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Deeply understanding virus-host interactions is a prerequisite for developing effective strategies to control frequently emerging infectious diseases, which have become a serious challenge for global public health. The type I interferon (IFN)-mediated JAK/STAT pathway is well known for playing an essential role in host antiviral immunity, but the exact regulatory mechanisms of various IFN-stimulated genes (ISGs) are not yet fully understood. We herein reported that SerpinA5, as a novel ISG, played a previously unrecognized role in antiviral activity. Mechanistically, SerpinA5 can upregulate the phosphorylation of STAT1 and promote its nuclear translocation, thus effectively activating the transcription of IFN-related signaling pathways to impair viral infections. Our data provide insights into SerpinA5-mediated innate immune signaling during virus-host interactions.

Inherited autosomal dominant gain-of-function (GOF) mutations of signal transducer and activator of transcription 1 (STAT1) cause a wide range of symptoms affecting multiple systems, including chronic mucocutaneous candidiasis (CMC), infections, and autoimmune disorders. We describe a rare case of STAT1 mutation with recurrent CMC, lung infections, and anemia. According to the whole-exome sequencing (WES), the patient was genetically mutated in STAT1 GOF (c.854A>G, p.Q285R), and bone marrow biopsy suggested pure red cell aplasia (PRCA). As a functional verification, STAT1 levels and phosphorylation (p-STAT1) of peripheral blood mononuclear cells (PBMCs) following IFN-γ stimulation in STAT1 GOF patient was higher than in the healthy control. Combination therapy of blood transfusion, antimicrobials, intravenous immunoglobulin, methylprednisolone, and the Janus Kinase (JAK) specific inhibitor ruxolitinib was used during treatment of patients. The patient also received a hematopoietic stem cell transplant (HSCT) to help with infections and anemia. This is the first reported case of STAT1 GOF disease complicated with PRCA. This complication might be attributed to immune disorders caused by STAT1 GOF. Furthermore, ruxolitinib may be a viable therapeutic option before HSCT to improve disease management.

PLA2G16 is a member of the phospholipase A2 family that catalyzes the generation of lysophosphatidic acids (LPAs) and free fatty acids (FFAs) from phosphatidic acid. Previously, PLA2G16 was found to be a host factor for picornaviruses. Here, we discovered that the Foot-and-Mouth Disease Virus (FMDV) infection led to an elevation in PLA2G16 transcription. We established PLA2G16 overexpression and knockdown cell lines in PK-15 cells to investigate the potential role of PLA2G16 in FMDV infection. Our findings revealed that during FMDV infection, PLA2G16-overexpressing cells had increased levels of phosphorylated STAT1 and the interferon-stimulating factors ISG15 and ISG56. In PLA2G16-overexpressing cells, p-STAT1 was observed at higher levels and earlier than in wild-type cells. Subsequent research demonstrated that PLA2G16 specifically promoted an antiviral innate immune response against FMDV. The host could detect the early release of FMDV viral nucleic acid in PLA2G16-overexpressing cells and trigger the interferon signaling pathway. Additionally, we discovered that the supernatants of PLA2G16-overexpressing cells stimulated the production of higher levels of ISG56 and phosphorylated STAT1. This suggests that PLA2G16-overexpressing cells can activate the innate immune pathway of uninfected cells after FMDV infection.

Objective: The Chinese medicine Jianpi-Huayu decoction (健脾化瘀方, JPHY) can alleviate cancer-related fatigue in patients with liver cancer. However, its mechanism remains unclear. In this study, we used BALB/c mice with liver cancer model to investigate whether JPHY alleviates cancer-related fatigue by regulating Th1/Th2 immune balance; and the possible association with the IL-27/STAT1 signaling pathway. Methods: We established a mouse model of liver cancer fatigue. Mice were gavaged with physiological saline, low, medium, or high concentrations of JPHY respectively; and intraperitoneal injection of fludarabine (STAT1 pathway inhibitor) with JPHY for 21 days. We recorded the general condition of the mice, and assessed fatigue using scoring criteria and Exhausted Swimming Test. We calculated the spleen and thymus indices, performed H&E staining and immunohistochemical analysis on liver tumor tissues to observe the tumor proliferation marker ki67. We quantified the secretion levels of IFN-γ and IL-2 produced by Th1 cells in serum and splenic lymphocytes, as well as the secretion of IL-4, IL-10 by Th2 cells, and IL-27 in the signaling pathway through ELISA analysis. We evaluated the expression levels of p-STAT1 and STAT1 in spleen tissues using Western blot analysis. Results: JPHY exhibits a therapeutic effect on hepatocellular carcinoma-induced splenomegaly in murine models by upregulating the pro-inflammatory cytokines IFN-γ and IL-2 and downregulating the anti-inflammatory cytokines IL-4 and IL-10. Moreover, JPHY suppresses ki67 expression, reduces tumor-related inflammation infiltration, and ameliorates cancer-associated fatigue. Additionally, the expression of phosphorylated protein p-STAT1 is down-regulated. Conclusion: JPHY may improve the Th1/Th2 immune balance through its anti-inflammatory effects and promotion of IL-27-induced STAT1 phosphorylation, thereby alleviating fatigue in mice with liver cancer.

This study aimed to evaluate the therapeutic effects of Ruxolitinib, a JAK1/2 inhibitor, on DSS-induced acute colitis in mice, with a focus on its impact on disease activity, inflammatory responses, modulation of myeloid-derived suppressor cells (MDSCs), and regulation of the JAK/STAT1 signaling pathway. Acute UC was induced in C57BL/6 mice by administering a 2.5% DSS solution. Mice were randomly assigned to three groups: the blank group (no DSS), the model group (DSS only), and the Ruxolitinib-treated group (DSS +30 mg/kg Ruxolitinib by gavage for 14 consecutive days). Body weight, disease activity index (DAI) scores, spleen weight, and colon length were measured. Spleen index and the spleen weight-to-colon length ratio were calculated. Flow cytometry was used to assess the proportion of MDSCs in the blood. , CCD841 and Jurkat cells were pretreated with 50 IU/mL IFN-γ for 2 h, followed by 24-h treatment with Ruxolitinib. PCR array analysis was performed to identify transcriptional changes in JAK-STAT pathway-related genes. Electrophoretic mobility shift assay (EMSA) and Western blot were used to investigate the inhibition of STAT1 activation and phosphorylation. , DSS-induced acute colitis in the model group, and Ruxolitinib treatment significantly alleviated colitis as evidenced by reduced body weight loss (p < 0.05), decreased DAI scores in the later stages (p < 0.05), a lower spleen index (p < 0.05), increased colon length (p < 0.01), and a reduced spleen weight-to-colon length ratio (p < 0.05). Flow cytometry revealed a significant reduction in the proportion of CD11b Gr-1 MDSCs in the blood of the Ruxolitinib group compared to the model group (p < 0.01). , PCR array analysis showed that Ruxolitinib notably downregulated the transcription of several JAK-STAT pathway-related genes, including B2M, IRF1, RQ1, SOCS1, STAT1, and STAT3, with STAT1 showing the most pronounced changes. EMSA and Western blot analysis confirmed that Ruxolitinib effectively inhibited IFN-γ-induced STAT1 activation and phosphorylation in a dose-dependent manner. Ruxolitinib effectively ameliorated DSS-induced acute colitis by reducing inflammation, modulating MDSC levels, and inhibiting STAT1 activation. These findings suggest that Ruxolitinib could be a promising therapeutic agent for UC, targeting both the immune response and the JAK/STAT1 signaling pathway.

Sepsis is a complex, multifactorial syndrome characterized by a dysregulated host response to infection, leading to severe organ dysfunction and high mortality rates among critically ill patients. Hypovitaminosis C and vitamin C deficiency are frequently observed in septic patients, prompting interest in the potential therapeutic role of ascorbic acid. Although intravenous administration of ascorbic acid has been investigated in multiple clinical trials for sepsis treatment, the specific immunomodulatory mechanisms underlying its effects remain elusive. This study aimed to investigate the protective effects of high-dose ascorbic acid on experimental sepsis. Results show that intravenous administration of high-dose ascorbic acid (250 mg/kg) attenuated sepsis-induced organ dysfunctions in a cecal ligation and puncture (CLP)-induced septic mouse model. Ascorbic acid improved splenic cell apoptosis and increased the number of CD3 + T cells in septic mice induced by CLP. Furthermore, ascorbic acid downregulated PD-L1 expression in livers, reduced PD-1 expression in spleens, and inhibited the phosphorylation of STAT1 at Y701 in multiple organs of CLP-induced septic mice. The in vitro experiments also revealed that 800 μM ascorbic acid suppressed STAT1 phosphorylation and inhibited lipopolysaccharide (LPS) and IFN-γ-induced PD-L1 expression in macrophages. These findings suggest that ascorbic acid prevents sepsis-associated organ dysfunction through the p-STAT1/PD-L1 signaling pathway. Our study provides new insights into the potential therapeutic use of ascorbic acid in sepsis. Graphical abstract

Background Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory disease of unknown cause, predominantly affecting teens and young adults. The early diagnosis and management are challenging due to the lack of reliable diagnostic markers and the occasional intractable cases despite conventional anti-inflammatory treatments. Janus kinase (JAK) inhibitors have recently shown potential utility; however, reports on their use for pediatric patients with CNO remain limited, and no established biomarkers exist to monitor disease activity. We aimed to investigate the pathophysiology of CNO and explore the rapid testing methods for accurate diagnosis and also assessing the disease activity. Methods We assessed intracellular phosphorylation of signal transducer and activator of transcription 1 (pSTAT1) in peripheral blood monocytes or T cells following interferon-gamma (IFNγ) stimulation, using flow cytometry in 9 patients under 15 years old with CNO. The pSTAT1 expression levels were compared with those in patients with STAT1-gain of function (STAT1-GOF) mutations (n = 5), other autoinflammatory diseases (n = 7), and healthy controls. Clinical and immunological data were monitored in 4 patients with intractable CNO treated with adjunctive JAK inhibitors, focusing on scoring scales, imaging data, lymphocyte subsets, cytokine profiles, and pSTAT1 levels. Results Monocyte pSTAT1 expression after IFNγ stimulation was elevated at diagnosis or during active CNO, similar to levels observed in STAT1-GOF cases. The pSTAT1 levels in CNO patients were significantly higher than those in other autoinflammatory diseases ( p  = 0.024) or controls ( p  < 0.001). Notably, pSTAT1 levels in CNO monocytes fluctuated with disease activity, decreasing in 5 patients during clinical remission following conventional therapies ( p  = 0.016). In four intractable cases, pSTAT1 levels remained high despite conventional treatments but significantly decreased after initiating JAK inhibitors ( p  = 0.036). This reduction correlated with improved patient pain visual analog scale ( p  = 0.008), CNO clinical disease activity score ( p  = 0.029), and better bone and joint imaging, though cytokine levels remained unchanged. Conclusions The monocyte pSTAT1 levels after IFNγ stimulation reflect the activity of CNO, indicating the diagnostic utility as well as the monitoring effect of disease control. Adjunctive JAK inhibitors successfully controlled inflammation in treatment-resistant cases. Rapid pSTAT1 testing may help reduce osteo-articular complications, although the long-term adverse effects and resistance should be further investigated.

MX2 is an interferon inducible gene that is mostly known for its antiviral activity. We have previously demonstrated that MX2 is also associated with the tumorigenesis process in melanoma. However, it remains unknown which molecular mechanisms are regulated by MX2 in response to interferon signaling in this disease. Here, we report that MX2 is necessary for the establishment of an interferon‐induced transcriptional profile partially through regulation of STAT1 phosphorylation and other interferon‐related downstream factors, including proapoptotic tumor suppressor XAF1. MX2 and XAF1 expression tightly correlate in both cultured melanoma cell lines and in patient‐derived primary and metastatic tumors, where they also are significantly related with survival. MX2 mediates IFN growth‐inhibitory signals in both XAF1 dependent and independent ways and in a cell type and context‐dependent manner. Higher MX2 expression renders melanoma cells more sensitive to targeted therapy drugs such as vemurafenib and trametinib; however, this effect is XAF1 independent. In summary, we uncovered a new mechanism in the complex regulation of interferon signaling in melanoma that can influence both survival and response to therapy. MX2 upregulation establishes an interferon‐induced transcriptional profile in melanoma cells. MX2 regulates tumor suppressor XAF1 and sensitizes melanoma cells to targeted therapy drugs such as vemurafenib and trametinib.

CDK8/19 kinases, which mediate transcriptional reprogramming, have become an active target for cancer drug discovery. Several small-molecule CDK8/19 inhibitors showed in vivo efficacy and two have entered clinical trials, with no significant toxicities reported. However, Clarke et al. (eLife 2016; 5; e20722) found severe systemic toxicity associated with two potent CDK8/19 inhibitors, Cmpd3 (CCT251921) and Cmpd4 (MSC2530818), and suggested that their toxicity was due to on-target effects. Here, we compared five CDK8/19 inhibitors: Cmpd3, Cmpd4, Senexin B, 16-didehydro-cortistatin A (dCA) and 15w, in different assays. Only Cmpd4 showed striking toxicity in developing zebrafish. In cell-based assays for CDK8 and CDK19 inhibition, Cmpd3, Cmpd4, dCA and 15w showed similar low-nanomolar potency and efficacy against CDK8 and CDK19, while Senexin B was less potent. Only dCA produced sustained inhibition of CDK8/19-dependent gene expression. While toxicity of different compounds did not correlate with their effects on CDK8 and CDK19, kinome profiling identified several off-target kinases for both Cmpd3 and Cmpd4, which could be responsible for their toxicity. Off-target activities could have been achieved in the study of Clarke et al. due to high in vivo doses of Cmpd3 and Cmpd4, chosen for the ability to inhibit STAT1 S727 phosphorylation in tumor xenografts. We show here that STAT1 S727 phosphorylation is induced by various cytokines and stress stimuli in CDK8/19-independent manner, indicating that it is not a reliable pharmacodynamic marker of CDK8/19 activity. These results illustrate the need for careful off-target analysis and dose selection in the development of CDK8/19 inhibitors.

The evasion of the Interferon response has important implications in Zika virus (ZIKV) disease. Mutations in ZIKV viral protein NS4B, associated with modulation of the interferon (IFN) system, have been linked to increased pathogenicity in animal models. In this study, we unravel ZIKV NS4B as antagonist of the IFN signaling cascade. Firstly, we reported the genomic characterization of NS4B isolated from a strain of the 2016 outbreak, ZIKV Brazil/2016/INMI1, and we predicted its membrane topology. Secondly, we analyzed its phylogenetic correlation with other flaviviruses, finding a high similarity with dengue virus 2 (DEN2) strains; in particular, the highest conservation was found when NS4B was aligned with the IFN inhibitory domain of DEN2 NS4B. Hence, we asked whether ZIKV NS4B was also able to inhibit the IFN signaling cascade, as reported for DEN2 NS4B. Our results showed that ZIKV NS4B was able to strongly inhibit the IFN stimulated response element and the IFN-γ-activated site transcription, blocking IFN-I/-II responses. mRNA expression levels of the IFN stimulated genes ISG15 and OAS1 were also strongly reduced in presence of NS4B. We found that the viral protein was acting by suppressing the STAT1 phosphorylation and consequently blocking the nuclear transport of both STAT1 and STAT2.