Deficiency of Tlr7 and Irf7 in mice increases the severity of COVID-19 through the reduced interferon production.

Toll-like receptor 7 (Tlr7) deficiency-accelerated severe COVID-19 is associated with reduced production of interferons (IFNs). However, the underlying mechanisms remain elusive. To address these questions, we utilize Tlr7 and Irf7 deficiency mice, single-cell RNA analysis together with bone marrow transplantation approaches. We demonstrate that at the early phase of infection, SARS-CoV-2 causes the upregulation of Tlr7, Irf7, and IFN pathways in the lungs of the infected mice. The deficiency of Tlr7 and Irf7 globally and/or in immune cells in mice increases the severity of COVID-19 via impaired IFN activation in both immune and/or non-immune cells, leading to increased lung viral loads. These effects are associated with reduced IFN alpha and gamma levels in the circulation. The deficiency of Tlr7 tends to cause the reduced production and nuclear translocation of interferon regulatory factor 7 (IRF7) in the lungs of the infected mice, indicative of reduced IRF7 activation. Despite higher amounts of lung viral antigen, Tlr7 or Irf7 deficiency resulted in substantially reduced production of antibodies against SARS-CoV-2, thereby delaying the viral clearance. These results highlight the importance of the activation of TLR7 and IRF7 leading to IFN production on the development of innate and adaptive immunity against COVID-19.

Loss of Cldn5 -and increase in Irf7-in the hippocampus and cerebral cortex of diabetic mice at the early symptomatic stage.

Analyzing changes in gene expression within specific brain regions of individuals with Type 2 Diabetes (T2DM) who do not exhibit significant cognitive deficits can yield valuable insights into the mechanisms underlying the progression towards a more severe phenotype. In this study, transcriptomic analysis of the cortex and hippocampus of mice with long-term T2DM revealed alterations in the expression of 28 genes in the cerebral cortex and 15 genes in the hippocampus. Among these genes, six displayed consistent changes in both the cortex and hippocampus: Interferon regulatory factor 7 (Irf7), Hypoxia-inducible factor 3 alpha (Hif-3α), period circadian clock 2 (Per2), xanthine dehydrogenase (Xdh), and Transforming growth factor ß-stimulated clone 22/TSC22 (Tsc22d3) were upregulated, while Claudin-5 (Cldn5) was downregulated. Confirmation of these changes was achieved through RT-qPCR. At the protein level, CLDN5 and IRF7 exhibited similar alterations, with CLDN5 being downregulated and IRF7 being upregulated. In addition, the hippocampus and cortex of the T2DM mice showed decreased levels of IκBα, implying the involvement of NF-κB pathways as well. Taken together, these results suggest that the weakening of the blood-brain barrier and an abnormal inflammatory response via the Interferon 1 and NF-κB pathways underlie cognitive impairment in individuals with long-standing T2DM.

Single-cell sequencing combined with spatial transcriptomics reveals that the IRF7 gene in M1 macrophages inhibits the occurrence of pancreatic cancer by regulating lipid metabolism-related mechanisms.

AIM: The main focus of this study is to explore the molecular mechanism of IRF7 regulation on RPS18 transcription in M1-type macrophages in pancreatic adenocarcinoma (PAAD) tissue, as well as the transfer of RPS18 by IRF7 via exosomes to PAAD cells and the regulation of ILF3 expression. METHODS: By utilising single-cell RNA sequencing (scRNA-seq) data and spatial transcriptomics (ST) data from the Gene Expression Omnibus database, we identified distinct cell types with significant expression differences in PAAD tissue. Among these cell types, we identified those closely associated with lipid metabolism. The differentially expressed genes within these cell types were analysed, and target genes relevant to prognosis were identified. Flow cytometry was employed to assess the expression levels of target genes in M1 and M2 macrophages. Cell lines with target gene knockout were constructed using CRISPR/Cas9 editing technology, and cell lines with target gene knockdown and overexpression were established using lentiviral vectors. Additionally, a co-culture model of exosomes derived from M1 macrophages with PAAD cells was developed. The impact of M1 macrophage-derived exosomes on the lipid metabolism of PAAD cells in the model was evaluated through metabolomics analysis. The effects of M1 macrophage-derived exosomes on the viability, proliferation, division, migration and apoptosis of PAAD cells were assessed using MTT assay, flow cytometry, EdU assay, wound healing assay, Transwell assay and TUNEL staining. Furthermore, a mouse PAAD orthotopic implantation model was established, and bioluminescence imaging was utilised to assess the influence of M1 macrophage-derived exosomes on the intratumoural formation capacity of PAAD cells, as well as measuring tumour weight and volume. The expression of proliferation-associated proteins in tumour tissues was examined using immunohistochemistry. RESULTS: Through combined analysis of scRNA-seq and ST technologies, we discovered a close association between M1 macrophages in PAAD samples and lipid metabolism signals, as well as a negative correlation between M1 macrophages and cancer cells. The construction of a prognostic risk score model identified RPS18 and IRF7 as two prognostically relevant genes in M1 macrophages, exhibiting negative and positive correlations, respectively. Mechanistically, it was found that IRF7 in M1 macrophages can inhibit the transcription of RPS18, reducing the transfer of RPS18 to PAAD cells via exosomes, consequently affecting the expression of ILF3 in PAAD cells. IRF7/RPS18 in M1 macrophages can also suppress lipid metabolism, cell viability, proliferation, migration, invasion and intratumoural formation capacity of PAAD cells, while promoting cell apoptosis. CONCLUSION: Overexpression of IRF7 in M1 macrophages may inhibit RPS18 transcription, reduce the transfer of RPS18 from M1 macrophage-derived exosomes to PAAD cells, thereby suppressing ILF3 expression in PAAD cells, inhibiting the lipid metabolism pathway, and curtailing the viability, proliferation, migration, invasion of PAAD cells, as well as enhancing cell apoptosis, ultimately inhibiting tumour formation in PAAD cells in vivo. Targeting IRF7/RPS18 in M1 macrophages could represent a promising immunotherapeutic approach for PAAD in the future.

SREBP2 restricts osteoclast differentiation and activity by regulating IRF7 and limits inflammatory bone erosion.

Osteoclasts are multinucleated bone-resorbing cells, and their formation is tightly regulated to prevent excessive bone loss. However, the mechanisms by which osteoclast formation is restricted remain incompletely determined. Here, we found that sterol regulatory element binding protein 2 (SREBP2) functions as a negative regulator of osteoclast formation and inflammatory bone loss. Cholesterols and SREBP2, a key transcription factor for cholesterol biosynthesis, increased in the late phase of osteoclastogenesis. The ablation of SREBP2 in myeloid cells resulted in increased in vivo and in vitro osteoclastogenesis, leading to low bone mass. Moreover, deletion of SREBP2 accelerated inflammatory bone destruction in murine inflammatory osteolysis and arthritis models. SREBP2-mediated regulation of osteoclastogenesis is independent of its canonical function in cholesterol biosynthesis but is mediated, in part, by its downstream target, interferon regulatory factor 7 (IRF7). Taken together, our study highlights a previously undescribed role of the SREBP2-IRF7 regulatory circuit as a negative feedback loop in osteoclast differentiation and represents a novel mechanism to restrain pathological bone destruction.

Selective autophagy receptor p62/SQSTM1 inhibits TBK1-IRF7 innate immune pathway in triploid hybrid fish.

The production of type I interferon is tightly regulated to prevent excessive immune activation. However, the role of selective autophagy receptor SQSTM1 in this regulation in teleost remains unknown. In this study, we cloned the triploid fish SQSTM1 (3nSQSTM1), which comprises 1371 nucleotides, encoding 457 amino acids. qRT-PCR data revealed that the transcript levels of SQSTM1 in triploid fish were increased both in vivo and in vitro following spring viraemia of carp virus (SVCV) infection. Immunofluorescence analysis confirmed that 3nSQSTM1 was mainly distributed in the cytoplasm. Luciferase reporter assay results showed that 3nSQSTM1 significantly blocked the activation of interferon promoters induced by 3nMDA5, 3nMAVS, 3nTBK1, and 3nIRF7. Co-immunoprecipitation assays further confirmed that 3nSQSTM1 could interact with both 3nTBK1 and 3nIRF7. Moreover, upon co-transfection, 3nSQSTM1 significantly inhibited the antiviral activity mediated by TBK1 and IRF7. Mechanistically, 3nSQSTM1 decreased the TBK1 phosphorylation and its interaction with 3nIRF7, thereby suppressing the subsequent antiviral response. Notably, we discovered that 3nSQSTM1 also interacted with SVCV N and P proteins, and these viral proteins may exploit 3nSQSTM1 to further limit the host's antiviral innate immune responses. In conclusion, our study demonstrates that 3nSQSTM1 plays a pivotal role in negatively regulating the interferon signaling pathway by targeting 3nTBK1 and 3nIRF7.

Kaempferol Alleviates Injury in Human Retinal Pigment Epithelial Cells via STAT1 Ubiquitination-Mediated Degradation of IRF7.

BACKGROUND: Retinal pigment epithelial (RPE) cells have a pivotal function in preserving the equilibrium of the retina and moderating the immunological interaction between the choroid and the retina. This study primarily focuses on delineating the protective effect offered by Kaempferol (Kae) against RPE cell damage. METHODS: Bioinformatics analysis was performed on the GSE30719 dataset to identify hub genes associated with RPE. Subsequently, we analyzed the impact of Kae on RPE apoptosis, cell viability, and inflammatory response through cell experiments, and explored the interaction between hub genes and Kae. RESULTS: Based on the GSE30719 dataset, nine hub genes (ISG15, IFIT1, IFIT3, STAT1, OASL, RSAD2, IRF7, MX2, and MX1) were identified, all of which were highly expressed in the GSE30719 case group. Kae could boost the proliferative activity of RPE cells caused by lipopolysaccharide (LPS), as well as reduce apoptosis and the generation of inflammatory factors (tumor necrosis factor receptor (TNFR), interleukin-1beta (IL-1ß)) and cytokines (IL-1, IL-6, IL-12). STAT1 was shown to inhibit cell proliferation, promote apoptosis, and secrete IL-1/IL-6/IL-12 in LPS-induced RPE cells. Moreover, IRF7 was found to interact with STAT1 in LPS-induced RPE cells, and STAT1 could maintain IRF7 levels through deubiquitination. In addition, we also found that the protective effect of Kae on LPS-induced RPE cell injury was mediated through STAT1/IRF7 axis. CONCLUSION: This study provided evidence that Kae protects RPE cells via regulating the STAT1/IRF7 signaling pathways, indicating its potential therapeutic relevance in the diagnosis and management of retinal disorders linked with RPE cell damage.

Novel goose parvovirus VP1 targets IRF7 protein to block the type I interferon upstream signaling pathway.

Outbreaks of short beak and dwarfism syndrome (SBDS), caused by a novel goose parvovirus (NGPV), have occurred in China since 2015. The NGPV, a single-stranded DNA virus, is thought to be vertically transmitted. However, the mechanism of NGPV immune evasion remains unclear. In this study, we investigated the impact of NGPV infection on the Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway in duck embryonic fibroblast (DEF) cells. Our findings demonstrate that NGPV infection stimulates the mRNA expression of cGAS but results in weak IFN-ß induction. NGPV impedes the expression of IFN-ß and downstream interferon-stimulated genes, thereby reducing the secretion of IFN-ß induced by interferon-stimulating DNA (ISD) and poly (I: C). RNA-seq results show that NGPV infection downregulates interferon mRNA expression while enhancing the mRNA expression of inflammatory factors. Additionally, the results of viral protein over-expression indicate that VP1 exhibits a remarkable ability to inhibit IFN-ß expression compared to other viral proteins. Results indicated that only the intact VP1 protein could inhibit the expression of IFN-ß, while the truncated proteins VP1U and VP2 do not possess such characteristics. The immunoprecipitation experiment showed that both VP1 and VP2 could interact with IRF7 protein, while VP1U does not. In summary, our findings indicate that NGPV infection impairs the host's innate immune response by potentially modulating the expression and secretion of interferons and interferon-stimulating factors via IRF7 molecules, which are regulated by the VP1 protein.

TLR10 (CD290) Is a Regulator of Immune Responses in Human Plasmacytoid Dendritic Cells.

TLRs are the most thoroughly studied group of pattern-recognition receptors that play a central role in innate immunity. Among them, TLR10 (CD290) remains the only TLR family member without a known ligand and clearly defined functions. One major impediment to studying TLR10 is its absence in mice. A recent study on TLR10 knock-in mice demonstrated its intrinsic inhibitory role in B cells, indicating that TLR10 is a potential drug target in autoimmune diseases. In this study, we interrogated the expression and function of TLR10 in human plasmacytoid dendritic cells (pDCs). We have seen that primary human pDCs, B cells, and monocytes constitutively express TLR10. Upon preincubation with an anti-TLR10 Ab, production of cytokines in pDCs was downregulated in response to stimulation with DNA and RNA viruses. Upon further investigation into the possible mechanism, we documented phosphorylation of STAT3 upon Ab-mediated engagement of TLR10. This leads to the induction of inhibitory molecule suppressor of cytokine signaling 3 (SOCS3) expression. We have also documented the inhibition of nuclear translocation of transcription factor IFN regulatory factor 7 (IRF7) in pDCs following TLR10 engagement. Our data provide the (to our knowledge) first evidence that TLR10 is constitutively expressed on the surface of human pDCs and works as a regulator of their innate response. Our findings indicate the potential of harnessing the function of pDCs by Ab-mediated targeting of TLR10 that may open a new therapeutic avenue for autoimmune disorders.

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.

Loss of RBM45 inhibits breast cancer progression by reducing the SUMOylation of IRF7 to promote IFNB1 transcription.

Type I interferons exhibit anti-proliferative and anti-cancer activities, but their detailed regulatory mechanisms in cancer have not been fully elucidated yet. RNA binding proteins are master orchestrators of gene regulation, which are closely related to tumor progression. Here we show that the upregulated RNA binding protein RBM45 correlates with poor prognosis in breast cancer. Depletion of RBM45 suppresses breast cancer progression both in cultured cells and xenograft mouse models. Mechanistically, RBM45 ablation inhibits breast cancer progression through regulating type I interferon signaling, particularly by elevating IFN-ß production. Importantly, RBM45 recruits TRIM28 to IRF7 and stimulates its SUMOylation, thereby repressing IFNB1 transcription. Loss of RBM45 reduced the SUMOylation of IRF7 by reducing the interaction between TRIM28 and IRF7 to promote IFNB1 transcription, leading to the inhibition of breast cancer progression. Taken together, our finding uncovers a vital role of RBM45 in modulating type I interferon signaling and cancer aggressive progression, implicating RBM45 as a potential therapeutic target in breast cancer.

IRF7 Exacerbates Candida albicans Infection by Compromising CD209-Mediated Phagocytosis and Autophagy-Mediated Killing in Macrophages.

IFN regulatory factor 7 (IRF7) exerts anti-infective effects by promoting the production of IFNs in various bacterial and viral infections, but its role in highly morbid and fatal Candida albicans infections is unknown. We unexpectedly found that Irf7 gene expression levels were significantly upregulated in tissues or cells after C. albicans infection in humans and mice and that IRF7 actually exacerbates C. albicans infection in mice independent of its classical function in inducing IFNs production. Compared to controls, Irf7-/- mice showed stronger phagocytosis of fungus, upregulation of C-type lectin receptor CD209 expression, and enhanced P53-AMPK-mTOR-mediated autophagic signaling in macrophages after C. albicans infection. The administration of the CD209-neutralizing Ab significantly hindered the phagocytosis of Irf7-/- mouse macrophages, whereas the inhibition of p53 or autophagy impaired the killing function of these macrophages. Thus, IRF7 exacerbates C. albicans infection by compromising the phagocytosis and killing capacity of macrophages via regulating CD209 expression and p53-AMPK-mTOR-mediated autophagy, respectively. This finding reveals a novel function of IRF7 independent of its canonical IFNs production and its unexpected role in enhancing fungal infections, thus providing more specific and effective targets for antifungal therapy.

SGIV VP82 inhibits the interferon response by degradation of IRF3 and IRF7.

During virus-host co-evolution, viruses have developed multiple strategies to dampen IFN response and prevent its antiviral activity in host cells. To date, the interactions between host IFN response and the immune evasion strategies exploited by fish iridoviruses still remain largely uncertain. Here, a potential immune evasion protein candidate of Singapore grouper iridovirus (SGIV), VP82 (encoded by SGIV ORF82) was screened and its roles during viral replication were investigated in detail. Firstly, VP82 overexpression dramatically decreased IFN or ISRE promoter activity and the transcription levels of IFN stimulated genes (ISGs) stimulated by grouper cyclic GMP-AMP synthase (EccGAS)/stimulator of interferon genes (EcSTING), TANK-binding kinase 1 (EcTBK1), IFN regulatory factor 3 (EcIRF3)and EcIRF7. Secondly, Co-IP assays indicated that VP82 interacted with EcIRF3 and EcIRF7, but not EcSTING and EcTBK1, which was consistent with the co-localization between VP82 and EcIRF3 or EcIRF7. Furthermore, VP82 promoted the degradation of EcIRF3 and EcIRF7 in a dose-dependent manner via the autophagy pathway. Finally, VP82 overexpression accelerated SGIV replication, evidenced by the increased transcriptions of viral core genes and viral production. Moreover, the antiviral action of EcIRF3 or EcIRF7 was significantly depressed in VP82 overexpressed cells. Together, VP82 was speculated to exert crucial roles for SGIV replication by inhibiting the IFN response via the degradation of IRF3 and IRF7. Our findings provided new insights into understanding the immune evasion strategies utilized by fish iridovirus through IFN regulation.

IRF7 overexpression alleviates CFA-induced inflammatory pain by inhibiting nuclear factor-κB activation and pro-inflammatory cytokines expression in rats.

BACKGROUND: It is known that nerve signals arising from sites of inflammation lead to persistent changes in the spinal cord and contribute to the amplification and persistence of pain. Nevertheless, the underlying mechanisms have not yet been completely elucidated. We identified differentially expressed genes in the lumbar (L4-L6) segment of the spinal cord from complete Freund's adjuvant (CFA) rats compared to control animals via high throughput sequencing. Based on differential gene expression analysis, we selected interferon regulatory factor 7 (IRF7) for follow-up experiments to explore its antinociceptive potential. METHODS: An animal model of inflammatory pain was induced by intraplantar injection of CFA. We evaluated the effects of adeno-associated viral (AAV)-mediated overexpression of IRF7 in the spinal cord on pain-related behavior after CFA injection. Moreover, the activation of the nuclear factor-κB (NF-κB) and the expression of inflammatory cytokines were investigated to understand the underlying mechanisms related to the contribution of IRF7 to inflammatory pain. RESULTS: CFA intraplantar injection caused a significant decrease in the level of spinal IRF7, which is mainly expressed in the dorsal horn neurons and astrocytes. Moreover, IRF7 overexpression significantly attenuated pain-related behaviors, as well as the activity of NF-κB/p65 and the production of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the spinal cord of CFA rats. CONCLUSIONS: Our data indicated that spinal IRF7 plays an important role in the regulation of inflammatory pain. Thus, IRF7 overexpression at the spinal cord level might represent a potential target for the treatment of inflammatory pain.

The dsRNA isolated from Escherichia coli infected with the MS2 bacteriophage induces the production of interferons.

Viral infections pose a significant threat to public health, and the production of interferons represents one of the most critical antiviral innate immune responses of the host. Consequently, the screening and identification of compounds or reagents that induce interferon production are of paramount importance. This study commenced with the cultivation of host bacterium 15,597, followed by the infection of Escherichia coli with the MS2 bacteriophage. Utilizing the J2 capture technique, a class of dsRNA mixtures (MS2+15,597) was isolated from the E. coli infected with the MS2 bacteriophage. Subsequent investigations were conducted on the immunostimulatory activity of the MS2+15,597 mixture. The results indicated that the dsRNA mixtures (MS2+15,597) extracted from E. coli infected with the MS2 bacteriophage possess the capability to activate innate immunity, thereby inducing the production of interferon-ß. These dsRNA mixtures can activate the RIG-I and TLR3 pattern recognition receptors, stimulating the expression of interferon stimulatory factors 3/7, which in turn triggers the NF-κB signaling pathway, culminating in the cellular production of interferon-ß to achieve antiviral effects. This study offers novel insights and strategies for the development of broad-spectrum antiviral drugs, potentially providing new modalities for future antiviral therapies.

Fish ubiquitin-specific protease 8 (USP8) inhibits IFN production through autophagy-lysosomal dependent degradation of IRF7.

Interferon regulatory factor 7 (IRF7) is considered the master regulator of virus-induced interferon (IFN) production. However, to avoid an autoimmune response, the expression of IRF7 must be tightly controlled. In this study, we report that zebrafish ubiquitin-specific protease 8 (USP8) promotes IRF7 degradation through an autophagy-lysosome-dependent pathway to inhibit IFN production. First, zebrafish usp8 is induced upon spring viremia of carp virus (SVCV) infection and polyinosinic/polycytidylic acid (poly I:C) stimulation. Second, overexpression of USP8 suppresses SVCV or poly I:C-mediated IFN expression. Mechanistically, USP8 interacts with IRF7 and promotes its degradation via an autophagy-lysosome-dependent pathway. Finally, USP8 significantly suppresses cellular antiviral responses and enhances SVCV proliferation. In summary, our discoveries offer a perspective on the role of zebrafish USP8 and provide additional understanding of the regulation of IRF7 in host antiviral immune response.

Mitochondrial (mt)DNA-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling promotes pyroptosis of macrophages via interferon regulatory factor (IRF)7/IRF3 activation to aggravate lung injury during severe acute pancreatitis.

BACKGROUND: Macrophage proinflammatory activation contributes to the pathology of severe acute pancreatitis (SAP) and, simultaneously, macrophage functional changes, and increased pyroptosis/necrosis can further exacerbate the cellular immune suppression during the process of SAP, where cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) plays an important role. However, the function and mechanism of cGAS-STING in SAP-induced lung injury (LI) remains unknown. METHODS: Lipopolysaccharide (LPS) was combined with caerulein-induced SAP in wild type, cGAS -/- and sting -/- mice. Primary macrophages were extracted via bronchoalveolar lavage and peritoneal lavage. Ana-1 cells were pretreated with LPS and stimulated with nigericin sodium salt to induce pyroptosis in vitro. RESULTS: SAP triggered NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation-mediated pyroptosis of alveolar and peritoneal macrophages in mouse model. Knockout of cGAS/STING could ameliorate NLRP3 activation and macrophage pyroptosis. In addition, mitochondrial (mt)DNA released from damaged mitochondria further induced macrophage STING activation in a cGAS- and dose-dependent manner. Upregulated STING signal can promote NLRP3 inflammasome-mediated macrophage pyroptosis and increase serum interleukin (IL)-6, IL-1ß, and tumor necrosis factor (TNF)-α levels and, thus, exacerbate SAP-associated LI (SAP-ALI). Downstream molecules of STING, IRF7, and IRF3 connect the mtDNA-cGAS-STING axis and the NLRP3-pyroptosis axis. CONCLUSIONS: Negative regulation of any molecule in the mtDNA-cGAS-STING-IRF7/IRF3 pathway can affect the activation of NLRP3 inflammasomes, thereby reducing macrophage pyroptosis and improving SAP-ALI in mouse model.

Non-transcriptional IRF7 interacts with NF-κB to inhibit viral inflammation.

Interferon (IFN) regulatory factors (IRF) are key transcription factors in cellular antiviral responses. IRF7, a virus-inducible IRF, expressed primarily in myeloid cells, is required for transcriptional induction of interferon α and antiviral genes. IRF7 is activated by virus-induced phosphorylation in the cytoplasm, leading to its translocation to the nucleus for transcriptional activity. Here, we revealed a nontranscriptional activity of IRF7 contributing to its antiviral functions. IRF7 interacted with the pro-inflammatory transcription factor NF-κB-p65 and inhibited the induction of inflammatory target genes. Using knockdown, knockout, and overexpression strategies, we demonstrated that IRF7 inhibited NF-κB-dependent inflammatory target genes, induced by virus infection or toll-like receptor stimulation. A mutant IRF7, defective in transcriptional activity, interacted with NF-κB-p65 and suppressed NF-κB-induced gene expression. A single-action IRF7 mutant, active in anti-inflammatory function, but defective in transcriptional activity, efficiently suppressed Sendai virus and murine hepatitis virus replication. We, therefore, uncovered an anti-inflammatory function for IRF7, independent of transcriptional activity, contributing to the antiviral response of IRF7.

Type I Interferon, Induced by Adenovirus or Adenoviral Vector Infection, Regulates the Cytokine Response to Lipopolysaccharide in a Macrophage Type-Specific Manner.

INTRODUCTION: While TLR ligands derived from microbial flora and pathogens are important activators of the innate immune system, a variety of factors such as intracellular bacteria, viruses, and parasites can induce a state of hyperreactivity, causing a dysregulated and potentially life-threatening cytokine over-response upon TLR ligand exposure. Type I interferon (IFN-αß) is a central mediator in the induction of hypersensitivity and is strongly expressed in splenic conventional dendritic cells (cDC) and marginal zone macrophages (MZM) when mice are infected with adenovirus. This study investigates the ability of adenoviral infection to influence the activation state of the immune system and underlines the importance of considering this state when planning the treatment of patients. METHODS: Infection with adenovirus-based vectors (Ad) or pretreatment with recombinant IFN-ß was used as a model to study hypersensitivity to lipopolysaccharide (LPS) in mice, murine macrophages, and human blood samples. The TNF-α, IL-6, IFN-αß, and IL-10 responses induced by LPS after pretreatment were measured. Mouse knockout models for MARCO, IFN-αßR, CD14, IRF3, and IRF7 were used to probe the mechanisms of the hypersensitive reaction. RESULTS: We show that, similar to TNF-α and IL-6 but not IL-10, the induction of IFN-αß by LPS increases strongly after Ad infection. This is true both in mice and in human blood samples ex vivo, suggesting that the regulatory mechanisms seen in the mouse are also present in humans. In mice, the scavenger receptor MARCO on IFN-αß-producing cDC and splenic marginal zone macrophages is important for Ad uptake and subsequent cytokine overproduction by LPS. Interestingly, not all IFN-αß-pretreated macrophage types exposed to LPS exhibit an enhanced TNF-α and IL-6 response. Pretreated alveolar macrophages and alveolar macrophage-like murine cell lines (MPI cells) show enhanced responses, while bone marrow-derived and peritoneal macrophages show a weaker response. This correlates with the respective absence or presence of the anti-inflammatory IL-10 response in these different macrophage types. In contrast, Ad or IFN-ß pretreatment enhances the subsequent induction of IFN-αß in all macrophage types. IRF3 is dispensable for the LPS-induced IFN-αß overproduction in infected MPI cells and partly dispensable in infected mice, while IRF7 is required. The expression of the LPS co-receptor CD14 is important but not absolutely required for the elicitation of a TNF-α over-response to LPS in Ad-infected mice. CONCLUSION: Viral infections or application of virus-based vaccines induces type I interferon and can tip the balance of the innate immune system in the direction of hyperreactivity to a subsequent exposure to TLR ligands. The adenoviral model presented here is one example of how multiple factors, both environmental and genetic, affect the physiological responses to pathogens. Being able to measure the current reactivity state of the immune system would have important benefits for infection-specific therapies and for the prevention of vaccination-elicited adverse effects.

A BET inhibitor, NHWD-870, can downregulate dendritic cells maturation via the IRF7-mediated signaling pathway to ameliorate imiquimod-induced psoriasis-like murine skin inflammation.

Psoriasis is a chronic, recurrent, inflammatory dermatosis accompanied by excessive activation of dendritic cells (DCs), which are primarily responsible for initiating an immune response. The bromodomain and extraterminal domain (BET) family plays a pivotal role in the transcriptional regulation of inflammation and its inhibitors can downregulate DCs maturation and activation. Here we investigated the effect of NHWD-870, a potent BET inhibitor, on inflammation in an imiquimod (IMQ)-induced psoriasis-like mouse model and murine bone marrow-derived dendritic cells (BMDCs) stimulated by lipopolysaccharide (LPS) and IMQ. Application of NHWD-870 significantly ameliorated IMQ-triggered skin inflammation in mice, and markers associated with DC maturation (CD40, CD80 and CD86) were decreased in skin lesions, spleen and lymph nodes. Additionally, NHWD-870 reduced LPS or IMQ induced DCs maturation and activation in vitro, with lower expression of inflammatory cytokines [interleukin (IL)-12, IL-23, tumor necrosis factor-α, IL-6, IL-1ß, chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10]. In addition, we found that interferon regulatory factor 7 (IRF7) significantly increased during DCs maturation, and inhibition of IRF7 could impair BMDCs maturation and activation. What's more, IRF7 was highly expressed in both psoriatic patients and IMQ-induced psoriasis-like mice. Single-cell RNA sequencing of normal and psoriatic skin demonstrated that IRF7 expression was increased in DCs of psoriatic skin. While NHWD-870 could inhibit IRF7 and phosphorylated-IRF7 expression in vivo and in vitro. These results indicate that NHWD-870 suppresses the maturation and activation of DCs by decreasing IRF7 proteins which finally alleviates psoriasis-like skin lesions, and NHWD-870 may be a potent therapeutic drug for psoriasis.

Evolutionary and functional conservation of IRF7 in the Tibetan frog Nanorana parkeri.

BACKGROUND: The production of interferons (IFNs) is essential for the control of viral infections, and interferon regulatory factor 7 (IRF7) is considered as a vital regulator for the transcription of type I IFNs. Amphibians appear to possess a highly expanded type I IFN repertoire, consisting of intron-containing genes as observed in fish, and intronless genes as in other higher vertebrates. However, the knowledge on transcriptional regulatory mechanism of these two types of type I IFN genes is rather scarce in amphibians. METHODS AND RESULTS: A IRF7 gene named as Np-IRF7 was identified in Tibetan frog (Nanorana parkeri), and bioinformatic analysis revealed that the predicted protein of Np-IRF7 contains several important structural features known in IRF7. Expression analysis showed that Np-IRF7 gene was widely expressed and rapidly induced by poly(I:C) in different organs/tissues. Interestingly, luciferase reporter assay revealed that intronless IFN promoters were more effectively activated than intron-containing IFN promoter in Np-IRF7-transfected cells. Moreover, the overexpression of Np-IRF7 could induce the expression of ISGs and suppress the replication of FV3 in A6 cells. CONCLUSION: Np-IRF7 is indeed the ortholog of known IRF7, and IRF7 is structurally conserved in different lineages of vertebrates. Np-IRF7 played distinct roles in the activation of intron-containing and intronless type I IFN promoters, thus inducing the expression of interferon-stimulated antiviral effectors and providing a protection against ranavirus infection. The present research thus contributes to a better understanding of regulatory function of IRF7 in the IFN-mediated antiviral response of anuran amphibians.