Interleukin 1 stimulates its own receptor expression on human fibroblasts through the endogenous production of prostaglandin(s)

P2Y11/IL-1 receptor crosstalk controls macrophage inflammation: a novel target for anti-inflammatory strategies?

Although first cloning of the human ATP receptor P2Y11 was successful 25 years ago, the exact downstream signaling pathways of P2Y11 receptor, which can couple to Gq and Gs proteins, have remained unclear. Especially the lack of rodent models as well as the limited availability of antibodies and pharmacological tools have hampered examination of P2Y11 expression and function. Many meaningful observations related to P2Y11 have been made in primary immune cells, indicating that P2Y11 receptors are important regulators of inflammation and cell migration, also by controlling mitochondrial activity. Our recent studies have shown that P2Y11 is upregulated during macrophage development and activates signaling through IL-1 receptor, which is well known for its ability to direct inflammatory and migratory processes. This review summarizes the results of the first transcriptomic and secretomic analyses of both, ectopic and native P2Y11 receptors, and discusses how P2Y11 crosstalk with the IL-1 receptor may govern anti-inflammatory and pro-angiogenic processes in human M2 macrophages.

Mechanisms by which dupilumab normalizes eicosanoid metabolism and restores aspirin-tolerance in AERD: A hypothesis

Aspirin-exacerbated respiratory disease (AERD) is associated with overproduction of proinflammatory cysteinyl leukotrienes (CysLTs), defective generation of anti-inflammatory prostaglandin E₂ (PGE₂), and reduced expression of the EP2 receptor for PGE₂. Reduced PGE₂ synthesis results from the downregulation of inducible COX-2. Because PGE₂ signaling via EP2 inhibits the 5-lipoxygenase/leukotriene C₄ synthase-dependent pathway, the deficient levels of both PGE₂ and EP2 likely contribute to the excessive baseline production of cysteinyl leukotrienes in patients with AERD compared with in patients with aspirin-tolerant asthma. The COX-2 pathway is regulated by an autocrine metabolic loop involving IL-1β, IL-1 receptor type I, EP2, COX-2, membrane-bound PGE₂ prostaglandin E₂ synthase-1, and PGE₂. Previous studies reported that this metabolic loop is dysregulated in patients with AERD. When the downexpressed EP2 receptor is normalized, the entire loop returns to its normal function. Cotreatment of airway cells from healthy subjects with IL-4 and IFN-γ induces alterations in the metabolic loop similar to those seen in patients with AERD. In these patients, IL-4, which is produced in excess in airways of patients with AERD, likely contributes to the alteration of normal functioning of the autocrine metabolic loop involving IL-1β, IL-1 receptor type I, EP2, COX-2, membrane-bound PGE₂ prostaglandin E₂ synthase-1, and PGE₂. We hypothesized that by blocking IL-4 action, dupilumab normalizes EP2 expression and restores the normal functioning of the COX-2 pathway autocrine metabolic loop, thereby normalizing the synthesis of PGE₂ and restoring aspirin tolerance.

The P2Y11 receptor of human M2 macrophages activates canonical and IL-1 receptor signaling to translate the extracellular danger signal ATP into anti-inflammatory and pro-angiogenic responses

The cytoprotective ATP receptor P2Y₁₁ is upregulated during M2 macrophage differentiation and contributes to the anti-inflammatory properties of this macrophage subset. Here, we studied P2Y₁₁-induced reprogramming of human M2 macrophages at the level of mRNA and protein expression. Upregulation of IL-1 receptor (IL-1R) and its known downstream effectors VEGF, CCL20 and SOCS3 as well as downregulation of the ATP-degrading ecto-ATPase CD39 emerged as hallmarks of P2Y₁₁ activation. The anti-inflammatory signature of the P2Y₁₁ transcriptome was further characterized by the downregulation of P2RX7, toll-like receptors and inflammasome components. P2Y₁₁-induced IL-1R upregulation formed the basis for reinforced IL-1 responsiveness of activated M2 macrophages, as IL-1α and IL-1ß each enhanced P2Y₁₁-induced secretion of VEGF and CCL20 as well as the previously reported shedding of soluble tumor necrosis factor receptor 2 (sTNFR2). Raising intracellular cyclic AMP (cAMP) in M2 macrophages through phosphodiesterase 4 inhibition enhanced P2Y₁₁-driven responses. The cAMP-binding effector, exchange protein activated by cAMP 1 (Epac1), which is known to induce SOCS3, differentially regulated the P2Y₁₁/IL-1R response because pharmacological Epac1 inhibition enhanced sTNFR2 and CCL20 release, but had no effect on VEGF secretion. In addition to cAMP, calcium and protein kinase C participated in P2Y₁₁ signaling. Our study reveals how P2Y₁₁ harnesses canonical and IL-1R signaling to promote an anti-inflammatory and pro-angiogenic switch of human M2 macrophages, which may be controlled in part by an Epac1-SOCS3 axis.

Inhibition of interleukin-1β reduces myelofibrosis and osteosclerosis in mice with JAK2-V617F driven myeloproliferative neoplasm

Interleukin-1β (IL-1β) is a master regulator of inflammation. Increased activity of IL-1β has been implicated in various pathological conditions including myeloproliferative neoplasms (MPNs). Here we show that IL-1β serum levels and expression of IL-1 receptors on hematopoietic progenitors and stem cells correlate with JAK2-V617F mutant allele fraction in peripheral blood of patients with MPN. We show that the source of IL-1β overproduction in a mouse model of MPN are JAK2-V617F expressing hematopoietic cells. Knockout of IL-1β in hematopoietic cells of JAK2-V617F mice reduces inflammatory cytokines, prevents damage to nestin-positive niche cells and reduces megakaryopoiesis, resulting in decrease of myelofibrosis and osteosclerosis. Inhibition of IL-1β in JAK2-V617F mutant mice by anti-IL-1β antibody also reduces myelofibrosis and osteosclerosis and shows additive effects with ruxolitinib. These results suggest that inhibition of IL-1β with anti-IL-1β antibody alone or in combination with ruxolitinib could have beneficial effects on the clinical course in patients with myelofibrosis.

A niche that triggers aggressiveness within BRCA1-IRIS overexpressing triple negative tumors is supported by reciprocal interactions with the microenvironment

Production of metastasis capable precursors begins within the primary tumor. Here, we define the bidirectional interactions with stromal cells involved in promoting these precursors within BRCA1-IRIS (hereafter IRIS) overexpressing (IRISOE) TNBC tumors. We define an aggressiveness niche, functionally defined as the necrotic/hypoxic core of the tumor, in which metabolically stressed, hypoxic, and inflamed IRISOE TNBC cells secrete higher levels of cytokines, chemokines and growth factors. One cytokine; IL-1β attracts mesenchymal stem cells (MSCs) to the niche and activates them to secrete CXCL1 that entrains IRISOE cells to secrete higher levels of CCL2 and VEGF. CCL2 attracts macrophages (TAMs) to the niche and activates them to secrete S100A8, and VEGF attracts endothelial cells (ECs) and activates them to secrete IL-8. In concert, CXCL1, S100A8 and IL-8 entrain aggressiveness in IRISOE TNBC cells within the niche. Indeed, compared to IRISOE cells alone, tumors developed by co-injecting IRISOE cells admixed with MSCs (10:1) in athymic mice were bigger and more aggressive. They contained more TAMs and ECs, expressed higher-levels of basal, epithelial to mesenchymal transition, and stemness biomarkers, quickly progressed to lymph-node or visceral metastases, and were highly sensitive to the IL-1β inhibitor “Anakinra”. Our findings supported by human data show that breast cancer patients with high-levels of IL-1β, CXCL1, CCL2, S100A8, VEGF, and IL-8 would show worse clinical outcomes. Our findings argue that this cytokine set is a diagnostic biomarker for patients who may benefit from an IRIS inhibitor-based therapy, and is a blue print for translation of approaches to combining that therapy with inhibitors of these bidirectional interactions to overcome TNBC metastasis.

Low E-prostanoid 2 receptor levels and deficient induction of the IL-1β/IL-1 type I receptor/COX-2 pathway: Vicious circle in patients with aspirin-exacerbated respiratory disease

BACKGROUND

We hypothesized that the 2 reported alterations in aspirin-exacerbated respiratory disease (AERD), reduced expression/production of COX-2/prostaglandin (PG) E2 and diminished expression of E-prostanoid (EP) 2 receptor, are closely linked.

OBJECTIVE

We sought to determine the mechanisms involved in the altered regulation of the COX pathway in patients with AERD.

METHODS

Fibroblasts were obtained from nasal mucosa; samples of control subjects (NM-C, n = 8) and from nasal polyps from patients with aspirin-exacerbated respiratory disease (NP-AERD, n = 8). Expression of the autocrine loop components regulating PGE2 production and signaling, namely IL-1 type I receptor (IL-1RI), COX-2, microsomal prostaglandin E synthase 1 (mPGES-1), and EP receptors, was assessed at baseline and after stimulation with IL-1β, PGE2, and specific EP receptor agonists.

RESULTS

Compared with NM-C fibroblasts, basal expression levels of IL-1RI and EP2 receptor were lower in NP-AERD fibroblasts. IL-1β-induced IL-1RI, COX-2, and mPGES-1 expression levels were also lower in these cells. Levels of IL-1RI positively correlated with COX-2 and mPGES-1 expression in both NM-C and NP-AERD fibroblasts. Incubation with either exogenous PGE2 or selective EP2 agonist significantly increased expression of IL-1RI in NM-C fibroblasts and had hardly any effect on NP-AERD fibroblasts. Alterations in IL-1RI, COX-2, and mPGES-1 expression that were found in NP-AERD fibroblasts were corrected when EP2 receptor expression was normalized by transfection of NP-AERD fibroblasts.

CONCLUSION

Altered expression of EP2 in patients with AERD contributes to deficient induction of IL-1RI, reducing the capacity of IL-1β to increase COX-2 and mPGES-1 expression, which results in low PGE2 production. This impairment in the generation of PGE2 subsequently reduces its ability to induce IL-1RI.

Multiple CD11c+ cells collaboratively express IL-1β to modulate stromal vascular endothelial growth factor and lymph node vascular-stromal growth

Lymphadenopathy in autoimmune and other lymphoproliferative diseases is in part characterized by immunoblasts and vascular proliferation. The lymph node vasculature, along with the nonvascular stromal compartment, supports lymphocyte function, and targeting vascular-stromal expansion in inflamed nodes may modulate lymphocyte function in disease. CD11c(+) cells are essential for vascular-stromal proliferation and the upregulation of vascular endothelial growth factor (VEGF) needed for vascular proliferation. However, targetable CD11c(+) cell-derived molecular mediators, the identity of relevant CD11c(+) cells, and whether CD11c(+) cells directly stimulate VEGF-expressing stromal cells are poorly understood. In this study we show that CD11c(+) CD11b(+) CCR2-dependent monocytes and CCR7-dependent dendritic cells express IL-1β. IL-1β blockade, IL-1β deficiency in radiosensitive cells, and CCR2/CCR7 double deficiency but not single deficiency all attenuate immunization-induced vascular-stromal proliferation. gp38(+) stromal fibroblastic reticular cells (FRCs) that express VEGF are enriched for Thy1(+) cells and partially overlap with CCL21-expressing FRCs, and FRC VEGF is attenuated with IL-1β deficiency or blockade. IL-1β localizes to the outer borders of the T zone, where VEGF-expressing cells are also enriched. Ex vivo, CD11b(+) cells enriched for IL-1β(+) cells can directly induce cultured gp38(+)Thy1(+) FRCs to upregulate VEGF. Taken together, these results suggest a mechanism whereby multiple recruited CD11c(+) populations express IL-1β and directly modulate FRC function to help promote the initiation of vascular-stromal growth in stimulated lymph nodes. These data provide new insight into how CD11c(+) cells regulate the lymph node vascular-stromal compartment, add to the evolving understanding of functional stromal subsets, and suggest a possible utility for IL-1β blockade in preventing inflammatory lymph node growth.

Hematopoietic growth factor receptors

The formation of the cellular constituents of the blood is regulated by a series of endogenous polypeptides with largely paracrine function. A number of these hematopoietic growth factors (HGF's), which include colony stimulating factors, interleukins, and erythropoietin, have been purified to homogeneity and cloned, which in turn has led to extensive investigations of their biochemical properties and biological effects and functions. The HGF's act on target cells by binding to receptors. The kinetics and, to an even larger extent, dynamics of the factor/receptor associations display several intriguing characteristics, most of which are still poorly understood. Herein, the biochemical characteristics of HGF's receptors as well as the binding properties, post-receptor binding events and receptor modulation resulting from the association of HGF's and their target cells are reviewed.

Systemic immune challenge activates an intrinsically regulated local inflammatory circuit in the adrenal gland

There is evidence from in vitro studies that inflammatory messengers influence the release of stress hormone via direct effects on the adrenal gland; however, the mechanisms underlying these effects in the intact organism are unknown. Here we demonstrate that systemic inflammation in rats elicited by iv injection of lipopolysaccharide results in dynamic changes in the adrenal immune cell population, implying a rapid depletion of dendritic cells in the inner cortical layer and the recruitment of immature cells to the outer layers. These changes are accompanied by an induced production of IL-1beta and IL-1 receptor type 1 as well as cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in these cells, implying local cytokine-mediated prostaglandin E(2) production in the adrenals, which also displayed prostaglandin E(2) receptors of subtypes 1 and 3 in the cortex and medulla. The IL-1beta expression was also induced by systemically administrated IL-1beta and was in both cases attenuated by IL-1 receptor antagonist, consistent with an autocrine signaling loop. IL-1beta similarly induced expression of cyclooxygenase-2, but the cyclooxygenase-2 expression was, in contrast, further enhanced by IL-1 receptor antagonist. These data demonstrate a mechanism by which systemic inflammatory agents activate an intrinsically regulated local signaling circuit that may influence the adrenals' response to immune stress and may help explain the dissociation between plasma levels of ACTH and corticosteroids during chronic immune perturbations.

Differential effects of anti-IL-1R accessory protein antibodies on IL-1alpha or IL-1beta-induced production of PGE(2) and IL-6 from 3T3-L1 cells

Soluble or cell-bound IL-1 receptor accessory protein (IL-1RAcP) does not bind IL-1 but rather forms a complex with IL-1 and IL-1 receptor type I (IL-1RI) resulting in signal transduction. Synthetic peptides to various regions in the Ig-like domains of IL-1RAcP were used to produce antibodies and these antibodies were affinity-purified using the respective antigens. An anti-peptide-4 antibody which targets domain III inhibited 70% of IL-1beta-induced productions of IL-6 and PGE(2) from 3T3-L1 cells. Anti-peptide-2 or 3 also inhibited IL-1-induced IL-6 production by 30%. However, anti-peptide-1 which is directed against domain I had no effect. The antibody was more effective against IL-1beta compared to IL-1alpha. IL-1-induced IL-6 production was augmented by coincubation with PGE(2). The COX inhibitor ibuprofen blocked IL-1-induced IL-6 and PGE(2) production. These results confirm that IL-1RAcP is essential for IL-1 signaling and that increased production of IL-6 by IL-1 needs the co-induction of PGE(2). However, the effect of PGE(2) is independent of expressions of IL-1RI and IL-1RAcP. Our data suggest that domain III of IL-1RAcP may be involved in the formation or stabilization of the IL-1RI/IL-1 complex by binding to epitopes on domain III of the IL-1RI created following IL-1 binding to the IL-1RI.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Marsupialization inhibits interleukin-1α expression and epithelial cell proliferation in odontogenic keratocysts

BACKGROUND

Marsupialization results in the reduction of odontogenic cyst size. Interleukin-1alpha (IL-1alpha) is thought to play a crucial role for the expansion of odontogenic keratocysts. The aim of this study was to investigate the effects of marsupialization on the expression of IL-1alpha and on the proliferating activity of a lining epithelium in odontogenic keratocysts.

METHODS

The concentrations of IL-1alpha, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in the intracystic fluids of odontogenic keratocysts were measured by the enzyme-linked immunosorbent assay (ELISA). The expression of IL-1alpha mRNA in odontogenic keratocysts was measured before and after marsupialization by in situ hybridization. The expression of IL-1alpha and epithelial cell-proliferating activities in odontogenic keratocysts were also measured by immunohistochemistry using antibodies for human IL-1alpha and Ki-67 antigen, respectively.

RESULTS

The intracystic fluid levels of IL-1alpha were significantly higher than those of IL-6 and TNF-alpha in odontogenic keratocysts. In situ hybridization and immunohistochemistry showed that strong expression of IL-1alpha mRNA and protein was mainly detected in the epithelial cells of odontogenic keratocysts. After marsupialization, the signal intensities for IL-1alpha mRNA and protein were significantly decreased. In addition, the Ki-67 labeling index of the epithelial cells was decreased proportionally with the grade of IL-1alpha mRNA expression after the marsupialization.

CONCLUSION

Our findings suggest that marsupialization may reduce the size of odontogenic keratocyst by inhibiting IL-1alpha expression and the epithelial cell proliferation.

Prostaglandin E2 suppressed IL-15-mediated human NK cell function through down-regulation of common gamma-chain

NK cell function is regulated by cytokines and certain biochemical mediators in a positive or negative manner. This study was performed to investigate the suppressive effects of PGE(2) on IL-15-activated human NK cell function. Purified NK cells were cultured with 200 ng/ml IL-15 for 2 days in the presence or absence of 10-200 ng/ml PGE(2). PGE(2) significantly suppressed NK cell-mediated cytotoxicity and IFN-gamma production at the secretional and the transcriptional levels. We also evaluated the effect of PGE(2) on the IL-15R complex that consists of IL-2Rbeta, common gamma-chain (gamma(c)-chain), and a specific chain IL-15Ralpha. Percentage of positive cells and number of binding sites for gamma(c)-chain were significantly increased after IL-15 treatment; however, a substantial decrease was observed with PGE(2) cotreatment. In contrast, constitutive expression of IL-2Rbeta was significantly decreased after IL-15 treatment, with no change detected in the presence of PGE(2.) At the transcriptional level, neither IL-15 nor PGE(2) had significant effects on the expression of beta- or gamma(c)-chains. There was a 3-fold increase in the expression of IL-15Ralpha at the transcriptional level that peaked at 8 h after IL-15 treatment; however, PGE(2) had no significant effect. Suppression of NK function by PGE(2) was not due to the endogenous production of IL-4, IL-10, or TGF-beta(1) by NK cells. These results suggest that down-regulation of surface expression of gamma(c)-chain on NK cells may be one mechanism through which PGE(2) mediates suppression of IL-15-activated NK cell function.

[In vitro and in vivo study of regulation mechanisms of type I interleukin-1 receptor]

Interleukin 1 (IL-1) is one of the inflammatory cytokines, which plays a pivotal role in both host defense and homeostasis. Its signal is transduced by type I IL-1 receptor (IL-1RI). This report gives an insight into the regulatory mechanism of IL-1RI in both in vitro and in vivo. IL-1 up-regulates IL-1RI through prostaglandin E2 (PGE2) production on human fibroblasts. However, in the presence of indomethacin, IL-1 down-regulates the receptor by destabilizing IL-1 receptor mRNA. Type I and type II interferons (IFNs) up-regulate the expression of IL-1RI. This up-regulation leads to the increasing susceptibility of IL-1RI to IL-1, as the DNA binding of IL-1-induced NF-kappa B and the production of IL-1-induced IL-6 from the fibroblasts are augmented by pretreatment with IFNs. On the other hand, the expression of cell surface IL-1RI is inhibited by tyrosine kinase inhibitors, herbimycin and genistein, resulting in reduction of the kinase activity of IRAK (IL-1 receptor associated kinase) and IL-1-induced IL-6 production from the fibroblasts. Lipopolysaccharide (LPS) augments the expression of IL-1RI mRNA and cell surface molecule in the hepatocytes of mice in vivo, and the augmentation is mediated by the interaction of IL-1, IL-6, and of glucocorticoid (GC). When hepatocytes were pretreated with dexamethasone (Dex) and IL-6, the activation of IRAK was augmented in response to IL-1, indicating that IL-1 signaling is also up-regulated. In addition, IL-1 treatment ather combined administration of Dex and IL-6 into mice markedly increased the serum level of serum amyloid A. These data suggest that the expression of IL-1RI is regulated by inflammatory cytokines, PGE2, GC and LPS in vitro and in vivo. This study shows that the biological activity of IL-1 can be controlled by regulating the expression of IL-1RI, and therefore proposes the use of pharmaceutical drugs for the regulation of cytokine expression.

Regulation of IL-1-induced gingival collagenase gene expression by activator protein-1 (c-Fos/c-Jun)

Matrix metalloproteinase-1 is probably involved in the progression of periodontal disease. The aim of this study was to investigate whether IL-1beta stimulates the expression of the activator protein 1 (AP-1) transcription factor and, consequently, if the AP-1 transcription factor participates in the regulation of collagenase gene expression in human gingival fibroblast cells. In this study, we demonstrate that the concentration of the protein components of AP-1 transcription factor, c-Fos and c-Jun, is enhanced by IL-1beta both at mRNA and protein levels, utilizing Northern blot analysis, electrophoretic mobility gel shift assay and Western blot analysis. The IL-1beta stimulated the collagenase-CAT and AP-1-CAT activities in a dose dependent manner with respect to the amount of DNA used in transfections. Further, overexpression of c-Fos and c-Jun proteins revealed a dose-dependent transcriptional activation of the collagenase promoter. These findings, coupled with the existence of AP-1 consensus DNA binding sites on the collagenase gene promoter, show that regulation of collagenase gene expression by IL-1beta involves the transcription factor AP-1 in gingival fibroblasts.

Augmentation of Type I IL-1 Receptor Expression and IL-1 Signaling by IL-6 and Glucocorticoid in Murine Hepatocytes

IL-1 signal is transduced through type I receptor (IL-1RI). We have recently reported that LPS augments IL-1RI mRNA expression in the hepatocytes of mice in vivo, and the augmentation is mediated by the interaction of IL-1, IL-6, and glucocorticoid (GC). In this study, we examined whether IL-1RI mRNA expression level in the hepatocytes reflects those of cell surface molecule and IL-1 signaling. When primary cultured murine hepatocytes were treated with dexamethasone (Dex) or IL-6, these two reagents synergistically up-regulated IL-1RI mRNA expression in the cells. 125I-labeled IL-1 binding experiment showed that the level of binding was also up-regulated by the treatment with Dex and IL-6. Scatchard analysis revealed that the number of IL-1R increased. The increased binding of IL-1 was completely inhibited by an Ab against murine IL-1RI, indicating that Dex and IL-6 augmented the expression of cell surface IL-1RI molecule. When hepatocytes were pretreated with Dex and IL-6, the activation of IL-1R-associated kinase was augmented in response to IL-1, indicating that IL-1 signaling was also augmented. In addition, IL-1 treatment following administration of the combination of Dex and IL-6 into mice markedly increased the serum level of serum amyloid A. These results indicate that GC and IL-6 augment the expression of cell surface IL-1RI in hepatocytes, as well as IL-1 signaling and IL-1R-associated kinase activation, through up-regulation of IL-1RI mRNA level, which represents a novel regulatory network between IL-1, GC, and IL-6.

The rat intraovarian interleukin (IL)-1 system: cellular localization, cyclic variation and hormonal regulation of IL-1beta and of the type I and type II IL-1 receptors

An increasing body of evidence supports the possibility that intraovarian interleukin (IL)-1 plays an intermediary role in the periovulatory cascade. To gain further insight into the intraovarian IL-1 hypothesis, we studied the cellular localization cyclic variation and hormonal regulation of IL-1beta, as well as of the type I and type II IL-1 receptors (IL-1R) in immature rats. In situ hybridization localized IL-1beta and type I IL-1R transcripts to the granulosa cell compartment, the innermost layers of the theca interna and to the oocyte of the untreated immature ovary. Molecular probing of whole ovarian material in the course of a simulated estrous cycle revealed a progressive preovulatory increase in IL-1beta and type I IL-1R transcripts to an in vivo peak at the time of ovulation (3.0- and 2.5-fold increases over untreated controls; P < 0.05). Comparable efforts to localize and probe for type II IL-IR transcripts failed to elicit a detectable signal. The basal in vitro expression pattern of IL-1beta and type II IL-1R transcripts by whole ovarian dispersates revealed an early (4 h) spontaneous increase to a peak (2.1- and 5.8-fold increases over time 0: P < 0.05) followed by a gradual decline to a 48 h nadir. Treatment of whole ovarian dispersates with the IL-1 receptor antagonist (IL-1RA) or with IL-1beta failed to alter the initial (4 h) burst of IL-1beta or of type II IL-1R expression thereby suggesting IL-1-independence. Treatment with hCG proved equally ineffective. However, longer-term treatment of whole ovarian dispersates with IL-1beta produced a significant secondary increase (5.9-fold over time 0; P < 0.05) in IL-1beta (but not type II IL-1R) transcripts by 48 h. This IL-1 effect was completely blocked by co-treatment with IL-1RA thereby suggesting mediation via a specific IL-1 receptor. Qualitatively comparable but quantitatively reduced results obtained for isolated granulosa cells. The basal in vitro expression pattern of type I IL-1R transcripts by whole ovarian dispersates revealed a progressive spontaneous increase (3.1-fold increase overall) over the 48 h culture. Treatment with IL-1beta produced a significant (P < 0.05) increase (5-fold) in type I IL-1R transcripts by 48 h, an effect which was completely blocked by co-treatment with IL-1RA. Taken together, these observations: (1) localize IL-1beta and its type I receptor to granulosa cells, the innermost layers of the theca interna and to the oocyte; (2) confirm their periovulatory in vivo expression pattern; (3) document their expression by untreated cultured whole ovarian dispersates; and (4) demonstrate their in vitro responsiveness to receptor-mediated/IL-1-driven autocrine amplification. The type II IL-1R was undetectable in vivo, its in vitro expression pattern proving IL-1- and hCG-independent. The periovulatory expression pattern of IL-1beta and its receptor (type I) is compatible with the notion that the intraovarian IL-1 system may play an intermediary role in the ovulatory process.

Down-regulation of the hepatic cytochrome P450 by an acute inflammatory reaction: implication of mediators in human and animal serum and in the liver

1. Infection and inflammation trigger a cascade of mediators that eventually will down-regulate the hepatic cytochrome P450 (P450). The present study aimed to characterize the mediators contained in the serum of rabbits with an acute inflammatory reaction (AIR) induced by the s.c. injection of turpentine (5 ml), and in the serum of humans with an acute upper respiratory tract viral infection. 2. Hepatocytes from control (H(CONT)) rabbits and rabbits with an AIR (H(INFLA)) were isolated and cultured. Compared with H(CONT) in H(INFLA) the production of theophylline metabolites, 3-methylxanthine (3MX), 1-methyluric acid (1MU), and 1,3-dimethyluric acid (1,3DMU) was reduced as was the amount of total P450, while lipid peroxidation was increased. Incubation of H(INFLA) with serum of rabbits with an AIR (RS(INFLA)) for 4 h further reduced the formation of the metabolites of theophylline as well as the amount of P450, and enhanced the lipid peroxidation. RS(INFLA) obtained 6, 12 and 24 h after the injection of turpentine showed the same ability to down-regulate hepatic P450 as the serum obtained at 48 h. 3. The efficacy (Emax) of RS(INFLA) to inhibit the formation of theophylline metabolites differed, i.e. 1,3DMU > 1MU > 3MX, and the potency of serum mediators (IC50) was similar for 3MX and 1MU, but lower for 1,3DMU. 4. Incubation of serum of human volunteers (HS(INFLA)) with a viral infection with H(CONT) or H(INFLA) reduced the production of theophylline metabolites, as well as the amount of P450, and increased the lipid peroxidation. HS(INFLA) depressed 1,3DMU more efficiently than 3MX and 1MU. HS(INFLA) reduced 3MX with greater efficacy than did RS(INFLA). Potency was very variable but not different from rabbits. 5. It is concluded that the serum of rabbits with an AIR or of humans with a viral infection contain several mediators that inhibit noncompetitively various isoenzymes of the hepatic P450. The decrease in P450 induced by HS(INFLA) or RS(INFLA) is closely associated with the increase in lipid peroxidation (r2= 0.8870) suggesting that lipid peroxidation could directly or indirectly be involved in the P450 down-regulation.

Role of glucocorticoid in the upregulation of type I interleukin-1 receptor mRNA expression in hepatocytes of endotoxin-administrated mice

The interleukin-1 (IL-1) signal is transduced through type I IL-1 receptor (IL-1RI). We have recently reported that lipopolysaccharide (LPS) upregulated IL-1RI mRNA expression in mouse liver in vivo and that IL-1 and IL-6 directly upregulated IL-1RI mRNA expression in primary cultured mouse hepatocytes. Glucocorticoid (GC) has been reported to increase IL-1 binding to the cell surface and the expression level of IL-1R mRNA in a variety of cell types. As serum GC level is elevated in an inflammatory response, we evaluated the role of GC in LPS-induced upregulation of IL-1RI mRNA in the mouse liver. When LPS was administered to adrenalectomized (ADX) mice, IL-1RI mRNA was upregulated at a level comparable to those of untreated or sham-operated mice. A high dose of dexamethasone (Dex), however, caused upregulation of the mRNA. When primary cultured mouse hepatocytes were treated with Dex, only a weak upregulation of IL-1RI mRNA was observed. However, Dex in combination with IL-1 or IL-6 markedly enhanced the IL-1RI mRNA expression. A marked upregulation of the mRNA was also induced by treatment with a combination of IL-1 and IL-6 in the absence of Dex, reflecting the observation in ADX mice. These results suggest that the upregulation of IL-1RI mRNA in response to LPS is induced by the interaction of IL-1 and IL-6 and that GC augments their effect.

Endotoxin-induced upregulation of type I interleukin-1 receptor mRNA expression in hepatocytes of mice: role of cytokines

Interleukin-1 (IL-1) signal is transduced through the type I IL-1 receptor (IL-1RI). Although regulation of IL-1R expression has been extensively studied in vitro, little is known about it in vivo. By using RT-PCR analysis, we investigated the regulation of the IL-1RI mRNA expression level in various organs of mice at 2, 6, and 24 h following lipopolysaccharide (LPS) administration. IL-1RI mRNA expression in response to LPS appeared to be different in various organs. As a marked and sustained increase of IL-1RI mRNA expression in the liver was observed, we investigated the mechanism of the upregulation. IL-1, IL-6, and tumor necrosis factor (TNF) all increased the mRNA expression in the liver when administrated in vivo. In situ hybridization revealed that upregulation of IL-1R mRNA was observed in parenchymal liver cells (hepatocytes) in response to LPS administration. When primary cultured hepatocytes were treated in vitro, IL-1, IL-6, conditioned medium from LPS-treated mouse macrophages, and serum from LPS-treated mouse upregulated IL-1RI mRNA expression, but LPS, TNF, and prostaglandin E2 failed to do so. Therefore, these results suggest that the upregulation of IL-1RI mRNA in the hepatocytes by LPS administration is mediated by cytokines, especially by IL-1 and IL-6. The results also indicate that the regulation is different in different organs, and microenvironmental factors may be important.

Increased expression of interleukin-1 receptors on fibroblasts derived from inflamed gingiva

We investigated the expression of interleukin-1 receptors (IL-1R) on the surfaces of cultured gingival fibroblasts derived from healthy and inflamed gingiva and the effects of IL-1 alpha and IL-1 beta and prostaglandin E2 (PGE2) on IL-1R expression. Fibroblasts were obtained from explant culture of both healthy and inflamed gingiva. IL-1R on cell surfaces was detected immunohistochemically using an anti-human IL-1R monoclonal antibody. IL-1R expression was assessed quantitatively using an enzyme linked immunosorbent assay (ELISA). Positive staining for IL-1R was more evident on cells from inflamed gingiva compared with cells from healthy gingiva. The ELISA showed a significantly increased number of IL-1R on cells from inflamed gingiva compared with cells from healthy gingiva (P < 0.05). Treatment with IL-1 but not PGE2 increased expression of IL-1R on fibroblasts. These findings suggest that gingival fibroblast responses to IL-1 may represent a mechanism for amplification of gingival inflammation.

Interleukin-1 beta and phenytoin reduce alpha 1 (I) procollagen mRNA expression in human gingival fibroblasts

Effects of and interactions between interleukin-1 beta (IL-1 beta) and phenytoin (PHT) on alpha 1 (I) procollagen gene and protein expression in human gingival fibroblasts and its relation to prostaglandin E2 (PGE2) formation were studied. IL-1 beta (300 pg/ ml) reduced the steady-state level of alpha 1 (I) procollagen mRNA by 50% and decreased the amount of procollagen I by 35%. PHT (10 micrograms/ml) reduced the level of alpha 1 (I) procollagen mRNA by 40% but the amount of procollagen I in the medium was unchanged. In combination with IL-1 beta, PHT potentiated the inhibitory effect of IL-1 beta on alpha 1 (I) procollagen mRNA level that was accompanied by an increased PGE2 formation. Preincubation with indomethacin (10(-6) M) partially reduced the inhibitory effect of IL-1 beta as well as of IL-1 beta in combination with PHT on the mRNA level of alpha 1 (I) procollagen. The inhibitory effect of PHT was unaffected by indomethacin treatment. Addition of exogenous PGE2 (> or = 10 nM) dose-dependently reduced steady-state level of alpha 1 (I) procollagen mRNA as well as the amount of procollagen 1. The study indicates that IL-1 reduces the expression of alpha 1 (I) procollagen mRNA in human gingival fibroblasts partly by a prostaglandin endoperoxide (PGH) synthase-mediated pathway and partly by a PGH-synthase independent pathway, whereas PHT reduces alpha 1 (I) procollagen gene expression by a PGH-synthase independent pathway. The potentiation of the inhibitory effect of IL-1 induced by PHT was mediated mainly by a PGH-synthase dependent pathway.

Role of fibroblasts in the regulation of proinflammatory interleukin IL-1, IL-6 and IL-8 levels induced by keratinocyte-derived IL-1

In the epidermis, the keratinocytes are the first cells to be encountered by external stimuli and they are able to promote the inflammatory response by increased production and release of various cytokines. In their turn, these cytokines may directly affect the production of proinflammatory cytokines in human dermal fibroblasts. In addition, in both epithelial and mesenchymal cells cytokine production may be modulated by their mutual interaction, and thereby regulate the inflammatory response. The present study aimed to examine the role of fibroblasts in the regulation of proinflammatory IL-1, IL-6 and IL-8 levels induced by keratinocyte-derived IL-1. The data show that in fibroblasts exposed to conditioned media derived from cultures of normal human keratinocytes or squamous carcinoma cells (SCC-4), both the IL-8 and IL-6 mRNA expression as well as protein production were elevated. In addition, it was shown that these effects were induced by IL-1 alpha. The IL-1 alpha-induced increase in IL-8 and IL-6 production, both on the protein level as well as on the mRNA level, were concentration dependent and occurred almost simultaneously. While the induction of IL-6 and IL-8 occurred simultaneously, the IL-6 mRNA remained elevated for longer. In contrast to increased IL-6 and IL-8 production the IL-1 alpha levels markedly decreased upon culturing of fibroblasts in keratinocyte-derived conditioned medium. From internalization experiments it could be concluded that binding of IL-1 to IL-1 receptors, and its subsequent internalization and intracellular degradation is the most likely mechanism involved in the reduction of IL-1 levels by fibroblasts. Comparing the rate of IL-1 reduction in the presence of various cell types indicated that the rate of IL-1 reduction is directly related to the number of IL-1 receptors found on these cell types. In conclusion, these results indicate that the release of IL-1 alpha by activated keratinocytes may act as an inducer of IL-8 and IL-6 production in neighbouring fibroblasts. This may be an important pathway for the amplification of the inflammatory response. The amounts of both cytokines produced by fibroblasts were at least two to three orders of magnitude higher than those produced by keratinocytes, suggesting an important role of fibroblasts in the general inflammatory response. Furthermore, fibroblasts might be involved in turning off this inflammatory response by reducing IL-1 levels, most likely via IL-1 receptor-mediated uptake.

Early cytokine synthesis in the excised mouse cornea

Corneas excised from normal BALB/c mice and incubated in vitro were analyzed for the production of "early-warning" cytokines via reverse transcription-polymerase chain reaction and ELISA. It was found that the trauma of excision stimulated rapid IL-1 alpha synthesis, with peak protein accumulation occurring at 6 h, whereas IL-6 synthesis was maximal at 18 h. Neither IL-1 beta protein nor message was detected at any point, and TNF-alpha synthesis never increased above constituted levels. Antibody neutralization of endogenous IL-1 alpha blocked IL-6 synthesis. Addition of exogenous IL-1 alpha induced IL-1 alpha and IL-6 synthesis in vitro. Inoculation of IL-1 alpha into the cornea induced IL-6 synthesis in vivo. Addition of IL-1 alpha could stimulate IL-1R, IL-1 alpha, and IL-6 mRNA synthesis in the epithelial, stromal, and endothelial components of the cornea. However, protein production was readily detected only in the epithelial layer. We concluded that mechanical trauma to the mouse cornea triggers the enhanced synthesis of IL-1 alpha and IL-1R, which in turn results in the production of IL-6 and more IL-1 alpha. That corneal excision did not stimulate the synthesis of IL-1 beta or TNF-alpha indicates that there is a selective induction of early cytokine expression in this specialized tissue.

Ex vivo evidence for PGE2 and LTB4 involvement in cutaneous leishmaniasis: relation with infection status and cytokine production

Ex vivo culture of spleen cells from BALB/c mice infected with 2 x 10(6) Leishmania major (L. major) promastigotes were cultured with ConcanavalinA (ConA) or leishmanial antigen (L. Ag) and tested for prostaglandin E2 (PGE2) and for leukotriene B4 (LTB4), in order to study their involvement in the evolution of cutaneous leishmaniasis and the connexion with lymphokine-mediated responses. The data were compared with those obtained in BALB/c mice protected against L. major by sublethal irradiation (550 rad; cured mice). In the unprotected BALB/c mice the levels of PGE2 that were responsible for the depression of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF alpha) Th1-associated cytokines and for the relative increase in the interleukin-4 (IL-4) became higher and higher as the lesion progressed. On the contrary, the cured mice produced levels of PGE2 similar to normal uninfected controls, high levels of TNF alpha and IFN-gamma and low levels of IL-4. Elevated levels of LTB4 were detected in the early stage of infection in the unprotected mice compared to cured ones, a sign of more intense inflammation and a stimulus for the recruitment of inflammatory cells. The observation that exogenous LTB4 was able to enhance in vitro both Th1 cytokines in cured mice and Th2 cytokines in unprotected ones suggests that LTB4 could act in the recruitment of the T cells already committed to Th1 or Th2 phenotype.

Type I and type II interferons upregulate functional type I interleukin-1 receptor in a human fibroblast cell line TIG-1

The regulation of type I interleukin-1 receptor (IL-1R) expression by type I, interferon (IFN)-alpha A/D, and type II IFN, IFN-gamma, in a human fibroblast cell line TIG-1 was investigated. After 2 h stimulation with human IFN-alpha A/D or IFN-gamma, the levels of type I IL-1R mRNA increased. We previously reported that IL-1 upregulates transcription and cell surface molecules of type I IL-1R in TIG-1 cells through induction of prostaglandin (PG) E2 and cAMP accumulation. However, indomethacin was unable to inhibit the effect of IFNs, indicating that IFNs augment IL-1R expression through a pathway distinct from that of IL-1. The augmentation was also observed in other fibroblast cell lines. Nuclear run-on assays and studies of the stability of mRNA suggested that the increase in IL-1R mRNA was a result of the enhanced transcription of IL-1R gene. Binding studies using 125I-IL-1 alpha revealed that the number of cell surface IL-1R increased with no change in binding affinity by treatment with these IFNs. Pretreatment of the cells with IFNs enhanced IL-1-induced IL-6 production, indicating that IFNs upregulate functional IL-1R. IL-1 and IFNs are produced by the same cell types, as well as by the adjacent different cell types, and are concomitantly present in lesions of immune and inflammatory reactions. These results therefore suggest that IFNs exhibit synergistic effects with IL-1 through upregulation of IL-1R. Augmented production of IL-6 may also contribute to the reactions.

Interleukin-1 and its inhibitors: implications for disease biology and therapy

IL-1 alpha and IL-1 beta are polypeptide hormones that exhibit a broad spectrum of beneficial and harmful biologic activities. Clinical trials designed to benefit from its stimulatory effects on human hematopoiesis and from its role in improving host defenses, are being currently conducted. Other in vivo studies, using IL-1 inhibitors with an attempts to block the detrimental effects of IL-1, are underway. Because of the multifunctional effects of IL-1 in human physiology and its pathogenetic role in several diseases, the capability to control the effects of IL-1 may prove to be a useful tool in medical practice.

The type II 'decoy' receptor: a novel regulatory pathway for interleukin 1

The interleukin 1 (IL-1) system plays a central role in inflammation and immunity. Of the two receptors that bind IL-1, the type I receptor is known to mediate signaling activity, whereas the function of the type II receptor remains unknown. Here, Francesco Colotta and colleagues review the properties of these receptors and summarize evidence indicating that the type II receptor acts as a regulated decoy target for IL-1.

The role of cytokines in the production of prostacyclin and thromboxane in human mononuclear cells

The aim of the present work was to study the regulatory effects of cytokines (TNF alpha, IL-1 beta and IL-2) on the production of the prostglandins (PGI2 and TXA2) from human mononuclear cells. Our major findings were: (1) TNF alpha, IL-1 beta and IL-2 were all able to induce PGI2 and TXA2 syntheses in mononuclear cells. (2) TNF alpha exerted a biphasic effect on prostaglandin production. The lower concentrations of TNF alpha enhanced prostaglandin synthesis while the higher concentrations did not. (3) TNF alpha had a positive effect after only a 30-minute incubation, whereas IL-1 beta and IL-2 required a 8-hour incubation to produce a significant effect. This suggests that the different mechanisms are involved in their actions. (4) The effects of cytokines on the production of PGI2 were greater than that on the production of TXA2. It is concluded that cytokines can not only regulate the production of prostaglandins but also change the pattern of their formation.

Uncoordinate regulation of collagenase, stromelysin, and tissue inhibitor of metalloproteinases genes by prostaglandin E2: selective enhancement of collagenase gene expression in human dermal fibroblasts in culture

The degradative effects of interleukin-1 (IL-1) on the extracellular matrix of connective tissue are mediated primarily by metalloproteinases and prostaglandins. Clinical observations suggest that these effects can be prevented, to some extent, by the use of non-steroidal anti-inflammatory drugs. We have examined the role of prostaglandin E2 (PGE2) in IL-1-induced gene expression by human skin fibroblasts in culture. Incubation of confluent fibroblast cultures with varying concentrations (0.01-1.0 microgram/ml) of PGE2 led to a dose-dependent elevation of collagenase mRNA steady-state levels, the promoter activity, and the secretion of the protein, whereas relatively little effect was observed on stromelysin and TIMP gene expression. Exogenous PGE2 had no additive or synergistic effect with IL-1 on collagenase gene expression. Furthermore, commonly used non-steroidal anti-inflammatory drugs (indomethacin, acetyl salicylic acid and ibuprofen), at doses which block prostaglandin synthesis in cultured fibroblasts, failed to counteract IL-1-induced collagenase and stromelysin gene expression, nor did they affect TIMP expression. Although the effects of PGE2 did not potentiate those of IL-1 on collagenase gene expression in vitro, one could speculate that massive production of PGE2 by connective tissue cells in vivo in response to inflammatory mediators such as IL-1 or tumor necrosis factor-alpha, could lead to sustained expression of collagenase in connective tissue cells after clearance of the growth factors.

Interleukin-1 beta stimulates prostaglandin E2 and F2 alpha synthesis in human ovarian granulosa cells in culture

To evaluate the roles of interleukin-1 (IL-1) in regulation of ovarian prostaglandin (PG) synthesis, we examined the effects of IL-1 beta on PGE2, PGE2 alpha, 6-keto-PGF 1 alpha and thromboxane (TX) B2 synthesis in cultures of human ovarian granulosa cells. Granulosa cells were obtained from hyperstimulated follicles in patients undergoing oocyte retrieval for in vitro fertilization-embryo transfer (IVF-ET). IL-1 beta increased immunoreactive concentrations of PGE2 and PGF2 alpha in culture medium in time- and dose-dependent manners. Concentration of PGE2 was significantly higher after 24 h incubation with 5 or more units/ml of IL-1 beta, when compared to the control value obtained without IL-1 beta (P < 0.05). Concentration of PGF2 alpha was significantly higher after 8 h incubation with more than 2 units/ml of IL-1 beta (P < 0.05). The increase in PGE2 was observed even in the presence of human chorionic gonadotropin (hCG), and blocked by indomethacin, an inhibitor of cyclooxygenase. During a 10 day incubation period, stimulatory effects of IL-1 beta on PG synthesis were observed only on the first 2 days incubations. Concentrations of 6-keto-PGF 1 alpha and TXB2 were below our measurement limits. This study demonstrated that IL-1 beta stimulates PG synthesis in human ovarian granulosa cells in vitro. IL-1 seems to play an important role in regulating ovarian functions.

Regulation of human normal and osteoarthritic chondrocyte interleukin-1 receptor by antirheumatic drugs

OBJECTIVE

To determine the effect of antirheumatic drugs and corticosteroids on interleukin-1 receptor (IL-1R) levels in, and IL-1-stimulated metalloprotease synthesis and expression by, normal and osteoarthritic (OA) human articular chondrocytes.

METHODS

IL-1R affinity and density of human chondrocytes were determined using radioligand binding experiments. Collagenase and stromelysin synthesis activities were analyzed by 14C-labeled type I collagen and Azocoll assays, respectively. Their messenger RNA (mRNA) levels were determined by Northern blot analysis. IL-1 alpha, IL-1 beta, IL-1 receptor antagonist, and beta 2-microglobulin were measured using enzyme-linked immunosorbent assays. Protein synthesis was determined by 3H-leucine incorporation.

RESULTS

Antirheumatic drugs reduced the IL-1R level in normal and OA chondrocytes in a dose-dependent manner. In normal chondrocytes, tenidap reduced the IL-1R level by 44% at 5 micrograms/ml to 88% at 100 micrograms/ml (50% inhibition constant [IC50] 10.1 micrograms/ml), indomethacin reduced IL-1R by 6% at 1.5 micrograms/ml to 43% at 60 micrograms/ml, and naproxen reduced IL-1R by 10% at 10 micrograms/ml to 41% at 300 micrograms/ml; the effects observed with indomethacin and naproxen occurred only when the drugs were used at levels above their therapeutic concentrations. In OA chondrocytes, the effect of indomethacin and naproxen on the IL-1R level was greatly reduced, whereas tenidap still had a marked effect (IC50 22.5 micrograms/ml). Dexamethasone and hydrocortisone had no consistent effect on the IL-1R level. At a therapeutic concentration (20 micrograms/ml), tenidap was found to reduce the IL-1R level in a time-dependent manner, with maximum inhibition (98%) by 48 hours. Tenidap was also found to markedly reduce collagenase and stromelysin synthesis and mRNA levels in IL-1-stimulated chondrocytes.

CONCLUSION

The suppressive effects of tenidap on IL-1-stimulated metalloprotease synthesis and expression in OA and normal chondrocytes are likely related to a decrease in IL-1R levels. At therapeutic concentrations, tenidap has a greater effect on the IL-1R level than is seen with indomethacin or naproxen, and glucocorticoids have no effect on IL-1R.

1,25-Dihydroxyvitamin D3 increases type 1 interleukin-1 receptor expression in a murine T cell line

The biologically active metabolite of vitamin D3, 1,25 (OH)2 D3, exerts important immunoregulatory effects in addition to being a central mediator of calcium/phosphate metabolism. Utilizing an interleukin 1 responsive murine T cell line and 125I-interleukin 1 alpha, we show that 1,25 (OH)2 D3 (5,50 nM) enhanced 125I-interleukin 1 alpha binding up to almost 2-fold over control. This 1,25 (OH)2 D3 effect occurred in a dose-dependent manner and was detectable after 24 h but not before 7 h of culture. Scatchard analysis of 125I-interleukin 1 alpha binding data demonstrated that 1,25 (OH)2 D3 enhanced interleukin 1 receptor number without a significant change in affinity. The biologically less potent metabolite of vitamin D3, 25 (OH) D3, also augmented 125I-interleukin 1 alpha binding but at steroid levels 2-3 log orders greater than 1,25 (OH)2 D3. This observation, combined with the presence of high-affinity 3H-1,25 (OH)2 D3 receptors (88 sites/cell, K = 0.45 nM) in cytosolic extracts, strongly suggests that the nuclear vitamin D receptor mediates this steroid's effect on interleukin 1 receptor expression. Based on the capacity of an anti-type 1 interleukin 1 receptor monoclonal antibody (35F5) to block 1,25 (OH)2 D3-enhanced 125I-interleukin 1 alpha binding, we conclude that this steroid augments type 1 interleukin 1 receptor expression. When combined with interleukin 1, a cytokine that also impacts MD10 interleukin 1 receptor expression, 1,25 (OH)2 D3 enhanced interleukin 1 receptor expression. Northern blots hybridized with a 32P-type 1 interleukin 1 receptor cDNA probe show that 1,25 (OH)2 D3 enhanced type 1 interleukin 1 receptor steady state mRNA levels. Functionally, 1,25 (OH)2 D3 pretreatment augmented the MD10 proliferative response to suboptimal levels of interleukin 1 (< 100 fM interleukin 1 alpha). These findings further support 1,25 (OH)2 D3's role as an immunoregulatory molecule and provides a possible mechanism by which this steroid could potentiate certain immune activities.

Epidermal growth factor potentiates interleukin 1 and tumor necrosis factor-induced prostaglandin biosynthesis in human gingival fibroblasts

The effects of and interactions between epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha) interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF-alpha) on arachidonic acid release and prostaglandin biosynthesis in human gingival fibroblasts were studied. IL-1 alpha, IL-1 beta and TNF-alpha, but not EGF nor TGF-alpha, stimulated prostaglandin E2 (PGE2) formation in the gingival fibroblasts. The effect of IL-1 alpha, IL-1 beta and TNF-alpha on PGE2 formation was significantly potentiated by EGF in a dose-dependent manner. Similarly, TGF-alpha synergistically potentiated IL-1 beta stimulated PGE2 formation. IL-1 beta but not EGF stimulated the release of 3H-arachidonic acid (3H-AA) from prelabelled gingival fibroblasts. In contrast to the effect on PGE2 formation, no synergistic interaction between EGF and IL-1 was seen on arachidonic acid (AA) release. Addition of unlabelled exogenous AA, in the presence of EGF, resulted in a significant increase in PGE2 formation compared to that seen in fibroblasts not exposed to EGF. The results demonstrate that EGF and IL-1 as well as EGF and TNF-alpha act in concert to enhance prostanoid formation in gingival fibroblasts. Data indicates that EGF potentiates the IL-1 and TNF-alpha induced PGE2 formation at the level of prostaglandin endoperoxide synthase (cyclooxygenase). The synergistic effects of inflammatory cytokines and growth factors may be of physiological importance for regulation of regenerative tissue growth during inflammation and repair.

IL-1-induced murine osteoblast IL-6 production is mediated by the type 1 IL-1 receptor and is increased by 1,25 dihydroxyvitamin D3

IL-1-induced osteoblast IL-6 production represents one possible mechanism by which IL-1 augments bone resorption. In this report, we show that the murine osteoblastic cell line (MC3T3-E1) expresses type 1 IL-1 receptors based on 125I-HrIL1 alpha binding, blocked by type 1 IL-1R antibodies (35F5), and analysis of MC3T3 RNA by reverse transcription (RT)-DNA amplification and Northern analysis. MC3T3 cells do not express detectable type 2 IL-1R mRNA by RT-DNA amplification. IL-1 induces (IL-1 ED50, 0.1 pM) IL-6 production through the type 1 IL-1R as 35F5 antibodies block IL-1-stimulated IL-6 production. Vitamin D3 increases IL-1R expression dose- and metabolite-dependently, with 1,25-(OH)2D3 having the greatest potency, and also enhances IL-1's capacity to stimulate IL-6 production at low IL-1 levels. Both IL-1 and 1,25-(OH)2D3 induce type 1 IL-1R and not type 2 IL-1R upregulation based on ligand binding and RT-DNA amplification. Increased IL-1R expression requires a 5-7-h treatment and is protein/RNA synthesis dependent. These observations imply that IL-1-induced IL-6 production in osteoblasts is mediated by type 1 IL-1Rs and that increased IL-1R expression could play a role in mediating IL-1-induced skeletal responses.

Interleukin-1 binding and prostaglandin E2 synthesis by amnion cells in culture: regulation by tumor necrosis factor-alpha, transforming growth factor-beta, and interleukin-1 receptor antagonist

Proinflammatory cytokines may promote preterm labor in the setting of intrauterine infection. Tumor necrosis factor (TNF) and interleukin-1 (IL-1) synergistically stimulate the production of prostaglandin E2 (PGE2) by amnion cells. Transforming growth factor-beta (TGF-beta) inhibits the cytokine-stimulated PGE2 production. In the present study, we investigated the binding of IL-1 beta on human amnion cells in culture. Untreated amnion cells possessed 540 +/- 60 IL-1 receptors per cell, with a dissociation constant of 1.4 +/- 0.4 nM. Cells treated with TGF-beta 1 (10 ng/ml) had 570 +/- 110 receptors per cell. TNF-alpha (50 ng/ml) increased the number of IL-1 receptors to 2930 +/- 590. TGF-beta 1 inhibited the receptor upregulation by TNF-alpha. Cells treated with TGF-beta 1 and TNF-alpha expressed 1140 +/- 590 receptors per cell. The binding affinity was not changed by the cytokines. IL-1 receptor antagonist (IL-1ra) inhibited the stimulation of amnion cell PGE2 production by IL-1 beta, but not by TNF-alpha. Amnion cells secreted large amounts of IL-1ra (1.1 +/- 0.3 ng/10(5) cells). Treatment of the cells with TGF-beta 1 or TNF-alpha did not affect the release of IL-1ra. We conclude that IL-1 receptor expression is an important step in the regulation of the effects of cytokines on amnion cell PGE2 production.

Identification of a specific receptor for interleukin-1 in vascular smooth muscle cells: regulation by interleukin-1 and interleukin-6

A fluorescently labeled ligand was utilized to establish the existence of an interleukin-1 (IL-1) receptor in vascular smooth muscle. The binding of the phycoerythrin-labeled IL-1 beta to the murine T cell line, EL-4, was examined as a positive control. The phycoerythrin-labeled IL-1 beta identified a specific IL-1 receptor in the EL-4 cells. Vascular smooth muscle cells were also positively stained by the fluorescent ligand. The binding of phycoerythrin-labeled IL-1 beta to these cells was saturable and reversed by 100-fold excess unlabeled IL-1 beta. Incubation of the vascular smooth muscle cells with IL-1 beta (25 ng/ml) or IL-6 (250 ng/ml) for 18 h increased and decreased, respectively, the percentage of cells positively stained by phycoerythrin-labeled IL-1 beta which suggests these cytokines regulate IL-1 receptor expression in these cells. These data indicate a specific receptor for IL-1 exists in vascular smooth muscle cells.

The phenytoin metabolite p-HPPH upregulates prostaglandin biosynthesis in human gingival fibroblasts challenged to interleukin-1

The effects of and interactions between the major phenytoin (PHT) metabolite 5-parahydroxyphenyl-5-phenylhydantoin (p-HPPH) and interleukin-1 (IL-1 alpha, IL-1 beta) or tumor necrosis factor alpha (TNF alpha) on prostaglandin biosynthesis in human gingival fibroblasts were studied. IL-1 alpha, IL-1 beta and TNF alpha, dose-dependently, stimulated PGE2 formation in gingival fibroblasts. The metabolite, p-HPPH (1.2-2.4 micrograms/ml), did not induce PGE2 formation itself but potentiated IL-1 alpha and IL1 beta induced PGE2 formation in the gingival fibroblasts in a manner dependent on the concentration of both IL-1 and p-HPPH. The metabolite also stimulated IL-1 induced formation of 6-Keto PGF1 alpha, the stable breakdown product of PGI2, in a dose dependent manner. IL-1 beta induces release of [3H]-arachidonic acid ([3H]-AA) from prelabelled fibroblasts, which was potentiated by p-HPPH (> or = 1.2 micrograms/ml). TNF alpha (> or = 1 ng/ml) significantly stimulated the biosynthesis of PGE2 by a process that was also potentiated by p-HPPH. Addition of exogenous, unlabelled AA (10 microM) caused an increase of PGE2 formation in the fibroblasts that was not potentiated by p-HPPH (1.6 micrograms/ml). The results indicate that treatment with p-HPPH results in upregulation of prostaglandin synthesis in gingival fibroblasts challenged to IL-1 or TNF alpha at the level of phospholipase A2.

Cytokines increase neutral endopeptidase activity in lung fibroblasts

Fibroblasts of the pulmonary interstitium are intimately involved in the response of the lung to inflammation as well as in repair of injured tissues. The response of fibroblasts within an inflammatory site appears to be directed, in part, by peptide mediators. Neutral endopeptidase (NEP), a metallopeptidase on the surface membrane of fibroblasts, can inactivate various vasoactive peptides, including kinins and tachykinins. Because lung fibroblasts both secrete cytokines and respond to mediators within the immediate environment, NEP might be regulated by locally generated cytokines. We found that several cytokines, including interleukin-1 alpha (IL-1), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor, interleukin-6, and granulocyte macrophage colony-stimulating factor, enhanced activity of NEP on the surface of intact fibroblasts. In contrast, cultured pleural mesothelial cells had much lower levels of NEP than fibroblasts, and the enzyme was not enhanced by either IL-1 or TNF-alpha. Further studies with IL-1 showed that the effect required at least 6 h of exposure to the cytokine and depended upon final cytokine concentration. Combinations of IL-1 with other cytokines increased NEP activity beyond that in cells treated with individual cytokines, but combinations had less than additive effects. Selected pharmacologic agents indicated that the mechanism involves second messenger pathways. The cytokine effect on NEP was attenuated by indomethacin, an inhibitor of cyclooxygenase, by N-[2-(methylamino) ethyl]-5-isoquinolinesulfonamide dihydrochloride, an inhibitor of protein kinase, and by adenosine 3',5' cyclic monophosphothionate, an analog of cyclic adenosine monophosphate (cAMP) that competitively inhibits the cAMP signal pathway. It was mimicked by dibutyryl cAMP and by forskolin, an activator of adenyl cyclase.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 and naproxen down-regulate the expression of IL-1 receptors in cultured human rheumatoid synovial cells (HRSC)

Using affinity binding of [125I]-IL-1 alpha and Scatchard analysis, we demonstrate here that exposure of cultured synovial cells (HRSC) to NPX (10(-4) M) for 96 h decreased the binding of IL-1 by 20 to 35%. This effect results from a down-regulation of the IL-1 receptors without change in the apparent binding affinity (kD: 770 pM). Pretreatment of cultures with IL-1 alpha (500 pg/ml) reduced the total binding of [125I]-IL-1 alpha on HRSC by 65%, indicating that IL-1 decreases the expression of its own receptors.

Regulation of synovial cell growth: basic fibroblast growth factor synergizes with interleukin 1 beta stimulating phospholipase A2 enzyme activity, phospholipase A2 activating protein production and release of prostaglandin E2 by rheumatoid arthritis synovial cells in culture

Cytokines have been implicated in the regulation of eicosanoid synthesis and synovial cell proliferation. To further define these mechanisms, we have compared the effects of basic fibroblast growth factor and platelet-derived growth factor on cell growth, prostaglandin E2 (PGE2) production and phospholipase A2 enzyme activity in long-term cultures of synovial cells from rheumatoid arthritis (RA) patients capable of proliferating in serum-free medium. Compared with serum-free medium alone, RA synovial cell growth was significantly enhanced by adding either basic fibroblast growth factor (bFGF) or platelet-derived growth factor (PDGF) to the culture medium. Growing RA synovial cells for 14 days in serum-free medium plus bFGF caused them to spontaneously release significant amounts of PGE2, an effect not seen if cells were grown in serum-free medium alone, or serum-free medium plus PDGF. Enhanced release of PGE2 occurred when arachidonic acid was added to bFGF but not PDGF-treated RA synovial cells, suggesting that bFGF increased cyclooxygenase enzyme activity in these cells. Moreover, phospholipase A2 (PLA2) enzyme activity was found to be significantly greater in RA synovial cells grown for 14 days in serum-free medium containing bFGF alone, or bFGF plus interleukin 1 beta (IL-1 beta) compared with cells grown in either serum-free medium alone, or serum-free medium plus PDGF. Similarly, bFGF plus IL-1 beta-stimulated release of PLA2 activating protein, a novel mammalian phospholipase stimulator found in high concentrations in RA synovial fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced prostaglandin biosynthesis in human gingival fibroblasts isolated from patients treated with phenytoin

Prostaglandin E2 (PGE2) formation was studied in human gingival fibroblasts derived from three epileptic patients before and after 9 months of phenytoin (PHT) therapy. Interleukin 1 (IL-1 alpha; 0.3-6.0 ng/ml), (IL-1 beta; 10-1000 pg/ml) and tumour necrosis factor (TNF alpha; 0.01-0.1 microgram/ml) dose-dependently stimulated the formation of PGE2 in 24 h cultures. In fibroblasts, derived after 9 months of PHT therapy, IL-1 alpha, IL-1 beta and TNF alpha induced a significantly higher formation of PGE2 compared to that in fibroblasts derived before PHT therapy. IL-1 beta induced a significantly higher release also of 3H-arachidonic acid (3H-AA) from prelabelled PHT fibroblasts compared to that in prelabelled gingival fibroblasts isolated before the drug therapy. Addition of exogenous AA caused a spontaneous increase of PGE2 formation in PHT fibroblasts compared to that in fibroblasts isolated before the PHT treatment. The results indicate that PHT medication results in an upregulation of prostanoid formation in gingival fibroblasts partly due to an increased phospholipase A2 activity and partly due to an increased cyclooxygenase activity.

Phenytoin potentiates interleukin-1-induced prostaglandin biosynthesis in human gingival fibroblasts

1. The effect of phenytoin (PHT) on prostaglandin E2 (PGE2) biosynthesis in human gingival fibroblasts stimulated by interleukin-1 (IL-1 alpha, IL-1 beta) or by tumour necrosis factor alpha (TNF alpha) was studied. 2. IL-1 alpha (1.5-6.0 ng ml-1) and IL-1 beta (30-300 pg ml-1), dose-dependently, stimulated PGE2 formation, in 24 h cultures, with IL-beta being the most potent agonist. 3. PHT (2.5-20 micrograms ml-1) did not induce PGE2 formation itself but potentiated IL-1 alpha- and IL-1 beta-induced PGE2 formation in the gingival fibroblasts in a manner dependent on the concentrations of both IL-1 and PHT. 4. IL-1 beta (0.1-1.0 ng ml-1) induced release of [3H]-arachidonic acid ([3H]-AA) from prelabelled fibroblasts that was potentiated by PHT (20 micrograms ml-1). 5. TNF-alpha (greater than or equal to 0.01 micrograms ml-1) significantly stimulated the biosynthesis of PGE2 by a process that was potentiated by PHT. 6. Addition of exogenous arachidonic acid (AA) (greater than or equal to 1 microM) caused an increase of PGE2 formation in the fibroblasts that was not potentiated by PHT (20 micrograms ml-1). 7. The results indicate that treatment with PHT results in upregulation of prostaglandin biosynthesis in gingival fibroblasts challenged with IL-1 or TNF alpha, at least partly due to enhanced level of phospholipase A2 activity.

Elevated cAMP is required for stimulation of eicosanoid synthesis by interleukin 1 and bradykinin in BALB/c 3T3 fibroblasts

In Swiss 3T3 murine fibroblasts, interleukin 1 (IL-1) and bradykinin stimulate prostaglandin E2 (PGE2) synthesis. However, in the present study, we found that neither agonist stimulated PGE2 synthesis in BALB/c 3T3 murine fibroblasts, this in spite of expression of similar numbers of receptors for each agonist compared to Swiss 3T3 cells. When BALB/c 3T3 cells were preincubated with cAMP analogs, both IL-1 and bradykinin stimulated PGE2 synthesis to levels similar to those observed in Swiss 3T3 cells. Similarly, when the cells were preincubated with forskolin, which activates the catalytic subunit of adenylate cyclase directly, or NECA, which stimulates cellular cAMP accumulation by activating adenosine receptors, IL-1 and bradykinin stimulated PGE2 synthesis. Rp-cAMPS, an inhibitor of cAMP-dependent protein kinase, blocked the ability of cAMP or NECA to render cells responsive to IL-1 and bradykinin. In basal BALB/c 3T3 cells, bradykinin and IL-1 stimulated arachidonate release in the absence of cAMP, but little conversion of released arachidonate to PGE2 occurred. cAMP, forskolin, and NECA all increased cyclooxygenase activity in the cells. SV-T2 is a clonal line originating from BALB/c 3T3 transformed with SV-40. In these cells, IL-1 and bradykinin stimulated PGE2 synthesis despite basal intracellular cAMP concentrations similar to BALB/c, and cAMP only modestly potentiated the response. In summary, cyclooxygenase expression appears to be regulated by cAMP in BALB/c 3T3 cells, and SV-40 transformation results in increased cyclooxygenase expression, apparently independent of cAMP.

Interleukin-1 up-regulates transcription of its own receptor in a human fibroblast cell line TIG-1: role of endogenous PGE2 and cAMP

The regulation of interleukin-1 receptor (IL-1R) mRNA expression by IL-1 in a human lung fibroblast cell line (TIG-1) was investigated. After 2 h of stimulation with human recombinant IL-1 alpha or IL-1 beta, the levels of T cell/fibroblast-type IL-1R mRNA increased, and the elevation was sustained for at least 72 h. IL-1 also stimulated synthesis of prostaglandin E2 (PGE2) and secondary cAMP accumulation. Exogenously added PGE2 increased the levels of both IL-1R mRNA and intracellular cAMP. Forskolin, cholera toxin and 8-Bromo adenosine (8-Br-cAMP) all increased IL-1R mRNA levels. Indomethacin blocked IL-1 stimulation of IL-1R mRNA expression, PGE2 production and cAMP. 125I-labeled IL-1 alpha-binding studies showed that this cell line expresses 2.6 x 10(4) IL-1R per cell with a Kd of 5.1 x 10(-10) M. After treatment of the cells with IL-1, the level of IL-1R increased over that of control cells. PGE2 also increased IL-1R without alteration in its affinity. Cross-linking experiments indicate that this cell line expresses the 80-kDa receptor molecule before and after treatment with PGE2; the molecular mass corresponds to the T cell/fibroblast type I IL-1R. These results indicate that IL-1 does not directly stimulate expression of IL-1R mRNA or cell surface IL-1R, but only indirectly by stimulation of endogenous PGE2.

The interleukin-1 receptor in normal and osteoarthritic human articular chondrocytes. Identification as the type I receptor and analysis of binding kinetics and biologic function

OBJECTIVE

To identify and investigate the kinetic binding properties of interleukin-1 receptors (IL-1R), and examine the abilities of the 2 IL-1 isoforms to stimulate metalloprotease synthesis, in normal and osteoarthritic (OA) chondrocytes.

METHODS

Receptor affinity and density were determined using radioligand binding experiments and flow cytometry. Immunocytochemical analysis and affinity cross-linking studies were performed for characterization of IL-1R.

RESULTS

While no difference in receptor affinity between normal and OA chondrocytes was noted in binding studies (Kd approximately 30 pM), a 2-fold increase in receptor density was found in OA chondrocytes as compared with normal chondrocytes (mean 4,069 sites/cell versus 2,315 sites/cell). Flow cytometry experiments also showed a significant increase in receptor density in OA cells, as well as an enhancement in the percentage of positive cells in diseased cartilage compared with normal. Binding data for both IL-1 isoforms revealed a single class of binding sites and receptor specificity. Factors such as IL-2, interferon-gamma, tumor necrosis factor alpha, and bovine insulin did not compete with IL-1 beta. By covalent ligand cross-linking and electrophoretic analysis, only type I IL-1R, a protein of 80 kd, was detected on chondrocytes. By immunocytochemical analysis, IL-1R was identified at the cell membrane level, in both normal and OA chondrocytes. The presence of nuclear staining was also observed, but only in OA chondrocytes. Recombinant human IL-1 (alpha and beta) induced the secretion of stromelysin and collagenase in a dose-dependent manner. The IL-1 concentration required for half-maximal metalloprotease stimulation was 3-4 times lower in OA chondrocytes than in normal cells.

CONCLUSION

These results indicate that OA chondrocytes have a higher sensitivity to the stimulation of metalloprotease synthesis by IL-1 than do normal cells. This could be related to the increased levels of IL-1R expressed in the OA cells. The implications of these findings with regard to the possible roles of IL-1 and IL-1R in the pathogenesis of OA are discussed.