Suppressor of cytokine signalling (SOCS) 1 and 3 enhance cell adhesion and inhibit migration towards the chemokine eotaxin/CCL11

Suppressors of cytokine signalling (SOCS) proteins regulate signal transduction, but their role in responses to chemokines remains poorly understood. We report that cells expressing SOCS1 and 3 exhibit enhanced adhesion and reduced migration towards the chemokine CCL11. Focal adhesion kinase (FAK) and the GTPase RhoA, control cell adhesion and migration and we show the presence of SOCS1 or 3 regulates expression and tyrosine phosphorylation of FAK, while also enhancing activation of RhoA. Our novel findings suggest that SOCS1 and 3 may control chemotaxis and adhesion by significantly enhancing both FAK and RhoA activity, thus localizing immune cells to the site of allergic inflammation.

[SOCS1 knockdown sensitize anti-tumor activity of IFN-alpha2a-NGR]

AIM

Search for key molecules to influence the tumor-targeted IFN-alpha2a-NGR anti-tumor sensitivity through signaling pathway study. Try to enhance the antitumor efficacy of IFN-alpha2a-NGR.

METHODS

MTT method was used to determine the growth inhibitory effects of IFN-alpha2a-NGR on A549 and MKN-45 cells. Flow cytometry and Western blot were employed to detect the expression of STAT1, p-STAT1, p53, OAS and SOCS1; SOCS1 gene knock down was carried out by synthesized siRNA.

RESULTS

When stimulated with IFN-alpha2a-NGR, the increased expression of STAT1, p-STAT1, p53, OAS and SOCS1 were observed in A549 cells, but only SOCS1 was notably increased in MKN-45 cells. The proliferation inhibition ability of MKN-45 to IFN-alpha2a-NGR was promoted by SOCS1 knocking down. (the inhibition rate was enhanced from 14.69%+/-1.05% to 36.97%+/-2.05%).

CONCLUSION

This study has further demonstrated that there were no differences on antitumor effects between IFN-alpha2a-NGR and IFN-alpha2a on cell or molecular level. Besides interferon-alpha receptor (IFNAR) which has been demonstrated before, p-STAT1, p53 and SOCS1 were important determinants of tumor resistance to IFNs therapy. The antitumor efficacy of IFN-alpha2a-NGR can be enhanced by RNA interference. These results might be helpful for the further development of IFN-alpha2a-NGR.

[Polymorphism and structural analysis of suppressor of cytokine signaling-1 of rat]

OBJECTIVE

To identify the suppressor of cytokine signaling-1 (SOCS-1) of rat from the amplified gene with the help of bioinformatics to predict the deduced protein's structure and function in order to lay the foundation for further theoretical study.

METHODS

The full-length rat SOCS-1 gene was amplified and identified from the GeneBank Nucleotide database, and the corresponding structure and function of its deduced protein was predicted by the bioinformatics analyzing tools online and the complicated bioinformatics software package Vector NTI suite 8.0, meanwhile the molecular cladogram was reconstructed.

RESULTS

Two sequences were obtained by polymerase chain reaction (PCR) amplification of different SOCS-1 gene. The gene was comprised of 639 base pairs in the length, deduced 212 amino acids (aa), contained a SOCS box (aa172-aa208), a SH2 domain (aa80-aa155) and a nuclear localization sequence (aa160-aa174). The primary structure contained two linear B cell epitopes, all of them were on the surface of the protein and far away from the spatial structure.

CONCLUSION

SOCS-1 gene has a polymorphism, its conservative SH2 region and SOCS box are related to its inhibitory effect on the signal transduction pathway. The nucleic localization sequence may affect other nuclear transduction factors. The B cell linear epitopes may be a candidate of immunodiagnosis with promising prospects.

Treatment with recombinant tumor necrosis factor-related apoptosis-inducing ligand alleviates the severity of streptozotocin-induced diabetes

OBJECTIVE

To evaluate the potential therapeutic effect of recombinant human tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) treatment in a model of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Recombinant TRAIL was added in vitro to primary human and mouse peripheral blood mononuclear cells (PBMCs) and isolated human islets to evaluate the expression of the immunoregulatory gene SOCS1. Diabetes was induced by five consecutive daily injections of low-concentration (50 mg/kg) streptozotocin (STZ) in C57 black mice (n = 24). A group of these mice (n = 12) was co-injected with recombinant TRAIL (20 microg/day) for 5 days, and the diabetic status (glycemia and body weight) was followed over time. After 6 weeks, circulating levels of insulin, TNF-alpha, and osteoprotegerin (OPG) were measured, and animals were killed to perform the histological analysis of the pancreas.

RESULTS

The in vitro exposure of both PBMCs and human islets to recombinant TRAIL significantly upregulated the expression of SOCS1. With respect to STZ-treated animals, mice co-injected with STZ+TRAIL were characterized by 1) lower levels of hyperglycemia, 2) higher levels of body weight and insulinemia, 3) a partial preservation of pancreatic islets with normal morphology, and 4) a lower expression of both systemic (TNF-alpha and OPG) and pancreatic (vascular cell adhesion molecule [VCAM]-1) inflammatory markers.

CONCLUSIONS

Overall, these data demonstrate that the administration of recombinant TRAIL ameliorates the severity of STZ-induced type 1 diabetes, and this effect was accompanied by the upregulation of SOCS1 expression.

Suppressor of cytokine signaling-1 ameliorates expression of MCP-1 in diabetic nephropathy

BACKGROUND

Janus kinase (JAK)/signal transducers and activators of transcription (STAT) contribute to diabetic nephropathy. Suppressor of cytokine signaling-1 (SOCS-1) is one of the negative feedback regulators of JAK/STAT signaling. This study investigated the effect of SOCS-1 on the JAK/STAT pathway and MCP-1 expression in diabetic nephropathy.

METHODS

Streptozotocin-induced diabetic mice received pEF-FLAG-I/mSOCS-1 plasmid or pEF-FLAG-I vector for 4 weeks and were compared with age-matched nondiabetic mice. Functional and pathologic markers, expression of monocyte chemoattractant protein-1 (MCP-1) and TGF-beta1 and phosphorylation of STAT1 and STAT3 were assessed. The effect of SOCS-1 on the expression of MCP-1 in mesangial cells under high glucose conditions was also examined.

RESULTS

Urine albumin excretion and renal hypertrophy were alleviated in diabetic mice by overexpression of SOCS-1. The expression of TGF-beta1 and MCP-1 and the activation of STAT1 and STAT3 were significantly inhibited in diabetic kidney by gene delivery of SOCS-1. In cultured mesangial cells, overexpression of SOCS-1 markedly suppressed high glucose-induced MCP-1 expression.

CONCLUSIONS

This study suggests that SOCS-1 may attenuate renal damage by ameliorating MCP-1 expression and regulation of the phosphorylation of JAK/STAT in diabetic mice.

IFN-gamma down-regulates TGF-beta1-induced IgA expression through Stat1 and p300 signaling

IFN-gamma has been shown to either up- or down-regulate the expression of specific TGF-beta1-induced target genes. We investigated the effect of IFN-gamma on TGF-beta1-induced IgA isotype expression. We found that IFN-gamma inhibited not only TGF-beta1-induced germ-line (GL) alpha transcription, but also IgA secretion by TGF-beta1-stimulated murine B cells. Overexpression of Stat1 diminished TGF-beta1-induced, Smad3/4-and Runx3-mediated GL alpha promoter activity. Overexpression of p300 also increased the promoter activity, while its effect was abrogated by co-transfected Stat1. Stat1 interfered with the Smad3:p300 interaction, likely due to a stronger Stat1:p300 binding affinity. These results indicate that Stat1 can inhibit GL alpha transcription through binding to p300. Further, overexpression of SOCS1, a JAK inhibitor, diminished the antagonistic effect of IFN-gamma on TGF-beta1-induced GL alpha transcription and IgA secretion. These results indicate that JAK/Stat1-mediated IFN-gamma signaling antagonizes TGF-beta1-induced GL alpha transcription, mainly through deprivation of p300 from Smad3, resulting in decreased IgA synthesis.

Suppressor of cytokine signaling-1 inhibits caspase activation and protects from cytokine-induced beta cell death

Pancreatic beta cell damage caused by proinflammatory cytokines interleukin-1beta (IL-1beta), interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha) is a key event in the pathogenesis of type 1 diabetes. The suppressor of cytokine signaling-1 (SOCS-1) blocks IFNgamma-induced signaling and prevents diabetes in the non-obese diabetic mouse. Here, we investigated if SOCS-1 overexpression in primary beta cells provides protection from cytokine-induced islet cell dysfunction and death. We demonstrate that SOCS-1 does not prevent increase in NO production and decrease in glucose-stimulated insulin secretion in the presence of IL-1beta, IFNgamma, TNFalpha. However, it decreases the activation of caspase-3, -8 and -9, and thereby, promotes a robust protection from cytokine-induced beta cell death. Our data suggest that SOCS-1 overexpression may not be sufficient in preventing all the biological activities of IFNgamma in beta cells. In summary, we show that interference with IFNgamma signal transduction pathways by SOCS-1 inhibits cytokine-stimulated pancreatic beta cell death.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

SOCS-1 binding to tyrosine 441 of IFN-gamma receptor subunit 1 contributes to the attenuation of IFN-gamma signaling in vivo

Suppressor of cytokine signaling (SOCS)-1 is a critical inhibitor of IFN-gamma signal transduction in vivo, but the precise biochemical mechanism of action of SOCS-1 is unclear. Studies in vitro have shown that SOCS-1 binds to Jaks and inhibits their catalytic activity, but recent studies indicate SOCS-1 may act in a similar manner to SOCS-3 by firstly interacting with cytokine receptors and then inhibiting Jak activity. Here, we have generated mice, termed Ifngr1(441F), in which a putative SOCS-1 binding site, tyrosine 441 (Y441), on the IFN-gamma receptor subunit 1 (IFNGR1) is mutated. We confirm that SOCS-1 binds to IFNGR1 in wild-type but not mutant cells. Mutation of Y441 results in impaired negative regulation of IFN-gamma signaling. IFN-gamma-induced STAT1 activation is prolonged in Ifngr1(441F) cells, but not to the extent seen in cells completely lacking SOCS-1, suggesting that SOCS-1 maintains activity to modulate IFN-gamma signaling via other mechanisms. Despite this, we show that hypersensitivity to IFN-gamma results in enhanced innate tumor protection in Ifngr1(441F) mice in vivo, and unregulated expression of an IFN-gamma-dependent chemokine, monokine-induced by IFN-gamma. Collectively, these data indicate that Y441 contributes to the regulation of signaling through IFNGR1 via the recruitment of SOCS-1 to the receptor.

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

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

Simvastatin acts as an inhibitor of interferon gamma-induced cycloxygenase-2 expression in human THP-1 cells, but not in murine RAW264.7 cells

Cyclooxygenase-2 (COX-2) is a key inflammatory response molecule, and associated with many immune functions of monocytes/macrophages. Particularly, interferon gamma (IFNgamma)-induced COX-2 expression appears in inflammatory conditions such as viral infection and autoimmune diseases. Recently, statins have been reported to show variable effects on COX-2 expression, and on their cell and species type dependences. Based on the above description, we compared the effect of simvastatin on IFNgamma-induced COX-2 expression in human monocytes versus murine macrophages. In a result, we found that simvastatin suppresses IFNgamma-induced COX-2 expression in human THP-1 monocytes, but rather, potentiates IFNgamma-induced COX-2 expression in murine RAW264.7 macrophages. However, signal transducer and activator of transcription 1/3 (STAT1/3), known as a transcription factor on COX-2 expression, is inactivated by simvastatin in both cells. Our findings showed that simvastatin is likely to suppress IFNgamma-induced COX-2 expression by inhibiting STAT1/3 activation in human THP-1 cells, but not in murine RAW264.7 cells. Thus, we concluded that IFNgamma-induced COX-2 expression is differently regulated by simvastatin depending on species specific mechanism.

Silencing of SOCS1 in macrophages suppresses tumor development by enhancing antitumor inflammation

Inflammation has been shown to contribute to both tumor development and antitumor immunity. However, conditions determining these opposing effects are not well understood. Suppressor of cytokine signaling 1 (SOCS1) has been shown to play an important role in regulating inflammation and tumor development. It has been reported that silencing of SOCS1 gene in dendritic cells potentiates antitumor immunity, while SOCS1-deficiency in whole organs except for T and B cells enhances inflammation-mediated colon tumor development. To determine which types of cells are important for the suppression of tumor development by SOCS1-deficiency, we employed the conditional knockout strategy. SOCS1 gene was deleted in macrophages and neutrophils by crossing SOCS1-flox/flox mice with LysM-cre mice. Resulting conditional knockout (cKO) mice showed enhanced sensitivity to endotoxin shock. SOCS1-cKO mice survived much longer than wild-type mice after B16 melanoma transplantation. Colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) plus dextran sulfate sodium (DSS) was also reduced in SOCS1-cKO mice. SOCS1-deficiency in monocytic cells enhanced tumor-killing activity of macrophages and tumor-specific cytotoxic T cell activity. These results suggest that inflammation induced by SOCS1-deficiency in monocytes potentiates antitumor immune responses rather than tumor-promoting inflammation.

Structural and functional analysis of a nuclear localization signal in SOCS1

Suppressor of cytokine signaling 1 (SOCS1) belongs to a family of genes involved in inducible feedback inhibition of janus kinases (JAKs) and signal transducers and activators of transcription (STATs) signaling pathway. Recently, we were able to show that SOCS1 surprisingly translocates to the nucleus due to the presence of a functional nuclear localization signal (NLS). However, the precise nature of the NLS remained ill-defined. Here we investigated further details of the SOCS1 NLS and analyzed its functional importance. We show that nuclear transport of SOCS1 particularly depends on the second cluster of basic amino acid residues within the NLS. Neither the first nor a nearby identified third cluster of basic amino acids were sufficient for mediating nuclear localization of SOCS1. Altering the subcellular localization of SOCS1 by mutating clusters of arginine residues within the NLS did not affect the inhibition of interferon mediated STAT1 tyrosine-phosphorylation, but surprisingly led to impaired inhibitory activity of STAT mediated reporter gene induction and IFN-gamma induced CD54 regulation. A SOCS-box deletion mutant (E176X) also had reduced inhibitory activity. In contrast, nuclear factor kappaB (NFkappaB) signaling was not affected by SOCS1 wt or mutants. Thus, SOCS1 may accomplish its inhibitory function in the IFN-pathway in part through nuclear localization.

Changes in the expression of suppressor of cytokine signalling (SOCS) 2 in the colonic mucosa of acromegalic patients are associated with hyperplastic polyps

BACKGROUND

Acromegalic patients have increased prevalence of colonic polyps. Development of hyperplastic polyps was related to suppressor of cytokine signalling (SOCS) 2 haploinsufficiency in animal models of acromegaly.

OBJECTIVE AND PATIENTS

To evaluate whether variations in SOCS2 expression in the colonic mucosa of acromegalic patients might be associated to hyperplastic polyps, patients with active acromegaly or disease in remission with or without hyperplastic polyps were studied; controls were non-acromegalic subjects age- and sex- matched with or without polyps.

MEASUREMENTS

Expression of SOCS1-3 was evaluated by RT-PCR, immunofluorescence and Western blot in the colonic mucosa. Coimmunoprecipatiton was used to evaluate multimeric protein complexes.

RESULTS

Acromegalic patients with active disease and hyperplastic polyps had higher levels of SOCS2 transcripts; on the contrary, SOCS1 and SOCS3 transcripts did not differ among the study groups. While the expression of SOCS2 and SOCS3 protein was indistinguishable with that of the corresponding transcripts, SOCS1 protein expression was reduced in active acromegalic patients with polyps. SOCS1 protein was reduced owing to its increased proteasome degradation mediated by SOCS2. The increased SOCS2 and reduced SOCS1 led to increased STAT5b expression, suggesting a higher GH signalling transduction.

CONCLUSIONS

Acromegalic patients with active disease and hyperplastic polyps have high levels of SOCS2 and increased SOCS1 degradation, leading to reduced negative feedback on GH signalling, likely favouring a hyperplastic polyps phenotype.

Endotoxin uptake in mouse liver is blocked by endotoxin pretreatment through a suppressor of cytokine signaling-1-dependent mechanism

The liver is the main organ that clears lipopolysaccharide (LPS) and hepatocytes are a major cell-type involved in LPS uptake. LPS tolerance, or desensitization, is important in negative regulation of responses to LPS, but little is known about its mechanisms in hepatocytes. Primary isolated C57BL/6 hepatocytes, and liver in vivo, internalized fluorescent LPS, and this was dependent on Toll-like receptor 4 (TLR4) at the cell surface but not on TLR4-TIR signaling through MyD88. LPS clearance from plasma was also TLR4-dependent. Pretreatment of C57BL/6 hepatocytes with LPS prevented uptake of LPS 24 hours later and this LPS-mediated suppression was dependent on TLR4 signaling through MyD88. Many regulators of TLR4 signaling have been identified and implicated in LPS desensitization, including suppressor of cytokine signaling 1 (SOCS1). SOCS1 mRNA and protein expression increased after LPS stimulation in hepatocytes and in whole liver. LPS uptake in hepatocytes and liver was significantly reduced following infection with adenoviral vectors overexpressing SOCS1. Similarly, inhibition of SOCS1 using small interfering (si)RNA-mediated knockdown prevented LPS desensitization in hepatocytes. SOCS1 is known to interact with Toll/IL-1 receptor associated protein (TIRAP) and cause TIRAP ubiquitination and degradation, which regulates TLR signaling. We have also shown previously that TIRAP regulates LPS uptake in hepatocytes. SOCS1 coimmunoprecipitated with TIRAP in wild type hepatocyte cell lysates up to 8 hours after LPS stimulation, but not at later times. In the same samples, ubiquitinated TIRAP was detected after 4 hours and up to 8 hours after LPS stimulation, but not at later times.

CONCLUSION

These data indicate hepatocytes are desensitized by LPS in a TLR4 signaling-dependent manner. LPS-induced SOCS1 upregulation increases degradation of TIRAP and prevents subsequent LPS uptake. The exploitation of these mechanisms of LPS desensitization in the liver may be important in future sepsis therapies.

SOCS1 and SOCS3 are the main negative modulators of the somatotrophic axis in liver of homozygous GH-transgenic zebrafish (Danio rerio)

Homozygote individuals (HO) of the GH-transgenic zebrafish lineage (F0104), despite expressing double the amount of growth hormone (GH) in relation to the hemizygote (HE) individuals, presented smaller growth in relation to the last, and similar to the non-transgenic (NT) group. Through the analysis of the expression of genes of the somatotrophic axis in the livers of HO and NT individuals, it was verified that GHR, JAK2 and STAT5.1 did not present significant differences among the analyzed genotypes (NT and HO). However, in the IGF-I gene expression, an accentuated decrease was observed in group HO (p<0.01), suggesting a resistance effect to excess GH. This resistance could be related to the insufficient amount of energy for supporting the accelerated metabolic demand caused by excess circulating GH. Analysis of the genes involved in the regulation of GH signalization by dephosphorylation (PTP-H1 and PTP-1B) did not show any significant alteration when comparing groups HO and NT. However, the analysis of the SOCS1 and SOCS3 genes showed an induction in homozygotes of 2.5 times (p<0.01) and 4.3 times (p<0.05), respectively, in relation to non-transgenics. The results of the present work demonstrate that, in homozygotes, GH signaling is reduced by the action of the SOCS1 and SOCS3 proteins.

A pilot study to evaluate gene expression profiles in peripheral blood mononuclear cells (PBMCs) from children with GH deficiency and Turner syndrome in response to GH treatment

Response to GH treatment is variable and dependent on diagnosis and dose. We used a pharmacogenomic approach to assess whether this variability is reflected in patterns of GH-induced gene expression in peripheral blood mononuclear cells (PBMCs) taken from three children with GH deficiency (GHD) and three girls with Turner syndrome (TS). Analysis of the response to GH treatment revealed that in GHD, 15 probe sets (11 genes) showed a fold change > +/- 1.4 at a P-value < 0.0005 (and a false detection rate <or= 15%). These genes included a suppressor of cytokine signalling (SOCS1) and a modulator of cAMP response elements (CREM). In marked contrast, in TS no genes fulfilled these criteria. ANOVA identified a subset of genes significantly affected by diagnosis, GH treatment or an interaction between diagnosis and treatment (P < 0.05, n = 2266). Cluster analysis indicated that genes up-regulated in both GHD and TS were related to DNA metabolism and transcription. Genes up-regulated in GHD but down-regulated in TS were involved in RNA processing and metabolism, whereas those down-regulated in GHD and up-regulated in TS were related to immune function. This pilot study has shown that major changes in gene expression in PBMCs can only be seen with confidence in GHD inferring that the pattern of gene expression in response to GH in GHD vs. TS is distinct and disease-specific. Further studies in larger cohorts will be required to evaluate whether GH-induced PBMCs gene expression patterns can predict responses to GH in a clinical setting.

Functional SOCS1 polymorphisms are associated with variation in obesity in whites

AIMS/HYPOTHESIS

The suppressor of cytokine signalling 1 (SOCS1) is a natural inhibitor of cytokine and insulin signalling pathways and may also play a role in obesity. In addition, SOCS1 is considered a candidate gene in the pathogenesis of both type 1 diabetes (T1D) and type 2 diabetes (T2D). The objective was to perform mutation analysis of SOCS1 and to test the identified variations for association to T2D-related quantitative traits, T2D or T1D.

METHODS

Mutation scanning was performed by direct sequencing in 27 white Danish subjects. Genotyping was carried out by TaqMan allelic discrimination. A total of more than 8100 individuals were genotyped.

RESULTS

Eight variations were identified in the 5' untranslated region (UTR) region. Two of these had allele frequencies below 1% and were not further examined. The six other variants were analysed in groups of T1D families (n = 1461 subjects) and T2D patients (n = 1430), glucose tolerant first-degree relatives of T2D patients (n = 212) and normal glucose tolerant (NGT) subjects. The rs33977706 polymorphism (-820G > T) was associated with a lower body mass index (BMI) (p = 0.004). In a second study (n = 4625 NGT subjects), significant associations of both the rs33977706 and the rs243330 (-1656G > A) variants to obesity were found (p = 0.047 and p = 0.015) respectively. The rs33977706 affected both binding of a nuclear protein to and the transcriptional activity of the SOCS1 promoter, indicating a relationship between this polymorphism and gene regulation.

CONCLUSIONS/INTERPRETATION

This study demonstrates that functional variations in the SOCS1 promoter may associate with alterations in BMI in the general white population.

The target cell response to cytokines governs the autoreactive T cell repertoire in the pancreas of NOD mice

AIMS/HYPOTHESIS

The pancreatic beta cell response to cytokines is crucial for the development of type 1 diabetes in the NOD mouse. For example, beta cell production of suppressor of cytokine signalling-1 (SOCS-1) protects against diabetes. This finding and other recent studies indicated that cytokine-stressed beta cells might contribute to disease progression by affecting the pancreatic lymphocyte infiltrate. The aim of this study was to provide insight into how the beta cell influences the pancreas-infiltrating T cell repertoire.

METHODS

Lymphocytes isolated from Socs1-transgenic (tg) and non-tg NOD mice were analysed by flow cytometry. mRNA and protein levels in pancreatic islets were measured by real-time PCR and immunofluorescence analysis, respectively.

RESULTS

The percentages of regulatory T cells, total counts and ratios between infiltrating CD8+ and CD4+ T cells, and the expression of killer cell lectin-like receptor subfamily K, member 1 (NKG2D) on CD8+ T cells did not differ in pancreases from prediabetic Socs1-tg and non-tg NOD mice. However, a striking difference in the percentages of CD8+ T cells specific for glucose 6-phosphatase catalytic subunit-related protein 206-214 was found, showing that SOCS-1 prevents the accumulation of high percentages of self-reactive CD8+ T cells in the pancreas. It was also found that protection from diabetes in Socs1-tg NOD mice correlated with a reduced expression of Cxcl10 mRNA in IFN-gamma treated islets.

CONCLUSIONS/INTERPRETATION

This study highlights an important role for the beta cell in the local regulation of the diabetogenic process. By responding to the pro-inflammatory pancreas milieu it strongly influences the islet-reactive T cell repertoire in the pancreas.

[Correlation of cell cycle alteration to SOCS-1 gene demethylation induced by arsenic trioxide in myeloma cell lines]

BACKGROUND & OBJECTIVE

Recent studies suggest strong therapeutic potentials of arsenic trioxide (As2O3) for multiple myeloma(MM), which may be due to As2O3-induced demethylation of tumor suppressor genes. This study was to explore the correlation of cell cycle alteration to SOCS-1 gene demethylation after As2O3 induction in MM cell lines in vitro.

METHODS

MM cell lines U266 and RPMI8226 were used. Cell proliferation and cell cycle of MM cells after the treatment of As2O3 were assessed by MTT assay and flow cytometry, respectively. Methylation status was detected by methylation specific PCR (MSP-PCR), and gene expression of SOCS-1 was measured by real-time PCR in MM cells before and after As2O3 treatment.

RESULTS

As2O3 significantly inhibited the growth of U266 and RPMI8226 cells in a dose-dependent manner. The cell cycle of U266 and RPMI8226 were arrested at G0/G1 phase. Compared with the wild type, the percentage of cells was increased at G0-G1 phase, but decreased at S phase after the treatment of As2O3 for 72 h (P < 0.05). The mRNA expression of SOCS-1 gene was significantly increased with hemi-methylation (As2O3, 0.5 micromol/L,72 h) or complete demethylation (As2O3, 1.0 micromol/L or As2O3, 2.0 micromol/L,72 h) of the SOCS-1 gene in comparison with the wide type (P<0.05).

CONCLUSIONS

As2O3 could induce cell cycle alteration of MM, which might be related to demethylation and reexpression of SOCS-1 gene in MM cell lines. The study might provide a new approach to elucidate the mechanism of the antitumor effect of As2O3 in MM.

The potential role of suppressors of cytokine signaling in the attenuation of inflammatory reaction and alveolar bone loss associated with apical periodontitis

Inflammatory cytokines contribute to periapical tissue destruction. Their activity is potentially regulated by suppressors of cytokine signaling (SOCS), which downregulate signal transduction as part of an inhibitory feedback loop. We investigated the expression of the cytokines tumor necrosis factor alpha (TNF-alpha); interleukin (IL)-10 and RANKL; and SOCS-1, -2, and -3 by real-time polymerase chain reaction in 57 periapical granulomas and 38 healthy periapical tissues. Periapical granulomas exhibited significantly higher SOCS-1, -2, and -3, TNF-alpha, IL-10, and RANKL messenger RNA levels when compared with healthy controls. Significant positive correlations were found between SOCS1 and IL-10 and between SOCS3 and IL-10. Significant inverse correlations were observed between SOCS1 and TNF-alpha, SOCS1 and RANKL, and SOCS3 and TNF-alpha. Increased SOCS-1, -2, and -3 messenger RNA levels in periapical granulomas may be related to the downregulation of inflammatory cytokines in these lesions; therefore, SOCS molecules may play a role in the dynamics of periapical granulomas development.

SOCS-1 deficiency does not prevent diet-induced insulin resistance

Obesity is associated with inflammation and increased expression of suppressor of cytokine signaling (SOCS) proteins, which inhibit cytokine and insulin signaling. Thus, reducing SOCS expression could prevent the development of obesity-induced insulin resistance. Using SOCS-1 knockout mice, we investigated the contribution of SOCS-1 in the development of insulin resistance induced by a high-fat diet (HFD). SOCS-1 knockout mice on HFD gained 70% more weight, displayed a 2.3-fold increase in epididymal fat pads mass and increased hepatic lipid content. This was accompanied by increased mRNA expression of leptin and the macrophage marker CD68 in white adipose tissue and of SREBP1c and FAS in liver. HFD also induced hyperglycemia in SOCS-1 deficient mice with impairment of glucose and insulin tolerance tests. Thus, despite the role of SOCS proteins in obesity-related insulin resistance, SOCS-1 deficiency alone is not able to prevent insulin resistance induced by a diet rich in fat.

[The study on the role of SOCS1 and SOCS3 in the livers of endotoxin tolerance rats]

OBJECTIVE

To explore the mechanism of endotoxin tolerance(ETT) through observing the gene expression of SOCS1 and SOCS3 in the livers of ETT rats.

METHODS

SD male rats were divided randomly into acute liver failure model group (ALF group) and ETT group. LPS 0.1 mg/kg (ETT group) or normal saline (ALF group) was administered five consecutive intraperitoneal injections at 24 h intervals, then, the two groups were treated with intraperitoneal injection of D-GalN 800 mg/Kg and LPS 8 microg/rat 24 h later. Liver histopathology and fine structure of rats were observed by HE staining and electron microscope. The TNF-alpha level were estimated by ELISA, the concentrations of endotoxin were determined by tachypleus amebocyte lysate and the gene expressions of SOCS1 and SOCS3 in the liver were measured by RT-PCR at 0, 2, 6, 12, 24 and 48 h after the injection of D-GalN/LPS.

RESULTS

D-GalN/LPS induced acute liver injury was attenuated significantly in ETT group. The concentrations of endotoxin and the TNF-alpha level were evidently lower in the ETT group than those in the ALF group (endotoxin: 6 h: 1.11 +/- 0.38 vs 0.74 +/- 0.22, 24 h: 1.12 +/- 0.24 vs 0.86 +/- 0.21, all P < 0.05, 12 h: 1.88 +/- 0.35 vs 0.62 +/- 0.16, 48 h: 1.10 +/- 0.13 vs 0.84 +/- 0.19, all P < 0.01; TNF-alpha: 6 h: 86.9 +/- 12.6 vs 70.0 +/- 12.8, P < 0.05, 12 h: 77.0 +/- 18.1 vs 48.8 +/- 12.8, 24 h: 63.8 +/- 9.2 vs 39.1 +/- 5.7, 48 h: 53.2 +/- 8.3 vs 38.2 +/- 9.9, all P < 0.01). In the ALF group, the expressions of SOCS-1 and SOCS-3 were obviously higher than those in the controls and reached peak at 12th hours and 6th hours respectively. The gene expression of SOCS1 and SOCS3 in the liver in ETT group were increased significantly and much higher than those in ALF groups. (SOCS1: 6 h: 0.955 +/- 0.186 vs 1.349 +/- 0.390, 48 h: 0.766 +/- 0.145 vs 0.970 +/- 0.205, all P < 0.05, 2 h: 0.554 +/- 0.164 vs 0.841 +/- 0.175, 12 h: 1.130 +/- 0.181 vs 1.888 +/- 0.573, 24 h: 0.990 +/- 0.212 vs 1.550 +/- 0.439, all P < 0.01; SOCS3: 6 h: 0.914 +/- 0.054 vs 1.039 +/- 0.109, 12 h: 0.781 +/- 0.044 vs 0.863 +/- 0.063, all P < 0.05, 2 h: 0.681 +/- 0.139 vs 0.898 +/- 0.058, 24 h: 0.700 +/- 0.065 vs 0.811 +/- 0.055, all P < 0.01).

CONCLUSIONS

LPS pretreatment can induce endotoxin tolerance of rats, inhibited the level of TNF-alpha and endotoxin. The up-regulation of SOCS1 and SOCS3 gene expression may be one of the possible mechanisms responsible for endotoxin tolerance.

Fibroblast growth factor inhibits interferon gamma-STAT1 and interleukin 6-STAT3 signaling in chondrocytes

Activation of fibroblast growth factor receptor 3 (FGFR3) leads to attenuation of cartilage growth. The members of the STAT family of transcription factors are believed to participate in FGFR3 signaling in cartilage, however the molecular mechanism of this action is poorly understood. Here, we demonstrate that a chronic FGF stimulus leads to accumulation of STAT1, 3, 5 and 6, evident in both in vitro chondrocyte model and murine limb explant cultures. Despite the accumulation, both endogenous and cytokine-induced activation of STAT1 and STAT3 is impaired by FGF, as demonstrated by imaging of active STAT nuclear translocation and analyses of STAT activatory phosphorylation and transcriptional activation. Further, we demonstrate that FGF induces expression of CIS, SOCS1 and SOCS3 inhibitors of gp130, a common receptor for the IL6-family of cytokines. Since cytokine-gp130 signaling represents an important positive regulator of cartilage, its inhibition may contribute to the growth-inhibitory effect of FGFR3 in cartilage.