ROLE OF IL-18 IN THE SECRETION OF IL-1β, sIL-1RII,AND IL-1Ra BY HUMAN NEUTROPHILS

In the present study we investigated the effect of IL-18 on the production of IL-1β, IL-1Ra and sIL-1RII by human neutrophils. Our observations indicate that rhIL-18 induces IL-1β and, to a lesser extend, IL-1Ra and sIL-1RII production by human neutrophils isolated form peripheral blood. However, this effect was less important in comparison with LPS-stimulation. Moreover, the results obtained suggest that IL-18 can induce priming of neutrophils for IL-1β and, to a lesser extend, IL-1Ra and sIL-1RII production by LPS-stimulated cells. The capacity of IL-18 to serve as an effective modulator for IL-1β and its regulatory proteins may have significance in the inflammatory and immune reactions mediated by IL-1β.     

EFFECT OF IL-18 ON THE RELEASE OF IL-6 AND ITS SOLUBLE RECEPTORS: sIL-6Rα AND sgp130 BY HUMAN NEUTROPHILS

The biological activities of IL-18 include its ability to induce the production of inflammatory cytokines such as IL-1 or IL-8 by immunocompetent cells.

Our previous study demonstrated that rhIL-18 induces IL-1β and, to a lesser exted, the secretion of IL-1β regulatory proteins involving interleukin-1 receptor antagonist (IL-1Ra) and soluble interleukin-1 receptor II (sIL-1RII) by neutrophils (PMN), suggesting a significant role of IL-18 in the reactions mediated by IL-1β.

In this study, we estimated the effect of rhIL-18 on the induction of IL-6 and its soluble receptors – sIL-6Rα and sgp130 by these cells. Results obtained indicate that IL-18 is a promising candidate for the enhanced secretion of IL-6 by human neutrophils. In contrast, we have not found a significant effect of IL-18 on the release of both soluble receptors of IL-6. The influence of IL-18 on the IL-6 production by PMN appears to indicate a potential role of IL-18 in the early steps of the inflammatory cascade and other immune reactions mediated by IL-6.     

The IL-1 system in HIV infection: peripheral concentrations of IL-1β, IL-1 receptor antagonist and soluble IL-1 receptor type II

The proinflammatory cytokine IL-1β is thought to be involved in ongoing HIV disease. Furthermore, its naturally occurring inhibitors soluble IL-1 receptor type II (sIL-1RII) and IL-1 receptor antagonist (IL-1Ra) may play a pivotal role in regulating its biological action. To investigate the involvement of the IL-1 system we determined serum levels of IL-1β, IL-1Ra and sIL-1RII in 90 HIV⁺ patients. The obtained values were compared with markers of disease progression such as CD⁺ count, 5′-neopterin, β₂-microglobulin and soluble tumour necrosis factor receptors (sTNF-R) p55 and p75 and then compared with C-reactive protein (CRP), granulocyte count, lL-6 and TNF-α. While IL-1Ra concentrations increased significantly with progressive CDC disease stages, sIL-1RII and IL-1β were not altered in our cohort. IL-1Ra showed statistical relation to decreasing CD4⁺ lymphocytes and increasing 5′-neopterin, β₂-microglobulin, sTNF-R p55, sTNF-R p75. Furthermore, IL-1Ra correlated positively with serum IL-6, TNF-α, CRP and granulocytes. In contrast, sIL-1RII and IL-1β tended to show an inverse correlation or showed no significant relationship to all these parameters. Il-1β was measurable only in a limited number of samples. IL-1Ra showed a clear relationship to acute inflammatory events as well as to the different disease stages. Our data suggest a dissociation between IL-1Ra and sIL-1RII serum levels which may indicate that the two IL-1 binding proteins have different pathophysiological roles in HIV infection.     

Effect of IL-18 on IL-1beta and sIL-1RII production by human neutrophils

In the present study we investigated the effect of interleukin 18 (IL-18) on the production of IL-1beta and soluble IL-1 receptor II (sIL-1RII) by human neutrophils. The results obtained indicate that recombinant human IL-18 (rhIL-18) induces IL-1beta and, to a lesser extent, sIL-1RII production by human neutrophil isolated from peripheral blood. However, this effect was less important than lipopolysaccharide (LPS) stimulation. Additionally, our observations suggest that IL-18 can induce priming of neutrophils for IL-1beta and, to a lesser extent, sIL-IRII production by LPS-stimulated cells. The ability of IL-18 to serve as an effective modulator for IL-1beta and its regulatory protein may have significance in the inflammatory and immune reactions mediated by IL-1beta.     

Effect of IL-18 on the release of IL-6 and its soluble receptors: sIL-6Ralpha and sgp130 by human neutrophils

The biological activities of IL-18 include its ability to induce the production of inflammatory cytokines such as IL-1 or IL-8 by immunocompetent cells. Our previous study demonstrated that rhIL-18 induces IL-1beta and, to a lesser exted, the secretion of IL-1beta regulatory proteins involving interleukin-1 receptor antagonist (IL-IRa) and soluble interleukin-1 receptor II (sIL-1RII) by neutrophils (PMN), suggesting a significant role of IL-18 in the reactions mediated by IL-1beta. In this study, we estimated the effect of rhIL-18 on the induction of IL-6 and its soluble receptors - sIL-6Ralpha and sgp130 by these cells. Results obtained indicate that IL-18 is a promising candidate for the enhanced secretion of IL-6 by human neutrophils. In contrast, we have not found a significant effect of IL-18 on the release of both soluble receptors of IL-6. The influence of IL-18 on the IL-6 production by PMN appears to indicate a potential role of IL-18 in the early steps of the inflammatory cascade and other immune reactions mediated by IL-6.     

IL-1beta, IL-1Ra and sIL-1RII in the culture supernatants of PMN and PBMC and the serum levels in patients with inflammation and patients with cancer disease of the same location.

An inflammation or an other malignant process may create a microenvironment that modulates the production and activity of cytokines and their regulators. In the present study we compared the secretion of IL-1beta and its regulatory proteins: IL-IRa and sIL-1RII by PMN and PBMC derived from patients with inflammation and patients with cancer disease of the same location. We also examined the serum levels of these mediators in groups of patients. The results obtained revealed changes in the secretion of IL-1beta and IL-1Ra which are more characteristic of PMN and PBMC from cancer patients than of the cells from patients with inflammation. In contrast, the secretion of sIL-1RII is more characteristic of PMN and PBMC derived from patients with inflammation. Furthermore, PMN appear to play more significant role in the secretion of IL-1Ra into the circulation of cancer patients than PBMC. In contrast, PBMC affect to a large extent the secretion of IL-1beta and sIL-1RII into the circulation of patients with inflammation than PMN. Concluding, the secretion of IL-1beta and its regulatory proteins may depend on the type of immune cells and the type of the disease.     

IL-1 receptor–type expression in relation to atopy

Background: IL-1 has 2 receptors, type I (IL-1RI) and type II (IL-1RII), which have 2 forms each, membrane (m) and soluble (s). When IL-1 binds to mIL-1RI, the active receptor, an inflammatory response is initiated, which does not occur when IL-1 binds to mIL-1RII, the decoy receptor. Both sIL-1RI and sIL-1RII function as IL-1–mopping mechanisms. We hypothesized that the ratio of active (mIL-1RI) to inactive (mIL-1RII, sIL-1RI, and sIL-1RII) receptors is important in determining the amount of inflammation produced in allergic reactions. Objective: Our aim was to compare the concentrations of mIL-1RI and mIL-1RII on cultured PBLs and sIL-1RI, sIL-1RII, and IL-1β in sera and supernatants of cultured PBMCs from atopic and nonatopic subjects. Methods: The membrane receptors, soluble receptors, and IL-1β concentrations were measured by ELISA with specific mAbs. Results: Although there was no difference in the level of serum IL-1β between the 2 groups, PBMCs from atopic persons spontaneously secreted higher levels of IL-1β than those from nonatopic donors (P < .05). PBLs from atopic subjects compared with those from nonatopic individuals expressed higher mIL-1RI (P < .0001) and mIL-1RII (P < .05). Levels of both the soluble receptors from both serum (P < .0001) and PBMCs (P < .05) of nonatopic donors were higher than those found in atopic donors. Conclusion: This augmentation of mIL-1RI concomitant with a reduction in soluble receptors may be an important contributory factor to the inflammation that occurs with allergen exposure. (J Allergy Clin Immunol 1999;103:1100-7.)     

The remedial effect of soluble interleukin-1 receptor type II on endometriosis in the nude mouse model

Objective

Recent studies have shown that the local expression of soluble interleukin (IL) -1 receptor type II (sIL-1 RII) in endometrial tissue of women with endometriosis is decreased, and the depression of IL-1 RII was more significant in infertile women than that in fertile women with endometriosis. In this research, we investigated the remedial effect of sIL-1-RII administration on endometriosis in the nude mouse model.

Methods

Nineteen nude model mice with endometriosis were randomly divided into three groups: group A was treated by intraperitoneal administration with only sIL-1 RII for two weeks, group B was similarly treated with only IL-1, and group C (control) was administered saline . After 2 weeks, the size of the ectopic endometrial lesions was calculated, and the expression of vascular endothelial growth factor (VEGF) and B-cell lymphoma leukemia-2 (Bcl-2) were detected by immunohistochemistry. The IL-8 and VEGF levels in the peritoneal fluid (PF) and serum were also measured by enzyme-linked immunosorbent assay (ELISA).

Results

The mean size of ectopic endometrial lesion did not differ between the three groups (P > 0.05). Compared with the control, the expression of VEGF and Bcl-2 was significantly lower in group A, and higher in group B. In the three groups, the levels of IL-8 in the PF and serum were highest in group A, and lowest in group B.

Conclusion

sIL-1 RII may suppresse hyperplasia of ectopic endometriosis, perhaps by reducing the expression of certain cytokines, such as VEGF, IL-8, and Bcl-2, which could provide a new clinical strategy for the treatment of endometriosis.     

Production of IL-1 receptor antagonist by hepatocytes is regulated as an acute-phase protein in vivo

IL-1 receptor antagonist (IL-1Ra) is produced by isolated human hepatocytes with characteristics of an acute-phase protein. There are multiple IL-1Ra peptides, one secreted (sIL-1Ra) and three intracellular (icIL-1Ra1, 2, 3). sIL-1Ra, but not icIL-1Ra1, mRNA is transcribed by cultured human hepatocytes. In this study, we examined in vivo production of IL-1Ra by the liver in mice in two experimental models of acute-phase response, systemic lipopolysaccharide (LPS) administration and local turpentine injection. Liver sIL-1Ra expression was up-regulated in response to both types of stimulation. After LPS injection, the hepatic production of sIL-1Ra correlated with the increase in plasma IL-1Ra levels. In addition, the total amount of IL-1Ra present in the liver after LPS injection was six- and tenfold higher than in the lung and spleen. As assessed by in situ hybridization, sIL-1Ra, but not icIL-1Ra, mRNA was produced by hepatocytes in vivo after LPS injection. Using IL-6(-/-) mice, we demonstrated that in turpentine-induced inflammation production of IL-1Ra mRNA by the liver is regulated by IL-6. In contrast, local production of IL-1Ra is independent of IL-6. Taken together, these results indicate that IL-1Ra is produced by the liver as an acute-phase protein in vivo.     

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

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

Significance of IL-1β and IL-1 receptor antagonist (IL-1Ra) in bronchoalveolar lavage fluid (BALF) in patients with diffuse panbronchiolitis (DPB)

We evaluated the effect of erythromycin therapy on pulmonary function tests and the airway inflammatory response of patients with DPB. The number of neutrophils in BALF obtained from DPB patients was significantly higher than that of healthy volunteers. Treatment with erythromycin (600 mg/day for 12·9 ± 9·5 months (mean ±s.d.)) significantly reduced the total number of cells and neutrophils in the airway, and significantly improved pulmonary function tests. The levels of IL-1β and IL-8 were significantly higher in DPB compared with healthy volunteers (P < 0·05, P < 0·05, respectively). IL-1 Ra in patients is considered to have a weak inhibitory activity for IL-1β, with approximately five-fold concentration of IL-1β compared with that in healthy volunteers (approx. nine-fold concentration of IL-1β). Erythromycin therapy significantly reduced these cytokines to levels comparable to those of healthy volunteers, and produced a trend toward reduction in the level of IL-1Ra in BALF. The level of IL-1β correlated significantly with the concentration of neutrophils in BALF (r = 0·72, P < 0·01), as well as with the level of IL-1Ra (r = 0·688, P < 0·05) and IL-8 (r = 0·653, P < 0·05). A nearly significant or significant correlation was observed between the concentration of neutrophils and levels of IL-1Ra or IL-8 in BALF (r = 0·526, P = 0·053 or r = 0·776, P < 0·01, respectively). There was also a significant relationship between FEV, and the concentration of neutrophils in BALF (r = 0·524, P < 0·05). Our results suggest that the relative amounts of IL-1β and IL-1Ra or IL-8 may contribute, at least in part, to the neutrophil-mediated chronic airway inflammation in patients with chronic airway disease, and long-term erythromycin therapy may down-regulate the vigorous cycle between the cytokine network and neutrophil accumulation, with resultant reduction of neutrophil-mediated inflammatory response.     

IL-1beta induces and TGF-beta reduces vitamin D3-induced bone resorption in mouse calvarial bone cells

Bone cells produce multiple growth factors and cytokines that have effects on bone metabolism and can be incorporated into the bone matrix. The present study was designed to extend these observations by examining the interactions between transforming growth factor-β (TGF-β) or interleukin-1β (IL-1β) and bone cells in a rat long bone culture model. IL-1β regulates several activities of the osteoblast cells derived from rat long bone explants in vitro. IL-1β stimulated cellular proliferation and the synthesis of prostaglandin E₂ and plasminogen activator activity in the cultured cells in a dose-dependent manner. TGF-β is present in the bone matrix and potentially can be released during bone resorption. TGF-β reduced basal bone resorption and inhibited vitamin D₃ [1,25(OH)₂D₃]-induced bone resorption in rat long bone cells. These studies support the role of IL-1β in the pathological modulation of bone cell metabolism, with regard to implication in the pathogenesis of osteoporosis by IL-1β, and that TGF-β is positively inhibiting the bone resorption.     

Mice transgenic for intracellular interleukin-1 receptor antagonist type 1 are protected from collagen-induced arthritis

Interleukin-1 receptor antagonist (IL-1Ra) is a natural IL-1 inhibitor, which competitively inhibits binding of IL-1 to its receptors. IL-1Ra is produced as four different isoforms, one secreted (sIL-1Ra) and three intracellular (icIL-1Ra1, 2, 3), derived from the same gene. We previously observed increased production of icIL-1Ra1 in the joints of mice with collagen-induced arthritis (CIA). However, due to its intracellular localization, the biological role of icIL-1Ra1 remains unknown. The aim of the present study was to examine the effect of the icIL-1Ra1 isoform, as compared to that of sIL-1Ra, in the CIA model by comparing transgenic (tg) mice overexpressing icIL-1Ra1 or sIL-1Ra to their wild-type littermates. Serum levels of tg human IL-1Ra were elevated in sIL-1Ra and, to a lesser extent, also in icIL-1Ra1 mice. Clinical scoring indicated that none of the icIL-1Ra1 or siL-1Ra tg mice developed CIA, whereas arthritis was present in, respectively, 60% and 100% of their wild-type littermates. Histological and radiological analyses confirmed the absence of arthritis in icIL-1Ra1 and sIL-1Ra tg mice. Accordingly, circulating levels of the acute-phase protein serum amyloid A tended to be lower in icIL-1Ra1 tg mice than in their wild-type littermates and were significantly lower in sIL-1Ra tg mice than in controls. In contrast, no difference was observed between the groups regarding serum levels of anti-type II collagen antibodies and ex vivo spleen cell proliferative response to collagen. In conclusion, icIL-1Ra1, which is released into the extracellular space when produced in high amounts, has a similar anti-arthritic effect as sIL-1Ra.     

IL-1, IL-18, and IL-33 families of cytokines

Summary: The interleukin-1 (IL-1), IL-18, and IL-33 families of cytokines are related by mechanism of origin, receptor structure, and signal transduction pathways utilized. All three cytokines are synthesized as precursor molecules and cleaved by the enzyme caspase-1 before or during release from the cell. The NALP-3 inflammasome is of crucial importance in generating active caspase-1. The IL-1 family contains two agonists, IL-1α and IL-1β, a specific inhibitor, IL-1 receptor antagonist (IL-1Ra), and two receptors, the biologically active type IL-1R and inactive type II IL-1R. Both IL-1RI and IL-33R utilize the same interacting accessory protein (IL-1RAcP). The balance between IL-1 and IL-1Ra is important in preventing disease in various organs, and excess production of IL-1 has been implicated in many human diseases. The IL-18 family also contains a specific inhibitor, the IL-18-binding protein (IL-18BP), which binds IL-18 in the fluid phase. The IL-18 receptor is similar to the IL-1 receptor complex, including a single ligand-binding chain and a different interacting accessory protein. IL-18 provides an important link between the innate and adaptive immune responses. Newly described IL-33 binds to the orphan IL-1 family receptor T1/ST2 and stimulates T-helper 2 responses as well as mast cells.     

Differential binding of human interleukin-1 (IL-1) receptor antagonist to natural and recombinant soluble and cellular IL-1 type I receptors

A recently described factor, interleukin-1 receptor antagonist binding factor (IL-IraBF), in serum of normal individuals is immunologically related to the interleukin-1 receptor type I (IL-1RI). It is presumably a soluble form of the receptor that binds exclusively to interleukin-1 receptor antagonist (IL-1ra). Recombinant soluble human IL-1RI expressed in COS cells (sIL-1RI) consists of the extracellular part of the receptor and binds all three known IL-1 species but preferentially to IL-1ra. We further characterized the sizes and binding of IL-1raBF and sIL-1RI to IL-1ra by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, ligand binding interference analyses, N-glycosidase treatment, concanavalin A affinity chromatography, and with the use of monoclonal antibodies (mAb) to human recombinant IL-1ra. We also evaluated the binding of IL-1ra to cellular IL-1RI on MRC5 fibroblasts and the interference afforded by the soluble receptors. The results show that the protein backbones of IL-1raBF and sIL-1RI are of similar size (≈ 35–40 kDa) and that there are differences in the glycosylation of the two molecules. These carbohydrates were necessary for optimal binding of both molecules to IL-1ra. Both factors blocked binding of IL-1ra to cellular IL-1RI, as did mAb to IL-1ra, but the sites on IL-1ra which bound to the mAb, and to IL-1raBF and sIL-1RI, differed. We conclude that there are important differences between the natural and recombinant forms of soluble IL-1RI and that IL-1ra binds differently to these molecules and to cellular IL-1RI.     

Anti-inflammatory properties of human serum IgA: induction of IL-1 receptor antagonist and FcαR (CD89)-mediated down-regulation of tumour necrosis factor-alpha (TNF-α) and IL-6 in human monocytes

A deregulated expression and/or release of large amounts of inflammatory cytokines such as IL-1 and TNF-α accounts for most pathophysiological events in a variety of systemic inflammatory diseases, the effect being mediated by the interaction of these cytokines with their respective receptors. IL-1 receptor antagonist (IL-1Ra), mainly produced by monocytes/macrophages, is an inhibitor of IL-1 activity. The present study shows that human serum IgA induces significant IL-1Ra release in human peripheral blood mononuclear cells and adherent monocytes. IgA induced higher levels of IL-1Ra than Haemophilus influenzae type b (Hib) expressing lipopolysaccharide (LPS), purified LPS or phorbol myristate acetate (PMA), without induction of IL-1β release, and even inhibited LPS-induced IL-1β release. Induction of IL-1Ra by IgA could be detected both at the mRNA and protein levels in resting and activated monocytes. Ligation of FcαR with MoAb MY-43 or treatment with human serum IgA induced protein tyrosine phosphorylation in human monocytes, and herbimycin A, a specific inhibitor of protein tyrosine kinase activity, inhibited IgA-induced IL-1Ra production, suggesting that FcαR-mediated induction of tyrosine phosphorylation is required for the IgA-induced stimulation of IL-1Ra release. In addition, triggering of FcαR with MoAb specifically down-regulated TNF-α and IL-6 release in human monocytes activated with Hib. By the induction of IL-1Ra and down-regulation of the release of inflammatory cytokines such as IL-1β, TNF-α and IL-6, interaction of IgA with human monocytes may actively contribute to the regulation of the inflammatory response.     

Modulation of the IL-1 cytokine network in keratinocytes by intracellular IL-1 alpha and IL-1 receptor antagonist.

The IL-1 cytokine network in epidermal cells was studied in vitro, using the spontaneously transformed HaCAT human keratinocyte line. Intracellular (ic) IL-1 alpha and IL-1 receptor antagonist protein (IL-1Ra) following cell lysis were readily identified assayed using a capture ELISA; whereas in culture supernatants IL-1Ra was not detected, and IL-1 alpha was present at only very low levels. Confluent cultures of HaCAT cells were shown to provide optimal conditions for the study, since confluence increased the icIL-1Ra:IL-1 alpha ratio to a level as seen in vivo, which was independent of Ca2+ concentration in the culture medium. The IL-1Ra extracted from HaCAT cell lysates was functionally active, as demonstrated in the mouse thymocyte co-proliferation assay which could be blocked using a rabbit anti-IL-1Ra antibody. Transforming growth factor-beta (TGF-beta 1) stimulated a dose-dependent increase in HaCAT cell IL-1 alpha without changing IL-1Ra concentration, with a resultant reduction in the icIL-1Ra: IL-1 alpha ratio from 320:1 to 100:1. Similarly, TGF-alpha, interferon-gamma (IFN-gamma), IL-6, and tumour necrosis factor-alpha (TNF-alpha) substantially increased HaCAT cell IL-1 alpha, but had no effect on the IL-1Ra, with a concomitant reduction in the icIL-1Ra:IL-1 alpha ratio. In contrast to their effects on monocytes, IL-4 and IL-10 at biologically active levels had no effect on IL-1 alpha, IL-1Ra or the icIL-1Ra: IL-1 alpha ratio in confluent HaCAT cells. Hydrocortisone reduced IL-1 alpha to below the limit of sensitivity of the ELISA, and induced a small increase in IL-1Ra of questionable biological significance. Thus, regulation of the IL-1 cytokine network in keratinocytes involves modulation of icIL-1 alpha rather than of icIL-1Ra levels, and is markedly different from that noted in monocytes.