Heterogeneous expression of suppressor of cytokine signalling 2 (SOCS-2) in liver tissue

Suppressor of cytokine signalling 2 (SOCS-2), a dual effector of growth hormone signalling, was found to be heterogeneously expressed in murine liver parenchyma. Data from Affymetrix gene arrays, confirmed by quantitative RT-PCR using preparations of periportal and pericentral hepatocyte subpopulations as well as immunohistochemical detection, showed a preferential expression of SOCS-2 in pericentral hepatocytes. Stimulation of cultured periportal and pericentral hepatocyte subpopulations by different concentrations of growth hormone for 1 h resulted at 100 ng mL⁻¹ in a 1.6-fold and 4.3-fold increase of SOCS-2 mRNA, respectively. Likewise, insulin-like growth factor-1, another physiological target of growth hormone, was stimulated preferentially in pericentral hepatocytes. As growth hormone receptor was found to be homogeneously expressed in mouse liver parenchyma, our data indicate that growth hormone signalling downstream of growth hormone receptor is more sensitive and/or effective in pericentral than in periportal hepatocytes. Presumably, the heterogeneous distribution of SOCS-2 may contribute to the pericentral preference of growth hormone action via differential feedback.     

Regulation of multiple cytokine signalling pathways by SOCS3 is independent of SOCS2

Suppressor of cytokine signalling (SOCS) 3 is an essential regulator of cytokine signalling, and in turn its expression is tightly regulated. Data from overexpression studies in cell lines suggest that SOCS2 regulates SOCS3 protein degradation, by forming a molecular bridge to an E3 ubiquitin-ligase complex. Whether this regulation is relevant in primary cells is unknown. In this study, we utilized Socs2 ^{? / ?} mice to examine the role of SOCS2 in modulating SOCS3 expression and degradation, and its impact on interleukin-2 (IL-2) and IL-6 signalling in primary haemopoietic cells. Both biochemical and biological analyses demonstrated unperturbed SOCS3 expression and cytokine signalling in the absence of SOCS2. Our results suggest that SOCS2 is not a physiological regulator of SOCS3 expression and action in primary haemopoietic cells.     

Suppressors of cytokine signalling (SOCS)-1 inhibits neuroinflammation by regulating ROS and TLR4 in BV2 cells

Inflammation Research - The suppressors of cytokine signaling (SOCS) proteins are physiological suppressors of cytokine signaling which have been identified as a negative feedback loop to weaken...     

Lactobacillus rhamnosus GG and Streptococcus thermophilus induce suppressor of cytokine signalling 3 (SOCS3) gene expression directly and indirectly via interleukin-10 in human primary macrophages

In the present study we have characterized T helper type 2 (Th2) [interleukin (IL)-10]/Th1 (IL-12) cytokine expression balance in human primary macrophages stimulated with multiple non-pathogenic Gram-positive bacteria used in the food industry and as probiotic substances. Bacteria representing Lactobacillus, Bifidobacterium, Lactococcus, Leuconostoc, Propionibacterium and Streptococcus species induced anti-inflammatory IL-10 production, although quantitative differences between the bacteria were observed. S. thermophilus was able to induce IL-12 production, while the production of IL-12 induced by other bacteria remained at a low level. The highest anti-inflammatory potential was seen with bifidobacteria, as evidenced by high IL-10/IL-12 induction ratios. All studied non-pathogenic bacteria were able to stimulate the expression of suppressor of cytokine signalling (SOCS) 3 that controls the expression of proinflammatory cytokine genes. Lactobacillus and Streptococcus species induced SOCS3 mRNA expression directly in the absence of protein synthesis and indirectly via bacteria-induced IL-10 production, as demonstrated by experiments with cycloheximide (CHX) and anti-IL-10 antibodies, respectively. The mitogen-activated protein kinase (MAPK) p38 signalling pathway played a key role in bacteria-induced SOCS3 gene expression. Enhanced IL-10 production and SOCS3 gene expression induced by live non-pathogenic Lactobacillus and Streptococcus is also likely to contribute to their immunoregulatory effects in vivo.     

Suppressor of cytokine signalling 1 (SOCS1) is a physiological regulator of the asthma response

Background The molecular determinants of the severity and persistence of allergic asthma remain poorly understood. Suppressor of cytokine signalling 1 (SOCS1) is a negative regulator of IL‐4‐dependent pathways in vitro and might therefore control T‐helper type 2 (Th2) immunity associated traits, such as IgE levels, mucin production, IL‐5 and IL‐13 induction, and eosinophilic mucosal inflammation, which are implicated in allergic asthma. Objective To investigate the role of SOCS1 in regulating Th2‐associated disease traits in a murine sub‐chronic aeroallergen‐driven asthma model. Methods Following sensitization and challenge with ovalbumin (OVA), bronchoalveolar lavage and serum were collected from mice lacking the Socs1 gene on an IFN‐γ null background (Socs1^?/?Ifnγ^?/?). The composition of infiltrating cells in the lung, serum IgE and IgG1 levels and cytokine levels were analysed. Results Serum IgE levels and infiltrating eosinophils were considerably increased in the lungs of OVA‐treated Socs1^?/?Ifnγ^?/? mice compared with Ifnγ^?/? and C57BL/6 controls. Expression of the Th2 cytokines, IL‐4, IL‐5 and IL‐13 was increased in CD4⁺ cells and lung tissue from OVA‐treated Socs1^?/?Ifnγ^?/? mice. IgE, IL‐5 levels and infiltrating eosinophils were also elevated in saline‐treated Socs1^?/?Ifnγ^?/? mice, suggesting that in the absence of SOCS1, mice are already biased towards a Th2 response. It is at present unclear whether the elevated cytokine levels are sufficient to result in the exacerbated Th2 response to OVA challenge or whether enhanced intra‐cellular signalling also contributes. Surprisingly, of the various IL‐4/IL‐13 responsive genes tested, only Arginase I appeared to be modestly up‐regulated in the lungs of OVA‐treated Socs1^?/?Ifnγ^?/? mice, suggesting that regulation by SOCS1 occurs primarily in haematopoietic cells and not in the airway epithelium. Conclusions Together these results indicate that SOCS1 is an important regulator of the Th2 response.     

Cortisol modulates the expression of cytokines and suppressors of cytokine signaling (SOCS) in rainbow trout hepatocytes

Although liver is a key target for corticosteroid action, its role in immune function is largely unknown. We tested the hypothesis that stress levels of cortisol down regulate immune-relevant genes in rainbow trout (Oncorhynchus mykiss) liver. Hepatocytes were treated with lipopolysaccharide (LPS) for 24h either in the presence or absence of cortisol. LPS stimulated heat shock protein 70 expression, enhanced glycolytic capacity, and reduced glucose output. LPS stimulated mRNA abundance of cytokines and serum amyloid protein A (SAA), while suppressors of cytokine signaling (SOCS)-3 was reduced. Cortisol increased mRNA abundances of IL-1β, SOCS-1 and SOCS-2, while inhibiting either basal or LPS-stimulated IL-8, TNF α2 and SAA. These cortisol-mediated effects were rescued by Mifepristone, a glucocorticoid receptor antagonist. Altogether, cortisol modulates the molecular immune response in trout hepatocytes. The upregulation of SOCS-1 and SOCS-2 by cortisol may be playing a key role in suppressing cytokine signaling and the associated inflammatory response.     

Kinase inhibition,competitive binding and proteasomal degradation: resolving the molecular function of the suppressor of cytokine signaling (SOCS) proteins

The suppressor of cytokine signaling (SOCS) family of proteins are key negative regulators of cytokine and growth factor signaling. They act at the receptor complex to modulate the intracellular signaling cascade, preventing excessive signaling and restoring homeostasis. This regulation is critical to the normal cessation of signaling, highlighted by the complex inflammatory phenotypes exhibited by mice deficient in SOCS1 or SOCS3. These two SOCS proteins remain the best characterized of the eight family members (CIS, SOCS1-7), and in particular, we now possess a sound understanding of the mechanism of action for SOCS3. Here, we review the mechanistic role of the SOCS proteins and identify examples where clear, definitive data have been generated and discuss areas where the information is less clear. From this functional viewpoint, we discuss how the SOCS proteins achieve exquisite and specific regulation of cytokine signaling and highlight outstanding questions regarding the function of the less well-studied SOCS family members.     

Regulation of innate immunity by suppressor of cytokine signaling (SOCS) proteins

Innate immunity represents the first line of defense against invading pathogens. Toll-like receptors (TLRs) are important for activation of innate immunity. Moreover, cytokines mediate communication of cells and are necessary to mount an appropriately regulated immune response. However, activation of innate immunity has to be tightly controlled to avoid overshooting immune reactions. Suppressor of cytokine signaling (SOCS) proteins have been identified as inducible feedback inhibitors of cytokine receptors and have been shown to be of crucial importance for the limitation of inflammatory responses. In this review, we describe the role of SOCS proteins in macrophages and dendritic cells (DCs). Based on our own findings, we show that SOCS proteins are directly induced by stimulation of TLRs. However, SOCS proteins do not interfere with direct TLR signaling, but avoid overshooting activation by regulating paracrine IFN-beta signaling. In addition, SOCS proteins in macrophages and DCs regulate the sensitivity towards IFN-gamma and GM-CSF, thereby modulating anti-microbial activity of macrophages and differentiation of DCs. We discuss that SOCS induction can also be used by microbes to evade immune defense, and this is exemplified by the parasite Toxoplasma gondii which induces SOCS1 to inhibit IFN-gamma-mediated macrophage activation. Taken together, the findings indicate that SOCS proteins play an important role in the balanced activation of innate immunity during infectious encounter.     

Suppressor of cytokine signalling 2 (SOCS-2) expression in breast carcinoma

AIMS: To investigate SOCS-2 (suppressor of cytokine signalling 2) protein expression in breast carcinoma samples in relation to biopathological parameters and survival. METHODS: A polyclonal antibody against SOCS-2 was used to study 50 archival breast carcinoma samples, collected from 1993 to 1995. The presence of SOCS-2 protein was investigated in relation to clinical and biological parameters used in breast cancer pathology. Fluorescence in situ hybridisation (FISH) was used to study whether SOCS-2 expression was related to SOCS-2 gene copy number. RESULTS: SOCS-2 protein was expressed in 34 of 50 breast carcinoma samples and was positively associated with low grade, low nuclear grade, and p27 protein. SOCS-2 expression was inversely related to Ki-67, cyclin A, retinoblastoma protein (pRb), and the epidermal growth factor receptor (EGFR). No relation with overall survival was demonstrated. SOCS-2 amplification was found in three samples. No relation between the number of FISH signals and SOCS-2 expression was found. CONCLUSIONS: The significant correlation seen between SOCS-2 expression, grade, nuclear grade, p27, Ki-67, cyclin A, pRb, and EGFR labelling strongly supports the hypothesis that SOCS-2 loss might be related to cell proliferation and tumour growth in breast carcinoma. Gene copy number changes did not seem to play a role in SOCS-2 regulation and expression; other mechanisms might be involved and deserve further study.     

Perturbed thymopoiesis in vitro in the absence of suppressor of cytokine signalling 1 and 3

Cytokine signals are central to the differentiation of thymocytes and their stepwise progression through defined developmental stages. The intensity and duration of cytokine signals are regulated by the suppressor of cytokine signalling (SOCS) proteins. A clear role for SOCS1 during the later stages of thymopoiesis has been established, but little is known about its role during early thymopoiesis, nor the function of its closest relative, SOCS3. Here, we find that both SOCS1 and SOCS3 are expressed during early thymopoiesis, with expression coincident during the double negative (DN)2 and DN3 stages. We examined thymocyte differentiation in vitro by co-culture of SOCS-deficient bone marrow cells with OP9 cells expressing the Notch ligand Delta-like1 (OP9-DL1). Cells lacking SOCS1 were retarded at the DN3:DN4 transition and appeared unable to differentiate into double positive (DP) thymocytes. Cells lacking both SOCS1 and SOCS3 were more severely affected, and displayed an earlier block in T cell differentiation at DN2, the stage at which expression of SOCS1 and SOCS3 coincides. This indicates that, in addition to their specific roles, SOCS1 and SOCS3 share overlapping roles during thymopoiesis. This is the first demonstration of functional redundancy within the SOCS family, and has uncovered a vital role for SOCS1 and SOCS3 during two important checkpoints in early T cell development.     

AngiostatinK（1—3）基因真核表达载体的构建,鉴定和表达

构建携带人ａｎｇｉｏｓｔａｔｉｎＫ（１－３）ｃＤＮＡ的真核表达载体,并将其在体外培养的脑胶质瘤细胞中表达。方法将带有分泌信号的ａｎｇｉｏｓｔａｔｉｎＫ（１－３）ｃＤＮＡ克隆入真核表达载体ｐｃＤＮＡ３,构建ＣＭＶ启动子控制的载体ｐｃＤ－ＮＡ－ＳＡＫ（１０３）,采用酶切鉴定结果。     

Therapeutic hope for psoriasis offered by SOCS (suppressor of cytokine signaling) mimetic peptide

The cytokine network has a pivotal role in maintaining skin homeostasis, and the disturbance of this network can lead to skin pathogenesis. Evidence published in this issue of the European Journal of Immunology by Madonna et al. [Eur. J. Immunol. 2013. 43: 1883–1895], together with other recent data, focuses attention on a negative cytokine regulator, namely SOCS 1 (suppressor of cytokine signaling 1) in immune‐mediated skin disease. In addition, Madonna et al. bring new perspectives regarding the therapeutic control of IFN‐γ‐mediated skin pathogenesis by use of a SOCS 1 mimetic peptide.     

Expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS) induced in Burkholderia pseudomallei--infected mouse macrophages requires bacterial internalization

We recently reported that Burkholderia pseudomallei was able to activate the expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS). In the present study, we presented evidence showing that the induction of these negative regulators was most probably triggered from within rather than at the cell surface of mouse macrophage cell line (RAW264.7) suggesting that macrophage activation most likely requires the interaction of bacteria with a putative host cell cytoplasmic component(s).     

Tumor necrosis factor‐α augments lipopolysaccharide‐induced suppressor of cytokine signalling 3 (SOCS‐3) protein expression by preventing the degradation

The regulatory role of tumour necrosis factor‐α (TNF‐α) on the expression of suppressor of cytokine signalling 3 (SOCS‐3) in response to lipopolysaccharide (LPS) was examined using peritoneal macrophages from TNF‐α‐deficient mice. The LPS‐induced SOCS‐3 expression was markedly augmented in macrophages from wild‐type mice whereas such augmentation was not seen in the cells from TNF‐α‐deficient mice. However, there was no significant difference in the level of SOCS‐3 messenger RNA expression between macrophages from wild‐type mice and those from TNF‐α‐deficient mice. The addition of exogenous TNF‐α augmented the LPS‐induced SOCS‐3 expression in macrophages from TNF‐α‐deficient mice. The pulse chase analysis suggested augmented degradation of LPS‐induced SOCS‐3 protein in macrophages from TNF‐α‐deficient mice. Moreover, MG 132, a 26S proteasome inhibitor, sustained the LPS‐induced SOCS‐3 expression in those cells. The tyrosine phosphorylation of SOCS‐3 was definitely induced in LPS‐stimulated macrophages from TNF‐α‐deficient mice but not wild‐type mice. A tyrosine phosphatase inhibitor enhanced the tyrosine phosphorylation of SOCS‐3 in wild‐type mice and accelerated the degradation. Therefore, it was suggested that TNF‐α prevented the degradation of SOCS‐3 protein via inhibition of the tyrosine phosphorylation in LPS‐stimulated macrophages.     

Topical administration of a suppressor of cytokine signaling-1 (SOCS1) mimetic peptide inhibits ocular inflammation and mitigates ocular pathology during mouse uveitis

Uveitis is a diverse group of potentially sight-threatening intraocular inflammatory diseases and pathology derives from sustained production of pro-inflammatory cytokines in the optical axis. Although topical or systemic steroids are effective therapies, their adverse effects preclude prolonged usage and are impetus for seeking alternative immunosuppressive agents, particularly for patients with refractory uveitis. In this study, we synthesized a 16 amino acid membrane-penetrating lipophilic suppressor of cytokine signaling 1 peptide (SOCS1-KIR) that inhibits JAK/STAT signaling pathways and show that it suppresses and ameliorates experimental autoimmune uveitis (EAU), the mouse model of human uveitis. Fundus images, histological and optical coherence tomography analysis of eyes showed significant suppression of clinical disease, with average clinical score of 0.5 compared to 2.0 observed in control mice treated with scrambled peptide. We further show that SOCS1-KIR conferred protection from ocular pathology by inhibiting the expansion of pathogenic Th17 cells and inhibiting trafficking of inflammatory cells into the neuroretina during EAU. Dark-adapted scotopic and photopic electroretinograms further reveal that SOCS1-KIR prevented decrement of retinal function, underscoring potential neuroprotective effects of SOCS1-KIR in uveitis. Importantly, SOCS1-KIR is non-toxic, suggesting that topical administration of SOCS1-Mimetics can be exploited as a non-invasive treatment for uveitis and for limiting cytokine-mediated pathology in other ocular inflammatory diseases including scleritis.