Suppressor Of Cytokine Signaling Proteins Research Articles

SOCS3 Phosphorylation In Myeloproliferative Neoplasms

AbstractAbstract 3083 Introduction:Suppressor of cytokine signaling protein 3 (SOCS3) is an important regulator of the erythropoietin receptor and the receptor-associated JAK2 kinase. We hypothesize that the mechanism of JAK2 mutant-mediated transformation in myeloproliferative neoplasms (MPN) involves overcoming SOCS3 inhibition. In co-expression studies SOCS3 protein is stabilized and tyrosine phosphorylated in the presence of JAK2 V617F (Hookham et al., Blood 2007) and exon 12 mutations (Elliott et al., Haematologica 2009) but not wild-type JAK2, rendering SOCS3 unable to downregulate phosphorylation of these JAK2 mutants. The purpose of this study was to determine if these observations can be reproduced in vivo, by comparing SOCS3 expression and phosphorylation in MPN patients and healthy volunteers. Methods:Patients with polycythaemia vera (PV) and essential thrombocythaemia (ET) were recruited from Belfast City Hospital. The mutational status of the JAK2 gene had been previously assessed. Granulocytes were isolated from peripheral blood of patients and healthy volunteers by Ficoll density gradient centrifugation, dextran sedimentation and hypotonic red cell lysis. Estimation of the JAK2 V617F/wild type allelic ratio was performed by pyrosequencing. SOCS3 expression levels were measured by quantitative real-time reverse transcriptase-PCR. Granulocyte whole cell lysate was immunoprecipitated with anti-SOCS3 and Western blots were probed with anti-phosphotyrosine. SOCS3 phosphorylation was estimated by densitometry. Results:To date, 63 MPN patients and 27 healthy volunteers have been recruited. This total is comprised of 47 patients with PV (JAK2 V617F n=38, JAK2 exon 12 n=4, unknown n=5) and 16 patients with ET (JAK2 V617F n=15). Median V617F allele burden was 45% in PV (range 0–99%) and 20% in ET (range 7–84%). In 67% of patients with PV, SOCS3 expression was greater than healthy volunteers. Compared to healthy volunteers, SOCS3 phosphorylation in PV patients was higher in 67%, equivalent in 17% and lower in 17% of cases. Similarly in ET, SOCS3 phosphorylation was higher in 73%, equivalent in 18% and lower in 9% of patients compared with healthy volunteers. SOCS3 tyrosine phosphorylation was observed in association with both JAK2 V617F and exon 12 mutants. Conclusion:The presence of aberrant tyrosine phosphorylation of SOCS3 protein observed in some PV and ET patients supports the hypothesis that this is a potential mechanism by which mutant JAK2 escapes inhibition and leads to constitutive downstream signaling in MPN. Disclosures:No relevant conflicts of interest to declare.

The anti‐inflammatory effects of interleukin‐4 are not mediated by suppressor of cytokine signalling‐1 (SOCS1)

While it is known that the anti-inflammatory effects of interleukin (IL)-4 require new protein synthesis, the exact mechanisms by which IL-4 suppresses the production of pro-inflammatory cytokines by human monocytes and macrophages is unclear. IL-4 rapidly induced suppressor of cytokine signalling-1 (SOCS1) mRNA and protein, which peaked at 60 min, much earlier than lipopolysaccharide (LPS)-induced SOCS1 mRNA and protein which were consistently maximal 4 hr post-exposure. SOCS1 is a molecule generally considered to be induced for negative feedback of inflammatory processes. We investigated whether the early induction of SOCS1 by IL-4 was responsible for the suppression of LPS-induced tumour necrosis factor (TNF)-alpha production by IL-4. IL-4 suppressed LPS-induced TNF-alpha in freshly isolated monocytes at the level of transcription but acted by a different, possibly translational, mechanism in monocytes cultured overnight in macrophage colony-stimulating factor (M-CSF). Despite different modes of regulation by IL-4, the kinetics and magnitude of induction of SOCS1 mRNA and protein by IL-4 in the two cell types were identical. There was no significant difference in the suppression by IL-4 of LPS-induced TNF-alpha production by bone-marrow derived macrophages from wild-type mice, Ifngamma(-/-) mice and mice lacking SOCS1 (Socs1(-/-)Ifngamma(-/-)). These data suggest that SOCS1 is not involved in the suppression of LPS-induced TNF-alpha production by IL-4.

Epstein-Barr Virus Interferes with the Amplification of IFNα Secretion by Activating Suppressor of Cytokine Signaling 3 in Primary Human Monocytes

BackgroundEpstein-Barr virus is recognized to cause lymphoproliferative disorders and is also associated with cancer. Evidence suggests that monocytes are likely to be involved in EBV pathogenesis, especially due to a number of cellular functions altered in EBV-infected monocytes, a process that may affect efficient host defense. Because type I interferons (IFNs) are crucial mediators of host defense against viruses, we investigated the effect of EBV infection on the IFNα pathway in primary human monocytes.Methodology/Principal FindingsInfection of monocytes with EBV induced IFNα secretion but inhibited the positive feedback loop for the amplification of IFNα. We showed that EBV infection induced the expression of suppressor of cytokine signaling 3 (SOCS3) and, to a lesser extent, SOCS1, two proteins known to interfere with the amplification of IFNα secretion mediated by the JAK/STAT signal transduction pathway. EBV infection correlated with a blockage in the activation of JAK/STAT pathway members and affected the level of phosphorylated IFN regulatory factor 7 (IRF7). Depletion of SOCS3, but not SOCS1, by small interfering RNA (siRNA) abrogated the inhibitory effect of EBV on JAK/STAT pathway activation and significantly restored IFNα secretion. Finally, transfection of monocytes with the viral protein Zta caused the upregulation of SOCS3, an event that could not be recapitulated with mutated Zta.Conclusions/SignificanceWe propose that EBV protein Zta activates SOCS3 protein as an immune escape mechanism that both suppresses optimal IFNα secretion by human monocytes and favors a state of type I IFN irresponsiveness in these cells. This immunomodulatory effect is important to better understand the aspects of the immune response to EBV.

Involvement of the JAK‐STAT pathway and SOCS3 in the regulation of adiponectin‐generated reactive oxygen species in murine macrophage RAW 264 cells

Adiponectin is a protein hormone produced by differentiating adipocytes and has been proposed to have anti-diabetic and immunosuppressive properties. We previously reported that the globular form of adiponectin (gAd) induces the generation of reactive oxygen species (ROS) and nitric oxide (NO), followed by caspase-dependent apoptotic cell death in RAW 264 cells. Here, we demonstrate that gAd-induced ROS generation and apoptosis were diminished by suppressor of cytokine signaling 3 (SOCS3). The phosphorylation level of signal transducer and activator of transcription (STAT) 3 detected by Western blotting was highest at 20 min in gAd-treated RAW 264 cells. This phosphorylation was inhibited by AG490, a specific inhibitor of janus-activator kinase (JAK). The gAd-induced ROS and NO were reduced by administration of AG490 and Jak-2-specific siRNA in RAW 264 cells. The gAd stimulation transiently induced SOCS3 mRNA expression and protein production. We examined SOCS3-overexpressing RAW 264 cells to investigate the role of the JAK-STAT pathway in gAd-induced ROS and NO generation. SOCS3 overexpression significantly reduced both ROS and NO generation. Additionally, gAd-induced caspase activation and apoptotic cell death were reduced in SOCS3 transfectants compared with vector control transfectants. These results suggest that the JAK-STAT pathway, which can be suppressed by SOCS3 expression, is involved in gAd-induced ROS and NO generation followed by apoptotic cell death.

Expression of suppressor of cytokine signaling 3 and its significance in human placenta with pregnant intrahepatic cholestasis

To detect the expression and significance of suppressor of cytokine signaling 3(SOCS3) in the placentas of pregnant women with intrahepatic cholestasis of pregnancy (ICP). Totally, 44 ICP gravidas, including 21 severe ICP and 23 mild ICP who delivered through cesarean section at the Second Xiangya Hospital of Central South University from April 2008 to January 2009, were selected as the ICP group, and another 25 healthy pregnant women were chosen as control. Placentas of the above gravidas were collected and the expression and localization of SOCS3 were determined by immunohistochemical peroxidase streptomyces-avidin link (SP) method (indicated by the percentage of positive cells and average gray scale) and the levels of interleukin-10 (IL-10) and interferon-γ (IFN-γ) from placenta homogenation were measured by enzyme linked immunoadsorbent assay (ELISA). (1) SOCS3 were expressed in placentas of both groups mainly in the intracytoplasma of trophocyte. However, weakly positive, positive, and strongly positive expressions were found in the severe ICP, mild ICP and the control group, respectively. Almost no expression was detected in membrane and nucleus of the trophoblasts. (2) The percentage of SOCS3 positive cells in the severe ICP group was significantly lower than in the control and the mild ICP group, respectively [(0.15 ± 0.08) % vs (0.69 ± 0.12) % and (0.42 ± 0.09) %, P < 0.01]. The average gay SOCS3 in placental tissue in the severe ICP group was significantly higher than that in control and mild ICP group, respectively (204 ± 7 vs 81 ± 7 and 147 ± 7, P < 0.01). (3) Significant lower level of IL-10 in placenta homogenation was found in the severe ICP group than in the control and mild ICP group [(1.16 ± 0.68) µg/L, vs (1.39 ± 0.08) µg/L and (1.22 ± 0.75) µg/L, P < 0.01]. (4) The opposite results were found in the level of IFN-γ in trophoblasts and the ratio of IFN-γ/IL-10 [severe ICP group: (16.8 ± 0.7) µg/L and 16.02 ± 2.79; control group: (10.5 ± 0.3) µg/L and 8.56 ± 0.14; mild ICP group: (13.4 ± 0.5) µg/L and 8.56 ± 0.14, P < 0.01]. (5) Negative correlation was shown between the percentage of SOCS3 positive cells in trophoblasts and the ratio of IFN-γ/IL-10 (r = -0.685 and -0.702, P < 0.01), and the average gay SOCS3 was positively correlated with the ratio of IFN-γ/IL-10 (r = 0.621 and 0.891, P < 0.01) in both mild and severe ICP group. SOCS3 may participate in the pathogenesis of ICP and its expression may affected by the severity of ICP, and SOCS3 may also play a role in the immunological regulation in ICP patients.

Extended Anti-inflammatory Action of a Degradation-resistant Mutant of Cell-penetrating Suppressor of Cytokine Signaling 3

Suppressor of cytokine signaling 3 (SOCS3) regulates the proinflammatory cytokine signaling mediated by the JAK/STAT signaling pathway. SOCS3 is rapidly induced and then targeted to the ubiquitin-proteasome pathway via a mechanism that requires the C-terminal SOCS box. Due to its rapid turnover, the intracellular stores of SOCS3 seem insufficient to control acute or protracted inflammatory diseases. Previously, we developed an intracellular protein therapy that uses a recombinant cell-penetrating form of SOCS3 (CP-SOCS3) to inhibit the JAK/STAT pathway and prevent cytokine-mediated lethal inflammation and apoptosis of the liver (Jo, D., Liu, D., Yao, S., Collins, R. D., and Hawiger, J. (2005) Nat. Med. 11, 892-898). The potent anti-inflammatory and cytoprotective activity of CP-SOCS3 prompted us to analyze its intracellular turnover, as compared with that of endogenous SOCS3 protein induced in macrophages by the proinflammatory agonists, interferon-gamma and lipopolysaccharide. We found that the half-life (t(1/2)) of endogenous SOCS3 is 0.7 h in activated macrophages, compared with a t(1/2) of 6.2 h for recombinant CP-SOCS3. Deletion of the SOCS box in CP-SOCS3 renders it more resistant to proteasomal degradation, extending its t(1/2) to 29 h. Consequently, this SOCS box-deleted form of CP-SOCS3 displays persistent inhibitory activity for 24 h toward interferon-gamma- and lipopolysaccharide-induced cytokine and chemokine production. Compared with the wild-type suppressor, this gain-of-function CP-SOCS3 mutant provides a longer acting inhibitor of cytokine signaling, a feature that offers a clear advantage for the intracellular delivery of proteins to treat acute or protracted inflammatory diseases.

IFNγ-dependent SOCS3 expression inhibits IL-6-induced STAT3 phosphorylation and differentially affects IL-6 mediated transcriptional responses in endothelial cells

IL-6 has pro- and anti-inflammatory effects and is involved in endothelial cell (EC) dysfunction. The anti-inflammatory effects of IL-6 are mediated by signal transducer and activator of transcription-3 (STAT3), which is importantly controlled by suppressor of cytokine signaling 3 (SOCS3). Therefore, cytokines that modulate SOCS3 expression might inhibit the anti-inflammatory effects of IL-6. We hypothesized that in EC, interferon-gamma (IFNgamma)-induced SOCS3 expression leads to inhibition of IL-6-induced STAT3 activation and IL-6-dependent expression of anti-, but not pro-inflammatory, target genes. IFNgamma activated STAT1 and STAT3 and increased SOCS3 expression in EC. IL-6 only activated STAT3 and induced SOCS3 expression. IFNgamma pretreatment of EC inhibited IL-6-induced STAT3 activation accompanied by increased SOCS3 protein. Inhibition of SOCS3 expression, using costimulation, Act-D, and small interfering RNA (siRNA), subsequently implicated the importance of IFNgamma-induced SOCS3 in this phenomenon. Pretreatment of EC with IFNgamma also affected the transcriptional program induced by IL-6. We identified 1) IL-6 anti-inflammatory target genes that were inhibited by IFNgamma, 2) IFNgamma-target genes of pro-inflammatory nature that were increased in response to IL-6 in the presence of IFNgamma, and 3) a set of target genes that were increased upon IL-6 or IFNgamma alone, or combined IFNgamma and IL-6. In summary, by increasing SOCS3 expression in EC, IFNgamma can selectively inhibit STAT3-dependent IL-6 signaling. This in turn leads to decreased expression of some EC protective genes. In contrast, other genes of pro-inflammatory nature are not inhibited or even increased. This IFNgamma-induced shift in IL-6 signaling to a pro-inflammatory phenotype could represent a novel mechanism involved in EC dysfunction.

Suppressor of Cytokine Signaling 3 Suppresses Hepatitis C Virus Replication in an mTOR-Dependent Manner

We and others have observed that hepatic levels of suppressor of cytokine signaling 3 (SOCS3) are significantly higher in persons with chronic hepatitis C, particularly those who are nonresponders to interferon (IFN) treatment, than in healthy individuals. However, the relationship between SOCS3 and hepatitis C virus (HCV) replication remains unclear. Given its putative role, we hypothesized that SOCS3 is permissive for viral replication. We therefore used the OR6 cell line, which harbors a genotype 1b full-length HCV replicon, and the genotype 2a full-length HCV strain JFH1 infection system to analyze the effects of SOCS3 overexpression and short hairpin RNA (shRNA)-mediated knockdown on HCV replication. We further analyzed the role of mTOR in the effects of SOCS3 by treating selected cells with rapamycin. OR6 cells and JFH1-infected Huh7.5.1 cells expressed significantly less SOCS3 than control cells. Furthermore, inhibition of HCV replication with the HCV protease inhibitor BILN 2061 restored SOCS3 protein levels. SOCS3 overexpression in OR6 cells and JFH1-infected Huh7.5.1 cells resulted in significantly lower HCV replication than that in the control cells, despite SOCS3-related inhibition of STAT1 phosphorylation and type I IFN signaling. In contrast, JFH1-infected cells with stable SOCS3 knockdown expressed higher levels of HCV proteins and RNA than did control cells. SOCS3-targeting shRNA also knocked down mTOR and phospho-mTOR. The mTOR inhibitor rapamycin reversed the inhibitory effects of SOCS3. In independent investigations, SOCS3 unexpectedly suppressed HCV replication in an mTOR-dependent manner. These findings suggest that increased SOCS3 levels consistently observed in chronic IFN nonresponders may reflect a compensatory host antiviral response to persistent infection and that manipulation of SOCS3/mTOR may offer benefit against HCV infection.

Hepatitis C virus core protein genotype 3a increases SOCS-7 expression through PPAR- in Huh-7 cells

Hepatitis C virus (HCV) core protein genotype 3a induces the expression of suppressor of cytokine signalling protein 7 (SOCS-7), which is partially involved in the development of insulin resistance. The aim of the present study was to investigate the mechanism through which the core protein regulates SOCS-7 expression. We have explored, in the in vitro model of Huh-7 cells expressing the HCV core protein of genotype 3a, whether the expression of SOCS-7 as well as of other members of the SOCS family (SOCS-1 and SOCS-3) was activated by the STAT3 pathway, using immunoblotting and real-time PCR upon alpha interferon (IFN-alpha) treatment. We found that, whilst IFN-alpha treatment induced STAT3 activation and consequently SOCS-1 and SOCS-3 upregulation in HCV genotype 3a core-expressing Huh-7 cells, SOCS-7 mRNA expression was independent of STAT3 and seemed to be modulated by peroxisome proliferator-activated receptor gamma (PPAR-gamma) activity, as demonstrated by quantitative real-time PCR and immunoblot detection after treatment with the PPAR-gamma agonist rosiglitazone or the PPAR-gamma antagonist GW9262. In contrast to the other studied members of the SOCS family (1 and 3), which are regulated by STAT3 activation, SOCS-7 expression appears to be STAT3-independent and seems to be regulated instead by PPAR-gamma. This is the first report proposing a molecular mechanism through which the HCV core protein (genotype 3a) modulates SOCS-7 expression.

SOCS-3 antagonises the proliferative and migratory effects of fibroblast growth factor-2 in prostate cancer by inhibition of p44/p42 MAPK signalling

Fibroblast growth factor-2 (FGF-2) is highly expressed in prostate cancer. It promotes tumour progression through multiple pathways including those of signal transducers and activators of transcription factor 3 (STAT3), mitogen-activated protein kinases (MAPKs) and Akt. In previous studies, we have reported that STAT3 phosphorylation inversely correlates with suppressor of cytokine signalling-3 (SOCS-3) expression in prostate cancer cells. Recently, it has become evident that SOCS-3-negative regulation is not only limited to the interleukin-6 (IL-6) receptor. We hypothesised that SOCS-3 interferes with FGF signalling, thus influencing the outcome of its action in prostate cancer cells. For this purpose, we treated DU-145 and LNCaP-IL-6+ cells with increasing concentrations of FGF-2, and verified protein phosphorylation. In the presence of FGF-2, neither STAT3, STAT1, nor Akt could be phosphorylated. Solely the p44/p42 MAPK pathway was activated after FGF-2 stimulation. We show for the first time that SOCS-3 interferes with the FGF-2 signalling pathway by modulating p44 and p42 phosphorylation in prostate cancer cells. Decreased SOCS-3 protein expression results in increased MAPK phosphorylation, whereas SOCS-3 overexpression leads to a decreased cellular proliferation and migration. On the basis of the present results, we propose that SOCS-3 is a novel modulator of FGF-2-regulated cellular events in prostate cancer.

Curcumin suppresses constitutive activation of STAT‐3 by up‐regulating protein inhibitor of activated STAT‐3 (PIAS‐3) in ovarian and endometrial cancer cells

Signal transducer and activator of transcription-3 (STAT-3) is constitutively activated in ovarian and endometrial cancers and is implicated in uncontrolled cell growth. Thus, its disruption could be an effective approach to control tumorigenesis. Curcumin is a dihydroxyphenolic compound, with proven anti-cancer efficacy in various cancer models. We examined the anti-tumor mechanism of curcumin on STAT-3 and on the negative regulators of STAT-3, including suppressors of cytokine signaling proteins (SOCS-1 and SOCS-3), protein inhibitors of activated STAT (PIAS-1 and PIAS-3), and SH2 domain-containing phosphatases (SHP-1 and SHP-2) in ovarian and endometrial cancer cell lines. Treatment of cancer cells with curcumin induced a dose- and time-dependent decrease of constitutive IL-6 expression and of constitutive and IL-6-induced STAT-3 phosphorylation, which is associated with decreased cell viability and increased cleavage of caspase-3. The inhibition of STAT-3 activation by curcumin was reversible, and phosphorylated STAT-3 levels returned to control levels 24 h after curcumin removal. Compared to normal cells baseline expression of SOCS-3 was high in cancer cells and a marked decrease in SOCS-3 expression was seen following curcumin treatment. Overexpression of SOCS-3 in curcumin-treated cells increased expression of phosphorylated STAT-3 and resulted in increased cell viability. Normal ovarian and endometrial cells exhibited high expression of PIAS-3 protein, whereas in cancer cells the expression was greatly reduced. Curcumin increased PIAS-3 expression in cancer cells. Of significance, siRNA-mediated knockdown of PIAS-3 overcomes the inhibitory effect of curcumin on STAT-3 phosphorylation and cell viability. In conclusion, curcumin suppresses JAK-STAT signaling via activation of PIAS-3, thus attenuating STAT-3 phosphorylation and tumor cell growth.

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.

Leptin receptor 170 kDa (OB‐R170) protein expression is reduced in obese human skeletal muscle: a potential mechanism of leptin resistance

To examine whether obesity-associated leptin resistance could be due to down-regulation of leptin receptors (OB-Rs) and/or up-regulation of suppressor of cytokine signalling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) in skeletal muscle, which blunt janus kinase 2-dependent leptin signalling and signal transducer and activator of transcription 3 (STAT3) phosphorylation and reduce AMP-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase (ACC) phosphorylation. Deltoid and vastus lateralis muscle biopsies were obtained from 20 men: 10 non-obese control subjects (mean +/- s.d. age, 31 +/- 5 years; height, 184 +/- 9 cm; weight, 91 +/- 13 kg; and percentage body fat, 24.8 +/- 5.8%) and 10 obese (age, 30 +/- 7 years; height, 184 +/- 8 cm; weight, 115 +/- 8 kg; and percentage body fat, 34.9 +/- 5.1%). Skeletal muscle OB-R170 (OB-R long isoform) protein expression was 28 and 25% lower (both P < 0.05) in arm and leg muscles, respectively, of obese men compared with control subjects. In normal-weight subjects, SOCS3 protein expression, and STAT3, AMPKalpha and ACCbeta phosphorylation, were similar in the deltoid and vastus lateralis muscles. In obese subjects, the deltoid muscle had a greater amount of leptin receptors than the vastus lateralis, whilst SOCS3 protein expression was increased and basal STAT3, AMPKalpha and ACCbeta phosphorylation levels were reduced in the vastus lateralis compared with the deltoid muscle (all P < 0.05). In summary, skeletal muscle leptin receptors and leptin signalling are reduced in obesity, particularly in the leg muscles.

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-a (TNF-a) on the expression of suppressor of cytokine signalling 3 (SOCS-3) in response to lipopolysaccharide (LPS) was examined using peritoneal macrophages from TNF-a-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-a-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-a-deficient mice. The addition of exogenous TNF-a augmented the LPS-induced SOCS-3 expression in macrophages from TNF-a-deficient mice. The pulse chase analysis suggested augmented degradation of LPS-induced SOCS-3 protein in macrophages from TNF-a-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-a-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-a prevented the degradation of SOCS-3 protein via inhibition of the tyrosine phosphorylation in LPS-stimulated macrophages.

Fms-Like Tyrosine Kinase 3 Ligand Decreases T Helper Type 17 Cells and Suppressors of Cytokine Signaling Proteins in the Lung of House Dust Mite–Sensitized and –Challenged Mice

We previously reported that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c(high)CD8α(high)CD11b(low) dendritic cells and CD4(+)CD25(+)ICOS(+)Foxp3(+)IL-10(+) T-regulatory cells in the lung of allergen-sensitized and -challenged mice. In this study, we evaluated the effect of Flt3-L on Th17 cells and expression of suppressors of cytokine signaling (SOCS) proteins in the lungs of house dust mite (HDM)-sensitized and -challenged mice. BALB/c mice were sensitized and challenged with HDM, and AHR to methacholine was established. Mice were treated with Flt3-L (5 μg, intraperitoneal) daily for 10 days. Levels of IL-4, -5, -6, -8, and -13, and transforming growth factor (TGF)-β in the bronchoalveolar lavage fluid (BALF) were examined by ELISA. Flt3-L treatment reversed existing AHR to methacholine and substantially decreased eosinophils, neutrophils, IL-5, -6, -8, and IL-13, and TGF-β levels in the BALF. HDM-sensitized and -challenged mice showed a significant increase in lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells with high expression of retinoic acid-related orphan receptor (ROR)-γt transcripts. However, administration of Flt3-L substantially decreased the number of lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells, with significantly decreased expression of ROR-γt mRNA in these cells. HDM sensitization caused a significant increase in the expression of SOCS-1, -3, and -5 in the lung. Flt3-L treatment abolished the increase in SOCS-1 and SOCS-3 proteins, whereas SOCS-5 expression was significantly reduced. These data suggest that the therapeutic effect of Flt3-L in reversing the hallmarks of allergic asthma in a mouse model is mediated by decreasing IL-6 and TGF-β levels in the BALF, which, in turn, decrease CD4(+)IL-17(+)IL-23R(+)ROR-γt(+)CD25⁻ T cells and the expression of SOCS-1 and SOCS-3 in the lung of HDM-sensitized and -challenged mice.

Immunomodulatory EFFECTS of Lenalidomide and Pomalidomide ON INTERACTION of TUMOR and BONE MARROW Accessory CELLS IN MULTIPLE MYELOMA.

Abstract 950The bone marrow (BM) microenvironment consists of extracellular matrix and the cellular compartment including bone marrow stromal cells (BMSCs) and immune cells. Interaction between multiple myeloma (MM) cells and BM cells induces growth, survival, migration, and drug resistance in MM, via both cell-cell contact and cytokines. Even though MM cell interaction with BMSCs has been extensively studied, the role of immune cells in the MM BM milieu is not yet defined. The IMiDs® immunomodulatory agents lenalidomide (len) and pomalidomide (pom) target not only MM cells, but also MM cell-immune cell interactions and cytokine signaling. For example, we and others have shown that len stimulates T cell proliferation, secretion of IL2 and IFNγ, as well as promotes CTL and NK cell activity against MM cells. Here we examined the in vitro immunomodulatory effects of len or pom on cytokine signaling triggered by interaction of effector immune cells with MM cells and BMSCs. PBMCs or BMMNCs obtained from patients with rel/ref MM or healthy donors after informed consent. PBMCs were cultured either alone or with BMSC, in the absence or presence of len (1μM) or pom (1μM) for 1-48h. To determine whether len or pom regulate cytokine signaling in effector cells, we used flow cytometry to analyze their effects on suppressor of cytokine signaling proteins (SOCS, including SOCS1, SOCS2, SOCS3, CIS) expression in effector cells from both healthy donors and patients with MM. Len or pom diminished IL2 and IFNγ regulators SOCS1 and SOCS3 expression in effector cells from both BM and PB of MM patients. Additionally, coculture of MM cell lines, MM1S, U266, OPM1, RPMI, LR5 and DOX40, with healthy PBMCs induced SOCS1 and SOCS3 expression in effector cells; conversely, treatment with len or pom downregulated the SOCS1 and SOCS3 expression in effector cells. To assess effects of immunomodulatory agents on immune cell proliferation in their milieu, healthy or MM-PBMCs and MM-BMMNCs were prelabeled with CFSE and stimulated with PHA (5μg/ml) or anti-CD3 (1μg/ml) in the absence or presence of len or pom for 7 days. The proliferation of CD4T and CD8T, NKT, and NK cells was assessed by CFSE flow cytometric analysis. Len or pom induced CD4T cell (%Divided: Cont:55, len or pom >72), CD8 T cell (%Div: Cont:34, len or pom>60) and NKT cell (%Div: Cont:3.5, len or pom >8) proliferation, as well as stimulated IL2 (2-4 fold) and IFNγ (2 fold) production in effector cells from MM. It has been demonstrated that SOCS1 gene negatively regulates IL6 signaling and is silenced by methylation in MM cells. To understand the mechanism of cytokine inhibitory signaling in both effector cells and MM cells, we next analysed the interaction of effector cell with MM cells that were epigenetically modified to express SOCS1. SOCS1 methylation in MM cells was confirmed by SOCS1 gene methylation-specific polymerase chain reaction (SOCS1-MSP). Genomic DNA was isolated from MM cell lines (MM1S, RPMI8226, OPM1, INA6 and U266), sodium bisulfite-modified, and then subjected to MSP using MSP primers that specifically recognize unmethylated or methylated SOCS1 gene. SOCS1 gene was methylated and resulted in silenced SOCS1 protein expression in all MM cell lines. To delineate the role of SOCS in effector cell response against MM cells, MM cell specific cytotoxic T lymphocytes (CTL) were generated. T cells from healthy donors were stimulated with dendritic cells pulsed with apoptotic bodies of MM1S or U266 cells for 4 weeks, and cytotoxicity was measured by standard 51Cr-release assay. To reverse SOCS1 methylation, target MM cells were cultured with 5'-Azacytidine (Aza) or trichostatin A (TsA), alone or in combination with len or pom. CTLs were pretreated with len or pom for 24h and cocultured with DNA-modified or unmodified 51Cr-labeled target cells. Len induced more potent CTL response against MM cells that were treated with len and Aza combination (83% specific killing) than len alone (%50 specific killing). Len also showed more potent anti-MM activity, assessed by 3[H]thymidine proliferation assay, in the presence of Aza than alone (p<0.05). These data demonstrate that modulation of SOCS genes by blocking BMSC derived inhibitory cytokine signaling may enhance effector cell response and promote efficacy of len or pom in MM. Ongoing analysis of effects of len or pom on immune cells in the BM environment will both define their role in disease pathogenesis and suggest novel immune-based targeted therapies. Disclosures:Munshi:Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Richardson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium: Research Funding; Novartis: Research Funding; Celgene: Research Funding.

Muscle hypertrophy and increased expression of leptin receptors in the musculus triceps brachii of the dominant arm in professional tennis players

In rodents, endurance training increases leptin sensitivity in skeletal muscle; however, little is known about the effects of exercise on the leptin signalling system in human skeletal muscle. Thus, to determine whether chronic muscle loading increases leptin receptor (OB-R170) protein expression, body composition dual-energy X-ray absorptiometry was assessed in nine professional male tennis players (24 +/- 4 years old) and muscle biopsies were obtained from the dominant (DTB) and non-dominant (NDTB) arm triceps brachii (TB), and also from the right vastus lateralis (VL). In each biopsy, the protein content of OB-R170, perilipin A, suppressor of cytokine signalling 3 (SOCS3), protein tyrosine phosphatase 1B (PTP1B) and signal transducer and activator of transcription 3 (STAT3) phosphorylation were determined by western blot. The DTB had 15% greater lean mass (P < 0.05) and 62% greater OB-R170 protein expression (P < 0.05) than the NDTB. SOCS3 and PTP1B protein expression was similar in both arms, while STAT3 phosphorylation was reduced in the NDTB. OB-R170 protein content was also higher in DTB than in VL (P < 0.05). In summary, this study shows that the functional isoform of the leptin receptor is up-regulated in the hypertrophied TB. The latter combined with the fact that both SOCS3 and PTP1B protein expression were unaltered is compatible with increased leptin sensitivity in this muscle. Our findings are also consistent with a role of leptin signalling in muscle hypertrophy in healthy humans.

Expression of suppressor of cytokine signaling in peripheral blood monocular cells of patients with Vogt-Koyanagi-Harada disease

To investigate suppressor of cytokine signaling (SOCS) mRNA and protein expression in peripheral blood mononuclear cells (PBMC) of patients with Vogt-Koyanagi-Harada (VKH) disease. Blood samples were taken from 15 VKH patients with active uveitis, 17 quiescent patients and 16 healthy individuals. IFN-gamma, IL-12 and IL-4 in the serum were measured by ELISA. PBMC were subjected to analysis of SOCS mRNA and protein expression using quantitative RT-PCR and western blot, respectively. The level of IL-4 in the serum of VKH patients and in controls were (28.40 +/- 5.93) ng/L, (34.5 +/- 9.47) ng/L and (11.25 +/- 4.43) ng/L, IL-12 were (24.33 +/- 8.55) ng/L, (11.53 +/- 6.11) ng/L and (5.19 +/- 2.43) ng/L, IFN-gamma were (18.05 +/- 2.23) ng/L, (15.53 +/- 2.63) ng/L and (1.61 +/- 3.47) ng/L, respectively. The level of IFN-gamma, IL-12 and IL-4 were all significantly higher in the serum of VKH patients than in controls(P < 0.01). IL-4 in quiescent patients was higher than in active patients (P < 0.01), IL-12 and IFN-gamma were lower in quiescent patients was higher than in active patients (P < 0.01, P < 0.05). Cytokine inducible SH2 containing protein (CIS) mRNA, SOCS1 mRNA, SOCS2 mRNA, SOCS3 mRNA and SOCS5 mRNA levels in PBMC of VKH patients with active uveitis are 0.72, 4.92, 1.09, 0.75 and 1.15 folds than that in healthy volunteers, respectively. They are 1.15, 2.25, 1.40, 0.69 and 1.16 folds in static patients, respectively. Marked decreased expression of CIS protein is detected in both active and quiescent patients with no significant difference between two groups (both P < 0.01). SOCS1 protein is up-regulated significantly in active patients compares to in quiescent patients nor in healthy volunteers (P < 0.01, P < 0.05). SOCS3 protein is significantly decreased in patients than in controls (both P < 0.05). SOCS5 protein is much higher in patients than in controls (both P < 0.01), and even higher in quiescent patients than in active episode (P < 0.05). Up regulation of SOCS1 and SOCS5 expression and down-regulation of SOCS3 and CIS may correlate with the development of a Th1 mediated immune response in VKH disease. There is insidious inflammation in VKH patients with clinically quiescent uveitis, and this may be one of the causes of persistence and recurrences of uveitis.

Experimental Endotoxemia Induces Adipose Inflammation and Insulin Resistance in Humans

OBJECTIVEAn emerging model of metabolic syndrome and type 2 diabetes is of adipose dysfunction with leukocyte recruitment into adipose leading to chronic inflammation and insulin resistance (IR). This study sought to explore potential mechanisms of inflammatory-induced IR in humans with a focus on adipose tissue.RESEARCH DESIGN AND METHODSWe performed a 60-h endotoxemia protocol (3 ng/kg intravenous bolus) in healthy adults (n = 20, 50% male, 80% Caucasian, aged 27.3 ± 4.8 years). Before and after endotoxin, whole-blood sampling, subcutaneous adipose biopsies, and frequently sampled intravenous glucose tolerance (FSIGT) testing were performed. The primary outcome was the FSIGT insulin sensitivity index (Si). Secondary measures included inflammatory and metabolic markers and whole-blood and adipose mRNA and protein expression.RESULTSEndotoxemia induced systemic IR as demonstrated by a 35% decrease in Si (3.17 ± 1.66 to 2.06 ± 0.73 × 10−4 [μU · ml−1 · min−1], P < 0.005), while there was no effect on pancreatic β-cell function. In adipose, endotoxemia suppressed insulin receptor substrate-1 and markedly induced suppressor of cytokine signaling proteins (1 and 3) coincident with local activation of innate (interleukin-6, tumor necrosis factor) and adaptive (monocyte chemoattractant protein-1 and CXCL10 chemokines) inflammation. These changes are known to attenuate insulin receptor signaling in model systems.CONCLUSIONSWe demonstrate, for the first time in humans, that acute inflammation induces systemic IR following modulation of specific adipose inflammatory and insulin signaling pathways. It also provides a rationale for focused mechanistic studies and a model for human proof-of-concept trials of novel therapeutics targeting adipose inflammation in IR and related consequences in humans.

Increase in Plasma Endotoxin Concentrations and the Expression of Toll-Like Receptors and Suppressor of Cytokine Signaling-3 in Mononuclear Cells After a High-Fat, High-Carbohydrate Meal

OBJECTIVETo compare the effect of a high-fat, high-carbohydrate meal (HFHC) with that of a high-fiber and fruit meal on the concentrations of endotoxin (lipopolysaccharide [LPS]), LPS-binding protein (LBP), the expression of toll-like receptors (TLRs), and the suppressor of cytokine signaling-3 (SOCS-3) in mononuclear cells.RESEARCH DESIGN AND METHODSHealthy lean subjects were given 910 calories of either an HFHC meal (n = 10) or an American Heart Association (AHA)-recommended meal rich in fiber and fruit (n = 10) after an overnight fast. Blood was collected before and at 1, 2, and 3 h after the meal. Cellular indexes of oxidative and inflammatory stress; the expression of SOCS-3, TLR2, and TLR4 in mononuclear cells; and plasma concentrations of LPS and LBP were measured.RESULTSHFHC meal intake induced an increase in plasma LPS concentration and the expression of SOCS-3, TLR2, and TLR4 protein, reactive oxygen species generation, and nuclear factor-κB binding activity (P < 0.05 for all). These increases were totally absent after the AHA meal rich in fiber and fruit.CONCLUSIONSThe novel changes described after the HFHC meal elucidate further the mechanisms underlying postprandial inflammation and also provide the first evidence explaining the pathogenesis of insulin and leptin resistance mediated by SOCS-3 after such meals. In contrast, an AHA meal does not induce these effects.