Overview of interleukin-18: more than an interferon-gamma inducing factor.

Initially described in 1989 as interferon-gamma (IFN-gamma) inducing factor (IGIF), interleukin-18 (IL-18) is a novel pro-inflammatory cytokine that is clearly more than an inducer of IFN-gamma. The cytokine possesses several biological properties such as activation of nuclear factor-kappaB (NF-kappaB), Fas ligand expression, the induction of both CC and CXC chemokines, and increased production of competent human immunodeficiency virus. Most activities are due to a receptor complex that recruits the IL-1 receptor-activating kinase (IRAK), leading to translocation of NF-kappaB. This property and others support the concept that IL-18 is related to the IL-1 family. Indeed, one of the IL-18 receptor chains is the IL-1 receptor-related protein, a member of the IL-1R family. In addition, IL-18 is structurally similar to IL-1beta and like IL-1beta is first synthesized as a leaderless precursor requiring the IL-1beta converting enzyme for cleavage into an active molecule. The biology of IL-18 is reviewed in the overview and the implication for a role for this cytokine in disease is presented.

Spontaneous and inducible cytokine responses in healthy humans receiving a single dose of IFN-alpha2b: increased production of interleukin-1 receptor antagonist and suppression of IL-1-induced IL-8.

The present study was to determine whether the administration of a single dose of interferon-alpha2B (IFN-alpha2B) to healthy humans affects endogenous (or basal level) or inducible cytokines in a whole blood, ex vivo culture. Twenty-four healthy volunteers received an s.c. injection of IFN-alpha2b (3 x 10(6)U), and 4 volunteers received the vehicle as placebo. The study was blinded. Blood was drawn before and 3, 6, 12, and 24 h after the injection and incubated in the presence or absence of lipopolysaccharide (LPS) or interleukin-1beta (IL-1beta). After 24 hs, the plasma was assayed for tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, IL-1beta, IL-1 receptor antagonist (IL-1Ra), and IL-8. Treatment with IFN-alpha2b was associated with a 4.8-fold increase in the endogenous production of IL-1Ra in cultured blood sustained over 24 hs. In contrast, no change in endogenous IL-1Ra production was detected in the controls. A significant suppression (75%, p < 0.001) of IL-1beta-induced IL-8 production 3 and 6 h after IFN-alpha2b compared with control subjects was observed. These effects were also observed when IFN-alpha2b was added directly to whole blood cultures in vitro. In contrast to IL-1 stimulation, LPS stimulation of blood from IFN-alpha2b-treated subjects resulted in enhanced IL-1beta and TNF-alpha production. These results suggest that a single dose of IFN-alpha2b induces an anti-inflammatory state for endogenous stimuli but a proinflammatory state for exogenous endotoxin.

Effect of advanced glycation end products on endotoxin-induced TNF-alpha, IL-1beta and IL-8 in human peripheral blood mononuclear cells.

BACKGROUND/AIMS: Advanced glycated end products (AGE) are endogenous proteins that have formed covalent complexes with sugars by a nonenzymatic process. Being proinflammatory molecules, AGE are thought to contribute to chronic systemic and local inflammatory processes associated with pathological changes in various diseases. In patients with end-stage renal disease, AGE are believed to play a role in the progression of atherosclerosis and worsening of renal failure. In patients receiving hemodialysis, AGE are thought to contribute to the inflammatory components of the therapy, particularly in diabetic patients. METHODS: In the present study, AGE were produced using 5% human serum albumin (HSA) and 50% glucose, both used for intravenous infusion into humans and both released after strict control for endotoxin content. The presence of AGE formed by HSA and glucose was confirmed using 2 independent assays. The inflammatory properties of these AGE were assessed using synthesis and release of the proinflammatory cytokines interleukin-1 (IL-1), tumor necrosis factor (TNF) and IL-8, a chemokine. RESULTS: Alone, AGE did not induce these cytokines from peripheral blood mononuclear cells (PBMC) obtained from 14 healthy human donors. However, in the presence of 1 or 10 ng/ml of endotoxin, AGE augmented the production of IL-1 and TNF above that induced by endotoxin alone. Although the amount of augmentation of LPS-induced cytokines by AGE varied between the blood donors, the response was consistently observed and reached statistical significance. The augmentation of cytokine production was confirmed using AGE prepared with different lots of HSA and glucose. CONCLUSION: These results demonstrate that in the strict absence ofendotoxins, AGE are formed that do not stimulate cytokine production from PBMC of healthy donors, however, AGE significantly augment the synthesis and release of proinflammatory cytokine in the presence of low concentrations of endotoxins. The data suggest that renal replacement therapies should consider the role of microbial products in potentiating the biological consequences of naturally formed AGE and their potential to contribute to systemic and local inflammation in renal replacement therapies. Therefore, although the formation of AGE is unavoidable, excluding microbial products during renal replacement therapy should reduce the pathological consequences of AGE.

[Use of the "Real" apparatus in a urological hospital]. / Primenenie apparata "Real" v urologicheskom statsionare.

The expediency of the "Real" device for enuresis treatment in the hospital environment was investigated. The role of the machine in the combined treatment of postoperative incontinence in patients with adenoma of the prostate gland is described. The device is recommended for wide usage in hospitals.

[Experience with the combined treatment of chronic prostatitis]. / Opyt kompleksnogo lecheniia khronicheskogo prostatita.

Available are the results of combined treatment of chronic prostatitis in 86 patients. The treatment schedule included ultraphonophoresis of highly dispersed drug mixtures, bitemporal UHF waves exposure, endourethral electrostimulation and laser radiation of prostatic tissue. The complex of interacting modalities has been substantiated pathogenetically. Clinical and laboratory assessment of the patients' response supports high effectiveness of the proposed combined schemes for management of chronic prostatitis.

[The immunological characteristics of the course of acute nonspecific epididymitis in relation to the treatment performed]. / Immunologicheskie osobennosti techeniia ostrogo nespetsificheskogo épididimita v zavisimosti ot provodimogo lecheniia.

Changes of parameters of cell immunity in the process of treatment of patients with acute epididymitis were studied. They were presented by three groups depending on the methods of therapy: surgical and conservative ones with the application of UHF or laser irradiation. The recovery of functions of the immunity system was peculiar to patients previously subjected to surgical treatment. However, most pronounced immuno-correcting effect was characteristic of patients given laser therapy.

Inhibition of caspase 1 reduces human myocardial ischemic dysfunction via inhibition of IL-18 and IL-1beta.

The proinflammatory cytokine IL-18 was investigated for its role in human myocardial function. An ischemia/reperfusion (I/R) model of suprafused human atrial myocardium was used to assess myocardial contractile force. Addition of IL-18 binding protein (IL-18BP), the constitutive inhibitor of IL-18 activity, to the perifusate during and after I/R resulted in improved contractile function after I/R from 35% of control to 76% with IL-18BP. IL-18BP treatment also preserved intracellular tissue creatine kinase levels (by 420%). Steady-state mRNA levels for IL-18 were elevated after I/R, and the concentration of IL-18 in myocardial homogenates was increased (control, 5.8 pg/mg vs. I/R, 26 pg/mg; P < 0.01). Active IL-18 requires cleavage of its precursor form by the IL-1beta-converting enzyme (caspase 1); inhibition of caspase 1 also attenuated the depression in contractile force after I/R (from 35% of control to 75.8% in treated atrial muscle; P < 0.01). Because caspase 1 also cleaves the precursor IL-1beta, IL-1 receptor blockade was accomplished by using the IL-1 receptor antagonist. IL-1 receptor antagonist added to the perifusate also resulted in a reduction of ischemia-induced contractile dysfunction. These studies demonstrate that endogenous IL-18 and IL-1beta play a significant role in I/R-induced human myocardial injury and that inhibition of caspase 1 reduces the processing of endogenous precursors of IL-18 and IL-1beta and thereby prevents ischemia-induced myocardial dysfunction.

[Laser therapy in acute nonspecific epididymo-orchitis]. / Lazernaia terapiia pri ostrom nespetsificheskom épididimoorkhite.

Laboratory experiments were followed by clinical investigations of low-intensity laser radiation (LR) feasibility in therapy of acute epididymo-orchitis. A total of 117 patients aged 15-68 were treated with mild, moderate and severe scrotal inflammation. The response was compared to that in physiotherapy (54 patients) and early surgery (40 patients). It proved higher by 38.5%, the proportion of the treatment failure diminished from 22.2% for conservative and 15% for surgical management to 7.7%. The duration of acute inflammation reduced to 3 days. There was a marked analgetic effect, arrest of intoxication, hyperthermia, autoimmune reactions. Scarring could be avoided. The discussion covers mechanisms of therapeutic action of laser therapy which is proposed for broad-scale application in any run of the inflammation. The test is suggested for the final choice of therapy to be made on day 2-3 of laser irradiation.

[Experience in treating residual urethritis and its complications with low-intensity laser radiation]. / Opyt lecheniia rezidual'nykh uretritov i ikh oslozhnenii nizkointensivnym lazernym izlucheniem.

The authors analyze the results of laser therapy of residual urethritis and complications of urethral inflammations: cystitis, prostatitis, epididymitis, urethral strictures. Laser therapy was found particularly effective in the treatment of residual urethritis and valuable in multiple-modality treatment of urethrogenic epididymitis, cystitis, and prostatitis. The authors discuss the possibility of palliative therapy of cicatricial strictures of the urethra developing after installations and instrumental invasions for urethritis.

[The use of endovascular laser therapy in the combined treatment of EPH gestosis]. / Primenenie éndovaskuliarnoi lazernoi terapii v kompleksnom lechenii OPG-gestoza.

Endovascular exposure to He-Ne laser in combination with routine therapy used in 61 pregnant women with OPH gestosis improved the results of treatment in comparison with the results in 30 women administered routine treatment alone. The efficacy of laser therapy is confirmed by its positive influence on induced lipid peroxidation, peroxide hemolysis, low- and medium-mass molecules, and by the data of routine clinical laboratory studies. Laser exposure stabilized the red cell membranes, this evidently improving the blood rheology and microcirculation in patients suffering from OPH gestosis.

Interleukin-18 binding protein: a novel modulator of the Th1 cytokine response.

An interleukin-18 binding protein (IL-18BP) was purified from urine by chromatography on IL-18 beads, sequenced, cloned, and expressed in COS7 cells. IL-18BP abolished IL-18 induction of interferon-gamma (IFNgamma), IL-8, and activation of NF-kappaB in vitro. Administration of IL-18BP to mice abrogated circulating IFNgamma following LPS. Thus, IL-18BP functions as an inhibitor of the early Th1 cytokine response. IL-18BP is constitutively expressed in the spleen, belongs to the immunoglobulin superfamily, and has limited homology to the IL-1 type II receptor. Its gene was localized on human chromosome 11q13, and no exon coding for a transmembrane domain was found in an 8.3 kb genomic sequence. Several Poxviruses encode putative proteins highly homologous to IL-18BP, suggesting that viral products may attenuate IL-18 and interfere with the cytotoxic T cell response.

Site-specific mutations in the mature form of human IL-18 with enhanced biological activity and decreased neutralization by IL-18 binding protein.

IL-18 can be considered a proinflammatory cytokine mediating disease as well as an immunostimulatory cytokine that is important for host defense against infection and cancer. The high-affinity, constitutively expressed, and circulating IL-18 binding protein (IL-18BP), which competes with cell surface receptors for IL-18 and neutralizes IL-18 activity, may act as a natural antiinflammatory as well as immunosuppressive molecule. In the present studies, the IL-18 precursor caspase-1 cleavage site was changed to a factor Xa site, and, after expression in Escherichia coli, mature IL-18 was generated by factor Xa cleavage. Mature IL-18 generated by factor Xa cleavage was fully active. Single point mutations in the mature IL-18 peptide were made, and the biological activities of the wild-type (WT) IL-18 were compared with those of the mutants. Mutants E42A and K89A exhibited 2-fold increased activity compared with WT IL-18. A double mutant, E42A plus K89A, exhibited 4-fold greater activity. Unexpectedly, IL-18BP failed to neutralize the double mutant E42A plus K89A compared with WT IL-18. The K89A mutant was intermediate in being neutralized by IL-18BP, whereas neutralization of the E42A mutant was comparable to that in the WT IL-18. The identification of E42 and K89 in the mature IL-18 peptide is consistent with previous modeling studies of IL-18 binding to IL-18BP and explains the unusually high affinity of IL-18BP for IL-18.

Functional reconstitution and regulation of IL-18 activity by the IL-18R beta chain.

IL-18 and IL-12 are major IFN-gamma-inducing cytokines but the unique synergism of IL-18 and IL-12 remains unclear. In the human NK cell line NKO, IL-18R alpha, and IL-18R beta are expressed constitutively but IL-18 did not induce IFN-gamma unless IL-12 was present. COS-1 fibroblasts, which produce the chemokine IL-8 when stimulated by IL-1 beta or TNF-alpha, do not respond to IL-18, despite abundant expression of the IL-18R alpha chain. COS-1 cells lack expression of the IL-18R beta chain. The IL-18R beta cDNA was cloned from a human T-B lymphoblast cDNA library and COS-1 cells were transiently transfected with the IL-18R beta chain and a luciferase reporter. In transfected COS-1 cells, IL-18 induced IL-8 and luciferase in the absence of IL-12 and independently of IL-1 and TNF. Ab against the IL-18R alpha chain, however, prevented IL-18 responsiveness in COS-1 cells transfected with the IL-18R beta chain, suggesting that both chains be functional. In NKO cells and PBMC, IL-12 increased steady-state mRNA levels of IL-18R alpha and IL-18R beta; the production of IFN-gamma corresponded to IL-12-induced IL-18R alpha and IL-18R beta chains. We conclude that functional reconstitution of the IL-18R beta chain is essential for IL-12-independent proinflammatory activity of IL-18-induced IL-8 in fibroblasts. The synergism of IL-18 plus IL-12 for IFN-gamma production is, in part, due to IL-12 up-regulation of both IL-18R alpha and IL-18R beta chains, although postreceptor events likely contribute to IFN-gamma production.

Interleukin-1beta deficiency results in reduced NF-kappaB levels in pregnant mice.

Interleukin (IL)-1beta-deficient (IL-1beta(-/-)) mice were assessed for cytokine production during pregnancy. A significant reduction in nuclear factor (NF)-kappaB p65 protein content was observed in the uteri and spleens of pregnant IL-1beta(-/-) mice, as demonstrated by immunohistochemistry and Western immunoblot analysis. In addition, electromobility gel shift assay revealed less DNA binding activity of NF-kappaB p65-containing complex in pregnant IL-1beta(-/-) mice. To investigate differences in cytokine production regulated by NF-kappaB, the levels of tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, and interferon-gamma were measured in the uterine wall, spleen homogenates, and spleen cell cultures obtained from pregnant mice. Endocervical administration of lipopolysaccharide (LPS) increased cytokine levels in both wild-type (IL-1beta(+/+)) and IL-1beta(-/-) animals, but in IL-1beta(-/-) mice this response was 50-75% lower. Splenocytes from nonpregnant mice exhibited decreased LPS-induced cytokine production when primed in vitro with progesterone. This suppression was 25% greater in IL-1beta(-/-) than in IL-1beta(+/+) mice. These data suggest that constitutive NF-kappaB p65 protein synthesis is regulated by IL-1beta, particularly during pregnancy.

IL-18 binding protein increases spontaneous and IL-1-induced prostaglandin production via inhibition of IFN-gamma.

IL-18 shares with IL-1 the same family of receptors and several identical signal transduction pathways. Because of these similarities, IL-18 was investigated for its ability to induce prostaglandin E(2) (PGE(2)) synthesis in human peripheral blood mononuclear cells (PBMC), a prominent, proinflammatory property of IL-1. IL-18 was highly active in PBMC by inducing the synthesis of the chemokine IL-8; however, no induction of PGE(2) synthesis nor cyclooxygenase type-2 gene expression was observed in PBMC stimulated with IL-18. In the same cultures, IL-1beta induced a 12-fold increase in PGE(2). Although IL-1beta-induced IL-8 synthesis was augmented 3-fold by IL-18, IL-18 suppressed IL-1beta-induced PGE(2) production by 40%. The suppressive effect of IL-18 on PGE(2) production was mediated by interferon (IFN)-gamma because anti-human IFN-gamma-antibody prevented IL-18-induced reduction in PGE(2). Consistent with these observations, IL-12, a known inducer of IFN-gamma, augmented IL-1beta-induced IFN-gamma but suppressed IL-1beta-induced PGE(2) by 75%. IL-18 binding protein (IL-18BP) is a naturally occurring and specific inhibitor of IL-18. When recombinant IL-18BP was added to PBMC cultures, unexpectedly, spontaneous PGE(2) production increased. PGE(2) production was also increased by the addition of IL-18BP to PBMC stimulated with either IL-1beta or IL-12 and also in whole blood cultures stimulated with Staphylococcus epidermidis. These studies demonstrate that IL-18BP decreases endogenous IL-18 activity by reducing IFN-gamma-mediated responses.

Utilization of endoscopic inoculation in a mouse model of intrauterine infection-induced preterm birth: role of interleukin 1beta.

A novel murine model of intrauterine infection/inflammation-induced preterm birth based on direct endoscopic intracervical inoculation is described. Using this model, we investigated infection-induced premature pregnancy loss in normal and interleukin (IL) 1beta-deficient mice. Seventy-four CD-1, HS, C57BL/6J wild type (IL-1beta+/+), and C57BL/6J IL-1beta-deficient (IL-1beta-/-) mice were inoculated intracervically using a micro-endoscope, at a time corresponding to 70% of average gestation. Intracervical injection of lipopolysaccharide (LPS) or Escherichia coli reliably induced premature birth: 100% of mice intracervically injected with LPS and 92% of mice with a positive endometrial E. coli culture delivered prematurely within 36 h after inoculation. No losses were observed in mice inoculated with saline. Pregnancy loss was associated with increased uterine tissue cyclooxygenase-2 gene expression and uterine content of IL-1beta, tumor necrosis factor alpha, macrophage inflammatory protein-1alpha, and IL-6, as well as elevation of nuclear factor-kappaB activity in uterine tissues. Although IL-1beta-/- mice exhibited decreased uterine cytokine production in response to bacteria and LPS, IL-1beta deficiency did not affect the rate of pregnancy loss. This model using direct intracervical bacterial or LPS inoculation is useful for studying preterm pregnancy loss in genetically altered mice in order to develop novel interventions for infection-associated preterm labor.

TNF receptor I is required for induction of macrophage heat shock protein 70.

Expression of heat shock proteins (HSP) is an adaptive response to cellular stress. Stress induces tumor necrosis factor (TNF)-alpha production. In turn, TNF-alpha induces HSP70 expression. However, osmotic stress or ultraviolet radiation activates TNF-alpha receptor I (TNFR-I) in the absence of TNF-alpha. We postulated that TNF-alpha receptors are involved in the induction of HSP70 by cellular stress. Peritoneal Mphi were isolated from wild-type (WT), TNF-alpha knockout (KO), and TNFR (I or II) KO mice. Cells were cultured overnight and then heat stressed at 43 +/- 0.5 degrees C for 30 min followed by a 4-h recovery at 37 degrees C. Cellular HSP70 expression was induced by heat stress or exposure to endotoxin [lipopolysaccharide (LPS)] as determined by immunoblotting. HSP70 expression induced by either heat or LPS was markedly decreased in TNFR-I KO Mphi, whereas TNFR-II KO Mphi exhibited HSP70 expression comparable to that in WT mice. Expression of HSP70 after heat stress in TNF-alpha KO Mphi was also similar to that in WT mice, suggesting that induction of HSP70 by TNFR-I occurs independently of TNF-alpha. In addition, levels of steady-state HSP70 mRNA were similar by RT-PCR in WT and TNFR-I KO Mphi despite differences in protein expression. Furthermore, the effect of TNFR-I appears to be cell specific, since HSP70 expression in splenocytes isolated from TNFR-I KO was similar to that in WT splenocytes. These studies demonstrate that TNFR-I is required for the synthesis of HSP70 in stressed Mphi by a TNF-independent mechanism and support an intracellular role for TNFR-I.