Differential regulation of Tetraodon nigroviridis Mx gene promoter activity by constitutively-active forms of STAT1, STAT2, and IRF9

Functional characterization of Malabar grouper (Epinephelus malabaricus) interferon regulatory factor 9 involved in antiviral response

IRF9 is a crucial component in the JAK-STAT pathway. IRF9 interacts with STAT1 and STAT2 to form IFN-I-stimulated gene factor 3 (ISGF3) in response to type I IFN stimulation, which promotes ISG transcription. However, the mechanism by which IFN signaling regulates Malabar grouper (Epinephelus malabaricus) IRF9 is still elusive. Here, we explored the nd tissue-specific mRNA distribution of the MgIRF9 gene, as well as its antiviral function in E. malabaricus. MgIRF9 encodes a protein of 438 amino acids with an open reading frame of 1317 base pairs. MgIRF9 mRNA was detected in all tissues of a healthy M. grouper, with the highest concentrations in the muscle, gills, and brain. It was significantly up-regulated by nervous necrosis virus infection and poly (I:C) stimulation. The gel mobility shift test demonstrated a high-affinity association between MgIRF9 and the promoter of zfIFN in vitro. In GK cells, grouper recombinant IFN-treated samples showed a significant response in ISGs and exhibited antiviral function. Subsequently, overexpression of MgIRF9 resulted in a considerable increase in IFN and ISGs mRNA expression (ADAR1, ADAR1-Like, and ADAR2). Co-immunoprecipitation studies demonstrated that MgIRF9 and STAT2 can interact in vivo. According to the findings, M. grouper IRF9 may play a role in how IFN signaling induces ISG gene expression in grouper species.

Feedback loop regulation between viperin and viral hemorrhagic septicemia virus through competing protein degradation pathways

Viperin is an antiviral protein that exhibits a remarkably broad spectrum of antiviral activity. Viperin-like proteins are found all kingdoms of life, suggesting it is an ancient component of the innate immune system. However, viruses have developed strategies to counteract viperin's effects. Here, we describe a feedback loop between viperin and viral hemorrhagic septicemia virus (VHSV), a common fish pathogen. We show that Lateolabrax japonicus viperin (Ljviperin) is induced by both IFN-independent and IFN-dependent pathways, with the C-terminal domain of Ljviperin being important for its anti-VHSV activity. Ljviperin exerts an antiviral effect by binding both the nucleoprotein (N) and phosphoprotein (P) of VHSV and induces their degradation through the autophagy pathway, which is an evolutionarily conserved antiviral mechanism. However, counteracting viperin's activity, N protein targets and degrades transcription factors that up-regulate Ljviperin expression, interferon regulatory factor (IRF) 1 and IRF9, through ubiquitin-proteasome pathway. Together, our results reveal a previously unknown feedback loop between viperin and virus, providing potential therapeutic targets for VHSV prevention.

Importance

Viral hemorrhagic septicaemia (VHS) is a contagious disease caused by the viral hemorrhagic septicaemia virus (VHSV), which poses a threat to over 80 species of marine and freshwater fish. Currently, there are no effective treatments available for this disease. Understanding the mechanisms of VHSV-host interaction is crucial for preventing viral infections. Here, we found that, as an ancient antiviral protein, viperin degrades the N and P proteins of VHSV through the autophagy pathway. Additionally, the N protein also impacts the biological functions of IRF1 and IRF9 through the ubiquitin-proteasome pathway, leading to the suppression of viperin expression. Therefore, the N protein may serve as a potential virulence factor for the development of VHSV vaccines and screening of antiviral drugs. Our research will serve as a valuable reference for the development of strategies to prevent VHSV infections.

Molecular cloning and expression analysis of Myxovirus resistance gene in Yangzhou goose (Anser cygnoides domesticus)

1. Myxovirus resistance (Mx) is a protein produced by the interferon-induced natural immune response with broad spectrum antiviral function. However, the role and expression characteristics of the Mx gene in immune defence against viral infection in goose have not yet been reported.2. This study found a 2576 bp genomic sequence and a 2112 bp mRNA sequence for Mx, encoding 703 amino acids. Multiple sequence alignments of the amino acid sequences showed that the Yangzhou goose Mx (goMx) had 86.99% similarity to the mallard duck (Anas platyrhynchos).3. Tissue-specific expression profiling revealed that the expression of goMx was highest in the lung and spleen. Both poly (I:C) and GPV were found to elevate the expression of goMx. The upregulated expression of goMx was associated with interferon pathway-related genes IRF7, JAK1, STAT1, and STAT2. Furthermore, overexpression of goMx significantly activated the transcription of poly (I:C) induced TNF-α, IL-1β, IL-6, and IL-18.4. The findings of this study suggest that the goMx modulation of the antiviral response is mediated by the interferon pathway.

Molecular cloning, expression and functional analysis of STAT2 in orange-spotted grouper, Epinephelus coioides

Signal transducer and activator of transcription 2 (STAT2) is an important molecule involved in the type I interferon signaling pathway. To better understand the functions of STAT2 in fish immune response, a STAT2 gene from orange-spotted grouper (Epinephelus coioides) (EcSTAT2) was cloned and characterized in this study. EcSTAT2 encoded a 802-amino acid peptide which shared 99.5% and 91.5% identity with giant grouper (Epinephelus lanceolatus) and leopard coral grouper (Plectropomus leopardus), respectively. Amino acid alignment analysis showed that EcSTAT2 contained five conserved domains, including N-terminal protein interaction domain, coiled coil domain (CCD), DNA binding domain (DBD), Src-homology 2 (SH2) domain, and C-terminal transactivation domain (TAD). Phylogenetic analysis indicated that EcSTAT2 clustered into fish STAT2 group and showed the nearest relationship to giant grouper STAT2. In healthy grouper, EcSTAT2 was distributed in all tissues tested, and the expression of EcSTAT2 was predominantly detected in spleen, kidney and gill. In vitro, EcSTAT2 expression was significantly increased in response to polyinosinic:polycytidylic acid [poly (I:C)] stimulation and red-spotted grouper nervous necrosis virus (RGNNV) infection. Subcellular localization showed that EcSTAT2 was located in the cytoplasm in a punctate manner. EcSTAT2 overexpression significantly inhibited RGNNV replication, as evidenced by the decreased severity of cytopathic effect (CPE) and the reduced expression levels of viral genes and protein. Consistently, knockdown of EcSTAT2 using small interfering RNA (siRNA) promoted RGNNV replication. Furthermore, EcSTAT2 overexpression increased both interferon (IFN) and interferon stimulated genes (ISGs) expression. In addition, EcSTAT2 knockdown decreased the transcription levels of IFN and ISGs. Together, our data demonstrated that EcSTAT2 exerted antiviral activity against RGNNV through up-regulation of host interferon response.

Characterization of three novel cell lines derived from the brain of spotted sea bass: Focusing on cell markers and susceptibility toward iridoviruses

Despite tens of cell lines originating from fish brain tissue have been constructed, little is known about the definite cell types they belong to. Whether fish cell lines derived from the brain shares similar characteristics is not well-answered yet. Here, we constructed three cell lines designated as LMB-S, LMB-M, LMB-L using brain tissue of spotted sea bass (Lateolabrax maculatus). Among them, LMB-L was identified as astroglia-like cells considering the high expression of GFAP, DCX, PTX, S100b, which are regarded as astrocyte-specific or astrocyte-associated cell markers. LMB-M exhibited smooth muscle-like features showing strong expression of LMOD1, SLAMP, M-cadherin, MGP, which are confirmed as muscle-restricted or myogenesis-involved cell markers. Although LMB-S was not definitely identified, it appeared an activation of WNT/β-catenin pathway. Besides the distinct expression profiles of cell markers, the three cell lines also presented differences in transfection efficiency and susceptibility to iridovirus infection. Relying on the established cell lines, a novel megalocytivirus, named LMIV (Lateolabrax maculatus iridovirus), was first isolated from diseased spotted sea bass. Genetic analysis of major capsid protein (MCP) and adenosine triphosphatase (ATPase) manifested that LMIV was clearly distinguishable from other representative teleost iridoviruses. Further investigations revealed that LMIV could replicate most efficiently in LMB-L cells obtaining the highest viral load (2.16 × 10¹⁰ copy/mL). By contrast, LMB-S cells gave rise to the highest viral load up to 3.86 × 10⁸ copy/mL, when the three cell lines were infected with MRV, a newly emerged ranavirus. Moreover, LMIV infection caused lots of cells to be detached from monolayers, generating adherent and non-adherent cells. An opposite expression profiling of type I IFN pathway-related genes (JAK1, STAT1, STAT2, IRF9, Mx1) was found between adherent and non-adherent cells. Combined with the analysis of MCP gene expression, it is speculated that inhibiting type I IFN pathway in non-adherent cells allowed the facilitation of virus duplication. Taken together, the present study broadens our understanding about the diversity of cell lines derived from fish brain tissue and screening cells more susceptible to virus is not only meaningful for the development of vaccine, but also provide clues for further clarification of cell-iridovirus interactions.

Structural and Functional Analyses of Type I IFNa Shed Light Into Its Interaction With Multiple Receptors in Fish

Teleost type I interferons (IFNs) are categorized into group I and II subgroups that bind to distinct receptors to activate antiviral responses. However, the interaction between ifn ligands and receptors has not fully been understood. In this study, the crystal structure of grass carp [Ctenopharyngodon idella (Ci)] IFNa has been solved at 1.58Å and consists of six helices. The CiIFNa displays a typical structure of type I IFNs with a straight helix F and lacks a helix element in the AB loop. Superposition modeling identified several key residues involved in the interaction with receptors. It was found that CiIFNa bound to cytokine receptor family B (CRFB) 1, CRFB2, and CRFB5, and the three receptors could form heterodimeric receptor complexes. Furthermore, mutation of Leu27, Glu103, Lys117, and His165 markedly decreased the phosphorylation of signal transducer and activator of transcription (STAT) 1a induced by CiIFNa in the Epithelioma papulosum cyprini (EPC) cells, and Glu103 was shown to be required for the CiIFNa-activated antiviral activity. Interestingly, wild-type and mutant CiIFNa proteins did not alter the phosphorylation levels of STAT1b. Our results demonstrate that fish type I IFNs, although structurally conserved, interact with the receptors in a manner that may differ from mammalian homologs.

A novel low-molecular-weight chitosan/gamma-polyglutamic acid polyplexes for nucleic acid delivery into zebrafish larvae

Many challenges, such as virus infection, extreme weather and long cultivation periods, during the development of fish larvae have been observed, especially in aquaculture. Gene delivery is a useful method to express functional genes to defend against these challengers. However, the methods for fish larvae are insufficient. In our earlier report, low-molecular-weight chitosan (LMWCS) showed a strong positive charge and may be useful for polyplex formulation. Herein, we present a simple self-assembly of LMWCS polyplexes (LMWCSrNPs) for gene delivery into zebrafish larvae. Different weight ratios of LMWCS/gamma-polyglutamic acid (γ-PGA)/plasmid DNA were analyzed by gel mobility assay. Delivery efficiency determined by green fluorescent protein (GFP) expression in zebrafish liver (ZFL) cells showed that delivery efficiency at a weight ratio of 20:8:1 was higher than others. Zeta potential and transmission electron microscopy (TEM) analysis showed that the round shape of the particle size varied. In our earlier reports, IRF9S2C could induce interferon-stimulated gene (ISG) expression to induce innate immunity in zebrafish and pufferfish. Further delivery of pcDNA3-IRF9S2C-HA plasmid DNA into ZFL cells and zebrafish larvae by LMWCSrNP successfully induced ISG expression. Collectively, LMWCSrNP could be a novel gene delivery system for zebrafish larvae and might be used to improve applications in aquaculture.

UBE2S activates NF-κB signaling by binding with IκBα and promotes metastasis of lung adenocarcinoma cells

PURPOSE

Nuclear factor (NF)-κB signaling in cancer cells has been reported to be involved in tumorigenesis. Phosphorylation and degradation of inhibitor of NF-κBα (IκBα) is a canonical pathway of NF-κB signaling. Here, we aimed to identify and characterize noncanonical activation of NF-κB signaling by ubiquitin-conjugating enzyme E2S (UBE2S) in lung adenocarcinoma cells.

METHODS

TCGA and the Human Atlas Protein Database were used to analyze the survival rate of lung adenocarcinoma patients in conjunction with UBE2S expression. In addition, PC9, H460, H441 and A549 lung adenocarcinoma cells were used in this study. PC9 and H460 cells were selected for further analysis because they expressed different UBE2S protein levels. Specific IKK inhibitors, PS1145 and SC514, were used to assess IκBα phosphorylation. Western blot analysis was used to assess protein levels in PC9 and H460 cells. A scratch wound-healing assay was used to analyze the migrative abilities of PC9 and H460 cells. Overexpression and knockdown of UBE2S in H460 and PC9 cells were used to analyze their effects on downstream protein levels. Immunoprecipitation, immunofluorescent staining, glutathione S transferase (GST) pull-down and in vitro binding assays were used to analyze the interaction between UBE2S and IκBα. A luciferase assay was used to analyze activation of NF-κB signaling regulated by UBE2S. An in vivo zebrafish xenograft model was used to assess metastasis of PC9 cells regulated by UBE2S.

RESULTS

We found that UBE2S expression in lung adenocarcinoma patients was negatively related to survival rate. The protein level of UBE2S was higher in PC9 cells than in H460 cells, which was opposite to that observed for IκBα. PC9 cells showed a higher UBE2S expression and migrative ability than H460 cells. Phosphorylation of IκBα was not changed by treatment with the IKK-specific inhibitors PS1145 and SC514 in PC9 and H460 cells. Overexpression and knockdown of UBE2S in H460 and PC9 cells revealed that the protein levels of IκBα were inversely regulated. Immunoprecipitation, immunofluorescent staining, GST pull-down and in vitro binding assays revealed direct binding of UBE2S with IκBα. Nuclear P65 protein levels and luciferase assays showed that NF-κB signaling was regulated by UBE2S. The expression of epithelial-to-mesenchymal (EMT) markers and the migrative ability of lung adenocarcinoma cells were also regulated by UBE2S. A zebrafish xenograft tumor model showed a reduction in the metastasis of PC9 cells that was induced by UBE2S knockdown.

CONCLUSIONS

Higher UBE2S expression in lung adenocarcinomas may lead to increased binding with IκBα to activate NF-κB signaling and promote adenocarcinoma cell metastasis. UBE2S may serve as a potential therapeutic target for lung adenocarcinomas.

A myxovirus resistance like protein involved in CgIFNLP mediated immune response of oyster Crassostrea gigas

The myxovirus resistance (Mx) proteins belong to interferon (IFN)-induced dynamin GTPase and play a pivotal role in the inhibition of replication of numerous viruses. In the present study, an Mx homologue (designated as CgMx1) was identified from oyster Crassostrea gigas. The open reading frame (ORF) of CgMx1 cDNA was of 1689 bp encoding a peptide of 562 amino acid residues. There was an N-terminal dynamin GTPase domain in the predicted peptide, which consisted of a tripartite GTP-binding motif (GDXXSGKS, DLPG and T/NKXD). The deduced amino acid sequence of CgMx1 shared 30-39% similarity with other Mx family members. And CgMx1 was clustered with Mx from H. discus, and then assigned into the invertebrate branch of the phylogenetic tree. The mRNA transcripts of CgMx1 were constitutively distributed in all the tested tissues, with the highest level in haemocytes (1342.45-fold of labial palps, p < 0.05). The mRNA expression of CgMx1 in haemocytes was significantly up-regulated to the highest level at 6 h (13.14-fold, p < 0.001) after poly (I:C) treatment and at 24 h (66.28-fold, p < 0.001) after recombinant IFN-like protein (rCgIFNLP) stimulation, respectively. CgMx1 protein was found to distribute in both the cytoplasm and nucleus of haemocytes. In the oysters with CgIFNLP and signal transducer and activator of transcription (CgSTAT) silenced by RNAi, the mRNA expression of CgMx1 decreased significantly in the haemocytes at 12 h after poly (I:C) stimulation, which was 0.02-fold and 0.04-fold of that in EGFP-RNAi oysters (p < 0.001), respectively. Meanwhile, EMSA assay revealed that CgSTAT was able to transactivate CgMx1 promoter through directly binding to its interferon-stimulated response element (ISRE) and gamma interferon activation site (GAS). The above results indicated that CgMx1 participated in the immune response of C. gigas through the signal pathway mediated by CgIFNLP and CgSTAT.

Type I interferons in ray-finned fish (Actinopterygii)

Interferons (IFNs) are proteins of vital importance in the body's immune response. They are formed in different types of cells and have been found in fish, amphibians, reptiles and mammals. Two types of IFN have been found in ray-finned fish (Superclass: Osteichthyes, Class: Actinopterygii) so far, i.e. IFN type I (IFN I) and IFN type II (IFN II), while the presence of IFN type III (IFN III), which is found in phylogenetically older cartilaginous fishes, was not confirmed in this taxonomic group of vertebrates. Currently, type I IFN in Actinopterygii is divided into three groups, I, II and III, within which there are subgroups. These cytokines in these animals show primarily antiviral activity through the use of a signalling pathway JAK-STAT (Janus kinases - Signal transducer and activator of transcription) and the ability to induce ISG (IFN-stimulated genes) expression, which contain ISRE complexes (IFN-stimulated response elements). On the other hand, in Perciformes and Cyprinidae, it was found that type I/I interferons also participate in the antimicrobial response, inter alia, by inducing the expression of the inducible nitric oxide synthase (iNOS) and influencing the production of reactive oxygen species (ROS) in cells carrying out the phagocytosis process.

Molecular insight, expression profile and subcellular localization of two STAT family members, STAT1a and STAT2, from Japanese eel, Anguilla japonica

Signal transducer and activator of transcription 1 (STAT1) and STAT2 are critical components of type I and type II IFNs signaling. To date, seven STAT family proteins have been identified from mammals. However, the information on STAT genes in teleost fish is still limited. In the present study, two STAT family genes (STAT1a and STAT2) were identified from Japanese eel, Anguilla japonica and designated as AjSTAT1a and AjSTAT2. The open reading frames of AjSTAT1a and AjSTAT2 are 2244 bp and 2421 bp, encoding for polypeptides of 747 aa and 806 aa, respectively. Both AjSTAT1a and AjSTAT2 contain the conserved domains of STAT proteins. Phylogenetic analysis was performed based on the STATs protein sequences, and showed that AjSTAT1a and AjSTAT2 shared the closest relationship with Oncorhynchus mykiss. Quantitative real-time PCR analysis revealed that AjSTAT1a and AjSTAT2 were expressed in most examined tissues, with the highest expression both in blood. Significantly up-regulated transcripts of AjSTAT1a and AjSTAT2 were detected in response to poly I:C stimulation, and Edwardsiella tarda induced increase in the expression of AjSTAT1a and AjSTAT2 genes. Subcellular localization analysis showed that in both IFNγ-stimulated and unstimulated EPC cells AjSTAT1a and AjSTAT2 were mainly distributed in the cytoplasm, but few AjSTAT1a was distributed in the nucleus. All these results suggested that AjSTAT1a and AjSTAT2 may be critical for regulating the host innate immune defense against pathogens invasion.

Myxovirus resistance (Mx) gene and its differential expression regulated by three type I and two type II IFNs in mandarin fish, Siniperca chuatsi

Interferons (IFNs) can induce the expression of IFN-stimulated genes (ISGs), such as myxovirus resistance (Mx) protein, to inhibit virus replication. In this study, the expression of Mx gene in mandarin fish, and the IFN-sensitive response elements (ISREs) and gamma-interferon activated sites (GASs) in the promoter of Mx gene were analyzed in relation to the stimulation of three distinct type I IFNs, IFNc, IFNd and IFNh, and two type II IFNs, IFN-γ and IFN-γ related molecule (IFN-γrel). A single Mx gene was found in mandarin fish, and its expression was highly and constitutively observed in all organs/tissues examined. The Mx gene was significantly induced in vivo for 120 h following infectious spleen and kidney necrosis virus (ISKNV) infection. Furthermore, the overexpression and recombinant of IFNh, IFNc, as well as IFN-γ can significantly induce Mx expression in MFF-1 cells at transcript and protein levels, although all the three type I IFNs and the two type II IFNs can activate the Mx promoter. In addition, ISRE1 which is the proximal one among the three predicted ISREs seems to be the important ISRE for the higher and efficient activation of the Mx promoter. However, the possible interaction between the GASs and type II IFN signalling molecules require further study.

Molecular characterization and functional analysis of interferon regulatory factor 9 (irf9) in common carp Cyprinus carpio: a pivotal molecule in the Ifn response against pathogens

In the present study, interferon (IFN) regulatory factor (IRF) 9 gene (irf9) was identified and characterized in common carp Cyprinus carpio. The predicted protein sequence of Irf9 contains a DNA binding domain (DBD) that possess five tryptophans, an IRF association domain (IAD) and two nuclear localisation signals (NLS). Alignment of Irf9 of C. carpio with the corresponding Irf9 proteins of other species showed that the DBD is more highly conserved than the IAD. The putative Irf9 protein sequence of C. carpio shares higher identities with teleosts (53.8-82.3%) and lower identities with mammals (30.2-31.0%). Phylogenetic studies of the putative amino-acid sequence of IRF9 based on the neighbour-joining method showed that Irf9 of C. carpio has the closest relationship with the grass carp Ctenopharyngodon idella. Tissue distribution analysis showed that irf9 transcripts were detectable in all examined tissues with the highest expression in the skin and the lowest expression in the head kidney. Poly I:C and Aeromonas hydrophila stimulation up-regulated irf9 expression in the spleen, head kidney, foregut and hindgut at different time intervals. In addition, irf9 was induced by Poly I:C and lipopolysaccharides (LPS) in vitro. These results indicate that Irf9 participates in antiviral and antibacterial immunity. Transfection of irf9 up-regulated the expression of cytokines, including type I IFN, protein kinase R (PKR), interferon-stimulated gene (ISG)15 and tumour necrosis factor (TNF)α in epithelioma papulosum cyprini cells (EPC) upon poly I:C and LPS stimulation. A dual-luciferase reporter assay revealed that Irf9 has no effect on NF-κB activation. The present study on Irf9 provides new insights into the IFN system of C. carpio and a valuable experimental platform for future studies on the immune system of fish.

STAT1a and STAT1b of black carp play important roles in the innate immune defense against GCRV

Signal transducer and activator of transcription 1 (STAT1) plays an important role in the Janus kinase (JAK)-STAT signaling of human and mammals; however, the mechanism of STAT1 in innate immune activation of teleost fishes remains largely unknown. In this study, two STAT1 homologues (bcSTAT1a and bcSTAT1b) of black carp (Mylopharyngodon piceus) have been cloned and characterized. Both bcSTAT1a and bcSTAT1b transcription in host cells was obviously increased in response to the stimulation of poly (I:C), lipopolysaccharide (LPS), grass carp reovirus (GCRV) and interferon (IFN); however, the increase rate of bcSTAT1b transcription post stimulation was obviously higher than that of bcSTAT1a. bcSTAT1a and bcSTAT1b were distributed in both cytoplasm and nucleus in the immunofluorescence staining assay. Self-association of bcSTAT1a and bcSTAT1b, and the interaction between bcSTAT1a and bcSTAT1b have been detected through co-immunoprecipitation (co-IP) assay; and the data of native polyacrylamide gel electrophoresis (PAGE) implied that bcSTAT1a and bcSTAT1b might form homodimer and heterodimer in vivo like their mammalian counterparts. Both bcSTAT1a and bcSTAT1b presented IFN-inducing ability in report assay, and both bcSTAT1a and bcSTAT1b showed antiviral activities against GCRV in EPC cells. Our data support the conclusion that both bcSTAT1a and bcSTAT1b play important roles in host antiviral innate immune activation initiated by GCRV.

OSMR gene effect on the pathogenesis of chronic autoimmune Urticaria via the JAK/STAT3 pathway

Background

Chronic autoimmune urticaria (CAU) is a common skin disease and remains unclear understanding of pathogenesis in the vast majority of cases. In order to explore a new therapy for CAU, the current study was performed to investigate the possible functioning of the Oncostatin M receptor (OSMR) gene in the autoimmunity of CAU via regulation of the JAK/STAT3 signaling pathway.

Methods

CAU skin tissues from 24 CAU patients and normal skin tissues from normal subjects were collected. Hematoxylin-eosin (HE) staining was conducted to count eosinophils, and immunohistochemistry was carried out to detect the positive rate of OSMR expression in two kinds of skin tissues. A total of 72 Kunming (KM) mice were selected, and 60 mice were used for establishing CAU models and later transfected with different plasmids. The expression of inflammatory factors was evaluated by enzyme-linked immunosorbent assays (ELISA). Expressions of janus kinase (JAK), signal transducer and activator of transcription 3 (STAT3), interferon-stimulated gene 15 (ISG15), CT10-regulated kinase (CRK), and interferon regulatory factor 9 (IRF9) were identified using Western blot assay and reverse transcription quantitative polymerase chain reaction (RT-qPCR). Epithelial cell proliferation was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and cell cycle distribution and cell apoptosis were assessed using flow cytometry.

Results

The findings confirm that OSMR protein expression and histamine release rate are highly elevated in human CAU skin tissues, and the expression of the JAK/STAT3 signaling pathway-related genes (OSMR, JAK2, STAT3, ISG15, CRK and IRF9) was up-regulated. OSMR gene silencing in CAU mice significantly decreases the content of inflammatory factors (IL-1, IL-6, IFN-γ, and IgE), the number of eosinophils, and reduces the expression of the JAK/STAT3 signaling pathway related genes, and further enhances cell proliferation, promotes cell cycle entry and inhibits apoptosis of epithelial cells.

Conclusion

All aforementioned results indicate that OSMR gene silencing inhibits the activation of the JAK/STAT3 signaling pathway, thereby suppressing the development of CAU.

IRF9-Stat2 Fusion Protein as an Innate Immune Inducer to Activate Mx and Interferon-Stimulated Gene Expression in Zebrafish Larvae

Virus infection often causes large amounts of mortality during teleost larvae stage. Strong induction of innate immunity to increase survival rates of teleost larvae has been less reported. In this study, we present a zebrafish IRF9-Stat2 fusion protein (zIRF9-S2C) as a strong innate immunity inducer and characterized induction of interferon-stimulated genes (ISGs) in zebrafish larvae. zIRF9-S2C could mimic IFN-stimulated gene factor 3 (ISGF3) complex to constitutively activate transcription of Mx promoter through IFN-stimulatory element (ISRE) sites. Mutation of two ISRE sites on Mx promoter reduced transactivation activities of Mx promoter induced by zIRF9-S2C. An electrophoretic mobility shift assay experiment shows that zIRF9-S2C could directly bind to two ISRE sites of Mx promoter. Induction of transactivation of Mx promoter by zIRF9-S2C shows significantly higher activity than by zebrafish IFN1 (zIFN1), IFNγ (zIFNγ), and Tetraodon IRF9-S2C (TnIRF9-S2C). zIRF9-S2C raises transcription of Mxa, Mxb, Mxc, Ifnφ1, Ifnφ2, and Ifnφ3 in zebrafish liver ((ZFL) cell line) cells and zebrafish larvae. Collectively, we suggest that IRF9-S2C could activate transcription of ISGs with species-specific recognition and could be an innate immunity inducer in teleost larvae.

Interaction of IRF9 and STAT2 synergistically up-regulates IFN and PKR transcription in Ctenopharyngodon idella

IRF9 is a key factor in the JAK-STAT pathway. Under the stimulation of type I IFN, IRF9 interacts with STAT1 and STAT2 to form the IFN-I-stimulated gene factor 3 (ISGF3) which activates the transcription of ISG. However, many studies also showed that the dimmer IRF9/STAT2 rather than the tripolymer IRF9/STAT1/STAT2 acts as the ISGF3 in cells in response to IFN signals. In the present study, the full-length cDNA sequence of IRF9 (termed CiIRF9, KT601055) and STAT2 (term CiSTAT2, KT781914) from grass carp were cloned and identified. A low level of constitutive expression of CiIRF9 was detected by RT-PCR in grass carp tissues, but it was significantly up-regulated by LPS and poly I:C stimulation. In vitro, a high-affinity interaction between CiIRF9 and the promoter of CiIFN or CiPKR was demonstrated by gel mobility shift assay. In vivo, the promoter activities of CiIFN and CiPKR were not only increased by transient transfection of CiIRF9, but also prominently increased by co-transfection of CiIRF9 and CiSTAT2. Moreover, the interaction of CiIRF9 and CiSTAT2 was further investigated by in vivo and in vitro protein interaction assays. Recombinant CiIRF9 and CiSTAT2, both tagged with FLAG (or HA), were expressed in HEK 293T cells by transient transfection experiment. Co-immunoprecipitation assays showed that CiIRF9 can interact with CiSTAT2 in vivo. Soluble GST-ST2-936 (containing the N-terminal and coiled-coil domain of CiSTAT2) was expressed and purified from E. coli. A GST pull-down assay suggested that GST-tagged ST2-936 efficiently bound to FLAG-tagged IRF9. The data indicated that interaction of IRF9 and STAT2 synergistically up-regulated the transcriptional level of IFN and ISG genes.

Epicatechin isolated from Tripterygium wilfordii extract reduces tau-GFP-induced neurotoxicity in zebrafish embryo through the activation of Nrf2

Tau plays important roles in the assembly and stabilization of the microtubule structure to facilitate axonal transport in mammalian brain. The intracellular tau aggregates to form paired helical filaments leading to neurodegenerative disorders, collectively called tauopathies. In our previous report, we established a zebrafish model to express tau-GFP to induce neuronal death, which could be directly traced in vivo. Recently, we used this model to screen 400 herbal extracts and found 45 of them to be effective on reducing tau-GFP-induced neuronal death. One of the effective herbal extracts is the Tripterygium wilfordii stem extract. HPLC analysis and functional assay demonstrated that epicatechin (EC) is the major compound of Tripterygium wilfordii stem extract to decrease the neurotoxicity induced by tau-GFP. Using a luciferase reporter assay in the zebrafish, we confirmed that EC could activate Nrf2-dependent antioxidant responses to significantly increase the ARE-controlled expression of luciferase reporter gene. These data suggest that EC from the Tripterygium wilfordii stem extract could diminish tau-GFP-induced neuronal death through the activation of Nrf2.

Anti-influenza virus effects of crude phenylethanoid glycosides isolated from ligustrum purpurascens via inducing endogenous interferon-γ

ETHNOPHARMACOLOGICAL RELEVANCE

Ligustrum purpurascens Y.C. Yang (Oleaceae) is traditionally recorded as "Ku Ding Cha", a kind of functional tea in southern China for about two thousand years, which has been reported with sore throat alleviating and pathogenic heat expelling effects. However, there are no scientific studies demonstrating its antiviral activity.

THE AIM OF THE STUDY

This study is aimed at investigating the anti-influenza virus effects of phenylethanoid glycosides isolated from L. purpurascens (LPG) as well as its corresponding mechanisms.

MATERIALS AND METHODS

In vitro, hemagglutination assay was employed to detect the influenza virus titer; In vivo, C57BL/6J mice were given oral administration of LPG (100mg/kg, 300mg/kg, 900mg/kg) or ribavirin (100mg/kg) once daily for 5 successive days. Meanwhile, on the second day, mice were infected intranasally (i.n.) with A/FM/1/47 H1N1 virus. Mice survival rate and other clinical index were monitored for 15 days. Infected mice were sacrificed to measure the lung lesion and stained with hematoxylin-eosin. Flow cytometry analyses spleen lymphocytes and interferon-γ (IFN-γ) level. The IFN-γ knockout mice (IFN-γ(-/-) mice, C57BL/6J) which had been verified lacking IFN-γ through Western Blot, were applied in the death-protection test to identify the role of IFN-γ played in LPG antiviral effect.

RESULTS

In vitro, LPG at 0.5mg/ml inhibited Influenza A Virus H1N1 type (H1N1) infection of MDCK cells. In vivo, LPG at 300 and 900mg/kg significantly decreased the mouse lung index (p<0.05), alleviated influenza-induced lethality and clinical symptoms, and therefore enhanced mouse survival (p<0.05). More detailed experiments demonstrated that antiviral cytokine IFN-γ was involved in the antiviral effect of LPG. Flow cytometric analysis revealed that LPG (900mg/kg) significantly induced secretion of IFN-γ by splenic CD4(+) and CD8(+) cells (p<0.05). Moreover, LPG (900mg/kg) protected wild-type C57BL/6J mice from H1N1 injury, whereas LPG-mediated survival protection disappeared in IFN-γ(-/-) mice.

CONCLUSION

These results suggest that up-regulating endogenous IFN-γ by LPG may represent a novel therapeutic approach for H1N1 infection.

Gilthead seabream (Sparus aurata) Mx gene promoters respond differentially to IPNV and VHSV infections in RTG-2 cells

The understanding of virus-host interactions relies on the knowledge of the regulatory mechanisms of the type I interferon (IFN I)-stimulated genes (ISGs). Among ISGs, those coding Mx proteins play a main role due to their direct antiviral activity. The study of these genes in gilthead seabream is interesting, since this species displays high natural resistance to viral diseases, being asymptomatic carrier of infectious pancreatic necrosis virus (IPNV) and viral haemorrhagic septicaemia virus (VHSV). Gilthead seabream has three Mx genes (Mx1, Mx2, and Mx3), encoding proteins with a wide spectrum of antiviral activity. The structure of the three promoters (pMx1, pMx2 and pMx3) has been previously disclosed, and their response to poly I:C in RTG-2 cells characterized. To further analyze these promoters, their response to two viral infections has been evaluated in the present study. For that purpose, RTG-2 cells transiently transfected with the luciferase gene under the control of each promoter were inoculated with either IPNV or VHSV at two different doses. The highest and lowest fold induction values were recorded for pMx2 and pMx3, respectively. The promoter induction was always stronger after VHSV inoculation than in IPNV-inoculated cells. In addition, the higher dose of VHSV tested induced higher response of the three promoters, whereas in IPNV-infected cells the highest induction was recorded after inoculation with the lower viral dose. To further study the response of the Mx2 promoter, RTG-2 cells stably transfected with the luciferase gene under the control of pMx2 were stimulated with poly I:C and subsequently infected with IPNV or VHSV. Interestingly, IPNV infection inhibited the induction caused by poly I:C, suggesting an antagonistic activity of IPNV on Mx2 transcription. In contrast, VHSV infection did not alter the response triggered by poly I:C. These results highlight the specific regulation that controls the activity of each promoter, and support the existence of complex interactions between host cells, specific Mx promoters, and viruses, which are responsible for the final outcome of a viral infection.