ALBERT

Description: Recent studies have examined the synergistic effects of granulocyte- macrophage colony-stimulating factor (GM-CSF) and hematopoietin-1 (now identified as Interleukin-1, IL-1) on bone marrow colony formation. In the present report, human peripheral blood mononuclear cells (MNCs) were stimulated in vitro with recombinant human GM-CSF (rGM-CSF) and production of IL-1 alpha, IL-1 beta, and tumor necrosis factor (TNF) was measured by specific radioimmunoassays. In the MNCs of 20 individuals, rGM-CSF's ability to induce the three cytokines was variable. Nearly all donors responded to low-dose rGM-CSF (0.02 to 2 ng/mL) with production of TNF, whereas some individuals did not produce IL-1 alpha or IL-1 beta. The MNCs from some subjects stimulated with high-dose rGM-CSF (10 to 80 ng/mL) produced as much cytokine as in response to 10 ng/mL endotoxin. Localization (ie, extracellular or cell- associated cytokine) was specific for the cytokine rather than the stimulus. Indomethacin increased the amount of cytokine produced in response to rGM-CSF for IL-1 beta and TNF but not for IL-1 alpha. In addition, interferon-gamma (INF-gamma) upregulated the amount of TNF induced by rGM-CSF in all donors examined, with variable effect on IL-1 alpha and IL-1 beta. Suboptimal levels of endotoxin incubated with rGM- CSF did not alter the amount of IL-1 produced as compared with cells stimulated with rGM-CSF alone, whereas TNF production showed either no change or a slight decrease in production. These data suggest that GM- CSF may play an important role in the host defense response by stimulating production of these cytokines.

Description: Stimulators of human erythroid burst-forming units (BFU-E) and multipotential colony-forming cells (CFU-GEMM) can be produced by a number of different cell types. A product of human peripheral blood monocytes, interleukin 1 (IL-1), was evaluated for its ability to stimulate fibroblast cultures to produce stimulators of human bone marrow BFU-E and CFU-GEMM colony formation. BFU-E and CFU-GEMM colony formation was evaluated using low-density, nonadherent low-density, and T lymphocyte-depleted nonadherent low-density human bone marrow cells cultured in the presence of a source of pure human erythropoietin. Both human monocyte conditioned medium (MCM) and human recombinant IL-1 (hrIL-1) induced fibroblasts to produce stimulators of BFU-E and CFU- GEMM in a dose-dependent fashion with maximal colony formation occurring when fibroblasts were stimulated by 25% MCM or 140 ng/mL ROO6B hrIL-1, or 1.25 to 5 ng/mL ROO6T hrIL-1. Preincubation of MCM and hrIL-1 with an antibody to IL-1 inactivated the ability of MCM and hrIL- 1 to induce the release of erythroid and multipotential colony stimulating activity from fibroblasts. These results suggest that monocyte-derived IL-1 is involved in regulating the production of humoral stimulators of early human hematopoietic progenitors.

Description: Ciliary neurotrophic factor (CNTF) and interleukin-6 (IL-6) potentiate the elevation of serum corticosterone induced by suboptimal doses of interleukin-1 (IL-1). CNTF also potentiates IL-1-induced serum IL-6. Here, we report that four other cytokines (leukemia inhibitory factor [LIF], oncostatin M [OSM], interleukin-11 and cardiotrophin-1) also potentiated the elevation of serum corticosterone and IL-6 levels induced by IL-1. Furthermore, all the six cytokines studied induced the acute-phase protein serum amyloid A when administered alone. Because these cytokines differ both in structure and in function, but share gp130 as a subunit of their receptors, these results indicate that signaling through gp130 mediates potentiation of IL-1 activities. The potentiation of IL-1-induced serum corticosterone levels is not a consequence of the increased serum IL-6 observed after IL-1 administration. In fact, in IL-6 deficient mice, IL-1 increased serum corticosterone to a level comparable to that observed in wild-type mice. Thus, either endogenous IL-6 does not mediate IL-1-induced corticosterone increase, or its role may be fulfilled by other cytokines. To the extent that gp130-dependent cytokines may serve this role, they may be important feedback regulators of inflammation through the activation of the hypothalamus-pituitary-adrenal axis and the potentiation of acute-phase protein synthesis.

Description: Interleukin-1 receptor antagonist (IL-1ra) is a 22-Kd protein that shares homology with IL-1 beta, binds to the IL-1 receptor, but has no known agonist properties. This inhibitor appears to be the first cytokine whose sole function is to block the actions of another cytokine. Exogenous IL-1ra administration has been shown to reduce mortality in experimental septic shock. We now report that IL-1ra is endogenously produced and circulates in experimental inflammation and in clinical disease. After experimental endotoxemia in human volunteers, IL-1ra concentrations increase from a baseline concentration of 460 +/- 200 pg mL-1 to 14,870 +/- 290 pg mL-1 at 3 hours (P less than .05). IL-1ra is also detectable in all plasma samples from critically ill patients with a mean concentration of 8,680 +/- 2,060 pg mL-1 (range 320 to 55,370 pgs mL-1). In nonhuman primates, Escherichia coli septic shock induces elevated plasma levels of IL-4ra (P less than .05). However, in animals that eventually succumb to septic shock, Il-1ra appears in quantities presumed inadequate to block the pathologic sequelae associated with high IL-1 beta levels. The findings suggest that IL-1ra may play a role in modulating the systemic host responses to a variety of nonlethal disease states by altering the balance between cytokines and their antagonists.

Description: Bone marrow (BM) and peripheral blood (PB) cells from patients with juvenile chronic myelogenous leukemia (JCML) exhibit spontaneous in vitro proliferation. Several cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 beta (IL-1 beta), and tumor necrosis factor alpha (TNF alpha) have been implicated in supporting the growth of leukemic monocyte-macrophage colonies either by autocrine or paracrine pathways. In seven untreated JCML patients, we investigated the role of IL-1 in the spontaneous growth of these cells by specifically blocking IL-1 receptors. The IL-1 receptor antagonist (IL-1 Ra) was added to the clonogenic assays, and in each case significant (mean = 63%, range = 35% to 82%) inhibition of spontaneous proliferation was observed. Uncultured circulating cells from PB or BM of four out of five patients expressed IL-1 beta-specific mRNA and secreted the protein into the culture supernatants. Moreover, by means of reverse transcriptase-polymerase chain reaction (RT-PCR), we demonstrated that most of the spontaneously growing leukemic colony- forming unit cells (CFU-C) obtained from BM cells of two patients were positive for the presence of the IL-1 beta-specific mRNA. Despite the presence of a measurable amount of GM-CSF in JCML cell culture supernatants, GM-CSF-specific mRNA in CFU-C cells of four cases was not detected by RT-PCR. These data further support a central role for IL-1 beta in the pathogenesis of JCML and suggest that the use of IL-1 Ra could represent a novel therapeutic strategy against this disorder.

Description: Cultured mononuclear phagocytes produce soluble factors that stimulate endothelial cells to release GM-colony-stimulating activity (GM-CSA). One such factor was recently identified as interleukin 1 (IL 1). Studies were designed to determine which types of granulopoietic factors are released by IL 1-stimulated endothelial cells. Supernatants from endothelial cells cultured for 3 days in medium containing IL 1 alpha and beta were tested in both murine and human CFU-GM colony growth assays. The effect of conditioned media on differentiation of WEHI-3B myelomonocytic leukemic cells was also examined. Control media containing IL 1 alone or unstimulated endothelial cell-conditioned media contained no detectable CSA in any bioassay. Medium conditioned by IL 1-stimulated endothelial cells stimulated the clonal growth of both human and murine CFU-GM and induced macrophage differentiation of WEHI-3B cells. Treatment of these conditioned media with a highly specific neutralizing monoclonal G-CSF antibody completely inhibited their activity in the murine CFU-GM assay, but only partially inhibited GM colony growth by human marrow. Treatment of the active conditioned media with a neutralizing rabbit anti-human GM-CSF antibody partially reduced the activity of the media in the human GM-colony growth assay. G-CSF radioimmunoassay of endothelial cell culture supernatants and Northern blot analysis of endothelial cell cytoplasmic RNA for GM-CSF gene transcripts confirmed that IL 1 induced expression of both G-CSF and GM-CSF genes. Because treatment of media with both antibodies abrogated all activity in the human GM colony growth assay, we conclude that IL 1-stimulated endothelial cells release both G and GM-CSF and that these are the only granulopoietic factors detectable in clonogenic assays released by these cells in vitro.

Description: Stimulators of human erythroid burst-forming units (BFU-E) and multipotential colony-forming cells (CFU-GEMM) can be produced by a number of different cell types. A product of human peripheral blood monocytes, interleukin 1 (IL-1), was evaluated for its ability to stimulate fibroblast cultures to produce stimulators of human bone marrow BFU-E and CFU-GEMM colony formation. BFU-E and CFU-GEMM colony formation was evaluated using low-density, nonadherent low-density, and T lymphocyte-depleted nonadherent low-density human bone marrow cells cultured in the presence of a source of pure human erythropoietin. Both human monocyte conditioned medium (MCM) and human recombinant IL-1 (hrIL-1) induced fibroblasts to produce stimulators of BFU-E and CFU- GEMM in a dose-dependent fashion with maximal colony formation occurring when fibroblasts were stimulated by 25% MCM or 140 ng/mL ROO6B hrIL-1, or 1.25 to 5 ng/mL ROO6T hrIL-1. Preincubation of MCM and hrIL-1 with an antibody to IL-1 inactivated the ability of MCM and hrIL- 1 to induce the release of erythroid and multipotential colony stimulating activity from fibroblasts. These results suggest that monocyte-derived IL-1 is involved in regulating the production of humoral stimulators of early human hematopoietic progenitors.

Description: 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.

Description: Interleukin-13 (IL-13) belongs to the IL-4 gene family. Like IL-4, IL- 13 induces IL-1 receptor antagonist (IL-1Ra) synthesis with no effect on IL-1beta synthesis. We investigated whether IL-13 induces IL-1Ra synthesis via a pathway similar to IL-4. In human peripheral blood mononuclear cells, IL-13 (1 to 100 ng/mL alone induced IL-1Ra synthesis in a dose-dependent manner. A single amino acid mutant form of IL-4 (hIL4.Yl24D) induced IL-1Ra synthesis, acting as a partial agonist. However, hIL-4.Yl24D inhibited IL-1Ra synthesis induced by either IL-4 or IL-13. IL-13 alone induced accumulation of IL-1Ra mRNA. Furthermore, IL-13 reduced steady- state levels for IL-1beta mRNA but enhanced those for IL-1Ra mRNA in cells stimulated with lipopolysaccharide (LPS) or IL- 1alpha. Accordingly, IL-13 suppressed IL-1beta synthesis but enhanced IL-1Ra synthesis in these cells. IL-13 reduced the stability of IL- 1beta mRNA (2.9 v 1.7 hours) but failed to modify the stability of IL- 1Ra mRNA (2.7 v 2.5 hours). Moreover, IL-13 induced transcriptional activation of the IL-1Ra gene, but reduced IL-1beta gene transcription. Our results suggest that the commonality between IL-13 and IL-4 in inducing IL-1Ra synthesis results from the engagement of a subunit common to both receptors.

Description: 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.