Fanconi anemia genes act to suppress a cross-linker-inducible p53- independent apoptosis pathway in lymphoblastoid cell lines

Hypersensitivity to cross-linking agents such as mitomycin C (MMC) is characteristic of cells from patients suffering from the inherited bone marrow failure syndrome. Fanconi anemia (FA). Here, we link MMC hypersensitivity of Epstein-Barr virus (EBV)-immortalized FA lymphoblasts to a high susceptibility for apoptosis and p53 activation. In MMC-treated FA cells belonging to complementation group C (FA-C), apoptosis followed cell cycle arrest in the G2 phase. In stably transfected FA-C cells, plasmid-driven expression of the wild-type cytoplasmic FAC protein relieved MMC-dependent G2 arrest and suppressed p53 activation. However, in both FA and non-FA lymphoblasts, p53 seemed not to be instrumental in the induction of MMC-dependent apoptosis, since overexpression of a dominant-negative p53 mutant failed to affect cell survival. In addition, no differences in the level of Bcl-2 expression, an inhibitor of apoptosis, were detected between FA and non- FA cells either in the absence or presence of MMC. Our findings suggest that FAC and the other putative FA gene products may function in a yet to be identified p53-independent apoptosis pathway.     

Production of tumor necrosis factor-alpha and interleukin-6 in mice infected with group B streptococci.

Group B streptococci (GBS) are a leading cause of sepsis and meningitis in neonates. Since cytokines are thought to play an important role in septic shock, we have studied serum levels of tumor necrosis factor-alpha (TNF alpha) and interleukin-6 (IL-6) in BALB/c mice infected with type III GBS. TNF alpha and IL-6 were detected by the L929 cytotoxicity and the B9 proliferation assays, respectively, in serial serum samples obtained after infection. After i.p. challenge with an LD50, serum TNF alpha rose above baseline values as early as 3 hr, peaked at 7 hr, and returned to baseline values at 20 hr. IL-6 serum levels rose concomitantly with TNF alpha, peaking 8 hr after challenge. No serum TNF alpha activity was detected in the course of sublethal infections. However, a transient rise in TNF alpha levels was observed after i.v. inoculation of high numbers (greater than or equal to 1 x 10(8) of heat-killed GBS. When groups of mice were injected i.v. with a single dose of anti-TNF alpha rabbit serum 2 hr before challenge with an LD90 or LD30, no effect was noted in terms of survival, although the serum TNF alpha peak was completely abrogated. Serum TNF alpha does not seem to play an obligatory role in GBS-induced lethality of adult mice. However, further studies are needed to assess better the role of this cytokine in the pathogenesis of GBS sepsis.     

Suppression of ligand-dependent estrogen receptor activity by bone-resorbing cytokines in human osteoblasts.

Estrogens are important for bone homeostasis and are classified as antiresorptive agents. One of the mechanisms for this effect is the inhibition of cytokine-induced bone resorption, which is mediated in part through an interaction between the estrogen receptor (ER) and nuclear factor (NF)-kappaB in osteoblasts. We present evidence that bone-resorbing cytokines that activate NF-kappaB conversely inhibit ligand-dependent ER activity in the conditionally immortalized human osteoblast cell line, HOB-03-CE6. Treatment of HOB-03-CE6 cells with 17beta-estradiol (17beta-E2) up-regulated reporter gene activity [ERE-thymidine kinase (tk)-luciferase] 3- to 5-fold in a dose-dependent manner (EC50 = 1.0 pM). However, cotreatment of the cells with 17beta-E2 and increasing concentrations of either tumor necrosis factor-alpha (TNF alpha), interleukin-1alpha (IL-1alpha), or IL-1beta completely suppressed ERE-tk-luciferase activity in a dose-dependent manner (IC50 = 0.05-5.0 pM). On the other hand, treatment of the cells with growth factors either up-regulated or had no effect on ERE-tk-luciferase expression. Neither TNF alpha, IL-1alpha, nor IL-1beta treatment affected basal reporter gene activity in the cells, and the TNF alpha effect was reversed by a neutralizing antibody to the cytokine. TNF alpha treatment also suppressed ligand-dependent ER activity in MCF-7 human breast cancer cells, but not in Chinese hamster ovary cells that overexpressed human ER alpha, even though both cell lines responded to the cytokine as measured by the up-regulation of NFkappaB-tk-luciferase activity. TNF alpha treatment did not affect the steady state levels of either ER alpha or ER beta messenger RNA expression by the HOB-03-CE6 cells, nor did it reduce [125I]17beta-E2 binding. Moreover, TNF alpha treatment only weakly inhibited ligand-dependent glucocorticoid receptor activity in the HOB-03-CE6 cells. Bone-resorbing cytokines, which do not signal through the NF-kappaB pathway, did not suppress ERE-tk-luciferase activity in HOB-03-CE6 cells. Treatment of the cells with 17beta-E2 partially suppressed the activation of NF-kappaB by TNF alpha, but did not block cytokine-induced IL-6 secretion. Finally, cotreatment of HOB-03-CE6 cells with an antisense oligonucleotide to NF-kappaB p50 partially reversed the suppression of ERE-tk-luciferase activity by TNF alpha. In summary, these data provide evidence for a potent feedback inhibition of estrogen action in human osteoblasts that is at least partly mediated by the activation of NF-kappaB.     

Detection of interleukin-1, interleukin-6, and tumor necrosis factor-alpha in the uterus during the second half of pregnancy in the mouse.

This study demonstrated interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF alpha) in the mouse uterus during the second half of pregnancy (days 9-18). High concentrations of IL-1 alpha mRNA and bioactive IL-1 were detected between days 12-17. IL-1 bioactivity decreased to very low levels as pregnancy approached parturition. IL-6 mRNA was detected from days 9-18, and IL-6 bioactivity approximately paralleled IL-1 bioactivity. High levels of IL-1 and IL-6 bioactivity, but not IL-1 or IL-6 mRNA, were detected in the placenta between days 12-17. Placental IL-1 and IL-6 also decreased to low levels near parturition. TNF alpha was expressed from days 9-17, and a peak of TNF alpha bioactivity was detected during the period immediately before parturition. TNF alpha mRNA and TNF alpha bioactivity were not detected in the placenta. On day 18, the day of parturition, the concentrations of IL-1, IL-6, and TNF alpha mRNA were very low relative to those on other pregnancy days. Immunocytochemistry with antibodies to IL-1, IL-6, and TNF alpha was used to confirm the presence of all three cytokines in uterine cells throughout the second half of pregnancy. Those data showing the kinetics of cytokine production during fetal development raise the possibility that cytokines and cytokine-induced mediators modulate cellular events during the late stages of pregnancy in the mouse.     

Circulating cytokine levels in patients with rheumatoid arthritis: results of a double blind trial with sulphasalazine.

Interleukin 1 (IL-1), IL-6, and tumour necrosis factor (TNF) alpha are pleiotropic cytokines produced predominantly by macrophages which have been implicated in the pathogenesis of rheumatoid arthritis (RA). Sulphasalazine has been shown to have disease modifying properties and to inhibit the production of cytokines in vitro. To evaluate the effect of sulphasalazine on cytokine production in vivo, serum cytokine levels were measured in a group of patients with RA entered into a randomised controlled trial. Serum levels of IL-1 alpha, IL-1 beta, IL-6, and TNF alpha were measured at baseline and at two monthly intervals for six months in 17 patients receiving sulphasalazine and in 22 patients treated with placebo. The two groups of patients had a similar age and sex distribution, had had RA for less than a year, had no joint erosions, and had not been treated previously with any other disease modifying drugs. In the 39 patients studied IL-1 alpha was detected (> 0.1 ng/ml) at baseline in 14 patients (median 0.24 ng/ml), IL-1 beta in 25 patients (median 1.0 ng/ml), TNF alpha in 27 patients (median 1.2 ng/ml), and IL-6 in 33 patients (median 0.44 ng/ml). In the group treated with sulphasalazine there was a progressive and significant decline in serum IL-1 alpha, IL-1 beta, and TNF alpha levels over the six month period (median levels at six months were < 0.1, 0.12, and 0.44 ng/ml respectively). Interleukin 6 levels were significantly reduced only at the four month time point (median level of 0.23 ng/ml). These reductions were associated with improvements in clinical and laboratory measures of disease activity. In contrast patients receiving the placebo showed no changes in serum cytokine levels and no improvement in clinical and laboratory indices of disease activity. These results suggest that sulphasalazine may exert its disease modifying effect partly by suppressing cytokine production in vivo.     

Decreased IL-1β and TNFα secretion in long-term bone marrow culture supernatant from Fanconi's anaemia patients

Abstracts: Recent studies have shown that abnormalities of cytokine and lymphokine secretion are involved in the pathophysiology of Fanconi's anaemia (FA). In the present study, we quantified IL-1β, IL-1 receptor antagonist (IL-1Ra), IL-6 and TNFα protein levels in the supernatant of long-term cultures generated from BM cells of FA patients. Cell-free conditioned medium from long-term bone marrow culture was harvested every week at confluence and tested for interleukin secretion. IL-1β, IL-1Ra, TNFα and IL-6 protein secretion was assessed using immunoassays. IL-6 secretion was similar between controls and FA supernatants from wk 1 to wk 4. TNFα released from FA cells was consistently found at very low levels compared to control cells during the first 3 wk. Furthermore, secretion of IL-1β by cells from FA was always more than 2 standard deviations below the value of IL-1β found in normal donor cells from wk 1 to wk 4. In conclusion, in addition to a stem cell defect, a marked decrease in IL-1β and TNFα secretion may be one of the mechanisms leading to bone marrow failure in individuals with Fanconi's anaemia.     

The Fanconi anemia complementation group C gene product: structural evidence of multifunctionality

The Fanconi anemia (FA) group C gene product (FANCC) functions to protect cells from cytotoxic and genotoxic effects of cross-linking agents. FANCC is also required for optimal activation of STAT1 in response to cytokine and growth factors and for suppressing cytokine-induced apoptosis by modulating the activity of double-stranded RNA-dependent protein kinase. Because not all FANCC mutations affect STAT1 activation, the hypothesis was considered that cross-linker resistance function of FANCC depends on structural elements that differ from those required for the cytokine signaling functions of FANCC. Structure-function studies were designed to test this notion. Six separate alanine-substituted mutations were generated in 3 highly conserved motifs of FANCC. All mutants complemented mitomycin C (MMC) hypersensitive phenotype of FA-C cells and corrected aberrant posttranslational activation of FANCD2 in FA-C mutant cells. However, 2 of the mutants, S249A and E251A, failed to correct defective STAT1 activation. FA-C lymphoblasts carrying these 2 mutants demonstrated a defect in recruitment of STAT1 to the interferon gamma (IFN-gamma) receptor and GST-fusion proteins bearing S249A and E251A mutations were less efficient binding partners for STAT1 in stimulated lymphoblasts. These same mutations failed to complement the characteristic hypersensitive apoptotic responses of FA-C cells to tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma. Cells bearing a naturally occurring FANCC mutation (322delG) that preserves this conserved region showed normal STAT1 activation but remained hypersensitive to MMC. The conclusion is that a central highly conserved domain of FANCC is required for functional interaction with STAT1 and that structural elements required for STAT1-related functions differ from those required for genotoxic responses to cross-linking agents. Preservation of signaling capacity of cells bearing the del322G mutation may account for the reduced severity and later onset of bone marrow failure associated with this mutation.     

Relation of serum cytokine concentrations to cardiovascular risk factors and coronary heart disease.

OBJECTIVE: To determine whether serum concentrations of the cytokines tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6), which regulate C reactive protein, are associated with cardiovascular risk factors and prevalent coronary heart disease. DESIGN: A population based cross sectional study. SUBJECTS AND METHODS: 198 men aged 50 to 69 years were part of a random population sample drawn from south London. Serum cytokine and C reactive protein concentrations were determined by enzyme linked immunosorbent assay. The presence of coronary heart disease was determined by Rose angina questionnaire and Minnesota coded electrocardiogram. RESULTS: Serum TNF alpha concentrations were positively related to body mass index and Helicobacter pylori infection, but inversely related to alcohol consumption. IL-6 concentrations were positively associated with smoking, symptoms of chronic bronchitis, age, and father having a manual occupation. TNF alpha was associated with increased IL-6 and triglycerides, and reduced high density lipoprotein cholesterol. IL-6 was associated with raised fibrinogen, sialic acid, and triglycerides. ECG abnormalities were independently associated with increases in IL-6 and TNF alpha, each by approximately 50% (P < 0.05 for TNF alpha, P < 0.1 for IL-6). The corresponding increases in men with an abnormal ECG or symptomatic coronary heart disease were 28% for TNF alpha and 36% for IL-6 (P = 0.14 for TNF alpha and P < 0.05 for IL-6). CONCLUSIONS: This study confirms that many of the phenomena with which C reactive protein is associated, are also associated with serum levels of cytokine, which may be the mechanism.     

Effects of Th1 and Th2 cytokines on cytokine production and ICAM-1 expression on synovial fibroblasts.

OBJECTIVES--To investigate the influence of the Th1 and Th2 lymphokines interleukins (IL)-4 and IL-13, interferon gamma (IFN gamma), and several monokines on the adhesion of mononuclear cells to synovial fibroblasts and intercellular adhesion molecule-1 (ICAM-1) expression and cytokine production of synovial fibroblasts in patients with osteoarthritis. METHODS--Synovial fibroblasts were isolated from patients with osteoarthritis and stimulated with IL-1 beta, IL-4, IL-6, IL-10, IL-12, IL-13, tumour necrosis factor alpha (TNF alpha), and IFN gamma. Subsequently, we determined the production of IL-1 alpha, IL-1 beta, IL-6, IL-10, IL-12, IFN alpha and TNF alpha, and the expression of ICAM-1 lymphocyte function associated antigen 3 (LFA-3), BB7, and major histocompatibility complex class II molecules on these cells. Furthermore, the adhesion of freshly isolated mononuclear cells from the peripheral blood was tested using a colourimetric cell-cell adhesion assay. RESULTS--Only production of IL-6 and the expression of ICAM-1 were observed. IL-1 beta and TNF alpha were the most potent stimulatory mediators of both cytokine production and ICAM-1 expression. IL-4 and IL-13 had differential effects as they upregulated cytokine production but downregulated IFN gamma induced ICAM-1 expression. In functional adhesion assays, TNF alpha, IL-1 alpha and, to a lesser extent, IFN gamma led to increased adhesion of mononuclear cells, whereas IL-4 and IL-13 had no effect. CONCLUSIONS--Our data indicate that Th1 and Th2 lymphokines can modulate the function (cytokine production and expression of adhesion molecules) of synovial fibroblasts.     

Tumor necrosis factor-alpha production by alveolar macrophages in heart-lung transplant recipients.

Tumor necrosis factor-alpha (TNF alpha) is a cytokine produced by mononuclear cells that amplifies inflammation and modulates expression of Class I and Class II histocompatibility antigens. Because of these properties, this cytokine may exert a central role in both the defense and the rejection of the transplanted lung. Utilizing an ELISA technique, we measured TNF alpha in vivo and in vitro in several compartments of lung transplant recipients and in normal subjects that included serum, bronchoalveolar lavage fluid (BAL), and media conditioned by alveolar macrophages (AM) and by autologous peripheral blood monocytes (PBM). Overall, stimulated production of TNF alpha by AM from lung recipients in vitro was less than that of cells from normal subjects in response to lipopolysaccharide (LPS) challenge, and stimulated production of TNF alpha by AM harvested during conditions of infection or acute and chronic rejection was less than that by cells from healthy lung recipients. AM from normal subjects and allograft recipients produced substantially more TNF alpha than autologous PBM, but release in vitro by PBM from recipients was the same as that from cells of normal subjects who were not immunosuppressed. Thus, systemic immunosuppression does not seem to affect the production of TNF alpha by PBM in vitro, but it may reduce production by AM, indicating different effects of immunosuppression on different compartments of mononuclear cells. This mediator was not detected at elevated levels in serum, and it was undetectable in BAL fluid. We conclude that AM from lung recipients are capable of producing TNF alpha, which would influence the defense and immunogenicity of the allograft.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production of various cytokines by normal human osteoblast-like cells in response to interleukin-1 beta and tumor necrosis factor-alpha: lack of regulation by 17 beta-estradiol.

We investigated, in five cell strains per experiment, whether several cytokines known or believed to have effects on bone resorption were produced by nearly homogeneous strains of cultured normal human osteoblast-like (hOB) cells that display virtually the complete phenotype of the mature osteoblast. In unstimulated hOB cells, we detected constitutive production of interleukin-6 (IL-6) (mean +/- SE, 122 +/- 32 pg/ml) and IL-8 (135 +/- 39 pg/ml), but not of IL-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), or tumor necrosis factor-alpha (TNF alpha). IL-1 beta in doses from 1-100 U/ml stimulated dose-dependent increases in IL-6 (r = 0.87; P less than 0.001) and IL-8 (r = 0.95; P less than 0.001). Similar increases occurred after stimulation with TNF alpha in doses from 3-300 U/ml. IL-1 beta and TNF alpha also stimulated GM-CSF production, but only at higher doses. 17 beta-Estradiol (10(-8) M) had no significant effect on the secretion of any of these cytokines, either constitutively or after stimulation with IL-1 beta or TNF alpha. Stimulated production of IL-4 was not detected after treatment with IL-1 beta or TNF alpha, and that of TNF alpha was not detected after treatment with IL-1 beta. We conclude that IL-6, IL-8, and GM-CSF, but not IL-4 and TNF alpha, are produced by highly differentiated normal human cells of the osteoblast lineage, but their secretion is not regulated by estrogen. However, we cannot exclude the possibility that estrogen regulation of these cytokines may occur during early stages of osteoblast differentiation.     

Effects of tumour necrosis factor-alpha on growth hormone and interleukin 6 mRNA in ovine pituitary cells.

The inflammatory cytokines tumour necrosis factor-alpha (TNF alpha), interleukin 1 (IL-1) and interleukin 6 (IL-6) have been demonstrated to influence pituitary hormone synthesis directly and via the hypothalamus. Furthermore, IL-6 is produced by some anterior pituitary cells suggesting a paracrine/autocrine role for this cytokine. We show that TNF alpha induces dispersed ovine pituitary cells to produce increased levels of growth hormone (GH) and IL-6 mRNA and secreted IL-6 in a dose and time dependent manner. TNF alpha at concentrations between 1-1000 U/ml increased GH and IL-6 mRNA, relative to control levels, by 5 h post-stimulation. For IL-6, TNF alpha increased specific mRNA at 5 h and 12 h but not 24 h post-stimulation. TNF alpha also induced secreted IL-6 to levels above that spontaneously secreted at all time points from 5 h to 48 h. Levels of common glycoprotein alpha-subunit and follicle stimulating hormone-beta (FSH beta) subunit mRNA were unaffected by TNF alpha. We conclude that TNF alpha can regulate both GH and IL-6 synthesis in dispersed ovine pituitary cells. The implications for paracrine/autocrine control of pituitary hormone synthesis in acute and chronic disease are discussed.     

Phenotypic correction of Fanconi anemia group C knockout mice

Fanconi anemia (FA) is a genetic disorder characterized by bone marrow failure, congenital anomalies, and a predisposition to malignancy. FA cells demonstrate hypersensitivity to DNA cross-linking agents, such as mitomycin C (MMC). Mice with a targeted disruption of the FANCC gene (fancc -/- nullizygous mice) exhibit many of the characteristic features of FA and provide a valuable tool for testing novel therapeutic strategies. We have exploited the inherent hypersensitivity of fancc -/- hematopoietic cells to assay for phenotypic correction following transfer of the FANCC complementary DNA (cDNA) into bone marrow cells. Murine fancc -/- bone marrow cells were transduced with the use of retrovirus carrying the human fancc cDNA and injected into lethally irradiated recipients. Mitomycin C (MMC) dosing, known to induce pancytopenia, was used to challenge the transplanted animals. Phenotypic correction was determined by assessment of peripheral blood counts. Mice that received cells transduced with virus carrying the wild-type gene maintained normal blood counts following MMC administration. All nullizygous control animals receiving MMC exhibited pancytopenia shortly before death. Clonogenic assay and polymerase chain reaction analysis confirmed gene transfer of progenitor cells. These results indicate that selective pressure promotes in vivo enrichment of fancc-transduced hematopoietic stem/progenitor cells. In addition, MMC resistance coupled with detection of the transgene in secondary recipients suggests transduction and phenotypic correction of long-term repopulating stem cells. (Blood. 2000;95:700-704)     

Interleukin-1 alpha also induces granulocyte-macrophage colony-stimulating factor in immature normal bone marrow cells.

The cytokine interleukin-1 (IL-1) plays a role in the regulation of normal as well as leukemic hematopoiesis. In acute myeloid leukemia (AML), IL-1 induces autocrine granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF) production, and these factors may then synergistically induce proliferation in AML blast cells. In this report, we show that IL-1 stimulates DNA synthesis of highly enriched normal bone marrow blast cells (CD34 positive, adherent cell depleted, CD3/CD14/CD15 negative). The stimulative effect of IL-1 can be blocked with neutralizing anti-TNF alpha and anti-GM-CSF antibodies and, most efficiently, by the combination of anti-TNF alpha and anti-GM-CSF, but not with anti-G-CSF antibody, suggesting that IL-1-induced proliferation was initiated through TNF and GM-CSF release. Concentrations of TNF and GM-CSF increased in the culture medium of normal bone marrow blast cells after IL-1 induction. Of the IL-1-induced cells, 12% were positive for GM-CSF mRNA by in situ hybridization, as opposed to 6% of non-induced cells. Thus, in addition to its effect on leukemic blast cells, IL-1 also acts on normal marrow blast cells. We propose a scheme where IL-1 stimulation of normal bone marrow blast cells leads to the induction of TNF alpha and GM-CSF, which in association stimulate DNA synthesis efficiently according to a paracrine or autocrine mechanism within the marrow blast cell compartment.     

A functionally active retrovirus vector for gene therapy in Fanconi anemia group C

Fanconi anemia (FA) is a rare genetic disorder characterized by progressive pancytopenia, congenital abnormalities, and a predisposition to malignancy. Recently, mutation in a novel gene named FACC (Fanconi anemia C complementing) has been identified as causing one type of FA. Here, we report successful functional complementation of four FA(C) cell lines using a retroviral vector to transfer a copy of the normal FACC gene. The hallmark of the FA cell phenotype is extreme sensitivity to cross-linking agents such as mitomycin C (MMC). Cell lines transduced by FACC viral vectors were distinguished by their ability to grow at concentrations of MMC several orders of magnitude higher than those concentrations inhibitory of parental controls. The genetically corrected cell lines were analyzed for susceptibility to MMC-induced chromosomal breakage and were found to have been normalized. These two different assays confirmed that our retroviral vectors were capable of transferring a functional FACC gene to lymphoid cell lines established from FA(C) patients. We next analyzed the ability of our viral vectors to functionally correct hematopoietic progenitor cells from a patient bearing a splice donor mutation. Progenitor cells were purified by an immunoaffinity column to enrich for cells with high CD34 expression. Similar to FA lymphoid cell lines, this patient's CD34-enriched cells were extremely sensitive to MMC. After infection of these progenitor cells with viral vectors bearing normal FACC, increased numbers of colonies formed both in the absence and presence of < or = 5 nmol/L MMC, but no colonies formed from uninfected cells, even in the absence of MMC. Polymerase chain amplification was used to confirm proviral DNA integration. Thus, retroviral vectors can be engineered to transfer a normal FACC gene to lymphoid cell lines and primary hematopoietic cells bearing four different FACC mutations. FA stem cells rescued by gene transduction should have a selective growth advantage within the hypoplastic FA marrow environment in vivo. These experiments suggest that gene therapy may be an effective treatment strategy for FA.     

Effect of interleukin-1 (IL-1) blockade on cytokine synthesis: I. IL-1 receptor antagonist inhibits IL-1-induced cytokine synthesis and blocks the binding of IL-1 to its type II receptor on human monocytes.

Interleukin-1 (IL-1) induces IL-1, tumor necrosis factor alpha (TNF alpha), and IL-6 gene expression and synthesis in a variety of cells. In this study, we investigated the ability of human recombinant IL-1 receptor antagonist (IL-1ra) to inhibit IL-1-induced cytokine production in human peripheral blood mononuclear cells (PBMC) and isolated monocytes. IL-1ra alone at concentrations as high as 1 microgram/mL did not induce IL-1 alpha, IL-1 beta, TNF alpha, or IL-6 synthesis. Suppression of IL-1-induced IL-1, TNF alpha, or IL-6 synthesis was dose-dependent (P less than or equal to .0001). At a twofold molar excess, IL-1ra inhibited IL-1-induced IL-1 or TNF alpha synthesis by 50% (P less than .01); an equimolar concentration of IL-1ra inhibited synthesis of these two cytokines by over 20% (P less than .05). A 10-fold molar excess of IL-1ra over IL-1 beta reduced IL-1 beta-induced IL-1 alpha by 95% (P = .01) and IL-1 alpha-induced IL-1 beta by 73% (P less than .01). IL-1ra added to PBMC 8 hours after stimulation with IL-1 beta was still able to inhibit IL-1 alpha, TNF alpha, and IL-6 synthesis (P less than or equal to .01). A similar reduction in IL-1 beta-induced IL-1 alpha was observed when IL-1 beta was removed from the cultures after 8 hours of stimulation (P less than .05), suggesting a prolonged presence of IL-1 or restimulation of IL-1 receptors on monocytes is required for the induction of cytokines. In elutriated monocytes, a 10-fold molar excess of IL-1ra reduced IL-1 beta-induced IL-1 alpha by 82% (P less than .05), TNF alpha by 64% (P = .05), and IL-6 by 47% (P less than .05). 125I-IL-1 beta was bound to purified monocytes, cross-linked, and immunoprecipitated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a band at 85 Kd corresponding to the 68-Kd IL-1 receptor type II (IL-1RtII). Excess unlabeled IL-1 beta or IL-1ra blocked the binding of 125I-IL-1 beta to the IL-1RtII. We conclude that IL-1ra inhibits IL-1-induced cytokine synthesis and competes with IL-1 for the IL-1RtII on human monocytes.     

Effect of flurbiprofen on cytokine production by human monocytes and U-937 and THP-1 cell lines.

Possible effects of nonsteroidal antiinflammatory drugs (NSAID) on inflammatory mediators other than arachidonic acid metabolites which might contribute to the antiinflammatory effects of these drugs have not been fully explored. We investigated the effects of an NSAID, flurbiprofen, on production of the cytokines tumor necrosis factor alpha (TNF alpha), interleukin 1 beta (IL-1 beta) and interleukin 6 (IL-6) by human peripheral blood monocytes and by the human cell lines U-937 and THP-1. Cytokine production was induced by 1 microgram/ml bacterial lipopolysaccharide (LPS) in both monocytes and cell lines, and cytokine levels in supernatants were measured by enzyme immunoassay. In monocytes, IL-6 was the major product while in both cell lines, TNF alpha was the major product. Flurbiprofen caused moderate inhibition of IL-1 beta and TNF alpha production by stimulated monocytes, but did not affect IL-6 production. In contrast, flurbiprofen completely abolished IL-6 production by both cell lines and substantially inhibited IL-1 beta and TNF alpha production. These observations raise the possibility that inhibition of cytokine production by flurbiprofen may contribute to the antiinflammatory properties of this drug.     

Interleukin-1 (IL-1)-induced IL-6- and IL-6-receptor-mediated release of human chorionic gonadotropin by choriocarcinoma cell lines (Jar and HCCM-5) activates adenosine 3',5'-monophosphate-independent signal transduction pathway.

The status of preservation of the ability to secrete cytokines, such as interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF alpha), and IL-6, and the cytokine-mediated regulatory cascade was investigated in four choriocarcinoma cell lines. Each cell line constitutively produced IL-6, but not IL-1 alpha, IL-1 beta, or TNF alpha. Jar and HCCM-5 cells responded to IL-6, releasing hCG by direct activation of IL-6 receptors (IL-6-R) with IL-6. Both cell lines also responded to IL-1, but failed to responded to TNF alpha. When stimulated with recombinant IL-1 alpha, both cell lines released IL-6 and activated the IL-6-R system to release hCG, whereas stimulation with TNF alpha failed to release hCG. The experiments showed that both the Jar and HCCM-5 cell lines possessed a partially intact cytokine-mediated cascade, suggesting that IL-1-induced IL-6 release and IL-6-R activation operate in an autocrine manner. In contrast, NUC-1 and SCH cells failed to respond to IL-6, IL-1, or TNF alpha. Although 8-bromo-cAMP, which is a cAMP analog, stimulates hCG release by Jar cells, it failed to stimulate IL-6 release. Moreover, cAMP-mediated hCG release was not blocked by PM1, an anti-IL-6-R antibody. This suggests that elevation of the cytoplasmic cAMP level might activate a pathway different from the IL-6- and IL-6-R-dependent pathway. Moreover, IL-1- and IL-6-mediated hCG release was not blocked by H8, a cAMP-dependent kinase inhibitor, which further suggests that the IL-1- and IL-6-mediated pathway functions independently of the cAMP-dependent pathway in releasing hCG in Jar cells.