Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1.

Introduction: Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown. Methods: Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure. Results: We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1). Discussion: These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.

Roles of Interferon Regulatory Factor 1 in Tumor Progression and Regression: Two Sides of a Coin.

IRF1 is a transcription factor well known for its role in IFN signaling. Although IRF1 was initially identified for its involvement in inflammatory processes, there is now evidence that it provides a function in carcinogenesis as well. IRF1 has been shown to affect several important antitumor mechanisms, such as induction of apoptosis, cell cycle arrest, remodeling of tumor immune microenvironment, suppression of telomerase activity, suppression of angiogenesis and others. Nevertheless, the opposite effects of IRF1 on tumor growth have also been demonstrated. In particular, the "immune checkpoint" molecule PD-L1, which is responsible for tumor immune evasion, has IRF1 as a major transcriptional regulator. These and several other properties of IRF1, including its proposed association with response and resistance to immunotherapy and several chemotherapeutic drugs, make it a promising object for further research. Numerous mechanisms of IRF1 regulation in cancer have been identified, including genetic, epigenetic, transcriptional, post-transcriptional, and post-translational mechanisms, although their significance for tumor progression remains to be explored. This review will focus on the established tumor-suppressive and tumor-promoting functions of IRF1, as well as the molecular mechanisms of IRF1 regulation identified in various cancers.

GRP/GRPR enhances alcohol-associated liver injury through the IRF1-mediated Caspase-1 inflammasome and NOX2-dependent ROS pathway.

BACKGROUND AND AIMS: The common characteristics of alcohol-associated liver injury (ALI) include abnormal liver function, infiltration of inflammatory cells, and generation of oxidative stress. The gastrin-releasing peptide receptor (GRPR) is activated by its neuropeptide ligand, gastrin-releasing peptide (GRP). GRP/GRPR appears to induce the production of cytokines in immune cells and promotes neutrophil migration. However, the effects of GRP/GRPR in ALI are unknown. APPROACH AND RESULTS: We found high GRPR expression in the liver of patients with alcohol-associated steatohepatitis and increased pro-GRP levels in peripheral blood mononuclear cells of these patients compared with that of the control. Increased expression of GRP may be associated with histone H3 lysine 27 acetylation induced by alcohol, which promotes the expression of GRP and then GRPR binding. Grpr-/- and Grprflox/floxLysMCre mice alleviated ethanol-induced liver injury with relieved steatosis, lower serum alanine aminotransferase, aspartate aminotransferase, triglycerides, malondialdehyde, and superoxide dismutase levels, reduced neutrophil influx, and decreased expression and release of inflammatory cytokines and chemokines. Conversely, the overexpression of GRPR showed opposite effects. The pro-inflammatory and oxidative stress roles of GRPR might be dependent on IRF1-mediated Caspase-1 inflammasome and NOX2-dependent reactive oxygen species pathway, respectively. In addition, we verified the therapeutic and preventive effects of RH-1402, a novel GRPR antagonist, for ALI. CONCLUSIONS: A knockout or antagonist of GRPR during excess alcohol intake could have anti-inflammatory and antioxidative roles, as well as provide a platform for histone modification-based therapy for ALI.

Direct and biologically significant interactions of human herpesvirus 8 interferon regulatory factor 1 with STAT3 and Janus kinase TYK2.

Human herpesvirus 8 (HHV-8) encodes four viral interferon regulatory factors (vIRFs) that target cellular IRFs and/or other innate-immune and stress signaling regulators and suppress the cellular response to viral infection and replication. For vIRF-1, cellular protein targets include IRFs, p53, p53-activating ATM kinase, BH3-only proteins, and antiviral signaling effectors MAVS and STING; vIRF-1 inhibits each, with demonstrated or likely promotion of HHV-8 de novo infection and productive replication. Here, we identify direct interactions of vIRF-1 with STAT3 and STAT-activating Janus kinase TYK2 (the latter reported previously by us to be inhibited by vIRF-1) and suppression by vIRF-1 of cytokine-induced STAT3 activation. Suppression of active, phosphorylated STAT3 (pSTAT3) by vIRF-1 was evident in transfected cells and vIRF-1 ablation in lytically-reactivated recombinant-HHV-8-infected cells led to increased levels of pSTAT3. Using a panel of vIRF-1 deletion variants, regions of vIRF-1 required for interactions with STAT3 and TYK2 were identified, which enabled correlation of STAT3 signaling inhibition by vIRF-1 with TYK2 binding, independently of STAT3 interaction. A viral mutant expressing vIRF-1 deletion-variant Δ198-222 refractory for TYK2 interaction and pSTAT3 suppression was severely compromised for productive replication. Conversely, expression of phosphatase-resistant, protractedly-active STAT3 led to impaired HHV-8 replication. Cells infected with HHV-8 mutants expressing STAT3-refractory vIRF-1 deletion variants or depleted of STAT3 displayed reduced vIRF-1 expression, while custom-peptide-promoted STAT3 interaction could effect increased vIRF-1 expression and enhanced virus replication. Taken together, our data identify vIRF-1 targeting and inhibition of TYK2 as a mechanism of STAT3-signaling suppression and critical for HHV-8 productive replication, the importance of specific pSTAT3 levels for replication, positive roles of STAT3 and vIRF-1-STAT3 interaction in vIRF-1 expression, and significant contributions to lytic replication of STAT3 targeting by vIRF-1.

IRF1 regulates self-renewal and stress responsiveness to support hematopoietic stem cell maintenance.

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.

Quantifying dynamic pro-inflammatory gene expression and heterogeneity in single macrophage cells.

Macrophages must respond appropriately to pathogens and other pro-inflammatory stimuli in order to perform their roles in fighting infection. One way in which inflammatory stimuli can vary is in their dynamics-that is, the amplitude and duration of stimulus experienced by the cell. In this study, we performed long-term live cell imaging in a microfluidic device to investigate how the pro-inflammatory genes IRF1, CXCL10, and CXCL9 respond to dynamic interferon-gamma (IFNγ) stimulation. We found that IRF1 responds to low concentration or short duration IFNγ stimulation, whereas CXCL10 and CXCL9 require longer or higherconcentration stimulation to be expressed. We also investigated the heterogeneity in the expression of each gene and found that CXCL10 and CXCL9 have substantial cell-to-cell variability. In particular, the expression of CXCL10 appears to be largely stochastic with a subpopulation of nonresponding cells across all the stimulation conditions tested. We developed both deterministic and stochastic models for the expression of each gene. Our modeling analysis revealed that the heterogeneity in CXCL10 can be attributed to a slow chromatin-opening step that is on a similar timescale to that of adaptation of the upstream signal. In this way, CXCL10 expression in individual cells can remain stochastic in response to each pulse of repeated stimulation, which we also validated by experiments. Together, we conclude that pro-inflammatory genes in the same signaling pathway can respond to dynamic IFNγ stimulus with very different response features and that upstream signal adaptation can contribute to shaping heterogeneous gene expression.

RSV replication modifies the XBP1s binding complex on the IRF1 upstream enhancer to potentiate the mucosal anti-viral response.

Introduction: The unfolded protein response (UPR) has emerged as an important signaling pathway mediating anti-viral defenses to Respiratory Syncytial Virus (RSV) infection. Earlier we found that RSV replication predominantly activates the evolutionarily conserved Inositol Requiring Enzyme 1α (IRE1α)-X-Box Binding Protein 1 spliced (XBP1s) arm of the Unfolded Protein Response (UPR) producing inflammation, metabolic adaptation and cellular plasticity, yet the mechanisms how the UPR potentiates inflammation are not well understood. Methods: To understand this process better, we examined the genomic response integrating RNA-seq and Cleavage Under Targets and Release Using Nuclease (CUT&RUN) analyses. These data were integrated with an RNA-seq analysis conducted on RSV-infected small airway cells ± an IRE1α RNAse inhibitor. Results: We identified RSV induced expression changes in ~3.2K genes; of these, 279 required IRE1α and were enriched in IL-10/cytokine signaling pathways. From this data set, we identify those genes directly under XBP1s control by CUT&RUN. Although XBP1s binds to ~4.2 K high-confidence genomic binding sites, surprisingly only a small subset of IL10/cytokine signaling genes are directly bound. We further apply CUT&RUN to find that RSV infection enhances XBP1s loading on 786 genomic sites enriched in AP1/Fra-1, RELA and SP1 binding sites. These control a subset of cytokine regulatory factor genes including IFN response factor 1 (IRF1), CSF2, NFKB1A and DUSP10. Focusing on the downstream role of IRF1, selective knockdown (KD) and overexpression experiments demonstrate IRF1 induction controls type I and -III interferon (IFN) and IFN-stimulated gene (ISG) expression, demonstrating that ISG are indirectly regulated by XBP1 through IRF1 transactivation. Examining the mechanism of IRF1 activation, we observe that XBP1s directly binds a 5' enhancer sequence whose XBP1s loading is increased by RSV. The functional requirement for the enhancer is demonstrated by targeting a dCas9-KRAB silencer, reducing IRF1 activation. Chromatin immunoprecipitation shows that XBP1 is required, but not sufficient, for RSV-induced recruitment of activated phospho-Ser2 Pol II to the enhancer. Discussion: We conclude that XBP1s is a direct activator of a core subset of IFN and cytokine regulatory genes in response to RSV. Of these IRF1 is upstream of the type III IFN and ISG response. We find that RSV modulates the XBP1s binding complex on the IRF1 5' enhancer whose activation is required for IRF1 expression. These findings provide novel insight into how the IRE1α-XBP1s pathway potentiates airway mucosal anti-viral responses.

Immune regulator IRF1 contributes to ZBP1-, AIM2-, RIPK1-, and NLRP12-PANoptosome activation and inflammatory cell death (PANoptosis).

The innate immune system provides the first line of defense against pathogens and cellular insults and is activated by pattern recognition receptors sensing pathogen- or damage-associated molecular patterns. This activation can result in inflammation via cytokine release as well as the induction of lytic regulated cell death (RCD). Innate immune signaling can also induce the expression of interferon regulatory factor 1 (IRF1), an important molecule in regulating downstream inflammation and cell death. While IRF1 has been shown to modulate some RCD pathways, a comprehensive evaluation of its role in inflammatory cell death pathways is lacking. Here, we examined the role of IRF1 in cell death during inflammasome and PANoptosome activation using live cell imaging, Western blotting, and ELISA in primary murine macrophages. IRF1 contributed to the induction of ZBP1- (Z-DNA binding protein 1), AIM2- (absent in melanoma-2), RIPK1- (receptor interacting protein kinase 1), and NLRP12 (NOD-like receptor family, pyrin domain-containing 12)-PANoptosome activation and PANoptosis. Furthermore, IRF1 regulated the cell death under conditions where inflammasomes, along with caspase-8 and RIPK3, act as integral components of PANoptosomes to drive PANoptosis. However, it was dispensable for other inflammasomes that form independent of the PANoptosome to drive pyroptosis. Overall, these findings define IRF1 as an upstream regulator of PANoptosis and suggest that modulating the activation of molecules in the IRF1 pathway could be used as a strategy to treat inflammatory and infectious diseases associated with aberrant inflammatory cell death.

Ginsenoside Rh2 promotes hepatic stellate cell ferroptosis and inactivation via regulation of IRF1-inhibited SLC7A11.

BACKGROUND: Sustained liver fibrosis may lead to cirrhosis. Activated hepatic stellate cells (HSCs) are crucial for liver fibrosis development. Ferroptosis, a newly iron-dependent regulated cell death, has been demonstrated to be involved in HSC inactivation. PURPOSE: Ginsenoside Rh2 (GRh2), a natural bioactive product derived from ginseng, has been shown to promote HSC inactivation. However, the effect of GRh2 on HSC ferroptosis remains unclear. METHODS: We explored the effects of GRh2 on liver fibrosis in vivo and in vitro. RNA-sequence analysis was performed in HSCs after GRh2 treatment. The crosstalk between ferroptotic HSCs and macrophages was also explored. RESULTS: GRh2 alleviated liver fibrosis in vivo. In vitro, GRh2 reduced HSC proliferation and activation via ferroptosis, with increased intracellular iron, reactive oxygen species, malondialdehyde and glutathione depletion. The expression of SLC7A11, a negative regulator of ferroptosis, was obviously reduced by GRh2. Interestingly, interferon regulatory factor 1 (IRF1), a transcription factor, was predicted to bind the promoter region of SCL7A11. The interaction between IRF1 and SCL7A11 was further confirmed by the results of chromatin immunoprecipitation and luciferase reporter assays. Furthermore, loss of IRF1 led to an increase in SCL7A11, which contributed to the suppression of HSC ferroptosis and the enhancement of HSC activation in GRh2-treated HSCs. Further studies revealed that GRh2-induced HSC ferroptosis contributed to the inhibition of macrophage recruitment via regulation of inflammation-related genes. Moreover, GRh2 caused a reduction in liver inflammation in vivo. CONCLUSION: Collectively, GRh2 up-regulates IRF1 expression, resulting in the suppression of SLC7A11, which contributes to HSC ferroptosis and inactivation. GRh2 ameliorates liver fibrosis through enhancing HSC ferroptosis and inhibiting liver inflammation. GRh2 may be a promising drug for treating liver fibrosis.

Immune evasion strategy involving propionylation by the KSHV interferon regulatory factor 1 (vIRF1).

Post-translational modifications (PTMs) are essential for host antiviral immune response and viral immune evasion. Among a set of novel acylations, lysine propionylation (Kpr) has been detected in both histone and non-histone proteins. However, whether protein propionylation occurs in any viral proteins and whether such modifications regulate viral immune evasion remain elusive. Here, we show that Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded viral interferon regulatory factor 1 (vIRF1) can be propionylated in lysine residues, which is required for effective inhibition of IFN-ß production and antiviral signaling. Mechanistically, vIRF1 promotes its own propionylation by blocking SIRT6's interaction with ubiquitin-specific peptidase 10 (USP10) leading to its degradation via a ubiquitin-proteasome pathway. Furthermore, vIRF1 propionylation is required for its function to block IRF3-CBP/p300 recruitment and repress the STING DNA sensing pathway. A SIRT6-specific activator, UBCS039, rescues propionylated vIRF1-mediated repression of IFN-ß signaling. These results reveal a novel mechanism of viral evasion of innate immunity through propionylation of a viral protein. The findings suggest that enzymes involved in viral propionylation could be potential targets for preventing viral infections.

Exosomal IRF1-loaded rat adipose-derived stem cell sheet contributes to wound healing in the diabetic foot ulcers.

BACKGROUND: Cell-based therapy has been recognized as a novel technique for the management of diabetic foot ulcers, and cell-sheet engineering leads to improved efficacy in cell transplantation. This study aims to explore the possible molecular mechanism of the rat adipose-derived stem cell (ASC) sheet loaded with exosomal interferon regulatory factor 1 (IRF1) in foot wound healing. METHODS: Rats were rendered diabetic with streptozotocin, followed by measurement of miR-16-5p expression in wound tissues. Relationship between IRF1, microRNA (miR)-16-5p, and trans-acting transcription factor 5 (SP5) was analyzed using luciferase activity, RNA pull-down, and chromatin immunoprecipitation assays. IRF1 was overexpressed in rat ASCs (rASCs) or loaded onto the rASC sheet, and then exosomes were extracted from rASCs. Accordingly, we assessed the effects of IRF1-exosome or IRF1-rASC sheet on the proliferation and migration of the fibroblasts along with endothelial cell angiogenesis. RESULTS: miR-16-5p was poorly expressed in the wound tissues of diabetic rats. Overexpression of miR-16-5p promoted fibroblast proliferation and migration as well as endothelial cell angiogenesis, thus expediting wound healing. IRF1 was an upstream transcription factor that could bind to the miR-16-5p promoter and increase its expression. In addition, SP5 was a downstream target gene of miR-16-5p. IRF1-exosome from rASCs or the IRF1-rASC sheet facilitated the foot wound healing in diabetic rats through miR-16-5p-dependent inhibition of SP5. CONCLUSION: The present study demonstrates that exosomal IRF1-loaded rASC sheet regulates miR-16-5p/SP5 axis to facilitate wound healing in diabetic rats, which aids in development of stem cell-based therapeutic strategies for diabetic foot wounds.

M1 Microglia-derived Exosomes Promote Activation of Resting Microglia and Amplifies Proangiogenic Effects through Irf1/miR-155-5p/Socs1 Axis in the Retina.

Activation of microglia plays a key role in the development of neovascular retinal diseases. Therefore, it is essential to reveal its pathophysiological and molecular mechanisms to interfere with disease progression. Here a publicly available single-cell RNA sequencing dataset is used to identify that intercellular communications from M1 microglia toward M0 microglia are increased in the retinal angiogenesis model via exosomes. Moreover, the results both in vitro and in vivo demonstrate that M1 microglia-derived exosomes promote the activation and enhance the proangiogenic ability of resting microglia. Based on miRNA sequencing of exosomes combined with gene interference, further results show that activated microglia-derived exosomes promoted microglial activation by transmitting polarized signals to M0 microglia via miR-155-5p. Subsequently, miR-155-5p suppresses Socs1 and activates the NFκB pathway, which ultimately causes the inflammatory cascade and amplifies the proangiogenic effect. In addition, upregulated Irf1 drives the expression of miR-155-5p in activated microglia, thus leading to an increase in the tendency of miR-155-5p to be encapsulated by exosomes. Thus, this study elucidates the critical role of intercellular communication among various types of microglia in the complex retinal microenvironment during angiogenesis, and contributes to the novel, targeted, and potential therapeutic strategies for clinical retinal neovascularization.

Triptolide reduces PD-L1 through the EGFR and IFN-γ/IRF1 dual signaling pathways.

As the principal ligand of programmed death 1 (PD-1), PD-L1 can induce the exhaustion of effector T cells and the escape of cancer cells through interacting with PD-1 in many solid malignancies. Therefore, targeting the PD-1/PD-L1 axis has become an attractive strategy in cancer immunotherapy. However, at present, no small-molecule agents targeting PD1/PD-L1 pathways have been successfully used in clinical applications. Here, we first found that the natural product Triptolide could significantly reduce the PD-L1 expression on the surface of NSCLC cells. This down-regulation is related to the activity of EGFR signaling pathway. Moreover, the reduction of PD-L1 caused by Triptolide could be substantially rescued by IFN-γ. Furthermore, our findings suggest that Triptolide significantly inhibits the activity of the IFN-γ-JAK-STAT-IRF1 signaling axis, as evidenced by the noticeable reduction in both basal and phosphorylated levels of STAT3. Thus, in NSCLC cells, Triptolide reduces PD-L1 expression both through the EGFR and IFN-γ/JAK1/JAK2/STAT1/STAT3/IRF1 signaling pathways. The results provide new insights into the application of Triptolide in the immune checkpoints treatment of NSCLCs.

IRF1 promotes the chondrogenesis of human adipose-derived stem cells through regulating HILPDA.

BACKGROUND: Osteoarthritis is a main cause of deformity in aging people. The chondrogenesis of human adipose-derived stem cells (hADSCs) has a positive effect on the cure of osteoarthritis. However, the regulatory mechanism of hADSC chondrogenesis still needs further exploration. This research investigates the role of interferon regulatory factor 1 (IRF1) in the chondrogenesis of hADSCs. METHODS: hADSCs were purchased and cultured. The interaction between IRF1 and hypoxia inducible lipid droplet associated (HILPDA) was predicted by bioinformatics analysis, and verified through dual-luciferase reporter and chromatin immunoprecipitation assays. The expressions of IRF1 and HILPDA in osteoarthritis cartilage samples were measured through qRT-PCR. After hADSCs were transfected or further induced for chondrogenesis, the chondrogenesis was visualized by Alcian blue staining, and the expressions of IRF1, HILPDA and chondrogenesis-related factors (SOX9, Aggrecan, COL2A1, MMP13, MMP3) were determined through qRT-PCR or Western blot. RESULTS: HILPDA bound to IRF1 in hADSCs. IRF1 and HILPDA levels were up-regulated during the chondrogenesis of hADSCs. Overexpressions of IRF1 and HILPDA promoted the chondrogenesis of hADSCs with the up-regulation of SOX9, Aggrecan and COL2A1 and the down-regulation of MMP13 and MMP3; however, IRF1 silencing generated the opposite effects. Besides, HILPDA overexpression reversed the effects of IRF1 silencing on inhibiting chondrogenesis of hADSCs and regulating the expressions of chondrogenesis-related factors. CONCLUSION: IRF1 promotes the chondrogenesis of hADSCs through up-regulating HILPDA level, providing novel biomarkers for treating osteoarthritis.

SUMOylated IL-33 in the nucleus stabilizes the transcription factor IRF1 in hepatocellular carcinoma cells to promote immune escape.

Interleukin-33 (IL-33) functions both as a secreted cytokine and as a nuclear factor, with pleiotropic roles in cancer and immunity. Here, we explored its role in hepatocellular carcinoma (HCC) and identified that a posttranslational modification altered its nuclear activity and promoted immune escape for HCC. IL-33 abundance was overall decreased but more frequently localized to the nucleus in patient HCC tissues than in normal liver tissues. In human and mouse HCC cells in culture and in vivo, IL-33 overexpression inhibited proliferation and repressed the abundance of programmed death ligand 1 (PD-L1) at the transcriptional level by promoting the ubiquitin-dependent degradation of interferon regulatory factor 1 (IRF1). However, this interaction was disrupted by SUMOylation of IL-33 at Lys54 mediated by the E3 ligase RanBP2. IL-33 SUMOylation correlated with its nuclear localization in HCC cells and tumors. An increase in SUMOylated IL-33 in HCC cells in cocultures and in vivo stabilized IRF1 and increased PD-L1 abundance and chemokine IL-8 secretion, which prevented the activation of cytotoxic T cells and promoted the M2 polarization of macrophages, respectively. Mutating the SUMOylation site in IL-33 reversed these effects and suppressed tumor growth. These findings indicate that SUMOylation of nuclear IL-33 in HCC cells impairs antitumor immunity.

FOXP1 inhibits pancreatic cancer growth by transcriptionally regulating IRF1 expression.

FOXP1, known as a Forkhead-box (FOX) family protein, plays an important role in human tumorigenesis. However, the function and molecular mechanism of FOXP1 in pancreatic cancer (PC) remain unclear. Here, we report that PC patients with FOXP1 overexpression had a higher survival rate compared to patients with low- FOXP1 expression. Additionally, high expression of FOXP1 can markedly inhibit the growth of pancreatic cancer in vivo and in vitro, whereas low expression of FOXP1 effectively promoted the tumorigenesis. Mechanistically, FOXP1 could directly bind the IRF1 promoter, which triggered the transcriptional activity of IRF1. Taken together, FOXP1 suppressed PC growth via IRF1-dependent manner, serving as a potential prognostic biomarker for patients with PC.

Interferon-α2a induces CD4+ T cell apoptosis and suppresses Th1/Th17 responses via upregulating IRF1-mediated PDL1 expression in dendritic cells from Behcet's uveitis.

Recombinant interferon-α2a (IFNα2a) has been widely used in the treatment of Behcet's uveitis (BU). However, the mechanism underlying its effects remains poorly understood. In this study, we investigated its effect on dendritic cells (DCs) and CD4+ T cells, which are essential for the development of BU. Our results showed that the expression of PDL1 and IRF1 was significantly decreased in DCs from active BU patients, and IFNα2a could significantly upregulate PDL1 expression in an IRF1-dependent manner. IFNα2a-treated DCs induced CD4+ T cells apoptosis and inhibited the Th1/Th17 immune response in association with reduced secretion of IFN-γ and IL-17. We also found that IFNα2a promoted Th1 cell differentiation and IL-10 secretion by CD4+ T cells. Finally, a comparison of patients before and after IFNα2a therapy revealed that the frequencies of Th1/Th17 cells significantly decreased in association with remission of uveitis after IFNα2a therapy. Collectively, these results show that IFNα2a could exert its effects by modulating the function of DCs and CD4+ T cells in BU.

Disrupting the phase separation of KAT8-IRF1 diminishes PD-L1 expression and promotes antitumor immunity.

Immunotherapies targeting the PD-1/PD-L1 axis have become first-line treatments in multiple cancers. However, only a limited subset of individuals achieves durable benefits because of the elusive mechanisms regulating PD-1/PD-L1. Here, we report that in cells exposed to interferon-γ (IFNγ), KAT8 undergoes phase separation with induced IRF1 and forms biomolecular condensates to upregulate PD-L1. Multivalency from both the specific and promiscuous interactions between IRF1 and KAT8 is required for condensate formation. KAT8-IRF1 condensation promotes IRF1 K78 acetylation and binding to the CD247 (PD-L1) promoter and further enriches the transcription apparatus to promote transcription of PD-L1 mRNA. Based on the mechanism of KAT8-IRF1 condensate formation, we identified the 2142-R8 blocking peptide, which disrupts KAT8-IRF1 condensate formation and consequently inhibits PD-L1 expression and enhances antitumor immunity in vitro and in vivo. Our findings reveal a key role of KAT8-IRF1 condensates in PD-L1 regulation and provide a competitive peptide to enhance antitumor immune responses.

Relief of Extracellular Matrix Deposition Repression by Downregulation of IRF1-Mediated TWEAK/Fn14 Signaling in Keloids.

Keloids represent a fibrotic disorder characterized by the excessive deposition of extracellular matrix (ECM). However, the mechanisms through which ECM deposition in keloids is regulated remain elusive. In this study, we found that the expression of both TWEAK and its cognate receptor Fn14 was significantly downregulated in keloids and that TWEAK/Fn14 signaling repressed the expression of ECM-related genes in keloid fibroblasts. The IRF1 gene was essential for this repression, and the TWEAK/Fn14 downstream transcription factor p65 directly bound to the promoter of the IRF1 gene and induced its expression. Furthermore, in patients with keloid, the expression of TWEAK and Fn14 was negatively correlated with that of ECM genes and positively correlated with that of IRF1. These observations indicate that relief of TWEAK/Fn14/IRF1-mediated ECM deposition repression contributes to keloid pathogenesis, and the identified mechanism and related molecules provide potential targets for keloid treatment in the future.

Interferon regulatory factor 1 (IRF1) controls the metabolic programmes of low-grade pancreatic cancer cells.

OBJECTIVE: Pancreatic ductal adenocarcinomas (PDACs) include heterogeneous mixtures of low-grade cells forming pseudoglandular structures and compact nests of high-grade cells organised in non-glandular patterns. We previously reported that low-grade PDAC cells display high expression of interferon regulatory factor 1 (IRF1), a pivotal transcription factor of the interferon (IFN) system, suggesting grade-specific, cell-intrinsic activation of IFN responses. Here, we set out to determine the molecular bases and the functional impact of the activation of IFN-regulated responses in human PDACs. DESIGN: We first confirmed the correlation between glandular differentiation and molecular subtypes of PDAC on the one hand, and the expression of IRF1 and IFN-stimulated genes on the other. We next used unbiased omics approaches to systematically analyse basal and IFN-regulated responses in low-grade and high-grade PDAC cells, as well as the impact of IRF1 on gene expression programmes and metabolic profiles of PDAC cells. RESULTS: High-level expression of IRF1 in low-grade PDAC cells was controlled by endodermal lineage-determining transcription factors. IRF1-regulated gene expression equipped low-grade PDAC cells with distinctive properties related to antigen presentation and processing as well as responsiveness to IFN stimulation. Notably, IRF1 also controlled the characteristic metabolic profile of low-grade PDAC cells, suppressing both mitochondrial respiration and fatty acid synthesis, which may in part explain its growth-inhibiting activity. CONCLUSION: IRF1 links endodermal differentiation to the expression of genes controlling antigen presentation and processing as well as to the specification of the metabolic profile characteristic of classical PDAC cells.