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Type I interferon (IFN-I) and IFN-γ foster antitumor immunity by facilitating T cell responses. Paradoxically, IFNs may promote T cell exhaustion by activating immune checkpoints. The downstream regulators of these disparate responses are incompletely understood. Here, we describe how interferon regulatory factor 1 (IRF1) orchestrates these opposing effects of IFNs. IRF1 expression in tumor cells blocks Toll-like receptor- and IFN-I-dependent host antitumor immunity by preventing interferon-stimulated gene (ISG) and effector programs in immune cells. In contrast, expression of IRF1 in the host is required for antitumor immunity. Mechanistically, IRF1 binds distinctly or together with STAT1 at promoters of immunosuppressive but not immunostimulatory ISGs in tumor cells. Overexpression of programmed cell death ligand 1 (PD-L1) in Irf1-/- tumors only partially restores tumor growth, suggesting multifactorial effects of IRF1 on antitumor immunity. Thus, we identify that IRF1 expression in tumor cells opposes host IFN-I- and IRF1-dependent antitumor immunity to facilitate immune escape and tumor growth.

Hematopoietic stem cells (HSCs) are tightly controlled to maintain a balance between blood cell production and self-renewal. While inflammation-related signaling is a critical regulator of HSC activity, the underlying mechanisms and the precise functions of specific factors under steady-state and stress conditions remain incompletely understood. We investigated the role of interferon regulatory factor 1 (IRF1), a transcription factor that is affected by multiple inflammatory stimuli, in HSC regulation. Our findings demonstrate that the loss of IRF1 from mouse HSCs significantly impairs self-renewal, increases stress-induced proliferation, and confers resistance to apoptosis. In addition, given the frequent abnormal expression of IRF1 in leukemia, we explored the potential of IRF1 expression level as a stratification marker for human acute myeloid leukemia. We show that IRF1-based stratification identifies distinct cancer-related signatures in patient subgroups. These findings establish IRF1 as a pivotal HSC controller and provide previously unknown insights into HSC regulation, with potential implications to IRF1 functions in the context of leukemia.

The clinical application and biological function of interferon regulatory factor 1 (IRF1) in non-small cell lung cancer (NSCLC) patients undergoing chemoimmunotherapy remain elusive. The aim of this study was to investigate the predictive and prognostic significance of IRF1 in NSCLC patients. We employed the cBioPortal database to predict frequency changes in IRF1 and explore its target genes. Bioinformatic methods were utilized to analyze the relationship between IRF1 and immune regulatory factors. Retrospective analysis of clinical samples was conducted to assess the predictive and prognostic value of IRF1 in chemoimmunotherapy. Additionally, A549 cells with varying IRF1 expression levels were constructed to investigate its effects on NSCLC cells, while animal experiments were performed to studythe roleof IRF1 in vivo. Our findings revealed that the primary mutation of IRF1 is deep deletion and it exhibits a close association with immune regulatory factors. KRAS and TP53 areamong the target genes of IRF1, with interferon and IL-2 being the predominantly affected pathways. Clinically, IRF1 levels significantly correlate with the efficacy of chemoimmunotherapy. Patients with high IRF1 levels exhibited a median progression-free survival (mPFS) of 9.5 months, whereas those with low IRF1 levels had a shortermPFS of 5.8 months. IRF1 levels positively correlate with PDL1 distribution and circulating IL-2 levels. IL-2 enhances the biological function of IRF1 and recapitulates its role in vivo in the knockdown group. Therefore, IRF1 may possess predictive and prognostic value for chemoimmunotherapy in NSCLC patients through the regulation of the IL-2 inflammatory pathway. [ABSTRACT FROM AUTHOR]

AimsMammalian target of rapamycin (mTOR) inhibitors used in drug-eluting stents (DES) to control restenosis have been found to delay endothelialization and increase incidence of late-stent thrombosis through mechanisms not completely understood. We revealed that mTOR inhibition (mTORi) upregulated the expression of cell growth suppressor IRF-1 in primary human arterial endothelial cells (HAEC). This study aimed to examine how mTOR-regulated IRF-1 expression contributes to the suppressive effect of mTORi on arterial endothelial proliferation.Methods and resultsWestern blotting, quantitative PCR, and a dual-luciferase reporter assay indicated that mTOR inhibitors rapamycin and torin 1 upregulated IRF-1 expression and increased its transcriptional activity. IRF-1 in turn contributed to the suppressive effect of mTORi by mediating HAEC apoptosis and cell cycle arrest in part through upregulation of caspase 1 and downregulation of cyclin D3, as revealed by CCK-8 assay, Annexin V binding assay, measurement of activated caspase 3, BrdU incorporation assay, and matrigel tube formation assay. In a mouse model of femoral artery wire injury, administration of rapamycin inhibited EC recovery, an effect alleviated by EC deficiency of IRF-1. Chromatin immunoprecipitation assay with HAEC and rescue expression of wild type or dominant-negative IRF-1 in EC isolated from Irf1-/- mice confirmed transcriptional regulation of IRF-1 on the expression of CASP1 and CCND3. Furthermore, mTORi activated multiple PKC members, among which PKCζ was responsible for the growth-inhibitory effect on HAEC. Activated PKCζ increased IRF1 transcription through JAK/STAT-1 and NF-κB signaling. Finally, overexpression of wild type or mutant raptor incapable of binding mTOR indicated that mTOR-free raptor contributed to PKCζ activation in mTOR-inhibited HAEC.ConclusionsThe study reveals an IRF-1-mediated mechanism that contributes to the suppressive effects of mTORi on HAEC proliferation. Further study may facilitate the development of effective strategies to reduce the side effects of DES used in coronary interventions.

Excessive alcohol consumption induces intestinal dysbiosis of the gut microbiome and reduces gut epithelial integrity. This often leads to portal circulation-mediated translocation of gut-derived microbial products, such as lipopolysaccharide (LPS), to the liver, where these products engage Toll-like receptor 4 (TLR4) and initiate hepatic inflammation, which promotes alcoholic liver disease (ALD). Although the key self-destructive process of autophagy has been well-studied in hepatocytes, its role in macrophages during ALD pathogenesis remains elusive. Using WT and myeloid cell-specific autophagy-related 7 (Atg7) knockout (Atg7 ΔMye) mice, we found that chronic ethanol feeding for 6 weeks plus LPS injection enhances serum alanine aminotransferase and IL-1β levels and augments hepatic C-C motif chemokine ligand 5 (CCL5) and C-X-C motif chemokine ligand 10 (CXCL10) expression in WT mice, a phenotype that was further exacerbated in Atg7 ΔMye mice. Atg7 ΔMye macrophages exhibited defective mitochondrial respiration and displayed elevated mitochondrial reactive oxygen species production and inflammasome activation relative to WT cells. Interestingly, compared with WT cells, Atg7 ΔMye macrophages also had a drastically increased abundance and nuclear translocation of interferon regulatory factor 1 (IRF1) after LPS stimulation. Mechanistically, LPS induced co-localization of IRF1 with the autophagy adaptor p62 and the autophagosome, resulting in subsequent IRF1 degradation. However, upon p62 silencing or Atg7 deletion, IRF1 started to accumulate in autophagy-deficient macrophages and translocated into the nucleus, where it induced CCL5 and CXCL10 expression. In conclusion, macrophage autophagy protects against ALD by promoting IRF1 degradation and removal of damaged mitochondria, limiting macrophage activation and inflammation.

Dysregulated NLRP3 inflammasome activity results in uncontrolled inflammation, which underlies many chronic diseases. Although mitochondrial damage is needed for the assembly and activation of the NLRP3 inflammasome, it is unclear how macrophages are able to respond to structurally diverse inflammasome-activating stimuli. Here we show that the synthesis of mitochondrial DNA (mtDNA), induced after the engagement of Toll-like receptors, is crucial for NLRP3 signalling. Toll-like receptors signal via the MyD88 and TRIF adaptors to trigger IRF1-dependent transcription of CMPK2, a rate-limiting enzyme that supplies deoxyribonucleotides for mtDNA synthesis. CMPK2-dependent mtDNA synthesis is necessary for the production of oxidized mtDNA fragments after exposure to NLRP3 activators. Cytosolic oxidized mtDNA associates with the NLRP3 inflammasome complex and is required for its activation. The dependence on CMPK2 catalytic activity provides opportunities for more effective control of NLRP3 inflammasome-associated diseases.

Respiratory syncytial virus (RSV) persists as a significant human pathogen that continues to contribute to morbidity and mortality. In children, RSV is the leading cause of lower respiratory tract infections, and in adults RSV causes pneumonia and contributes to exacerbations of chronic lung diseases. RSV induces airway epithelial inflammation by activation of the epidermal growth factor receptor (EGFR), a tyrosine kinase receptor. Recently, EGFR inhibition was shown to decrease RSV infection, but the mechanism(s) for this effect are not known. Interferon (IFN) signaling is critical for innate antiviral responses, and recent experiments have implicated IFN-λ (lambda), a type III IFN, as the most significant IFN for mucosal antiviral immune responses to RSV infection. However, a role for RSV-induced EGFR activation to suppress airway epithelial antiviral immunity has not been explored. Here, we show that RSV-induced EGFR activation suppresses IFN regulatory factor (IRF) 1-induced IFN-λ production and increased viral infection, and we implicate RSV F protein to mediate this effect. EGFR inhibition, during viral infection, augmented IRF1, IFN-λ, and decreased RSV titers. These results suggest a mechanism for EGFR inhibition to suppress RSV by activation of endogenous epithelial antiviral defenses, which may be a potential target for novel therapeutics.

Deciphering gene regulatory networks requires identification of gene expression modules. We describe a novel bottom-up approach to identify gene modules regulated by cis-regulatory motifs from a human gene co-expression network. Target genes of a cis-regulatory motif were identified from the network via the motif's enrichment or biased distribution towards transcription start sites in the promoters of co-expressed genes. A gene sub-network containing the target genes was extracted and used to derive gene modules. The analysis revealed known and novel gene modules regulated by the NF-Y motif. The binding of NF-Y proteins to these modules' gene promoters were verified using ENCODE ChIP-Seq data. The analyses also identified 8,048 Sp1 motif target genes, interestingly many of which were not detected by ENCODE ChIP-Seq. These target genes assemble into house-keeping, tissues-specific developmental, and immune response modules. Integration of Sp1 modules with genomic and epigenomic data indicates epigenetic control of Sp1 targets' expression in a cell/tissue specific manner. Finally, known and novel target genes and modules regulated by the YY1, RFX1, IRF1, and 34 other motifs were also identified. The study described here provides a valuable resource to understand transcriptional regulation of various human developmental, disease, or immunity pathways.

The striking rise of obesity-related metabolic disorders has focused attention on adipocytes as critical mediators of disease phenotypes. To better understand the role played by excess adipose in metabolic dysfunction it is crucial to decipher the transcriptional underpinnings of the low-grade adipose inflammation characteristic of diseases such as type 2 diabetes. Through employing a comparative transcriptomics approach, we identified IRF1 as differentially regulated between primary and in vitro-derived genetically matched adipocytes. This suggests a role as a mediator of adipocyte inflammatory phenotypes, similar to its function in other tissues. Utilizing adipose-derived mesenchymal progenitors we subsequently demonstrated that expression of IRF1 in adipocytes indeed contributes to upregulation of inflammatory processes, both in vitro and in vivo. This highlights IRF1's relevance to obesity-related inflammation and the resultant metabolic dysregulation.

PD-L1 and PD-L2 are ligands for the PD-1 immune inhibiting checkpoint that can be induced in tumors by interferon exposure, leading to immune evasion. This process is important for immunotherapy based on PD-1 blockade. We examined the specific molecules involved in interferon-induced signaling that regulates PD-L1 and PD-L2 expression in melanoma cells. These studies revealed that the interferon-gamma-JAK1/JAK2-STAT1/STAT2/STAT3-IRF1 axis primarily regulates PD-L1 expression, with IRF1 binding to its promoter. PD-L2 responded equally to interferon beta and gamma and is regulated through both IRF1 and STAT3, which bind to the PD-L2 promoter. Analysis of biopsy specimens from patients with melanoma confirmed interferon signature enrichment and upregulation of gene targets for STAT1/STAT2/STAT3 and IRF1 in anti-PD-1-responding tumors. Therefore, these studies map the signaling pathway of interferon-gamma-inducible PD-1 ligand expression.

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Abstract Background Ischemia and reperfusion (I/R) induces cytokines, and up-regulates inducible nitric oxide synthase (iNOS), interferon regulatory factor-1(IRF1) and p53 up-regulated modulator of apoptosis (PUMA), which contribute to cell death and tissue injury. However, the mechanisms that I/R induces IRF1-PUMA through iNOS/NO is still unknown. Methods Ischemia was induced by occluding structures in the portal triad (hepatic artery, portal vein, and bile duct) to the left and median liver lobes for 60 min, and reperfusion was initiated by removal of the clamp. Induction of iNOS, IRF1 and PUMA in response to I/R were analyzed. I/R induced IRF1 and PUMA expression were compared between iNOS wild-type and iNOS knockout (KO) mice. Human iNOS gene transfected-cells were used to determine iNOS/NO signals targeting IRF1. To test whether HDAC2 was involved in the mediation of iNOS/NO-induced IRF1 transcriptional activities and its target gene (PUMA and p21) expression, NO donors were used in vitro and in vivo. Results IRF1 nuclear translocation and PUMA transcription elevation were markedly induced following I/R in the liver of iNOS wild-type mice compared with that in knock-out mice. Furthermore, I/R induced hepatic HDAC2 expression and activation, and decreased H3AcK9 expression in iNOS wild-type mice, but not in the knock-out mice. Mechanistically, over-expression of human iNOS gene increased IRF1 transcriptional activity and PUMA expression, while iNOS inhibitor L-NIL reversed these effects. Cytokine-induced PUMA through IRF1 was p53 dependent. IRF1 and p53 synergistically up-regulated PUMA expression. iNOS/NO-induced HDAC2 mediated histone H3 deacetylation and promoted IRF1 transcriptional activity. Moreover, treating the cells with romidepsin, an HDAC1/2 inhibitor decreased NO-induced IRF1 and PUMA expression. Conclusions This study demonstrates a novel mechanism that iNOS/NO is required for IRF1/PUMA signaling through a positive-feedback loop between iNOS and IRF1, in which HDAC2-mediated histone modification is involved to up-regulate IRF1 in response to I/R in mice.

The clinical application and biological function of interferon regulatory factor 1 (IRF1) in non-small cell lung cancer (NSCLC) patients undergoing chemoimmunotherapy remain elusive. The aim of this study was to investigate the predictive and prognostic significance of IRF1 in NSCLC patients. We employed the cBioPortal database to predict frequency changes in IRF1 and explore its target genes. Bioinformatic methods were utilized to analyze the relationship between IRF1 and immune regulatory factors. Retrospective analysis of clinical samples was conducted to assess the predictive and prognostic value of IRF1 in chemoimmunotherapy. Additionally, A549 cells with varying IRF1 expression levels were constructed to investigate its effects on NSCLC cells, while animal experiments were performed to study the role of IRF1 in vivo . Our findings revealed that the primary mutation of IRF1 is deep deletion and it exhibits a close association with immune regulatory factors. KRAS and TP53 are among the target genes of IRF1, with interferon and IL-2 being the predominantly affected pathways. Clinically, IRF1 levels significantly correlate with the efficacy of chemoimmunotherapy. Patients with high IRF1 levels exhibited a median progression-free survival (mPFS) of 9.5 months, whereas those with low IRF1 levels had a shorter mPFS of 5.8 months. IRF1 levels positively correlate with PD-L1 distribution and circulating IL-2 levels. IL-2 enhances the biological function of IRF1 and recapitulates its role in vivo in the knockdown group. Therefore, IRF1 may possess predictive and prognostic value for chemoimmunotherapy in NSCLC patients through the regulation of the IL-2 inflammatory pathway., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Su, Tan, Li, Chen, Liu, Luo, Pan and Zhang.)

Infection of cells with DNA viruses triggers innate immune responses mediated by DNA sensors. cGMP-AMP synthase (cGAS) is a key DNA sensor that produces the cyclic dinucleotide cGMP-AMP (cGAMP) upon activation, which binds to and activates stimulator of interferon genes (STING), leading to IFN production and an antiviral response. Kaposi's sarcoma-associated herpesvirus (KSHV) is a DNA virus that is linked to several human malignancies. We report that KSHV infection activates the cGAS-STING pathway, and that cGAS and STING also play an important role in regulating KSHV reactivation from latency. We screened KSHV proteins for their ability to inhibit this pathway and identified six viral proteins that block IFN-β activation through this pathway. This study is the first report identifying multiple viral proteins encoded by a human DNA virus that inhibit the cGAS-STING DNA sensing pathway. One such protein, viral interferon regulatory factor 1 (vIRF1), targets STING by preventing it from interacting with TANK binding kinase 1 (TBK1), thereby inhibiting STING's phosphorylation and concomitant activation, resulting in an inhibition of the DNA sensing pathway. Our data provide a unique mechanism for the negative regulation of STING-mediated DNA sensing. Moreover, the depletion of vIRF1 in the context of KSHV infection prevented efficient viral reactivation and replication, and increased the host IFN response to KSHV. The vIRF1-expressing cells also inhibited IFN-β production following infection with DNA pathogens. Collectively, our results demonstrate that gammaherpesviruses encode inhibitors that block cGAS-STING-mediated antiviral immunity, and that modulation of this pathway is important for viral transmission and the lifelong persistence of herpesviruses in the human population.

Objective To investigate the effect of interferon regulatory factor-1 (IRF-1) on the pyroptosis of liver ischemia reperfusion injury (LIRI) in mice. Methods (1) Twenty four C57BL / 6 normal male mice were randomly divided into sham operation group (Sham) and ischemia-reperfusion (IR) 2 h, 6 h and 12 h groups, 6 mice in each group. The Sham group was not treated with IR, while in the other three groups, the LIRI model was established by clamping the middle lobe and left lobe of liver with vascular clamp for 60 min and reperfusion for 2,6 and 12 h respectively. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and interleukin (IL)-1β were detected by enzyme-linked immunosorbent assay (ELISA). The pathological changes of liver were observed by HE staining. The expression of IRF-1 was detected by immunohistochemical staining. The apoptosis and pyroptosis of liver cells were detected by TUNEL. The protein levels of IRF-1, Caspase-1 and gasdermin D (GSDMD) were detected by Western blot assay. The morphological changes of hepatocytes were detected by transmission electron microscope. (2) The AML12 cells in the normal liver of mice were over expressed and silenced of IRF-1, and then subjected to the simulated IR treatment. The AML12 cells were divided into over expression IRF-1+IR group, empty vector + IR group, IRF-1 siRNA + IR group and control group (NC+IR group). Western blot assay was used to detect the levels of IRF-1, Caspase-1, Cleaved-Caspase-1 and GSDMD proteins in the four groups. Transmission electron microscopy was used to detect cell morphological changes. Apoptosis and pyroptosis of cells were detected by flow cytometry. The release of lactate dehydrogenase (LDH) in cell supernatant was detected by microplate reader. Results (1) The results in vivo showed that compared with the Sham group, the serum levels of ALT, AST and IL- 1β were significantly increased in the IR 6 h and IR 12 h groups (P < 0.05), and the expression levels of IRF-1, Caspase-1 and GSDMD proteins were increased (P < 0.05). At the same time, liver cells appeared swelling, disordered arrangement, vacuoles, pathcy necrosis and erythrocyte siltation, accompanied by nuclear membrane damage and mitochondrial swelling. (2) After the over expression of IRF-1 in AML12 cells in vitro, the expressions of Cleaved-Caspase-1 and GSDMD increased, while the expressions of Caspase-1 and GSDMD decreased after the down-regulation of IRF-1 expression (P＜ 0.05). After silencing IRF-1 expression, the damage of cytoplasmic membrane and nuclear membrane was reduced in IRF-1 siRNA + IR group than that of NC + IR group, the pyroptosis rate was decreased, and the LDH release was reduced by about 20%. Conclusion IRF-1 can induce LIRI in mice by regulating the expressions of Caspase-1 and GSDMD and the release of IL-1β. [ABSTRACT FROM AUTHOR]

Airway epithelial cells are the primary cell type involved in respiratory viral infection. Upon infection, airway epithelium plays a critical role in host defense against viral infection by contributing to innate and adaptive immune responses. Influenza A virus, rhinovirus, and respiratory syncytial virus (RSV) represent a broad range of human viral pathogens that cause viral pneumonia and induce exacerbations of asthma and chronic obstructive pulmonary disease. These respiratory viruses induce airway epithelial production of IL-8, which involves epidermal growth factor receptor (EGFR) activation. EGFR activation involves an integrated signaling pathway that includes NADPH oxidase activation of metalloproteinase, and EGFR proligand release that activates EGFR. Because respiratory viruses have been shown to activate EGFR via this signaling pathway in airway epithelium, we investigated the effect of virus-induced EGFR activation on airway epithelial antiviral responses. CXCL10, a chemokine produced by airway epithelial cells in response to respiratory viral infection, contributes to the recruitment of lymphocytes to target and kill virus-infected cells. While respiratory viruses activate EGFR, the interaction between CXCL10 and EGFR signaling pathways is unclear, and the potential for EGFR signaling to suppress CXCL10 has not been explored. Here, we report that respiratory virus-induced EGFR activation suppresses CXCL10 production. We found that influenza virus-, rhinovirus-, and RSV-induced EGFR activation suppressed IFN regulatory factor (IRF) 1-dependent CXCL10 production. In addition, inhibition of EGFR during viral infection augmented IRF1 and CXCL10. These findings describe a novel mechanism that viruses use to suppress endogenous antiviral defenses, and provide potential targets for future therapies.

Viruses suppress host responses to increase infection, and understanding these mechanisms has provided insights into cellular signaling and led to novel therapies. Many viruses (e.g., Influenza virus, Rhinovirus [RV], Cytomegalovirus, Epstein-Barr virus, and Hepatitis C virus) activate epithelial epidermal growth factor receptor (EGFR), a tyrosine kinase receptor, but the role of EGFR in viral pathogenesis is not clear. Interferon (IFN) signaling is a critical innate antiviral host response and recent experiments have implicated IFN-λ, a type III IFN, as the most significant IFN for mucosal antiviral immune responses. Despite the importance of IFN-λ in epithelial antiviral responses, the role and mechanisms of epithelial IFN-λ signaling have not been fully elucidated. We report that respiratory virus-induced EGFR activation suppresses endogenous airway epithelial antiviral signaling. We found that Influenza virus- and RV-induced EGFR activation suppressed IFN regulatory factor (IRF) 1-induced IFN-λ production and increased viral infection. In addition, inhibition of EGFR during viral infection augmented IRF1 and IFN-λ, which resulted in decreased viral titers in vitro and in vivo. These findings describe a novel mechanism that viruses use to suppress endogenous antiviral defenses, and provide potential targets for future therapies.

N 6 -methyladenosine (m 6 A) and its associated reader protein insulin like growth factor 2 mRNA binding protein 3 (IGF2BP3) are involved in tumor initiation and progression via regulating RNA metabolism. This study aims to investigate the biological function and clinical significance of IGF2BP3 in gastric cancer (GC). The clinical significance of IGF2BP3 was evaluated using tumor related databases and clinical tissues. The biological role and molecular mechanism of IGF2BP3 in GC progression were investigated by multi-omics analysis including Ribosome sequence (Ribo-seq), RNA sequence (RNA-seq) and m 6 A sequence (m 6 A-seq) combined with gain- and loss- of function experiments. IGF2BP3 expression is significantly elevated in GC tissues and associated with poor prognosis of GC patients. Knockdown of IGF2BP3 significantly weakens the migration and clonogenic ability, promotes the apoptosis, inhibits translation, and suppresses in vitro growth and progression of GC cells. Mechanistically, IGF2BP3 regulates the mRNA stability and translation of the nuclear factor of activated T cells 1(NFAT1) in a m 6 A dependent manner. Then NFAT1 induced by IGF2BP3 acts as a transcription factor (TF) to negatively regulates the promoter activities of interferon regulatory factor 1 (IRF1) to inhibit its expression. Inhibition of IGF2BP3-induced expression of IRF1 activates interferon (IFN) signaling pathway and then exerts its anti-tumor effect. Elevated IGF2BP3 promotes in vivo and in vitro GC progression via regulation of NFAT1/IRF1 pathways. Targeted inhibition of IGF2BP3 might be a potential therapeutic approach for GC treatment., (© 2024. The Author(s).)

Host defense against the parasite Toxoplasma gondii requires the cytokine interferon-gamma (IFNγ). However, Toxoplasma inhibits the host cell transcriptional response to IFNγ, which is thought to allow the parasite to establish a chronic infection. It is not known whether all strains of Toxoplasma block IFNγ-responsive transcription equally and whether this inhibition occurs solely through the modulation of STAT1 activity or whether other transcription factors are involved. We find that strains from three North American/European clonal lineages of Toxoplasma, types I, II, and III, can differentially modulate specific aspects of IFNγ signaling through the polymorphic effector proteins ROP16 and GRA15. STAT1 tyrosine phosphorylation is activated in the absence of IFNγ by the Toxoplasma kinase ROP16, but this ROP16-activated STAT1 is not transcriptionally active. Many genes induced by STAT1 can also be controlled by other transcription factors and therefore using these genes as specific readouts to determine Toxoplasma inhibition of STAT1 activity might be inappropriate. Indeed, GRA15 and ROP16 modulate the expression of subsets of IFNγ responsive genes through activation of the NF-κB/IRF1 and STAT3/6 transcription factors, respectively. However, using a stable STAT1-specific reporter cell line we show that strains from the type I, II, and III clonal lineages equally inhibit STAT1 transcriptional activity. Furthermore, all three of the clonal lineages significantly inhibit global IFNγ induced gene expression.

Abstract Background Hip fracture is commonly associated with an overwhelming inflammatory response, which may lead to high rates of morbidity and mortality in the elderly. MicroRNAs (miRNAs) play important roles in the functions of immune system. However, the association between miRNA dysregulation and immune disturbance (IMD) related to elderly hip fracture is largely unknown. Methods In this study, microarray profiling was carried out to evaluate the differential expression patterns of miRNAs in plasma of the aged hip fracture rats with IMD, those without IMD, and normal aged rats, followed by validation using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Genes and signaling pathways of the dysregulated miRNAs related to elderly hip fracture-induced IMD were investigated in silico using Gene Ontology and analysis of Kyoto Encyclopedia of Genes or Genomes. Results Dead or moribund rats with hip fracture exhibited significantly reduced TNF-α/IL-10 ratio compared with healthy controls and other hip fracture rats, which were therefore named as hip fracture rats with IMD. Seven serum miRNAs in hip fracture rats with IMD were significantly downregulated. qRT-PCR and in silico analysis revealed that miR-130a-3p likely participated in regulating the hip fracture-induced IMD. Furthermore, Western blot experiment demonstrated that in lung tissue, the reduction of miR-130a-3p was accompanied with the increase of the protein expression of interferon regulatory factor-1 (IRF1) and sphingosine-1-phosphate receptor 1 (SIPR1). Conclusions miR-130a-3p desregulation may be associated with elderly hip fracture-induced IMD, which might act as a new potential biomarker for the diagnosis and prognosis of elderly hip fracture-induced IMD and a potential therapeutic target as well.

Background: Ischemia and reperfusion (I/R) induces cytokines, and up-regulates inducible nitric oxide synthase (iNOS), interferon regulatory factor-1(IRF1) and p53 up-regulated modulator of apoptosis (PUMA), which contribute to cell death and tissue injury. However, the mechanisms that I/R induces IRF1-PUMA through iNOS/NO is still unknown. Methods: Ischemia was induced by occluding structures in the portal triad (hepatic artery, portal vein, and bile duct) to the left and median liver lobes for 60 min, and reperfusion was initiated by removal of the clamp. Induction of iNOS, IRF1 and PUMA in response to I/R were analyzed. I/R induced IRF1 and PUMA expression were compared between iNOS wild-type and iNOS knockout (KO) mice. Human iNOS gene transfected-cells were used to determine iNOS/NO signals targeting IRF1. To test whether HDAC2 was involved in the mediation of iNOS/NO-induced IRF1 transcriptional activities and its target gene (PUMA and p21) expression, NO donors were used in vitro and in vivo. Results: IRF1 nuclear translocation and PUMA transcription elevation were markedly induced following I/R in the liver of iNOS wild-type mice compared with that in knock-out mice. Furthermore, I/R induced hepatic HDAC2 expression and activation, and decreased H3AcK9 expression in iNOS wild-type mice, but not in the knock-out mice. Mechanistically, over-expression of human iNOS gene increased IRF1 transcriptional activity and PUMA expression, while iNOS inhibitor L-NIL reversed these effects. Cytokine-induced PUMA through IRF1 was p53 dependent. IRF1 and p53 synergistically up-regulated PUMA expression. iNOS/NO-induced HDAC2 mediated histone H3 deacetylation and promoted IRF1 transcriptional activity. Moreover, treating the cells with romidepsin, an HDAC1/2 inhibitor decreased NO-induced IRF1 and PUMA expression. Conclusions: This study demonstrates a novel mechanism that iNOS/NO is required for IRF1/PUMA signaling through a positive-feedback loop between iNOS and IRF1, in which HDAC2-mediated histone modification is involved to up-regulate IRF1 in response to I/R in mice. [ABSTRACT FROM AUTHOR]

SAMHD1 (S terile A lpha M otif and H istidine-aspartate D omain containing protein 1) has been documented as a host factor that restricts HIV-1 and some DNA viruses. In this work, we attempted to explore possible effects of SAMHD1 on exogenous DNA and show that SAMHD1 exerts a general inhibition on the expression of exogenous DNA in vitro and in mice. This inhibition is achieved through repressing transcription of exogenous DNA. Intriguingly, unlike SAMHD1's restriction of HIV-1, such restriction does not require the dNTPase or RNase activities, or T592 phosphorylation of SAMHD1. Mechanistically, SAMHD1 enhances the expression of interferon regulatory factor-1 (IRF1), while IRF1 upregulation was demonstrated to inhibit exogenous DNA expression in a similar fashion as SAMHD1. IFNλ1, whose induction has been associated with IRF1 activation, is dispensable for SAMHD1/IRF1-mediated restriction of exogenous DNA, and neither type I nor II interferons appear to be involved. We also demonstrate that SAMHD1/IRF1-mediated restriction can effectively inhibit hepatitis B virus (HBV) antigen expression and progeny virus production in mouse models. In conclusion, these data support restriction of exogenous DNA as a novel function of SAMHD1. [ABSTRACT FROM AUTHOR]

Background: Recent evidences have implicated neuroprotective effects of CX3CR1 in multiple sclerosis (MS). But whether CX3CR1 is involved in modulation of antigen-presenting cell (APC)-related molecular MHC-II and what the possible mechanism is remain unidentified.Objective: In this study, we intended to investigate the effects of CX3CR1 on MHC-II expressions on brain myeloid cells in experimental autoimmune encephalomyelitis (EAE) mice and explore the possible regulators for it.Methods: CX3CR1-deficient EAE mice were created. Disease severity, pathological damage, and the expressions of MHC-II and its mediators on myeloid cells were detected.Results: We found that compare with wile-typed EAE mice, CX3CR1-deficient EAE mice exhibited more severe disease severity. An accumulation of CD45+CD115+Ly6C-CD11c+ cells was reserved in the affected EAE brain of CX3CR1-deficient mice, consistent with disease severity and pathological damage in the brain. The expressions of MHC-II on the brain CD45+CD115+Ly6C-CD11c+ cells of CX3CR1-deficient EAE mice were elevated, in accord with the increased protein and mRNA expressions of class II transactivator (CIITA) and interferon regulatory factor-1 (IRF-1).Conclusions: The findings indicated that CX3CR1 might be an important regulator for MHC-II expressions on APCs, playing a beneficial role in EAE. The mechanism was probably through regulation on the MHC-II regulators CIITA and IRF-1. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that neutrophil extracellular traps (NETs) play an essential role in lipopolysaccharide (LPS)-induced acute lung injury. However, the underlying mechanism is unclear. In this study, we showed that knockout of interferon regulatory factor 1 (IRF-1) in mice strongly attenuated the generation of NETs and reactive oxygen species (ROS) production in neutrophils from bronchoalveolar lavage fluid and alleviated LPS-induced lung injury and systemic inflammation. Our in vitro experiments demonstrated that LPS-stimulated platelets induce NET release through two distinct processes: an ROS-independent early/rapid NETosis and a later ROS-dependent classical NETosis. Notably, the classical ROS-dependent pathway plays a dominant role in the generation of NETs. Furthermore, we showed that IRF-1 knockout does not affect the formation of NETs in early/rapid NETosis, but significantly attenuates ROS production and the generation of NETs in classical NETosis, which determines the total levels of NETs released by LPS-stimulated platelets. In conclusion, IRF-1 deficiency plays a key role in moderating the excessive NETs formed via ROS in the classical pathway and retaining the protective role of the low-NET levels generated in early/rapid NETosis, which may serve as a novel target in acute lung injury/acute respiratory distress syndrome. [ABSTRACT FROM AUTHOR]

Interleukin-23 (IL-23) is a proinflammatory cytokine initially studied in autoimmune disease that has been more recently linked to innate immunity. We observed that the expression of IL-23 is upregulated during hypoxia in a hepatocyte and nonparenchymal cell (NPC) coculture system, as well as during ischemia-reperfusion (I/R) injury in the liver. Interferon regulatory factor-1 (IRF-1) is a transcription factor that induces expression of multiple inflammatory cytokines and has been shown to play a critical role in liver I/R injury. We observed that IL-23 signaling induces not only the IL-17/chemokine (C-X-C motif) ligand 2 (CXCL2) pathway but also the IFN-γ/IRF-1 pathway. Quantification of cytokine genes revealed increased liver expression of IL-17a, CXCL2, and IRF-1 messenger RNA during liver transplantation. Recombinant IL-23 treated hepatocytes, and NPC coculture led to IL-17, CXCL2, IFN-γ, and IRF-1 expression. With anti-IL-17 and anti-Ly6G antibody neutralization, neutrophil recruitment and IFN-γ production were decreased during warm I/R injury. Overexpression of IL-23 in vivo through use of an adenovirus vector also led to expression of IL-17, CXCL2, IFN-γ, and IRF-1. The increased expression of IL-23 also led to increased apoptosis in the liver. By neutralization of IL-23 through use of an anti-IL-23p19 antibody, we were able to attenuate liver damage in a wild-type but not a natural killer T (NKT) cell-deficient mouse. This suggests that IL-23 signaling shares a common pathway with NKT cells. In conclusion, IL-23 is induced early by I/R in the liver. Its signaling leads to activation of the IL-17/CXCL2 and IFN-γ/IRF-1 pathways, resulting in increased apoptosis and necrosis. [ABSTRACT FROM AUTHOR]