Sequential inspiratory muscle exercise-noninvasive positive pressure ventilation alleviates oxidative stress in COPD by mediating SOCS5/JAK2/STAT3 pathway.

BACKGROUND: Pulmonary rehabilitation training is of great significance for the prognosis of chronic obstructive pulmonary disease (COPD) patients. The purpose of this study was to investigate the therapeutic effect and pathway of a new sequential noninvasive positive pressure ventilation (NIPPV) + inspiratory muscle training (IMT) therapy. METHODS: A total of 100 COPD patients were enrolled and randomly divided into oxygen therapy (OT), NIPPV, IMT and sequential (NIPPV + IMT) group. Lung function, exercise endurance, quality of life, and dyspnea symptoms were examined and recorded. Then, reactive oxygen species (ROS), malonaldehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) levels were detected by enzyme-linked immunoassay, and suppressor of cytokine signaling 5 (SOCS5)/janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway expression changes were detected by quantitative real time-polymerase chain reaction (qRT-PCR) and western blot. A mouse model of COPD was then established to further verify the effects of SOCS5/JAK2/STAT3 pathways on lung function and oxidative stress. RESULTS: After 8 weeks of treatment, NIPPV, IMT or sequential (NIPPV + IMT) significantly improved exercise endurance, quality of life and dyspnea, reduced oxidative stress, promoted SOCS5 expression and inhibited the activation of JAK2/STAT3 pathway, and no significant effect was observed on lung function of COPD patients. Notably, sequential (NIPPV + IMT) showed better therapeutic outcomes than either IMT or NIPPV alone. Moreover, results at the animal level showed that overexpression of SOCS5 significantly reduced pulmonary inflammatory infiltration, pathological changes and oxidative stress levels in COPD mice, enhanced lung function, and inhibited the activation of JAK2/STAT3 pathway. CONCLUSION: Our results elucidated that sequential (NIPPV + IMT) significantly relieved COPD development by regulating SOCS5/JAK2/STAT3 signaling-mediated oxidative stress.

Upregulation of SOCS2 causes mitochondrial dysfunction and promotes ferroptosis in pancreatic cancer cells.

SOCS2 exerts oncogenic effects in a variety of tumors, but its role in pancreatic cancer has not been studied. The purpose of this study was to explore the role of SOCS2 in pancreatic cancer. The expression level of SOCS2 and the content of mitochondrial DNA (mtDNA) in the cells were detected by real-time PCR (qRT-PCR), and SOCS2 was overexpressed in PANC-1 and Capan-2 cells by transfection with pcDNA3.2-SOCS2. CCK-8, cell colony formation assay, and flow cytometry were used respectively to detect the cell proliferation rate, cell colony formation ability, and the level of ROS in the cells. The ATP level, glucose consumption level, and Fe2 + level in the cells were assessed by biochemical assays. And Western blot determined the protein expression levels of SOCS2 as well as ferroptosis-related proteins, namely, SLC7A11, DMT1, TFRC, and FTH. We found that SOCS2 was significantly down-regulated in pancreatic cancer cells. Overexpression of SOCS2 significantly decreased the viability of PANC-1 and Capan-2 cells, reduced the content of mtDNA and the level of ATP, and caused mitochondrial dysfunction with an accumulation of ROS. Aside from these effects, up-regulation of SOCS2 raised the levels of Fe2 +, DMT1 and TFRC, and decreased the level of SLC7A11 and FTH in PANC-1 and Capan-2 cells, thereby inducing the occurrence of ferroptosis. In conclusion, up-regulated SOCS2 may enhance mitochondrial dysfunction and ferroptosis in pancreatic cancer cells, which can be used as a molecular target for the diagnosis and treatment of pancreatic carcinoma.

Protective mechanism of gold nanoparticles on human neural stem cells injured by ß-amyloid protein through miR-21-5p/SOCS6 pathway.

Alzheimer's disease (AD) is a neurodegenerative disorder with progressive memory loss in dementia. Gold nanoparticles (AuNPs) were reported beneficial for human neural stem cells (hNSCs) treated with Amyloid-beta (Aß), but the neuroprotective mechanisms still are unknown. First, the hNSCs induced by Aß to construct AD cell model in vitro and AuNPs was performed to assess the therapeutic effect of Aß-targeted AD treatment. Then, we investigated the effects of AuNPs on hNSCs viability and proinflammatory factors (interleukin 6 and tumor necrosis factor-alpha) by Cell Counting Kit-8 (CCK-8) and enzyme-linked immunosorbent (ELISA). FACS was carried out to determinate Tuj-1 and glial fibrillary acidic protein (GFAP). Reactive oxygen species (ROS) generation and mitochondrial membrane potential was evaluated by ROS and JC-1 assay kit. In addition, miRNA array was used to systematically detect the differential miRNAs. Dual-luciferase reporter assay was applied to verify the targeting relationship between miR-21-5p and the suppressor of cytokine signalling 6(SOCS6). Quantitative PCR (qPCR) and Western blot assessments were also used to detect related gene expression intracellularly or in the supernatant. The results demonstrate that AuNPs co-treatment repressed the high expression of total tau (T-tau), phosphorylated tau (P-tau), and Aß protein, and reduced apoptosis rate of hNSCs. Aß-induced decreased mitochondrial membrane potential and mitochondria in the hNSCs were damaged, while AuNPs co-treatment showed a protective effect on mitochondrial membrane potential. Co-treatment with AuNPs significantly increased dynamin-related protein 1 (DRP1), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (TFAM) mRNA levels. AuNPs may improve mitochondrial function impairment due to Aß by elevating mitochondrial membrane potential, upregulating regulators of mitochondrial biogenesis, and inhibiting ROS production. hNSCs transfected with miR-21-5p inhibitor reversed AuNPs mediated cytoprotection induced by Aß. AuNPs upregulation of miR-21-5p expression and exert a mitochondrial protective function. Overexpression of miR-21-5p contributes to enhancing the effect of cytoprotection of AuNPs. MiR-21-5p direct targeting SOCS6 and overexpression SOCS6 exerted opposite effects on hNSCs compared with miR-21-5p mimic group. In conclusion, AuNPs can protect hNSCs from Aß injury and decrease mitochondrial damage by regulating the miR-21-5p/SOCS6 pathway.

Upregulation of miR-144-3p alleviates Doxorubicin-induced heart failure and cardiomyocytes apoptosis via SOCS2/PI3K/AKT axis.

MicroRNAs (miRs) are implicated in heart failure (HF). Thereby, we aim to uncover the role of miR-144-3p in HF. Doxorubicin (Dox)-induced HF model was constructed in rats and cardiomyocytes H9C2, and the cardiac function was determined using ultrasound cardiogram. Morphology of cardiac tissue was observed using hematoxylin-eosin (H&E) staining. The viability and apoptosis of Dox-treated and transfected cardiomyocytes were determined using Cell Counting Kit-8 (CCK-8) assay and flow cytometry. Relative expressions of the HF-associated miRs (including miR-144-3p), suppressor of cytokine signaling 2 (SOCS2), apoptosis- and phosphoinositide 3-kinase (PI3K)/AKT pathway-related factors (B-cell lymphoma 2, Bcl-2; Bcl-2 associated X protein, Bax; cleaved [C] capsase-3; phosphoinositide 3-kinase, PI3K; phosphorylated-PI3K, p-PI3K; p-AKT; AKT) were measured with quantitative real-time polymerase chain reaction or Western blot. Target gene of miR-144-3p was predicted by Starbase and TargetScan and confirmed with dual-luciferase reporter assay. Dox caused rat cardiac dysfunction, aggravated cardiac injury, decreased cardiomyocytes viability, and the expression of miR-144-3p, Bcl-2, and phosphorylation of both PI3K and AKT yet the upregulated those of Bax and C caspase-3, which was reversed by upregulating miR-144-3p, whereas downregulating miR-144-3p did oppositely. SOCS2 was the target gene of miR-144-3p, Dox promoted SOCS2 expression, which was reversed by upregulating miR-144-3p, while downregulating miR-144-3p did conversely. In addition, silencing SOCS2 reversed the effects of miR-144-3p downregulation in Dox-treated cardiomyocytes. Upregulating miR-144-3p alleviated Dox-induced cardiac dysfunction and cell apoptosis via targeting SOCS2, providing a novel evidence of miR-144-3p in HF.

SOCS5 contributes to temozolomide resistance in glioblastoma by regulating Bcl-2-mediated autophagy.

Temozolomide (TMZ) is the primary chemotherapeutic drug for treating glioblastoma (GBM); however, the final clinical outcome is considerably limited by the poor response and resistance to TMZ. Although autophagy is thought to be associated with chemotherapy resistance and cancer cell survival, the precise molecular mechanisms underlying this process remain elusive. The suppressor of cytokine signaling (SOCS) family is widely distributed in vivo and exerts a range of effects on tumors; however, the expression pattern and role of SOCS in GBM remains unknown. In this study, we determined that high SOCS5 expression level was associated with poor prognosis and TMZ resistance in GBM. TMZ induced an increase in SOCS5 expression level and upregulated autophagy during the acquisition of drug resistance. The observed increase in the extent of autophagy was mediated by SOCS5. Mechanistically, SOCS5 enhances the transcription of Bcl-2. Knockdown of SOCS5 inhibited TMZ chemoresistance in GBM cells through the inhibition of Bcl-2 recruited autophagy; upregulation of Bcl-2 blocked this effect. In summary, our findings revealed the involvement and underlying mechanism of SOCS5 in TMZ resistance. SOCS5 plays a critical role in GBM chemoresistance and may serve as a novel prognostic marker and therapeutic target for chemotherapeutically treating drug-resistant GBM.

RPL38 knockdown inhibits the inflammation and apoptosis in chondrocytes through regulating METTL3-mediated SOCS2 m6A modification in osteoarthritis.

BACKGROUND: Ribosomal protein L38 (RPL38) was found upregulated in osteoarthritic peripheral blood mononuclear cells, however, its role in progression of osteoarthritis has not been characterized. METHODS: The protein levels of RPL38 and SOCS2 in cartilage tissues from OA patients and controls were detected with Western blotting. IL-1ß was used to stimulate primary chondrocytes to establish an OA cell model, and RPL38 siRNA (si-RPL38) was transfected into chondrocytes to investigate the effect of RPL38 knockdown on cell viability, apoptosis, inflammatory factor secretion and extracellular matrix degradation. Then, the mechanism that RPL38 regulate the SOCS2 expression and SOCS2-induced chondrocyte dysfunction was explored. The methyltransferase-like 3 (METTL3)-mediated m6A modification of SOCS2 mRNA was confirmed, and the interaction of RPL38 and METTL3 was verified. Moreover, the effects of SOCS2 overexpression on IL-1ß-induced chondrocyte dysfunction and SOCS2 knockdown on the restoration of chondrocyte function by siRPL38 were investigated. Finally, RPL38 was knocked down in vivo and its role in OA progression was validated. RESULTS: RPL38 was upregulated and SOCS2 was downregulated in OA cartilages. RPL38 knockdown or SOCS2 overexpression either attenuated IL-1ß-induced chondrocyte apoptosis, inflammatory cytokine secretion, and ECM degradation. RPL38 directly interacted with METTL3 and it inhibited SOCS2 expression through METTL3-mediated m6A modification. SOCS2 knockdown activated the JAK2/STAT3 proinflammatory pathway and reversed the effects of RPL38 knockdown on IL-1ß-induced chondrocyte apoptosis, inflammation and ECM degradation. RPL38 knockdown alleviated cartilage tissue damage and ECM degradation in OA mice. CONCLUSION: RPL38 knockdown inhibited osteoarthritic chondrocyte dysfunction and alleviated OA progression through promoting METTL3-m6A-mediated SOCS2 expression.

BC-Box Motif in SOCS6 Induces Differentiation of Epidermal Stem Cells into GABAnergic Neurons.

The BC-box motif in suppressor of cytokine signaling 6 (SOCS6) promotes the neuronal differentiation of somatic stem cells, including epidermal stem cells. SOCS6 protein belongs to the group of SOCS proteins and inhibits cytokine signaling. Here we showed that epidermal stem cells were induced to differentiate into GABAnergic neurons by the intracellular delivery of a peptide composed of the amino-acid sequences encoded by the BC-box motif in SOCS6 protein. The BC-box motif (SLQYLCRFVI) in SOCS6 corresponded to the binding site of elongin BC. GABAnergic differentiation mediated by the BC-box motif in SOCS6 protein was caused by ubiquitination of JAK2 and inhibition of the JAK2-STAT3 pathway. Furthermore, GABAnergic neuron-like cells generated from epidermal stem cells were transplanted into the brain of a rodent ischemic model. Then, we demonstrated that these transplanted cells were GAD positive and that the cognitive function of the ischemic model rodents with the transplanted cells was improved. This study could contribute to not only elucidating the mechanism of GABAnergic neuronal differentiation but also to neuronal regenerative medicine utilizing GABAnergic neurons.

Induction of SOCS Expression by EV71 Infection Promotes EV71 Replication.

Enterovirus 71 (EV71) is the causative pathogen of hand, foot, and mouth disease (HFMD). However, no effective antiviral therapy is currently available. Some viruses could escape the host's innate immunity by upregulating suppressor of cytokine signaling (SOCS) proteins. Until now, whether EV71 evades the host immune system by regulating the expression of SOCS proteins remains unknown. In this study, we found that EV71 infection promoted SOCS expression at both mRNA and protein levels in vitro and in vivo. Consistently, the infectivity of EV71 was decreased significantly in the SOCS3 or SOCS1 knockdown cells, suggesting that SOCS1 and especially SOCS3 are crucial for EV71 infection. Further investigation showed that SOCS3 promoted virus infection by inhibiting interferon-induced STAT3 phosphorylation. SOCS1 and SOCS3 mRNA expressions were independent on virus-induced type I interferon expression but were blocked by the inhibitor of NF-κB. Therefore, EV71 infection stimulates the expression of SOCS proteins in an interferon-independent way and negatively regulates the JAK/STAT signaling pathway, thus escaping host immunity. All these results may add new information to the mechanism of EV71 in fighting against type I interferon responses.

Galectins regulate the inflammatory response in airway epithelial cells exposed to microbial neuraminidase by modulating the expression of SOCS1 and RIG1.

Influenza patients frequently display increased susceptibility to Streptococcus pneumoniae co-infection and sepsis, the prevalent cause of mortality during influenza pandemics. However, the detailed mechanisms by which an influenza infection predisposes patients to suffer pneumococcal pneumonia are not fully understood. A murine model for influenza infection closely reflects the observations in human patients, since if the animals that have recovered from influenza A virus (IAV) sublethal infection are challenged with S. pneumoniae, they undergo a usually fatal uncontrolled cytokine response. We have previously demonstrated both in vitro and in vivo that the expression and secretion of galectin-1 (Gal1) and galectin-3 (Gal3) are modulated during IAV infection, and that the viral neuraminidase unmasks galactosyl moieties in the airway epithelia. In this study we demonstrate in vitro that the binding of secreted Gal1 and Gal3 to the epithelial cell surface modulates the expression of SOCS1 and RIG1, and activation of ERK, AKT or JAK/STAT1 signaling pathways, leading to a disregulated expression and release of pro-inflammatory cytokines. Our results suggest that the activity of the viral and pneumococcal neuraminidases on the surface of the airway epithelial cells function as a "danger signal" that leads to rapid upregulation of SOCS1 expression to prevent an uncontrolled inflammatory response. The binding of extracellular Gal1 or Gal3 to the galactosyl moieties unmasked on the surface of airway epithelial cells can either "fine-tune" or severely disregulate this process, respectively, the latter potentially leading to hypercytokinemia.

Ac2PIM-responsive miR-150 and miR-143 target receptor-interacting protein kinase 2 and transforming growth factor beta-activated kinase 1 to suppress NOD2-induced immunomodulators.

Specific and coordinated regulation of innate immune receptor-driven signaling networks often determines the net outcome of the immune responses. Here, we investigated the cross-regulation of toll-like receptor (TLR)2 and nucleotide-binding oligomerization domain (NOD)2 pathways mediated by Ac2PIM, a tetra-acylated form of mycobacterial cell wall component and muramyl dipeptide (MDP), a peptidoglycan derivative respectively. While Ac2PIM treatment of macrophages compromised their ability to induce NOD2-dependent immunomodulators like cyclooxygenase (COX)-2, suppressor of cytokine signaling (SOCS)-3, and matrix metalloproteinase (MMP)-9, no change in the NOD2-responsive NO, TNF-α, VEGF-A, and IL-12 levels was observed. Further, genome-wide microRNA expression profiling identified Ac2PIM-responsive miR-150 and miR-143 to target NOD2 signaling adaptors, RIP2 and TAK1, respectively. Interestingly, Ac2PIM was found to activate the SRC-FAK-PYK2-CREB cascade via TLR2 to recruit CBP/P300 at the promoters of miR-150 and miR-143 and epigenetically induce their expression. Loss-of-function studies utilizing specific miRNA inhibitors establish that Ac2PIM, via the miRNAs, abrogate NOD2-induced PI3K-PKCδ-MAPK pathway to suppress ß-catenin-mediated expression of COX-2, SOCS-3, and MMP-9. Our investigation has thus underscored the negative regulatory role of Ac2PIM-TLR2 signaling on NOD2 pathway which could broaden our understanding on vaccine potential or adjuvant utilities of Ac2PIM and/or MDP.

Serine 307 on insulin receptor substrate 1 is required for SOCS3 and TNF-α signaling in the rMC-1 cell line.

PURPOSE: To establish the key insulin receptor substrate 1 (IRS-1) structural elements required in this insulin regulatory pathway, we investigated the effects of substituting alanine for serine 307 in IRS-1 on the ability of tumor necrosis factor-α (TNF-α) and a related mediator, suppressor of cytokine signaling 3 (SOCS3), to phosphorylate IRS-1 and regulate insulin signaling in the rat retinal Müller cell (rMC-1) cell line. METHODS: rMC-1 cells were grown in normal (5 mM) or high (25 mM) glucose medium and transfected with either normal IRS-1(Ser307)plasmid or a mutated IRS-1(Ser307Ala) plasmid. Cells were also treated with recombinant TNF-α or SOCS3 to induce increased levels of these proteins. RESULTS: In cells with IRS-1(Ser307Ala), TNF-α and SOCS3 failed to phosphorylate IRS-1. Likewise, resulting downstream effects, including changes in phosphorylation of insulin receptor(Tyr960), antiapoptotic Akt phosphorylation, and proapoptotic cleavage of caspase 3 were also blocked. We also report for the first time that SOCS3 and TNF-α are reciprocally stimulatory leading to a mutual enhancement of levels of both factors, thus forming a potential positive feedback loop that contributes to insulin receptor resistance. CONCLUSIONS: Increases in TNF-α and SOCS3 are triggered by high glucose and through reciprocal stimulation of expression of these two factors, which in turn could be major drivers of insulin resistance and related cell death. The demonstration that a single phosphorylation site is key for these pathways suggests that drugs targeted to this site might be effective in protecting against diabetic damage to the retina.

Suppressor of cytokine signaling 1-derived peptide inhibits Janus kinase/signal transducers and activators of transcription pathway and improves inflammation and atherosclerosis in diabetic mice.

OBJECTIVE: Activation of Janus kinase/signal transducers and activators of transcription (STAT) pathway by hyperglycemia and dislypidemia contributes to the progression of diabetic complications, including atherosclerosis. Suppressor of cytokine signaling (SOCS) proteins negatively regulate Janus kinase/STAT and have emerged as promising target for anti-inflammatory therapies. We investigated whether a cell-permeable lipopeptide corresponding to the kinase inhibitory region of SOCS1 could reduce atherosclerosis in diabetic mice and identified the mechanisms involved. APPROACH AND RESULTS: Streptozotocin-induced diabetic apolipoprotein E-deficient mice (aged 8 and 22 weeks) were given intraperitoneal injections of vehicle, SOCS1-derived peptide, or control mutant peptide for 6 to 10 weeks. SOCS1 therapy suppressed STAT1/STAT3 activation in atherosclerotic plaques of diabetic mice and significantly reduced lesion size at both early and advanced stages of lesion development compared with vehicle group. Plaque characterization demonstrated that SOCS1 peptide decreased the accumulation of lipids, macrophages, and T lymphocytes, whereas increasing collagen and smooth muscle cell content. This atheroprotective effect was accompanied by systemic (reduced proinflammatory Ly6C(high) monocytes and splenic cytokine expression) and local (reduced aortic expression of chemokines and cytokines) mechanisms, without impact on metabolic parameters. In vitro, SOCS1 peptide dose dependently inhibited STAT1/STAT3 activation and target gene expression in vascular smooth muscle cells and macrophages and also suppressed cytokine-induced cell migration and adhesion processes. CONCLUSIONS: SOCS1-based targeting Janus kinase/STAT restrains key mechanisms of atherogenesis in diabetic mice, thereby preventing plaque formation and increasing plaque stability. Approaches to mimic native SOCS1 functions may have a therapeutic potential to retard the progression of diabetic complications.

Suppressor of cytokine signaling 1 inhibits apoptosis of islet grafts through caspase 3 and apoptosis-inducing factor pathways in rats.

A significant portion of pancreatic islet grafts can be destroyed by apoptosis, failing to engraft in the early period after transplantation. Recently, we observed that overexpression of suppressor of cytokine signaling 1 (SOCS1) in islet grafts achieved an antiapoptotic effect, prolonging graft survival in a rat transplant model. Caspase 3 is the central executioner caspase that is activated by upstream cascades in a caspase-dependent apoptosis pathway. Apoptosis inducing factor (AIF) is a key protein that can be released from mitochondria, translocating to the nucleus in the caspase-independent apoptosis pathway. In this study, we investigated whether these two pathways were involved in cytoprotection afforded by SOCS1 on islet grafts. We used a chimeric adenovirus vector (Ad5F35-SOCS1) to enhance SOCS1 expression in isolated Sprague-Dawley rat islets, which were transplanted into recipients experiencing streptozotocin-induced diabetes. We analyzed the expressions of active (cleaved) caspase 3 and AIF on islets. The Ad5F35-SOCS1-infected islets with higher SOCS1 expression showed decreased levels of active caspase 3 and intranuclear AIF after treatment with tumor necrosis factor-α and cycloheximide in vitro. The diabetic recipients transplanted with Ad5F35-SOCS1-infected islets showed longer periods of normoglycemia versus recipients transplanted with mock-infected islets (P < .05) due to prolonged graft survival. A histological analysis indicated that the Ad5F35-SOCS1-infected islet grafts displayed decreased caspase 3 activation and AIF translocation (to nucleus) in the early posttransplant period. These results demonstrated that the expression of SOCS1 in islet grafts protected them from apoptosis through caspase 3 dependent and AIF caspase-independent-pathways.

SOCS3 inhibits insulin signaling in porcine primary adipocytes.

Insulin resistance is a major player in the pathogenesis of type II diabetes, the metabolic syndrome, and obesity. SOCS3 plays an important role in the development of insulin resistance. To investigate the role of SOCS3 in porcine adipocyte insulin signaling, we first detected the effect of insulin on SOCS3 mRNA and protein expression in porcine primary adipocytes by real-time RT-PCR and Western blotting. Then, we constructed a recombinant adenovirus encoding SOCS3 gene (Ad-SOCS3) which was used to infect differentiated porcine primary adipocytes for 3 days. The expression and phosphorylation of main insulin signaling components were detected by Western blotting. The results showed that 100 nM insulin could induce SOCS3 mRNA expression but not protein expression, and overexpression of SOCS3 decreased IRS1 protein level, insulin-stimulated IRS1 tyrosine phosphorylation, PI3K activation, and Akt phosphorylation, but increased IRS1 serine phosphorylation in porcine primary adipocytes. These results indicate that SOCS3 is an important negative regulator of insulin signaling in porcine adipocytes. Thus, SOCS3 may be a novel therapeutic target for the prevention or treatment of insulin resistance and type II diabetes.

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

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

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.

Transfer of suppressor of cytokine signaling 3 by an oncolytic adenovirus induces potential antitumor activities in hepatocellular carcinoma.

UNLABELLED: The constitutive activation of signal transducer and activator of transcription 3 (STAT3) participates in carcinogenesis through up-regulation of genes encoding apoptosis inhibitors and cell cycle regulators, such as Bcl-xL, cyclins D1 and D2, and c-myc. Suppressor of cytokine signaling 3 (SOCS3) is one of the negative regulators of cytokine signaling and is frequently silenced in diverse cancers. In this study, we explored whether restoration of SOCS3 by oncolytic adenoviral vectors could inhibit the constitutive activation of the Janus kinase/STAT pathway and suppress tumor growth. Our data showed that SOCS3 was down-expressed in all liver tumor cell lines. The incorporation of SOCS3 or SOCS3 fused with cell-penetrating peptides (cpp-SOCS3) did not alter adenoviral replication selectively in liver tumor cells. The infection of cells with adenovirus CN305 (AdCN305)-SOCS3 and AdCN305-cpp-SOCS3 resulted in dramatic cytotoxicity in liver tumor cells. However, no cytotoxic effect was observed in normal cells infected with these vectors. Infection of liver tumor cells with AdCN305-SOCS3 and AdCN305-cpp-SOCS3 resulted in nearly complete inhibition of STAT3 phosphorylation and down-regulation of cyclin D1 and Bcl-xL. Treatment of the established tumor by AdCN305-SOCS3 and AdCN305-cpp-SOCS3 caused significant suppression of tumor growth. The suppression of tumor growth was due to the inhibition of STAT3 phosphorylation and induction of tumor cell death. CONCLUSION: This study suggests that transfer of SOCS3 by an oncolytic adenovirus represents a potent approach for cancer therapy.

Induction of suppressors of cytokine signaling (SOCS) in the retina during experimental autoimmune uveitis (EAU): potential neuroprotective role of SOCS proteins.

Suppressors of cytokine signaling (SOCS) are implicated in immunopathogenic mechanisms of autoimmune diseases. We show here that SOCS expression in retina is temporarily correlated with progression of experimental autoimmune uveitis (EAU), an organ-specific autoimmune disease that serves as model of human uveitis. Peak of EAU correlates with highest SOCS genes expression while disease resolution coincides with their down-regulation. Surprisingly, SOCS5 is constitutively expressed in retina. SOCS5 expression increases significantly during EAU and remains elevated even after disease resolution. Our data suggest that cytokine-inducible SOCS members may be involved in negative regulation of inflammatory cytokines activities during EAU, while constitutively expressed SOCS5 may have neuroprotective functions.

Intracellular protein therapy with SOCS3 inhibits inflammation and apoptosis.

Suppressor of cytokine signaling (SOCS) 3 attenuates proinflammatory signaling mediated by the signal transducer and activator of transcription (STAT) family of proteins. But acute inflammation can occur after exposure to pathogen-derived inducers staphylococcal enterotoxin B (SEB) and lipopolysaccharide (LPS), or the lectin concanavalin A (ConA), suggesting that physiologic levels of SOCS3 are insufficient to stem proinflammatory signaling under pathogenic circumstances. To test this hypothesis, we developed recombinant cell-penetrating forms of SOCS3 (CP-SOCS3) for intracellular delivery to counteract SEB-, LPS- and ConA-induced inflammation. We found that CP-SOCS3 was distributed in multiple organs within 2 h and persisted for at least 8 h in leukocytes and lymphocytes. CP-SOCS3 protected animals from lethal effects of SEB and LPS by reducing production of inflammatory cytokines and attenuating liver apoptosis and hemorrhagic necrosis. It also reduced ConA-induced liver apoptosis. Thus, replenishing the intracellular stores of SOCS3 with CP-SOCS3 effectively suppresses the devastating effects of acute inflammation.