Death domain-associated protein 6 (Daxx) selectively represses IL-6 transcription through histone deacetylase 1 (HDAC1)-mediated histone deacetylation in macrophages

The death domain-associated protein suppresses porcine epidemic diarrhea virus replication by interacting with signal transducer and activator of transcription 1 and inducing downstream ISG15 expression

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes acute enteric disease in piglets and severely threatens the pig industry all over the world. Death domain-associated protein (DAXX) is a classical chaperone protein involved in multiple biological processes, such as cell apoptosis, transcriptional regulation, DNA damage repair, and host innate immunity. However, whether DAXX functions in the anti-PEDV innate immune responses remains unclear. In this study, we found that PEDV infection upregulated DAXX expression and induced its nucleocytoplasmic translocation in IPEC-J2 cells. Furthermore, we found that DAXX overexpression was inhibitory to PEDV replication, while downregulation of DAXX by RNA interference facilitated PEDV replication. The antiviral activity of DAXX was due to its positive effect on IFN-λ3-STAT1 signaling, as DAXX positively regulated STAT1 activation through their interaction in cytoplasm and enhancing the downstream ISG15 expression. Mutation of tryptophan at 621 to alanine in DAXX increased its abundance in the cytoplasm, leading to the upregulation of STAT1 phosphorylation and ISG15 expression. It indicated that cytoplasmic fraction of DAXX was advantageous for the STAT1-ISG15 signaling axis and PEDV inhibition. In summary, these results show that DAXX inhibits PEDV infection by increasing IFN-λ3-induced STAT1 phosphorylation and the downstream ISG15 expression.

Targeting 'histone mark': Advanced approaches in epigenetic regulation of telomere dynamics in cancer

Telomere integrity is required for the maintenance of genome stability and prevention of oncogenic transformation of cells. Recent evidence suggests the presence of epigenetic modifications as an important regulator of mammalian telomeres. Telomeric and subtelomeric regions are rich in epigenetic marks that regulate telomere length majorly through DNA methylation and post-translational histone modifications. Specific histone modifying enzymes play an integral role in establishing telomeric histone codes necessary for the maintenance of structural integrity. Alterations of crucial histone moieties and histone modifiers cause deregulations in the telomeric chromatin leading to carcinogenic manifestations. This review delves into the significance of histone modifications and their influence on telomere dynamics concerning cancer. Additionally, it highlights the existing research gaps that hold the potential to drive the development of therapeutic interventions targeting the telomere epigenome.

Supplementation of dietary areca nut extract modulates the growth performance, cecal microbiota composition, and immune function in Wenchang chickens

Introduction

The study was aimed at evaluating the effects of areca nut extract (ANE) on the growth performance, cecal microbiota, and immunity of Wenchang chickens.

Methods

For this study, 42-day-old healthy Wenchang chickens (n = 450) with similar body weight were chosen. The animals were randomly divided into five groups, with six replicates per group and 15 chickens per replicate. One group was fed a basal diet (control; CCK). The remaining four groups were fed a basal diet supplemented with varying ANE concentrations: 0.038, 0.063, 0.100, and 0.151 g/kg, with the groups denoted as CNT1, CNT2, CNT3, and CNT4, respectively. The feeding experiment lasted 35 days. The ligated cecum segments of the control and experimental groups were collected for metabolomic and metagenomic analysis, while the bone marrow samples were extracted for tandem mass tag (TMT)-based proteomic analysis.

Results

All the experimental groups exhibited significantly higher average daily gain (ADG) and significantly lower feed-to-weight (F/G) ratios than CCK. Metabolomic screening of the cecum contents revealed the presence of 544 differential metabolites, including several gut health-related metabolites, such as xanthine, hydroxy hypoxanthine, 2,5-dimethylhydrazine, ganoderic acid, and 2-aminohexanoic acid. Metagenomic analysis of the cecum contents showed an upregulation in the abundance of Prevotella spp. in the experimental groups. However, we observed no significant differences in the abundances of other cecal microbes at phylum and genus levels. Furthermore, we observed significant associations between Prevotella spp. and the differentially abundant metabolites, such as cherubins, thiaburimamide, and 3,4-dihydroxy-L-phenylalanine, (r)-mevalonate, 5-O-methylalloptaeroxylin, nalidixic acid, and deoxyloganin (p < 0.05). Proteomic analysis revealed that the differentially expressed proteins (such as interferon-induced protein with tetratricopeptide repeats 5 (IFIT5), MHC-BF1, and death domain-associated protein (Daxx)) in the bone marrow of the chickens were primarily enriched in the immune network for IgA production and B cell receptor signaling pathway.

Conclusion

In conclusion, dietary ANE supplementation was found to enhance metabolic activity and energy utilization, improve growth performance, modulate cecal microbiota, and strengthen the immunity of Wenchang chickens.

Exosomal RNF157 mRNA from prostate cancer cells contributes to M2 macrophage polarization through destabilizing HDAC1

Background

Exosomes have been identified to mediate the transmission of RNAs among different cells in tumor microenvironment, thus affecting the progression of different diseases. However, exosomal messenger RNAs (mRNAs) have been rarely explored. RNF157 mRNA has been found to be up-regulated in PCa patients’ exosomes, but the role of exosomal RNF157 mRNA in PCa development remains unclear.

Methods

Online databases were utilized for predicting gene expression and binding correlation between different factors. RT-qPCR and western blot assays were respectively done to analyze RNA and protein expressions. Flow cytometry analysis was implemented to analyze M2 polarization.

Results

RNF157 expression was high in PCa tissues and cells. M2 polarization of macrophages was enhanced after co-culture with PCa cells or with exosomes released by PCa cells. Upon RNF157 knockdown in PCa cells, the extracted exosomes could not lead to the facilitated M2 polarization. Mechanistically, RNF157 could bind to HDAC1 and contribute to HDAC1 ubiquitination, which led to HDAC1 degradation and resulting in promoting M2 polarization of macrophages. Animal experiments validated that exosomal RNF157 accelerated PCa tumor growth through facilitating macrophage M2 polarization.

Conclusion

Exosome-mediated RNF157 mRNA from PCa cells results in M2 macrophage polarization via destabilizing HDAC1, consequently promoting PCa tumor progression.

Mechanisms of TLR4-Mediated Autophagy and Nitroxidative Stress

Pathogenic infections have badly affected public health and the development of the breeding industry. Billions of dollars are spent every year fighting against these pathogens. The immune cells of a host produce reactive oxygen species and reactive nitrogen species which promote the clearance of these microbes. In addition, autophagy, which is considered an effective method to promote the destruction of pathogens, is involved in pathological processes. As research continues, the interplay between autophagy and nitroxidative stress has become apparent. Autophagy is always intertwined with nitroxidative stress. Autophagy regulates nitroxidative stress to maintain homeostasis within an appropriate range. Intracellular oxidation, in turn, is a strong inducer of autophagy. Toll-like receptor 4 (TLR4) is a pattern recognition receptor mainly involved in the regulation of inflammation during infectious diseases. Several studies have suggested that TLR4 is also a key regulator of autophagy and nitroxidative stress. In this review, we describe the role of TLR4 in autophagy and oxidation, and focus on its function in influencing autophagy-nitroxidative stress interactions.

Porcine Epidemic Diarrhea Virus Inhibits HDAC1 Expression To Facilitate Its Replication via Binding of Its Nucleocapsid Protein to Host Transcription Factor Sp1

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus causing acute intestinal infection in pigs, with high mortality often seen in neonatal pigs. The newborns rely on innate immune responses against invading pathogens because of lacking adaptive immunity. However, how PEDV disables the innate immunity of newborns toward severe infection remains unknown. We found that PEDV infection led to reduced expression of histone deacetylases (HDACs), especially HDAC1, in porcine IPEC-J2 cells. HDACs are considered important regulators of innate immunity. We hypothesized that PEDV interacts with certain host factors to regulate HDAC1 expression in favor of its replication. We show that HDAC1 acted as a negative regulator of PEDV replication in IPEC-J2 cells, as shown by chemical inhibition, gene knockout, and overexpression. A GC-box (GCCCCACCCCC) within the HDAC1 promoter region was identified for Sp1 binding in IPEC-J2 cells. Treatment of the cells with Sp1 inhibitor mithramycin A inhibited HDAC1 expression, indicating direct regulation of HDAC1 expression by Sp1. Of the viral proteins that were overexpressed in IPEC-J2 cells, the N protein was found to be present in the nuclei and more inhibitory to HDAC1 transcription. The putative nuclear localization sequence ²⁶¹PKKNKSR²⁶⁷ contributed to its nuclear localization. The N protein interacted with Sp1 and interfered with its binding to the promoter region, thereby inhibiting its transcriptional activity for HDAC1 expression. Our findings reveal a novel mechanism of PEDV evasion of the host responses, offering implications for studying the infection processes of other coronaviruses. IMPORTANCE The enteric coronavirus porcine epidemic diarrhea virus (PEDV) causes fatal acute intestinal infection in neonatal pigs that rely on innate immune responses. Histone deacetylases (HDACs) play important roles in innate immune regulation. Our study found PEDV suppresses HDAC1 expression via the interaction of its N protein and porcine Sp1, which identified a novel mechanism of PEDV evasion of the host responses to benefit its replication. This study suggests that other coronaviruses, including SARS-CoV and SARS-CoV-2, also make use of their N proteins to intercept the host immune responses in favor of their infection.

Cytokines and pregnancy: Potential regulation by histone deacetylases

Cytokines are important regulators of pregnancy and parturition. Aberrant expression of proinflammatory cytokines during pregnancy contributes towards preterm labor, pre-eclampsia, and gestational diabetes mellitus. The regulation of cytokine expression in human cells is highly complex, involving interactions between environment, transcription factors, and feedback mechanisms. Recent developments in epigenetic research have made tremendous advancements in exploring histone modifications as a key epigenetic regulator of cytokine expression and the effect of their signaling molecules on various organ systems in the human body. Histone acetylation and subsequent deacetylation by histone deacetylases (HDACs) are major epigenetic regulators of protein expression in the human body. The expression of various proinflammatory cytokines, their role in normal and abnormal pregnancy, and their epigenetic regulation via HDACs will be discussed in this review.

ATRX limits the accessibility of histone H3-occupied HSV genomes during lytic infection

Histones are rapidly loaded on the HSV genome upon entry into the nucleus of human fibroblasts, but the effects of histone loading on viral replication have not been fully defined. We showed recently that ATRX is dispensable for de novo deposition of H3 to HSV genomes after nuclear entry but restricted infection through maintenance of viral heterochromatin. To further investigate the roles that ATRX and other histone H3 chaperones play in restriction of HSV, we infected human fibroblasts that were systematically depleted of nuclear H3 chaperones. We found that the ATRX/DAXX complex is unique among nuclear H3 chaperones in its capacity to restrict ICP0-null HSV infection. Only depletion of ATRX significantly alleviated restriction of viral replication. Interestingly, no individual nuclear H3 chaperone was required for deposition of H3 onto input viral genomes, suggesting that during lytic infection, H3 deposition may occur through multiple pathways. ChIP-seq for total histone H3 in control and ATRX-KO cells infected with ICP0-null HSV showed that HSV DNA is loaded with high levels of histones across the entire viral genome. Despite high levels of H3, ATAC-seq analysis revealed that HSV DNA is highly accessible, especially in regions of high GC content, and is not organized largely into ordered nucleosomes during lytic infection. ATRX reduced accessibility of viral DNA to the activity of a TN5 transposase and enhanced accumulation of viral DNA fragment sizes associated with nucleosome-like structures. Together, these findings support a model in which ATRX restricts viral infection by altering the structure of histone H3-loaded viral chromatin that reduces viral DNA accessibility for transcription. High GC rich regions of the HSV genome, especially the S component inverted repeats of the HSV-1 genome, show increased accessibility, which may lead to increased ability to transcribe the IE genes encoded in these regions during initiation of infection.

Transcriptional, Epigenetic and Metabolic Programming of Tumor-Associated Macrophages

Macrophages are key innate immune cells in the tumor microenvironment (TME) that regulate primary tumor growth, vascularization, metastatic spread and tumor response to various types of therapies. The present review highlights the mechanisms of macrophage programming in tumor microenvironments that act on the transcriptional, epigenetic and metabolic levels. We summarize the latest knowledge on the types of transcriptional factors and epigenetic enzymes that control the direction of macrophage functional polarization and their pro- and anti-tumor activities. We also focus on the major types of metabolic programs of macrophages (glycolysis and fatty acid oxidation), and their interaction with cancer cells and complex TME. We have discussed how the regulation of macrophage polarization on the transcriptional, epigenetic and metabolic levels can be used for the efficient therapeutic manipulation of macrophage functions in cancer.

Reduced DAXX Expression Is Associated with Reduced CD24 Expression in Colorectal Cancer

The presence of an activating mutation of the Wnt/β-catenin signaling pathway is found in ~90% of colorectal cancer (CRC) cases. Death domain-associated protein (DAXX), a nuclear protein, interacts with β-catenin in CRC cells. We investigated DAXX expression in 106 matched sample pairs of CRC and adjacent normal tissue by Western blotting. This study evaluated DAXX expression and its clinical implications in CRC. The results revealed that DAXX expression was significantly lower in the patients with the positive serum carcinoembryonic antigen (CEA) screening results compared to the patients with negative CEA screening levels (p < 0.001). It has been reported that CD24 is a Wnt target in CRC cells. Here, we further revealed that DAXX expression was significantly correlated with CD24 expression (rho = 0.360, p < 0.001) in 106 patients. Consistent with this, in the CEA-positive subgroup, of which the carcinomas expressed DAXX at low levels, they were significantly correlated with CD24 expression (rho = 0.461, p < 0.005). Therefore, reduced DAXX expression is associated with reduced CD24 expression in CRC. Notably, in the Hct116 cells, DAXX knockdown using short-hairpin RNA against DAXX (shDAXX) not only caused significant cell proliferation, but also promoted metastasis. The DAXX-knockdown cells also demonstrated significantly decreased CD24 expression, however the intracellular localization of CD24 did not change. Thus, DAXX might be considered as a potential regulator of CD24 or β-catenin expression, which might be correlated with proliferative and metastatic potential of CRC.

DAXX, as a Tumor Suppressor, Impacts DNA Damage Repair and Sensitizes BRCA-Proficient TNBC Cells to PARP Inhibitors

Treatment options are limited for patients with triple negative breast cancer (TNBC). Understanding genes that participate in cancer progression and DNA damage response (DDR) may improve therapeutic strategies for TNBC. DAXX, a death domain-associated protein, has been reported to be critically involved in cancer progression and drug sensitivity in multiple cancer types. However, its role in breast cancer, especially for TNBC, remains unclear. Here, we demonstrated a tumor suppressor function of DAXX in TNBC proliferation, colony formation, and migration. In Mouse Xenograft Models, DAXX remarkably inhibited tumorigenicity of TNBC cells. Mechanistically, DAXX could directly bind to the promoter region of RAD51 and impede DNA damage repair, which impacted the protection mechanism of tumor cells that much depended on remaining DDR pathways for cell growth. Furthermore, DAXX-mediated inefficient DNA damage repair could sensitize BRCA-proficient TNBC cells to PARP inhibitors. Additionally, we identified that dual RAD51 and PARP inhibition with RI-1 and ABT888 significantly reduced TNBC growth both in vitro and in vivo, which provided the first evidence of combining RAD51 and PARP inhibition in BRCA-proficient TNBC. In conclusion, our data support DAXX as a modulator of DNA damage repair and suppressor of TNBC progression to sensitize tumors to the PARP inhibitor by repressing RAD51 functions. These provide an effective strategy for a better application of PARP inhibition in the treatment of TNBC.

SUMO-defective c-Maf preferentially transactivates Il21 to exacerbate autoimmune diabetes

SUMOylation is involved in the development of several inflammatory diseases, but the physiological significance of SUMO-modulated c-Maf in autoimmune diabetes is not completely understood. Here, we report that an age-dependent attenuation of c-Maf SUMOylation in CD4+ T cells is positively correlated with the IL-21-mediated diabetogenesis in NOD mice. Using 2 strains of T cell-specific transgenic NOD mice overexpressing wild-type c-Maf (Tg-WTc) or SUMOylation site-mutated c-Maf (Tg-KRc), we demonstrated that Tg-KRc mice developed diabetes more rapidly than Tg-WTc mice in a CD4+ T cell-autonomous manner. Moreover, SUMO-defective c-Maf preferentially transactivated Il21 to promote the development of CD4+ T cells with an extrafollicular helper T cell phenotype and expand the numbers of granzyme B-producing effector/memory CD8+ T cells. Furthermore, SUMO-defective c-Maf selectively inhibited recruitment of Daxx/HDAC2 to the Il21 promoter and enhanced histone acetylation mediated by CREB-binding protein (CBP) and p300. Using pharmacological interference with CBP/p300, we illustrated that CBP30 treatment ameliorated c-Maf-mediated/IL-21-based diabetogenesis. Taken together, our results show that the SUMOylation status of c-Maf has a stronger regulatory effect on IL-21 than the level of c-Maf expression, through an epigenetic mechanism. These findings provide new insights into how SUMOylation modulates the pathogenesis of autoimmune diabetes in a T cell-restricted manner and on the basis of a single transcription factor.

Epigenetic control of macrophage polarization: implications for targeting tumor-associated macrophages

The progression of cancer is a result of not only the growth of the malignant cells but also the behavior of other components of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are key components of the TME that influence tumor growth and disease progression. TAMs can either inhibit or support tumor growth depending on their polarization to classically-activated macrophages (M1s) or alternatively-activated macrophages (M2s), respectively. Epigenetic regulation plays a significant role in determining this polarization and manipulating the epigenetic regulation in macrophages would provide a means for selectively targeting M2s thereby eliminating tumor-supporting TAMs while sparing tumor-inhibiting M1 TAMs. Many pharmacologic modulators of epigenetic enzymes are currently used clinically and could be repurposed for treating tumors with high TAM infiltrate. While much research involving epigenetic enzymes and their modulators has been performed in M1s, significantly less is known about the epigenetic regulation of M2s. This review highlights the field’s current knowledge of key epigenetic enzymes and their pharmacologic modulators known to influence macrophage polarization.

Structural and mechanistic insights into ATRX-dependent and -independent functions of the histone chaperone DAXX

The ATRX–DAXX histone chaperone complex incorporates the histone variant H3.3 at heterochromatic regions in a replication-independent manner. Here, we present a high-resolution x-ray crystal structure of an interaction surface between ATRX and DAXX. We use single amino acid substitutions in DAXX that abrogate formation of the complex to explore ATRX-dependent and ATRX-independent functions of DAXX. We find that the repression of specific murine endogenous retroviruses is dependent on DAXX, but not on ATRX. In support, we reveal the existence of two biochemically distinct DAXX-containing complexes: the ATRX–DAXX complex involved in gene repression and telomere chromatin structure, and a DAXX–SETDB1–KAP1–HDAC1 complex that represses endogenous retroviruses independently of ATRX and H3.3 incorporation into chromatin. We find that histone H3.3 stabilizes DAXX protein levels and can affect DAXX-regulated gene expression without incorporation into nucleosomes. Our study demonstrates a nucleosome-independent function for the H3.3 histone variant.

The ATRX-DAXX histone chaperone complex incorporates H3.3 in heterochromatin in a replication-independent manner. Here, the authors present a high-resolution x-ray crystal structure of an interaction surface between ATRX and DAXX, and characterize ATRX-dependent and-independent functions of DAXX.

Menin and Daxx Interact to Suppress Neuroendocrine Tumors through Epigenetic Control of the Membrane Metallo-Endopeptidase

Neuroendocrine tumors (NET) often harbor loss-of-function mutations in the MEN1 and DAXX tumor suppressor genes. Here, we report that the products of these genes, menin and Daxx, interact directly with each other to suppress the proliferation of NET cells, to a large degree by inhibiting expression of the membrane metallo-endopeptidase (MME). Menin and Daxx were required to enhance histone H3 lysine9 trimethylation (H3K9me3) at the MME promoter, as mediated partly by the histone H3 methyltransferase SUV39H1. Notably, the menin T429K mutation associated with a NET syndrome reduced Daxx binding, MME repression, and proliferation of NET cells. Conversely, inhibition of MME in NET cells repressed proliferation and tumor growth in vivo Our findings reveal a previously unappreciated cross-talk between two crucial tumor suppressor genes thought to work by independent pathways, focusing on MME as a common target of menin/Daxx to treat NET. Cancer Res; 77(2); 401-11. ©2016 AACR.

Daxx inhibits hypoxia-induced lung cancer cell metastasis by suppressing the HIF-1α/HDAC1/Slug axis

Hypoxia is a major driving force of cancer invasion and metastasis. Here we show that death domain-associated protein (Daxx) acts to negatively regulate hypoxia-induced cell dissemination and invasion by inhibiting the HIF-1α/HDAC1/Slug pathway. Daxx directly binds to the DNA-binding domain of Slug, impeding histone deacetylase 1 (HDAC1) recruitment and antagonizing Slug E-box binding. This, in turn, stimulates E-cadherin and occludin expression and suppresses Slug-mediated epithelial–mesenchymal transition (EMT) and cell invasiveness. Under hypoxic conditions, stabilized hypoxia-inducible factor (HIF)-1α downregulates Daxx expression and promotes cancer invasion, whereas re-expression of Daxx represses hypoxia-induced cancer invasion. Daxx also suppresses Slug-mediated lung cancer metastasis in an orthotopic lung metastasis mouse model. Using clinical tumour samples, we confirmed that the HIF-1α/Daxx/Slug pathway is an outcome predictor. Our results support that Daxx can act as a repressor in controlling HIF-1α/HDAC1/Slug-mediated cancer cell invasion and is a potential therapeutic target for inhibition of cancer metastasis.

Hypoxia and epithelial-to-mesenchymal transition promotes cancer metastasis. Here the authors show that Daxx inhibits hypoxia-induced lung cancer metastasis by attenuating Slug-mediated transcriptional repression of epithelial-like markers that in turn cause cells to exhibit low invasiveness.

Innate recognition of microbial-derived signals in immunity and inflammation

Microbes generate a vast array of different types of conserved structural components called pathogen-associated molecular patterns (PAMPs), which can be recognized by cells of the innate immune system. This recognition of "nonself" signatures occurs through host pattern recognition receptors (PRRs), suggesting that microbial-derived signals are good targets for innate immunity to discriminate between self- and nonself. Such PAMP-PRR interactions trigger multiple but distinct downstream signaling cascades, subsequently leading to production of proinflammatory cytokines and interferons that tailor immune responses to particular microbes. Aberrant PRR signals have been associated with various inflammatory diseases and fine regulation of PRR signaling is essential for avoiding excessive inflammatory immune responses and maintaining immune homeostasis. In this review we summarize the ligands and signal transduction pathways of PRRs and highlight recent progress of the mechanisms involved in microbe-specific innate immune recognition during immune responses and inflammation, which may provide new targets for therapeutic intervention to the inflammatory disorders.

Anomaly Detection in Host Signaling Pathways for the Early Prognosis of Acute Infection

Clinical diagnosis of acute infectious diseases during the early stages of infection is critical to administering the appropriate treatment to improve the disease outcome. We present a data driven analysis of the human cellular response to respiratory viruses including influenza, respiratory syncytia virus, and human rhinovirus, and compared this with the response to the bacterial endotoxin, Lipopolysaccharides (LPS). Using an anomaly detection framework we identified pathways that clearly distinguish between asymptomatic and symptomatic patients infected with the four different respiratory viruses and that accurately diagnosed patients exposed to a bacterial infection. Connectivity pathway analysis comparing the viral and bacterial diagnostic signatures identified host cellular pathways that were unique to patients exposed to LPS endotoxin indicating this type of analysis could be used to identify host biomarkers that can differentiate clinical etiologies of acute infection. We applied the Multivariate State Estimation Technique (MSET) on two human influenza (H1N1 and H3N2) gene expression data sets to define host networks perturbed in the asymptomatic phase of infection. Our analysis identified pathways in the respiratory virus diagnostic signature as prognostic biomarkers that triggered prior to clinical presentation of acute symptoms. These early warning pathways correctly predicted that almost half of the subjects would become symptomatic in less than forty hours post-infection and that three of the 18 subjects would become symptomatic after only 8 hours. These results provide a proof-of-concept for utility of anomaly detection algorithms to classify host pathway signatures that can identify presymptomatic signatures of acute diseases and differentiate between etiologies of infection. On a global scale, acute respiratory infections cause a significant proportion of human co-morbidities and account for 4.25 million deaths annually. The development of clinical diagnostic tools to distinguish between acute viral and bacterial respiratory infections is critical to improve patient care and limit the overuse of antibiotics in the medical community. The identification of prognostic respiratory virus biomarkers provides an early warning system that is capable of predicting which subjects will become symptomatic to expand our medical diagnostic capabilities and treatment options for acute infectious diseases. The host response to acute infection may be viewed as a deterministic signaling network responsible for maintaining the health of the host organism. We identify pathway signatures that reflect the very earliest perturbations in the host response to acute infection. These pathways provide a monitor the health state of the host using anomaly detection to quantify and predict health outcomes to pathogens.

Daxx from Pacific white shrimp Litopenaeus vannamei is involved in activation of NF-κB pathway

Death domain-associated factor 6 (Daxx) is a Fas-binding protein that mediates the activation of Jun amino-terminal kinase (JNK) pathway and Fas-induced apoptosis. In this study, a crustacean Daxx (LvDaxx) was firstly cloned and identified from Pacific white shrimp Litopenaeus vannamei. The LvDaxx cDNA was 2644 bp in length with an Open Reading Frame (ORF) of 2217 bp. Sequence analysis indicated that LvDaxx contained a single Daxx domain and two nuclear localization signals (NLSs) and shared a similarity with Drosophila melanogaster Daxx. LvDaxx was a nuclear-localized protein that was expressed highest in hemocytes and could be up-regulated in pathogen- and stimulant-challenge shrimps. LvDaxx could activate the artificial promoter containing an NF-κB binding site and the promoters of white spot syndrome virus (WSSV) ie1 gene and arthropod antimicrobial peptides (AMPs), suggesting LvDaxx could be involved in the activation of the NF-κB pathway. Knock-down of LvDaxx in vivo resulted in down-regulation of shrimp AMPs and reduction of WSSV copies in tissues. Furthermore, suppression of LvDaxx significantly decreased the mortality of WSSV-infected shrimps, but increased the mortality of Vibrio Parahaemolyticus-infected shrimps. Thus, these suggested that LvDaxx could play a role in the innate immunity against Vibrio parahaemolyticus in L. vannamei, while in the antiviral response, LvDaxx may be hijacked by WSSV and play a complex role in WSSV pathogenesis.

Trek1 contributes to maintaining nasal epithelial barrier integrity

Epithelial barrier integrity is critical to maintain the homeostasis in the body. The regulatory mechanism of the epithelial barrier function has not been fully understood. This study aims to elucidate the role of the TWIK-related potassium channel-1 (Trek1) in the regulation of the epithelial barrier function of the nasal mucosa. In this study, the levels of Trek1 were assessed by real time RT-PCR and Western blotting. The epithelial barrier function of the rat nasal epithelia was evaluated by the Ussing chamber system. The results showed that Trek1 was detected in the human and rat nasal epithelia, which were significantly lower in patients and rats with allergic rhinitis than that in healthy controls. Exposure to the signature T helper 2 cytokine, interleukin (IL)-4, markedly suppressed the expression of Trek1 in the nasal mucosa via up regulating the expression of the histone deacetylase (HDAC)1. The IL-4-induced rat nasal epithelial barrier dysfunction could be blocked by HDAC1 inhibitor (Trichostatin A), or sodium butyrate, or administration of Clostridium Butyricum. We conclude that Trek1 is critical to maintain the nasal epithelial barrier function.

Histone lysine methyltransferase Ezh1 promotes TLR-triggered inflammatory cytokine production by suppressing Tollip

Histone modifications play critical roles in the regulation of gene expression; however, their roles in the regulation of the innate response remain to be fully investigated. Using transcriptome analysis of mouse immature dendritic cells (DCs) and LPS-induced mature DCs, we identified that Ezh1 was the most upregulated histone methyltransferase during DC maturation. In this study, we investigated the role of Ezh1 in regulating the innate immune response. We found that silencing of Ezh1 significantly suppressed TLR-triggered production of cytokines, including IL-6, TNF-α, and IFN-β, in DCs and macrophages. Accordingly, TLR-activated signaling pathways were impaired in Ezh1-silenced macrophages. By transcriptome analysis of Ezh1-silenced macrophages, we found that Toll-interacting protein (Tollip), one well-known negative regulator of TLR signaling, was upregulated. Silencing of Tollip rescued TLR-triggered cytokine production in Ezh1-silenced macrophages. The SET domain of Ezh1 is essential for its enhancing effect on the TLR-triggered innate immune response and downstream signaling, indicating that Ezh1 promotes a TLR-triggered innate response through its lysine methyltransferase activity. Finally, Ezh1 was found to suppress the transcription of Tollip by directly targeting the proximal promoter of tollip and maintaining the high level of trimethylation of histone H3 lysine 27 there. Therefore, Ezh1 promotes TLR-triggered inflammatory cytokine production by suppressing the TLR negative regulator Tollip, contributing to full activation of the innate immune response against invading pathogens.