Type I IFN induced IL1-Ra expression in hepatocytes is mediated by activating STAT6 through the formation of STAT2: STAT6 heterodimer

Proximal protein landscapes of the type I interferon signaling cascade reveal negative regulation by PJA2

Deciphering the intricate dynamic events governing type I interferon (IFN) signaling is critical to unravel key regulatory mechanisms in host antiviral defense. Here, we leverage TurboID-based proximity labeling coupled with affinity purification-mass spectrometry to comprehensively map the proximal human proteomes of all seven canonical type I IFN signaling cascade members under basal and IFN-stimulated conditions. This uncovers a network of 103 high-confidence proteins in close proximity to the core members IFNAR1, IFNAR2, JAK1, TYK2, STAT1, STAT2, and IRF9, and validates several known constitutive protein assemblies, while also revealing novel stimulus-dependent and -independent associations between key signaling molecules. Functional screening further identifies PJA2 as a negative regulator of IFN signaling via its E3 ubiquitin ligase activity. Mechanistically, PJA2 interacts with TYK2 and JAK1, promotes their non-degradative ubiquitination, and limits the activating phosphorylation of TYK2 thereby restraining downstream STAT signaling. Our high-resolution proximal protein landscapes provide global insights into the type I IFN signaling network, and serve as a valuable resource for future exploration of its functional complexities.

Characterization of fish-specific IFNγ-related binding with a unique receptor complex and signaling through a novel pathway

Unlike mammals, fish express two type II interferons, IFNγ and fish-specific IFNγ (IFNγ-related or IFNγrel). We previously reported the presence of two IFNγrel genes, IFNγrel 1 and IFNγrel 2, which exhibit potent antiviral activity in the Ginbuna crucian carp, Carassius auratus langsdorfii. We also found that IFNγrel 1 increased allograft rejection; however, the IFNγrel 1 receptor(s) and signaling pathways underlying this process have not yet been elucidated. In this study, we examined the unique signaling mechanism of IFNγrel 1 and its receptors. The phosphorylation and transcriptional activation of STAT6 in response to recombinant Ginbuna IFNγrel 1 (rgIFNγrel 1) was observed in Ginbuna-derived cells. Binding of rgIFNγrel 1 to Class II cytokine receptor family members (Crfbs), Crfb5 and Crfb17, which are also known as IFNAR1 and IFNGR1-1, respectively, was detected by flow cytometry. Expression of the IFNγrel 1-inducible antiviral gene, Isg15, was highest in Crfb5- and Crfb17-overexpressing GTS9 cells. Dimerization of Crfb5 and Crfb17 was detected by chemical crosslinking. The results indicate that IFNγrel 1 activates Stat6 through an interaction with unique pairs of receptors, Crfb5 and Crfb17. Indeed, this cascade is distinct from not only that of IFNγ but also that of known IFNs in other vertebrates. IFNs may be classified by their receptor and signal transduction pathways. Taken together, IFNγrel 1 may be classified as a novel type of IFN family member in vertebrates. Our findings provide important information on interferon gene evolution in bony fish.

Transcription factor signal transducer and activator of transcription 6 (STAT6) is an inhibitory factor for adult myogenesis

Background

The signal transducer and activator of transcription 6 (STAT6) transcription factor plays a vitally important role in immune cells, where it is activated mainly by interleukin-4 (IL-4). Because IL-4 is an essential cytokine for myotube formation, STAT6 might also be involved in myogenesis as part of IL-4 signaling. This study was conducted to elucidate the role of STAT6 in adult myogenesis in vitro and in vivo.

Methods

Myoblasts were isolated from male mice and were differentiated on a culture dish to evaluate the change in STAT6 during myotube formation. Then, the effects of STAT6 overexpression and inhibition on proliferation, differentiation, and fusion in those cells were studied. Additionally, to elucidate the myogenic role of STAT6 in vivo, muscle regeneration after injury was evaluated in STAT6 knockout mice.

Results

IL-4 can increase STAT6 phosphorylation, but STAT6 phosphorylation decreased during myotube formation in culture. STAT6 overexpression decreased, but STAT6 knockdown increased the differentiation index and the fusion index. Results indicate that STAT6 inhibited myogenin protein expression. Results of in vivo experiments show that STAT6 knockout mice exhibited better regeneration than wild-type mice 5 days after cardiotoxin-induced injury. It is particularly interesting that results obtained using cells from STAT6 knockout mice suggest that this STAT6 inhibitory action for myogenesis was not mediated by IL-4 but might instead be associated with p38 mitogen-activated protein kinase phosphorylation. However, STAT6 was not involved in the proliferation of myogenic cells in vitro and in vivo.

Conclusion

Results suggest that STAT6 functions as an inhibitor of adult myogenesis. Moreover, results suggest that the IL-4-STAT6 signaling axis is unlikely to be responsible for myotube formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-021-00271-8.

STAT6 Signaling Mediates PPARγ Activation and Resolution of Acute Sterile Inflammation in Mice

The signal transducer and activator of transcription 6 (STAT6) transcription factor promotes activation of the peroxisome proliferator-activated receptor gamma (PPARγ) pathway in macrophages. Little is known about the effect of proximal signal transduction leading to PPARγ activation for the resolution of acute inflammation. Here, we studied the role of STAT6 signaling in PPARγ activation and the resolution of acute sterile inflammation in a murine model of zymosan-induced peritonitis. First, we showed that STAT6 is aberrantly activated in peritoneal macrophages after zymosan injection. Utilizing STAT6^−/− and wild-type (WT) mice, we found that STAT6 deficiency further enhanced zymosan-induced proinflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-6, and macrophage inflammatory protein-2 in peritoneal lavage fluid (PLF) and serum, neutrophil numbers and total protein amount in PLF, but reduced proresolving molecules, such as IL-10 and hepatocyte growth factor, in PLF. The peritoneal macrophages and spleens of STAT6^−/− mice exhibited lower mRNA and protein levels of PPARγ and its target molecules over the course of inflammation than those of WT mice. The deficiency of STAT6 was shown to impair efferocytosis by peritoneal macrophages. Taken together, these results suggest that enhanced STAT6 signaling results in PPARγ-mediated macrophage programming, contributing to increased efferocytosis and inflammation resolution.

Functional characterization of STATa/b genes encoding transcription factors from Branchiostoma belcheri

The signal transducer and activator of transcription (STAT), as an important transcription factor of the Janus kinase (JAK)-STAT signaling pathway, is pivotal for development and immunity and well documented in vertebrates. However, the STAT gene has not been reported in chordate amphioxus (Branchiostoma belcheri). In this study, we firstly identify and characterize two STAT genes from Branchiostoma belcheri (designed as AmphiSTATa and AmphiSTATb). Secondly, our results reveal that AmphiSTATa is clustered with vertebrate STAT1, STAT2, STAT3 and STAT4, whereas AmphiSTATb is grouped with STAT5 and STAT6 based on phylogenetic analysis. Thirdly, AmphiSTATa and AmphiSTATb are found to widely express in five representative tissues of amphioxus (gill, hepatic cecum, intestine, muscle and notochord) by RT-qPCR analysis. Importantly, both AmphiSTATa and AmphiSTATb can be involved in innate immune responses to LPS stimulation. Fourthly, we demonstrate that AmphiSTATa and AmphiSTATb can form homodimers or heterodimers by Co-IP and Native-PAGE assay, and that AmphiSTATa and AmphiSTATb proteins can also distribute in cytoplasm and nucleus by the subcellular localization. Taken together, our findings not only reveal the roles of AmphiSTATa and AmphiSTATb in amphioxus innate immune responses to LPS stimulation, but provide a new insight into further elucidating the evolution and function of STATs in animals.

Role of the JAK/STAT Pathway in Cervical Cancer: Its Relationship with HPV E6/E7 Oncoproteins

The janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway is associated with the regulation of essential cellular mechanisms, such as proliferation, invasion, survival, inflammation, and immunity. Aberrant JAK/STAT signaling contributes to cancer progression and metastatic development. STAT proteins play an essential role in the development of cervical cancer, and the inhibition of the JAK/STAT pathway may be essential for enhancing tumor cell death. Persistent activation of different STATs is present in a variety of cancers, including cervical cancer, and their overactivation may be associated with a poor prognosis and poor overall survival. The oncoproteins E6 and E7 play a critical role in the progression of cervical cancer and may mediate the activation of the JAK/STAT pathway. Inhibition of STAT proteins appears to show promise for establishing new targets in cancer treatment. The present review summarizes the knowledge about the participation of the different components of the JAK/STAT pathway and the participation of the human papillomavirus (HPV) associated with the process of cellular malignancy.

The Combination of IFN β and TNF Induces an Antiviral and Immunoregulatory Program via Non-Canonical Pathways Involving STAT2 and IRF9

Interferon (IFN) β and Tumor Necrosis Factor (TNF) are key players in immunity against viruses. Compelling evidence has shown that the antiviral and inflammatory transcriptional response induced by IFNβ is reprogrammed by crosstalk with TNF. IFNβ mainly induces interferon-stimulated genes by the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway involving the canonical ISGF3 transcriptional complex, composed of STAT1, STAT2, and IRF9. The signaling pathways engaged downstream of the combination of IFNβ and TNF remain elusive, but previous observations suggested the existence of a response independent of STAT1. Here, using genome-wide transcriptional analysis by RNASeq, we observed a broad antiviral and immunoregulatory response initiated in the absence of STAT1 upon IFNβ and TNF costimulation. Additional stratification of this transcriptional response revealed that STAT2 and IRF9 mediate the expression of a wide spectrum of genes. While a subset of genes was regulated by the concerted action of STAT2 and IRF9, other gene sets were independently regulated by STAT2 or IRF9. Collectively, our data supports a model in which STAT2 and IRF9 act through non-canonical parallel pathways to regulate distinct pool of antiviral and immunoregulatory genes in conditions with elevated levels of both IFNβ and TNF.

The anti-proliferative effects of type I IFN involve STAT6-mediated regulation of SP1 and BCL6

Type I IFN-induced STAT6 has been shown to have anti-proliferative effects in Daudi and B cells. IFN-sensitive (DS) and IFN-resistant (DR) subclones of Daudi cells were used to study the role of STAT6 in the anti-proliferative activities. Type I IFN significantly increased STAT6 mRNA and protein expression in DS but not DR cells. STAT6 knockdown significantly reduced the sensitivity to IFN in both cell lines. The molecular targets and functional importance of IFN-activated STAT6 were performed by chromatin immunoprecipitation-on-chip (ChIP-on-chip) experiments in type I IFN-treated Daudi cells. Two target genes (Sp1 and BCL6) were selected from the ChIP-on-chip data. IFN-induced STAT6 activation led to Sp1 upregulation and BCL6 downregulation in DS cells, with only minimal effects in DR cells. siRNA inhibition of STAT6 expression resulted in decreased Sp1 and BCL6 mRNA and protein levels in both DS and DR cells. IFN treatment did not increase Sp1 and BCL6 expression in a STAT2-deficient RST2 cell line, and this effect was mitigated by plasmid overexpression of STAT2, indicating that STAT2 is important for STAT6 activation. These results suggest that STAT6 plays an important role in regulating Sp1 and BCL6 through STAT2 to exert the anti-proliferative effects of type I IFN.

Differential Type I Interferon Signaling Is a Master Regulator of Susceptibility to Postinfluenza Bacterial Superinfection

Bacterial superinfections are a primary cause of death during influenza pandemics and epidemics. Type I interferon (IFN) signaling contributes to increased susceptibility of mice to bacterial superinfection around day 7 post-influenza A virus (IAV) infection. Here we demonstrate that the reduced susceptibility to methicillin-resistant Staphylococcus aureus (MRSA) at day 3 post-IAV infection, which we previously reported was due to interleukin-13 (IL-13)/IFN-γ responses, is also dependent on type I IFN signaling and its subsequent requirement for protective IL-13 production. We found, through utilization of blocking antibodies, that reduced susceptibility to MRSA at day 3 post-IAV infection was IFN-β dependent, whereas the increased susceptibility at day 7 was IFN-α dependent. IFN-β signaling early in IAV infection was required for MRSA clearance, whereas IFN-α signaling late in infection was not, though it did mediate increased susceptibility to MRSA at that time. Type I IFN receptor (IFNAR) signaling in CD11c⁺ and Ly6G⁺ cells was required for the observed reduced susceptibility at day 3 post-IAV infection. Depletion of Ly6G⁺ cells in mice in which IFNAR signaling was either blocked or deleted indicated that Ly6G⁺ cells were responsible for the IFNAR signaling-dependent susceptibility to MRSA superinfection at day 7 post-IAV infection. Thus, during IAV infection, the temporal differences in type I IFN signaling increased bactericidal activity of both CD11c⁺ and Ly6G⁺ cells at day 3 and reduced effector function of Ly6G⁺ cells at day 7. The temporal differential outcomes induced by IFN-β (day 3) and IFN-α (day 7) signaling through the same IFNAR resulted in differential susceptibility to MRSA at 3 and 7 days post-IAV infection.

Approximately 114,000 hospitalizations and 40,000 annual deaths in the United States are associated with influenza A virus (IAV) infections. Frequently, these deaths are due to community-acquired Gram-positive bacterial species, many of which show increasing resistance to antibiotic therapy. Severe complications, including parapneumonic empyema and necrotizing pneumonia, can arise, depending on virulence factors expressed by either the virus or bacteria. Unfortunately, we are unable to control the expression of these virulence factors, making host responses a logical target for therapeutic interventions. Moreover, interactions between virus, host, and bacteria that exacerbate IAV-related morbidities and mortalities are largely unknown. Here, we show that type I interferon (IFN) expression can modulate susceptibility to methicillin-resistant Staphylococcus aureus (MRSA) infection, with IFN-β reducing host susceptibility to MRSA infection while IFN-α increases susceptibility. Our data indicate that treatments designed to augment IFN-β and/or inhibit IFN-α production around day 7 post-IAV infection could reduce susceptibility to deadly superinfections.

Plasma levels of interleukin-1 receptor antagonist (IL1Ra) predict radiographic progression of symptomatic knee osteoarthritis

OBJECTIVE

Pro- and anti-inflammatory mediators, such as IL-1β and IL1Ra, are produced by joint tissues in osteoarthritis (OA), where they may contribute to pathogenesis. We examined whether inflammatory events occurring within joints are reflected in plasma of patients with symptomatic knee osteoarthritis (SKOA).

DESIGN

111 SKOA subjects with medial disease completed a 24-month prospective study of clinical and radiographic progression, with clinical assessment and specimen collection at 6-month intervals. The plasma biochemical marker IL1Ra was assessed at baseline and 18 months; other plasma biochemical markers were assessed only at 18 months, including IL-1β, TNFα, VEGF, IL-6, IL-6Rα, IL-17A, IL-17A/F, IL-17F, CRP, sTNF-RII, and MMP-2.

RESULTS

In cross-sectional studies, WOMAC (total, pain, function) and plasma IL1Ra were modestly associated with radiographic severity after adjustment for age, gender and body mass index (BMI). In addition, elevation of plasma IL1Ra predicted joint space narrowing (JSN) at 24 months. BMI did associate with progression in some but not all analyses. Causal graph analysis indicated a positive association of IL1Ra with JSN; an interaction between IL1Ra and BMI suggested either that BMI influences IL1Ra or that a hidden confounder influences both BMI and IL1Ra. Other protein biomarkers examined in this study did not associate with radiographic progression or severity.

CONCLUSIONS

Plasma levels of IL1Ra were modestly associated with the severity and progression of SKOA in a causal fashion, independent of other risk factors. The findings may be useful in the search for prognostic biomarkers and development of disease-modifying OA drugs.

The impact of anti-inflammatory cytokines on the pancreatic β-cell

Considerable efforts have been invested to understand the mechanisms by which pro-inflammatory cytokines mediate the demise of β-cells in type 1 diabetes but much less attention has been paid to the role of anti-inflammatory cytokines as potential cytoprotective agents in these cells. Despite this, there is increasing evidence that anti-inflammatory molecules such as interleukin (IL)-4, IL-10 and IL-13 can exert a direct influence of β-cell function and viability and that the circulating levels of these cytokines may be reduced in type 1 diabetes. Thus, it seems possible that targeting of anti-inflammatory pathways might offer therapeutic potential in this disease. In the present review, we consider the evidence implicating IL-4, IL-10 and IL-13 as cytoprotective agents in the β-cell and discuss the receptor components and downstream signaling pathways that mediate these effects.

STAT2 and IRF9: Beyond ISGF3

Cytokine signaling is mediated by the combinatorial usage of seven STAT proteins that form homo- or heterodimers involved in the regulation of specific transcriptional programs. Among STATs, STAT2 is classically known to dimerize with STAT1 and together with IRF9 forms the ISGF3 transcription factor complex that has long been considered a hallmark of activation by type I and type III interferons. However, accumulating evidence reveal distinct facets of STAT2 and IRF9 activity mediated by the segregation in alternative STAT1-independent complexes/pathways that are thought to trigger different transcriptional programs. The goal of this review is to summarize our current knowledge of the stimuli, regulatory mechanisms, and function of these alternative pathways.

The impact of polymorphisms in STAT6 on treatment outcome in HCV infected Taiwanese Chinese

Genetic polymorphisms observed in various disease states associated with sensitivity or resistance to specific treatments have been a robust area of investigation for decades, with the potential to allow clinicians to make evidence-based decisions on the appropriate course of treatment. This study aimed to evaluate whether genetic polymorphisms of the signal transducer and activator of transcription 6 gene (STAT6) could be associated with a sustained virological response (SVR) among patients infected with hepatitis C virus genotypes 1 and 2 (HCV-1 and HCV-2) who were treated with peginterferon plus ribavirin (PEG-IFNα-RBV). We analyzed the associations between SVR to PEG-IFNα-RBV therapy and 4 single nucleotide polymorphisms (SNPs) in STAT6. This study included Taiwanese Chinese patients infected with either HCV-1 (n = 265) or HCV-2 (n = 195) in the presence or absence of an SVR. Among the STAT6 SNPs examined, the dosage effect of the A allele and allele frequency in rs1059513 were inversely correlated with SVR in patients infected with HCV-1 (P = 0.0179 and P = 0.0235, respectively). This effect was not observed in patients infected with HCV-2. The GG, GGG, and GGGC STAT6 haplotypes comprising 2, 3, and 4 SNPs (rs1059513, rs703817, rs324015, and rs3024974) were found to be associated with SVR, and their presence may increase the probability of a successful treatment outcome in patients infected with HCV-1 (P = 0.0273, 0.0352, and 0.0368, respectively). Moreover, a multivariate logistic regression model for predicting an SVR revealed that the presence of the GGGC haplotype carriers mutually affected the outcome of PEG-IFNα-RBV treatment. The presence of STAT6 SNPs and the association with SVR demonstrated that STAT6 polymorphisms might influence the therapeutic outcomes of patients infected with HCV-1 under standard-of-care (SOC) treatment.

Biological characterization of a novel class of toll-like receptor 7 agonists designed to have reduced systemic activity

BACKGROUND AND PURPOSE Toll-like receptor 7 (TLR7) agonists have potential in the treatment of allergic diseases. However, the therapeutic utility of current low molecular weight TLR7 agonists is limited by their systemic activity, resulting in unwanted side effects. We have developed a series of TLR7-selective 'antedrugs', including SM-324405 and AZ12441970, which contain an ester group rapidly cleaved in plasma to reduce systemic exposure. EXPERIMENTAL APPROACH Agonist activity at TLR7 of the parent ester and acid metabolite was assessed in vitro in reporter cells and primary cells from a number of species. Pharmacokinetics following a dose to the lungs was assessed in mice and efficacy evaluated in vivo with a mouse allergic airway model. KEY RESULTS Compounds were selective agonists for TLR7 with no crossover to TLR8 and were metabolically unstable in plasma with the acid metabolite showing substantially reduced activity in a number of assays. The compounds inhibited IL-5 production and induced IFN-α, which mediated the inhibition of IL-5. When dosed into the lung the compounds were rapidly metabolized and short-term exposure of the 'antedrug' was sufficient to activate the IFN pathway. AZ12441970 showed efficacy in a mouse allergic airway model with minimal induction of systemic IFN-α, consistent with the low plasma levels of compound. CONCLUSIONS AND IMPLICATIONS The biological and metabolic profiles of these TLR7-selective agonist 'antedrug' compounds are consistent with a new class of compound that could be administered locally for the treatment of allergic diseases, while reducing the risk of systemic side effects. LINKED ARTICLE This article is commented on by Kaufman and Jacoby, pp. 569-572 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2011.01758.x.

JAK-1 rs2780895 C-related genotype and allele but not JAK-1 rs10789166, rs4916008, rs2780885, rs17127114, and rs3806277 are associated with higher susceptibility to asthma

BACKGROUND

Asthma, one major respiratory consequence, might be caused by a complex interaction between multiple candidate genes and environmental factors. Herein, we aimed to investigate whether Janus kinase (JAK)-1 gene polymorphisms are associated with asthma susceptibility.

MATERIALS AND METHODS

Patients were divided into two groups: (1) asthma (n=117) and (2) nonasthma (n=60). The JAK-1 polymorphisms (rs2780895, rs10789166, rs4916008, rs2780885, rs17127114, and rs3806277) were amplified by polymerase chain reaction and detected by electrophoresis after restriction enzyme (HpyCH4IV, Tsp45I, HpaII, XmnI, MspI, and HpaII) digestions. Genotypes, allelic frequencies, and association of haplotypes in both groups were compared.

RESULTS

JAK-1 rs2780895 gene polymorphism is associated with susceptibility to asthma. Distributions of JAK-1 rs2780895*CC/CT/TT and C/T allele in both groups are: (1) 80/4/16% and 82/18%; (2) 48/45/7% and 71/29%. Other 5 JAK-1 SNPs (rs10789166, rs4916008, rs2780885, rs17127114, and rs3806277) are not associated with asthma susceptibilities. Distributions of JAK-1 rs10789166*AA/AG/GG, rs4916008*CC/CT/TT, rs2780885*CC/CT/TT, rs17127114*AA/AG/GG, rs3806277*AA/AG/GG in both groups are: (1) 50/40/10%, 42/49/9%, 50/40/10%, 9/37/54%, 8/35/57%; (2) 43/50/7%, 40/50/10%, 50/43/7%, 7/48/45%, 6/42/52%. Haplotype analyses for JAK-1 gene polymorphisms (rs2780895-rs10789166-rs4916008-rs2780885-rs17127114-rs3806277) revealed that JAK-1 haplotypes are not associated with asthma susceptibilities.

CONCLUSIONS

JAK-1 rs2780895 C-related genotype and allele are associated with higher susceptibility to asthma. JAK-1 rs10789166, rs4916008, rs2780885, rs17127114, and rs3806277 single-nucleotide polymorphisms are not associated with asthma development. Some JAK-related genetic variations might be associated with asthma pathogenesis, which deserve further surveys.

Effect of interferon-α2b on the expression of various drug-metabolizing enzymes and transporters in co-cultures of freshly prepared human primary hepatocytes

The purpose of this study was to assess the impact of interferon-α2b (IFN-α2b) on the expression of various drug-metabolizing enzymes and transporters in freshly prepared co-cultures (parenchymal and non-parenchymal cells) of human primary hepatocytes. At therapeutically relevant concentrations (from 1000 to 3000 IU/mL), IFN-α2b up-regulated STAT1 (signal transducer and activator of transcription factor 1) mRNA expression. Conversely, three cytochrome P450s (CYP1A2, CYP2B6, CYP2E1), a UDP-glucuronosyltransferase (UGT2B7), a sulphotransferase (SULT1A1) and organic anion transporter (OAT2) were significantly down-regulated (~50%; P < 0.05). Western blot analysis of CYP1A2, UGT2B7 and OAT2 protein supported the mRNA data. Two peroxisome proliferator activator receptor alpha (PPARα)-controlled genes (pyruvate dehydrogenase kinase 4 and adipose differentiation-related protein), CYP3A4 and multidrug resistance-associated protein 2 were significantly up-regulated (up to 223%; P < 0.05). On the other hand, SULT2A1, carboxylesterase 2, organic anion transporting peptide (OATP1B1, OATP1B3, OATP2B1), organic cation transporter 1, P-glycoprotein and breast cancer resistance protein mRNA expression was not significantly affected. Western blot analysis of CYP3A4 supported the mRNA data also. The present results demonstrated complex interactions between IFN-α2b and hepatocytes and the observed down-regulation of CYP1A2, OAT2 and UGT2B7 is consistent with reports of drug interactions between IFN-α2b and drugs such as theophylline, clozapine and gemfibrozil.

Type I interferons protect from Toll-like receptor 9-associated liver injury and regulate IL-1 receptor antagonist in mice

BACKGROUND & AIMS

Liver inflammation and injury are mediated by the innate immune response, which is regulated by Toll-like receptors (TLR). Activation of TLR9 induces type I interferons (IFNs) via the interferon regulatory factor (IRF)-7. We investigated the roles of type I IFNs in TLR9-associated liver injury.

METHODS

Wild-type (WT), IRF7-deficient, and IFN-α/β receptor 1 (IFNAR1)-deficient mice were stimulated with TLR9 or TLR2 ligands. Findings from mice were verified in cultured hepatocytes and liver mononuclear cells (LMNCs) as well as in vivo experiments using recombinant type I IFN and interleukin-1 receptor antagonist (IL-1ra).

RESULTS

Type I IFNs were up-regulated during TLR9-associated liver injury in WT mice. IRF7- and IFNAR1-deficient mice, which have disruptions in type I IFN production or signaling, respectively, had increased liver damage and inflammation, decreased recruitment of dendritic cells, and increased production of tumor necrosis factor α by LMNCs. These findings indicate that type I IFNs have anti-inflammatory activities in liver. IL-1ra, which is produced by LMNCs and hepatocytes, is an IFN-regulated antagonist of the proinflammatory cytokine IL-1β; IRF7- and IFNAR1-deficient mice had decreased levels of IL-1ra compared with WT mice. IL-1ra protected cultured hepatocytes from IL-1β-mediated sensitization to cytotoxicity from tumor necrosis factor α. In vivo exposure to type I IFN, which induced IL-1ra, or administration of IL-1ra reduced TLR9-associated liver injury; the protective effect of type I IFNs therefore appears to be mediated by IFN-dependent induction of IL-1ra.

CONCLUSIONS

Type I IFNs have anti-inflammatory effects mediated by endogenous IL-1ra, which regulates the extent of TLR9-induced liver damage. Type I IFN signaling is therefore required for protection from immune-mediated liver injury.

Counter-regulation mechanism of IL-4 and IFN-α signal transduction through cytosolic retention of the pY-STAT6:pY-STAT2:p48 complex

IFN-α and IL-4 induce Th1 and Th2 responses, respectively, and often display antagonistic actions against each other. To elucidate the molecular mechanism of counter-regulation, we have investigated the signal interception by IFN-α and IL-4, employing a human B-cell line Ramos, sensitive to both cytokines. In these cells, IFN-α effectively inhibited IL-4-induced Fc epsilon receptor II (CD23) expression, whereas IL-4 suppressed IFN-α-mediated IRF7 expression. The counter-regulatory action by IL-4 and IFN-α proceeded with a delayed kinetics requiring 4 h. Notably, IFN-α did not affect the IL-4-induced tyrosine phosphorylation of STAT6, but induced a time-dependent cytoplasmic accumulation of phosphotyrosine(pY)-STAT6 and a corresponding decrease in nuclear pY-STAT6. By confocal analysis and co-immunoprecipitation assays, we demonstrated the colocalization and molecular interaction of IL-4-induced pY-STAT6 with IFN-α-induced pY-STAT2:p48 in the cytosol. In addition, the over-expression of STAT2 or STAT6 induced the concomitant cytosolic accumulation of pY-STAT6 or pY-STAT2, leading to the suppression of IL-4-induced CD23 or IFN-α-induced IRF7 gene expression, respectively. Our data suggest that the signals ensued by IFN-α and IL-4 induce cytoplasmic sequestration of IL-4-activated STAT6 and IFN-α-activated STAT2:p48 in B cells through the formation of pY-STAT6:pY-STAT2:p48 complex, which provides a novel mechanism by which IFN-α and IL-4 cross-regulate their signaling into the nucleus.

The detrimental effects of IFN-α on vasculogenesis in lupus are mediated by repression of IL-1 pathways: potential role in atherogenesis and renal vascular rarefaction

Systemic lupus erythematosus (SLE) is characterized by increased vascular risk due to premature atherosclerosis independent of traditional risk factors. We previously proposed that IFN-α plays a crucial role in premature vascular damage in SLE. IFN-α alters the balance between endothelial cell apoptosis and vascular repair mediated by endothelial progenitor cells (EPCs) and myeloid circulating angiogenic cells (CACs). In this study, we demonstrate that IFN-α promotes an antiangiogenic signature in SLE and control EPCs/CACs, characterized by transcriptional repression of IL-1α and β, IL-1R1, and vascular endothelial growth factor A, and upregulation of IL-1R antagonist and the decoy receptor IL-1R2. IL-1β promotes significant improvement in the functional capacity of lupus EPCs/CACs, therefore abrogating the deleterious effects of IFN-α. The beneficial effects from IL-1 are mediated, at least in part, by increases in EPC/CAC proliferation, by decreases in EPC/CAC apoptosis, and by preventing the skewing of CACs toward nonangiogenic pathways. IFN-α induces STAT2 and 6 phosphorylation in EPCs/CACs, and JAK inhibition abrogates the transcriptional antiangiogenic changes induced by IFN-α in these cells. Immunohistochemistry of renal biopsies from patients with lupus nephritis, but not anti-neutrophil cytoplasmic Ab-positive vasculitis, showed this pathway to be operational in vivo, with increased IL-1R antagonist, downregulation of vascular endothelial growth factor A, and glomerular and blood vessel decreased capillary density, compared with controls. Our study introduces a novel putative pathway by which type I IFNs may interfere with vascular repair in SLE through repression of IL-1-dependent pathways. This could promote atherosclerosis and loss of renal function in this disease.

Rationale and efficacy of interleukin-1 targeting in Erdheim-Chester disease

Erdheim-Chester disease (ECD) pathophysiology remains largely unknown. Its treatment is not codified and usually disappointing. Interferon (IFN)-α therapy lacks efficacy for some life-threatening manifestations and has a poor tolerance profile. Because interleukin (IL)-1Ra synthesis is naturally induced after stimulation by IFN-α, we hypothesized that recombinant IL-1Ra (anakinra) might have some efficacy in ECD. We treated 2 patients who had poor tolerance or contraindication to IFN-α with anakinra as a rescue therapy and measured their serum C-reactive protein, IL-1β, IL-6, and monocytic membranous IL-1α (mIL-1α) levels before, under, and after therapy. Another untreated ECD patient and 5 healthy subjects were enrolled as controls. After treatment, fever and bone pains rapidly disappeared in both patients, as well as eyelid involvement in one patient. In addition, retroperitoneal fibrosis completely or partially regressed, and C-reactive protein, IL-6, and mIL-1α levels decreased to within the normal and control range. Beside injection-site reactions, no adverse event was reported. Therefore, our results support a central role of the IL-1 network, which seemed to be overstimulated in ECD. Its specific blockade using anakinra thereby opens new pathophysiology and therapeutic perspectives in ECD.

Dual regulation of mu opioid receptors in SK-N-SH neuroblastoma cells by morphine and interleukin-1β: evidence for opioid-immune crosstalk

Treatment of SK-N-SH cells with morphine and interleukin-1beta (IL-1β) produced dual regulation of the mRNA for the human mu opioid receptor (MOR) protein. Morphine produced a decrease in the MOR mRNA while IL-1β increased it, as assessed by real-time quantitative PCR. These data were consistent with immunocytochemical studies of treated and untreated cells. Morphine-mediated down-regulation of MOR was blocked by naltrexone and IL-1β-induced up-regulation of MOR was blocked by interleukin-1 receptor type 1 antagonist. Immune-opioid crosstalk was examined by IL-1β and morphine co-treatment. These data are the first to show dual regulation of MOR in neuroblastoma cells.

IRF-9/STAT2 [corrected] functional interaction drives retinoic acid-induced gene G expression independently of STAT1

Retinoic acid-induced gene G (RIG-G), a gene originally identified in all-trans retinoic acid-treated NB4 acute promyelocytic leukemia cells, is also induced by IFNalpha in various hematopoietic and solid tumor cells. Our previous work showed that RIG-G possessed a potent antiproliferative activity. However, the mechanism for the transcriptional regulation of RIG-G gene remains unknown. Here, we report that signal transducer and activator of transcription (STAT) 2 together with IFN regulatory factor (IRF)-9 can effectively drive the transcription of RIG-G gene by their functional interaction through a STAT1-independent manner, even without the tyrosine phosphorylation of STAT2. The complex IRF-9/STAT2 is both necessary and sufficient for RIG-G gene expression. In addition, IRF-1 is also able to induce RIG-G gene expression through an IRF-9/STAT2-dependent or IRF-9/STAT2-independent mechanism. Moreover, the induction of RIG-G by retinoic acid in NB4 cells resulted, to some extent, from an IFNalpha autocrine pathway, a finding that suggests a novel mechanism for the signal cross-talk between IFNalpha and retinoic acid. Taken together, our results provide for the first time the evidence of the biological significance of IRF-9/STAT2 complex, and furnish an alternative pathway modulating the expression of IFN-stimulated genes, contributing to the diversity of IFN signaling to mediate their multiple biological properties in normal and tumor cells.

Yellow fever vaccine induces integrated multilineage and polyfunctional immune responses

Correlates of immune-mediated protection to most viral and cancer vaccines are still unknown. This impedes the development of novel vaccines to incurable diseases such as HIV and cancer. In this study, we have used functional genomics and polychromatic flow cytometry to define the signature of the immune response to the yellow fever (YF) vaccine 17D (YF17D) in a cohort of 40 volunteers followed for up to 1 yr after vaccination. We show that immunization with YF17D leads to an integrated immune response that includes several effector arms of innate immunity, including complement, the inflammasome, and interferons, as well as adaptive immunity as shown by an early T cell response followed by a brisk and variable B cell response. Development of these responses is preceded, as demonstrated in three independent vaccination trials and in a novel in vitro system of primary immune responses (modular immune in vitro construct [MIMIC] system), by the coordinated up-regulation of transcripts for specific transcription factors, including STAT1, IRF7, and ETS2, which are upstream of the different effector arms of the immune response. These results clearly show that the immune response to a strong vaccine is preceded by coordinated induction of master transcription factors that lead to the development of a broad, polyfunctional, and persistent immune response that integrates all effector cells of the immune system.