Suppressors of cytokine signaling in health and disease

The role of suppressor of cytokine signaling 3 in inflammatory bowel disease and its associated colorectal cancer

Inflammatory bowel disease (IBD) and colorectal cancer (CRC), as two of the major human intestinal diseases, provide challenges for the medical field. Suppressor of cytokine signaling 3 (SOCS3), a protein molecule that negatively regulates cytokine signaling through multiple pathways, is involved in the regulation of various inflammatory diseases and tumors. In IBD, SOCS3 acts on a variety of cells to repair mucosal damage and balance the immune response, including epithelial cells, macrophages, dendritic cells, neutrophils, and T cells. In CRC, SOCS3 is inextricably linked to tumor cell proliferation, invasion, metastasis, and drug resistance. Therefore, it is crucial to systematically investigate the pathogenic involvement of SOCS3 in IBD and CRC. This article reviews the mechanisms and pathways by which SOCS3 is involved in the inhibition of IBD and the mitigation of CRC, and details the therapeutic options for targeting SOCS3.

Advancing immunomodulatory functions in mesenchymal stem/stromal cells through targeting the GATA6-mediated pathway

BACKGROUND AIMS

The immunomodulatory capacity of mesenchymal stem/stromal cells (MSCs) is a key feature that makes them particularly valuable for regenerative medicine. However, this potential is affected by the chronological aging of the donors and the cell expansion procedures in culture. We have demonstrated that GATA binding protein 6 (GATA6) plays a pivotal role in the aging of MSCs and inhibiting GATA6 rejuvenates the characteristics of MSCs.

METHODS

In this study, we compared the immunomodulatory capabilities of young and old MSC models, using induced pluripotent stem cells-derived rejuvenated MSCs (rMSCs) and their parental MSCs (pMSCs), respectively, to identify a key mechanism involved in the differential regulation of these capabilities. Additionally, we explored the role of GATA6 in mediating the mechanism.

RESULTS

Our results demonstrated that rMSCs exhibited downregulated aging-associated regulators, including p53, p21 and GATA6, and showed enhanced suppression of T cell proliferation compared to pMSCs. Through analyzing our previous RNA-seq data and employing target gene knockdown, we determined both suppressors of cytokine signaling 3 (SOCS3) and interleukin 6 were involved in GATA6-induced regulation, collectively affecting the expression of programmed death ligand 1 (PDL1) in both pMSCs and rMSCs.

CONCLUSIONS

Our findings underline the significance of the GATA6/SOCS3/PDL1 pathway in regulating aging-associated changes in MSC immunomodulatory activity, providing valuable insights into the potential use of rMSCs in the treatment of immune diseases and regenerative medicine.

Indoxyl Sulfate Contributes to Impaired Height Velocity in (Pre)School Children

Introduction

Growth failure is considered the most important clinical outcome parameter in childhood chronic kidney disease (CKD). Central to the pathophysiology of growth failure is the presence of a chronic proinflammatory state, presumed to be partly driven by the accumulation of uremic toxins. In this study, we assessed the association between uremic toxin concentrations and height velocity in a longitudinal multicentric prospective pediatric CKD cohort of (pre)school-aged children and children during pubertal stages.

Methods

In a prospective, multicentric observational study, a selection of uremic toxin levels of children (aged 0-18 years) with CKD stage 1 to 5D was assessed every 3 months (maximum 2 years) along with clinical growth parameters. Linear mixed models with a random slope for age and a random intercept for child were fitted for height (in cm and SD scores [SDS]). A piecewise linear association between age and height was assumed.

Results

Data analysis included data from 560 visits of 81 children (median age 9.4 years; 2/3 male). In (pre)school aged children (aged 2-12 years), a 10% increase in concurrent indoxyl sulfate (IxS, total) concentration resulted in an estimated mean height velocity decrease of 0.002 SDS/yr (P < 0.05), given that CKD stage, growth hormone (GH), bicarbonate concentration, and dietary protein intake were held constant. No significant association with height velocity was found in children during pubertal stages (aged >12 years).

Conclusion

The present study demonstrated that, especially IxS contributes to a lower height velocity in (pre)school children, whereas we could not find a role for uremic toxins with height velocity during pubertal stages.

Snapshots of nascent RNA reveal cell- and stimulus-specific responses to acute kidney injury

The current strategy to detect acute injury of kidney tubular cells relies on changes in serum levels of creatinine. Yet serum creatinine (sCr) is a marker of both functional and pathological processes and does not adequately assay tubular injury. In addition, sCr may require days to reach diagnostic thresholds, yet tubular cells respond with programs of damage and repair within minutes or hours. To detect acute responses to clinically relevant stimuli, we created mice expressing Rosa26-floxed-stop uracil phosphoribosyltransferase (Uprt) and inoculated 4-thiouracil (4-TU) to tag nascent RNA at selected time points. Cre-driven 4-TU-tagged RNA was isolated from intact kidneys and demonstrated that volume depletion and ischemia induced different genetic programs in collecting ducts and intercalated cells. Even lineage-related cell types expressed different genes in response to the 2 stressors. TU tagging also demonstrated the transient nature of the responses. Because we placed Uprt in the ubiquitously active Rosa26 locus, nascent RNAs from many cell types can be tagged in vivo and their roles interrogated under various conditions. In short, 4-TU labeling identifies stimulus-specific, cell-specific, and time-dependent acute responses that are otherwise difficult to detect with other technologies and are entirely obscured when sCr is the sole metric of kidney damage.

Epac activation ameliorates tubulointerstitial inflammation in diabetic nephropathy

Tubulointerstitial inflammation plays an important role in the progression of diabetic nephropathy (DN), and tubular epithelial cells (TECs) are crucial promoters of the inflammatory cascade. Exchange protein activated by cAMP (Epac) has been shown to suppress the angiotensin II (Ang-II)-induced release of inflammatory cytokines in tubular cells. However, the role of Epac in TEC-mediated tubulointerstitial inflammation in DN remains unknown. We found that administering the Epac agonist 8-pCPT-2'-O-Me-cAMP (8-O-cAMP) to db/db mice inhibited tubulointerstitial inflammation characterized by macrophage infiltration and increased inflammatory cytokine release and consequently alleviated tubulointerstitial fibrosis in the kidney. Furthermore, 8-O-cAMP administration restored CCAAT/enhancer binding protein β (C/EBP-β) expression and further upregulated the expression of Suppressor of cytokine signaling 3 (SOCS3), while inhibiting p-STAT3, MCP-1, IL-6, and TNF-α expression in the kidney cortex in db/db mice. And in vitro study showed that macrophage migration and MCP-1 expression induced by high glucose (HG, 30 mM) were notably reduced by 8-O-cAMP in human renal proximal tubule epithelial (HK-2) cells. In addition, 8-O-cAMP treatment restored C/EBP-β expression in HK-2 cells and promoted C/EBP-β translocation to the nucleus, where it transcriptionally upregulated SOCS3 expression, subsequently inhibiting STAT3 phosphorylation. Under HG conditions, siRNA-mediated knockdown of C/EBP-β or SOCS3 in HK-2 cells partially blocked the inhibitory effect of Epac activation on the release of MCP-1. In contrast, SOCS3 overexpression inhibited HG-induced activation of STAT3 and MCP-1 expression in HK-2 cells. These findings indicate that Epac activation via 8-O-cAMP ameliorates tubulointerstitial inflammation in DN through the C/EBP-β/SOCS3/STAT3 pathway.

Activation of peroxisome proliferator-activated receptor delta suppresses BACE1 expression by up-regulating SOCS1 in a JAK2/STAT1-dependent manner

Neuronal expression of beta-secretase 1 (BACE1) has been implicated in the progression of Alzheimer's disease. However, the mechanisms that regulate BACE1 expression are unclear. Here, we show that peroxisome proliferator-activated receptor delta (PPARδ) decreases BACE1 expression by up-regulating suppressor of cytokine signaling 1 (SOCS1) in SH-SY5Y neuroblastoma cells. The activation of PPARδ by GW501516, a specific PPARδ agonist, inhibited expression of BACE1. This effect was abrogated by shRNA-mediated knockdown of PPARδ and by treatment with the PPARδ antagonist GSK0660, indicating that PPARδ is involved in GW501516-mediated suppression of BACE1 expression. On the other hand, GW501516-activated PPARδ induced expression of SOCS1, which is a negative regulator of cytokine signal transduction, at the transcriptional level by binding to a PPAR response element in its promoter. This GW501516-mediated induction of SOCS1 expression led to down-regulation of BACE1 expression via inactivation of signal transducer and activator of transcription 1. GW501516-activated PPARδ suppressed the generation of neurotoxic amyloid beta (Aβ) in accordance with the decrease in BACE1 expression. Taken together, these results indicate that PPARδ attenuates BACE1 expression via SOCS1-mediated inhibition of signal transducer and activator of transcription 1 signaling, thereby suppressing BACE1-associated generation of neurotoxic Aβ.

The novel exchange protein activated by cyclic AMP 1 (EPAC1) agonist, I942, regulates inflammatory gene expression in human umbilical vascular endothelial cells (HUVECs)

Exchange protein activated by cyclic AMP (EPAC1) suppresses multiple inflammatory actions in vascular endothelial cells (VECs), partly due to its ability to induce expression of the suppressor of cytokine signalling 3 (SOCS3) gene, the protein product of which inhibits interleukin 6 (IL6) signalling through the JAK/STAT3 pathway. Here, for the first time, we use the non-cyclic nucleotide EPAC1 agonist, I942, to determine its actions on cellular EPAC1 activity and cyclic AMP-regulated gene expression in VECs. We demonstrate that I942 promotes EPAC1 and Rap1 activation in HEK293T cells and induces SOCS3 expression and suppresses IL6-stimulated JAK/STAT3 signalling in HUVECs. SOCS3 induction by I942 in HUVECs was blocked by the EPAC1 antagonist, ESI-09, and EPAC1 siRNA, but not by the broad-spectrum protein kinase A (PKA) inhibitor, H89, indicating that I942 regulates SOCS3 gene expression through EPAC1. RNA sequencing was carried out to further identify I942-regulated genes in HUVECs. This identified 425 I942-regulated genes that were also regulated by the EPAC1-selective cyclic AMP analogue, 007, and the cyclic AMP-elevating agents, forskolin and rolipram (F/R). The majority of genes identified were suppressed by I942, 007 and F/R treatment and many were involved in the control of key vascular functions, including the gene for the cell adhesion molecule, VCAM1. I942 and 007 also inhibited IL6-induced expression of VCAM1 at the protein level and blocked VCAM1-dependent monocyte adhesion to HUVECs. Overall, I942 represents the first non-cyclic nucleotide EPAC1 agonist in cells with the ability to suppress IL6 signalling and inflammatory gene expression in VECs.

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The novel EPAC1 ligand I942 activates cellular EPAC1 and Rap1 GTPase.

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I942 induces SOCS3 gene expression in vascular endothelial cells (VECs).

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I942 suppresses JAK/STAT3 signalling from the IL6 receptor in VECs.

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I942 regulates 425 novel gene targets in VECs.

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I942 suppresses VCAM1 expression and monocyte adhesion in VECs.

miR-885-5p upregulation promotes colorectal cancer cell proliferation and migration by targeting suppressor of cytokine signaling

The aim of the present study was to investigate the role of microRNA (miR)-885-5p in colorectal cancer cell proliferation and migration, and to determine the possible underlying molecular mechanisms. The expression of miR-885-5p in colorectal cancer tissue and cells was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression levels of three suppressor of cytokine signaling (SOCS) factors were detected by RT-qPCR and western blotting. The effects of miR-885-5p on tumor cell proliferation and migration were studied using MTT and Transwell assays, respectively. Additionally, the expression levels of epithelial-mesenchymal transition (EMT)-related proteins (N-cadherin, E-cadherin, vimentin and Snail) were detected by RT-qPCR and western blot analysis. Furthermore, the target of miR-885-5p was predicted and confirmed using a luciferase reporter assay. miR-885-5p was demonstrated to be upregulated and SOCS was downregulated in colorectal cancer tissue, and cells. miR-885-5p suppression significantly inhibited tumor cell proliferation and migration, promoted E-cadherin expression, and inhibited the expression levels of N-cadherin, vimentin and Snail. Further studies showed that SOCS5, SOCS6 and SOCS7 were direct targets of miR-885-5p. The results suggest that miR-885-5p suppression inhibited cell proliferation and migration, and the EMT process by targeting SOCS5, SOCS6 and SOCS7 genes in colorectal cancer. miR-885-5p and SOCS may be used for the diagnosis and treatment of colorectal cancer.

Kidney-Replenishing Herb Induces SOCS-3 Expression via ERK/MAPK Pathway and Improves Growth of the First-Trimester Human Trophoblast Cells

Kidney-replenishing herb is a traditional medicine formula in China which has been widely used for clinical treatment of recurrent miscarriage. Our previous study showed that Kidney-replenishing herb could promote proliferation and inhibit apoptosis of the human first-trimester trophoblasts. In the present study, we further explored the potential mechanism and signal pathway of Kidney-replenishing herb on human trophoblast cells. Our research showed that Kidney-replenishing herb stimulated proliferation and reduced apoptosis of human trophoblast cells in vitro, and this appeared to be positive correlation with SOCS-3 transcription, suggesting that Kidney-replenishing herb regulated biological functions of human trophoblast cells by inducing SCOS-3 expression. Furthermore, the Kidney-replenishing herb treatment stimulated the phosphorylation of ERK1/2, and blocking the signaling pathway by mitogen-activated protein MAPK (MEK) inhibitor, U0126, inhibited Kidney-replenishing herb-induced SOCS-3 transcription, depressed proliferation, and promoted apoptosis of human trophoblasts. Kidney-replenishing herbs still induced ERK1/2 phosphorylation after SOCS-3 siRNA silence. Overexpression of SOCS-3 stimulated the proliferation of trophoblast. These findings suggest that SOCS-3 expression is induced by Kidney-replenishing herbs via activation of MAPK pathways, and this may possibly be involved in promoting human trophoblast cells growth which is contributed to embryo development.

Calcineurin inhibitor-induced complement system activation via ERK1/2 signalling is inhibited by SOCS-3 in human renal tubule cells

One factor that significantly contributes to renal allograft loss is chronic calcineurin inhibitor (CNI) nephrotoxicity (CIN). Among other factors, the complement (C-) system has been proposed to be involved CIN development. Hence, we investigated the impact of CNIs on intracellular signalling and the effects on the C-system in human renal tubule cells. In a qPCR array, CNI treatment upregulated C-factors and downregulated SOCS-3 and the complement inhibitors CD46 and CD55. Additionally, ERK1/-2 was required for these regulations. Following knock-down and overexpression of SOCS-3, we found that SOCS-3 inhibits ERK1/-2 signalling. Finally, we assessed terminal complement complex formation, cell viability and apoptosis. Terminal complement complex formation was induced by CNIs. Cell viability was significantly decreased, whereas apoptosis was increased. Both effects were reversed under complement component-depleted conditions. In vivo, increased ERK1/-2 phosphorylation and SOCS-3 downregulation were observed at the time of transplantation in renal allograft patients who developed a progressive decline of renal function in the follow-up compared to stable patients. The progressive cohort also had lower total C3 levels, suggesting higher complement activity at baseline. In conclusion, our data suggest that SOCS-3 inhibits CNI-induced ERK1/-2 signalling, thereby blunting the negative control of C-system activation.

Biomarkers identification for acute myocardial infarction detection via weighted gene co-expression network analysis

The study aimed to seek potential biomarkers for acute myocardial infarction (AMI) detection and treatment.The dataset GSE48060 was used, consisting of 52 peripheral blood samples (31 AMI samples and 21 normal controls). By limma package, differentially expressed genes (DEGs) between 2 kinds of samples were identified, followed by enrichment analysis, subpathway analysis, protein-protein interaction (PPI) network analysis, and transcription factor network (TFN) analysis. Weighted gene co-expression network analysis was used to further extract key modules relating to AMI, followed by enrichment and TFN analyses. Expression validation was performed via meta-analysis of 2 datasets, GSE22229 and GSE29111.A set of 428 DEGs in AMI were screened out, and the upregulated toll-like receptor (TLR) family genes (TLR1, TLR2, and TLR10) were enriched in wound response, immune response and inflammatory response functions, and downregulated genes (GBP5, CXCL5, GZMA, CCL5, and CCL4) were correlated with immune response. CCL5, GZMA, GZMB, TLR2, and formyl peptide receptor 1 (FPR1) were predicted as crucial nodes in the PPI network. Signal transducer and activator of transcription 1 (STAT1) was the key transcription factor (TF) with multiple targets. The grey module was highly related to AMI. Genes in this module were closely related to regulation of macrophage activation, and spermatogenic leucine zipper 1 (SPZ1) was identified as a TF. Expressions of TLR2 and FPR1 were confirmed via the integrated matrix.Several potential biomarkers for AMI detection were identified, such as GZMB, GBP5, FPR1, TLR2, STAT1, and SPZ1. They might exert their functions via regulation of immune and inflammation responses. Genes in grey module play significant roles in AMI via regulation of macrophage activation.

Cytokine signal suppressor (SOCS) 1-1478 CA/del gene polymorphism in Turkish patients with polycystic ovary syndrome

Eighty-four subjects, premenopausal female patients (n = 42, mean (SD) age: 26.4 (4.2) years) diagnosed with polycystic ovary syndrome (PCOS) and age-matched healthy volunteers (n = 42, mean (SD) age: 27.6(3.4) years), were included in this study. Data on physical examination, anthropometric measurements and blood biochemistry analysis were recorded for each subject along with analysis for SOCS1-1478 CA/del polymorphism by polymerase chain reaction-restriction fragment length polymorphism. The relation of SOCS1-1478 CA/del polymorphism to PCOS status and insulin resistance was analysed via logistic regression analysis. Mean (SD) levels for BMI (28.5(6.5) vs.22.5 (4.9) kg/m², p < .001), HOMA-IR (3.1(1.8) vs.1.5 (1.0), p < .001), LDL-cholesterol (115.9(32.7) vs.100.7 (27.3)mg/dL, p = .03) and triglyceride (113.8(64.9) vs.83.3(36.3)mg/dL, p = .017) were significantly higher in patients. Groups were similar in terms of SOCS1-1478 CA/del polymorphism. No significant relation of this polymorphism was noted to PCOS and HOMA-IR. Our findings revealed no difference between groups in terms of the rate of SOCS1-1478 CA/del polymorphism, and no significant relation of this polymorphism to insulin resistance and PCOS status. Impact statement Polycystic ovary syndrome (PCOS), the most common cause of anovulation and the most commonly encountered form of female endocrine disease. SOCS proteins have been suggested to play a fundamental role in the negative feedback regulation of the JAK-STAT pathway, which is the major signalling pathway involved in a wide range of physiologic and pathologic processes, including inflammatory diseases, malignancies and immune disorders. Pathways involving the induction of suppression of SOCS proteins were also shown likely to be involved in mediating cytokine-induced insulin resistance. The present study was designed to determine the frequency of SOCS1-1478 CA/del gene polymorphism in patients with PCOS in relation to healthy controls and insulin resistance. Our findings revealed significantly higher rates of insulin resistance, obesity and dyslipidaemia in Turkish patients with PCOS compared with age-matched healthy controls, while no difference between study groups in terms of the rate of SOCS1-1478 CA/del polymorphism along with no significant relation of SOCS1-1478 CA/del polymorphism to insulin resistance and PCOS status. Future larger scale studies with the application of standardised diagnostic methods and criteria, and of state-of-the-art modern techniques including genomics, proteomics and pharmacogenetics would provide better understanding of the association between PCOS and genomic variants.

Molecular identification and immunological characteristics of goose suppressor of cytokine signaling 1 (SOCS-1) in vitro and vivo following DTMUV challenge

Purpose suppressor of cytokine signaling 1 (SOCS-1) is inducible feedback inhibitors of cytokine signaling and involved in viral infection through regulation of both innate and adaptive immunity. In this study, we firstly cloned SOCS-1 (goSOCS-1) from duck Tembusu virus (DTMUV) infected goose. The full-length sequence of goSOCS-1 ORF is 624bp and encoded 108 amino acids. Structurally, the mainly functional regions (KIR, SH2, SOCS-box) were conserved between avian and mammalian. The tissues distribution data showed SOCS-1 highly expressed in immune related tissues (SP, LU, HG) of both gosling and adult goose. Moreover, the goSOCS-1 transcripts were induced by goIFNs in GEFs and by TLR ligands in PBMCs. Notably, upon DTMUV infection, highly expression level of goSOCS-1 was detected in vitro and in vivo with high viral load. Our results indicated that goSOCS-1 might involve in both innate and adaptive antiviral immunity of waterfowl.

Identification of a Novel, Small Molecule Partial Agonist for the Cyclic AMP Sensor, EPAC1

Screening of a carefully selected library of 5,195 small molecules identified 34 hit compounds that interact with the regulatory cyclic nucleotide-binding domain (CNB) of the cAMP sensor, EPAC1. Two of these hits (I942 and I178) were selected for their robust and reproducible inhibitory effects within the primary screening assay. Follow-up characterisation by ligand observed nuclear magnetic resonance (NMR) revealed direct interaction of I942 and I178 with EPAC1 and EPAC2-CNBs in vitro. Moreover, in vitro guanine nucleotide exchange factor (GEF) assays revealed that I942 and, to a lesser extent, I178 had partial agonist properties towards EPAC1, leading to activation of EPAC1, in the absence of cAMP, and inhibition of GEF activity in the presence of cAMP. In contrast, there was very little agonist action of I942 towards EPAC2 or protein kinase A (PKA). To our knowledge, this is the first observation of non-cyclic-nucleotide small molecules with agonist properties towards EPAC1. Furthermore, the isoform selective agonist nature of these compounds highlights the potential for the development of small molecule tools that selectively up-regulate EPAC1 activity.

Estrogen receptors alpha mediates postischemic inflammation in chronically estrogen-deprived mice

Estrogens are known to exert neuroprotective and immuneomodulatory effects after stroke. However, at present, little is known about the role of estrogens and its receptors in postischemic inflammation after menopause. Here, we provide important in vivo evidence of a distinct shift in microglial phenotypes in the model of postmenopause brain. Using a model-system for live imaging of microglial activation in the context of chronic estrogen- and ERα-deficiency associated with aging, we observed a marked deregulation of the TLR2 signals and/or microglial activation in ovariectomized and/or ERα knockout mice. Further analysis revealed a 5.7-fold increase in IL-6, a 4.7-fold increase in phospho-Stat3 levels suggesting an overactivation of JAK/STAT3 pathway and significantly larger infarction in ERα knockouts chronically deprived of estrogen. Taken together, our results suggest that in the experimental model of menopause and/or aging, ERα mediates innate immune responses and/or microglial activation, and ischemia-induced production of IL-6. Based on our results, we propose that the loss of functional ERα may lead to deregulation of postischemic inflammatory responses and increased vulnerability to ischemic injury in aging female brains.

Expression of proinflammatory cytokine interleukin-6 in tissue samples of human prostate obtained by needle biopsy

Interleukin-6 (IL-6) has been associated with the development of prostate cancer. The aim of the study was to clarify whether IL-6 expression in prostate tissue could be a useful marker in differentiation of prostate diseases in small foci by pathologist visual scoring. Archival paraffin-embedded specimens of benign prostate hyperplasia (BPH), high-grade prostatic intraepithelial neoplasia (PIN), prostatitis and prostate adenocarcinoma were studied by immunohistochemistry with a mouse monoclonal antibody IL-6 using the streptavidin-biotin method. Significantly, lower IL-6 immunoreactivity was observed in normal epithelial cells (p=0.000) and basal cells (p=0.000) in the samples of prostate adenocarcinoma in comparison to the samples with BPH, PIN and prostatitis. There was no significant difference in IL-6 expression in malignant and premalignant cells (p=0.814) as well as in stromal cells among the four diagnoses (p=0.22). IL-6 was expressed in normal epithelial cells, premalignant epithelial cells and malignant epithelial cells as well as in stromal cells. However, in our research IL-6 was of limited utility as a single marker for differential diagnosis of the prostate diseases in small foci needle biopsy by pathologist visual scoring. The standardization of immunohistochemical (IHC) staining protocol for IL-6 is required to determine IL-6 expression in order to avoid possible misinterpretation of the IHC results.

The future of EPAC-targeted therapies: agonism versus antagonism

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Although tractable to drug development, targeting of cAMP signalling has side effects.

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Selectively targeting EPAC1 and EPAC2 cAMP sensor enzymes may limit some of these off-target effects.

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EPAC agonists could be used to treat vascular inflammation (EPAC1) or type 2 diabetes (EPAC2).

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EPAC1 and EPAC2 antagonists could be used to treat heart disease.

Pharmaceutical manipulation of cAMP levels exerts beneficial effects through the regulation of the exchange protein activated by cAMP (EPAC) and protein kinase A (PKA) signalling routes. Recent attention has turned to the specific regulation of EPAC isoforms (EPAC1 and EPAC2) as a more targeted approach to cAMP-based therapies. For example, EPAC2-selective agonists could promote insulin secretion from pancreatic β cells, whereas EPAC1-selective agonists may be useful in the treatment of vascular inflammation. By contrast, EPAC1 and EPAC2 antagonists could both be useful in the treatment of heart failure. Here we discuss whether the best way forward is to design EPAC-selective agonists or antagonists and the current strategies being used to develop isoform-selective, small-molecule regulators of EPAC1 and EPAC2 activity.

Ablation of proximal tubular suppressor of cytokine signaling 3 enhances tubular cell cycling and modifies macrophage phenotype during acute kidney injury

Suppressor of cytokine signaling 3 (SOCS-3) is an important intracellular negative regulator of several signaling pathways. We found that SOCS-3 is highly expressed in renal proximal tubules during acute kidney injury. To test the impact of this, conditional proximal tubular knockout mice (SOCS-3(sglt2Δ/sglt2Δ)) were created. These mice had better kidney function than their wild-type counterparts in aristolochic acid nephropathy and after ischemia/reperfusion injury. Kidneys of these knockout mice showed significantly more proximal tubular cell proliferation during the repair phase. A direct effect of SOCS-3 on tubular cell cycling was demonstrated by in vitro experiments showing a JAK/STAT pathway-dependent antimitotic effect of SOCS-3. Furthermore, acute damaged kidneys of the knockout mice contained increased numbers of F4/80(+) cells. Phenotypic analysis of these F4/80(+) cells indicated a polarization from classically activated to alternatively activated macrophages. In vitro, SOCS-3-overexpressing renal epithelial cells directly induced classical activation in cocultured macrophages, supporting the observed in vivo phenomenon. Thus, upregulation of SOCS-3 in stressed proximal tubules plays an important role during acute kidney injury by inhibition of reparative proliferation and by modulation of the macrophage phenotype. Antagonizing SOCS-3 could have therapeutic potential for acute kidney injury.

Characterization and regulation of mechanical loading-induced compensatory muscle hypertrophy

In mammalian systems, skeletal muscle exists in a dynamic state that monitors and regulates the physiological investment in muscle size to meet the current level of functional demand. This review attempts to consolidate current knowledge concerning development of the compensatory hypertrophy that occurs in response to a sustained increase in the mechanical loading of skeletal muscle. Topics covered include: defining and measuring compensatory hypertrophy, experimental models, loading stimulus parameters, acute responses to increased loading, hyperplasia, myofiber-type adaptations, the involvement of satellite cells, mRNA translational control, mechanotransduction, and endocrinology. The authors conclude with their impressions of current knowledge gaps in the field that are ripe for future study.

Flavanoids induce expression of the suppressor of cytokine signalling 3 (SOCS3) gene and suppress IL-6-activated signal transducer and activator of transcription 3 (STAT3) activation in vascular endothelial cells

The atherogenic cytokine IL-6 (interleukin-6) induces pro-inflammatory gene expression in VECs (vascular endothelial cells) by activating the JAK (Janus kinase)/STAT3 (signal transducer and activator of transcription 3) signalling pathway, which is normally down-regulated by the STAT3-dependent induction of the E3 ubiquitin ligase component SOCS3 (suppressor of cytokine signalling 3). Novel treatments based on the regulation of SOCS3 protein levels could therefore have value in the treatment of diseases with an inflammatory component, such as atherosclerosis. To this end we carried out a screen of 1031 existing medicinal compounds to identify inducers of SOCS3 gene expression and identified the flavanoids naringenin and flavone as effective inducers of SOCS3 protein, mRNA and promoter activity. This was in contrast with the action of traditional JAK/STAT3 inhibitors and the polyphenol resveratrol, which effectively suppress SOCS3 gene expression. Both naringenin and flavone also effectively suppressed IL-6-stimulated phosphorylation of STAT3 (Tyr⁷⁰⁵) which led to suppression of IL-6-induction of the atherogenic STAT3 target gene MCP1 (monocyte chemotactic protein-1), suggesting that their ability to induce SOCS3 gene expression is STAT3-independent. Supporting this idea was the observation that the general kinase inhibitor compound C inhibits flavone- and cAMP-dependent, but not JAK-dependent, SOCS3 induction in VECs. Indeed, the ability of flavanoids to induce SOCS3 expression requires activation of the ERK (extracellular-signal-regulated kinase)-dependent transcription factor SP3, and not STAT3. In the present paper we therefore describe novel molecular actions of flavanoids, which control SOCS3 gene induction and suppression of STAT3 signalling in VECs. These mechanisms could potentially be exploited to develop novel anti-atherogenic therapies.

Hnf-1β transcription factor is an early hif-1α-independent marker of epithelial hypoxia and controls renal repair

Epithelial repair following acute kidney injury (AKI) requires epithelial-mesenchyme-epithelial cycling associated with transient re-expression of genes normally expressed during kidney development as well as activation of growth factors and cytokine-induced signaling. In normal kidney, the Hnf-1β transcription factor drives nephrogenesis, tubulogenesis and epithelial homeostasis through the regulation of epithelial planar cell polarity and expression of developmental or tubular segment-specific genes. In a mouse model of ischemic AKI induced by a 2-hours hemorrhagic shock, we show that expression of this factor is tightly regulated in the early phase of renal repair with a biphasic expression profile (early down-regulation followed by transient over-expression). These changes are associated to tubular epithelial differentiation as assessed by KSP-cadherin and megalin-cubilin endocytic complex expression analysis. In addition, early decrease in Hnf1b expression is associated with the transient over-expression of one of its main target genes, the suppressor of cytokine signaling Socs3, which has been shown essential for renal repair. In vitro, hypoxia induced early up-regulation of Hnf-1β from 1 to 24 hours, independently of the hypoxia-inducible factor Hif-1α. When prolonged, hypoxia induced Hnf-1β down-regulation while normoxia led to Hnf-1β normalization. Last, Hnf-1β down-regulation using RNA interference in HK-2 cells led to phenotype switch from an epithelial to a mesenchyme state. Taken together, we showed that Hnf-1β may drive recovery from ischemic AKI by regulating both the expression of genes important for homeostasis control during organ repair and the state of epithelial cell differentiation.

Inflammation and linear bone growth: the inhibitory role of SOCS2 on GH/IGF-1 signaling

Linear bone growth is widely recognized to be adversely affected in children with chronic kidney disease (CKD) and other chronic inflammatory disorders. The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) pathway is anabolic to the skeleton and inflammatory cytokines compromise bone growth through a number of different mechanisms, which include interference with the systemic as well as the tissue-level GH/IGF-1 axis. Despite attempts to promote growth and control disease, there are an increasing number of reports of the persistence of poor growth in a substantial proportion of patients receiving rhGH and/or drugs that block cytokine action. Thus, there is an urgent need to consider better and alternative forms of therapy that are directed specifically at the mechanism of the insult which leads to abnormal bone health. Suppressor of cytokine signaling 2 (SOCS2) expression is increased in inflammatory conditions including CKD, and is a recognized inhibitor of GH signaling. Therefore, in this review, we will focus on the premise that SOCS2 signaling represents a critical pathway in growth plate chondrocytes through which pro-inflammatory cytokines alter both GH/IGF-1 signaling and cellular function.

Osteoporosis in chronic inflammatory disease: the role of malnutrition

Osteoporosis is a metabolic bone disorder affecting million of people worldwide. Increased understanding of bone disease has led to a greater recognition of factors affecting bones, and consequently many secondary causes of osteoporosis were demonstrated. In this study, we aim to explore possible causes of bone loss and fractures in subjects affected by chronic inflammatory disease and to suggest new targets for intervention. In fact several studies, evaluated to perform this study, suggest that the patients with chronic inflammatory disease could be at high risk for fractures due to bone loss as consequence of malnutrition, caused by inflammation and hormonal change. Consequently, some actions could derive from the considerations of these mechanisms: a change in actual approach of chronic patients, that may include the investigation on the possible presence of osteoporosis, as well as further research on this topic to find a better therapy to prevent osteoporosis considering all the mechanisms described.

The Jak/STAT signaling pathway is downregulated at febrile temperatures

BACKGROUND

The Janus family of kinases (JAKs), Jak1, Jak2, Jak3, and Tyk2, constitute a subgroup of non-receptor protein tyrosine kinases. Upon cytokine binding, the receptor-associated kinases are activated and phosphorylate tyrosine residues in their cognate cytokine receptors. Their activities are controlled at several levels and include cellular concentration, auto-activation, and degradation.

PRINCIPAL FINDINGS

Our findings show that elevated temperatures in the fever range irreversibly aggregate Jak2 and considerably reduce functional Jak2 protein levels. Jak2 synthesis remains unaltered. We observed that also the protein level of the signal transducer and activator of transcription, STAT5b, is transiently decreased at temperatures above 37°C. Consequently, the signaling response, e.g. via the growth hormone receptor, is reduced.

CONCLUSIONS/SIGNIFICANCE

These findings predict that elevated body temperatures lower the responsiveness of cytokine receptors.

Galectin-3 is required for resident microglia activation and proliferation in response to ischemic injury

Growing evidence suggests that galectin-3 is involved in fine tuning of the inflammatory responses at the periphery, however, its role in injured brain is far less clear. Our previous work demonstrated upregulation and coexpression of galectin-3 and IGF-1 in a subset of activated/proliferating microglial cells after stroke. Here, we tested the hypothesis that galectin-3 plays a pivotal role in mediating injury-induced microglial activation and proliferation. By using a galectin-3 knock-out mouse (Gal-3KO), we demonstrated that targeted disruption of the galectin-3 gene significantly alters microglia activation and induces ∼4-fold decrease in microglia proliferation. Defective microglia activation/proliferation was further associated with significant increase in the size of ischemic lesion, ∼2-fold increase in the number of apoptotic neurons, and a marked deregulation of the IGF-1 levels. Next, our results revealed that contrary to WT cells, the Gal3-KO microglia failed to proliferate in response to IGF-1. Moreover, the IGF-1-mediated mitogenic microglia response was reduced by N-glycosylation inhibitor tunicamycine while coimmunoprecipitation experiments revealed galectin-3 binding to IGF-receptor 1 (R1), thus suggesting that interaction of galectin-3 with the N-linked glycans of receptors for growth factors is involved in IGF-R1 signaling. While the canonical IGF-1 signaling pathways were not affected, we observed an overexpression of IL-6 and SOCS3, suggesting an overactivation of JAK/STAT3, a shared signaling pathway for IGF-1/IL-6. Together, our findings suggest that galectin-3 is required for resident microglia activation and proliferation in response to ischemic injury.

Activation of farnesoid X receptor increases the expression of cytokine inducible SH2-containing protein in HepG2 cells

Cytokine inducible SH2-containing protein (CISH), which negatively regulates cytokine signaling by inhibiting JAK2/STAT5 activity, is regarded as a therapeutic target for inflammatory diseases. Farnesoid X receptor (FXR), a ligand-activated transcription factor, has been proposed to play a protective function in the inflammatory responses. However, the role of FXR in modulation of CISH expression is unknown. In the present study, we for the first time identified that in human hepatoma cell line HepG2 the activation of FXR by the natural agonist chenodeoxycholic acid (CDCA) and the synthetic specific agonist GW4064 upregulated CISH at both transcriptional and translational levels, and inhibited interleukin (IL)6-induced STAT5 activation. Moreover, the in vivo experiment demonstrated that gavaging mice with CDCA increased CISH expression and reduced basal STAT5 phosphorylation in liver tissues. Reporter assay showed that FXR agonists enhanced the transcriptional activity of CISH promoter. These data suggest that FXR may serve as a novel molecular target for manipulating CISH expression in hepatocytes. FXR-mediated upregulation of CISH may play an important role in the homeostasis of cytokine signal networks and be beneficial to control cytokine-associated inflammatory diseases.

Erythropoietin attenuated vascular dysfunction and inflammation by inhibiting NADPH oxidase-derived superoxide production in nitric oxide synthase-inhibited hypertensive rat aorta

Erythropoietin (EPO), used clinically for renal anemia, reportedly exerts beneficial pleiotropic effects in various tissues. Recent studies suggest that nitric oxide (NO) plays an important role in EPO-induced tissue protection. The present study investigated whether recombinant human EPO (rHuEPO) exhibits vasoprotective effects even in the NO synthase-inhibited state. Rats that received a NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), in drinking water (0.7 mg/ml) were treated with rHuEPO (75 U/kg, s.c.) three times a week for 2 weeks. The administration of rHuEPO to L-NAME-treated rats had no effect on hematocrit values or increased blood pressure. Vasodilation in response to acetylcholine in the aortic ring was impaired in the L-NAME-treated rats, and improved by rHuEPO. Immunohistochemical staining revealed that infiltration by macrophages and expression of osteopontin were enhanced in the L-NAME-treated rat aorta, and the overexpression was suppressed by rHuEPO. rHuEPO also attenuated medial hyperplasia. Activation of Akt signaling was evident in rHuEPO-treated rats as the increased expression of phosphorylated Akt. rHuEPO enhanced the expression of antioxidant enzymes such as Cu/Zn-superoxide dismutase and heme oxygenase-1 in the aorta. In addition, rHuEPO reduced NADPH oxidase-dependent superoxide production and enhanced the expression of suppressor of cytokine signaling-1(SOCS-1) in the L-NAME-treated rat aorta. These results suggest that a low dose of rHuEPO results in the normalization of endothelial function and vascular inflammation beyond hematopoiesis even in a pharmacologically NO synthase-inhibited state. These effects might be due to the antioxidant properties of rHuEPO. SOCS-1 overexpression would play an important role in suppressing NADPH oxidase activation.

Evidence for neuroinflammatory and microglial changes in the cerebral response to sleep loss

STUDY OBJECTIVES

Sleep loss has pro-inflammatory effects, but the roles of specific cell populations in mediating these effects have not been delineated. We assessed the modulation of the electroencephalographic and molecular responses to sleep deprivation (S-DEP) by minocycline, a compound that attenuates microglial activation occurring in association with neuroinflammatory events.

DESIGN

Laboratory rodents were subjected to assessment of sleep and wake in baseline and sleep deprived conditions.

PARTICIPANTS

Adult male CD-1 mice (30-35 g) subjected to telemetric electroencephalography.

INTERVENTIONS

Minocycline was administered daily. Mice were subjected to baseline data collection on the first day of minocycline administration and, on subsequent days, 2 S-DEP sessions, 1 and 3 h in duration, followed by recovery sleep. Following EEG studies, mice were euthanized either at the end of a 3 h S-DEP or as time-of day controls for sampling of brain messenger RNAs. Gene expression was measured by real-time polymerase chain reaction.

MEASUREMENTS AND RESULTS

Minocycline-treated mice exhibited a reduction in time spent asleep, relative to saline-treated mice, in the 3-h interval immediately after administration. S-DEP resulted in an increase in EEG slow wave activity relative to baseline in saline-treated mice. This response to S-DEP was abolished in animals subjected to chronic minocycline administration. S-DEP suppressed the expression of the microglial-specific transcript cd11b and the neuroinflammation marker peripheral benzodiazepine receptor, in the brain at the mRNA level. Minocycline attenuated the elevation of c-fos expression by S-DEP. Brain levels of pro-inflammatory cytokine mRNAs interleukin-1β (il-1β), interleukin-6 (il-6), and tumor necrosis factor-α (tnfα) were unaffected by S-DEP, but were elevated in minocycline-treated mice relative to saline-treated mice.

CONCLUSIONS

The anti-neuroinflammatory agent minocycline prevents either the buildup or expression of sleep need in rodents. The molecular mechanism underlying this effect is not known, but it is not mediated by suppression of il-1β, il-6, and tnfα at the transcript level.

Cisplatin ototoxicity involves cytokines and STAT6 signaling network

We herein investigated the role of the STAT signaling cascade in the production of pro-inflammatory cytokines and cisplatin ototoxicity. A significant hearing impairment caused by cisplatin injection was observed in Balb/c (wild type, WT) and STAT4(-/-), but not in STAT6(-/-) mice. Moreover, the expression levels of the protein and mRNA of pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6, were markedly increased in the serum and cochlea of WT and STAT4(-/-), but not STAT6(-/-) mice. Organotypic culture revealed that the shape of stereocilia bundles and arrays of sensory hair cell layers in the organ of Corti from STAT6(-/-) mice were intact after treatment with cisplatin, whereas those from WT and STAT4(-/-) mice were highly distorted and disarrayed after the treatment. Cisplatin induced the phosphorylation of STAT6 in HEI-OC1 auditory cells, and the knockdown of STAT6 by STAT6-specific siRNA significantly protected HEI-OC1 auditory cells from cisplatin-induced cell death and inhibited pro-inflammatory cytokine production. We further demonstrated that IL-4 and IL-13 induced by cisplatin modulated the phosphorylation of STAT6 by binding with IL-4 receptor alpha and IL-13Rα1. These findings suggest that STAT6 signaling plays a pivotal role in cisplatin-mediated pro-inflammatory cytokine production and ototoxicity.

The role of pro-inflammatory and immunoregulatory cytokines in tendon healing and rupture: new insights

Owing to limited self-healing capacity, tendon ruptures and healing remain major orthopedic challenges. Increasing evidence suggests that post-traumatic inflammatory responses, and hence, cytokines are involved in both cases, and also in tendon exercise and homeostasis. This review summarizes interrelations known between the cytokines interleukin (IL)-1β, tumor necrosis factor (TNF)α, IL-6 and vascular endothelial growth factor (VEGF) in tendon to assess their role in tendon damage and healing. Exogenic cytokine sources are blood-derived leukocytes that immigrate in damaged tendon. Endogenous expression of IL-1β, TNFα, IL-6, IL-10 and VEGF was demonstrated in tendon-derived cells. As tendon is a highly mechanosensitive tissue, cytokine homeostasis and cell survival underlie an intimate balance between adequate biomechanical stimuli and disturbance through load deprivation and overload. Multiple interrelations between cytokines and tendon extracellular matrix (ECM) synthesis, catabolic mediators e.g. matrix-degrading enzymes, inflammatory and angiogenic factors (COX-2, PGE2, VEGF, NO) and cytoskeleton assembly are evident. Pro-inflammatory cytokines affect ECM homeostasis, accelerate remodeling, amplify biomechanical adaptiveness and promote tenocyte apoptosis. This multifaceted interplay might both contribute to and interfere with healing. Much work must be undertaken to understand the particular interrelation of these inflammatory and regulatory mediators in ruptured tendon and healing, which has relevance for the development of novel immunoregulatory therapeutic strategies.

Does fat fuel the fire: independent and interactive effects of genetic, physiological, and environmental factors on variations in fat deposition and distribution across populations

Markers of inflammation (MOI) have been reported to influence bone health in adults, with reports of inverse associations. Adipose has also been linked to bone. In children, the interrelationships are unclear. The objective of this study was to evaluate the relationship between MOI (i.e. CRP, TNFR2, IL-6) and bone mineral content (BMC) and determine the contribution of fat deposition/distribution in children. Forty-nine children (59% male) 7-12 y participated. Body composition was evaluated by DXA, and MOI and insulin sensitivity (S(I)) were obtained during an IVGTT. Multiple linear regression was used for analyses. TNFR2 was inversely associated with BMC. In boys, TNFR2 was inversely associated with BMC, and in girls IL-6 was inversely associated with BMC, and total and percent fat influenced the relationships. Our results suggest a potential inhibitory role of inflammation on bone as well as a negative impact of adiposity. Future investigations are warranted to further investigate these relationships.

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

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

Effect of pro-inflammatory and immunoregulatory cytokines on human tenocytes

Tendon injury induces a local inflammatory response, characterized by the induction of pro-inflammatory cytokines. The aim of the present study was to analyze the effects of TNFalpha, IL-6 and IL-10 on key parameters of tendon homeostasis. Cultured primary human tenocytes were treated with the recombinant cytokines IL-6, IL-10, TNFalpha, or combinations of TNFalpha with IL-6 and IL-10 (10 ng/mL, 6, 24 h). Expression of type I collagen, elastin, MMP-1, TNFalpha, IL-1beta, IL-6, IL-10, and suppressors of cytokine signaling (SOCS1, 3) was analyzed with the use of RTD-PCR, immunocytochemistry, and Western blot analysis. In response to TNFalpha, tenocytes reduced their type I collagen deposition but increased their elastin gene expression and highly upregulated their expression for MMP-1, pro-inflammatory (TNFalpha, IL-1beta) and immunoregulatory (IL-6, IL-10) cytokines. TNFalpha stimulation augmented SOCS1, whereas SOCS3 expression in tenocytes was also induced by IL-6. The treatment of tenocytes with IL-6 and IL-10 had no effect on cytokine expression. Neither IL-6 nor IL-10 modulated the observed effects of TNFalpha significantly. These results indicate that TNFalpha strongly activates the tenocytes to amplify their own TNFalpha expression and, subsequently, that of other regulatory cytokines and matrix degrading enzymes. However, the impact of IL-6 and IL-10 on tenocytes remains unclear.

Uremia attenuates growth hormone-stimulated insulin-like growth factor-1 expression, a process worsened by inflammation

Growth hormone (GH) resistance is common in uremia and together with resistance to insulin-like growth factor-1 (IGF-1) contributes to uremic growth retardation and muscle wasting. Previously, we found decreased GH-stimulated janus-kinase 2-signal transducers and activators of transcription 5 (STAT5) phosphorylation and nuclear translocation in uremia; however, it is unclear whether there are more distal defects. Therefore, we tested whether the binding of phosphorylated STAT5b to DNA is intact in uremia. Using uremic rats we found that in addition to impaired hepatic STAT5b phosphorylation, the binding of available phospho-STAT5b to DNA is decreased thus contributing to impaired IGF-1 gene expression. As sepsis-induced inflammation causes a loss of body protein and as Gram-negative infections are relatively common in uremia, we also characterized mechanisms in which acute inflammation might contribute to GH resistance in uremia. Endotoxin-induced inflammation markedly increased the resistance to GH-mediated STAT5b signaling, and further decreased STAT5b binding to DNA and IGF-1 gene expression. These perturbations appear to be related to increased cytokine expression. Thus, our findings indicate that hepatic resistance to GH-induced IGF-1 expression in uremia arises due to defects in STAT5b phosphorylation and its impaired binding to DNA, processes further aggravated by inflammation.

Insulin-like growth factor I signaling in skeletal muscle and the potential for cytokine interactions

Recent research has demonstrated that intracellular signaling components associated with several proinflammatory cytokines have the potential to interact with signaling pathways that regulate anabolic processes in skeletal muscle. This presentation and the ensuing brief review are intended to present a selection of the potential interactions between these two critical processes.

Expression of JAKs/STATs pathway molecules in rat model of rapid focal segmental glomerulosclerosis

The objective of this study was to investigate the role of the Janus kinase-signal transducers and activators of transcription (JAKs/STATs) pathway in focal segmental glomerulosclerosis. Sixty specific pathogen-free male Wistar rats were randomly divided into two groups: a model group (MG) and a control group (CG). In the MG group, nephropathy was induced by unilateral nephrectomy and a single tail vein injection of adriamycin (5 mg/kg). Ten rats were sacrificed every 2 weeks in each group. The expressions of smooth muscle alpha actin (alpha-SMA), collagen (COL)-IV, STAT1, and STAT3 were examined using histochemical techniques, and Western blotting was used to examine the protein levels of STAT1, STAT3, phosphorylated (P)-STAT1, P-STAT3, and transforming growth factor beta1 (TGFbeta(1)). The expressions of JAK1, JAK2, STAT1, STAT3, suppressors of cytokine signaling (SOCS)1, SOCS3, protein inhibitors of activated STAT (PIAS)1, and PIAS3 were also measured by real-time quantitative reverse transcriptase-PCR. A steady and significant increase in the expressions of alpha-SMA, COL-IV and TGFbeta(1) were observed in MG rats over the whole experimental course. Increased STAT1 and P-STAT1 levels in MG rats were observed by week 6, whereas increased levels of STAT3 and P-STAT3 were noted by week 2. At the mRNA levels, JAK1, STAT1, and PIAS1 were significantly increased in MG rats in week 2, whereas JAK2 mRNA showed a significant decrease by weeks 2 and 4, followed by an significant increase in week 6. Significantly increased STAT3 levels were noted in week 2, followed by a steady and significant decrease in weeks 4 and 6. Significantly reduced levels of SOCS1, SOCS3, and PIAS3 mRNA were noted at all time points. We conclude that the JAKs/STATs signaling pathway may play an important role in the pathological process of rapid focal segmental glomerulosclerosis in the rat model.

Endotoxin-induced growth hormone resistance in skeletal muscle

Inflammation-induced skeletal muscle wasting is a serious clinical problem and arises in part because of resistance to GH-stimulated IGF-I expression. Although it is established that in the liver, resistance develops because of impaired signaling through the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 5 (STAT5) transduction pathway, together with a more distal defect in STAT5 DNA-binding activity, the situation in skeletal muscle is unclear. Accordingly, we set out to characterize the mechanisms behind the skeletal muscle resistance to GH in rats with acute inflammation induced by endotoxin. Endotoxin caused significant declines in GH-stimulated STAT5a/b phosphorylation and IGF-I gene expression, and this occurred despite a lack of change in signaling protein levels or phosphorylation of JAK2. In whole muscle, GH-stimulated phospho-STAT5a/b levels were reduced by half, and in the nucleus, phospho-STAT5b levels were similarly reduced. Furthermore, the binding of phosphorylated STAT5b to DNA was reduced and to a similar extent to the reduction in nuclear phosphorylated STAT5b. Interestingly, GH-induced androgen receptor gene expression was also suppressed. Thus, it appears that skeletal muscle resistance to GH-stimulated IGF-I expression in acute endotoxemia arises from a defect in STAT5b signaling, with a proportionate reduction in STAT5b DNA binding. Finally, it appears that resistance to GH-induced androgen receptor expression also develops and, together with the attenuated GH-induced IGF-I expression, likely plays an important role in the muscle wasting that arises in endotoxin-induced inflammation.

A novel role for the chemokine receptor Cxcr4 in kidney morphogenesis: an in vitro study

The CXCR4 chemokine receptor is involved in hematopoietic stem cell homing, neuronal development, and angiogenesis. We show a significant new role for this receptor in epithelial patterning and renal morphogenesis. This receptor is expressed in the ureteric bud (UB) and the metanephric mesenchyme (MM). Stimulation of Cxcr4 in renal tubular cells leads to activation of multiple signaling pathways and tubulogenesis and cell migration. Knocking down of this receptor in tubular cells leads to cyst formation. Inactivation of this receptor in embryonic kidney explants results in impaired UB branching and mesenchymal tubulogenesis. The data presented here point to its importance in the process of mesenchymal-to-epithelial transitioning (MET), a crucial developmental process in the embryonic kidney. A number of genes important for normal tubulogenesis and MET are decreased upon CXCR4 inactivation.

Induction of suppressors of cytokine signaling by the trichothecene deoxynivalenol in the mouse

Deoxynivalenol (DON), a trichothecene mycotoxin found in grains and cereal-based foods worldwide, impairs weight gain in experimental animals but the underlying mechanisms remain undetermined. Oral exposure to DON induces rapid and transient upregulation of proinflammatory cytokine expression in the mouse. The latter are known to induce several suppressors of cytokine signaling (SOCS), some of which impair growth hormone (GH) signaling. We hypothesized that oral exposure to DON will induce SOCS expression in the mouse. Real-time PCR and cytokine bead array revealed that oral gavage with DON rapidly (1 h) induced tumor necrosis factor-alpha and interleukin-6 mRNA and protein expression in several organs and plasma, respectively. Upregulation of mRNAs for four well-characterized SOCS (CIS [cytokine-inducible SH2 domain protein], SOCS1, SOCS2, and SOCS3) was either concurrent with (1 h) or subsequent to cytokine upregulation (2 h). Notably, DON-induced SOCS3 mRNAs in muscle, spleen and liver, with CIS1, SOCS1, and SOCS2 occurring to a lesser extent. Hepatic SOCS3 mRNA was a very sensitive indicator of DON exposure with SOCS3 protein being detectable in the liver well after the onset of cytokine decline (5 h). Furthermore, hepatic SOCS upregulation was associated with about 75% suppression of GH-inducible insulin-like growth factor acid labile subunit. Taken together, DON-induced cytokine upregulation corresponded to increased expression of several SOCS, and was associated with suppression of GH-inducible gene expression in the liver.

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

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

Polymorphisms near SOCS3 are associated with obesity and glucose homeostasis traits in Hispanic Americans from the Insulin Resistance Atherosclerosis Family Study

The SOCS3 gene product participates in the feedback inhibition of a range of cytokine signals. Most notably, SOCS3 inhibits the functioning of leptin and downstream steps in insulin signaling after being expressed by terminal transcription factors, such as STAT3 and c-fos. The SOCS3 gene is located in the chromosome region 17q24-17q25, previously linked to body mass index (BMI), visceral adipose tissue (VAT), and waist circumference (WAIST) in Hispanic families in the Insulin Resistance Atherosclerosis Family Study (IRASFS). A high density map of 1,536 single nucleotide polymorphisms (SNPs) was constructed to cover a portion of the 17q linkage interval in 1,425 Hispanic subjects from 90 extended families in IRASFS. Analysis of this dense SNP map data revealed evidence of association of rs9914220 (located 10 kb 5' of the SOCS3 gene) with BMI, VAT, and WAIST (P-value ranging from 0.003 to 0.017). Using a tagging SNP approach, rs9914220 and 22 additional SOCS3 SNPs were genotyped for genetic association analysis with measures of adiposity and glucose homeostasis. The adiposity phenotypes utilized in association analyses included BMI, WAIST, waist to hip ratio (WHR), subcutaneous adipose tissue, VAT, and visceral to subcutaneous ratio (VSR). Linkage disequilibrium calculations revealed three haplotype blocks near SOCS3. Haplotype Block 3 (5' of SOCS3) contained SNPs consistently associated with BMI, WAIST, WHR, and VAT (P-values ranging from 2.00 x 10(-4) to 0.036). Haplotype Block 1 contained single-SNPs that were associated with most adiposity traits except for VSR (P-values ranging from 0.002 to 0.047). When trait associated SNPs were included in linkage analyses as covariates, a reduction of VAT LOD score from 1.26 to 0.76 above the SOCS3 locus (110 cM) was observed. Multi-SNP haplotype testing using the quantitative pedigree disequilibrium test was broadly consistent with the single-SNP associations. In conclusion, these results support a role for SOCS3 genetic variants in human obesity.

The signal transduction mediated by erythropoietin and proinflammatory cytokines in the JAK/STAT pathway in the children with cerebral palsy

It is well established that erythropoietin (EPO) is a pleiotropic cytokine, which has a brain-derived neuroprotective effect in the central nervous system (CNS). Immune abnormality has a close relationship with cerebral palsy (CP), and may be even involved in the development of CP. There is evidence that the amount of EPO in CP children is lower than in normal children, but the levels of proinflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, are higher in the CP children. The signal transduction mediated by EPO that has a neuroprotective effect and mediated by proinflammatory cytokines that lead to brain damage shares the common JAK/STAT pathway. Under acute stress, the JAK/STAT pathway is occupied by massive proinflammatory cytokines, and the negative feedback inhibition factors like suppressor of cytokine signaling (SOCS) proteins are simultaneously activated, which exist in reciprocal inhibition to EPO in the JAK/STAT pathway. As a result, the signal transduction mediated by EPO is prevented or reduced, and the neuroprotective effect of EPO is eventually weakened. In this review, a novel approach to CP treatment through neurodevelopmental treatment (NDT) is put forward by analysis of the interrelationship of signal transduction mediated by EPO and proinflammatory cytokines in the JAK/STAT pathway and their roles in the development of CP, and some reasonable ideas for CP treatment are provided.

Insulin-like growth factor-I receptor signal transduction and the Janus Kinase/Signal Transducer and Activator of Transcription (JAK-STAT) pathway

The insulin-like growth factor IGF-I is an important fetal and postnatal growth factor, which is also involved in tissue homeostasis via regulation of proliferation, differentiation, and cell survival. To understand the role of IGF-I in the pathophysiology of a variety of disorders, including growth disorders, cancer, and neurodegenerative diseases, a detailed knowledge of IGF-I signal transduction is required. This knowledge may also contribute to the development of new therapies directed at the IGF-I receptor or other signaling molecules. In this review, we will address IGF-I receptor signaling through the JAK/STAT pathway in IGF-I signaling and the role of cytokine-induced inhibitors of signaling (CIS) and suppressors of cytokine signaling (SOCS). It appears that, in addition to the canonical IGF-I signaling pathways through extracellular-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K)-Akt, IGF-I also signals through the JAK/STAT pathway. Activation of this pathway may lead to induction of SOCS molecules, well-known feedback inhibitors of the JAK/STAT pathway, which also suppress of IGF-I-induced JAK/STAT signaling. Furthermore, other IGF-I-induced signaling pathways may also be modulated by SOCS. It is conceivable that the effect of these classical inhibitors of cytokine signaling directly affect IGF-I receptor signaling, because they are able to associate to the intracellular part of the IGF-I receptor. These observations indicate that CIS and SOCS molecules are key to cross-talk between IGF-I receptor signaling and signaling through receptors belonging to the hematopoietic/cytokine receptor superfamily. Theoretically, dysregulation of CIS or SOCS may affect IGF-I-mediated effects on body growth, cell differentiation, proliferation, and cell survival.

Increased expression of SOCS3 in monocytes and SOCS1 in lymphocytes correlates with progressive loss of renal function and cardiovascular risk factors in chronic kidney disease

Inflammation, an independent cardiovascular disease risk factor is common in patients with chronic kidney disease. Suppressors of cytokine signaling (SOCS) are induced by cytokines in a variety of cells and modulate inflammatory responses. We hypothesized that in chronic kidney disease, SOCS expression in peripheral blood mononuclear cells is increased, and related to inflammation and renal function. We also tested correlations between SOCS expression and biomarkers and risk factors of cardiovascular disease. Whether monocytes and lymphocytes differentially respond to interleukin-6 (IL-6) was tested ex vivo. Monocytes and lymphocytes were isolated from peripheral blood of chronic kidney disease patients (n=9) and controls (n=11). In three other healthy subjects, whole blood was incubated with IL-6 before cell isolation. SOCS expression was assessed by real-time quantitative PCR. Plasma cytokines were measured as well as pulse wave velocity. SOCS3 expression was increased in monocytes and SOCS1 in lymphocytes along with increased plasma levels of IL-6 and tumor necrosis factor-alpha (TNFalpha) in chronic kidney disease patients. While monocyte SOCS3 correlated with glomerular filtration rate, urea and diastolic blood pressure, lymphocyte SOCS1 correlated with TNFalpha, pulse wave velocity and systolic blood pressure. IL-6 stimulation of whole blood caused expression of different SOCS genes in monocytes and lymphocytes. Increased expression of SOCS3 in monocytes versus SOCS1 in lymphocytes coincided with elevated plasma levels of IL-6 and TNFalpha, suggesting that these cell types process the uremic milieu differently. This could reflect cell-specific responses to inflammation, as supported by our ex vivo study. Moreover, increased SOCS expression in peripheral blood mononuclear cells correlated with decreased renal function. Since chronic kidney disease predisposes to cardiovascular disease, we speculate that increased SOCS expression in peripheral blood mononuclear cells could be a new marker of cardiovascular disease in chronic kidney disease patients.

Reduced nitric oxide production and iNOS mRNA expression in IFN-gamma-stimulated chicken macrophages transfected with iNOS siRNAs

Utilizing RNA interference technology with siRNA in the HD11 macrophage cell line, we determined how the inhibition or knock-down of the iNOS (inducible nitric oxide synthase) gene affected IFN-gamma-induced macrophage production of nitric oxide (NO) and mRNA expression of genes involved in this biological pathway in the chicken. Chicken macrophages produce NO when stimulated with recombinant chicken IFN-gamma, however, when transfected with iNOS siRNAs, the production of NO is significantly decreased. We observed a 14-28% reduction in NO production by IFN-gamma-stimulated HD11 cells at 48h after initial siRNA transfection compared to non-transfected IFN-gamma-stimulated macrophages. Significant knock-down of iNOS mRNA expression (15 to 50-fold lower) was observed for each of four iNOS siRNAs, when compared to non-transfected IFN-gamma-stimulated macrophages and to those treated with a negative control siRNA. The IFN-gamma-stimulated chicken macrophages transfected with iNOS siRNAs did not show altered levels of mRNA expression for genes involved in IFN-gamma signaling and iNOS pathways (IL-1beta, IL-6, IFN-gamma, TGF-beta4, or SOCS-3) suggesting that the observed decrease in NO production is a direct result of siRNA mediated knock-down of iNOS, rather than IFN-gamma-induced changes in the other genes tested.