The combination of endotoxin and dexamethasone induces type II interleukin 1 receptor (IL-1r II) in monocytes: a comparison to interleukin 1 beta (IL-1 beta) and interleukin 1 receptor antagonist (IL-1ra)

Airway Epithelial Expression Quantitative Trait Loci Reveal Genes Underlying Asthma and Other Airway Diseases

Genome-wide association studies (GWASs) have identified loci that are robustly associated with asthma and related phenotypes; however, the molecular mechanisms underlying these associations need to be explored. The most relevant tissues to study the functional consequences of asthma are the airways. We used publically available data to derive expression quantitative trait loci (eQTLs) for human epithelial cells from small and large airways and applied the eQTLs in the interpretation of GWAS results of asthma and related phenotypes. For the small airways (n = 105), we discovered 660 eQTLs at a 10% false discovery rate (FDR), among which 315 eQTLs were not previously reported in a large-scale eQTL study of whole lung tissue. A large fraction of the identified eQTLs is supported by data from Encyclopedia of DNA Elements (ENCODE) showing that the eQTLs reside in regulatory elements (57.5 and 67.6% of cis- and trans-eQTLs, respectively). Published pulmonary GWAS hits were enriched as airway epithelial eQTLs (9.2-fold). Further, genes regulated by asthma GWAS loci in epithelium are significantly enriched in immune response pathways, such as IL-4 signaling (FDR, 5.2 × 10(-4)). The airway epithelial eQTLs described in this study are complementary to previously reported lung eQTLs and represent a powerful resource to link GWAS-associated variants to their regulatory function and thus elucidate the molecular mechanisms underlying asthma and airway-related conditions.

IL-1β is overexpressed and aberrantly regulated in corticosteroid nonresponders with autoimmune inner ear disease

Autoimmune inner ear disease is an enigmatic disorder characterized by recurring episodes of sudden or progressive sensorineural hearing loss. Hearing loss can be improved by timely corticosteroid administration, but only half of those treated respond, and for many responders, that response is lost over time. The mechanisms that control corticosteroid responsiveness in this disorder are largely uncharacterized. We have previously identified that the induction by dexamethasone of IL-1R type II (IL-1R2) expression in PBMC predicts corticosteroid responsiveness in this disorder. In this study, we asked whether IL-1β was overexpressed, and whether clinical corticosteroid responders differentially regulated IL-1β expression or release in response to dexamethasone, as compared with nonresponders. IL-1β has been reported to induce matrix metalloproteinase-9 (MMP-9) expression. Given that metalloproteinases can cleave IL-1R2, we also asked whether MMP-9 expression was altered in this disorder. In this study, we demonstrate that corticosteroid nonresponders have elevated plasma levels of IL-1β and MMP-9 as compared with clinically responsive patients (p = 0.0008 and p = 0.037, respectively). Increasing MMP-9 expression correlated with increasing IL-1β concentration, suggesting that IL-1β expression regulates MMP-9 expression. As expected, monocytes were the predominant producers of IL-1β. In vitro exposure of PBMC to dexamethasone from clinical corticosteroid responders suppressed IL-1β release. PBMC of corticosteroid nonresponders have substantially higher release of IL-1β into the conditioned media, and when exposed to dexamethasone, failed to repress IL-1β release (p = 0.05). Treatment of PBMC from clinical corticosteroid nonresponders with anakinra resulted in repression of IL-1β release, suggesting that IL-1β blockade may be a viable therapy for these patients.

Pharmacological strategies for improving the efficacy and therapeutic ratio of glucocorticoids in inflammatory lung diseases

Glucocorticoids are widely used to treat various inflammatory lung diseases. Acting via the glucocorticoid receptor (GR), they exert clinical effects predominantly by modulating gene transcription. This may be to either induce (transactivate) or repress (transrepress) gene transcription. However, certain individuals, including those who smoke, have certain asthma phenotypes, chronic obstructive pulmonary disease (COPD) or some interstitial diseases may respond poorly to the beneficial effects of glucocorticoids. In these cases, high dose, often oral or parental, glucocorticoids are typically prescribed. This generally leads to adverse effects that compromise clinical utility. There is, therefore, a need to enhance the clinical efficacy of glucocorticoids while minimizing adverse effects. In this context, a long-acting beta(2)-adrenoceptor agonist (LABA) can enhance the clinical efficacy of an inhaled corticosteroid (ICS) in asthma and COPD. Furthermore, LABAs can augment glucocorticoid-dependent gene expression and this action may account for some of the benefits of LABA/ICS combination therapies when compared to ICS given as a monotherapy. In addition to metabolic genes and other adverse effects that are induced by glucocorticoids, there are many other glucocorticoid-inducible genes that have significant anti-inflammatory potential. We therefore advocate a move away from the search for ligands of GR that dissociate transactivation from transrepression. Instead, we submit that ligands should be functionally screened by virtue of their ability to induce or repress biologically-relevant genes in target tissues. In this review, we discuss pharmacological methods by which selective GR modulators and "add-on" therapies may be exploited to improve the clinical efficacy of glucocorticoids while reducing potential adverse effects.

Alternate splicing of interleukin-1 receptor type II (IL1R2) in vitro correlates with clinical glucocorticoid responsiveness in patients with AIED

Autoimmune Inner Ear Disease (AIED) is poorly characterized clinically, with no definitive laboratory test. All patients suspected of having AIED are given glucocorticoids during periods of acute hearing loss, however, only half initially respond, and still fewer respond over time.

We hypothesized that AIED is a systemic autoimmune disease characterized by dysfunctional peripheral blood mononuclear cells (PBMC) responses to a unique cochlear antigen(s). To test this hypothesis, we examined end-stage AIED patients undergoing cochlear implant surgery and compared autologous perilymph stimulated PBMC from AIED patients to controls. We determined that autologous perilymph from AIED patients was unable to induce expression of a long membrane-bound Interleukin-1 Receptor Type II (mIL1R2) transcript in PBMC as compared with controls, despite similar expression of the short soluble IL1R2 (sIL1R2) transcript (p<0.05). IL1R2 is a molecular decoy that traps interleukin-1β (IL-1β) and does not initiate subsequent signaling events, thereby suppressing an inflammatory response. IL1R2 transcript length is regulated by alternate splicing, and the major inhibitory function is attributed to the full-length mIL1R2. In addition, IL1R2 expression is induced by dexamethasone.

Separately, we prospectively examined patients with newer onset glucocorticoid-responsive AIED. Immediately prior to clinical treatment for acute deterioration of hearing thresholds, their PBMC demonstrated a robust induction of mIL1R2 in PBMC in response to dexamethasone in vitro that correlated with a clinical response to prednisone in vivo (p<0.0001) as measured by hearing restoration. In contrast, clinically steroid unresponsive patients demonstrated high basal levels of mIL1R2 in their PBMC and only minimally augmented expression in response to dexamethasone. Thus, induced expression of mIL1R2 appears to be a protective mechanism in hearing homeostasis and warrants further investigation in a large prospective clinical trial to determine if IL1R2 can be used as a specific biomarker for AIED.

Anti-inflammatory functions of glucocorticoid-induced genes

There is a broad consensus that glucocorticoids (GCs) exert anti-inflammatory effects largely by inhibiting the function of nuclear factor kappaB (NFkappaB) and consequently the transcription of pro-inflammatory genes. In contrast, side effects are thought to be largely dependent on GC-induced gene expression. Biochemical and genetic evidence suggests that the positive and negative effects of GCs on transcription can be uncoupled from one another. Hence, novel GC-related drugs that mediate inhibition of NFkappaB but do not activate gene expression are predicted to retain therapeutic effects but cause fewer or less severe side effects. Here, we critically re-examine the evidence in favor of the consensus, binary model of GC action and discuss conflicting evidence, which suggests that anti-inflammatory actions of GCs depend on the induction of anti-inflammatory mediators. We propose an alternative model, in which GCs exert anti-inflammatory effects at both transcriptional and post-transcriptional levels, both by activating and inhibiting expression of target genes. The implications of such a model in the search for safer anti-inflammatory drugs are discussed.

Glucocorticoids in the regulation of transcription factors that control cytokine synthesis

The interaction at different levels between intracellular signals elicited by cytokines and activated glucocorticoid receptors (GR) is essential for the regulation of immune responses. We describe different levels of interaction between glucocorticoids and cytokines which result in the induction or repression of gene transcription. These include the regulation of cytokine receptor expression, the molecular cross-talk between the GR and transcription factors (TFs) activated by cytokine signaling, the interaction with several signaling pathways and also posttranslational modifications of both GR and TFs. Also, an overview of the implications of chromatin remodeling in this interplay is discussed. The complexity of the intricate network involved in the interaction between GR and TFs is pivotal for the final outcome of cytokines biological action.

TLR2 expression in relation to IL-6 and IL-1beta and their natural regulators production by PMN and PBMC in patients with Lyme disease

Recently, it has been reported that TLR2 on macrophages plays a unique role in the inflammatory response and host defense to infection with Borrelia burgdorferi (Bb) which is an etiologic agent of Lyme disease. Experimental studies show that PMNs also play an essential role in infection control by Bb. However, there is no available data about TLR2 expression on PMN in the course of Lyme disease. In the present study, TLR2 expression and production of IL-1beta and IL-6 as well as their natural regulators (sIL-1RII, IL-1Ra and sIL-6Ralpha, sgp130, resp) by PMN of peripheral blood in patients with Lyme disease were examined. For the purpose of comparison, the same activity of autologous peripheral blood mononuclear cells (PBMCs) was estimated. An effect of rhIL-15 on TLR2 and cytokine secretion was also studied. Increased TLR2 expression in unstimulated neutrophils suggests an important role of these cells in mechanism recognition of B burgdorferi in patients with Lyme disease. The relationship between IL-1beta and IL-6 as well as their regulators by unstimulated PMN and PBMC, observed in the present study, may lead to enhanced IL-6- and to inhibition of IL-1beta-mediated reactions in this patient group. Changes in the TLR2 expression after rhIL-15 stimulation appear to have a favorable effect on mechanism recognition of Bb. The relations between IL-6 and its regulators (sIL-6Ralpha and sgp130) as well as between IL-1beta and its regulators (IL-1Ra and sIL-1RII) after rhIL-15 stimulation may lead to enhanced IL-1beta- and IL-6-mediated inflammatory reactions in the course of Lyme disease.

TNFα Measurement in Rat and Human Whole Blood as an in vitro Method to Assay Pyrogens and its Inhibition by Dexamethasone and Erythromycin

To ensure the safety of potential drugs, pyrogen tests are traditionally performed in rabbits. New methods have been developed as alternatives to the test to reduce the use of experimental animals. Among these methods there are the Limulus amoebocyte lysate test and the determination of cytokine production by human leukocytes and whole blood. When exposed to a range of concentrations of endotoxins, human and rat whole blood release TNFalpha at amounts that are detectable by a commercially available enzyme-linked immunosorbent assay (ELISA). Our results show that the sensitivity of human and rat blood to endotoxins from Salmonella abortus equi and Escherichia coli is similar. In rat blood, TNFalpha was detected after contact with the pyrogens only in fresh blood, collected on the same day of incubation with the pyrogenic substances. The measurement of TNFalpha production would be a reliable alternative to the rabbit pyrogen test. However, given that the addition of erythromycin and dexamethasone inhibited the production of this cytokine, this method is limited when parenteral formulations contain these two drugs. Similar inhibition has been observed in the rabbit test. Additional experiments will be necessary to demonstrate that the rat whole blood test system is useful and reliable for the pyrogens evaluation.

Dexamethasone enhances LPS induction of tissue factor expression in human monocytic cells by increasing tissue factor mRNA stability

Glucocorticoids, such as dexamethasone (Dex), are used clinically in the treatment of various inflammatory diseases. Dex acts by inhibiting the expression of inflammatory mediators, such as tumor necrosis factor alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1). It is surprising that Dex enhances bacterial lipopolysaccharide (LPS) induction of tissue factor (TF) expression in human monocytic cells. TF is a transmembrane glycoprotein that activates the coagulation protease cascade. In this study, we analyze the mechanism by which Dex enhances LPS-induced TF expression in human monocytic cells. We found that Dex reduced LPS-induced TF gene transcription but increased the stability of TF mRNA. Dex decreased the stability of MCP-1 mRNA and did not affect TNF-alpha mRNA stability. Finally, we showed that Dex increased the stability of a transcript consisting of the final 297 nucleotides of the TF mRNA in in vitro decay assays. This region contains AU-rich elements that regulate mRNA stability and may mediate the Dex response. Therefore, despite an inhibition of TF gene transcription, Dex enhances TF expression in human monocytic cells by increasing the stability of TF mRNA.

Inflammatory mediator production in swine following endotoxin challenge with or without co-administration of dexamethasone

The inflammatory response in swine challenged with lipopolysaccharide (LPS) has only been partially characterized. As swine are increasingly used in biomedical research, it is important to determine if they respond to endotoxin challenge in a manner similar to other model systems. Accordingly, 24 Poland China x Landrace barrows were treated with saline, LPS, dexamethasone, or LPS and dexamethasone, with six animals in each treatment group. The kinetics of TNFalpha, IL-1beta, IL-6, IL-8, IL-10, nitric oxide (nitrate/nitrite), and neopterin production in swine plasma were examined at 1, 3, 6, 9, and 24 h after acute LPS challenge. Lipopolysaccharide increased plasma TNFalpha levels, which peaked 1 h post-challenge. Dexamethasone decreased LPS-induced TNFalpha by approximately 60%. Plasma IL-6 levels peaked 3 h post-LPS challenge, returning to basal levels by 9 h. Swine given both LPS and dexamethasone had minimal IL-6 levels. Control and dexamethasone-only treated animals never exhibited systemic TNFalpha or IL-6 levels. Lipopolysaccharide increased plasma IL-10 1 h after challenge. Dexamethasone did not alter plasma IL-10 levels in LPS-challenged swine. Interleukin-1beta was constitutively present in plasma and was not altered by any combination of treatments. Plasma IL-8 was not observed in any treatment group. Plasma nitrate/nitrite levels were maximal 24 h post-challenge. Dexamethasone treatment prevented increases in plasma nitrate/nitrite levels in LPS-treated animals. Lipopolysaccharide induced levels of neopterin; dexamethasone served to further increase plasma neopterin levels in LPS-challenged animals. The discordant regulation of inflammatory mediators suggests that the immunological responses by swine to LPS are distinct from the responses seen in rodent and human studies.

Expression of cytokine- and chemokine-related genes in peripheral blood mononuclear cells from lupus patients by cDNA array

Systemic lupus erythematosus (SLE) is characterized by diverse and complex immune abnormalities. In an effort to begin to characterize the full complexity of immune abnormalities, the expression pattern of 375 potentially relevant genes was analyzed using peripheral blood mononuclear cells (PBMC) from 21 SLE patients and 12 controls by cDNA arrays. When mean gene expression for patients was compared to controls, 50 genes were identified that exhibited more than 2.5-fold difference in expression level. By the Mann-Whitney U test, 20 genes were significantly different (P < 0.05) between patients and controls. Most of these genes have not been previously associated with SLE and belong to a variety of families such as TNF/death receptor, IL-1 cytokine family, and IL-8 and its receptors. Hierarchical clustering of samples and differentially expressed genes revealed that with few exceptions, patients clustered separately from controls. These results highlight the potential use of the microarray data in identifying genes associated with SLE, which could become candidate molecular markers or future therapeutic targets.

Role of IL-18 in the secretion of Il-1beta, sIL-1RII, and IL-1Ra by human neutrophils

In the present study we investigated the effect of IL- 18 on the production of IL-1beta, IL-1Ra and sIL-1RII by human neutrophils. Our observations indicate that rhIL-18 induces IL-1beta and, to a lesser extend, IL-1Ra and sIL-1RII production by human neutrophils isolated form peripheral blood. However, this effect was less important in comparison with LPS-stimulation. Moreover, the results obtained suggest that IL-18 can induce priming of neutrophils for IL-1beta and, to a lesser extend, IL- Ra and sIL-1RII production by LPS-stimulated cells. The capacity of IL-18 to serve as an effective modulator for IL-1beta and its regulatory proteins may have significance in the inflammatory and immune reactions mediated by IL-1beta.

Decoy receptors: a strategy to regulate inflammatory cytokines and chemokines

The canonical concept of a receptor includes specific ligand recognition, usually with high affinity and specificity, and signaling. Decoy receptors recognize certain inflammatory cytokines with high affinity and specificity, but are structurally incapable of signaling or presenting the agonist to signaling receptor complexes. They act as a molecular trap for the agonist and for signaling receptor components. The interleukin-1 type II receptor (IL-1RII) was the first pure decoy to be identified. Decoy receptors have subsequently been identified for members of the tumor necrosis factor receptor and IL-1R families. Moreover, silent nonsignaling receptors could act as decoys for chemokines. Therefore, the use of decoy receptors is a general strategy to regulate the action of primary pro-inflammatory cytokines and chemokines.

Differential gene regulation of interleukin-1 ligands and receptors in bovine peripheral blood neutrophils and mononuclear cells in response to E. coli lipopolysaccharide (LPS)

The proinflammatory cytokine, interleukin-1, plays a prominent role in the inflammatory reactions that characterize numerous diseases. In this study, we examined the gene expression for bovine IL-1 ligands and receptors by bovine peripheral blood mononuclear cells (MNCs) and neutrophils (PMNs) in response to E. coli lipopolysaccharide (LPS) in vitro. Gene expression of mRNA for IL-1alpha, IL-1beta, IL-1 receptor antagonist (IL-1ra), type 1 IL-1 receptor, type 2 IL-1 receptor, and IL-1 beta converting enzyme (ICE), were measured by a semi-quantitative RT-PCR technique. LPS had little effect on type 1 IL-1R expression in MNC, whereas, it strongly up-regulated type 1 IL-1R expression in PMNs. Co-incubation of PMNs with LPS and bovine recombinant IL-1beta had little additional effect on type 1 IL-1R expression. Incubation of MNCs with LPS resulted in up-regulation of IL-1beta, IL-1ra, and type 2 IL-1R, no change in IL-1alpha, and a decrease in ICE gene expression. Incubation of PMNs with LPS up-regulated IL-1beta gene expression, whereas, IL-1alpha, IL-1ra, type 2 IL-1R and ICE were unchanged. This study provides evidence for differential regulation of gene products of the bovine IL-1 family by peripheral blood mononuclear cells (MNC) and neutrophils (PMNs) in response to E. coli LPS.

Cloning and characterization of the rainbow trout (Oncorhynchus mykiss) type II interleukin-1 receptor cDNA

A homologue of mammalian type II interleukin-1 receptor (IL-1RII) was isolated from a rainbow trout cDNA library by differential hybridization using a suppression subtractive hybridization generated probe enriched for sequences upregulated after immune stimulation. The trout cDNA has an ORF encoding 441 amino acids, and represents the first piscine IL-1 receptor described. The predicted amino-acid sequence has 29 and 26% identity with human and mouse IL-1RII, respectively. The trout IL-1 receptor has a domain organization similar to that of mammalian type II receptor, with a short cytoplasmic tail of 24 amino acids. These results suggest that type II receptor is also present in lower vertebrates, and therefore the duplication of an ancestral gene that generated type I and type II IL-1 receptors occurred prior to the time mammals emerged.

Glucocorticoid sensitivity of interleukin-1 agonist and antagonist secretion: the effects of age and gender

Interleukin-1 (IL-1) is a primary mediator of inflammation that is regulated, in part, by the hypothalamic-pituitary-adrenal axis. The purpose of this study was to determine if gender- or age-related differences exist in the sensitivity of IL-1-producing cells to hydrocortisone. Peripheral blood mononuclear cells (PBMC) isolated from men and women (21-77 yr old) were incubated with hydrocortisone (0, 50, 100, 500, or 1,000 ng/ml) with or without lipopolysaccharide (LPS). Secretion of IL-1beta and IL-1 receptor antagonist was inhibited in a dose-dependent manner (P = 0.001) without age- or gender-related differences. Hydrocortisone decreased soluble IL-1 receptor type II (sIL-1RII) secretion by unstimulated cells (P = 0. 0001), but it increased secretion by LPS-stimulated cells (P = 0. 0001) in all groups. Unstimulated cell supernatants from men contained greater concentrations of sIL-1RII than the supernatants from women (P = 0.011). Compared with men, PBMCs from women were less responsive to hydrocortisone inhibition of sIL-1RII secretion, regardless of age (P = 0.001), and compared with the follicular phase, sIL-1RII secretion was lower in the luteal phase of the menstrual cycle (P < 0.05). These data indicate that basal secretion and glucocorticoid modulation of sIL-1RII secretion by cultured PBMCs are gender dependent. Moreover, glucocorticoid influences on sIL-1RII secretion depend on the presence or absence of gram-negative bacterial toxins.

Dynamic regulation of the proinflammatory cytokine, interleukin-1beta: molecular biology for non-molecular biologists

Interleukin-1beta (IL-1beta) is a key mediator and modulator of a wide array of physiological responses important for survival. It is created by a variety of cell types, including immune cells, glia, and neurons. It is a very potent biological molecule, acting both at the periphery as well as within the central nervous system. The production and release of IL-1beta is tightly regulated by far more complex processes than previously thought. An appreciation of this complexity is necessary for proper interpretation of apparent contradictions in the literature where different aspects of IL-1beta expression are measured. Given that many researchers are not molecular biologists by training, yet need an appreciation of the controls that regulate the function of key proteins such as IL-1beta, this review is aimed at both: (a) clarifying the multiple levels at which IL-1beta production is modulated and (b) using IL-1beta regulation to explain the dynamics of gene regulation to non-molecular biologists. Three major topics will be discussed. First, regulation of IL-1beta production will be examined at every level from extracellular signals that trigger gene activation through release of active protein into the extracellular fluid. Second, regulation of IL-1beta bioavailability and bioactivity will be discussed. This section examines the fact that even after IL-1beta is released, it may or may not be able to exert a biological action due to multiple modulatory factors. Last is the introduction of the idea that IL-1beta regulation is, at times, beyond the direct control of host; that is, when IL-1beta production becomes dysregulated by pathogens.

Extracellular regulation of interleukin (IL)-1beta through lung epithelial cells and defective IL-1 type II receptor expression

Interleukin (IL)-1beta is produced primarily by activated mononuclear phagocytic cells in the lung airway and functions as a potent proinflammatory cytokine. Release of IL-1beta in the airway microenvironment induces the production of proinflammatory factors from parenchymal airway cells, including IL-8. To study the regulation of lung epithelial cell responsiveness to IL-1beta, the human type II-like airway epithelial cell line A549 and primary normal human bronchial epithelial (NHBE) cells were assayed for IL-1-specific response modifiers. Specifically, the IL-1 type I receptor (IL-1RI), IL-1 type II receptor (IL-1RII), IL-1 receptor accessory protein (IL-1RAcP), and IL-1 receptor antagonist (IL-1Ra) were analyzed. Constitutive expression of IL-1RI, IL-1RAcP, and IL-1Ra was detected in both immortalized and primary human airway epithelial cells. Interestingly, a complete absence of IL-1RII expression was demonstrated under all study conditions in both A549 and NHBE cells. Both cell types were responsive to IL-1beta at concentrations as low as 50 to 500 pg/ml when measured by IL-8 release into cell supernatants. IL-1beta-induced chemokine production and release were inhibited by a 10- to 1,000-fold molar excess of recombinant IL-1RII or IL-1Ra, whereas IL-1RI was a less effective inhibitor. On the basis of our results, we propose that human lung epithelial cells lack the ability to downregulate IL-1beta activity extracellularly because of an inability to express IL-1RII. Release of extracellular IL-1 inhibitors, including soluble IL-1Ra and soluble IL-1RII, by other inflammatory cells present in the airway may be critical for regulation of IL-1beta activity in the airway microenvironment.

The interleukin-1 type 2 receptor gene displays immediate early gene responsiveness in glucocorticoid-stimulated human epidermal keratinocytes

Human epidermal keratinocytes (HEKs) in primary culture (P2-P4) were used to study glucocorticoid (GC)-mediated transcription of the genes encoding the constitutively expressed interleukin-1 type 1 receptor (IL-1R1) and the inducible interleukin-1 type 2 receptor (IL-1R2). Utilizing Northern dot blot analysis and a quantitative reverse transcription-polymerase chain reaction protocol for IL-1R1 and IL-1R2, dexamethasone and, in particular, the budesonide epimer R were shown to effectively and rapidly induce transcription from the IL-IR2 gene when compared with IL-1R1 or beta-actin RNA message levels in the same sample. Southern blot analysis of newly generated IL-1R2 reverse transcription-polymerase chain reaction products using end-labeled IL-1R2 intron probes suggested that GC enhancement of IL-1R2 expression was regulated primarily at the level of de novo transcription. GC-induced IL-1R2 gene transcription displayed features characteristic of a classical immediate early gene response, including a signal transduction function, a relatively low basal abundance, a rapid, transient induction, cycloheximide superinduction, actinomycin D suppression, and a rapid decay of IL-1R2 RNA message. Parallel time course kinetic analysis of IL-1R2 RNA message levels with Western immunoblotting revealed tight coupling of de novo IL-IR2 gene transcription with translation of the IL-1R2 RNA message; a newly synthesized ( approximately 46-kDa) IL-1R2 protein was detected in the HEK growth medium as early as 1 h after budesonide epimer R treatment. These data indicate that different GC compounds can variably up-regulate the IL-1R2 response in HEKs through transcription-mediated mechanisms and, for the first time, suggest that a gene encoding a soluble cytokine receptor can respond like an immediate early gene.

Treatment of rheumatoid arthritis with IL-1 inhibitors

Extensive evidence from both in vivo and in vitro experiments indicate that IL-1, a prototypic proinflammatory cytokine, is involved in the mechanisms that lead to progressive joint destruction in RA. IL-1Ra, a member of the IL-1 family, binds IL-1 receptors but does not induce any cellular responses. IL-1Ra competitively inhibits the binding of IL-1 to its cell surface receptors and thus, acts as an endogenous antiinflammatory mediator. However, the results of several studies suggest that a relatively deficient production in IL-1Ra as compared to that of IL-1 in RA synovium may predispose to the perpetuation of chronic inflammation. Systemic administration of IL-1Ra, or local delivery into the joint by gene therapy, in different experimental animal models of arthritis attenuated the severity of the inflammatory response and reduced articular destruction. In addition, treatment of rheumatoid patients with IL-1Ra led to an improvement in different clinical and biological parameters and to a reduction in the radiological signs of joint erosions. Encouraging results also have been reported in both in vitro and in vivo experimental animal models of arthritis through using other strategies designed to block the effects of IL-1 at the level of production, prevent the binding of IL-1 to its cell surface receptors, or interfere with the effects of IL-1 at the post-receptor level.

Interleukin 1 receptor antagonist (IL-1Ra) is an acute-phase protein

Interleukin 1 receptor antagonist (IL-1Ra) levels are elevated in the blood of patients with a variety of infectious, immune, or traumatic conditions. To examine whether IL1Ra is produced by liver cells with characteristics resembling an acute-phase protein, human primary hepatocytes isolated from liver biopsies and HepG2 hepatoma cells were stimulated with IL-1beta, IL-6, and TNFalpha. IL-1Ra was present in the supernatants of both cells, with production significantly enhanced by IL-1beta, and by the combination of IL-1beta and IL-6. The term IL-1Ra refers to two different proteins encoded by the same gene, but generated by alternative splicing of two different first exons. One isoform is secreted (17-kD sIL-1Ra), and the other isoform remains in the cytoplasm (18-kD icIL-1Ra). By Western blot analysis, the supernatants of human hepatoma (HepG2) cells contained only sIL-1Ra, whereas the lysates contained a novel smaller molecular mass isoform of 16 kD. RT-PCR and ribonuclease protection assay with RNA from HepG2 cells showed that only sIL-1Ra mRNA was expressed, and confirmed the inducing effect of IL-1beta and IL-6. Transfection studies were performed using constructs containing the promoters of either sIL-1Ra or icIL-1Ra coupled to the luciferase reporter gene. The sIL-1Ra promoter was active in HepG2 cells stimulated by IL-1beta and/or IL-6, whereas the icIL-1Ra promoter was inactive. Mutation of binding sites for transcription factors NF-kappaB and/or C/EBP within the proximal sIL-1Ra promoter led to significant decreases in response to IL-1beta and IL-6 in comparison to the wild-type promoter. Electromobility gel shift assays confirmed the presence of NF-kappaB and C/EBP binding sites within the sIL-1Ra promoter, and indicated a significant increase in the binding activities of nuclear proteins from HepG2 cells treated with IL-1beta and IL-6. In summary, sIL-1Ra, but not icIL-1Ra, is produced by hepatocytes, and is regulated by proinflammatory cytokines as an acute-phase protein. In addition, NF-kappaB and C/EBP family members are likely to play important roles in the full expression of IL-1Ra by hepatocytes during inflammatory conditions.