5-lipoxygenase-activating protein gene expression. Key role of CCAAT/enhancer-binding proteins (C/EBP) in constitutive and tumor necrosis factor (TNF) alpha-induced expression in THP-1 cells

Bacteroides Fragilis in the gut microbiomes of Alzheimer's disease activates microglia and triggers pathogenesis in neuronal C/EBPβ transgenic mice

Gut dysbiosis contributes to Alzheimer's disease (AD) pathogenesis, and Bacteroides strains are selectively elevated in AD gut microbiota. However, it remains unknown which Bacteroides species and how their metabolites trigger AD pathologies. Here we show that Bacteroides fragilis and their metabolites 12-hydroxy-heptadecatrienoic acid (12-HHTrE) and Prostaglandin E2 (PGE2) activate microglia and induce AD pathogenesis in neuronal C/EBPβ transgenic mice. Recolonization of antibiotics cocktail-pretreated Thy1-C/EBPβ transgenic mice with AD patient fecal samples elicits AD pathologies, associated with C/EBPβ/Asparaginyl endopeptidase (AEP) pathway upregulation, microglia activation, and cognitive disorders compared to mice receiving healthy donors' fecal microbiota transplantation (FMT). Microbial 16S rRNA sequencing analysis shows higher abundance of proinflammatory Bacteroides fragilis in AD-FMT mice. Active components characterization from the sera and brains of the transplanted mice revealed that both 12-HHTrE and PGE2 activate primary microglia, fitting with poly-unsaturated fatty acid (PUFA) metabolites enrichment identified by metabolomics. Strikingly, recolonization with live but not dead Bacteroides fragilis elicited AD pathologies in Thy1-C/EBPβ transgenic mice, so did 12-HHTrE or PGE2 treatment alone. Collectively, our findings support a causal role for Bacteroides fragilis and the PUFA metabolites in activating microglia and inducing AD pathologies in Thy1- C/EBPβ transgenic mice.

Gut microbiota regulate Alzheimer's disease pathologies and cognitive disorders via PUFA-associated neuroinflammation

OBJECTIVE

This study is to investigate the role of gut dysbiosis in triggering inflammation in the brain and its contribution to Alzheimer's disease (AD) pathogenesis.

DESIGN

We analysed the gut microbiota composition of 3×Tg mice in an age-dependent manner. We generated germ-free 3×Tg mice and recolonisation of germ-free 3×Tg mice with fecal samples from both patients with AD and age-matched healthy donors.

RESULTS

Microbial 16S rRNA sequencing revealed Bacteroides enrichment. We found a prominent reduction of cerebral amyloid-β plaques and neurofibrillary tangles pathology in germ-free 3×Tg mice as compared with specific-pathogen-free mice. And hippocampal RNAseq showed that inflammatory pathway and insulin/IGF-1 signalling in 3×Tg mice brain are aberrantly altered in the absence of gut microbiota. Poly-unsaturated fatty acid metabolites identified by metabolomic analysis, and their oxidative enzymes were selectively elevated, corresponding with microglia activation and inflammation. AD patients' gut microbiome exacerbated AD pathologies in 3×Tg mice, associated with C/EBPβ/asparagine endopeptidase pathway activation and cognitive dysfunctions compared with healthy donors' microbiota transplants.

CONCLUSIONS

These findings support that a complex gut microbiome is required for behavioural defects, microglia activation and AD pathologies, the gut microbiome contributes to pathologies in an AD mouse model and that dysbiosis of the human microbiome might be a risk factor for AD.

Differential gene expression analysis of corneal endothelium indicates involvement of phagocytic activity in Fuchs' endothelial corneal dystrophy

Fuchs' endothelial corneal dystrophy (FECD) is a progressive vision impairing disease caused by thickening of Descemet's membrane and gradual degeneration and loss of corneal endothelial cells. The aim of this study was to identify differentially expressed genes between FECD-affected and unaffected corneal endothelium to gain insight into the pathophysiological mechanisms underlying this disease. Microarray gene expression analysis was performed on total RNA from FECD-affected and unaffected corneal endothelium-Descemet's membrane (CE-DM) specimens using the Illumina HumanHT-12 v4.0 expression array. RNA from pools of FECD-affected (n = 3 per pool) and individual unaffected (n = 3) specimens was used for comparison. Altered expression of a sub-set of differentially expressed genes was validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in independent specimens. Bioinformatics analysis was performed using InnateDB to reveal functional relationships among the differentially expressed genes and molecular pathways involved in the disease. A total of 16,513 genes were found expressed in the corneal endothelium of which 142 genes were differentially expressed between FECD-affected and unaffected endothelium (log₂ fold-change ≥1.5, corrected p-value ≤0.05). Most of the genes were up-regulated (126) and a small proportion down-regulated (16) in affected corneal endothelium. Of the twelve genes prioritised for validation, differential expression of 10 genes, including those ranked 57th and 81st by significance validated by qRT-PCR (8 up-regulated and 2 downregulated, corrected p ≤ 0.05), one gene showed a trend for up-regulation in affected endothelium, consistent with the microarray analysis and another was up-regulated in an independent study indicating robustness of the differential expression dataset. Bioinformatic analysis revealed significant over-representation of differentially expressed genes in extracellular matrix reorganisation, cellular remodelling, immune response, and inflammation. Network analysis showed functional inter-relatedness of the majority of the dysregulated genes and revealed known direct functional relationships between 20 of the genes; many of these genes have roles in macrophage differentiation, phagocytosis and inflammation. This is the second report of microarray gene expression analysis in FECD. This study revealed a set of highly dysregulated genes in the corneal endothelium in FECD. More than a third of the dysregulated genes in the disease have been discovered for the first time and thus are novel. The dysregulated genes strongly suggest the presence of phagocytic cells, most likely immune cells, and inflammation in corneal endothelium in the disease. This study provides a molecular framework for delineating the mechanisms underlying these cellular processes in FECD.

Emerging role of cysteinyl LTs in cancer

Cysteinyl leukotrienes (CysLTs) are inflammatory lipid mediators that play a central role in the pathophysiology of several inflammatory diseases. Recently, there has been an increased interest in determining how these lipid mediators orchestrate tumour development and metastasis through promoting a pro-tumour micro-environment. Up-regulation of CysLTs receptors and CysLTs production is found in a number of cancers and has been associated with increased tumorigenesis. Understanding the molecular mechanisms underlying the role of CysLTs and their receptors in cancer progression will help investigate the potential of targeting CysLTs signalling for anti-cancer therapy. This review gives an overview of the biological effects of CysLTs and their receptors, along with current knowledge of their regulation and expression. It also provides a recent update on the molecular mechanisms that have been postulated to explain their role in tumorigenesis and on the potential of anti-CysLTs in the treatment of cancer.

Differential Gene Expression in Circulating CD14+ Monocytes Indicates the Prognosis of Critically Ill Patients with Sepsis

Critical illness and sepsis are characterized by drastic changes in the systemic innate immune response, particularly involving monocytes. The exact monocyte activation profile during sepsis, however, has remained obscure. Therefore, we prospectively analyzed the gene expression profile of circulating CD14⁺ monocytes from healthy volunteers (n = 54) and intensive care unit (ICU) patients (n = 76), of which n = 36 had sepsis. RNA sequencing of selected samples revealed that monocytes from septic ICU patients display a peculiar activation pattern, which resembles characteristic functional stages of monocyte-derived macrophages and is distinct from controls or non-sepsis ICU patients. Focusing on 55 highly variable genes selected for further investigation, arachidonate 5-lipoxygenase-activating protein (ALOX5AP) was highly upregulated in monocytes of ICU patients and only normalized during 7 days in the ICU in non-sepsis patients. Strikingly, low monocytic guanine nucleotide exchange factor 10-like protein (ARHGEF10L) mRNA expression was associated with the disease severity and mortality of ICU patients. Collectively, our comprehensive analysis of circulating monocytes in critically ill patients revealed a distinct activation pattern, particularly in ICU patients with sepsis. The association with disease severity, the longitudinal recovery or lack thereof during the ICU stay, and the association with prognosis indicate the clinical relevance of monocytic gene expression profiles during sepsis.

miR-146a suppresses 5-lipoxygenase activating protein (FLAP) expression and Leukotriene B4 production in lung cancer cells

Arachidonic acid (AA) can be converted into prostaglandins (PGs) or leukotrienes (LTs) by the enzymatic actions of cyclooxygenases (COX-1 and COX-2) or 5-lipoxygenase (5-LO), respectively. PGs and LTs are lipid signaling molecules that have been implicated in various diseases, including multiple cancers. 5-LO and its activating protein (FLAP) work together in the first two conversion steps of LT production. Previous work has suggested a role for LTs in cancer development and progression. MicroRNAs (miRNAs) are small RNA molecules that negatively regulate gene expression post-transcriptionally, and have previously been shown to be involved in cancer. Here, we show that high FLAP expression is associated with lower overall survival in lung adenocarcinoma patients, and FLAP protein is overexpressed in lung cancer cells compared to normal lung cells. Our lab has previously shown that miR-146a regulates COX-2 in lung cancer cells, and this miRNA is also predicted to target FLAP. Transient and stable transfections of miR-146a repress endogenous FLAP expression in lung cancer cells, and reporter assays show this regulation occurs through a direct interaction between the FLAP 3′ untranslated region (UTR) and miR-146a. Restoration of miR-146a also results in decreased cancer cell Leukotriene B4 (LTB₄) production. Additionally, methylation analysis indicates the miR-146a promoter is hypermethylated in lung cancer cell lines. Taken together, this study and previous work from our lab suggest miR-146a is an endogenous dual inhibitor of AA metabolism in lung cancer cells by regulating both PG and LT production through direct targeting of the COX-2 and FLAP 3’ UTRs.

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ are transcription factors of the basic-leucine zipper class which share phylogenetic, structural and functional features. In this review we first describe in depth their basic molecular biology which includes fascinating aspects such as the regulated use of alternative initiation codons in the C/EBPβ mRNA. The physical interactions with multiple transcription factors which greatly opens the number of potentially regulated genes or the presence of at least five different types of post-translational modifications are also remarkable molecular mechanisms that modulate C/EBPβ and C/EBPδ function. In the second part, we review the present knowledge on the localization, expression changes and physiological roles of C/EBPβ and C/EBPδ in neurons, astrocytes and microglia. We conclude that C/EBPβ and C/EBPδ share two unique features related to their role in the CNS: whereas in neurons they participate in memory formation and synaptic plasticity, in glial cells they regulate the pro-inflammatory program. Because of their role in neuroinflammation, C/EBPβ and C/EBPδ in microglia are potential targets for treatment of neurodegenerative disorders. Any strategy to reduce C/EBPβ and C/EBPδ activity in neuroinflammation needs to take into account its potential side-effects in neurons. Therefore, cell-specific treatments will be required for the successful application of this strategy.

Interaction of C/EBP-beta and NF-Y factors constrains activity levels of the nutritionally controlled promoter IA expressing the acetyl-CoA carboxylase-alpha gene in cattle

Background

The enzyme acetyl-CoA carboxylase-alpha (ACC-α) is rate limiting for de novo fatty acid synthesis. Among the four promoters expressing the bovine gene, promoter IA (PIA) is dominantly active in lipogenic tissues. This promoter is in principal repressed but activated under favorable nutritional conditions. Previous analyses already coarsely delineated the repressive elements on the distal promoter but did not resolve the molecular nature of the repressor. Knowledge about the molecular functioning of this repressor is fundamental to understanding the nutrition mediated regulation of PIA activity. We analyzed here the molecular mechanism calibrating PIA activity.

Results

We finely mapped the repressor binding sites in reporter gene assays and demonstrate together with Electrophoretic Mobility Shift Assays that nuclear factor-Y (NF-Y) and CCAAT/enhancer binding protein-β (C/EBPβ) each separately repress PIA activity by binding to their cognate low affinity sites, located on distal elements of the promoter. Simultaneous binding of both factors results in strongest repression. Paradoxically, over expression of NFY factors, but also - and even more so - of C/EBPβ significantly activated the promoter when bound to high affinity sites on the proximal promoter. However, co-transfection experiments revealed that NF-Y may eventually diminish the strong stimulatory effect of C/EBPβ at the proximal PIA in a dose dependent fashion. We validated by chromatin immunoprecipitation, that NF-Y and C/EBP factors may physically interact.

Conclusion

The proximal promoter segment of PIA appears to be principally in an active state, since even minute concentrations of both, NF-Y and C/EBPβ factors can saturate the high affinity activator sites. Higher factor concentrations will saturate the low affinity repressive sites on the distal promoter resulting in reduced and calibrated promoter activity. Based on measurements of the mRNA concentrations of those factors in different tissues we propose that the interplay of both factors may set tissue-specific limits for PIA activity.

Mechanisms of induction of cytosolic and microsomal glutathione transferase (GST) genes by xenobiotics and pro-inflammatory agents

Glutathione transferase (GST) isoezymes are encoded by three separate families of genes (designated cytosolic, microsomal and mitochondrial transferases), with distinct evolutionary origins, that provide mammalian species with protection against electrophiles and oxidative stressors in the environment. Members of the cytosolic class Alpha, Mu, Pi and Theta GST, and also certain microsomal transferases (MGST2 and MGST3), are up-regulated by a diverse spectrum of foreign compounds typified by phenobarbital, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, pregnenolone-16α-carbonitrile, 3-methylcholanthrene, 2,3,7,8-tetrachloro-dibenzo-p-dioxin, β-naphthoflavone, butylated hydroxyanisole, ethoxyquin, oltipraz, fumaric acid, sulforaphane, coumarin, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole, 12-O-tetradecanoylphorbol-13-acetate, dexamethasone and thiazolidinediones. Collectively, these compounds induce gene expression through the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), the aryl hydrocarbon receptor (AhR), NF-E2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor-γ (PPARγ) and CAATT/enhancer binding protein (C/EBP) β. The microsomal T family includes 5-lipoxygenase activating protein (FLAP), leukotriene C(4) synthase (LTC4S) and prostaglandin E(2) synthase (PGES-1), and these are up-regulated by tumour necrosis factor-α, lipopolysaccharide and transforming growth factor-β. Induction of genes encoding FLAP, LTC4S and PGES-1 is mediated by the transcription factors C/EBPα, C/EBPδ, C/EBPϵ, nuclear factor-κB and early growth response-1. In this article we have reviewed the literature describing the mechanisms by which cytosolic and microsomal GST are up-regulated by xenobiotics, drugs, cytokines and endotoxin. We discuss cross-talk between the different induction mechanisms, and have employed bioinformatics to identify cis-elements in the upstream regions of GST genes to which the various transcription factors mentioned above may be recruited.

CCAAT/enhancer-binding protein delta mediates tumor necrosis factor alpha-induced Aurora kinase C transcription and promotes genomic instability

Epidemiologic and clinical research indicates that chronic inflammation increases the risk of certain cancers, possibly through chromosomal instability. However, the mechanism of inflammation-dependent chromosomal instability associated with tumorigenesis is not well characterized. The transcription factor CCAAT/enhancer-binding protein δ (C/EBPδ, CEBPD) is induced by tumor necrosis factor α (TNFα) and expressed in chronically inflamed tissue. In this study, we show that TNFα promotes aneuploidy. Loss of CEBPD attenuated TNFα-induced aneuploidy, and CEBPD caused centromere abnormality. Additionally, TNFα-induced CEBPD expression augmented anchorage-independent growth. We found that TNFα induced expression of aurora kinase C (AURKC) through CEBPD, and that AURKC also causes aneuploidy. Furthermore, high CEBPD expression correlated with AURKC expression in inflamed cervical tissue specimens. These data provide insight into a novel function for CEBPD in inducing genomic instability through the activation of AURKC expression in response to inflammatory signals.

Autosome-wide Copy Number Variation Association Analysis for Rheumatoid Arthritis Using the WTCCC High-density SNP Genotype Data

Objective.

Rheumatoid arthritis (RA) is a complex autoimmune rheumatic disease that is strongly influenced by genetic factors. Numerous genes are convincingly associated with RA, including genes in tumor necrosis factor signaling (TNF) and the nuclear factor-κB pathway. To date, except for genes within the HLA region, no data exist regarding potential copy number variations (CNV) involving RA-associated genes. We set out to identify genes affected by CNV that are associated with RA at a genome-wide level.

Methods.

Data from the Wellcome Trust Case Control Consortium (WTCCC) were used in our analyses. The initial WTCCC cohort genotyped 3004 controls and 1999 RA cases using the GeneChip 500k Mapping Array Set. We performed a comparative intensity analysis using the PennCNV algorithm, which uses a hidden Markov model to detect CNV. A total of 2271 controls and 1572 RA samples passed quality control criteria and were included for association analysis. Association analysis was performed in 2 phases: (1) to identify CNV that are < 1 Mb with a population frequency < 5%; and (2) to identify large CNV that are > 1 Mb. Fishers’ exact test was performed to quantify significance of the CNV.

Results.

We observed that the genome-wide CNV burden is 2-fold higher in patients with RA compared with controls. We identified 11 rare copy number variable regions with < 5% frequency that had an association with RA that reached a p < 1 × 10−4. These include TNFAIP3 and TNIP1, which has been implicated in association studies for RA, systemic lupus erythematosus, and psoriasis. We identified CNV involving IRF1, which functions as a transcription activator of genes induced by interferons; ALOX5AP and LCP2, involved in inflammatory mediation; B2M, an MHC-class I associated gene; and PRKCH, a gene involved in T cell signaling pathways. A 57 kb deletion with 1% frequency in RA cases at 7p21.3 was also observed. Six of these loci overlap with CNV catalogued in the Database of Genomic Variants.

Conclusion.

This is the first study to identify non-HLA RA-associated CNV using genome-wide analyses. Validation and functional significance of these deletions/duplications in RA and other autoimmune diseases need to be further investigated.

CCAAT/enhancer binding protein delta in microglial activation

The transcription factor CCAAT/enhancer binding protein delta (C/EBP delta) regulates transcription of genes that play important roles in glial activation. Previous studies have shown the astroglial expression of C/EBP delta but the microglial expression of C/EBP delta remains virtually unexplored, with the exception of two microarray studies. In this report, using murine primary cultures and BV2 cells we clearly demonstrate that C/EBP delta is expressed by microglia and it is upregulated in microglial activation. Lipopolysaccharide upregulates C/EBP delta both in microglia and in astrocytes. This effect is time-dependent, with a maximum effect at 3 hr at mRNA level and at 4-8 hr at protein level, and concentration-dependent, with a maximum effect at 100 ng/mL. The lipopolysaccharide-induced C/EBP delta upregulation in BV2 microglia is mimicked by agonists of the toll-like receptors 2, 3 and 9 and can be prevented by an inhibitor of extracellular signal-regulated kinase activation. C/EBP delta from activated BV2 microglia binds to the cyclooxygenase-2 promoter and forms complexes with C/EBP beta isoforms. These results point to C/EBP delta as a putative key regulator of proinflammatory gene expression in microglial activation.

Placenta growth factor-induced early growth response 1 (Egr-1) regulates hypoxia-inducible factor-1alpha (HIF-1alpha) in endothelial cells

Leukotrienes, the lipid inflammatory products derived from arachidonic acid, are involved in the pathogenesis of respiratory and cardiovascular diseases and reactive airway disease in sickle cell disease. Placenta growth factor (PlGF), elaborated from erythroid cells, increased the mRNA expression of 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP) in human pulmonary microvascular endothelial cells. PlGF-induced both promoter activity and mRNA expression of hypoxia-inducible factor-1alpha (HIF-1alpha), which was abrogated by early growth response-1 (EGR-1) small interfering RNA. PlGF showed a temporal reciprocal relationship in the mRNA levels of EGR-1 and NAB2, the latter a repressor of Egr-1. Moreover, Nab2, but not mutant Nab2, significantly reduced promoter activity and mRNA expression of HIF-1alpha and also reduced expression of the HIF-1alpha target gene FLAP. Furthermore, overexpression of Egr-1 led to increased promoter activities for both HIF-1alpha and FLAP in the absence of PlGF. Additionally, the Egr-1-mediated induction of HIF-1alpha and FLAP promoters was reduced to basal levels by EGR-1 small interfering RNA. The binding of Egr-1 to HIF-1alpha promoter was corroborated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay, which showed increased Egr-1 binding to the HIF-1alpha promoter in response to PlGF stimulation. These studies provide a novel mechanism for PlGF-mediated regulation of HIF-1alpha via Egr-1, which results in increased FLAP expression. This study provides a new therapeutic target, namely Egr-1, for attenuation of elevated leukotriene levels in patients with sickle cell disease and other inflammatory diseases.

Hypoxia-mediated expression of 5-lipoxygenase-activating protein involves HIF-1alpha and NF-kappaB and microRNAs 135a and 199a-5p

Hypoxia occurs in a number of pathological states, such as pulmonary, hematological, and cardiovascular disorders. In this study, we examined the molecular mechanism by which hypoxia contributes to increased leukotriene formation. Our studies showed hypoxia augmented the expression of 5-lipoxygenase activating protein (FLAP), a key enzyme in leukotriene formation, in both human pulmonary microvascular endothelial cells and a transformed human brain endothelial cell line. Hypoxia-induced FLAP mRNA expression involved activation of NADPH-oxidase, PI-3 kinase, mitogen-activated protein kinase, NF-kappaB, and hypoxia-inducible factor (HIF)-1alpha. Hypoxia-induced FLAP promoter activity was attenuated on mutation of hypoxia-response elements (HREs) and NF-kappaB binding motif in the FLAP promoter. Hypoxia also augmented binding of HIF-1alpha to HREs in FLAP promoter as demonstrated by EMSA with nuclear extracts. Furthermore, chromain immunoprecipitation analysis showed HIF-1alpha bound to HREs in native chromatin obtained from hypoxia-treated cells. Next, we examined the role of HIF-1alpha regulated microRNAs on FLAP expression. Our studies showed decreased expression of miR-135a and miR-199a-5p in response to hypoxia. However, overexpression of anti-miR-135a and anti-miR-199a-5p oligonucleotides led to a several fold increased FLAP mRNA and protein expression. These studies demonstrate for the first time that hypoxia-mediated FLAP expression is regulated by HREs and NF-kappaB site in its promoter, and negatively regulated by miR-135a and miR-199a-5p, which target the 3'-UTR of FLAP mRNA. An understanding of these regulatory pathways provides new avenues to ameliorate leukotriene formation and hence reactive airway disease, and inflammation in individuals who have sickle cell disease.

Rho iso-alpha acids from hops inhibit the GSK-3/NF-kappaB pathway and reduce inflammatory markers associated with bone and cartilage degradation

Background

Rho iso-alpha acids (RIAA) from hops have been shown to have anti-inflammatory properties. To understand the mechanisms, we evaluated the effect of RIAA in cell signaling pathways and inflammatory markers using various in vitro models. We also investigated their therapeutic effect in mice with collagen-induced arthritis.

Methods

The LPS-stimulated RAW 264.7 macrophages were used to evaluate the effect of RIAA on the NF-κB and MAPK signaling pathways; phosphorylation of ERK1/2, p38 and JNK was assessed by western blotting and NF-κB binding by electrophoretic mobility shift assays. Effect on the NF-κB activity was evaluated by the luciferase reporter assays in LPS-stimulated RAW 264.7 cells. GSK-3α/β kinase activity was measured in cell-free assays. The inhibitory effect of RIAA on inflammatory markers was assessed by measuring nitric oxide in LPS-stimulated RAW 264.7 cells, RANKL-mediated TRAP activity in transformed osteoclasts, and TNF-α/IL-1β-mediated MMP-13 expression in SW1353 cells. Mice with collagen-induced arthritis were fed with RIAA for 2 weeks. Symptoms of joint swelling, arthritic index and joint damage were assessed.

Results

RIAA selectively inhibited the NF-κB pathway while having no effect on ERK1/2, p38 and JNK phosphorylation in LPS-stimulated RAW 264.7 cells. RIAA also inhibited GSK-3α/β kinase activity and GSK-3β dependent phosphorylation of β-catenin in RAW 264.7 cells. In addition, RIAA inhibited NF-κB-mediated inflammatory markers in various cell models, including nitric oxide in LPS-stimulated RAW 264.7 cells, RANKL-mediated TRAP activity in transformed osteoclasts, and TNF-α/IL-1β-mediated MMP-13 expression in SW1353 human chondrosarcoma cells. Finally, in a mouse model of collagen-induced arthritis, RIAA ameliorated joint damage as evidenced by significant reduction of the arthritis index and histology score; at 250 mg/kg-body weight, RIAA had efficacy similar to that of 20 mg/kg-body weight of celecoxib.

Conclusion

RIAA may have potential as an anti-inflammatory therapeutic.

Placenta growth factor induces 5-lipoxygenase-activating protein to increase leukotriene formation in sickle cell disease

Individuals with sickle cell disease (SCD) have increased inflammation, a high incidence of airway hyperreactivity (AH), and increased circulating leukotrienes (LT). We show that expression of 5-lipoxygenase and 5-lipoxygenase activating protein (FLAP), key catalytic molecules in the LT pathway, were significantly increased in peripheral blood mononuclear cells (MNCs) in patients with SCD, compared with healthy controls. Placenta growth factor (PlGF), elaborated from erythroid cells, activated MNC and THP-1 monocytic cells to induce LT production. PlGF-mediated increased FLAP mRNA expression occurred via activation of phosphoinositide-3 (PI-3) kinase, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and hypoxia inducible factor-1alpha (HIF-1alpha). HIF-1alpha small interfering RNA (siRNA) reduced PlGF-induced FLAP expression. FLAP promoter-driven luciferase constructs demonstrated that PlGF-mediated luciferase induction was abrogated upon mutation of HIF-1alpha response element (HRE), but not the nuclear factor-kappaB (NF-kappaB) site in the FLAP promoter; a finding confirmed by chromatin immunoprecipitation (ChIP) analysis. PlGF also increased HIF-1alpha binding to the HRE in the FLAP promoter. Therefore, it is likely that the intrinsically elevated levels of PlGF in SCD subjects contribute to increased LT, which in turn, mediate both inflammation and AH. Herein, we identify a mechanism of increased LT in SCD and show HIF-1alpha as a hypoxia-independent target of PlGF. These studies provide new avenues to ameliorate these complications.

Transcription factors Sp1 and C/EBP regulate NRAMP1 gene expression

The natural resistance-associated macrophage protein 1 (Nramp1), which belongs to a conserved family of membrane metal transporters, contributes to phagocyte-autonomous antimicrobial defense mechanisms. Genetic polymorphisms in the human NRAMP1 gene predispose to susceptibility to infectious or inflammatory diseases. To characterize the transcriptional mechanisms controlling NRAMP1 expression, we previously showed that a 263 bp region upstream of the ATG drives basal promoter activity, and that a 325 bp region further upstream confers myeloid specificity and activation during differentiation of HL-60 cells induced by vitamin D. Herein, the major transcription start site was mapped in the basal region by S1 protection assay, and two cis-acting elements essential for myeloid transactivation were characterized by in vitro DNase footprinting, electrophoretic mobility shift experiments, in vivo transfection assays using linker-mutated constructs, and chromatin immunoprecipitation assays in differentiated monocytic cells. One distal cis element binds Sp1 and is required for NRAMP1 myeloid regulation. Another site in the proximal region binds CCAAT enhancer binding proteins alpha or beta and is crucial for transcription. This study implicates Sp1 and C/EBP factors in regulating the expression of the NRAMP1 gene in myeloid cells.

Identification of a responsible promoter region and a key transcription factor, CCAAT/enhancer-binding protein epsilon, for up-regulation of PHGPx in HL60 cells stimulated with TNF alpha

In the present study we investigated promoter regions of the PHGPx [phospholipid hydroperoxide GPx (glutathione peroxidase)] gene and transcription factors involved in TNFalpha (tumour necrosis factor alpha)-induced up-regulation of PHGPx in non-differentiated HL60 cells. Non-differentiated HL60 cells displayed up-regulation of non-mitochondrial and mitochondrial PHGPx mRNA in response to TNFalpha stimulation. The promoter activity was up-regulated by TNFalpha stimulation in cells transfected with a luciferase reporter vector encoding the region from -282 to -123 of the human PHGPx gene compared with the non-stimulated control. The up-regulated promoter activity was effectively abrogated by a mutation in the C/EBP (CCAAT/enhancer-binding protein)-binding sequence in this region. ChIP (chromatin immunoprecipitation) assays demonstrated that C/EBPepsilon bound to the -247 to -34 region in HL60 cells, but C/EBPalpha, beta, gamma and delta did not. The binding of C/EBPepsilon to the promoter region was increased in HL60 cells stimulated with TNFalpha compared with that of the non-stimulated control. An increased binding of nuclear protein to the C/EBP-binding sequence was observed by EMSA (electrophoretic mobility-shift assay) in cells stimulated with TNFalpha, and it was inhibited by pre-treatment with an anti-C/EBPepsilon antibody, but not with other antibodies. The C/EBPepsilon mRNA was expressed in PMNs (polymorphonuclear cells), non-differentiated HL60 cells and neutrophil-like differentiated HL60 cells displaying TNFalpha-induced up-regulation of PHGPx mRNA, but not in macrophage-like differentiated HL60 cells, HEK-293 cells (human embryonic kidney-293 cells) and other cell lines exhibiting no up-regulation. The up-regulation of PHGPx mRNA, however, was detected in HEK-293 cells overexpressing C/EBPepsilon as a result of TNFalpha stimulation. These results indicate that C/EBPepsilon is a critical transcription factor in TNFalpha-induced up-regulation of PHGPx expression.

Plasma C-reactive protein and 5-lipoxygenase-activating protein gene promoter poly-A polymorphism in patients with coronary artery disease

OBJECTIVES

The purpose of this study was to explore the possible associations of the 5-lipoxygenase-activating protein (FLAP) poly-A genotype, plasma high-sensitivity C-reactive protein (hsCRP) and the extent score of coronary artery disease (CAD).

METHODS

The 17A/21A genotypes and plasma hsCRP levels were determined in 555 Chinese patients, 424 with and 131 without CAD. The luciferase reporter assay was performed to explore the functional significance of promoter poly-A polymorphism.

RESULTS

CAD patients showed significantly higher plasma hsCRP (p = 0.007) than non-CAD subjects, but no differences in the 17A allele carriers and frequency. The extent score of CAD was significantly correlated with plasma hsCRP (p = 0.03). Furthermore, the 17A allele carriers showed significantly higher hsCRP than the 21A homozygotes (p = 0.02). Multiple linear regression analysis documented an impact of the poly-A genotype on plasma hsCRP (p = 0.03). In vitro, the 17A construct was found to have greater promoter activity than the 21A construct (p = 0.02).

CONCLUSIONS

The present study demonstrated a significant correlation of FLAP gene promoter 17A allele carriers with higher plasma hsCRP levels in patients with CAD. This association might be related to the increased transcriptional activity of the FLAP gene and the resulting pro-inflammatory effect on the 5-lipoxygenase pathway.

A Novel Role of Hypoxia-Inducible Factor in Cobalt Chloride- and Hypoxia-Mediated Expression of IL-8 Chemokine in Human Endothelial Cells

Tissue hypoxemia is common in several pathological diseases, including vaso-occlusion in sickle cell disease and myocardial infarction. One finds increased presence of leukocytes during lung injury and at sites of inflammation in vascular endothelium. In this study, we used human pulmonary microvascular endothelial cells and human dermal microvascular endothelial immortalized cell line to delineate the cellular signaling mechanism of hypoxia- and CoCl2 (a mimetic of hypoxia)-induced IL-8 expression, and the latter's role in chemotaxis of polmorphonuclear neutrophils. We show that hypoxia- and CoCl2-induced IL-8 mRNA and protein expression involved activation of PI3K/Akt and p38 MAPK, but not MEK kinase. Analysis of some transcription factors associated with IL-8 promoter revealed that hypoxia and CoCl2 increased DNA-binding activity of hypoxia-inducible factor-1alpha (HIF-1alpha), NF-kappaB, and AP-1. In addition, we show that hypoxia- and CoCl2-induced IL-8 expression requires activation of HIF as demonstrated by the following: 1) EMSA; 2) transfection studies with IL-8 promoter reporter constructs with mutation in HIF-1alpha binding site; 3) attenuation of IL-8 expression by both HIF-1alpha small interfering RNA and R59949; 4) augmentation of IL-8 expression by either transfection with HIF-prolyl hydroxylase-2 small interfering RNA or overexpression of HIF-1alpha; and 5) chromatin immunoprecipitation analysis. Moreover, conditioned medium from hypoxia-treated endothelial cells augmented chemotaxis of neutrophils, due to release of IL-8. These data indicate that hypoxia-induced signaling in vascular endothelium for transcriptional activation of IL-8 involves PI3K/Akt, p38 MAPK, and HIF-1alpha. Pharmacological agents, which inhibit HIF-1alpha, may possibly ameliorate inflammation associated with hypoxia in pathological diseases.

Distinct Effects of Annexin A7 and p53 on Arachidonate Lipoxygenation in Prostate Cancer Cells Involve 5-Lipoxygenase Transcription

Tumor suppressor function for Annexin A7 (ANXA7; 10q21) is based on cancer-prone phenotype in Anxa7(+/-) mouse and ANXA7 prognostic role in human cancers. Because ANXA7-caused liposome aggregation can be promoted by arachidonic acid (AA), we hypothesized that the phospholipid-binding tumor suppressor ANXA7 is associated with AA cascade. In a comparative study of ANXA7 versus canonical tumor suppressor p53 effects on AA lipoxygenation pathway in the p53-mutant and androgen-insensitive DU145 prostate cancer cells, both tumor suppressors altered gene expression of major 5-lipoxygenase (LOX) and 15-LOXs, including response to T helper 2 (Th2)-cytokine [interleukin-4 (IL-4)] and endogenous steroids (mimicked by dexamethasone). Wild-type and mutant ANXA7 distinctly affected expression of the dexamethasone-induced 15-LOX-2 (a prostate-specific endogenous tumor suppressor) as well as the IL-4-induced 15-LOX-1. On the other hand, wild-type p53 restored 5-LOX expression in DU145 to levels comparable to benign prostate epithelial cells. Using mass spectrometry of DNA affinity-enriched nuclear proteins, we detected different proteins that were bound to adjacent p53 and estrogen response elements in the 5-LOX promoter in DU145 cells introduced with ANXA7 versus p53. Sex hormone regulator 17-beta hydroxysteroid dehydrogenase 4 was identified under p53 introduction, which induced the 5-LOX expression. Meantime, nuclear proteins bound to the same 5-LOX promoter site under introduction of ANXA7 (that was associated with the repressed 5-LOX) were identified as zinc finger proteins ZNF433 and Aiolos, pyrin domain-containing NALP10, and the p53-regulating DNA repair enzyme APEX1. Thus, ANXA7 and p53 can distinctly regulate LOX transcription that is potentially relevant to the AA-mediated cell growth control in tumor suppression.

TNF-alpha downregulates the leukotriene C4 synthase gene in mononuclear phagocytes

We studied the effect of tumor necrosis factor (TNF)-alpha exposure on cysteinyl leukotriene (LT) synthesis by cells of monocyte/macrophage lineage. TNF-alpha conditioning of monocytic THP-1 cells and primary human monocytes resulted in a decreased capacity for LTC(4) release. TNF-alpha exposure (for 16-24 h) decreased LTC(4) synthase mRNA in THP-1 cells, primary mouse bone marrow-derived macrophages, and eosinophilic AML14.3D10 cells. TNF-alpha downregulated LTC(4) synthase mRNA in THP-1 cells in a dose- and time-dependent manner, with downregulation observed as early as 4 h. The effect of TNF-alpha on LTC(4) synthase mRNA expression was mediated via the MEK/ERK pathway, but not via cyclooxygenase or nitric oxide synthase pathways. Conditioning of actinomycin D-treated cells with TNF-alpha did not accelerate degradation of LTC(4) synthase mRNA. TNF-alpha produced sustained activation of p50 and p65, which were previously reported by our group to decrease LTC(4) synthase promoter activity. In transiently transfected THP-1 cells, TNF-alpha decreased promoter activity via an element located within the first 620 bp of the promoter. We conclude that TNF-alpha exposure downregulates the synthetic capacity for cysteinyl LT release and LTC(4) synthase gene expression in monocytes/macrophages via a transcriptional mechanism.

Heterogeneity in lipopolysaccharide responsiveness of endothelial cells identified by gene expression profiling: role of transcription factors

Interindividual differences of endothelial cells in response to endotoxins might contribute to the diversity in clinical outcome among septic patients. The present study was conducted to test the hypothesis that endothelial cells (EC) with high and low proinflammatory potential exist and to dissect the molecular basis underlying this phenomenon. Thirty human umbilical vein endothelial cell (HUVEC) lines were stimulated for 24 h with lipopolysaccharide (LPS) and screened for interleukin (IL)-8 production. Based on IL-8 production five low and five high producers, tentatively called types I and II responders, respectively, were selected for genome-wide gene expression profiling. From the 74 genes that were modulated by LPS in all type II responders, 33 genes were not influenced in type I responders. Among the 41 genes that were increased in both responders, 17 were expressed significantly stronger in type II responders. Apart from IL-8, significant differences in the expression of proinflammatory related genes between types I and II responders were found for adhesion molecules [intercellular adhesion molecule (ICAM-1), E-selectin)], chemokines [monocyte chemoattractant protein (MCP-1), granulocyte chemotactic protein (GCP-2)], cytokines (IL-6) and the transcription factor CCAAT/enhancer binding protein-delta (C/EBP-delta). Type I responders also displayed a low response towards tumour necrosis factor (TNF)-alpha. In general, maximal activation of nuclear factor (NF)-kappaB was achieved in type I responders at higher concentrations of LPS compared to type II responders. In the present study we demonstrate that LPS-mediated gene expression differs quantitatively and qualitatively in types I and II responders. Our results suggest a pivotal role for common transcription factors as a low inflammatory response was also observed after TNF-alpha stimulation. Further studies are required to elucidate the relevance of these findings in terms of clinical outcome in septic patients.

P2X7 receptor activation in rat brain cultured astrocytes increases the biosynthetic release of cysteinyl leukotrienes

Astrocytes have been recognized as important elements in controlling inflammatory as well as immune processes in the central nervous system (CNS). Recently, glial cells have been shown to produce cysteinyl leukotrienes (CysLTs) which are known lipid mediators of inflammation and whose extracellular concentrations rise under different pathological conditions in the brain. In the same conditions also extracellular concentrations of ATP dramatically increase reaching levels able to activate P2X7 ionotropic receptors for which an emerging role in neuroinflammation and neurodegeneration has been claimed. RTPCR analysis showed that primary cultures of rat brain astrocytes express P2X7 receptors. Application of the selective P2X7 agonist benzoyl benzoly ATP (BzATP) markedly increased [Ca2+]i which was mediated by a calcium influx from the extracellular milieu. The P2X7 antagonist, oATP, suppressed the BzATP-induced calcium increase. Consistent with the evidence that increased calcium levels activate the leukotriene biosynthetic pathway, challenge of astrocytes with either the calcium ionophore A23187 or BzATP significantly increased CysLT production and the cell pre-treatment with EGTA abolished these effects. Again the P2X7 antagonist prevented the BzATP-mediated CysLT efflux, whereas the astrocyte pretreatment with MK-571, a CysLT1 receptor antagonist, was ineffective. The astrocyte pre-treatment with a cocktail of inhibitors of ATP binding cassette (ABC) proteins reduced the BzATP-mediated CysLT production confirming that ABC transporters are involved in the release of CysLTs. The astrocyte P2X7- evoked rise of CysLT efflux was abolished in the presence of MK-886, an inhibitor of 5-lipoxygenase activating protein (FLAP) whose expression, along with that of 5-lipoxygenase (5-LO) was reported by Northern Blot analysis. The stimulation of P2X7 induced an up-regulation of FLAPmRNA that was reduced by the antagonist oATP. These data suggest that in rat brain cultured astrocytes P2X7ATP receptors may participate in the control of CysLT release thus further supporting a role for extracellular ATP as an integral component of the inflammatory brain response.

Mechanism of amyloid peptide induced CCR5 expression in monocytes and its inhibition by siRNA for Egr-1

In Alzheimer's disease (AD), one finds increased presence of monocytes/macrophages and activated microglial cells in the brain. Immunohistochemical studies show increased expression of chemokine receptor 5 (CCR5) on reactive microglia associated with amyloid deposits in AD, suggesting that CCR5 may play a role in the regulation of the immune response in AD. In this study, we used peripheral blood monocytes and human monocytic THP-1 cell line as a model of microglia to delineate the cellular signaling mechanism of Aβ-induced CCR5 expression and the latter's role in the chemotaxis of monocytes. We observed that Aβ peptides at pathophysiological concentrations (125 nM) increased CCR5 mRNA and cell surface protein expression. The cellular signaling involved activation of c-Raf, ERK-1/ERK-2, and c-Jun NH2-terminal kinase. Analysis of some transcription factors associated with CCR5 promoter revealed that Aβ increased DNA binding activity of Egr-1 and AP-1. In addition, we show that CCR5 promoter contains an Egr-1 like consensus sequence GCGGGGGTG as demonstrated by 1) electrophoretic mobility shift assay, 2) transfection studies with truncated CCR5 gene promoter construct, and 3) chromatin immunoprecipitation analysis. Moreover, transfection of Egr-1 siRNA, but not of scrambled Egr-1 siRNA, in THP-1 cells resulted in >75% reduction in both Aβ-mediated CCR5 expression and concomitant chemotaxis to its ligands. We suggest that inhibition of Egr-1 by either Egr-1 siRNA or pharmacological agents may reduce activation of monocytes/microglia and possibly ameliorate the inflammation and progression of AD.

Lipopolysaccharide induces 5-lipoxygenase-activating protein gene expression in THP-1 cells via a NF-κB and C/EBP-mediated mechanism

We examined induced expression of the 5-lipoxygenase-activating protein (FLAP), which is critical for leukotriene synthesis in mononuclear phagocytes. Prolonged exposure to the bacterial component, lipopolysaccharide (LPS), increased FLAP gene transcription, mRNA expression, and protein expression in the human monocyte-like THP-1 cell line. Activation and inhibition of the NF-κB pathway modulated LPS induction of FLAP gene expression. An NF-κB-mediated mechanism of action was supported by overexpression of dominant-negative IκBα and p50/p65 proteins. EMSA/supershift and DNase I footprint analyses revealed that p50 binds to an NF-κB site located in the proximal FLAP promoter, while chromatin immunoprecipitation assays demonstrated that LPS induced binding of p50 but not of p65. Moreover, EMSA/supershift analyses demonstrated that LPS induced time-dependent binding of THP-1 nuclear extracts (containing p50) to this promoter region. Mutation of the NF-κB site decreased basal promoter activity and abolished the p50- and p65-associated induction. EMSA/supershift analyses also demonstrated that LPS induced binding of THP-1 nuclear extracts [containing CCAAT/enhancer binding protein (C/EBP)-α, -δ, and -ε] to a C/EBP site located adjacent to the NF-κB site in the FLAP promoter. We conclude that LPS enhances FLAP gene expression via both NF-κB- and C/EBP-mediated transcriptional mechanisms in mononuclear phagocytes.

Curcumin, the active constituent of turmeric, inhibits amyloid peptide-induced cytochemokine gene expression and CCR5-mediated chemotaxis of THP-1 monocytes by modulating early growth response-1 transcription factor

Epidemiological studies show reduced risk of Alzheimer's disease (AD) among patients using non-steroidal inflammatory drugs (NSAID) indicating the role of inflammation in AD. Studies have shown a chronic CNS inflammatory response associated with increased accumulation of amyloid peptide and activated microglia in AD. Our previous studies showed that interaction of Abeta1-40 or fibrilar Abeta1-42 caused activation of nuclear transcription factor, early growth response-1 (Egr-1), which resulted in increased expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in monocytes. We determined whether curcumin, a natural product known to have anti-inflammatory properties, suppressed Egr-1 activation and concomitant expression of cytochemokines. We show that curcumin (12.5-25 microm) suppresses the activation of Egr-1 DNA-binding activity in THP-1 monocytic cells. Curcumin abrogated Abeta1-40-induced expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in both peripheral blood monocytes and THP-1 cells. We found that curcumin inhibited Abeta1-40-induced MAP kinase activation and the phosphorylation of ERK-1/2 and its downstream target Elk-1. We observed that curcumin inhibited Abeta1-40-induced expression of CCR5 but not of CCR2b in THP-1 cells. This involved abrogation of Egr-1 DNA binding in the promoter of CCR5 by curcumin as determined by: (i) electrophoretic mobility shift assay, (ii) transfection studies with truncated CCR5 gene promoter constructs, and (iii) chromatin immunoprecipitation analysis. Finally, curcumin inhibited chemotaxis of THP-1 monocytes in response to chemoattractant. The inhibition of Egr-1 by curcumin may represent a potential therapeutic approach to ameliorate the inflammation and progression of AD.

Analysis of genes isolated from lipopolysaccharide-stimulated rainbow trout (Oncorhynchus mykiss) macrophages

A primary cell culture system was used to obtain differentiated rainbow trout (Oncorhynchus mykiss) macrophages that were stimulated with Escherichia coli lipopolysaccharide (LPS-10 microg/ml) for 12 h in vitro. Messenger RNA from the LPS-stimulated cells was used to create two cDNA libraries from which a total of 1048 sequences were analyzed. A large number of cDNAs were obtained that could be related to immune function including structural proteins, proteases and antiproteases, regulators of transcription and translation, cell death regulators, receptors, lectins and immunoglobulins, cytokines and chemokines, cell surface antigens, signal transduction proteins, antimicrobial peptides, and enzymes involved in eicosanoid synthesis. Selected genes that were analyzed by RT-PCR and real time PCR and found to be upregulated by LPS, included vascular cell adhesion molecule, the CCAAT/enhancer binding protein beta, the inhibitor of NF-kB alpha, CD209, a major histocompatibility class II-invariant chain protein, cyclin L1, acute phase serum amyloid A, and prostaglandin endoperoxide synthase 2.

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