Prostacyclin synthesis induced in vascular cells by interleukin-1

Additive effects of IL-1 and TNF on induction of prostacyclin synthesis in human vascular endothelial cells

The effect of interleukin 1 (IL-1) and tumor necrosis factor (TNF) on the induction of prostacyclin (PGI2) synthesis in human vascular endothelial cells (EC) was investigated. Both IL-1 and TNF increased PGI2 production by EC in both a time- and dose-dependent manner, and a combination of the two cytokines additively enhanced PGI2 production. Metabolic inhibitors including indomethacin and cycloheximide abolished cytokine induced PGI2 synthesis. Since, the effect of TNF was not inhibited by neutralization with antibody to IL-1 alpha and IL-1 beta, it seems that the mechanism is not mediated by endogenous IL-1 induced by TNF.

The complement system in atherosclerosis

Complement is a term referring to a collection of plasma proteins, specific cellular receptors and cell surface regulatory molecules. Activation of the complement system to completion results in the formation of C5b-9 terminal complexes. These complexes have been observed in human atherosclerotic lesions by immunohistochemistry. Although the structure(s) which activate complement in lesions have not been defined, cholesterol and oxysterols exhibit this property in vitro. Endothelial cell damage leads to complement activation and endothelial cells overlying atherosclerotic lesions have been observed to contain C3 and C5b-9 antigens. Cardiac myocytes stain for complement proteins (C3, C4 and C5b-9) following myocardial infarction. Infarct size and extent of inflammatory cell infiltrates are diminished by decomplementation prior to experimentally-induced myocardial ischemia. Following myocardial infarction and ulceration of atherosclerotic lesions in human patients there is an increase in circulating complement activation products and a decrease in the level of native C1 through C4 proteins. Thus, it appears that complement plays a role in atherogenesis and its sequelae. Little is known however, about the pathophysiological effects complement activation products exert on lesion development, for example through modulation of macrophage functions, or how complement activation is regulated in lesions. Implications for complement in atherogenesis are discussed.

Human monocyte/macrophage activation and interleukin 1 generation by biomedical polymers

In vitro cell culture techniques were used to evaluate the effect of several clinically significant biomedical polymers on monocyte activation and Interleukin 1 (IL1) production. Isolated human peripheral blood monocytes were cultured in the presence of a panel of five biomedical polymers routinely used in a variety of clinical applications: Polyethylene (PE), silica-free poly-dimethylsiloxane (PDMS), woven Dacron fabric, expanded polytetrafluoroethylene (ePTFE) and the segmented polyurethane, Biomer. Monocytes generated IL1 in the presence of all five materials. Maximal levels of IL1 were generated at 24 h in monocyte-polymer cultures supplemented with serum and additionally stimulated with lipopolysaccharide (LPS). No difference was observed due to serum source. Results from cultures supplemented with fetal bovine serum were not significantly different from those obtained with human serum supplemented cultures. The thymocyte proliferative activity generated by monocytes in the presence of these biomedical polymers was neutralized by a specific polyclonal anti-IL1 antiserum. Statistically significant differences in IL1 production were observed between polymers, allowing their classification according to reactivity into high (Dacron, PE), intermediate (ePTFE) and low (Biomer, PDMS) reactive groups.

Interleukin-1 induces c-fos protooncogene expression in cultured human endothelial cells

In the present study we have evaluated the expression of c-fos protooncogene in normal human endothelial cells (HEC) by Northern blot analysis. HEC do not show neither constitutive nor cycloheximide-induced expression of c-fos protooncogene. When HEC were treated with cytokines known to modulate a number of specialized functions of these cells, we observed that, unlike interferon-gamma, interleukin-1 (IL-1) and tumor necrosis factor (TNF) were able to induce appreciable levels of c-fos in HEC. Both IL-1 alpha and IL-1 beta induced c-fos transcripts in HEC. Maximal levels of c-fos mRNA induced by IL-1 were found after 1 hour of treatment, with undetectable levels at 4 and 7 hours. c-fos induction in HEC by IL-1 and TNF may play a role in the acquisition of functional properties induced in HEC by these cytokines.

Endothelium from diverse vascular sources synthesizes platelet-activating factor

Stimulation of cultured bovine endothelial cells from aorta, pulmonary artery, coronary artery, and vena cava with calcium ionophore A23187, adenosine triphosphate (ATP), bradykinin, and angiotensin II resulted in production of platelet-activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine. In pulmonary artery endothelial cells, maximal accumulation occurred within 20 minutes, and the PAF remained cell-associated. This response was concentration-dependent with a maximal effect at 10(-8)M bradykinin and 10(-6)M angiotensin II. Stimulation of in situ endothelial cells on isolated strips of bovine pulmonary artery with calcium ionophore, ATP, and bradykinin also resulted in production of PAF. In cultured pulmonary artery endothelial cells, PAF appeared only in response to the same agonists that caused prostacyclin (PGI2) release. These findings are similar to earlier studies with human umbilical vein endothelial cells and suggest that the production of PAF and the arachidonate metabolite PGI2 are tightly linked in these vessels. Aortic endothelial cells, both in culture and on isolated strips of aorta, also produced PAF in response to bradykinin in a time-and concentration-dependent fashion. Cultured endothelial cells from coronary vessels and the inferior vena cava accumulated PAF when appropriately stimulated as well. The finding that both cultured endothelial cells and in situ, ex vivo endothelium from diverse vascular sites produce PAF when appropriately stimulated suggests that this is a generalized response of endothelial cells. Because PAF has potent vasoactive, pro-aggregatory, and pro-inflammatory effects, the results from these experiments suggest that the local accumulation of this lipid may be important in vascular injury and inflammation.

Interleukin-1

IL-1 is a polypeptide product of various cells that mediates several components of the acute-phase response to infection and injury. Its most dramatic biological property is its ability to induce arachidonate metabolites in a variety of cells including PGE in the brain, fibroblasts, synovial cells, and chondrocytes; in addition, IL-1 induces lipoxygenase products in lymphocytes and other cells. IL-1 has been cloned. There are two forms. The predominant form of IL-1 from human monocytes has a pI of 7 (also called beta) and is initially synthesized as a precursor molecule (31 kD). A minor form (less than 100-fold) also exists (pI 5, also called alpha). IL-1 seems unique among the lymphokines and monokines in that there is no signal peptide sequence for cleavage. Depending on the stimulus, intracellular levels of precursor IL-1 can be high, whereas some cell activators result in large amounts of processed IL-1. Precursor IL-1 is cleaved into a 17.5-kD peptide, which is the predominant extracellular form. IL-1 induces prostaglandins and lymphocyte activation as well as many different biological activities. These include fever, PGE production, protease release from synovial cells and chondrocytes, bone resorption, acute-phase protein synthesis, and other effects. Although there are few studies showing an IL-1 effect on the gastrointestinal tract, the multiple biological properties of IL-1 suggest that IL-1 plays a role in inflammatory bowel disease as well as in mediating some of the gastrointestinal changes observed in systemic acute-phase responses.

Glucocorticoids selectively inhibit the transcription of the interleukin 1 beta gene and decrease the stability of interleukin 1 beta mRNA

Transcription of the interleukin 1 beta (IL-1 beta) gene was studied by mRNA hybridization with a cDNA probe in the human promonocytic cell line U-937. Phorbol ester and lipopolysaccharide increased the steady-state level of IL-1 beta mRNA. Glucocorticoids markedly decreased IL-1 beta mRNA levels by two mechanisms. Transcription of the IL-1 gene was inhibited, as shown by in vitro transcription assays with nuclei isolated from glucocorticoid-treated cells. Moreover, kinetic analyses and pulse-labeling of mRNAs showed that glucocorticoids selectively decrease the stability of IL-1 beta mRNA, without affecting the stability of beta-actin and FOS mRNAs. Inhibition of the formation and effects IL-1 is a mechanism by which glucocorticoids can exert antiinflammatory and immunosuppressive effects.

Interleukin 1: a mitogen for human vascular smooth muscle cells that induces the release of growth-inhibitory prostanoids

There is much interest in defining the signals that initiate abnormal proliferation of cells in a variety of states characterized by the presence of mononuclear phagocytes. Since IL-1 is a major secretory product of activated human monocytes we examined whether this cytokine can stimulate the growth of human vascular smooth muscle cells (SMC). Neither recombinant IL-1 (rIL-1) alpha (less than or equal to 5.0 ng/ml) nor beta (less than or equal to 100 ng/ml) stimulated SMC growth during 2-d incubations under usual conditions. IL-1 did stimulate SMC to produce prostanoids such as PGE1 or PGE2 that can inhibit SMC proliferation. When prostaglandin synthesis was inhibited by indomethacin or aspirin both rIL-1 alpha and beta (greater than or equal to 1 ng/ml) markedly increased SMC growth. In longer-term experiments (7-28 d) rIL-1 stimulated the growth of SMC even in the absence of cyclooxygenase inhibitors. The addition of exogenous PGE1 or PGE2 (but not PGF1 alpha, PGF2 alpha, PGI2) to indomethacin-treated SMC blocked their mitogenic response to rIL-1. Antibody to IL-1 (but not to platelet-derived growth factor [PDGF]) abolished the mitogenic response of SMC to rIL-1. Exposure of SMC to rIL-1 or PDGF caused rapid (maximal at 1 h) and transient (baseline by 3 h) expression of the c-fos proto-oncogene, determined by Northern analysis. We conclude that IL-1 is a potent mitogen for human SMC. Endogenous prostanoid production simultaneously induced by IL-1 appears to antagonize this growth-promoting effect in the short term (2 d) but not during more prolonged exposures. IL-1 produced by activated monocytes at sites of tissue inflammation or injury may thus mediate both positive and negative effects on SMC proliferation that are temporally distinct.

Interleukin 1 or endotoxin increases the release of von Willebrand factor from human endothelial cells

von Willebrand factor (vWF), a large adhesive glycoprotein, is synthesized by vascular endothelial cells (EC). Plasma levels of vWF manifest a broad normal range, and are elevated during sepsis and in inflammatory states. Since the inflammatory mediator, interleukin 1 (IL1) and bacterial endotoxin (LPS) both initiate procoagulant changes in vascular endothelium, we investigated the effect of these substances on endothelial cell release and residual endothelial cell content of vWF-antigen (vWFAg). Cultured human EC exposed to either IL1 or LPS released greater amounts of vWFAg compared to control EC. The augmented release could be detected within 1-2 h after exposure to IL1 or LPS and was not inhibited by cycloheximide, suggesting that de novo protein synthesis was not required for release to occur. Residual cellular vWFAg was reciprocally lower in IL1- or LPS-treated EC at 24 and 48 h, indicating that compensatory increase in synthesis of vWFAg did not occur during this time interval. Released vWF contained the higher molecular weight multimers observed in normal endothelial cells, and it possessed ristocetin cofactor activity. We propose that release of functional vWF from EC exposed to inflammatory mediators may be at a mechanism for localization of platelets and enhanced thrombogenicity at inflammatory foci.

In vitro and in vivo interactions of cells with biomaterials

The biocompatibility of materials at an implant site involves a complex interaction of cells and tissues with the biomaterial. This cell-cell and cell-polymer interaction evokes the release of mediators such as chemotactic and growth factors that elicit and sustain inflammatory responses at the implant site. In this review, we summarize the interaction of cells with biomaterials in vitro and in vivo.

Recombinant human interleukin-1 inhibits the induction by dexamethasone of alkaline phosphatase activity in murine capillary endothelial cells

A mutual antagonism exists between interleukin-1s (IL-1s) as pro-inflammatory and glucocorticoids as anti-inflammatory mediators. This report examines the effects of IL-1 on the induction by dexamethasone of alkaline phosphatase in LEII murine endothelial cells. Dexamethasone increases the specific activity of alkaline phosphatase in a time- and dose-dependent fashion (maximum 14-fold induction at 10(-6) M, IC50 = 10(-8) M), and this induction can be completely inhibited by simultaneous incubation with picomolar concentrations of recombinant human IL-1 alpha or IL-1 beta. This IL-1-mediated antagonism of dexamethasone activity is not due to a down-regulation of glucocorticoid receptors in the cell line used, because the number of receptors and their affinity for dexamethasone is unchanged in IL-1-treated cells. However, induction of alkaline phosphatase by dexamethasone in LEII cells is receptor-mediated, since it can also be inhibited by glucocorticoid-receptor antagonists.

The biology of interleukin 1 and comparison to tumor necrosis factor

Interleukin 1 (IL-1) is a major product of the stimulated monocyte and is responsible for diverse biological effects. The systemic effects of IL-1 include fever, increased circulating neutrophils, hepatic acute phase proteins, slow wave sleep, elevated insulin levels and hypotension. In vitro, IL-1 induces increased synthesis of a number of lymphokines (IL-2, IL-3, IL-4 and IL-6), a variety of colony stimulating factors, and endothelial factors leading to clot formation and vascular congestion. IL-1 also induces histamine release and granule release from basophils, eosinophils and neutrophils. IL-1 dramatically increases arachidonic acid metabolites in a variety of cells; increased PGE2 synthesis accounts for its inflammatory properties. Tumor necrosis factor shares with IL-1 many of the systemic and local effects of IL-1; these include fever, acute phase protein synthesis and sleep. Some of the in vitro effects of IL-1 are not shared with TNF, but the combination of TNF with IL-1 often enhances the response several-fold. A dramatic synergism between IL-1 and TNF occurs on islets of Langerhans. In vivo, these two cytokines induce shock and pulmonary hemorrhage when given together but at doses at which neither cytokine is effective alone. Profound leukopenia and thromocytopenia are present. Since both cytokines are produced in large amounts following appropriate stimulation, the end result for the host is the combined effect of both cytokines.

Interleukin-1 inhibits the synthesis of von Willebrand factor in endothelial cells, which results in a decreased reactivity of their matrix toward platelets

We have studied the influence of recombinant human and murine interleukin-1 (IL-1) on the synthesis and secretion of von Willebrand factor by human endothelial cells. Treatment of endothelial cells with IL-1 caused a decline in the steady-state level of von Willebrand factor mRNA in endothelial cells. This decline resulted in a decreased secretion to the culture medium, a decreased storage of von Willebrand factor in the Weibel-Palade bodies, and a decreased incorporation into the extracellular matrix. As a consequence of the decreased amount of von Willebrand factor in the extracellular matrix we have found a strongly impaired platelet adhesion to these matrices. When the matrices of IL-1-treated cells were incubated with purified von Willebrand factor, their ability to support platelet adhesion was restored. These results suggest that perturbation of endothelial cells by inflammatory mediators like IL-1 results in a decreased adhesion of platelets to the subendothelium owing to a diminished synthesis of von Willebrand factor.

Interleukin 1 or endotoxin increases the release of von Willebrand factor from human endothelial cells

von Willebrand factor (vWF), a large adhesive glycoprotein, is synthesized by vascular endothelial cells (EC). Plasma levels of vWF manifest a broad normal range, and are elevated during sepsis and in inflammatory states. Since the inflammatory mediator, interleukin 1 (IL1) and bacterial endotoxin (LPS) both initiate procoagulant changes in vascular endothelium, we investigated the effect of these substances on endothelial cell release and residual endothelial cell content of vWF-antigen (vWFAg). Cultured human EC exposed to either IL1 or LPS released greater amounts of vWFAg compared to control EC. The augmented release could be detected within 1-2 h after exposure to IL1 or LPS and was not inhibited by cycloheximide, suggesting that de novo protein synthesis was not required for release to occur. Residual cellular vWFAg was reciprocally lower in IL1- or LPS-treated EC at 24 and 48 h, indicating that compensatory increase in synthesis of vWFAg did not occur during this time interval. Released vWF contained the higher molecular weight multimers observed in normal endothelial cells, and it possessed ristocetin cofactor activity. We propose that release of functional vWF from EC exposed to inflammatory mediators may be at a mechanism for localization of platelets and enhanced thrombogenicity at inflammatory foci.

Interleukin-1 and osteoarthritis

Il-1, a multifunctional monokine, can stimulate both synoviocytes and articular chondrocytes to release neutral proteases and prostaglandin E2. It is also capable of promoting bone resorption. Therefore, this molecule (or family of molecules) is likely to play an important role in the mechanism of articular cartilage destruction that occurs in degenerative arthropathies. The synovial tissue itself can produce Il-1 (Catabolin) in some conditions, such as a slight traumatism, so that the presence of local inflammation is not necessary for "Il-1-cartilage" interaction to occur. Fundamental macromolecules of cartilage (collagens, proteoglycans) exert a stimulatory effect on Il-1 production, either as such or in the form of immune complexes. Some activated complement fractions (C3a and C5a) may also be actively involved. Studies on the mechanisms which regulate Il-1 synthesis and release, as well as investigations on the response of target cells to Il-1, are presently fascinating goals that could lead to new strategies in therapeutic research.

Functional heterogeneity of vascular endothelial cells

This review has highlighted some of the well-described differences in endothelial cells derived from different sites of the vascular tree. In presenting a select group of endothelial properties, there was no intention to imply that these are the only properties of endothelial cells that exhibit heterogeneity. Nonetheless, having described endothelial heterogeneity in regard to a number of defined properties, we are left with persistent questions including: Are these divergent properties of endothelial cells fixed? Alternatively, can we alter the properties of endothelial cells by affecting the signals from the environment? A number of reports strongly suggest that endothelial cells are capable of acquiring new properties. Stewart and Wiley investigated the role of the neural tissue environment on the differentiation of brain capillary endothelial cells. These authors transplanted ectopic sites, i.e. vascular segments of brain from very young quail embryos to chick coeliac cavity, and a quail somites to chick brain ventricles. The distinctive morphology of quail cells provided a cell marker to differentiate host from graft. The results of this study demonstrated that mesenteric or somatic vessels growing into grafted brain developed functional, structural and histochemical features specific for neural capillaries. Conversely, capillaries in mesodermal tissue that had been grafted to the brain were devoid of the neural capillary characteristics, indicating that brain vessels do not form a barrier when they are made to vascularize non-neural tissue. Milici and Carley reported that bovine adrenal capillary cells cultured on plastic exhibited occasional diaphragmed fenestrations and no transendothelial channels. However, if these same cells were cultured on a basement membrane (matrix) laid down by MDCK cells (a canine nephron epithelial cell line), the cells responded by increasing the number of diaphragmed fenestrations and transendothelial channels. This cell culture study supported an earlier whole animal study in which the importance of the epithelium and/or epithelial basal lamina in the maintenance of endothelial ultrastructure was demonstrated in a developmental study of rat intestinal capillaries. In this earlier study, it was noted that epithelial development coincided with the formation of fenestrations by the endothelium. Enzymatic activities of endothelial cells can also be altered by environmental signals. For example, primary cerebral microvascular endothelial cells exhibit barrier features and are enriched in gamma-glutamyl transpeptidase activity, yet rapidly lose the activity when subcultured.(ABSTRACT TRUNCATED AT 400 WORDS)

An in vitro model for the study of acute release of von Willebrand factor from human endothelial cells

An in vitro model is described which utilizes human umbilical vein endothelial cells cultured on plastic microcarrier spheres and perfused with serum-free medium. This model was used to study the acute release of von Willebrand factor following stimulation of the cells with putative agonists. Thrombin, plasmin and interleukin-1 were found to release von Willebrand factor. Adrenaline and bradykinin also stimulated release but only at high dosage. 1-desamino-8-D-arginine vasopressin (DDAVP) was inactive.

Enhanced release of von Willebrand factor by human endothelial cells in culture in the presence of phorbol myristate acetate and interleukin 1

Human umbilical vein endothelial cells (EC) were cultured in the presence of 4 beta-phorbol 12-myristate 13-acetate (PMA), interleukin 1 (IL-1) and interleukin 2 (IL-2), and secretion of von Willebrand factor activity (vWF, Ristocetin Co-factor) and von Willebrand factor antigen (vWFAg) measured at intervals. The levels of both vWF and vWFAg in cultures containing IL-1 were significantly higher than those in control cultures after longer than 5-6 days growth. Similarly, the levels of vWF and vWFAg were significantly increased in cultures containing PMA, but in these instances the rate of cell growth appeared to be enhanced, and confluence was observed after 6 days compared to 9-10 days in control cultures. vWF and vWFAg also increased significantly in the supernatant of confluent control EC incubated further with IL-1. Moreover, the immuno-fluorescence pattern of vWFAg in these treated cells was markedly less granular than that of control cells. Immuno-fluorescence of PMA-treated cells suggested that vWFAg might be less granular than in control EC but the mean levels of vWF and vWFAg in the supernatant of cells incubated with PMA were not significantly different from control values. The results of all assays in the presence of IL-2 were not significantly different from those of control cells. In all instances no morphological evidence of endothelial injury was observed, and more than 90% of cells remained viable at the termination of cultures. The results indicated that the synthesis and release of vWF were increased in the presence of PMA, and secretion of vWF was stimulated by IL-1.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of PGE2 on the activation of quiescent lung fibroblasts

The effect of prostaglandin E2 (PGE2) on fibroblast proliferation was examined. The presence of PGE2 for 24 h inhibited the growth of quiescent cells stimulated with serum, platelet-derived growth factor and macrophage-derived factors. Maximal inhibition of nuclear labeling with [3H]thymidine occurred at concentrations greater than 10(-7) M. The inhibitory effect of PGE2 was less potent in exponentially growing cells and was not the result of conversion of PGE2 to PGA2 during incubation in growth medium. The G1 phase was determined to be 12-14 h in untreated cultures. The extent of growth inhibition by PGE2 was similar with addition of PGE2 at 0, 3, 6, or 9 h following restimulation of quiescent cell cultures. Approximately 25% of the cells that enter S phase are refractory to PGE2-induced growth inhibition. Short-term exposure to PGE2 (5 min and 30 min) caused substantial growth inhibition. The serum-induced proliferation was also inhibited by the cAMP analogue, dibutyrl cAMP. Our results suggest that PGE2 affects a distinct subpopulation of cells. Restimulation of quiescent cells treated with PGE2 for 24 h, indicated that release from PGE2 exposure is associated with prolongation of the G1 phase of the cell cycle.

Human interleukin 1 induces interleukin 1 gene expression in human vascular smooth muscle cells

The recognition that cells of the vascular wall can secrete cytokines such as IL-1 suggests new mechanisms for initiating or sustaining inflammatory responses in blood vessels. We report that purified human monocyte-derived IL-1 or recombinant human IL-1 (rIL-1 beta and rIL-1 alpha) induce cultured human smooth muscle cells derived from veins or arteries to synthesize IL-1 beta mRNA and produce and release biologically active IL-1. rIL-1 beta also stimulated the production of PGE2 by smooth muscle cells. Exposure to rIL-1 beta (1-100 ng/ml), or rIL-1 alpha (0.01-10 ng/ml) increased IL-1 beta mRNA levels within 30 min. Actinomycin D (1 microgram/ml) prevented the induction of IL-1 beta mRNA by rIL-1. IL-1 alpha mRNA was detected in SMC treated with cycloheximide (1 microgram/ml) and rIL-1 beta, or cycloheximide alone. rIL-1 alpha and rIL-1 beta produced maximal levels of IL-1 beta mRNA after 4 h, and intracellular IL-1 biological activity after 6 h of exposure. Release of IL-1 activity in the extracellular medium began after 1 h of incubation with rIL-1 beta or rIL-1 alpha, and continued for up to 24 h. Anti-TNF antiserum that neutralized the biological activity of rTNF did not affect rIL-1-induced production of IL-1 beta mRNA or IL-1 release, suggesting that the release of TNF does not mediate these processes. Several experimental approaches indicated that the release of IL-1 by smooth muscle cells was not due to endotoxin contamination of the IL-1 preparations. Anti-IL-1 antiserum blocked the induction of smooth muscle cell IL-1 gene expression by rIL-1 beta. Polymyxin B did not prevent IL-1-induced IL-1 expression by these cells, but blocked the effect of endotoxin. Heat treatment destroyed the stimulatory capacity of rIL-1 beta, but did not affect the ability of bacterial endotoxin to induce IL-1 expression. The production of IL-1 by human vascular smooth muscle cells was not due to contamination of the cell cultures with blood monocytes, inasmuch as treatment with an antimonocyte antibody (anti-Mo2) and complement did not alter IL-1 beta mRNA content or the amount of IL-1 released from the cells in response to endotoxin, rIL-1 alpha, or rIL-1 beta.(ABSTRACT TRUNCATED AT 400 WORDS)

Patients with bone marrow failure demonstrate decreased cutaneous reactivity to human C5a

In vivo studies have shown that human C5a, a potent complement-derived anaphylatoxin and chemoattractant, produces immediate inflammatory reactions following intradermal injection in human skin. At concentrations within its potential physiologic range, intradermal injection of C5a elicits immediate wheal and flare reactions, increased vascular permeability, mast cell degranulation, and neutrophil-rich infiltrates. To assess the relative contribution of interacting cellular elements to C5a-induced inflammation in normal human skin, purified human C5a was tested intradermally in 8 patients with bone marrow failure (BMF). Reactions to C5a in patients with BMF were compared with responses at identical test sites in healthy volunteers and other patients with cutaneous disorders. Patients with BMF demonstrated significantly less wheal and flare reactivity following intradermal injection of C5a than controls (p less than 0.05 and less than 0.02, respectively). In these studies, patients with the greatest cytopenia generally showed the least cutaneous reactivity to human C5a. Biopsies of C5a test sites in patients with BMF revealed an absence of leukocytes in marked contrast to neutrophil-rich infiltrates observed at test sites in healthy volunteers. Avidin-fluorescent and/or Giemsa staining of skin biopsies revealed no difference between the number of dermal mast cells in patients with BMF and samples of normal human skin. In addition, skin test studies with histamine (2 micrograms) and morphine (5 micrograms) performed to assess cutaneous vascular and mast cell responsiveness in patients with BMF, normal volunteers and controls with rhinitis revealed no significant differences in cutaneous reactivity to these pharmacologic agents. These in vivo studies demonstrate that patients with BMF specifically exhibit decreased cutaneous reactivity to human C5a and suggest that neutrophils make an important and an immediate contribution to inflammatory responses elicited by this anaphylatoxin.

Thrombin stimulates arachidonate metabolism in murine tumor cells

Thrombin can be formed in the tumor cell microenvironment following activation of the clotting cascade by procoagulants of cancer or host cells. We have tested here the effects of thrombin, either "endogenous" or "exogenous" (see below), on arachidonate mobilization from membrane phospholipids of mouse mammary tumor virus-induced (MMTV) carcinoma cells. These tumor cells exhibit in vitro a tissue type procoagulant activity (130 thromboplastin units/10(4) cells) and are therefore able to induce thrombin formation in a plasmatic milieu. To verify the effect of thrombin formation by tumor cell procoagulant ("endogenous thrombin"), either human or mouse platelet-free plasma (20% in DMEM) was added to the cell layer (prelabelled for 5 hr with a trace amount (0.013 microM) of 3H-arachidonate) and the system was recalcified (15 mM CaCl2). Thin-layer radiochromatography of the culture medium showed a significant release of 3H-labelled arachidonate products PGE2, PGF2 alpha and 6-ketoPGF1 alpha after 1 hr of incubation. To verify the effect of thrombin formation from host sources ("exogenous thrombin"), either bovine or purified human alpha-thrombin (0.1-10 U/ml) was added to the cells for different periods (from 5 min to 20 hr). Exogenous thrombin stimulated arachidonate release and metabolism in a dose-related manner. With short labelling periods (0.013 microM 3H-arachidonate for 30 min-1 hr) thrombin stimulated the release of unmetabolized 3H-arachidonate, but not of 3H-arachidonate metabolites. These processes were inhibited by a specific inhibitor of thrombin enzymatic activity (alpha-NAPAP, 140 microM) and by a cyclo-oxygenase inhibitor (ASA 4mM). Tumor-associated procoagulants may thus contribute not only to fibrin deposition but also to generation of multipotent mediators such as arachidonate metabolites.

The recruitment of leukocytes and their interaction with the vessel wall: the role of interleukin-1 and tumor necrosis factor

The vascular endothelium has long been considered to have very little or no active function in inflammatory reactions and hemostasis. However, it has been recently discovered that endothelial cells can dramatically change their functional competence in response to the mononuclear phagocyte products interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 induces synthesis of prostacyclin, platelet activating factor, thromboplastin and plasminogen activator inhibitor. Both IL-1 and TNF cause leukocyte adhesion to the endothelium. On the other hand endothelial cells can themselves initiate the immune response through synthesis and release of IL-1. TNF, released in tissues may act as a chemoattractant and further promote interaction of leukocytes with the vascular lining. IL-1 and TNF can therefore act as a communications signal between circulating cells and the vessel wall and play an important role in the inflammatory and coagulation disorders.

Acute glomerular thrombosis with CsA treatment

Cyclosporin A (CsA) is used widely as an immunosuppressive in organ transplantation. Although it is highly effective, acute and chronic nephrotoxicity of CsA are of continuing concern. A case of acute glomerular thrombosis secondary to CsA therapy in a renal transplant recipient is described. The course of the accompanying acute renal failure and its reversal following discontinuation of CsA and therapy with intra-arterial streptokinase is outlined. CsA-induced capillary thrombosis is rare but has been described in renal transplant recipients as well as in hepatic and bone marrow transplantation. It may give rise to diagnostic confusion in the early days following renal transplantation, where it may mimic acute rejection. The etiology of CsA-induced glomerular capillary thrombosis remains speculative.

Cachectin/TNF as well as interleukin-1 induces prostacyclin synthesis in cultured vascular endothelial cells

Cachectin/tumor necrosis factor (cachectin/TNF) has been shown to be capable of stimulating prostacyclin (PGI2) production by vascular endothelial cells in vitro. The stimulation of PGI2 by cachectin/TNF is comparable to that observed with interleukin-1, the monokine previously suggested to be the principal mediator of this effect. The ability of cachectin/TNF to stimulate PGI2 production suggests that it may play a role in producing depressed blood pressure or shock. If so, it might be possible to prevent such adverse effects with the aid of anti-inflammatory agents.

Role of interleukin-1 in the depression of liver drug metabolism by endotoxin

Endotoxin-resistant C3H/HeJ mice were used to test the hypothesis that a macrophage product, possibly interleukin-1, might mediate the depression of liver cytochrome P-450-dependent drug metabolism in endotoxin-treated mice. Depression of liver drug metabolism by endotoxin was observed in normal mice (C3H/HeN) but not in C3H/HeJ mice. Serum transfer experiments demonstrated that a serum factor was responsible for the depression of liver drug metabolism. Experiments of passive transfer of peritoneal macrophages showed that this endotoxin-induced factor might be a macrophage product. In vitro experiments showed that endotoxin-stimulated monocytes produced a factor that depressed cytochrome P-450-dependent metabolism in cultured hepatocytes. Homogeneous human monocyte and recombinant interleukin-1 also depressed liver drug metabolism both in vivo and in vitro, suggesting that this macrophage product might be involved in the regulation of liver function by the immune system.

Inducible interleukin-1 gene expression in human vascular smooth muscle cells

Interleukin-1 (IL-1) mediates many components of generalized host response to injury and may also contribute to local vascular pathology during immune or inflammatory responses. Because altered function of smooth muscle cells (SMC) accompanies certain vascular diseases, we tested whether SMC themselves might produce this hormone. Unstimulated SMC contain little or no IL-1 mRNA. However, exposure to bacterial endotoxin caused accumulation of IL-1 mRNA in SMC cultured from human vessels. Endotoxin maximally increased IL-1 beta mRNA in SMC after 4-6 h. The lowest effective concentration of endotoxin was 10 pg/ml. 10 ng/ml produced maximal increases in IL-1 beta mRNA. Interleukin-1 alpha mRNA was detected when SMC were incubated with endotoxin under "superinduction" conditions with cycloheximide. Endotoxin-stimulated SMC also released biologically functional IL-1, measured as thymocyte costimulation activity inhibitable by anti-IL-1 antibody. Thus, human SMC can express IL-1 beta and IL-1 alpha genes, or very similar ones, and secrete biologically active product in response to a pathological stimulus. Endogenous local production of this inflammatory mediator by the blood vessel wall's major cell type could play an important early role in the pathogenesis of vasculitis and arteriosclerosis.

Two monokines, interleukin 1 and tumor necrosis factor, render cultured vascular endothelial cells susceptible to lysis by antibodies circulating during Kawasaki syndrome

Kawasaki syndrome (KS) is an acute febrile illness of early childhood characterized by diffuse vasculitis and marked immune activation. The present study was undertaken to determine whether the acute phase of KS is associated with circulating cytotoxic antibodies directed to target antigens induced on vascular endothelium by the monokines, IL-1, or tumor necrosis factor (TNF). Sera from 20 patients with acute KS, 11 patients in the convalescent phase of KS, and 17 age-matched controls were assessed for complement-dependent cytotoxic activity against 111In-labeled human endothelial cells (HEC), dermal fibroblasts, and vascular smooth muscle cells. Sera from patients with acute KS but not the other subject groups caused significant (p less than 0.01) complement-mediated killing of IL-1- or TNF-stimulated HEC. None of the sera tested had cytotoxicity against control HEC cultures or the other target cell types, with or without IL-1 or TNF pretreatment. Expression of the IL-1- or TNF-inducible target antigens on endothelial cells was rapid and transient, peaking at 4 h and disappearing after 24 h despite continued incubation with monokine. In contrast, we have previously shown that IFN-gamma requires 72 h to render HEC susceptible to lysis with acute KS sera. Serum adsorption studies demonstrated that IL-1- and TNF-inducible endothelial target antigens are distinct from IFN-gamma-inducible antigens. These observations suggest that mediator secretion by activated monocyte/macrophages could be a predisposing factor to the development of vascular injury in acute KS. Although our present observations have been restricted to KS, the development of cytotoxic antibodies directed to monokine-inducible endothelial cell antigens may also be found in other vasculitides accompanied by immune activation.

Cyclosporine nephrotoxicity: pathogenesis, prophylaxis, therapy, and prognosis

Although cyclosporine (CsA) therapy has improved the outcome of allotransplantation, drug-induced nephrotoxicity presents a potentially serious complication in a significant proportion of patients. The nephrotoxic injury, which may present acutely in the peritransplant period, subacutely in the first few months, or chronically, may be caused by toxic effects at various levels of the nephron: arteriole, glomerulus, and/or proximal tubule. The nephrotoxic picture of decreased glomerular filtration rate, impaired urea secretion, hyperkalemia, hypertension, and tubular dysfunction with preserved sodium reabsorption occurs not only in the renal allotransplant setting, wherein it obscures the diagnosis of rejection, but also in recipients of other grafts and patients under treatment for autoimmune disease. Because conversion from CsA to other immunosuppressive agents carries a high risk of rejection and allograft loss (or recrudescence of autoimmune disease), the present management strategy uses cautious CsA does reduction with concomitant institution of full-dose azathioprine (Aza) therapy. Definition of pharmacokinetic and pharmacodynamic properties that predict patients at risk for nephrotoxic complications may lead to new CsA dosing regimens yielding an improved therapeutic index.

Stimulation of arachidonic acid metabolism: differences in potencies of recombinant human interleukin-1 alpha and interleukin-1 beta on two cell types

Recombinant human interleukin-l (rIL-1) alpha and beta, which have 26% homology in their amino acid sequence, stimulated arachidonic acid metabolism by squirrel monkey smooth muscle cells and rat liver cells; their relative effectiveness, however, varied with the two cells. Recombinant IL-1 alpha was 3 times more effective than rIL-1 beta at stimulating arachidonic acid metabolism by the primate smooth muscle cells. Recombinant IL-1 alpha was 3 times less effective than rIL-1 beta when measured by their capacity to synergistically stimulate arachidonic acid metabolism of rat liver cells in the presence of palytoxin and anti-diuretic hormone (ADH). The rIL-1 alpha and rIL-1 beta also stimulated the release of radiolabelled arachidonic acid from the smooth muscle cells prelabelled with [3H]arachidonic acid. The two recombinant IL-1s have different heat stabilities, again when measured by their capacity to stimulate arachidonic acid metabolism; IL-1 alpha was more heat stable than IL-1 beta.

Enhancement by interleukin-1 (IL-1) of plasminogen activator inhibitor (PA-I) activity in cultured human endothelial cells

Cultured human endothelial cells produce increased levels of PA-I when stimulated with IL-1. The stimulatory effect was elicited by both alpha (pI 5) and beta (pI 7) IL-1 molecules. The effect was both dose and time-dependent, plateau reached after 8 h. The PA-I measured in cell extracts was SDS-resistant with an apparent m.w. of 53 Kd and inhibited both tissue-type plasminogen activator (t-PA) and urokinase (UK). No change in t-PA antigen level was detected with any of the IL-1 preparations tested.

Regulation of the fibrinolytic system of cultured human vascular endothelium by interleukin 1

We examined the effects of human interleukin 1 (IL-1) on the production of fibrinolytic components by cultured human vascular endothelium. Conditioned media collected from IL-1-treated (5 U/ml, 24 h) monolayers exhibited decreased tissue-type plasminogen activator (tPA) activity and increased plasminogen activator inhibitor (PAI) activity, as assessed by fibrin and reverse fibrin-autography. Quantitative immunological assays revealed a 35% decrease in tPA antigen and a 360% increase in active PAI antigen, after incubation for 24 h with 0.6 U/ml IL-1. Maximal effects (approximately 50% decrease in tPA antigen; 400-800% increase in active PAI antigen) were observed with 2.5-5 U/ml IL-1. Changes in tPA and PAI reached a maximum at approximately 24 h and persisted for greater than 48 h. IL-1 induction of endothelial procoagulant activity was more rapid and transient, peaking by 6 h and subsiding by 24 h. Natural monocyte-derived IL-1 and two species of recombinant IL-1 had comparable effects. Heat and polymyxin-B treatments differentiated IL-1 actions from those of endotoxin, which promoted similar endothelial alterations. IL-1 effects on endothelial procoagulant and fibrinolytic activities may contribute to the generation and maintenance of fibrin in pathophysiological settings in vivo.

Interleukin 1 stimulates platelet activating factor production in cultured human endothelial cells

Monocyte-derived interleukin 1 (IL 1) induced the platelet activating factor (PAF) production in cultured human endothelial cells (HEC). The product was identified as PAF by the chemical properties, the susceptibility to phospholipase A2 and C and to lipase A1, its behaviour in thin layer chromatography and in high pressure liquid chromatography and the recovery of biological activity tested on rabbit platelets. The action of IL 1 was concentration-dependent and took more than 2 hours to became apparent. Most of the PAF produced was cell-associated and only the 25% of the total was released.