Spontaneous Interleukin-1 Production Research Articles

EFFECTS OF DIESEL EXHAUST PARTICLES (DEP), CARBON BLACK, AND SILICA ON MACROPHAGE RESPONSES TO LIPOPOLYSACCHARIDE: EVIDENCE OF DEP SUPPRESSION OF MACROPHAGE ACTIVITY

The effects of diesel exhaust particle (DEP) exposure on alveolar macrophage (AM) response to ex vivo and in vivo lipopolysaccharide (LPS) challenge were determined by monitoring LPS-stimulated production of interleukin-1 (IL-1) and tumor necrosis factoralpha (TNF-alpha). The roles of the insoluble particulate and the organic compounds of DEP in altering pulmonary responses were evaluated by comparing the DEP-induced pulmonary responses to those of carbon black (CB), a carbonaceous particle with few adsorbed organic compounds, or to silica, a known pneumotoxic dust. Male SpragueDawley rats were exposed to a single intratracheal dose (5 or 35 mg/ kg body weight) of DEP, CB, or silica, or to saline vehicle. Rats were sacrificed 1, 3, or 7 d postexposure. To study the responsiveness to the bacterial product LPS, AM isolated from particleexposed rats were challenged ex vivo with LPS (0.1 mug/ 10 6 AM) and LPS-stimulated cytokine release was monitored. In addition, rats were exposed intratracheally to a single dose of DEP (5 mg/kg) and 3 d later exposed in vivo to 1 mg/kg LPS for 3 h prior to measurement of cytokine production by AM. DEP exposure resulted in neutrophil infiltration and elevated levels of albumin and lactate dehydrogenase (LDH) activity in the bronchoalveolar lavage fluid; these responses were not substantially different from those elicited by CB or silica exposure. AM from DEP-exposed rats showed increased spontaneous production of IL-1, but not TNF-alpha, while the opposite was true for CB or silica. Upon ex vivo challenge with LPS, AM from DEP-exposed rats showed a significant decrease in the secretion of TNF- and, to a lesser extent, IL-1, compared to the sum of the DEP and LPS effects. In contrast, AM from CB- or silica-exposed rats did not show this decreased responsiveness to subsequent LPS challenge. This inhibitory action of DEP on LPS-stimulated AM production of IL-1 and TNF- was further confirmed by the results obtained from rats exposed to both DEP and LPS in vivo. In summary, these results indicate that while DEP, CB, and silica all induce pulmonary inflammatory responses due to particle stimulation, only DEP suppress AM cytokine release in response to LPS stimulation. The contrasting cellular response with respect to DEP and CB exposures may be due to the presence of adsorbed organic compounds on DEP, which may contribute to the increased susceptibility of hosts to pulmonary infections after DEP exposure.

Hypoxia/reoxygenation stimulates endothelial cells to promote interleukin-1 and interleukin-6 production. Effects of free radical scavengers.

Vascular endothelium produces and/or interferes with various cytokines. Previous studies have demonstrated interactions of these inflammatory and immunological mediators with oxygen-derived free radicals. The present work examines the relationship between hypoxia/reoxygenation (H/R) and cytokine production by cultured endothelial cells. Human umbilical vein endothelial cell (HUVEC) monolayers were incubated for 24 h in normoxia or submitted to 5 h hypoxia/19 h reoxygenation. Then, interleukin-1 (IL-1) alpha and beta, and interleukin-6 (IL-6), were measured in culture supernatants by specific enzyme immunoassays and bioassays, respectively. Under these conditions, the spontaneous production of IL-1 and IL-6, detected in normoxic HUVEC, greatly increased after H/R treatment. The observed enhancement was cycloheximide-sensitive and, consequently, reflected a de novo protein synthesis. Superoxide dismutase and glutathione peroxidase prevented H/R-induced IL-1 and IL-6 increase. These results constitute the first demonstration that H/R stimulates HUVEC to promote IL-1 and IL-6 production and strongly suggest a role for oxygen-derived free radicals in the cytokine synthesis.

Modulation of Cell Proliferation and Cytokine Production in Acute Myeloblastic Leukemia by Interleukin-1 Receptor Antagonist and Lack of its Expression by Leukemic Cells

Interleukin-1 (IL-1) is spontaneously produced by acute myeloblastic leukemia (AML) cells. IL-1 also induces synthesis of colony-stimulating factors (CSFs) and sustains leukemic growth. An IL-1-specific inhibitor has been recently purified and cloned; this molecule binds to IL-1 receptors but has no IL-1 activity, fulfilling the characteristics of an IL-1 receptor antagonist (IL-1ra). Because high-affinity binding sites for IL-1ra were shown on AML cells by radioligand binding studies, we studied the effect of IL-1ra on the proliferative activity of blast cells isolated from 16 cases of AML. In each case, spontaneous proliferation was inhibited by addition of the IL-1ra in a dose-dependent manner (1 to 100 ng/mL). Culture supernatants of unstimulated leukemic cells contained IL-1 beta and granulocyte-macrophage CSF (GM-CSF), but when incubated with the IL-1ra, a reduction or disappearance of GM-CSF was observed in 8 of 10 cases, whereas spontaneous IL-1 production was reduced in four of seven cases. By Northern hybridization, IL-1 beta gene transcripts were shown in 20 of 23 AML cases, whereas IL-1ra-specific messenger RNA was present in only two of the patients studied. These data show a role for IL-1 in the spontaneous proliferation and cytokine production of AML cells and suggest that an imbalanced synthesis of IL-1 and of its natural receptor antagonist may contribute to the unrestricted growth of AML cells.

Modulation of cell proliferation and cytokine production in acute myeloblastic leukemia by interleukin-1 receptor antagonist and lack of its expression by leukemic cells

Interleukin-1 (IL-1) is spontaneously produced by acute myeloblastic leukemia (AML) cells. IL-1 also induces synthesis of colony-stimulating factors (CSFs) and sustains leukemic growth. An IL-1-specific inhibitor has been recently purified and cloned; this molecule binds to IL-1 receptors but has no IL-1 activity, fulfilling the characteristics of an IL-1 receptor antagonist (IL-1ra). Because high-affinity binding sites for IL-1ra were shown on AML cells by radioligand binding studies, we studied the effect of IL-1ra on the proliferative activity of blast cells isolated from 16 cases of AML. In each case, spontaneous proliferation was inhibited by addition of the IL-1ra in a dose- dependent manner (1 to 100 ng/mL). Culture supernatants of unstimulated leukemic cells contained IL-1 beta and granulocyte-macrophage CSF (GM- CSF), but when incubated with the IL-1ra, a reduction or disappearance of GM-CSF was observed in 8 of 10 cases, whereas spontaneous IL-1 production was reduced in four of seven cases. By Northern hybridization, IL-1 beta gene transcripts were shown in 20 of 23 AML cases, whereas IL-1ra-specific messenger RNA was present in only two of the patients studied. These data show a role for IL-1 in the spontaneous proliferation and cytokine production of AML cells and suggest that an imbalanced synthesis of IL-1 and of its natural receptor antagonist may contribute to the unrestricted growth of AML cells.

INHIBITORY EFFECT OF TNFα ANTIBODIES ON SYNOVIAL CELL INTERLEUKIN-1 PRODUCTION IN RHEUMATOID ARTHRITIS

The effect of tumour necrosis factor (TNFα) antibodies on synovial cell interleukin-1 (IL-1) production was investigated in 7 patients with rheumatoid arthritis and in 7 with osteoarthritis. Synovial cell IL-1 production was significantly reduced by anti-TNFα antibody in cultures from patients with rheumatoid arthritis, but antilymphotoxin antibody did not have this effect (except in 1 culture). In cultures from patients with osteoarthritis spontaneous IL-1 production was low, despite high concentrations of TNFα, and IL-1 production was not inhibited by anti-TNFα antibody. In rheumatoid arthritis, TNFα may be the main inducer of IL-1, and anti-TNFα agents may be useful in treatment.

Increased spontaneous production of interleukin-1 together with inhibitory activity in systemic sclerosis.

1. Increased spontaneous production of interleukin-1, measured as lymphocyte-activating factor activity, was seen in unstimulated monocytes from systemic sclerosis patients. 2. Inhibitory activity to interleukin-1 was seen in both normal and patient monocyte supernatants. 3. Inhibitory activity was significantly higher in unstimulated and stimulated monocyte supernatants from systemic sclerosis patients. 4. The net effect was an apparent decrease in lymphocyte-activating factor activity in the monocyte supernatants from systemic sclerosis patients. 5. These findings suggest a possible mechanism by which collagen deposition could be enhanced, thereby giving rise to the extensive fibrosis characteristic of systemic sclerosis.

Spontaneous production of interleukin-1—like factors from pregnant rabbit uterine cervix

Uterine cervical explants in culture from pregnant rabbits at term spontaneously synthesized and secreted three species of interleukin-1—like factors in culture medium. The addition of the exogenous mitogen lipopolysaccharide to the culture system induced further release of these factors. However, these phenomena were not observed with explants from nonpregnant cervices. The molecular weights of these factors estimated by gel filtration were approximately 49, 22, and 12 kDa, respectively, and were identical to those of interleukin-1 from rabbit macrophages and polymorphonuclear leukocytes. These results indicate that interleukin-1—like factors are involved in cervical ripening and dilatation, especially in the acceleration of collagenase production, at term.

Spontaneous and inducible interleukin 1 production from peripheral blood monocytes in bacterial and viral infections in children

Peripheral blood monocytes from children with severe bacterial infection showed a high level of spontaneous (unstimulated) production of interleukin 1 (IL-1). In viral respiratory or gastrointestinal infections there usually was little or no spontaneous IL-1 production from monocytes, and the values did not differ from those of children with no infections or inflammatory disease. Lipopolysaccharide-induced IL-1 production from monocytes was slightly but not significantly greater in bacterial infections than in viral infections and controls. Tuberculin (purified protein derivative)-induced IL-1 production from monocytes of patients with viral infections was significantly less than in bacterial infections and also slightly less than in controls. These results indicate that systemic bacterial infections activate spontaneous release of IL-1 from monocytes whereas uncomplicated viral infections usually do not. Tuberculin-inducible IL-1 activity of monocytes appears decreased in viral infections; this might be associated with suppressed cell-mediated immunity in such infections.

Idiopathic production of interleukin-1 in acquired immune deficiency syndrome.

We determined the capacity of peripheral blood monocytes from 19 patients with acquired immune deficiency syndrome (AIDS) or related conditions (1 with lymphadenopathy, 8 with AIDS-related complex, and 10 with AIDS) to produce intracellular and extracellular interleukin-1 (IL-1) spontaneously and upon stimulation with bacterial endotoxin. All patients were anti-human T-cell lymphotropic virus type III antibody positive. Results were compared with those obtained with 10 normal controls of similar age. A subset of patients who spontaneously produced high amounts of intracellular and extracellular IL-1 was identified. Total production of IL-1 in this subset was an average of 2.9 times that of controls. It is suggested that spontaneous production of IL-1 in this group represents an in vivo phenomenon since it was associated with more than 3 g of globulins per deciliter of serum, more than 2,300 mg of immunoglobulins per deciliter of serum, higher IgA values, higher titers of anti-Epstein-Barr virus antibodies, and lower neutrophil counts in peripheral blood. The role of Epstein-Barr virus, human immunodeficiency virus itself, or other infectious agents in spontaneous IL-1 production by these patients remains to be determined. Stimulation with endotoxin induced intracellular and extracellular IL-1 production to similar levels in patients and controls. These results show that AIDS patients are able to produce and release IL-1. High idiopathic production of IL-1 identified in some patients can help to explain the hypergammaglobulinemia seen in AIDS patients and might also be related to progression and severity of the disease.

Spontaneous production of Interleukin-1 by human alveolar macrophages

A culture system was developed in which human peripheral blood mononuclear cells depleted of monocytes did not proliferate in response to the lectin mitogen phytohemagglutinin (PHA). The response of these cells to PHA was reconstituted with both autologous and heterologous alveolar macrophages. In addition, a partial restoration of PHA responsiveness was seen when the monocyte-depleted cells (MDC) were cultured with supernatants from purified alveolar macrophages, indicating the presence of Interleukin-1 (IL-1) activity in these supernatants. This is the first evidence suggesting the production of IL-1 by tissue macrophages from normal human subjects. In contrast to previous studies of IL-1 production by blood macrophages, it was found to be unnecessary to stimulate the alveolar macrophages in vitro to generate soluble factor activity. It was also found that alveolar macrophages produced active supernatants after only 2 hr in culture, whereas previous studies have indicated that blood monocytes must be cultured for at least 24 hr before active supernatants are produced. These differences may provide evidence that macrophages within the alveolar spaces are in an activated state.