Comparative production of IL-1 beta and IL-1 alpha by LPS-stimulated human monocytes: ELISAs measurement revisited

Staphylococcus epidermidis-derived protease Esp mediates proteolytic activation of pro-IL-1beta in human keratinocytes

The gram-positive bacterium Staphylococcus epidermidis (SE) is an abundant skin commensal. It plays an important role in cutaneous defense by activation of IL-1 signaling. In keratinocytes, SE induces the release of mature IL-1beta. IL-1beta serves as an important cytokine of host defense. It contains an N-terminal prodomain that has to be cleaved off to generate active mature IL-1beta. Typically, processing and release of IL-1beta are associated with inflammasome assembly and activation of the protease caspase-1. Here we report that bacterial challenge of keratinocytes with SE induced the release of mature IL-1beta in a caspase-1-independent manner. Instead, the SE -derived serine protease Esp was identified as a pro-IL-1beta processing factor leading to a proteolytic maturation of active IL-1beta. Esp production and secretion by various SE strains correlated with their capacity to induce release of mature IL-1beta in human primary keratinocytes. Reconstitution of Esp-lacking SE strains with Esp enhanced their capacity to induce IL-1beta release in keratinocytes and skin. Intracellular abundance of pro-IL-1beta and cytotoxic effects of SE suggest release of pro-IL-1beta during injury followed by extracellular Esp-mediated processing to mature IL-1beta. These findings provide further insights into how a skin commensal interacts with keratinocytes to activate cutaneous host innate defense.

Bone and bone marrow interactions: hematological activity of osteoblastic growth peptide (OGP)-derived carboxy-terminal pentapeptide

The increase of megakaryocytes and platelets that characterizes essential thrombocythemia (ET) appears to be secondary to a deregulation of megakaryocytopoiesis. The carboxy-terminal fragment of osteogenic growth peptide (OGP10-14) promotes bone formation and hemopoiesis, while it inhibits megakaryocytopoiesis. In this paper we show that treatment with synthetic OGP10-14 (sOGP10-14) induces a significant reduction of mid and large colony-forming unit-megakaryocytes (CFU-Mk) in ET patients as well as in controls, and is associated with a significant inhibition of thrombopoietin (TPO)-primed MO-7e megakaryoblastic cells proliferation. These actions appear to be related to sOGP10-14 modulation of TGF-beta(1) synthesis and/or secretion, although a direct effect on TGF-beta receptor expression cannot be excluded.

Ribavirin inhibits DNA, RNA, and protein synthesis in PHA-stimulated human peripheral blood mononuclear cells: possible explanation for therapeutic efficacy in patients with chronic HCV infection

The treatment of choice for patients infected chronically with HCV is the combination of IFN-alpha and ribavirin. Monotherapy with ribavirin leads to a clinical and histological improvement, but its exact mechanism of action is unknown. Therefore, the effect of ribavirin on synthesis of inflammatory cytokines and on apoptosis in stimulated peripheral blood mononuclear cells (PBMCs) was investigated. PBMCs were isolated from the blood of HCV infected patients and from healthy volunteers. The effect of ribavirin on IFN-gamma and IL-1beta release in the supernatant of unstimulated and phytohemagglutinin (PHA) stimulated PBMCs was investigated by enzyme linked immunosorbent assay (ELISA). The effect on total DNA, RNA, and protein synthesis was analyzed by measurement of 3H-thymidine, 3H-uridine and 3H-leucine incorporation into cellular macromolecules. Ribavirin led to a dose-dependent decrease of the IFN-gamma but an increase of IL-1beta release into the supernatant of PHA-stimulated PBMCs. At the same time, a dose-dependent decrease of total DNA, RNA, and protein synthesis in cultures of PHA-stimulated PBMCs was demonstrated. These effects could be compensated by the addition of equimolar amounts of guanosine. The rate of apoptotic CD45+ and CD14+ cells in PBMCs cultures increased in a dose-dependent manner. Our data suggest that ribavirin administration to chronically HCV-infected patients could lead to a decrease of the synthesis of proinflammatory cytokines (e.g., IFN-gamma) by an inhibition of total DNA-, RNA-, and protein-synthesis and by induction of apoptosis in the cells of the inflammatory infiltrate. Furthermore, ribavirin could influence the synthesis of viral particles in the hepatocytes.

Structure-based design of caspase-1 inhibitor containing a diphenyl ether sulfonamide

A series of compounds was designed and prepared as inhibitors of interleukin-1beta converting enzyme (ICE), also known as caspase-1. These inhibitors, which employ a diphenyl ether sulfonamide, were designed to improve potency by forming favorable interactions between the diphenyl ether rings and the prime side hydrophobic region. An X-ray crystal structure of a representative member of the diphenyl ether sulfonamide series bound to the active site of caspase-1 was obtained.

Quantitative analysis of proinflammatory cytokines (IL-1beta, IL-6, TNF-alpha) in human skin wounds

Proinflammatory cytokines play an important role in the mediation of inflammation and trauma. They could be useful for the determination of vitality and wound age. In the present study, 144 human skin wounds due to sharp force were investigated. The material was collected during operations (N=96) and postmortem examinations (N=48). The wound age varied from several seconds or minutes to 9 days. Control skin was available in each individual. The tissue specimens were homogenized and extracted in a solution of PBS and protease inhibitors. Interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) were measured by quantitative ELISA analysis. Statistical evaluation was performed by the t-test using the quotients of levels (wound sample/control skin). In surgical specimens the cytokine levels revealed a clear tendency to increase with wound age. IL-1beta in early skin wounds (</=30 min) and TNF-alpha after a wound age of 1-2 h demonstrated statistically significant changes in comparison with control skin (P<0.05). In autopsy samples with severe traumatization excessive elevation of cytokine levels was observed: IL-1beta, IL-6 and TNF-alpha showed significant increases (P<0.001-0.05) in stab and incised wounds with very short survival times of less than 5 min, but not in possibly supravital injuries. Elevated IL-6 levels persisted in older wounds (>24 h, P<0.05). The quantitative analysis of proinflammatory cytokines in wound extracts can contribute to the determination of vitality and wound age, in particular in the very early post-traumatic interval (classic stab wounds).

Measurement of cytokines in clinical samples using immunoassays: problems and pitfalls

With the explosion in interest in cytokines and an increasing understanding of their possible involvement in the pathogenesis of many diseases, the number of studies measuring cytokines in body fluids has increased markedly over the last 5 to 10 years. However, it is readily apparent from the literature that the level of awareness of the many factors that can potentially influence the results obtained is very low. Such factors are likely to contribute considerably to the disparities seen among similar types of study. These include assay properties such as standardization and specificity, type of sample and sample handling, and many biological influences such as age, sex, ethnic background, and diurnal rhythmicity. Clearly, it is not possible to control for all these factors, but a minimum evaluation of assays should be carried out as described, including recovery and parallelity studies using relevant samples and the establishment of reproducibility and normal healthy population levels. An awareness of these factors, which is the purpose of this review, may hopefully lead to an improvement in the quality of studies incorporating the measurement of cytokines in clinical samples and should aid in the interpretation of the data.

Colonic explant production of IL-1and its receptor antagonist is imbalanced in inflammatory bowel disease (IBD)

IBD is associated with an increased activation of intestinal immune cells, which causes overproduction of proinflammatory cytokines such as IL-1beta. IL-1beta is implicated in mediating the sustained inflammatory response. IL-1 receptor antagonist (IL-1Ra), the naturally occurring inhibitor of IL-1, has been shown to have beneficial effects in experimental models of colitis. In this study we investigated the hypothesis that an imbalance between IL-1 and IL-1Ra exists in IBD by measuring their secretion by explant cultures of colonic biopsies. Freshly homogenized biopsies from involved tissue in IBD patients exhibited significantly lower IL-1Ra/IL-1beta ratios than control and uninvolved IBD mucosal tissue. Using explant cultures, in vitro production of IL-1beta and IL-1Ra increased progressively during the 4-18-h culture periods. IL-1beta secretion was higher in supernatants from involved Crohn's disease (CD) and ulcerative colitis tissue compared with control tissue, and IL-1beta levels increased with severity of inflammation. IL-1Ra secretion was not elevated in involved IBD samples, but significantly higher levels were released when moderate to severely involved tissue samples were compared with noninflammatory controls. Similar to freshly homogenized tissue, explant studies showed that the IL-1Ra/IL-1beta ratios were significantly decreased in involved IBD tissue, but not in uninvolved CD or inflammatory control specimens. These data support the hypothesis of an imbalance between IL-1beta and IL-1Ra in IBD.

Preanalytical factors and the measurement of cytokines in human subjects

Cytokines are widely measured in research. However, cytokine analyses are influenced by a myriad of factors. For instance, a delay in the separation of plasma from cells may lead to a 50% decrease in the concentration of tumor necrosis factor in plasma. Another example is the secretion of interleukin-1 beta in women which can be twice as high during the follicular phase as in the luteal phase. The factors influencing the outcome of these tests can be divided into in vivo preanalytical factors (e.g., aging, chronobiological rhythms, diet, etc), in vitro preanalytical factors (e.g., specimen collection, equipment, transport, storage, etc), and analytical factors. To improve the value of the cytokine tests, factors strongly influencing the results have to be controlled. This can be done by using standardized assays and specimen collection procedures. In general, sufficient attention is not given to the preanalytical factors, especially in the measurement of cytokines. This article reviews the preanalytical factors which may influence the outcome of these tests in human subjects.

Reduction of inflammation and pyrexia in the rat by oral administration of SDZ 224-015, an inhibitor of the interleukin-1 beta converting enzyme

1. The aim of this study was to determine whether a synthetic inhibitor of the interleukin-1 beta converting enzyme (ICE) displays oral activity in models of inflammation. 2. To this end, the ICE inhibitor, SDZ 224-015, was examined in rat paw oedema, pyrexia and nociception tests. 3. SDZ 224-015 (0.3-300 micrograms kg-1) potently reduced carrageenin-induced paw oedema, with an oral ED50 of approximately 25 micrograms kg-1. This effect was independent of endogenous glucocorticoid, as shown by retention of activity upon adrenalectomy. 4. Pyrexia induced by lipopolysaccharide (0.1 mg kg-1 s.c.) or by interleukin-1 beta (100 ng i.v.) was also reduced, over a similar dose-range to oedema (oral ED50s 11 micrograms kg-1 and 4 micrograms kg-1 respectively). 5. SDZ 224-015 (0.2-5 mg kg-1, p.o.) displayed analgesic activity in the Randall-Selitto yeast-inflamed paw pressure test, significant at a dose of 1 mg kg-1, p.o. 6. Thus, SDZ 224-015 has potent oral activity in several acute models for inflammation, suggesting that ICE inhibitors may constitute a novel type of anti-inflammatory agent.

Monocyte-induced cytokine expression in cultured human retinal pigment epithelial cells

Monocytes and retinal pigment epithelial cells are intimately associated in membranes of eyes with proliferative vitreoretinopathy and in certain types of uveitis. The goal of this study was to determine whether monocytes modulate cytokine expression in retinal pigment epithelial cells, and if so, to identify the monocyte products responsible for this effect. Cultured human retinal pigment epithelial cells were exposed to varying concentrations of monocyte-conditioned medium from unstimulated human monocytes for 1-48 hr, or from monocytes prestimulated with lipopolysaccharide. mRNA expression of interleukin-1 beta, interleukin-6, interleukin-8, melanoma growth stimulating activity/gro alpha and gamma, macrophage colony stimulating factor, transforming growth factor-beta 2, basic fibroblast growth factor and activin beta A chain was determined by reverse transcription polymerase chain reaction. Protein secretion of selected cytokines, interleukin-1 beta, interleukin-6, interleukin-8, macrophage colony stimulating factor and transforming growth factor-beta 2 was measured in RPE-conditioned medium by ELISA. Retinal pigment epithelial cells constitutively expressed mRNA for interleukin-6, macrophage colony stimulating factor, transforming growth factor-beta 2, basic fibroblast growth factor and activin beta A chain. Interleukin-1 beta, melanoma growth stimulating activity/gro alpha and gamma and interleukin-8 were not expressed under basal conditions. Stimulated monocyte-conditioned medium markedly induced mRNA of all cytokines except basic fibroblast growth factor and transforming growth factor-beta 2 in a dose- and time-dependent manner. Unstimulated monocyte-conditioned medium was a less potent inducing agent, but still enhanced mRNA expression of interleukin-6, interleukin-8 and melanoma growth stimulating activity/gro alpha. Stimulated monocyte-conditioned medium also induced a time-dependent increase in interleukin-6, Interleukin-8, macrophage colony stimulation factor and transforming growth factor-beta 2, but not interleukin-1 beta protein secretion (p < 0.05 for all time points). Neutralizing antibodies to interleukin-1 beta, or tumour necrosis factor alpha, but not interleukin-1 alpha, significantly reduced cytokine mRNA expression induced by stimulated monocyte-conditioned medium. The combination of all three neutralizing antibodies almost entirely eliminated monocyte-induced mRNA expression and protein production of all cytokines studied. Activated monocytes secrete a heterogeneous mixture of products that together strongly induce expression of multiple cytokines in human retinal pigment epithelial cells. Most if not all of the inducing effect can be accounted for by interleukin-1 beta and tumour necrosis factor alpha. Because cytokines have been implicated in proliferative vitreoretinopathy and uveitis, monocyte-mediated cytokine expression by RPE cells may serve to initiate and perpetuate these diseases.