Phosphorylation of aryl hydrocarbon receptor interacting protein by TBK1 negatively regulates IRF7 and the type I interferon response.

The innate antiviral response to RNA viruses is initiated by sensing of viral RNAs by RIG-I-like receptors and elicits type I interferon (IFN) production, which stimulates the expression of IFN-stimulated genes that orchestrate the antiviral response to prevent systemic infection. Negative regulation of type I IFN and its master regulator, transcription factor IRF7, is essential to maintain immune homeostasis. We previously demonstrated that AIP (aryl hydrocarbon receptor interacting protein) functions as a negative regulator of the innate antiviral immune response by binding to and sequestering IRF7 in the cytoplasm, thereby preventing IRF7 transcriptional activation and type I IFN production. However, it remains unknown how AIP inhibition of IRF7 is regulated. We show here that the kinase TBK1 phosphorylates AIP and Thr40 serves as the primary target for TBK1 phosphorylation. AIP Thr40 plays critical roles in regulating AIP stability and mediating its interaction with IRF7. The AIP phosphomimetic T40E exhibited increased proteasomal degradation and enhanced interaction with IRF7 compared with wildtype AIP. AIP T40E also blocked IRF7 nuclear translocation, which resulted in reduced type I IFN production and increased viral replication. In sharp contrast, AIP phosphonull mutant T40A had impaired IRF7 binding, and stable expression of AIP T40A in AIP-deficient mouse embryonic fibroblasts elicited a heightened type I IFN response and diminished RNA virus replication. Taken together, these results demonstrate that TBK1-mediated phosphorylation of AIP at Thr40 functions as a molecular switch that enables AIP to interact with and inhibit IRF7, thus preventing overactivation of type I IFN genes by IRF7.

Insight into the role of IRF7 in skin and connective tissue diseases.

Interferons (IFNs) are signalling proteins primarily involved in initiating innate immune responses against pathogens and promoting the maturation of immune cells. Interferon Regulatory Factor 7 (IRF7) plays a pivotal role in the IFNs signalling pathway. The activation process of IRF7 is incited by exogenous or abnormal nucleic acids, which is followed by the identification via pattern recognition receptors (PRRs) and the ensuing signalling cascades. Upon activation, IRF7 modulates the expression of both IFNs and inflammatory gene regulation. As a multifunctional transcription factor, IRF7 is mainly expressed in immune cells, yet its presence is also detected in keratinocytes, fibroblasts, and various dermal cell types. In these cells, IRF7 is critical for skin immunity, inflammation, and fibrosis. IRF7 dysregulation may lead to autoimmune and inflammatory skin conditions, including systemic scleroderma (SSc), systemic lupus erythematosus (SLE), Atopic dermatitis (AD) and Psoriasis. This comprehensive review aims to extensively elucidate the role of IRF7 and its signalling pathways in immune cells and keratinocytes, highlighting its significance in skin-related and connective tissue diseases.

Interferon regulatory factor 7 impairs cellular metabolism in aging adipose-derived stromal cells.

Dysregulated immunity and widespread metabolic dysfunctions are the most relevant hallmarks of the passing of time over the course of adult life, and their combination at midlife is strongly related to increased vulnerability to diseases; however, the causal connection between them remains largely unclear. By combining multi-omics and functional analyses of adipose-derived stromal cells established from young (1 month) and midlife (12 months) mice, we show that an increase in expression of interferon regulatory factor 7 (IRF7) during adult life drives major metabolic changes, which include impaired mitochondrial function, altered amino acid biogenesis and reduced expression of genes involved in branched-chain amino acid (BCAA) degradation. Our results draw a new paradigm of aging as the 'sterile' activation of a cell-autonomous pathway of self-defense and identify a crucial mediator of this pathway, IRF7, as driver of metabolic dysfunction with age.

DHAV 3CD targets IRF7 and RIG-I proteins to block the type I interferon upstream signaling pathway.

Duck hepatitis A virus type 1 (DHAV-1) is an acute, highly lethal infectious agent that infects ducklings and causes up to 95% mortality in ducklings up to 1 week of age, posing a significant economic threat to the duck farming industry. Previous studies have found that the proteolytic enzyme 3 C encoded by DHAV-1 can inhibit the IRF7 protein from blocking the upstream signaling pathway of the type I interferon to promote viral replication. However, there are still few studies on the mechanism of DHAV-1 in immune evasion. Here, we demonstrate that the DHAV-1 3CD protein can interact with IRF7 protein and reduce IRF7 protein expression without directly affecting IRF7 protein nuclear translocation. Further studies showed that the 3CD protein could reduce the expression of RIG-I protein without affecting its transcription level. Furthermore, we found that the 3CD protein interacted with the N-terminal structural domain of RIG-I protein, interfered with the interaction between RIG-I and MAVS, and degraded RIG-I protein through the proteasomal degradation pathway, thereby inhibiting its mediated antiviral innate immunity to promote DHAV-1 replication. These data suggest a novel immune evasion mechanism of DHAV-1 mediated by the 3CD protein, and the results of this experiment are expected to improve the understanding of the biological functions of the viral precursor protein and provide scientific data to elucidate the mechanism of DHAV-1 infection and pathogenesis.

IRF7 suppresses hematopoietic regeneration under stress via CXCR4.

Hematopoietic stem cells (HSCs) maintain quiescence under steady state; however, they are compelled to proliferate and expand to replenish the blood system under stress. The molecular basis underlying stress hematopoiesis remains to be fully understood. In this study, we reported that IRF7 represents an important regulator of stress hematopoiesis. Interferon regulatory factor 7 (IRF7) was dispensable for normal hematopoiesis, whereas its deficiency significantly enhanced hematopoietic stem and progenitor cells (HSPCs) regeneration and improved long-term repopulation of HSCs under stress. Mechanistic studies showed that CXCR4 was identified as a downstream target of IRF7. Overexpression of CXCR4 abrogated the enhanced proliferation and regeneration of IRF7-deficient HSPCs under stress. Similar results were obtained in HSCs from human umbilical cord blood. These observations demonstrated that IRF7 plays an important role in hematopoietic regeneration under stress.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is associated with IRF7, BANK1 and TBX21 polymorphisms in two populations.

BACKGROUND AND PURPOSE: Autoantibodies targeting the GluN1(NR1) subunit of the anti-N-methyl-D-aspartate receptor (NMDAR) cause encephalitis. Although it has been shown that anti-NMDAR encephalitis is associated with human leukocyte antigen (HLA) loci, susceptibility genes for the disease outside the HLA loci remain unidentified. In this study, we aimed to explore the association of anti-NMDAR encephalitis with non-HLA genes. METHODS: Two Chinese anti-NMDAR encephalitis cohorts from Han populations were recruited for this study. The North Chinese case-control set consisted of 98 patients and 460 controls, while the South Chinese case-control set included 78 patients and 541 controls. All participants were genotyped for 28 single nucleotide polymorphisms that are associated with autoimmune disorders or infectious diseases. RESULTS: In two independent case-control sets, we identified significant associations of anti-NMDAR encephalitis with IRF7 rs1131665 (odds ratio [OR] 3.34, 95% confidence interval [CI] 1.99-5.63; P < 0.000001, Padjusted  = 0.00004), BANK1 rs4522865 (OR 1.44, 95% CI 1.15-1.82; P = 0.0017, Padjusted  = 0.0149), and TBX21 rs17244587 (OR 2.03, 95% CI 1.35-3.05; P = 0.00051, Padjusted  = 0.0066). Furthermore, analysis of the three polymorphisms with clinical features of the disease revealed that the IRF7 rs1131665 was associated with tumor status. CONCLUSION: The present study has for the first time identified non-HLA susceptibility genes for anti-NMDAR encephalitis. The association of IRF7, BANK1 and TBX21 with anti-NMDAR encephalitis suggests that B-cell activation, Th1 responses, virus infection and the type I interferon signaling pathway are involved in the pathogenesis of the disease.

Attenuation of interferon regulatory factor 7 activity in local infectious sites of trachea and lung for preventing the development of acute lung injury caused by influenza A virus.

The excessive activation of interferon regulatory factor 7 (IRF7) promotes the development of acute lung injury (ALI) caused by influenza A virus (IAV). However, the deficiency of IRF7 increases the susceptibility to deadly IAV infection in both humans and mice. To test whether the attenuation rather than the abolishment of IRF7 activity in local infectious sites could alleviate IAV-induced ALI, we established IAV-infected mouse model and trachea/lung-tissue culture systems, and designed two IRF7-interfering oligodeoxynucleotides, IRF7-rODN M1 and IRF7-rODN A1, based on the mouse and human consensus sequences of IRF7-binding sites of Ifna/IFNA genes, respectively. In the model mice, we found a close relationship between the IAV-induced ALI and the level/activity of IRF7 in local infectious sites, and also found that the reduced IRF7 level or activity in the lungs of mice treated with IRF7-rODN M1 led to decreased mRNA levels of Ifna genes, reduced neutrophil infiltration in the lungs and prolonged survival of mice. Furthermore, we found that the effects of IRF7-rODN M1 on alleviating IAV-induced ALI could be correlated to the reduced translocation of IRF7, caused by the IRF7-rODN M1, from cytosol to nucleus in IAV-infected cells. These data suggest that the proper attenuation of IRF7 activity in local infectious sites could be a novel approach for treating IAV-induced ALI.

Associations of gene polymorphisms in interferon-alpha signature-related genes with autoimmune thyroid diseases.

Interferon (IFN)-α treatment predisposes patients to the occurrence of autoimmune thyroid disease (AITD). METHODS: We investigated associations of single nucleotide polymorphisms (SNPs) of molecules participating in the IFN-α signature, including rs2304204 and rs2304206 of IFN regulatory factor 3 (IRF3), rs1061501 of IRF7, and rs7708392 of TNFA1P3-interacting protein 1 with serum IFN-α levels and AITD in an ethnic Chinese (ie Taiwanese) population. Totally, 319 patients with Graves' disease (GD), 83 patients with Hashimoto's thyroiditis (HT) and 351 healthy controls were recruited. RESULTS: There were increased percentages of the C allele, and CC and TC + CC genotypes of rs1061501 in GD patients compared to the controls. HT patients had higher serum IFN-α levels compared to the controls, while there was no difference in serum IFN-α levels between patients with GD and controls. However, patients with GD in a remission status had lower serum IFN-α levels than those without remission. On the other hand, the C allele of rs1061501 was only associated with serum IFN-α levels in patients with HT. CONCLUSIONS: The SNP rs1061501 of IRF7 was associated with the development of GD. Serum IFN-α levels were associated with HT, while they might modify the disease status of GD. Moreover, a genetic effect of rs1061501 on regulating serum IFN-α production was observed in HT.

Molecular cloning and functional characterization of interferon regulatory factor 7 of the barbel chub, Squaliobarbus curriculus.

The interferon regulatory factor 7 (IRF7) is a critical regulator of type-I interferon-dependent immune reaction that defense against virus. To investigate the antiviral function of IRF7 of barbel chub Squaliobarbus curriculus (ScIRF7), the cDNA of ScIRF7 was cloned and characterized. The full length cDNA of ScIRF7 was 1870 bp, consisted of 41 bp 5'-UTR, 560 bp 3'-UTR and a 1269 bp open reading frame (ORF). The ORF encoded 423 amino acids with a molecular weight of 49.426 KDa and a theoretical isoelectric point of 5.71. The putative ScIRF7 protein possesses typical domains of IRF family including a conserved N-terminal DBD-binding domain (DBD), a C-terminal IRF association domain and a serine-rich domain. In the DBD, four tryptophans were found to be highly conserved among all species, whilst in another conserved tryptophan site of mammals, the corresponding amino acids were methionine for fishes. The expression level of ScIRF7 was highest in the spleen and lowest in the liver. The expression level of IFN-ß was highest in the gill and lowest in the liver. After GCRV infection, expression levels changes of ScIRF7 showed an overall tendency of firstly up-regulation and then down-regulation in the spleen and the gill; and expression levels of ScIRF7 in peripheral blood lymphocyte at 24 h post-infection was highest among all time points. In pEGFP-ScIRF7 overexpressing cells, the mRNA level of ScIRF7 was firstly up-regulation and then down-regulation; and the expression of IFN-ß was significantly up-regulated at 12 h post-infection than that of control group (P < 0.05), which was significantly higher than those in pEGFP-N1 overexpressing cells. The results indicated that ScIRF7 may play a key role in immune responses of barbel chub Squaliobarbus curriculus against GCRV and may also functions in the Ctenopharyngodon idellus kidney cells.

Cloning and expression analysis of interferon regulatory factor 7 in the Pacific cod, Gadus macrocephalus.

Interferon regulatory factor 7 (IRF7) plays an important role in regulating the response of type I interferon (IFN) to viral infection. To understand the mechanisms underlying immune reactions in the Pacific cod, Gadus macrocephalus, the gene encoding G. macrocephalus IRF7 was cloned and characterized. The cDNA of G. macrocephalus IRF7 was also cloned and sequenced. A cDNA sequence of 2032 bp was assembled using polymerase chain reaction (PCR) products. It contains an open reading frame of 1323 bp in length, which encoded a 440-amino acid polypeptide that comprised a DNA-binding domain (DBD), an IRF association domain (IAD), and a serine-rich domain (SRD). In the DBD, the tryptophan cluster consisted of only four tryptophans, which is a unique characteristic in fish IRF7. The mRNA of IRF7 was detected in various tissues, including in the spleen, thymus, kidney, intestine, and gills, using relative quantification PCR (R-qPCR). Dynamic expression of IRF7 was observed in larvae throughout post-hatching (ph) development, with the highest level detected at day of ph (dph) 25. Response to immune stimulation was examined by challenging larvae with polyriboinosinic polyribocytidylic acid (pIC) to mimic viral infection and elicit an immune reaction. R-qPCR revealed that the expression of IRF7 significantly increased in pIC-treated groups relative to that in the control groups, in a time-dependent manner, with peak responses at 48 and 72 h after pIC-treatment. These results show that IRF7 is expressed in various tissues of adult fish and larvae and is sensitive to viral infection, suggesting that it plays a role in antiviral immune defense in G. macrocephalus.

Identification of novel gene signatures in patients with atopic dermatitis complicated by eczema herpeticum.

BACKGROUND: A subset of patients with atopic dermatitis (AD) is prone to disseminated herpes simplex virus (HSV) infection (ie, atopic dermatitis with a history of eczema herpeticum [ADEH+]). Biomarkers that identify ADEH+ are lacking. OBJECTIVE: We sought to search for novel ADEH+ gene signatures in PBMCs. METHODS: An RNA-sequencing approach was applied to evaluate global transcriptional changes by using PBMCs from patients with ADEH+ and patients with atopic dermatitis without a history of eczema herpeticum (ADEH-). Candidate genes were confirmed by means of quantitative PCR or ELISA. RESULTS: PBMCs from patients with ADEH+ had distinct changes to the transcriptome when compared with those from patients with ADEH- after HSV-1 stimulation: 792 genes were differentially expressed at a false discovery rate of less than 0.05 (ANOVA), and 15 type I and type III interferon genes were among the top 20 most downregulated genes in patients with ADEH+. We further validated that IFN-α and IL-29 mRNA and protein levels were significantly decreased in HSV-1-stimulated PBMCs from patients with ADEH+ compared with those from patients with ADEH- and healthy subjects. Ingenuity Pathway Analysis demonstrated that the upstream regulators of type I and type III interferons, interferon regulatory factor (IRF) 3 and IRF7, were significantly inhibited in patients with ADEH+ based on the downregulation of their target genes. Furthermore, we found that gene expression of IRF3 and IRF7 was significantly decreased in HSV-1-stimulated PBMCs from patients with ADEH+. CONCLUSIONS: PBMCs from patients with ADEH+ have a distinct immune response after HSV-1 exposure compared with those from patients with ADEH-. Inhibition of the IRF3 and IRF7 innate immune pathways in patients with ADEH+ might be an important mechanism for increased susceptibility to disseminated viral infection.

ALDH2 regulates mesenchymal stem cell senescence via modulation of mitochondrial homeostasis.

Although mitochondrial aldehyde dehydrogenase 2 (ALDH2) is involved in aging and aging-related diseases, its role in the regulation of human mesenchymal stem cell (MSC) senescence has not been investigated. This study aimed to determine the role of ALDH2 in regulating MSC senescence and illustrate the potential mechanisms. MSCs were isolated from young (YMSCs) and aged donors (AMSCs). Senescence-associated ß-galactosidase (SA-ß-gal) staining and Western blotting were used to assess MSC senescence. Reactive oxygen species (ROS) generation and mitochondrial membrane potential were determined to evaluate mitochondrial function. We showed that the expression of ALDH2 increased alongside cellular senescence of MSCs. Overexpression of ALDH2 accelerated YMSC senescence whereas down-regulation alleviated premature senescent phenotypes of AMSCs. Transcriptome and biochemical analyses revealed that an elevated ROS level and mitochondrial dysfunction contributed to ALDH2 function in MSC senescence. Using molecular docking, we identified interferon regulatory factor 7 (IRF7) as the potential target of ALDH2. Mechanistically, ectopic expression of ALDH2 led to mitochondrial dysfunction and accelerated senescence of MSCs by increasing the stability of IRF7 through a direct physical interaction. These effects were partially reversed by knockdown of IRF7. These findings highlight a crucial role of ALDH2 in driving MSC senescence by regulating mitochondrial homeostasis, providing a novel potential strategy against human aging-related diseases.

3,3'-Diindolylmethane inhibits Th17 cell differentiation via impairing IRF-7-mediated plasmacytoid dendritic cell activation in imiquimod-induced psoriasis mice.

Psoriasis is a paradigmatic condition characterised by a heightened autoimmune response and chronic inflammation. However, the exact nature and the pathological causes behind it are still unknown. Growing evidence suggest dysregulated cytokine network as a result of over-activated T cells and plasmacytoid dendritic cells (pDCs) as the critical drivers in the development of psoriasis. In the present study, we aimed to investigate the therapeutic efficacy of 3,3'-diindolylmethane (DIM) on pDC activation and Th17 cell development in imiquimod (IMQ)-induced psoriasis mice. Our in vitro research investigated the IRF-7 signalling in pDCs that explained the reduced expression of the transcription factor IRF-7 responsible for pDC activation as a result of DIM treatment. Concurrently, DIM treatment decreased the release of Th17 cell polarising cytokines (IFN-α, IL-23, and IL-6) by pDCs which validated a reduction in differentiated pathogenic Th17 cell population and associated cytokine IL-17A in IMQ-induced psoriatic mice. Thus, our recent findings provide therapeutic evidence in targeting the early potential contributors for psoriasis treatment by preventing IRF-7-mediated pDC activation and Th17 cell development in IMQ-induced psoriasis mice.

Multi-omics reveals the switch role of abnormal methylation in the regulation of decidual macrophages function in recurrent spontaneous abortion.

RSA, recurrent spontaneous abortion, often causes serious physical damage and psychological pressure in reproductive women with unclarified pathogenesis. Abnormal function of decidual cells and aberrant DNA methylation have been reported to cause RSA, but their association remains unclear. Here, we integrated transcriptome, DNA methylome, and scRNA-seq to clarify the regulatory relationship between DNA methylation and decidual cells in RSA. We found that DNA methylation mainly influenced the function of decidual macrophages (DMs), of which four hub genes, HLA-A, HLA-F, SQSTM1/P62, and Interferon regulatory factor 7 (IRF7), related to 22 hypomethylated CpG sites, regulated 16 hub pathways to participate in RSA pathogenesis. In particular, using transcription factor analysis, it is suggested that the upregulation of IRF7 transcription was associated with enhanced recruitment of the transcription factor STAT1 by the hypomethylated promoter region of IRF7. As the current research on DNA methylation of macrophages in the uterine microenvironment of RSA is still blank, our systematic picture of abnormal DNA methylation in regulating DM function provides new insights into the role of DNA methylation in RSA occurrence, which may aid in further prevention and treatment of RSA.

The neuroprotective effect of near infrared light therapy in aged mice with postoperative neurocognitive disorder by upregulating IRF7.

BACKGROUND: Postoperative neurocognitive disorder (PND) is a common central nervous system complication after undergoing surgery and anesthesia especially in elderly patients, while the therapeutic options are very limited. This study was carried out to investigate the beneficial effects of transcranial near infrared light (NIRL) which was employed to the treatment of PND and propose the involved mechanisms. METHODS: The PND mice were established through left carotid artery exposure under isoflurane anesthesia and received transcranial NIRL treatment. Behavioral testing was performed to evaluate the cognitive function of PND mice after transcranial NIRL therapy. Changes in the transcriptomic profiles of prefrontal cortex (PFC) and hippocampus (HP) were identified by next generation sequencing (NGS), and the molecular mechanisms involved were examined by both in vivo mouse model and in vitro cell culture studies. RESULTS: We found that transcranial NIRL therapy effectively ameliorated learning and memory deficit induced by anesthesia and surgery in aged mice. Specifically, we identified down-regulation of interferon regulatory factor 7 (IRF7) in the brains of PND mice that was mechanistically associated with increased pro-inflammatory M1 phenotype of microglia and elevated neuroinflammatory. NIRL treatment produced protective effects through the upregulation of IRF7 expression and reversing microglial phenotypes from pro-inflammatory to neuroprotective, resulting in reduced brain damage and improved cognitive function in PND mice. CONCLUSION: Our results indicate that transcranial NIRL is an effective and safe therapy for PND via alleviating neuroinflammation, and IRF7 plays a key transcription factor in regulating the M1-to-M2 switch of microglia.

Effect of cigarette smoke on mucosal vaccine response with activation of plasmacytoid dendritic cells: The outcomes of in vivo and in vitro experiments.

Mucosal vaccines offer several advantages over transdermal vaccines, including the ability to acquire systemic and mucosal immunities. Smoking is a huge public health threat and major risk factor for various diseases that exacerbate or prolong respiratory symptoms and conditions. However, its impact on the efficacy of mucosal vaccines remains partially explored. Thus, this study investigates the effects of smoking on mucosal vaccine reactivity by assessing the induction of Th1 immunity, a vital response in infection defense. Cigarette smoke condensate was prepared as a substitute for mainstream smoke. We intranasally administered diphtheria toxoid as an antigen and natural CpG oligonucleotide G9.1, which enhances the Th1-type antibody (Ab) response in a plasmacytoid dendritic cells (pDCs) dependent manner, as an adjuvant to mice to assess the effect of cigarette smoke condensate on Ab responses. The mechanism of its effect was evaluated using human peripheral blood mononuclear cells and their pDC-rich fraction cultured with or without G9.1. In mice, cigarette smoke condensate tended to decrease diphtheria toxoid-specific Ab response, with a higher reduction in Th1-type IgG2 Ab response than in Th2-type IgG1 Ab response. In human peripheral blood mononuclear cells, cigarette smoke condensate significantly reduced the induction of IFN-α production by G9.1. Moreover, G9.1-induced increases in the CD83 expression in pDCs and the CD80 expression in DCs were suppressed via treatment with cigarette smoke condensate. Among the mechanisms suggested were decreased expression of toll-like receptor 9 mRNA, decreased expression of mRNA for IFN regulatory factor 7, and increased CpG methylation of its promoter region. The analysis of Tbet and GATA3 expressions revealed that cigarette smoke condensate exhibits Th1-directed immunostimulatory activity at a steady state but becomes more Th2-directed under G9.1 stimulation. In conclusion, smoking could reduce mucosal vaccine responses by decreasing pDC activation and, consequently, Th1-dominant immunity.

Chicken anemia virus VP1 negatively regulates type I interferon via targeting interferon regulatory factor 7 of the DNA-sensing pathway.

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway plays a vital role in sensing viral DNA in the cytosol, stimulating type I interferon (IFN) production and triggering the innate immune response against DNA virus infection. However, viruses have evolved effective inhibitors to impede this sensing pathway. Chicken anemia virus (CAV), a nonenveloped ssDNA virus, is a ubiquitous pathogen causing great economic losses to the poultry industry globally. CAV infection is reported to downregulate type I IFN induction. However, whether the cGAS-STING signal axis is used by CAV to regulate type I IFN remains unclear. Our results demonstrate that CAV infection significantly elevates the expression of cGAS and STING at the mRNA level, whereas IFN-ß levels are reduced. Furthermore, IFN-ß activation was completely blocked by the structural protein VP1 of CAV in interferon stimulatory DNA (ISD) or STING-stimulated cells. VP1 was further confirmed as an inhibitor by interacting with interferon regulatory factor 7 (IRF7) by binding its C-terminal 143-492 aa region. IRF7 dimerization induced by TANK binding kinase 1 (TBK1) could be inhibited by VP1 in a dose-dependent manner. Together, our study demonstrates that CAV VP1 is an effective inhibitor that interacts with IRF7 and antagonizes cGAS-STING pathway-mediated IFN-ß activation. These findings reveal a new mechanism of immune evasion by CAV.

Delayed CO2 postconditioning promotes neurological recovery after cryogenic traumatic brain injury by downregulating IRF7 expression.

AIMS: Few treatments are available in the subacute phase of traumatic brain injury (TBI) except rehabilitation training. We previously reported that transient CO2 inhalation applied within minutes after reperfusion has neuroprotective effects against cerebral ischemia/reperfusion injury. In this study, it was hypothesized that delayed CO2 postconditioning (DCPC) starting at the subacute phase may promote neurological recovery of TBI. METHODS: Using a cryogenic TBI (cTBI) model, mice received DCPC daily by inhaling 5%/10%/20% CO2 for various time-courses (one/two/three cycles of 10-min inhalation/10-min break) at Days 3-7, 3-14 or 7-18 after cTBI. Beam walking and gait tests were used to assess the effect of DCPC. Lesion size, expression of GAP-43 and synaptophysin, amoeboid microglia number and glia scar area were detected. Transcriptome and recombinant interferon regulatory factor 7 (Irf7) adeno-associated virus were applied to investigate the molecular mechanisms. RESULTS: DCPC significantly promoted recovery of motor function in a concentration and time-course dependent manner with a wide therapeutic time window of at least 7 days after cTBI. The beneficial effects of DCPC were blocked by intracerebroventricular injection of NaHCO3 . DCPC also increased puncta density of GAP-43 and synaptophysin, and reduced amoeboid microglia number and glial scar formation in the cortex surrounding the lesion. Transcriptome analysis showed many inflammation-related genes and pathways were altered by DCPC, and Irf7 was a hub gene, while overexpression of IRF7 blocked the motor function improvement of DCPC. CONCLUSIONS: We first showed that DCPC promoted functional recovery and brain tissue repair, which opens a new therapeutic time window of postconditioning for TBI. Inhibition of IRF7 is a key molecular mechanism for the beneficial effects of DCPC, and IRF7 may be a potential therapeutic target for rehabilitation after TBI.

Enterovirus D68 VP3 Targets the Interferon Regulatory Factor 7 To Inhibit Type I Interferon Response.

Enterovirus D68 (EV-D68) is a globally emerging pathogen causing severe respiratory illnesses mainly in children. The protease from EV-D68 could impair type I interferon (IFN-I) production. However, the role of the EV-D68 structural protein in antagonizing host antiviral responses remains largely unknown. We showed that the EV-D68 structural protein VP3 interacted with IFN regulatory factor 7 (IRF7), and this interaction suppressed the phosphorylation and nuclear translocation of IRF7 and then repressed the transcription of IFN. Furthermore, VP3 inhibited the TNF receptor associated factor 6 (TRAF6)-induced ubiquitination of IRF7 by competitive interaction with IRF7. IRF7Δ305-503 showed much weaker interaction ability to VP3, and VP3Δ41-50 performed weaker interaction ability with IRF7. The VP3 from enterovirus A71 (EV-A71) and coxsackievirus A16 (CV-A16) was also found to interact with the IRF7 protein. These results indicate that the enterovirus structural protein VP3 plays a pivotal role in subverting host innate immune responses and may be a potential target for antiviral drug research. IMPORTANCE EV-D68 is a globally emerging pathogen that causes severe respiratory illnesses. Here, we report that EV-D68 inhibits innate immune responses by targeting IRF7. Further investigations revealed that the structural protein VP3 inhibited the TRAF6-induced ubiquitination of IRF7 by competitive interaction with IRF7. These results indicate that the control of IRF7 by VP3 may be a mechanism by which EV-D68 represses IFN-I production.

Sustained induction of IP-10 by MRP8/14 via the IFNß-IRF7 axis in macrophages exaggerates lung injury in endotoxemic mice.

Background: As a damage-associated molecular pattern, the myeloid-related protein 8/14 (MRP8/14) heterodimer mediates various inflammatory diseases, such as sepsis. However, how MRP8/14 promotes lung injury by regulating the inflammatory response during endotoxemia remains largely unknown. This study aims at illuminating the pathological functions of MRP8/14 in endotoxemia. Methods: An endotoxemic model was prepared with wild-type and myeloid cell-specific Mrp8 deletion (Mrp8ΔMC) mice for evaluating plasma cytokine levels. Lung injury was evaluated by hematoxylin and eosin (H&E) staining, injury scoring and wet-to-dry weight (W/D) ratio. The dynamic profile of interferon γ (IFNγ)-inducible protein 10 (IP-10) mRNA expression induced by macrophage MRP8/14 was determined by quantitative real-time polymerase chain reaction (qPCR). Immunoblotting was used to evaluate the increase in IP-10 level induced by activation of the JAK-STAT signaling pathway. Luciferase reporter assay was performed to detect the involvement of IRF7 in Ip-10 gene transcription. In vivo air pouch experiments were performed to determine the biological function of IP-10 induced by MRP8/14. Results: Experiments with Mrp8ΔMC mice showed that MRP8/14 promoted the production of cytokines, including IP-10, in the bronchoalveolar lavage fluid (BALF) and lung injury in endotoxic mice. The result of qPCR showed sustained expression of Ip-10 mRNA in macrophages after treatment with MRP8/14 for 12 h. Neutralization experiments showed that the MRP8/14-induced Ip-10 expression in RAW264.7 cells was mediated by extracellular IFNß. Western blotting with phosphorylation-specific antibodies showed that the JAK1/TYK2-STAT1 signaling pathway was activated in MRP8/14-treated RAW264.7 cells, leading to the upregulation of Ip-10 gene expression. IRF7 was further identified as a downstream regulator of the JAK-STAT pathway that mediated Ip-10 gene expression in macrophages treated with MRP8/14. In vivo air pouch experiments confirmed that the IFNß-JAK1/TYK2-STAT1-IRF7 pathway was required for chemokine (C-X-C motif) receptor 3 (CXCR3)+ T lymphocyte migration, which promoted lung injury in the context of endotoxemia. Conclusions: In summary, our study demonstrates that MRP8/14 induces sustained production of IP-10 via the IFNß-JAK1/TYK2-STAT1-IRF7 pathway to attract CXCR3+ T lymphocytes into lung tissues and ultimately results in lung injury by an excessive inflammatory response in the context of endotoxemia.