Enhanced induction of LPS-induced fibroblast MCP-1 by interferon-gamma: involvement of JNK and MAPK phosphatase-1

An Improved Model of Moderate Sleep Apnoea for Investigating Its Effect as a Comorbidity on Neurodegenerative Disease

Sleep apnoea is a highly prevalent disease that often goes undetected and is associated with poor clinical prognosis, especially as it exacerbates many different disease states. However, most animal models of sleep apnoea (e.g., intermittent hypoxia) have recently been dispelled as physiologically unrealistic and are often unduly severe. Owing to a lack of appropriate models, little is known about the causative link between sleep apnoea and its comorbidities. To overcome these problems, we have created a more realistic animal model of moderate sleep apnoea by reducing the excitability of the respiratory network. This has been achieved through controlled genetically mediated lesions of the preBötzinger complex (preBötC), the inspiratory oscillator. This novel model shows increases in sleep disordered breathing with alterations in breathing during wakefulness (decreased frequency and increased tidal volume) as observed clinically. The increase in dyspnoeic episodes leads to reduction in REM sleep, with all lost active sleep being spent in the awake state. The increase in hypoxic and hypercapnic insults induces both systemic and neural inflammation. Alterations in neurophysiology, an inhibition of hippocampal long-term potentiation (LTP), is reflected in deficits in both long- and short-term spatial memory. This improved model of moderate sleep apnoea may be the key to understanding why this disorder has such far-reaching and often fatal effects on end-organ function.

3',4',7-Trihydroxyflavone Downregulates NO Production in LPS- or IFN-γ-Activated MG6 Microglial Cells by Attenuating the JNK-STAT1 Pathway

Neuroinflammation induced by activated microglia is a key feature of neurodegenerative diseases such as Alzheimer's disease. The natural flavonoid 3',4',7-trihydroxyflavone protects nerve cells from oxidative stress-mediated apoptosis and inhibits the aggregation of amyloid β protein in vitro. However, little is known about its effects on microglial activation. In this study, we investigated the effects of 3',4',7-trihydroxyflavone on lipopolysaccharide (LPS)- or interferon-γ (IFN-γ)-induced neuroinflammatory responses in MG6 microglial cells. 3',4',7-Trihydroxyflavone inhibited LPS- or IFN-γ-mediated nitric oxide (NO) generation and the upregulation of inducible NO synthase (iNOS) in MG6 cells. 3',4',7-Trihydroxyflavone also suppressed LPS- or IFN-γ-mediated phosphorylation of signal transducer and activator of transcription 1 (STAT1), which is crucial for iNOS expression. LPS stimulation induced rapid phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase (ERK) in MG6 cells. 3',4',7-Trihydroxyflavone significantly inhibited the LPS-mediated phosphorylation of JNK, but not that of ERK and p38 MAPK. The inhibitory effect of 3',4',7-trihydroxyflavone on NO generation was mimicked by pharmacological inhibition of the JNK signaling pathway with SP600125. Furthermore, SP600125 significantly inhibited LPS- or IFN-γ-mediated phosphorylation of STAT1 in MG6 cells. These results suggest that 3',4',7-trihydroxyflavone exerts anti-neuroinflammatory effects via inhibition of the JNK-STAT1 pathway in microglia.

Recombinant Treponema pallidum protein Tp0136 promotes fibroblast migration by modulating MCP-1/CCR2 through TLR4

BACKGROUND

Chancre self-healing is an important clinical feature in the early stages of syphilis infection. Wound healing may involve an important mechanism by the migration of fibroblasts filling the injured lesion. However, the specific mechanism underlying this process is still unknown.

OBJECTIVES

We aimed to analyse the role of Tp0136 in the migration of fibroblasts and the related mechanism.

METHODS

The migration ability of fibroblasts was detected by a wound-healing assay. RT-PCR and ELISA detected the expression of MCP-1, IL-6 and MMP-9. TLR4 expression was detected by RT-PCR. The protein levels of CCR2 and relevant signalling pathway molecules were measured by Western blotting.

RESULTS

Tp0136 significantly promoted fibroblast migration. Subsequently, the levels of MCP-1 and its receptor CCR2 were increased in this process. The migration of fibroblasts was significantly inhibited by an anti-MCP-1 neutralizing antibody or CCR2 inhibitors. Furthermore, studies demonstrated that Tp0136 could activate the ERK/JNK/PI3K/NF-κB signalling pathways through TLR4 activity and that signalling pathways inhibitors could weaken MCP-1 secretion and fibroblast migration.

CONCLUSIONS

These findings demonstrate that Tp0136 promotes the migration of fibroblasts by inducing MCP-1/CCR2 expression through signalling involving the TLR4, ERK, JNK, PI3K and NF-κB signalling pathways, which could contribute to the mechanism of chancre self-healing in syphilis.

Targeting interferons as a strategy for systemic sclerosis treatment

Systemic Sclerosis (SSc) is an autoimmune disease characterised by vasculopathy, uncontrolled inflammation and enhanced fibrosis which can subsequently lead to the loss of organ function or even premature death. Interferons (IFNs) are pleiotropic cytokines that are critical not only in mounting an effective immune response against viral and bacterial infections but also strongly contribute to the pathogenesis of SSc. Furthermore, elevated levels of IFNs are found in SSc patients and correlate with skin thickness and disease activity suggesting potential role of IFNs as biomarkers. In this review, we summarise existing knowledge regarding all types of IFNs and IFN-inducible genes in the pathogenesis of SSc. We then argue why IFN-blocking strategies are promising therapeutic targets in SSc and other autoimmune diseases.

Dissecting cellular senescence and SASP in Drosophila

Cellular senescence can act as both tumor suppressor and tumor promoter depending on the cellular contexts. On one hand, premature senescence has been considered as an innate host defense mechanism against carcinogenesis in mammals. In response to various stresses including oxidative stress, DNA damage, and oncogenic stress, suffered cells undergo irreversible cell cycle arrest, leading to tumor suppression. On the other hand, recent studies in mammalian systems have revealed that senescent cells can drive oncogenesis by secreting diverse proteins such as inflammatory cytokines, matrix remodeling factors, and growth factors, the phenomenon called senescence-associated secretory phenotype (SASP). However, the mechanisms by which these contradictory effects regulate tumor growth and metastasis in vivo have been elusive. Here, we review the recent discovery of cellular senescence in Drosophila and the mechanisms underlying senescence-mediated tumor regulation dissected by Drosophila genetics.

3,5,4'-Tri-O-acetylresveratrol Attenuates Lipopolysaccharide-Induced Acute Respiratory Distress Syndrome via MAPK/SIRT1 Pathway

The aim of the present research was to investigate the protecting effects of 3,5,4′-tri-O-acetylresveratrol (AC-Rsv) on LPS-induced acute respiratory distress syndrome (ARDS). Lung injuries have been evaluated by histological examination, wet-to-dry weight ratios, and cell count and protein content in bronchoalveolar lavage fluid. Inflammation was assessed by MPO activities and cytokine secretion in lungs and cells. The results showed that AC-Rsv significantly reduced the mortality of mice stimulated with LPS. Pretreatment of AC-Rsv attenuated LPS-induced histological changes, alleviated pulmonary edema, reduced blood vascular leakage, and inhibited the MPO activities in lungs. What was more, AC-Rsv and Rsv treatment reduced the secretion of TNF-α, IL-6, and IL-1β in lungs and NR8383 cells, respectively. Further exploration revealed that AC-Rsv and Rsv treatment relieved LPS-induced inhibition on SIRT1 expression and restrained the activation effects of LPS on MAPKs and NF-κB activation both in vitro and in vivo. More importantly, in vivo results have also demonstrated that the protecting effects of Rsv on LPS-induced inflammation would be neutralized when SIRT1 was in-hibited by EX527. Taken together, these results indicated that AC-Rsv protected lung tissue against LPS-induced ARDS by attenuating inflammation via p38 MAPK/SIRT1 pathway.

MD-2 is involved in the stimulation of matrix metalloproteinase-1 expression by interferon-γ and high glucose in mononuclear cells - a potential role of MD-2 in Toll-like receptor 4-independent signalling

We reported recently that treatment of diabetic apolipoprotein E-deficient mice with the Toll-like receptor 4 (TLR4) antagonist Rs-LPS, a lipopolysaccharide isolated from Rhodobacter sphaeroides, inhibited atherosclerosis. Since it is known that Rs-LPS antagonizes TLR4 by targeting TLR4 co-receptor MD-2, this finding indicates that MD-2 is a potential target for the treatment of atherosclerosis. In this study, we determined if MD-2 is involved in the gene expression regulated by signalling pathways independent of TLR4. Given that interferon-γ (IFNγ) and hyperglycaemia play key roles in atherosclerosis, we determined if MD-2 is involved in IFN-γ and high-glucose-regulated gene expression in mononuclear cells. Results showed that IFN-γ and high glucose synergistically stimulated matrix metalloproteinase 1 (MMP-1), a proteinase essential for vascular tissue remodelling and atherosclerosis, in U937 mononuclear cells, but Rs-LPS inhibited the MMP-1 stimulation. To provide more evidence for a role of MD-2 in IFN-γ-stimulated MMP-1, studies using antibodies and small interfering RNA demonstrated that MD-2 blockade or knockdown attenuated the effect of IFN-γ on MMP-1. Furthermore, studies using PCR arrays showed that MD-2 blockade had a similar effect as IFN-γ receptor blockade on the inhibition of IFN-γ-stimulated pro-inflammatory molecules. Although these findings indicate the involvement of MD-2 in IFN-γ signalling, we also observed that MD-2 was up-regulated by IFN-γ and high glucose. We found that MD-2 up-regulation by IFN-γ played an essential role in the synergistic effect of IFN-γ and LPS on MMP-1 expression. Taken together, these findings indicate that MD-2 is involved in IFN-γ signalling and IFN-γ-augmented MMP-1 up-regulation by LPS.

Cross-talk between skeletal muscle and immune cells: muscle-derived mediators and metabolic implications

Skeletal muscles contain resident immune cell populations and their abundance and type is altered in inflammatory myopathies, endotoxemia or different types of muscle injury/insult. Within tissues, monocytes differentiate into macrophages and polarize to acquire pro- or anti-inflammatory phenotypes. Skeletal muscle macrophages play a fundamental role in repair and pathogen clearance. These events require a precisely regulated cross-talk between myofibers and immune cells, involving paracrine/autocrine and contact interactions. Skeletal muscle also undergoes continuous repair as a result of contractile activity that involves participation of myokines and anti-inflammatory input. Finally, skeletal muscle is the major site of dietary glucose disposal; therefore, muscle insulin resistance is essential to the development of whole body insulin resistance. Notably, muscle inflammation is emerging as a potential contributor to insulin resistance. Recent reports show that inflammatory macrophage numbers within muscle are elevated during obesity and that muscle cells in vitro can mount autonomous inflammatory responses under metabolic challenge. Here, we review the nature of skeletal muscle inflammation associated with muscle exercise, damage, and regeneration, endotoxin presence, and myopathies, as well as the new evidence of local inflammation arising with obesity that potentially contributes to insulin resistance.

Modulation of gut microbiota by antibiotics improves insulin signalling in high-fat fed mice

AIMS/HYPOTHESIS

A high-fat dietary intake induces obesity and subclinical inflammation, which play important roles in insulin resistance. Recent studies have suggested that increased concentrations of circulating lipopolysaccharide (LPS), promoted by changes in intestinal permeability, may have a pivotal role in insulin resistance. Thus, we investigated the effect of gut microbiota modulation on insulin resistance and macrophage infiltration.

METHODS

Swiss mice were submitted to a high-fat diet with antibiotics or pair-feeding for 8 weeks. Metagenome analyses were performed on DNA samples from mouse faeces. Blood was collected to determine levels of glucose, insulin, LPS, cytokines and acetate. Liver, muscle and adipose tissue proteins were analysed by western blotting. In addition, liver and adipose tissue were analysed, blinded, using histology and immunohistochemistry.

RESULTS

Antibiotic treatment greatly modified the gut microbiota, reducing levels of Bacteroidetes and Firmicutes, overall bacterial count and circulating LPS levels. This modulation reduced levels of fasting glucose, insulin, TNF-α and IL-6; reduced activation of toll-like receptor 4 (TLR4), c-Jun N-terminal kinase (JNK), inhibitor of κ light polypeptide gene enhancer in B cells, kinase β (IKKβ) and phosphorylated IRS-1 Ser307; and consequently improved glucose tolerance and insulin tolerance and action in metabolically active tissues. In addition, there was an increase in portal levels of circulating acetate, which probably contributed to an increase in 5'-AMP-activated protein kinase (AMPK) phosphorylation in mice. We observed a striking reduction in crown-like structures (CLS) and F4/80(+) macrophage cells in the adipose tissue of antibiotic-treated mice.

CONCLUSIONS/INTERPRETATION

These results suggest that modulation of gut microbiota in obesity can improve insulin signalling and glucose tolerance by reducing circulating LPS levels and inflammatory signalling. Modulation also appears to increase levels of circulating acetate, which activates AMPK and finally leads to reduced macrophage infiltration.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) mediates p38 mitogen-activated protein kinase activation and signal transduction in peripheral blood mononuclear cells from patients with lupus nephritis

Forty-two patients with systemic lupus erythematosus (SLE), including 26 patients with renal damage and 16 without, and 20 healthy controls were included in the study. The isolated peripheral blood mononuclear cells (PBMCs) were treated with a p38 inhibitor (SB203580) or anti-tumor necrosis factor-like weak inducer of apoptosis (TWEAK) mAb, with or without phytohemagglutinin/phorbol myristate acetate (PHA/PMA) stimulation. Western blot experiments were used to evaluate the protein expression of TWEAK and p38 MAPK in PBMCs .Next, the contents of interleukin-10 (IL-10) and monocyte chemoattractant protein-1 (MCP-1) in the supernatant were measured by ELISA. The results showed that expression of TWEAK protein in PBMCs from lupus nephritis patients was significantly higher than that from SLE patients without renal damage and healthy controls. PHA/PMA simulation could upregulate the productions of TWEAK and p-p38MAPK in PBMCs from patients with SLE. Anti-TWEAK mAb treatment downregulated both TWEAK and p-p38 MAPK expression in PBMCs, as well as IL-10 and MCP-1 in the supernatant; SB203580 had the same effect on cytokine production in PBMC, but had no effect on the expression of TWEAK. Our results suggested that TWEAK-p38 MAPK-IL-10, MCP-1 signaling pathway in PBMC played an important pathogenic role in lupus nephritis.

Soluble epoxide hydrolase expression in a porcine model of arteriovenous graft stenosis and anti-inflammatory effects of a soluble epoxide hydrolase inhibitor

Synthetic arteriovenous (AV) grafts, placed between an artery and vein, are used for hemodialysis but often fail due to stenosis, typically at the vein-graft anastomosis. This study recorded T lymphocyte and macrophage accumulation at the vein-graft anastomosis, suggesting a role for inflammation in stenosis development. Epoxyeicosatrienoic acids (EETs), products of cytochrome P-450 epoxidation of arachidonic acid, have vasculoprotective and anti-inflammatory effects including inhibition of platelet activation, cell migration, and adhesion. EETs are hydrolyzed by soluble epoxide hydrolase (sEH) to less active diols. The effects of a specific inhibitor of sEH (sEHI) on cytokine release from human monocytes and mouse bone marrow-derived macrophages (BMMΦ) from wild-type (WT) and sEH knockout (KO) animals were investigated. Expression of sEH protein increased over time at the anastomosis as evaluated by immunohistochemistry. Pre-exposure of adherent human monocytes to sEHI (5 μM) significantly inhibited lipopolysaccharide-induced release of monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor-α and enhanced the EET-to-diol ratio. Release of MCP-1 from WT BMMΦ was significantly inhibited but release from sEH KO BMMΦ was not attenuated indicating the specificity of the sEHI. In contrast, sEHI did not inhibit the release of macrophage inflammatory protein-1 or interleukin-6. Nuclear translocation of NF-κB, as assessed by immunocytochemical staining, was not decreased with sEHI in monocytes, but the phosphorylation of JNK was completely abrogated, suggesting this pathway is the target of sEHI effects in monocytes. These results suggest that sEHI may be useful for inhibition of inflammation and subsequently stenosis in AV grafts.

β (CCL2) and α (CXCL10) chemokine modulations by cytokines and peroxisome proliferator-activated receptor-α agonists in Graves' ophthalmopathy

No data are present in the literature about the effect of cytokines on the prototype β chemokine (C-C motif) ligand 2 (CCL2) or of peroxisome proliferator-activated receptor α (PPARα (PPARA)) activation on CCL2 and CXCL10 chemokines secretion in fibroblasts or preadipocytes in Graves' ophthalmopathy (GO). We have tested the effect of interferon γ (IFNγ (IFNG)) and tumor necrosis factor α (TNFα) on CCL2, and for comparison on the prototype α chemokine (C-X-C motif) ligand 10 (CXCL10), and the possible modulatory role of PPARα activation on secretion of these chemokines in normal and GO fibroblasts or preadipocytes in primary cell cultures. This study shows that IFNγ alone, or in combination with TNFα, stimulates the secretion of CCL2 in primary orbital fibroblasts or preadipocytes from patients with GO at levels similar to those observed in controls. IFNγ and TNFα also stimulated CXCL10 chemokine secretion as expected. The presence of PPARα and PPARγ (PPARG) in primary fibroblasts or preadipocytes of patients with GO has been confirmed. PPARα activators were able to inhibit the secretion of CXCL10 and CCL2, while PPARγ activators were confirmed to be able to inhibit CXCL10 but had no effect on CCL2. PPARα activators were stronger inhibitors of chemokine secretions than PPARγ agonists. In conclusion, CCL2 and CXCL10 are modulated by IFNγ and TNFα in GO. PPARα activators inhibit the secretion of the main prototype α (CXCL10) and β (CCL2) chemokines in GO fibroblasts or preadipocytes, suggesting that PPARα may be involved in the modulation of the immune response in GO.

Systemic Sclerosis Fibroblasts Show Specific Alterations of Interferon-γ and Tumor Necrosis Factor-α-induced Modulation of Interleukin 6 and Chemokine Ligand 2

Objective.

We evaluated the effect of interferon-γ (IFN-γ) and/or tumor necrosis factor-α (TNF-α) on the secretion of prototype proinflammatory cytokine interleukin 6 (IL-6), compared to T-helper 1 [Th1; chemokine (C-X-C motif) ligand 10 (CXCL10)] or Th2 [chemokine (C-C motif) ligand 2 (CCL2)] chemokines, in primary cultured fibroblasts from patients with systemic sclerosis (SSc) at an early stage of the disease.

Methods.

Fibroblast cultures from 5 SSc patients (disease duration < 2 yrs) and 5 healthy controls were evaluated for the production of IL-6, CXCL10, and CCL2 at the basal level and after stimulation with IFN-γ and/or TNF-α.

Results.

SSc fibroblasts basally produced higher levels of IL-6 than controls, while no difference was observed about CCL2 and CXCL10. TNF-α was able to dose-dependently induce IL-6 and CCL2 secretion in SSc, but not in control fibroblasts. By stimulation with increasing doses of IFN-γ, SSc fibroblasts were induced to secrete CCL2 and CXCL10, while no effect was observed on IL-6. The combination of IFN-γ and TNF-α induced a strong secretion of IL-6 and CCL2 in SSc fibroblasts but not in controls. In contrast, the synergistic effect of IFN-γ and TNF-α on CXCL10 secretion was similar in SSc fibroblasts and in controls.

Conclusion.

SSc fibroblasts participate in the self-perpetuation of inflammation by releasing IL-6, CXCL10, and CCL2 under the influence of IFN-γ and/or TNF-α. SSc fibroblasts are more active than controls in the secretion of IL-6 at baseline, and in the production of IL-6 and CCL2 under the combined IFN-γ/TNF-α stimulation.

Reconstruction of monocyte transcriptional regulatory network accompanies monocytic functions in human fibroblasts

Transcriptional regulatory networks (TRN) control the underlying mechanisms behind cellular functions and they are defined by a set of core transcription factors regulating cascades of peripheral genes. Here we report SPI1, CEBPA, MNDA and IRF8 as core transcription factors of monocyte TRN and demonstrate functional inductions of phagocytosis, inflammatory response and chemotaxis activities in human dermal fibroblasts. The Gene Ontology and KEGG pathway analyses also revealed notable representation of genes involved in immune response and endocytosis in fibroblasts. Moreover, monocyte TRN-inducers triggered multiple monocyte-specific genes based on the transcription factor motif response analysis and suggest that complex cellular TRNs are uniquely amenable to elicit cell-specific functions in unrelated cell types.

Poly(I:C) drives type I IFN- and TGFβ-mediated inflammation and dermal fibrosis simulating altered gene expression in systemic sclerosis

Immune activation of fibrosis likely has a crucial role in the pathogenesis of systemic sclerosis (SSc). The aim of this study was to better understand the innate immune regulation and associated IFN- and transforming growth factor-β (TGFβ)-responsive gene expression in SSc skin and dermal fibroblasts, in particular the effect of different Toll-like receptor (TLR) ligands. To better understand the relationship between inflammation and fibrosis in vivo, we developed a murine model for chronic innate immune stimulation. We found that expression of both IFN- and TGFβ-responsive genes is increased in SSc skin and SSc fibroblasts when stimulated by TLR ligands. In contrast, cutaneous lupus skin showed much more highly upregulated IFN-responsive and much less highly upregulated TGFβ-responsive gene expression. Of the TLRs ligands tested, the TLR3 ligand, polyinosinic/polycytidylic acid (Poly(I:C)), most highly increased fibroblast expression of both IFN- and TGFβ-responsive genes as well as TLR3. Chronic subcutaneous immune stimulation by Poly(I:C) stimulated inflammation, and IFN- and TGFβ-responsive gene expression. However, in this model, type I IFNs had no apparent role in regulating TGFβ activity in the skin. These results suggest that TLR agonists may be important stimuli of dermal fibrosis, which is potentially mediated by TLR3 or other innate immune receptors.