Increased plasma concentrations of interleukin-18 in acute coronary syndromes.

OBJECTIVE: To examine the relation between plasma concentrations of interleukin-18 (IL-18), the interferon gamma inducing factor, and clinical instability of coronary artery disease. DESIGN AND SETTING: Observational study in a university hospital. PATIENTS: 11 patients with unstable angina and negative troponin I, 21 patients with acute non-Q wave myocardial infarction (MI), 21 patients with acute Q wave MI, 9 patients with stable angina, and 11 controls. MAIN OUTCOME MEASURES: Plasma IL-18 concentrations and their relation to clinical instability and myocardial dysfunction. RESULTS: Plasma concentrations of IL-18 were significantly increased in the unstable angina and MI groups in comparison with the stable angina and control groups (p < 0.01). No difference in IL-18 concentrations were found between patients with unstable angina, patients with non-Q wave MI, and patients with Q wave MI. Plasma IL-18 concentrations significantly correlated with decreased left ventricular ejection fraction (p = 0.01). CONCLUSIONS: Plasma IL-18 concentrations are increased in patients with acute coronary syndromes and correlate with the severity of myocardial dysfunction.

Therapeutic effect of neutralizing endogenous IL-18 activity in the collagen-induced model of arthritis.

Two distinct IL-18 neutralizing strategies, i.e. a rabbit polyclonal anti-mouse IL-18 IgG and a recombinant human IL-18 binding protein (rhIL-18BP), were used to treat collagen-induced-arthritic DBA/1 mice after clinical onset of disease. The therapeutic efficacy of neutralizing endogenous IL-18 was assessed using different pathological parameters of disease progression. The clinical severity in mice undergoing collagen-induced arthritis was significantly reduced after treatment with both IL-18 neutralizing agents compared to placebo treated mice. Attenuation of the disease was associated with reduced cartilage erosion evident on histology. The decreased cartilage degradation was further documented by a significant reduction in the levels of circulating cartilage oligomeric matrix protein (an indicator of cartilage turnover). Both strategies efficiently slowed disease progression, but only anti-IL-18 IgG treatment significantly decreased an established synovitis. Serum levels of IL-6 were significantly reduced with both neutralizing strategies. In vitro, neutralizing IL-18 resulted in a significant inhibition of TNF-alpha, IL-6, and IFN-gamma secretion by macrophages. These results demonstrate that neutralizing endogenous IL-18 is therapeutically efficacious in the murine model of collagen-induced arthritis. IL-18 neutralizing antibody or rhIL-18BP could therefore represent new disease-modifying anti-rheumatic drugs that warrant testing in clinical trials in patients with rheumatoid arthritis.

Interleukin-18/interleukin-18 binding protein signaling modulates atherosclerotic lesion development and stability.

Interleukin (IL)-18 is the interferon-gamma-inducing factor and has other proinflammatory properties. The precise role of IL-18 in immunoinflammatory diseases remains poorly understood. In this study, we show that in vivo electrotransfer of an expression-plasmid DNA encoding for murine IL-18 binding protein (BP) (the endogenous inhibitor of IL-18) prevents fatty streak development in the thoracic aorta of apoE knockout mice and slows progression of advanced atherosclerotic plaques in the aortic sinus. More importantly, transfection with the IL-18BP plasmid induces profound changes in plaque composition (decrease in macrophage, T cell, cell death, and lipid content and increase in smooth muscle cell and collagen content) leading to a stable plaque phenotype. These results identify for the first time a critical role for IL-18/IL-18BP regulation in atherosclerosis and suggest a potential role for IL-18 inhibitors in reduction of plaque development/progression and promotion of plaque stability. The full text of this article is available at http://www.circresaha.org.

A key role for CC chemokine receptor 4 in lipopolysaccharide-induced endotoxic shock.

CC chemokine receptor (CCR)4, a high affinity receptor for the CC chemokines thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC), is expressed in the thymus and spleen, and also by peripheral blood T cells, macrophages, platelets, and basophils. Recent studies have shown that CCR4 is the major chemokine receptor expressed by T helper type 2 (Th2) polarized cells. To study the in vivo role of CCR4, we have generated CCR4-deficient (CCR4(-/-)) mice by gene targeting. CCR4(-/-) mice developed normally. Splenocytes and thymocytes isolated from the CCR4(-/-) mice failed to respond to the CCR4 ligands TARC and MDC, as expected, but also surprisingly did not undergo chemotaxis in vitro in response to macrophage inflammatory protein (MIP)-1alpha. The CCR4 deletion had no effect on Th2 differentiation in vitro or in a Th2-dependent model of allergic airway inflammation. However, CCR4(-/-) mice exhibited significantly decreased mortality on administration of high or low dose bacterial lipopolysaccharide (LPS) compared with CCR4(+/+) mice. After high dose LPS treatment, serum levels of tumor necrosis factor alpha, interleukin 1beta, and MIP-1alpha were reduced in CCR4(-/-) mice, and decreased expression of MDC and MIP-2 mRNA was detected in peritoneal exudate cells. Analysis of peritoneal lavage cells from CCR4(-/)- mice by flow cytometry also revealed a significant decrease in the F4/80(+) cell population. This may reflect a defect in the ability of the CCR4(-/-) macrophages to be retained in the peritoneal cavity. Taken together, our data reveal an unexpected role for CCR4 in the inflammatory response leading to LPS-induced lethality.

Amino-terminally modified RANTES analogues demonstrate differential effects on RANTES receptors.

Modification of the amino terminus of regulated on activated normal T-cell expressed (RANTES) has been shown to have a significant effect on biological activity and produces proteins with antagonist properties. Two amino-terminally modified RANTES proteins, Met-RANTES and aminooxypentane-RANTES (AOP-RANTES), exhibit differential inhibitory properties on both monocyte and eosinophil chemotaxis. We have investigated their binding properties as well as their ability to activate the RANTES receptors CCR1, CCR3, and CCR5 in cell lines overexpressing these receptors. We show that Met-RANTES has weak activity in eliciting a calcium response in Chinese hamster ovary cells expressing CCR1, CCR3, and CCR5, whereas AOP-RANTES has full agonist activity on CCR5 but is less effective on CCR3 and CCR1. Their ability to induce chemotaxis of the murine pre-B lymphoma cell line, L1.2, transfected with the same receptors, consolidates these results. Monocytes have detectable mRNA for CCR1, CCR2, CCR3, CCR4, and CCR5, and they respond to the ligands for these receptors in chemotaxis but not always in calcium mobilization. AOP-RANTES does not induce calcium mobilization in circulating monocytes but is able to do so as these cells acquire the macrophage phenotype, which coincides with a concomitant up-regulation of CCR5. We have also tested the ability of both modified proteins to induce chemotaxis of freshly isolated monocytes and eosinophils. Cells from most donors do not respond, but occasionally cells from a particular donor do respond, particularly to AOP-RANTES. We therefore hypothesize that the occasional activity of AOP-RANTES to induce leukocyte chemotaxis is due to donor to donor variation of receptor expression.

The distribution of IL-13 receptor alpha1 expression on B cells, T cells and monocytes and its regulation by IL-13 and IL-4.

To study the expression of IL-13 receptor alpha1 (IL-13Ralpha1), specific monoclonal antibodies (mAb) were generated. Surface expression of the IL-13Ralpha1 on B cells, monocytes and T cells was assessed by flow cytometry using these specific mAb. Among tonsillar B cells, the expression was the highest on the IgD+ CD38- B cell subpopulation which is believed to represent naive B cells. Expression was also detectable on a large fraction of the IgD-CD38- B cells but not on CD38+ B cells. Activation under conditions which promote B cell Ig class switching up-regulated the expression of the receptor. However, the same stimuli had an opposite effect for IL-13Ralpha1 expression levels on monocytes. While IL-13Ralpha1 mRNA was clearly detectable in T cell preparations, no surface expression was detected. However, permeabilization of the T cells showed a clear intracellular expression of the receptor. A soluble form of the receptor was immunoprecipitated from the supernatant of activated peripheral T cells, suggesting that T cell IL-13Ralpha1 might have functions unrelated to the capacity to form a type II IL-4/IL-13R with IL-4Ralpha.

HIV-1 Tat protein mimicry of chemokines.

The HIV-1 Tat protein is a potent chemoattractant for monocytes. We observed that Tat shows conserved amino acids corresponding to critical sequences of the chemokines, a family of molecules known for their potent ability to attract monocytes. Synthetic Tat and a peptide (CysL24-51) encompassing the "chemokine-like" region of Tat induced a rapid and transient Ca2+ influx in monocytes and macrophages, analogous to beta-chemokines. Both monocyte migration and Ca2+ mobilization were pertussis toxin sensitive and cholera toxin insensitive. Cross-desensitization studies indicated that Tat shares receptors with MCP-1, MCP-3, and eotaxin. Tat was able to displace binding of beta-chemokines from the beta-chemokine receptors CCR2 and CCR3, but not CCR1, CCR4, and CCR5. Direct receptor binding experiments with the CysL24-51 peptide confirmed binding to cells transfected with CCR2 and CCR3. HIV-1 Tat appears to mimic beta-chemokine features, which may serve to locally recruit chemokine receptor-expressing monocytes/macrophages toward HIV producing cells and facilitate activation and infection.

Characterisation of macrophage inflammatory protein-5/human CC cytokine-2, a member of the macrophage-inflammatory-protein family of chemokines.

A human monocyte-activating CC chemokine has been identified based on sequences in an expressed sequence tag (EST) cDNA database. The protein shows highest sequence identity to the macrophage inflammatory protein (MIP) group of chemokines, particularly MIP-3 (76.7%) and MIP-1alpha (75.4%), and has been named MIP-5. Model building confirms that the protein has a similar three dimensional structure to other chemokines, but has an additional third disulphide bond. Northern blot analysis and reverse-transcriptase PCR show that the mRNA for MIP-5 is expressed at a high levels in liver, intestine and in lung leukocytes. MIP-5 induces chemotaxis of human monocytes, T-lymphocytes and, to a lesser degree, eosinophils at nanomolar concentrations; it has no effect on neutrophil migration. In receptor-binding assays, MIP-5 shows IC50 values of 12 nM for competition with 125I-MIP-1alpha for binding to CC-chemokine receptor (CCR)1, and 2.5 nM for competition with 125I-MCP-3 for binding to CCR3. It shows no ability to compete with ligand for binding to the two interleukin (IL)-8 receptors (CXC-chemokine receptors 1 and 2) or to CCR2, CCR4 or CCR5. Consistent with this binding data, MIP-5 was only able to induce calcium fluxes in CHO cells stably transfected with CCR1 or CCR3.

A broad-spectrum chemokine antagonist encoded by Kaposi's sarcoma-associated herpesvirus.

Kaposi's sarcoma-associated herpesvirus encodes a chemokine called vMIP-II. This protein displayed a broader spectrum of receptor activities than any mammalian chemokine as it bound with high affinity to a number of both CC and CXC chemokine receptors. Binding of vMIP-II, however, was not associated with the normal, rapid mobilization of calcium from intracellular stores; instead, it blocked calcium mobilization induced by endogenous chemokines. In freshly isolated human monocytes the virally encoded vMIP-II acted as a potent and efficient antagonist of chemotaxis induced by chemokines. Because vMIP-II could inhibit cell entry of human immunodeficiency virus (HIV) mediated through CCR3 and CCR5 as well as CXCR4, this protein may serve as a lead for development of broad-spectrum anti-HIV agents.

Cloning and characterization of a specific receptor for the novel CC chemokine MIP-3alpha from lung dendritic cells.

Dendritic cells are potent antigen-presenting cells involved in the initiation of immune responses. The trafficking of these cells to tissues and lymph nodes is mediated by members of the chemokine family. Recently, a novel CC chemokine known as MIP-3alpha or liver and activation-regulated chemokine has been identified from the EMBL/GenBank/DDBJ expressed sequence tag database. In the present study, we have shown that the messenger RNA for MIP-3alpha is expressed predominantly in inflamed and mucosal tissues. MIP-3alpha produced either synthetically or by human embryonic kidney 293 cells is chemotactic for CD34(+)-derived dendritic cells and T cells, but is inactive on monocytes and neutrophils. MIP-3alpha was unable to displace the binding of specific CC or CXC chemokines to stable cell lines expressing their respective high affinity receptors, namely CCR1-5 and CXCR1 and CXCR2, suggesting that MIP-3alpha acts through a novel CC chemokine receptor. Therefore, we used degenerate oligonucleotide-based reverse transcriptase PCR to identify candidate MIP-3alpha receptors in lung dendritic cells. Our results show that the orphan receptor known as GCY-4, CKRL-3, or STRL-22 is a specific receptor for MIP-3alpha, and that its activation leads to pertussis toxin-sensitive and phospholipase C-dependent intracellular Ca2+ mobilization when it is expressed in HEK 293 cells.

ApoE genotype does not affect plasma tPA and PAI-1 antigen levels.

The presence of one or two apoliprotein E4 (apoE4) alleles constitutes a major risk factor for Alzheimer's disease (AD) and coronary heart disease (CHD). Numerous observations have suggested that misregulation of proteases may be instrumental in both diseases. Tissue-type plasminogen activator (tPA) has been recently demonstrated to play a key role in neuronal plasticity and in experimental neurodegeneration. One receptor for the ApoE protein is the LRP/alpha 2 macroglobulin receptor, which also binds to and endocytoses tPA and plasminogen activator inhibitor I (PAI-1). Here we tested whether the apoE genotype has an influence on the plasma levels of these proteins. We demonstrate that there is no difference in plasma levels of tPA- and PAI-1-antigens between middled-aged individuals with one apoE4 allele and those having none. This suggests that the impact of apoE4 on Alzheimer's disease is not the result of altered clearance of tPA or PAI-1 by the LRP receptor.

A novel 4-kb interleukin-13 receptor alpha mRNA expressed in human B, T, and endothelial cells encoding an alternate type-II interleukin-4/interleukin-13 receptor.

A 4 kb human interleukin-13 receptor (IL-13R) chain cDNA was cloned from a B cell cDNA library using expressed sequence tags homologous to mouse IL-13R as probes. The deduced protein sequence shows a significant level of sequence identity with the IL-5R and the human IL-13R identified recently by expression cloning. The cytoplasmic region is very highly conserved between human and mouse homologs and contains a consensus binding motif for a signal transducer and activator of transcription. The cDNA encodes a protein binding IL-13 when expressed alone which participates in a receptor complex for both IL-4 and IL-13 when expressed in conjunction with the IL-4R alpha chain. Transcripts for this IL-13R chain could be detected in most tissues and organs studied and in T, B, endothelial cells, basophilic, immature mast cell, and monocytic cell lines. The pattern of expression is different from the other recently cloned IL-13R molecule, and correlates with sites where IL-4 and IL-13 signaling is known to occur. This novel receptor is therefore likely to be implicated in reactions involved in IgE responses, T helper 2 differentiation, adhesion of leukocytes to endothelium, and therefore in pathological phenomena such as allergy, atopy, and asthma.

The Molecular Basis of the Chemokine/Chemokine Receptor Interaction-Scope for Design of Chemokine Antagonists

Chemokines are a family of small proteins that are present in a variety of inflammatory conditions and have been shown to activate and recruit a wide variety of cell types. They bind to a family of seven transmembrane G-protein-coupled receptors. Models for the interaction of the chemokines with their receptors suggest a two-step mechanism. Initially, the main body of the chemokine interacts with the outside of the receptor (Site 1), and this interaction directs receptor selectivity. Subsequently, the flexible amino-terminus of the chemokine interacts with the receptor core (Site 2) to initiate the signaling response. Mutagenesis studies of IL-8, the archetypal CXC chemokine, show that altering the protein on the third beta-sheet can change the receptor selectivity from that of a CXC chemokine and introduce CC chemokine activity-confirming the role of this region in Site 1. Mutagenesis studies of the amino-terminal region of IL-8 showed that a tripeptide, ELR, was essential for the interaction with Site 2. We have shown, using synthetic peptides and site-directed mutagenesis, that the amino-terminus of RANTES is important in the signaling response (Site 2). Mutations that alter only the interaction with Site 2 are capable of binding the receptor and not signaling and are therefore potential antagonists. Such antagonists have now been made by several groups, for a number of the chemokine receptors, and are active at nanomolar concentrations. These can now be used to test the hypothesis that antagonism of chemokine receptors will lead to a reduction in inflammation in vivo.

Mutation of Leu25 and Val27 introduces CC chemokine activity into interleukin-8.

Interleukin-8 (IL-8) is a member of the CXC branch of the chemokine superfamily and activates neutrophils but not monocytes. The related CC chemokine branch, which includes monocyte chemoattractant protein-1 (MCP-1) and RANTES are potent chemoattractants for monocytes but not neutrophils. Examination of the sequences of the CXC chemokines reveals that the highly conserved leucine, corresponding to Leu25 in IL-8, is always replaced by tyrosine in CC chemokines. There is also a high degree of conservation among the CXC chemokines of the adjacent Val27 residue, which points out from the same side of the beta-sheet as Leu25. In RANTES, Val27 is also replaced by a tyrosine. In order to investigate the role of these residues in controlling cell specificity, we have made the single mutants Leu25-->Tyr, Val27-->Tyr and the double mutant Leu25-->Tyr, Val27--> Tyr of IL-8. These proteins have been expressed in Escherichia coli and purified to homogeneity from inclusion body material. All three mutants have lower potency and efficacy in chemotaxis and calcium mobilization assays using neutrophils. The mutants also show lowered affinity to both IL-8 receptors A and B expressed recombinantly in HL-60 cells and to neutrophils in [125I]IL-8 competition assays. Additionally, the Leu25-->Tyr mutation introduces a novel monocyte chemoattractant activity into IL-8. We therefore studied the displacement of [125I]MIP-1 alpha by IL-8 Leu25-->Tyr from the CC-CKR-1 receptor. The mutant displaces MIP-1 alpha ligand with an affinity only 12-fold less than MIP-1 alpha itself. This suggests that mutations in this region of IL-8 are involved in receptor binding and activation and in the control of specificity between CC and CXC chemokines.

A fluorescent interleukin-8 receptor probe produced by targetted labelling at the amino terminus.

Interleukin-8 is the most extensively characterised member of the structurally related chemotactic and pro-inflammatory proteins collectively called chemokines. It binds to two closely related members of the seven transmembrane chemokine receptor family found on a variety of leukocyte cell types. In order to study the interaction of interleukin-8 with its receptors, and their distribution, we have produced a fluorescently labelled protein as an alternative to the radioactive 125I-interleukin-8 ligand. Interleukin-8 is naturally produced as two forms, a 72-residue polypeptide by monocytes and a 77-residue form produced by endothelial cells which has an extension of five amino acids at the amino terminal. Both forms are active at nanomolar concentrations, implying that chemical modification to the amino terminus of the 72-residue form will not destroy activity. The 72-residue interleukin-8 sequence starts with a serine residue, which can be oxidised under mild conditions to give a reactive glyoxylyl function which is then reacted with a nucleophilic fluorescein derivative. The site-specifically labelled protein was easily isolated by reverse-phase HPLC. The dissociation constant of the fluorescently labelled interleukin-8 from its receptors on neutrophils was measured by displacement of 125I-interleukin-8 and found to be 10 nM compared to 1 nM for the unmodified protein. The modified protein is highly active in in vitro bioassays using human neutrophils, giving an EC50 of 7 nM in chemotaxis and an EC50 of 0.62 nM for shape change. The binding of the fluorescent protein to neutrophils can also be measured by fluorescent automatic cell sorter (FACS) analysis, and can be competed by unlabelled interleukin-8. The amino-terminal modification of interleukin-8 has produced a reagent which is useful for the quantification of interleukin-8 receptor expression, and will also be useful in monitoring the fate of the ligand after receptor binding.

Inducible inhibition of eukaryotic gene expression.

A regulatable binary expression system for eukaryotes was recently developed based on the tetracycline repressor and its operator. Here we show that this system can be successfully applied to express antisense RNA and completely inhibit gene expression in a tetracycline-repressible fashion.

Transcriptional activity of the neuron-specific enolase (NSE) promoter in murine embryonic stem (ES) cells and preimplantation embryos.

Mouse embryonic stem (ES) cells were transfected with a plasmid composed of an E. coli lacZ gene fused to 1.8 kb of rat neuron-specific enolase (NSE) promoter sequences. While this reporter construct had been shown previously to function exclusively in postmitotic neurons and neuro-endocrine cells of transgenic mice, stably transfected ES cell clones unexpectedly displayed beta-galactosidase (beta-Gal) activity in the undifferentiated state. This transcriptional activity of the heterologous NSE promoter was confirmed by the identification of endogenous NSE mRNA in undifferentiated ES cells, mouse morulae and blastocysts. NSE protein, however, could not be found in undifferentiated ES cells. Interestingly, in ES cells which were cultured for 7 days under differentiation conditions in vitro, beta-Gal activity decreased to basal levels consistent with the parallel down-regulation of endogenous NSE mRNA. In contrast, prolonged culture of ES cells under differentiation conditions led to the reappearance of NSE mRNA and beta-Gal activity after 17 days. Significant increases in beta-Gal activity were also observed in ES cells which were cultured either on dishes coated with attachment factors such as laminin and gelatin or in the presence of nerve growth factor (NGF). These results suggest that i) transcriptional control mechanisms regulating neuronal gene expression are present at early developmental stages in the mouse and ii) ES cells provide a useful in vitro model system for the analysis of developmentally regulated cellular and molecular events coupled to neuron-specific enolase promoter activity.

Concomitant cellular expression of heat shock regulated genes of hepatitis B virus surface antigen and of human growth hormone by a NIH-3T3 cell line.

A plasmid carrying a DNA fragment of hepatitis B virus, coding for the pre-S2 and the entire S region of the surface antigen (HBsAg), placed under the control of the promoter of the human 70 kDa heat shock protein gene (hsp70), was introduced into Line 6, a recombinant cell line that was selected from NIH-3T3 cells previously transfected with a similar construct coding for the human growth hormone cDNA gene (chGH) and with the plasmid pEJ carrying the Ha-rasEJ activated cellular oncogene. The resulting cell line, EMS8, expressed: (1) hsp70/HBsAg and hsp70/hGH hybrid genes, (2) the human Ha-rasEJ oncogene, and (3) the neomycin resistance gene, the two last plasmid markers being used for cell selection. EMS8 cells were able to carry out post-translational modifications of the middle M and the major S envelope proteins of HBV, such as assembly and glycosylation. Accordingly, the cells synthesized and secreted both free and glycosylated M and S viral proteins, and the human growth hormone protein. In addition concomitant expression of HBsAg and hGH proteins as well as their mRNA were detected in EMS8 cells at least up to 72 hr after heat induction instead of 24 hr in the case of hGH in Line 6 cells.