IL-10 attenuates IFN-alpha-activated STAT1 in the liver: involvement of SOCS2 and SOCS3

New insight into the role of SOCS family in immune regulation and autoimmune pathogenesis

BACKGROUND

Suppressor of cytokine signaling (SOCS) proteins regulate signal transduction by interacting with cytokine receptors and signaling proteins and targeting associated proteins for degradation. Recent studies have demonstrated that the SOCS proteins serve as crucial inhibitors in cytokine signaling networks and play a pivotal role in both innate and adaptive immune responses.

AIM OF REVIEW

In this review, we aim to discuss recent advancements in understanding the complex functions of SOCS proteins in various immune cells, as well as the effects of SOCS proteins in human health and diseases. Increasing evidence indicates that SOCS proteins are frequently dysregulated in developing autoimmune diseases, suggesting that therapeutic targeting of SOCS proteins could provide clinical benefit.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of SOCS proteins in immune regulation and autoimmune pathogenesis, it also highlights the role of SOCS-related mimetic peptides in immunotherapy.

Therapeutic Effects and Underlying Mechanism of SOCS-com Gene-Transfected ADMSCs in Pressure Ulcer Mouse Models

Although the proportion of ulcer patients with medical problems among the elderly has increased with the extension of human life expectancy, treatment efficiency is drastically low, incurring substantial social costs. MSCs have independent regeneration potential, making them useful in clinical trials of difficult-to-treat diseases. In particular, ADMSCs are promising in the stem cell therapy industry as they can be obtained in vast amounts using non-invasive methods. Furthermore, studies are underway to enhance the regeneration potential of ADMSCs using cytokines, growth factors, and gene delivery to generate highly functional ADMSCs. In this study, key regulators of wound healing, SOCS-1, -3, and -5, were combined to maximize the regenerative potential of ADMSCs in pressure ulcer treatments. After transfecting SOCS-1, -3, -5, and SOCS-com into ADMSCs using a non-viral method, the expression of the inflammatory factors TNF-alpha, INF-gamma, and IL-10 was confirmed. ADMSCs transfected with SOCS-com showed decreased overall expression of inflammatory factors and increased expression of anti-inflammatory factors. Based on these results, we implanted ADMSCs transfected with SOCS-com into a pressure ulcer mouse model to observe their subsequent wound-healing effects. Notably, SOCS-com improved wound closure in ulcers, and reconstruction of the epidermis and dermis was observed. The healing mechanism of ADMSCs transfected with SOCS-com was examined by RNA sequencing. Gene analysis results confirmed that expression changes occurred in genes of key regulators of wound healing, such as chemokines, MMP-1, 9, CSF-2, and IL-33, and that such genetic changes enhanced wound healing in ulcers. Based on these results, we demonstrate the potential of ADMSCs transfected with SOCS-com as an ulcer treatment tool.

Role of SOCS and VHL Proteins in Neuronal Differentiation and Development

The basic helix-loop-helix factors play a central role in neuronal differentiation and nervous system development, which involve the Notch and signal transducer and activator of transcription (STAT)/small mother against decapentaplegic signaling pathways. Neural stem cells differentiate into three nervous system lineages, and the suppressor of cytokine signaling (SOCS) and von Hippel-Lindau (VHL) proteins are involved in this neuronal differentiation. The SOCS and VHL proteins both contain homologous structures comprising the BC-box motif. SOCSs recruit Elongin C, Elongin B, Cullin5(Cul5), and Rbx2, whereas VHL recruits Elongin C, Elongin B, Cul2, and Rbx1. SOCSs form SBC-Cul5/E3 complexes, and VHL forms a VBC-Cul2/E3 complex. These complexes degrade the target protein and suppress its downstream transduction pathway by acting as E3 ligases via the ubiquitin-proteasome system. The Janus kinase (JAK) is the main target protein of the E3 ligase SBC-Cul5, whereas hypoxia-inducible factor is the primary target protein of the E3 ligase VBC-Cul2; nonetheless, VBC-Cul2 also targets the JAK. SOCSs not only act on the ubiquitin-proteasome system but also act directly on JAKs to suppress the Janus kinase-signal transduction and activator of transcription (JAK-STAT) pathway. Both SOCS and VHL are expressed in the nervous system, predominantly in brain neurons in the embryonic stage. Both SOCS and VHL induce neuronal differentiation. SOCS is involved in differentiation into neurons, whereas VHL is involved in differentiation into neurons and oligodendrocytes; both proteins promote neurite outgrowth. It has also been suggested that the inactivation of these proteins may lead to the development of nervous system malignancies and that these proteins may function as tumor suppressors. The mechanism of action of SOCS and VHL involved in neuronal differentiation and nervous system development is thought to be mediated through the inhibition of downstream signaling pathways, JAK-STAT, and hypoxia-inducible factor-vascular endothelial growth factor pathways. In addition, because SOCS and VHL promote nerve regeneration, they are expected to be applied in neuronal regenerative medicine for traumatic brain injury and stroke.

Mechanism of herpesvirus protein kinase UL13 in immune escape and viral replication

Upon infection, the herpes viruses create a cellular environment suitable for survival, but innate immunity plays a vital role in cellular resistance to viral infection. The UL13 protein of herpesviruses is conserved among all herpesviruses and is a serine/threonine protein kinase, which plays a vital role in escaping innate immunity and promoting viral replication. On the one hand, it can target various immune signaling pathways in vivo, such as the cGAS-STING pathway and the NF-κB pathway. On the other hand, it phosphorylates regulatory many cellular and viral proteins for promoting the lytic cycle. This paper reviews the research progress of the conserved herpesvirus protein kinase UL13 in immune escape and viral replication to provide a basis for elucidating the pathogenic mechanism of herpesviruses, as well as providing insights into the potential means of immune escape and viral replication of other herpesviruses that have not yet resolved the function of it.

Upregulated lncARAT in Schwann cells promotes axonal regeneration by recruiting and activating proregenerative macrophages

Background

Axonal regeneration following peripheral nerve injury (PNI) depends on the complex interaction between Schwann cells (SCs) and macrophages, but the mechanisms underlying macrophage recruitment and activation in axonal regeneration remain unclear.

Methods

RNA sequencing (RNA-seq) was conducted to identify differentially expressed long noncoding RNAs (DElncRNAs) between crushed sciatic nerves and intact contralateral nerves. The putative role of lncRNAs in nerve regeneration was analyzed in vitro and in vivo.

Results

An lncRNA, called axon regeneration-associated transcript (lncARAT), was upregulated in SCs and SC-derived exosomes (SCs-Exo) after sciatic nerve injury. LncARAT contributed to axonal regeneration and improved motor function recovery. Mechanistically, lncARAT epigenetically activated C–C motif ligand 2 (CCL2) expression by recruiting KMT2A to CCL2 promoter, resulting in increased histone 3 lysine 4 trimethylation (H3K4me3) and CCL2 transcription in SCs. CCL2 facilitated the infiltration of macrophages into the injured nerves. Meanwhile, lncARAT-enriched exosomes were released from SCs and incorporated into macrophages. LncARAT functioned as an endogenous sponge to adsorb miRNA-329-5p in macrophages, resulting in increased suppressor of cytokine signaling (SOCS) 2 expression, which induced a proregenerative function of macrophages through a signal transducer and activator of transcription (STAT) 1/6-dependent pathway.

Conclusions

LncARAT may represent a promising therapeutic avenue for peripheral nerve repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00501-9.

Interleukin-17A pretreatment attenuates the anti-hepatitis B virus efficacy of interferon-alpha by reducing activation of the interferon-stimulated gene factor 3 transcriptional complex in hepatitis B virus-expressing HepG2 cells

Background

Some cytokine signaling pathways can interact with interferon (IFN)-α pathway and thus regulate cell responses to IFN-α. Levels of the pro-inflammatory cytokine interleukin-17A (IL-17A) were found to be elevated in both the peripheral blood and liver in chronic hepatitis B (CHB) patients. However, how IL-17A affects the anti-HBV activity of IFN-α remains unclear.

Methods

The effects of IL-17A on anti-HBV activity of IFN-α were evaluated in HBV-expressing HepG2 cells (HepG2-HBV1.3) with IL-17A pretreatment and IFN-α stimulation. Culture supernatant levels of HBsAg, HBeAg, and HBV DNA, or intracellular expression of HBsAg and HBcAg were detected by ELISA, real-time quantitative PCR (RT-qPCR), or western blotting (WB). The expression of canonical IFN-α signaling pathway components, including the interferon-α/β receptor (IFNAR), Janus Kinase 1 (JAK1), Tyrosine Kinase 2 (TYK2), the Interferon Stimulated Gene Factor 3 complex (ISGF3) and IFN-stimulated genes (ISGs), was also examined by RT-qPCR, Immunofluorescence or WB. The effects of IL-17A were further investigated by the suppression of the IL-17A pathway with a TRAF6 inhibitor.

Results

Compared to IFN-α stimulation alone, IL-17A pretreatment followed by IFN-α stimulation increased the levels of HBsAg, HBeAg, and HBV DNA, and decreased the levels of ISGF3 complex (phosphorylated (p)-signal transducer and activator of transcription (STAT1)/p-STAT2/IRF9) and antiviral-related ISGs (ISG15, ISG20 and Mx1). Interestingly, IL-17A pretreatment increased the expression of suppressor of cytokine signaling (SOCS) 1, SOCS3 and USP18, which were also the ISGs negatively regulating activity of ISGF3. Moreover, IFNAR1 protein expression declined more sharply in the group with IL-17A pretreatment than in the group with IFN-α stimulation alone. Blocking the IL-17A pathway reversed the effects of IL-17A on the IFN-α-induced activation of ISGF3 and anti-HBV efficacy.

Conclusions

Our results demonstrate that IL-17A pretreatment could attenuate IFN-α-induced anti-HBV activity by upregulating negative regulators of the critical transcriptional ISGF3 complex. Thus, this might be a potential target for improving response to IFN-α therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01753-x.

Association of cytokine gene polymorphisms with chronic hepatitis C virus genotype 1b infection in Chinese Han population: An observational study

Cytokines are extensively involved in the process of hepatitis C virus (HCV) infection and take a crucial part in host immune regulation. We aimed to explore the potential correlation of cytokine single nucleotide polymorphisms (SNPs) with HCV susceptibility and response rate of interferon (IFN)-based antiviral therapy in Chinese Han population.A case-control genetic association study was conducted between 198 patients with chronic HCV genotype 1b infection and 142 healthy controls. Genetic polymorphisms of TNF-α (rs1800629), TGF-β (rs1800469), IL-10 (rs1800896, rs1800871, and rs1800872), IL-6 (rs1800795, rs1800796), IFN-γ (rs2430561), and IL-28B (rs12979860, rs12980275, and rs8099917) were analyzed by MassARRAY SNP technology. Patients were treated with IFNα-2b or pegylated-IFNα-2a plus ribavirin for 48 weeks. Sustained virological response (SVR) was assessed 6 months after the completion of the treatment.The IL-28B rs12979860-CC (odds ratio [OR] = 4.35, 95% confidence interval [CI]: 1.69-11.21, P = .001), rs12980275-AA (OR = 3.41, 95% CI: 1.08-10.76, P = .028), and rs8099917-TT (OR = 3.86, 95% CI: 1.49-10.12, P = .004) were significantly associated with SVR, and IL-10 rs1800871-TT (OR = .50, 95% CI: 0.25-1.00, P = .049) and rs1800872-AA (OR = .50, 95% CI: 0.25-1.00, P = .049) were also significant for SVR. No association was found between the cytokine SNPs and HCV susceptibility. Additionally, multivariate analysis showed that low baseline viral load (OR = 3.63, 95% CI: 1.01-13.02, P = .048), pegylated-IFN (OR = 9.68, 95% CI: 1.14-82.13, P = .037) and rs12979860-CC (OR = 6.08, 95% CI: 2.00-18.46, P = .001) were independent factors for SVR.IL-28 and IL-10 gene polymorphisms played an important role in predicting host response to IFN-based antiviral therapy in HCV genotype 1b infection.

Insulin- and Lipopolysaccharide-Mediated Signaling in Adipose Tissue Macrophages Regulates Postprandial Glycemia through Akt-mTOR Activation

The physiological role of immune cells in the regulation of postprandial glucose metabolism has not been fully elucidated. We have found that adipose tissue macrophages produce interleukin-10 (IL-10) upon feeding, which suppresses hepatic glucose production in cooperation with insulin. Both elevated insulin and gut-microbiome-derived lipopolysaccharide in response to feeding are required for IL-10 production via the Akt/mammalian target of rapamycin (mTOR) pathway. Indeed, myeloid-specific knockout of the insulin receptor or bone marrow transplantation of mutant TLR4 marrow cells results in increased expression of gluconeogenic genes and impaired glucose tolerance. Furthermore, myeloid-specific Akt1 and Akt2 knockout results in similar phenotypes that are rescued by additional knockout of TSC2, an inhibitor of mTOR. In obesity, IL-10 production is impaired due to insulin resistance in macrophages, whereas adenovirus-mediated expression of IL-10 ameliorates postprandial hyperglycemia. Thus, the orchestrated response of the endogenous hormone and gut environment to feeding is a key regulator of postprandial glycemia.

Therapeutic Potential of Brassinosteroids in Biomedical and Clinical Research

Steroids are a pivotal class of hormones with a key role in growth modulation and signal transduction in multicellular organisms. Synthetic steroids are widely used to cure large array of viral, fungal, bacterial, and cancerous infections. Brassinosteroids (BRs) are a natural collection of phytosterols, which have structural similarity with animal steroids. BRs are dispersed universally throughout the plant kingdom. These plant steroids are well known to modulate a plethora of physiological responses in plants leading to improvement in quality as well as yield of food crops. Moreover, they have been found to play imperative role in stress-fortification against various stresses in plants. Over a decade, BRs have conquered worldwide interest due to their diverse biological activities in animal systems. Recent studies have indicated anticancerous, antiangiogenic, antiviral, antigenotoxic, antifungal, and antibacterial bioactivities of BRs in the animal test systems. BRs inhibit replication of viruses and induce cytotoxic effects on cancerous cell lines. Keeping in view the biological activities of BRs, this review is an attempt to update the information about prospects of BRs in biomedical and clinical application.

Transplantation of human adipose tissue derived-SVF enhance liver function through high anti-inflammatory property

Although human adipose tissue-derived stromal vascular fraction (SVF) has been considered a promising source of stem cells, its characteristics relevant to treatment of a damaged liver have not been fully elucidated. In the present study, we sought to characterize the property of human SVF and determine the therapeutic utility of SVF in the liver cirrhosis model. We performed microarray, quantitative (q)-PCR experiments, and in vivo therapeutic assays using a liver cirrhotic mouse model. q-PCR results revealed that hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF)-A, Interleukin (IL)-10 and microRNA (miR)-146 were more highly upregulated in SVF than in human adipose-derived mesenchymal stem cells (ASCs). The SVF culture medium (CM) inhibited the activation of hepatic stellate cells in vitro. Injection of SVF significantly suppressed TAA-induced liver fibrosis and repaired liver function by inhibition of infiltrating inflammatory cells and induction of capillary/hepatocyte regeneration in vivo. Injection of IL-10 siRNA treated SVF cells decreased anti-inflammation and anti-fibrotic effects in TAA-induced mice liver. Our data indicate that SVF show a high anti-inflammatory property for treating fibrotic liver diseases through IL-10 secretion. Therefore, SVF might be a novel therapeutic alternative for the treatment of liver cirrhosis in clinical settings.

The molecular details of cytokine signaling via the JAK/STAT pathway

More than 50 cytokines signal via the JAK/STAT pathway to orchestrate hematopoiesis, induce inflammation and control the immune response. Cytokines are secreted glycoproteins that act as intercellular messengers, inducing proliferation, differentiation, growth, or apoptosis of their target cells. They act by binding to specific receptors on the surface of target cells and switching on a phosphotyrosine-based intracellular signaling cascade initiated by kinases then propagated and effected by SH2 domain-containing transcription factors. As cytokine signaling is proliferative and often inflammatory, it is tightly regulated in terms of both amplitude and duration. Here we review molecular details of the cytokine-induced signaling cascade and describe the architectures of the proteins involved, including the receptors, kinases, and transcription factors that initiate and propagate signaling and the regulatory proteins that control it.

Immunoprofiling of Adult-Derived Human Liver Stem/Progenitor Cells: Impact of Hepatogenic Differentiation and Inflammation

Adult-derived human liver stem/progenitor cells (ADHLSCs) are, nowadays, developed as therapeutic medicinal product for the treatment of liver defects. In this study, the impact of hepatogenic differentiation and inflammation priming on the ADHLSCs' immune profile was assessed in vitro and compared to that of mature hepatocytes. The constitutive immunological profile of ADHLSCs was greatly different from that of hepatocytes. Differences in the expression of the stromal markers CD90 and CD105, adhesion molecules CD44 and CD49e, immunoregulatory molecules CD73 and HO-1, and NK ligands CD112 and CD155 were noted. While they globally preserved their immunological profile in comparison to undifferentiated counterparts, differentiated ADHLSCs showed a significant downregulation of CD200 expression as in hepatocytes. This was mainly induced by signals issued from EGF and OSM. On the other hand, the impact of inflammation was quite similar for all studied cell populations with an increased expression level of CD54 and CD106 and induction of that of CD40 and CD274. In conclusion, our immune profiling study suggests CD200 as a key factor in regulating the immunobiology of differentiated ADHLSCs. A better understanding of the molecular and physiological events related to such marker could help in designing the optimal conditions for an efficient therapeutic use of ADHLSCs.

Interleukin 10 gene single nucleotide polymorphisms in Polish patients with chronic hepatitis C: Analysis of association with severity of disease and treatment outcome

It is suggested that interleukin 10 (IL-10), as a modulator of immune response, is likely to influence the elimination of hepatitis C virus (HCV), the progression of chronic hepatitis C (CHC) and the response to interferon-based therapy in CHC patients. The aim of the study was to analyze the association of single nucleotide polymorphisms (SNPs) of IL-10 gene with severity of liver disease (degree of inflammation and stage of fibrosis) and outcome of pegylated interferon alpha and ribavirin combined therapy (sustained virological response (SVR) and relapse) in 196 Polish CHC patients infected with HCV genotype 1. The analysis included IL-10 promoter SNPs: -1082(A/G) rs1800896, -819(C/T) rs1800871, -592(C/A) rs1800872 and SNP in the 3' UTR of IL-10 gene: +4529(A/G) rs3024498. Genotyping was performed using PCR-RFLP and HRM analysis. It was demonstrated that the -592C allele is associated with mild hepatic inflammation. Moreover, it was found that the -819C allele might be associated with SVR and that the ACCA haplotype and intermediate IL-10 producer ACC haplotype are associated with SVR and non-relapse. It can be concluded that IL-10 SNPs are associated with severity of disease and response to therapy and may be considered as potential prognostic and predictive markers in CHC.

Suppression of the inflammatory response by disease-inducible interleukin-10 gene therapy in a three-dimensional micromass model of the human synovial membrane

Background

Gene therapy has the potential to provide long-term production of therapeutic proteins in the joints of osteoarthritis (OA) patients. The objective of this study was to analyse the therapeutic potential of disease-inducible expression of anti-inflammatory interleukin-10 (IL-10) in the three-dimensional micromass model of the human synovial membrane.

Methods

Synovial tissue samples from OA patients were digested and the cells were mixed with Matrigel to obtain 3D micromasses. The CXCL10 promoter combined with the firefly luciferase reporter in a lentiviral vector was used to determine the response of the CXCL10 promoter to tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and lipopolysaccharide (LPS). The effects of recombinant IL-10 on gene expression were determined by quantitative PCR. The production of IL-10 from the CXCL10p-IL10 vector and the effects on pro-inflammatory cytokine production were assessed by multiplex ELISA.

Results

Micromasses made from whole synovial membrane cell suspensions form a distinct surface composition containing macrophage and fibroblast-like synoviocytes thus mimicking the synovial lining. This lining can be transduced by lentiviruses and allow CXCL-10 promoter-regulated transgene expression. Adequate amounts of IL-10 transgene were produced after stimulation with pro-inflammatory factors able to reduce the production of synovial IL-1β and IL-6.

Conclusions

Synovial micromasses are a suitable model to test disease-regulated gene therapy approaches and the CXCL10p-IL10 vector might be a good candidate to decrease the inflammatory response implicated in the pathogenesis of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1083-1) contains supplementary material, which is available to authorized users.

Mycobacterium leprae-induced Insulin-like Growth Factor I attenuates antimicrobial mechanisms, promoting bacterial survival in macrophages

Mycobacterium leprae (ML), the etiologic agent of leprosy, can subvert macrophage antimicrobial activity by mechanisms that remain only partially understood. In the present study, the participation of hormone insulin-like growth factor I (IGF-I) in this phenomenum was investigated. Macrophages from the dermal lesions of the disseminated multibacillary lepromatous form (LL) of leprosy expressed higher levels of IGF-I than those from the self-limited paucibacillary tuberculoid form (BT). Higher levels of IGF-I secretion by ML-infected macrophages were confirmed in ex vivo and in vitro studies. Of note, the dampening of IGF-I signaling reverted the capacity of ML-infected human and murine macrophages to produce antimicrobial molecules and promoted bacterial killing. Moreover, IGF-I was shown to inhibit the JAK/STAT1-dependent signaling pathways triggered by both mycobacteria and IFN-γ most probably through its capacity to induce the suppressor of cytokine signaling-3 (SOCS3). Finally, these in vitro findings were corroborated by in vivo observations in which higher SOCS3 expression and lower phosphorylation of STAT1 levels were found in LL versus BT dermal lesions. Altogether, our data strongly suggest that IGF-I contributes to the maintenance of a functional program in infected macrophages that suits ML persistence in the host, reinforcing a key role for IGF-I in leprosy pathogenesis.

Gene polymorphisms of IL-10 and MxA in responders and non-responders to interferon therapy in HCV Egyptian patients genotype 4

Hepatitis C virus (HCV) is a major cause of chronic liver disease, with about 170 million people infected worldwide. The standard regimen for treatment of HCV consists of a combination of pegylated interferon with ribavirin. Failure of interferon-α treatment in patients with chronic HCV infection remains a challenging obstacle. Both viral and host environmental factors have been implicated in reducing responsiveness to IFN-α therapy. Host genetic diversity is also believed to contribute to the different clinical outcomes in HCV infection. The objective of the study was to investigate the association of both IL-10 (-819 and -592) and MxA (-88 and -123) single-nucleotide polymorphisms (SNPs) of the promoter regions, with response to interferon (IFN) therapy in Egyptian patients infected with HCV genotype 4. Polymorphisms of both genes in 85 HCV patients and 100 controls were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The frequency of SNP was compared between sustained responders (n = 52) and non-responders (n = 33), as determined by biochemical and virological response to IFN and ribavirin combined therapy. The frequency of the -819T/T and the -592A/A genotypes of IL-10 was significantly higher among responders compared to non-responders (51.92 vs 39.4 %, P = 0.03; 51.92 vs 42.42 %;P = 0.046 respectively). The G/G genotype at position -88 of the MxA gene was significantly lower in responders than in non-responders (25 vs 75.76 %, P = 0.046), whereas heterozygotes (G/T) were more likely responders (65.38 vs 18.18 %, P = 0). The -123C/A genotype was significantly associated with responders (48.08 vs 30.30 %, P = 0.014). Findings suggest that homozygosity for both -819T/T and -592A/A polymorphisms of IL-10 gene and that heterozygosity for both -88G/T and -123C/A polymorphisms of the MxA gene are important host factors that influence the response to IFN therapy in patients with chronic HCV infection.

Potential roles of suppressor of cytokine signaling in wound healing

Wound healing is a dynamic process comprising three overlapping, highly orchestrated stages known as inflammation, proliferation and re-epithelialization, and tissue remodeling. This complex process is regulated by numerous cytokines, with dysregulation of cytokine-induced signaling leading to impaired wound healing. Suppressor of cytokine signaling (SOCS) proteins are a family of eight intracellular proteins which may hold the potential to maintain homeostasis during wound healing through their negative feedback inhibition of cytokine signaling. To date, the roles of SOCS proteins in inflammation, autoimmunity and cancer have been comprehensively illustrated; however, only a limited number of studies focused on their role in wound healing. This review demonstrates the possible links between SOCS proteins and wound healing, and also highlights the potential importance of this family in a variety of other aspects of regenerative medicine.

Roquin--a multifunctional regulator of immune homeostasis

Roquin-1 (Rc3h1) is an E3 ubiquitin ligase originally discovered in a mutational screen for genetic factors contributory to systemic lupus erythematosus-like symptoms in mice. A single base-pair mutation in the Rc3h1 gene resulted in the manifestation of autoantibody production and sustained immunological inflammation characterized by excessive T follicular helper cell activation and formation of germinal centers. Subsequent studies have uncovered a multifactorial process by which Roquin-1 contributes to the maintenance of immune homeostasis. Through its interactions with partner proteins, Roquin-1 targets mRNAs for decay with inducible costimulator being a primary target. In this review, we discuss newly discovered functions of Roquin-1 in the immune system and inflammation, and in disease manifestation, and discuss avenues of further research. A model is presented for the role of Roquin in health and disease.

HCV infection, IFN response and the coding and non-coding host cell genome

HCV is an ideal model to study how the infected cell is altered to allow the establishment of a chronic infection. After infection, the transcriptome of the cell changes in response to the virus or to the antiviral pathways induced by infection. The cell has evolved to sense HCV soon after infection and to activate antiviral pathways. In turn, HCV has evolved to block the antiviral pathways induced by the cell and, at the same time, to use some for its own benefit. In this review, we summarize the proviral and antiviral factors induced in HCV infected cells. These factors can be proteins and microRNAs, but also long noncoding RNAs (lncRNAs) that are induced by infection. Interestingly, several of the lncRNAs upregulated after HCV infection have oncogenic functions, suggesting that upregulation of lncRNAs could explain, at least in part, the increased rate of liver tumors observed in HCV-infected patients. Other lncRNAs induced by HCV infection may regulate the expression of coding genes required for replication or control genes involved in the cellular antiviral response. Given the evolutionary pressure imposed by viral infections and that lncRNAs are specially targeted by evolution, we believe that the study of proviral and antiviral lncRNAs may lead to unexpected discoveries that may have a strong impact on basic science and translational research.

Bone marrow mononuclear cell transplantation improves mitochondrial bioenergetics in the liver of cholestatic rats

Mitochondrial dysfunction has been associated with liver cholestatis. Toxic bile salt accumulation leads to chronic injury with mitochondrial damage, ROS increase and apoptosis, resulting in liver dysfunction. This study aimed to analyze mitochondrial bioenergetics in rats with hepatic fibrosis induced by bile duct ligation (BDL) after BMMNC transplantation. Livers were collected from normal rats, fibrotic rats after 14 and 21 days of BDL (F14d and F21d) and rats that received BMMNC at 14 days of BDL, analyzed after 7 days. F21d demonstrated increased collagen I content and consequently decrease after BMMNC transplantation. Both F14d and F21d had significantly reduced mitochondrial oxidation capacity and increased mitochondrial uncoupling, which were restored to levels similar to those of normal group after BMMNC transplantation. In addition, F21d had a significantly increase of UCP2, and reduced PGC-1α content. However, after BMMNC transplantation both proteins returned to levels similar to normal group. Moreover, F14d had a significantly increase in 4-HNE content compared to normal group, but after BMMNC transplantation 4-HNE content significantly reduced, suggesting oxidative stress reduction. Therefore, BMMNC transplantation has a positive effect on hepatic mitochondrial bioenergetics of cholestatic rats, increasing oxidative capacity and reducing oxidative stress, which, in turn, contribute to liver function recover.

The role of suppressors of cytokine signalling in human neoplasms

Suppressors of cytokine signalling 1-7 (SOCS1-7) and cytokine-inducible SH2-containing protein (CIS) are a group of intracellular proteins that are well known as JAK-STAT and several other signalling pathways negative feedback regulators. More recently several members have been identified as tumour suppressors and dysregulation of their biological roles in controlling cytokine and growth factor signalling may contribute to the development of many solid organ and haematological malignancies. This review explores their biological functions and their possible tumour suppressing role in human neoplasms.

Investigation of biomarkers in peripheral blood cells of Pakistani chronic HCV patients with genotype 3a: an assessment of HCV-induced pathogenesis

ABSTRACT: 

Aim: The main objective of the current study was to measure the mRNA expression of potent genes involved in oxidative stress, fibrosis and insulin resistance in chronic HCV patients using peripheral white blood cells. Materials & methods: A total of 50 individuals were selected for this study, including 40 chronic HCV patients and ten healthy individuals. RNA was extracted from human peripheral white blood cells of chronic HCV-infected patients and healthy individuals. Transcript analysis of selected genes was performed using real-time PCR. Results: A significant increase was observed in the mRNA expression of Nox4, TGF-β, TNF-α and collagen, while a significant decrease was observed in mRNA expression of Cu/Zn SOD and IL-10. However, there was no significant change found in mRNA expression of SOCS3 and SOCS7 level. Conclusion: The current study confirms the significant expression of different genes in peripheral white blood cells of chronic HCV patients. This could be an easy, cost-efficient approach for the assessment of HCV-induced pathologies at extrahepatic sites, which could be further validated in comparison with liver tissue biopsies.

Bridging the species divide: transgenic mice humanized for type-I interferon response

We have generated transgenic mice that harbor humanized type I interferon receptors (IFNARs) enabling the study of type I human interferons (Hu-IFN-Is) in mice. These “HyBNAR” (Hybrid IFNAR) mice encode transgenic variants of IFNAR1 and IFNAR2 with the human extracellular domains being fused to transmembrane and cytoplasmic segments of mouse sequence. B16F1 mouse melanoma cells harboring the HyBNAR construct specifically bound Hu-IFN-Is and were rendered sensitive to Hu-IFN-I stimulated anti-proliferation, STAT1 activation and activation of a prototypical IFN-I response gene (MX2). HyBNAR mice were crossed with a transgenic strain expressing the luciferase reporter gene under the control of the IFN-responsive MX2 promoter (MX2-Luciferase). Both the HyBNAR and HyBNAR/MX2-Luciferase mice were responsive to all Hu-IFN-Is tested, inclusive of IFNα2A, IFNβ, and a human superagonist termed YNSα8. The mice displayed dose-dependent pharmacodynamic responses to Hu-IFN-I injection, as assessed by measuring the expression of IFN-responsive genes. Our studies also demonstrated a weak activation of endogenous mouse interferon response, especially after high dose administration of Hu-IFNs. In sharp contrast to data published for humans, our pharmacodynamic readouts demonstrate a very short-lived IFN-I response in mice, which is not enhanced by sub-cutaneous (SC) injections in comparison to other administration routes. With algometric differences between humans and mice taken into account, the HyBNAR mice provides a convenient non-primate pre-clinical model to advance the study of human IFN-Is.

Is interleukin-10 gene polymorphism a predictive marker in HCV infection?

The clinical outcome of hepatitis C virus (HCV) infection varies between individuals - from spontaneous viral clearance and persistence without complication, to chronic hepatitis, cirrhosis and hepatocellular carcinoma. Also patterns of response to interferon-based anti-HCV therapy are different from person to person. This diversity may be affected by host genetic factors, including alterations in genes encoding cytokines. Interleukin-10, as an anti-inflammatory cytokine and immune response modulator, may influence on HCV infection susceptibility as well as spontaneous and treatment-induced HCV eradication. Moreover, it is stated that IL-10 has antifibrotic properties and play a role in progression of liver disease. This review summarized studies on interleukin-10 gene polymorphisms (mainly promoter SNPs at positions -1082(G/A), -819(C/T) and -592(C/A)), which may determine IL-10 production, regarding susceptibility to HCV infection, course of HCV-related liver disease (fibrosis, cirrhosis, hepatocellular carcinoma, ALT abnormalities), spontaneous viral elimination as well as hepatitis C treatment outcomes. Analysis of hereby summarized studies shows that it is difficult to unambiguously determine the importance of IL-10 polymorphism as a predictor of clinical outcome of hepatitis C and response to anti-HCV therapy before its beginning. Thus, future larger studies need to address these issues. Continuation of studies on interleukin-10 polymorphisms as well as identification of other candidate predictive markers in HCV infection has important practical implications and there is a chance that may contribute to reduce the scale of hepatitis C problem.

Interferon-α induces G1 cell-cycle arrest in renal cell carcinoma cells via activation of Jak-Stat signaling

The purpose of this study was to clarify the mechanism of IFN-α resistance in RCC. The effects of IFN-α on induction of apoptosis and cell-cycle arrest were analyzed by flow cytometric analysis. Jak-Stat pathway components induced by IFN-α was evaluated using Western blotting. The results suggested that IFN-α caused growth inhibition of RCC cell lines via arrest in the G1 phase without inducing apoptosis. The resistance of RCC to IFN-α was associated with the low expression of Stat1. This study indicated that the Jak-Stat pathway should be considered a primary target for improving the response of RCC to IFN-α treatment.

Alterations in gene expression after induction of profound hypothermia for the treatment of lethal hemorrhage

INTRODUCTION

We have previously demonstrated that induction of profound hypothermia improves long-term survival in animal models of complex injuries/lethal hemorrhage. However, the precise mechanisms have not been well defined. The aim of this high-throughput study was to investigate the impact of profound hypothermia on gene expression profiles.

METHODS

Wistar-Kyoto rats underwent 40% blood volume arterial hemorrhage over 10 minutes and were randomized into two groups based on core body temperatures (n = 7 per group): hypothermia (H, 15 degrees C) and normothermia (N, 37 degrees C). Hypothermia was induced by infusing cold isotonic solution using a cardiopulmonary bypass (CPB) setup. After reaching target body temperature, low-flow state (CPB flow rate of 20 mL x kg x min) was maintained for 60 minutes. Hypothermic rats were rewarmed to baseline temperature, and all rats were resuscitated on CPB and monitored for 3 hours. The N group underwent identical CPB management. Sham rats (no hemorrhage and no instrumentation) were used as controls. Blood samples were collected serially, and hepatic tissues were harvested after 3 hours. Affymatrix Rat Gene 1.0 ST Array (27,342 genes, >700,000 probes) was used to determine gene expression profiles (n = 3 per group), which were further analyzed using GeneSpring (Agilent Technologies, Santa Clara, CA) and GenePattern (Broad Institute, Cambridge, MA) programs. Data were further queried using network analysis tools including Gene Ontology, and Ingenuity Pathway Analysis (Ingenuity Systems). Key findings were verified using real-time polymerase chain reaction and Western blots.

RESULTS

Induction of hypothermia significantly (p < 0.05) decreased the magnitude of lactic acidosis and increased the survival rates (100% vs. 0% in normothermia group). Five hundred seventy-one of 23,000 genes had altered expression in response to the induction of hypothermia: 382 were up-regulated and 187 were down-regulated. Twelve key pathways were specifically modulated by hypothermia. Interleukin-6, interleukin-10, p38 mitogen-activated protein kinase (MAPK), nuclear factor kappa-light-chain-enhancer of activated B cells, glucocorticoids, and other signaling pathways involved with acute phase reactants were up-regulated. Multiple metabolic pathways were down- regulated. The largest change was in the peroxisome proliferator-activated receptor gamma gene that codes for a transcriptional coactivator, which in turn controls mitochondrial biogenesis, glycerolipid, and other metabolic pathways in the liver. Apoptotic cell death cascades were activated in response to blood loss (H and N groups), but multiple specific anti-apoptotic genes (baculoviral Inhibitor of apoptosis protein repeat-containing 3, BCL3L1, NFKB2) displayed an increased expression specifically in the hypothermia treated animals, suggesting an overall pro-survival phenotype.

CONCLUSIONS

Profound hypothermia increases survival in a rodent model of hemorrhagic shock. In addition to decreasing tissue oxygen consumption, induction of hypothermia directly alters the expression profiles of key genes, with an overall up-regulation of pro-survival pathways and a down- regulation of metabolic pathways.

Neutralization of osteopontin inhibits obesity-induced inflammation and insulin resistance

OBJECTIVE

Obesity is associated with a state of chronic low-grade inflammation mediated by immune cells that are primarily located to adipose tissue and liver. The chronic inflammatory response appears to underlie obesity-induced metabolic deterioration including insulin resistance and type 2 diabetes. Osteopontin (OPN) is an inflammatory cytokine, the expression of which is strongly upregulated in adipose tissue and liver upon obesity. Here, we studied OPN effects in obesity-induced inflammation and insulin resistance by targeting OPN action in vivo.

RESEARCH DESIGN AND METHODS

C57BL/6J mice were fed a high-fat diet to induce obesity and were then intravenously treated with an OPN-neutralizing or control antibody. Insulin sensitivity and inflammatory alterations in adipose tissue and liver were assessed.

RESULTS

Interference with OPN action by a neutralizing antibody for 5 days significantly improved insulin sensitivity in diet-induced obese mice. Anti-OPN treatment attenuated liver and adipose tissue macrophage infiltration and inflammatory gene expression by increasing macrophage apoptosis and significantly reducing c-Jun NH(2)-terminal kinase activation. Moreover, we report OPN as a novel negative regulator for the activation of hepatic signal transducer and activator of transcription 3 (STAT3), which is essential for glucose homeostasis and insulin sensitivity. Consequently, OPN neutralization decreased expression of hepatic gluconeogenic markers, which are targets of STAT3-mediated downregulation.

CONCLUSIONS

These findings demonstrate that antibody-mediated neutralization of OPN action significantly reduces insulin resistance in obesity. OPN neutralization partially decreases obesity-associated inflammation in adipose tissue and liver and reverses signal transduction related to insulin resistance and glucose homeostasis. Hence, targeting OPN could provide a novel approach for the treatment of obesity-related metabolic disorders.

Hepatitis B virus overexpresses suppressor of cytokine signaling-3 (SOCS3) thereby contributing to severity of inflammation in the liver

The mechanism by which hepatitis B virus (HBV) infection causes severe inflammatory liver diseases is multifactorial and related to interactions with cell signaling pathways and the ensuing inflammatory response. Activation of JAK/STAT/SOCS signaling is essential for the induction of cellular antiviral responses, contributes to apoptosis and is negatively regulated by SOCS proteins. Recent reports have shown that SOCS3 activation interferes with viral protein expression and treatment response and thereby plays a major role in hepatitis virus infections. We analyzed the expression of SOCS3 in liver specimens from HBV-infected patients using immunohistochemistry (IHC) and determined the effect of HBV on STAT/SOCS signaling in functional cell culture experiments (HuH-7) using HBV-expressing adenoviral constructs (AdHBV). Increased expression of SOCS3 protein was identified in liver specimens from patients with chronic HBV-infection and this correlated with the severity of liver inflammation. In accordance with the IHC-findings, in vitro analyses demonstrated that HBV infection of HuH7 cells was associated with increased expression of SOCS3 protein. In spite of the over expression of its negative regulator SOCS3 we observed a constitutive activation of STAT3. SOCS1 levels were not increased while pSTAT1 was suppressed in HBV-infected HuH7 cells. Our results demonstrate that STAT/SOCS-signaling is dysregulated in HBV-infected hepatocytes both in vivo and in vitro and this correlated with the severity of liver inflammatory changes. This interference of STAT/SOCS signaling by HBV may result in an ineffective immune response against HBV and potentially contributes to viral pathogenesis, malignant transformation and may represent an important mechanism of viral persistence.

Deficient SOCS3 and SHP-1 expression in psoriatic T cells

IFN-alpha and skin-infiltrating activated T lymphocytes have important roles in the pathogenesis of psoriasis. T cells from psoriatic patients display an increased sensitivity to IFN-alpha, but the pathological mechanisms behind the hyperresponsiveness to IFN-alpha remained unknown. In this study, we show that psoriatic T cells display deficient expression of the suppressor of cytokine signaling (SOCS)3 in response to IFN-alpha and a low baseline expression of the SH2-domain-containing protein-tyrosine phosphatase (SHP)-1 when compared with skin T cells from nonpsoriatic donors. Moreover, IFN-alpha-stimulated psoriatic T cells show enhanced activation of JAKs (JAK1 and TYK2) and signal transducers and activators of transcription. Increased expression of SOCS3 proteins resulting from proteasomal blockade partially inhibits IFN-alpha response. Similarly, forced expression of SOCS3 and SHP-1 inhibits IFN-alpha signaling in psoriatic T cells. In conclusion, our data suggest that loss of regulatory control is involved in the aberrant hypersensitivity of psoriatic T cells to IFN-alpha.

Alpha interferon induces long-lasting refractoriness of JAK-STAT signaling in the mouse liver through induction of USP18/UBP43

Recombinant alpha interferon (IFN-alpha) is used for the treatment of viral hepatitis and some forms of cancer. During these therapies IFN-alpha is injected once daily or every second day for several months. Recently, the long-acting pegylated IFN-alpha (pegIFN-alpha) has replaced standard IFN-alpha in therapies of chronic hepatitis C because it is more effective, supposedly by inducing a long-lasting activation of IFN signaling pathways. IFN signaling in cultured cells, however, becomes refractory within hours, and little is known about the pharmacodynamic effects of continuously high IFN-alpha serum concentrations. To investigate the behavior of the IFN system in vivo, we repeatedly injected mice with IFN-alpha and analyzed its effects in the liver. Within hours after the first injection, IFN-alpha signaling became refractory to further stimulation. The negative regulator SOCS1 was rapidly upregulated and likely responsible for early termination of IFN-alpha signaling. For long-lasting refractoriness, neither SOCS1 nor SOCS3 were instrumental. Instead, we identified the inhibitor USP18/UBP43 as the key mediator. Our results indicate that the current therapeutic practice using long-lasting pegIFN-alpha is not well adapted to the intrinsic properties of the IFN system. Targeting USP18 expression may allow to exploit the full therapeutic potential of recombinant IFN-alpha.

Immunological and mutagenic actions of ribavirin monotherapy preceding combination therapy with interferon for patients with chronic hepatitis C

Background

We aimed to investigate the effects of ribavirin on hepatitis C virus (HCV). Immunological and virological effects were analysed in patients undergoing treatment with ribavirin monotherapy prior to the initiation of combination therapy with interferon-α.

Methods

A total of 25 patients with chronic HCV infection were enrolled in this study. All patients received ribavirin for 4 weeks during monotherapy; subsequently, interferon-α2b was additionally given as combined therapy. Patients were divided into two groups according to virological response. A rapid viral responder (RVR) was defined as a patient in whom HCV RNA became undetectable within 4 weeks after combination therapy. The changes of the T-helper (Th)1/Th2 subset of peripheral blood CD4+ T-cells, serum cytokine levels and the alignment of the interferon sensitivity- determining region (ISDR) during ribavirin monotherapy were analysed by flow cytometry, ELISAs and sequencing methods.

Results

A total of 17 patients were classed as RVR. In the RVR group, the mean ±sd serum alanine aminotransferase levels significantly decreased (before treatment 103 ±92 IU/l and after treatment 57 ±46 IU/l; P<0.05) during ribavirin monotherapy. The mean ±sd Th1/Th2 ratio significantly increased (before treatment 13.9 ±5.1 and after treatment 16.7 ±6.2; P<0.05), but did not change in the non-RVR group. The levels of Th2 cytokines (interleukin-10 and soluble CD30) significantly decreased, especially in the RVR group. The mean ±sd mutation rates of ISDR at the nucleotide level increased in the RVR group (before treatment 2.6 ±0.9 sites/clone and after treatment 3.9 ±1.6 sites/clone; P<0.05), but did not change in the non-RVR group.

Conclusions

Ribavirin administration might increase the efficacy of interferon therapy for patients with chronic hepatitis C by stimulating the host immune system and promoting HCV gene mutation.

Gene expression signatures of peripheral CD4+ T cells clearly discriminate between patients with acute and chronic hepatitis B infection

CD4+ T and regulatory T cells (Tregs) seem to play a key role in persistence of hepatitis B virus (HBV) infection. However, the molecular events by which Tregs exert their modulatory activity are largely unknown. The transcriptional profiles of CD4+ T cells of healthy controls (HCs) and patients affected by acute hepatitis B (AVH-B) or chronic hepatitis B (CHB) infection were established using a custom expression array consisting of 350 genes relevant for CD4+ T cell and Treg function. These studies were complemented by real-time reverse-transcription polymerase chain reaction. Peripheral blood mononuclear cells (PBMCs) were also analyzed for the presence of Tregs, which were more abundant in the acute stage of the disease (7%) than in HCs and CHB infection (HCs versus AVH-B, P = 0.003; AVH-B versus CHB, P = 0.04). One hundred eighteen genes (34%) intrinsically differentiate HBV-infected patients from HCs. Using gene ontology, we identified T cell receptor signaling and clusterization, mitogen-activated protein kinase kinase signaling, cell adhesion, cytokines and inflammatory responses, cell cycle/cell proliferation, and apoptosis as the most prominent affected modules. A higher expression of CCR1, CCR3, CCR4, CCR5, and CCR8 was seen in AVH-B than in CHB-infected patients and HCs. Annotation of the interconnected functional network of genes provided a unique representation of global immune activation during acute infection. Almost all genes were down-regulated in patients with CHB infection.

CONCLUSION

The fingerprints enable clear discrimination between patients suffering from AVH-B or CHB infection. The observed profiles suggest accumulation of effector T cells with a potential role in necro-inflammation during the acute stage. Subsequent down-regulated effector functions support the hypothesis of suppressed CD4+ effector T cells favoring viral persistence in the chronic infection stage.

Increased bone mass, altered trabecular architecture and modified growth plate organization in the growing skeleton of SOCS2 deficient mice

Suppressor of cytokine signalling-2 (SOCS2) negatively regulates the signal transduction of several cytokines. Socs2(-/-) mice show increased longitudinal skeletal growth associated with deregulated GH/IGF-1 signalling. The present study examined the role of SOCS2 in endochondral ossification and trabecular and cortical bone formation, and investigated whether pro-inflammatory cytokines associated with pediatric chronic inflammatory disorders mediate their effects through SOCS2. Seven-week-old Socs2(-/-) mice were heavier (27%; P < 0.001) and longer (6%; P < 0.001) than wild-type mice. Socs2(-/-) tibiae were longer (8%; P < 0.001) and broader (18%; P < 0.001) than that of wild-type mice, and the Socs2(-/-) mice had wider growth plates (24%; P < 0.001) with wider proliferative and hypertrophic zones (10% (P < 0.05) and 14% (P < 0.001) respectively). Socs2(-/-) mice showed increased total cross-sectional bone area (16%: P < 0.001), coupled to increased total tissue area (17%; P < 0.05) compared to tibia from wild-type mice. Socs2(-/-) mice showed increased percent bone volume (101%; P < 0.001), trabecular number (82%; P < 0.001) and trabecular thickness (11%; P < 0.001), with associated decreases in trabecular separation (19%; P < 0.001). TNFalpha exposure to growth plate chondrocytes for 48 h increased SOCS2 protein expression. Growth of metatarsals from 1-day-old Socs2(-/-) and Socs2(+/+) mice, as well as expression of Aggrecan, Collagen Type II and Collagen Type X, were inhibited by TNFalpha, with no effect of genotype. Our data indicate that physiological levels of SOCS2 negatively regulate bone formation and endochondral growth. Our results further suggest that pro-inflammatory cytokines mediate their inhibitory effects on longitudinal bone growth through a mechanism that is independent of SOCS2.

Interleukin 10 deficiency exacerbates halothane induced liver injury by increasing interleukin 8 expression and neutrophil infiltration

The prediction and prevention of drug-induced liver injury (DILI) have been hindered by limited knowledge of the underlying mechanisms, in part the result of a lack of animal models. Using a newly established DILI model induced by halothane, we found increased liver damage susceptibility in interleukin 10 (IL-10) knockout (KO) mice. Extensive neutrophil infiltration and chemoattractant factor interleukin 8 (IL-8) expression in IL-10 KO mice were observed after halothane administration. The elevation of IL-8 expression was NF-kappaB- and P38 MAPK-dependent. In addition, increased signal transducer and activator of transcription factors (STAT) 1 and STAT3 were observed in halothane treated IL-10 KO mice. Exogenous IL-10 treatment protected susceptible mice from halothane induced liver injury (HILI). In conclusion, IL-10 deficiency increases susceptibility to HILI and increased IL-8 expression as well as neutrophil infiltration may be responsible for this phenomenon.

The analysis of CIS, SOCS1, SOSC2 and SOCS3 transcript levels in peripheral blood mononuclear cells of systemic lupus erythematosus and rheumatoid arthritis patients

Being expressed in immune cells, cytokine-inducible SH2 protein (CIS) and suppressors of cytokine signaling proteins, SOCS1, SOCS2 and SOCS3, can regulate cytokine signaling and immune responses. To evaluate the possible expressional dysregulation of CIS, SOCS1, SOCS2 and SOCS3 in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) patients, the transcript levels of these genes in peripheral blood mononuclear cells (PBMCs) from SLE and RA patients were determined and statistically compared with those in PBMCs from normal individuals. It was found that SLE patients with the active disease activity significantly express higher CIS transcript levels than normal individuals and SLE patients with the inactive disease activity, whereas the difference in SOCS1, SOCS2 and SOCS3 transcript levels between normal individuals and SLE patients is not statistically significant. However, transcript levels of these CIS/SOCS genes in RA patients were not significantly different from those in normal individuals, except that treatment with a TNF-alpha-blocking agent in RA patients appears to enhance the CIS transcript expression, but down-regulates the SOCS2 transcript expression in PBMCs. These data suggest that CIS can serve as an SLE disease marker and may be involved in the pathogenesis of SLE, and that TNF-alpha may play an important role in the regulation of CIS and SOCS2 gene expression in PBMCs in vivo.

Roles of unphosphorylated STATs in signaling

The seven members of the signal transducer and activator of transcription (STAT) family of transcription factors are activated in response to many different cytokines and growth factors by phosphorylation of specific tyrosine residues. The STAT1 and STAT3 genes are specific targets of activated STATs 1 and 3, respectively, resulting in large increases in the levels of these unphosphorylated STATs (U-STATs) in response to the interferons (STAT1) or ligands that active gp130, such as IL-6 (STAT3). U-STATs drive gene expression by novel mechanisms distinct from those used by phosphorylated STAT (P-STAT) dimers. In this review, we discuss the roles of U-STATs in transcription and regulation of gene expression.

Cell type-dependent pro- and anti-inflammatory role of signal transducer and activator of transcription 3 in alcoholic liver injury

BACKGROUND & AIMS

Signal transducer and activator of transcription 3 (STAT3) is known to be activated in human alcoholic liver disease, but its role in the pathogenesis of alcoholic liver injury remains obscure.

METHODS

The role of STAT3 in alcoholic liver injury was investigated in hepatocyte-specific STAT3 knockout (H-STAT3KO) mice and macrophage/neutrophil-specific STAT3 KO (M/N-STAT3KO) mice. Alcoholic liver injury was achieved by feeding mice a liquid diet containing 5% ethanol for up to 8 weeks.

RESULTS

Compared with wild-type mice, feeding H-STAT3KO mice with an ethanol-containing diet induced greater hepatic steatosis, hypertriglyceridemia, and hepatic expression of lipogenic genes (sterol regulatory element-binding protein, fatty acid synthase, acetyl-CoA carboxylase-1, and stearoyl-CoA desaturase 1), but less inflammation and lower expression of hepatic proinflammatory cytokines. In contrast, ethanol-fed M/N-STAT3KO mice showed more hepatic inflammation, worse injury, and increased hepatic expression of proinflammatory cytokines compared with wild-type mice. Kupffer cells isolated from ethanol-fed H-STAT3KO mice produced similar amounts of reactive oxygen species and tumor necrosis factor alpha, whereas Kupffer cells from M/N-STAT3KO mice produced more reactive oxygen species and tumor necrosis factor alpha compared with wild-type controls.

CONCLUSIONS

These findings suggest that STAT3 regulates hepatic inflammation in a cell type-dependent manner during alcoholic liver injury: STAT3 in hepatocytes promotes whereas STAT3 in macrophages/Kupffer cells suppresses inflammation. In addition, activation of hepatocellular STAT3 ameliorates alcoholic fatty liver via inhibition of sterol regulatory element-binding protein 1c expression.

Transcriptomic analysis reveals early signs of liver toxicity in female MRL +/+ mice exposed to the acylating chemicals dichloroacetyl chloride and dichloroacetic anhydride

Dichloroacetyl chloride (DCAC) is a reactive metabolite of trichloroethene (TCE). TCE and its metabolites have been implicated in the induction of organ-specific and systemic autoimmunity, in the acceleration of autoimmune responses, and in the development of liver toxicity and hepatocellular carcinoma. In humans, effects of environmental toxicants are often multifactorial and detected only after long-term exposure. Therefore, we developed a mouse model to determine mechanisms by which DCAC and related acylating agents affect the liver. Autoimmune-prone female MRL +/+ mice were injected intraperitoneally with 0.2 mmol/kg of DCAC or dichloroacetic anhydride (DCAA) in corn oil twice weekly for six weeks. No overt liver pathology was detectable. Using microarray gene expression analysis, we detected changes in the liver transcriptome consistent with inflammatory processes. Both acylating toxicants up-regulated the expression of acute phase response and inflammatory genes. Furthermore, metallothionein genes were strongly up-regulated, indicating effects of the toxicants on zinc ion homeostasis and stress responses. In addition, DCAC and DCAA induced the up-regulation of several genes indicative of tumorigenesis. Our data provide novel insight into early mechanisms for the induction of liver disease by acylating agents. The data also demonstrate the power of microarray analysis in detecting early changes in liver function following exposure to environmental toxicants.

Cross-inhibition of interferon-induced signals by GM-CSF through a block in Stat1 activation

We investigated the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on biologic signals induced by interferon-alpha (IFN-alpha) and IFN-gamma. In hematopoietic cell lines, IFN-induced signaling was investigated by Western blotting, electrophoretic mobility shift assays (EMSA), flow cytometry, protein-tyrosine phosphatase (PTP) assays, and RT-PCR. GM-CSF inhibited IFN-alpha-induced and IFN-gamma-induced Stat1 tyrosine phosphorylation in a time-dependent manner. EMSA showed that GM-CSF inhibited IFN-alpha-induced and IFN-gamma-induced IFN-gamma activator sequence (GAS) binding activity. As a consequence, IFN-induced transcription of the early response gene, IFN-stimulated gene 54 (ISG54), was inhibited. The expression of IFN regulatory factor-1 (IRF-1) and MHC class I antigens was downregulated at protein levels in hematopoietic cell lines (U937, THP1). In contrast to GM-CSF, granulocyte colony-stimulating factor (G-CSF) and interleukin-3 (IL-3) did not influence the IFN-induced Stat1 activation. To explore the molecular mechanism of suppression of Stat1 tyrosine phosphorylation, we investigated the induction and activation of cytokine-inducible SH2-containing protein/suppressor of cytokine signaling (CIS/SOCS) molecules and phosphatases on GM-CSF treatment. In contrast to G-CSF and IL-3, GM-CSF strongly induced the expression of CIS1 and SOCS2 at mRNA levels, but overexpression of CIS1 or SOCS2 in HEK293 cells did not show inhibition of Stat1 tyrosine phosphorylation upon IFN treatment. In PTP assays, on GM-CSF incubation, no enhanced src homology 2 domain tyrosine phosphatase 1 and 2 (SHP1 and SHP2) activity was detectable. However, GM-CSF-induced downregulation of Tyk2 and Jak1 tyrosine phosphorylation as well as Tyk2 protein levels likely contributed to the reduced Stat1 tyrosine phosphorylation. In hematopoietic cells, GM-CSF antagonizes IFN-induced signals by a block in Stat1 activation.

Defective Jak-Stat activation in renal cell carcinoma is associated with interferon-alpha resistance

Chemotherapy is ineffective against metastatic renal cell carcinoma (RCC). Interferon (IFN)-alpha has become the most common agent used in clinical therapy to overcome this malignant tumor, although a satisfactory response has not been achieved and the mechanism of resistance of RCC to IFN-alpha remains unclear. The purpose of the present study was to evaluate the susceptibility of RCC cells to IFN-alpha and clarify the mechanism of IFN-alpha resistance in RCC. Six RCC cell lines and three types of IFN-alpha were used, and the expression, activation and effects of transfection of possible proteins or factors reported to be involved in IFN-alpha signaling were examined to clarify the mechanism of resistance. The results suggest that the resistance of RCC to IFN-alpha is associated with the lack of Jak1, Tyk2 and Stat1 expression and defective Jak-Stat activation, but not with a lack of IFN-alpha receptor, suppressors of cytokine signaling induction or other factors examined. Moreover, phosphorylation of Jak-Stat pathway components and reversion of IFN-alpha resistance in RCC were observed upon transfection with Jak1, Tyk2 or Stat1 vector. These results suggest that restoring the expression of Jak or Stat1 might strikingly increase the susceptibility of RCC to IFN-alpha and may be a new strategy for improving the response of RCC to IFN-alpha treatment. The Jak-Stat pathway should therefore be an appropriate target for the treatment of RCC.

Infection of human dendritic cells with a Mycobacterium tuberculosis sigE mutant stimulates production of high levels of interleukin-10 but low levels of CXCL10: impact on the T-cell response

The Mycobacterium tuberculosis genome encodes 13 sigma factors. We have previously shown that mutations in some of these transcriptional activators render M. tuberculosis sensitive to various environmental stresses and can attenuate the virulence phenotype. In this work, we focused on extracytoplasmic factor sigmaE and studied the effects induced by the deletion of its structural gene (sigE) in the infection of human monocyte-derived dendritic cells (MDDC). We found that the wild-type M. tuberculosis strain (H37Rv), the sigE mutant (ST28), and the complemented strain (ST29) were able to infect dendritic cells (DC) to similar extents, although at 4 days postinfection a reduced ability to grow inside MDDC was observed for the sigE mutant ST28. After mycobacterium capture, the majority of MDDC underwent full maturation and expressed both inflammatory cytokines, such as tumor necrosis factor alpha, and the regulatory cytokines interleukin-12 (IL-12), IL-18, and beta interferon (IFN-beta). Conversely, a higher level of production of IL-10 was observed in ST28-infected MDDC compared to H37Rv- or ST29-infected cell results. However, in spite of the presence of IL-10, supernatants from ST28-infected DC induced IFN-gamma production by T cells similarly to those from H37Rv-infected DC culture. On the other hand, IL-10 impaired CXCL10 production in sigE mutant-infected DC and, indeed, its neutralization restored CXCL10 secretion. In line with these results, supernatants from ST28-infected cells showed a decreased capability to recruit CXCR3+ CD4+ T cells compared to those obtained from H37Rv-infected DC culture. Thus, our findings suggest that the sigE mutant-induced secretion of IL-10 inhibits CXCL10 expression and, in turn, the recruitment of activated-effector cells involved in the formation of granulomas.

Role of STAT3 in type I interferon responses. Negative regulation of STAT1-dependent inflammatory gene activation

Type I interferons (IFNalpha/beta) induce antiviral responses and have immunomodulatory effects that can either promote or suppress immunity and inflammation. In myeloid cells IFNalpha/beta activates signal transducers and activators of transcription STAT1, STAT2, and STAT3. STAT1 and STAT2 mediate the antiviral and inflammatory effects of IFNalpha/beta, but the function of IFNalpha/beta-activated STAT3 is not known. We investigated the role of STAT3 in type I IFN signaling in myeloid cells by modulating STAT3 expression and the intensity of STAT3 activation using overexpression and RNA interference and determining the effects on downstream signaling and gene expression. IFNalpha-activated STAT3 inhibited STAT1-dependent gene activation, thereby down-regulating IFNalpha-mediated induction of inflammatory mediators such as the chemokines CXCL9 (Mig) and CXCL10 (IP-10). At the same time, IFNalpha-activated STAT3 supported ISGF-3-dependent induction of antiviral genes. STAT3 did not suppress STAT1 tyrosine phosphorylation or nuclear translocation but instead sequestered STAT1 and suppressed the formation of DNA-binding STAT1 homodimers. These results identify a regulatory function for STAT3 in attenuating the inflammatory properties of type I IFNs and provide a mechanism of suppression of STAT1 function that differs from previously described suppression of tyrosine phosphorylation. The results suggest that changes in the relative expression and activation of STAT1 and STAT3 that occur during immune responses determine the nature of cellular responses to type I IFNs.

Controlling cytokine signaling by constitutive inhibitors

Cytokines are secreted proteins that regulate diverse biological functions by binding to receptors at the cell surface to activate complex signal transduction pathways including the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. Stringent mechanisms of signal attenuation are essential for ensuring an appropriate, controlled cellular response. Three families of proteins, the SH2-containing phosphatases (SHP), the protein inhibitors of activated STATs (PIAS), and the suppressors of cytokine signaling (SOCS), inhibit specific and distinct aspects of cytokine signal transduction. The analysis of mice lacking genes for members of the SHP has shed much light on the roles of these proteins in vivo. In recent in vitro studies, the protein modifiers ubiquitin and small ubiquitin-like modifier (SUMO) have emerged as key players in the strategies employed by SOCS and PIAS to repress signaling. This review throws light on the mechanisms of action of these regulators as being evolved by the latest researches.

Lipopolysaccharide primes neutrophils for a rapid response to IL-10

Responsiveness of human neutrophils to IL-10 was recently shown to be strictly dependent on the levels of IL-10R1 expression. Activation of signal transducer and activator of transcription 3 (STAT3) phosphorylation and induction of suppressor of cytokine signaling (SOCS)-3 protein by IL-10 are in fact negligible in circulating or freshly isolated ("time 0") neutrophils, but become readily measurable in neutrophils cultured for 4 h in the presence or absence of LPS. In this study, we show that modulation by IL-10 of LPS-induced TNF-alpha, CXCL8/IL-8 and IL-1 receptor antagonist (IL-1ra) mRNA accumulation in neutrophils already expressing a functional IL-10R and antigenic SOCS-3 (i.e. in "4-h-cultured" neutrophils) occurs with kinetics that are similar to those observed in "time 0" neutrophils, depends on de novo protein synthesis, but does not require SOCS-1, SOCS-3, heme oxygenase and Bcl-3 induction. By contrast, we show that IL-10 alone rapidly modulates the expression of TNF-alpha, CXCL8/IL-8 and IL-1ra mRNA, without any new protein synthesis requirement, if neutrophils have been previously exposed to LPS for at least 4 h. These findings suggest that LPS prepares neutrophils to optimally respond to IL-10 in terms of rapid gene modulation via mechanisms that, presumably, depend on specific LPS-induced protein(s).

IL-10 promoter haplotype influence on interferon treatment response in multiple sclerosis

The level of interleukin-10 (IL-10) expression is related to polymorphisms -1082 (G/A), -819 (T/C) and -592 (A/C) in the promoter region of the IL-10 gene, which constitute three haplotypes, GCC, ATA, and ACC. The ATA (a non-GCC) haplotype, which is associated with low IL-10 expression, has been shown to improve interferon (IFN) treatment response in hepatitis C. We analysed the distribution of IL-10 promoter haplotype combinations to determine whether they could influence initial IFN treatment response in 63 patients with relapsing-remitting multiple sclerosis (MS). The patients were grouped into non-GCC or GCC haplotypes, and the clinical and magnetic resonance imaging (MRI) disease activity was compared in the two groups. During the first 6 months of treatment, MS patients with non-GCC haplotypes experienced fewer new MRI T1-contrast enhancing lesions [0.77+/-0.36 (SEM)] than patients with the GCC haplotype (2.45+/-0.57) (P=0.05, Mann-Whitney U test). No differences were detected on clinical disease activity. The results suggest an influence of IL-10 promoter polymorphisms on IFN treatment response in MS.

Novel Roles of Unphosphorylated STAT3 in Oncogenesis and Transcriptional Regulation

Signal transducer and activator of transcription 3 (STAT3) is phosphorylated on tyrosine residue 705 in response to growth factors or cytokines to form activated homodimers that drive gene expression. Because the stat3 promoter has a binding site for STAT3 dimers, the amount of STAT3 protein increases when STAT3 is activated (e.g., in response to interleukin 6). Unphosphorylated STAT1 is known to drive the expression of certain genes. To explore the possibility of a similar role for the induced expression of unphosphorylated STAT3, we overexpressed either Y705F STAT3, which can not be phosphorylated on residue 705, or wild-type STAT3 in normal human mammary epithelial cells or STAT3-null mouse cells. The levels of many mRNAs were affected strongly by high levels of either form of STAT3. Some genes whose expression was increased by overexpressed STAT3, but not by activated STAT3 dimers, encode well-known oncoproteins (e.g., MRAS and MET). In many tumors, STAT3 is activated constitutively, and thus the unphosphorylated form is likely to be expressed highly, driving oncogene expression by a novel mechanism. In addition, expression of the stat3 gene is increased strongly in response to interleukin 6, and the high levels of unphosphorylated STAT3 that result drive a substantial late phase of gene expression in response to this cytokine. Thus, unphosphorylated STAT3, which activates gene expression by a novel mechanism distinct from that used by STAT3 dimers, is very likely to be an important transcription factor both in cancer and in responses to cytokines.

Autoregulatory role of interleukin-10 in hepatitis C patients treated with IFN-alpha

Interferon-alpha2 (IFN-alpha2) is used as standard treatment of patients with chronic hepatitis C (cHCV), but little is known about the immunomodulatory effects of this cytokine in vivo. We have studied immunologic parameters in freshly isolated peripheral blood mononuclear cells (PBMC) of 26 patients with cHCV 12 h before and 12 h after the first s.c. injection of 5-6 MU IFN-alpha2. In PBMC obtained after IFN injection, a substantial increase in IL-10 production after antigen-specific and nonspecific stimulation was observed, whereas IFN-gamma production and proliferation were significantly diminished compared with PBMC obtained before IFN injection. Patients were stratified according to single nucleotide polymorphisms (SNPs) in the interleukin-10 (IL-10) promoter, which have been associated with the response to IFN therapy. Induction of IL-10 and suppression of IFN-gamma levels were more prominent in patients with genotype CC at position -592 (n = 15) compared with patients with genotype AA/AC (n = 11). In conclusion, our data indicate that IFN-alpha2 therapy can potently enhance IL-10 and suppress IFN-gamma production of PBMC, which is, at least partially, dependent on an SNP in the IL-10 promoter. This suggests an autoregulatory role of IL-10 in IFN therapy.