Prostacyclin synthesis induced in vascular cells by interleukin-1

Prostaglandin biosynthesis by human decidual cells: effects of inflammatory mediators

There is substantial evidence that decidual activation, in association with infection, is linked with the onset of both preterm and term labor. We therefore undertook the present study to evaluate prostaglandin production and its potential regulation by inflammatory mediators in human decidual cells in primary monolayer culture. Upon attaining confluence, the cells were incubated with endotoxin, interleukin 1 alpha (IL1 alpha), interleukin 1 beta (IL1 beta); or tumor necrosis factor (TNF). Production of prostaglandin (PG) E2 and PGF2 alpha was determined using specific radioimmunoassays. Endotoxin and these cytokines all induced significant concentration-dependent increases in PGE2 and PGF2 alpha production. Our results suggest that term human decidual cells are responsive to endotoxin and cytokines and that generation of these substances in the decidua or nearby (eg. in response to infection) will lead to increased prostaglandin production and uterine contractions.

Human recombinant interleukin-1 beta- and tumor necrosis factor alpha-mediated suppression of heparin-like compounds on cultured porcine aortic endothelial cells

Cytokines are known to tip the balance of the coagulant-anticoagulant molecules on the endothelial cell surface toward intravascular coagulation. Their effects on endothelial cell surface-associated heparin-like compounds have not been examined yet. Incorporation of [35S]sulfate into heparan sulfate on cultured porcine aortic endothelial cells was suppressed by human recombinant interleukin-1 beta (rIL-1 beta) or tumor necrosis factor alpha (rTNF alpha) in a dose- and time-dependent manner with little effect on cell number, protein content, and [3H]leucine incorporation of cells. Maximal inhibition was achieved by incubation of cells with 100 ng/ml of rIL-1 beta or 5 ng/ml of rTNF alpha for 12-24 hours, resulting in a reduction of the synthesis of heparan sulfate on the cell surface by approximately 50%. The dose dependency was consistent with that seen in the stimulation of endothelial cell procoagulant activity by each cytokine. The suppression of heparan sulfate synthesis was sustained for at least 48 hours after pretreatment of cells with cytokines and was unchanged after the addition of indomethacin or polymyxin B. The rate of degradation of prelabeled 35S-heparan sulfate on the cell surface was not altered by cytokine treatments. Neither the size, the net negative charge, nor the proportion of the molecule with high affinity for antithrombin III of endothelial cell heparan sulfate was changed by cytokines. Furthermore, specific binding of 125I-labeled antithrombin III to the endothelial cell surface was reduced to 40-60% of control by cytokines. In parallel with reduction in binding, antithrombin III cofactor (heparin-like) activity was partially diminished in cytokine-treated endothelial cells. Thus, cytokine-mediated suppression of heparin-like substance on endothelial cells appears to be another cytokine-inducible endothelial effects affecting coagulation.

Correlation of leukocyte interleukin-1 production with the stimulation of prostaglandin and tissue factor synthesis by human umbilical vein endothelial cells

Human leukocyte suspensions (neutrophils 80-85%, monocyte 15-20%) were incubated alone or with cultured human umbilical vein endothelial cells. Leukocytes were either directly added to the endothelial cell cultures or separated from them by a 0.4 micron insert filter. Supernatants or cell lysates were obtained at 0.5, 1, 2, and 4 hours of incubation. Supernatants were assayed for the prostacyclin (PGI2) metabolite 6-keto prostaglandin F1 alpha and prostaglandin E2 (PGE2) by radioimmunoassay and for interleukin-1 (IL-1) by the thymocyte co-mitogen assay. Cell lysates were analyzed for cell-associated procoagulant activity (PCA). Co-incubation of endothelial cells with leukocytes stimulated the synthesis of PGI2, PGE2, and PCA. These biochemical changes correlated partially with the release of IL-1 beta. The results suggest that IL-1 released in monocyte neutrophil co-cultures can produce prothrombotic (increased PCA expression) and inflammatory changes (increased synthesis of vasodilatory and permeability enhancing PGI2 and PGE2) in endothelial cells. Neutrophils may represent a source of the released IL-1 and/or may act to stimulate monocyte release of this cytokine and thus play an important role in vascular pathology by a mechanism unrelated to their more direct cytotoxic activity.

Effect of growth factors on human vascular endothelial cell prostacyclin production

Prostacyclin (PGI2) is an antithrombotic factor, which may prevent the initiation and the complications of arteriosclerosis. The most important site of PGI2 production is the vascular endothelium, but little is known about how this process is regulated. In this connection, there is special interest in the roles of various growth factors released from platelets, macrophages, vascular smooth muscle cells, and the endothelial cells themselves. We investigated the effects of transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), and acidic and basic fibroblast growth factors (aFGF and bFGF) on the PGI2 production of cultured human umbilical vein endothelial cells by measuring the stable metabolite of PGI2, 6-keto-prostaglandin F1 alpha, by radioimmunoassay. TGF-beta induced dose- and time-dependent stimulation of PGI2 production. The lowest stimulatory concentration of TGF-beta was 0.1 ng/ml, and the maximal response, a 2.1-fold rise, was obtained with 1.0 ng/ml. The effect of TGF-beta lasted 48 hours and was blocked by inhibitors of transcription, translation, and cyclooxygenase. Maximal stimulation by TGF-beta was enhanced by epidermal growth factor. PDGF and bFGF had no effect on PGI2 production, but aFGF inhibited it. This is the first demonstration that TGF-beta enhances PGI2 production by human vascular cells, and this phenomenon may be part of negative feedback mechanisms that prevent thrombosis and arteriosclerosis.

Potent inflammatory properties in human skin of interleukin-1 alpha-like material isolated from normal skin

Recombinant human interleukin 1 (IL-1) possesses potent inflammatory properties in both animal and human skin. However, IL-1-like material has been isolated from normal epidermal samples. In view of the uncertainty concerning the structure and biologic properties of human epidermal IL-1, heel stratum corneum, and chamber fluid samples from normal skin have been purified by successive reversed phase and anion exchange high-performance liquid chromatography (HPLC), and aliquots of each HPLC fraction tested for IL-1 activity in an EL-4 NOB-1 assay and for inflammatory activity by intradermal injection of autologous material. The results consistently indicated the presence of inflammatory quantities of IL-1 alpha-like material, which induced persistent erythema lasting at least 24 h, associated in 4-h biopsies with mixed dermal leukocyte infiltrates containing increased numbers of neutrophils, monocytes, and T helper cells. Biologically active quantities of IL-1 beta were not recovered following HPLC purification in most experiments. Analysis of heel stratum corneum extract also showed that the majority of the dilution-related IL-1 activity detected in the EL-4 NOB-1 bioassay was neutralized by IL-1 alpha but not IL-1 beta antiserum. These findings suggest that IL-1 alpha-like material is present in inflammatory amounts in normal human epidermis, and its release may represent a primary inflammatory mechanism in human skin.

LPS-stimulated bovine aortic endothelial cells produce IL-1 and IL-6 like activities

Vascular endothelium is known to closely interact with leukocytes and immunocompetent cells. We report here that cultured bovine aortic endothelial cells (BAEC) synthesize both interleukin 1 (IL-1) and interleukin 6 (IL-6) like activities in response to bacterial lipopolysaccharide stimulation. Our results agree with previous data obtained from human venous endothelia and support the concept that IL-1 and IL-6 synthesis are properties common to endothelial cells from different vascular beds. The IL-1 activity was measured by murine thymocyte proliferation assay and by an indirect bioassay using NOB1 cells, which evidenced higher IL-1 amounts than the former. This discrepancy appeared to be partly due to the simultaneous production of one or more inhibitor(s) of the thymocyte proliferation by BAEC. The IL-6 assay was performed with the murine hybridoma cell line B9. In other respects, the cyclooxygenase inhibitor indomethacin enhanced the IL-1 like production, but was ineffective on IL-6 like production. The present study provides additional evidence that endothelial cells from large arteries may also participate in inflammatory and immunological processes.

Vasodilator actions of interleukin-1 in the canine coronary circulation

The effects of intracoronary ultrapure human Interleukin-1 on the regional distribution of coronary blood flow (radioactive microspheres), contractile function (subendocardial ultrasonic length gauges) and systemic hemodynamics were studied in open-chest, anesthetized dogs (n = 7). Bolus doses of Interleukin-1 (10, 20, and 30 u) administered directly into the left anterior descending coronary artery increased coronary blood flow from 43 to 71, 80 and 87 ml/min, respectively. The increase in blood flow produced by Interleukin-1 was distributed uniformly to the subendocardium, midmyocardium, and subepicardium of the left ventricular free wall without effect on regional function or systemic hemodynamics. Indomethacin (1 mg/kg i.v.) attenuated the increase in blood flow, especially to the subepicardium. Due to the selective diminution of the Interleukin-1-mediated increase in subepicardial blood flow by indomethacin, the subendocardial to subepicardial perfusion ratio was increased by Interleukin-1 in the presence of indomethacin. The present results demonstrate that Interleukin-1 has direct coronary vasodilator actions, a portion of which is mediated by a product of cyclooxygenase metabolism.

Pro-inflammatory mediators induce sustained release of prostaglandin E2 from human dermal microvascular endothelial cells

The vasodilator prostaglandin E2 has been proposed as a mediator of erythema in a variety of cutaneous inflammatory reactions and prostacyclin levels have been found to be elevated in ultraviolet induced erythema. Human recombinant interleukin 1 alpha and lipopolysaccharide induced a concentration- and time-dependent release of prostaglandin E2, but not prostacyclin, from cultured neonatal and adult human dermal microvascular endothelial cells. Prostaglandin E2 was measurable at 2 h after stimulation with 1 U/ml interleukin 1 alpha, levels increased rapidly up to 6 h and more slowly up to 24 h. Lipopolysaccharide (20 micrograms/ml) induced measurable release of prostaglandin E2 between 2 and 4 h after stimulation and release continued up to 24 h when incubation was terminated. With both agonists, release of prostaglandin E2 was inhibited by indomethacin and significantly reduced by cycloheximide. The sensitivity and magnitude of responses of the cutaneous endothelial cells to these pro-inflammatory stimuli appeared to be dependent on their derivation.

Prostacyclin and vascular function: implications for hypertension and atherosclerosis

Prostacyclin and endothelium-derived relaxing factor (or nitric oxide) are unstable mediators produced by the vascular endothelium, that are important for local regulation of platelet behavior and blood flow. This review focuses on the basic biochemistry and pharmacology of prostacyclin, its interactions with nitric oxide and nitrovasodilator drugs, and the implications of disturbances in this system for vascular disease, particularly hypertension and atherosclerosis. Prostacyclin and its stable analogs are also finding limited therapeutic applications in preservation of platelet function, pulmonary hypertension, and investigation into the cytoprotective and antiatherosclerotic properties is continuing.

Interleukin-1 stimulates prostacyclin production by cultured human endothelial cells by increasing arachidonic acid mobilization and conversion

Interleukin-1 (IL-1) induced slow, lasting activation of human endothelial cells (EC) to release prostacyclin (PGI2). This was accompanied by endogenous 3H-arachidonic acid (3H-AA) release and by a time-dependent increase in the cells' ability to convert exogenous AA. The continuous presence of IL-1 was not required, but about a 1-hour stimulation with the cytokine was sufficient to trigger the cells to synthesize PGI2 for several hours. The spectrum of 3H-AA conversion shows that, in addition to 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha also was raised after IL-1. The recovery of PGI2 synthesis after aspirin was faster in IL-1-treated EC than in control cells. These data define some of the characteristics of IL-1 stimulation of PGI2 and suggest that this process is mediated both by endogenous AA mobilization and by an increase in cyclooxygenase activity.

Interleukin 1: the first interleukin

The name 'interleukin' and the designation of interleukin 1 (IL-1) derived from the Second International Lymphokine Workshop held in Switzerland in 1979. Since then interest in the original interleukin (IL-1) has increased exponentially as measured by the numbers of publications and meetings. The main reasons for this can be seen in the accompanying centrefold. The perception of IL-1 as a biological mediator in every organ system has attracted scientists from widely different backgrounds into this area and a steady succession of important and often surprising insights into IL-1 biology has ensured that interest has been sustained at a high level. This overview of the biology of IL-1 on the tenth anniversary of its turbulent life has been compiled by Franco di Giovine and Gordon Duff. It is of necessity selective and biased towards human IL-1 and begins with some general points (mainly cautionary) as a backdrop to the centrefold.

Protection against pulmonary oxygen toxicity by interleukin-1 and tumor necrosis factor: role of antioxidant enzymes and effect of cyclooxygenase inhibitors

Rats injected with interleukin-1 (10 micrograms) and tumor necrosis factor (10 micrograms) and then exposed continuously to hyperoxia (greater than 99% O2, 1 atm) survived longer, had increased lung reduced/oxidized glutathione ratios, smaller pleural effusions, less pulmonary hypertension and improved arterial blood gases. The percentage of animals surviving for 72 hours in hyperoxia increased from 8% to 94%. Although relatively small increases in glutathione redox cycle enzymes occurred four and sixteen hours following cytokine injection, dramatic increases in all major antioxidant enzymes including superoxide dismutase, glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase, and catalase had occurred following 72 hours of exposure to hyperoxia. The protective effect of IL-1 + TNF against lethal pulmonary O2 toxicity could be partially inhibited by pre-injection of lysine acetylsalicylate or, less effectively, of ibuprofen. Recent studies have suggested that both IL-1 and TNF can induce manganese (mitochondrial) superoxide dismutase mRNA and protein synthesis in a variety of cell types. Preliminary studies suggest that IL-1 alone, in ample dosage, can provide protection against lethal pulmonary O2 toxicity. Future studies should be directed toward identification of acute phase changes in lung antioxidant enzymes, surfactant proteins and/or lipid components, enzymes needed for synthesis of surfactant phospholipids, and/or other protective proteins. Additional work also needs to be done in identifying the lung cell types in which early enzyme induction occurs. These studies should provide a better understanding of mechanisms whereby protection against pulmonary O2 toxicity can occur. An understanding of the molecular mechanisms inducing protective proteins should lead to more precise pharmacologic control of these processes.

IL-1 and IL-6 release by tumor-associated macrophages from human ovarian carcinoma

Our study was designed to investigate the production of interleukin-1 (IL-1) and IL-6 in tumor-associated macrophages (TAM) isolated from ascites (18 cases) or solid (7 cases) human ovarian carcinoma. These are pleiotropic monokines which, in addition to affecting proliferation and differentiation of lymphocytes, act on various targets, including vascular cells and liver, and may therefore be involved in the pathogenesis of certain manifestations of malignancy. IL-1 was measured by the thymocyte co-stimulator assay, under conditions in which IL-6 was inactive, and, in 8 cases, by radioimmunoassay (RIA). IL-6 was measured as hybridoma growth factor (HGF) on the 7TD1 cell line. TAM did not release appreciable levels of IL-1 spontaneously and, upon LPS stimulation, were poor producers of this monokine compared to blood monocytes. In contrast, TAM supernatants contained a high level of HGF in the absence of deliberate stimulation, and exposure to LPS either did not affect or further augmented production of this monokine. HGF activity of TAM supernatants was completely blocked by anti-IL-6 antibodies. Ascites fluid from 8 ovarian-carcinoma patients contained high levels of HGF activity, blocked by anti-IL-6 antibodies. Thus, TAM exhibit a dissociation in their capacity to release the functionally related monokines IL-1 and IL-6. IL-6 produced by TAM may account for the elevation of liver-derived acute-phase proteins associated with malignancy.

Interleukin 1 enhances arterial thrombogenicity in vitro

An in vitro model of platelet adhesion, the annular perfusion chamber, was utilized to test the effects of Interleukin 1 on vascular thrombogenicity for platelets. De-endothelialized, everted human umbilical arteries were placed in cell culture media with or without Interleukin 1. The arteries were later perfused with citrated human blood and then fixed. Platelet adhesion and aggregate formation on artery segments was quantified by blinded morphometric analysis. A monolayer of contact platelets was seen on control artery segments, but arteries exposed to 100 Units/ml Interleukin 1 for 2-20 hours had increased numbers and size of platelet aggregates. Ultrastructurally, intact endothelial cells were not present on any segment. Both prostacyclin and thromboxane were released by vascular cells in the artery segments, but the quantity and ratio of these eicosanoids was not altered by artery exposure to Interleukin 1. Arterial thrombogenicity is modulated by non-endothelial vascular cells in response to Interleukin 1, and this does not appear to be mediated by changes in vascular production of thromboxane or prostacyclin.

Cytokines as communication signals between leukocytes and endothelial cells

Hemostasis, inflammatory reactions and immunity involve close interactions between immunocompetent cells and the vascular endothelium. Cytokines, produced by and acting on endothelial cells, are mediators of the complex bidirectional interactions between leukocytes and vascular cells. Cytokines affect endothelial cell function in inflammation, thrombosis and angiogenesis, in addition to their role as accessory cells. As well as acting as targets for the action of cytokines, endothelial cells are important producers of polypeptide mediators that regulate hematopoiesis, the differentiation and proliferation of T and B cells and the extravasation of leukocytes. In this review, Alberto Mantovani and Elisabetta Dejana discuss endothelial cells as important participants in the induction and regulation of coagulation, inflammation and immunity and cytokines as crucial mediators of the symbiotic interactions between vascular cells and leukocytes.

Antithrombin III stimulates prostacyclin production by cultured aortic endothelial cells

Prostacyclin (PGI2) is a potent vasodilator and an inhibitor of platelet aggregation. We found that antithrombin III (AT III), an anticoagulant present in circulating blood, stimulated PGI2 production by cultured bovine aortic endothelial cells in a dose- and time-dependent manner. The stimulation of PGI2 production by AT III was observed at physiological concentrations and was inhibited by the addition of anti-AT III antiserum and heparin. These results suggest that AT III may stimulate PGI2 production by binding to heparin-like molecules on the endothelial cell membrane.

Abnormality in prostacyclin-stimulatory activity in sera from diabetics

A reduction in prostacyclin (PGI2) production by vascular wall may cause platelet hyperaggregability in diabetics, which is considered to be a possible pathogenesis of diabetic vascular complications. In the present study, the presence of PGI2-stimulatory activity (PSA) in rat and human plasma-derived serum (PDS) was confirmed by cultured bovine aortic endothelial cells. PSA in PDS was significantly decreased in streptozotocin-induced diabetic rats and in patients with non-insulin-dependent diabetes mellitus (NIDDM). PDS from patients with NIDDM showed less PSA prior to the clinical onset of diabetic vascular complications, such as retinopathy and proteinuria. The reduction in PSA was still observed in dialyzed PDS from the patients with NIDDM. The nondialyzable PSA was heat-stable at 56 degrees C for 30 minutes and partially stable at 100 degrees C for five minutes. This activity was not extractable with diethylether and was precipitable with trichloroacetic acid. The study of Sephadex G-50 column chromatography showed that a major part of PSA in dialyzed PDS was found in the area of the molecular weight of 12,000 to 17,000 daltons. In conclusion, the reduction in PSA from diabetics may cause a reduction of PGI2 production by vascular wall, subsequently contributing to the development of diabetic vascular complications.

Bacterial endotoxin and tumor necrosis factor stimulate prostaglandin production by human decidua

The purpose of these studies was to determine the effect of bacterial endotoxin and tumor necrosis factor (TNF) on prostaglandin (PG) secretion by human decidua. Decidual explants were established from women undergoing elective cesarean sections before the onset of labor. Escherichia Coli endotoxin and purified human recombinant TNF (rh TNF) were incubated with decidual explants. PGF2 alpha and PGE2 biosynthesis was measured by radioimmunoassay. A significant increase in the release of all PGs into the media occurred in response to LPS and TNF. In the setting of an extraamniotic infection, bacterial and host secretory products (TNF) could trigger the onset of labor, activating the decidua to produce PGs.

Subtype-specific increase in G-protein alpha-subunit mRNA by interleukin 1 beta

The guanine nucleotide regulatory proteins (G-proteins) which are substrates for ADP-ribosylation by pertussis toxin (alpha i-1, alpha i-2, alpha i-3 and alpha o) transduce a variety of hormonal signals. Endothelial cells express mRNA for three alpha i subtypes although the level of alpha i-1 mRNA is very low. Interleukin 1 beta (IL 1 beta), a pleiotropic inflammatory mediator which stimulates a complex series of responses in human endothelial cells leading to increased coagulation and platelet adhesion, increases expression of one subtype of alpha i (alpha i-2) mRNA in human endothelial cells as determined by Northern blot analysis without affecting the level of mRNA for other alpha-subunits. These studies show that mRNA levels for alpha i subtypes are independently regulated, suggesting that there may be subtype specificity in the cell's requirements for the Gi class of signal-transducing proteins.

Interleukin-1 and the response to injury

Traumatic injury is the leading cause of morbidity and mortality in Americans less than 45 years old. People surviving the initial insult undergo metabolic, hemodynamic and immunologic changes which contribute to both early and late complications. Though necessary for normal immunologic response and for wound healing, pathologic alterations of IL-1 synthesis, degradation, and binding to receptors on both a local and systemic level could lead to these changes. Manipulation of IL-1-mediated effects might be of therapeutic utility in the management of trauma in the future.

Microvascular permeability to IgG in the rat testis at puberty

Immunoglobulin G (IgG) spaces and permeability surface area products (PS) were calculated separately in the testis parenchyma, capsule and interstitial tissue in four age groups of rats to see if there were regional differences in microvascular permeability in the rat testis and if there were changes in PS with age. The results demonstrated a marked increase in PS to IgG at 27 days of age in the testicular interstitial tissue, whereas PS in the capsule did not show such consistent changes. Blood volumes per gram, as indicated by the 3 min IgG spaces, were considerably greater in the testicular capsule than in the interstitial tissue, although the weight of the capsule was only about one-third of the interstitial tissue weight. Maximal IgG spaces were reached at 5 h in the testicular parenchyma, but in most groups only at 20 h in the capsule. IgG was demonstrated immunohistochemically in the testicular interstitial tissue from 33 days of age onwards.

Release of prostacyclin from cultured human endothelial cells following prolonged exposure to histamine

Histamine is an important pro-inflammatory molecule mediating leukocyte margination, plasma extravasation and vasodilation, but its precise mode of action on vascular endothelium is unclear. We report that histamine is able to induce prolonged release of prostacyclin (PGI2) from human endothelial cells via occupancy of the H1 receptor, without an absolute requirement for the presence of histamine or synthesis of new enzyme protein to facilitate continued release of PGI2.

Regional variability of prostacyclin biosynthesis

To investigate the regional variability in arterial and venous endothelial prostacyclin (PGI2) biosynthesis, we obtained 1-cm segments of carotid arteries, external jugular veins, femoral arteries and veins, iliac arteries and veins, inferior venae cavae (IVC), and aortas from 17 dogs. Vessel luminal PGI2 production was measured in the basal state by radioimmunoassay of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). A total of 90 arterial specimens (57, 19, and 14 segments, respectively, of femoral/carotid arteries, iliac arteries, and aorta) and 41 venous specimens (15, 10, and 16 segments, respectively, of femoral/jugular veins, iliac veins, and IVC) were analyzed. Overall, arterial endothelial 6-keto-PGF1 alpha was higher than venous (8.1 +/- 0.5 ng/ml vs. 4.9 +/- 0.7 ng/ml, p less than 0.0004); 6-keto-PGF1 alpha levels were greater in the arteries than in their corresponding veins [femoral/carotid arteries (6.3 +/- 0.4 ng/ml) vs. femoral/jugular vein (2.1 +/- 0.4 ng/ml), p less than 0.0002; iliac arteries (9.3 +/- 1.0 ng/ml) vs. iliac veins (4.8 +/- 0.9 ng/ml), p less than 0.005; aorta (14.0 +/- 1.6 ng/ml) vs. IVC (7.5 +/- 1.4 ng/ml), p less than 0.006].(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 promotes proliferation of vascular smooth muscle cells in coordination with PDGF or a monocyte derived growth factor

We report that interleukin-1 (IL-1) potentiates the proliferation of vascular smooth muscle cells. Growth of early passage smooth muscle cells was not significantly affected by IL-1 alone. Treatment with IL-1 together with the platelet derived growth factor (PDGF) or another polypeptide growth factor derived from mitogen activated human monocytes (MDGF) resulted in a significant enhancement of cell growth over either PDGF or MDGF alone. DNA synthesis was enhanced only marginally (30-40%) in quiescent cultures treated with an optimal concentration of IL-1 alone. In the presence of 5 units/ml of PDGF or MDGF, IL-1 produced about six- to eightfold higher DNA synthesis than the untreated cultures. Induction of DNA synthesis was linear between 0.1 and 1.0 pM IL-1, dependent on PDGF concentration, and was effectively neutralized by monoclonal antibodies against IL-1 beta. The growth promoting activity of IL-1 was extremely potent producing half-maximum stimulation at a concentration of 0.5 pM. These results suggest that IL-1 may play an important role in the modulation of growth and other activities of vascular smooth muscle cells. These observations are especially important with regard to defining the potential macrophage derived mediators contributing to vascular cell proliferation during inflammation and the pathogenesis of atherosclerosis. It is shown here that elicitation of IL-1 induced growth response requires a coordinated action with another priming growth factor such as PDGF. In this regard, IL-1 mediated proliferation of smooth muscle cells may have analogy with the IL-1 mediated T-cell activation and IL-2 production where concerted actions of antigen/mitogen and IL-1 are required.

Angiogenin stimulates endothelial cell prostacyclin secretion by activation of phospholipase A2

Angiogenin stimulates capillary and umbilical vein endothelial cell prostacyclin secretion but not that of prostaglandins of the E series. The response was quantitated by radioimmunoassay and by [3H]arachidonate labeling followed by analysis of the secreted prostaglandins. The stimulated secretion lasts for several minutes and is optimal at 2-4 min. The dose-response (peak at 1-10 ng/ml) is similar to that previously observed for activation of endothelial cell phospholipase C. Stimulated secretion was blocked by pretreatment with the inhibitors of prostacyclin synthesis, indomethacin and tranylcypromine, and also the specific inhibitor of phospholipase A2, quinacrine, as well as pertussis toxin and the diglyceryl and monoglyceryl lipase inhibitor RHC 80267. Stimulated secretion was also abolished in cells that were either pretreated for 48 hr with phorbol ester to down-regulate protein kinase C or incubated with the protein kinase inhibitor H7. Hydrolysis of phosphatidylinositol by phospholipase A2 appears to be the source of angiogenin-mobilized arachidonate; angiogenin-induced hydrolysis of phosphatidylcholine was not detected. Activation of phospholipase A2 occurs in the absence of an angiogenin-induced calcium flux. The results are discussed in terms of mechanisms of agonist-induced intracellular arachidonate mobilization and relevance to angiogenesis.

Human endothelial cell response to lipopolysaccharide, interleukin-1, and tumor necrosis factor is regulated by protein synthesis

In this study we assessed the viability of cultured human umbilical vein endothelial cells (HUVE) treated with bacterial lipopolysaccharide (LPS), recombinant human interleukin-1 (rhIL-1), or recombinant human tumor necrosis factor-alpha (rhTNF-alpha) during inhibition of RNA or protein synthesis. Cytotoxicity was determined by 51Cr activity retained in labeled HUVE monolayers after exposure to LPS, rhIL-1 or rhTNF-alpha, and cycloheximide (Cx) or actinomycin D (Act D). Lipopolysaccharide (150 ng/ml), rhIL-1 (100 pg/ml), or rhTNF-alpha (20 ng/ml) alone was not toxic to HUVE in an 18-hr incubation. Cycloheximide alone (1 microgram/ml for 18 hr) or Act D alone (1 microgram/ml for 6 hr) was also not toxic to HUVE. However, coincubation of HUVE with Cx and LPS (150 ng/ml), rhIL-1 (10 pg/ml), or rhTNF-alpha (20 ng/ml) produced significant cytotoxicity at 18 hr (70 +/- 4% for LPS, 75 +/- 5% for rhIL-1, and 52 +/- 5% for rhTNF-alpha; mean +/- SEM of 18, 16, and 19 separate experiments, respectively). Similarly, coincubation of HUVE with Act D and LPS, rhIL-1, or rhTNF-alpha resulted in 82 +/- 5%, 85 +/- 3%, and 67 +/- 4% cytotoxicity, respectively, at 6 hr (mean +/- SEM of 5 separate experiments for LPS, and 7 separate experiments each for rhIL-1 and rhTNF-alpha). At the highest concentrations of LPS, rhIL-1, or rhTNF-alpha, cytotoxicity during coincubation with Cx or Act D was detected as early as 2 hr and was near maximal by 6 hr. In contrast to LPS, rhIL-1, or rhTNF-alpha, recombinant human interferon-gamma (up to 100 U/ml), or human alpha-thrombin (up to 10 U/ml), produced no cytotoxicity in the presence of Cx. Recombinant human lymphotoxin (up to 50 ng/ml) had a detectable cytotoxic effect in the presence of Cx although it was significantly less than that seen with rhTNF-alpha. Furthermore, coincubation of human fibroblasts and human smooth muscle cells with Cx and LPS, rhIL-1, or rhTNF-alpha produced no cytotoxicity. We conclude that under these culture conditions, LPS, rhIL-1, or rhTNF-alpha produces a lethal injury to HUVE when de novo RNA or protein synthesis is inhibited. These results suggest that LPS, rhIL-1, and rhTNF-alpha may act via a common pathway in endothelial cells and that protein synthesis is important in regulating the response to these stimuli.

Effect of human recombinant interleukin-I alpha on release of prostacyclin from human endothelial cells

Incubation of human recombinant IL-1 alpha (hrIL-1 alpha) with cultured human endothelial cells induced a dose- and time-dependent increase in the release of prostacyclin (PGI2). Above a dose of hrIL-1 alpha 0.05 units/ml and following a variable lag phase of between 2 and 4 h, PGI2 release (measured as the stable hydrolysis product 6-keto-prostaglandin F1 alpha) was detected in the culture supernatant and levels continued to rise throughout a 48-h incubation. The release of PGI2 required the continued presence of hrIL-1 alpha, did not demonstrate tachyphylaxis and was not reduced by pre-incubation with the protein synthesis inhibitors cycloheximide, tunicamycin and actinomycin or by the calmodulin antagonist trifluoroperazine. The relationship of these results to ultraviolet radiation induced erythema is discussed.

Regulation of expression of the cell adhesion receptors, integrins, by recombinant human interleukin-1 beta in human osteosarcoma cells: inhibition of cell proliferation and stimulation of alkaline phosphatase activity

Recombinant human interleukin-1 beta, a mediator of osteoblastic cell function, was found to regulate the expression of the cell adhesion receptors, integrins, on human osteosarcoma cells. Interleukin-1 beta (IL-1 beta) at picomolar concentrations, specifically elevated approximately six- to tenfold the expression of the beta 1 subunit and its associated alpha subunits, but not the related vitronectin receptor, within 20 hours. Integrin beta 1 messenger RNA levels were elevated within 6 hours and peaked to tenfold higher levels after 20 hours exposure to IL-1 beta in two human osteosarcoma cell lines. The increase in the cell-surface beta 1 integrins resulted in a stronger binding of the IL-1 beta-treated cells to fibronectin. Cell growth was also inhibited by IL-1 beta, cell morphology was altered, and IL-1 beta-treated cells expressed an approximately two- to threefold higher alkaline phosphatase. This increase in alkaline phosphatase activity was found to be independent of the inhibition of cell proliferation. These data indicate that the beta 1 integrin family of cell surface receptors is a target for regulation by IL-1 beta, which also regulates cell proliferation and the expression of the osteoblastic phenotype in human osteosarcoma cells.

Mediators and the anti-thrombotic properties of the vascular endothelium

This review discusses the role of three mediators synthesized by the vascular endothelium, which are involved in maintaining the surface of the endothelial cells in a non-thrombogenic state. Prostacyclin, discovered in 1976, is a product of arachidonic acid metabolism. This labile prostanoid, with a chemical half life of approximately three minutes, relaxes vascular smooth muscle and inhibits the aggregation of blood platelets. Endothelium-derived relaxing factor (EDRF), discovered in 1980, is even more labile than prostacyclin with a half life counted in seconds. It also relaxes smooth muscle and inhibits the aggregation and adhesion of platelets. Recently, it has been identified as nitric oxide. Prostacyclin and EDRF are released together following stimulation of receptors on endothelial cells and cooperate to inhibit platelet aggregation and adhesion. 13-HODE, acts from inside the cell to make the endothelial surface less adhesive and is not released. These mediators act together to form the endothelial defence mechanism against adhering blood cells. Underproduction can lead to diseases such as hypertension or atherosclerosis. A mainly fish diet, rich in eicosapentaenoic acid alters the prostacyclin/thromboxane balance in favour of prostacyclin-like activity. This type of diet may provide protection against atherosclerosis and myocardial infarction.

Interleukin-1 stimulates prostaglandin biosynthesis by human amnion

The purpose of these studies was to determine if Interleukin-1 (IL-1) alters the rate of prostaglandin biosynthesis by human amnion. Primary monolayer cultures of amnion cells were established from women undergoing elective cesarean section before the onset of labor. Natural purified and recombinant human IL-1 alpha and IL-1 beta were incubated with amnion cells in culture, and prostaglandin E2 (PGE2) biosynthesis was measured by radioimmunoassay in cell-free media. A concentration-dependent increase in PGE2 production by amnion cells occurred in response to natural purified and recombinant IL-1 preparations. No differences in the parameters of the dose-response curves between the two IL-1 gene products could be determined (p greater than 0.05). Indomethacin blocked the effect of IL-1 in prostaglandin biosynthesis by human amnion. Interleukin-1, a fever mediator, could serve as a signal for the initiation of labor in cases of intrauterine or systemic infection.

Interleukin 1 inhibits contraction of vascular smooth muscle

Interleukin 1 has been implicated as a mediator of both systemic and local responses to infection and injury. Since systemic and local vasodilatation are hallmarks of sepsis and infection, we studied the direct effect of IL-1 on vascular contractility. We report here that human recombinant IL-1-beta potently inhibits the response of rat thoracic aorta to vasoconstrictor agents. Exposure of isolated rat aortic rings to IL-1 (20 ng/ml) for 1 h did not affect phenylephrine-induced contractions during the exposure period. However, when rings were retested 150-200 min after initiation of IL-1 exposure, contractions were markedly decreased. The cytokine had a similar effect in rings from which the endothelium was removed. Contractions caused by potassium depolarization also were depressed, indicating the effect of IL-1 is not specific to the alpha-adrenoceptor agonist. The inhibitory effect of IL-1 was concentration-dependent (0.2 to 20 ng/ml), and eliminated by pretreatment with cycloheximide (20 micrograms/ml). Indomethacin (10(-5) M) did not prevent the inhibition caused by IL-1. These studies identify IL-1 as a potent inhibitor of vascular contraction, via an endothelium-independent mechanism. Studies with inhibitors suggest that the action of IL-1 is independent of prostanoid synthesis, and may involve synthesis of protein.

Induction of articular cartilage degradation by recombinant interleukin 1 alpha and 1 beta

The purpose of this study was to compare the effects of human recombinant interleukin 1, alpha and beta, on articular cartilage. The effects of rIL-1 alpha and rIL-1 beta on proteoglycan degradation and synthesis following treatment of bovine articular cartilage in serum-free organ culture were quantified. Purified human IL-1 and both rIL-1 alpha and rIL-1 beta induced a two-fold or greater increase in glycosaminoglycan (GAG) release from cultured articular cartilage. Levels or rIL-1 alpha as low as 15 pM induced increased proteoglycan degradation whereas identical levels of rIL-1 beta did not. Killing of the cartilage cells abolished induced GAG release by all forms of IL-1. Analysis of proteoglycan size following IL-1 treatment showed limited degradation of material released into the culture medium or remaining within cartilage. Both forms of recombinant IL-1 inhibited GAG synthesis when continually present in the culture medium. Actinomycin D and cycloheximide inhibited IL-1 dependent cartilage destruction whereas indomethacin did not.

Interleukin-1 and tumor necrosis factor production in acute non-lymphoid leukemia

We have investigated interleukin-1 (IL-1) and tumor necrosis factor (TNF) release in 20 patients with acute non-lymphoid leukemia (ANLL) after culture with bacterial lipopolysaccharide (LPS) or in the absence of deliberate stimulation. IL-1 and TNF were identified by appropriate bioassays inhibitable by specific antibodies. The capacity to produce IL-1 was expressed by most ANLL cases investigated irrespective of the FAB (French, American, British) subtype. However, the M4 and M5 cases tended to be better producers of IL-1 than M1-M3 cases. In contrast, TNF release was only restricted to M5 leukemias (3 out of 4 cases examined). Cytokine production may therefore provide additional criteria for a functional classification of ANLL. A considerable proportion of ANLL cases (7/18 bone marrow samples and 12/20 blood samples) released appreciable quantities of IL-1 in culture in the absence of deliberate stimulation. "Spontaneous" TNF production was also detected in 1 out of 3 M5 cases. Cells were cultured under LPS-negative conditions and polymixin B did not affect spontaneous cytokine release. Moreover, Northern blot analysis showed that freshly isolated, non-cultured ANLL cells expressed IL-1 beta transcripts. Inasmuch as IL-1 is responsible for hemopoietin-1 activity and IL-1 induces colony stimulating factor production in various cell types, the observation of IL-1 production in ANLL suggests that this mediator may be involved in regulatory amplifying circuits of leukemic cell proliferation.

Stimulation of cytotoxic and non-cytotoxic functions of natural killer cells by bacterial membrane proteoglycans and ribosomes

The present study was designed to investigate the effect of membrane proteoglycans (MPG) from Klebsiella pneumoniae on the function of human natural killer (NK) cells. MPG combined with bacterial ribosomes from Klebsiella pneumoniae, Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae, constitute a bacterial immunomodulator (MS D 53), currently in clinical use. Human peripheral blood lymphocytes (PBL) exposed in vitro to MPG or MS D 53 for 20 h showed enhanced NK cytotoxicity. Augmentation of NK cytotoxicity depended upon a direct effect on NK cells, inasmuch as these compounds were also effective on highly purified large granular lymphocytes (LGL). We also studied the effects of MPG on non-cytotoxic functions of NK cells, namely in vitro locomotion and production of IL-1. MPG (and MS D 53) induced IL-1 release in LGL. Moreover, MPG-treated LGL showed enhanced locomotory activity, as assessed by measuring the penetration into nitrocellulose filters. The capacity of MPG (and MS D 53) to activate cytotoxic and noncytotoxic functions of NK cells may contribute to enhancement of nonspecific resistance in vivo after treatment with this agent.

Mediators produced by the endothelial cell

This review discusses the role of three mediators, synthesized by vascular endothelial cells, that help to keep the surface of the normal endothelium nonthrombogenic. The first is prostacyclin, a product of arachidonic acid metabolism discovered in 1976. This labile prostanoid, with a half-life of approximately 3 minutes, relaxes vascular smooth muscle and inhibits the aggregation of blood platelets. Prostacyclin and its analogues are currently being tested clinically for use in cardiovascular diseases such as primary pulmonary hypertension. The second mediator discussed is endothelium-derived relaxing factor (EDRF), discovered in 1980, which also relaxes smooth muscle and inhibits the aggregation and adhesion of platelets. Substances that stimulate the release of EDRF include acetylcholine, bradykinin, and adenosine 5'-diphosphate. EDRF is even more labile than prostacyclin, with a half-life of about 6 seconds, and it has recently been identified as nitric oxide. Prostacyclin and EDRF are released together following stimulation of endothelial receptors and synergize to inhibit platelet aggregation. 13-Hydroxy-9,11-octadecadienoic acid, a third suggested mediator, is not released but acts from inside the cell to make the endothelial surface nonadhesive for circulating blood cells. It is proposed that these three mediators form the endothelial defense mechanism against blood-borne cells and chemicals and that breakdown of this barrier results in diseases such as hypertension and atherosclerosis.

Comparison of the in vivo inflammatory activities after intra-articular injection of natural and recombinant IL-1 alpha and IL-1 beta in the rabbit

Comparison has been made of the in vivo pro-inflammatory activities or procine natural and human recombinant alpha and beta interleukin 1 (IL-1) after injection into the knee joints of rabbits. Both forms of pig IL-1 and human IL-1 were separately equiactive in vitro in stimulating rabbit synovial fibroblasts and articular chondrocytes to synthesize prostaglandin E2 (PGE2). Injection of IL-1 into the rabbit knee joint was not associated with swelling of the joint nor with the appearance of PGE2 in the synovial fluid. However, all preparations of IL-1 induced a dose-dependent increase in inflammatory leukocytes in the synovial lining and joint cavity. In addition, both the alpha and beta forms of IL-1 from both species caused loss of proteoglycan from the matrix of articular cartilage. This study demonstrates that both genetically distinct forms of IL-1 have the same range of inflammatory actions within the joint and that they have similar potencies in these respects.