Effect of interleukin-1 (IL-1) blockade on cytokine synthesis: I. IL-1 receptor antagonist inhibits IL-1-induced cytokine synthesis and blocks the binding of IL-1 to its type II receptor on human monocytes.

Interleukin-1 (IL-1) induces IL-1, tumor necrosis factor alpha (TNF alpha), and IL-6 gene expression and synthesis in a variety of cells. In this study, we investigated the ability of human recombinant IL-1 receptor antagonist (IL-1ra) to inhibit IL-1-induced cytokine production in human peripheral blood mononuclear cells (PBMC) and isolated monocytes. IL-1ra alone at concentrations as high as 1 microgram/mL did not induce IL-1 alpha, IL-1 beta, TNF alpha, or IL-6 synthesis. Suppression of IL-1-induced IL-1, TNF alpha, or IL-6 synthesis was dose-dependent (P less than or equal to .0001). At a twofold molar excess, IL-1ra inhibited IL-1-induced IL-1 or TNF alpha synthesis by 50% (P less than .01); an equimolar concentration of IL-1ra inhibited synthesis of these two cytokines by over 20% (P less than .05). A 10-fold molar excess of IL-1ra over IL-1 beta reduced IL-1 beta-induced IL-1 alpha by 95% (P = .01) and IL-1 alpha-induced IL-1 beta by 73% (P less than .01). IL-1ra added to PBMC 8 hours after stimulation with IL-1 beta was still able to inhibit IL-1 alpha, TNF alpha, and IL-6 synthesis (P less than or equal to .01). A similar reduction in IL-1 beta-induced IL-1 alpha was observed when IL-1 beta was removed from the cultures after 8 hours of stimulation (P less than .05), suggesting a prolonged presence of IL-1 or restimulation of IL-1 receptors on monocytes is required for the induction of cytokines. In elutriated monocytes, a 10-fold molar excess of IL-1ra reduced IL-1 beta-induced IL-1 alpha by 82% (P less than .05), TNF alpha by 64% (P = .05), and IL-6 by 47% (P less than .05). 125I-IL-1 beta was bound to purified monocytes, cross-linked, and immunoprecipitated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a band at 85 Kd corresponding to the 68-Kd IL-1 receptor type II (IL-1RtII). Excess unlabeled IL-1 beta or IL-1ra blocked the binding of 125I-IL-1 beta to the IL-1RtII. We conclude that IL-1ra inhibits IL-1-induced cytokine synthesis and competes with IL-1 for the IL-1RtII on human monocytes.     

Interleukin-1 alpha upregulates tumor necrosis factor receptors expressed by a human bone marrow stromal cell strain: implications for cytokine redundancy and synergy

To explore the biochemical and physiologic basis of the overlapping effects of interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor alpha (TNF-alpha) on myeloid cytokine production, we have studied the dynamics of granulocyte colony-stimulating factor (G-CSF) and granulocyte-monocyte colony-stimulating factor (GM-CSF) production as well as IL-1 receptor and TNF receptor expression in a clonally derived bone marrow stromal cell strain (CDCL). IL-1 alpha and TNF alpha act in a synergistic manner to stimulate G-CSF and GM-CSF production by CDCL, resulting in an increase in CSF secretion that is 250-fold greater than that observed with either cytokine alone. This synergism in protein secretion is paralleled by synergistic increases the steady-state level of GM- and G-CSF mRNA, with supra-additive levels achieved by 24 hours. Coincident with this synergistic induction of myeloid CSFs, treatment of CDCL cells with IL-1 alpha induces a 300% increase in the expression of TNF receptors. IL-1 alpha induction of TNF receptors reaches a peak after 6 hours and gradually returns to baseline level by 24 hours. IL-1 alpha does not affect TNF receptor ligand binding affinity. A kinetic study comparing IL-1/TNF synergistic induction of growth factor secretion with IL-1 alpha induction of TNF receptors shows that these events occur in parallel. In contrast with the induction of TNF receptors by IL-1 alpha, treatment with TNF alpha has no effect on either the number of IL-1 receptors expressed by CDCL cells or IL-1 receptor ligand binding affinity. Brief treatment of IL-1 alpha/TNF alpha-stimulated CDCL cells with cycloheximide before receptor induction reduces the synergistic increase in growth factor mRNA by 40% to 60% compared with cells not treated with CHX. Taken together, these results raise the possibility that IL-1 alpha cross-induction of TNF receptors may contribute to the biochemical mechanisms underlying the synergistic stimulation of G-CSF and GM-CSF production by IL-1 alpha and TNF alpha.     

Regulatory effects of interleukin (IL)-1, interferon-beta, and IL-4 on the production of IL-1 receptor antagonist by human adipose tissue

Adipose tissue is the source of production and site of action of several pro- and antiinflammatory cytokines. We have recently shown that white adipose tissue (WAT) is a major producer of the antiinflammatory IL-1 receptor antagonist (IL-1Ra). Because IL-1Ra serum levels are elevated 7-fold in human obesity and an excess of this protein has been implicated in the acquired resistance to leptin and insulin, we investigated the regulation of IL-1Ra in human WAT. We demonstrate that IL-1Ra is mainly produced by adipocytes, rather than the stromal fraction of WAT, and that IL-1alpha and beta, as well as interferon-beta (IFN-beta), strongly up-regulate the expression and secretion of IL-1Ra in WAT. Moreover, human WAT expresses the receptors and proteins known to be required for the action of IL-1 (IL-1 receptor type I, IL-1 receptor accessory protein) and IFN-beta (IFN-alpha/beta receptor subunits 1 and 2). Finally, human WAT actively secretes these regulatory cytokines, suggesting that they up-regulate IL-1Ra through a local autocrine/paracrine action, which is hypothesized to play a regulatory role in adipogenesis and metabolism.     

Interleukin-6 (IL-6) as an anti-inflammatory cytokine: induction of circulating IL-1 receptor antagonist and soluble tumor necrosis factor receptor p55

The aim of this study was to investigate whether interleukin (IL)-6 induces the production of IL-1 and tumor necrosis factor (TNF) antagonists. Serial plasma samples were obtained from cancer patients participating in phase I and II trials of recombinant IL-6 administered as a 120-hour continuous intravenous (IV) infusion. Plasma IL-1 receptor antagonist (IL-1Ra) and soluble TNF receptor p55 (TNFsRp55) levels were measured by specific radioimmunoassays (RIAs). IL-1Ra levels increased rapidly, reaching peak values (9.6 +/- 1.7 ng/mL) within 2 to 4 hours of beginning treatment. Thereafter, levels promptly declined, reaching near baseline within 24 hours despite continuation of IL-6. TNFsRp55 plasma levels increased within 4 to 8 hours after initiating treatment and increased progressively throughout the duration of therapy. IL-1 beta and TNF-alpha plasma levels were below the detection limit in all samples tested. Peripheral blood mononuclear cells (PBMC) exposed to IL-6 produced only small amounts (1.56 +/- 0.3 ng/mL) of IL-1Ra, even in the presence of exogenous soluble IL-6 receptor (gp80). TNFsRp55 levels measured in the supernatants of IL-6- stimulated PBMC were below the detection limit of the assay. Macrophages generated by culturing monocytes in granulocyte-macrophage colony-stimulating factor (GM-CSF) were much more responsive to IL-6 than freshly isolated unfractionated or adherent PBMC and synthesized almost as much IL-1Ra when stimulated with IL-6 as with endotoxin. These results suggest that the antinflammatory properties of IL-6 may be due; in part, to the induction of IL-1Ra synthesis and the release of soluble TNF receptors. Our findings also suggest that tissue macrophages may be an important source of IL-6-induced IL-1Ra.     

Pretreatment with ibuprofen augments circulating tumor necrosis factor-alpha, interleukin-6, and elastase during acute endotoxinemia

Plasma levels of tumor necrosis factor-alpha (TNF alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) were monitored after intravenous administration of Escherichia coli endotoxin with or without ibuprofen pretreatment to healthy volunteers. Intravenous endotoxin (n = 7) resulted in elevated plasma TNF alpha concentrations with maximal levels at 90 min (369 +/- 44 pg/ml, P less than .001 vs. saline controls, n = 7). The rise in TNF-alpha was followed by a rise in plasma IL-6 (27 +/- 12.8 ng/ml), peaking 30-90 min thereafter. Pretreatment with ibuprofen (n = 6) caused a significant augmentation and temporal shift in cytokine elaboration with maximal TNF alpha levels (627 +/- 136 pg/ml) at 120 min and IL-6 peaks (113 +/- 66 ng/ml) at 180 min. In ibuprofen-treated volunteers, the additional increase in TNF alpha was paralleled by increased levels of circulating elastase. In vitro experiments suggest a causal relationship between these events. Thus, the cyclooxygenase inhibitor ibuprofen blunts the clinical response to endotoxin but augments circulating cytokine levels and leukocyte degranulation.     

Effect of interleukin-1 and tumor necrosis factor/cachectin on glucose turnover in the rat

We studied the effect of recombinant human interleukin-1 beta (IL-1) and recombinant human tumor necrosis factor alpha/cachectin (TNF) on glucose kinetics in healthy rats by means of a primed constant infusion of D-(6-3H)glucose and D-[U-14C]glucose. During the isotope (6-hour) and monokine (4-hour) infusion, plasma levels of glucagon and insulin were determined and correlated with changes in glucose metabolism. The rates of glucose appearance (Ra) and disappearance (Rd) were elevated only with IL-1 and were associated with an increase in glucagon and a concomitant decrease in the ratio of insulin to glucagon. Plasma glucose concentration was increased early after IL-1 administration and coincided with the peak in the Ra. The augmentation of the metabolic clearance rate (MCR) and percent of flux oxidized by IL-1 suggest that this monokine induces the utilization of glucose as a substrate. TNF administration failed to modify the Ra or Rd, percent of flux oxidized, or MCR. TNF-treated rats increased the percent of glucose recycling, but not the total rate of glucose production. The results of this experiment suggest that endogenous macrophage products participate in the diverse alterations of carbohydrate metabolism seen during injury and/or infection.     

Effects of carbon monoxide inhalation during experimental endotoxemia in humans

Data show that carbon monoxide (CO) exerts direct antiinflammatory effects in vitro and in vivo after LPS challenge in a mouse model. We hypothesized that CO may act as an antiinflammatory agent in human endotoxemia. The aim of this trial was to study the effects of CO inhalation on cytokine production during experimental human endotoxemia. The main study was a randomized, double-blinded, placebo-controlled, two-way cross-over trial in healthy volunteers. Each volunteer inhaled synthetic air (as placebo) and 500 ppm CO for 1 hour in random order with a washout period of 6 weeks and received a 2-ng/kg intravenous bolus of LPS after inhalation. Carboxyhemoglobin levels were assessed as a safety parameter. CO inhalation increased carboxyhemoglobin levels from 1.2% (95% confidence interval, 1.0 to 1.4%) to peak values of 7.0% (95% confidence interval, 6.5 to 7.7%). LPS infusion transiently increased plasma concentrations of tumor necrosis factor-alpha, interleukin (IL)-6 (approximately 150-fold increases), and IL-8, as well as IL-1alpha and IL-1beta mRNA levels (an approximately 200-fold increase). These LPS-induced changes were not influenced by CO inhalation. Inhalation of 500 ppm CO for 1 hour had no antiinflammatory effects in a systemic inflammation model in humans, as 250 ppm for 1 hour did in rodents.     

Overproduction of proinflammatory cytokines imbalanced by their antagonists in POEMS syndrome

The polyneuropathy, organomegaly, endocrinopathy, M protein, skin changes (POEMS) syndrome is a rare multisystem disorder of obscure pathogenesis associated with osteosclerotic myeloma. Circulating levels of proinflammatory cytokines (tumor necrosis factor-alpha (TNF-alpha) interleukin-1 beta [IL-1 beta], IL-2, IL-6, and interferon-gamma [IFN- gamma]), anti-inflammatory cytokines (transforming growth factor beta 1 [TGF beta 1], IL-4, IL-10, and IL-13), the cytokine carrier protein alpha 2 macroglobulin, IL-1 receptor antagonist (IL-1ra), soluble TNF receptors (sTNFr) p55 and p75, and soluble IL-6 receptor (sIL-6r) were determined in 15 patients with POEMS syndrome and 15 with multiple myeloma. Patients with POEMS syndrome had higher serum levels of IL-1 beta, TNF-alpha, and IL-6 and lower serum levels of TGF beta 1 than did patients with multiple myeloma. Serum levels of IL-2, IL-4, IL-10, IL- 13, IFN-gamma, alpha 2 macroglobulin, and sIL-6r were similar in both groups. IL-1ra and sTNFrs were increased in POEMS syndrome, but out of proportion to the increase of IL-1 beta and TNF-alpha. Serial evaluations in 1 patient showed that proinflammatory cytokine serum levels paralleled disease activity assessed by platelet count and neurologic involvement. Our results suggest that the manifestations of POEMS syndrome might be regarded as the result of a marked activation of the proinflammatory cytokine network (IL-1 beta, IL-6, and TNF- alpha) associated with a weak or even decreased (TGF beta 1) antagonistic reaction insufficient to counteract the noxious effects of cytokines.     

Interleukin-1 alpha and tumor necrosis factor-alpha differentially regulate enkephalin, vasoactive intestinal polypeptide, neurotensin, and substance P biosynthesis in chromaffin cells.

The pattern of expression of at least four neuropeptides contained in adrenomedullary chromaffin cells is altered by exposure to the cytokines interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF alpha), alone or in combination with stimulation of other second messenger pathways. Vasoactive intestinal polypeptide (VIP) was elevated 2- to 3-fold by 1 nM IL-1 alpha within 48 h of exposure, while neurotensin and substance P synthesis were unaffected, and met-enkephalin levels were decreased 25-35%. Stimulation of VIP and substance P biosynthesis by forskolin was markedly enhanced by IL-1 alpha, while forskolin stimulation of enkephalin and neurotensin biosynthesis was unaffected. IL-1 alpha amplified the effect of phorbol myristate acetate to increase the VIP content of chromaffin cells, but antagonized phorbol ester-induced elevation of neurotensin levels. TNF alpha also demonstrated a neuropeptide-specific pattern of modulation of second-messenger effects on chromaffin cell neuropeptide levels similar to those seen with IL-1 alpha. The neuroendocrine actions of IL-1 alpha described above, unlike IL-1 action in the immune system, do not appear to be mediated through IL-2 as this cytokine did not affect VIP or enkephalin expression in the presence or absence of protein kinase stimulation. Neither IL-1 alpha nor TNF alpha affected the calcium-coupled stimulation of neuropeptide secretion and biosynthesis that occurs in response to cell depolarization in these and other neuroendocrine cells in vitro and in vivo. These data provide a functional demonstration of IL-1 and TNF receptors in chromaffin cell cultures and suggest a physiological role for cytokine production in the adrenal medulla. Since both the magnitude and direction of neuropeptide synthesis modulation by IL-1 alpha and TNF alpha are highly peptide-specific, it appears that these cytokines do not merely augment second messenger pathways that affect neuropeptide synthesis, but potentially regulate the activity of factors controlling the pattern of neuropeptide gene expression in chromaffin cells.     

Effect of flurbiprofen on cytokine production by human monocytes and U-937 and THP-1 cell lines.

Possible effects of nonsteroidal antiinflammatory drugs (NSAID) on inflammatory mediators other than arachidonic acid metabolites which might contribute to the antiinflammatory effects of these drugs have not been fully explored. We investigated the effects of an NSAID, flurbiprofen, on production of the cytokines tumor necrosis factor alpha (TNF alpha), interleukin 1 beta (IL-1 beta) and interleukin 6 (IL-6) by human peripheral blood monocytes and by the human cell lines U-937 and THP-1. Cytokine production was induced by 1 microgram/ml bacterial lipopolysaccharide (LPS) in both monocytes and cell lines, and cytokine levels in supernatants were measured by enzyme immunoassay. In monocytes, IL-6 was the major product while in both cell lines, TNF alpha was the major product. Flurbiprofen caused moderate inhibition of IL-1 beta and TNF alpha production by stimulated monocytes, but did not affect IL-6 production. In contrast, flurbiprofen completely abolished IL-6 production by both cell lines and substantially inhibited IL-1 beta and TNF alpha production. These observations raise the possibility that inhibition of cytokine production by flurbiprofen may contribute to the antiinflammatory properties of this drug.     

Intravenous (IV) anti-D and IV immunoglobulin achieve acute platelet increases by different mechanisms: modulation of cytokine and platelet responses to IV anti-D by FcgammaRIIa and FcgammaRIIIa polymorphisms

Intravenous (IV) anti-D and IV immunoglobulin (IVIG) slow the Fcgamma receptor (FcgammaR)-mediated destruction of antibody-coated platelets in patients with immune thrombocytopenic purpura (ITP). This pilot study explored the mechanism of these immunoglobulin preparations by measuring interleukin-10 (IL-10), monocyte chemoattractant protein-1 (MCP-1), IL-6 and tumour necrosis factor alpha (TNFalpha), before and after infusion and by assessing the effect of FcgammaRIIa and FcgammaRIIIa polymorphisms on both cytokine and haematologic responses to anti-D. Following IVIG, only IL-10 was increased at 2 h and MCP-1 on day 7 (P < 0.05). In contrast, 2 h after anti-D infusion, plasma levels of all four cytokines were increased (P < 0.01); five of six patients with the highest MCP-1, IL-6 and TNFalpha levels had chills. Higher IL-10 levels correlated with platelet increases at 24 h and haemoglobin decreases at day 7 (P < 0.025). Patients with the FcgammaRIIa-131HH genotype had significantly higher MCP-1, IL-6 and TNFalpha levels. Patients with the FcgammaRIIIa-158VF genotype had higher platelet increments at day 7 (P < 0.05). Soluble CD16 (sCD16) was increased 2 h after IV anti-D; day 7 levels correlated with day 7 haemoglobin decreases (P < 0.01). In conclusion, the relationship of FcgammaRIIa and FcgammaRIIIa polymorphisms with both cytokine levels and platelet increments implicated these receptors in responses to anti-D and supported different mechanisms of FcgammaR interaction to those seen with IVIG.     

Pro- versus anti-inflammatory cytokine profile in patients with severe sepsis: a marker for prognosis and future therapeutic options

Serum concentrations of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6, and the anti-inflammatory cytokine Il-10, and IL-1 receptor antagonists (IL-1ra) and soluble TNF receptors (sTNFRs) were measured in 65 patients with severe sepsis. All patients were evaluated clinically and microbiologically and were followed up for clinical outcome. Levels of both pro- and anti-inflammatory cytokines were significantly elevated in patients with sepsis. Elevated serum IL-10 and TNF-alpha levels and a high IL-10 to TNF-alpha ratio were associated with death, whereas higher levels of TNF-alpha, IL-6, IL-1ra, and sTNFR were detected in patients with an early hemodynamic deterioration. Interleukin-10 and IL-10:TNF-alpha ratio remained higher in nonsurvivors, whereas IL-10 paralleled the sepsis score. Although both the inflammatory and anti-inflammatory response is profoundly augmented in patients with severe sepsis, the sustained overproduction of the anti-inflammatory cytokine IL-10 is the main predictor of severity and fatal outcome.     

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

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

Effect of interleukin-1 (IL-1) blockade on cytokine synthesis: II. IL-1 receptor antagonist inhibits lipopolysaccharide-induced cytokine synthesis by human monocytes.

Lipopolysaccharide (LPS) stimulates interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) gene expression and synthesis in human peripheral blood mononuclear cells (PBMC). IL-1 can also induce PBMC to synthesize IL-1 and TNF alpha. In the present study, we used IL-1 receptor antagonist (IL-1ra) to determine the relative contribution of an IL-1-positive feedback loop to the total amount of LPS-induced cytokine synthesis. Pretreatment of PBMC with human recombinant IL-1ra reduced LPS-induced cytokine synthesis in a dose-dependent manner (P less than .001). Maximal inhibition was 33% for IL-1 alpha (P less than .01), 43% for IL-1 beta (P = .001), and 20% for TNF alpha (P less than .05). We consistently observed IL-1ra suppression of LPS-induced cytokines in PBMC of 38 volunteers. However, this phenomenon was not specific for LPS; 1 microgram/mL IL-1ra inhibited IL-1 beta synthesized in response to human recombinant IL-2 by 44% (P less than .001), toxic shock syndrome toxin-1 by 26% (P less than .05), and phorbol 12-myristate 13-acetate by 76% (P less than .001). IL-1ra added to PBMC 4 or 8 hours after stimulation with LPS still inhibited IL-1 beta synthesis by 44% (P less than .001) or 25% (P = .01), respectively. The steady state messenger RNA levels of IL-1 beta were reduced in PBMC stimulated by LPS in the presence of IL-1ra. In monocytes isolated by elutriation, IL-1ra reduced LPS-induced IL-1 alpha by 16% (P less than .001), IL-1 beta by 14% (P less than .05), and TNF alpha by 24% (P = .01). We conclude that IL-1-induced IL-1 significantly contributes to LPS-induced cytokine synthesis.     

Autocrine regulation of collagenase 3 (matrix metalloproteinase 13) during osteoarthritis

OBJECTIVE: To correlate the increased collagenase production previously seen in chondrocytes isolated from osteoarthritic (OA) lesions and the expression of cytokines and cytokine receptors. METHODS: Chondrocytes were isolated from OA cartilage and characterized for synthesis of collagenases, cytokines, and cytokine receptors by Northern and Western blot analyses, RNA protection assay, and flow cytometry. RESULTS: Chondrocytes located in cartilage proximal to the macroscopic OA lesions bound more tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta) compared with chondrocytes isolated from morphologically normal cartilage from the same joint. In response to TNFalpha stimulation, messenger RNA (mRNA) levels for the IL-1 receptor I (IL-1RI), IL-1RII, TNF receptor II (TNFR II), and IL-6 receptor as well as the level of proinflammatory cytokines, such as IL-1alpha, IL-1beta, lymphotoxin beta, TNFalpha, and IL-6, also increased. In contrast, treatment with transforming growth factor beta1 (TGFbeta1) resulted in down-regulation of matrix metalloproteinase 1 (MMP-1) and MMP-13 concomitant with a reduction in the levels of mRNA for IL-1RI, IL-1RII, TNFRI, and TNFRII and proinflammatory cytokine levels. In contrast, the levels of mRNA for TGFbeta receptor I, TGFbeta1, and TGFbeta3 were up-regulated. CONCLUSION: These data show that TGFbeta1 has antagonistic effects upon OA chondrocytes, in contrast to the effects seen with TNFalpha. The cyclical course of OA, where a period of active disease is followed by a period of remission, can be explained by a sequential pattern of cytokine stimulation followed by a feedback inhibition of autocrine cytokine production and cytokine receptor expression, thus affecting collagenase synthesis.     

Dexamethasone inhibits tumor necrosis factor-alpha-induced apoptosis and interleukin-1 beta release in human subcutaneous adipocytes and preadipocytes

Tumor necrosis factor-alpha (TNF alpha) can decrease adipose tissue mass, but in obesity, adipose tissue hypertrophy persists despite increased TNF alpha expression. The hormonal milieu of obesity may antagonize the adipostat effects of TNF alpha. We examined the effects of insulin and the synthetic glucocorticoid, dexamethasone (Dex), on TNF alpha-induced apoptosis and gene expression in human adipocytes and preadipocytes. Using RT multiplex PCR, the expression of the proapoptotic genes interleukin-1 beta (IL-1 beta)-converting enzyme (ICE) and TNF alpha and the antiapoptotic genes bcl-2, nuclear factor-kappa B (NF kappa B), and NF kappa B inhibitory subunit, I kappa B, were examined. The expression and release of IL-1 beta, a postulated downstream effector of ICE-mediated apoptosis, were also determined. TNF alpha increased the messenger ribonucleic acid levels of ICE, TNF alpha, IL-1 beta, bcl-2, and NF kappa B in preadipocytes and adipocytes (P < 0.01). Dex inhibited TNFalpha-induced messenger ribonucleic acid expression of ICE, TNF alpha, and IL-1 beta (P < 0.01), but not that of bcl-2 and NF kappa B. TNF alpha stimulated IL-1 beta release from preadipocytes and adipocytes up to 20-fold, but the effect was abrogated by Dex. Apoptosis induced by TNF alpha was reduced to control levels (P < 0.01) by Dex. Insulin had no significant effect on TNF alpha-induced apoptosis and gene expression. In obesity, glucocorticoids may reduce TNF alpha actions in adipose tissue by inhibiting TNF alpha-induced apoptosis, IL-1 beta release, and TNF alpha expression.     

Interleukin-1beta up-regulates tumor necrosis factor receptors in the mouse airways

Cytokines like interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha), released during the inflammatory process, play important roles in the development of airway hyperresponsiveness. The effects of these cytokines are mediated by cell surface receptors, specific for each cytokine. The expression of cytokine receptors is a dynamic process, where receptors can be up- or down-regulated in response to changes in the environment. One such environmental factor is the presence of cytokines per se. The present study was designed to evaluate the effects of IL-1beta on the expression of its corresponding receptor IL-1 RI, as well as on the closely related TNFalpha receptors TNF RI and TNF RII in airways using a mouse organ culture assay and intranasal inoculation model. Immunohistochemical staining was used to quantify expressional differences between fresh and cultured tracheal segments. In the fresh, uncultured, segments, IL-1 RI and TNF RI were seen in the epithelial layer and TNF RI in the smooth muscle layer. After 4 days of culture, the expression of TNF RI decreased in the epithelial layer, whereas the corresponding expression of IL-1 RI and TNF RI in the smooth muscle remained unchanged. When culture was performed in the presence of IL-1beta, the expression of IL-1 RI and TNF RI in the epithelial cells and TNF RI in the smooth muscle cells increased. TNF RII was not detected in either fresh or cultured trachea, but after treatment with IL-1beta an expression was found in both the epithelial layer and in the smooth muscle cells. The IL-1beta-induced increased expression, on TNF RI and TNF RII in the smooth muscle ex vivo and in the lung parenchyma after intranasal challenge in vivo, was verified at the mRNA level using real-time RT PCR. To summarize, presence of IL-1beta increases the expression of IL-1 R1 and TNF RI and induces expression of TNF RII in the airway wall. It is not inconceivable that these alterations of the IL-1 and TNF receptors may have important functional implications for the development of hyperresponsiveness in inflammatory airway diseases like asthma.     

Expression of inflammatory cytokines in placentas from women with preeclampsia

It is postulated that inadequate remodeling of the uterine spiral arteries in preeclampsia leads to focal ischemia and generation of inflammatory cytokines, such as tumor necrosis factor (TNF alpha) and interleukins (ILs), by the placenta. Our objective was to compare TNF alpha, IL-1 alpha, IL-1 beta, and IL-6 levels in placentas from patients with preeclampsia and normal term pregnancies. Because the placenta is a large heterogeneous organ, we analyzed multiple sites per placenta. On the average, there was a 3-fold variation in cytokine protein levels across the eight sites analyzed for each placenta. However, there were no significant overall differences among the normal term, preeclamptic, and preterm placentas from women without preeclampsia. There were also no significant differences in TNF alpha messenger ribonucleic acid between the normal term and preeclamptic placentas, although TNF alpha messenger ribonucleic acid levels were lower in placentas from preterm patients without diagnosis of preeclampsia than in the normal term placentas. In vitro, hypoxia stimulated the production of TNF alpha, IL-1 alpha and IL-1 beta, but not that of IL-6, by placental villous explants from both groups of patients, and this was not exaggerated in preeclampsia. Finally, although peripheral and uterine venous levels of TNF alpha were elevated in preeclamptic women compared with normal term patients, the ratio of uterine to peripheral venous TNF alpha levels was not significantly different from 1.0 for either patient group. Taken together, these results suggest that sources other than the placenta contribute to the elevated concentrations of TNF alpha and IL-6 found in the circulation of preeclamptic women.     

Atherosclerosis and inflammation. Patterns of cytokine regulation in patients with peripheral arterial disease.

Inflammatory phenomena at sites of atherosclerotic plaques are increasingly thought to be major determinants of the progression and clinical outcome of atherosclerotic disease. Therefore, attention is being paid to systemic markers/mediators which may reflect the inflammatory activity in the plaques. This study evaluates the pattern of the main proinflammatory cytokines tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), their soluble receptors/antagonist, and a variety of inflammatory markers, in patients with peripheral arterial disease (PAD). Eight patients with PAD suffering from claudicatio intermittens (CI), eight with critical limb ischemia (CLI) and eight controls (C) were studied. Blood samples were collected at baseline in all groups and. for C and CI, immediately after and 4 h after a 30-min treadmill test. Baseline: no differences in cytokine plasma levels were detected among the three groups. In contrast, soluble receptors of TNF (type I and II) and of IL-6, and IL-1beta receptor antagonist (IL-1ra) were increased in CI and CLI patients, as compared to C. Of note, IL-Ira correlated with the occurrence and stage of the disease in a highly significant proportion of the patients, reaching a predictive value for the disease of P < 0.0001. The opposite trend was observed for the soluble receptor of IL-1beta. Notably, in the patients no alterations could be found in white blood cell counts, expression of CD11c adherence molecule by circulating monocytes or, in vitro. O2- release from zymosan-activated neutrophils. Moreover, plasma levels of platelet activating factor (PAF), of neutrophil elastase and of the acute phase reactants C-reactive protein (CRP) and alpha1-acid glycoprotein were not found to be significantly altered. In contrast, the acute-phase proteins alpha1-antitrypsin (alpha1AT) and haptoglobin (HG) were found to be increased. Effect of treadmill: IL-1beta and TNFalpha remained at baseline levels following exercise, and IL-6 dropped to undetectable levels. Among cytokine antagonists, again the most relevant changes concerned the IL-1ra, which was significantly increased immediately after the treadmill test, both in CI and C, and returned to baseline levels after 4 h. In contrast, soluble TNFalpha, IL-1beta and IL-6 receptors, PAF, and the other markers of leukocyte activation were not found to be altered. Soluble TNFalpha and IL-6 receptors were shown to inhibit the biological effects of their ligands. Similarly, IL-1ra and the acute phase proteins alpha1AT and HG have been reported to exert anti-inflammatory functions. The increased plasma levels of these agents, together with low levels of inflammatory cytokines and other pro-inflammatory mediators such as PAF and alpha1-acid glycoprotein, appear to draw an undescribed picture, so far, of upregulation of a composite systemic anti-inflammatory mechanism in atherosclerotic patients. IL-1ra appears to be a reliable marker of the state of activation of this mechanism. These results may provide a basis for developing new insights into the pathogenesis of the atherosclerotic disease.