IL-6-regulated transcription factors

A critical role for HNF4α in polymicrobial sepsis-associated metabolic reprogramming and death

In sepsis, limited food intake and increased energy expenditure induce a starvation response, which is compromised by a quick decline in the expression of hepatic PPARα, a transcription factor essential in intracellular catabolism of free fatty acids. The mechanism upstream of this PPARα downregulation is unknown. We found that sepsis causes a progressive hepatic loss-of-function of HNF4α, which has a strong impact on the expression of several important nuclear receptors, including PPARα. HNF4α depletion in hepatocytes dramatically increases sepsis lethality, steatosis, and organ damage and prevents an adequate response to IL6, which is critical for liver regeneration and survival. An HNF4α agonist protects against sepsis at all levels, irrespectively of bacterial loads, suggesting HNF4α is crucial in tolerance to sepsis. In conclusion, hepatic HNF4α activity is decreased during sepsis, causing PPARα downregulation, metabolic problems, and a disturbed IL6-mediated acute phase response. The findings provide new insights and therapeutic options in sepsis.

FAM3C/ILEI protein is elevated in psoriatic lesions and triggers psoriasiform hyperproliferation in mice

FAM3C/ILEI is an important cytokine for tumor progression and metastasis. However, its involvement in inflammation remains elusive. Here, we show that ILEI protein is highly expressed in psoriatic lesions. Inducible keratinocyte-specific ILEI overexpression in mice (K5-ILEIind ) recapitulates many aspects of psoriasis following TPA challenge, primarily manifested by impaired epidermal differentiation and increased neutrophil recruitment. Mechanistically, ILEI triggers Erk and Akt signaling, which then activates STAT3 via Ser727 phosphorylation. Keratinocyte-specific ILEI deletion ameliorates TPA-induced skin inflammation. A transcriptomic ILEI signature obtained from the K5-ILEIind model shows enrichment in several signaling pathways also found in psoriasis and identifies urokinase as a targetable enzyme to counteract ILEI activity. Pharmacological inhibition of urokinase in TPA-induced K5-ILEIind mice results in significant improvement of psoriasiform symptoms by reducing ILEI secretion. The ILEI signature distinguishes psoriasis from healthy skin with uPA ranking among the top "separator" genes. Our study identifies ILEI as a key driver in psoriasis, indicates the relevance of ILEI-regulated genes for disease manifestation, and shows the clinical impact of ILEI and urokinase as novel potential therapeutic targets in psoriasis.

IL-33 promotes increased replication of Theiler's Murine Encephalomyelitis Virus in RAW264.7 macrophage cells with an IRF3-dependent response

Interleukin-33 (IL-33), which promotes M2 macrophage development, may influence the control of viruses, such as Theiler's Murine Encephalomyelitis Virus (TMEV) that infect macrophages. Because Interferon Regulatory Factor-3 (IRF3) is also critical to control of TMEV infection in macrophages, information on the relationship between IL-33 and IRF3 is important. Thus, RAW264.7 Lucia murine macrophage lineage cells with an endogenous IRF3-ISRE promoter driving secreted luciferase and IRF3KO RAW Lucia, a subline deficient in IRF3, were challenged with TMEV. After the challenge, considerable TMEV RNA detected at 18 and 24 h in RAW cells was significantly elevated in IRF3KO RAW cells. TMEV induction of ISRE-IRF3 promoter activity, IFN-β and IL-33 gene expression, and IL-6 and IL-10 protein production, which was strong in RAW cells, was less in IRF3KO RAW cells. In contrast, expression of CD206 and ARG1, classical M2 macrophage markers, was significantly elevated in IRF3KO RAW cells. Moreover, RAW and IRF3KO RAW cells produced extracellular IL-33 prior to and after infection with TMEV and antibody blockade of the IL-33 receptor, ST2, reduced CD206 and ARG1 expression, but increased IL-6 gene expression. Pre-treating both RAW and IRF3KO RAW cells with IL-33 prior to challenge significantly increased TMEV infection, but also increased IL-33, IL-10, IL-6 mRNA expression, and NO production without increasing IFN-β. Notably, IL-33 induction of IL-33, IRF3-ISRE promoter activity, and IL-10 by TMEV or poly I:C/IFN-γ was significantly dependent upon IRF3. The results show that the expression of IL-33 and the repression of M2 macrophage phenotypic markers are dependent on IRF3 and that IL-33 decreases the ability of macrophages to control infection with macrophage-tropic viruses.

Glial functions in the blood-brain communication at the circumventricular organs

The circumventricular organs (CVOs) are located around the brain ventricles, lack a blood-brain barrier (BBB) and sense blood-derived molecules. This review discusses recent advances in the importance of CVO functions, especially glial cells transferring periphery inflammation signals to the brain. The CVOs show size-limited vascular permeability, allowing the passage of molecules with molecular weight <10,000. This indicates that the lack of an endothelial cell barrier does not mean the free movement of blood-derived molecules into the CVO parenchyma. Astrocytes and tanycytes constitute a dense barrier at the distal CVO subdivision, preventing the free diffusion of blood-derived molecules into neighboring brain regions. Tanycytes in the CVOs mediate communication between cerebrospinal fluid and brain parenchyma via transcytosis. Microglia and macrophages of the CVOs are essential for transmitting peripheral information to other brain regions via toll-like receptor 2 (TLR2). Inhibition of TLR2 signaling or depletion of microglia and macrophages in the brain eliminates TLR2-dependent inflammatory responses. In contrast to TLR2, astrocytes and tanycytes in the CVOs of the brain are crucial for initiating lipopolysaccharide (LPS)-induced inflammatory responses via TLR4. Depletion of microglia and macrophages augments LPS-induced fever and chronic sickness responses. Microglia and macrophages in the CVOs are continuously activated, even under normal physiological conditions, as they exhibit activated morphology and express the M1/M2 marker proteins. Moreover, the microglial proliferation occurs in various regions, such as the hypothalamus, medulla oblongata, and telencephalon, with a marked increase in the CVOs, due to low-dose LPS administration, and after high-dose LPS administration, proliferation is seen in most brain regions, except for the cerebral cortex and hippocampus. A transient increase in the microglial population is beneficial during LPS-induced inflammation for attenuating sickness response. Transient receptor potential receptor vanilloid 1 expressed in astrocytes and tanycytes of the CVOs is responsible for thermoregulation upon exposure to a warm environment less than 37°C. Alternatively, Nax expressed in astrocytes and tanycytes of the CVOs is crucial for maintaining body fluid homeostasis. Thus, recent findings indicate that glial cells in the brain CVOs are essential for initiating neuroinflammatory responses and maintaining body fluid and thermal homeostasis.

CEBPD modulates the airway smooth muscle transcriptomic response to glucocorticoids

Background

CCAAT/Enhancer Binding Protein D (CEBPD), a pleiotropic glucocorticoid-responsive transcription factor, modulates inflammatory responses. Of relevance to asthma, expression of CEBPD in airway smooth muscle (ASM) increases with glucocorticoid exposure. We sought to characterize CEBPD-mediated transcriptomic responses to glucocorticoid exposure in ASM by measuring changes observed after knockdown of CEBPD and its impact on asthma-related ASM function.

Methods

Primary ASM cells derived from four donors were transfected with CEBPD or non-targeting (NT) siRNA and exposed to vehicle control, budesonide (100 nM, 18 h), TNFα (10 ng/ml, 18 h), or both budesonide and TNFα. Subsequently, RNA-Seq was used to measure gene expression levels, and pairwise differential expression results were obtained for exposures versus vehicle and knockdown versus control conditions. Weighted gene co-expression analysis was performed to identify groups of genes with similar expression patterns across the various experimental conditions (i.e., CEBPD knockdown status, exposures).

Results

CEBPD knockdown altered expression of 3037 genes under at least one exposure (q-value < 0.05). Co-expression analysis identified sets of 197, 152 and 290 genes that were correlated with CEBPD knockdown status, TNFα exposure status, and both, respectively. JAK-STAT signaling pathway genes, including IL6R and SOCS3, were among those influenced by both TNFα and CEBPD knockdown. Immunoblot assays revealed that budesonide-induced IL-6R protein expression and augmented IL-6-induced STAT3 phosphorylation levels were attenuated by CEBPD knockdown in ASM.

Conclusions

CEBPD modulates glucocorticoid responses in ASM, in part via modulation of IL-6 receptor signaling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02119-1.

The hormetic and hermetic role of IL-6

Interleukin-6 is a pleiotropic cytokine regulating different tissues and organs in diverse and sometimes discrepant ways. The dual and sometime hermetic nature of IL-6 action has been highlighted in several contexts and can be explained by the concept of hormesis, in which beneficial or toxic effects can be induced by the same molecule depending on the intensity, persistence, and nature of the stimulation. According with hormesis, a low and/or controlled IL-6 release is associated with anti-inflammatory, antioxidant, and pro-myogenic actions, whereas increased systemic levels of IL-6 can induce pro-inflammatory, pro-oxidant and pro-fibrotic responses. However, many aspects regarding the multifaceted action of IL-6 and the complex nature of its signal transduction remains to be fully elucidated. In this review we collect mechanistic insight into the molecular networks contributing to normal or pathologic changes during advancing age and in chronic diseases. We point out the involvement of IL-6 deregulation in aging-related diseases, dissecting the hormetic action of this key mediator in different tissues, with a special focus on skeletal muscle. Since IL-6 can act as an enhancer of detrimental factor associated with both aging and pathologic conditions, such as chronic inflammation and oxidative stress, this cytokine could represent a "Gerokine", a determinant of the switch from physiologic aging to age-related diseases.

Lagerstroemia indica extract regulates human hair dermal papilla cell growth and degeneration via modulation of β-catenin, Stat6 and TGF-β signaling pathway

BACKGROUND

Lagerstroemia indica (L. indica) is reported to have diverse biological activities including anti-inflammatory, anti-cancer, neuro-regulatory, antidiabetic and antioxidant activity.

AIMS

The purpose of the present study is to examine the potential of hair growth promotion and/or hair loss prevention by L. indica extract.

PATIENTS/METHODS

The effects of L. indica on hair growth have been studied in human hair follicle dermal papillary (hHFDP) cells and follicular organ culture ex vivo by cell proliferation assay, PCR, western blot analysis and reporter gene activity assay. Moreover, a clinical trial was conducted in healthy volunteers.

RESULTS

L. indica significantly promoted the proliferation of hHFDP cells, which was associated with increased expression of TCF/LEF, VEGF and Gli1 mRNA, and inhibition of STAT6 and Smad2 mRNA. Treatment with L. indica also increased the TCF/LEF reporter gene activity but downregulated the SBE- and STAT6-luciferase activities. The expression of total β-catenin, CDK4 and CDK2 were elevated, while that of STAT6 and SMAD2/3 was suppressed upon treatment with L. indica. In human hair follicles organ culture, L. indica significantly inhibited hair follicular degeneration. The clinical trial showed a statistically significant rise in total hair count in test group (n=24) after 24 weeks of applying the hair tonic enriched with L. indica (141.46 ± 21.27 number/cm² , p < 0.05).

CONCLUSION

We suggest that L. indica extract prevents hair loss as well as stimulate hair growth by regulating the Wnt-β-catenin, JAK3-STAT6 and TGF-β1-Smad signaling pathways, and may be further developed as a novel functional cosmetic for preventing hair loss.

IL-6 Revisited: From Rheumatoid Arthritis to CAR T Cell Therapy and COVID-19

The diverse biological activity of interleukin-6 (IL-6) contributes to the maintenance of homeostasis. Emergent infection or tissue injury induces rapid production of IL-6 and activates host defense through augmentation of acute-phase proteins and immune responses. However, excessive IL-6 production and uncontrolled IL-6 receptor signaling are critical to pathogenesis. Over the years, therapeutic agents targeting IL-6 signaling, such as tocilizumab, a humanized anti-IL-6 receptor antibody, have shown remarkable efficacy for rheumatoid arthritis, Castleman disease, and juvenile idiopathic arthritis, and their efficacy in other diseases is continually being reported. Emerging evidence has demonstrated the benefit of tocilizumab for several types of acute inflammatory diseases, including cytokine storms induced by chimeric antigen receptor T-cell therapy and coronavirus disease 2019 (COVID-19). Here, we refocus attention on the biology of IL-6 and summarize the distinct pathological roles of IL-6 signaling in several acute and chronic inflammatory diseases. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Identification of Druggable Genes for Asthma by Integrated Genomic Network Analysis

Asthma is a common and heterogeneous disease characterized by chronic airway inflammation. Currently, the two main types of asthma medicines are inhaled corticosteroids and long-acting β2-adrenoceptor agonists (LABAs). In addition, biological drugs provide another therapeutic option, especially for patients with severe asthma. However, these drugs were less effective in preventing severe asthma exacerbation, and other drug options are still limited. Herein, we extracted asthma-associated single nucleotide polymorphisms (SNPs) from the genome-wide association studies (GWAS) and phenome-wide association studies (PheWAS) catalog and prioritized candidate genes through five functional annotations. Genes enriched in more than two categories were defined as “biological asthma risk genes.” Then, DrugBank was used to match target genes with FDA-approved medications and identify candidate drugs for asthma. We discovered 139 biological asthma risk genes and identified 64 drugs targeting 22 of these genes. Seven of them were approved for asthma, including reslizumab, mepolizumab, theophylline, dyphylline, aminophylline, oxtriphylline, and enprofylline. We also found 17 drugs with clinical or preclinical evidence in treating asthma. In addition, eleven of the 40 candidate drugs were further identified as promising asthma therapy. Noteworthy, IL6R is considered a target for asthma drug repurposing based on its high target scores. Through in silico drug repurposing approach, we identified sarilumab and satralizumab as the most promising drug for asthma treatment.

Poly(dA:dT) Suppresses HSV-2 Infection of Human Cervical Epithelial Cells Through RIG-I Activation

Epithelial cells of the female reproductive tract (FRT) participate in the initial innate immunity against viral infections. Poly(dA:dT) is a synthetic analog of B form double-stranded (ds) DNA which can activate the interferon (IFN) signaling pathway-mediated antiviral immunity through DNA-dependent RNA Polymerase III. Here we investigated whether poly(dA:dT) could inhibit herpes simplex virus type 2 (HSV-2) infection of human cervical epithelial cells (End1/E6E7). We demonstrated that poly(dA:dT) treatment of End1/E6E7 cells could significantly inhibit HSV-2 infection. Mechanistically, poly(dA:dT) treatment of the cells induced the expression of the intracellular IFNs and the multiple antiviral IFN-stimulated genes (ISGs), including IFN-stimulated gene 15 (ISG15), IFN-stimulated gene 56 (ISG56), 2'-5'-oligoadenylate synthetase 1 (OAS1), 2'-5'-oligoadenylate synthetase 2 (OAS2), myxovirus resistance protein A (MxA), myxovirus resistance protein B (MxB), virus inhibitory protein, endoplasmic reticulum-associated, IFN-inducible (Viperin), and guanylate binding protein 5 (GBP5). Further investigation showed that the activation of RIG-I was largely responsible for poly(dA:dT)-mediated HSV-2 inhibition and IFN/ISGs induction in the cervical epithelial cells, as RIG-I knockout abolished the poly(dA:dT) actions. These observations demonstrate the importance for design and development of AT-rich dsDNA-based intervention strategies to control HSV-2 mucosal transmission in FRT.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

STX-0119, a novel STAT3 dimerization inhibitor, prevents fibrotic gene expression in a mouse model of kidney fibrosis by regulating Cxcr4 and Ccr1 expression

Kidney fibrosis is a histological hallmark of chronic kidney disease (CKD) and is believed to be involved in the progression of CKD. Therefore, inhibition of kidney fibrosis is a potential strategy for slowing CKD progression. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that is activated by interleukin-6 and is reported to be involved in fibrosis. Previously, S3I-201, an inhibitor of STAT3 phosphorylation, was shown to inhibit renal fibrosis in a mouse model, but its mechanism was not clarified completely. In this study, we investigated whether STX-0119, a new inhibitor of STAT3 dimerization, suppressed kidney fibrotic gene expression using a mouse model of kidney fibrosis and examined the underlying mechanisms. Kidney fibrosis was induced by unilateral ureteral obstruction (UUO), which was accompanied by upregulation of STAT3 target genes. STX-0119 administration suppressed the expression of fibrotic genes in UUO kidneys without affecting STAT3 phosphorylation. STX-0119 decreased Cxcr4 mRNA in cultured rat kidney fibroblasts and Ccr1 mRNA in blood cells from UUO mice, both of which are reported to be involved in the progression of kidney fibrosis. These results suggest that STX-0119 inhibits fibrotic gene expression in kidney by suppressing Cxcr4 and Ccr1 expression. This is the first report to indicate a part of the mechanism of the antifibrotic effects of a STAT3 inhibitor and suggests that STX-0119 may be a lead compound for the treatment of kidney fibrosis.

A Phosphomimetic Study Implicates Ser557 in Regulation of FOXP2 DNA Binding

FOXP2 is a transcription factor expressed in multiple tissues during embryonic development. FOXP2 regulates transcription by binding to DNA at its DNA binding domain, the forkhead domain (FHD) through the recognition helix. Ser557 is a residue located within the recognition helix that has the potential to become phosphorylated posttranslationally. In this study we investigated whether phosphorylation of Ser557 can influence the structure and DNA binding of the FOXP2 FHD. We did this by constructing S557E, a phosphomimetic mutant, and comparing its behaviour to the wild type. The mutation did not affect the secondary or tertiary structure of the protein although it did decrease the propensity of the FOXP2 FHD to form dimers. Most notably, the mutation showed significantly reduced DNA binding compared to the wild type as detected using electrophoretic mobility shift assays. Molecular docking was also performed in which the wild type, phosphomimetic mutant and phosphorylated wild-type were docked to DNA and their interactions with DNA were compared. These results indicated that the wild type forms more interactions with the DNA and that the phosphomimetic mutant as well as the phosphorylated wild type did not associate as favourably with the DNA. This indicates that phosphorylation of Ser557 could disrupt DNA binding likely due to electrostatic and steric hindrance. This suggests that phosphorylation of Ser557 in the FOXP2 FHD could act as a control mechanism for FOXP2 and ultimately could be involved in regulation of transcription.

Serum Levels of Leptin in Multiple Myeloma Patients and Its Relation to Angiogenic and Inflammatory Cytokines

Background

Leptin, apart from the regulation of food intake, has been implicated in hematopoiesis, the immune response and angiogenesis. Leptin has been found to be decreased in various hematological malignancies. In the present study leptin was measured in multiple myeloma (MM) patients before and after treatment and correlated with other angiogenic molecules and markers of disease activity.

Methods

Serum leptin, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (b-FGF), interleukin-1 beta (IL-1β), beta 2 microglobulin (β2M) and C-reactive protein (CRP) were measured in 62 newly diagnosed MM patients, 22 of whom obtaining disease stabilization after treatment. The same parameters were measured in 20 healthy controls. Disease stage was defined according to the Durie-Salmon criteria.

Results

Leptin, VEGF, b-FGF, IL-1β, and β2M were significantly higher in newly diagnosed MM patients than in controls (p<0.05). VEGF, b-FGF, IL-1β, β2M, CRP but not leptin increased with advancing stage of disease (p<0.01). All parameters decreased significantly following treatment (p<0.001). Although IL-1β correlated positively with VEGF, β2M, b-FGF and CRP, leptin did not correlate with any of the measured parameters.

Conclusion

Leptin serum levels do not reflect disease severity in MM. However, there seems to be a decrease in leptin following treatment, which may be associated with an alteration in the metabolic state or the chemokine milieu.

Toll-Like Receptor-3 Mediates HIV-1-Induced Interleukin-6 Expression in the Human Brain Endothelium via TAK1 and JNK Pathways: Implications for Viral Neuropathogenesis

HIV-1-associated neurocognitive disorders (HAND) is associated with blood-brain-barrier (BBB) inflammation, and inflammation involves toll-like receptors (TLRs) signaling. It is not known whether primary human brain microvascular endothelial cells (HBMEC), the major BBB component, express TLRs or whether TLRs are involved in BBB dysfunction and HAND. We demonstrate that HBMEC express TLR3, 4, 5, 7, 9, and 10, and TLR3 was the most abundant. HIV-1 and TLR3 activation increased endothelial TLR3 transcription and expression. HIV-1-positive human subjects showed significantly higher TLR3 expression in brain tissues and blood vessels, with higher TLR3 levels in subjects with HAND. HIV-1 and TLR3 activation increased endothelial IL6 expression by 6-to-127-fold (P < 0.001), activated c-jun(serine-63) and SAPK/JNK(Thr183/Tyr185). HIV-1 upregulated IL6 through interleukin-1 receptor-associated-kinase (IRAK)-1/4/TAK1/JNK pathways, via ATP-dependent JNK activation. TLR3 activation upregulated IL6 through TAK1/JNK pathways, via ATP-dependent or -independent JNK activation. HIV-1 and TLR3 activation also upregulated transcription factors associated with IL6 and TAK1/JNK pathways (Jun, CEBPA, STAT1). Blocking TLR3 activation prevented HIV-1- and TLR3 ligands-induced upregulation of these transcription factors, prevented IL6 transcription and expression, c-jun and JNK activation. HIV-1 and TLR3 ligands significantly increased monocytes adhesion and migration through the BBB, and decreased endothelial claudin-5 expression. Blocking TLR3 and JNK activation prevented HIV-1- and TLR3 ligands-induced claudin-5 downregulation, monocytes adhesion and transendothelial migration. These data suggest that viral immune recognition via endothelial TLR3 is involved in endothelial inflammation and BBB dysfunction in HIV/AIDS and HAND. Our data provides novel insights into the molecular basis of these HIV-1- and TLR3-mediated effects.

Immunopathogenesis of HPV-Associated Cancers and Prospects for Immunotherapy

Human papillomavirus (HPV) infection is a causative factor for various cancers of the anogenital region and oropharynx, and is supposed to play an important cofactor role for skin carcinogenesis. Evasion from immunosurveillance favors viral persistence. However, there is evidence that the mere presence of oncogenic HPV is not sufficient for malignant progression and that additional tumor-promoting steps are required. Recent studies have demonstrated that HPV-transformed cells actively promote chronic stromal inflammation and conspire with cells in the local microenvironment to promote carcinogenesis. This review highlights the complex interplay between HPV-infected cells and the local immune microenvironment during oncogenic HPV infection, persistence, and malignant progression, and discusses new prospects for diagnosis and immunotherapy of HPV-associated cancers.

Influence of haplotypes, gene expression and soluble levels of L-selectin on the risk of acute coronary syndrome

BACKGROUND

L-selectin gene (SELL) is a candidate gene for the development of acute coronary syndrome (ACS) that contributes to endothelial dysfunction. The -642C>T (rs2205849) and 725C>T (rs2229569) polymorphisms have been associated with changes in gene expression, ligand affinity and increased risk of cardiovascular disease. The aim of this study was to investigate the association between the haplotypes constructed with the -642C>T and 725C>T polymorphisms of the SELL gene, the expression levels of its mRNA and the serum levels of soluble L-selectin with ACS.

METHODS

We recruited 615 individuals of Mexican origin matched by age, including 342 patients with ACS and 273 individuals without personal history of ischemic cardiopathy as control group (CG). Genotyping was performed by PCR-RFLP. The qPCR technique was used to analyze the expression of mRNA using TaqMan® UPL probes. The levels of soluble L-selectin were measured with ELISA.

RESULTS

The allele variants in both polymorphisms were over-represented in the CG compared to the ACS (OR range: 0.371-0.716, p<0.006). The CT and TT haplotypes had a protective effect against the development of ACS (OR=0.401, p<0.0001; OR=0.628, p<0.0001, respectively). SELL expression was 3.076 times higher in the ACS group compared to CG (p<0.001). The levels of soluble L-selectin were similar between ACS and CG.

CONCLUSIONS

Both polymorphisms had no effect on mRNA expression and soluble protein levels. The polymorphisms -642C>T and 725C>T of the SELL gene are protective factors against the development of ACS. There is an increased gene expression of L-selectin in ACS compared to CG in the population of Western Mexico.

Tumor-derived exosomes educate dendritic cells to promote tumor metastasis via HSP72/HSP105-TLR2/TLR4 pathway

How the tumor microenvironment educates dendritic cells (DCs) to promote tumorigenesis remains largely unknown, and the role of tumor-derived exosomes (TEXs) in tumorigenesis is controversial. Here, we report that in addition to the activation of DCs, TEXs induce DCs to produce increased interleukin-6 (IL-6), which dramatically promotes tumor invasion by increasing signal transducer and activator of transcription 3 (STAT3)-dependent matrix metalloproteinases 9 transcription activity in tumor cells. HSP72 and HSP105 on the TEX surface induce IL-6 secretion of DCs in a TLR2- and TLR4-dependent manner. In addition, HSP72 and HSP105 are predominantly present on exosomes from sera of tumor patients but not healthy people, indicating their value in tumor prediction. Furthermore, TEXs are powerful activators of DCs, and the depletion of IL-6 converts TEXs from tumor promoters to tumor inhibitors in vivo. Therefore, our results reveal a novel mechanism for the TEX-mediated education of DCs and shed light on the conundrum that TEXs present by playing dual roles in tumorigenesis.

Actin filament-associated protein 1 (AFAP-1) is a key mediator in inflammatory signaling-induced rapid attenuation of intrinsic P-gp function in human brain capillary endothelial cells

The purpose of this study was to identify regulatory molecule(s) involved in the inflammatory signaling-induced decrease in P-glycoprotein (P-gp) efflux function at the blood-brain barrier (BBB) that may occur in brain diseases. We confirmed that in vivo P-gp efflux activity at the BBB was decreased without any change in P-gp protein expression level in a mouse model of acute inflammation induced by 3 mg/kg lipopolysaccharide. In a human BBB model cell line (human brain capillary endothelial cells; hCMEC/D3), 1-h treatment with 10 ng/mL tumor necrosis factor-α (TNF-α; an inflammatory mediator) rapidly reduced P-gp efflux activity, but had no effect on P-gp protein expression level. To clarify the non-transcriptional mechanism that causes the decrease in intrinsic efflux activity of P-gp in acute inflammation, we applied comprehensive quantitative phosphoproteomics to compare hCMEC/D3 cells treated with TNF-α and vehicle (control). Actin filament-associated protein-1 (AFAP-1), MAPK1, and transcription factor AP-1 (AP-1) were significantly phosphorylated in TNF-α-treated cells, and were selected as candidate proteins. In validation experiments, knockdown of AFAP-1 expression blocked the reduction in P-gp efflux activity by TNF-α treatment, whereas inhibition of MAPK function or knockdown of AP-1 expression did not. Quantitative targeted absolute proteomics revealed that the reduction in P-gp activity by TNF-α did not require any change in P-gp protein expression levels in the plasma membrane. Our results demonstrate that AFAP-1 is a key mediator in the inflammatory signaling-induced, translocation-independent rapid attenuation of P-gp efflux activity in human brain capillary endothelial cells.

Evaluation of inflammatory markers interleukin-6 (IL-6) and matrix metalloproteinase-9 (MMP-9) in asthma

INTRODUCTION

Even though IL-6 and MMP-9 are associated with airway inflammation in asthma, there is paucity of data in Indian population.

OBJECTIVE

To determine the levels of IL-6 and MMP-9 in the serum of patients suffering from asthma, and correlate with (a) disease severity, as per GINA guidelines; (b) clinical phenotypes; and (c) response to treatment.

METHODOLOGY

The levels of IL-6 and MMP-9 were compared between moderate persistent asthma (n = 25), severe persistent asthma (n = 25) and normal controls (n = 30). IL-6 and MMP-9 were measured by ELISA (R&D Systems Inc., USA and Canada) and compared between controls and asthmatics and between groups of different asthma severity, clinical variables, spirometry, and allergen sensitization. Spirometry was repeated after 2 months of ICS+LABA to assess response to treatment in relation to baseline IL-6 and MMP-9 levels.

RESULTS

We observed a significant difference in both IL-6 and MMP-9 levels among asthmatics versus controls (p < 0.001), moderate versus severe persistent asthma (p < 0.001). A significant negative correlation was observed between MMP-9 and pre-bronchodilator FEV₁ and FVC, but not with IL-6. There was no association between IL-6 and MMP-9 with asthma duration, total IgE, AEC, number of allergens sensitized and degree of sensitization. No significant correlation (p > 0.5) was observed with IL-6 and MMP-9 levels and FEV₁ improvement after 2 months of ICS+LABA.

CONCLUSION

Higher levels of IL-6 and MMP-9 were observed in asthmatics as compared to controls and in severe persistent asthma as compared to moderate persistent asthma, higher levels of MMP-9 was associated with lower lung functions.

IL-6 ameliorates defective leptin sensitivity in DIO ventromedial hypothalamic nucleus neurons

Rats selectively bred to develop diet-induced obesity (DIO) have an early onset reduction in the sensitivity of their ventromedial hypothalamic nucleus (VMN) neurons to leptin compared with diet-resistant (DR) rats. This reduced sensitivity includes decreased leptin receptor (Lepr-b) mRNA expression, leptin receptor binding, leptin-induced phosphorylation of STAT3 (pSTAT3), and impaired leptin excitation (LepE) of VMN neurons. When administered exogenously, the pancreatic peptide, amylin, acts synergistically to reduce food intake and body weight in obese, leptin-resistant DIO rats by increasing VMN leptin signaling, likely by stimulation of microglia IL-6, which acts on its receptor to increase leptin-induced pSTAT3. Here, we demonstrate that incubation of cultured VMN neurons of outbred rats with IL-6 increases their leptin sensitivity. Control, dissociated DIO VMN neurons express 66% less Lepr-b and 75% less Bardet Biedl Syndrome-6 (BBS6) mRNA and have reduced leptin-induced activation of LepE neurons compared with DR neurons. Incubation for 4 days with IL-6 increased DIO neuron Lepr-b expression by 77% and BBS6 by 290% and corrected their defective leptin activation of LepE neurons to DR levels. Since BBS6 enhances trafficking of Lepr-b to the cell membrane, the increases in Lepr-b and BBS6 expression appear to account for correction of the reduced leptin excitation of DIO LepE neurons to that of control DR rats. These data support prior findings suggesting that IL-6 mediates the leptin-sensitizing effects of amylin on VMN neurons and that the inherent leptin resistance of DIO rats can be effectively reversed at a cellular level by IL-6.

STAT3 Represses Nitric Oxide Synthesis in Human Macrophages upon Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis is a successful intracellular pathogen. Numerous host innate immune responses signaling pathways are induced upon mycobacterium invasion, however their impact on M. tuberculosis replication is not fully understood. Here we reinvestigate the role of STAT3 specifically inside human macrophages shortly after M. tuberculosis uptake. We first show that STAT3 activation is mediated by IL-10 and occurs in M. tuberculosis infected cells as well as in bystander non-colonized cells. STAT3 activation results in the inhibition of IL-6, TNF-α, IFN-γ and MIP-1β. We further demonstrate that STAT3 represses iNOS expression and NO synthesis. Accordingly, the inhibition of STAT3 is detrimental for M. tuberculosis intracellular replication. Our study thus points out STAT3 as a key host factor for M. tuberculosis intracellular establishment in the early stages of macrophage infection.

Extraction of Flavonoids from the Flowers of Abelmoschus manihot (L.) Medic by Modified Supercritical CO₂ Extraction and Determination of Antioxidant and Anti-Adipogenic Activity

Abelmoschus manihot (L.) Medic has been used for many years in Chinese traditional medicine. In this study, supercritical CO₂ plus a modifier was utilized to extract flavonoids from the flowers of Abelmoschus manihot (L.) Medic. The effects of temperature (40 °C–60 °C), pressure (10–30 MPa) and different concentrations of ethanol as modifier (60%–90%, ethanol:water, v/v) on major flavonol content and the antioxidant activity of the extracts were studied by response surface methodology (RSM) using a Box-Behnken design. The flavonol content was calculated as the sum of the concentrations of seven major flavonoids, namely rutin, hyperin, isoquercetin, hibifolin, myricetin, quercetin-3′-O-glucoside and quercetin, which were simultaneously determined by a HPLC method. The antioxidant activity was evaluated by a 2,2-diphenyl-1-picrylhydarzyl (DPPH) free radical-scavenging assay. The results showed that three factors and their interactions could be well fitted to second-order polynomial models (p < 0.05). At the optimal extraction conditions for flavonol content (20 MPa, 52 °C, and 85% ethanol content), the yield of flavonoids was 41.96 mg/g and the IC₅₀ value was 0.288 mg/mL, respectively, suggesting the extract has high antioxidant activity. Furthermore, the anti-adipogenic activity of the extract on the 3T3-L1 cell line was investigated. The results indicated that it can downregulate PPARγ and C/EBPα expression at mRNA. In summary, in this study, we have established a cost-effective method for the extraction of flavonoids from the flowers of Abelmoschus manihot (L.) Medic using supercritical fluid extraction and the extracts exhibited potent antioxidant and anti-adipogenic effects, suggesting a possible therapeutic approach for the prevention and treatment of obesity.

TRPV1 is crucial for proinflammatory STAT3 signaling and thermoregulation-associated pathways in the brain during inflammation

Transient receptor potential vanilloid receptor 1 (TRPV1) is a non-selective cation channel that is stimulated by heat (>43 °C), mechanical/osmotic stimuli, and low pH. The importance of TRPV1 in inflammatory responses has been demonstrated, whereas its participation in brains remains unclear. In the present study, the intracerebroventricular (icv) administration of the TRPV1 agonist resiniferatoxin (RTX) induced the activation of signal transducer and activator of transcription 3 (STAT3) in circumventricular organs (CVOs) and thermoregulation-associated brain regions with a similar patttern to the peripheral and icv administration of lipopolysaccharide (LPS). With the peripheral and icv LPS stimuli, STAT3 activation was significantly lower in Trpv1^−/− mice than in Trpv1^+/+ mice. The icv administration of RTX induced transient hypothermia, whereas that of the TRPV1 antagonist capsazepine enhanced the magnitude and period of LPS-induced hyperthermia. These results indicate that TRPV1 is important for activating proinflammatory STAT3 signaling and thermoregulation-associated brain pathways in the brain.

Structural Mimicry of Receptor Interaction by Antagonistic Interleukin-6 (IL-6) Antibodies

Interleukin 6 plays a key role in mediating inflammatory reactions in autoimmune diseases and cancer, where it is also involved in metastasis and tissue invasion. Neutralizing antibodies against IL-6 and its receptor have been approved for therapeutic intervention or are in advanced stages of clinical development. Here we describe the crystal structures of the complexes of IL-6 with two Fabs derived from conventional camelid antibodies that antagonize the interaction between the cytokine and its receptor. The x-ray structures of these complexes provide insights into the mechanism of neutralization by the two antibodies and explain the very high potency of one of the antibodies. It effectively competes for binding to the cytokine with IL-6 receptor (IL-6R) by using side chains of two CDR residues filling the site I cavities of IL-6, thus mimicking the interactions of Phe²²⁹ and Phe²⁷⁹ of IL-6R. In the first antibody, a HCDR3 tryptophan binds similarly to hot spot residue Phe²⁷⁹. Mutation of this HCDR3 Trp residue into any other residue except Tyr or Phe significantly weakens binding of the antibody to IL-6, as was also observed for IL-6R mutants of Phe²⁷⁹. In the second antibody, the side chain of HCDR3 valine ties into site I like IL-6R Phe²⁷⁹, whereas a LCDR1 tyrosine side chain occupies a second cavity within site I and mimics the interactions of IL-6R Phe²²⁹.

MiR-26 down-regulates TNF-α/NF-κB signalling and IL-6 expression by silencing HMGA1 and MALT1

MiR-26 has emerged as a key tumour suppressor in various cancers. Accumulating evidence supports that miR-26 regulates inflammation and tumourigenicity largely through down-regulating IL-6 production, but the underlying mechanism remains obscure. Here, combining a transcriptome-wide approach with manipulation of cellular miR-26 levels, we showed that instead of directly targeting IL-6 mRNA for gene silencing, miR-26 diminishes IL-6 transcription activated by TNF-α through silencing NF-κB signalling related factors HMGA1 and MALT1. We demonstrated that miR-26 extensively dampens the induction of many inflammation-related cytokine, chemokine and tissue-remodelling genes that are activated via NF-κB signalling pathway. Knocking down both HMGA1 and MALT1 by RNAi had a silencing effect on NF-κB-responsive genes similar to that caused by miR-26. Moreover, we discovered that poor patient prognosis in human lung adenocarcinoma is associated with low miR-26 and high HMGA1 or MALT1 levels and not with levels of any of them individually. These new findings not only unravel a novel mechanism by which miR-26 dampens IL-6 production transcriptionally but also demonstrate a direct role of miR-26 in down-regulating NF-κB signalling pathway, thereby revealing a more critical and broader role of miR-26 in inflammation and cancer than previously realized.

Central Insulin Action Activates Kupffer Cells by Suppressing Hepatic Vagal Activation via the Nicotinic Alpha 7 Acetylcholine Receptor

Central insulin action activates hepatic IL-6/STAT3 signaling, which suppresses the gene expression of hepatic gluconeogenic enzymes. The vagus nerve plays an important role in this centrally mediated hepatic response; however, the precise mechanism underlying this brain-liver interaction is unclear. Here, we present our findings that the vagus nerve suppresses hepatic IL-6/STAT3 signaling via α7-nicotinic acetylcholine receptors (α7-nAchR) on Kupffer cells, and that central insulin action activates hepatic IL-6/STAT3 signaling by suppressing vagal activity. Indeed, central insulin-mediated hepatic IL-6/STAT3 activation and gluconeogenic gene suppression were impeded in mice with hepatic vagotomy, pharmacological cholinergic blockade, or α7-nAchR deficiency. In high-fat diet-induced obese and insulin-resistant mice, control of the vagus nerve by central insulin action was disturbed, inducing a persistent increase of inflammatory cytokines. These findings suggest that dysregulation of the α7-nAchR-mediated control of Kupffer cells by central insulin action may affect the pathogenesis of chronic hepatic inflammation in obesity.

Central insulin-mediated regulation of hepatic glucose production [Review]

Insulin controls hepatic glucose production (HGP) and maintains glucose homeostasis through the direct action of hepatic insulin receptors, as well as the indirect action of insulin receptors in the central nervous system. Insulin acts on insulin receptors in the hypothalamic arcuate nucleus, activates ATP-sensitive potassium channels in a phosphoinositide 3-kinase (PI3K)-dependent manner, induces hyperpolarization of the hypothalamic neurons, and regulates HGP via the vagus nerve. In the liver, central insulin action augments IL-6 expression in Kupffer cells and activates STAT3 transcription factors in hepatocytes. Activated STAT3 suppresses the gene expression of gluconeogenic enzymes, thereby reducing HGP. It has become evident that nutrients such as glucose, fatty acids, and amino acids act upon the hypothalamus together with insulin, affecting HGP. On the other hand, HGP control by central insulin action is impeded in obesity and impeded by insulin resistance due to disturbance of PI3K signaling and inflammation in the hypothalamus or inhibition of STAT3 signaling in the liver. Although the mechanism of control of hepatic gluconeogenic gene expression by central insulin action is conserved across species, its importance in human glucose metabolism has not been made entirely clear and its elucidation is anticipated in the future.

New aspects in fenestrated capillary and tissue dynamics in the sensory circumventricular organs of adult brains

The blood-brain barrier (BBB) generally consists of endothelial tight junction barriers that prevent the free entry of blood-derived substances, thereby maintaining the extracellular environment of the brain. However, the circumventricular organs (CVOs), which are located along the midlines of the brain ventricles, lack these endothelial barriers and have fenestrated capillaries; therefore, they have a number of essential functions, including the transduction of information between the blood circulation and brain. Previous studies have demonstrated the extensive contribution of the CVOs to body fluid and thermal homeostasis, energy balance, the chemoreception of blood-derived substances, and neuroinflammation. In this review, recent advances have been discussed in fenestrated capillary characterization and dynamic tissue reconstruction accompanied by angiogenesis and neurogliogenesis in the sensory CVOs of adult brains. The sensory CVOs, including the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and area postrema (AP), have size-selective and heterogeneous vascular permeabilities. Astrocyte-/tanycyte-like neural stem cells (NSCs) sense blood- and cerebrospinal fluid-derived information through the transient receptor potential vanilloid 1, a mechanical/osmotic receptor, Toll-like receptor 4, a lipopolysaccharide receptor, and Nax, a Na-sensing Na channel. They also express tight junction proteins and densely and tightly surround mature neurons to protect them from blood-derived neurotoxic substances, indicating that the NSCs of the CVOs perform BBB functions while maintaining the capacity to differentiate into new neurons and glial cells. In addition to neurogliogenesis, the density of fenestrated capillaries is regulated by angiogenesis, which is accompanied by the active proliferation and sprouting of endothelial cells. Vascular endothelial growth factor (VEGF) signaling may be involved in angiogenesis and neurogliogenesis, both of which affect vascular permeability. Thus, recent findings advocate novel concepts for the CVOs, which have the dynamic features of vascular and parenchymal tissues.

T-helper1/T-helper2 cytokine imbalance in the iris of patients with glaucoma

The mechanistic study of glaucoma pathogenesis has shifted to seeking to understand the effects of immune responses on retinal ganglion cell damage and protection. Cytokines mediate the biological effects of the immune system, and our previous study revealed an imbalance of T-helper (Th) 1-derived and Th2-derived cytokines in the serum of patients with glaucoma. In this study, we collected irises from normal individuals and patients with primary open-angle closure (POAG) or chronic angle-closure glaucoma (CACG). We used real-time polymerase chain reaction (PCR) to measure the expression of Th1 (interleukin (IL)-2, interferon-gamma (IFN-γ)), Th2 (IL-4, IL-6, IL-10), and Th3 (transforming growth factor-beta (TGF-β)) cytokines. We then performed immunohistochemical staining to characterize the localization of the upregulated cytokines in iris cryosections. We observed an upward trend in the expression of IL-2 and IFN-γ and a downward trend in IL-6 expression in the iris of POAG and CACG patients. Expression of TGF-β also increased. Immunohistochemistry revealed that IL-2 expression in POAG and CACG patients was localized in the anterior surface of the blood vessel wall in the stroma of the iris, in the cytoplasm of some cells, in the anterior epithelium, and in the posterior pigment epithelium. These findings indicate that immune status differed between the iris tissues of POAG and CACG patients and those of normal individuals. A T-helper cytokine imbalance may modulate the immune microenvironment in glaucomatous eyes and thus influence optic neuropathy.

Secretome from human adipose-derived stem cells protects mouse liver from hepatic ischemia-reperfusion injury

BACKGROUND

Despite widespread interest in stem cells, their clinical application is largely limited owing to safety and cost concerns. We intended to overcome these limitations by evaluating whether the secretome of human adipose tissue-derived stem cells (ASCs) could be used to reverse ischemia/reperfusion (IR) injury in mice.

METHODS

After establishment of hepatic IR injury in BALB/c mice, the mice were infused with saline solution (saline group), 1.0 × 10⁶ human ASCs (ASC group), 25-fold-concentrated ASC-conditioned medium (ASC-secretome group), which was the same volume as used for the ASC infusion, or concentrated control medium (medium-only group). After reperfusion, we obtained serum and liver specimens and compared parameters reflecting the degree of injury and mechanisms between the groups.

RESULTS

At 6 hours after reperfusion, serum interleukin (IL)-6 levels were decreased in both ASC and ASC-secretome groups (P < .05). At 12 and 24 hours after reperfusion, both ASC and ASC-secretome groups also demonstrated lesser histologic scores than did their controls (P < .05). In addition, the decreases in the expression of the cell adhesion markers intercellular adhesion molecule-1 and platelet-endothelial cell adhesion molecule-1 and in neutrophil infiltration into the liver were noted in the ASC-secretome group as well as in the ASC group.

CONCLUSION

ASC and ASC-secretome infusions both alleviated liver damage and improved the liver microenvironment after hepatic IR injury. Our results indicate that the therapeutic potential of ASCs may result from a paracrine effect mediated by the ASC secretome; our work suggests a novel secretome-based therapeutic strategy to treat hepatic IR injury.

Acanthamoeba castellanii STAT protein

STAT (signal transducers and activators of transcription) proteins are one of the important mediators of phosphotyrosine-regulated signaling in metazoan cells. We described the presence of STAT protein in a unicellular, free-living amoebae with a simple life cycle, Acanthamoeba castellanii. A. castellanii is the only, studied to date, Amoebozoan that does not belong to Mycetozoa but possesses STATs. A sequence of the A. castellanii STAT protein includes domains similar to those of the Dictyostelium STAT proteins: a coiled coil (characteristic for Dictyostelium STAT coiled coil), a STAT DNA-binding domain and a Src-homology domain. The search for protein sequences homologous to A. castellanii STAT revealed 17 additional sequences from lower eukaryotes. Interestingly, all of these sequences come from Amoebozoa organisms that belong to either Mycetozoa (slime molds) or Centramoebida. We showed that there are four separated clades within the slime mold STAT proteins. The A. castellanii STAT protein branches next to a group of STATc proteins from Mycetozoa. We also demonstrate that Amoebozoa form a distinct monophyletic lineage within the STAT protein world that is well separated from the other groups.

Phosphatase of regenerating liver-3 is regulated by signal transducer and activator of transcription 3 in acute myeloid leukemia

Overexpression of protein-tyrosine phosphatase of regenerating liver 3 (PRL-3) has been identified in about 50% of patients with acute myeloid leukemia (AML). The mechanism of regulation of PRL-3 remains obscure. Signal transducer and activator of transcription 3 (STAT3), a latent transcriptional factor, has also been often found to be activated in AML. We first identified STAT3-consensus-binding sites in the promoter of PRL-3 genes. Then we experimentally validated the direct binding and transcriptional activation. We applied shRNA-mediated knockdown and overexpression approaches in STAT3(-/-) liver cells and leukemic cells to validate the functional regulation of PRL-3 by STAT3. A STAT3 core signature, derived through data mining from publicly available gene expression data, was employed to correlate PRL-3 expression in large AML patient samples. We discovered that STAT3 binds to the -201 to -210 region of PRL-3, which was conserved between human and mouse. Importantly, PRL-3 protein was significantly reduced in mouse STAT3-knockout liver cells compared with STAT3-wild type counterparts, and ectopic expression of STAT3 in these cells led to a pronounced increase in PRL-3 protein. We demonstrated that STAT3 functionally regulated PRL-3, and STAT3 core signature was enriched in AML with high PRL-3 expression. Targeting either STAT3 or PRL-3 reduced leukemic cell viability. Silencing PRL-3 impaired invasiveness and induced leukemic cell differentiation. In conclusion, PRL-3 was transcriptionally regulated by STAT3. The STAT3/PRL-3 regulatory loop contributes to the pathogenesis of AML, and it might represent an attractive therapeutic target for antileukemic therapy.

CCAAT/enhancer-binding protein β regulates interleukin-6-induced transmembrane and ubiquitin-like domain containing 1 gene expression in hepatocytes

Transmembrane and ubiquitin-like domain containing 1 (Tmub1) protein has a negative effect on liver regeneration; however, the mechanisms of Tmub1 expression regulation are currently unknown. CCAAT/enhancer-binding protein β (C/EBPβ) is a key transcription factor associated with interleukin-6 (IL-6) in liver regeneration. The present study aimed to investigate the involvement of C/EBPβ in the IL-6‑induced upregulation of Tmub1. A series of Tmub1 luciferase reporter vectors were constructed to detect the effects of IL‑6 on the transcriptional activity of Tmub1. Small interfering RNA and overexpression vectors were employed to either inhibit or enhance the expression of C/EBPβ, respectively, to determine the effect of C/EBPβ on Tmub1 expression in liver cells. Additionally, chromatin immunoprecipitation experiments were performed to determine whether C/EBPβ bound to the Tmub1 gene, and the sequences associated with the regulation of Tmub1 expression by C/EBPβ were subsequently determined. Several potential binding sites of C/EBPβ were identified in the 5'‑upstream region of the Tmub1 gene. C/EBPβ expression was positively correlated with Tmub1 gene expression in rat liver cells. Furthermore, it was demonstrated that C/EBPβ bound to 5'‑upstream sequences of the Tmub1 gene to enhance the promoter activity. The present study demonstrated that C/EBPβ is a key transcription factor, which can positively regulate the expression of Tmub1 during liver cell proliferation through a possible association with IL-6.

STAT3 and importins are novel mediators of early molecular and cellular responses in experimental duodenal ulceration

OBJECTIVES

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that directly upregulates VEGF, Ref-1, p21, and anti-apoptotic genes such as Bcl-xL. In this study, we hypothesized that STAT3 signaling is activated and provides a critical protective role that is required for enterocyte survival during the early phases of cysteamine-induced duodenal ulcers.

METHODS

We studied the effect of inhibition of STAT3 activity on cysteamine-induced duodenal ulcers in rats and egr-1 knockout mice using STAT3/DNA binding assay, immunohistochemistry, immunoblot, and quantitative reverse transcriptase PCR analyses.

RESULTS

We found that G-quartet oligodeoxynucleotides T40214, a specific inhibitor of STAT3/DNA binding, aggravated cysteamine-induced duodenal ulcers in rats 2.8-fold (p < 0.05). In the pre-ulcerogenic stage, cysteamine induced STAT3 tyrosine phosphorylation, its translocation to nuclei, an increased expression and nuclear translocation of importin α and β in the rat duodenal mucosa. Cysteamine enhanced the binding of STAT3 to its DNA consensus sequences at 6, 12, and 24 h after cysteamine by 1.5-, 1.8-, and 3.5-fold, respectively, and activated the expression of STAT3 target genes such as VEGF, Bcl-xL, Ref-1, and STAT3-induced feedback inhibitor, a suppressor of cytokine signaling 3. We also demonstrated that egr-1 knockout mice, which are more susceptible to cysteamine-induced duodenal ulcers, had lower levels of STAT3 expression, its phosphorylation, expression of importin α or β, and STAT3/DNA binding than wild-type mice in response to cysteamine.

CONCLUSIONS

Thus, STAT3 represents an important new molecular mechanism in experimental duodenal ulceration.

STAT3 and MCL-1 associate to cause a mesenchymal epithelial transition

Embryo implantation is effected by a myriad of signaling cascades acting on the embryo-endometrium axis. Here we show, by using MALDI TOF analysis, far-western analysis and colocalization and co-transfection studies, that STAT3 and MCL-1 are interacting partners during embryo implantation. We show in vitro that the interaction between the two endogenous proteins is strongly regulated by estrogen and progesterone. Implantation, pregnancy and embryogenesis are distinct from any other process in the body, with extensive, but controlled, proliferation, cell migration, apoptosis, cell invasion and differentiation. Cellular plasticity is vital during the early stages of development for morphogenesis and organ homeostasis, effecting the epithelial to mesenchymal transition (EMT) and, the reverse process, mesenchymal to epithelial transition (MET). STAT3 functionally associates with MCL-1 in the mammalian breast cancer cell line MCF7 that overexpresses STAT3 and MCL-1, which leads to an increased rate of apoptosis and decreased cellular invasion, disrupting the EMT. Association of MCL-1 with STAT3 modulates the normal, anti-apoptotic, activity of MCL-1, resulting in pro-apoptotic effects. Studying the impact of the association of STAT3 with MCL-1 on MET could lead to an enhanced understanding of pregnancy and infertility, and also metastatic tumors.

IRF3 helps control acute TMEV infection through IL-6 expression but contributes to acute hippocampus damage following TMEV infection

IRF3 is an innate anti-viral factor whose role in limiting Theiler's murine encephalomyelitis virus (TMEV) infection and preventing TMEV-induced disease is unclear. Acute disease and innate immune responses of macrophages were examined in IRF3 knockout mice compared with C57Bl/6 mice following in vitro or intracranial infection with either TMEV GDVII or DA. IRF3 deficiency augmented viral infection, as well as morbidity and mortality following intracranial infection with neurovirulent TMEV GDVII. In contrast, IRF3 deficiency prevented hippocampal injury following intracranial infection with persistent TMEV DA. The extent of TMEV infection in macrophages from C57Bl/6 mice was significantly less than that in IRF3 deficient macrophages, which was associated with poor IFN-β and IL-6 expression in response to TMEV. Reestablishing IRF3 expression in IRF3 deficient macrophages increased control of TMEV replication and increased expression of IFN-β and IL-6. In addition, IRF3 deficient macrophages failed to exhibit IL-6 antiviral effects, which was associated with inability to sustain IL-6-induced STAT1 activation compared with C57BL/6 macrophages. Altogether, IRF3 contributes to early control of TMEV replication through induction of IL-6 and IFN-β and support of IL-6 antiviral effects, but contributes to TMEV-induced hippocampal injury.

Targeting interleukin-6 in inflammatory autoimmune diseases and cancers

Interleukin-6 (IL-6) is a pleiotropic cytokine with significant functions in the regulation of the immune system. As a potent pro-inflammatory cytokine, IL-6 plays a pivotal role in host defense against pathogens and acute stress. However, increased or deregulated expression of IL-6 significantly contributes to the pathogenesis of various human diseases. Numerous preclinical and clinical studies have revealed the pathological roles of the IL-6 pathway in inflammation, autoimmunity, and cancer. Based on the rich body of studies on biological activities of IL-6 and its pathological roles, therapeutic strategies targeting the IL-6 pathway are in development for cancers, inflammatory and autoimmune diseases. Several anti-IL-6/IL-6 receptor monoclonal antibodies developed for targeted therapy have demonstrated promising results in both preclinical studies and clinical trials. Tocilizumab, an anti-IL-6 receptor antibody, is effective in the treatment of various autoimmune and inflammatory conditions notably rheumatoid arthritis. It is the only IL-6 pathway targeting agent approved by the regulatory agencies for clinical use. Siltuximab, an anti-IL-6 antibody, has been shown to have potential benefits treating various human cancers either as a single agent or in combination with other chemotherapy drugs. Several other anti-IL-6-based therapies are also under clinical development for various diseases. IL-6 antagonism has been shown to be a potential therapy for these disorders refractory to conventional drugs. New strategies, such as combination of IL-6 blockade with inhibition of other signaling pathways, may further improve IL-6-targeted immunotherapy of human diseases.

Cell-Type Specific Determinants of NRAMP1 Expression in Professional Phagocytes

The Natural resistance-associated macrophage protein 1 (Nramp1 or Solute carrier 11 member 1, Slc11a1) transports divalent metals across the membrane of late endosomes and lysosomes in professional phagocytes. Nramp1 represents an ancient eukaryotic cell-autonomous defense whereas the gene duplication that yielded Nramp1 and Nramp2 predated the origin of Sarcopterygians (lobe-finned fishes and tetrapods). SLC11A1 genetic polymorphisms associated with human resistance to tuberculosis consist of potential regulatory variants. Herein, current knowledge of the regulation of SLC11A1 gene expression is reviewed and comprehensive analysis of ENCODE data available for hematopoietic cell-types suggests a hypothesis for the regulation of SLC11A1 expression during myeloid development and phagocyte functional polarization. SLC11A1 is part of a 34.6 kb CTCF-insulated locus scattered with predicted regulatory elements: a 3' enhancer, a large 5' enhancer domain and four elements spread around the transcription start site (TSS), including several C/EBP and PU.1 sites. SLC11A1 locus ends appear mobilized by ETS-related factors early during myelopoiesis; activation of both 5' and 3' enhancers in myelo-monocytic cells correlate with transcription factor binding at the TSS. Characterizing the corresponding cis/trans determinants functionally will establish the mechanisms involved and possibly reveal genetic variation that impacts susceptibility to infectious or immune diseases.

Suppression of vascular inflammation by kinin B1 receptor antagonism in a rat model of insulin resistance

BACKGROUND

Kinin B1 receptor (B1R) intervenes in a positive feedback loop to amplify and perpetuate the vascular oxidative stress in glucose-fed rats, a model of insulin resistance. This study aims at determining whether B1R blockade could reverse vascular inflammation in this model.

METHODS/RESULTS

Young male Sprague-Dawley rats were fed with 10% D-glucose or tap water (controls) for 8 weeks, and during the last week, rats were administered the B1R antagonist SSR240612 (10 mg/kg/day, gavage) or the vehicle. The outcome was determined on glycemia, insulinemia, insulin resistance (homeostasis model assessment index), and on protein or mRNA expression of the following target genes in the aorta (by Western blot and real-time quantitative polymerase chain reaction): B1R, endothelial nitric oxide synthase, inducible nitric oxide synthase, macrophage CD68, macrophage/monocyte CD11b, interleukin (IL) -1β, tumor necrosis factor-α, IL-6, macrophage migration inhibitory factor, intercellular adhesion molecule-1, and E-selectin (endothelial adhesion molecule). Data showed increased expression of all these markers in the aorta of glucose-fed rats except endothelial nitric oxide synthase and tumor necrosis factor-α, which were not affected. SSR240612 reversed hyperglycemia, hyperinsulinemia, insulin resistance, and the upregulation of B1R, inducible nitric oxide synthase, macrophage CD68, and CD11b, IL-1β, inter-cellular adhesion molecule-1, macrophage migration inhibitory factor, and E-selectin in glucose-fed rats, yet it had no significant effect on IL-6 and in control rats.

CONCLUSIONS

Kinin B1R antagonism reversed the upregulation of its own receptor and several pro-inflammatory markers in the aorta of glucose-fed rats. These data provide the first evidence that B1R may contribute to the low-grade vascular inflammation in insulin resistance, an early event in the development of type-2 diabetes.

Role of IL-6 in asthma and other inflammatory pulmonary diseases

The incidence and severity of chronic lung diseases is growing and affects between 100 and 150 million people worldwide and is associated with a significant rate of mortality. Unfortunately, the initial cause that triggers most chronic lung diseases remains unknown and current available therapies only ameliorate, but do not cure the disease. Thus, there is a need for identification of new targets and development of novel therapies especially for those most severely affected. IL-6, like other inflammatory cytokines, has been shown to be elevated in different lung diseases, but it was considered a byproduct of ongoing inflammation in the lung. However, recent studies support a dissociation of IL-6 from inflammation in the lung and suggest that this cytokine plays an active role in pathogenesis of asthma and, in all likelihood, COPD. IL-6 may therefore be a germane target for treatment of these and other chronic lung disease. Here, we provide an overview of the studies in mouse models and human patients that provide support for the involvement of IL-6 in lung diseases.

Interleukin-6: from an inflammatory marker to a target for inflammatory diseases

The incidence and diversity of chronic inflammatory diseases is increasing worldwide. However, the complexity of clinical symptoms has made it difficult to develop therapies that provide a substantial improvement for extended periods of time in a wide range of patient groups. Thus, there is a need for new therapies that target inflammatory responses without compromising immune defense. Interleukin (IL)-6, one of the first identified cytokines, has recently been recognized as a potential target in inflammatory disease. Here, I discuss how this cytokine has evolved from being a marker of inflammation to a successful target to control inflammation. I will summarize the results from the recent clinical studies using IL-6 receptor blockade, and describe potential mechanisms by which IL-6 can contribute to the progression of inflammatory diseases.

Endoplasmic reticulum stress inhibits STAT3-dependent suppression of hepatic gluconeogenesis via dephosphorylation and deacetylation

In the liver, signal transducer and activator of transcription 3 (STAT3) plays an important role in the suppression of gluconeogenic enzyme expression. While obesity-associated endoplasmic reticulum (ER) stress has been shown to increase hepatic gluconeogenic enzyme expression, the role of ER stress in STAT3-dependent regulation of such expression is unclear. The current study aimed to elucidate the effect of ER stress on the STAT3-dependent regulation of hepatic gluconeogenic enzyme expression. Genetically obese/diabetic db/db mice and db/db mouse-derived isolated hepatocytes were used as ER stress models. A tyrosine phosphatase inhibitor, a deacetylation inhibitor, and an acetylated mutant of STAT3 were used to examine the effect of ER stress on hepatic STAT3 action. ER stress inhibited STAT3-dependent suppression of gluconeogenic enzyme gene expression by suppressing hepatic Janus kinase (JAK)2 and STAT3 phosphorylation. A tyrosine phosphatase inhibitor restored ER stress-induced suppression of JAK2 phosphorylation but exhibited no improving effect on suppressed STAT3 phosphorylation. STAT3 acetylation is known to correlate with its phosphorylation. ER stress also decreased STAT3 acetylation. An acetylated mutant of STAT3 was resistant to ER stress-induced inhibition of STAT3-phosphorylation and STAT3-dependent suppression of hepatic gluconeogenic enzyme gene expression in vitro and in vivo. Trichostatin A, a histone deacetylase (HDAC) inhibitor, ameliorated ER stress-induced inhibition of STAT3 acetylation and phosphorylation. The current study revealed that ER stress inhibits STAT3-dependent suppression of hepatic gluconeogenic enzymes via JAK2 dephosphorylation and HDAC-dependent STAT3 deacetylation, playing an important role in the increase of hepatic glucose production in obesity and diabetes.

IL-6/IL-6R as a potential key signaling pathway in prostate cancer development

Interleukin-6 (IL-6) is a pleiotropic cytokine involved in prostate regulation and in prostate cancer (PC) development/progression. IL-6 acts as a paracrine and autocrine growth stimulator in benign and tumor prostate cells. The levels of IL-6 and respective receptors are increased during prostate carcinogenesis and tumor progression. Several studies reported that increased serum and plasma IL-6 and soluble interleukin-6 receptor levels are associated with aggressiveness of the disease and are associated with a poor prognosis in PC patients. In PC treatment, patients diagnosed with advanced stages are frequently submitted to hormonal castration, although most patients will eventually fail this therapy and die from recurrent castration-resistant prostate cancer (CRPC). Therefore, it is important to understand the mechanisms involved in CRPC. Several pathways have been proposed to be involved in CRPC development, and their understanding will improve the way to more effective therapies. In fact, the prostate is known to be dependent, not exclusively, on androgens, but also on growth factors and cytokines. The signaling pathway mediated by IL-6 may be an alternative pathway in the CRPC phenotype acquisition and cancer progression, under androgen deprivation conditions. The principal goal of this review is to evaluate the role of IL-6 pathway signaling in human PC development and progression and discuss the interaction of this pathway with the androgen recepto pathway. Furthermore, we intend to evaluate the inclusion of IL-6 and its receptor levels as a putative new class of tumor biomarkers.The IL-6/IL-6R signaling pathway may be included as a putative molecular marker for aggressiveness in PC and it may be able to maintain tumor growth through the AR pathway under androgen-deprivation conditions. The importance of the IL-6/IL-6R pathway in regulation of PC cells makes it a good candidate for targeted therapy.