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P Libby

Publications and source records attributed to P Libby.

At least 217 records · Page 12Linked to original sources
PubMed1990

Proliferating or interleukin 1-activated human vascular smooth muscle cells secrete copious interleukin 6.

The cells that make up blood vessel walls appear to participate actively in local immune and inflammatory responses, as well as in certain vascular diseases. We tested here whether smooth muscle cells (SMC) can produce the important inflammatory mediator IL6. Unstimulated SMC in vitro elaborated 5 X 10(3) pg recIL6/24h (i.e., biological activity equivalent to 5 X 10(3) pg recombinant IL6 (recIL6), as determined in B9-assay with a recIL6 standard). Several pathophysiologically relevant factors augmented IL6 release from SMC including 10 micrograms LPS/ml (10(4) pg recIL6), 10 ng tumor necrosis factor/ml (4 X 10(4) pg recIL6), and most notably 10 ng IL1/ml (greater than or equal to 3.2 X 10(5) pg recIL6). Production of IL6 activity corresponded to IL6 mRNA accumulation and de novo synthesis. SMC released newly synthesized IL6 rapidly, as little metabolically labeled material remained cell-associated. In supernatants of IL1-stimulated SMC, IL6 accounted for as much as 4% of the secreted proteins. In normal vessels SMC seldom divide, but SMC proliferation can occur in hypertension or during atherogenesis. We therefore tested the relationship between IL6 production and SMC proliferation in response to platelet-derived growth factor (PDGF) in vitro. Quiescent SMC released scant IL6 activity, whereas PDGF (1-100 ng/ml) produced concentration-dependent and coordinate enhancement of SMC proliferation and IL6 release (linear regression of growth vs. IL6 release yielded r greater than 0.9). IL6 itself neither stimulated nor inhibited SMC growth or IL6 production. Intact medial strips studied in short-term organoid culture produced large quantities of IL6, similar to the results obtained with cultured SMC. These findings illustrate a new function of vascular SMC by which these cells might participate in local immunoregulation and in the pathogenesis of various important vascular diseases as well as in inflammatory responses generally.

Cell Division↗
PubMed1989

Activated endothelial cells resist lymphokine-activated killer cell-mediated injury. Possible role of induced cytokines in limiting capillary leak during IL-2 therapy.

We previously demonstrated that IL-2 promotes the adhesion of NK cells to endothelial cells (EC) and that EC are readily lysed by lymphokine-activated killer (LAK) cells in vitro, suggesting that cell mediated endothelial injury may contribute to the capillary leak syndrome observed in patients treated with IL-2. In this investigation, we sought to determine the effects of EC activation on the in vitro susceptibility of EC to LAK cell-mediated cytolysis. Despite increased binding of CD16+ lymphocytes to TNF-activated EC monolayers, prior exposure of EC to any of several IL-2-inducible cytokines including TNF-alpha, IL-1 beta, and IFN-gamma not only failed to render the EC more vulnerable to cytolysis but increased their resistance to LAK cells in 111Indium release cytolysis assays. This decrement in susceptibility to cytolysis resulting from prior exposure to cytokines preceded any detectable increase in HLA class I or II Ag expression. In cold target competition experiments with LAK cell effectors and radiolabeled K562 target cells, TNF-primed EC were no more competitive than unstimulated EC, and in assays with unstimulated PBMC effectors, the addition of unlabeled TNF-activated EC actually increased the cytolysis of the radiolabeled tumor cells. The effects of various cytokines and lymphocyte preparations on EC permeability were also evaluated. In these experiments, saphenous vein EC were cultured on porous filter disks, exposed to cytokines or lymphocytes, and the diffusion of 125I-BSA through the filters was then measured. Exposure to IL-2, IFN-gamma, or TNF-alpha did not increase the diffusion of the BSA through the EC-coated filters, whereas LAK cells markedly increased their permeability. Consistent with the results of the cytolysis assays, pretreatment of the EC with TNF, IL-1, or IFN-gamma diminished the LAK cell-induced increase in BSA diffusion. These results suggest that although circulating IL-2-inducible cytokines such as TNF and IFN-gamma may activate EC in vivo and contribute to lymphocyte margination and lymphopenia, they may not be directly responsible for the IL-2-induced capillary leak syndrome and may actually protect EC from LAK cell-mediated injury.

Antigens, Differentiation↗
PubMed1989

Implantation of vascular grafts lined with genetically modified endothelial cells.

The possibility of using the vascular endothelial cell as a target for gene replacement therapy was explored. Recombinant retroviruses were used to transduce the lacZ gene into endothelial cells harvested from mongrel dogs. Prosthetic vascular grafts seeded with the genetically modified cells were implanted as carotid interposition grafts into the dogs from which the original cells were harvested. Analysis of the graft 5 weeks after implantation revealed genetically modified endothelial cells lining the luminal surface of the graft. This technology could be used in the treatment of atherosclerosis disease and the design of new drug delivery systems.

Animals↗
PubMed1989

PDGF-dependent tyrosine phosphorylation stimulates production of novel polyphosphoinositides in intact cells.

A phosphatidylinositol (PI) kinase activity associated with certain protein tyrosine kinases important in cell proliferation phosphorylates the 3' hydroxyl position of PI to produce phosphatidylinositol-3-phosphate (PI-3-P). Here we report that, in addition to PI-3' kinase activity, anti-phosphotyrosine (alpha-P-tyr) immunoprecipitates from platelet-derived growth factor (PDGF)-stimulated smooth muscle cells (SMC) contain lipid kinase activities that utilize the substrates phosphatidylinositol-4-phosphate (PI-4-P) and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2). These activities are absent in alpha-P-tyr immunoprecipitates from quiescent SMC. The product of PI-4-P phosphorylation appears to be phosphatidylinositol-3,4-bisphosphate (PI-3,4-P2), a lipid not previously reported. The product of PI-4,5-P2 phosphorylation is phosphatidylinositol-trisphosphate (PIP3). PI-3-P was detected in quiescent SMC and increased only slightly in response to PDGF. PIP3 and the putative PI-3,4-P2 appeared only after the addition of mitogen. Both the temporal production of these novel phospholipids after PDGF stimulation and the observation of the enzymatic activities that produce them in alpha-P-tyr immunoprecipitates suggest that these phospholipids are excellent candidates for mediators of the PDGF mitogenic response.

1-Phosphatidylinositol 4-Kinase↗
PubMed1989

Human vascular smooth muscle cells. Target for and source of tumor necrosis factor.

TNF-alpha (also known as cachectin) may produce many of its important effects in vivo by actions on blood vessels. Endothelial cells are well known to respond to TNF-alpha. We investigated whether vascular smooth muscle cells (SMC), the most abundant cell type in most vessels, also respond to TNF-alpha and the related cytokine lymphotoxin (TNF-beta). Both human rTNF-alpha and beta (0.1 to 100 ng/ml) induced transient accumulation of IL-1 mRNA by adult human vascular SMC that peaked between 1 and 4 h. The inhibitor of RNA synthesis actinomycin D (1 microgram/ml) blocked the induction of IL-1 mRNA, whereas inhibition of protein synthesis with cycloheximide (1 microgram/ml) resulted in a marked "superinduction" of both IL-1 alpha and IL-1 beta mRNA species. TNF-alpha treatment also increased intracellular biologically active IL-1 and subsequent release of IL-1 activity from SMC. Metabolic labeling and immunoprecipitation with specific antibodies demonstrated de novo synthesis of IL-1 alpha and IL-1 beta precursors in TNF-treated or lymphotoxin-treated SMC. TNF-alpha also activated other SMC functions including the concentration-dependent release of PGE2 from SMC, and time-dependent induction of the gene for (2'-5')-oligoadenylate synthetase, an enzyme thought to mediate the anti-viral and anti-proliferative actions of IFN. We also explored whether SMC, which both produce and respond to IL-1, might also express either of the TNF genes. Bacterial LPS (10 micrograms/ml) caused slight accumulation of TNF-alpha transcripts. Incubation of SMC for 4 h with inhibitors of protein synthesis alone caused little or no elevation of TNF-alpha mRNA, but simultaneous addition of LPS ("superinduction" conditions) induced large amounts of TNF-alpha (but not TNF-beta) mRNA. Cells treated with anisomycin (1 microgram/ml) and LPS, then washed to remove this reversible inhibitor of protein synthesis, released TNF-alpha into the medium, as assessed by the L929 cytotoxicity assay and by metabolic labeling and immunoprecipitation. Thus, SMC both respond to both TNF and lymphotoxin and can produce TNF-alpha, a cytokine with numerous effects on vascular cells of potential significance in the pathophysiology of septic shock and other inflammatory conditions.

2',5'-Oligoadenylate Synthetase↗
PubMed1989

Adult human vascular endothelial cells express the IL6 gene differentially in response to LPS or IL1.

We investigated the regulation of IL6 biological activity, de novo synthesis, and mRNA levels in adult vascular endothelial cells (EC) by bacterial endotoxin or inflammatory cytokines. Cells incubated without stimulus released scant IL6 activity. IFN gamma, IL2, or PDGF did not augment IL6 release from EC. LPS, lipid A, and TNF increased IL6 release modestly (5 to 20-fold), while recombinant IL1s (rIL1s) stimulated this process 100 to 400-fold. Differential release of IL6 from EC treated with LPS or rIL1 continued for at least 144 hr. Exposure to LPS or rIL1 caused EC to synthesize IL6 de novo. EC secreted the newly synthesized IL6 into the supernatant, rather than retaining it within or bound to cells. EC accumulated IL6 mRNA after 3 hr of exposure to rIL1. However, we could only detect IL6 message in cells incubated with LPS under "superinduction" conditions with cycloheximide, consistent with lower levels of IL6 biological activity in response to LPS compared to IL1 stimulation. We propose that local production of IL6 by vascular EC, which comprise the barrier between tissues and the blood, may influence regional immune and inflammatory responses.

Antigen-Antibody Reactions↗
PubMed1989

Observations on human smooth muscle cell cultures from hyperplastic lesions of prosthetic bypass grafts: production of a platelet-derived growth factor-like mitogen and expression of a gene for a platelet-derived growth factor receptor--a preliminary study.

Prosthetic bypass grafts placed to the distal lower extremity often fail because of an occlusive tissue response in the perianastomotic region. The origin of the cells that comprise this occlusive lesion and the causes of the cellular proliferation are not known. To increase our understanding of this process we cultured cells from hyperplastic lesions obtained from patients at the time of reexploration for lower extremity graft failure, and we studied their identity and growth factor production in tissue culture. These cultures contain cells that express muscle-specific actin isoforms, shown by immunohistochemical staining, consistent with vascular smooth muscle origin. These cultures also released material that stimulated smooth muscle cell growth. A portion of this activity was similar to platelet-derived growth factor, since preincubation with antibody-to-human platelet-derived growth factor partially blocked the mitogenic effect of medium conditioned by human anastomotic hyperplastic cells. These conditioned media also contained material that competed with platelet-derived growth factor for its receptor, as measured in a radioreceptor assay. Northern blot analysis showed that these cells contain messenger RNA that encodes the A chain but not the B chain of platelet-derived growth factor. In addition, these cells contain messenger RNA that encodes a platelet-derived growth factor receptor. We conclude that cultured smooth muscle cells from human anastomotic hyperplastic lesions express genes for platelet-derived growth factor A chain and a platelet-derived growth factor receptor and secrete biologically active molecules similar to platelet-derived growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Immune interferon inhibits proliferation and induces 2'-5'-oligoadenylate synthetase gene expression in human vascular smooth muscle cells.

Proliferation of vascular smooth muscle cells (SMC) contributes to formation of the complicated human atherosclerotic plaque. These lesions also contain macrophages, known to secrete SMC mitogens, and T lymphocytes. Many of the SMC in the lesions express class II major histocompatibility antigens, an indication that activated T cells secrete immune IFN-gamma locally in the plaque. We therefore studied the effect of IFN-gamma on the proliferation of cultured SMC derived from adult human blood vessels. IFN-gamma (1,000 U/ml) reduced [3H]thymidine (TdR) incorporation into DNA by SMC stimulated with the well-defined mitogens IL 1 (from 15.3 +/- 0.7 to 6.2 +/- 0.7 dpm X 10(-3)/24 h) or platelet-derived growth factor (PDGF) (from 18.5 +/- 1.0 to 7.3 +/- 0.7 dpm X 10(-3)/24 h). Kinetic and nuclear labeling studies indicated that this effect of IFN-gamma was not due to altered thymidine transport or specific radioactivity of TdR in the cell. In longer term experiments (4-16 d) IFN-gamma prevented net DNA accumulation by SMC cultures stimulated by PDGF. IFN-gamma also delayed (from 30 to 60 min) the time to peak level of c-fos RNA in IL 1-treated SMC. It is unlikely that cytotoxicity caused these effects of IFN-gamma, as the inhibition of growth was reversible and we detected no cell death in SMC cultures exposed to this cytokine. Activation of 2'-5' oligoadenylate synthetase gene expression may mediate certain antiproliferative and antiviral effects of interferons. Both IFN-gamma and type I IFNs (IFN-alpha or IFN-beta) induced 2'-5' oligoadenylate synthetase mRNA and enzyme activity in SMC cultures, but with concentration dependence and time course that may not account for all of IFN-gamma's cytostatic effect on SMC. The accumulation of SMC in human atherosclerotic lesions is a long-term process that must involve altered balance between growth stimulatory and inhibitory factors. The cytostatic effect of IFN-gamma on human SMC demonstrated here may influence this balance during human atherogenesis, because T cells present in the complicated atherosclerotic plaque likely produce this cytokine.

2',5'-Oligoadenylate Synthetase↗
PubMed1989

Functions of vascular wall cells related to development of transplantation-associated coronary arteriosclerosis.

The accelerated form of arteriosclerosis that occurs in the coronary circulation of transplanted hearts currently presents a major limitation to the long-term success of this therapy. The pathogenesis of this lesion is unclear. Recent advances in vessel wall biology have disclosed interplay between mediators of the immune response and functions of vascular cells of potential significance in the formation of this accelerated form of arterial disease. We hypothesize that the development of accelerated arteriosclerosis in the arteries of transplanted hearts represents a form of chronic immunologic reaction resembling delayed-type hypersensitivity localized in the graft's arteries, a manifestation of cellular immunity mediated in large part by a regionally acting cytokine network. We emphasize the active responses of intrinsic vessel wall cells, including inappropriate expression of HLA and the likely participation of cytokines derived from vascular cells as well as from infiltrating leukocytes in amplification and propagation of this localized chronic immune reaction. This mechanism, which involves helper T cells interacting with class II HLA, may distinguish transplantation-associated arteriosclerosis from typical acute rejection, which may involve primarily cytolytic T cells interacting with class I HLA. Lesions of the common variety of atherosclerosis manifest certain features of immune activation. Therefore, we further hypothesize that the transplantation-associated form represents an extreme case of processes that also contribute to usual coronary atherosclerosis. For this reason, study of the accelerated disease may aid understanding of atherogenesis in general. Unraveling the basic pathobiology of these clinically important arterial diseases should lay the groundwork for rational design of selective therapeutic strategies to prevent or retard their development.

Animals↗
PubMed1989

Comparative analysis of cytokine induction in human vascular endothelial and smooth muscle cells.

Cells of the blood vessel wall are both targets for and sources of certain cytokines. Various stimuli including bacterial lipopolysaccharides (LPS) or Interleukin 1 (IL1) induce elaboration of immunoregulatory and inflammatory mediators by human vascular endothelial cells (EC) and smooth muscle cells (SMC). We compared the capacity of EC and SMC to produce interleukin 6 (IL6) in response to LPS or its lipid A moiety. Cultured SMC release IL6 even without addition of stimuli, this basal IL6 secretion increased 2 to 4 fold in response to LPS. In contrast, unstimulated EC released little IL6, but exposure to LPS increased IL6 elaboration approximately 10 fold. Lipid A also augmented IL6 production by both EC and SMC. Radioimmunoprecipitation experiments compared de novo IL6 synthesis by EC and SMC in response to LPS, and yielded results consistent with the studies of biological activity. Unstimulated EC produced no precipitable IL6, LPS-stimulated EC released newly synthesized IL6, although to a lesser extent than did IL1-stimulated cells. SMC secreted precipitable IL6 without added stimulus and in increasing amounts following exposure to LPS or IL1. Thus EC and SMC exhibit substantial quantitative differences in IL6 synthesis and release, basally and in response to LPS. The capacity of these intrinsic vessel wall cells to secrete this important immunomodulator might contribute to local regulation of the immune or inflammatory responses.

Cells, Cultured↗
PubMed1988

IL-2 rapidly induces natural killer cell adhesion to human endothelial cells. A potential mechanism for endothelial injury.

NK cells promptly disappear from the circulation of patients treated with high dose i.v. rIL-2. To further study this process, we evaluated the effects of IL-2 (1000 U/ml) on normal donor PBMC incubated for 1 h on cultured human saphenous vein endothelial cells (EC). Although the NK activity of non-adherent PBMC recovered from flasks coated only with fibronectin increased in the presence of supplemental IL-2, the activity of cells recovered from flasks coated with EC decreased when IL-2 was added to the medium. The percentage of NK (CD16+) cells among the EC-non-adherent PBMC was reduced relative to that of the input cells when IL-2 was added. The percentage of CD16+ cells in the EC-adherent PBMC, as well as their NK activity, increased in the presence of added IL-2. Although EC had no effect on the lysis of labeled K-562 cells by unstimulated PBMC in cold target competition experiments, they were able to compete in cytolytic assays using PBMC previously activated by exposure to IL-2 for 1 h. EC were not lysed by these briefly activated PBMC in 3-h cytotoxicity assays but were lysed by these effectors in 18-h assays and in 3-h assays using PBMC pre-activated by more prolonged culture with IL-2. The ability of IL-2 to induce NK cell adhesion to EC was not blocked by a mixture of neutralizing antisera raised against rTNF-alpha, rIL-1 alpha, and rIL-1 beta, factors known to promote leukocyte adhesion to EC. We conclude that IL-2 rapidly induces NK cell adhesion to EC and propose that this effect accounts for the disappearance of circulating NK cells after the infusion of high doses of IL-2. In addition, these results suggest that NK cells activated by IL-2 in vivo may injure the endothelium and contribute to the extravasation of plasma and the retention of fluid characteristic of IL-2 treatment.

Binding, Competitive↗
PubMed1988

Production of platelet-derived growth factor-like mitogen by smooth-muscle cells from human atheroma.

Proliferation of vascular smooth-muscle cells occurs during the development of atherosclerosis and the remodeling of arteries that accompanies chronic systemic or pulmonary hypertension. To help define the signals that initiate this abnormal growth, we cultured smooth-muscle cells from human atherosclerotic plaques. These cells (n = 9) released material into their culture medium that stimulated the proliferation of aortic smooth-muscle cells to a mean (+/- SD) level 5.1 +/- 1 times that in control medium. Part of this activity was due to molecules that resemble a mitogen first isolated from platelets and known as platelet-derived growth factor (PDGF), since these cells released PDGF measured in a radioreceptor assay (355 +/- 117 pg per milliliter per 48 hours; n = 6) and since anti-PDGF antibody neutralized 38 +/- 7 percent of this mitogenic activity (range, 13 to 60 percent; n = 6 carotid-plaque isolates). Two human genes encode distinct PDGF subunits that form dimers in different combinations to create biologically active PDGF. Cells cultured from human atheroma contained mRNAs for the PDGF A chain (16 of 17 isolates) but none (of 13) that encoded PDGF B chain (the c-sis proto-oncogene product). We conclude that smooth-muscle cells from diseased human arteries can secrete mitogenic activity, some of which resembles PDGF, and that these cells express the gene for the PDGF A chain selectively. This capacity to produce an endogenous, potentially self-stimulatory (autocrine) growth factor may help to explain how replication of smooth-muscle cells can begin, even while the endothelial barrier remains morphologically intact, early in atherogenesis.

Aged↗
PubMed1988

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.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Interleukin 1 induces interleukin 1. I. Induction of circulating interleukin 1 in rabbits in vivo and in human mononuclear cells in vitro.

Interleukin 1 (IL-1) plays an important role in host defense mechanisms by increasing body temperature, inducing the synthesis of a variety of lymphokines and hepatic acute phase proteins and acting as a chemoattractant for lymphocytes. However, in some microenvironments such as injured tissue or joint spaces, elevated IL-1 levels may contribute to pathologic processes, for example, proliferation and fibrosis of tissue involved in pannus formation as well as degradation of matrix and abnormal tissue architecture. To investigate potential mechanisms that may lead to excessive production of IL-1, we have examined the ability of IL-1 to participate in an amplification event by inducing its own gene expression leading to synthesis of biologically active IL-1. When injected into rabbits, recombinant human IL-1-alpha induced biphasic fevers, and during the second temperature elevation 3 hr later, a circulating pyrogenic material was detected by passive transfer of plasma to other rabbits. Induction of the biphasic fever was not caused by endotoxin contamination of the recombinant IL-1. The 3-hr circulating pyrogen was heat-labile and was not residual injected IL-1-alpha. Chromatographic separation of this plasma and biologic assay suggested that it was new IL-1 of rabbit origin. We next incubated human blood mononuclear cells with recombinant IL-1-alpha and measured the intracellular and extracellular levels of IL-1 by bioassay using the D10.G4.1 murine T cell line. In order to control for the carryover of recombinant IL-1-alpha used to stimulate the mononuclear cells (MNC), we used neutralizing antibodies that were specific for IL-1-alpha or IL-1-beta. The results of these neutralizations showed that recombinant human IL-1-alpha induces the synthesis of IL-1-beta in human MNC in vitro. These results were verified with a radioimmunoassay specific for IL-1-beta. At concentrations of 100 ng/ml, IL-1-alpha induced prostaglandin E2 production in the MNC culture, and this was associated with decreased production of immunoreactive IL-1-beta. Adding indomethacin to the cultures prevented the decreased production of IL-1-beta induced by high concentrations of IL-1-alpha. Using nonadherent MNC, we observed an increase in IL-1-beta as well as IL-1-alpha mRNA after 4 hr of exposure to recombinant IL-1-alpha. These results demonstrate that IL-1-alpha induces biologically active and immunoreactive IL-1-beta from MNC in vitro and that the same concentrations of IL-1-alpha induce gene expression for both forms of IL-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Interleukin 1 induces interleukin 1. II. Recombinant human interleukin 1 induces interleukin 1 production by adult human vascular endothelial cells.

Interleukin 1 (IL-1) alters several potentially pathogenic endothelial cell (EC) functions. The authors report here that recombinant human IL-1 (rIL-1) alpha (0.1 to 10 ng/ml) or IL-1-beta (1 to 100 ng/ml) induce concentration- and time-dependent increases in IL-1-beta mRNA levels in EC derived from adult human saphenous vein. rIL-1 induced IL-1-alpha mRNA only in EC treated concomitantly with cycloheximide (2 micrograms/ml). IL-1-beta mRNA production began within 1 hr of exposure to rIL-1, peaked after 24 hr, and declined thereafter. Actinomycin D prevented the appearance of IL-1 mRNA in rIL-1-treated EC. rIL-1 also induced the release of biologically active IL-1 from EC, which was inhibited by cycloheximide (1 microgram/ml). When compared on the basis of their activity in the thymocyte costimulation assay, rIL-1-alpha and rIL-1-beta were equipotent as inducers of IL-1 production by EC. EC stimulated with rIL-1 produced prostaglandin E2, which inhibits IL-1 production by other cell types and also decreases the responsiveness of thymocytes to IL-1. When EC were exposed to rIL-1 in the presence of indomethacin (1 microgram/ml), which blocked prostaglandin E2 production, greater amounts of rIL-1-induced IL-1 release were detected, although the inhibitor did not affect IL-1-beta mRNA levels. IL-1-induced IL-1 production was unlikely to be caused by endotoxin contamination of tissue culture media or IL-1 preparations, because the lipopolysaccharide (LPS) antagonist polymyxin B (10 micrograms/ml) blocked LPS-induced IL-1 production by EC but did not affect IL-1 release in response to rIL-1-beta (100 ng/ml). The IL-1-inducing property of rIL-1-beta was heat-labile, whereas heated LPS stimulated EC IL-1 production. The source of IL-1 in our cultures was not monocyte/macrophages, as treatment of EC with monoclonal antibody to the monocyte antigen Mo2 under conditions that lysed adherent peripheral blood monocytes did not affect production of IL-1 by EC in response to LPS (1 microgram/ml) or rIL-1-beta (100 ng/ml). IL-1 elicits a coordinated program of altered endothelial function that increases adhesiveness for leukocytes and coagulability. IL-1-induced IL-1 gene expression in human adult EC could thus provide a positive feedback mechanism in the pathogenesis of vascular disease including atherosclerosis, vasculitis, and allograft rejection.

Cells, Cultured↗