upregulated by the addition of H₂O₂. The H₂O₂ augmented IFNγ induced IL-32 mRNA expression was suppressed by a JNK inhibitor, but not by MEK inhibitor, p38 inhibitor, and JAK inhibitor I. Significant binding of c-Jun and CREB to the IL-32 promoter was observed in the IFNγ + H₂O₂ stimulated HBE cells. Introducing mutations into the c-Jun/CREB binding sites in the IL-32 promoter prominently suppressed its transcriptional activity. Further, knocking down CREB expression by siRNA resulted in significant suppression of IL-32 induction by IFNγ and H₂O₂ in HBE cells.

Conclusion

IL-32 expression in airway epithelium may be augmented by inflammation and oxidative stress, which may occur in COPD acute exacerbation. c-Jun and CREB are key transcriptional factors in IFNγ and H₂O₂ induced IL-32 expression.

Structural variants of IFNα preferentially promote antiviral functions

IFNα, a cytokine with multiple functions in innate and adaptive immunity and a potent inhibitor of HIV, exerts antiviral activity, in part, by enhancing apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3 (APOBEC3) family members. Although IFNα therapy is associated with reduced viral burden, this cytokine also mediates immune dysfunction and toxicities. Through detailed mapping of IFNα receptor binding sites, we generated IFNα hybrids and mutants and determined that structural changes in the C-helix alter the ability of IFN to limit retroviral activity. Selective IFNα constructs differentially block HIV replication and their directional magnitude of inhibition correlates with APOBEC3 levels. Importantly, certain mutants exhibited reduced toxicity as reflected by induced indoleamine 2,3-dioxygenase (IDO), suggesting discreet and shared intracellular signaling pathways. Defining IFN structure and function relative to APOBEC and other antiviral genes may enable design of novel IFN-related molecules preserving beneficial antiviral roles while minimizing negative effects.

NF-κB and innate immunity

Members of the NF-κB transcription factor family play a critical role in the development of innate immunity. Upon recognition of pathogen infections or tissue damage, the NF-κB pathway is strongly activated by cellular pattern recognition receptors, including Toll-like receptors and multiple cytosolic receptors such as RIG-I-like helicases and NOD family proteins. NF-κB is required not only for the expression, but also for subsequent signal transduction of numerous downstream cytokines. NF-κB-responsive genes affect a diverse array of cellular processes including apoptosis and cell survival, and often directly control the course of a pathogen infection. In this review, we will examine signaling pathways leading to NF-κB activation during the innate immune response and mechanisms of pathogen-modulation of these pathways; the specifics of NF-κB-dependent gene programs, and the physiological consequences for the immune system caused by the absence of individual NF-κB subunits.

The role of nuclear factor κB in the interferon response

The nuclear factor κB (NF-κB) transcription factor regulates the expression of genes involved in cell survival and immune responses. We have identified a novel interferon (IFN)-activated signaling pathway that leads to NF-κB activation and demonstrate that a subset of IFN-stimulated genes and microRNAs that play key roles in cellular response to IFN is regulated by NF-κB. This review focuses on the IFN-induced NF-κB activation pathway and the role of NF-κB in the expression of IFN-induced coding and noncoding genes, antiviral activity and apoptosis, and the therapeutic application of IFN in cancer and infectious disease.

Role of p38 protein kinase in the ligand-independent ubiquitination and down-regulation of the IFNAR1 chain of type I interferon receptor

Phosphorylation-dependent ubiquitination and degradation of the IFNAR1 chain of type I interferon (IFN) receptor is a robust and specific mechanism that limits the magnitude and duration of IFNα/β signaling. Besides the ligand-inducible IFNAR1 degradation, the existence of an "inside-out" signaling that accelerates IFNAR1 turnover in the cells undergoing the endoplasmic reticulum (ER) stress and activated unfolded protein responses has been recently described. The latter pathway does not require either presence of ligands (IFNα/β) or catalytic activity of Janus kinases (JAK). Instead, this pathway relies on activation of the PKR-like ER kinase (PERK) and ensuing specific priming phosphorylation of IFNAR1. Here, we describe studies that identify the stress activated p38 protein kinase as an important regulator of IFNAR1 that acts downstream of PERK. Results of the experiments using pharmacologic p38 kinase inhibitors, RNA interference approach, and cells from p38α knock-out mice suggest that p38 kinase activity is required for priming phosphorylation of IFNAR1 in cells undergoing unfolded protein response. We further demonstrate an important role of p38 kinase in the ligand-independent stimulation of IFNAR1 ubiquitination and degradation and ensuing attenuation of IFNα/β signaling and anti-viral defenses. We discuss the distinct importance of p38 kinase in regulating the overall responses to type I IFN in cells that have been already exposed to IFNα/β versus those cells that are yet to encounter these cytokines.

Direct effects of type I interferons on cells of the immune system

Type I interferons (IFN-I) are well-known inducers of tumor cell apoptosis and antiangiogenesis via signaling through a common receptor interferon alpha receptor (IFNAR). IFNAR induces the Janus activated kinase-signal transducer and activation of transcription (JAK-STAT) pathway in most cells, along with other biochemical pathways that may differentially operate, depending on the responding cell subset, and jointly control a large collection of genes. IFNs-I were found to systemically activate natural killer (NK) cell activity. Recently, mouse experiments have shown that IFNs-I directly activate other cells of the immune system, such as antigen-presenting dendritic cells (DC) and CD4 and CD8 T cells. Signaling through the IFNAR in T cells is critical for the acquisition of effector functions. Cross-talk between IFNAR and the pathways turned on by other surface lymphocyte receptors has been described. Importantly, IFNs-I also increase antigen presentation of the tumor cells to be recognized by T lymphocytes. These IFN-driven immunostimulatory pathways offer opportunities to devise combinatorial immunotherapy strategies.

Human cytomegalovirus IE1 protein elicits a type II interferon-like host cell response that depends on activated STAT1 but not interferon-γ

Human cytomegalovirus (hCMV) is a highly prevalent pathogen that, upon primary infection, establishes life-long persistence in all infected individuals. Acute hCMV infections cause a variety of diseases in humans with developmental or acquired immune deficits. In addition, persistent hCMV infection may contribute to various chronic disease conditions even in immunologically normal people. The pathogenesis of hCMV disease has been frequently linked to inflammatory host immune responses triggered by virus-infected cells. Moreover, hCMV infection activates numerous host genes many of which encode pro-inflammatory proteins. However, little is known about the relative contributions of individual viral gene products to these changes in cellular transcription. We systematically analyzed the effects of the hCMV 72-kDa immediate-early 1 (IE1) protein, a major transcriptional activator and antagonist of type I interferon (IFN) signaling, on the human transcriptome. Following expression under conditions closely mimicking the situation during productive infection, IE1 elicits a global type II IFN-like host cell response. This response is dominated by the selective up-regulation of immune stimulatory genes normally controlled by IFN-γ and includes the synthesis and secretion of pro-inflammatory chemokines. IE1-mediated induction of IFN-stimulated genes strictly depends on tyrosine-phosphorylated signal transducer and activator of transcription 1 (STAT1) and correlates with the nuclear accumulation and sequence-specific binding of STAT1 to IFN-γ-responsive promoters. However, neither synthesis nor secretion of IFN-γ or other IFNs seems to be required for the IE1-dependent effects on cellular gene expression. Our results demonstrate that a single hCMV protein can trigger a pro-inflammatory host transcriptional response via an unexpected STAT1-dependent but IFN-independent mechanism and identify IE1 as a candidate determinant of hCMV pathogenicity.

Single nucleotide polymorphisms in the promoter region of the IL1B gene influence outcome in multiple myeloma patients treated with high-dose chemotherapy independently of relapse treatment with thalidomide and bortezomib

Little is known on the impact of polymorphisms in the IL1B gene on outcome in multiple myeloma. In a population-based study of 348 Danish myeloma patients treated with high-dose treatment (HDT), 146 patients treated with INF-α maintenance treatment, and in 243 patients with relapse, we analysed the impact on outcome of HDT, INF-α maintenance treatment, and treatment with thalidomide and bortezomib at relapse, in relation to the major identified functional polymorphisms in the promoter region of IL1B. The wild-type C-allele of IL1B C-3737T and non-carriage of the IL1B promoter haplotype TGT (-3737(T), -1464(G) and -31(T)), giving high IL1B promoter activity, were associated with longer time-to-treatment failure (TTF) (HR, 1.4 (1.0-1.9) and 1.5 (1.1-2.0)) and overall survival (HR, 1.8 (1.2-2.6) and 1.6 (1.1-2.3)) after HDT. Among INF-α treated patients, a trend towards better TTF was found in patients carrying the wild-type C-allele of IL1B C-3737T (HR, 1.6 (1.1-2.4)). Furthermore, among INF-α treated patients, gene-gene interaction studies on IL1B C-3737T and NFКB1-94ins/del ATTG revealed a fourfold increase in TTF for homozygous carriers of wild-type alleles at both loci as compared to variant allele carriers at both loci. No relation to genotype and outcome was found for relapse patients treated with thalidomide or bortezomib. Our results indicate that a subpopulation of myeloma patients carrying the wild-type C-allele of IL1B C-3737T and non-carriers of the promoter haplotype TGT (-3737(T), -1464(G) and -31(T)) benefit from a better outcome of HDT and INF-α treatment, an effect that may be related to the NF-κB pathway.

Distinct roles for the NF-kappa B RelA subunit during antiviral innate immune responses

Production of type I interferons (IFNs; prominently, IFN-α/β) following virus infection is a pivotal antiviral innate immune response in higher vertebrates. The synthesis of IFN-β proceeds via the virus-induced assembly of the transcription factors IRF-3/7, ATF-2/c-Jun, and NF-κB on the ifnβ promoter. Surprisingly, recent data indicate that the NF-κB subunit RelA is not essential for virus-stimulated ifnβ expression. Here, we show that RelA instead sustains autocrine IFN-β signaling prior to infection. In the absence of RelA, virus infection results in significantly delayed ifnβ induction and consequently defective secondary antiviral gene expression. While RelA is not required for ifnβ expression after infection, it is nonetheless essential for fully one-fourth of double-stranded RNA (dsRNA)-activated genes, including several mediators of inflammation and immune cell recruitment. Further, RelA directly regulates a small subset of interferon-stimulated genes (ISGs). Finally, RelA also protects cells from dsRNA-triggered RIP1-dependent programmed necrosis. Taken together, our findings suggest distinct roles for RelA in antiviral innate immunity: RelA maintains autocrine IFN-β signaling in uninfected cells, facilitates inflammatory and adaptive immune responses following infection, and promotes infected-cell survival during this process.

Ligand-stimulated downregulation of the alpha interferon receptor: role of protein kinase D2

Alpha interferon (IFN-α) controls homeostasis of hematopoietic stem cells, regulates antiviral resistance, inhibits angiogenesis, and suppresses tumor growth. This cytokine is often used to treat cancers and chronic viral infections. The extent of cellular responses to IFN-α is limited by the IFN-induced ubiquitination and degradation of the IFN-α/β receptor chain 1 (IFNAR1) chain of the cognate receptor. IFNAR1 ubiquitination is facilitated by the βTrcp E3 ubiquitin ligase that is recruited to IFNAR1 upon its degron phosphorylation, which is induced by the ligand. Here we report identification of protein kinase D2 (PKD2) as a kinase that mediates the ligand-inducible phosphorylation of IFNAR1 degron and enables binding of βTrcp to the receptor. Treatment of cells with IFN-α induces catalytic activity of PKD2 and stimulates its interaction with IFNAR1. Expression and kinase activity of PKD2 are required for the ligand-inducible stimulation of IFNAR1 ubiquitination and endocytosis and for accelerated proteolytic turnover of IFNAR1. Furthermore, inhibition or knockdown of PKD2 robustly augments intracellular signaling induced by IFN-α and increases the efficacy of its antiviral effects. The mechanisms of the ligand-inducible elimination of IFNAR1 are discussed, along with the potential medical significance of this regulation.

Interferon-induced TRAIL-independent cell death in DNase II-/- embryos

The chromosomal DNA of apoptotic cells and the nuclear DNA expelled from erythroid precursors is cleaved by DNase II in lysosomes after the cells or nuclei are engulfed by macrophages. DNase II(-/-) embryos suffer from lethal anemia due to IFN-beta produced in the macrophages carrying undigested DNA. Here, we show that Type I IFN induced a caspase-dependent cell death in human epithelial cells that were transformed to express a high level of IFN type I receptor. During this death process, a set of genes was strongly activated, one of which encoded TRAIL, a death ligand. A high level of TRAIL mRNA was also found in the fetal liver of the lethally anemic DNase II(-/-) embryos, and a lack of IFN type I receptor in the DNase II(-/-) IFN-IR(-/-) embryos blocked the expression of TRAIL mRNA. However, a null mutation in TRAIL did not rescue the lethal anemia of the DNase II(-/-) embryos, indicating that TRAIL is dispensable for inducing the apoptosis of erythroid cells in DNase II(-/-) embryos, and therefore, that there is a TRAIL-independent mechanism for the IFN-induced apoptosis.

Inhibition of the ubiquitin-proteasome system affects influenza A virus infection at a postfusion step

We have demonstrated that influenza A virus (IAV) RNA synthesis depends on the ubiquitin-proteasome system. IAV replication was reduced both by proteasome inhibitors and in E36ts20 cells, which contain the thermolabile ubiquitin-activating enzyme E1. While virus entry was not affected in E36ts20 cells, the proteasome inhibitor MG132 retained viral particles in the cytoplasm. Addition-removal experiments of MG132 in combination with bafilomycin A1, a well-established inhibitor of IAV entry and fusion, showed that MG132 affected IAV infection at a postfusion step. This was confirmed by the lack of inhibition of IAV entry by proteasome inhibitors in a virus-like particle fusion assay.

Type I interferons mediate the innate cytokine response to recombinant fowlpox virus but not the induction of plasmacytoid dendritic cell-dependent adaptive immunity

Type I interferons (IFNs) are considered to be important mediators of innate immunity due to their inherent antiviral activity, ability to drive the transcription of a number of genes involved in viral clearance, and their role in the initiation of innate and adaptive immune responses. Due to the central role of type I IFNs, we sought to determine their importance in the generation of immunity to a recombinant vaccine vector fowlpox virus (FPV). In analyzing the role of type I IFNs in immunity to FPV, we show that they are critical to the secretion of a number of innate and proinflammatory cytokines, including type I IFNs themselves as well as interleukin-12 (IL-12), tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-1beta, and that deficiency leads to enhanced virus-mediated antigen expression. Interestingly, however, type I IFNs were not required for adaptive immune responses to recombinant FPV even though plasmacytoid dendritic cells (pDCs), the primary producers of type I IFNs, have been shown to be requisite for this to occur. Furthermore, we provide evidence that the importance of pDCs may lie in their ability to capture and present virally derived antigen to T cells rather than in their capacity as professional type I IFN-producing cells.

Japanese encephalitis virus utilizes the canonical pathway to activate NF-kappaB but it utilizes the type I interferon pathway to induce major histocompatibility complex class I expression in mouse embryonic fibroblasts

Flaviviruses have been shown to induce cell surface expression of major histocompatibility complex class I (MHC-I) through the activation of NF-kappaB. Using IKK1(-/-), IKK2(-/-), NEMO(-/-), and IKK1(-/-) IKK2(-/-) double mutant as well as p50(-/-) RelA(-/-) cRel(-/-) triple mutant mouse embryonic fibroblasts infected with Japanese encephalitis virus (JEV), we show that this flavivirus utilizes the canonical pathway to activate NF-kappaB in an IKK2- and NEMO-, but not IKK1-, dependent manner. NF-kappaB DNA binding activity induced upon virus infection was shown to be composed of RelA:p50 dimers in these fibroblasts. Type I interferon (IFN) production was significantly decreased but not completely abolished upon virus infection in cells defective in NF-kappaB activation. In contrast, induction of classical MHC-I (class 1a) genes and their cell surface expression remained unaffected in these NF-kappaB-defective cells. However, MHC-I induction was impaired in IFNAR(-/-) cells that lack the alpha/beta IFN receptor, indicating a dominant role of type I IFNs but not NF-kappaB for the induction of MHC-I molecules by Japanese encephalitis virus. Our further analysis revealed that the residual type I IFN signaling in NF-kappaB-deficient cells is sufficient to drive MHC-I gene expression upon virus infection in mouse embryonic fibroblasts. However, NF-kappaB could indirectly regulate MHC-I expression, since JEV-induced type I IFN expression was found to be critically dependent on it.

CBP knockdown inhibits angiotensin II-induced vascular smooth muscle cells proliferation through downregulating NF-kB transcriptional activity

CREB binding protein (CBP), a powerful transcriptional co-activator for various transcriptional factors, regulates cell behavior in many cell types. Angiotensin II (Ang II) contributes to vascular lesion by promoting vascular smooth muscle cells (VSMCs) proliferation and migration. Therefore, we examined whether CBP knockdown could suppress Ang II-induced VSMCs proliferation, and elucidated its underlying molecular mechanism. We constructed lentiviral vector expressing CBP-specific short hairpin RNAs (shRNAs) that efficiently silenced CBP. VSMCs proliferation was evaluated by bromodeoxyuridine (BrdU) incorporation assay. Protein and mRNA expression of CBP and relevant cytokines were examined by Western blot, ELISA, and real-time PCR, respectively. We also used luciferase reporter gene and electrophoretic mobility shift assay (EMSA) to detect Nuclear factor kappaB (NF-kB) transcriptional activity and DNA binding. Meanwhile, NF-kB p65 subunit nuclear translocation was confirmed by immunoblotting. Lentiviral-mediated CBP-shRNAs at different multiplicities of infection (MOI = 100, 150) both significantly suppressed Ang II-induced CBP expression. Knockdown of CBP markedly inhibited Ang II-stimulated VSMCs proliferation and cytokines (TNF-alpha and IL-6) production. However, this inhibitory effect was not enhanced at MOI of 150 compared with MOI of 100 (P > 0.05). CBP siRNA showed the potent inhibition on Ang II-induced NF-kB transcriptional activity. Similarly, no significant difference was found between CBP siRNA lentivirus treatment groups. Furthermore, CBP gene silencing had no effect on NF-kB nuclear translocation and DNA binding. These findings suggest that CBP knockdown inhibits Ang II-induced VSMCs proliferation and the mechanism is involved with downregulation of NF-kB transcriptional activity, not through reduction in NF-kB nuclear translocation or DNA binding. Maintaining proper CBP level may be a potential therapeutic target for Ang II-induced cardiovascular disorders.

Deregulation of Interferon Signaling in Malignant Cells

Interferons (IFNs) are a family of cytokines with potent antiproliferative, antiviral, and immunomodulatory properties. Much has been learned about IFNs and IFN-activated signaling cascades over the last 50 years. Due to their potent antitumor effects in vitro and in vivo, recombinant IFNs have been used extensively over the years, alone or in combination with other drugs, for the treatment of various malignancies. This review summarizes the current knowledge on IFN signaling components and pathways that are deregulated in human malignancies. The relevance of deregulation of IFN signaling pathways in defective innate immune surveillance and tumorigenesis are discussed.

Viral induction of the zinc finger antiviral protein is IRF3-dependent but NF-kappaB-independent

The zinc finger antiviral protein (ZAP) is an interferon-stimulated gene that restricts the replication of retroviruses, alphaviruses, and filoviruses. Relatively little is known, however, regarding the detailed mechanism of ZAP induction during viral infections. We show that, although being inducible by either interferon or virus, expression of ZAP is more efficiently activated by virus than are several other classical interferon-stimulated genes and that viral induction of ZAP occurs under the direct control of interferon regulatory factor 3 (IRF3) independent of interferon paracrine/autocrine signaling. ZAP was up-regulated in cells unresponsive to type I and III interferons upon engagement of TLR3, retinoic inducible gene I/melanoma differentiation-associated gene 5 pathways, or ectopic expression of a constitutively active IRF3 mutant. Conversely, induction of ZAP by virus or dsRNA was severely impaired in cells expressing a dominant-negative mutant IRF3 and completely abrogated in cells lacking IRF3. In contrast to IRF3, ZAP induction was independent of NF-kappaB activity. Mutational analysis of the human ZAP promoter revealed that multiple interferon-stimulated response elements far distal to the transcription start site serve redundantly to control IRF3-dependent induction of ZAP transcription. Chromatin immunoprecipitation assays demonstrated that IRF3 selectively binds the distal interferon-stimulated response elements in human ZAP promoter following viral infection. Collectively, these data suggest that ZAP is a direct target gene of IRF3 action in cellular antiviral responses.

The alpha/beta interferon receptor provides protection against influenza virus replication but is dispensable for inflammatory response signaling

The innate immune response provides the first line of defense against foreign pathogens by responding to molecules that are a signature of a pathogenic infection. Certain RNA viruses, such as influenza virus, produce double-stranded RNA as an intermediate during the replication life cycle, which activates pathogen recognition receptors capable of inducing interferon production. By engaging interferon receptors, interferon activates the JAK-STAT pathway and results in the positive feedback of interferon production, amplifying the response to viral infection. To examine how deficiencies in interferon signaling affect the cellular response to infection, we performed influenza virus infections of mouse embryonic fibroblasts lacking the alpha/beta interferon receptor, the gamma interferon receptor, or both. In the absence of the alpha/beta interferon receptor, we observed increased viral replication but decreased activation of PKR, Stat1, and NF-kappaB; the presence or absence of the gamma interferon receptor did not exhibit discernible differences in these readouts. Analysis of gene expression profiles showed that while cells lacking the alpha/beta interferon receptor exhibited decreased levels of transcription of antiviral genes, genes related to inflammatory and apoptotic responses were transcribed to levels similar to those of cells containing the receptor. These results indicate that while the alpha/beta interferon receptor is needed to curb viral replication, it is dispensable for the induction of certain inflammatory and apoptotic genes. We have identified potential pathways, via interferon regulatory factor 3 (IRF3) activation or Hoxa13, Polr2a, Nr4a1, or Ing1 induction, that contribute to this redundancy. This study illustrates another way in which the host has evolved to establish several overlapping mechanisms to respond to viral infections.