Production Of IL-1alpha Research Articles

Endogenous interferon alpha/beta produced by Kupffer cells inhibits interleukin-1, tumor necrosis factor alpha production and interleukin-2-induced activation of nonparenchymal liver cells.

We have previously reported liver-specific interferon (IFN) alpha/beta production by murine Kupffer cells that was not observed with other tissue macrophages incubated in the absence of stimulators such as IFN gamma or lipopolysaccharide (LPS). Consequently, while interleukin-2 (IL-2) alone induced pronounced lymphokine-activated killer (LAK) activity from splenocytes, combination of anti-IFN alpha/beta antibody with IL-2 was required to generate significant LAK activity from nonparenchymal liver cells. This endogenous IFN alpha/beta production by Kupffer cells was not induced by LPS because (a) addition of polymyxin B did not abolish the positive effects of anti-IFN alpha/beta antibody on nonparenchymal liver cells, and (b) similar results were obtained when comparing the responses of LPS-responsive C3HeB/FeJ and LPS-hyporesponsive C3H/HeJ mice. The possibility of hepatotropic infection was also ruled out in that anti-IFN alpha/beta antibody enhanced hepatic but not splenic LAK cell induction in vitro in both conventional and germ-free C3H/HeN mice. IFN alpha/beta played an autoregulatory role by down-regulating the production of IL-1 and tumor necrosis factor alpha by Kupffer cells. However, the augmenting effect of anti-IFN alpha/beta antibody on LAK induction from non-parenchymal liver cells was not mediated through an increase in the level of either IL-1 or TNF alpha, as specific antisera against either cytokine did not abrogate this positive effect. Finally, flow-cytometry analysis showed that IFN alpha/beta significantly diminished the expression of IL-2 receptor alpha chain, indicating an inhibition of LAK cell generation at a relatively early stage of induction.

Monokine production by human T cells; IL-1 alpha production restricted to memory T cells.

The production of cytokines is a key event of inflammation. In this report we demonstrate that normal human T cells are capable to produce IL-1 alpha, IL-6, and TNF-alpha, cytokines formerly considered to be monokines. This production was optimal after stimulation with a combination of anti-CD2, PMA, and anti-CD28. All three cytokines were produced in a bioactive form. Both naive (CD4+CD45RA+) and memory (CD4+CD45RO+) subsets of T cells were shown to produce similar amounts of IL-6 and TNF-alpha. In contrast the production of IL-1 alpha was found to be completely restricted to the CD4+CD45RO+ subset. The finding that T cells are such potent producers of these important mediators of the inflammatory response might be a key observation in the appreciation of the role of T cells in chronic inflammation.

Human keratinocytes produce but do not process pro-interleukin-1 (IL-1) beta. Different strategies of IL-1 production and processing in monocytes and keratinocytes.

Keratinocytes comprise the majority of cells in the epidermis, the interleukin-1 rich layer of tissue contiguous with the outside world. Keratinocytes produce IL-1 alpha and beta mRNA in vitro, but only IL-1 alpha biological activity has been identified in keratinocyte cultures. In contrast, monocytes secrete biological activities attributable to both species of IL-1. Using several monoclonal antibodies to IL-1 beta, significant amounts of IL-1 beta protein could be found in keratinocyte cultures; all of this immunoreactive IL-1 beta was in the 31-kD form. This latent cytokine has been shown to bind inefficiently to the IL-1 receptor and to be (in relative terms) biologically inactive. Chymotrypsin cleaves 31-kD IL-1 beta at Tyr 113-Val 114, generating an 18-kD IL-1 species with activity equivalent to the authentic mature IL-1 beta (NH2-terminal Ala 117). Treatment of 31-kD keratinocyte IL-1 beta with chymotrypsin also generated an 18-kD molecule and significant IL-1 activity. Monocytes contain an IL-1 convertase enzyme that cleaves the IL-1 beta promolecule at Ala 117. We demonstrate here that keratinocytes do not contain such an IL-1 convertase activity, nor do they contain any activity capable of productively processing 31-kD IL-1 beta into a biologically active form. These data suggest that keratinocytes (and other non-bone marrow-derived cells) produce IL-1 beta in an inactive form that can be processed only after leaving the cell.

THE EFFECT OF CYCLOSPORINE ON THP-1 CELLS

Two culture conditions were used: for production of IL-1 alpha and beta THP-1 cells were cultured in RPMI-1640 supplemented with 1% nonessential amino acids, 2% penicillin-streptomycin, 5% L-glutamine, 5×10 −5 M 2-mercaptoethanol, and 10% fetal calf serum at a cell density of 1×10 6 cells/ml at 37°C in a 5% CO 2 atmosphere. For the prostaglandin E 2 assays, THP-1 cells were cultured in RPMI complete medium with 1% FCS. Cyclosporine was dissolved in ethanol and 20% tween 80 and diluted in complete medium to make a stock solution of 1 mg/ml. The latter was added to cell cultures at a final concentration of 1 μg/ml except where otherwise noted

Ncitural Killer (NK) Cell Generation in Bone Marrow Cultures: Role of IL-1α

Previous studies have demonstrated that IL-2 is able to induce the development of NK cells from bone marrow (BM) cultures, and that other cytokines acted synergistically with IL-2 in determining an increase of NK cells development. The addition of TNF alpha greatly enhanced the IL-2-mediated induction of NK effector. However, the effect of IL-2 and TNF alpha could be due to direct stimulation of NK progenitors, or to the endogenous production of other factors, which are then responsible of the development of NK cells. As results show that the mRNA specific for IL-1 alpha could be detected in BM cells cultured with IL-2, but not in that supplemented with IL-2 + TNF alpha, it would seem that this lymphokine plays a role only in IL-2-dependent development of NK cells. Studies with Ab anti-IL-1 alpha, showed that the antibody abrograted the IL-2-driven generation of NK cells, but did not affect the NK differentiation induced by IL-2 + TNF alpha. The cytotoxic cells generated by IL-2 or by IL-2 + TNF alpha had the phenotype of mature NK cells including expression of NK 1.1, asialo GM1, Lyt-5, LFA-1, and Thy-1. These data suggest that in spite of phenotypical and morphological similarity of the cells generated with IL-2 or IL-2 + TNF alpha, the endogenous production of IL-1 alpha, appears functionally important only for the differentiation of NK cells induced by IL-2 alone.

Lipopolysaccharide from Actinobacillus actinomycetemcomitans stimulates macrophages to produce interleukin‐1 and tumor necrosis factor mRNA and protein

Actinobacillus actinomycetemcomitans is associated with periodontal disease in children and adults. We report that low concentrations of lipopolysaccharide (LPS) from A. actinomycetemcomitans stimulated human macrophages to increase dramatically their accumulation of mRNA coding for interleukin-1 alpha (IL-1 alpha), IL-1 beta as well as tumor necrosis factor (TNF). Protein levels of IL-1 and TNF alpha also increased. Levels of these mRNAs increased by 4-5 fold as compared with unstimulated macrophages when these cells were cultured with as little as 2 ng/ml LPS from A. actinomycetemcomitans. Polymyxin binds and blocks the action of LPS; polymyxin inhibited the ability of LPS from A. actinomycetemcomitans to increase levels of IL-1 beta mRNA. The LPS of A. actinomycetemcomitans stimulated increased levels of IL-1 beta mRNA in the presence of cycloheximide, showing that stimulation by this LPS did not require new synthesis of protein. Furthermore, dexamethasone inhibited the ability of LPS from A. actinomycetemcomitans to stimulate the accumulation of mRNA coding for IL-1 beta. A. actinomycetemcomitans is an invasive microorganism of the gingiva; high intragingival numbers correlate with sites undergoing local destruction of the periodontium. IL-1 alpha, IL-1 beta, and TNF are potent monokines that mediate inflammation and resorption of bone. Out studies suggest that macrophages migrating to these gingival sites of A. actinomycetemcomitans infection will be stimulated by LPS of A. actinomycetemcomitans to produce IL-1 alpha, IL-1 beta and TNF. These cytokines will mediate gingival inflammation and stimulate resorption of alveolar bone.

Macrophage Control of Normal and Leukemic Erythropoiesis: Identification of the Macrophage-Derived Erythroid Suppressing Activity as Interleukin-1 and the Mediator of its In Vivo Action as Tumor Necrosis Factor

Macrophages have been shown to directly influence the growth and development of mature erythroid progenitors (CFU-E) in normal and erythroleukemic mice. We examined the mechanism by which macrophages mediate their effect on in vivo erythropoiesis. As reported for whole macrophages, serum-free supernatants (SN) from normal resident peritoneal macrophages suppressed in vivo normal and conventional Friend virus (CFV)-infected CFU-E and caused clinical regression of CFV-induced leukemia in mice. Macrophage SN had no effect on the erythropoietin (EPO)-independent CFU-E characteristic of infection with the polycythemia-inducing strain of Friend virus (FVP), or progression of FVP leukemia. Using biochemical, immunologic, and functional assays, the erythrosuppressive factor in macrophage SN was identified as interleukin-1 alpha (IL-1 alpha). The in vivo erythroid suppressive effects of macrophages, macrophage SN, and IL-1 alpha were reversed by simultaneous treatment with EPO. IL-1 alpha itself had no effect on CFU-E colony formation in vitro. Pretreatment of animals with antibodies to murine tumor necrosis factor-alpha (TNF-alpha) completely abrogated the suppression of CFU-E by macrophages, macrophage SN, or human recombinant IL-1 alpha. These results suggest that macrophages regulate erythropoiesis by production of IL-1 alpha, which in turn mediates its in vivo suppressive effects on CFU-E through TNF.

Macrophage control of normal and leukemic erythropoiesis: identification of the macrophage-derived erythroid suppressing activity as interleukin-1 and the mediator of its in vivo action as tumor necrosis factor

Macrophages have been shown to directly influence the growth and development of mature erythroid progenitors (CFU-E) in normal and erythroleukemic mice. We examined the mechanism by which macrophages mediate their effect on in vivo erythropoiesis. As reported for whole macrophages, serum-free supernatants (SN) from normal resident peritoneal macrophages suppressed in vivo normal and conventional Friend virus (CFV)-infected CFU-E and caused clinical regression of CFV- induced leukemia in mice. Macrophage SN had no effect on the erythropoietin (EPO)-independent CFU-E characteristic of infection with the polycythemia-inducing strain of Friend virus (FVP), or progression of FVP leukemia. Using biochemical, immunologic, and functional assays, the erythrosuppressive factor in macrophage SN was identified as interleukin-1 alpha (IL-1 alpha). The in vivo erythroid suppressive effects of macrophages, macrophage SN, and IL-1 alpha were reversed by simultaneous treatment with EPO. IL-1 alpha itself had no effect on CFU- E colony formation in vitro. Pretreatment of animals with antibodies to murine tumor necrosis factor-alpha (TNF-alpha) completely abrogated the suppression of CFU-E by macrophages, macrophage SN, or human recombinant IL-1 alpha. These results suggest that macrophages regulate erythropoiesis by production of IL-1 alpha, which in turn mediates its in vivo suppressive effects on CFU-E through TNF.

Ligand binding to the LFA-3 cell adhesion molecule induces IL-1 production by human thymic epithelial cells.

We have shown that human thymic epithelial (TE) cells produce IL-1 alpha, IL-1 beta, and TE cells bind to thymocytes by CD2 and LFA-1 molecules on thymocytes and LFA-3, ICAM-1 on TE cells. We investigated whether ligand binding to LFA-3 on human TE cells can modulate TE cell IL-1 production. First, we investigated the ability of human thymocytes to regulate IL-1 release by TE cells. Both autologous and allogenic emetine-treated thymocytes when cultured with TE cells augmented IL-1 release by TE cells. The augmentation of IL-1 release was cell density dependent. Inasmuch as the interaction between thymocytes and TE cells is mediated in part by CD2 molecules on thymocytes and LFA-3 molecules on TE cells we next determined the effect on IL-1 release of ligand binding (anti-LFA-3 mAb TS2/9) to TE cell surface LFA-3. Purified anti-LFA-3 mAb augmented IL-1 release in a concentration-dependent fashion. The anti-LFA-3-mediated augmentation of IL-1 release required both new protein and RNA synthesis as shown by the ability of cycloheximide and actinomycin-D to inhibit augmentation of IL-1 production by TE cells, and by direct quantitation of IL-1 alpha and IL-1 beta mRNA by Northern blot analysis. Both F(ab)'2 and Fab' fragments of anti-LFA-3 mAb augmented IL-1 alpha and IL-1 beta mRNA production, indicating that monovalent binding to cell surface LFA-3 was sufficient to provide the inducing signal. The identification of LFA-3, the cell surface ligand for thymocyte CD2 molecules, as a molecule via which TE cell-derived cytokine production may be regulated suggests a mechanism at the cell surface by which direct TE cell-thymocyte interaction might result in the triggering of local IL-1 release within the human thymic microenvironment.

Human Peripheral Blood‐Derived Dendritic Cells do not Produce Interleukin 1α, Interleukin 1β, or Interleukin 6

Little is known about the non-antigen-specific signals delivered to T cells by dendritic cells (DC). Because several monocyte-derived factors like interleukins 1 alpha, 1 beta, and 6 (IL-1 alpha, IL-1 beta, and IL-6) enhance the T-cell proliferative responses, we studied the production of the above-mentioned cytokines by DC separated from human peripheral blood. The intracellular expression of the proteins (IL-1 alpha and IL-6) was studied at a single-cell level using an immunolabelling technique. The supernatants and cell lysates were studied with ELISA (IL-1 alpha and IL-1 beta). Northern blotting analysis was used to quantitate the mRNA levels. Several approaches were taken to stimulate the production of IL-1 alpha, IL-1 beta, and IL-6 by DC. These included the incubation of the DC in the presence of either LPS, rIL-1, or monoclonal anti-HLA-DR antibody, or the stimulation of cells with resting allogeneic T cells. None of the stimuli was able to induce the production of IL-1 alpha, IL-1 beta, or IL-6 by DC, whereas LPS-stimulated monocytes were strong producers of these mentioned cytokines and expressed the respective mRNA. Thus we concluded that IL-1 alpha, IL-1 beta, and IL-6 are primarily monocyte-derived factors and that these factors are not needed or produced during the activation of resting T cells by DC.

Production of Interleukin-1α and Interleukin-2 by Mononuclear Cells from Children with Growth Delay in Relation to the Degree of Growth Hormone Deficiency: Effects of Substitutive Treatment

Interleukin-1 alpha (IL-1 alpha) and interleukin-2 (IL-2) levels were measured by radioimmunoassay in samples of conditioned medium from mononuclear cells taken from 20 normal subjects (14 adults ranging in age from 20 to 45 years and 6 children ranging in age from 3 to 11 years) and from 49 children with growth delay. Cultures were performed with 10(6) cells/ml in medium containing 1% normal human serum and 4.8 g/l phytohemagglutinin M. The incubation was performed for 48 h in an atmosphere containing 5% CO2. In normal subjects, the production of IL-1 alpha was 38.5 +/- 9.8 fmol/ml of conditioned medium (mean +/- SEM) in 14 adults and 41.6 +/- 3.0 fmol/ml in 6 children. The production of IL-2 was 46.9 +/- 6.5 and 57.3 +/- 10.5 fmol/ml, respectively. In the 16 patients with growth hormone (GH) deficiency studied before treatment, the production of ILs was significantly decreased in relation to the degree of deficiency. We observed a positive correlation between the production of IL-1 alpha and the values of insulin-like growth factor I but not with serum GH values. IL-1 alpha production was normalized after 15 days of substitutive GH therapy and IL-2 was normalized after 3 months of therapy. In 10 other patients with GH deficiency (4 with total and 6 with partial isolated GH deficiency) studied after long-term GH treatment (5 months or more), the mean of IL production was not significantly different from that of GH-deficient children treated for 3 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of cytokines by mouse B cells: B lymphomas and normal B cells produce interleukin 10

We have examined a panel of murine Ly-1+ B lymphomas and purified normal murine peritoneal B cells separated into subsets on the basis of expression of the Ly-1 surface antigen, for their ability to produce cytokines. Where possible, we have used a combination of cytokine detection methods in order to compensate for differences in sensitivity and specificity, and the possibility of inhibitors masking an activity. All the lymphomas tested were shown to constitutively express TGF-beta and CSIF/IL-10. In addition, varying levels of IL-6, TNF-alpha and TNF-beta, and G-CSF, were demonstrable in most of the lymphomas, and variants of one lymphoma (CH12) additionally produced varying levels of IL-3, IL-4, and GM-CSF. FACS purified normal Ly-1+ and Ly-1- peritoneal B cells, were also shown to express RNA encoding CSIF/IL-10, IL-6, TNF-alpha and TNF-beta, and very low levels of G-CSF, following stimulation with LPS. These data were supported by the detection of IL-6 and CSIF/IL-10 in supernatants from LPS-stimulated Ly-1+ and Ly-1- B cells using specific immunoassays. None of the lymphomas or B cell preparations produced IL-1 alpha, IL-2, IL-5, IL-7, or IFN-gamma. The purity of our normal B cell populations was assessed by phenotypic analysis on the FACS and also by the disappearance of certain mRNA transcripts after purification, e.g. CD4, c-fms, GM-CSF, and IFN-gamma, most of which could be detected in LPS-stimulated total peritoneal cell populations. This suggested that our B cell purification method had reduced, to a level undetectable in our assays, contaminating T cells (CD4), macrophages (c-fms, GM-CSF), and NK cells (IFN-gamma). Absence of IL-3, IL-4, IL-5, and GM-CSF expression by LPS-stimulated Ly-1+ and Ly-1- B cells reduced the concern that contaminating peritoneal mast cells could account for the observed cytokine production. We therefore believe our data provide strong support for production of a subset of cytokines by LPS-stimulated normal B cells. Both the Ly-1+ B lymphomas and normal Ly-1+ and Ly-1- B cells appear capable of expressing IL-6, TNF-alpha, TNF-beta, and CSIF/IL-10.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of Interleukin-1 Production by 1,25-Dihydroxyvitamin D3

The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], inhibits the proliferation of T lymphocytes and production of growth-promoting factors (including interleukin-2) (IL2) in CTLL2 murine cells. In this study, we investigated the role of monocytes in this hormone-mediated inhibitory effect, by testing the effects of 1,25-(OH)2D3 on the ability of the mitogenic lectin phytohemagglutinin (PHA) to induce T cell activation in either a monocyte-dependent or phorbol myristate acetate (PMA)-driven (monocyte-independent) system. The results indicate that proliferation of T cells and production of growth-promoting factors are inhibited by 1,25-(OH)2D3 only in the monocyte-dependent system. Preincubation of monocytes with 1,25-(OH)2D3 for various periods of time and subsequent removal of the hormone resulted in inhibition of the PHA-driven proliferation of T cells. Preincubation for 2 h resulted in 20% inhibition, while preincubation for 36 h reduced proliferation to 50% of the control value [no 1,25-(OH)2D3 exposure]. These data suggested that monocytes are important participants in 1,25-(OH)2D3-mediated events. Therefore, we tested the effects of the hormone on the production of IL1, a monocyte-derived product thought to be involved in the induction of IL2 release and the subsequent development of the T cell proliferative response. 1,25-(OH)2D3 inhibited the production of both extracellular and cell-associated immunoreactive IL1 alpha and IL1 beta. Indomethacin, a prostaglandin synthetase inhibitor, did not alter the inhibitory properties of 1,25-(OH)2D3, suggesting that prostaglandins are not responsible for the inhibitory phenomenon. We conclude that part of the ability of 1,25-(OH)2D3 to inhibit T cell proliferation may be due to direct effects on monocytes by down-regulating IL-1 production. However, it is unlikely that the immunoregulatory properties of 1,25-(OH)2D3 on T cells are mediated solely through monocytes, and it is possible that the hormone also exerts its influence directly on T cells.

Two peaks of interleukin 1 expression in human leukocytes cultured with tobacco glycoprotein.

We have previously shown that tobacco glycoprotein (TGP), a polyphenol-rich glycoprotein isolated from tobacco or from cigarette smoke, affects the immune system. In this study we show that TGP induces human PBL and adherent cells to produce IL-1 alpha and IL-1 beta. Two peaks of IL-1 activity were observed; one at 18-24 h, the second at 4-6 d after initiation of culture. A similar pattern was observed for the steady state level of IL-1 mRNA. These data suggest that the production of IL-1 by cells stimulated with TGP might be a factor in cardiovascular disease associated with cigarette smoking.

The effect of dietary supplementation with n-3 polyunsaturated fatty acids on the synthesis of interleukin-1 and tumor necrosis factor by mononuclear cells.

We examined whether the synthesis of interleukin-1 or tumor necrosis factor, two cytokines with potent inflammatory activities, is influenced by dietary supplementation with n-3 fatty acids. Nine healthy volunteers added 18 g of fish-oil concentrate per day to their normal Western diet for six weeks. We used a radioimmunoassay to measure interleukin-1 (IL-1 beta and IL-1 alpha) and tumor necrosis factor produced in vitro by stimulated peripheral-blood mononuclear cells. With endotoxin as a stimulus, the synthesis of IL-1 beta was suppressed from 7.4 +/- 0.9 ng per milliliter at base line to 4.2 +/- 0.5 ng per milliliter after six weeks of supplementation (43 percent decrease; P = 0.048). Ten weeks after the end of n-3 supplementation, we observed a further decrease to 2.9 +/- 0.5 ng per milliliter (61 percent decrease; P = 0.005). The production of IL-1 alpha and tumor necrosis factor responded in a similar manner. Twenty weeks after the end of supplementation, the production of IL-1 beta, IL-1 alpha, and tumor necrosis factor had returned to the presupplement level. The decreased production of interleukin-1 and tumor necrosis factor was accompanied by a decreased ratio of arachidonic acid to eicosapentaenoic acid in the membrane phospholipids of mononuclear cells. We conclude that the synthesis of IL-1 beta, IL-1 alpha, and tumor necrosis factor can be suppressed by dietary supplementation with long-chain n-3 fatty acids. The reported antiinflammatory effect of these n-3 fatty acids may be mediated in part by their inhibitory effect on the production of interleukin-1 and tumor necrosis factor.

IL-2 stimulates the production of IL-1 alpha and IL-1 beta by human peripheral blood mononuclear cells.

Human PBMC were cultured in medium containing human rIL-2, and the supernatants and cell lysates were analyzed for IL-1 alpha and IL-1 beta using specific RIA. IL-2, but not the excipient detergents included in the rIL-2 preparation, induced the synthesis of both cytokines. The concentrations of IL-1 alpha and IL-1 beta in the cell lysates and supernatants depended on both the concentration of rIL-2 in the culture medium and the duration of the incubation. After 24 h of stimulation, IL-2-induced IL-1 alpha remained almost entirely cell-associated. In contrast, IL-1 beta was present in both cell lysates and supernatants and was more abundant in the latter. SDS-PAGE analysis after radioimmunoprecipitation with anti-IL-1 antibodies indicates that cell-associated IL-1 resulting from IL-2 stimulation was in the form of the 35 kDa IL-1 precursor whereas secreted IL-1 was almost entirely in the form of the mature 18 kDa product. Depletion of monocytes from the PBMC culture substantially reduced IL-2-induced IL-1 production. In addition, Leu M3+ monocytes obtained through FACS, but not CD16+ NK cells, produced both IL-1 alpha and IL-1 beta in response to IL-2. The low level of endotoxin present in the IL-2 preparation used in our studies and the selective inhibition by polymyxin B of LPS-induced, but not IL-2-induced, IL-1 production by PBMC indicate that IL-2-induced IL-1 production was not due to endotoxin contamination. Furthermore, an anti-IL-2 antiserum selectively inhibited IL-1 production in response to IL-2 stimulation. We conclude that IL-2 is a potent inducer of IL-1 synthesis and secretion in vitro and propose that IL-1 may be generated in vivo in patients undergoing IL-2 immunotherapy.

Interleukin 1 binds to specific receptors on human keratinocytes and induces granulocyte macrophage colony-stimulating factor mRNA and protein. A potential autocrine role for interleukin 1 in epidermis.

Cultured human keratinocytes have been shown to produce IL-1 alpha and beta mRNA and protein. IL-1 biological activity has been identified in normal human epidermis; in vitro, most biologically active IL-1 resides in a cell-associated compartment. The potential for autocrine effects of IL-1 on human keratinocytes was assessed by measurement of keratinocyte IL-1 receptors. Both high- and low-affinity cell surface receptors that bound recombinant (r) IL-1 alpha and beta with comparable affinities could be identified on cultured human keratinocytes, using 125I-labeled rIL-1. Chemical crosslinking experiments identified a cell surface molecule of roughly 72,500 Mr that bound 125I-labeled IL-1, similar to the molecular weight of previously described IL-1 receptors on fibroblasts, B cells, and T cells. To assess the biological consequences of keratinocyte IL-1 binding, granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression was measured. The addition of exogenous rIL-1 alpha led to a dose-dependent increase in the accumulation of GM-CSF mRNA, as measured by a sensitive and specific S1 nuclease assay. This increase in mRNA was reflected in a marked increase in GM-CSF biological activity as measured by proliferation of blast cells from chronic myelogenous leukemia patients. The biological activity was completely inhibitable by an antibody to human rGM-CSF. GM-CSF activates mature neutrophils and macrophages and appears to enhance the efficiency of Langerhans cell antigen presentation to T cells. Release of IL-1 from injured or activated keratinocytes may lead to enhanced epidermal GM-CSF gene expression via an autocrine mechanism, thus enhancing local host defense.

Production of interleukin-1 alpha, interleukin-1 beta and tumor necrosis factor by human mononuclear cells stimulated with granulocyte- macrophage colony-stimulating factor [see comments

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.

Phosphorylation of intracellular precursors of human IL-1.

The human IL-1 molecules (IL-1 alpha and IL-1 beta) are post-translationally cleaved from 31-kDa precursor to 18-kDa biologically active molecules. During the course of studies of post-translational modifications of human IL-1, we have observed that although LPS induced the production of both intracellular IL-1 alpha and IL-1 beta in human monocytes, [32P]orthophosphate labeling of these cells revealed that intracellular precursor of IL-1 alpha (pre-IL-1 alpha) to be phosphorylated at least 10-fold more than intracellular pre-IL-1 beta. However, no 32P-incorporation could be detected in the 18-kDa processed IL-1 alpha and IL-1 beta. Analysis by TLC revealed that the major phosphorylation site occurred at serine residue(s). The 32P was incorporated into multiply cleaved precursors of IL-1 alpha, which appeared in the absence of protease inhibitors. Since the smallest Mr pre-IL-1 alpha that was labeled with 32P was 22 kDa, the phosphorylated serine residue is presumably located adjacent to a sequence of four basic amino acids located in the 4-kDa region at the amino terminus of the 22-kDa precursor of IL-1 alpha. This serine residue might also be a major phosphorylation site for a cAMP-dependent protein kinase. This hypothesis was substantiated by the demonstration that a synthetic peptide analogue of this region (residue 84 to 112) could be similarly phosphorylated in vitro by a cAMP-dependent protein kinase. Furthermore, a truncated pre-IL-1 alpha (residue 64 to 271) and a "fusion" protein containing staphylococcal protein A and an amino-terminal half-portion of pre-IL-1 alpha (residue 1 to 112), but not mature IL-1 alpha (residue 113 to 271), could also be phosphorylated by cAMP-dependent protein kinase. There is no comparable amino acid sequence in IL-1 beta which could be expected to be phosphorylated by a cAMP-dependent protein kinase. The physiologic relevance of phosphorylation of pre-IL-1 alpha was investigated. The data showed that phosphorylation of truncated pre-IL-1 alpha greatly enhanced its susceptibility to digestion by trypsin and promoted the conversion of pre-IL-1 alpha to the more biologically active IL-1. Although the precise role of the rather selective phosphorylation of pre-IL-1 alpha is not known, our findings do suggest that the phosphorylation of serine close to dibasic/tetrabasic amino acid sequence functions to facilitate the processing and/or release of IL-1 alpha.

Analysis of the suppression of IL-1 alpha and IL-1 beta production in human peripheral blood mononuclear adherent cells by a glucocorticoid hormone.

The suppression of IL-1 production in human adherent PBMC by a glucocorticoid hormone was studied. From 10(-5) to 10(-8) M glucocorticoid hormone (prednisolone) inhibited both IL-1 alpha and IL-1 beta production by LPS-stimulated adherent human PBMC in a dose-dependent fashion, as assayed by Western blotting of cell-associated IL-1 and a thymocyte comitogenic bioassay. IL-1 alpha and -beta mRNA levels were concomitantly suppressed by glucocorticoid treatment, as determined by Northern blotting analysis. These data suggest that the suppression of IL-1 activity by glucocorticoids is consistently associated with decreased levels of IL-1 proteins and mRNA expression and therefore presumably regulated at the transcriptional level.