Suppressor of Cytokine Signaling-3 Inhibits Interleukin-1 Signaling by Targeting the TRAF-6/TAK1 Complex

Regulation of SOCS3-STAT3 in urate-induced cytokine production in human myeloid cells

OBJECTIVE

Hyperuricaemia is necessary for gout. High urate concentrations have been linked to inflammation in mononuclear cells. Here, we explore the role of the suppressor of cytokine signaling 3 (SOCS3) in urate-induced inflammation.

METHODS

Peripheral blood mononuclear cells (PBMCs) from gout patients, hyperuricemic and normouricemic individuals were cultured for 24h with varying concentrations of soluble urate, followed by 24h restimulation with lipopolysaccharides (LPS)±monosodium urate (MSU) crystals. Transcriptomic profiling was performed using RNA-Sequencing. DNA methylation was assessed using Illumina Infinium® MethylationEPIC BeadChip system (EPIC array). Phosphorylation of signal transducer and activator of transcription 3 (STAT3) was determined by flow cytometry. Cytokine responses were also assessed in PBMCs from patients with JAK2 V617F tyrosine kinase mutation.

RESULTS

PBMCs pre-treated with urate produced more interleukin-1beta (IL-1β) and interleukin-6 (IL-6) and less interleukin-1 receptor anatagonist (IL-1Ra) after LPS simulation. In vitro, urate treatment enhanced SOCS3 expression in control monocytes but no DNA methylation changes were observed at the SOCS3 gene. A dose-dependent reduction in phosphorylated STAT3 concomitant with a decrease in IL-1Ra was observed with increasing concentrations of urate. PBMCs with constitutively activated STAT3 (JAK2 V617F mutation) could not be primed by urate.

CONCLUSION

In vitro, urate exposure increased SOCS3 expression, while urate priming, and subsequent stimulation resulted in decreased STAT3 phosphorylation and IL-1Ra production. There was no evidence that DNA methylation constitutes a regulatory mechanism of SOCS3. Elevated SOCS3 and reduced pSTAT3 could play a role in urate-induced hyperinflammation since urate priming had no effect in PBMCs from patients with constitutively activated STAT3.

Characterization and functional analysis of SOCS9 from orange-spotted grouper (Epinephelus coioides) during virus infection

The suppressor of cytokine signaling (SOCS) proteins family have twelve members including eight known mammalian SOCS members (CISH, SOCS1-7) and four new discovery members (SOCS3b, SOCS5b, SOCS8 and SOCS9) that is regarded as a classic feedback inhibitor of cytokine signaling. Although the function of the mammalian SOCS proteins have been well studied, little is known about the roles of SOCS in fish during viral infection. In this study, the molecular characteristics of SOCS9 from orange-spotted grouper (Epinephelus coioides, EcSOCS9) is investigated. The EcSOCS9 protein encoded 543 amino acids with typical SH2 (389-475aa) and SOCS_box (491-527aa), sharing high identities with reported fish SOCS9. EcSOCS9 was expressed in all detected tissues and highly expressed in kidney. After red-spotted grouper nervous necrosis virus (RGNNV) infection, the expression of EcSOCS9 was significantly induced in vitro. Furthermore, EcSOCS9 overexpression enhanced RGNNV replication, promoted virus-induced mitophagy that evidenced by the increased level of LC3-Ⅱ, BCL2, PGAM5 and decreased level of BNIP3 and FUNDC1. Besides, EcSOCS9 overexpression suppressed the expression levels of ATP6, CYB, ND4, ATP level and induced ROS level. The expression levels of interferon (IFN) related factors (IRF1, IRF3, IRF7, P53), inflammatory factors (IL1-β, IL8, TLR2, TNF-α) and IFN-3, ISRE, NF-κB, AP1 activities were also reduced by overexpressing EcSOCS9. These date suggests that EcSOCS9 impacts RGNNV infection through modulating mitophagy, regulating the expression levels of IFN- related and inflammatory factors, which will expand our understanding of fish immune responses during viral infection.

P2Y11/IL-1 receptor crosstalk controls macrophage inflammation: a novel target for anti-inflammatory strategies?

Although first cloning of the human ATP receptor P2Y11 was successful 25 years ago, the exact downstream signaling pathways of P2Y11 receptor, which can couple to Gq and Gs proteins, have remained unclear. Especially the lack of rodent models as well as the limited availability of antibodies and pharmacological tools have hampered examination of P2Y11 expression and function. Many meaningful observations related to P2Y11 have been made in primary immune cells, indicating that P2Y11 receptors are important regulators of inflammation and cell migration, also by controlling mitochondrial activity. Our recent studies have shown that P2Y11 is upregulated during macrophage development and activates signaling through IL-1 receptor, which is well known for its ability to direct inflammatory and migratory processes. This review summarizes the results of the first transcriptomic and secretomic analyses of both, ectopic and native P2Y11 receptors, and discusses how P2Y11 crosstalk with the IL-1 receptor may govern anti-inflammatory and pro-angiogenic processes in human M2 macrophages.

RNA Sequencing (RNA-Seq) Analysis Reveals Liver Lipid Metabolism Divergent Adaptive Response to Low- and High-Salinity Stress in Spotted Scat (Scatophagus argus)

Spotted scat (Scatophagus argus) can tolerate a wide range of salinity fluctuations. It is a good model for studying environmental salinity adaptation. Lipid metabolism plays an important role in salinity adaptation in fish. To elucidate the mechanism of lipid metabolism in the osmoregulation, the liver transcriptome was analyzed after 22 d culture with a salinity of 5 ppt (Low-salinity group: LS), 25 ppt (Control group: Ctrl), and 35 ppt (High-salinity group: HS) water by using RNA sequencing (RNA-seq) in spotted scat. RNA-seq analysis showed that 1276 and 2768 differentially expressed genes (DEGs) were identified in the LS vs. Ctrl and HS vs. Ctrl, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the pathways of steroid hormone biosynthesis, steroid biosynthesis, glycerophospholipid metabolism, glycerolipid metabolism, and lipid metabolism were significantly enriched in the LS vs. Ctrl. The genes of steroid biosynthesis (sqle, dhcr7, and cyp51a1), steroid hormone biosynthesis (ugt2a1, ugt2a2, ugt2b20, and ugt2b31), and glycerophospholipid metabolism (cept1, pla2g4a, and ptdss2) were significantly down-regulated in the LS vs. Ctrl. The pathways related to lipid metabolisms, such as fatty acid metabolism, fatty acid biosynthesis, peroxisome proliferator-activated receptor (PPAR) signaling pathway, adipocytokine signaling pathway, fatty acid degradation, and unsaturated fatty acid biosynthesis, were significantly enriched in the HS vs. Ctrl. The genes of unsaturated fatty acid biosynthesis (scd1, hacd3, fads2, pecr, and elovl1) and adipocytokine signaling pathway (g6pc1, socs1, socs3, adipor2, pck1, and pparα) were significantly up-regulated in the HS vs. Ctrl. These results suggest that the difference in liver lipid metabolism is important to adapt to low- and high-salinity stress in spotted scat, which clarifies the molecular regulatory mechanisms of salinity adaptation in euryhaline fish.

Opening KATP channels induces inflammatory tolerance and prevents chronic pain

Current treatments for chronic pain are unsatisfactory, therefore, new therapeutics are urgently needed. Our previous study indicated that K_ATP channel openers have analgesic effects, but the underlying mechanism has not been elucidated. We speculated that K_ATP channel openers might increase suppressor of cytokine signaling (SOCS)-3 expression to induce inflammatory tolerance and attenuate chronic pain. Postoperative pain was induced by plantar incision to establish a chronic pain model. Growth arrest-specific 6 (Gas6)^-/- and Axl^-/- mice were used for signaling studies. The microglia cell line BV-2 was cultured for the in vitro experiments. The K_ATP channel opener significantly attenuated incision-induced mechanical allodynia in mice associated with the upregulated expression of SOCS3. Opening K_ATP channels induced the expression of SOCS3 in the Gas6/Axl signaling pathway in microglia, inhibited incision-induced mechanical allodynia by activating the Gas6/Axl-SOCS3 signaling pathway, and induced inflammatory tolerance to relieve neuroinflammation and postoperative pain. We demonstrated that opening of the K_ATP channel opening activated Gas6/Axl/SOCS3 signaling to induce inflammatory tolerance and relieve chronic pain. We explored a new target for anti-inflammatory and analgesic effects by regulating the innate immune system and provided a theoretical basis for clinical preemptive analgesia.

The P2Y11 receptor of human M2 macrophages activates canonical and IL-1 receptor signaling to translate the extracellular danger signal ATP into anti-inflammatory and pro-angiogenic responses

The cytoprotective ATP receptor P2Y₁₁ is upregulated during M2 macrophage differentiation and contributes to the anti-inflammatory properties of this macrophage subset. Here, we studied P2Y₁₁-induced reprogramming of human M2 macrophages at the level of mRNA and protein expression. Upregulation of IL-1 receptor (IL-1R) and its known downstream effectors VEGF, CCL20 and SOCS3 as well as downregulation of the ATP-degrading ecto-ATPase CD39 emerged as hallmarks of P2Y₁₁ activation. The anti-inflammatory signature of the P2Y₁₁ transcriptome was further characterized by the downregulation of P2RX7, toll-like receptors and inflammasome components. P2Y₁₁-induced IL-1R upregulation formed the basis for reinforced IL-1 responsiveness of activated M2 macrophages, as IL-1α and IL-1ß each enhanced P2Y₁₁-induced secretion of VEGF and CCL20 as well as the previously reported shedding of soluble tumor necrosis factor receptor 2 (sTNFR2). Raising intracellular cyclic AMP (cAMP) in M2 macrophages through phosphodiesterase 4 inhibition enhanced P2Y₁₁-driven responses. The cAMP-binding effector, exchange protein activated by cAMP 1 (Epac1), which is known to induce SOCS3, differentially regulated the P2Y₁₁/IL-1R response because pharmacological Epac1 inhibition enhanced sTNFR2 and CCL20 release, but had no effect on VEGF secretion. In addition to cAMP, calcium and protein kinase C participated in P2Y₁₁ signaling. Our study reveals how P2Y₁₁ harnesses canonical and IL-1R signaling to promote an anti-inflammatory and pro-angiogenic switch of human M2 macrophages, which may be controlled in part by an Epac1-SOCS3 axis.

S100A9 and SOCS3 as diagnostic biomarkers of acute myocardial infarction and their association with immune infiltration

Acute myocardial infarction (AMI) is one of the leading causes of death globally, with a mortality rate of over 20%. However, the diagnostic biomarkers frequently used in current clinical practice have limitations in both sensitivity and specificity, likely resulting in delayed diagnosis. This study aimed to identify potential diagnostic biomarkers for AMI and explored the possible mechanisms involved. Datasets were retrieved from the Gene Expression Omnibus. First, we identified differentially expressed genes (DEGs) and preserved modules, from which we identified candidate genes by LASSO (least absolute shrinkage and selection operator) regression and the SVM-RFE (support vector machine-recursive feature elimination) algorithm. Subsequently, we used ROC (receiver operating characteristic) analysis to evaluate the diagnostic accuracy of the candidate genes. Thereafter, functional enrichment analysis and an analysis of immune infiltration were implemented. Finally, we assessed the association between biomarkers and biological processes, infiltrated cells, clinical traits, tissues and time points. We identified nine preserved modules containing 1,016 DEGs and managed to construct a diagnostic model with high accuracy (GSE48060: AUC = 0.923; GSE66360: AUC = 0.973) incorporating two genes named S100A9 and SOCS3. Functional analysis revealed the pivotal role of inflammation; immune infiltration analysis indicated that eight cell types (monocytes, epithelial cells, neutrophils, CD8+ T cells, Th2 cells, NK cells, NKT cells and platelets) were likely involved in AMI. Furthermore, we observed that S100A9 and SOCS3 were correlated with inflammation, variably infiltrated cells, clinical traits of patients, sampling tissues and sampling time points. In conclusion, we suggested S100A9 and SOCS3 as diagnostic biomarkers of AMI and discovered their association with inflammation, infiltrated immune cells and other factors.

Paeoniflorin Inhibits ASK1-TF Axis by Up-Regulating SOCS3 to Alleviate Radiation Enteritis

Radiation enteritis is one of the main adverse effects of radiotherapy, presenting with a poorly understood etiology and limited options for therapy. Intestinal inflammation and ischemia are the core mechanisms of radiation enteritis. Suppressor of cytokine signaling 3 (SOCS3) is an endogenous “inflammation brake.” We hypothesized that paeoniflorin, a pinane monoterpene bitter glycoside, could increase SOCS3 expression to reduce inflammation and ischemia and improve enteritis in mice. Laser Doppler flowmetry was used to detect changes in intestinal blood flow. RAW264.7 and human umbilical vein endothelial cells were used to investigate the mechanism of action of paeoniflorin. It was observed that radiation caused high mortality, intestinal inflammatory responses, and low blood flow in mice. Paeoniflorin effectively alleviated intestinal atrophy, prevented thrombosis, improved radiation enteritis, and reduced mortality in mice undergoing radiotherapy. In addition, paeoniflorin increased the release of growth arrest-specific gene 6 (Gas6) and phosphorylation of the Axl receptor, subsequently inducing the expression of SOCS3 and inhibiting the expression of p-apoptosis signal-regulating kinase 1 and tissue factor in vivo and in vitro. Based on our findings, we suggest that paeoniflorin is potentially effective in alleviating radiation enteritis via the activation of the Gas6/Axl/SOCS3 axis and subsequent reduction in intestinal inflammation and ischemia.

AMPK-autophagy-mediated inhibition of microRNA-30a-5p alleviates morphine tolerance via SOCS3-dependent neuroinflammation suppression

BACKGROUND

The development of morphine tolerance is a clinical challenge for managing severe pain. Studies have shown that neuroinflammation is a critical aspect for the development of analgesic tolerance. We found that AMPK-autophagy activation could suppress neuroinflammation and improve morphine tolerance via the upregulation of suppressor of cytokine signaling 3 (SOCS3) by inhibiting the processing and maturation of microRNA-30a-5p.

METHODS

CD-1 mice were utilized for the tail-flick test to evaluate morphine tolerance. The microglial cell line BV-2 was utilized to investigate the mechanism of AMPK-autophagy-mediated posttranscriptional regulation of SOCS3. Proinflammatory cytokines were measured by western blotting and real-time PCR. The levels of SOCS3 and miRNA-processing enzymes were evaluated by western blotting, real-time PCR and immunofluorescence staining.

RESULTS

Based on experimental verification, miRNA-30a-5p could negatively regulate SOCS3. The AMPK activators AICAR, resveratrol and metformin downregulated miRNA-30a-5p. We found that AMPK activators specifically inhibited the processing and maturation of miRNA-30a-5p in microglia by degrading DICER and AGO2 via autophagy. Furthermore, a miRNA-30a-5p inhibitor significantly improved morphine tolerance via upregulation of SCOS3 in mice. It markedly increased the level of SOCS3 in the spinal cord of mice and subsequently inhibited morphine-induced phosphorylation of NF-κB p65. In addition, a miRNA-30a-5p inhibitor decreased the levels of IL-1β and TNF-α caused by morphine in microglia.

CONCLUSION

AMPK-autophagy activation suppresses neuroinflammation and improves morphine tolerance via the upregulation of SOCS3 by inhibiting miRNA-30a-5p.

Lidocaine Alleviates Sepsis-Induced Acute Lung Injury in Mice by Suppressing Tissue Factor and Matrix Metalloproteinase-2/9

Acute lung injury (ALI) is one of the fatal symptoms of sepsis. However, there were no effective clinical treatments. TF accumulation-induced fibrin deposit formations and coagulation abnormalities in pulmonary vessels contribute to the lethality of ALI. Suppressor of cytokine signaling 3 (SOCS3) acts as an endogenous negative regulator of the TLR4/TF pathway. We hypothesized that inducing SOCS3 expression using lidocaine to suppress the TLR4/TF pathway may alleviate ALI. Hematoxylin and eosin (H&E), B-mode ultrasound, and flow cytometry were used to measure the pathological damage of mice. Gelatin zymography was used to measure matrix metalloproteinase-2/9 (MMP-2/9) activities. Western blot was used to assay the expression of protein levels. Here, we show that lidocaine could increase the survival rate of ALI mice and ameliorate the lung injury of ALI mice including reducing the edema, neutrophil infiltration, and pulmonary thrombosis formation and increasing blood flow velocity. Moreover, in vitro and in vivo, lidocaine could increase the expression of p-AMPK and SOCS3 and subsequently decrease the expression of p-ASK1, p-p38, TF, and the activity of MMP-2/9. Taken together, our study demonstrated that lidocaine could inhibit the TLR4/ASK1/TF pathway to alleviate ALI via activating AMPK-SOCS3 axis.

Unravelling the Immunomodulatory Effects of Viral Ion Channels, towards the Treatment of Disease

The current COVID-19 pandemic has highlighted the need for the research community to develop a better understanding of viruses, in particular their modes of infection and replicative lifecycles, to aid in the development of novel vaccines and much needed anti-viral therapeutics. Several viruses express proteins capable of forming pores in host cellular membranes, termed "Viroporins". They are a family of small hydrophobic proteins, with at least one amphipathic domain, which characteristically form oligomeric structures with central hydrophilic domains. Consequently, they can facilitate the transport of ions through the hydrophilic core. Viroporins localise to host membranes such as the endoplasmic reticulum and regulate ion homeostasis creating a favourable environment for viral infection. Viroporins also contribute to viral immune evasion via several mechanisms. Given that viroporins are often essential for virion assembly and egress, and as their structural features tend to be evolutionarily conserved, they are attractive targets for anti-viral therapeutics. This review discusses the current knowledge of several viroporins, namely Influenza A virus (IAV) M2, Human Immunodeficiency Virus (HIV)-1 Viral protein U (Vpu), Hepatitis C Virus (HCV) p7, Human Papillomavirus (HPV)-16 E5, Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) Open Reading Frame (ORF)3a and Polyomavirus agnoprotein. We highlight the intricate but broad immunomodulatory effects of these viroporins and discuss the current antiviral therapies that target them; continually highlighting the need for future investigations to focus on novel therapeutics in the treatment of existing and future emergent viruses.

Toll-like receptor 3 (TLR3) regulation mechanisms and roles in antiviral innate immune responses

Toll-like receptor 3 (TLR3) is a member of the TLR family, mediating the transcriptional induction of type I interferons (IFNs), proinflammatory cytokines, and chemokines, thereby collectively establishing an antiviral host response. Studies have shown that unlike other TLR family members, TLR3 is the only RNA sensor that is utterly dependent on the Toll-interleukin-1 receptor (TIR)‍-domain-containing adaptor-inducing IFN-‍β (TRIF). However, the details of how the TLR3-TRIF signaling pathway works in an antiviral response and how it is regulated are unclear. In this review, we focus on recent advances in understanding the antiviral mechanism of the TRIF pathway and describe the essential characteristics of TLR3 and its antiviral effects. Advancing our understanding of TLR3 may contribute to disease diagnosis and could foster the development of novel treatments for viral diseases.

Inhibitory feedback control of NF-κB signalling in health and disease

Cells must adapt to changes in their environment to maintain cell, tissue and organismal integrity in the face of mechanical, chemical or microbiological stress. Nuclear factor-κB (NF-κB) is one of the most important transcription factors that controls inducible gene expression as cells attempt to restore homeostasis. It plays critical roles in the immune system, from acute inflammation to the development of secondary lymphoid organs, and also has roles in cell survival, proliferation and differentiation. Given its role in such critical processes, NF-κB signalling must be subject to strict spatiotemporal control to ensure measured and context-specific cellular responses. Indeed, deregulation of NF-κB signalling can result in debilitating and even lethal inflammation and also underpins some forms of cancer. In this review, we describe the homeostatic feedback mechanisms that limit and ‘re-set’ inducible activation of NF-κB. We first describe the key components of the signalling pathways leading to activation of NF-κB, including the prominent role of protein phosphorylation and protein ubiquitylation, before briefly introducing the key features of feedback control mechanisms. We then describe the array of negative feedback loops targeting different components of the NF-κB signalling cascade including controls at the receptor level, post-receptor signalosome complexes, direct regulation of the critical ‘inhibitor of κB kinases’ (IKKs) and inhibitory feedforward regulation of NF-κB-dependent transcriptional responses. We also review post-transcriptional feedback controls affecting RNA stability and translation. Finally, we describe the deregulation of these feedback controls in human disease and consider how feedback may be a challenge to the efficacy of inhibitors.

The role of SOCS proteins in the development of virus- induced hepatocellular carcinoma

Background

Liver cancer has become one of the most common cancers and has a high mortality rate. Hepatocellular carcinoma is one of the most common liver cancers, and its occurrence and development process are associated with chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections.

Main body

The serious consequences of chronic hepatitis virus infections are related to the viral invasion strategy. Furthermore, the viral escape mechanism has evolved during long-term struggles with the host. Studies have increasingly shown that suppressor of cytokine signaling (SOCS) proteins participate in the viral escape process. SOCS proteins play an important role in regulating cytokine signaling, particularly the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway. Cytokines stimulate the expression of SOCS proteins, in turn, SOCS proteins inhibit cytokine signaling by blocking the JAK-STAT signaling pathway, thereby achieving homeostasis. By utilizing SOCS proteins, chronic hepatitis virus infection may destroy the host’s antiviral responses to achieve persistent infection.

Conclusions

This review provides recent knowledge regarding the role of SOCS proteins during chronic hepatitis virus infection and provides some new ideas for the future treatment of chronic hepatitis.

Suppressors of cytokine signaling (SOCS) proteins in inflammatory bone disorders

Suppressor of cytokine signaling (SOCS) proteins are significant regulators of cellular immune responses. Therefore, the role of SOCS in bone-inflammatory disorders, including arthritis and periodontitis, has been investigated in experimental and clinical conditions. Recent evidence shows that SOCS proteins are expressed in major bone-related cells, including osteoblasts, osteoclasts, chondrocytes and synoviocytes, although their direct role in these cells is not fully described. These signaling molecules, especially SOCS1, 2 and 3, were shown to play critical roles in the control of bone resorption associated to inflammation. This review focuses on the involvement of SOCS proteins in inflammatory bone remodeling, including their direct and indirect role in the control of osteoclast hyperactivation, during arthritis and periodontitis. The description of the roles of SOCS proteins in inflammatory bone diseases highlights the pathways involved in the pathophysiology of these conditions and, thus, may contribute to the development and improvement of potential therapeutic interventions.

SOCS Proteins Participate in the Regulation of Innate Immune Response Caused by Viruses

The host immune system has multiple innate immune receptors that can identify, distinguish and react to viral infections. In innate immune response, the host recognizes pathogen-associated molecular patterns (PAMP) in nucleic acids or viral proteins through pathogen recognition receptors (PRRs), especially toll-like receptors (TLRs) and induces immune cells or infected cells to produce type I Interferons (IFN-I) and pro-inflammatory cytokines, thus when the virus invades the host, innate immunity is the earliest immune mechanism. Besides, cytokine-mediated cell communication is necessary for the proper regulation of immune responses. Therefore, the appropriate activation of innate immunity is necessary for the normal life activities of cells. The suppressor of the cytokine signaling proteins (SOCS) family is one of the main regulators of the innate immune response induced by microbial pathogens. They mainly participate in the negative feedback regulation of cytokine signal transduction through Janus kinase signal transducer and transcriptional activator (JAK/STAT) and other signal pathways. Taken together, this paper reviews the SOCS proteins structures and the function of each domain, as well as the latest knowledge of the role of SOCS proteins in innate immune caused by viral infections and the mechanisms by which SOCS proteins assist viruses to escape host innate immunity. Finally, we discuss potential values of these proteins in future targeted therapies.

Sinomenine Inhibited Interleukin-1β-Induced Matrix Metalloproteinases Levels via SOCS3 Up-Regulation in SW1353 Cells

Matrix metalloproteinases (MMPs) are required for collagen degradation which play a key pathological role in arthritis progression. Herein, the effect of sinomenine (SN) on Interleukin 1 beta (IL-1β)-induced MMPs production and its underlying mechanism were explored in SW1353 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that 200 and 400 µM SN significantly inhibited SW1353 cell proliferation, thus the lower dose of SN (25-100 µM) were used in the subsequent experiments. Notably, the increased mRNA and protein levels of suppressor of cytokine signaling (SOCS) 3 were dose-dependently induced by SN. SN significantly suppressed mRNA and protein levels of MMPs in IL-1β-induced SW1353 cells. Through Western blot analysis, SN showed inhibitory effect on IL-1β-induced TAK1 and p65 phosphorylation. Moreover, SN blocked the interaction of TRAF6 and TAK1 resulting in inactivation of IL-1β pathway. Mechanistically, the inhibitory effect of SN on MMPs levels alongside TRAF6 and TAK1 interactions was abrogated by silencing SOCS3. Moreover, SN did not inhibit TAK1 kinase activity. In TAK1 silencing cells, the levels of MMPs and p65 phosphorylation of SN-treatedcells were lower than dimethyl sulfoxide (DMSO)-treated cells, indicating that blocking interaction was not a unique way for SN to inhibit MMPs levels. Finally, SN significantly inhibited IL-6-induced Janus tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) phosphorylation in SW1353 cells. The levels of JAK2 phosphorylation and MMPs did not show a significant difference between IL-6 + SOCS3-small interfering RNA (siRNA) + SN group and IL-6 + SOCS3-siRNA + DMSO group. These findings demonstrated that SOCS3 expression was increased by SN blocked IL-1β-induced interaction between TRAF6 and TAK1 as well as IL-6 pathway activation, thereby culminating in the inhibition of MMPs levels.

Ubiquitination of interleukin-1α is associated with increased pro-inflammatory polarization of murine macrophages deficient in the E3 ligase ITCH

Macrophages play critical roles in homeostasis and inflammation. Macrophage polarization to either a pro-inflammatory or anti-inflammatory status is controlled by activating inflammatory signaling pathways. Ubiquitination is a posttranslational modification that regulates these inflammatory signaling pathways. However, the influence of protein ubiquitination on macrophage polarization has not been well studied. We hypothesized that the ubiquitination status of key proteins in inflammatory pathways contributes to macrophage polarization, which is regulated by itchy E3 ubiquitin ligase (ITCH), a negative regulator of inflammation. Using ubiquitin proteomics, we found that ubiquitination profiles are different among polarized murine macrophage subsets. Interestingly, interleukin-1α (IL-1α), an important pro-inflammatory mediator, was specifically ubiquitinated in lipopolysaccharide-induced pro-inflammatory macrophages, which was enhanced in ITCH-deficient macrophages. The ITCH-deficient macrophages had increased levels of the mature form of IL-1α and exhibited pro-inflammatory polarization, and reduced deubiquitination of IL-1α protein. Finally, IL-1α neutralization attenuated pro-inflammatory polarization of the ITCH-deficient macrophages. In conclusion, ubiquitination of IL-1α is associated with increased pro-inflammatory polarization of macrophages deficient in the E3 ligase ITCH.

MerTK negatively regulates Staphylococcus aureus induced inflammatory response via SOCS1/SOCS3 and Mal

OBJECTIVE

Staphylococcus aureus (S. aureus), one of Gram-positive pathogen, is frequently associated with acute lung inflammation. The central feature of S. aureus acute lung inflammation are pulmonary dysfunctioning and impeded host defence response, which cause failure in inflammatory cytokines homeostasis and leads to serious tissue damage. However, the role of the Mer receptor tyrosine kinase (MerTK) in the lung following S. aureus infection remains elusive. Here, we investigate whether MerTK alleviates S. aureus induced uncontrolled inflammation through negatively regulating toll-like receptor 2 and 6 (TLR2/ TLR6) via suppressor of cytokine signalling 1, 3 (SOCS1/SOCS3).

METHODS AND RESULTS

We found in mice lung tissues and RAW 264.7 macrophages upon S. aureus infection activates TLR2 and TLR6 driven mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-κB) signalling pathways, resulting in production of inflammatory cytokines including tumour necrosis factor-α (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6). Furthermore, S. aureus-infection groups showed a significant up-regulation of MerTK which serves as mediator of SOCS1 and SOCS3. Subsequently, through feedback mechanism SOCS1/3 degrade Mal, resulting in inhibition of downstream TLR mediated inflammatory pathways. Moreover, MerTK^-/- mice lung tissues and silencing MerTK in RAW 264.7 inhibited the S. aureus-induced activation of MerTK, which significantly upregulated the phosphorylation of crucial protein in MAPKs (ERK, JNK, p38) and NF-κB (IĸBα, p65) signalling pathways, as well as the production of pro-inflammatory cytokines.

CONCLUSION

Collectively, these findings indicate the important role of MerTK in self-regulatory resolution of S. aureus-induced inflammatory pathways and cytokines through intrinsic SOCS1 and SOCS3 repressed feedback on TLR2, TLR6 both in vivo and in vitro.

CDK6 Inhibition: A Novel Approach in AML Management

Acute myeloid leukemia (AML) is a complex disease with an aggressive clinical course and high mortality rate. The standard of care for patients has only changed minimally over the past 40 years. However, potentially useful agents have moved from bench to bedside with the potential to revolutionize therapeutic strategies. As such, cell-cycle inhibitors have been discussed as alternative treatment options for AML. In this review, we focus on cyclin-dependent kinase 6 (CDK6) emerging as a key molecule with distinct functions in different subsets of AML. CDK6 exerts its effects in a kinase-dependent and -independent manner which is of clinical significance as current inhibitors only target the enzymatic activity.

MerTK negatively regulates Staphylococcus aureus induced inflammatory response via Toll-like receptor signaling in the mammary gland

Mastitis is the most commonly diagnosed infectious disease reducing milk yield and quality and is accompanied by mammary tissue damage in both humans and animals. Mastitis incurs welfare and economic costs as well as environmental concerns regarding treatment. Staphylococcus aureus (S. aureus) is a prevalent Gram-positive bacteria and a major cause of mastitis, however, pathogenesis of the intrinsic anti-inflammatory response in mammary tissues is still principally unknown. Our aim, in combatting the S. aureus induced inflammatory response in mammary tissues, was to elucidate the intrinsic anti-inflammatory role of MerTK signaling. Here, we demonstrate that Mer receptor tyrosine kinase (MerTK) regulates an intrinsic negative feedback to balance the over-reaction of the host defense system. S. aureus elicits toll-like receptors 2 and 6 (TLR2/TLR6) signaling pathways, subsequently recruiting TRAF6, whose ubiquitination is intricate to the downstream signaling including MAPKs and NF-κB. We observed that TLR2/TLR6 activation, in response to S. aureus, was concomitant with induced MerTK activation, leading to raised expression of suppressor of cytokine signaling 1 and 3 (SOCS1, SOCS3) in wild type mice mammary tissues and epithelial cells. Meanwhile, S. aureus infection in MerTK-/- mice showed significant increased phosphorylation of p65, IκBα, p38, JNK and ERK along with production of pro-inflammatory cytokines. Moreover, MerTK-/- evidently inhibited S. aureus induced phosphorylation of STAT1 and subsequent SOCS1/SOCS3 expression which are pivotal in the negative feedback mechanism for targeting TRAF6 to inhibit the TLR2/TLR6 mediated immune response. Taken together, our findings demonstrate the importance of MerTK in the regulation of the intrinsic feedback during the inflammatory response induced by S. aureus through STAT1/SOCS1/SOCS3 in mice mammary tissues and mice mammary epithelial cells (MMECs).

Inhibition of the IL-18 Receptor Signaling Pathway Ameliorates Disease in a Murine Model of Rheumatoid Arthritis

Interleukin (IL)-18 expression in synovial tissue correlates with the severity of joint inflammation and the levels of pro-inflammatory cytokines. However, the role of the IL-18/IL-18 receptor-alpha (Rα) signaling pathway in autoimmune arthritis is unknown. Wild-type (WT) and IL-18Rα knockout (KO) mice were immunized with bovine type II collagen before the onset of arthritis induced by lipopolysaccharide injection. Disease activity was evaluated by semiquantitative scoring and histologic assessment. Serum inflammatory cytokine and anticollagen antibody levels were quantified by an enzyme-linked immunosorbent assay. Joint cytokine and matrix metalloproteinases-3 levels were determined by a quantitative polymerase chain reaction. Splenic suppressors of cytokine signaling (SOCS) were determined by Western blot analysis as indices of systemic immunoresponse. IL-18Rα KO mice showed lower arthritis and histological scores in bone erosion and synovitis due to reductions in the infiltration of CD4+ T cells and F4/80+ cells and decreased serum IL-6, -18, TNF, and IFN-γ levels. The mRNA expression and protein levels of SOCS3 were significantly increased in the IL-18Rα KO mice. By an up-regulation of SOCS, pro-inflammatory cytokines were decreased through the IL-18/IL-18Rα signaling pathway. These results suggest that inhibitors of the IL-18/IL-18Rα signaling pathway could become new therapeutic agents for rheumatoid arthritis.

Dissociating STAT4 and STAT5 Signaling Inhibitory Functions of SOCS3: Effects on CD8 T Cell Responses

Cytokines are critical for guiding the differentiation of T lymphocytes to perform specialized tasks in the immune response. Developing strategies to manipulate cytokine-signaling pathways holds promise to program T cell differentiation toward the most therapeutically useful direction. Suppressor of cytokine signaling (SOCS) proteins are attractive targets, as they effectively inhibit undesirable cytokine signaling. However, these proteins target multiple signaling pathways, some of which we may need to remain uninhibited. SOCS3 inhibits IL-12 signaling but also inhibits the IL-2–signaling pathway. In this study, we use computational protein design based on SOCS3 and JAK crystal structures to engineer a mutant SOCS3 with altered specificity. We generated a mutant SOCS3 designed to ablate interactions with JAK1 but maintain interactions with JAK2. We show that this mutant does indeed ablate JAK1 inhibition, although, unexpectedly, it still coimmunoprecipitates with JAK1 and does so to a greater extent than with JAK2. When expressed in CD8 T cells, mutant SOCS3 preserved inhibition of JAK2-dependent STAT4 phosphorylation following IL-12 treatment. However, inhibition of STAT phosphorylation was ablated following stimulation with JAK1-dependent cytokines IL-2, IFN-α, and IL-21. Wild-type SOCS3 inhibited CD8 T cell expansion in vivo and induced a memory precursor phenotype. In vivo T cell expansion was restored by expression of the mutant SOCS3, and this also reverted the phenotype toward effector T cell differentiation. These data show that SOCS proteins can be engineered to fine-tune their specificity, and this can exert important changes to T cell biology.

Correlation between angiotensin 1-7-mediated Mas receptor expression with motor improvement, activated STAT3/SOCS3 cascade, and suppressed HMGB-1/RAGE/NF-κB signaling in 6-hydroxydopamine hemiparkinsonian rats

In the current investigation, a Parkinson's disease (PD) model was established by a single direct right intrastriatal injection of the 6-hydroxydopamine (OHDA) in male Wistar rats followed by 7 daily unilateral injection of angiotensin (Ang) 1-7 in the striatum. To confirm the putative role of Mas receptor (MasR), the selective antagonist A779 was also injected intrastriatally prior to Ang 1-7 injections and a correlation analysis was performed between MasR expression and the assessed parameters. Ang 1-7 upregulated MasR expression to correlate strongly with the improved rotarod (r = 0.95, p = 0.003) and spontaneous activity task (r = 0.99, p < 0.0001). This correlation extends to involve other effects of Ang 1-7, such as the increased striatal dopamine content (r = 0.98, p = 0.0005), substantia nigra pars compacta tyrosine hydroxylase immune-reactivity (r = 0.97, p = 0.001), active pY705-STAT3 (r = 0.99, p < 0.0001) and SOCS3 (r = 0.99, p < 0.0001). Conversely, Ang 1-7 inhibited inflammatory markers to correlate negatively with NF-κBp65 (r = -0.99, p < 0.0003) and its downstream targets, high mobility group box-1 (HMGB-1; r = -0.97, p = 0.002), receptor for advanced glycation end products (RAGE; r = -0.98, p = 0.0004), and TNF-α (r = -0.99, p < 0.0003), besides poly-ADP-ribose polymerase-1 (r = -0.99, p = 0.0002). In confirmation, the pre-administration of the selective MasR antagonist, A779, partially attenuated Ang 1-7-induced alterations towards 6-OHDA neurodegeneration. Collectively, our findings support a novel role for the anti-inflammatory capacity of the MasR axis to prove potential therapeutic relevance in PD via the upregulation/activation of MasR-dependent STAT3/SOCS3 cascade to negatively control the HMGB-1/RAGE/NF-κB axis hindering PD associated neuro-inflammation along with DA depletion and motor deficits.

MiR-142a-3p alleviates Escherichia coli derived lipopolysaccharide-induced acute lung injury by targeting TAB2

Acute lung Injury (ALI) is the clinical syndrome of parenchymal lung disease, leading to an extremely high mortality. The pathogenesis of ALI is suggested to be a consequence of uncontrolled inflammation. Lipopolysaccharide (LPS)-induced ALI mice model is often used for the mechanism. Studies show that TGF-beta activated kinase 1 (MAP3K7) binding protein 1/2 (TAB2) plays a crucial role in LPS-induced inflammation response. Furthermore, microRNA-142a-3p (miR-142a-3p) has been observed to be involved in inflammation-induced disease. Thus, we investigated the role of miR-142a-3p and TAB2 on LPS-induced ALI, which involved the TLR4/TAB2/NF-κB signaling. ALI and normal lung tissues were collected to access the relative expression of pro-inflammatory cytokines and miR-142a-3p. Histopathological examination and Wet to Dry weight ratios of lung tissues were used to access the establishment of ALI models. Raw264.7 cells were transfected with si-TAB2 or miR-142a-3p mimics to elucidate the role of TAB2 or miR-142a-3p in the inflammatory cascade in ALI. Additionally, the relationship between miR-142a-3p and TAB2 was validated by dual-luciferase report system. Our study discovered that miR-142-3p was up-regulated both in LPS-induced ALI mice model and RAW264.7 cells model. MiR-142a-3p mimics group experienced significant decrease in the secretion of pro-inflammatory cytokines as a result of the inhibition of NF-κB signaling pathway. Bioinformatics database showed that the adaptor protein, TAB2, was critical in this pathway and it is the target gene of miR-142a-3p. Their relation was first confirmed by us via dual-luciferase report system. Results of our study demonstrated that miR-142a-3p exerts as a protective role in LPS-induced ALI through down-regulation of NF-κB signaling pathway.

Electric Stimulation Hyperthermia Relieves Inflammation via the Suppressor of Cytokine Signaling 3-Toll Like Receptor 4 Pathway in a Prostatitis Rat Model

Purpose

Chronic prostatitis (CP), including chronic pelvic pain syndrome (CPPS), is the most commonly encountered manifestation of prostatitis. The aim of this study was to evaluate the effect of electric stimulation hyperthermia treatment (ESHT) on CP/CPPS and to explore the underlying mechanism.

Materials and Methods

RWPE-2 cells with lipopolysaccharide-induced inflammation and a prostatitis rat model induced by 17β-estradiol and dihydrotestosterone underwent sham, electric stimulation, or ESHT treatment. Four weeks later, cells, supernatants, and rat prostates were collected for analysis using immunohistochemistry, Western blots, and enzyme-linked immunosorbent assays.

Results

We found that ESHT improved prostatitis in vivo and attenuated inflammation in vitro. ESHT significantly induced suppressor of cytokine signaling 3 (SOCS3) expression and subsequently promoted HSP70. It attenuated inflammation through decreased expression of toll-like receptor 4 (TLR4), nuclear factor kappa B, and subsequent inflammatory cytokines. ESHT also inhibited apoptosis and released growth factor in tissue affected by prostatitis.

Conclusions

ESHT improved CP/CPPS and reversed pathologic changes of prostatitis by inhibiting the SOCS3-TLR4 pathway.

The hepatitis C virus (HCV) protein, p7, suppresses inflammatory responses to tumor necrosis factor (TNF)-α via signal transducer and activator of transcription (STAT)3 and extracellular signal-regulated kinase (ERK)-mediated induction of suppressor of cytokine signaling (SOCS)3

Viruses use a spectrum of immune evasion strategies that enable infection and replication. The acute phase of hepatitis C virus (HCV) infection is characterized by nonspecific and often mild clinical symptoms, suggesting an immunosuppressive mechanism that, unless symptomatic liver disease presents, allows the virus to remain largely undetected. We previously reported that HCV induced the regulatory protein suppressor of cytokine signaling (SOCS)3, which inhibited TNF-α-mediated inflammatory responses. However, the mechanism by which HCV up-regulates SOCS3 remains unknown. Here we show that the HCV protein, p7, enhances both SOCS3 mRNA and protein expression. A p7 inhibitor reduced SOCS3 induction, indicating that p7's ion channel activity was required for optimal up-regulation of SOCS3. Short hairpin RNA and chemical inhibition revealed that both the Janus kinase-signal transducer and activator of transcription (JAK-STAT) and MAPK pathways were required for p7-mediated induction of SOCS3. HCV-p7 expression suppressed TNF-α-mediated IκB-α degradation and subsequent NF-κB promoter activity, revealing a new and functional, anti-inflammatory effect of p7. Together, these findings identify a molecular mechanism by which HCV-p7 induces SOCS3 through STAT3 and ERK activation and demonstrate that p7 suppresses proinflammatory responses to TNF-α, possibly explaining the lack of inflammatory symptoms observed during early HCV infection.-Convery, O., Gargan, S., Kickham, M., Schroder, M., O'Farrelly, C., Stevenson, N. J. The hepatitis C virus (HCV) protein, p7, suppresses inflammatory responses to tumor necrosis factor (TNF)-α via signal transducer and activator of transcription (STAT)3 and extracellular signal-regulated kinase (ERK)-mediated induction of suppressor of cytokine signaling (SOCS)3.

Granulin 1 Promotes Retinal Regeneration in Zebrafish

Purpose

Retinal degenerative diseases can progress to severe reductions of vision. In general, the changes are permanent in higher vertebrates, including humans; however, retinal regeneration can occur in lower vertebrates, such as amphibians and teleost fish. Progranulin is a secreted growth factor that is involved in normal development and wound-healing processes. We have shown that progranulin promotes the proliferation of retinal precursor cells in mouse retinas. The purpose of this study was to investigate the role played by granulin 1 (grn1) in the retinal regeneration in zebrafish.

Methods

We injured the retina of zebrafish with needle puncturing, and the retinas were examined at different times after the injury. We also checked the proliferation and the expression of retinal regeneration–related genes after knockdown of grn1 by electroporation with morpholino oligonucleotides (MO) and intravitreal injection of recombinant grn1.

Results

Our results showed that the level of grn1 was highly increased after retinal injury, and it was expressed in various types of retinal cells. A knockdown of grn1 reduced the proliferation of Müller glial cells in zebrafish eyes undergoing retinal regeneration. The knockdown of grn1 also reduced the expression of achaete-scute homolog 1a (ascl1a), an important factor in retinal regeneration. An intravitreal injection of recombinant grn1 led to a proliferation of Müller glial cells and an increase in the expression of retinal regeneration–related genes, such as ascl1a and lin28.

Conclusions

These findings suggested that grn1 should be considered as a target for stimulating the dedifferentiation of Müller glial cells and retinal regeneration.

Conserved Gammaherpesvirus Protein Kinase Selectively Promotes Irrelevant B Cell Responses

Gammaherpesviruses are ubiquitous pathogens that are associated with B cell lymphomas. In the early stages of chronic infection, these viruses infect naive B cells and subsequently usurp the B cell differentiation process through the germinal center response to ensure latent infection of long-lived memory B cells. A unique feature of early gammaherpesvirus chronic infection is a robust differentiation of irrelevant, virus-nonspecific B cells with reactivities against self-antigens and antigens of other species. In contrast, protective, virus-specific humoral responses do not reach peak levels until a much later time. While several host factors are known to either promote or selectively restrict gammaherpesvirus-driven germinal center response, viral mechanisms that contribute to the irrelevant B cell response have not been defined. In this report we show that the expression and the enzymatic activity of the gammaherpesvirus-encoded conserved protein kinase selectively facilitates the irrelevant, but not virus-specific, B cell responses. Further, we show that lack of interleukin-1 (IL-1) receptor attenuates gammaherpesvirus-driven B cell differentiation and viral reactivation. Because germinal center B cells are thought to be the target of malignant transformation during gammaherpesvirus-driven lymphomagenesis, identification of host and viral factors that promote germinal center responses during gammaherpesvirus infection may offer an insight into the mechanism of gammaherpesvirus pathogenesis.IMPORTANCE Gammaherpesviruses are ubiquitous cancer-associated pathogens that usurp the B cell differentiation process to establish life-long latent infection in memory B cells. A unique feature of early gammaherpesvirus infection is the robust increase in differentiation of B cells that are not specific for viral antigens and instead encode antibodies that react with self-antigens and antigens of other species. Viral mechanisms that are involved in driving such irrelevant B cell differentiation are not known. Here, we show that gammaherpesvirus-encoded conserved protein kinase and host IL-1 signaling promote irrelevant B cell responses and gammaherpesvirus-driven germinal center responses, with the latter thought to be the target of viral transformation.

CDK6 coordinates JAK2 V617F mutant MPN via NF-κB and apoptotic networks

Over 80% of patients with myeloproliferative neoplasms (MPNs) harbor the acquired somatic JAK2 ^V617F mutation. JAK inhibition is not curative and fails to induce a persistent response in most patients, illustrating the need for the development of novel therapeutic approaches. We describe a critical role for CDK6 in MPN evolution. The absence of Cdk6 ameliorates clinical symptoms and prolongs survival. The CDK6 protein interferes with 3 hallmarks of disease: besides regulating malignant stem cell quiescence, it promotes nuclear factor κB (NF-κB) signaling and contributes to cytokine production while inhibiting apoptosis. The effects are not mirrored by palbociclib, showing that the functions of CDK6 in MPN pathogenesis are largely kinase independent. Our findings thus provide a rationale for targeting CDK6 in MPN.

Ethanol Extract of Aurantiochytrium mangrovei 18W-13a Strain Possesses Anti-inflammatory Effects on Murine Macrophage RAW264 Cells

In this study, the effects of an ethanolic extract of Aurantiochytrium mangrovei 18W-13a strain (AM18W-13a) on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264 murine macrophages were studied. Pre-treatment with the AM18W-13a extract significantly suppressed the LPS-induced production of nitric oxide and pro-inflammatory cytokines. RAW264 cells treated with the AM18W-13a extract for 1 and 24 h were subjected to DNA microarray analyses for detecting the differentially expressed genes. The treatment of RAW264 cells with the AM18W-13a extract for 24 h significantly suppressed the expression of several genes associated with inflammation or chemotaxis. Furthermore, treatment with the AM18W-13a extract for 1 h suppressed the expression of Pde4b, but induced the expression of Egr2 and Egr3 in RAW264 cells. Additionally, the AM18W-13a extract significantly enhanced the expression of certain anti-inflammatory mediators. This study is the first report of the anti-inflammatory effects of the AM18W-13a extract and its mechanism of action in LPS-stimulated murine macrophages.

MiRNA-155 Regulates the Th17/Treg Ratio by Targeting SOCS1 in Severe Acute Pancreatitis

Acute pancreatitis (AP) is a serious condition associated with intestinal barrier disruption or inflammation of the pancreatic tissue. Specific microRNAs are involved in the pathogenesis of AP, during which IL-17-producing CD4⁺ T helper (Th17) cells accumulate in the pancreas. In this study, significantly increased levels of miR-155 were detected in clinical samples from patients with AP, and overexpression of miR-155 correlated with severe AP (SAP). To identify the effect of miR-155 on T cell differentiation, we isolated CD4⁺ T lymphocytes and in vitro experiments showed that inhibition of miR-155 significantly reversed the stress-induced increase in the Th17/Treg ratio. The results also showed that miR-155 increased the Th17-mediated inflammatory response by targeting SOCS1. The interaction between miR-155 and the 3^′-UTR of SOCS1 was confirmed by a dual luciferase reporter assay and RT-PCR. Experimental AP of varying severity was induced in BALB/c mice by caerulein hyperstimulation and miR-155 expression was found to increase with disease progression. Inhibition of miR-155 expression significantly improved the pathology of the pancreas. We also observed downregulation of expression of inflammatory factors, IL-17, SOCS1 and phosphorylated STAT1 after miR-155 inhibition. In summary, miR-155 regulates the Th17/Treg ratio by targeting SOCS1, most probably via direct binding to its 3^′-UTR region, indicating that this microRNA may be a potential biomarker and/or therapeutic target for AP.

SOCS1 and SOCS3 Target IRF7 Degradation To Suppress TLR7-Mediated Type I IFN Production of Human Plasmacytoid Dendritic Cells

Type I IFN production of plasmacytoid dendritic cells (pDCs) triggered by TLR-signaling is an essential part of antiviral responses and autoimmune reactions. Although it was well-documented that members of the cytokine signaling (SOCS) family regulate TLR-signaling, the mechanism of how SOCS proteins regulate TLR7-mediated type I IFN production has not been elucidated yet. In this article, we show that TLR7 activation in human pDCs induced the expression of SOCS1 and SOCS3. SOCS1 and SOCS3 strongly suppressed TLR7-mediated type I IFN production. Furthermore, we demonstrated that SOCS1- and SOCS3-bound IFN regulatory factor 7, a pivotal transcription factor of the TLR7 pathway, through the SH2 domain to promote its proteasomal degradation by lysine 48-linked polyubiquitination. Together, our results demonstrate that SOCS1/3-mediated degradation of IFN regulatory factor 7 directly regulates TLR7 signaling and type I IFN production in pDCs. This mechanism might be targeted by therapeutic approaches to either enhance type I IFN production in antiviral treatment or decrease type I IFN production in the treatment of autoimmune diseases.

Induction of suppressor of cytokine signaling 3 via HSF-1-HSP70-TLR4 axis attenuates neuroinflammation and ameliorates postoperative pain

Postoperative pain is a common form of acute pain that, if not managed effectively, can become chronic pain. Evidence has shown that glia, especially microglia, mediate neuroinflammation, which plays a vital role in pain sensitization. Moreover, toll-like receptor 4 (TLR4), the tumor necrosis factor receptor (TNF-R), the interleukin-1 receptor (IL-1R), and the interleukin-6 receptor (IL-6R) have been considered key components in central pain sensitization and neuroinflammation. Therefore, we hypothesized that activation of the body's endogenous "immune brakes" will inhibit these receptors and achieve inflammation tolerance as well as relieve postoperative pain. After searching for potential candidates to serve as this immune brake, we identified and focused on the suppressor of cytokine signaling 3 (SOCS3) gene. To regulate SOCS3 expression, we used paeoniflorin to induce heat shock protein 70 (HSP70)/TLR4 signaling. We found that paeoniflorin significantly induced SOCS3 expression both in vitro and in vivo and promoted the efflux of HSP70 from the cytoplasm to the extracellular environment. Furthermore, paeoniflorin markedly attenuated incision-induced mechanical allodynia, and this effect was abolished by small interfering RNAs targeting SOCS3. These findings demonstrated an effective and safe strategy to alleviate postoperative pain.

SOCS Proteins as Regulators of Inflammatory Responses Induced by Bacterial Infections: A Review

Severe bacterial infections can lead to both acute and chronic inflammatory conditions. Innate immunity is the first defense mechanism employed against invading bacterial pathogens through the recognition of conserved molecular patterns on bacteria by pattern recognition receptors (PRRs), especially the toll-like receptors (TLRs). TLRs recognize distinct pathogen-associated molecular patterns (PAMPs) that play a critical role in innate immune responses by inducing the expression of several inflammatory genes. Thus, activation of immune cells is regulated by cytokines that use the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway and microbial recognition by TLRs. This system is tightly controlled by various endogenous molecules to allow for an appropriately regulated and safe host immune response to infections. Suppressor of cytokine signaling (SOCS) family of proteins is one of the central regulators of microbial pathogen-induced signaling of cytokines, principally through the inhibition of the activation of JAK/STAT signaling cascades. This review provides recent knowledge regarding the role of SOCS proteins during bacterial infections, with an emphasis on the mechanisms involved in their induction and regulation of antibacterial immune responses. Furthermore, the implication of SOCS proteins in diverse processes of bacteria to escape host defenses and in the outcome of bacterial infections are discussed, as well as the possibilities offered by these proteins for future targeted antimicrobial therapies.

Clinical and functional significance of STEAP4-splice variant in CD14+ monocytes in patients with rheumatoid arthritis

Tumour necrosis factor alpha (TNF)-α-induced adipose-related protein (TIARP) is a negative regulator of inflammation in arthritis model mice. In humans, six-transmembrane epithelial antigen of prostate 4 (STEAP4) (human counterpart of TIARP) is also expressed in CD14⁺ monocytes from patients with rheumatoid arthritis (RA). Recently, highly levels of exon 3-spliced variant STEAP4 (v-STEAP4) expression have been observed in porcine lung. The aim of this study is to elucidate the expression and functional role of v-STEAP4, comparing it with that of STEAP4, in the pathogenesis of arthritis. We identified v-STEAP4 in CD14⁺ cells. The expression of STEAP4 and v-STEAP4 was higher in patients with RA than in healthy participants. We also found that STEAP4 and v-STEAP4 were correlated positively with C-reactive protein and that their expression was decreased after treatment with an interleukin (IL)-6 antagonist in patients with RA. To investigate further the role of STEAP4 and v-STEAP4, we produced STEAP4 and v-STEAP4 over-expressing human monocytic cell lines (THP-1) for functional analysis. In the v-STEAP4 over-expressing cells, the production of IL-6 was suppressed significantly, but TNF-α was increased significantly through lipopolysaccharide (LPS) stimulation. Immunoblot analysis revealed that phosphorylated (p-)nuclear factor kappa B (NF-κB) was increased after LPS stimulation and degradation of nuclear factor kappa B inhibitor alpha (IκBα) was sustained, whereas p-signal transducer and activator of transcription 3 (STAT-3) was decreased with v-STEAP4. We identified specific up-regulation of v-STEAP4 in RA monocytes. V-STEAP4 might play a crucial role in the production of TNF-α and IL-6 through NF-κB and STAT-3 pathways, resulting in the generation of RA.

Productive replication of avian influenza viruses in chicken endothelial cells is determined by hemagglutinin cleavability and is related to innate immune escape

Endotheliotropism is a hallmark of gallinaceous poultry infections with highly pathogenic avian influenza (HPAI) viruses and a feature that distinguishes HPAI from low pathogenic avian influenza (LPAI) viruses. Here, we used chicken aortic endothelial cells (chAEC) as a novel in vitro infection model to assess the susceptibility, permissiveness, and host response of chicken endothelial cells (EC) to infections with avian influenza (AI) viruses. Our data show that productive replication of AI viruses in chAEC is critically determined by hemagglutinin cleavability, and is thus an exclusive trait of HPAI viruses. However, we provide evidence for a link between limited (i.e. trypsin-dependent) replication of certain LPAI viruses, and the viruses' ability to dampen the antiviral innate immune response in infected chAEC. Strikingly, this cell response pattern was also detected in HPAI virus-infected chAEC, suggesting that viral innate immune escape might be a prerequisite for robust AI virus replication in chicken EC.

MST-4 and TRAF-6 expression in the peripheral blood mononuclear cells of patients with Graves' disease and its significance

BACKGROUND

MST-4 and TRAF-6 are involved in the regulation of inflammatory and immune responses. However, whether they participate in the pathogenesis of Graves' disease (GD) has not yet been reported. Therefore, the purpose of this study was to investigate the expression of MST-4 and TRAF-6 in the peripheral blood of patients with GD to understand their role in the pathogenesis of GD.

METHODS

Thirty newly diagnosed GD patients, 24 GD patients in remission (eGD) and 30 normal controls (NC) were recruited. Thyroid function and autoantibody levels were determined using a chemiluminescence immunoassay. Peripheral blood mononuclear cells (PBMCs) were extracted, and MST-4 and TRAF-6 mRNA and protein levels were determined using real-time PCR and Western blotting, respectively.

RESULTS

1. Thyroid function in the GD group was significantly different from that in the eGD and NC groups (P < 0.05); however, there was no difference in thyroid function between the eGD group and the NC group (P > 0.05). The autoantibody levels in the NC group were significantly different from those in the GD and eGD groups (P < 0.05); however, the difference in the levels between the GD group and eGD group was not statistically significant (P > 0.05). 2. The MST-4 and TRAF-6 mRNA and protein levels in the GD group were significantly lower than those in the NC group (P < 0.05); however, there were no differences in mRNA and protein levels between the GD group and the eGD group or between the eGD group and the NC group (P > 0.05). 3. The correlation between the MST-4 and TRAF-6 mRNA and protein levels was not significant. However, there was a significant correlation between the TRAF-6 mRNA and TPO Ab levels in the eGD group and between the TRAF-6 mRNA and TR Ab levels in the NC group.

CONCLUSION

The MST-4 and TRAF-6 mRNA and protein levels were lower in the GD group than in the NC group, suggesting that MST-4 and TRAF-6 may be important in the pathogenesis of GD. Whether MST-4 influences the innate immune response through TRAF-6 and thus regulates the imbalance in downstream effector T cells requires further study. Investigating the expression of MST-4 and TRAF-6 in GD can provide a new perspective and targets for further study of the upstream mechanism responsible for effector T cell imbalance.

An ethanol extract of Aster yomena (Kitam.) Honda inhibits lipopolysaccharide-induced inflammatory responses in murine RAW 264.7 macrophages

Aster yomena (Kitam.) Honda has been widely used as a traditional herbal medicine for centuries to treat cough, asthma, insect bites, etc. Recent reports indicate that A. yomena possesses a wide spectrum of pharmacological activities; however, few experiments have described its anti-inflammatory properties. The present study examined the anti-inflammatory effects of an ethanol extract of A. yomena leaves (EEAY) on lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophages. Treatment with EEAY significantly reduced the secretion of pro-inflammatory molecules, such as nitric oxide and interleukin-1β, in LPS-stimulated RAW 264.7 cells, without incurring any significant cytotoxicity. These protective effects were accompanied by a marked reduction in the expression of regulatory genes at the transcription level. Treatment with EEAY also inhibited the DNA-binding activity of nuclear factor-κB (NF-κB) by suppression of nuclear translocation of NF-κB and by degradation of the inhibitor of NF-κB; these effects were associated with suppression of the phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase signaling pathways. The EEAY treatment also potently suppressed LPS-induced toll like receptor (TLR) 4 expression and attenuated the binding of LPS to the macrophage cell surface. In addition, EEAY treatment markedly inhibited LPS-induced accumulation of intracellular reactive oxygen species in RAW 264.7 macrophages. Therefore, the inhibitory effects of EEAY on LPS-stimulated inflammatory responses in RAW 264.7 macrophages were apparently associated with suppression of the TLR-mediated NF-κB signaling pathway. More work is needed to fully understand the critical role and clinical usefulness of EEAY treatment, but the findings of the present study provide some insights into the potential of EEAY as a therapeutic agent for treatment of inflammatory disorders.

SOCS3 revisited: a broad regulator of disease, now ready for therapeutic use?

Since their discovery, SOCS have been characterised as regulatory cornerstones of intracellular signalling. While classically controlling the JAK/STAT pathway, their inhibitory effects are documented across several cascades, underpinning their essential role in homeostatic maintenance and disease. After 20 years of extensive research, SOCS3 has emerged as arguably the most important family member, through its regulation of both cytokine- and pathogen-induced cascades. In fact, low expression of SOCS3 is associated with autoimmunity and oncogenesis, while high expression is linked to diabetes and pathogenic immune evasion. The induction of SOCS3 by both viruses and bacteria and its impact upon inflammatory disorders, underscores this protein's increasing clinical potential. Therefore, with the aim of highlighting SOCS3 as a therapeutic target for future development, this review revisits its multi-faceted immune regulatory functions and summarises its role in a broad ranges of diseases.

Single-cell analyses reveal an attenuated NF-κB response in the Salmonella-infected fibroblast

The eukaryotic transcriptional regulator Nuclear Factor kappa B (NF-κB) plays a central role in the defense to pathogens. Despite this, few studies have analyzed NF-κB activity in single cells during infection. Here, we investigated at the single cell level how NF-κB nuclear localization - a proxy for NF-κB activity - oscillates in infected and uninfected fibroblasts co-existing in cultures exposed to Salmonella enterica serovar Typhimurium. Fibroblasts were used due to the capacity of S. Typhimurium to persist in this cell type. Real-time dynamics of NF-κB was examined in microfluidics, which prevents cytokine accumulation. In this condition, infected (ST+) cells translocate NF-κB to the nucleus at higher rate than the uninfected (ST-) cells. Surprisingly, in non-flow (static) culture conditions, ST- fibroblasts exhibited higher NF-κB nuclear translocation than the ST+ population, with these latter cells turning refractory to external stimuli such as TNF-α or a second infection. Sorting of ST+ and ST- cell populations confirmed enhanced expression of NF-κB target genes such as IL1B, NFKBIA, TNFAIP3, and TRAF1 in uninfected (ST-) fibroblasts. These observations proved that S. Typhimurium dampens the NF-κB response in the infected fibroblast. Higher expression of SOCS3, encoding a "suppressor of cytokine signaling," was also observed in the ST+ population. Intracellular S. Typhimurium subverts NF-κB activity using protein effectors translocated by the secretion systems encoded by pathogenicity islands 1 (T1) and 2 (T2). T1 is required for regulating expression of SOCS3 and all NF-κB target genes analyzed whereas T2 displayed no role in the control of SOCS3 and IL1B expression. Collectively, these data demonstrate that S. Typhimurium attenuates NF-κB signaling in fibroblasts, an effect only perceptible when ST+ and ST- populations are analyzed separately. This tune-down in a central host defense might be instrumental for S. Typhimurium to establish intracellular persistent infections.

Anti-Inflammatory Activity of Bee Venom in BV2 Microglial Cells: Mediation of MyD88-Dependent NF-κB Signaling Pathway

Bee venom has long been used as a traditional folk medicine in Korea. It has been reportedly used for the treatment of arthritis, cancer, and inflammation. Although its anti-inflammatory activity in lipopolysaccharide- (LPS-) stimulated inflammatory cells has been reported, the exact mechanism of its anti-inflammatory action has not been fully elucidated. Therefore, the aim of this study was to investigate the anti-inflammatory mechanism of bee venom in BV2 microglial cells. We first investigated whether NO production in LPS-activated BV2 cells was inhibited by bee venom, and further iNOS mRNA and protein expressions were determined. The mRNA and protein levels of proinflammatory cytokines were examined using semiquantitative RT-PCR and immunoblotting, respectively. Moreover, modulation of the transcription factor NF-κB by bee venom was also investigated using a luciferase assay. LPS-induced NO production in BV2 microglial cells was significantly inhibited in a concentration-dependent manner upon pretreatment with bee venom. Bee venom markedly reduced the mRNA expression of COX-2, TNF-α, IL-1β, and IL-6 and suppressed LPS-induced activation of MyD88 and IRAK1 and phosphorylation of TAK1. Moreover, NF-κB translocation by IKKα/β phosphorylation and subsequent IκB-α degradation were also attenuated. Thus, collectively, these results indicate that bee venom exerts its anti-inflammatory activity via the IRAK1/TAK1/NF-κB signaling pathway.

Mer receptor tyrosine kinase negatively regulates lipoteichoic acid-induced inflammatory response via PI3K/Akt and SOCS3

Activation of toll-like receptor (TLR) signaling that initiates an innate immune response to pathogens must be strictly regulated to prevent excessive inflammatory damage in the host. Here, we demonstrate that Mer receptor tyrosine kinase (MerTK) is a negative regulatory molecule in the lipoteichoic acid (LTA)-induced inflammatory response. LTA that activated TLR2 signaling concomitantly induced activation of MerTK signaling in RAW264.7 macrophages, including phosphoinositide 3-kinase (PI3K)/Akt and suppressor of cytokine signaling 3 (SOCS3). Moreover, LTA induced MerTK activation in a time-dependent manner, and LTA-induced MerTK activation was dependent on the ligand Gas6. Additionally, pretreatment with a specific Mer-blocking antibody significantly inhibited LTA-induced phosphorylation of MerTK, while further enhancing LTA-induced phosphorylation of IκB-α and NF-κBp65 as well as production of TNF-α and IL-6. Meanwhile, the antibody blockade of MerTK markedly prevented LTA-induced Akt phosphorylation and SOCS3 expression, both of which were crucial for the inhibition of TLR2-mediated immune response. Collectively, these results suggest, for the first time, that MerTK is an intracellular negative feedback regulator that inhibits the inflammatory response of LTA-stimulated macrophages through the PI3K/Akt pathway and SOCS3 protein.

TRIF-dependent TLR signaling, its functions in host defense and inflammation, and its potential as a therapeutic target

Toll/IL-1R domain-containing adaptor-inducing IFN-β (TRIF)-dependent signaling is required for TLR-mediated production of type-I IFN and several other proinflammatory mediators. Various pathogens target the signaling molecules and transcriptional regulators acting in the TRIF pathway, thus demonstrating the importance of this pathway in host defense. Indeed, the TRIF pathway contributes to control of both viral and bacterial pathogens through promotion of inflammatory mediators and activation of antimicrobial responses. TRIF signaling also has both protective and pathologic roles in several chronic inflammatory disease conditions, as well as an essential function in wound-repair processes. Here, we review our current understanding of the regulatory mechanisms that control TRIF-dependent TLR signaling, the role of the TRIF pathway in different infectious and noninfectious pathologic states, and the potential for manipulating TRIF-dependent TLR signaling for therapeutic benefit.

TRAF2 mediates JNK and STAT3 activation in response to IL-1β and IFNγ and facilitates apoptotic death of insulin-producing β-cells

Interleukin-1β (IL-1β) and interferon-γ (IFNγ) contribute to type 1 diabetes (T1D) by inducing β-cell death. Tumor necrosis factor (TNF) receptor-associated factor (TRAF) proteins are adaptors that transduce signaling from a variety of membrane receptors including cytokine receptors. We show here that IL-1β and IFNγ upregulate the expression of TRAF2 in insulin-producing INS-1E cells and isolated rat pancreatic islets. siRNA-mediated knockdown (KD) of TRAF2 in INS-1E cells reduced IL-1β-induced phosphorylation of JNK1/2, but not of p38 or ERK1/2 mitogen-activated protein kinases. TRAF2 KD did not modulate NFκB activation by cytokines, but reduced cytokine-induced inducible nitric oxide synthase (iNOS) promotor activity and expression. We further observed that IFNγ-stimulated phosphorylation of STAT3 required TRAF2. KD of TRAF2 or STAT3 reduced cytokine-induced caspase 3/7 activation, but, intriguingly, potentiated cytokine-mediated loss of plasma membrane integrity and augmented the number of propidium iodide-positive cells. Finally, we found that TRAF2 KD increased cytokine-induced production of reactive oxygen species (ROS). In summary, our data suggest that TRAF2 is an important mediator of IL-1β and IFNγ signaling in pancreatic β-cells.

Socs1 and Socs3 degrades Traf6 via polyubiquitination in LPS-induced acute necrotizing pancreatitis

Mechanisms involved in inflammatory development during acute pancreatitis (AP) are largely vague, especially in the transformation of acute edematous pancreatitis (AEP) into acute necrotizing pancreatitis (ANP). This current study aims to investigate the functions of Traf6 in different AP models in vitro and in vivo, and to identify the possible regulatory mechanism in the progression of inflammation from mild to severe. Our data revealed that the level of Traf6 expression was significantly increased in the mild AP induced by caerulein, and the upregulation of Traf6 played a protective role in acinar cells against caerulein-induced apoptosis. In contrast, only Traf6 protein but not mRNA was downregulated in the severe ANP induced by combination treatment of caerulein and LPS. Mechanistic studies showed that LPS upregulated the levels of Socs1 and Socs3 expressions in acinar cells, Socs1 and Socs3 interacted Traf6 directly and degraded Traf6 protein via polyubiquitination, thereby counteracted the protective function of Traf6. In vivo study further showed that combination treatment of caerulein and LPS failed to induce an ANP model in the TLR4 knockout mice, and the level of Traf6 expression in the pancreatic tissues remained the same as that from the acute edematous pancreatitis (AEP) mouse. Taken together, our study reveals that Traf6 functioned as a protective factor in the progression of AP, and LPS-induced Socs1 and Socs3 exacerbate mild AP to severe AP, which provides evidence for developing a new therapeutic target to combat AP.

Methylation and microRNA-mediated epigenetic regulation of SOCS3

Epigenetic gene silencing of several genes causes different pathological conditions in humans, and DNA methylation has been identified as one of the key mechanisms that underlie this evolutionarily conserved phenomenon associated with developmental and pathological gene regulation. Recent advances in the miRNA technology with high throughput analysis of gene regulation further increased our understanding on the role of miRNAs regulating multiple gene expression. There is increasing evidence supporting that the miRNAs not only regulate gene expression but they also are involved in the hypermethylation of promoter sequences, which cumulatively contributes to the epigenetic gene silencing. Here, we critically evaluated the recent progress on the transcriptional regulation of an important suppressor protein that inhibits cytokine-mediated signaling, SOCS3, whose expression is directly regulated both by promoter methylation and also by microRNAs, affecting its vital cell regulating functions. SOCS3 was identified as a potent inhibitor of Jak/Stat signaling pathway which is frequently upregulated in several pathologies, including cardiovascular disease, cancer, diabetes, viral infections, and the expression of SOCS3 was inhibited or greatly reduced due to hypermethylation of the CpG islands in its promoter region or suppression of its expression by different microRNAs. Additionally, we discuss key intracellular signaling pathways regulated by SOCS3 involving cellular events, including cell proliferation, cell growth, cell migration and apoptosis. Identification of the pathway intermediates as specific targets would not only aid in the development of novel therapeutic drugs, but, would also assist in developing new treatment strategies that could successfully be employed in combination therapy to target multiple signaling pathways.

Bone morphogenetic protein 4 inhibits insulin secretion from rodent beta cells through regulation of calbindin1 expression and reduced voltage-dependent calcium currents

AIMS/HYPOTHESIS

Type 2 diabetes is characterised by progressive loss of pancreatic beta cell mass and function. Therefore, it is of therapeutic interest to identify factors with the potential to improve beta cell proliferation and insulin secretion. Bone morphogenetic protein 4 (BMP4) expression is increased in diabetic animals and BMP4 reduces glucose-stimulated insulin secretion (GSIS). Here, we investigate the molecular mechanism behind this inhibition.

METHODS

BMP4-mediated inhibition of GSIS was investigated in detail using single cell electrophysiological measurements and live cell Ca(2+) imaging. BMP4-mediated gene expression changes were investigated by microarray profiling, quantitative PCR and western blotting.

RESULTS

Prolonged exposure to BMP4 reduced GSIS from rodent pancreatic islets. This inhibition was associated with decreased exocytosis due to a reduced Ca(2+) current through voltage-dependent Ca(2+) channels. To identify proteins involved in the inhibition of GSIS, we investigated global gene expression changes induced by BMP4 in neonatal rat pancreatic islets. Expression of the Ca(2+)-binding protein calbindin1 was significantly induced by BMP4. Overexpression of calbindin1 in primary islet cells reduced GSIS, and the effect of BMP4 on GSIS was lost in islets from calbindin1 (Calb1) knockout mice.

CONCLUSIONS/INTERPRETATION

We found BMP4 treatment to markedly inhibit GSIS from rodent pancreatic islets in a calbindin1-dependent manner. Calbindin1 is suggested to mediate the effect of BMP4 by buffering Ca(2+) and decreasing Ca(2+) channel activity, resulting in diminished insulin exocytosis. Both BMP4 and calbindin1 are potential pharmacological targets for the treatment of beta cell dysfunction.