Lipopolysaccharide induces human interleukin-1 receptor antagonist and interleukin-1 production in the same cell

Relationships Between Age, Frailty, Length of Care Home Residence and Biomarkers of Immunity and Inflammation in Older Care Home Residents in the United Kingdom

Aging is associated with changes to the immune system, collectively termed immunosenescence and inflammageing. However, the relationships among age, frailty, and immune parameters in older people resident in care homes are not well described. We assessed immune and inflammatory parameters in 184 United Kingdom care home residents aged over 65 years and how they relate to age, frailty index, and length of care home residence. Linear regression was used to identify the independent contribution of age, frailty, and length of care home residence to the various immune parameters as dependent variables. Participants had a mean age (±SD) of 85.3 ± 7.5 years, had been residing in the care home for a mean (±SD) of 1.9 ± 2.2 years at the time of study commencement, and 40.7% were severely frail. Length of care home residence and frailty index were correlated but age and frailty index and age and length of care home residence were not significantly correlated. All components of the full blood count, apart from total lymphocytes, were within the reference range; 31% of participants had blood lymphocyte numbers below the lower value of the reference range. Among the components of the full blood count, platelet numbers were positively associated with frailty index. Amongst plasma inflammatory markers, C-reactive protein (CRP), interleukin-1 receptor antagonist (IL-1ra), soluble E-selectin and interferon gamma-induced protein 10 (IP-10) were positively associated with frailty. Plasma soluble vascular cell adhesion molecule 1 (sVCAM-1), IP-10 and tumor necrosis factor receptor II (TNFRII) were positively associated with age. Plasma monocyte chemoattractant protein 1 was positively associated with length of care home residence. Frailty was an independent predictor of platelet numbers, plasma CRP, IL-1ra, IP-10, and sE-selectin. Age was an independent predictor of activated monocytes and plasma IP-10, TNFRII and sVCAM-1. Length of care home residence was an independent predictor of plasma MCP-1. This study concludes that there are independent links between increased frailty and inflammation and between increased age and inflammation amongst older people resident in care homes in the United Kingdom. Since, inflammation is known to contribute to morbidity and mortality in older people, the causes and consequences of inflammation in this population should be further explored.

Cytokines of the IL-1 family: recognized targets in chronic inflammation underrated in organ transplantations

Interleukin 1 (IL-1) family is a group of cytokines with multiple local and systemic effects, which regulates both innate and adaptive immune responses. Generally, most IL-1 family cytokines express prevailing pro-inflammatory activities (IL-1α, IL-1β, IL-18, IL-33, IL-36 α, β, γ), whereas others are anti-inflammatory (IL-1Ra (IL-1 receptor antagonist), IL-36Ra, IL-38, IL-37). In addition to their immunomodulatory roles, some of them are also involved in the physiological modulation of homeostatic processes and directly affect mRNA transcription. IL-1 family cytokines bind to specific receptors composed of a ligand-binding chain and an accessory chain. The pro-inflammatory effects of IL-1 family cytokines are regulated on the level of transcription, enzymatic processing of precursors, release of soluble antagonists, and expression of decoy receptors. Members of the IL-1 family regulate the recruitment and activation of effector cells involved in innate and adaptive immunity, but they are also involved in the pathogenesis of chronic disorders, including inflammatory bowel disease, rheumatoid arthritis, and various autoimmune and autoinflammatory diseases. There are only limited data regarding the role of IL-1 cytokines in transplantation. In recent years, targeted therapeutics affecting IL-1 have been used in multiple clinical studies. In addition to the recombinant IL-1Ra, anakinra (highly effective in autoinflammatory diseases and tested for other chronic diseases), the monoclonal antibodies canakinumab, gevokizumab, and rilonacept (a long-acting IL-1 receptor fusion protein) provide further options to block IL-1 activity. Furthermore, new inhibitors of IL-18 (GSK 1070806, ABT-325, rIL-18BP (IL-18 binding protein)) and IL-33 (CNTO-7160) are presently under clinical studies and other molecules are being developed to target IL-1 family cytokines.

Phosphodiesterase 4B negatively regulates endotoxin-activated interleukin-1 receptor antagonist responses in macrophages

Activation of TLR4 by lipopolysaccharide (LPS) induces both pro-inflammatory and anti-inflammatory cytokine production in macrophages. Type 4 phosphodiesterases (PDE4) are key cAMP-hydrolyzing enzymes, and PDE4 inhibitors are considered as immunosuppressors to various inflammatory responses. We demonstrate here that PDE4 inhibitors enhance the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1Ra) secretion in LPS-activated mouse peritoneal macrophages, and this response was regulated at the transcriptional level rather than an increased IL-1Ra mRNA stability. Studies with PDE4-deficient macrophages revealed that the IL-1Ra upregulation elicited by LPS alone is PKA-independent, whereas the rolipram-enhanced response was mediated by inhibition of only PDE4B, one of the three PDE4 isoforms expressed in macrophages, and it requires PKA but not Epac activity. However, both pathways activate CREB to induce IL-1Ra expression. PDE4B ablation also promoted STAT3 phosphorylation (Tyr⁷⁰⁵) to LPS stimulation, but this STAT3 activation is not entirely responsible for the IL-1Ra upregulation in PDE4B-deficient macrophages. In a model of LPS-induced sepsis, only PDE4B-deficient mice displayed an increased circulating IL-1Ra, suggesting a protective role of PDE4B inactivation in vivo. These findings demonstrate that PDE4B negatively modulates anti-inflammatory cytokine expression in innate immune cells, and selectively targeting PDE4B should retain the therapeutic benefits of nonselective PDE4 inhibitors.

Differential regulation of LPS-induced IL-1β and EL-1 receptor antagonist mRNA by IFNα and IFNγ in murine peritoneal macrophages

IL-1 and its naturally occurring receptor antagonist, IL-1ra, are primarily synthesized by cells of the monocyte-macrophage lineage. The balance of the relative amounts of these secreted cytokines has major importance in the pathophysiology of various inflammatory disorders, especially bacterial sepsis and some autoimmune diseases. While both the agonist and the antagonist genes belong to the same family, IL-1β and IL-1ra are differentially regulated. In the present study, we examined the effects of macrophage activating factors, bacterial lipopolysaccharide (LPS), IFNα, and IFNγ, on the regulation of IL-1ra and IL-1β mRNA levels in thioglycollate-elicited mouse peritoneal macrophages. LPS-treatment of cultured macrophages resulted in a 3 to 4-fold increase in IL-1ra mRNA which peaked between 6-12 h, then started to decline but remained well above background levels at 24 h. In comparison to IL-1ra, the LPS-induced increase in IL-1β mRNA was larger, peaked earlier (at 2-4 h), and sharply decreased thereafter. In vivo analysis of mRNA from LPS-injected mice showed a similar temporal pattern of IL-1β and IL-1ra gene expression in bone marrow, spleen, and liver. In contrast to the effects of LPS, treatment with IFNα and IFNγ alone failed to affect the expression of either IL-1ra or IL-1β mRNA in vitro. However, in combination with LPS, IFNα and IFNγ had differential effects on the induction of these cytokines: IFNγ, but not IFNα, augmented the expression of LPS-induced IL-1ra. Conversely, both IFNα and IFNγ suppressed the induction of IL-1β mRNA by LPS. Thus, while IFNα only affects LPS-induced IL-1β gene expression, IFNγ exerts opposing effects on the LPS-induction of the agonist and antagonist, illustrating the complex role of interferons during the inflammatory process.

α1-antitrypsin increases interleukin-1 receptor antagonist production during pancreatic islet graft transplantation

Although islet transplantation for individuals with type 1 diabetes has been shown to yield superior blood glucose control, it remains inadequate for long-term control. This is partly due to islet injuries and stresses that can lead to beta cell loss. Inhibition of excess IL-1β activity might minimize islet injuries, thus preserving function. The IL-1 receptor antagonist (IL-1Ra), an endogenous inhibitor of IL-1β, protects islets from cytokine-induced necrosis and apoptosis. Therefore, an imbalance between IL-1β and IL-1Ra might influence the courses of allogeneic and autoimmune responses to islets. Our group previously demonstrated that the circulating serine-protease inhibitor human alpha-1-antitrypsin (hAAT), the levels of which increase in circulation during acute-phase immune responses, exhibits anti-inflammatory and islet-protective properties, as well as immunomodulatory activity. In the present study, we sought to determine whether the pancreatic islet allograft-protective activity of hAAT was mediated by IL-1Ra induction. Our results demonstrated that hAAT led to a 2.04-fold increase in IL-1Ra expression in stimulated macrophages and that hAAT-pre-treated islet grafts exhibited a 4.851-fold increase in IL-1Ra transcript levels, which were associated with a moderate inflammatory profile. Unexpectedly, islets that were isolated from IL-1Ra-knockout mice and pre-treated with hAAT before grafting into wild-type mice yielded an increase in intragraft IL-1Ra expression that was presumably derived from infiltrating host cells, albeit in the absence of hAAT treatment of the host. Indeed, hAAT-pre-treated islets generated hAAT-free conditioned medium that could induce IL-1Ra production in cultured macrophages. Finally, we demonstrated that hAAT promoted a distinct phosphorylation and nuclear translocation pattern for p65, a key transcription factor required for IL-1Ra expression.

Neuroinflammation in ischemic brain injury as an adaptive process

Cerebral ischaemia triggers various physiological processes, some of which have been considered deleterious and others beneficial. These processes have been characterized in one influential model as being part of a transition from injury to repair processes. We argue that another important distinction is between dysregulated and regulated processes. Although intervening in the course of dysregulated processes may be neuroprotective, this is unlikely to be true for regulated processes. This is because from an evolutionary perspective, regulated complex processes that are conserved across many species are likely to be adaptive and provide a survival advantage. We argue that the neuroinflammatory cascade is an adaptive process in this sense, and contrast this with a currently popular theory which we term the maladaptive immune response theory. We review the evidence from clinical and preclinical pharmacology with respect to this theory, and deduced that the evidence is inconclusive at best, and probably falsifies the theory. We argue that this is why there are no anti-inflammatory treatments for cerebral ischaemia, despite 30 years of seemingly promising preclinical results. We therefore propose an opposing theory, which we call the adaptive immune response hypothesis.

9E,11E-conjugated linoleic acid increases expression of the endogenous antiinflammatory factor, interleukin-1 receptor antagonist, in RAW 264.7 cells

Despite having a similar structure, various conjugated linoleic acid (CLA) isomers have a distinct gene expression pattern in RAW 264.7 (RAW) cells, a mouse macrophage cell line. Among the 5 CLA isomers tested [9cis(Z),11trans(E)-, 9Z,11Z-, 9E,11E-, 10E,12Z-, and 11Z,13E-CLA], only 9E,11E-CLA induced the endogenous antiinflammatory molecule, interleukin (IL)-1 receptor antagonist (IL-1Ra), in RAW cells. In this study, the mechanism and effects of IL-1Ra regulation by 9E,11E-CLA in RAW cells was studied in detail. 9E,11E-CLA induced IL-1Ra in a dose- and time-dependent manner, whereas it decreased lipopolysaccharide (LPS)-induced IL-1alpha, IL-1beta, and IL-6 mRNA levels and protein levels. To determine the importance of IL-1Ra in the antiinflammatory effects of this particular CLA isomer, IL-1Ra protein levels were repressed in RAW cells using small interference RNA inhibitor expression. In the presence of IL-1Ra small interference RNA, the induction of this molecule was ablated, as was the decrease of LPS-induced IL-1alpha and IL-6 mRNA levels by 9E,11E-CLA. The IL-1Ra increase due to this CLA isomer was transcriptionally regulated, although there was no response element(s) affected by 9E,11E-CLA in the first 1.5 kb of the IL-1Ra promoter. The phosphoinositide 3-kinase inhibitors, LY294002 and the mammalian target of rapamycin inhibitor rapamycin, abolished the IL-1Ra induction by 9E,11E-CLA, whereas other kinase inhibitors did not affect this response. Taken together, 9E,11E-CLA exerts unique antiinflammatory effects by increasing an endogenous repressor of IL-1 signaling.

Convergence of IL-1beta and VDR activation pathways in human TLR2/1-induced antimicrobial responses

Antimicrobial effector mechanisms are central to the function of the innate immune response in host defense against microbial pathogens. In humans, activation of Toll-like receptor 2/1 (TLR2/1) on monocytes induces a vitamin D dependent antimicrobial activity against intracellular mycobacteria. Here, we report that TLR activation of monocytes triggers induction of the defensin beta 4 gene (DEFB4), requiring convergence of the IL-1β and vitamin D receptor (VDR) pathways. TLR2/1 activation triggered IL-1β activity, involving the upregulation of both IL-1β and IL-1 receptor, and downregulation of the IL-1 receptor antagonist. TLR2/1L induction of IL-1β was required for upregulation of DEFB4, but not cathelicidin, whereas VDR activation was required for expression of both antimicrobial genes. The differential requirements for induction of DEFB4 and cathelicidin were reflected by differences in their respective promoter regions; the DEFB4 promoter had one vitamin D response element (VDRE) and two NF-κB sites, whereas the cathelicidin promoter had three VDREs and no NF-κB sites. Transfection of NF-κB into primary monocytes synergized with 1,25D3 in the induction of DEFB4 expression. Knockdown of either DEFB4 or cathelicidin in primary monocytes resulted in the loss of TLR2/1-mediated antimicrobial activity against intracellular mycobacteria. Therefore, these data identify a novel mechanism of host defense requiring the induction of IL-1β in synergy with vitamin D activation, for the TLR-induced antimicrobial pathway against an intracellular pathogen.

Immunolocalization of interleukin-1 receptors in the sarcolemma and nuclei of skeletal muscle in patients with idiopathic inflammatory myopathies

OBJECTIVE

Interleukin-1 (IL-1) acts via its receptors to induce gene expression that mediates protein synthesis involved in inflammation. Increased expression of IL-1alpha and IL-1beta in muscle tissue from patients with polymyositis and dermatomyositis has been demonstrated. It is not known whether the reciprocal IL-1 receptors are expressed in human muscle tissue. The purpose of this study was to investigate the expression of IL-1 receptors and their ligands in muscle tissue from patients with myositis and from healthy controls.

METHODS

Muscle biopsy tissues from 10 patients with polymyositis or dermatomyositis and 7 healthy control subjects were investigated by immunohistochemistry using antibodies against IL-1 receptor type I (IL-1RI), IL-1RII, IL-1alpha, IL-1beta, and IL-1 receptor antagonist (IL-1Ra). Quantification was performed by computerized image analysis, and localization of expression was determined by double staining using immunofluorescence and confocal microscopy.

RESULTS

In tissue samples from the patients, IL-1RI and IL-1RII were expressed in muscle fibers, inflammatory cells, and endothelial cells. Expression in muscle fibers was localized to the sarcolemma and nuclei. IL-1alpha was expressed in endothelial cells and inflammatory cells, whereas IL-1beta and IL-1Ra were expressed only in inflammatory cells. Expression of the two IL-1 receptors and their ligands was significantly higher in patients than in controls. IL-1 receptor expression on muscle fibers was most pronounced in the vicinity of cells expressing IL-1alpha and IL-1beta.

CONCLUSION

The increased expression of IL-1 receptor and the colocalization with reciprocal ligands in patients with myositis but not in healthy controls support the hypothesis of a crucial role of IL-1 in the pathogenesis of polymyositis and dermatomyositis.

(Peri)vascular production and action of pro-inflammatory cytokines in brain pathology

In response to tissue injury or infection, the peripheral tissue macrophage induces an inflammatory response through the release of IL-1β (interleukin-1β) and TNFα (tumour necrosis factor α). These cytokines stimulate macrophages and endothelial cells to express chemokines and adhesion molecules that attract leucocytes into the peripheral site of injury or infection. The aims of the present review are to (i) discuss the relevance of brain (peri)vascular cells and compartments to bacterial meningitis, HIV-1-associated dementia, multiple sclerosis, ischaemic and traumatic brain injury, and Alzheimer's disease, and (ii) to provide an overview of the production and action of pro-inflammatory cytokines by (peri)vascular cells in these pathologies of the CNS (central nervous system). The brain (peri)vascular compartments are highly relevant to pathologies affecting the CNS, as infections are almost exclusively blood-borne. Insults disrupt blood and energy flow to neurons, and active brain-to-blood transport mechanisms, which are the bottleneck in the clearance of unwanted molecules from the brain. Perivascular macrophages are the most reactive cell type and produce IL-1β and TNFα after infection or injury to the CNS. The main cellular target for IL-1β and TNFα produced in the brain (peri)vascular compartment is the endothelium, where these cytokines induce the expression of adhesion molecules and promote leucocyte infiltration. Whether this and other effects of IL-1 and TNF in the brain (peri)vascular compartments are detrimental or beneficial in neuropathology remains to be shown and requires a clear understanding of the role of these cytokines in both damaging and repair processes in the CNS.

Mycobacterium tuberculosis induces interleukin-32 production through a caspase- 1/IL-18/interferon-gamma-dependent mechanism

BACKGROUND

Interleukin (IL)-32 is a newly described proinflammatory cytokine that seems likely to play a role in inflammation and host defense. Little is known about the regulation of IL-32 production by primary cells of the immune system.

METHODS AND FINDINGS

In the present study, freshly obtained human peripheral blood mononuclear cells were stimulated with different Toll-like receptor (TLR) agonists, and gene expression and synthesis of IL-32 was determined. We demonstrate that the TLR4 agonist lipopolysaccharide induces moderate (4-fold) production of IL-32, whereas agonists of TLR2, TLR3, TLR5, or TLR9, each of which strongly induced tumor necrosis factor alpha and IL-6, did not stimulate IL-32 production. However, the greatest amount of IL-32 was induced by the mycobacteria Mycobacterium tuberculosis and M. bovis BCG (20-fold over unstimulated cells). IL-32-induced synthesis by either lipopolysaccharide or mycobacteria remains entirely cell-associated in monocytes; moreover, steady-state mRNA levels are present in unstimulated monocytes without translation into IL-32 protein, similar to other cytokines lacking a signal peptide. IL-32 production induced by M. tuberculosis is dependent on endogenous interferon-gamma (IFNgamma); endogenous IFNgamma is, in turn, dependent on M. tuberculosis-induced IL-18 via caspase-1.

CONCLUSIONS

In conclusion, IL-32 is a cell-associated proinflammatory cytokine, which is specifically stimulated by mycobacteria through a caspase-1- and IL-18-dependent production of IFNgamma.

The effect of interleukin-1 receptor antagonist on arteries and cholesterol metabolism

This review summarizes both the structure and function of IL-1 receptor antagonist (IL-1Ra), and relates our new findings, particularly those obtained in IL-1Ra-deficient mice (IL-1Ra(-/-)), to the role of IL-1Ra in arterial diseases and cholesterol metabolism. IL-1Ra(-/-) mice show an increase in neointima-formation after arterial injury. Heterozygosity in the IL-1Ra gene against the apolipoprotein E-deficient background revealed a role for IL-1 in promoting atherogenic cell signaling and that the larger lesions of IL-1Ra(-/-) mice are enriched in macrophages and depleted of smooth muscle cells. Furthermore, IL-1Ra(-/-) mice developed severe fatty livers and hypercholesteroremia following 20 weeks on a atherogenic diet compared to WT mice. Taken together, these results suggest that IL-1Ra plays important roles in restenosis after angioplasty, the development of atherosclerosis, and the metabolism of cholesterol in vivo.

Differential effects of alpha- and beta-defensin on cytokine production by cultured human bronchial epithelial cells

Defensins are cysteine-rich cationic antimicrobial peptides that play an important role in innate immunity and are known to contribute to the regulation of host adaptive immunity. In addition to direct antimicrobial activities, it has been recently reported that alpha-defensins, mainly present in neutrophils in the lung, have a cytotoxic effect and induce IL-8 production from airway epithelial cells. Although beta-defensins are expressed in epithelial cells in various tissues, including lung, there are no reports of their effects on cytokine synthesis in airway epithelial cells. The aim of the present study was to determine the effects of both alpha- and beta-defensins on the cytokine production, transcription factor binding activity, and cytotoxicity in primary cultured human bronchial epithelial cells (HBECs). We used human neutrophil peptide-1 (HNP-1; alpha-defensin) and human beta-defensin-2 (HBD-2) to stimulate HBECs. The results showed that treatment of HBECs with HNP-1, but not HBD-2, increased IL-8 and IL-1beta mRNA expression in a dose-dependent manner and also enhanced IL-8 protein secretion and NF-kappaB DNA binding activity. The 24-h treatments with >20 microg/ml of HNP-1 or >50 microg/ml of HBD-2 were cytotoxic to HBECs. These results suggest that alpha- and beta-defensins have different effects on cytokine synthesis by airway epithelial cells, and we speculate that they play different roles in inflammatory lung diseases.

Effects of plaque, psychological stress and gender on crevicular Il-1beta and Il-1ra secretion

OBJECTIVES

The study aimed to analyse (a) whether the effects of psychological stress and of experimental gingivitis on interleukin-1beta (Il-1beta) described before are compensated by concomitant increases in Il-1 receptor antagonist (Il-1ra), and (b) whether there do exist any gender differences in the Il-1 responses to experimental gingivitis and to psychological stress.

MATERIALS AND METHODS

Thirteen medical students participating in a major academic exam (seven males, six females) and 14 medical students without academic stress (eight males, six females) refrained from oral hygiene in two antagonistic quadrants for 28 days (plaque) while they maintained oral hygiene in the remaining quadrants (hygiene). Weekly crevicular fluid samples of plaque and hygiene sites were assayed for Il-1beta and Il-1ra.

RESULTS

Neither stress nor experimental gingivitis exerted significant effects on Il-1ra. In controls, we observed significant gender and gender x time effects on Il-1beta; comparing stress groups, gender x time and stress x gender x time interactions became significant. Women show a reduced Il-1beta response to plaque at rest and an increased response under stress. Similar results were found with respect to bleeding on probing.

CONCLUSIONS

Gender must be controlled in studies on periodontal responses to pathogens. Stress plays a role in these responses.

Morphological and immunological evidence of a unique selective production and endoplasmic reticular accumulation of interleukin-1alpha in rat peritoneal macrophages induced by Pseudomonas aeruginosa exotoxin A

The immunotoxicity of Pseudomonas aeruginosa exotoxin A (ETA) on macrophages was evaluated by incubating rat peritoneal macrophages (RPM) with 1-100 ng/ml ETA for 3-60 h. Although the overall changes in cell viability and DNA, RNA, and protein synthesis of the ETA-treated RPM (E-RPM) were reduced in a dose- and time-dependent manner, there was a transient but evident rebound in RNA and/or protein synthesis at 24-36 h post-incubation (HPI) at 1-50 ng/ml ETA. However, a more apparent enhancement appeared in RNA and protein synthesis at 36-48 HPI in 10 and 50 ng/ml E-RPM after normalized on the basis of viable cell. Most 50-100 ng/ml E-RPM underwent necrosis/apoptosis before 24 HPI. By 36 HPI, 41% of 10 ng/ml E-RPM remained viable but were full of cytoplasmic granules due to the accumulation of glycoprotein in segmentally dilated endoplasmic reticulum. Immunological staining of the granules revealed strong IL-1alpha but weak or no signals for IL-1beta, IL-1 receptor antagonist, IL-6, and TNF-alpha. A time-dependent increase in IL-1alpha but no IL-1beta was detected in cell lysate of 10 ng/ml E-RPM; however, neither IL-1alpha nor IL-1beta was detected in culture supernatant. Thus, besides cytopathic and functional effects, ETA could induce a unique selective production and endoplasmic reticular accumulation of IL-1alpha in RPM.

Evolution of interleukin-1beta

All jawed vertebrates possess a complex immune system, which is capable of anticipatory and innate immune responses. Jawless vertebrates possess an equally complex immune system but with no evidence of an anticipatory immune response. From these findings it has been speculated that the initiation and regulation of the immune system within vertebrates will be equally complex, although very little has been done to look at the evolution of cytokine genes, despite well-known biological activities within vertebrates. In recent years, cytokines, which have been well characterised within mammals, have begun to be cloned and sequenced within non-mammalian vertebrates, with the number of cytokine sequences available from primitive vertebrates growing rapidly. The identification of cytokines, which are mammalian homologues, will give a better insight into where immune system communicators arose and may also reveal molecules, which are unique to certain organisms. Work has focussed on interleukin-1 (IL-1), a major mediator of inflammation which initiates and/or increases a wide variety of non-structural, function associated genes that are characteristically expressed during inflammation. Other than mammalian IL-1beta sequences there are now full cDNA sequences and genomic organisations available from bird, amphibian, bony fish and cartilaginous fish, with many of these genes having been obtained using an homology cloning approach. This review considers how the IL-1beta gene has changed through vertebrate evolution and whether its role and regulation are conserved within selected non-mammalian vertebrates.

Toll-like receptor 2 and 4 (TLR2 and TLR4) agonists differentially regulate secretory interleukin-1 receptor antagonist gene expression in macrophages

Treatment of macrophages with lipopolysaccharide (LPS) from Gram-negative bacteria or peptidoglycan (PGN) from Gram-positive bacteria activates multiple intracellular signaling pathways and a large, diverse group of nuclear transcription factors. The signaling receptors for PGN and LPS are now known to be the Toll-like receptors 2 and 4 (TLR2 and -4, respectively). While a large body of literature indicates that the members of the TLR family activate nearly identical cytoplasmic signaling programs, several recent reports have suggested that the functional outcomes of signaling via TLR2 or TLR4 are not equivalent. In the current studies, we compared the responses of the secretory IL-1 receptor antagonist (sIL-1Ra) gene to both LPS and PGN. Both LPS and PGN induced IL-1Ra gene expression; however, the combination of both stimuli synergistically increased sIL-1Ra mRNA expression and promoter activity, suggesting that the signals induced by PGN and LPS are not equivalent. While both LPS and PGN utilized the PU.1-binding sites in the proximal sIL-1Ra promoter region to generate a full response, additional distinct promoter elements were utilized by LPS or PGN. Activation of p38 stress-activated protein kinase was required for LPS- or PGN-induced IL-1Ra gene expression, but the p38-responsive promoter elements localized to distinct regions of the sIL-1Ra gene. Additionally, while the LPS-induced, p38-dependent response was dependent upon PU.1 binding, the PGN-induced, p38 response was not. Collectively, these data indicated that while some of the intracellular signaling events by TLR2 and TLR4 agonists are similar, there are clearly distinct differences in the responses elicited by these two bacterial products.

The roles of interleukin-1 and interleukin-1 receptor antagonist in antigen-specific immune responses

Despite evidence that interleukin (IL)-1 promotes the proliferation of some T helper 2 (Th2) cell clones in vitro, the physiological role of IL-1 in the regulation of antigen-specific immune responses remains undefined. Using a liposome-DNA delivery system, we transiently expressed IL-1 receptor antagonist (IL-1Ra) to suppress IL-1 functions at the site of the antigen-specific primary immune response. Our data indicate, for the first time, that IL-1Ra downregulates antigen-specific IL-4 and IgE responses, with concomitant enhancement of interferon-gamma and IgG2a responses in vivo. In addition, IL-1 can promote Th2 development in an IL-4-independent manner in vitro. Thus, the balance between endogenous IL-1 and IL-1Ra during the primary immune response can be an important factor in determining the antigen-specific effector function of T cells.

Expression and localization of IL-1beta mRNA is interrelated with cytoskeletal rearrangement in monocytes stimulated by adherence: a light microscopy in situ hybridization study

Differences in IL-1beta mRNA expression, stability and translation between non-adherent monocytes and those stimulated by adherence suggest that cytokine regulation is coupled to the function and assembly of cytoskeletal structures. In situ hybridization studies were performed to visualize expression and positioning of IL-1beta mRNA in adherently cultivated monocytes. IL-1beta mRNA expression was heterogeneous with high transcript levels found in spread or polarized cells. Transcripts were compartmentalized to the perinuclear region in spread cells, and partially redistributed with polarization. In contrast to mRNA distribution in other motile cell populations, IL-1beta mRNA did not localize to the distal or proximal actin cytoskeleton. Perinuclear confinement of transcripts required intact actin microfilaments. Treatment with cytoskeleton disruption and detergent extraction suggested that most non-translated IL-1beta mRNA was associated with intermediate filaments. In monocytes stimulated by LPS, IL-1beta, but not IL-1Ra transcripts were redistributed and partially associated, yet not bound to actin microfilaments. The present study demonstrates that IL-1beta mRNA expression and localization in adherent monocytes is interrelated with the cytoskeletal rearrangement upon adherence, spreading and polarization.

Escherichia coli-induced expression of IL-1 alpha, IL-1 beta, IL-6 and IL-8 in normal human renal tubular epithelial cells

The aim of the present study was to investigate whether the IL-1 family cytokines, in addition to IL-6 and IL-8, could be induced in normal human cortical epithelial cells in response to bacterial stimuli. Human renal tissue was obtained from 9 patients undergoing elective tumour nephrectomy. Renal cortical epithelial cells of tubular origin were prepared from the unaffected tissue. The proximal tubular cells were stimulated for 2, 6 and 24 h with a heat-inactivated pyelonephritogenic Escherichia coli strain DS-17. Cultured unstimulated tubular cells served as controls. IL-1 alpha, IL-1 beta, IL-1 receptor antagonist, IL-6, IL-8, IL-10, TNF-alpha, G-CSF and GM-CSF were analysed using immunohistochemistry at the single cell level. The nonstimulated cells were found to express low levels of IL-6 and IL-8 (mean value < 3% of total cells). In contrast, E. coli exposure resulted in significantly increased incidences of IL-6 and IL-8 expressing cells (mean values approximately 18% of total cells) peaking within two hours of stimulation (P < 0.008 and P < 0.02 versus non-stimulated cells, respectively). A gradual decrease was thereafter observed at 6 and 24 h, respectively, although persistently higher compared to controls. A different kinetic response was found for IL-1 alpha, IL-1 beta and IL-1 receptor antagonist-expressing cells, which peaked 24 h after E. coli stimulation (mean values 3--10%) (P < 0.008, P < 0.02, P < 0.02 versus non-stimulated cells, respectively). Low levels of TNF-alpha and GM-CSF were found in 3 of the 9 donated epithelial cells, peaking at 2 h, and IL-10 and G-CSF producing cells in 1 patient each. In conclusion we found that heat-inactivated pyelonephritic E. coli induced a proinflammatory cytokine response in the normal human proximal tubular cells including the IL-1 family, IL-6 and IL-8.

Cell culture conditions affect LPS inducibility of the inflammatory mediators in J774A.1 murine macrophages

Peripheral blood monocytes and tissue macrophages contribute significantly to the inflammatory response. Bacterial lipopolysaccharide (LPS) has profound effects on these cells including, but not limited, to differentiation into macrophages, production of reactive nitrogen and oxygen species and secretion of pro-inflammatory cytokines. Herein, we describe a variant of the J774A.1 murine macrophage line that is reversibly resistant to multiple effects of LPS when cultured in different types of media. J774A.1 cells are adherent and spread out when cultured in DMEM/F12; however, when cultured in RPMI 1640, the cells are rounded and relatively non-adherent. Different types of tissue culture plates, sera, and media supplements were not responsible for these changes. We examined LPS-induced reactive nitrogen species using the Greiss reagent. J774A.1 cells cultured in RPMI exhibit a 5-fold increase in nitrites in culture supernatants after LPS stimulation whereas those in DMEM/F12 do not. Zinc staining of total cellular protein of cells in COHLY ET AL. RPMI and DMEM/F12 electrophoresed on a SDS-PAGE showed noticeable banding differences. LPS-induced cytokine gene expression was studied by RT-PCR. LPS induced TNF-alpha, IL-1alpha, IL-1beta, and sIL-1Ra in cells cultured in RPMI but not those cultured in DMEM/F12 with the exception of TNFalpha. This report shows that environmental factors contained in the culture medium alone can reversibly alter the biochemical nature of monocytes and macrophages.

Interleukin-1 receptor antagonist synthesis by peripheral blood mononuclear cells: a novel predictor of morbidity among hemodialysis patients

Proinflammatory cytokines have been implicated in the short- and long-term morbidity experienced by hemodialysis (HD) patients. The present study, which is based on long-term follow-up of a cohort of 37 patients, relates peripheral blood mononuclear cell (PBMC) interleukin-1 receptor antagonist (IL-1Ra) synthesis (a reliable marker of IL-1beta synthesis in HD patients) and plasma levels of an acute phase reactant, lipopolysaccharide binding protein (LBP), to clinical outcomes. In July 1993, predialysis blood samples from these patients were collected and IL-1Ra synthesis by PBMC and plasma LBP was measured. Hospital records were reviewed and patient follow-up data were obtained until December 1997 (54 mo) or death, whichever occurred earlier. The effect of age, diabetes, endotoxin- and IgG-stimulated IL-1Ra synthesis, and plasma LBP levels on mortality was assessed using the Cox proportional hazard regression model. Poisson regression was used to determine potential relationships between the number of outcome events and each continuous risk factor. Twenty-two patients (59%) died during the follow-up period. Mortality was unrelated to IL-1Ra synthesis but did increase with age (relative risk, 1.05/yr; P: = 0.01) and diabetes (relative risk, 3.00/yr; P: = 0.03). Cardiovascular event rates were higher among older individuals and in those with higher endotoxin-stimulated PBMC IL-1Ra synthesis. Cardiovascular events increased with plasma LBP levels in the range of 9,000 to 12,000 pg/ml but then seemed to decrease. In contrast, older age and low IgG-stimulated IL-1Ra synthesis were associated with an increased risk of infectious events. The results of this study demonstrate an interesting link between stimulus-dependent variability in IL-1Ra synthesis by PBMC and clinical outcomes among patients on chronic HD and provide interesting targets for therapeutic interventions in this vulnerable patient population.

Gene expression profiling in human peripheral blood mononuclear cells using high-density filter-based cDNA microarrays

Microarray technology has provided the ability to analyse the expression profiles for thousands of genes in parallel. The need for highly specialised equipment to use certain types of microarrays has restricted the application of this technology to a small number of dedicated laboratories. High-density filter-based cDNA microarrays provide a low-cost option for performing high-throughput gene expression analysis. We have used a model system in which filter-based cDNA microarrays representing over 4000 known human genes were used to monitor the kinetics of gene expression in human peripheral blood mononuclear cells (PBMCs) stimulated with phytohaemagluttinin (PHA). Using software-based cluster analysis, we identified 104 genes that altered in expression levels in response to PHA stimulation of PBMCs and showed that there was a considerable overlap between genes with similar temporal expression profiles and similar functional roles. Comparison of microarray quantitation with quantitative PCR showed almost identical expression profiles for a number of genes. Coupled with the fact that our findings are in agreement with a large number of independent observations, we conclude that the use of filter-based cDNA microarrays is a valid and accurate method for high-throughput gene expression profiling.

Expression of interleukin 1 alpha and beta, and interleukin 1 receptor antagonist mRNA in the rat central nervous system after peripheral administration of lipopolysaccharides

Interleukin 1alpha (IL-1alpha) and IL-1beta, and the endogenous IL-1 receptor antagonist (IL-1ra) are known members of the IL-1 family. Using in situ hybridization histochemistry we demonstrated that following endotoxin injection (lipopolysaccharides, LPS, 2.0 mg/kg, i.p.) a time dependent expression and partly different expression patterns of the cytokines occurred within the rat brain and pituitary gland. All cytokines were observed in the choroid plexus. In addition, IL-1ra mRNA expressing cells were observed scattered in the brain parenchyma, whereas scattered IL-1beta mRNA expressing cells were restricted to central thalamic nuclei, the dorsal hypothalamus, and cortical regions, such as the parietal and frontal cortex. A strong IL-1beta mRNA expression was found in the circumventricular organs. In the pituitary gland, a low IL-1alpha and a high IL-1beta mRNA expression was observed, with the highest density of cytokine-expressing cells seen in the posterior pituitary. The cell types expressing the mRNA's of IL-1alpha, IL-1beta and IL-1ra were identified as monocytes in the circumventricular organs and the pituitary gland, and as microglia in the brain parenchyma. In conclusion, the present findings revealed that cytokine production in response to a peripheral endotoxin challenge mainly occurs in peripherally derived monocytes in the circumventricular organs and the pituitary gland. IL-1beta is the predominant form expressed, whereas the expression of IL-1alpha mRNA and IL-1ra mRNA is lower. Our observations support the view that peripherally derived IL-1 may play a role in the induction of centrally mediated illness symptoms.

Identification of rat IL-1beta, IL-2, IFN-gamma and TNF-alpha in activated splenocytes by intracellular immunostaining

We have developed a sensitive three-step indirect immunofluorescence method to identify individual rat cells that produce cytokines including IL-1beta, IL-2, IFN-gamma and TNF-alpha. Cultured rat splenocytes were polyclonally activated to cytokine synthesis by mitogens such as lipopolysaccharide or a combination of a protein kinase C activator (phorbol 12-myristate 13-acetate) and a calcium ionophore (ionomycin). Careful selection of either antigen affinity-purified polyclonal or monoclonal cytokine-detecting antibodies combined with gentle fixation and permeabilization of the cells enabled discrimination of cytokine-producing cells based on distinct morphological staining criteria. Cells making IL-2, IFN-gamma and TNF-alpha could be identified by a characteristic, intracellular, rounded, juxtanuclear immunofluorescence signal. This staining pattern reflected the accumulation of the intracellularly processed cytokines in the Golgi organelle of producer cells. The staining of cells that synthesized IL-1beta, which is not transported intracellularly via the endoplasmatic reticulum-Golgi pathway, generated a different, but distinct and reproducible staining pattern, IL-1beta producing macrophages expressed intense nuclear immunofluorescence with additional reticular, cytoplasmic signals. Furthermore, the use of biologically neutralizing detecting antibodies against the cytokines under study prevented recognition of surface-stained target cells that had bound secreted cytokines by cytokine-specific receptors. This modified staining technology enabled analysis of the kinetic pattern and the frequency of cytokine-producing cells in cultures of rat splenocytes after various modes of polyclonal activation.

Increased interleukin-1 (IL-1) and imbalance between IL-1 and IL-1 receptor antagonist during acute inflammation in experimental Shigellosis

Infection by the enteric bacterial pathogen Shigella results in intense mucosal inflammation and destruction of the colonic and rectal epithelium in infected humans. Initial bacterial translocation occurs through the follicle-associated epithelium. Previous experiments suggest that interleukin-1 (IL-1) is crucial to trigger inflammation, particularly in the follicular zones. During the first 4 hours of infection in a rabbit ligated-loop model of intestinal invasion, there are two salient characteristics: (i) a high concentration of IL-1alpha and IL-1beta, both in infected Peyer's patch tissue and in the corresponding efferent mesenteric blood, and (ii) a very low level of expression of IL-1 receptor antagonist (IL-1ra). These may reflect a combination of regulation of expression and secretion of IL-1alpha, IL-1beta, and IL-1ra by both resident and recruited phagocytes and the induction of mononuclear phagocyte apoptosis by Shigella. This low IL-1ra/IL-1 ratio likely accounts for the rapid, uncontrolled inflammation characteristic of shigellosis.

HIV-1 exposed dendritic cells show increased pro-inflammatory cytokine production but reduced IL-1ra following lipopolysaccharide stimulation

OBJECTIVES

Dendritic cells (DC) are potential first target cells in sexually transmitted HIV-1 infection. They are also considered to be central in the activation of naive T cells, which thereupon can become permissive for HIV-1. In addition, activated DC express effector molecules, which likely contribute to the direction of T helper (Th1/Th2)-specific immune responses.

METHODS

The capacity of cytokine and chemokine production in in vitro DC infected and uninfected with HIV-1 was assessed by enzyme-linked immunosorbent assay (ELISA) and by in situ immunocytochemical detection at the single cell level. Fluorescent in situ 5'-nuclease assay (FISNA) was used for quantitative evaluation of HIV-1 gag-positive cells.

RESULTS

Macrophage-tropic HIV-1 effectively infected 20-40% of in vitro cultured DC. However, this activity alone did not induce detectable cytokine or chemokine protein expression in DC. In contrast, lipopolysaccharide (LPS) stimulation of these HIV-1-infected DC resulted in a significantly increased level of cells producing tumour necrosis factor alpha (TNF-alpha) and interleukin (IL) 1beta but reduced frequencies of cells producing IL-1 receptor antagonist (IL-1ra) compared with the LPS-stimulated but uninfected DC cultures (P < 0.05). Furthermore, an extensive production of the beta-chemokines [RANTES, macrophage inflammatory proteins (MIP) 1alpha and 1beta] was detected in DC in response to both LPS and HIV-1 plus LPS.

CONCLUSIONS

These findings indicate that HIV-1 infected DC may have an increased proinflammatory activity. Elevated production of cytokines such as TNF-alpha and IL-1beta and reduced IL-1ra may contribute to enhanced replication of HIV-1 in bystander T cells. Gram-negative bacterial infection and gut-associated bacterial translocation in HIV-1-infected individuals may also result in endotoxin-mediated reactivation of HIV-1 in bystander CD4 CD45RO T cells caused by the increased production of proinflammatory cytokines in DC.

Immunohistochemical localization of interleukin-1beta, interleukin-1 receptor antagonist and interleukin-1beta converting enzyme/caspase-1 in the rat brain after peripheral administration of kainic acid

The temporal and anatomical distribution of members of the interleukin-1 system in the rat brain following intraperitoneal kainic acid administration was studied in relation to neurodegeneration as detected with in situ end labelling. Kainic acid administration (10 mg/kg, i.p.) resulted in the induced expression of interleukin-1beta, interleukin- receptor antagonist and caspase-1p10 immunoreactivity in areas known to display neuronal and tissue damage upon excitotoxic lesions. The induction of these proteins was transient. Interleukin-1 immunoreactivity appeared at 5 h, and the interleukin-1 receptor antagonist-immunoreactive cells were first detected at 12 h, whereas the induction of caspase- 1p10 expression was first detected 24 h after kainic acid injection. Double labelling with the microglial marker Ox42 confirmed that both interleukin-1beta and interleukin-1 receptor antagonist were mainly localized in microglial cells. The regional distribution of in situ end-labelled neurons was similar to the distribution of cells expressing interleukin-1beta and interleukin-1 receptor antagonist, whereas the distribution of caspase-1 was more limited. The in situ end-labelled neurons, were, similarly to the interleukin-1beta-positive cells, first detected at 5 h, which is earlier than the induction of caspase-1. Our results show that the induction of IL-1beta and IL-1 receptor antagonist proteins after kainic acid are closely associated with the temporal as well as the anatomical distribution of in situ end-labelled neurons, whereas the induction of caspase-1 protein exhibited a delayed temporal profile and limited distribution. Since cytokine production occurs in activated microglial cells, the inflammatory component seems to be a strong mediator of this type of excitotoxic damage. The late onset of the caspase-1 expression would seem to indicate that this enzyme has no fundamental role in directly causing neuronal cell death induced by systemic kainic acid.

Pathophysiological role of the cytokine network in the anterior pituitary gland

Recent evidence has demonstrated that cytokines and other growth factors act in the anterior pituitary gland. Using the traditional criteria employed to determine autocrine or paracrine functions our review shows that, in addition to their role as lymphocyte messengers, certain cytokines are autocrine or paracrine regulators of anterior pituitary function and growth. The cytokines known to regulate and/or be expressed in the anterior pituitary include the inflammatory cytokine family (IL-1 and its endogenous antagonist, IL-1ra; TNF-alpha, and IL-6), the Th1-cytokines (IL-2 and IFN-gamma), and other cytokines such as LIF, MIF, and TGF-beta. This review examines at the cellular, molecular, and physiological levels whether: (1) each cytokine alters some aspect of pituitary physiology; (2) receptors for the cytokine are expressed in the gland; and (3) the cytokine is produced in the anterior pituitary. Should physiological stimuli regulate pituitary cytokine production, this would constitute additional proof of their autocrine/paracrine role. In this context, we analyze in this review the current literature on the actions of cytokines known to regulate anterior pituitary hormone secretion, selecting the in vivo studies that support the direct action of the cytokine in the anterior pituitary. Further support for direct regulatory action is provided by in vitro studies, in explant cultures or pituitary cell lines. The cytokine receptors that have been demonstrated in the pituitary of several species are also discussed. The endogenous production of the homologous cytokines and the regulation of this expression are analyzed. The evidence indicating that cytokines also regulate the growth and proliferation of pituitary cells is reviewed. This action is particularly important since it suggests that intrinsically produced cytokines may play a role in the pathogenesis of pituitary adenomas. The complex cell to cell communication involved in the action of these factors is discussed.

Retinoic acid differentially regulates interleukin-1beta and interleukin-1 receptor antagonist production by human alveolar macrophages

Mechanism in the pathogenesis of acute respiratory distress syndrome which is the clinical feature of pulmonary involvement in retinoic acid (RA) syndrome has been investigated. Pulmonary infiltration of matured neutrophils and leukemic cells is thought to be associated with the pathogenesis of pulmonary involvement in RA syndrome; however. Little is known about the mechanism in pulmonary infiltration of these cells. In the present study, we examined the effect of RA on IL-1beta and IL-1ra production by human alveolar macrophages in order to clarify the mechanism in pulmonary infiltration of neutrophils, since IL-1 has been shown to initiate neutrophil recruitment into the lung through up-regulated expression of adhesion molecules on vascular endothelium. RA enhanced IL-1beta and inhibited IL-1ra production by 4beta phorbol 12beta-myristate-13alpha acetate (PMA)- and lipopolysaccharide (LPS)-stimulated human alveolar macrophages. These results show that RA differentially regulates IL-1beta and IL-1ra production by alveolar macrophages and indicate that an imbalanced production between IL-1beta and IL-1ra may contribute to initiating neutrophil recruitment into the lung through up-regulated expression of adhesion molecules.

The Differential Production of Three Forms of IL-1 Receptor Antagonist by Human Neutrophils and Monocytes

IL-1R antagonist (IL-1Ra) exists as three well-characterized isoforms. The 17-kDa secretory IL-1Ra (sIL-1Ra) and 18-kDa intracellular IL-1Ra (icIL-1RaI) arise by alternative transcription of the same IL-1Ra gene. The recently described 16-kDa intracellular IL-1Ra (icIL-1RaII) is formed by alternative translation initiation of sIL-1Ra mRNA. Transcription and translation of IL-1Ra isoforms were examined in LPS-stimulated human neutrophils and PBMC using RT-PCR, ELISA, and Western blot analysis. LPS stimulation of neutrophils resulted in elevated sIL-1Ra mRNA levels by 1 h, whereas icIL-1RaI mRNA remained undetectable through 22 h of culture. Extracellular glycosylated sIL-1Ra protein and intracellular icIL-1RaII were observed in LPS-stimulated neutrophils by 3 h of culture; no icIL-1RaI protein was detected by immunoblot. LPS stimulation of PBMC resulted in elevated sIL-1Ra mRNA levels by 1 h and detectable icIL-1RaI mRNA at 8 h of culture. LPS-stimulated PBMC demonstrated extracellular glycosylated sIL-1Ra protein and intracellular icIL-1RaII within 3 h of stimulation, whereas detection of icIL-1RaI protein was delayed until 15 h of culture. Subcellular localization experiments established that both icIL-1RaI and icIL-1RaII were present primarily within the cytoplasmic compartment, as expected by their lack of a signal peptide. These results demonstrate that although both LPS-stimulated neutrophils and PBMC synthesize sIL-1Ra and icIL-1RaII, only PBMC transcribe and translate icIL-1RaI. Furthermore, sIL-Ra transcription and translation (and translation of icIL-1RaII) are early events, whereas icIL-1RaI transcription in PBMC is delayed.

Attenuation of ischemic inflammatory response in mouse brain using an adenoviral vector to induce overexpression of interleukin-1 receptor antagonist

It has been demonstrated that administration of an interleukin-1 receptor antagonist protein (IL-1ra) reduces ischemic brain injury; however, the detrimental mechanism initiated by interleukin-1 (IL-1) in ischemic brain injury is unclear. In this study, we used mice that were transfected to overexpress human IL-1ra to elucidate the role of IL-1 in the activation of the inflammatory response after middle cerebral artery occlusion (MCAO). Myeloperoxidase (MPO) activity and immunohistostaining were used as a marker of polymorphonuclear leukocytes (PMNL) infiltration. Adenoviral vector (1 x 10(9) particles) was administered by injection into the right lateral ventricle in mice. Five days later, MCAO was performed on the mice using a suture technique. Permanent MCAO was achieved for 24 hours in the Ad.RSVIL-1ra-transfected. Ad.RSVlacZ-transfected, and saline (control) mice. Myeloperoxidase activity was quantified in each region and localization of MPO was determined by immunohistochemistry. After 2 hours of MCAO, the surface cerebral blood flow was reduced to 13.5% +/- 3.4%, 10.75% +/- 2.6%, and 10.9% +/- 2.6% of baseline in the ischemic hemisphere in Ad.RSVIL-1ra-transfected, Ad.RSVlacZ-transfected, and saline-treated mice, respectively. The MPO activity in the ischemic hemisphere in the Ad.RSVlacZ group was similar to that in the saline control group (cortex: 0.40 +/- 0.22 versus 0.33 +/- 0.11; basal ganglia: 0.46 +/- 0.23 versus 0.49 +/- 0.17; P > 0.05); however, it was significantly reduced in the Ad.RSVIL-1ra group (cortex: 0.18 +/- 0.07; basal ganglia: 0.26 +/- 0.15; P < 0.05). Myeloperoxidase immunohistochemistry showed that the massive accumulation of MPO-positive cells in the ischemic cortex, striatum, and corpus callosum regions was greatly attenuated in Ad.RSVIL-1ra-transfected mice. Our results indicate that Ad.RSVIL-1ra-transfected mice provide a useful tool to study the mechanism of action of IL-1. The MPO activity assay and immunostaining after 24 hours of focal ischemia were significantly reduced in IL-1ra gene-transfected mice, suggesting that IL-1 may play an important role in the activation of inflammatory cells during focal cerebral ischemia.

Kainic acid induced expression of interleukin-1 receptor antagonist mRNA in the rat brain

The endogenous interleukin-1 receptor antagonist (IL-1ra), a protein with partial homology with the proinflammatory cytokine interleukin-1beta (IL-1beta), prevents binding of IL-1beta to the signalling receptor. Exogenous IL-1ra has been shown to reduce the neuronal damage occurring after excitotoxic amino acid administration and ischemia. In the present study, in situ hybridization histochemistry was employed to investigate the regulation of endogenous IL-1ra mRNA expression in the rat brain after peripheral administration of kainic acid (10 mg/kg). IL-1ra mRNA expression was markedly induced in the hippocampus, thalamus, amygdala, piriform cortex, perirhinal cortex, entorhinal cortex, and to a lesser extent in the hypothalamus, and parietal and temporal cortex. The expression was first detected at 5 h after the kainic acid administration and it was markedly increased at 24 h. No signal was detected at 4 days after the injection. The majority of the cells expressing IL-1ra mRNA displayed the morphological characteristics of microglia. Expression of IL-1ra mRNA in neurons occurred mainly in the piriform and perirhinal cortex. The distribution pattern of IL-1ra mRNA expressing microglia-like cells was similar to that of cells labelled with ED1, a marker for activated microglia. The induction of IL-1ra mRNA expression may represent an endogenous response to balance IL-1 receptor mediated activity in the brain following kainic acid administration, conceivably to elicit neuroprotective and/or antiinflammatory effects.

Interleukin-1, interleukin-1 receptors and interleukin-1 receptor antagonist

IL-1 (IL-1 alpha or IL-1 beta) is the prototypic "multifunctional" cytokine. Unlike the lymphocyte and colony stimulating growth factors, IL-1 affects nearly every cell type, and often in concert with other cytokines or small mediator molecules. Although some lymphocyte and colony stimulating growth factors may be therapeutically useful, IL-1 is a highly inflammatory cytokine and the margin between clinical benefit and unacceptable toxicity in humans is exceedingly narrow. In contrast, agents that reduce the production and/or activity of IL-1 are likely to have an impact on clinical medicine. In support of this concept, there is growing evidence that the production and activity of IL-1, particularly IL-1 beta, are tightly regulated events as if nature has placed specific "road blocks" to reduce the response to IL-1 during disease. In addition to controlling gene expression, synthesis and secretion, this regulation extends to surface receptors, soluble receptors and a receptor antagonist. Investigators have studied how production of the different members of the IL-1 family is controlled, the various biological activities of IL-1, the distinct and various functions of the IL-1 receptor (IL-1R) family and the complexity of intracellular signaling. Mice deficient in IL-1 beta, IL-1 beta converting enzyme (ICE) and IL-1R type I have also been studied. Humans have been injected with IL-1 (either IL-1 alpha or IL-1 beta) for enhancing bone marrow recovery and for cancer treatment. The IL-1 specific receptor antagonist (IL-1Ra) has also been tested in clinical trials.

The Th1 and Th2 cytokines IFN-gamma and IL-4 antagonize the inhibition of monocyte IL-1 receptor antagonist by glucocorticoids: involvement of IL-1

Monocytes express IL-1 and IL-1 receptor antagonist (IL-1Ra) in response to lipopolysaccharide (LPS). IL-1 self-induction contributes to the increase in IL-1 following LPS stimulation. LPS-stimulated IL-1 and IL-1Ra production are inhibited by glucocorticoids. In the present work we examined the regulation of IL-1Ra by Th1 cytokine IFN-gamma, Th2 cytokine IL-4, glucocorticoids and IL-1 in human monocytes. We demonstrate that IL-1 contributes to LPS-induced IL-1 Ra expression as shown by IL-1 blockade in LPS-stimulated monocytes using a specific anti-IL-1beta antibody or recombinant IL-1Ra. Glucocorticoids inhibited IL-1beta-stimulated IL-1Ra mRNA expression and protein production. Glucocorticoids inhibited both IL-1-mediated and non-mediated LPS stimulation of IL-1Ra expression. Both IFN-gamma and IL-4 reversed the inhibitory effect of glucocorticoids on IL-1Ra expression and secretion. The effect of IFN-gamma was blocked by pretreatment of monocytes with an anti-IL-1beta blocking antibody, whereas the effect of IL-4 could not be blocked, demonstrating that IFN-gamma acts through a mechanism dependent on endogenous IL-1 production, whereas IL-4 acts through an IL-1-independent one. Consistent with this finding, IFN-gamma (but not IL-4) failed to reverse the inhibitory effect of glucocorticoids when stimulated by IL-1, and only IL-4 combined with IL-1 showed synergism resulting in an increase in IL-1 Ra production. The differential regulation and involvement of IL-1 in the expression of IL-1Ra by IFN-gamma, IL-4 and glucocorticoids sets the level of monocyte responsiveness during the Th1 or Th2 responses.

Interleukin-1 receptor antagonist: role in biology

The interleukin-1 receptor antagonist (IL-1Ra) is a member of the IL-1 family that binds to IL-1 receptors but does not induce any intracellular response. Two structural variants of IL-1Ra have previously been described: a 17-kDa form that is secreted from monocytes, macrophages, neutrophils, and other cells (sIL-1Ra) and an 18-kDa form that remains in the cytoplasm of keratinocytes and other epithelial cells, monocytes, and fibroblasts (icIL-1Ra). An additional 16-kDa intracellular isoform of IL-1Ra has recently been described in neutrophils, monocytes, and hepatic cells. Both of the major isoforms of IL-1Ra are transcribed from the same gene through the use of alternative first exons. The two promoters regulating transcription of the secreted and intracellular forms have been cloned, and some of the functional cis-acting DNA regions have been characterized. The production of IL-1Ra is stimulated by many substances including adherent IgG, other cytokines, and bacterial or viral components. The tissue distribution of IL-1Ra in mice indicates that sIL-1Ra is found predominantly in peripheral blood cells, lungs, spleen, and liver, while icIL-1Ra is found in large amounts in skin. Studies in transgenic and knockout mice indicate that IL-1Ra is important in host defense against endotoxin-induced injury. IL-1Ra is produced by hepatic cells with the characteristics of an acute phase protein. Endogenous IL-1Ra is produced in numerous experimental animal models of disease as well as in human autoimmune and chronic inflammatory diseases. The use of neutralizing anti-IL-1Ra antibodies has demonstrated that endogenous IL-1Ra is an important natural antiinflammatory protein in arthritis, colitis, and granulomatous pulmonary disease. Treatment of human diseases with recombinant human IL-1Ra showed an absence of benefit in sepsis syndrome. However, patients with rheumatoid arthritis treated with IL-1Ra for six months exhibited improvements in clinical parameters and in radiographic evidence of joint damage.

Interleukin-1

Interleukin-1 (IL-1) is the prototypic pro-inflammatory cytokine. There are two forms of IL-1, IL-1alpha and IL-1beta and in most studies, their biological activities are indistinguishable. IL-1 affects nearly every cell type, often in concert with another pro-inflammatory cytokine, tumor necrosis factor (TNF). Although IL-1 can upregulate host defenses and function as an immunoadjuvant, IL-1 is a highly inflammatory cytokine. The margin between clinical benefit and unacceptable toxicity in humans is exceedingly narrow. In contrast, agents that reduce the production and/or activity of IL-1 are likely to have an impact on clinical medicine. The synthesis, processing, secretion and activity of IL-1, particularly IL-1beta, are tightly regulated events. A unique aspect of cytokine biology is the naturally occurring IL-1 receptor antagonist (IL-1Ra). IL-1Ra is structurally similar to IL-1beta but lacking agonist activity is used in clinical trials to reduce disease severity. In addition, regulation of IL-1 activity extends to low numbers of surface receptors, circulating soluble receptors and a cell surface "decoy" receptor to down-regulate responses to IL-1beta. This review updates the current knowledge on IL-1.

Interleukin-1 and interleukin-1 receptor antagonist in systemic lupus erythematosus

Interleukin-1 (IL-1) is thought to play an important role in the immunopathology of systemic lupus erythematosus (SLE). IL-1 receptor antagonist (IL-1ra) exhibits a dose-responsive inhibition of IL-1 effects, and Fcr receptors play a key role in IL-1ra production. To clarify the relationship between IL-1, IL-1 receptor antagonist (IL-1ra) production, and Fcr receptors in SLE, fifteen untreated lupus patients (9 females and 6 males) were evaluated. IL-1 and IL-1ra production from both monocytes and neutrophils was determined by both a murine thymocyte proliferation assay and ELISA. The expression of Fcr receptors on both monocytes and polymorphonuclear cells was measured by flow cytometry. There was no significant difference between IL-1 beta and IL-1ra production from ex vivo monocytes between lupus patients and normals. However, serum IL-1ra was significantly higher in lupus patients than in normals. The expression of FcrRII (CD32) on monocytes was lower in lupus patients than in normals. There was no correlation between the expression of FcrRII and the serum immune complexes; the production of IL-1ra and the expression of CD32, serum immune complex levels, and serum IgG. Both serum IL-ra and the production of IL-1ra had no correlation to SLEDAI, C3, C4, C1q, or ESR. These observations suggest that although IL-1 and IL-1ra may not play a major role in the initiation of pathogenesis of lupus, the low FcrRII expression in lupus may reflect low immune complex clearance and contribute to disease pathogenesis.

Interstitial pneumonitis in bone marrow transplant recipients is associated with local production of TH2-type cytokines and lack of T cell-mediated cytotoxicity

BACKGROUND

Interstitial pneumonitis, especially associated with cytomegalovirus (CMV) infection, is a serious complication after bone marrow transplantation (BMT), with a high fatality rate despite adequate antiviral treatment. The aim of this study was to elucidate the local immunopathogenesis of interstitial pneumonitis caused by CMV or other agents in BMT recipients.

METHODS

Cryopreserved lung tissue obtained from 12 patients with interstitial pneumonitis following BMT was analyzed for cytokine production at the single-cell level using a cytokine-specific monoclonal antibody and immunohistochemical technique. Cytokine production in individual cells was analyzed using monoclonal antibodies to 23 different human cytokines: interleukin (IL)-1 to IL-13, tumor necrosis factor (TNF)-alpha, TNF-beta, interferon-gamma (IFNgamma), granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and transforming growth factor (TGF)-beta1 to 3.

RESULTS

Marrow transplant patients with interstitial pneumonia had increased numbers of infiltrating alveolar macrophages, CD3+, CD4+ T cells, and CD40+ B cells and significantly increased numbers of IL-4-, IL-10-, IL-1-, TGF-beta1-, TGF-beta2-, and TGF-beta3-producing cells than controls. IL-2-, IFN-gamma-, and TNF-beta-producing cells were undetectable in most patients with CMV pneumonitis (n=7). Neither perforin-positive CD8+ T lymphocytes nor up-regulation of the apoptotic pathway was detected in lung tissue from patients with interstitial pneumonia. In contrast, extensive local production of IgA, IgG, and IgM was demonstrated in all patients. Intracellular and extensive extracellular deposition of CD68, the L-1 antigen synthesized in CD14+ macrophages, was found.

CONCLUSIONS

The cytokine profile suggested that Th1-type cytokine production was absent, whereas production of Th2-type cytokines was significantly up-regulated. Interstitial pneumonitis in BMT recipients with fatal outcome (11/12 patients) was associated with dysregulation in the local cytokine network notable for a predominant Th2 immune response with minimal or absent T cell-mediated cytotoxicity.

Plasma interleukin-1alpha, interleukin-1beta and interleukin-1 receptor antagonist levels in pre-eclampsia

The values of plasma interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta) and interleukin-1 receptor antagonist (IL-1ra) levels were evaluated as the markers of pre-eclampsia in 35 serial plasma samples from ten pregnant women who subsequently developed pre-eclampsia and in 74 plasma samples from 20 uncomplicated pregnancies, retrospectively. No correlation was found between plasma IL-1alpha, IL-1beta and IL-1ra levels, liver and renal function tests, thrombocyte and white blood cell counts, proteinuria, systolic and diastolic blood pressures and gestational weeks. Almost equal levels of IL-1alpha and IL-1beta were measured in all corresponding groups, but these were too few in number to statistically analyze. IL-1ra values were higher in the pre-eclampsia group than in the uncomplicated pregnancy group, at 20-25 and 31-35 gestational weeks significantly and 26-30 gestational weeks insignificantly and showed an increase during labor in both groups. It was found to have 58% positive predictivity, 100% negative predictivity, 50% specificity and 100% sensitivity at gestational weeks 20-25. According to these results, IL-1ra seems to be considered for its high negative predictivity in the exclusion of the probability of pre-eclampsia development during antenatal visits, but its plasma level is not correlated with the severity of the disease.

Human Th1 cells preferentially induce interleukin (IL)-1beta while Th2 cells induce IL-1 receptor antagonist production upon cell/cell contact with monocytes

The role of human T cells in the induction and regulation, upon cell/cell contact, of inflammatory responses by monocytic cells was investigated. The production of interleukin (IL)-1beta and IL-1 receptor antagonist (IL-1Ra) by the monocytic THP-1 cell line was measured upon contact with either Th1 or Th2 cell clones. CD4+ T cell clones specific for purified protein derivative of Mycobacterium tuberculosis, predominantly Th1 [high interferon (IFN)-gamma and low IL-4 producers], or tetanus toxoid, predominantly Th2 (low IFN-gamma and high IL-4 producers), were generated. Cell membranes from antigen-stimulated, but not from resting T cell clones induced dose-dependent cytokine production by THP-1 cells. Th1 clones induced higher levels of IL-1beta production (484-806 pg/ml) than did Th2 clones (21-114 pg/ml). In contrast, Th1 clones induced lower levels of IL-IRa (0.9-7.8 ng/ml) than did Th2 clones (7.0-49.6 ng/ml). Similar results were obtained when T cell clones were activated by cross-linked CD3 and CD28. IL-1beta production by THP-1 cells correlated with IFN-gamma production by T cell clones but was unaffected by IFN-gamma neutralization. IL-1Ra production by THP-1 cells correlated with IL-4 production by T cells and was partially inhibited by IL-4 neutralization. These data indicate that activated Th1 and Th2 cells express different molecules on the cell surface able to induce distinct pro-inflammatory (IL-1beta) or anti-inflammatory (IL-1Ra) responses in monocytes. This differential induction of molecules with opposite effects on inflammation stresses the functional heterogeneity in CD4+ T cells.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

Release of cytokines and proteases from human peripheral blood mononuclear and polymorphonuclear cells following phagocytosis and LPS stimulation

Release and cellular contents of pro- and anti-inflammatory cytokines, neutrophilic elastase and secretory leukocyte proteinase inhibitor (SLPI) were measured with enzyme-linked immunosorbent assay in peripheral blood mono- and polymorphonuclear cells stimulated with preopsonized yeast cells or lipopolysaccharide. Tumour necrosis factor alpha (TNF alpha) was also measured with a bioassay. TNF alpha production and soluble TNF alpha receptor I (sTNF RI) were demonstrated in the environment of both cell populations. The bioassay indicated levels of TNF alpha far below those detected by ELISA. The overall secretion of cytokines and their inhibitors was found to favour an anti-inflammatory balance in the environment of the stimulated cells. The interleukin-1 receptor antagonist (IL1-ra), compared with interleukin-1 beta (IL-1 beta), dominated the secretions from both cell types with a 100- to 1000-fold excess respectively. Most of the translated IL-1 beta was not secreted but found associated with the cellular compartments. In contrast to lipopolysaccharide (LPS) stimulation, preopsonized yeast cells stimulated a massive release of elastase from neutrophil cells.

Localization of IL-1, IL-2, IL-4, IL-8 and TNF in superficial bladder tumors treated with intravesical bacillus Calmette-Guerin

PURPOSE

Cytokines have been detected in the urine during the first hours after intravesical Bacillus Calmette Guerin (BCG) treatment against superficial bladder cancer. To investigate the long-lasting mucosal inflammatory response, we analyzed intracellular cytokines by immunohistochemistry in biopsies taken 2 weeks after BCG treatment.

MATERIALS AND METHODS

Tumor biopsies were obtained from 8 patients with noninvasive, papillary transitional cell carcinoma (TCC), and intracellular cytokines were visualized by immunohistochemistry using cytokine-specific monoclonal antibodies.

RESULTS

Interleukin (IL)-1 beta+ or tumor necrosis factor (TNF)-alpha+ cells were abundant in tumor and stroma. Interleukin-1 alpha, IL-2, IL-4, IL-8 and TNF-beta were variably expressed, while IL-10+ and interferon (IFN)-gamma+ cells were not detected. Among the few patients studied (5 responders and 3 nonresponders to BCG treatment) no single cytokine or cytokine profile was associated with clinical response to BCG therapy.

CONCLUSION

We conclude that the in situ cytokine response after BCG treatment is highly complex, since cytokine profiles differed among the 8 patients investigated and between tumor and surrounding tumor-free mucosa. Further studies, investigating larger numbers of patients, is required to clarify whether cytokine profiles correlate with the clinical response to BCG.

Elevated circulating levels of interleukin-1 receptor antagonist but not IL-1 agonists in hemophagocytic lymphohistiocytosis

The familial form of hemophagocytic lymphohistiocytosis (HLH) is an inherited disease with disturbed immunomodulation and characterized by fever, hepatosplenomegaly, cytopenia, hypertriglyceridemia, and coagulopathy, i.e., findings which are similar to many of the reported biological effects of the inflammatory cytokines. Due to the previously shown hypercytokinemia in active HLH with elevated levels of interleukin (IL)-6, tumor necrosis factor-alpha, and interferon-gamma, it has been suggested that cytokine dysregulation may be of pathophysiological importance. Here we have assayed the serum levels of the members of the IL-1 ligand family, the two agonists IL-1 alpha and IL-1 beta and the antagonist IL-1 receptor antagonist (IL-1ra), in nine children with HLH and cerebrospinal fluid (CSF) specimens from four children. Serum IL-1ra was elevated in all patients with active disease to a degree which correlated well with disease activity. Furthermore, the levels decreased day by day during treatment of a patient who suffered a relapse. Moreover, high levels of IL-1ra were also detected in CSF during active disease. However, IL-1 beta levels were all within normal limits and circulating IL-1 alpha levels were normal in all but two patients.

Antibody-targeted superantigen therapy induces tumor-infiltrating lymphocytes, excessive cytokine production, and apoptosis in human colon carcinoma

Bacterial superantigens are the most potent known activators of human T lymphocytes. To engineer superantigens for immunotherapy of human colon carcinoma, the superantigen, staphylococcal enterotoxin A (SEA) was genetically fused to the Fab region of the colon carcinoma-reactive monoclonal antibody C242. In the present study the effector mechanisms involved in the anti-tumor response to C242 Fab-SEA were characterized. Immunohistochemistry and computer-aided image analysis were used in studies of cryopreserved tumor tissue to evaluate the phenotype of infiltrating cells and their cytokine profiles in response to therapy. Human T cells and monocytes were recruited to the tumor area and penetrated the entire tumor mass within hours after injection of C242 Fab-SEA. The production of cytokines at the single-cell level was found to be dominated by tumor necrosis factor (TNF)-alpha, interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12, interferon (IFN)-gamma, granulocyte-macrophage colony-stimulating factor, and transforming growth factor-beta, whereas IL-1-alpha, IL-1ra, IL-1 beta, TNF-beta, IL-3, IL-6, and IL-8 were undetectable. Most of the TNF-alpha, IL-2, IL-12, and IFN-gamma were made by the infiltrating human leukocytes, while the colon carcinoma cells were induced to produce IL-4, IL-10, and TNF-alpha. Up-regulation of IFN-gamma receptors and TNF R p60 receptors was found, while the TNF R p80 receptor was absent. The cytokine production, T cell infiltration, and CD95 Fas receptor expression concomitantly occurred to induce programmed cell death in the tumor cells. This was followed by a strong reduction of the tumor mass that was seen within 24 h after C242 Fab-SEA infusion. These findings demonstrate that antibody-superantigen proteins efficiently recruit tumor-infiltrating lymphocytes actively producing a variety of cytokines likely to be essential for the therapeutic effects observed in the model. Although the humanized SCID model has obvious limitations in its predictive value for treatment of human cancer, we believe that these results encourage clinical evaluation of antibody-targeted superantigens.