Role of a distal enhancer containing a functional NF-kappa B-binding site in lipopolysaccharide-induced expression of a novel alpha 1-antitrypsin gene

Fractalkine Induces Hepcidin Expression of BV-2 Microglia and Causes Iron Accumulation in SH-SY5Y Cells

Fractalkine (CX3CL1) is a potent inflammatory mediator of the central nervous system, which is expressed by neurons and regulates microglial functions by binding to fractalkine receptor (CX3CR1). It has been demonstrated that neuroinflammation plays an important role in iron accumulation of the brain leading to neuronal cell death. The major regulator of iron homeostasis is the peptide hormone hepcidin. Hepcidin expression is triggered by inflammatory conditions, which may contribute to the neuronal iron accumulation. In the present study, we established a bilaminar co-culture system of differentiated SH-SY5Y cells and BV-2 microglia as a neuronal model to examine the effect of soluble fractalkine on iron homeostasis of microglia and SH-SY5Y cells. We determined the hepcidin expression of fractalkine-treated microglia which showed significant elevation. We examined the relation between increased hepcidin secretion, the known hepcidin regulators and the signalling pathways controlled by fractalkine receptor. Our data revealed that TMPRSS6 and alpha 1-antitrypsin levels decreased due to fractalkine treatment, as well as the activity of NFκB pathway and the tyrosine phosphorylation of STAT5 factor. Moreover, fractalkine-induced hepcidin production of microglia initiated ferroportin internalisation of SH-SY5Y cells, which contributed to iron accumulation of neurons. Our results demonstrate that soluble form of fractalkine regulates hepcidin expression of BV-2 cells through fractalkine-mediated CX3CR1 internalisation. Moreover, fractalkine indirectly contributes to the iron accumulation of SH-SY5Y cells by activating ferroportin internalisation and by triggering the expressions of divalent metal transporter-1, ferritin heavy chain and mitochondrial ferritin.

Identification of Pathway-Specific Serum Biomarkers of Response to Glucocorticoid and Infliximab Treatment in Children with Inflammatory Bowel Disease

OBJECTIVE

Serum biomarkers may serve to predict early response to therapy, identify relapse, and facilitate drug development in inflammatory bowel disease (IBD). Biomarkers are particularly important in children, in whom achieving early remission and minimizing procedures are especially beneficial.

METHODS

We profiled protein and micro RNA (miRNA) in serum from patients pre- and post-therapy, to identify molecular markers of pharmacodynamic effect. Serum was obtained from children with IBD before and after treatment with either corticosteroids (prednisone; n=12) or anti-tumor necrosis factor-α biologic (infliximab; n=7). Over 1,100 serum proteins were assayed using aptamer-based SOMAscan proteomics, and 22 miRNAs analyzed by quantitative real time PCR. Concordance of longitudinal changes between the groups was used to identify markers responsive to treatment. Bioinformatic analysis was used to build insight into mechanisms of changes in response to treatment.

RESULTS

We identified 18 proteins and three miRNAs responsive to both prednisone and infliximab. Eight markers that decreased are associated with inflammation and have gene promoters regulated by nuclear factor (NF)-κB. Several that increased are associated with resolving inflammation and tissue damage. We also identified six markers that appear to be steroid-specific, three of which have glucocorticoid receptor binding elements in their promoter region.

CONCLUSIONS

Serum markers regulated by the inflammatory transcription factor NF-κB are potential candidates for pharmacodynamic biomarkers that, if correlated with later outcomes like endoscopic or histologic healing, could be used to monitor treatment, optimize dosing, and enhance drug development. The pharmacodynamic biomarkers identified here hold potential to improve both clinical care and drug development. Further studies are warranted to investigate these markers as early predictors of response, or possibly surrogate outcomes.

Multiple functions of FADD in apoptosis, NF-κB-related signaling, and heart development in Xenopus embryos

FADD is an adaptor protein that transmits apoptotic signals from death receptors. Additionally, FADD has been shown to play a role in various functions including cell proliferation. However, the physiological role of FADD during embryonic development remains to be delineated. Here, we show the novel roles FADD plays in development and the molecular mechanisms of these roles in Xenopus embryos. By whole-mount in situ hybridization and RT-PCR analysis, we observed that fadd is constantly expressed in early embryos. The upregulation or downregulation of FADD proteins by embryonic manipulation resulted in induction of apoptosis or size changes in the heart during development. Expression of a truncated form of FADD, FADDdd, which lacks pro-apoptotic activity, caused growth retardation of embryos associated with dramatic expressional fluctuations of genes that are regulated by NF-κB. Moreover, we isolated a homolog of mammalian cullin-4 (Cul4), a component of the ubiquitin E3 ligase family, as a FADDdd-interacting molecule in Xenopus embryos. Thus, our study shows that FADD has multiple functions in embryos; it plays a part in the regulation of NF-κB activation and heart formation, in addition to apoptosis. Furthermore, our findings provide new insights into how Cul4-based ligase is related to FADD signaling in embryogenesis.

Coupling proton movement to ATP synthesis in the chloroplast ATP synthase

The chloroplast F(0)F(1)-ATP synthase-ATPase is a tiny rotary motor responsible for coupling ATP synthesis and hydrolysis to the light-driven electrochemical proton gradient. Reversible oxidation/reduction of a dithiol, located within a special regulatory domain of the gamma subunit of the chloroplast F(1) enzyme, switches the enzyme between an inactive and an active state. This regulatory mechanism is unique to the ATP synthases of higher plants and its physiological significance lies in preventing nonproductive depletion of essential ATP pools in the dark. The three-dimensional structure of the chloroplast F(1) gamma subunit has not yet been solved. To examine the mechanism of dithiol regulation, a model of the chloroplast gamma subunit was obtained through segmental homology modeling based on the known structures of the mitochondrial and bacterial gamma subunits, together with de novo construction of the unknown regulatory domain. The model has provided considerable insight into how the dithiol might modulate catalytic function. This has, in turn, suggested a mechanism by which rotation of subunits in F(0), the transmembrane proton channel portion of the enzyme, can be coupled, via the epsilon subunit, to rotation of the gamma subunit of F(1) to achieve the 120 degrees (or 90 degrees +30 degrees) stepping action that is characteristic of F(1) gamma subunit rotation.

Oncostatin M induced alpha1-antitrypsin (AAT) gene expression in Hep G2 cells is mediated by a 3' enhancer

alpha(1)-Antitrypsin (AAT) is the major serine proteinase inhibitor (SERPIN A1) in human plasma. Its target proteinase is neutrophil elastase and its main physiological function is protection of the lower respiratory tract from the destructive effects of neutrophil elastase during an inflammatory response. Circulating levels of AAT rise 2-3-fold during inflammation and the liver produces most of this increase. The cytokines oncostatin M (OSM) and interleukin-6 have been shown to be mainly responsible for this effect, which is mediated via the interaction of cytokine-inducible transcription factors with regulatory elements within the gene. In the present study, we report for the first time that OSM stimulation of hepatocyte AAT occurs via an interaction between the hepatocyte promoter and an OSM-responsive element at the 3'-end of the AAT gene. This effect is mediated by the transcription factor signal transducer and activator of transcription 3 ('STAT 3') binding to an OSM-responsive element (sequence TTCTCTTAA), and this site is distinct from, but close to, a previously reported interleukin-6-responsive element.

THECHLOROPLASTATP SYNTHASE: A Rotary Enzyme?

The chloroplast adenosine triphosphate (ATP) synthase is located in the thylakoid membrane and synthesizes ATP from adenosine diphosphate and inorganic phosphate at the expense of the electrochemical proton gradient formed by light-dependent electron flow. The structure, activities, and mechanism of the chloroplast ATP synthase are discussed. Emphasis is given to the inherent structural asymmetry of the ATP synthase and to the implication of this asymmetry to the mechanism of ATP synthesis and hydrolysis. A critical evaluation of the evidence in support of and against the notion that one part of the enzyme rotates with respect to other parts during catalytic turnover is presented. It is concluded that although rotation can occur, whether it is required for activity of the ATP synthase has not been established unequivocally.

Activators and target genes of Rel/NF-kappaB transcription factors

The vertebrate transcription factor NF-kappaB is induced by over 150 different stimuli. Active NF-kappaB, in turn, participates in the control of transcription of over 150 target genes. Because a large variety of bacteria and viruses activate NF-kappaB and because the transcription factor regulates the expression of inflammatory cytokines, chemokines, immunoreceptors, and cell adhesion molecules, NF-kappaB has often been termed a 'central mediator of the human immune response'. This article contains a complete listing of all NF-kappaB inducers and target genes described to date. The collected data argue that NF-kappaB functions more generally as a central regulator of stress responses. In addition, NF-kappaB activation blocks apoptosis in several cell types. Coupling stress responsiveness and anti-apoptotic pathways through the use of a common transcription factor may result in increased cell survival following stress insults.

Activators and target genes of Rel/NF-kappaB transcription factors

The vertebrate transcription factor NF-kappaB is induced by over 150 different stimuli. Active NF-kappaB, in turn, participates in the control of transcription of over 150 target genes. Because a large variety of bacteria and viruses activate NF-kappaB and because the transcription factor regulates the expression of inflammatory cytokines, chemokines, immunoreceptors, and cell adhesion molecules, NF-kappaB has often been termed a 'central mediator of the human immune response'. This article contains a complete listing of all NF-kappaB inducers and target genes described to date. The collected data argue that NF-kappaB functions more generally as a central regulator of stress responses. In addition, NF-kappaB activation blocks apoptosis in several cell types. Coupling stress responsiveness and anti-apoptotic pathways through the use of a common transcription factor may result in increased cell survival following stress insults.

Atherosclerosis and inflammation. Patterns of cytokine regulation in patients with peripheral arterial disease

Inflammatory phenomena at sites of atherosclerotic plaques are increasingly thought to be major determinants of the progression and clinical outcome of atherosclerotic disease. Therefore, attention is being paid to systemic markers/mediators which may reflect the inflammatory activity in the plaques. This study evaluates the pattern of the main proinflammatory cytokines tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), their soluble receptors/antagonist, and a variety of inflammatory markers, in patients with peripheral arterial disease (PAD). Eight patients with PAD suffering from claudicatio intermittens (CI), eight with critical limb ischemia (CLI) and eight controls (C) were studied. Blood samples were collected at baseline in all groups and. for C and CI, immediately after and 4 h after a 30-min treadmill test. Baseline: no differences in cytokine plasma levels were detected among the three groups. In contrast, soluble receptors of TNF (type I and II) and of IL-6, and IL-1beta receptor antagonist (IL-1ra) were increased in CI and CLI patients, as compared to C. Of note, IL-Ira correlated with the occurrence and stage of the disease in a highly significant proportion of the patients, reaching a predictive value for the disease of P < 0.0001. The opposite trend was observed for the soluble receptor of IL-1beta. Notably, in the patients no alterations could be found in white blood cell counts, expression of CD11c adherence molecule by circulating monocytes or, in vitro. O2- release from zymosan-activated neutrophils. Moreover, plasma levels of platelet activating factor (PAF), of neutrophil elastase and of the acute phase reactants C-reactive protein (CRP) and alpha1-acid glycoprotein were not found to be significantly altered. In contrast, the acute-phase proteins alpha1-antitrypsin (alpha1AT) and haptoglobin (HG) were found to be increased. Effect of treadmill: IL-1beta and TNFalpha remained at baseline levels following exercise, and IL-6 dropped to undetectable levels. Among cytokine antagonists, again the most relevant changes concerned the IL-1ra, which was significantly increased immediately after the treadmill test, both in CI and C, and returned to baseline levels after 4 h. In contrast, soluble TNFalpha, IL-1beta and IL-6 receptors, PAF, and the other markers of leukocyte activation were not found to be altered. Soluble TNFalpha and IL-6 receptors were shown to inhibit the biological effects of their ligands. Similarly, IL-1ra and the acute phase proteins alpha1AT and HG have been reported to exert anti-inflammatory functions. The increased plasma levels of these agents, together with low levels of inflammatory cytokines and other pro-inflammatory mediators such as PAF and alpha1-acid glycoprotein, appear to draw an undescribed picture, so far, of upregulation of a composite systemic anti-inflammatory mechanism in atherosclerotic patients. IL-1ra appears to be a reliable marker of the state of activation of this mechanism. These results may provide a basis for developing new insights into the pathogenesis of the atherosclerotic disease.

Refolding of recombinant alpha and beta subunits of the Rhodospirillum rubrum F(0)F(1) ATP synthase into functional monomers that reconstitute an active alpha(1)beta(1)-dimer

The alpha subunit from the Rhodospirillum rubrum F(0)F(1) ATP synthase (RrF(1)alpha) was over-expressed in unc operon-deleted Escherichia coli strains under various growth conditions only in insoluble inclusion bodies. The functional refolding of urea-solubilized RrF(1)alpha was followed by measuring its ability to stimulate the restoration of ATP synthesis and hydrolysis in beta-less R. rubrum chromatophores reconstituted with pure native or recombinant RrF(1)beta [Nathanson, L. & Gromet-Elhanan, Z. (1998) J. Biol. Chem. 273, 10933-10938]. The refolding efficiency was found to increase with decreasing RrF(1)alpha concentrations and required high concentrations of MgATP, saturating approximately 60% when 50 microgram protein.mL(-1) were refolded in presence of 50 mM MgATP. Size-exclusion HPLC of such refolded RrF(1)alpha revealed a 50-60% decrease in its aggregated form and a parallel appearance of its monomeric peak. RrF(1)beta refolded under identical conditions appeared almost exclusively as a monomer. This procedure enabled the isolation of large amounts of a stable RrF(1)alpha monomer, which stimulated the restoration of ATP synthesis and hydrolysis much more efficiently than the refolded alpha mixture, and bound ATP and ADP in a Mg-dependent manner. Incubation of both RrF(1)alpha and beta monomers, which by themselves had no ATPase activity, resulted in a parallel appearance of activity and assembled alpha(1)beta(1)-dimers, but showed no formation of alpha(3)beta(3)-hexamers. The RrF(1)-alpha(1)beta(1)-ATPase activity was, however, very similar to the activity observed in isolated native chloroplast CF(1)-alpha(3)beta(3), indicating that these dimers contain only the catalytic nucleotide-binding site at their alpha/beta interface. Their inability to associate into an alpha(3)beta(3)-hexamer seems therefore to reflect a much lower stability of the noncatalytic RrF(1) alpha/beta interface.

Regulation of the human protein C inhibitor gene expression in HepG2 cells: role of Sp1 and AP2

Protein C inhibitor (PCI) is the plasma inhibitor of activated protein C, which is the main protease of the anticoagulant protein C pathway. In this study the transcriptional regulation of human PCI gene in the human hepatoma cell line, HepG2, was characterized by evaluating the transient expression of a luciferase reporter gene. The 5' flanking region (residues -1587 to +2) of the PCI gene showed an adequate transcriptional activity, the maximum transcriptional activity being in a region between residues -452 and -94, which contains an Sp1-binding site, two AP2-binding sites and an inverted AP2-binding site. Transient expression assays with various deletion mutants and site-directed mutants showed that the Sp1-binding site (residues -302 to -294) has a potent promoter activity and that the upstream AP2-binding site (residues -350 to -343) has a potent enhancer activity; no activity was detected in the inverted (residues -413 to -404) and downstream (residues -136 to -127) AP2-binding sites. In addition, a region of the PCI gene (residues -452 to -414) containing the STATx-binding site, the A-activator (AA)-binding site, and the interferon alpha (IFN-alpha) response element, and another region of the PCI gene (residues -176 to -147) containing the GATA-1 and the IFN-gamma response element showed potent silencer activities. Gel mobility-shift assays with various DNA fragments indicated that the Sp1-binding site, the upstream AP2-binding site, the AA-binding site and the IFN-gamma response element interact with nuclear protein(s) of HepG2 cells. These findings suggest that the Sp1-binding site is the promoter, the AP2-binding site (residues -350 to -343) the enhancer, and both the AA-binding site and the IFN-gamma response element are the silencers of human PCI gene expression in HepG2 cells.

Decoy administration of NF-kappaB into the subarachnoid space for cerebral angiopathy

Subarachnoid hemorrhage (SAH), encephalitis, meningitis, and autoimmune diseases sometimes lead to cerebral angiopathy, characterized specifically by narrowing of vessels, morphological changes in the structure of vessel walls, and a concomitant decrease in cerebral blood flow. Many patients also develop delayed ischemic neurological deficits. Thus, preventing vascular reactions is of paramount importance in treating SAH. Although cerebral vasospasm has some relationship with the inflammatory reaction of major cerebral vessels against the autologous blood, and many trials have attempted to prevent angiopathy after SAH, an effective treatment has not yet been established. The purpose of this article is to evaluate the preventive effect of nuclear factor KB (NF-kappaB) decoy oligo-DNA after SAH; since NF-kappaB is closely related to inflammation. In the rabbit angiopathy model after SAH, we evaluated the effectiveness of the decoy oligo-DNA using the angiographic (digital subtraction angiography) and histological (hematoxylin-eosin and Masson's trichrome staining) methods. Moreover, a gel-shift assay for NF-kappaB was also performed in order to evaluate the activity of NF-kappaB. We describe a new concept for treating cerebral angiopathy after SAH and for successfully inhibiting cerebral vasospasm and morphological changes in vessel walls in a rabbit model. In this treatment, we used synthetic double-strand oligo-DNA with a high affinity for transcription factor NF-kappaB, and cationic liposome complex administered through the cerebrospinal fluid.

Regulation of the serine proteinase inhibitor (SERPIN) gene alpha 1-antitrypsin: a paradigm for other SERPINs

alpha 1-antitrypsin (AAT) is the archetypal member of the serine proteinase inhibitor (SERPIN) gene family. AAT is an acute-phase reactant and the plasma concentration increases three- to four-fold during the inflammatory response. In hepatocytes this increase is mediated primarily by the cytokine interleukin-6 (IL-6) via the transcription factor NF-IL6. The AAT gene contains at least two enhancer elements, one at the 5' end of the gene and the other at the 3' end. Functional studies performed in mammalian hepatoma cells (Hep G2) using constructs containing these AAT enhancer regions linked to a reporter gene have demonstrated that the 5' enhancer is dominant under basal conditions and that, following stimulation with IL-6, both enhancers are essential and the 3' enhancer plays a major role. We have identified a mutation associated with lung disease which occurs in the 3' AAT enhancer; the mutation occurs at a binding site for the ubiquitous transcription factor Oct-1. The functional significance of this mutation is a deficient IL-6 response. Using the AAT gene as a model, we describe the interactions which occur between transcription factors within the 3' enhancer and also those which take place between the 5' and 3' enhancers. These studies shed light on the molecular mechanism of the acute-phase response which could possibly be extended to other members of the SERPIN gene family.

Mutation in an alpha1-antitrypsin enhancer results in an interleukin-6 deficient acute-phase response due to loss of cooperativity between transcription factors

We previously reported that a mutation in a 3' enhancer region of the alpha1-antitrypsin (AAT) gene is associated with chronic obstructive airways disease (COAD). During the acute-phase response the plasma concentration of AAT increases approximately 3-fold and this effect is mediated primarily by interleukin-6 (IL-6). We demonstrate, by transfection of Hep G2 cells, that the AAT gene contains at least two enhancers, one at the 5' end of the gene which is dominant under basal conditions, and another at the 3' end of the gene which exhibits weak basal activity. However, both enhancers must be present to modulate the IL-6-induced response which is diminished as a consequence of the 3' enhancer mutation. These results suggest that the 3' enhancer modulates the IL-6 response through an interaction with the 5' enhancer. The mutation occurs at a DNA binding site for the ubiquitous transcription factor octamer-1 (Oct-1) and results in a loss of cooperativity between Oct-1 and the tissue-specific transcription factor, NF-IL6 (C/EBPbeta), a member of the C/EBP family of transcription factors. NF-IL6 is a key transcription factor for a major pathway through which IL-6 mediates its effects. These observations provide a novel mechanism for a diminished IL-6-induced response.

The regulatory functions of the gamma and epsilon subunits from chloroplast CF1 are transferred to the core complex, alpha3beta3, from thermophilic bacterial F1

The expression plasmids for the subunit gamma (gamma(c)) and the subunit epsilon (epsilon(c)) of chloroplast coupling factor (CF1) from spinach were constructed, and the desired proteins were expressed in Escherichia coli. Both expressed subunits were obtained as inclusion bodies. When recombinant gamma(c) was mixed with recombinant alpha and beta subunits of F1 from thermophilic Bacillus PS3 (TF1), a chimeric subunit complex (alpha3beta3gamma(c)) was reconstituted and it showed significant ATP hydrolysis activity. The ATP hydrolysis activity of this complex was enhanced in the presence of dithiothreitol and suppressed by the addition of CuCl2, which induces formation of a disulfide bond between two cysteine residues in gamma(c). Hence, this complex has similar modulation characteristics as CF1. The effects of recombinant epsilon(c) and epsilon subunit from TF1 (epsilon(t)) on alpha3beta3gamma(c) were also investigated. Epsilon(c) strongly inhibited the ATP hydrolysis activity of chimeric alpha3beta3gamma(c) complex but epsilon(t) did not. The inhibition was abolished and the ATP hydrolysis activity was recovered when methanol was added to the assay medium. The addition of epsilon(c) or epsilon(t) to the alpha3beta3gamma(t) complex, which is the authentic subunit complex from TF1, resulted in weak stimulation of the ATP hydrolysis activity. These results suggest that (a) the specific regulatory function of gamma(c) can be transferred to the bacterial subunit complex; (b) the interaction between the gamma(c) subunit and epsilon(c) strongly affects the enzyme activity, which was catalyzed at the catalytic sites that reside on the alpha3beta3 core.