Transcriptional regulation of the interleukin-6 gene in mesangial cells

Effect of IL-6 -174G/C and -572G/C variants on susceptibility to osteoarthritis in Turkish population

Osteoarthritis (OA) is a complex disorder characterized by degenerative articular cartilage in which inflammatory mechanisms play a major role in the pathogenesis. Interleukin-6 (IL6), a multifunctional cytokine, can trigger osteoclast differentiation and bone resorption. Our purpose in this study was to evaluate the association of IL-6 -174 G/C (rs1800795) and -572 G/C (rs1800796) variants with the susceptibility to OA. One hundred fifty OA patients and 150 healthy individuals were enrolled in the study. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was used for genotyping the IL-6 gene variants. The results of analyses were evaluated for statistical significance. The pain intensity was assessed using the Visual Analogue Scale (VAS). There was a statistically significant difference in the genotype and allele frequencies of the IL-6 -174 G/C variant between patients with OA and control groups (p = 0.001, p = 0.002, respectively). IL-6 -174 G/C GG genotype and G allele were more prevalent in patients with OA. We found that the IL-6 -572 G/C variant was not different between patients and controls in either genotype distribution and allele frequency. IL-6 174 G/C and -572 G/C loci GG-GG combined genotype was significantly higher in OA patients (p = 0.00). Our study suggests that there was a strong association between the IL-6 -174 G/C variant and OA in the Turkish population. Further studies on populations of different ethnic background are necessary to prove the association of IL-6 variants with OA.

Alveolar macrophage-derived progranulin mediated pro-inflammatory Il-6 expression via regulating Creb1 in silicosis model

Progranulin (PGRN) is a secreted factor involved in inflammatory diseases. However, the function of PGRN in silica-induced lung inflammation has not been elucidated. In this study, we demonstrated that PGRN in serum and lung tissues was markedly increased in silicosis mouse model. And immunohistochemistry results showed that PGRN was mainly expressed in alveolar macrophages, which was further confirmed in silica-treated alvelar macrophages cell line (MH-S) in vitro. PGRN promoted pro-inflammatory cytokines transcription such as interleukin (Il)-6, tumor necrosis factor-α (Tnf-α) and Il-1β in MH-S cells, and the increasing of Il-6 was most obvious. Knockdown of PGRN blocked the silica-induced elevation of intracellular Il-6 in MH-S cells. Furthermore, we also found that PGRN could increase the phosphorylation of Cyclic AMP-responsive element-binding protein 1 (Creb1), a transcriptional regulator of Il-6. Inhibition of p-Creb1 by the phosphorylation inhibitor of Creb1 (666-15) decreased PGRN-induced intracellular Il-6 production in MH-S cells. In conclusion, PGRN was highly increased in silicosis mouse model and upregulated inflammatory cytokines expression. These findings suggested that PGRN might be a key mediator in silica-induced inflammation and provided a new clue for the diagnosis and drug therapy of silicosis.

SARS-CoV-2 Nsp14 protein associates with IMPDH2 and activates NF-κB signaling

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to NF-κB activation and induction of pro-inflammatory cytokines, though the underlying mechanism for this activation is not fully understood. Our results reveal that the SARS-CoV-2 Nsp14 protein contributes to the viral activation of NF-κB signaling. Nsp14 caused the nuclear translocation of NF-κB p65. Nsp14 induced the upregulation of IL-6 and IL-8, which also occurred in SARS-CoV-2 infected cells. IL-8 upregulation was further confirmed in lung tissue samples from COVID-19 patients. A previous proteomic screen identified the putative interaction of Nsp14 with host Inosine-5'-monophosphate dehydrogenase 2 (IMPDH2), which is known to regulate NF-κB signaling. We confirmed the Nsp14-IMPDH2 protein interaction and identified that IMPDH2 knockdown or chemical inhibition using ribavirin (RIB) and mycophenolic acid (MPA) abolishes Nsp14- mediated NF-κB activation and cytokine induction. Furthermore, IMPDH2 inhibitors (RIB, MPA) or NF-κB inhibitors (bortezomib, BAY 11-7082) restricted SARS-CoV-2 infection, indicating that IMPDH2-mediated activation of NF-κB signaling is beneficial to viral replication. Overall, our results identify a novel role of SARS-CoV-2 Nsp14 in inducing NF-κB activation through IMPDH2 to promote viral infection.

Monoamine Oxidase-B Inhibitor Reduction in Pro-Inflammatory Cytokines Mediated by Inhibition of cAMP-PKA/EPAC Signaling

Mucosal epithelial cell integrity is an important component of innate immunity and it protects the host from an environment rich in microorganisms. Virulence factors from Gram-negative bacteria [e.g. lipopolysaccharide (LPS)] induce significant pro-inflammatory cytokine expression. Monoamine oxidase (MAO) inhibitors reduce cytokine expression in a variety of inflammatory models and may therefore have therapeutic potential for a number of inflammatory diseases. We tested the anti-inflammatory therapeutic potential of a recently developed reversible MAO-B inhibitor (RG0216) with reduced transport across the blood–brain barrier. In an epithelial cell culture model, RG0216 significantly decreased LPS-induced interleukin (IL)-6 and IL-1β gene and protein expression and was as effective as equimolar concentrations of deprenyl (an existing irreversible MAO-B inhibitor). Hydrogen peroxide and modulating dopamine receptor signaling had no effect on cytokine expression. We showed that LPS-induced expression of IL-6 and IL-1β was cAMP dependent, that IL-6 and IL-1β expression were induced by direct cAMP activation (forskolin) and that RG0216 and deprenyl effectively reduced cAMP-mediated cytokine expression. Targeted protein kinase A (PKA) and Exchange Protein Activated by cAMP (EPAC) activation regulated IL-6 and IL-1β expression, albeit in different ways, but both cytokines were effectively decreased with RG0216. RG0216 reduction of LPS-induced cytokine expression occurred by acting downstream of the cAMP-PKA/EPAC signaling cascade. This represents a novel mechanism by which MAO-B selective inhibitors regulate LPS-induced IL-6 and IL-1β expression.

Regulation of B cell functions by S-nitrosoglutathione in the EAE model

B cells play both protective and pathogenic roles in T cell-mediated autoimmune diseases by releasing regulatory vs. pathogenic cytokines. B cell-depleting therapy has been attempted in various autoimmune diseases but its efficacy varies and can even worsen symptoms due to depletion of B cells releasing regulatory cytokines along with B cells releasing pathogenic cytokines. Here, we report that S-nitrosoglutathione (GSNO) and GSNO-reductase (GSNOR) inhibitor N6022 drive upregulation of regulatory cytokine (IL-10) and downregulation of pathogenic effector cytokine (IL-6) in B cells and protected against the neuroinflammatory disease of experimental autoimmune encephalomyelitis (EAE). In human and mouse B cells, the GSNO/N6022-mediated regulation of IL-10 vs. IL-6 was not limited to regulatory B cells but also to a broad range of B cell subsets and antibody-secreting cells. Adoptive transfer of B cells from N6022 treated EAE mice or EAE mice deficient in the GSNOR gene also regulated T cell balance (Treg > Th17) and reduced clinical disease in the recipient EAE mice. The data presented here provide evidence of the role of GSNO in shifting B cell immune balance (IL-10 > IL-6) and the preclinical relevance of N6022, a first-in-class drug targeting GSNOR with proven human safety, as therapeutics for autoimmune disorders including multiple sclerosis.

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GSNO and GSNOR inhibitor (N6022) upregulates IL-10 and downregulates IL-6 in B cells.

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GSNO/N6022-mediated cytokine regulation occurs in a broad range of B cell subsets.

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GSNO/N6022 treatment ameliorates autoimmune disease of EAE.

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B cell transfer from N6022-treated or GSNOR null EAE mice to EAE mice shifts T cell balance (Treg > Th17) and alleviates EAE.

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The data provide the first insight into the therapeutic potential of GSNO/N6022 targeting B cells in multiple sclerosis.

SARS-CoV-2 Nsp14 activates NF-κB signaling and induces IL-8 upregulation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to NF-κB activation and induction of pro-inflammatory cytokines, though the underlying mechanism for this activation is not fully understood. Our results reveal that the SARS-CoV-2 Nsp14 protein contributes to the viral activation of NF-κB signaling. Nsp14 caused the nuclear translocation of NF-κB p65. Nsp14 induced the upregulation of IL-6 and IL-8, which also occurred in SARS-CoV-2 infected cells. IL-8 upregulation was further confirmed in lung tissue samples from COVID-19 patients. A previous proteomic screen identified the putative interaction of Nsp14 with host Inosine-5'-monophosphate dehydrogenase 2 (IMPDH2) protein, which is known to regulate NF-κB signaling. We confirmed the Nsp14-IMPDH2 protein interaction and found that IMPDH2 knockdown or chemical inhibition using ribavirin (RIB) and mycophenolic acid (MPA) abolishes Nsp14-mediated NF-κB activation and cytokine induction. Furthermore, IMDPH2 inhibitors (RIB, MPA) efficiently blocked SARS-CoV-2 infection, indicating that IMDPH2, and possibly NF-κB signaling, is beneficial to viral replication. Overall, our results identify a novel role of SARS-CoV-2 Nsp14 in causing the activation of NF-κB.

Plasticity of Naturally Occurring Regulatory T Cells in Allergic Airway Disease Is Modulated by the Transcriptional Activity of Il-6

The impact of naturally occurring regulatory T cells (nTregs) on the suppression or induction of lung allergic responses in mice depends on the nuclear environment and the production of the pro-inflammatory cytokine interleukin 6 (IL-6). These activities were shown to be different in nTregs derived from wild-type (WT) and CD8-deficient mice (CD8^−/−), with increased IL-6 levels in nTregs from CD8^−/− mice in comparison to WT nTregs. Thus, identification of the molecular mechanisms regulating IL-6 production is critical to understanding the phenotypic plasticity of nTregs. Electrophoretic mobility shift assays (EMSA) were performed to determine transcription factor binding to four Il-6 promoter loci using nuclear extracts from nTregs of WT and CD8^−/− mice. Increased transcription factor binding for each of the Il-6 loci was identified in CD8^−/− compared to WT nTregs. The impact of transcription factor binding and a novel short tandem repeat (STR) on Il-6 promoter activity was analyzed by luciferase reporter assays. The Il-6 promoter regions closer to the transcription start site (TSS) were more relevant to the regulation of Il-6 depending on NF-κB, c-Fos, and SP and USF family members. Two Il-6 promoter loci were most critical for the inducibility by lipopolysaccharide (LPS) and tumor necrosis factor α (TNFα). A novel STR of variable length in the Il-6 promoter was identified with diverging prevalence in nTregs from WT or CD8^−/− mice. The predominant GT repeat in CD8^−/− nTregs revealed the highest luciferase activity. These novel regulatory mechanisms controlling the transcriptional regulation of the Il-6 promoter are proposed to contribute to nTregs plasticity and may be central to disease pathogenesis.

Expression of trophoblast derived prostaglandin E2 receptor 2 (EP2) is reduced in patients with recurrent miscarriage and EP2 regulates cell proliferation and expression of inflammatory cytokines

BACKGROUD

Prostaglandin E2 (PGE2), an inflammatory mediator, modulates cytokines, regulates immune responses in reproductive processes and stimulates inflammatory reactions via the prostaglandin E2 receptor 2 (EP2). However, the regulatory effects of EP2 signaling on trophoblasts and its role in unexplained recurrent miscarriage (uRM) remains unclear.

PATIENTS AND METHODS

A total of 19 placentas from patients with a history of more than two consecutive pregnancy losses of unknown cause (uRM group) and placentas of 19 healthy patients following a legal termination of their pregnancy were used for PGE2 receptor (EP1, EP2 and EP4) expression analyses via immunohistochemistry. Double immunofluorescence was also used to identify EP2 expressing cells in the decidua. Finally, HTR-8/SVneo cells were used to clarify the role of EP2 in in vitro experiments.

RESULTS

The expression of EP2 and EP4 was found to be reduced in the syncytiotrophoblast and decidua of uRM patients. A selective EP2 receptor antagonist (PF-04,418,948) reduced the proliferation and secretion of ß-hCG, inhibited interleukin -6 (IL-6) and interleukin-8 (IL-8) and up-regulated the production of the tumor necrosis factor-α (TNF-α) and plasminogen activator inhibitor type 1 (PAI-1) in HTR-8/SVneo cells in vitro.

CONCLUSION

PGE2-EP2 signaling pathway may represent a novel therapy option for uRM. The involvement of EP2 in uRM acts perhaps via inflammatory cytokines and indicates that the PGE2-EP2 signaling pathway might represent an unexplored etiology for uRM.

Brain-kidney interaction: Renal dysfunction following ischemic stroke

Stroke is a leading cause of mortality and morbidity, with long-term debilitating effects. Accumulating evidence from experimental studies as well as observational studies in patients suggests a cross talk between the brain and kidney after stroke. Stroke may lead to kidney dysfunction which can adversely impact patient outcome. In this review article, we discuss the epidemiology and mechanisms of brain–kidney interaction following ischemic stroke. Specifically, we discuss the role of the central autonomic network, autoregulation, inflammatory and immune responses, the role of extracellular vesicles and their cargo microRNA, in mediating brain–kidney interaction following stroke. Understanding the bidirectional nature of interaction between the brain and kidney after cerebral injury would have clinical implications for the treatment of stroke and overall patient outcome.

Human Skin Keratinocytes on Sustained TGF-β Stimulation Reveal Partial EMT Features and Weaken Growth Arrest Responses

Defects in wound closure can be related to the failure of keratinocytes to re-epithelize. Potential mechanisms driving this impairment comprise unbalanced cytokine signaling, including Transforming Growth Factor-β (TFG-β). Although the etiologies of chronic wound development are known, the relevant molecular events are poorly understood. This lack of insight is a consequence of ethical issues, which limit the available evidence to humans. In this work, we have used an in vitro model validated for the study of epidermal physiology and function, the HaCaT cells to provide a description of the impact of sustained exposure to TGF-β. Long term TGF-β1 treatment led to evident changes, HaCaT cells became spindle-shaped and increased in size. This phenotype change involved conformational re-arrangements for actin filaments and E-Cadherin cell-adhesion structures. Surprisingly, the signs of consolidated epithelial-to-mesenchymal transition were absent. At the molecular level, modified gene expression and altered protein contents were found. Non-canonical TGF-β pathway elements did not show relevant changes. However, R-Smads experienced alterations best characterized by decreased Smad3 levels. Functionally, HaCaT cells exposed to TGF-β1 for long periods showed cell-cycle arrest. Yet, the strength of this restraint weakens the longer the treatment, as revealed when challenged by pro-mitogenic factors. The proposed setting might offer a useful framework for future research on the mechanisms driving wound chronification.

S1P promotes IL-6 expression in osteoblasts through the PI3K, MEK/ERK and NF-κB signaling pathways

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, in which the immune system attacks joint tissue. Interleukin (IL)-6 is a key proinflammatory cytokine in RA progression. Sphingosine-1-phosphate (S1P), a platelet-derived lysophospholipid mediator, reportedly regulates osteoimmunology. Here, we examined the effects of S1P on IL-6 expression in osteoblasts. Our results and records from the Gene Expression Omnibus (GEO) database demonstrate higher levels of IL-6 in patients with RA compared with those with osteoarthritis. Stimulation of osteoblasts with S1P increased mRNA and protein expression of IL-6. PI3K, MEK, ERK and NF-κB inhibitors and their small interfering RNAs (siRNAs) reduced S1P-promoted IL-6 expression. S1P also facilitated PI3K, MEK/ERK and NF-κB signaling cascades. Our results indicate that S1P promotes the expression of IL-6 in osteoblasts via the PI3K, MEK/ERK and NF-κB signaling pathways.

The role of interleukin-6 in intracellular signal transduction after chronic β-adrenergic stimulation in mouse myocardium

INTRODUCTION

Inflammatory mediators play an important role in development and progression of cardiovascular disease. Both adrenergic stimulation and high levels of interleukin-6 (IL-6) indicate an unfavorable outcome in patients with myocardial infarction or heart failure. Understanding the interaction between β-adrenergic stimulation and IL-6 in the myocardium may contribute to developing more effective treatments. The aim of this study was to verify the role of IL-6 in the effects of β-adrenergic stimulation in activating selected intracellular signaling pathways in mouse myocardium.

MATERIAL AND METHODS

Experiments were performed on 12-week-old male mice: 16 C57BL/6JIL6^{‑/‑TMKopf} (IL-6 KO) and 17 C57BL/6J (WT). Animals received intraperitoneal injections of isoproterenol (ISO, 50 mg/kg) or placebo (0.9% NaCl) once a day for 16 days. The phosphorylation of STAT3 (signal transducer and activator of transcription 3), ERK1/2 (extracellular-regulated kinases 1/2), Akt1/2/3, p-38, c-Raf and expression of SOCS3 (suppressor of cytokine signaling 3), PIAS1/3 (protein inhibitors of activated STAT) was assessed by western blotting in the myocardium 24 h after the last injection. Evaluation of gene expression downstream of these pathways was performed by real-time PCR.

RESULTS

Chronic ISO treatment leads to increased fibrosis of the myocardium in mice lacking IL-6, which is accompanied by increased activity of ERK1/2, p38 and reduced expression of SOCS3. Administration of ISO in IL-6 KO animals intensified gene expression of proteins activated by MAPK/ERK (myc; CEBPB; BMP4; Fasn; Tank), while it reduced expression of genes repressed by ERK 1/2 (Wisp1, Wnt1).

CONCLUSIONS

IL-6 plays an important role in regulating the activation of MAPK pathways in the mouse myocardium in response to chronic β-adrenergic stimulation.

Apigenin Inhibits IL-6 Transcription and Suppresses Esophageal Carcinogenesis

Esophagus cancer is the seventh cause of cancer-related deaths globally. In this study, we analyzed interleukin 6 (IL-6) gene expression in human esophagus cancer patients and showed that IL-6 mRNA levels are significantly higher in tumor tissues and negatively correlated with overall survival, suggesting that IL-6 is a potential therapeutic target for esophagus cancer. We further demonstrated that apigenin, a nature flavone product of green plants, inhibited IL-6 transcription and gene expression in human esophagus cancer Eca-109 and Kyse-30 cells. Apigenin significantly and dose-dependently inhibited cell proliferation and promoted apoptosis while stimulating the cleaved PARP (poly ADP-ribose polymerase) (C-PARP) and caspase-8 expression. It suppressed VEGF (Vascular endothelial growth Factor) expression and tumor-induced angiogenesis. Pretreatment of cells with IL-6 could completely reverse apigenin-induced cellular changes. Finally, using a preclinical nude mice model subcutaneously xenografted with Eca-109 cells, we demonstrated the in vivo antitumor activity and mechanisms of apigenin. Taken together, this study revealed for the first time that apigenin is a new IL-6 transcription inhibitor and that inhibiting IL-6 transcription is one of the mechanisms by which apigenin exhibits its anticancer effects. The potential clinical applications of apigenin in treating esophagus cancer warrant further investigations.

MiR-200b attenuates IL-6 production through IKKβ and ZEB1 in human gingival fibroblasts

OBJECTIVE

MicroRNAs (miRNAs) play important roles in biological processes such as cell differentiation, development, infection, immune response, inflammation and tumorigenesis. We previously reported that the expression of miR-200b was significantly increased in inflamed gingiva compared with non-inflamed gingiva. To elucidate the roles of miR-200b in the inflamed gingiva, we have analyzed the effects of miR-200b on the expression of IL-6 in human gingival fibroblasts (HGF).

MATERIALS AND METHODS

Total RNA and protein were extracted from HGF after stimulation by interleukin-1β (IL-1β; 1 ng/ml) or tumor necrosis factor-α (TNF-α; 10 ng/ml) and transfected with miR-200b expression plasmid or miR-200b inhibitor. IL-6, IL-1β, inhibitor of nuclear factor kappa-B kinaseβ (IKKβ), Zinc-finger E-box-binding homeobox 1 (ZEB1) and E-cadherin mRNA and protein levels were analyzed by real-time PCR and Western blot.

RESULTS

IL-1β and TNF-α increased IL-6 mRNA and protein levels, and they were significantly suppressed by miR-200b overexpression, whereas they were further increased by miR-200b inhibitor in HGF. IKKβ and ZEB1 which are target genes of miR-200b negatively regulate E-cadherin. MiR-200b suppressed the expression of IKKβ and ZEB1 and increased E-cadherin mRNA and protein levels in HGF.

CONCLUSIONS

These results suggest that miR-200b attenuates inflammatory response via IKKβ and ZEB1 in periodontal tissue.

Reactive oxygen species and colorectal cancer

Colorectal cancer (CRC) has become the fourth leading cause of cancer-related death in the worldwide. It is urgent to find more effective therapeutic strategies for it. Reactive oxygen species (ROS) play multiple roles in normal cellular physiology processes. Thus, a certain level of ROS is essential to keep normal cellular function. However, the accumulation of ROS shows dual roles for cells, which is mainly dependent on the concentration of ROS, the origin of the cancer cell and the activated signaling pathways during tumor progression. In general, moderate level of ROS leads to cell damage, DNA mutation and inflammation, which promotes the initiation and development of cancer. Excessive high level of ROS induces cancer cell death, showing an anti-cancer role. ROS are commonly higher in CRC cells than their normal counterpart cells. Therefore, it is possible that ROS induce cell death in cancer cells while not affecting the normal cells, demonstrating lower side effects. Besides, ROS also play a role in tumor microenvironment and drug resistance. These multiple roles of ROS make them a promising therapeutic target for cancer. To explore potential ROS-target therapies against CRC, it is worth to comprehensively understanding the role of ROS in CRC and therapy. In this review, we mainly discuss the strategies of ROS in CRC therapy, including direct CRC cell target and indirect tumor environment target. In addition, the influences of ROS in drug resistance will also been discussed.

Epigenetic modifications of interleukin-6 in synovial fibroblasts from osteoarthritis patients

Osteoarthritis (OA) is the most common degenerative disease of the synovial joint. The synovial membrane is responsible for the inflammatory reaction leading to the secretion of macrophage-derived pro-inflammatory cytokines, such as IL-6. Suppressing IL-6 over-expression in synovial fibroblasts (SF) is a promising method to prevent OA development and progression, in which the prerequisite is the elucidation of the molecular mechanisms underlying IL-6 over-expression in SF. Currently, there are few reports concerning epigenetic modifications in IL-6 in OA SF. In the present study, we attempted to investigate this phenomenon. SF over-expressing IL-6 was collected from OA patients. DNA hypomethylation and histone hyperacetylation were observed in the IL-6 promoter regions in OA SF compared with normal SF. No differences in the status of H3K9 di-methylation, H3K27 tri-methylation and H3K4 tri-methylation were observed in the IL-6 promoter regions between normal and OA SF. DNA (cytosine-5-)-methyltransferase 3 alpha (Dnmt3a) overexpression and anacardic acid (histone acetyltransferase inhibitor) treatment increased DNA methylation and decreased histone acetylation in the IL-6 promoter, and IL-6 over-expression in OA SF was suppressed. These observations provide deeper insight into the pathogenesis of OA and can be used to design new drugs and develop new therapeutic methods to treat OA.

Harpagoside suppresses IL-6 expression in primary human osteoarthritis chondrocytes

There is growing evidence in support of the involvement of inflammatory response in the pathogenesis of osteoarthritis (OA). Harpagoside, one of the bioactive components of Harpagophytum procumbens (Hp), has been shown to possess anti-inflammatory properties. Here we used an in vitro model of inflammation in OA to investigate the potential of harpagoside to suppress the production of inflammatory cytokines/chemokines such as IL-6 and matrix degrading proteases. We further investigated the likely targets of harpagoside in primary human OA chondrocytes. OA chondrocytes were pre-treated with harpagoside before stimulation with IL-1β. mRNA expression profile of 92 cytokines/chemokines was determined using TaqMan Human Chemokine PCR Array. Expression levels of selected mRNAs were confirmed using TaqMan assays. Protein levels of IL-6 and MMP-13 were assayed by ELISA and immunoblotting. Total protein levels and phosphorylation of signaling proteins were determined by immunoblotting. Cellular localization of IL-6 and c-Fos was performed by immunofluorescence and confocal microscopy. DNA binding activity of c-FOS/AP-1 was determined by ELISA. Harpagoside significantly altered the global chemokine expression profile in IL-1β-stimulated OA chondrocytes. Expression of IL-6 was highly induced by IL-1β, which was significantly inhibited by pre-treatment of OA chondrocytes with harpagoside. Harpagoside did not inhibit the IL-1β-induced activation of NF-κB and C/EBPβ transcription factors but suppressed the IL-1β-triggered induction, phosphorylation, and DNA binding activity of c-FOS, one of the main components of AP-1 transcription factors. Further, harpagoside significantly inhibited the expression of MMP-13 in OA chondrocytes under pathological conditions. siRNA-mediated knockdown of IL-6 resulted in suppressed expression and secretion of MMP-13 directly linking the role of IL-6 with MMP-13 expression. Taken together, the present study suggests that harpagoside exerts a significant anti-inflammatory effect by inhibiting the inflammatory stimuli mediated by suppressing c-FOS/AP-1 activity in OA chondrocytes under pathological conditions. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:311-320, 2017.

Hall of Fame among Pro-inflammatory Cytokines: Interleukin-6 Gene and Its Transcriptional Regulation Mechanisms

Pro-inflammatory cytokines that are generated by immune system cells and mediate many kinds of immune responses are kinds of endogenous polypeptides. They are also the effectors of the autoimmune system. It is generally accepted that interleukin (IL)-4, IL-6, IL-9, IL-17, and tumor necrosis factor-α are pro-inflammatory cytokines; however, IL-6 becomes a protagonist among them since it predominately induces pro-inflammatory signaling and regulates massive cellular processes. It has been ascertained that IL-6 is associated with a large number of diseases with inflammatory background, such as anemia of chronic diseases, angiogenesis acute-phase response, bone metabolism, cartilage metabolism, and multiple cancers. Despite great progress in the relative field, the targeted regulation of IL-6 response for therapeutic benefits remains incompletely to be understood. Therefore, it is conceivable that understanding mechanisms of IL-6 from the perspective of gene regulation can better facilitate to determine the pathogenesis of the disease, providing more solid scientific basis for clinical treatment translation. In this review, we summarize the candidate genes that have been implicated in clinical target therapy from the perspective of gene transcription regulation.

Heat induces interleukin-6 in skeletal muscle cells via TRPV1/PKC/CREB pathways

Interleukin-6 (IL-6) is released from skeletal muscle cells and induced by exercise, heat, catecholamine, glucose, lipopolysaccharide, reactive oxygen species, and inflammation. However, the mechanism that induces release of IL-6 from skeletal muscle cells remains unknown. Thermosensitive transient receptor potential (TRP) proteins such as TRPV1-4 play vital roles in cellular functions. In this study we hypothesized that TRPV1 senses heat, transmits a signal into the nucleus, and produces IL-6. The purpose of the present study is to investigate the underlying mechanisms whereby skeletal muscle cells sense and respond to heat. When mouse myoblast cells were exposed to 37-42°C for 2 h, mRNA expression of IL-6 increased in a temperature-dependent manner. Heat also increased IL-6 secretion in myoblast cells. A fura 2 fluorescence dual-wavelength excitation method showed that heat increased intracellular calcium flux in a temperature-dependent manner. Intracellular calcium flux and IL-6 mRNA expression were increased by the TRPV1 agonists capsaicin and N-arachidonoyldopamine and decreased by the TRPV1 antagonists AMG9810 and SB366791 and siRNA-mediated knockdown of TRPV1. TRPV2, 3, and 4 agonists did not change intracellular calcium flux. Western blotting with inhibitors demonstrated that heat increased phosphorylation levels of TRPV1, followed by PKC and cAMP response element-binding protein (CREB). PKC inhibitors, Gö6983 and staurosporine, CREB inhibitors, curcumin and naphthol AS-E, and knockdown of CREB suppressed the heat-induced increases in IL-6. These results indicate that heat increases IL-6 in skeletal muscle cells through the TRPV1, PKC, and CREB signal transduction pathway.NEW & NOTEWORTHY Heat increases the release of interleukin-6 (IL-6) from skeletal muscle cells. IL-6 has been shown to serve immune responses and metabolic functions in muscle. It can be anti-inflammatory as well as proinflammatory. However, the mechanism that induces release of IL-6 from skeletal muscle cells remains unknown. Here we show that heat increases IL-6 in skeletal muscle cells through the transient receptor potential vannilloid 1, PKC, and cAMP response element-binding protein signal transduction pathway.

A critical role of transcription factor YY1 in rheumatoid arthritis by regulation of interleukin-6

Previous studies have revealed a critical role of YY1, a "Yin Yang" transcription factor, in cancer development and progression. However, whether YY1 has any role in rheumatoid arthritis (RA) remains unknown. This study aims to explore the potential role of YY1 in RA pathogenesis. In this study, we found that YY1 was over-expressed in RA patients and CIA mice. Blocking of YY1 action with YY1 shRNA lentivirus ameliorated disease progression in CIA mice. We further analyzed the signaling pathway involved by ingenuity pathway analysis (IPA), results showed IL-6 signaling and JAK/Stat signaling pathway was significantly inhibited by LV-YY1-shRNA treatment. Moreover, we observed that blocking of YY1 reduced IL-6 production and downregulated Th17 population. Finally, we showed YY1 positively regulated IL-6 transcription by binding to the promoter region of the IL-6 gene. In conclusion, YY1 plays a critical role in promoting IL-6 transcription in RA which contribute to the inflammation of RA via stimulation of Th17 differentiation. Thus, YY1 is likely a key molecule involved in the inflammation process of RA. Targeting of YY1 may be a novel therapeutic strategy for RA.

Lapatinib increases motility of triple-negative breast cancer cells by decreasing miRNA-7 and inducing Raf-1/MAPK-dependent interleukin-6

Lapatinib, a dual epidermal growth factor receptor (EGFR) and HER2 tyrosine kinase inhibitor (TKI), has been approved for HER2-positive breast cancer patients. Nevertheless, its inhibitory effect on EGFR did not deliver clinical benefits for triple-negative breast cancer (TNBC) patients even EGFR overexpression was frequently found in this disease. Moreover, lapatinib was unexpectedly found to enhance metastasis of TNBC cells, but the underlying mechanisms are not fully understood. In this study, we explored that the level of interleukin-6 (IL-6) was elevated in lapatinib-treated TNBC cells. Treatment with IL-6 antibody abolished the lapatinib-induced migration. Mechanistically, the signaling axis of Raf-1/mitogen-activated protein kinases (MAPKs), c-Jun N-terminal kinases (JNKs), p38 MAPK, and activator protein 1 (AP-1) was activated in response to lapatinib treatment to induce IL-6 expression. Furthermore, our data showed that microRNA-7 directly binds and inhibits Raf-1 3'UTR activity, and that down-regulation of miR-7 by lapatinib contributes to the activation of Raf-1 signaling pathway and the induction of IL-6 expression. Our results not only revealed IL-6 as a key regulator of lapatinib-induced metastasis, but also explored the requirement of miR7/Raf-1/MAPK/AP-1 axis in lapatinib-induced IL-6 expression.

TLR4-Activated MAPK-IL-6 Axis Regulates Vascular Smooth Muscle Cell Function

Migration of vascular smooth muscle cells (VSMCs) into the intima is considered to be a vital event in the pathophysiology of atherosclerosis. Despite substantial evidence supporting the pathogenic role of Toll-like receptor 4 (TLR4) in the progression of atherogenesis, its function in the regulation of VSMC migration remains unclear. The goal of the present study was to elucidate the mechanism by which TLR4 regulates VSMC migration. Inhibitor experiments revealed that TLR4-induced IL-6 secretion and VSMC migration were mediated via the concerted actions of MyD88 and TRIF on the activation of p38 MAPK and ERK1/2 signaling. Neutralizing anti-IL-6 antibodies abrogated TLR4-driven VSMC migration and F-actin polymerization. Blockade of p38 MAPK or ERK1/2 signaling cascade inhibited TLR4 agonist-mediated activation of cAMP response element binding protein (CREB). Moreover, siRNA-mediated suppression of CREB production repressed TLR4-induced IL-6 production and VSMC migration. Rac-1 inhibitor suppressed TLR4-driven VSMC migration but not IL-6 production. Importantly, the serum level of IL-6 and TLR4 endogenous ligand HMGB1 was significantly higher in patients with coronary artery diseases (CAD) than in healthy subjects. Serum HMGB1 level was positively correlated with serum IL-6 level in CAD patients. The expression of both HMGB1 and IL-6 was clearly detected in the atherosclerotic tissue of the CAD patients. Additionally, there was a positive association between p-CREB and HMGB1 in mouse atherosclerotic tissue. Based on our findings, we concluded that, upon ligand binding, TLR4 activates p38 MAPK and ERK1/2 signaling through MyD88 and TRIF in VSMCs. These signaling pathways subsequently coordinate an additive augmentation of CREB-driven IL-6 production, which in turn triggers Rac-1-mediated actin cytoskeleton to promote VSMC migration.

TLR4 induces CREB-mediated IL-6 production via upregulation of F-spondin to promote vascular smooth muscle cell migration

Toll-like receptor 4 (TLR4) is important in promoting inflammation and vascular smooth muscle cell (VSMC) migration, both of which contribute to atherosclerosis development and progression. But the mechanism underlying the regulation of TLR4 in VSMC migration remains unclear. Stimulation of VSMCs with LPS increased the cellular level of F-spondin which is associated with the regulation of proinflammatory cytokine production. The LPS-induced F-spondin expression depended on TLR4-mediated PI3K/Akt pathway. Suppression of F-spondin level by siRNA inhibited not only F-spondin expression but also LPS-induced phosphorylation of cAMP response element binding protein (CREB) and IL-6 expression, VSMC migration and proliferation as well as MMP9 expression. Moreover, suppression of CREB level by siRNA inhibited TLR4-induced IL-6 production and VSMC migration. Inhibition of F-spondin siRNA on LPS-induced migration was restored by addition of exogenous recombinant mouse IL-6. We conclude that upon ligand binding, TLR4 activates PI3K/Akt signaling to induce F-spondin expression, subsequently control CREB-mediated IL-6 production to promote VSMC migration. These findings provide vital insights into the essential role of F-spondin in VSMC function and will be valuable for developing new therapeutic strategies against atherosclerosis.

A homeobox protein, NKX6.1, up-regulates interleukin-6 expression for cell growth in basal-like breast cancer cells

Among breast cancer subtypes, basal-like breast cancer is particularly aggressive, and research on the molecules involved in its pathology might contribute to therapy. In this study, we found that expression of NKX6.1, a homeobox transcription factor, is higher in basal-like breast cancer than in other subtypes. In loss-of-function experiments on basal-like breast cancer cell lines, NKX6.1-depleted cells exhibited reduced cell growth. Because cytokine interleukin-6 (IL-6) is expressed in basal-like breast cancer, and increases cell growth, we analyzed expression levels of IL6, an IL-6 gene, and observed reduced IL6 expression in NKX6.1-depleted cells. In a reporter assay, IL6 promoter activity was reduced by loss of NKX6.1 function. A pull-down assay showed that NKX6.1 binds to the proximal region in IL6 promoter. These results indicate that NKX6.1 directly up-regulates IL6 expression. To investigate further, we established cells with forced expression of IL-6. We observed that exogenous IL-6 expression restored the reduced cell growth of NKX6.1-depleted cells. Furthermore, orthotopic xenografts showed that NKX6.1-depleted cells lost the capacity for tumor formation. We therefore conclude that NKX6.1 is a factor for IL-6-regulated growth and tumor formation in basal-like breast cancer. Our findings facilitate profound understanding of basal-like breast cancer, and the development of suitable therapy.

Sulfasalazine augments a pro-inflammatory response in interleukin-1β-stimulated amniocytes and myocytes

Preterm birth occurs in 10% of pregnancies and is a major cause of neonatal morbidity and mortality. The majority of cases of early preterm labour are associated with infection/inflammation, which places the fetal central nervous system at risk. Targeting immune activation is therefore an appealing therapeutic strategy for the prevention of preterm labour and neonatal brain injury. The expression of many labour-associated and inflammatory-response genes is controlled by the transcription factors nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), which makes them therapeutic targets of interest. Sulfasalazine (SASP) has been shown to inhibit NF-κB and reduce lipopolysaccharide-induced cytokine concentrations in fetal membrane explants and reduce the rate of Escherichia coli-induced preterm labour in mice. Its effects upon AP-1 in the context of pregnancy are unknown. In this study the effect of SASP on interleukin-1β (IL-1β) -induced NF-κB and AP-1 activity, cytokine production and cyclo-oxygenase-2 (COX-2) expression was examined in amniocytes and myocytes. A supra-therapeutic concentration (5 mm) was required to inhibit IL-1β-induced NF-κB (P < 0·0001) in amniocytes and IL-1β-induced NF-κB (P < 0·01), AP-1 (P < 0·01) and COX-2 (P < 0·05) in myocytes. Despite inhibiting IL-1β-induced cytokines, a basal increase in IL-6 (P < 0·01), IL-8 (P < 0·0001) and tumour necrosis factor-α (TNF-α) (P < 0·001) was seen with 5 mm SASP in amniocytes, and significant cytotoxic effects were seen in myocytes. The therapeutic concentration of 0·015 mm had no inhibitory effects on pro-inflammatory mediators, but led to an augmented response to IL-1β-induced IL-6 (P < 0·01), IL-8 (P < 0·05) and TNF-α (P < 0·05) in amniocytes and IL-8 (P < 0·05) in myocytes. SASP is therefore an unlikely therapeutic candidate for the prevention of inflammation-induced preterm labour.

Multiple Protein Kinases via Activation of Transcription Factors NF-κB, AP-1 and C/EBP-δ Regulate the IL-6/IL-8 Production by HIV-1 Vpr in Astrocytes

Neurocognitive impairments affect a substantial population of HIV-1 infected individuals despite the success of anti-retroviral therapy in controlling viral replication. Astrocytes are emerging as a crucial cell type that might be playing a very important role in the persistence of neuroinflammation seen in patients suffering from HIV-1 associated neurocognitive disorders. HIV-1 viral proteins including Vpr exert neurotoxicity through direct and indirect mechanisms. Induction of IL-8 in microglial cells has been shown as one of the indirect mechanism through which Vpr reduces neuronal survival. We show that HIV-1 Vpr induces IL-6 and IL-8 in astrocytes in a time-dependent manner. Additional experiments utilizing chemical inhibitors and siRNA revealed that HIV-1 Vpr activates transcription factors NF-κB, AP-1 and C/EBP-δ via upstream protein kinases PI3K/Akt, p38-MAPK and Jnk-MAPK leading to the induction of IL-6 and IL-8 in astrocytes. We demonstrate that one of the mechanism for neuroinflammation seen in HIV-1 infected individuals involves induction of IL-6 and IL-8 by Vpr in astrocytes. Understanding the molecular pathways involved in the HIV-1 neuroinflammation would be helpful in the design of adjunct therapy to ameliorate some of the symptoms associated with HIV-1 neuropathogenesis.

A critical role of the transcription factor fli-1 in murine lupus development by regulation of interleukin-6 expression

OBJECTIVE

The Fli-1 transcription factor is implicated in the pathogenesis of systemic lupus erythematosus (SLE), both in humans and in animal models. Dysregulation of interleukin-6 (IL-6) is also associated with SLE. The purpose of this study was to investigate whether Fli-1 directly regulates the expression of IL-6.

METHODS

Sera were collected from wild-type and Fli-1-heterozygous (Fli-1(+/-) ) MRL/lpr mice, and the concentration of IL-6 was measured by enzyme-linked immunosorbent assay (ELISA). Expression of IL-6 in the kidney was measured by real-time polymerase chain reaction analysis. T cells were isolated from wild-type and Fli-1(+/-) MRL/lpr mice and stimulated with CD3/CD28 beads, and the concentration of IL-6 in the supernatants was measured by ELISA. MS1 endothelial cells were transfected with Fli-1 and control small interfering RNA, and the production of IL-6 was compared after lipopolysaccharide stimulation. A chromatin immunoprecipitation (ChIP) assay was performed to determine whether Fli-1 binds to the IL-6 promoter region. Transient transfections with the NIH3T3 cell line were performed to examine whether Fli-1 regulates the expression of IL-6.

RESULTS

Fli-1(+/-) MRL/lpr mice had significantly decreased IL-6 levels in sera and reduced expression of IL-6 in kidneys as compared to their wild-type littermates. T cells isolated from Fli-1(+/-) MRL/lpr mice produced less IL-6 than did those from wild-type mice. Inhibiting the expression of Fli-1 in endothelial cells resulted in reduced production of IL-6. The ChIP assay revealed direct binding of Fli-1 to 3 regions within the IL-6 promoter. Fli-1 activated transcription from the IL-6 promoter in a dose-dependent manner.

CONCLUSION

The direct regulation of IL-6 expression by Fli-1 represents one possible mechanism for the protective effect of decreased Fli-1 expression in lupus.

Bacterial flagellin induces IL-6 expression in human basophils

Binding of allergen to IgE on basophils positively affects allergic inflammation by releasing inflammatory mediators. Recently, basophils were shown to express pattern-recognition receptors, such as toll-like receptors (TLRs), for recognizing microbe-associated molecular patterns (MAMPs) that are independent of allergen-IgE binding. In this study, we investigated whether MAMP alone can induce IL-6 production in a human basophil cell line, KU812. Stimulation with flagellin in the absence of allergen-IgE association induced IL-6 expression in KU812 cells, while stimulation with lipoteichoic acid, peptidoglycan, or poly I:C did not under the same condition. Flagellin-induced IL-6 expression was also observed in human primary basophils. Flow cytometric analysis showed that KU812 cells expressed flagellin-recognizing TLR5 both on the cell surface and in the cytoplasm while TLR2 and TLR3 were observed only in the cytoplasm. We further demonstrated that although flagellin augmented the phosphorylation of mitogen-activated protein kinases including p38 kinase, ERK, and JNK, flagellin-induced IL-6 production was attenuated by inhibitors for p38 kinase and ERK, but not by JNK inhibitors. In addition, flagellin enhanced phosphorylation of signaling molecules including CREB, PKCδ, and AKT. The inhibitors for PKA and PKC also showed inhibitory effects. Interestingly, flagellin-induced IL-6 production was further enhanced by pretreatment with inhibitors for PI3K, implying that PI3K negatively affects the flagellin-induced IL-6 production. Furthermore, DNA binding activities of NF-κB, AP-1, and CREB, which play pivotal roles in the induction of IL-6 gene expression, were increased by flagellin. These results suggest that flagellin alone is sufficient to induce IL-6 gene expression via TLR5 signaling pathways in human basophils.

Whole blood gene expression and interleukin-6 levels

BACKGROUND

Circulating interleukin-6 levels increase with advancing age and are a risk factor for various diseases and mortality. The characterization of gene expression profiles associated with interleukin-6 levels might suggest important molecular events underlying its regulation.

METHODS AND RESULTS

We studied the association of transcriptional profiles with interleukin-6 levels in 2422 participants from the Framingham Heart Study Offspring Cohort using Affymetrix Human Exon 1.0 ST Array. We identified 4139 genes that were significantly associated with interleukin-6 levels (FDR<0.05) after adjusting for age, sex and blood cell components. We then replicated 807 genes in the InCHIANTI study with 694 participants. Many of the top genes are involved in inflammation-related pathways or erythrocyte function, including JAK/Stat signaling pathway and interleukin-10 signaling pathway.

CONCLUSION

We identified and replicated 807 genes that were associated with circulating interleukin-6 levels. Future characterization of interleukin-6 regulation networks may facilitate the identification of additional potential targets for treating inflammation-related diseases.

Homeobox transcription factor VentX regulates differentiation and maturation of human dendritic cells

Dendritic cells (DCs) are specialized antigen presentation cells that play critical roles in the initiation and regulation of immune responses. The molecular determinants of DC differentiation and maturation are target of extensive investigation. VentX is a human homeobox transcriptional factor that regulates proliferation and differentiation of hematopoietic cells. In the current study, we report that ablation of VentX expression in monocytes significantly impaired their differentiation into DCs. Conversely, overexpression of VentX in monocytic THP1 cells accelerated their differentiation toward DCs. We showed that VentX regulates DC differentiation, in part, through modulating IL6 expression. Clinically, we found that VentX expression was elevated in intestinal lamina propria DCs (LPDCs) of inflamed mucosa from inflammatory bowel disease patients. Knockdown experiments suggested that VentX is essential for the maturation of LPDCs. In addition, corticosteroid treatment markedly decreased VentX expression in LPDCs and enforced expression of VentX counteracted the effects of corticosteroid on DCs maturation. Our data suggest that VentX is a critical transcriptional regulator of DC differentiation and maturation, and a potential target of immune regulation and therapy.

Leptin induces IL-6 expression through OBRl receptor signaling pathway in human synovial fibroblasts

BACKGROUND

Leptin, an adipocyte-secreted hormone that centrally regulates weight control, may exert proinflammatory effects in the joint, depending on the immune response. Leptin is abundantly expressed in osteoarthritis (OA) cartilage and synovium. However, the relationship between leptin and interleukin-6 (IL-6) in OA synovial fibroblasts (OASFs) remains obscure.

METHODOLOGY/PRINCIPAL FINDINGS

Stimulation of OASFs with leptin induced IL-6 expression in a concentration- and time-dependent manner. OASFs expressed the long (OBRl) and short (OBRs) isoforms of the leptin receptor. However, OBRl, but not OBRs, antisense oligonucleotide (AS-ODN) abolished the leptin-mediated increase of IL-6 expression. Transfection with insulin receptor substrate (IRS)-1 siRNA decreased leptin-induced IL-6 production. In addition, pretreatment of cells with PI3K, Akt, or AP-1 inhibitor also inhibited the potentiating action of leptin. Leptin-induced AP-1 activation was inhibited by OBRl, IRS-1, PI3K, or Akt inhibitors and siRNAs.

CONCLUSIONS/SIGNIFICANCE

Our results showed that leptin activates the OBRl receptor, which in turn activates IRS-1, PI3K, Akt, and AP-1 pathway, leading to up-regulation of IL-6 expression.

Thyrotropin regulates IL-6 expression in CD34+ fibrocytes: clear delineation of its cAMP-independent actions

IL-6 plays diverse roles in normal and disease-associated immunity such as that associated with Graves’ disease (GD). In that syndrome, the orbit undergoes remodeling during a process known as thyroid-associated ophthalmopathy (TAO). Recently, CD34⁺ fibrocytes were found to infiltrate the orbit in TAO where they transition into CD34⁺ orbital fibroblasts. Surprisingly, fibrocytes display high levels of functional thyrotropin receptor (TSHR), the central antigen in GD. We report here that TSH and the pathogenic anti-TSHR antibodies that drive hyperthyroidism in GD induce IL-6 expression in fibrocytes and orbital fibroblasts. Unlike TSHR signaling in thyroid epithelium, that occurring in fibrocytes is completely independent of adenylate cyclase activation and cAMP generation. Instead TSH activates PDK1 and both AKT/PKB and PKC pathways. Expression and use of PKCβII switches to that of PKCµ as fibrocytes transition to TAO orbital fibroblasts. This shift is imposed by CD34⁻ orbital fibroblasts but reverts when CD34⁺ fibroblasts are isolated. The up-regulation of IL-6 by TSH results from coordinately enhanced IL-6 gene promoter activity and increased IL-6 mRNA stability. TSH-dependent IL-6 expression requires activity at both CREB (−213 to −208 nt) and NF-κB (–78 to −62 nt) binding sites. These results provide novel insights into the molecular action of TSH and signaling downstream for TSHR in non-thyroid cells. Fibrocytes neither express adenylate cyclase nor generate cAMP and thus these findings are free from any influence of cAMP-related signaling. They identify potential therapeutic targets for TAO.

Transcriptional regulation of the gilthead seabream (Sparus aurata) interleukin-6 gene promoter

Interleukin-6 (IL-6) has been identified and characterized from several fish species and its mRNA expression is induced by pathogen-associated molecular patterns (PAMPs) and cytokines in immune cells and tissues. However, the transcriptional regulation of the IL-6 gene in fish is not well understood. In the present study, we have cloned and sequenced a 1028 bp 5'-flanking DNA region from the IL-6 gene in seabream (Sparus aurata). Sequence analysis of the seabream IL-6 promoter (sbIL-6P) evidenced the presence of a conserved TATA motif and conserved response elements for NF-κB, C/EBPβ (NF-IL6), AP-1 and GRE, similar to other vertebrate IL-6 promoters. Functional characterization of sbIL-6P was performed by cloning sbIL-6P into a luciferase expression vector and by transfecting it into L6 muscle cells, a mammalian cell line shown previously to express IL-6 in response to pro-inflammatory stimuli. We show here that the activity of sbIL-6P was significantly induced by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα), IL-6 and IL-2, as well as by lipopolysaccharide (LPS), but significantly repressed by dexamethasone. In addition, the stimulatory effects of TNFα on sbIL-6P activity appeared to be mediated by the NF-κB, p38 MAPK and JNK signaling pathways. Deletion analyses of sbIL-6P suggested that activation of sbIL-6P by TNFα and IL-6 required the presence of binding motifs present in the proximal promoter (-171 to -84) whereas activation by IL-2 required binding motifs present in the distal promoter (-1024 to -864). The results from this study indicate, for the first time in fish, that pro-inflammatory cytokines, LPS and glucocorticoids can regulate the activity of the IL-6 gene at a transcriptional level and identify important regions in its response to cytokines.

CCN4 induces IL-6 production through αvβ5 receptor, PI3K, Akt, and NF-κB singling pathway in human synovial fibroblasts

Introduction

Osteoarthritis (OA) is the most common degenerative joint disease that is involved in the degradation of articular cartilage. The exact etiology of OA is not completely understood. CCN4 is related to up-regulation in the cartilage of patients with osteoarthritis. Previous studies have shown that CCN4 might be associated with the pathogenesis of OA, but the exact signaling pathways in CCN4-mediated IL-6 expression in synovial fibroblasts (SF) are largely unknown. Therefore, we explored the intracellular signaling pathway involved in CCN4-induced IL-6 production in human synovial fibroblast cells.

Methods

CCN4-induced IL-6 production was assessed with quantitative real-time qPCR and ELISA. The mechanisms of action of CCN4 in different signaling pathways were studied by using Western blotting. Neutralizing antibodies of integrin were used to block the integrin signaling pathway. Luciferase assays were used to study IL-6 and NF-κB promoter activity. Immunocytochemistry was used to examine the translocation activity of p65.

Results

Osteoarthritis synovial fibroblasts (OASFs) showed significant expression of CCN4 and the expression was higher than in normal SFs. OASF stimulation with CCN4 induced concentration- and time-dependent increases in IL-6 production. Pretreatment of OASFs with αvβ5 but not α5β1 and αvβ3 integrin antibodies reduced CCN4-induced IL-6 production. CCN4-mediated IL-6 production was attenuated by PI3K inhibitor (LY294002 and Wortmannin), Akt inhibitor (Akti), and NF-κB inhibitor (PDTC and TPCK). Stimulation of cells with CCN4 also increased PI3K, Akt, and NF-κB activation.

Conclusions

Our results suggest that CCN4 activates αvβ5 integrin, PI3K, Akt, and NF-κB pathways, leading to up-regulation of IL-6 production. According to our results, CCN4 may be an appropriate target for drug intervention in OA in the future.

CTGF increases IL-6 expression in human synovial fibroblasts through integrin-dependent signaling pathway

Background

Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. CTGF is abundantly expressed in osteoarthritis (OA). However, the relationship between CTGF and IL-6 in OA synovial fibroblasts (OASFs) is mostly unknown.

Methodology/Principal Findings

OASFs showed significant expression of CTGF, and expression was higher than in normal SFs. OASFs stimulation with CTGF induced concentration-dependent increases in IL-6 expression. CTGF mediated IL-6 production was attenuated by αvβ5 integrin neutralized antibody and apoptosis signal-regulating kinase 1 (ASK1) shRNA. Pretreatment with p38 inhibitor (SB203580), JNK inhibitor (SP600125), AP-1 inhibitors (Curcumin and Tanshinone IIA), and NF-κB inhibitors (PDTC and TPCK) also inhibited the potentiating action of CTGF. CTGF-mediated increase of NF-κB and AP-1 luciferase activity was inhibited by SB203580 and SP600125 or ASK1 shRNA or p38 and JNK mutant.

Conclusions/Significance

Our results suggest that CTGF increased IL-6 production in OASFs via the αvβ5 integrin, ASK1, p38/JNK, and AP-1/NF-κB signaling pathways.

TLR 2 induces vascular smooth muscle cell migration through cAMP response element-binding protein-mediated interleukin-6 production

OBJECTIVE

Migration of vascular smooth muscle cells (VSMCs) from the media into intima contributes to the development of atherosclerosis. Gene deletion experiments implicate a role for toll-like receptor 2 (TLR2) in atherogenesis. However, the underlying mechanisms remain unclear. We postulate that TLR2 promotes VSMC migration by enhancing interleukin (IL)-6 production.

METHODS AND RESULTS

Migration assays revealed that TLR2 agonists promoted VSMC migration but not cell proliferation or viability. TLR2 deficiency or inhibition of TLR2 signaling with anti-TLR2 antibody suppressed TLR2 agonist-induced VSMC migration and IL-6 production, which was mediated via p38 mitogen-associated protein kinase and extracellular signal-regulated kinase 1/2 signaling pathways. Neutralizing anti-IL-6 antibodies impaired TLR2-mediated VSMC migration and formation of filamentous actin fiber and lamellipodia. Blockade of p38 mitogen-associated protein kinase or extracellular signal-regulated kinase 1/2 activation inhibited TLR2 agonist pam3CSK4-induced phosphorylation of cAMP response element-binding protein, which regulates IL-6 promoter activity through the cAMP response element site. Moreover, cAMP response element-binding protein small interfering RNA inhibited pam3CSK4-induced IL-6 production and VSMC migration. Additionally, Rac1 small interfering RNA inhibited pam3CSK4-induced VSMC migration but not IL-6 production.

CONCLUSIONS

Our results suggest that on ligand binding, TLR2 activates p38 mitogen-associated protein kinase and extracellular signal-regulated kinase 1/2 signaling in VSMCs. These signaling pathways act in concert to activate cAMP response element-binding protein and subsequent IL-6 production, which in turn promotes VSMC migration via Rac1-mediated actin cytoskeletal reorganization.

Control of early Theiler's murine encephalomyelitis virus replication in macrophages by interleukin-6 occurs in conjunction with STAT1 activation and nitric oxide production

During Theiler's murine encephalomyelitis virus (TMEV) infection of macrophages, it is thought that high interleukin-6 (IL-6) levels contribute to the demyelinating disease found in chronically infected SJL/J mice but absent in B10.S mice capable of clearing the infection. Therefore, IL-6 expression was measured in TMEV-susceptible SJL/J and TMEV-resistant B10.S macrophages during their infection with TMEV DA strain or responses to lipopolysaccharide (LPS) or poly(I · C). Unexpectedly, IL-6 production was greater in B10.S macrophages than SJL/J macrophages during the first 24 h after stimulation with TMEV, LPS, or poly(I · C). Further experiments showed that in B10.S, SJL/J, and RAW264.7 macrophage cells, IL-6 expression was dependent on extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) and enhanced by exogenous IL-12. In SJL/J and RAW264.7 macrophages, exogenous IL-6 resulted in decreased TMEV replication, earlier activation of STAT1 and STAT3, production of nitric oxide, and earlier upregulation of several antiviral genes downstream of STAT1. However, neither inhibition of IL-6-induced nitric oxide nor knockdown of STAT1 diminished the early antiviral effect of exogenous IL-6. In addition, neutralization of endogenous IL-6 from SJL/J macrophages with Fab antibodies did not exacerbate early TMEV infection. Therefore, endogenous IL-6 expression after TMEV infection is dependent on ERK MAPK, enhanced by IL-12, but too slow to decrease viral replication during early infection. In contrast, exogenous IL-6 enhances macrophage control of TMEV infection through preemptive antiviral nitric oxide production and antiviral STAT1 activation. These results indicate that immediate-early production of IL-6 could protect macrophages from TMEV infection.

In vivo effects of Ginkgo biloba extract on interleukin-6 cytokine levels in patients with neurological disorders

OBJECTIVE

To evaluate the effect of Ginkgo biloba extract (EGB) on the serum levels of cytokines in patients suffering from chronic, age-related neurological disorders (NDs).

MATERIALS AND METHODS

Patients received 9.6 mg of EGB twice daily for 8 weeks. Serum levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA) before and after treatment.

RESULTS

The serum level of IL-6 was significantly higher in ND patients as compared to the healthy controls. After these patients underwent 4 and 8 weeks of EGB treatment, their IL-6 levels were shown a statistically significant (P<0.05) decline to near normal values. No significant changes were observed in serum levels of IL-1β and TNF-α after EGB treatment. We also observed an inverse relationship between ND and serum cholesterol levels.

CONCLUSIONS

EGB may exert its beneficial effects in patients suffering from NDs through down-regulation and suppression of IL-6 secretion.

Prevention and mitigation of acute radiation syndrome in mice by synthetic lipopeptide agonists of Toll-like receptor 2 (TLR2)

Bacterial lipoproteins (BLP) induce innate immune responses in mammals by activating heterodimeric receptor complexes containing Toll-like receptor 2 (TLR2). TLR2 signaling results in nuclear factor-kappaB (NF-κB)-dependent upregulation of anti-apoptotic factors, anti-oxidants and cytokines, all of which have been implicated in radiation protection. Here we demonstrate that synthetic lipopeptides (sLP) that mimic the structure of naturally occurring mycoplasmal BLP significantly increase mouse survival following lethal total body irradiation (TBI) when administered between 48 hours before and 24 hours after irradiation. The TBI dose ranges against which sLP are effective indicate that sLP primarily impact the hematopoietic (HP) component of acute radiation syndrome. Indeed, sLP treatment accelerated recovery of bone marrow (BM) and spleen cellularity and ameliorated thrombocytopenia of irradiated mice. sLP did not improve survival of irradiated TLR2-knockout mice, confirming that sLP-mediated radioprotection requires TLR2. However, sLP was radioprotective in chimeric mice containing TLR2-null BM on a wild type background, indicating that radioprotection of the HP system by sLP is, at least in part, indirect and initiated in non-BM cells. sLP injection resulted in strong transient induction of multiple cytokines with known roles in hematopoiesis, including granulocyte colony-stimulating factor (G-CSF), keratinocyte chemoattractant (KC) and interleukin-6 (IL-6). sLP-induced cytokines, particularly G-CSF, are likely mediators of the radioprotective/mitigative activity of sLP. This study illustrates the strong potential of LP-based TLR2 agonists for anti-radiation prophylaxis and therapy in defense and medical scenarios.

Cyclic AMP: a selective modulator of NF-κB action

It has been known for several decades that cyclic AMP (cAMP), a prototypical second messenger, transducing the action of a variety of G-protein-coupled receptor ligands, has potent immunosuppressive and anti-inflammatory actions. These actions have been attributed in part to the ability of cAMP-induced signals to interfere with the function of the proinflammatory transcription factor Nuclear Factor-kappaB (NF-κB). NF-κB plays a crucial role in switching on the gene expression of a plethora of inflammatory and immune mediators, and as such is one of the master regulators of the immune response and a key target for anti-inflammatory drug design. A number of fundamental molecular mechanisms, contributing to the overall inhibitory actions of cAMP on NF-κB function, are well established. Paradoxically, recent reports indicate that cAMP, via its main effector, the protein kinase A (PKA), also promotes NF-κB activity. Indeed, cAMP actions appear to be highly cell type- and context-dependent. Importantly, several novel players in the cAMP/NF-κB connection, which selectively direct cAMP action, have been recently identified. These findings not only open up exciting new research avenues but also reveal novel opportunities for the design of more selective, NF-κB-targeting, anti-inflammatory drugs.

Interleukin 6 underlies angiotensin II-induced hypertension and chronic renal damage

Chronic kidney disease (CKD) is a prevalent life-threatening disease frequently associated with hypertension, progression to renal fibrosis, and eventual renal failure. Although the pathogenesis of CKD remains largely unknown, an increased inflammatory response is known to be associated with the disease and has long been speculated to contribute to disease development. However, the causative factors, the exact role of the increased inflammatory cascade in CKD, and the underlying mechanisms for its progression remain unidentified. Here we report that interleukin 6 (IL-6) expression levels were significantly increased in the kidneys collected from CKD patients and further elevated in CKD patients characterized with hypertension. Functionally, we determined that angiotensin II is a causative factor responsible for IL-6 induction in the mouse kidney and that genetic deletion of IL-6 significantly reduced hypertension and key features of CKD, including renal injury and progression to renal fibrosis in angiotensin II-infused mice. Mechanistically, we provide both human and mouse evidence that IL-6 is a key cytokine functioning downstream of angiotensin II signaling to directly induce fibrotic gene expression and preproendothelin 1 mRNA expression in the kidney. Overall, both the mouse and human studies reported here provide evidence that angiotensin II induces IL-6 production in the kidney, and that, in addition to its role in hypertension, increased IL-6 may play an important pathogenic role in CKD by inducing fibrotic gene expression and ET-1 gene expression. These findings immediately suggest that the IL-6 signaling is a novel therapeutic target to manage this devastating disorder affecting millions worldwide.

Cutting edge: Calcium/Calmodulin-dependent protein kinase type IV is essential for mesangial cell proliferation and lupus nephritis

Renal involvement in systemic lupus erythematosus remains a major cause of morbidity and mortality. Although immune parameters that instigate renal damage have been characterized, their link to local processes, which execute tissue damage, is poorly understood. Using genetic-deletion and pharmacological-inhibition approaches, we demonstrated that calcium/calmodulin-dependent protein kinase type IV, which contributes to altered cytokine production in systemic lupus erythematosus patients, controls spontaneous and platelet-derived growth factor-stimulated mesangial cell proliferation and promotes IL-6 production through AP-1. Our studies identified calcium/calmodulin-dependent protein kinase type IV as a valuable treatment target for lupus nephritis and point out the importance of local kidney factors in the expression of tissue damage that, if properly targeted, should enhance clinical benefit and limit toxicity.

Comprehensive analysis of tumor microenvironment cytokines in Waldenstrom macroglobulinemia identifies CCL5 as a novel modulator of IL-6 activity

Although proinflammatory and chemotactic cytokines can profoundly affect the tumor microenvironment, and many of them have been shown to have therapeutic efficacy in preclinical models, the role of these molecules in Waldenström macroglobulinemia (WM) remains poorly understood. In this study, simultaneous analysis of WM patient sera and bone marrow biopsies identified a set of dysregulated cytokines including CCL5, G-CSF, and soluble IL-2 receptor, that were significantly elevated in WM patients whereas IL-8 and EGF levels were significantly lower in these patients compared with healthy controls. Interestingly, CCL5 levels positively correlated with features of disease aggressiveness such as elevated IgM levels and bone marrow involvement. Functional analysis of tumor microenvironment revealed a functional correlation between CCL5 levels and IL-6 levels, a proinflammatory cytokine with an important role in normal and malignant B-cell biology. Furthermore, CCL5 stimulated IL-6 secretion in WM stromal cells resulting in increased IgM secretion by WM malignant cells via the JAK/STAT signaling pathway. Thus, together these results define a novel signaling network in the WM tumor microenvironment controlling IgM secretion and suggest CCL5 as a potential target for the treatment of this disease.

Stromal cell-derived factor-1/CXCR4 promotes IL-6 production in human synovial fibroblasts

The production of chemokine stromal cell-derived factor (SDF)-1 is significantly higher in synovial fluid of patients with osteoarthritis (OA). IL-6 is a multifunctional cytokine that plays a central role in both OA and rheumatoid arthritis. However, the effects of SDF-1α on human synovial fibroblasts are largely unknown. In this study, we investigated the intracellular signaling pathway involved in SDF-1α-induced IL-6 production in human synovial fibroblast cells. SDF-1α caused concentration- and time-dependent increases in IL-6 production. SDF-1α also increased the mRNA and surface expression of CXCR4 receptor in human synovial fibroblasts. CXCR4-neutralizing antibody, CXCR4-specific inhibitor (AMD3100), or small interfering RNA against CXCR4 inhibited the SDF-1α-induced increase of IL-6 expression. The transcriptional regulation of IL-6 by SDF-1α was mediated by phosphorylation of phosphatidylinositol 3-kinase (PI3K)/Akt and activation of the activator protein (AP)-1 component of c-Jun. The binding of c-Jun to the AP-1 element on the IL-6 promoter and the increase in AP-1 luciferase activity was enhanced by SDF-1α. Co-transfection with CXCR4, PI3K, Akt, and c-Jun mutants or siRNA inhibited the potentiating action of SDF-1α on AP-1 promoter activity. Taken together, our results suggest that SDF-1α-increased IL-6 production in human synovial fibroblasts via the CXCR4 receptor, PI3K, Akt, c-Jun, and AP-1 signaling pathways.

HMGB-1 induces IL-6 production in human synovial fibroblasts through c-Src, Akt and NF-κB pathways

High mobility group box chromosomal protein 1 (HMGB-1) is a widely studied, ubiquitous nuclear protein that is present in eukaryotic cells, and plays a crucial role in inflammatory response. However, the effects of HMGB-1 on human synovial fibroblasts are largely unknown. In this study, we investigated the intracellular signaling pathway involved in HMGB-1-induced IL-6 production in human synovial fibroblast cells. HMGB-1 caused concentration- and time-dependent increases in IL-6 production. HMGB-1-mediated IL-6 production was attenuated by receptor for advanced glycation end products (RAGE) monoclonal antibody (Ab) or siRNA. Pretreatment with c-Src inhibitor (PP2), Akt inhibitor and NF-κB inhibitor (pyrrolidine dithiocarbamate and L-1-tosylamido-2-phenylenylethyl chloromethyl ketone) also inhibited the potentiating action of HMGB-1. Stimulation of cells with HMGB-1 increased the c-Src and Akt phosphorylation. HMGB-1 increased the accumulation of p-p65 in the nucleus, as well as NF-κB luciferase activity. HMGB-1-mediated increase of NF-κB luciferase activity was inhibited by RAGE Ab, PP2 and Akt inhibitor or RAGE siRNA, or c-Src and Akt mutant. Our results suggest that HMGB-1-increased IL-6 production in human synovial fibroblasts via the RAGE receptor, c-Src, Akt, p65, and NF-κB signaling pathways.

A novel intronic cAMP response element modulator (CREM) promoter is regulated by activator protein-1 (AP-1) and accounts for altered activation-induced CREM expression in T cells from patients with systemic lupus erythematosus

The transcriptional repressor cAMP response element modulator (CREM) α has important roles in normal T cell physiology and contributes to aberrant T cell function in patients with systemic lupus erythematosus (SLE). Recently, we characterized a specificity protein-1-dependent promoter located upstream of the CREM gene that accounts for increased basal CREM expression in SLE T cells and reflects disease activity. Here, we identify a novel intronic CREM promoter (denoted P2) in front of the second exon of the CREM gene that harbors putative binding sites for TATA-binding proteins and the transcriptional activator AP-1. DNA binding studies, chromatin immunoprecipitation, and reporter assays confirmed the functional relevance of these sites, and T cell activation through CD3/CD28 stimulation or phorbol 12-myristate 13-acetate/ionomycin treatment enhances P2 promoter activity. Although the basal CREM levels are increased in T cells from SLE patients compared with healthy controls, there are remarkable differences in the regulation of CREM expression in response to T cell activation. Whereas T cells from healthy individuals display increased CREM expression after T cell activation, most likely through AP-1-dependent up-regulation of the P2 promoter, SLE T cells fail to further increase their basal CREM levels upon T cell activation due to a decreased content of the AP-1 family member c-Fos. Because CREM trans-represses c-fos transcription in SLE T cells, we propose an autoregulatory feedback mechanism between CREM and AP-1. Our findings extend the understanding of CREM gene regulation in the context of T cell activation and disclose another difference in the transcriptional machinery in SLE T cells.