Regulation of cytokine signaling by SOCS family molecules

Suppressor of cytokine signaling 1 is a positive regulator of TGF-β-induced prostaglandin production in human follicular dendritic cell-like cells

PGs are emerging as important immune modulators. Since our report on the expression of PG synthases in human follicular dendritic cells, we investigated the potential immunoregulatory function of PGs and their production mechanisms. In this study, we explored the intracellular signaling molecules mediating TGF-β-induced cyclooxygenase (COX)-2 augmentation in follicular dendritic cell-like cells. TGF-β triggered phosphorylation of Smad3 and ERK, which were essential for the increase in COX-2 protein. Interestingly, depletion of suppressor of cytokine signaling 1 (SOCS1) resulted in an almost complete inhibition of Smad3 phosphorylation and COX-2 induction. Nuclear translocation of Smad3 was inhibited in SOCS1-depleted cells. SOCS1 knockdown also downregulated TGF-β-stimulated Snail expression and its binding to the Cox-2 promoter. In contrast, overexpression of SOCS1 gave rise to a significant increase in Snail and COX-2 proteins. SOCS1 was reported to be a negative regulator of cytokine signaling by various investigators. However, our current data suggest that SOCS1 promotes TGF-β-induced COX-2 expression and PG production by facilitating Smad3 phosphorylation and Snail binding to the Cox-2 promoter. The complete understanding of the biological function of SOCS1 might be obtained via extensive studies with diverse cell types.

Transcriptomic and proteomic analyses reveal key innate immune signatures in the host response to the gastrointestinal pathogen Campylobacter concisus

Pathogenic species within the genus Campylobacter are responsible for a considerable burden on global health. Campylobacter concisus is an emergent pathogen that plays a role in acute and chronic gastrointestinal disease. Despite ongoing research on Campylobacter virulence mechanisms, little is known regarding the immunological profile of the host response to Campylobacter infection. In this study, we describe a comprehensive global profile of innate immune responses to C. concisus infection in differentiated THP-1 macrophages infected with an adherent and invasive strain of C. concisus. Using RNA sequencing (RNA-seq), quantitative PCR (qPCR), mass spectrometry, and confocal microscopy, we observed differential expression of pattern recognition receptors and robust upregulation of DNA- and RNA-sensing molecules. In particular, we observed IFI16 inflammasome assembly in C. concisus-infected macrophages. Global profiling of the transcriptome revealed the significant regulation of a total of 8,343 transcripts upon infection with C. concisus, which included the activation of key inflammatory pathways involving CREB1, NF-κB, STAT, and interferon regulatory factor signaling. Thirteen microRNAs and 333 noncoding RNAs were significantly regulated upon infection, including MIR221, which has been associated with colorectal carcinogenesis. This study represents a major advance in our understanding of host recognition and innate immune responses to infection by C. concisus.

MicroRNA-mediated mechanism of vitamin D regulation of innate immune response

Macrophages play a critical role in innate immune response to protect the host from pathogenic microorganisms. Inflammatory response is regulated by negative feedback mechanisms to prevent detrimental effects. The SOCS family of proteins is key component of the negative feedback loop that regulates the intensity, duration and quality of cytokine signaling, whereas miR-155 is a key regulator of Toll-like receptor (TLR) signaling that targets SOCS1 in activated macrophages to block the negative feedback loop. Recently we showed that 1,25-dihydroxyvitamin D (1,25(OH)2D3) modulates innate immune response by targeting the miR-155-SOCS1 axis. We found that Vdr deletion leads to hyper inflammatory response in mice and macrophage cultures when challenged with lipopolysaccharide (LPS), due to miR-155 overproduction to excessively suppress SOCS1. Using mice with bic/miR-155 deletion we confirmed that 1,25(OH)2D3 suppresses inflammation and stimulates SOCS1 by down-regulating miR-155. Mechanistically 1,25(OH)2D3 down-regulates bic transcription by blocking NF-κB activation, which is mediated by a κB cis-DNA element identified within the first intron of the bic gene. At the molecular level, we demonstrated that VDR inhibits NF-κB activation by directly interacting with IKKβ protein. Our studies identified a novel mechanism whereby VDR signaling attenuates TLR-mediated inflammation by enhancing the negative feedback regulation. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

SOCS genes expression during physiological and perturbed implantation in bovine endometrium

In mammals, suppressor of cytokine signalling (CISH, SOCS1 to SOCS7) factors control signalling pathways involved in the regulation of numerous physiological processes including pregnancy. In order to gain new insights into the biological functions of SOCS in the endometrium, a comprehensive analysis of SOCS gene expression was carried out in bovine caruncular (CAR) and intercaruncular (ICAR) tissues collected i) during the oestrous cycle, ii) at the time of maternal recognition of pregnancy and at implantation in inseminated females, iii) following uterine interferon-tau (IFNT) infusion at day 14 post-oestrus, iv) following a period of controlled intravaginal progesterone release and v) following transfer of embryos by somatic-cell nuclear transfer (SCNT). The regulatory effects of IFNT on in vitro cultured epithelial and stromal cells were also examined. Altogether, our data showed that CISH, SOCS4, SOCS5 and SOCS7 mRNA levels were poorly affected during luteolysis and pregnancy. In contrast, SOCS1, SOCS2, SOCS3 and SOCS6 mRNA levels were strongly up-regulated at implantation (day 20 of pregnancy). Experimental in vitro and in vivo models demonstrated that only CISH, SOCS1, SOCS2 and SOCS3 were IFNT-induced genes. Immunohistochemistry showed an intense SOCS3 and SOCS6 staining in the nucleus of luminal and glandular epithelium and of stromal cells of pregnant endometrium. Finally, SOCS3 expression was significantly increased in SCNT pregnancies in keeping with the altered immune function previously reported in this model of compromised implantation. Collectively, our data suggest that spatio-temporal changes in endometrial SOCS gene expression reflect the acquisition of receptivity, maternal recognition of pregnancy and implantation.

SOCS3: A novel therapeutic target for cardioprotection

The suppressors of cytokine signaling (SOCS) family of proteins are cytokine-inducible inhibitors of Janus kinase (JAK)-signal transducer and activator of the transcription (STAT) signaling pathways. Among the family, SOCS1 and SOCS3 potently suppress cytokine actions by inhibiting JAK kinase activities. The generation of mice lacking individual SOCS genes has been instrumental in defining the role of individual SOCS proteins in specific cytokine pathways in vivo; SOCS1 is an essential negative regulator of interferon-γ (IFNγ) and SOCS3 is an essential negative regulator of leukemia inhibitory factor (LIF). JAK-STAT3 activating cytokines have exhibited cardioprotective roles in the heart. The cardiac-specific deletion of SOCS3 enhances the activation of cardioprotective signaling pathways, inhibits myocardial apoptosis and fibrosis and results in the inhibition of left ventricular remodeling after myocardial infarction (MI). We propose that myocardial SOCS3 is a key determinant of left ventricular remodeling after MI, and SOCS3 may serve as a novel therapeutic target to prevent left ventricular remodeling after MI. In this review, we discuss the signaling pathways mediated by JAK-STAT and SOCS proteins and their roles in the development of myocardial injury under stress (e.g., pressure overload, viral infection and ischemia).

High expression of suppressor of cytokine signaling-2 predicts poor outcome in pediatric acute myeloid leukemia: a report from the Children's Oncology Group

Deregulated cytokine signaling is a characteristic feature of acute myeloid leukemia (AML), and expression signatures of cytokines and chemokines have been identified as a significant prognostic factor in this disease. Given this aberrant signaling, we hypothesized that expression of suppressor of cytokine signaling-2 (SOCS2), a negative regulator of cytokine signaling, might be altered in AML and could provide predictive information. Among 188 participants of the Children's Oncology Group AAML03P1 trial, SOCS2 mRNA levels varied > 6000-fold. Higher (> median) SOCS2 expression was associated with inferior overall (60 ± 10% vs. 75 ± 9%, p = 0.026) and event-free (44 ± 10% vs. 59 ± 10%, p = 0.031) survival. However, these differences were accounted for by higher prevalence of high-risk and lower prevalence of low-risk disease among patients with higher SOCS2 expression, limiting the clinical utility of SOCS2 as a predictive marker. It remains untested whether high SOCS2 expression identifies a subset of leukemias with deregulated cytokine signaling that could be amenable to therapeutic intervention.

Genetic contribution of CISH promoter polymorphisms to susceptibility to tuberculosis in Chinese children

Tuberculosis (TB) is the leading cause of death due to an infectious disease worldwide, particularly in developing countries. A series of candidate genes have been suggested to be associated with development of TB disease. Among them, the human Cytokine-inducible Src homology 2(SH2) domain protein (CISH) gene has been very recently reported to be involved in T cell activation and differentiation in response to Mycobacterium tuberculosis infection. Here, we studied the association between CISH promoter polymorphisms and pediatric TB. A case-control study enrolled 352 TB patients and 527 healthy controls, who were of Han Chinese ethnicity and aged from 0.2 to 18 years. CISH gene promoter SNPs rs414171, rs622502 and rs809451 were genotyped in all subjects and transcriptional activity, mRNA level, and plasma cytokine level of subjects with different genotypes were further examined. Carriers with rs414171TT homozygotes and rs809451GC heterozygotes had a 1.78-fold (95% CI,1.16–2.74) and 1.86-fold (95% CI, 1.26–2.74) excess risk of developing TB compared to those with wild-type genotypes. A greater risk of TB disease was observed in population carrying C_−809451-T_−414171-C_−622502 haplotype (OR 3.66, 95% CI:2.12–6.32). The G_−809451-A_−414171-C_−622502-containing CISH promoter drove a 5.43-fold increased reporter expression compared to the C_−809451-T_−414171-C_−622502-containing counterpart in Hela cell lines (P = 0.0009). PBMCs carrying rs414171TT homozygotes and rs809451GC heterozygotes showed a reduced CISH mRNA level compared to cells carrying wild type genotypes. Individuals with the rs414171TT genotype had significantly increased IL-12p40 and IL-10 production. In conclusion, CISH promoter rs414171 and rs809451 polymorphisms may play a vital role in mediating individual susceptibility to tuberculosis.

Toxoplasma gondii Inhibits gamma interferon (IFN-γ)- and IFN-β-induced host cell STAT1 transcriptional activity by increasing the association of STAT1 with DNA

The gamma interferon (IFN-γ) response, mediated by the STAT1 transcription factor, is crucial for host defense against the intracellular pathogen Toxoplasma gondii, but prior infection with Toxoplasma can inhibit this response. Recently, it was reported that the Toxoplasma type II NTE strain prevents the recruitment of chromatin remodeling complexes containing Brahma-related gene 1 (BRG-1) to promoters of IFN-γ-induced secondary response genes such as Ciita and major histocompatibility complex class II genes in murine macrophages, thereby inhibiting their expression. We report here that a type I strain of Toxoplasma inhibits the expression of primary IFN-γ response genes such as IRF1 through a distinct mechanism not dependent on the activity of histone deacetylases. Instead, infection with a type I, II, or III strain of Toxoplasma inhibits the dissociation of STAT1 from DNA, preventing its recycling and further rounds of STAT1-mediated transcriptional activation. This leads to increased IFN-γ-induced binding of STAT1 at the IRF1 promoter in host cells and increased global IFN-γ-induced association of STAT1 with chromatin. Toxoplasma type I infection also inhibits IFN-β-induced interferon-stimulated gene factor 3-mediated gene expression, and this inhibition is also linked to increased association of STAT1 with chromatin. The secretion of proteins into the host cell by a type I strain of Toxoplasma without complete parasite invasion is not sufficient to block STAT1-mediated expression, suggesting that the effector protein responsible for this inhibition is not derived from the rhoptries.

The suppressor of cytokine signaling 2 (SOCS2) modulating the neurotransmitters release in Eriocheir sinensis

The SOCS proteins appear to define an important mechanism for the negative regulation of the cytokine-JAK-STAT pathway. In the present study, the mRNA expression profiles of a SOCS2 from Chinese mitten crab Eriocheir sinensis (EsSOCS2) after pentachlorophenol (PCP) treatment or RNA interference (RNAi) were analyzed to understand its possible regulatory roles in modulating the neurotransmitter release. The EsSOCS2 expression level in the PCP treated group was significantly higher than that of blank at 1.5, 3, 12 and 24 h after exposure, suggesting that EsSOCS2 might be involved in controlling and reducing neuronal cell damage resulted from PCP treatment. After the expression of EsSOCS2 gene was silenced by RNAi, the concentrations of catecholamines and nitric oxide (NO) were examined to evaluate the modulation of EsSOCS2 on the release of neurotransmitters. At 48 h after the treatment with sequence-specific dsRNA targeting EsSOCS2, the expression of EsSOCS2 was reduced to half compared to the original level, and the concentrations of norepinephrine and NO increased, while dopamine decreased significantly in haemolymph. The preliminary results indicated that EsSOCS2 regulated catecholaminergic neuroendocrine system to release catecholamines into haemolymph and might be an important feedback inhibitor of tyrosine kinase signaling pathways in crab, which subsequently regulated NO synthesis and prevented excessive NO release. This information is helpful to further understand the modulation of EsSOCS2 on neurotransmitter release in crab.

Innate immunity in pluripotent human cells: attenuated response to interferon-β

Type I interferon (IFN-α/β) binds to cell surface receptors IFNAR1 and IFNAR2 and triggers a signaling cascade that leads to the transcription of hundreds of IFN-stimulated genes. This response is a crucial component in innate immunity in that it establishes an "antiviral state" in cells and protects them against further damage. Previous work demonstrated that, compared with their differentiated counterparts, pluripotent human cells have a much weaker response to cytoplasmic double-stranded RNA (dsRNA) and are only able to produce a minimal amount of IFN-β. We show here that human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) also exhibit an attenuated response to IFN-β. Even though all known type I IFN signaling components are expressed in these cells, STAT1 phosphorylation is greatly diminished upon IFN-β treatment. This attenuated response correlates with a high expression of suppressor of cytokine signaling 1 (SOCS1). Upon differentiation of hESCs into trophoblasts, cells acquire the ability to respond to IFN-β, and this is accompanied by a significant induction of STAT1 phosphorylation as well as a decrease in SOCS1 expression. Furthermore, SOCS1 knockdown in hiPSCs enhances their ability to respond to IFN-β. Taken together, our results suggest that an attenuated cellular response to type I IFNs may be a general feature of pluripotent human cells and that this is associated with high expression of SOCS1.

Reduced expression of SOCS2 and SOCS6 in hepatocellular carcinoma correlates with aggressive tumor progression and poor prognosis

To investigate the clinical significance of suppressor of cytokine signaling (SOCS)-2 and SOCS6 in human hepatocellular carcinoma (HCC). The expression levels of SOCS2 and SOCS6 mRNA and protein in tumor, para-tumor and normal liver tissues were detected in 106 HCC patients by real-time quantitative RT-PCR (qRT-PCR) and Western blot. According to qRT-PCR and western blot analyses, we first found that both the expression levels of SOCS2 and SOCS6 mRNA and protein in HCC were significantly lower than those in para-tumor (both P < 0.001) and normal liver tissues (both P < 0.001). Then, the correlation analysis showed that both SOCS2 and SOCS6 protein downregulation were significantly correlated with advanced TNM stage (both P < 0.001) and high serum AFP (P = 0.008 and 0.01, respectively). Especially, the reduced expression of SOCS2 more frequently occurred in HCC patients with vascular invasion (P = 0.03), and that of SOCS6 was also associated with tumor recurrence (P = 0.01). Moreover, HCC patients with low expression of SOCS2 and SOCS6 had significantly shorter overall (P = 0.008 and 0.01, respectively) and disease-free survival (both P = 0.01). Furthermore, multivariate analysis showed that both SOCS2 and SOCS6 downregulation were independent prognostic factors of overall (P = 0.01 and 0.03, respectively) and disease-free survival (P = 0.01 and 0.03, respectively) in HCC. Our data demonstrate for the first time that SOCS2 and SOCS6 expression were remarkably reduced in HCC and may be served as potential prognostic markers for patients with this deadly disease.

Gene cloning and function analysis of cytokine-induced suppressor of cytokine signaling (SOCS) from pearl oyster Pinctada fucata

Cytokine-induced suppressor of cytokine signaling (SOCS) family acts as a negative regulator of cytokine receptor signaling to control excessive cytokine effects and inhibit a variety of signal transduction pathways, particularly the Janus kinases/signal transducers and activators of transcription (JAK/STAT) pathway. In present study, SOCS-2 homolog (PfSOCS-2) from pearl oyster Pinctada fucata was cloned and its gene has no intron. Multiple sequence alignments and phylogenetic analysis showed that PfSOCS-2 was clustered with other mollusk SOCS-2. LPS or polyI:C challenge and gene expression analysis revealed that PfSOCS-2 involved the innate immune response against bacterial and viral infections and that induction of PfSOCS-2 was varied with the different challenge stimulations. Furthermore, Dual-luciferase reporter assays showed that PfSOCS-2 involved in the regulation of vertebrate target genes containing the IFN-stimulated response element or NF-κB binding site in vitro. These results indicated that SOCS-2 from P. fucata plays a regulatory role against the stimulation.

1,25-Dihydroxyvitamin D promotes negative feedback regulation of TLR signaling via targeting microRNA-155-SOCS1 in macrophages

The negative feedback mechanism is essential to maintain effective immunity and tissue homeostasis. 1,25-dihydroxyvitamin D (1,25[OH]2D3) modulates innate immune response, but the mechanism remains poorly understood. In this article, we report that vitamin D receptor signaling attenuates TLR-mediated inflammation by enhancing the negative feedback inhibition. Vitamin D receptor inactivation leads to hyperinflammatory response in mice and macrophage cultures when challenged with LPS, because of microRNA-155 (miR-155) overproduction that excessively suppresses suppressor of cytokine signaling 1, a key regulator that enhances the negative feedback loop. Deletion of miR-155 attenuates vitamin D suppression of LPS-induced inflammation, confirming that 1,25(OH)2D3 stimulates suppressor of cytokine signaling 1 by downregulating miR-155. 1,25(OH)2D3 downregulates bic transcription by inhibiting NF-κB activation, which is mediated by a κB cis-DNA element located within the first intron of the bic gene. Together, these data identify a novel regulatory mechanism for vitamin D to control innate immunity.

SC-1, a sorafenib derivative, shows anti-tumor effects in osteogenic sarcoma cells

Despite significant advances in the treatment of osteosarcoma (OS), overall survival rate of OS patients has remained relatively constant for over two decades and novel approaches are needed to further improve prognosis. Here, we report the anti-tumor effect of SC-1, a novel sorafenib derivative that closely resembles sorafenib structurally but is devoid of kinase inhibitory activity, on OS cells through mediation of signal transducer and activator of transcription 3 (STAT3). SC-1 showed similar effects to sorafenib on growth inhibition and apoptosis, and downregulated phospho-STAT3 (p-STAT3) at tyrosine 705 in all tested OS cell lines (U2OS, HOS, and 143B). Expression of STAT3-driven genes, including cylcin D1 and c-myc, were also repressed by SC-1. Ectopic expression of STAT3 in 143B cells abolished apoptosis in SC-1-treated cells. Inhibition of SHP-1 decreased SC-1-induced apoptosis. SC-1 upregulated the activity of SHP-1 in tested OS cell lines in a dose-dependent manner. Finally, SC-1 reduced 143B tumor growth significantly in vivo, which was associated with downregulation of p-STAT3 and upregulation of SHP-1 activity. These data demonstrate that SC-1 has clinical potential for the treatment of OS patients.

Long-term fasting in the anadromous Arctic charr is associated with down-regulation of metabolic enzyme activity and up-regulation of leptin A1 and SOCS expression in the liver

The life-strategy of the anadromous Arctic charr (Salvelinus alpinus) includes several months of voluntary fasting during overwintering in fresh water leading to emaciation prior to seawater migration in spring. In this study we compared changes in condition, substrate utilization and liver metabolism between captive anadromous charr subjected to food-deprivation during late winter and spring, and conspecifics fed in excess. In March, 9 out of the 10 sampled fed fish had not eaten, indicating that they were a voluntary anorexic state. In June, the fed fish were eating and all had higher body mass (BM), condition factor (CF) and adiposity than in March. In fasted fish there were only small decreases in BM, CF and adiposity between March and May, but all these parameters decreased markedly from May to June. The fasted fish were fat- and glycogen-depleted in June, had suppressed activity of hepatic enzymes involved in lipid metabolism (G6PDH and HOAD) and seemed to rely on protein-derived glucose as a major energy source. This was associated with up-regulated liver gene expression of leptin A1, leptin A2, SOCS1, SOCS2 and SOCS3, and reduced IGF-I expression. In an in vitro study with liver slices it was shown that recombinant rainbow trout leptin stimulated SOCS1 and SOCS3 expression, but not SOCS2, IGF-I or genes of enzymes involved in lipid (G6PDH) and amino acid (AspAT) metabolism. It is concluded that liver leptin interacts with SOCS in a paracrine fashion to suppress lipolytic pathways and depress metabolism when fat stores are depleted.

IL-6 is not necessary for the regulation of adipose tissue mitochondrial content

BACKGROUND

Adipose tissue mitochondria have been implicated as key mediators of systemic metabolism. We have shown that IL-6 activates AMPK, a mediator of mitochondrial biogenesis, in adipose tissue; however, IL-6(-/-) mice fed a high fat diet have been reported to develop insulin resistance. These findings suggest that IL-6 may control adipose tissue mitochondrial content in vivo, and that reductions in adipose tissue mitochondria may be causally linked to the development of insulin resistance in IL-6(-/-) mice fed a high fat diet. On the other hand, IL-6 has been implicated as a negative regulator of insulin action. Given these discrepancies the purpose of the present investigation was to further evaluate the relationship between IL-6, adipose tissue mitochondrial content and whole body insulin action.

METHODOLOGY AND PRINCIPAL FINDINGS

In cultured epididymal mouse adipose tissue IL-6 (75 ng/ml) induced the expression of the transcriptional co-activators PGC-1α and PRC, reputed mediators of mitochondrial biogenesis. Similarly, IL-6 increased the expression of COXIV and CPT-1. These effects were absent in cultured subcutaneous adipose tissue and were associated with lower levels of GP130 and IL-6 receptor alpha protein content. Markers of mitochondrial content were intact in adipose tissue from chow fed IL-6(-/-) mice. When fed a high fat diet IL-6(-/-) mice were more glucose and insulin intolerant than controls fed the same diet; however this was not explained by decreases in adipose tissue mitochondrial content or respiration.

CONCLUSIONS AND SIGNIFICANCE

Our findings demonstrate depot-specific differences in the ability of IL-6 to induce PGC-1α and mitochondrial enzymes and demonstrate that IL-6 is not necessary for the maintenance of adipose tissue mitochondrial content in vivo. Moreover, reductions in adipose tissue mitochondria do not explain the greater insulin resistance in IL-6(-/-) mice fed a high fat diet. These results question the role of adipose tissue mitochondrial dysfunction in the etiology of insulin resistance.

SOCS proteins in infectious diseases of mammals

As for most biological processes, the immune response to microbial infections has to be tightly controlled to remain beneficial for the host. Inflammation is one of the major consequences of the host's immune response. For its orchestration, this process requires a fine-tuned interplay between interleukins, endothelial cells and various types of recruited immune cells. Suppressors of cytokine signalling (SOCS) proteins are crucially involved in the complex control of the inflammatory response through their actions on various signalling pathways including the JAK/STAT and NF-κB pathways. Due to their cytokine regulatory functions, they are frequent targets for exploitation by infectious agents trying to escape the host's immune response. This review article aims to summarize our current knowledge regarding SOCS family members in the different mammalian species studied so far, and to display their complex molecular interactions with microbial pathogens.

Cell Biology Symposium: feed efficiency: mitochondrial function to global gene expression

Understanding the cellular basis of feed efficiency (FE) is instrumental to helping poultry and livestock industries continue to provide high-quality protein for an increasingly crowded world. To understand relationships of FE and gene expression, global RNA transcription was investigated in breast muscle obtained from a male broiler line fed the same diet and individually phenotyped for FE. In these studies, RNA samples obtained from broilers that exhibited either high FE (0.65 ± 0.01) or low FE (0.46 ± 0.01) were analyzed with an Agilent 44K chicken oligoarray. A 1.3-fold cutoff in expression (30% difference between groups) resulted in 782 genes that were differentially expressed (P < 0.05) in muscle between the high- and low-FE phenotypes. Ingenuity Pathway Analysis, an online software program, was used to identify genes, gene networks, and pathways associated with the phenotypic expression of FE. The results indicate that the high-FE phenotype exhibited increased expression of genes associated with 1) signal transduction pathways, 2) anabolic activities, and 3) energy-sensing and energy coordination activities, all of which would likely be favorable to cell growth and development. In contrast, the low-FE broiler phenotype exhibited upregulation of genes 1) associated with actin-myosin filaments, cytoskeletal architecture, and muscle fibers and 2) stress-related or stress-responsive genes. Because the low-FE broiler phenotype exhibits greater oxidative stress, it would appear that the low-FE phenotype is the product of inherent gene expression that is modulated by oxidative stress. The results of these studies begin to provide a comprehensive picture of gene expression in muscle, a major organ of energy demand in an animal, associated with phenotypic expression of FE.

Gene expression in breast muscle associated with feed efficiency in a single male broiler line using a chicken 44K microarray. II. Differentially expressed focus genes

Global RNA expression in breast muscle obtained from a male broiler line phenotyped for high or low feed efficiency (FE) was investigated using microarray analysis. Microarray procedures and validation were reported previously. By using an overlay function of a software program (Ingenuity Pathway Analysis, IPA) in which canonical pathways are projected onto a set of genes, a subset of 27 differentially expressed focus genes were identified. Focus genes that were upregulated in the high FE phenotype were associated with important signal transduction pathways (Jnk, G-coupled, and retinoic acid) or in sensing cell energy status and stimulating energy production that would likely enhance growth and development of muscle tissue. In contrast, focus genes that were upregulated in the low FE muscle phenotype were associated with cytoskeletal architecture (e.g., actin-myosin filaments), fatty acid oxidation, growth factors, or ones that would likely be induced in response to oxidative stress. The results of this study provide additional information on gene expression and the cellular basis of feed efficiency in broilers.

Granulocyte colony-stimulating factor receptor signaling: implications for G-CSF responses and leukemic progression in severe congenital neutropenia

Following activation by their cognate ligands, cytokine receptors undergo intracellular routing toward lysosomes, where they are degraded. This review focuses on the signaling function of the G-CSFR in relation to the dynamics of endosomal routing of the G-CSFR. Mechanisms involving receptor lysine ubiquitination and redox-controlled phosphatase activities are discussed. Specific attention is paid to the consequences of G-CSFR mutations, acquired in patients with severe congenital neutropenias who receive G-CSF therapy, particularly in the context of leukemic transformation, a major clinical complication of the disease.

Proteasomal degradation of Nod2 protein mediates tolerance to bacterial cell wall components

The innate immune system serves as the first line of defense by detecting microbes and initiating inflammatory responses. Although both Toll-like receptor (TLR) and nucleotide binding domain and leucine-rich repeat (NLR) proteins are important for this process, their excessive activation is hazardous to hosts; thus, tight regulation is required. Endotoxin tolerance is refractory to repeated lipopolysaccharide (LPS) stimulation and serves as a host defense mechanism against septic shock caused by an excessive TLR4 response during gram-negative bacterial infection. Gram-positive bacteria as well as their cell wall components also induce shock. However, the mechanism underlying tolerance is not understood. Here, we show that activation of Nod2 by its ligand, muramyl dipeptide (MDP) in the bacterial cell wall, induces rapid degradation of Nod2, which confers MDP tolerance in vitro and in vivo. Nod2 is constitutively associated with a chaperone protein, Hsp90, which is required for Nod2 stability and protects Nod2 from degradation. Upon MDP stimulation, Hsp90 rapidly dissociates from Nod2, which subsequently undergoes ubiquitination and proteasomal degradation. The SOCS-3 protein induced by Nod2 activation further facilitates this degradation process. Therefore, Nod2 protein stability is a key factor in determining responsiveness to MDP stimulation. This indicates that TLRs and NLRs induce a tolerant state through distinct molecular mechanisms that protect the host from septic shock.

Characterization and evaluation of sex-specific expression of suppressors of cytokine signaling (SOCS)-1 and -3 in juvenile yellow perch (Perca flavescens) treated with lipopolysaccharide

The suppressor of cytokine signaling (SOCS) proteins are a family of intracellular proteins that are centrally involved with vertebrate growth, development and immunity via their effects as negative feed-back regulators of cytokine (and hormone) signaling. The genes for SOCS-1 & -3 were cloned, sequences analyzed and expression patterns examined in the commercially-important teleost, yellow perch (Perca flavescens). The deduced (mature) proteins for yellow perch (yp)SOCS-1 and (yp)SOCS-3 consist of 211 and 205 amino acids, respectively. Functional domains such as the Src homology-2 (SH2) and SOCS-box were present in ypSOCS-1 and ypSOCS-3 and these domains were well conserved between teleost species. Sequence analysis showed that ypSOCS-1 & -3 share highest homology (among similar teleost sequences), to the stickleback (Gasterosteus aculatus) SOCS-1 & -3 protein homologs. To investigate sex-specific expression of the ypSOCS-1 and ypSOCS-3 mRNAs, juvenile male and female yellow perch were immunologically challenged with a single injection (10 μg/g bw) of lipopolysaccharide (LPS) and tissues (gill, head kidney, kidney, liver and spleen) were sampled over a 48-h time-course. Quantitative real-time PCR analysis showed that ypSOCS-1 & -3 were expressed in all tissues examined and at all sampling time-points. LPS injection significantly induced ypSOCS-1 & -3 mRNA levels in gill, head kidney, liver, kidney and spleen, with maximal induction occurring at 6 h post-injection in each tissue. By 48-h post-injection, expression levels for ypSOCS-1 & -3 mRNAs approached, or reached, control levels in all tissues examined. While there were statistical interactions among variables (treatment, time and sex) for ypSOCS-1, we only found a main effect of sex on SOCS-3 mRNA expression in head kidney with higher copy numbers occurring in males than in females treated with LPS. Sexually-dimorphic expression of SOCS-1 or -3 mRNA has not been examined, or described, in a teleost. Our findings suggest the involvement of the SOCS genes in the yellow perch immune response and that differences among the sexes are evident and should be explored further.

IL-6 indirectly modulates the induction of glyceroneogenic enzymes in adipose tissue during exercise

BACKGROUND

Glyceroneogenesis is an important step in the control of fatty acid re-esterification with PEPCK and PDK4 being identified as key enzymes in this process. We have previously shown that glyceroneogenic enzymes such as PDK4 are rapidly induced in white adipose tissue during exercise. Recent studies have suggested that IL-6 regulates adipose tissue metabolism and gene expression during exercise. Interestingly, IL-6 has been reported to directly decrease PEPCK expression. The purpose of this investigation was to determine the role of IL-6 in modulating the effects of exercise on the expression of glyceroneogenic enzymes in mouse adipose tissue. We hypothesized that the exercise-mediated induction of PDK4 and PEPCK would be greater in adipose tissue from IL-6 deficient mice compared to wild type controls.

METHODOLOGY AND PRINCIPLE FINDINGS

Treatment of cultured epididymal adipose tissue (eWAT) with IL-6 (150 ng/ml) increased the phosphorylation of AMPK, ACC and STAT3 and induced SOCS3 mRNA levels while decreasing PEPCK and PDK4 mRNA. AICAR decreased the expression of PDK4 and PEPCK. The activation of AMPK by IL-6 was independent of increases in lipolysis. An acute bout of treadmill running (15 meters/minute, 5% incline, 90 minutes) did not induce SOCS3 or increase phosphorylation of STAT3 in eWAT, indicating that IL-6 signalling was not activated. Exercise-induced increases in PEPCK and PDK4 mRNA expression were attenuated in eWAT from IL-6(-/-) mice in parallel with a greater relative increase in AMPK phosphorylation compared to exercised WT mice. These changes occurred independent of alterations in beta-adrenergic signalling in adipose tissue from IL-6(-/-) mice.

CONCLUSIONS AND SIGNIFICANCE

Our findings question the role of IL-6 signalling in adipose tissue during exercise and suggest an indirect effect of this cytokine in the regulation of adipose tissue gene expression during exercise.

Different partners, opposite outcomes: a new perspective of the immunobiology of indoleamine 2,3-dioxygenase

Indoleamine 2,3-dioxygenase (IDO), a metabolic enzyme that catalyzes tryptophan conversion into kynurenines, is a crucial regulator of immunity. Altered IDO activity is often associated with pathology, including neoplasia and autoimmunity. IDO is highly expressed in dendritic cells (DCs) that exploit the enzyme's activity and the production of tryptophan catabolites to regulate immune responses by acting on several cell types, including T lymphocytes, of which they promote a regulatory phenotype. IDO also contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that, once bound by distinct molecular partners, will either promote degradation or initiate signaling activity and self-maintenance of the enzyme. We here discuss how ITIM-dependent molecular events can affect the functional plasticity of IDO by modifying the protein half-life and its enzymic and nonenzymic functions.

Anti-inflammatory effects of interleukin-19 in vascular disease

Despite aggressive dietary modification, lipid-lowering medications, and other interventional medical therapy, vascular disease continues to be a leading cause of mortality in the western world. It is a significant medical and socioeconomic problem contributing to mortality of multiple diseases including myocardial infarction, stroke, renal failure, and peripheral vascular disease. Morbidity and mortality of vascular disease are expected to worsen with the increasing number of patients with comorbid conditions such as obesity, metabolic syndrome, and diabetes mellitus type 2. Vascular diseases such as atherosclerosis, restenosis, and allograft vasculopathy are recognized to be driven by inflammation, and as such, cytokines which mediate inflammation not only represent important targets of rational therapy, but also can be considered as possible therapeutic modalities themselves. In this paper, we will examine the role of inflammatory cytokines and lymphocyte T(h)1/T(h)2 polarity in vascular inflammation, with a focus on atherosclerotic vascular disease. We will then introduce a recently described T(h)2 interleukin, interleukin-19 (IL-19), as a previously unrecognized mediator of vascular inflammatory disorders. We will review our current understanding of this interleukin in health and disease and present the possibility that IL-19 could represent a potential therapeutic to combat vascular inflammatory disease.

A review of experimental evidence linking neurotoxic organophosphorus compounds and inflammation

Organophosphorus (OP) nerve agents and pesticides inhibit acetylcholinesterase (AChE), and this is thought to be a primary mechanism mediating the neurotoxicity of these compounds. However, a number of observations suggest that mechanisms other than or in addition to AChE inhibition contribute to OP neurotoxicity. There is significant experimental evidence that acute OP intoxication elicits a robust inflammatory response, and emerging evidence suggests that chronic repeated low-level OP exposure also upregulates inflammatory mediators. A critical question that is just beginning to be addressed experimentally is the pathophysiologic relevance of inflammation in either acute or chronic OP intoxication. The goal of this article is to provide a brief review of the current status of our knowledge linking inflammation to OP intoxication, and to discuss the implications of these findings in the context of therapeutic and diagnostic approaches to OP neurotoxicity.

Interferon-γ biphasically regulates angiotensinogen expression via a JAK-STAT pathway and suppressor of cytokine signaling 1 (SOCS1) in renal proximal tubular cells

Renal inflammation modulates angiotensinogen (AGT) production in renal proximal tubular cells (RPTCs) via inflammatory cytokines, including interleukin-6, tumor necrosis factor α, and interferon-γ (IFN-γ). Among these, the effects of IFN-γ on AGT regulation in RPTCs are incompletely delineated. This study aimed to elucidate mechanisms by which IFN-γ regulates AGT expression in RPTCs. RPTCs were incubated with or without IFN-γ up to 48 h. AGT expression, STAT1 and STAT3 activities, and SOCS1 expression were evaluated. RNA interference studies against STAT1, SOCS1, and STAT3 were performed to elucidate a signaling cascade. IFN-γ decreased AGT expression at 6 h (0.61±0.05, ratio to control) and 12 h (0.47±0.03). In contrast, longer exposure for 24 and 48 h increased AGT expression (1.76±0.18, EC(50)=3.4 ng/ml, and 1.45±0.08, respectively). IFN-γ treatment for 6 h strongly induced STAT1 phosphorylation and SOCS1 augmentation, and decreased STAT3 activity. However, STAT1 phosphorylation and SOCS1 augmentation waned at 24 h, while STAT3 activity increased. RNA interference studies revealed that activation of STAT1-SOCS1 axis decreased STAT3 activity. Thus, IFN-γ biphasically regulates AGT expression in RPTCs via STAT3 activity modulated by STAT1-SOCS1 axis, suggesting the STAT1-SOCS1 axis is important in IFN-γ-induced activation of the intrarenal renin-angiotensin system.

Combinations of ketamine and atropine are neuroprotective and reduce neuroinflammation after a toxic status epilepticus in mice

Epileptic seizures and status epilepticus (SE) induced by the poisoning with organophosphorus nerve agents (OP), like soman, are accompanied by neuroinflammation whose role in seizure-related brain damage (SRBD) is not clear. Antagonists of the NMDA glutamate ionotropic receptors are currently among the few compounds able to arrest seizures and provide neuroprotection even during refractory status epilepticus (RSE). Racemic ketamine (KET), in combination with atropine sulfate (AS), was previously shown to counteract seizures and SRBD in soman-poisoned guinea-pigs. In a mouse model of severe soman-induced SE, we assessed the potentials of KET/AS combinations as a treatment for SE/RSE-induced SRBD and neuroinflammation. When starting 30min after soman challenge, a protocol involving six injections of a sub-anesthetic dose of KET (25mg/kg) was evaluated on body weight loss, brain damage, and neuroinflammation whereas during RSE, anesthetic protocols were considered (KET 100mg/kg). After confirming that during RSE, KET injection was to be repeated despite some iatrogenic deaths, we used these proof-of-concept protocols to study the changes in mRNA and related protein contents of some inflammatory cytokines, chemokines and adhesion molecules in cortex and hippocampus 48h post-challenge. In both cases, the KET/AS combinations showed important neuroprotective effects, suppressed neutrophil granulocyte infiltration and partially suppressed glial activation. KET/AS could also reduce the increase in mRNA and related pro-inflammatory proteins provoked by the poisoning. In conclusion, the present study confirms that KET/AS treatment has a strong potential for SE/RSE management following OP poisoning. The mechanisms involved in the reduction of central neuroinflammation remain to be studied.

Pre-treatment of recombinant mouse MFG-E8 downregulates LPS-induced TNF-α production in macrophages via STAT3-mediated SOCS3 activation

Milk fat globule-epidermal growth factor factor 8 (MFG-E8) regulates innate immune function by modulating cellular signaling, which is less understood. Herein, we aimed to investigate the direct anti-inflammatory role of MFG-E8 in macrophages by pre-treatment with recombinant murine MFG-E8 (rmMFG-E8) followed by stimulation with LPS in RAW264.7 cells and in peritoneal macrophages, isolated from wild-type (WT) or MFG-E8^−/− mice. RAW264.7 cells and mouse peritoneal macrophages treated with rmMFG-E8 significantly downregulated LPS-induced TNF-α mRNA by 25% and 24%, and protein levels by 29% and 23%, respectively (P<0.05). Conversely, peritoneal macrophages isolated from MFG-E8^−/− mice produced 28% higher levels of TNF-α, as compared to WT mice when treated with LPS. In in vivo, endotoxemia induced by intraperitoneal injection of LPS (5 mg/kg BW), at 4 h after induction, serum level of TNF-α was significantly higher in MFG-E8^−/− mice (837 pg/mL) than that of WT (570 pg/mL, P<0.05). To elucidate the direct anti-inflammatory effect of MFG-E8, we examined STAT3 and its target gene, SOCS3. Treatment with rmMGF-E8 significantly induced pSTAT3 and SOCS3 in macrophages. Similar results were observed in in vivo treatment of rmMFG-E8 in peritoneal cells and splenic tissues. Pre-treatment with rmMFG-E8 significantly reduced LPS-induced NF-κB p65 contents. These data clearly indicated that rmMFG-E8 upregulated SOCS3 which in turn interacted with NF-κB p65, facilitating negative regulation of TLR4 signaling for LPS-induced TNF-α production. Our findings strongly suggest that MFG-E8 is a direct anti-inflammatory molecule, and that it could be developed as a therapy in attenuating inflammation and tissue injury.

Signal transducer and activator of transcription 3 is a major kinase-independent target of sorafenib in hepatocellular carcinoma

BACKGROUND & AIMS

Recently, we reported that sorafenib sensitizes hepatocellular carcinoma (HCC) cells to TRAIL through the inhibition of signal transducer and activator of transcription 3 (STAT3). Here, we report that sorafenib inhibits HCC via a kinase-independent mechanism: SHP-1 dependent STAT3 inactivation.

METHODS

SC-1 is a sorafenib derivative that closely resembles sorafenib structurally but with no kinase inhibition activity. HCC cell lines (PLC5, Huh-7, Hep3B, and Sk-Hep1) were treated with sorafenib or SC-1 and apoptosis and signal transduction were analyzed. In vivo efficacy was determined in nude mice with Huh-7 xenografts.

RESULTS

SC-1 showed similar effects to sorafenib on growth inhibition and apoptosis in all tested HCC cell lines. SC-1 down-regulated phosphorylation of phospho-STAT3 (p-STAT3) at tyrosine 705 in all tested HCC cells. Expression of STAT3-driven genes, including Cyclin D1 and Survivin, was also repressed by SC-1. Luciferase reporter assay confirmed the inhibition of transcriptional activity of STAT3 in both sorafenib-treated and SC-1-treated cells. Ectopic expression of STAT3 in PLC5 cells abolished apoptosis in SC-1-treated cells. Sorafenib and SC-1 up-regulated SHP-1 activity. Knockdown of SHP-1, but not SHP-2 or PTP-1B, by small interference RNA reduced apoptosis induced by SC-1. Finally, SC-1 reduced Huh-7 tumor growth significantly in vivo, which was associated with down-regulation of p-STAT3 and up-regulation of SHP-1 activity.

CONCLUSIONS

STAT3 is a major kinase-independent target of sorafenib in HCC.

Human T cell leukemia virus type 1 Tax inhibits innate antiviral signaling via NF-kappaB-dependent induction of SOCS1

Human T cell leukemia virus type 1 (HTLV-1) inhibits host antiviral signaling pathways although the underlying mechanisms are unclear. Here we found that the HTLV-1 Tax oncoprotein induced the expression of SOCS1, an inhibitor of interferon signaling. Tax required NF-κB, but not CREB, to induce the expression of SOCS1 in T cells. Furthermore, Tax interacted with SOCS1 in both transfected cells and in HTLV-1-transformed cell lines. Although SOCS1 is normally a short-lived protein, in the presence of Tax, the stability of SOCS1 was greatly increased. Accordingly, Tax enhanced the replication of a heterologous virus, vesicular stomatitis virus (VSV), in a SOCS1-dependent manner. Surprisingly, Tax required SOCS1 to inhibit RIG-I-dependent antiviral signaling, but not the interferon-induced JAK/STAT pathway. Inhibition of SOCS1 by RNA-mediated interference in the HTLV-1-transformed cell line MT-2 resulted in increased IFN-β expression accompanied by reduced HTLV-1 replication and p19(Gag) levels. Taken together, our results reveal that Tax inhibits antiviral signaling, in part, by hijacking an interferon regulatory protein.

T-cell tolerance and the multi-functional role of IL-2R signaling in T-regulatory cells

Signaling through the interleukin-2 receptor (IL-2R) contributes to T-cell tolerance by controlling three important aspects of regulatory T-cell (Treg) biology. IL-2 is essential for thymic Treg development and regulates Treg homeostasis and suppressive function. Analogous to activated conventional T lymphocytes, IL-2R signaling also plays an important part in Treg cell growth, survival, and effector differentiation. However, Treg cells somewhat distinctively assimilate IL-2R signaling. In particular, Treg cells require essentially only IL-2-dependent receptor proximal signal transducer and activator of transcription 5 (Stat5) activation, as they contain inhibitory pathways to minimize IL-2R-dependent activation of the phosphatidyinositol 3-kinase/Akt pathway. Moreover, many IL-2R-dependent activities, including full induction of Foxp3 expression, in Treg cells require minimal and transient Stat5 activation. Thus, Treg cells are equipped to sense and then develop and function within biological niches containing minimal IL-2. These distinguishing features of IL-2R signaling provide a mechanistic underpinning for using IL-2 as an agent to selectively target Treg cells in immunotherapy to induce tolerance in autoimmune diseases and in allogeneic transplant recipients.

Suppressors of cytokine signaling 3 expression in eosinophils: regulation by PGE₂ and Th2 cytokines

Asthma and nonasthmatic eosinophilic bronchitis (NAEB) are respiratory disorders characterized by a predominance of Th2 cells and eosinophilic inflammation. Suppressors of cytokine signaling (SOCS) proteins play an important role in Th2-mediated allergic responses through control of the balance between Th1 and Th2 cells, particularly, SOCS3 and SOCS5. The aim of this study was to analyze SOCS expression in human peripheral blood eosinophils from patients with asthma, NAEB and healthy controls. SOCS expression in eosinophils from subjects was demonstrated by different techniques. Results showed that expression of SOCS3 in eosinophils and CD4 T cells from patients was higher than in healthy subjects. In addition, we demonstrated that prostaglandin E₂ (PGE₂) and Th2 cytokines are able to upregulate SOCS3 production in eosinophils and attenuate its degranulation. In conclusion, eosinophils are able to transcribe and translate SOCS3 protein and can contribute to the regulation of the Th1/Th2 balance through SOCS3 production.

Gene expression profiling in lungs of chronic asthmatic mice treated with galectin-3: downregulation of inflammatory and regulatory genes

Background. Asthma is a disorder characterized by a predominance of Th2 cells and eosinophilic inflammation. Suppressors of cytokine signaling (SOCS) proteins act as negative regulators of cytokine signaling. In particular, SOCS1 and SOCS3 play an important role in immune response by controlling the balance between Th1 and Th2 cells. In a previous study, we demonstrated that treatment of chronic asthmatic mice with gene therapy using plasmid encoding galectin-3 (Gal-3) led to an improvement in Th2 allergic inflammation. Methods. Using a microarray approach, this study endeavored to evaluate the changes produced by therapeutic Gal-3 delivered by gene therapy in a well-characterized mouse model of chronic airway inflammation. Results were confirmed by real-time RT-PCR, Western blot and immunohistochemical analysis. Results. We identify a set of genes involved in different pathways whose expression is coordinately decreased/increased in mice treated with Gal-3 gene therapy. We report a correlation between Gal-3 treatment and inhibition of SOCS1 and SOCS3 expression in lungs. Conclusion. These results suggest that negative regulation of SOCS1 and 3 following Gal-3 treatment could be a valuable therapeutic approach in allergic disease.

Increased expression of suppressor of cytokine signaling 1 mRNA in patients with rheumatoid arthritis

The objective of this study was to investigate the associations between suppressor of cytokine signaling 1 (SOCS1) mRNA expression and SOCS1 polymorphisms with the development of rheumatoid arthritis (RA). One hundred and eighty-one patients with RA and 96 healthy controls were enrolled in this study. The SOCS1 mRNA level in peripheral blood mononuclear cells (PBMCs) was detected by quantitative real-time polymerase chain reaction. SOCS1 polymorphisms were determined by the polymerase chain reaction/restriction fragment length polymorphism method. We found that the expression of SOCS1 mRNA in PBMCs was significantly greater in patients with RA than in healthy controls. There were no significant differences in the expression of SOCS1 mRNA among patients with different disease activities. The increment in SOCS1 mRNA after stimulation with various cytokines was slightly lower in the patients with RA than in the healthy controls. This study also demonstrated that the SOCS1 polymorphisms were not associated with susceptibility to RA. In conclusion, the expression of SOCS1 mRNA in PBMCs is higher in patients with RA than in healthy controls. The increment in SOCS1 mRNA expression in PBMCs after stimulation with different cytokines seems to be lower in patients with RA than in healthy controls.

SOCS1, a Negative Regulator of Cytokine Signals and TLR Responses, in Human Liver Diseases

Toll-like receptor (TLR) signaling pathways are strictly coordinated by several mechanisms to regulate adequate innate immune responses. Recent lines of evidence indicate that the suppressor of cytokine signaling (SOCS) family proteins, originally identified as negative-feedback regulators in cytokine signaling, are involved in the regulation of TLR-mediated immune responses. SOCS1, a member of SOCS family, is strongly induced upon TLR stimulation. Cells lacking SOCS1 are hyperresponsive to TLR stimulation. Thus, SOCS1 is an important regulator for both cytokine and TLR-induced responses. As an immune organ, the liver contains various types of immune cells such as T cells, NK cells, NKT cells, and Kupffer cells and is continuously challenged with gut-derived bacterial and dietary antigens. SOCS1 may be implicated in pathophysiology of the liver. The studies using SOCS1-deficient mice revealed that endogenous SOCS1 is critical for the prevention of liver diseases such as hepatitis, cirrhosis, and cancers. Recent studies on humans suggest that SOCS1 is involved in the development of various liver disorders in humans. Thus, SOCS1 and other SOCS proteins are potential targets for the therapy of human liver diseases.

Endotoxin-induced lung injury in α-galactosylceramide-sensitized mice is caused by failure of interleukin-4 production in lung natural killer T cells

Administration of bacterial lipopolysaccharide (LPS) known as endotoxin into α-galactosylceramide (α-GalCer)-sensitized mice causes severe lung lesions but few hepatic lesions in lethal shock, and interferon (IFN)-γ is suggested to play a pivotal role in preparation of the lung lesions. In order to clarify the mechanism of how α-GalCer sensitization causes lung lesions exclusively in mice, we examined the differential responsiveness of lungs and livers to α-GalCer sensitization. Although lung and liver natural killer T (NK T) cells both produced IFN-γ in response to α-GalCer, IFN-γ signalling was triggered only in the lungs of α-GalCer-sensitized mice. Lung NK T cells did not produce interleukin (IL)-4 in response to α-GalCer and it did not induce the expression of suppressor of cytokine signalling 1 (SOCS1) in the lungs. Conversely, IL-4 produced by liver NK T cells led to the expression of SOCS1 in the livers of the mice. Neutralization of IL-4 reduced SOCS1 expression in the livers and exacerbated LPS-induced hepatic lesions. IL-10 was produced by liver NK T cells but not lung NK T cells. However, IL-10 was produced constitutively by alveolar epithelial cells in normal lung. Lung NK T cells and liver NK T cells might express CD8 and CD4, respectively. Based on the fact that IL-4 inhibited IFN-γ signalling in the livers of α-GalCer-sensitized mice via SOCS1 expression and signal transducer and activator of transcription 1 (STAT-1) activation, no inhibition of the IFN-γ signalling in the lungs caused LPS-induced lung lesions in α-GalCer-sensitized mice. The detailed mechanism of development of the lung lesions in α-GalCer-sensitized mice is discussed.

Loss of SOCS3 expression is associated with an increased risk of recurrent disease in breast carcinoma

PURPOSE

Constitutive activation of JAK/STAT pathway is observed in various solid tumors and hematological malignancies. SOCS3 acts as a key negative regulator of JAK/STAT pathway and represents one of the candidate tumor suppressor genes. In the current study, we aimed to evaluate SOCS3 expression in breast carcinoma and to explore the prognostic significance of SOCS3.

METHODS

The expression of SOCS3 was measured by Western blot and immunohistochemistry in breast carcinoma cells and a large cohort of tissue microarray, respectively.

RESULTS

Among 367 human primary breast tumors, SOCS3 protein was detected in 103 patients. Deficient SOCS3 expression correlated significantly with lymph node metastasis (P = 0.003), blood vessel invasion (P = 0.029), VEGF (P = 0.001) and Ki-67 (P = 0.027). Univariate and multivariate analyses revealed that SOCS3 expression was an independent prognostic factor for disease-free survival (P < 0.0001). A positive SOCS3 protein expression correlated significantly with a low pSTAT3 protein expression in breast carcinoma (P = 0.015). The patients with a SOCS3 (+)/pSTAT3 (-) phenotype had a better prognosis than any other combination (DFI: P < 0.0001, BCSS: P = 0.013).

CONCLUSIONS

Deficient expression of SOCS3 is associated with an aggressive phenotype and portends a poor clinical outcome in breast carcinoma.

Cloning of common carp SOCS-3 gene and its expression during embryogenesis, GH-transgene and viral infection

As a member of a newly discovered protein family, the suppressor of cytokine signalling 3 (SOCS-3) has been shown to regulate the responses of many immune cytokines in a negative auto-regulatory manner. The full-length cDNA of common carp SOCS-3 was 1603 bp and contained a 630 bp open reading frame (ORF) coding for a protein of 209 amino acids. Carp SOCS-3 molecule was well conserved especially in the SRC homology 2 (SH2) and the SOCS box. The kinase inhibitory region (KIR) and ESS domains, upstream of the SH2 domain, were conserved in carp SOCS-3, except for a specific insertion (PHRYK) in the KIR domain at the N-terminal region. Three conserved cysteine (Cys-102, 124 and 193) residues, and one additional cysteine (Cys-168) residue, were also found in carp SOCS-3. The 2015 bp genomic DNA of carp SOCS-3 contained two exons and one intron. Phylogenetic analysis showed that carp SOCS-3 sequence grouped with other known fish SOCS-3 sequences with zebrafish SOCS-3 as the closest neighbour. RT-PCR analysis showed that carp SOCS-3 was initially expressed at 4 h pf (post-fertilization) and gradually increased up to 4 w pf during embryogenesis. By RT-qPCR analysis, carp SOCS-3 gene was predominantly detected in gill, head kidney, thymus and skin, followed by spleen and peripheral blood, lower expression level was detected in kidney, intestine, liver and muscle; the SOCS-3 transcript was significantly increased in thymus, head kidney, spleen and intestine of GH (growth hormone)-transgenic carp; after SVCV (spring viraemia of carp virus) infection, the carp SOCS-3 transcript was significantly up-regulated in gill, intestine, thymus, spleen, head kidney and kidney tissues in a time-dependent manner. These results suggest that teleost SOCS-3 may play an active role in the modulation of viral-induced innate immune response and in preventing the overaction of some cytokines with viral stimulation.

Suppressor of cytokine signaling 1 gene expression and polymorphisms in systemic lupus erythematosus

With the aim of investigating the role of suppressor of cytokine signaling 1 (SOCS1) in the pathogenesis of systemic lupus erythematosus, 107 patients with systemic lupus erythematosus, 101 healthy controls, and 151 patients with ankylosing spondylitis were enrolled in this study. SOCS1 mRNA level was measured by the method of quantitative real-time polymerase chain reaction. SOCS1 polymorphisms were detected by the polymerase chain reaction/restriction fragment length polymorphisms method. Systemic lupus erythematosus disease activity was evaluated with the SLEDAI. This study showed that the SOCS1 mRNA expression was significantly higher in the patients with systemic lupus erythematosus than in the healthy controls (p = 0.0014). Patients with active systemic lupus erythematosus had a higher expression of SOCS1 mRNA than the patients with inactive systemic lupus erythematosus (p = 0.035). There was no significant difference in the frequencies of the SOCS1-1478CA/del polymorphisms among the patients with systemic lupus erythematosus, healthy controls, and patients with ankylosing spondylitis. The genotype frequency of the SOCS1-1478 polymorphisms in the dominant model (CA/del+del/del versus CA/CA) was significantly decreased in the patients with thrombocytopenia compared with those without thrombocytopenia (p(c) = 0.035). Moreover, the allele frequency of SOCS1-1478del was also significantly lower in the patients with thrombocytopenia than in those without thrombocytopenia (p( c) = 0.02). In conclusion, this study demonstrated that the expression of SOCS1 mRNA was significantly increased in patients with systemic lupus erythematosus. Moreover, SOCS1 mRNA levels in patients with active systemic lupus erythematosus were significantly higher than those in the inactive patients. We also found that the systemic lupus erythematosus patients with thrombocytopenia have a lower frequency of SOCS1-1478del compared with patients without thrombocytopenia.

Anti-inflammatory actions of probiotics through activating suppressor of cytokine signaling (SOCS) expression and signaling in Helicobacter pylori infection: a novel mechanism

BACKGROUND AND AIMS

In spite of the International Agency for Research on Cancer's definition that Helicobacter pylori is the definite carcinogen of gastric cancer, the simple eradication of the bug is not enough to prevent resultant gastric cancer, and increasing microbial resistance further limits the eradication application. Therefore, probiotics, non-pathogenic microbial feed that can affect the host in a beneficial manner, could be an alternate way to enhance anti-inflammation against H. pylori. However, the mechanism of their anti-inflammatory actions is still unclear. In the current study, we hypothesized that suppressor of cytokine signaling (SOCS) signaling could be a feasible anti-inflammatory mechanism of probiotics against H. pylori infection.

RESULTS

H. pylori infection or their lipopolysaccharide stimulation led to significant increased expressions of inflammatory mediators including tumor necrosis factor-alpha, interleukin-8, inducible nitric oxide synthase and cyclooxygenase-2 in AGS cells and pretreatment of Lactobacillus plantarum, Lactobacillus rhamnosis and Lactobacillus acidophilus significantly attenuated the expressions of these inflammatory mediators in accordance with the blocking action of nuclear factor-kappaB nuclear translocation. Probiotic administration increased expression of SOCS-2 and SOCS-3 and exerted the active SOCS signaling featured with earlier and higher expressions of SOCS-2 and SOCS-3. In contrast to weak inactivation of mitogen-activated protein kinases including p-38 and extracellular signal-regulated kinase 1/2, probiotic-induced SOCS expressions were mediated through either significant phosphorylation of signal transducers and activation of transcription (STAT)-1 and STAT-3 or simultaneous inhibition of Janus kinase (JAK)2 phosphorylation, which is known to signal SOCS-2/SOCS-3 negatively.

CONCLUSION

Anti-inflammatory signals of SOCS through STAT-1/STAT-3 activation and JAK2 inactivation might be a key anti-inflammatory mechanism of probiotics, setting probiotics as a non-microbial strategy to H. pylori infection.

Suppressors of cytokine signaling (SOCS) in T cell differentiation, maturation, and function

Cytokines are key modulators of T cell biology, but their influence can be attenuated by suppressors of cytokine signaling (SOCS), a family of proteins consisting of eight members, SOCS1-7 and CIS. SOCS proteins regulate cytokine signals that control the polarization of CD4(+) T cells into Th1, Th2, Th17, and T regulatory cell lineages, the maturation of CD8(+) T cells from naïve to "stem-cell memory" (Tscm), central memory (Tcm), and effector memory (Tem) states, and the activation of these lymphocytes. Understanding how SOCS family members regulate T cell maturation, differentiation, and function might prove critical in improving adoptive immunotherapy for cancer and therapies aimed at treating autoimmune and infectious diseases.

Control of gluconeogenic genes during intense/prolonged exercise: hormone-independent effect of muscle-derived IL-6 on hepatic tissue and PEPCK mRNA

Prolonged intense exercise is challenging for the liver to maintain plasma glucose levels. Hormonal changes cannot fully account for exercise-induced hepatic glucose production (HGP). Contracting skeletal muscles release interleukin-6 (IL-6), a cytokine able to increase endogenous glucose production during exercise. However, whether this is attributable to a direct effect of IL-6 on liver remains unknown. Here, we studied hepatic glycogen, gluconeogenic genes, and IL-6 signaling in response to one bout of exhaustive running exercise in rats. To determine whether IL-6 can modulate gluconeogenic gene mRNA independently of exercise, we injected resting rats with recombinant IL-6. Exhaustive exercise resulted in a profound decrease in liver glycogen and an increase in gluconeogenic gene mRNA levels, phosphoenolpyruvate-carboxykinase (PEPCK), glucose-6-phosphatase (G6P), and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), suggesting a key role for gluconeogenesis in hepatic glucose production. This was associated to an active IL-6 signaling in liver tissue, as shown by signal transducer and activator of transcription and CAAT/enhancer binding protein-beta phosphorylation and IL-6-responsive gene mRNA levels at the end of exercise. Recombinant IL-6 injection resulted in an increase in IL-6-responsive gene mRNA levels in the liver. We found a dose-dependent increase in PEPCK gene mRNA strongly correlated with IL-6-induced gene mRNA levels. No changes in G6P and PGC-1alpha mRNA levels were found. Taken together, our results suggest that, during very demanding exercise, muscle-derived IL-6 could help increase HGP by directly upregulating PEPCK mRNA abundance.

Constitutive expression of suppressor of cytokine signalling-3 in skeletal muscle leads to reduced mobility and overweight in mice

AIMS/HYPOTHESIS

Due to their ability to regulate various signalling pathways (cytokines, hormones, growth factors), the suppressor of cytokine signalling (SOCS) proteins are thought to be promising therapeutic targets for metabolic and inflammatory disorders. Hence, their role in vivo has to be precisely determined.

METHODS

We generated transgenic mice constitutively producing SOCS-3 in skeletal muscle to define whether the sole abundance of SOCS-3 is sufficient to induce metabolic disorders and whether SOCS-3 is implicated in physiological roles distinct from metabolism.

RESULTS

We demonstrate here that chronic expression of SOCS-3 in skeletal muscle leads to overweight in mice and worsening of high-fat diet-induced systemic insulin resistance. Counter-intuitively, insulin sensitivity in muscle of transgenic mice appears to be unaltered. However, following constitutive SOCS-3 production, several genes had deregulated expression, among them other members of the SOCS family. This could maintain the insulin signal into skeletal muscle. Interestingly, we found that SOCS-3 interacts with calcineurin, which has been implicated in muscle contractility. In Socs-3 transgenic muscle, this leads to delocalisation of calcineurin to the fibre periphery. Relevant to this finding, Socs-3 transgenic animals had dilatation of the sarcoplasmic reticulum associated with swollen mitochondria and decreased voluntary activity.

CONCLUSIONS/INTERPRETATION

Our results show that constitutive SOCS-3 production in skeletal muscle is not in itself sufficient to induce the establishment of metabolic disorders such as diabetes. In contrast, we reveal a novel role of SOCS-3, which appears to be important for muscle integrity and locomotor activity.

Retinal Astrocytes respond to IL-17 differently than Retinal Pigment Epithelial cells

IL-17+ T cells make up the majority of the infiltrating cells in the inflamed eye during the development of EAU. However, the role of IL-17 in ocular inflammation is poorly defined. Given that the primary target cells for IL-17 are parenchymal cells of the tissue, we investigated the in vitro effect of IL-17 on mouse RACs and RPE cells. Our results showed that although RACs and RPE cells expressed the IL-17R, RACs responded to IL-17 by producing increased amounts of proinflammatory cytokines and chemokines, leading to increased migration of granulocytes, whereas RPE cells responded to the same concentration of IL-17 by expressing increased levels of SOCS proteins, resulting in only limited production of proinflammatory cytokines and chemokines and an increased amount of suppressive cytokines, such as LIF. The combination of IL-17 and IFN-gamma had a synergistic effect on cell migration with RACs but an antagonistic effect with RPE. In addition, specific inhibitors of the PI3K/Akt signaling pathway completely blocked inflammatory cell migration induced by chemokines released by IL-17-stimulated RACs. Our results demonstrate that IL-17 can induce a pro- or anti-inflammatory effect in the eye, depending on the parenchymal cells stimulated.

Intracellular delivery of a cell-penetrating SOCS1 that targets IFN-gamma signaling

Suppressor of cytokine signaling-1 (SOCS1) is an intracellular inhibitor of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway that couples interferon-gamma (IFN-gamma) signaling to the nucleus. Because several inflammatory diseases are associated with uncontrolled IFN-gamma signaling, we engineered a recombinant cell-penetrating SOCS1 (CP-SOCS1) to target this pathway. Here, we show that CP-SOCS1, analogous to endogenous SOCS1, interacted with components of the IFN-gamma signaling complex and functionally attenuated the phosphorylation of STAT1, which resulted in the subsequent inhibition of the production of proinflammatory chemokines and cytokines. Thus, controlled, intracellular delivery of recombinant CP-SOCS1 boosted the anti-inflammatory potential of the cell by restoring the homeostatic balance between pro- and anti-inflammatory signaling. This approach to controlling signal transduction has potential use for therapeutic targeting of signaling pathways associated with inflammatory diseases.